WorldWideScience

Sample records for dynamic thermal performance

  1. Dynamic thermal performance of alveolar brick construction system

    Energy Technology Data Exchange (ETDEWEB)

    Gracia, A. de; Castell, A.; Medrano, M. [GREA Innovacio Concurrent, Edifici CREA, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain); Cabeza, L.F., E-mail: lcabeza@diei.udl.ca [GREA Innovacio Concurrent, Edifici CREA, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain)

    2011-07-15

    Highlights: {yields} Even though U-value does not measure thermal inertia, it is the commonly used parameter. {yields} The thermal performance analysis of buildings must include the evaluation of transient parameters. {yields} Transient parameters of alveolar brick constructive system show good agreement with its low energy consumption. -- Abstract: Alveolar bricks are being introduced in building sector due to the simplicity of their construction system and to the elimination of the insulation material. Nevertheless, it is not clear if this new system is energetically efficient and which is its thermal behaviour. This paper presents an experimental and theoretical study to evaluate the thermal behaviour of the alveolar brick construction system, compared with a traditional Mediterranean brick system with insulation. The experimental study consists of measuring the thermal performance of four real house-like cubicles. The thermal transmittance in steady-state, also known as U-value, is calculated theoretically and experimentally for each cubicle, presenting the insulated cubicles as the best construction system, with differences around 45% in comparison to the alveolar one. On the other hand, experimental results show significantly smaller differences on the energy consumption between the alveolar and insulated construction systems during summer period (around 13% higher for the alveolar cubicle). These values demonstrate the high thermal efficiency of the alveolar system. In addition, the lack of agreement between the measured energy consumption and the calculated U-values, guides the authors to analyze the thermal inertia of the different building components. Therefore, several transient parameters, extracted from the heat transfer matrix and from experimental data, are also evaluated. It can be concluded that the alveolar brick construction system presents higher thermal inertia than the insulated one, justifying the low measured energy consumption.

  2. Experimental investigations of fluid dynamic and thermal performance of nanofluids

    Science.gov (United States)

    Kulkarni, Devdatta Prakash

    The goal of this research was to investigate the fluid dynamic and thermal performance of various nanofluids. Nanofluids are dispersions of metallic nanometer size particles (choice of base fluid is an ethylene or propylene glycol and water mixture in cold regions. Initially the rheological characterization of copper oxide (CuO) nanofluids in water and in propylene glycol was performed. Results revealed that higher concentrations of CuO nanoparticles (5 to 15%) in water exhibited time-independent pseudoplastic and shear-thinning behavior. Lower concentrations (1 to 6%) of CuO nanofluids in propylene glycol revealed that these nanofluids behaved as Newtonian fluids. Both nanofluids showed that viscosity decreased exponentially with increase in temperature. Subsequent correlations for viscosities as a function of volume concentration and temperature were developed. Effects of different thermophysical properties on the Prandtl number of CuO, silicon dioxide (SiO2) and aluminum oxide (A12O 3) nanofluids were investigated. Results showed that the Prandtl number increased with increasing volume concentrations, which in turn increased the heat transfer coefficients of the nanofluids. Various nanofluids were compared for their heat transfer rates based on the Mouromtseff number, which is a Figure of Merit for heat transfer fluids. From this analysis, the optimal concentrations of nanoparticles in base fluids were found for CuO-water nanofluids. Experiments were performed to investigate the convective heat transfer enhancement and pressure loss of CuO, SiO2 and A12O 3 nanofluids in the turbulent regime. The increases in heat transfer coefficient by nanofluids for various volume concentrations compared to the base fluid were determined. Pressure loss was observed to increase with nanoparticle volume concentration. It was observed that an increase in particle diameter increased the heat transfer coefficient. Calculations showed that application of nanofluids in heat

  3. Addressing Thermal and Performance Variability Issues in Dynamic Processors

    Energy Technology Data Exchange (ETDEWEB)

    Yoshii, Kazutomo [Argonne National Lab. (ANL), Argonne, IL (United States); Llopis, Pablo [Univ. Carlos III de Madrid (Spain); Zhang, Kaicheng [Northwestern Univ., Evanston, IL (United States); Luo, Yingyi [Northwestern Univ., Evanston, IL (United States); Ogrenci-Memik, Seda [Northwestern Univ., Evanston, IL (United States); Memik, Gokhan [Northwestern Univ., Evanston, IL (United States); Sankaran, Rajesh [Argonne National Lab. (ANL), Argonne, IL (United States); Beckman, Pete [Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-03-01

    As CMOS scaling nears its end, parameter variations (process, temperature and voltage) are becoming a major concern. To overcome parameter variations and provide stability, modern processors are becoming dynamic, opportunistically adjusting voltage and frequency based on thermal and energy constraints, which negatively impacts traditional bulk-synchronous parallelism-minded hardware and software designs. As node-level architecture is growing in complexity, implementing variation control mechanisms only with hardware can be a challenging task. In this paper we investigate a software strategy to manage hardwareinduced variations, leveraging low-level monitoring/controlling mechanisms.

  4. A facility for characterizing the steady-state and dynamic thermal performance of microelectromechanical system thermal switches.

    Science.gov (United States)

    Cho, J H; Richards, C D; Richards, R F

    2008-03-01

    A facility to characterize microelectromechanical system (MEMS) thermal switches by measuring two pertinent figures of merit is described. The two figures of merit measured are the ratio of thermal resistance of the switch in the off and on states, Roff/Ron, and the time required to switch from the off to the on state, tauswitch. The facility consists of two pieces of equipment. A guard-heated calorimeter is used to measure heat transfer across the thermal switch under steady-state conditions. Measuring heat transfer across a thermal switch in both the off and on states then gives the thermal resistance ratio Roff/Ron. A thin-film radial heat-flux sensor is used to measure heat transfer across the thermal switch under dynamic conditions. Measuring heat transfer across a thermal switch as the switch changes from the off to the on state gives the thermal switching time tauswitch. The test facilities enable the control of the applied force on the thermal switch when the thermal switch is on, the thickness of the gas gap when the thermal switch is off, and the gas species and pressure in the thermal switch gas gap. The thermal performance of two MEMS thermal switches employing two different thermal contact materials, a polished silicon surface and an array of liquid-metal microdroplets, is characterized and compared.

  5. Dynamic Modeling and Performance Analysis of Sensible Thermal Energy Storage Systems

    OpenAIRE

    Nash, Austin Lee; Jain, Neera

    2016-01-01

    In this paper we consider the problem of dynamic performance evaluation for sensible thermal energy storage (TES), with a specific focus on hot water storage tanks. We derive transient performance metrics from second law principles that can be used to guide real-time decision-making aimed toward improving demand response. We show how the transient nature of the metrics can be used not only to influence the values of control variables within the system, but also to mitigate adverse effects...

  6. Thermal effects on the performance, motor control and muscle dynamics of ballistic feeding in the salamander Eurycea guttolineata.

    Science.gov (United States)

    Anderson, Christopher V; Larghi, Nicholas P; Deban, Stephen M

    2014-09-01

    Temperature strongly affects muscle contractile rate properties and thus may influence whole-organism performance. Movements powered by elastic recoil, however, are known to be more thermally robust than muscle-powered movements. We examined the whole-organism performance, motor control and muscle contractile physiology underlying feeding in the salamander Eurycea guttolineata. We compared elastically powered tongue projection with the associated muscle-powered retraction to determine the thermal robustness of each of these functional levels. We found that tongue-projection distance in E. guttolineata was unaffected by temperature across the entire 4-26°C range, tongue-projection dynamics were significantly affected by temperature across only the 4-11°C interval, and tongue retraction was affected to a higher degree across the entire temperature range. The significant effect of temperature on projection dynamics across the 4-11°C interval corresponds to a significant decline in projector muscle burst intensity and peak contractile force of the projector muscle across the same interval. Across the remaining temperature range, however, projection dynamics were unaffected by temperature, with muscle contractile physiology showing typical thermal effects and motor patterns showing increased activity durations and latencies. These results reveal that elastically powered tongue-projection performance in E. guttolineata is maintained to a higher degree than muscle-powered tongue retraction performance across a wide temperature range. These results further indicate that thermal robustness of the elastically powered movement is dependent on motor control and muscle physiology that results in comparable energy being stored in elastic tissues across a range of temperatures.

  7. Dynamic thermal performance analysis of two solar air collectors with and without porous media

    Directory of Open Access Journals (Sweden)

    Abed Qahtan A.

    2016-01-01

    Full Text Available The paper presents the thermal performance comparison between two types of solar air collectors, with and without porous absorber material. In order to simulate the transient processes which occur in the collectors two mathematical models were developed. Each model consists of a set of time dependent equations which describe the energy balance for the main components of the collector considering time-dependent thermo-physical properties and heat transfer coefficients. The theoretical models were validated by experimental data obtained from measurements performed in different meteorological conditions characteristic to the city of Bucharest – Romania (latitude 44°26′ N, longitude 26°6′ E. Good agreement between the simulation results and experimental data was achieved.

  8. Dynamic thermal performance analysis of two solar air collectors with and without porous media

    Directory of Open Access Journals (Sweden)

    Abed Qahtan A.

    2016-01-01

    Full Text Available The paper presents the thermal performance comparison between two types of solar air collectors, with and without porous absorber material. In order to simulate the transient processes which occur in the collectors two mathematical models were developed. Each model consists of a set of time dependent equations which describe the energy balance for the main components of the collector considering time-dependent thermo-physical properties and heat transfer coefficients. The theoretical models were validated by experimental data obtained from measurements performed in different meteorological conditions characteristic to the city of Bucharest – Romania (latitude 44°26′ N, longitude 26°6′ E. Good agreement between the simulation results and experimental data was achieved.

  9. Thermal Performance Benchmarking

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xuhui; Moreno, Gilbert; Bennion, Kevin

    2016-06-07

    The goal for this project is to thoroughly characterize the thermal performance of state-of-the-art (SOA) in-production automotive power electronics and electric motor thermal management systems. Information obtained from these studies will be used to: evaluate advantages and disadvantages of different thermal management strategies; establish baseline metrics for the thermal management systems; identify methods of improvement to advance the SOA; increase the publicly available information related to automotive traction-drive thermal management systems; help guide future electric drive technologies (EDT) research and development (R&D) efforts. The thermal performance results combined with component efficiency and heat generation information obtained by Oak Ridge National Laboratory (ORNL) may then be used to determine the operating temperatures for the EDT components under drive-cycle conditions. In FY16, the 2012 Nissan LEAF power electronics and 2014 Honda Accord Hybrid power electronics thermal management system were characterized. Comparison of the two power electronics thermal management systems was also conducted to provide insight into the various cooling strategies to understand the current SOA in thermal management for automotive power electronics and electric motors.

  10. Thermal effects on the dynamics and motor control of ballistic prey capture in toads: maintaining high performance at low temperature.

    Science.gov (United States)

    Deban, Stephen M; Lappin, A Kristopher

    2011-04-15

    Temperature has a strong influence on biological rates, including the contractile rate properties of muscle and thereby the velocity, acceleration and power of muscle-powered movements. We hypothesized that the dynamics of movements powered by elastic recoil have a lower thermal dependence than muscle-powered movements. We examined the prey capture behavior of toads (Bufo terrestris) using high speed imaging and electromyography to compare the effects of body temperature (11-35°C) on the kinematics, dynamics and motor control of two types of movement: (1) ballistic mouth opening and tongue projection, which are powered by elastic recoil, and (2) non-ballistic prey transport, including tongue retraction and mouth closing, which are powered directly by muscle contraction. Over 11-25°C, temperature coefficients of ballistic mouth opening and tongue projection dynamics (Q(10) of 0.99-1.25) were not significantly different from 1.00 and were consistently lower than those of prey transport movements (Q(10) of 1.77-2.26), supporting our main hypothesis. The depressor mandibulae muscle, which is responsible for ballistic mouth opening and tongue projection via the recovery of elastic strain energy stored by the muscle prior to the onset of the movement, was activated earlier and for a longer duration at lower temperatures (Q(10) of 2.29-2.41), consistent with a slowing of its contractile rates. Muscle recruitment was unaffected by temperature, as revealed by the lack of thermal dependence in the intensity of activity of both the jaw depressor and jaw levator muscles (Q(10) of 0.754-1.12). Over the 20-35°C range, lower thermal dependence was found for the dynamics of non-elastic movements and the motor control of both elastic and non-elastic movements, in accord with a plateau of high performance found in other systems.

  11. Dynamic thermal environment and thermal comfort.

    Science.gov (United States)

    Zhu, Y; Ouyang, Q; Cao, B; Zhou, X; Yu, J

    2016-02-01

    Research has shown that a stable thermal environment with tight temperature control cannot bring occupants more thermal comfort. Instead, such an environment will incur higher energy costs and produce greater CO2 emissions. Furthermore, this may lead to the degeneration of occupants' inherent ability to combat thermal stress, thereby weakening thermal adaptability. Measured data from many field investigations have shown that the human body has a higher acceptance to the thermal environment in free-running buildings than to that in air-conditioned buildings with similar average parameters. In naturally ventilated environments, occupants have reported superior thermal comfort votes and much greater thermal comfort temperature ranges compared to air-conditioned environments. This phenomenon is an integral part of the adaptive thermal comfort model. In addition, climate chamber experiments have proven that people prefer natural wind to mechanical wind in warm conditions; in other words, dynamic airflow can provide a superior cooling effect. However, these findings also indicate that significant questions related to thermal comfort remain unanswered. For example, what is the cause of these phenomena? How we can build a comfortable and healthy indoor environment for human beings? This article summarizes a series of research achievements in recent decades, tries to address some of these unanswered questions, and attempts to summarize certain problems for future research.

  12. Thermal and Fluid Dynamic Performance of Pin Fin Heat Transfer Surfaces

    OpenAIRE

    Sahiti, Naser

    2006-01-01

    This thesis is organized into nine Chapters. Chapter 2 gives an overview of some highly effec-tive heat transfer surfaces used basically for the enhancement of single-phase convective heat transfer in the air conditioning, refrigeration, unit air heater and automobile industries. It follows the analysis of basic parameters that influence the performance of the fins and at the end a rela-tively simple analytical method for the assessment of the order of the magnitude of heat transfer enhanceme...

  13. Thermal Performance Benchmarking (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, G.

    2014-11-01

    This project will benchmark the thermal characteristics of automotive power electronics and electric motor thermal management systems. Recent vehicle systems will be benchmarked to establish baseline metrics, evaluate advantages and disadvantages of different thermal management systems, and identify areas of improvement to advance the state-of-the-art.

  14. Investigation of Thermal Performance of Flat Plate and Evacuated Tubular Solar Collectors According to a New Dynamic Test Method

    DEFF Research Database (Denmark)

    Kong, Weiqiang; Wang, Zhifeng; Fan, Jianhua;

    2012-01-01

    obtain fluid thermal capacitance in data processing. Then theoretical analysis and experimental verification are carried out to investigate influencing factors of obtaining accurate and stable second order term. A flat plate and ETC solar collector are compared using both the new dynamic method......A new dynamic test method is introduced. This so called improved transfer function method features on two new collector parameters. One is time term which can indicate solar collector's inner heat transfer ability and the other is a second order term of collector mean fluid temperature which can...... and a standard method. The results show that the improved function method can accurately and robustly estimate these two kinds of solar collectors....

  15. Thermal dynamics of thermoelectric phenomena from frequency resolved methods

    OpenAIRE

    2016-01-01

    Understanding the dynamics of thermoelectric (TE) phenomena is important for the detailed knowledge of the operation of TE materials and devices. By analyzing the impedance response of both a single TE element and a TE device under suspended conditions, we provide new insights into the thermal dynamics of these systems. The analysis is performed employing parameters such as the thermal penetration depth, the characteristic thermal diffusion frequency and the thermal diffusion time. It is show...

  16. Dynamic performance management system

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An integrated, efficient and effective performance management system, "dynamic performance management system", is presented, which covers the entire performance management process including measures design, analysis, and dynamic update. The analysis of performance measures using causal loop diagrams, qualitative inference and analytic network process is mainly discussed. A real world case study is carried out throughout the paper to explain how the framework works. A software tool for DPMS, Performance Analyzer, is also introduced.

  17. Thermal Performance Benchmarking: Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, Gilbert

    2016-04-08

    The goal for this project is to thoroughly characterize the performance of state-of-the-art (SOA) automotive power electronics and electric motor thermal management systems. Information obtained from these studies will be used to: Evaluate advantages and disadvantages of different thermal management strategies; establish baseline metrics for the thermal management systems; identify methods of improvement to advance the SOA; increase the publicly available information related to automotive traction-drive thermal management systems; help guide future electric drive technologies (EDT) research and development (R&D) efforts. The performance results combined with component efficiency and heat generation information obtained by Oak Ridge National Laboratory (ORNL) may then be used to determine the operating temperatures for the EDT components under drive-cycle conditions. In FY15, the 2012 Nissan LEAF power electronics and electric motor thermal management systems were benchmarked. Testing of the 2014 Honda Accord Hybrid power electronics thermal management system started in FY15; however, due to time constraints it was not possible to include results for this system in this report. The focus of this project is to benchmark the thermal aspects of the systems. ORNL's benchmarking of electric and hybrid electric vehicle technology reports provide detailed descriptions of the electrical and packaging aspects of these automotive systems.

  18. Dynamic Capabilities and Performance

    DEFF Research Database (Denmark)

    Wilden, Ralf; Gudergan, Siegfried P.; Nielsen, Bo Bernhard

    2013-01-01

    Dynamic capabilities are widely considered to incorporate those processes that enable organizations to sustain superior performance over time. In this paper, we argue theoretically and demonstrate empirically that these effects are contingent on organizational structure and the competitive...... are contingent on the competitive intensity faced by firms. Our findings demonstrate the performance effects of internal alignment between organizational structure and dynamic capabilities, as well as the external fit of dynamic capabilities with competitive intensity. We outline the advantages of PLS...

  19. Tribological Studies of Dynamic Thermal Seal Materials

    Science.gov (United States)

    DeMange, Jeffrey J.; Taylor, Shawn C.

    2016-01-01

    Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

  20. Thermal stress and human performance.

    Science.gov (United States)

    Enander, A E; Hygge, S

    1990-01-01

    There is evidence that the thermal stress encountered in many work environments may negatively affect various aspects of human performance and behavior. Evaluation of the empirical research is, however, complicated by differences in both the methodology and the definition of the basic stimulus. Effects of heat and cold stress are briefly reviewed, with particular regard to theoretical considerations.

  1. Thermal dynamics of bomb calorimeters

    Science.gov (United States)

    Lyon, Richard E.

    2015-12-01

    The thermal dynamics of bomb calorimeters are modeled using a lumped heat transfer analysis in which heat is released in a pressure vessel/bomb immersed in a stirred water bath that is surrounded by a static air space bounded by an insulated (static) jacket, a constant/controlled temperature jacket (isoperibol), or a changing temperature (adiabatic) jacket. The temperature history of the water bath for each of these boundary conditions (methods) is well described by the two-term solution for the calorimeter response to a heat impulse (combustion), allowing the heat transfer coefficients and thermal capacities of the bomb and water bath to be determined parametrically. The validated heat transfer model provides an expression for direct calculation of the heat released in an arbitrary process inside a bomb calorimeter using the temperature history of the water bath for each of the boundary conditions (methods). This result makes possible the direct calculation of the heat of combustion of a sample in an isoperibol calorimeter from the recorded temperature history without the need for semi-empirical temperature corrections to account for non-adiabatic behavior. Another useful result is that the maximum temperature rise of the water bath in the static jacket method is proportional to the total heat generated, and the empirical proportionality constant, which is determined by calibration, accounts for all of the heat losses and thermal lags of the calorimeter.

  2. Validation of a simple dynamic thermal performance characterization model based on the piston flow concept for flat-plate solar collectors

    DEFF Research Database (Denmark)

    Deng, Jie; Yang, Ming; Ma, Rongjiang

    2016-01-01

    dynamic model based on the first-order difference method is compared to that of the numerical solution of the collector ordinary differential equation (ODE) model using the fourth-order Runge-Kutta method. The improved thermal inertia model (TIM) on the basis of closed-form solution presented by Deng et...

  3. Thermal Power Plant Performance Analysis

    CERN Document Server

    2012-01-01

    The analysis of the reliability and availability of power plants is frequently based on simple indexes that do not take into account the criticality of some failures used for availability analysis. This criticality should be evaluated based on concepts of reliability which consider the effect of a component failure on the performance of the entire plant. System reliability analysis tools provide a root-cause analysis leading to the improvement of the plant maintenance plan.   Taking in view that the power plant performance can be evaluated not only based on  thermodynamic related indexes, such as heat-rate, Thermal Power Plant Performance Analysis focuses on the presentation of reliability-based tools used to define performance of complex systems and introduces the basic concepts of reliability, maintainability and risk analysis aiming at their application as tools for power plant performance improvement, including: ·         selection of critical equipment and components, ·         defini...

  4. Thermal debinding dynamics of novel binder system

    Institute of Scientific and Technical Information of China (English)

    周继承; 黄伯云; 张传福; 刘业翔

    2001-01-01

    The thermal debinding dynamics of newly developed binders for cemented carbides extrusion molding was studied. It is shown that the thermal debinding processes can be divided into two stages: low temperature region, in which the low molecular mass components (LMMCs) are removed; and high temperature region, in which the polymer components are removed. The rate of thermal debinding is controlled by diffusion mechanism. The thermal debinding activation energies were solved out by differential method and integral method. The results show that the addition of other components acted as a catalyzer can effectively decrease the activation energy of thermal debinding processes.

  5. Performance maps for the control of thermal energy storage

    DEFF Research Database (Denmark)

    Finck, Christian; Li, Rongling; Zeiler, Wim

    2017-01-01

    Predictive control in building energy systems requires the integration of the building, building system, and component dynamics. The prediction accuracy of these dynamics is crucial for practical applications. This paper introduces performance maps for the control of water tanks, phase change mat...... material tanks, and thermochemical material tanks. The results show that these performance maps can fully account for the dynamics of thermal energy storage tanks.......Predictive control in building energy systems requires the integration of the building, building system, and component dynamics. The prediction accuracy of these dynamics is crucial for practical applications. This paper introduces performance maps for the control of water tanks, phase change...

  6. Enhanced performance thermal diode via thermal boundary resistance at nanoscale

    Science.gov (United States)

    Tovar-Padilla, M.; Licea-Jimenez, L.; Pérez-Garcia, S. A.; Alvarez-Quintana, J.

    2015-08-01

    Hypothetically, a thermal rectifier is a device which leads a greater heat flux in one direction than another one, similarly as the electrical diode works for the electrical flux. Here, a drastic increment in the rectification factor has been obtained in nanoscale layered thermal diodes due to the effect of thermal boundary resistance present on an asymmetrical stack of nanofilms. Measurements show a thermal rectification factor as large as 3.3 under a temperature bias well below 1 K, which is the biggest thermal rectification factor reported at room temperature compared to previously reported thermal diodes so far. According to the direction of the applied heat flux, the observed impact of the thermal boundary resistance on the device is manifested through the presence of an asymmetric temperature rise along the heat transfer axis. Such effect provides an alternative route for the development of high performance thermal diodes.

  7. Thermal Hydraulic Performance of Tight Lattice Bundle

    Science.gov (United States)

    Yamamoto, Yasushi; Akiba, Miyuki; Morooka, Shinichi; Shirakawa, Kenetsu; Abe, Nobuaki

    Recently, the reduced moderation spectrum BWR has been studied. The fast neutron spectrum is obtained through triangular tight lattice fuel. However, there are few thermal hydraulic test data and thermal hydraulic correlation applicable to critical power prediction in such a tight lattice bundle. This study aims to enhance the database of the thermal hydraulic performance of the tight lattice bundle whose rod gap is about 1mm. Therefore, thermal hydraulic performance measurement tests of tight lattice bundles for the critical power, the pressure drop and the counter current flow limiting were performed. Moreover, the correlations to evaluate the thermal-hydraulic performance of the tight lattice bundle were developed.

  8. Dynamic thermal analysis of machines in running state

    CERN Document Server

    Wang, Lihui

    2014-01-01

    With the increasing complexity and dynamism in today’s machine design and development, more precise, robust and practical approaches and systems are needed to support machine design. Existing design methods treat the targeted machine as stationery. Analysis and simulation are mostly performed at the component level. Although there are some computer-aided engineering tools capable of motion analysis and vibration simulation etc., the machine itself is in the dry-run state. For effective machine design, understanding its thermal behaviours is crucial in achieving the desired performance in real situation. Dynamic Thermal Analysis of Machines in Running State presents a set of innovative solutions to dynamic thermal analysis of machines when they are put under actual working conditions. The objective is to better understand the thermal behaviours of a machine in real situation while at the design stage. The book has two major sections, with the first section presenting a broad-based review of the key areas of ...

  9. Thermal dynamics of thermoelectric phenomena from frequency resolved methods

    Directory of Open Access Journals (Sweden)

    J. García-Cañadas

    2016-03-01

    Full Text Available Understanding the dynamics of thermoelectric (TE phenomena is important for the detailed knowledge of the operation of TE materials and devices. By analyzing the impedance response of both a single TE element and a TE device under suspended conditions, we provide new insights into the thermal dynamics of these systems. The analysis is performed employing parameters such as the thermal penetration depth, the characteristic thermal diffusion frequency and the thermal diffusion time. It is shown that in both systems the dynamics of the thermoelectric response is governed by how the Peltier heat production/absorption at the junctions evolves. In a single thermoelement, at high frequencies the thermal waves diffuse semi-infinitely from the junctions towards the half-length. When the frequency is reduced, the thermal waves can penetrate further and eventually reach the half-length where they start to cancel each other and further penetration is blocked. In the case of a TE module, semi-infinite thermal diffusion along the thickness of the ceramic layers occurs at the highest frequencies. As the frequency is decreased, heat storage in the ceramics becomes dominant and starts to compete with the diffusion of the thermal waves towards the half-length of the thermoelements. Finally, the cancellation of the waves occurs at the lowest frequencies. It is demonstrated that the analysis is able to identify and separate the different physical processes and to provide a detailed understanding of the dynamics of different thermoelectric effects.

  10. Thermal dynamics of thermoelectric phenomena from frequency resolved methods

    Science.gov (United States)

    García-Cañadas, J.; Min, G.

    2016-03-01

    Understanding the dynamics of thermoelectric (TE) phenomena is important for the detailed knowledge of the operation of TE materials and devices. By analyzing the impedance response of both a single TE element and a TE device under suspended conditions, we provide new insights into the thermal dynamics of these systems. The analysis is performed employing parameters such as the thermal penetration depth, the characteristic thermal diffusion frequency and the thermal diffusion time. It is shown that in both systems the dynamics of the thermoelectric response is governed by how the Peltier heat production/absorption at the junctions evolves. In a single thermoelement, at high frequencies the thermal waves diffuse semi-infinitely from the junctions towards the half-length. When the frequency is reduced, the thermal waves can penetrate further and eventually reach the half-length where they start to cancel each other and further penetration is blocked. In the case of a TE module, semi-infinite thermal diffusion along the thickness of the ceramic layers occurs at the highest frequencies. As the frequency is decreased, heat storage in the ceramics becomes dominant and starts to compete with the diffusion of the thermal waves towards the half-length of the thermoelements. Finally, the cancellation of the waves occurs at the lowest frequencies. It is demonstrated that the analysis is able to identify and separate the different physical processes and to provide a detailed understanding of the dynamics of different thermoelectric effects.

  11. Thermalization Using Quantum Field Dynamics?

    CERN Document Server

    Salle, M; Vink, Jeroen C

    2001-01-01

    We describe a Hartree ensemble method to approximately solve the Heisenberg equations for the \\phi^4 model in 1+1 dimensions. We compute the energies and number densities of the quantum particles described by the \\phi field and find that the particles initially thermalize with a Bose-Einstein distribution for the particle density. Gradually, however, the distribution changes towards classical equipartition. Using suitable initial conditions quantum thermalization is achieved much faster than the onset of this undesirable equipartition. We also show how the numerical efficiency of our method can be significantly improved.

  12. The Effect of Core Configuration on Thermal Barrier Thermal Performance

    Science.gov (United States)

    DeMange, Jeffrey J.; Bott, Robert H.; Druesedow, Anne S.

    2015-01-01

    Thermal barriers and seals are integral components in the thermal protection systems (TPS) of nearly all aerospace vehicles. They are used to minimize heat transfer through interfaces and gaps and protect underlying temperature-sensitive components. The core insulation has a significant impact on both the thermal and mechanical properties of compliant thermal barriers. Proper selection of an appropriate core configuration to mitigate conductive, convective and radiative heat transfer through the thermal barrier is challenging. Additionally, optimization of the thermal barrier for thermal performance may have counteracting effects on mechanical performance. Experimental evaluations have been conducted to better understand the effect of insulation density on permeability and leakage performance, which can significantly impact the resistance to convective heat transfer. The effect of core density on mechanical performance was also previously investigated and will be reviewed. Simple thermal models were also developed to determine the impact of various core parameters on downstream temperatures. An extended understanding of these factors can improve the ability to design and implement these critical TPS components.

  13. Dynamic validation of the Planck/LFI thermal model

    CERN Document Server

    Tomasi, M; Gregorio, A; Colombo, F; Lapolla, M; Terenzi, L; Morgante, G; Bersanelli, M; Butler, R C; Galeotta, S; Mandolesi, N; Maris, M; Mennella, A; Valenziano, L; Zacchei, A; 10.1088/1748-0221/5/01/T01002

    2010-01-01

    The Low Frequency Instrument (LFI) is an array of cryogenically cooled radiometers on board the Planck satellite, designed to measure the temperature and polarization anisotropies of the cosmic microwave backgrond (CMB) at 30, 44 and 70 GHz. The thermal requirements of the LFI, and in particular the stringent limits to acceptable thermal fluctuations in the 20 K focal plane, are a critical element to achieve the instrument scientific performance. Thermal tests were carried out as part of the on-ground calibration campaign at various stages of instrument integration. In this paper we describe the results and analysis of the tests on the LFI flight model (FM) performed at Thales Laboratories in Milan (Italy) during 2006, with the purpose of experimentally sampling the thermal transfer functions and consequently validating the numerical thermal model describing the dynamic response of the LFI focal plane. This model has been used extensively to assess the ability of LFI to achieve its scientific goals: its valid...

  14. Dynamic Boiler Performance

    DEFF Research Database (Denmark)

    Sørensen, Kim

    Traditionally, boilers have been designed mainly focussing on the static operation of the plant. The dynamic capability has been given lower priority and the analysis has typically been limited to assuring that the plant was not over-stressed due to large temperature gradients. New possibilities...... for buying and selling energy has increased the focus on the dynamic operation capability, efciency, emissions etc. For optimizing the design of boilers for dynamic operation a quantication of the dynamic capability is needed. A framework for optimizing design of boilers for dynamic operation has been...... developed. Analyzing boilers for dynamic operation gives rise to a number of opposing aims: shrinking and swelling, steam quality, stress levels, control system/philosophy, pressurization etc. Common for these opposing aims is that an optimum can be found for selected operation conditions. The framework has...

  15. Thermal performance testing of the Explorer Platform

    Science.gov (United States)

    Wasson, David; Ducas, William; Ousley, Wes

    1993-01-01

    The Explorer Platform (EP) has been designed to accommodate on-orbit payload and bus module changeout via Space Transportation System (STS) servicing. Such a versatile spacecraft platform designed to experience widely different environmental exposures and operational conditions, coupled with program constraints on schedule and budget, presented a challenge to implementing a technically sound thermal vacuum/thermal balance test program. This paper discusses thermal performance tests implemented at the subsystem and system levels, and the risks accepted resulting from test sequence, configuration. and tests omitted from the program. No thermal cycling or thermal balance tests were performed on the integrated spacecraft level, although both the Payload (EUVE) and Platform (EP) received independent testing. The decision to take this approach is discussed with respect to the thermal design and the associated risks taken to maintain budget and schedule.

  16. Low thermal conductivity of graphyne nanotubes from molecular dynamics study

    Science.gov (United States)

    Hu, Ming; Jing, Yuhang; Zhang, Xiaoliang

    2015-04-01

    It is well known that carbon nanotubes (CNTs) possess ultrahigh thermal conductivity that is comparable to bulk diamond. However, no research has studied the possible low thermal conductivity of different CNTs so far. By performing nonequilibrium molecular dynamic simulations, we reveal that the perfect graphyne nanotube (GNT) exhibits an unprecedentedly low thermal conductivity (below 10 W/mK at room temperature), which is generally two orders of magnitude lower than that of ordinary CNTs and even lower than the values reported for defected, doped, and chemically functionalized CNTs. By performing phonon polarization and spectral energy density analysis, we observe that the ultralow thermal conductivity stems from the unique atomic structure of the GNT, consisting of the weak acetylenic linkage (s p C-C bonds) and the strong hexagonal ring (s p2 C-C bonds), which results in a large vibrational mismatch between these two components, and thus induces significantly inefficient heat transfer. Moreover, the thermal transport in GNT with a large number of acetylenic linkages is dominated by the low frequency longitudinal modes in the linkage. Such strong confinement of the low frequency thermal energy results in the extremely low thermal conductivity due to the flattened phonon dispersion curves (low phonon group velocities). The exploration of the abnormal thermal transport of GNTs paves the way for design and application of the relevant devices that could benefit from the ultralow thermal conductivity, such as thermoelectrics for energy conversion.

  17. Structural-Thermal-Optical-Performance (STOP) Analysis

    Science.gov (United States)

    Bolognese, Jeffrey; Irish, Sandra

    2015-01-01

    The presentation will be given at the 26th Annual Thermal Fluids Analysis Workshop (TFAWS 2015) hosted by the Goddard Spaceflight Center (GSFC) Thermal Engineering Branch (Code 545). A STOP analysis is a multidiscipline analysis, consisting of Structural, Thermal and Optical Performance Analyses, that is performed for all space flight instruments and satellites. This course will explain the different parts of performing this analysis. The student will learn how to effectively interact with each discipline in order to accurately obtain the system analysis results.

  18. Transmutation Fuel Performance Code Thermal Model Verification

    Energy Technology Data Exchange (ETDEWEB)

    Gregory K. Miller; Pavel G. Medvedev

    2007-09-01

    FRAPCON fuel performance code is being modified to be able to model performance of the nuclear fuels of interest to the Global Nuclear Energy Partnership (GNEP). The present report documents the effort for verification of the FRAPCON thermal model. It was found that, with minor modifications, FRAPCON thermal model temperature calculation agrees with that of the commercial software ABAQUS (Version 6.4-4). This report outlines the methodology of the verification, code input, and calculation results.

  19. Dynamic validation of the Planck-LFI thermal model

    Energy Technology Data Exchange (ETDEWEB)

    Tomasi, M; Bersanelli, M; Mennella, A [Universita degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Cappellini, B [INAF IASF Milano, Via Bassini, 15, 20133, Milano (Italy); Gregorio, A [University of Trieste, Department of Physics, via Valerio 2, 34127 Trieste (Italy); Colombo, F; Lapolla, M [Thales Alenia Space Italia S.p.A., IUEL - Scientific Instruments, S.S. Padana Superiore 290, 20090 Vimodrone (Mi) (Italy); Terenzi, L; Morgante, G; Butler, R C; Mandolesi, N; Valenziano, L [INAF IASF Bologna, via Gobetti 101, 40129 Bologna (Italy); Galeotta, S; Maris, M; Zacchei, A [LFI-DPC INAF-OATs, via Tiepolo 11, 34131 Trieste (Italy)

    2010-01-15

    The Low Frequency Instrument (LFI) is an array of cryogenically cooled radiometers on board the Planck satellite, designed to measure the temperature and polarization anisotropies of the cosmic microwave background (CMB) at 30, 44 and 70 GHz. The thermal requirements of the LFI, and in particular the stringent limits to acceptable thermal fluctuations in the 20 K focal plane, are a critical element to achieve the instrument scientific performance. Thermal tests were carried out as part of the on-ground calibration campaign at various stages of instrument integration. In this paper we describe the results and analysis of the tests on the LFI flight model (FM) performed at Thales Laboratories in Milan (Italy) during 2006, with the purpose of experimentally sampling the thermal transfer functions and consequently validating the numerical thermal model describing the dynamic response of the LFI focal plane. This model has been used extensively to assess the ability of LFI to achieve its scientific goals: its validation is therefore extremely important in the context of the Planck mission. Our analysis shows that the measured thermal properties of the instrument show a thermal damping level better than predicted, therefore further reducing the expected systematic effect induced in the LFI maps. We then propose an explanation of the increased damping in terms of non-ideal thermal contacts.

  20. The dynamics of the thermal memory of C. elegans

    Science.gov (United States)

    Ryu, William; Palanski, Konstantine; Bartumeus, Frederic; Nemenman, Ilya

    2014-03-01

    C. elegans has the capacity to learn associatively. For example, C. elegans associates temperature with food and performs thermotaxis towards this temperature when placed on a spatial thermal gradient. However, very little is understood how C. elegans acquires this thermal memory. We have developed a novel droplet-based microfluidic assay to measure the dynamics of the thermal memory of C. elegans. Individual animals are placed in an array of microdroplets on a slide, and a linear temperature gradient of 0.5 deg/cm is applied to the array. By measuring the swimming motions of C. elegans in the droplets, we show that they can perform thermotaxis. By calculating an index of this taxis behavior over time, we quantify the worm's thermal memory and measure its dynamics when the animals are exposed to different conditions of feeding and starvation. Over a time scale of hours, we find that the thermal preference of wild-type worms decays and will actually become inverted and that mutations in the insulin signaling pathway perturb the dynamics. This biphasic conditional association can be explained with a reinforcement learning model with independent reinforcement and avoidance pathways with distinct time scales. Human Frontier Science Program.

  1. The thermal radiation from dynamic black holes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using the related formula of dynamic black holes, the instantaneous radiation energy density of the general spherically symmetric charged dynamic black hole and the arbitrarily accelerating charged dynamic black hole is calculated. It is found that the instantaneous radiation energy density of black hole is always proportional to the quartic of the temperature of event horizon in the same direction. The proportional coefficient of generalized Stefan-Boltzmann is no longer a constant, and it becomes a dynamic coefficient that is related to the event horizon changing rate, space-time structure near event horizon and the radiation absorption coefficient of the black hole. It is shown that there should be an internal relation between the gravitational field around black hole and its thermal radiation.

  2. Dynamics of 3D isolated thermal filaments

    CERN Document Server

    Walkden, N R; Militello, F; Omotani, J T

    2016-01-01

    Simulations have been carried out to establish how electron thermal physics, introduced in the form of a dynamic electron temperature, affects isolated filament motion and dynamics in 3D. It is found that thermal effects impact filament motion in two major ways when the filament has a significant temperature perturbation compared to its density perturbation: They lead to a strong increase in filament propagation in the bi-normal direction and a significant decrease in net radial propagation. Both effects arise from the temperature dependence of the sheath current which leads to a non-uniform floating potential, with the latter effect supplemented by faster pressure loss. The reduction in radial velocity can only occur when the filament cross-section loses angular symmetry. The behaviour is observed across different filament sizes and suggests that filaments with much larger temperature perturbations than density perturbations are more strongly confined to the near SOL region.

  3. Dynamics of 3D isolated thermal filaments

    Science.gov (United States)

    Walkden, N. R.; Easy, L.; Militello, F.; Omotani, J. T.

    2016-11-01

    Simulations have been carried out to establish how electron thermal physics, introduced in the form of a dynamic electron temperature, affects isolated filament motion and dynamics in 3D. It is found that thermal effects impact filament motion in two major ways when the pressure perturbation within the filament is supported primarily through a temperature increase as opposed to density: they lead to a strong increase in filament propagation in the bi-normal direction and a significant decrease in net radial propagation. Both effects arise from the temperature dependence of the sheath current which leads to a non-uniform floating potential, with the latter effect supplemented by faster pressure loss. The reduction in radial velocity can only occur when the filament cross-section loses angular symmetry. The behaviour is observed across different filament sizes and suggests that filaments with much larger temperature perturbations than density perturbations are more strongly confined to the near SOL region.

  4. Thermal performance of a PCM thermal storage unit

    Energy Technology Data Exchange (ETDEWEB)

    Liu Ming; Bruno, Frank; Saman, Wasim [Sustainable Energy Centre, Inst. for Sustainable Systems and Technologies, Univ. of South Australia, Mawson Lakes, Adelaide (Australia)

    2008-07-01

    The thermal performance of a PCM thermal storage unit (TSU) is studied numerically and experimentally. The TSU under analysis consists of several flat slabs of phase change material (PCM) with melting temperature of -26.7 C. Liquid heat transfer fluid (HTF) passes between the slabs to charge and discharge the storage unit. A one dimensional mathematical model was employed to analyze the transient thermal behavior of the storage unit during the melting and freezing processes. The model takes into consideration the temperature variations in the wall along the flow direction of the HTF. The paper compares the experimental and numerical simulation results in terms of HTF outlet temperatures during the melting period. (orig.)

  5. Thermal Performance of Tropical Atrium

    Science.gov (United States)

    Baharvand, Mohammad; Bin Ahmad, Mohd Hamdan; Safikhan, Tabassom; Mirmomtaz, Sayyed Mohammad Mahdi

    2013-12-01

    Atrium is a popular architectural feature utilized widely by building designers and owners to bring various benefits such as adequate daylight, circulation spaces and surfaces for landscape applications. But atrium problems in tropical climates such as excessive daylight, glare and high temperature, which lead to increase building energy demand, have been reported. To avoid and reduce these unpleasant features, a side-lit atrium has been suggested. Although researchers proposed side-lit atrium to prevent common problems of atria, the lack of precedent research on this issue compels these authors to study atrium performance in hot and humid climate. So the research aims to examine two different atrium roof form types in terms of temperature and ventilation impacts in hot and humid climate of Malaysia using DesignBuilder as a simulation program. The results indicate lower temperature of side-lit model with better airflow pattern in comparison with top-lit model while the top-lit model provides higher air velocity at the air inlet and outlet.

  6. Thermographic measurement of thermal bridges in buildings under dynamic behavior

    Science.gov (United States)

    Ferrarini, G.; Bison, P.; Bortolin, A.; Cadelano, G.; De Carli, M.

    2016-05-01

    The accurate knowledge of the thermal performance could reduce significantly the impact of buildings on global energy consumption. Infrared thermography is widely recognized as one of the key technologies for building surveys, thanks to its ability to acquire at a glance thermal images of the building envelope. However, a spot measurement could be misleading when the building is under dynamic thermal conditions. In this case data should be acquired for hours or days, depending on the thermal properties of the walls. Long term thermographic monitoring are possible but imply strong challenges from a practical standpoint. This work investigates the possibilities and limitations of spot thermographic surveys coupled with contact probes, that are able to acquire continuously the thermal signal for days, to investigate the thermal bridges of a building. The goal is the estimation of the reliability and accuracy of the measurement under realistic environmental conditions. Firstly, numerical simulations are performed to determine the reference value of an experimental case. Then a long term thermographic survey is performed and integrated with the contact probe measurement, assessing the feasibility of the method.

  7. Size effects in molecular dynamics thermal conductivity predictions

    Science.gov (United States)

    Sellan, D. P.; Landry, E. S.; Turney, J. E.; McGaughey, A. J. H.; Amon, C. H.

    2010-06-01

    We predict the bulk thermal conductivity of Lennard-Jones argon and Stillinger-Weber silicon using the Green-Kubo (GK) and direct methods in classical molecular dynamics simulations. While system-size-independent thermal conductivities can be obtained with less than 1000 atoms for both materials using the GK method, the linear extrapolation procedure [Schelling , Phys. Rev. B 65, 144306 (2002)] must be applied to direct method results for multiple system sizes. We find that applying the linear extrapolation procedure in a manner consistent with previous researchers can lead to an underprediction of the GK thermal conductivity (e.g., by a factor of 2.5 for Stillinger-Weber silicon at a temperature of 500 K). To understand this discrepancy, we perform lattice dynamics calculations to predict phonon properties and from these, length-dependent thermal conductivities. From these results, we find that the linear extrapolation procedure is only accurate when the minimum system size used in the direct method simulations is comparable to the largest mean-free paths of the phonons that dominate the thermal transport. This condition has not typically been satisfied in previous works. To aid in future studies, we present a simple metric for determining if the system sizes used in direct method simulations are sufficiently large so that the linear extrapolation procedure can accurately predict the bulk thermal conductivity.

  8. ISCCS Thermal Performance Based on Real-time Dynamic Simulation Model%基于动态仿真模型的ISCCS热力特性研究

    Institute of Scientific and Technical Information of China (English)

    马士英; 崔凝; 刘洋; 吴铭棉

    2016-01-01

    The direct steam generation in parabolic trough collectors systems (DSG-PTC) with different capacities and working-medium flow path were designed. The integration schemes for the integrated solar combined cycle system (ISCCS) taking DSG-PTC as the auxiliary heat source were put forward. The real-time dynamic simulation models for the ISCCS were studied based on the previous research achievements. With these dynamic simulation models, the operating characteristics of ISCCS were analyzed, the matching principle of the working-medium flow and energy flow between two energy systems were indicated, the control strategy improving suggestions in ISCCS are put forward, the dynamic response characteristics of the ISCCS are researched, the thermal economy of the ISCCS in different integration schemes are calculated, and the optimal integration scheme is proposed.%设计了6套不同容量和流程的直接产生蒸汽型槽式聚光集热系统(direct steam generation in parabolic trough collectors,DSG-PTC);提出以DSG-PTC为辅助热源的整体太阳能联合循环发电系统(integrated solar combined cycle system,ISCCS)的6种集成方案;基于已取得的研究成果,研究 ISCCS 系统实时动态仿真模型.利用模型从系统层面分析了ISCCS系统的运行特性,反映了2个能源系统间工质流和能量流的匹配规律;揭示控制系统在 ISCCS 中的适用性并提出了控制策略的改进建议;研究 ISCCS 系统动态响应特性,提出 ISCCS 系统改进措施;从热力学的角度计算分析不同集成方式的 ISCCS 系统热经济性,给出了最佳集成方案.

  9. Estimating thermal performance curves from repeated field observations

    Science.gov (United States)

    Childress, Evan; Letcher, Benjamin H.

    2017-01-01

    Estimating thermal performance of organisms is critical for understanding population distributions and dynamics and predicting responses to climate change. Typically, performance curves are estimated using laboratory studies to isolate temperature effects, but other abiotic and biotic factors influence temperature-performance relationships in nature reducing these models' predictive ability. We present a model for estimating thermal performance curves from repeated field observations that includes environmental and individual variation. We fit the model in a Bayesian framework using MCMC sampling, which allowed for estimation of unobserved latent growth while propagating uncertainty. Fitting the model to simulated data varying in sampling design and parameter values demonstrated that the parameter estimates were accurate, precise, and unbiased. Fitting the model to individual growth data from wild trout revealed high out-of-sample predictive ability relative to laboratory-derived models, which produced more biased predictions for field performance. The field-based estimates of thermal maxima were lower than those based on laboratory studies. Under warming temperature scenarios, field-derived performance models predicted stronger declines in body size than laboratory-derived models, suggesting that laboratory-based models may underestimate climate change effects. The presented model estimates true, realized field performance, avoiding assumptions required for applying laboratory-based models to field performance, which should improve estimates of performance under climate change and advance thermal ecology.

  10. Estimating thermal performance curves from repeated field observations.

    Science.gov (United States)

    Childress, Evan S; Letcher, Benjamin H

    2017-03-08

    Estimating thermal performance of organisms is critical for understanding population distributions and dynamics and predicting responses to climate change. Typically, performance curves are estimated using laboratory studies to isolate temperature effects, but other abiotic and biotic factors influence temperature-performance relationships in nature reducing these models' predictive ability. We present a model for estimating thermal performance curves from repeated field observations that includes environmental and individual variation. We fit the model in a Bayesian framework using MCMC sampling, which allowed for estimation of unobserved latent growth while propagating uncertainty. Fitting the model to simulated data varying in sampling design and parameter values demonstrated that the parameter estimates were accurate, precise, and unbiased. Fitting the model to individual growth data from wild trout revealed high out-of-sample predictive ability relative to laboratory-derived models, which produced more biased predictions for field performance. The field-based estimates of thermal maxima were lower than those based on laboratory studies. Under warming temperature scenarios, field-derived performance models predicted stronger declines in body size than laboratory-derived models, suggesting that laboratory-based models may underestimate climate change effects. The presented model estimates true, realized field performance, avoiding assumptions required for applying laboratory-based models to field performance, which should improve estimates of performance under climate change and advance thermal ecology. This article is protected by copyright. All rights reserved.

  11. Dynamic Measurements of the Thermal Conductivity of Insulators

    Science.gov (United States)

    Bezjak, Mladen; Zvizdić, Davor

    2011-08-01

    Measurements of the thermal conductivity of insulators that are commonly used in civil engineering are as a rule performed using Pönsgen's guarded hot-plate method under steady-state conditions. Achieving these steady-state conditions is a time consuming and relatively expensive procedure. Therefore, the application of a method that is less time consuming and less costly to common building insulating materials is of interest. The method should also have the accuracy and repeatability comparable to that of presently used methods. One such method is the transient hot-wire method (predominantly used for liquids, non-Newtonian fluids, plastics, semi-plastics, and similar materials), a dynamic method that uses a very thin pure platinum wire that functions as a thermal source in combination with a temperature sensor that detects temperature transients. This article describes the application of the transient hot-wire method to most commonly used building thermal insulating materials. The transient hot-wire measurements of the thermal conductivity were performed on many building material samples. For the sake of comparison, the thermal conductivity of samples made from the same materials was also tested using the stationary Pönsgen's guarded hot-plate method. This article describes the comparison and evaluation of the measurement results obtained from both methods as well as the estimation of pertinent measurement uncertainties. The results are presented in graphical and numerical form in tables and diagrams for each type of thermal insulator.

  12. Thermal Spin Dynamics of Yttrium Iron Garnet

    Science.gov (United States)

    Barker, Joseph; Bauer, Gerrit E. W.

    2016-11-01

    The magnetic insulator yttrium iron garnet can be grown with near perfection and is therefore and ideal conduit for spin currents. It is a complex material with 20 magnetic moments in the unit cell. In spite of being a ferrimagnet, YIG is almost always modeled as a simple ferromagnet with a single spin wave mode. We use the method of atomistic spin dynamics to study the temperature evolution of the full spin wave spectrum, in quantitative agreement with neutron scattering experiments. The antiferromagnetic or optical mode is found to suppress the spin Seebeck effect at room temperature and beyond due to thermally pumped spin currents with opposite polarization to the ferromagnetic mode.

  13. Spacelab carrier complement thermal design and performance

    Science.gov (United States)

    Bancroft, S.; Key, R.; Kittredge, S.

    1992-01-01

    The present discussion of the Spacelab carrier complement, which encompasses a Module Carrier, a Module-Pallet Carrier, and a Multiplexer/Demultiplexer Pallet, gives attention to both active and passive thermal performance capabilities, and presents ground testing and analytical results obtained to date. An account is given of the prospective use of a Spacelab Multipurpose Experiment Support Structure.

  14. Molecular dynamics simulation on influence of guest molecule number on methane hydrate thermal performance%客体分子数对甲烷水合物导热性能影响的分子动力学模拟

    Institute of Scientific and Technical Information of China (English)

    万丽华; 梁德青; 吴能友; 关进安

    2012-01-01

    采用EMD方法Green-Kubo理论计算263.15 K晶穴占有率0~100% sI甲烷水合物的热导率,研究客体分子数对甲烷水合物导热性能的影响.模拟结果显示,甲烷水合物的低导热性能由主体分子构建的笼形结构决定.而在相同温压条件下,随着客体分子甲烷进入晶胞数目增多,晶穴占有率增大后,密度增大,同时客体分子对声子的散射也增强,二者均导致导热性能增强.%Thermal conductivity of methane hydrate is an important physical parameter in processes of methane hydrate exploration, mining, gas hydrate storage and transportation as well as other applications. In this paper, equilibrium molecular dynamics (EMD) simulation and the Green-Kubo method are used for the systems with 0-100% occupancy of sI methane hydrate to evaluate the influence of guest molecule number on the thermal performance of methane hydrate. The EMD simulation for the thermodynamics of equilibrium state of si methane hydrate is performed via the Green-Kubo approach for the thermal conductivity of methane hydrates. The DL-POLY molecular dynamics simulation package is employed. TIP4P/Ice water model is used for water-water interactions and the Lennard-Jones potential for methane-methane and methane-water interactions. The Lorentz-Berthelot combination rule is used to determine the parameters of Lennard-Jones potentials between water and methane molecules. The equations of motion are integrated using the Verlet algorithm and the Ewald method is used to handle long-range electrostatic interactions. Results indicate that the poor thermal conduction of methane hydrate is resultedfrom the framework of cage. The thermal conduction of methane hydrate is improved when the framework of cage has slightly higher thermal conductivity with more guest molecules enclosed in the cage> since higher cage occupancy ratio by guest molecules increases the density and their scattering.

  15. Multiphase Flow Dynamics 3 Thermal Interactions

    CERN Document Server

    Kolev, Nikolay Ivanov

    2012-01-01

    Multi-phase flows are part of our natural environment such as tornadoes, typhoons, air and water pollution and volcanic activities as well as part of industrial technology such as power plants, combustion engines, propulsion systems, or chemical and biological industry. The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. .In its fourth extended edition the successful monograph package “Multiphase Flow Daynmics” contains theory, methods and practical experience for describing complex transient multi-phase processes in arbitrary geometrical configurations, providing a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics. In the present third volume methods for describing of the thermal interactions in multiphase dynamics are provided. In addition a large number of valuable experiments is collected and predicted using the methods introduced in this monograph. In this way the accuracy of the methods is reve...

  16. Multiphase Flow Dynamics 5 Nuclear Thermal Hydraulics

    CERN Document Server

    Kolev, Nikolay Ivanov

    2012-01-01

    The present Volume 5 of the successful book package "Multiphase Flow Dynamics" is devoted to nuclear thermal hydraulics which is a substantial part of nuclear reactor safety. It provides knowledge and mathematical tools for adequate description of the process of transferring the fission heat released in materials due to nuclear reactions into its environment. It step by step introduces into the heat release inside the fuel, temperature fields in the fuels, the "simple" boiling flow in a pipe described using ideas of different complexity like equilibrium, non equilibrium, homogeneity, non homogeneity. Then the "simple" three-fluid boiling flow in a pipe is described by gradually involving the mechanisms like entrainment and deposition, dynamic fragmentation, collisions, coalescence, turbulence. All heat transfer mechanisms are introduced gradually discussing their uncertainty. Different techniques are introduced like boundary layer treatments or integral methods. Comparisons with experimental data at each step...

  17. Multiphase flow dynamics 5 nuclear thermal hydraulics

    CERN Document Server

    Kolev, Nikolay Ivanov

    2015-01-01

    This Volume 5 of the successful book package "Multiphase Flow Dynamics" is devoted to nuclear thermal hydraulics which is a substantial part of nuclear reactor safety. It provides knowledge and mathematical tools for adequate description of the process of transferring the fission heat released in materials due to nuclear reactions into its environment. It step by step introduces into the heat release inside the fuel, temperature fields in the fuels, the "simple" boiling flow in a pipe described using ideas of different complexity like equilibrium, non equilibrium, homogeneity, non homogeneity. Then the "simple" three-fluid boiling flow in a pipe is described by gradually involving the mechanisms like entrainment and deposition, dynamic fragmentation, collisions, coalescence, turbulence. All heat transfer mechanisms are introduced gradually discussing their uncertainty. Different techniques are introduced like boundary layer treatments or integral methods. Comparisons with experimental data at each step demons...

  18. Thermal comfort, physiological responses and performance during exposure to a moderate temperature drift

    DEFF Research Database (Denmark)

    Schellen, Lisje; van Marken Lichtenbelt, Wouter; de Wit, Martin;

    2008-01-01

    The objective of this research was to study the effects of a moderate temperature drift on human thermal comfort, physiological responses, productivity and performance. A dynamic thermophysiological model was used to examine the possibility of simulating human thermal responses and thermal comfor...

  19. Mercury's Thermal Evolution, Dynamical Topography and Geoid

    Science.gov (United States)

    Ziethe, Ruth; Benkhoff, Johannes

    Among the terrestrial planets Mercury is not only the smallest, but also the densest (after correction for self-compression). To explain Mercury's high density it is considered likely that the planet's mantle was removed during a giant impact event, when proto-Mercury was already differentiated into an iron core and a silicate mantle. Beside the damage to the planet's mantle the vaporization would cause a significant loss of volatile elements, leaving the remaining planet molten and dominated by extremely refractory material.Since the arrival of a spacecraft at the enigmatic planet is not to be expected before 2011 (Messenger) or 2019 (BepiColombo) we might already prepare ourselves for the upcoming results and perform tests that allow some anticipation of the measured data. The hermean mantle is modelled as an internally and bottom heated, isochemical fluid in a spherical shell. The principle of this convection model is widely accepted and is used for various models of thermal evolution of terrestrial planets, e.g., the Earth, Mars or the Moon. We are solving the hydrodynamical equations, derived from the conservation of mass, momentum and energy. A program originally written by S. Zhang is used to solve the temperature field which employs a combination of a spectral and a finite difference method. Beside the large core as a heat source 'from below' the decay of radioactive isotopes provides internal heating of the hermean mantle. The viscosity of the mantel material depends exponentially on the inverse temperature. The model results show the typical behaviour of a one-plate-planet, meaning the surface is not broken into several tectonic plates but the outside is a single rigid shell. The thermal evolution is generally charaterized by the growth of a massive lithosphere on top of the convecting mantle. The lower mantle and core cool comparatively little and stay at temperatures between 1900K and 2000K until about 2.0Ga after the simulation was started. The

  20. Thermal Performance Benchmarking; NREL (National Renewable Energy Laboratory)

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, Gilbert

    2015-06-09

    This project proposes to seek out the SOA power electronics and motor technologies to thermally benchmark their performance. The benchmarking will focus on the thermal aspects of the system. System metrics including the junction-to-coolant thermal resistance and the parasitic power consumption (i.e., coolant flow rates and pressure drop performance) of the heat exchanger will be measured. The type of heat exchanger (i.e., channel flow, brazed, folded-fin) and any enhancement features (i.e., enhanced surfaces) will be identified and evaluated to understand their effect on performance. Additionally, the thermal resistance/conductivity of the power module’s passive stack and motor’s laminations and copper winding bundles will also be measured. The research conducted will allow insight into the various cooling strategies to understand which heat exchangers are most effective in terms of thermal performance and efficiency. Modeling analysis and fluid-flow visualization may also be carried out to better understand the heat transfer and fluid dynamics of the systems.

  1. Investigation of Thermal Performance for Atria: a Method Overview

    Directory of Open Access Journals (Sweden)

    Moosavi Leila

    2016-01-01

    Full Text Available The importance of low energy design in large buildings has encouraged researchers to implement different methods for predicting a building’s thermal performance. Atria, as energy efficient features, have been implemented to improve the indoor thermal environment in large modern buildings. Though widely implemented, the thorough study of atrium performance is restricted due to its large size, complex thermodynamic behavior and the inaccuracies and limitations of available prediction tools. This study reviews the most common research tools implemented in previous researches on atria thermal performance, to explore the advantages and limitation of different methods for future studies. The methods reviewed are analytical, experimental, computer modelling and a combination of any or all of these methods. The findings showed that CFD (computational fluid dynamic models are the most popular tools of recent due to their higher accuracy, capabilities and user-friendly modification. Although the experimental methods were reliable for predicting atria thermal and ventilation performance, they have mostly been used to provide data for validation of CFD models. Furthermore, coupling CFD with other experimental models could increase the reliability and accuracy of the models and provide a more comprehensive analysis.

  2. Pharmaceutical applications of dynamic mechanical thermal analysis.

    Science.gov (United States)

    Jones, David S; Tian, Yiwei; Abu-Diak, Osama; Andrews, Gavin P

    2012-04-01

    The successful development of polymeric drug delivery and biomedical devices requires a comprehensive understanding of the viscoleastic properties of polymers as these have been shown to directly affect clinical efficacy. Dynamic mechanical thermal analysis (DMTA) is an accessible and versatile analytical technique in which an oscillating stress or strain is applied to a sample as a function of oscillatory frequency and temperature. Through cyclic application of a non-destructive stress or strain, a comprehensive understanding of the viscoelastic properties of polymers may be obtained. In this review, we provide a concise overview of the theory of DMTA and the basic instrumental/operating principles. Moreover, the application of DMTA for the characterization of solid pharmaceutical and biomedical systems has been discussed in detail. In particular we have described the potential of DMTA to measure and understand relaxation transitions and miscibility in binary and higher-order systems and describe the more recent applications of the technique for this purpose.

  3. Modelling of single bubble-dynamics and thermal effects

    Science.gov (United States)

    Papoulias, D.; Gavaises, M.

    2015-12-01

    This paper evaluates the solution effects of different Rayleigh-Plesset models (R-P) for simulating the growth/collapse dynamics and thermal behaviour of homogeneous gas bubbles. The flow inputs used for the discrete cavitation bubble calculations are obtained from Reynolds-averaged Navier-Stokes simulations (RANS), performed in high-pressure nozzle holes. Parametric 1-D results are presented for the classical thermal R-P equation [1] as well as for refined models which incorporated compressibility corrections and thermal effects [2, 3]. The thermal bubble model is coupled with the energy equation, which provides the temperature of the bubble as a function of conduction/convection and radiation heat-transfer mechanisms. For approximating gas pressure variations a high-order virial equation of state (EOS) was used, based on Helmholtz free energy principle [4]. The coded thermal R-P model was validated against experimental measurements [5] and model predictions [6] reported in single-bubble sonoluminescence (SBSL).

  4. Thermal performance of lightweight construction systems: Performance of `Solar One`

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, R. [Queensland Univ., St. Lucia, QLD (Australia)

    1995-12-31

    Research is currently under way to asses the thermal performance of building which use new lightweight systems of construction. In particular, comparison is made between expected performance and performance found in buildings. This paper outlines the basic direction of the research and examines one particular building case study, that of Solar One. Solar One is located at Mount Coolum to the north of Brisbane on the Sunshine Coast in Queensland. This building is designed based on climatic criteria and departs from the conventional timber framed house in a number of respects. The important difference in this building is that it is a hybrid construction. Mass is used for some walls and ground floor slab and timber framing with fibre-cement for other walls. The research demonstrates to what extent the building performs to characteristics of lightweight construction systems and to what extent it performs as a heavyweight system. Focus is placed on the thermal response of the building. Conclusions reached from this case study suggest that the building does not match expected patterns of thermal response particularly in winter, there appears to be a complex heat interchange process showing clear benefits for the hybrid construction. (author). 10 figs., 4 refs.

  5. Thermal Performance of Ablative/ Ceramic Composite

    Directory of Open Access Journals (Sweden)

    Adriana STEFAN

    2014-12-01

    Full Text Available A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on top of ceramic matrix composites is investigated for the protection of the metallic structure in oxidative and high temperature environment of the space vehicles. The paper focuses on the joints of ablative material (carbon fiber based CALCARB® or cork based NORCOAT TM and Ceramic Matrix Composite (CMC material (carbon fibers embedded in silicon carbide matrix, Cf/SiC, SICARBON TM or C/C-SiC using commercial high temperature inorganic adhesives. To study the thermal performance of the bonded materials the joints were tested under thermal shock at the QTS facility. For carrying out the test, the sample is mounted into a holder and transferred from outside the oven at room temperature, inside the oven at the set testing temperature (1100°C, at a heating rate that was determined during the calibration stage. The dwell time at the test temperature is up to 2 min at 1100ºC at an increasing rate of temperature up to ~ 9,5°C/s. Evaluating the atmospheric re-entry real conditions we found that the most suited cooling method is the natural cooling in air environment as the materials re-entering the Earth atmosphere are subjected to similar conditions. The average weigh loss was calculated for all the samples from one set, without differentiating the adhesive used as the weight loss is due to the ablative material consumption that is the same in all the samples and is up to 2%. The thermal shock test proves that, thermally, all joints behaved similarly, the two parts withstanding the test successfully and the assembly maintaining its integrity.

  6. The thermal performance of earth buildings

    Directory of Open Access Journals (Sweden)

    Heathcote, K.

    2011-09-01

    Full Text Available This paper examines the theoretical basis for the thermal performance of earth walls and links it to some test results on buildings constructed by the author, and to their predicted performance using a sophisticated computer modelling program. The analysis shows that for all earth walls the steady state thermal resistance is low but that for walls greater than about 450 mm thick the cyclic thermal resistance is high and increases exponentially. Whilst the steady state resistance of all thickness walls is low and results in higher than normal average temperatures in summer and lower than normal in winter the ability of thick earth walls to even out the swings in temperature is thought to be responsible for the materials reputation. The paper notes that good passive design principles (such as providing internal thermal mass and large areas of glazing for winter performance will greatly improve the performance of earth buildings with thin walls, but it is the author’s opinion that external earth walls should be at least 450 mm thick to gain the full benefit of thermal mass.

    Este artículo examina la base teórica del comportamiento térmico de las paredes de tierra y la relaciona con varios resultados de test realizados sobre edificios construidos por el autor, y con su comportamiento previsto utilizando un sofisticado programa de modelado por ordenador. El análisis muestra que la resistencia térmica constante es baja para todas las paredes de tierra, pero que para muros con un grosor mayor que 450 mm la resistencia térmica cíclica es alta y se incrementa exponencialmente. Mientras que la resistencia térmica constante de las paredes de cualquier grosor es baja y se traduce en temperaturas más altas que la media en verano y más bajas que la media en invierno, la capacidad de las paredes gruesas de tierra para amortiguar las variaciones de temperatura es la responsable de la reputación de los materiales. El artículo señala que los

  7. Dynamics of Collective Decoherence and Thermalization

    CERN Document Server

    Merkli, M; Sigal, I M

    2008-01-01

    We analyze the dynamics of N interacting spins (quantum register) collectively coupled to a thermal environment. Each spin experiences the same environment interaction, consisting of an energy conserving and an energy exchange part. We find the decay rates of the reduced density matrix elements in the energy basis. We show that if the spins do not interact among each other, then the fastest decay rates of off-diagonal matrix elements induced by the energy conserving interaction is of order N^2, while that one induced by the energy exchange interaction is of the order N only. Moreover, the diagonal matrix elements approach their limiting values at a rate independent of N. For a general spin system the decay rates depend in a rather complicated (but explicit) way on the size N and the interaction between the spins. Our method is based on a dynamical quantum resonance theory valid for small, fixed values of the couplings. We do not make Markov-, Born- or weak coupling (van Hove) approximations.

  8. Dynamics of collective decoherence and thermalization

    Science.gov (United States)

    Merkli, M.; Berman, G. P.; Sigal, I. M.

    2008-12-01

    We analyze the dynamics of N interacting spins (quantum register) collectively coupled to a thermal environment. Each spin experiences the same environment interaction, consisting of an energy conserving and an energy exchange part. We find the decay rates of the reduced density matrix elements in the energy basis. We show that if the spins do not interact among each other, then the fastest decay rates of off-diagonal matrix elements induced by the energy conserving interaction is of order N2 , while that one induced by the energy exchange interaction is of the order N only. Moreover, the diagonal matrix elements approach their limiting values at a rate independent of N. For a general spin system the decay rates depend in a rather complicated (but explicit) way on the size N and the interaction between the spins. Our method is based on a dynamical quantum resonance theory valid for small, fixed values of the couplings. We do not make Markov-, Born- or weak coupling (van Hove) approximations.

  9. Shuttle TPS thermal performance and analysis methodology

    Science.gov (United States)

    Neuenschwander, W. E.; Mcbride, D. U.; Armour, G. A.

    1983-01-01

    Thermal performance of the thermal protection system was approximately as predicted. The only extensive anomalies were filler bar scorching and over-predictions in the high Delta p gap heating regions of the orbiter. A technique to predict filler bar scorching has been developed that can aid in defining a solution. Improvement in high Delta p gap heating methodology is still under study. Minor anomalies were also examined for improvements in modeling techniques and prediction capabilities. These include improved definition of low Delta p gap heating, an analytical model for inner mode line convection heat transfer, better modeling of structure, and inclusion of sneak heating. The limited number of problems related to penetration items that presented themselves during orbital flight tests were resolved expeditiously, and designs were changed and proved successful within the time frame of that program.

  10. Thermally induced dynamics in ultrathin magnetic tunnel junctions

    NARCIS (Netherlands)

    Ogrodnik, P.; Bauer, G.E.W.; Xia, K.

    2013-01-01

    We consider the magnetization dynamics induced by thermally induced spin transfer torques in thin Fe|MgO|Fe tunnel junctions. The magnetization dynamics is described by the Landau-Lifshitz-Gilbert equation, including the thermal torques as computed from first principles. We show that the angular ske

  11. Numerical evaluation of the thermal performances of roof-mounted radiant barriers

    OpenAIRE

    Miranville, Frédéric; Boyer, Harry; Lucas, Franck; Johan, Seriacaroupin

    2014-01-01

    International audience; This paper deals with the thermal performances of roof-mounted radiant barriers. Using dynamic simulations of a mathematical model of a whole test cell including a radiant barrier installed between the roof top and the ceiling, the thermal performance of the roof is calculated. The mean method is more particularly used to assess the thermal resistance of the building component and lead to a value which is compared to the one obtained for a mass insulation product such ...

  12. Characterization of Inlet Diffuser Performance for Stratified Thermal Storage

    Science.gov (United States)

    Cimbala, John M.; Bahnfleth, William; Song, Jing

    1999-11-01

    Storage of sensible heating or cooling capacity in stratified vessels has important applications in central heating and cooling plants, power production, and solar energy utilization, among others. In stratified thermal storage systems, diffusers at the top and bottom of a stratified tank introduce and withdraw fluid while maintaining a stable density gradient and causing as little mixing as possible. In chilled water storage applications, mixing during the formation of the thermocline near an inlet diffuser is the single greatest source of thermal losses. Most stratified chilled water storage tanks are cylindrical vessels with diffusers that are either circular disks that distribute flow radially outward or octagonal rings of perforated pipe that distribute flow both inward and outward radially. Both types produce gravity currents that are strongly influenced by the inlet Richardson number, but the significance of other parameters is not clear. The present investigation considers the dependence of the thermal performance of a perforated pipe diffuser on design parameters including inlet velocity, ambient and inlet fluid temperatures, and tank dimensions for a range of conditions representative of typical chilled water applications. Dimensional analysis is combined with a parametric study using results from computational fluid dynamics to obtain quantitative relationships between design parameters and expected thermal performance.

  13. Monte Carlo analysis: error of extrapolated thermal conductivity from molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Andersson, Anders David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-07

    In this short report, we give an analysis of the extrapolated thermal conductivity of UO2 from earlier molecular dynamics (MD) simulations [1]. Because almost all material properties are functions of temperature, e.g. fission gas release, the fuel thermal conductivity is the most important parameter from a model sensitivity perspective [2]. Thus, it is useful to perform such analysis.

  14. Thermal Performance of the XRS Helium Insert

    Science.gov (United States)

    Breon, Susan R.; DiPirro, Michael J.; Tuttle, James G.; Shirron, Peter J.; Warner, Brent A.; Boyle, Robert F.; Canavan, Edgar R.

    1999-01-01

    The X-Ray Spectrometer (XRS) is an instrument on the Japanese Astro-E satellite, scheduled for launch early in the year 2000. The XRS Helium Insert comprises a superfluid helium cryostat, an Adiabatic Demagnetization Refrigerator (ADR), and the XRS calorimeters with their cold electronics. The calorimeters are capable of detecting X-rays over the energy range 0.1 to 10 keV with a resolution of 12 eV. The Helium Insert completed its performance and verification testing at Goddard in January 1999. It was shipped to Japan, where it has been integrated with the neon dewar built by Sumitomo Heavy Industries. The Helium Insert was given a challenging lifetime requirement of 2.0 years with a goal of 2.5 years. Based on the results of the thermal performance tests, the predicted on-orbit lifetime is 2.6 years with a margin of 30%. This is the result of both higher efficiency in the ADR cycle and the low temperature top-off, more than compensating for an increase in the parasitic heat load. This paper presents a summary of the key design features and the results of the thermal testing of the XRS Helium Insert.

  15. Thermal insulation performance of green roof systems

    Energy Technology Data Exchange (ETDEWEB)

    Celik, Serdar; Morgan, Susan; Retzlaff, William; Once, Orcun [southern Illinois University (United States)], e-mail: scelik@siue.edu, e-mail: smorgan@siue.edu, e-mail: wretzla@siue.edu, e-mail: oonce@siue.edu

    2011-07-01

    With the increasing costs of energy, good building insulation has become increasingly important. Among existing insulation techniques is the green roof system, which consists of covering the roof of a building envelop with plants. The aim of this paper is to assess the impact of vegetation type and growth media on the thermal performance of green roof systems. Twelve different green roof samples were made with 4 different growth media and 3 sedum types. Temperature at the sample base was recorded every 15 minutes for 3 years; the insulation behavior was then analysed. Results showed that the insulation characteristics were achieved with a combination of haydite and sedum sexangulare. This study demonstrated that the choice of growth media and vegetation is important to the green roof system's performance; further research is required to better understand the interactions between growth media and plant roots.

  16. Thermal performance and heat transport in aquifer thermal energy storage

    NARCIS (Netherlands)

    Sommer, W.T.; Doornenbal, P.J.; Drijver, B.C.; Gaans, van P.F.M.; Leusbrock, I.; Grotenhuis, J.T.C.; Rijnaarts, H.H.M.

    2014-01-01

    Aquifer thermal energy storage (ATES) is used for seasonal storage of large quantities of thermal energy. Due to the increasing demand for sustainable energy, the number of ATES systems has increased rapidly, which has raised questions on the effect of ATES systems on their surroundings as well as t

  17. WMAP Observatory Thermal Design and On-Orbit Thermal Performance

    Science.gov (United States)

    Glazer, Stuart D.; Brown, Kimberly D.; Michalek, Theodore J.; Ancarrow, Walter C.

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) observatory, launched June 30, 2001, is designed to measure the cosmic microwave background radiation with unprecedented precision and accuracy while orbiting the second Lagrange point (L2). The instrument cold stage must be cooled passively to <95K, and systematic thermal variations in selected instrument components controlled to less than 0.5 mK (rms) per spin period. This paper describes the thermal design and testing of the WMAP spacecraft and instrument. Flight thermal data for key spacecraft and instrument components are presented from launch through the first year of mission operations. Effects of solar flux variation due to the Earth's elliptical orbit about the sun, surface thermo-optical property degradations, and solar flares on instrument thermal stability are discussed.

  18. Molecular dynamics simulation of thermal conductivities of superlattice nanowires

    Institute of Scientific and Technical Information of China (English)

    杨决宽; 陈云飞; 颜景平

    2003-01-01

    Nonequilibrium molecular dynamics simulations were carried out to investigate heat transfer in superlattice nanowires. Results show that for fixed period length superlattice nanowires, the ratio of the total interfacial thermal resistance to the total thermal resistance and the effective thermal conductivities are invariant with the changes in interface numbers. Increasing the period length leads to an increase in the average interfacial thermal resistance, which indicates that the interfacial thermal resistance depends not only on the materials that constitute the alternating segments of superlattice nanowires, but also on the lattice strain throughout the segments. The modification of the lattice structure due to the lattice mismatch should be taken into account in the acoustic mismatch model. Simulation results also demonstrated the size confinement effect on the thermal conductivities for low dimensional structures, i.e. the thermal conductivities and the interfacial thermal resistance increase as the nanowire cross-sectional area increases.

  19. Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

    Science.gov (United States)

    Ku, Jentung; Robinson, Franklin; Patel, Deepak; Ottenstein, Laura

    2013-01-01

    The second Ice, Cloud, and Land Elevation Satellite mission currently planned by National Aeronautics and Space Administration will measure global ice topography and canopy height using the Advanced Topographic Laser Altimeter System {ATLAS). The ATLAS comprises two lasers; but only one will be used at a time. Each laser will generate between 125 watts and 250 watts of heat, and each laser has its own optimal operating temperature that must be maintained within plus or minus 1 degree Centigrade accuracy by the Laser Thermal Control System (LTCS) consisting of a constant conductance heat pipe (CCHP), a loop heat pipe (LHP) and a radiator. The heat generated by the laser is acquired by the CCHP and transferred to the LHP, which delivers the heat to the radiator for ultimate rejection. The radiator can be exposed to temperatures between minus 71 degrees Centigrade and minus 93 degrees Centigrade. The two lasers can have different operating temperatures varying between plus 15 degrees Centigrade and plus 30 degrees Centigrade, and their operating temperatures are not known while the LTCS is being designed and built. Major challenges of the LTCS include: 1) A single thermal control system must maintain the ATLAS at 15 degrees Centigrade with 250 watts heat load and minus 71 degrees Centigrade radiator sink temperature, and maintain the ATLAS at plus 30 degrees Centigrade with 125 watts heat load and minus 93 degrees Centigrade radiator sink temperature. Furthermore, the LTCS must be qualification tested to maintain the ATLAS between plus 10 degrees Centigrade and plus 35 degrees Centigrade. 2) The LTCS must be shut down to ensure that the ATLAS can be maintained above its lowest desirable temperature of minus 2 degrees Centigrade during the survival mode. No software control algorithm for LTCS can be activated during survival and only thermostats can be used. 3) The radiator must be kept above minus 65 degrees Centigrade to prevent ammonia from freezing using no more

  20. Dynamic Analysis of the Titanium Alloy Plate under Thermal-acoustic Loadings

    Directory of Open Access Journals (Sweden)

    Zou Xuefeng

    2015-01-01

    Full Text Available Hypersonic vehicles structures suffer complex combined loadings generally. For the thin-walled structures and thermal protection systems of the aircraft, high temperature and intensity acoustic loadings are the significant factors that leading to their break. The object of this paper is typical simply supported titanium alloy plate, the finite element method was adopted to calculate the critical thermal buckling temperature the ordinal coupling method and Newmark method were adopted to calculate the thermal-acoustic dynamic response. Based on the FEM analysis, the power spectrum densities (PSD of center point was presented. Research results show that the thermal buckling of the typical simply supported titanium alloy plate occurs easily because of the low critical thermal buckling temperature, dynamic response of the thermal buckled plate suffering acoustic loads performs strong nonlinear characteristics and complex forms of exercise.

  1. Thermally activated repolarization of antiferromagnetic particles: Monte Carlo dynamics

    Science.gov (United States)

    Soloviev, S. V.; Popkov, A. F.; Knizhnik, A. A.; Iskandarova, I. M.

    2017-02-01

    Based on the equation of motion of an antiferromagnetic moment, taking into account a random field of thermal fluctuations, we propose a Monte Carlo (MC) scheme for the numerical simulation of the evolutionary dynamics of an antiferromagnetic particle, corresponding to the Langevin dynamics in the Kramers theory for the two-well potential. Conditions for the selection of the sphere of fluctuations of random deviations of the antiferromagnetic vector at an MC time step are found. A good agreement with the theory of Kramers thermal relaxation is demonstrated for varying temperatures and heights of energy barrier over a wide range of integration time steps in an overdamped regime. Based on the developed scheme, we performed illustrative calculations of the temperature drift of the exchange bias under the fast annealing of a ferromagnet-antiferromagnet structure, taking into account the random variation of anisotropy directions in antiferromagnetic grains and their sizes. The proposed approach offers promise for modeling magnetic sensors and spintronic memory devices containing heterostructures with antiferromagnetic layers.

  2. Thermal performance measurements on ATLAS-SCT KB forward modules

    CERN Document Server

    Donegà, M; D'Onofrio, M; Ferrère, D; Hirt, C; Ikegami, Y; Kohriki, T; Kondo, T; Lindsay, S; Mangin-Brinet, M; Niinikoski, T O; Pernegger, H; Perrin, E; Taylor, G; Terada, S; Unno, Y; Wallny, R; Weber, M

    2003-01-01

    The thermal design of the KB module is presented. A Finite Elements Analysis (FEA) has been used to finalize the module design. The thermal performance of an outer irradiated KB module has been measured at different cooling conditions. The thermal runaway of the module has been measured. The FEA model has been compared with the measurements and has been used to predict the thermal performance in a realistic SCT scenario.

  3. Optical Thermal Characterization Enables High-Performance Electronics Applications

    Energy Technology Data Exchange (ETDEWEB)

    2016-02-01

    NREL developed a modeling and experimental strategy to characterize thermal performance of materials. The technique provides critical data on thermal properties with relevance for electronics packaging applications. Thermal contact resistance and bulk thermal conductivity were characterized for new high-performance materials such as thermoplastics, boron-nitride nanosheets, copper nanowires, and atomically bonded layers. The technique is an important tool for developing designs and materials that enable power electronics packaging with small footprint, high power density, and low cost for numerous applications.

  4. Thermal instability and runaway criteria: the dangers of disregarding dynamics

    CERN Document Server

    Ball, Rowena

    2012-01-01

    Two exemplary exothermic processes, synthesis of nitroglycerine in a continuous stirred tank reactor (CSTR) and synthesis of the explosive RDX in a CSTR, are used to demonstrate the dangers of ignoring the system dynamics when defining criteria for thermal criticality or runaway. Stability analyses are necessary to prescribe such criteria, and for these systems prove the presence of dangerous oscillatory thermal instability which cannot be detected using the steady state thermal balances.

  5. Thermal conductivity of penta-graphene from molecular dynamics study.

    Science.gov (United States)

    Xu, Wen; Zhang, Gang; Li, Baowen

    2015-10-21

    Using classical equilibrium molecular dynamics simulations and applying the original Tersoff interatomic potential, we study the thermal transport property of the latest two dimensional carbon allotrope, penta-graphene. It is predicted that its room-temperature thermal conductivity is about 167 W/mK, which is much lower than that of graphene. With normal mode decomposition, the accumulated thermal conductivity with respect to phonon frequency and mean free path is analyzed. It is found that the acoustic phonons make a contribution of about 90% to the thermal conductivity, and phonons with mean free paths larger than 100 nm make a contribution over 50%. We demonstrate that the remarkably lower thermal conductivity of penta-graphene compared with graphene results from the lower phonon group velocities and fewer collective phonon excitations. Our study highlights the importance of structure-property relationship and provides better understanding of thermal transport property and valuable insight into thermal management of penta-graphene.

  6. Numerical evaluation of the thermal performances of roof-mounted radiant barriers

    CERN Document Server

    Miranville, Frédéric; Lucas, Franck; Johan, Seriacaroupin

    2014-01-01

    This paper deals with the thermal performances of roof-mounted radiant barriers. Using dynamic simulations of a mathematical model of a whole test cell including a radiant barrier installed between the roof top and the ceiling, the thermal performance of the roof is calculated. The mean method is more particularly used to assess the thermal resistance of the building component and lead to a value which is compared to the one obtained for a mass insulation product such as polyurethane foam. On a further stage, the thermal mathematical model is replaced by a thermo-aeraulic model which is used to evaluate the thermal resistance of the roof as a function of the airflow rate. The results shows a better performance of the roof in this new configuration, which is widely used in practice. Finally, the mathematical relation between the thermal resistance and the airflow rate is proposed.

  7. Comparative study for thermal-hydraulic performance

    Directory of Open Access Journals (Sweden)

    Alok Kumar

    2016-03-01

    Full Text Available Several researchers have worked on the passive approach of heat transfer enhancement in tube heat exchangers. Some of them tried to modify the surface by creating dimple or using wire coil of different cross-section, while some worked on core fluid disturbance by using some insert geometries such as twisted tapes. But the ultimate aim of all was to create some disturbance in the flow in order to obtain enhanced heat transfer. This paper focuses on comparison of some of the most commonly used insert geometries. Insert geometry selected for this comparison is collection of core fluid disturbance, surface modification and combination of both. Different geometries taken in this study include twisted tape, twisted tape with ring, circular band, multiple twisted tape, twisted tape with conical rings, and so on and used air under turbulent flow regime as working fluid. On the basis of comparison made, it is observed that, in case of “single twisted tape insert” the thermal performance factor was maximum and in the event of “twisted tape with circular ring” the overall heat transfer rate is maximum. Future aspect is also proposed, which includes perforation in circular ring, and causes decrease in friction factor value because of less flow blockage.

  8. Thermal performances of vertical hybrid PV/T air collector

    Science.gov (United States)

    Tabet, I.; Touafek, K.; Bellel, N.; Khelifa, A.

    2016-11-01

    In this work, numerical analyses and the experimental validation of the thermal behavior of a vertical photovoltaic thermal air collector are investigated. The thermal model is developed using the energy balance equations of the PV/T air collector. Experimental tests are conducted to validate our mathematical model. The tests are performed in the southern Algerian region (Ghardaïa) under clear sky conditions. The prototype of the PV/T air collector is vertically erected and south oriented. The absorber upper plate temperature, glass cover temperature, air temperature in the inlet and outlet of the collector, ambient temperature, wind speed, and solar radiation are measured. The efficiency of the collector increases with increase in mass flow of air, but the increase in mass flow of air reduces the temperature of the system. The increase in efficiency of the PV/T air collector is due to the increase in the number of fins added. In the experiments, the air temperature difference between the inlet and the outlet of the PV/T air collector reaches 10 ° C on November 21, 2014, the interval time is between 10:00 and 14:00, and the temperature of the upper plate reaches 45 ° C at noon. The mathematical model describing the dynamic behavior of the typical PV/T air collector is evaluated by calculating the root mean square error and mean absolute percentage error. A good agreement between the experiment and the simulation results is obtained.

  9. Thermal transport properties of uranium dioxide by molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Taku; Sinnott, Susan B. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Tulenko, James S. [Department of Nuclear and Radiological Engineering, University of Florida, Gainesville, FL 32611 (United States); Grimes, Robin W. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Schelling, Patrick K. [AMPAC and Department of Physics, University of Central Florida, Orlando, FL 32816 (United States); Phillpot, Simon R. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)], E-mail: sphil@mse.ufl.edu

    2008-04-30

    The thermal conductivities of single crystal and polycrystalline UO{sub 2} are calculated using molecular dynamics simulations, with interatomic interactions described by two different potential models. For single crystals, the calculated thermal conductivities are found to be strongly dependent on the size of the simulation cell. However, a scaling analysis shows that the two models predict essentially identical values for the thermal conductivity for infinite system sizes. By contrast, simulations with the two potentials for identical fine polycrystalline structures yield estimated thermal conductivities that differ by a factor of two. We analyze the origin of this difference.

  10. Dynamic nonlinear thermal optical effects in coupled ring resonators

    Directory of Open Access Journals (Sweden)

    Chenguang Huang

    2012-09-01

    Full Text Available We investigate the dynamic nonlinear thermal optical effects in a photonic system of two coupled ring resonators. A bus waveguide is used to couple light in and out of one of the coupled resonators. Based on the coupling from the bus to the resonator, the coupling between the resonators and the intrinsic loss of each individual resonator, the system transmission spectrum can be classified by three different categories: coupled-resonator-induced absorption, coupled-resonator-induced transparency and over coupled resonance splitting. Dynamic thermal optical effects due to linear absorption have been analyzed for each category as a function of the input power. The heat power in each resonator determines the thermal dynamics in this coupled resonator system. Multiple “shark fins” and power competition between resonators can be foreseen. Also, the nonlinear absorption induced thermal effects have been discussed.

  11. Dynamic thermal characteristics of heat pipe via segmented thermal resistance model for electric vehicle battery cooling

    Science.gov (United States)

    Liu, Feifei; Lan, Fengchong; Chen, Jiqing

    2016-07-01

    Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a "segmented" thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed "segmented" model shows more precise than the "non-segmented" model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the "segmented" model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

  12. Molecular dynamics simulations of thermal effects in nanometric cutting process

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Understanding the basic action of how material removing in nanoscale is a critical issue of producing well-formed components.In order to clarify thermal effects on material removal at atomic level,molecular dynamics(MD)simulations of nanometric cutting of mono-crystalline copper are performed with Morse,EAM and Tersoff potential.The effects of cutting speed on temperature distribution are investigated.The simulation results demonstrate that the temperature distribution shows a roughly concentric shape around shear zone and a steep temperature gradient lies in diamond tool,a relative high temperature is located in shear zone and machined surface,but the highest temperature is found in chip.At a high cutting speed mode,the atoms in shear zone with high temperature implies a large stress is built up in a local region.

  13. Image based performance analysis of thermal imagers

    Science.gov (United States)

    Wegner, D.; Repasi, E.

    2016-05-01

    Due to advances in technology, modern thermal imagers resemble sophisticated image processing systems in functionality. Advanced signal and image processing tools enclosed into the camera body extend the basic image capturing capability of thermal cameras. This happens in order to enhance the display presentation of the captured scene or specific scene details. Usually, the implemented methods are proprietary company expertise, distributed without extensive documentation. This makes the comparison of thermal imagers especially from different companies a difficult task (or at least a very time consuming/expensive task - e.g. requiring the execution of a field trial and/or an observer trial). For example, a thermal camera equipped with turbulence mitigation capability stands for such a closed system. The Fraunhofer IOSB has started to build up a system for testing thermal imagers by image based methods in the lab environment. This will extend our capability of measuring the classical IR-system parameters (e.g. MTF, MTDP, etc.) in the lab. The system is set up around the IR- scene projector, which is necessary for the thermal display (projection) of an image sequence for the IR-camera under test. The same set of thermal test sequences might be presented to every unit under test. For turbulence mitigation tests, this could be e.g. the same turbulence sequence. During system tests, gradual variation of input parameters (e. g. thermal contrast) can be applied. First ideas of test scenes selection and how to assembly an imaging suite (a set of image sequences) for the analysis of imaging thermal systems containing such black boxes in the image forming path is discussed.

  14. Dynamic residual stress in thermal sprayed coatings

    Institute of Scientific and Technical Information of China (English)

    Wang Zhiping; Yang Yuanyuan

    2005-01-01

    With the modified Almen method, the forming and development process of residual stress in a thermal sprayed coating has been obtained. The test results identify that the residual stress in a coating is depend on coating material properties, technique and coating thickness. The paper pays much attention to the hysteresis between the coating temperature and residual stress in the coating or between the applied stress and the strain of the coating, and confirms that the fact is resulted from the"Gas Fix" character of a thermal sprayed coating.

  15. Thermal imaging cameras characteristics and performance

    CERN Document Server

    Williams, Thomas

    2009-01-01

    The ability to see through smoke and mist and the ability to use the variances in temperature to differentiate between targets and their backgrounds are invaluable in military applications and have become major motivators for the further development of thermal imagers. As the potential of thermal imaging is more clearly understood and the cost decreases, the number of industrial and civil applications being exploited is growing quickly. In order to evaluate the suitability of particular thermal imaging cameras for particular applications, it is important to have the means to specify and measur

  16. Performance of a solar-thermal collector

    Science.gov (United States)

    Higa, W. H.

    1975-01-01

    Possible means of achieving the technology required for field application of solar thermal power systems are discussed. Simplifications in construction techniques as well as in measurement techniques for parabolic trough collectors are described. Actual measurement data is also given.

  17. Investigation of the Mechanical Performance of Compliant Thermal Barriers

    Science.gov (United States)

    DeMange, Jeffrey J.; Bott, Robert J.; Dunlap, Patrick H.

    2011-01-01

    Compliant thermal barriers play a pivotal role in the thermal protection systems of advanced aerospace vehicles. Both the thermal properties and mechanical performance of these barriers are critical in determining their successful implementation. Due to the custom nature of many thermal barriers, designers of advanced spacecraft have little guidance as to the design, selection, and implementation of these elements. As part of an effort to develop a more fundamental understanding of the interrelationship between thermal barrier design and performance, mechanical testing of thermal barriers was conducted. Two different types of thermal barriers with several core insulation density levels ranging from 62 to 141 kg/cu m were investigated. Room-temperature compression tests were conducted on samples to determine load performance and assess thermal barrier resiliency. Results showed that the loading behavior of these thermal barriers was similar to other porous, low-density, compliant materials, such as elastomeric foams. Additionally, the insulation density level had a significant non-linear impact on the stiffness and peak loads of the thermal barriers. In contrast, neither the thermal barrier type nor the level of insulation density significantly influenced the room-temperature resiliency of the samples.

  18. Extending Our Understanding of Compliant Thermal Barrier Performance

    Science.gov (United States)

    Demange, Jeffrey J.; Finkbeiner, Joshua R.; Dunlap, Patrick H.

    2014-01-01

    Thermal barriers and seals are integral components in the thermal protection systems (TPS) of nearly all aerospace vehicles. They are used to minimize the flow of hot gases through interfaces and protect underlying temperature-sensitive components and systems. Although thermal barriers have been used extensively on many aerospace vehicles, the factors affecting their thermal and mechanical performance are not well-understood. Because of this, vehicle TPS designers are often left with little guidance on how to properly design and optimize these barriers. An ongoing effort to better understand thermal barrier performance and develop models and design tools is in progress at the NASA Glenn Research Center. Testing has been conducted to understand the degree to which insulation density influences structural performance and permeability. In addition, the development of both thermal and mechanical models is ongoing with the goal of providing an improved ability to design and implement these critical TPS components.

  19. Quantitative reconstruction of thermal and dynamic characteristics of lava flow from surface thermal measurements

    Science.gov (United States)

    Korotkii, Alexander; Kovtunov, Dmitry; Ismail-Zadeh, Alik; Tsepelev, Igor; Melnik, Oleg

    2016-06-01

    We study a model of lava flow to determine its thermal and dynamic characteristics from thermal measurements of the lava at its surface. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. We develop a numerical approach to the mathematical problem in the case of steady-state flow. Assuming that the temperature and the heat flow are prescribed at the upper surface of the model domain, we determine the flow characteristics in the entire model domain using a variational (adjoint) method. We have performed computations of model examples and showed that in the case of smooth input data the lava temperature and the flow velocity can be reconstructed with a high accuracy. As expected, a noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. Also we analyse the influence of optimization methods on the solution convergence rate. The proposed method for reconstruction of physical parameters of lava flows can also be applied to other problems in geophysical fluid flows.

  20. Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.

    2008-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

  1. Thermal Performance Analysis of LED with Multichips

    Institute of Scientific and Technical Information of China (English)

    HAN Yuanyuan; GUO Hong; ZHANG Ximin; YIN Fazhang; CHU Ke; FAN Yeming

    2011-01-01

    The package and system level temperature and thermal stress distributions of 10 W light emitting diode (LED) with 4 chips and 100 W LED with 100 chips were investigated using finite element analysis.The chips were arranged on a Si sheet which is soldered on the copper/diamond composite slug with very high conductivity.The experimental results show that the maximal temperature appears in the chips of both two high power LEDs packages.Compared with the 10 W LEDs package with 4 chips array,the heat issue caused by stacking and coupling of the heat in 100 W LEDs package with 100 chips array is more serious.The chip temperature in the center of the array is much higher,and it decreases with the distance between the chip and the center of LEDs increases.Great thermal stress lies between the chips and the solder,which will reduce the reliability of the package.

  2. Thermal Performance of an Annealed Pyrolytic Graphite Solar Collector

    Science.gov (United States)

    Jaworske, Donald A.; Hornacek, Jennifer

    2002-01-01

    A solar collector having the combined properties of high solar absorptance, low infrared emittance, and high thermal conductivity is needed for applications where solar energy is to be absorbed and transported for use in minisatellites. Such a solar collector may be used with a low temperature differential heat engine to provide power or with a thermal bus for thermal switching applications. One concept being considered for the solar collector is an Al2O3 cermet coating applied to a thermal conductivity enhanced polished aluminum substrate. The cermet coating provides high solar absorptance and the polished aluminum provides low infrared emittance. Annealed pyrolytic graphite embedded in the aluminum substrate provides enhanced thermal conductivity. The as-measured thermal performance of an annealed pyrolytic graphite thermal conductivity enhanced polished aluminum solar collector, coated with a cermet coating, will be presented.

  3. Thermal performance of concrete masonry unit wall systems

    Energy Technology Data Exchange (ETDEWEB)

    Kosny, J.

    1995-12-31

    New materials, modern building wall technologies now available in the building marketplace, and unique, more accurate, methods of thermal analysis of wall systems create an opportunity to design and erect buildings where thermal envelopes that use masonry wall systems can be more efficient. Thermal performance of the six masonry wall systems is analyzed. Most existing masonry systems are modifications of technologies presented in this paper. Finite difference two-dimensional and three-dimensional computer modeling and unique methods of the clear wall and overall thermal analysis were used. In the design of thermally efficient masonry wall systems is t to know how effectively the insulation material is used and how the insulation shape and its location affect the wall thermal performance. Due to the incorrect shape of the insulation or structural components, hidden thermal shorts cause additional heat losses. In this study, the thermal analysis of the clear wall was enriched with the examination of the thermal properties of the wall details and the study of a quantity defined herein the Thermal Efficiency of the insulation material.

  4. Novel dynamic thermal characterization of multifunctional concretes with microencapsulated phase change materials

    Science.gov (United States)

    Pisello, Anna Laura; Fabiani, Claudia; D'Alessandro, Antonella; Cabeza, Luisa F.; Ubertini, Filippo; Cotana, Franco

    2017-04-01

    Concrete is widely applied in the construction sector for its reliable mechanical performance, its easiness of use and low costs. It also appears promising for enhancing the thermal-energy behavior of buildings thanks to its capability to be doped with multifunctional fillers. In fact, key studies acknowledged the benefits of thermally insulated concretes for applications in ceilings and walls. At the same time, thermal capacity also represents a key property to be optimized, especially for lightweight constructions. In this view, Thermal-Energy Storage (TES) systems have been recently integrated into building envelopes for increasing thermal inertia. More in detail, numerical experimental investigations showed how Phase Change materials (PCMs), as an acknowledged passive TES strategy, can be effectively included in building envelope, with promising results in terms of thermal buffer potentiality. In particular, this work builds upon previous papers aimed at developing the new PCM-filled concretes for structural applications and optimized thermalenergy efficiency, and it is focused on the development of a new experimental method for testing such composite materials in thermal-energy dynamic conditions simulated in laboratory by exposing samples to environmentally controlled microclimate while measuring thermal conductivity and diffusivity by means of transient plane source techniques. The key findings show how the new composites are able to increasingly delay the thermal wave with increasing the PCM concentration and how the thermal conductivity varies during the course of the phase change, in both melting and solidification processes. The new analysis produces useful findings in proposing an effective method for testing composite materials with adaptive thermal performance, much needed by the scientific community willing to study building envelopes dynamics.

  5. Determination of thermal inactivation kinetics of Listeria monocytogenes in chicken meat by isothermal and dynamic methods

    Science.gov (United States)

    The objective of this research is to determine the thermal inactivation kinetics of Listeria monocytogenes in chicken breast meat using both isothermal and dynamic conditions. A four-strain cocktail of L. monocytogenes was inoculated to chicken breast meat. Isothermal studies were performed by sub...

  6. Ultrafast Non-Thermal Electron Dynamics in Single Layer Graphene

    Directory of Open Access Journals (Sweden)

    Novoselov K.S.

    2013-03-01

    Full Text Available We study the ultrafast dynamics of non-thermal electron relaxation in graphene upon impulsive excitation. The 10-fs resolution two color pump-probe allows us to unveil the non-equilibrium electron gas decay at early times.

  7. Enhancing thermal barrier coatings performance through reinforcement of ceramic topcoat

    Science.gov (United States)

    Bogdanovich, V. I.; Giorbelidze, M. G.

    2016-11-01

    This paper studies structure of thermal barrier coatings applied to hot gas path components in gas turbine engines and produced in a number of ways, and its impact on performance. Methods of structural reinforcement for ceramic topcoat in thermal barrier coatings are considered.

  8. Thermal performance of a hot-air solar collector

    Science.gov (United States)

    1978-01-01

    Report contains procedures and results of thermal-performance tests on double-glazed air solar collector. Four types of tests were carried out including thermal-efficiency and stagnation tests, collector time-constant tests to assess effects of transients, and incident-angle modifier tests. Data are presented in tables and as graphs and are discussed and analyzed.

  9. Dynamic optimization of building performance

    DEFF Research Database (Denmark)

    Maslesa, Esmir; Nielsen, Susanne Balslev; Birkved, Morten;

    D develops a methodological basis and purpose-based software for simultaneous calculation of total value and environmental performance of non-residential buildings. So far, a literature study has identified 8 indicator categories that should be considered when addressing environmental performance of building....... The next step of the project combines research and practice through various case studies in which environmental building performance of non-residential buildings will be studied. Case studies will investigate which environmental indicators are used in practice and why, and disclose how building data...... management, energy management, asset management etc. The research focus of this industrial PhD is to study how these different building data sets can be used and combined for improving total value of buildings, with special emphasis on environmental building performance from lifecycle perspective...

  10. Thermal Mass & Dynamic Effects Danish Building Regulation

    DEFF Research Database (Denmark)

    Le Dreau, Jerome; Selman, Ayser Dawod; Heiselberg, Per

    This report is part of the work performed under the project “Multifunktionelle betonkonstruktioner til renovering og nybyg (EUDP projekt)”. The main purpose of this task is to develop a calculation tool that takes into consideration night-time ventilation in the program Be10. Therefore this report...

  11. Physical-Perceptual Correspondence for Dynamic Thermal Stimulation.

    Science.gov (United States)

    Ho, Hsin-Ni; Sato, Katsunari; Kuroki, Scinob; Watanabe, Junji; Maeno, Takashi; Nishida, Shin'ya

    2017-01-01

    Thermal displays have been applied in various haptic applications, from material simulation to interpersonal communication; however, there is insufficient knowledge about the temporal processing in human thermal sense to provide a knowledge basis for thermal display design. In this study, we investigated the physical-perceptual correspondence for dynamic thermal stimulation to shed a light on the temporal processing of human thermal sense. In the experiments, participants reported subjective timings of the temperature onset and temperature peak of continuous temperature changes applied to the thenar eminence. We found that the physical-perceptual correspondence was not consistent for warm and cold stimulations. For warm stimulation, the subjective experience always came after the corresponding physical event. On the other hand, for cold stimulation, while the subjective onset always lagged the physical onset, the subjective temperature peak preceded the physical temperature peak. We analyzed these results in the framework of linear systems theory. The results suggest that the senses of warmth and cold have distinct temporal filtering properties, with the sense of cold being more transient than the sense of warmth. These findings advance our knowledge regarding temporal processing in human thermal sense and serve as a basis for thermal display design.

  12. Thermal Components Boost Performance of HVAC Systems

    Science.gov (United States)

    2012-01-01

    As the International Space Station (ISS) travels 17,500 miles per hour, normal is having a constant sensation of free-falling. Normal is no rain, but an extreme amount of shine.with temperatures reaching 250 F when facing the Sun. Thanks to a number of advanced control systems onboard the ISS, however, the interior of the station remains a cool, comfortable, normal environment where astronauts can live and work for extended periods of time. There are two main control systems on the ISS that make it possible for humans to survive in space: the Thermal Control System (TCS) and the Environmental Control and Life Support system. These intricate assemblies work together to supply water and oxygen, regulate temperature and pressure, maintain air quality, and manage waste. Through artificial means, these systems create a habitable environment for the space station s crew. The TCS constantly works to regulate the temperature not only for astronauts, but for the critical instruments and machines inside the spacecraft as well. To do its job, the TCS encompasses several components and systems both inside and outside of the ISS. Inside the spacecraft, a liquid heat-exchange process mechanically pumps fluids in closed-loop circuits to collect, transport, and reject heat. Outside the ISS, an external system circulates anhydrous ammonia to transport heat and cool equipment, and radiators release the heat into space. Over the years, NASA has worked with a variety of partners.public and private, national and international. to develop and refine the most complex thermal control systems ever built for spacecraft, including the one on the ISS.

  13. Keystroke Dynamics Performance Enhancement With Soft Biometrics

    OpenAIRE

    Syed Idrus, Syed Zulkarnain; Cherrier, Estelle; Rosenberger, Christophe; Mondal, Soumik; Bours, Patrick

    2015-01-01

    International audience; It is accepted that the way a person types on a key-board contains timing patterns, which can be used to classify him/her, is known as keystroke dynamics. Keystroke dynamics is a behavioural biometric modality, whose perfor-mances, however, are worse than morphological modalities such as fingerprint, iris recognition or face recognition. To cope with this, we propose to combine keystroke dynamics with soft biometrics. Soft biometrics refers to biometric characteristics...

  14. Thermal performance of stratospheric airship with photovoltaic array

    Science.gov (United States)

    Liu, Qiang; Yang, Yanchu; Cui, Yanxiang; Cai, Jingjing

    2017-03-01

    The increase of airship applications makes it necessary for a comprehensive understanding of the thermal performance of stratospheric airships. A numerical model was proposed to simulate the thermal performance of a stratospheric airship with photovoltaic array, an analysis code was developed based on the thermal model and was verified by experimental data. A further inspection into the temperature field and flow field distribution of the airship was analyzed in detail. The simulation results suggest that solar radiation can exert great influence on the thermal performance of the airship. The higher temperature Helium was gathered in the upper part inside of the airship, the flow of Helium was regular at nighttime but was chaotic in the middle and upper part of the airship at daytime. The temperature and velocity performance of fin was different from that of the hull and other fins due to the shadow of hull and other fins.

  15. Thermal Model Predictions of Advanced Stirling Radioisotope Generator Performance

    Science.gov (United States)

    Wang, Xiao-Yen J.; Fabanich, William Anthony; Schmitz, Paul C.

    2014-01-01

    This presentation describes the capabilities of three-dimensional thermal power model of advanced stirling radioisotope generator (ASRG). The performance of the ASRG is presented for different scenario, such as Venus flyby with or without the auxiliary cooling system.

  16. Thermal Performance of Microencapsulated Phase Change Material Survey

    Science.gov (United States)

    2008-03-01

    ER D C TR -0 8 -4 Basic Research/Military Construction Thermal Performance of Microencapsulated Phase Change Material Slurry Jorge L...distribution is unlimited. Basic Research/Military Construction ERDC TR-08-4 March 2008 Thermal Performance of Microencapsulated Phase Change... microencapsulated PCM (MPCM) slurries is enhanced significantly, even when using low volume fractions. MPCM slurries have potential to decrease costs and improve

  17. Thermal Performance of Microencapsulated Phase Change Material Slurry

    Science.gov (United States)

    2008-03-01

    ER D C TR -0 8 -4 Basic Research/Military Construction Thermal Performance of Microencapsulated Phase Change Material Slurry Jorge L...distribution is unlimited. Basic Research/Military Construction ERDC TR-08-4 March 2008 Thermal Performance of Microencapsulated Phase Change... microencapsulated PCM (MPCM) slurries is enhanced significantly, even when using low volume fractions. MPCM slurries have potential to decrease costs and improve

  18. Patterning Multicomponent Polymer Thin Films via Dynamic Thermal Processing

    Science.gov (United States)

    Singh, Gurpreet

    Bottom-up patterning is gaining increased importance owing to the physical limitations and rising costs of top-down patterning. One example of bottom-up patterning is self-assembling polymer thin films. Although there are several pathways to facilitate polymer thin film self-assembly, this presentation will focus on dynamic thermal field based processes for patterning multicomponent polymer thin films. Dynamic thermal field processing is an attractive roll­to­roll (R2R) amenable directed self­assembly (DSA) method for molecular level organization of multicomponent polymer systems such as block copolymer thin films over large areas without requiring guiding templates. The talk will first outline how parameters such as magnitude of the temperature gradient, velocity of annealing, thermal expansion, and molecular weight of the polymer can be optimized to finely tune the morphology of the block copolymer thin films and also elucidate their associated physical mechanisms. The second part of the talk will outline application of dynamic thermal field processes for fabricating functional nanomaterials and discuss the recent advancements achieved using these processes.

  19. Space Shuttle Orbiter leading edge structural subsystem thermal performance

    Science.gov (United States)

    Curry, D. M.; Cunningham, J. A.; Frahm, J. R.

    1982-01-01

    An extensive qualification test program and the STS-1 flight of the Space Shuttle Orbiter have provided the data necessary to verify the performance of the Orbiter thermal protection system. The reinforced carbon-carbon leading edge structural subsystem is used on areas of the orbiter where temperatures exceed 2300 F. The subsystem consists of the ROC nose cap and wing leading edge panels, metallic attachments, internal insulation, and interface tiles. Thermal response data from the qualification tests and the STS-1 flight, postflight inspection, and analytical predictions support the conclusion that the thermal performance of the subsystem verified the design.

  20. Thermal adaptation and phosphorus shape thermal performance in an assemblage of rainforest ants.

    Science.gov (United States)

    Kaspari, Michael; Clay, Natalie A; Lucas, Jane; Revzen, Shai; Kay, Adam; Yanoviak, Stephen P

    2016-04-01

    We studied the Thermal Performance Curves (TPCs) of 87 species of rainforest ants and found support for both the Thermal Adaptation and Phosphorus-Tolerance hypotheses. TPCs relate a fitness proxy (here, worker speed) to environmental temperature. Thermal Adaptation posits that thermal generalists (ants with flatter, broader TPCs) are favored in the hotter, more variable tropical canopy compared to the cooler, less variable litter below. As predicted, species nesting in the forest canopy 1) had running speeds less sensitive to temperature; 2) ran over a greater range of temperatures; and 3) ran at lower maximum speeds. Tradeoffs between tolerance and maximum performance are often invoked for constraining the evolution of thermal generalists. There was no evidence that ant species traded off thermal tolerance for maximum speed, however. Phosphorus-Tolerance is a second mechanism for generating ectotherms able to tolerate thermal extremes. It posits that ants active at high temperatures invest in P-rich machinery to buffer their metabolism against thermal extremes. Phosphorus content in ant tissue varied three-fold, and as predicted, temperature sensitivity was lower and thermal range was higher in P-rich species. Combined, we show how the vertical distribution of hot and variable vs. cooler and stable microclimates in a single forest contribute to a diversity of TPCs and suggest that a widely varying P stoichiometry among these ants may drive some of these differences.

  1. Modeling of droplet dynamic and thermal behaviour during spray deposition

    Indian Academy of Sciences (India)

    N S Mahesh; Johnson Mendonca; M K Muralidhara; B K Muralidhara; C Ramachandra

    2003-04-01

    Mathematical modeling of supersonic gas atomization for spray forming has been investigated. Influence of the droplet dynamic and thermal behaviour on the resultant microstructure has been studied. Analytical models have been constructed taking into account the higher Reynolds number owing to supersonic gas flow. The impact velocity profiles of the droplets lend credence to the evolution of equiaxed grain morphology through dendrite fragmentation. The thermal history profile along with the fraction solid plot could yield optimized standoff distance to obtain a mushy droplet. A comparison of secondary dendrite arm spacing obtained from the mathematical model showed good agreement with experimental observations.

  2. Analysis of Thermal Performance in a Bidirectional Thermocycler by Including Thermal Contact Characteristics

    Directory of Open Access Journals (Sweden)

    Jyh Jian Chen

    2014-12-01

    Full Text Available This paper illustrates an application of a technique for predicting the thermal characteristics of a bidirectional thermocycling device for polymerase chain reaction (PCR. The micromilling chamber is oscillated by a servo motor and contacted with different isothermal heating blocks to successfully amplify the DNA templates. Because a comprehensive database of contact resistance factors does not exist, it causes researchers to not take thermal contact resistance into consideration at all. We are motivated to accurately determine the thermal characteristics of the reaction chamber with thermal contact effects existing between the heater surface and the chamber surface. Numerical results show that the thermal contact effects between the heating blocks and the reaction chamber dominate the temperature variations and the ramping rates inside the PCR chamber. However, the influences of various temperatures of the ambient conditions on the sample temperature during three PCR steps can be negligible. The experimental temperature profiles are compared well with the numerical simulations by considering the thermal contact conductance coefficient which is empirical by the experimental fitting. To take thermal contact conductance coefficients into consideration in the thermal simulation is recommended to predict a reasonable temperature profile of the reaction chamber during various thermal cycling processes. Finally, the PCR experiments present that Hygromycin B DNA templates are amplified successfully. Furthermore, our group is the first group to introduce the thermal contact effect into theoretical study that has been applied to the design of a PCR device, and to perform the PCR process in a bidirectional thermocycler.

  3. Parametric study of closed wet cooling tower thermal performance

    Science.gov (United States)

    Qasim, S. M.; Hayder, M. J.

    2017-08-01

    The present study involves experimental and theoretical analysis to evaluate the thermal performance of modified Closed Wet Cooling Tower (CWCT). The experimental study includes: design, manufacture and testing prototype of a modified counter flow forced draft CWCT. The modification based on addition packing to the conventional CWCT. A series of experiments was carried out at different operational parameters. In view of energy analysis, the thermal performance parameters of the tower are: cooling range, tower approach, cooling capacity, thermal efficiency, heat and mass transfer coefficients. The theoretical study included develops Artificial Neural Network (ANN) models to predicting various thermal performance parameters of the tower. Utilizing experimental data for training and testing, the models simulated by multi-layer back propagation algorithm for varying all operational parameters stated in experimental test.

  4. Temperature Distribution and Thermal Performance of an Aquifer Thermal Energy Storage System

    Science.gov (United States)

    Ganguly, Sayantan

    2017-04-01

    Energy conservation and storage has become very crucial to make use of excess energy during times of future demand. Excess thermal energy can be captured and stored in aquifers and this technique is termed as Aquifer Thermal Energy Storage (ATES). Storing seasonal thermal energy in water by injecting it into subsurface and extracting in time of demand is the principle of an ATES system. Using ATES systems leads to energy savings, reduces the dependency on fossil fuels and thus leads to reduction in greenhouse gas emission. This study numerically models an ATES system to store seasonal thermal energy and evaluates the performance of it. A 3D thermo-hydrogeological numerical model for a confined ATES system is presented in this study. The model includes heat transport processes of advection, conduction and heat loss to confining rock media. The model also takes into account regional groundwater flow in the aquifer, geothermal gradient and anisotropy in the aquifer. Results show that thermal injection into the aquifer results in the generation of a thermal-front which grows in size with time. Premature thermal-breakthrough causes thermal interference in the system when the thermal-front reaches the production well and consequences in the fall of system performance and hence should be avoided. This study models the transient temperature distribution in the aquifer for different flow and geological conditions. This may be effectively used in designing an efficient ATES project by ensuring safety from thermal-breakthrough while catering to the energy demand. Based on the model results a safe well spacing is proposed. The thermal energy discharged by the system is determined and strategy to avoid the premature thermal-breakthrough in critical cases is discussed. The present numerical model is applied to simulate an experimental field study which is found to approximate the field results quite well.

  5. Determination of thermal/dynamic characteristics of lava flow from surface thermal measurements

    Science.gov (United States)

    Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander; Tsepelev, Igor; Kovtunov, Dmitry

    2016-04-01

    Rapid development of ground based thermal cameras, drones and satellite data allows getting repeated thermal images of the surface of the lava flow. Available instrumentation allows getting a large amount of data during a single lava flow eruption. These data require development of appropriate quantitative techniques to link subsurface dynamics with observations. We present a new approach to assimilation of thermal measurements at lava's surface to the bottom of the lava flow to determine lava's thermal and dynamic characteristics. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. Using an adjoint method we develop a numerical approach to the mathematical problem based on the determination of the missing boundary condition and lava flow characteristics. Numerical results show that in the case of smooth input data lava temperature and velocity can be determined with a high accuracy. A noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. The proposed approach to assimilate measured data brings an opportunity to estimate thermal budget of the lava flow.

  6. Thermal Transport in Carbon Nanotubes using Molecular Dynamics

    Science.gov (United States)

    Moore, Andrew; Khatun, Mahfuza

    2011-10-01

    We will present results of thermal transport phenomena in Carbon Nanotube (CNT) structures. CNTs have many interesting physical properties, and have the potential for device applications. Specifically, CNTs are robust materials with high thermal conductance and excellent electrical conduction properties. A review of electrical and thermal conduction of the structures will be discussed. The research requires analytical analysis as well as simulation. The major thrust of this study is the usage of the molecular dynamics (MD) simulator, LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). A significant investigation using the LAMMPS code is conducted on the existing Beowulf Computing Cluster at BSU. NanoHUB, an open online resource to the entire nanotechnology community developed by the researchers of Purdue University, is used for further supplementary resources. Results will include the time-dependence of temperature, kinetic energy, potential energy, heat flux correlation, and heat conduction.

  7. Dynamical thermal conductivity of the spin Lieb lattice

    Science.gov (United States)

    Yarmohammadi, Mohsen

    2016-05-01

    In the ferromagnetic insulator with the Dzyaloshinskii-Moriya interaction (DMI), we have theoretically investigated the dynamical thermal conductivity (DTC). In other words, we have investigated the frequency dependence of thermal conductivity, κ, of the Lieb lattice, a face-centered square lattice, subjected to a time dependence temperature gradient. Using linear response theory and Green's function approach, DTC has been obtained in the context of Heisenberg Hamiltonian. At low frequencies, DTC is found to be monotonically increasing with DMI strength (DMIS), temperature and next-nearest-neighbor (NNN) coupling. Also we have found that DTC includes a peak for different values of temperature, DMIS and NNN coupling. Furthermore we study the temperature dependence of thermal conductivity of Lieb lattice for different values of DMIS, NNN coupling and external magnetic filed. We witness a decrease in DTC with temperature due to the quantum effects in the system.

  8. Thermal models of electric machines with dynamic workloads

    Directory of Open Access Journals (Sweden)

    Christian Pohlandt

    2015-07-01

    Full Text Available Electric powertrains are increasingly used in off-highway machines because of easy controllability and excellent overall efficiency. The main goals are increasing the energy efficiency of the machine and the optimization of the work process. The thermal behaviour of electric machines with dynamic workloads applied to is a key design factor for electric powertrains in off-highway machines. This article introduces a methodology to model the thermal behaviour of electric machines. Using a noncausal modelling approach, an electric powertrain is analysed for dynamic workloads. Cause-effect relationships and reasons for increasing temperature are considered as well as various cooling techniques. The validation of the overall simulation model of the powertrain with measured field data workloads provides convincing results to evaluate numerous applications of electric machines in off-highway machines.

  9. Thermal characterization of nanoscale phononic crystals using supercell lattice dynamics

    Science.gov (United States)

    Davis, Bruce L.; Hussein, Mahmoud I.

    2011-12-01

    The concept of a phononic crystal can in principle be realized at the nanoscale whenever the conditions for coherent phonon transport exist. Under such conditions, the dispersion characteristics of both the constitutive material lattice (defined by a primitive cell) and the phononic crystal lattice (defined by a supercell) contribute to the value of the thermal conductivity. It is therefore necessary in this emerging class of phononic materials to treat the lattice dynamics at both periodicity levels. Here we demonstrate the utility of using supercell lattice dynamics to investigate the thermal transport behavior of three-dimensional nanoscale phononic crystals formed from silicon and cubic voids of vacuum. The periodicity of the voids follows a simple cubic arrangement with a lattice constant that is around an order of magnitude larger than that of the bulk crystalline silicon primitive cell. We consider an atomic-scale supercell which incorporates all the details of the silicon atomic locations and the void geometry. For this supercell, we compute the phonon band structure and subsequently predict the thermal conductivity following the Callaway-Holland model. Our findings dictate that for an analysis based on supercell lattice dynamics to be representative of the properties of the underlying lattice model, a minimum supercell size is needed along with a minimum wave vector sampling resolution. Below these minimum values, a thermal conductivity prediction of a bulk material based on a supercell will not adequately recover the value obtained based on a primitive cell. Furthermore, our results show that for the relatively small voids and void spacings we consider (where boundary scattering is dominant), dispersion at the phononic crystal unit cell level plays a noticeable role in determining the thermal conductivity.

  10. Thermal characterization of nanoscale phononic crystals using supercell lattice dynamics

    Directory of Open Access Journals (Sweden)

    Bruce L. Davis

    2011-12-01

    Full Text Available The concept of a phononic crystal can in principle be realized at the nanoscale whenever the conditions for coherent phonon transport exist. Under such conditions, the dispersion characteristics of both the constitutive material lattice (defined by a primitive cell and the phononic crystal lattice (defined by a supercell contribute to the value of the thermal conductivity. It is therefore necessary in this emerging class of phononic materials to treat the lattice dynamics at both periodicity levels. Here we demonstrate the utility of using supercell lattice dynamics to investigate the thermal transport behavior of three-dimensional nanoscale phononic crystals formed from silicon and cubic voids of vacuum. The periodicity of the voids follows a simple cubic arrangement with a lattice constant that is around an order of magnitude larger than that of the bulk crystalline silicon primitive cell. We consider an atomic-scale supercell which incorporates all the details of the silicon atomic locations and the void geometry. For this supercell, we compute the phonon band structure and subsequently predict the thermal conductivity following the Callaway-Holland model. Our findings dictate that for an analysis based on supercell lattice dynamics to be representative of the properties of the underlying lattice model, a minimum supercell size is needed along with a minimum wave vector sampling resolution. Below these minimum values, a thermal conductivity prediction of a bulk material based on a supercell will not adequately recover the value obtained based on a primitive cell. Furthermore, our results show that for the relatively small voids and void spacings we consider (where boundary scattering is dominant, dispersion at the phononic crystal unit cell level plays a noticeable role in determining the thermal conductivity.

  11. Thermal Performance Testing of EMU and CSAFE Liquid Cooling Garments

    Science.gov (United States)

    Rhodes, Richard; Bue, Grant; Hakam, Mark; Radford, Tamara

    2013-01-01

    Future exploration missions require the development of a new liquid cooling garment (LCG) that offers greater system reliability, is more comfortable, and maximizes thermal performance. To inform the development of a future LCG a thermal performance test was conducted to evaluate three factors: (1) the effect of the thermal comfort undergarment (TCU) on tactile and thermal comfort, (2) the comparable thermal performance of an CSAFE developed engineering evaluation unit (EEU) LCG, which uses a commercial-off-the-shelf (COTS) wicking garment as the base, and (3) the performance of a torso or upper body only LCG configuration to evaluate a proposed auxiliary loop configuration. To evaluate the thermal performance of each configuration a metabolic suit test was conducted, utilizing suited subjects to generate metabolic heat by walking on a treadmill at various speeds. Three (3) test subjects of similar height and weight produced a metabolic load for five tests by either resting (300-600 BTU/hr), walking at a slow pace (1200 BTU/hr), and walking at a brisk pace (2200 BTU/hr). During the test, data was collected that would allow us to track the heat transfer to the LCG and ventilation system to determine the thermal performance of the LCG configurations. Four different test configurations were tested, with one configuration tested twice. The test results show that the CSAFE EEU LCG and EMU LCG had comparable performance. The testing also showed that an auxiliary loop LCG, sized similarly to the shirt-only configuration, should provide adequate cooling for contingency scenarios. Finally, the testing showed the previous analysis that assumed a UA deterioration from the TCU was too conservative and the TCU may prove to be acceptable for future development with additional analysis and testing.

  12. Micronutrient dynamics after thermal pretreatment of olive mill solid waste.

    Science.gov (United States)

    Almansa, Ana R; Rodriguez-Galan, Monica; Borja, Rafael; Fermoso, Fernando G

    2015-09-01

    This study investigated metal dynamics, and their bioavailability, before and after thermal pretreatment of olive mill solid waste (OMSW), using a sequential metal extraction scheme. The 11.5% increase of cobalt in the most available fraction after the pretreatment coupled to the increase of methane production rate have been a good indicator that the OMSW anaerobic digestion might be metal limited due to the lack of cobalt.

  13. Charismatic leadership, environmental dynamism, and performance

    OpenAIRE

    Hoogh,, Kees de; Hartog, den, H.; Koopman, Paul L.; Thierry, Henk; Berg, van den, G.J.; Weide, van der, R.Y.; Celeste P M Wilderom

    2004-01-01

    Most studies relating charismatic leadership to performance have limitations concerning selection of criterion measures and investigation of moderators. Therefore, this study examines relationships between charismatic leadership and multiple performance outcomes under different levels of environmental dynamism (i.e., level of environmental uncertainty, degree of technological change) and per type of Chief Executive Officer (firm owner versus managing director). Results revealed that charismat...

  14. Inflationary quasiparticle creation and thermalization dynamics in coupled Bose-Einstein condensates

    CERN Document Server

    Posazhennikova, Anna; Kroha, Johann

    2016-01-01

    A Bose gas in a double-well potential, exhibiting a true Bose-Einstein condensate (BEC) amplitude and initially performing Josephson oscillations, is a prototype of an isolated, non-equilibrium many-body system. We investigate the quasiparticle (QP) creation and thermalization dynamics of this system by solving the time-dependent Keldysh-Bogoliubov equations. We find avalanche-like QP creation due to a parametric resonance between BEC and QP oscillations, followed by slow, exponential relaxation to a thermal state at an elevated temperature, controlled by the initial excitation energy of the oscillating BEC above its ground state. The crossover between the two regimes occurs because of an effective decoupling of the QP and BEC oscillations. This dynamics is analogous to elementary particle creation in models of the early universe. The thermalization in our set-up occurs because the BEC acts as a grand canonical reservoir for the quasiparticle system.

  15. High Performance Flat Plate Solar Thermal Collector Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Rockenbaugh, Caleb [National Renewable Energy Lab. (NREL), Golden, CO (United States); Dean, Jesse [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lovullo, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lisell, Lars [National Renewable Energy Lab. (NREL), Golden, CO (United States); Barker, Greg [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hanckock, Ed [National Renewable Energy Lab. (NREL), Golden, CO (United States); Norton, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-09-01

    This report was prepared for the General Services Administration by the National Renewable Energy Laboratory. The Honeycomb Solar Thermal Collector (HSTC) is a flat plate solar thermal collector that shows promising high efficiencies over a wide range of climate zones. The technical objectives of this study are to: 1) verify collector performance, 2) compare that performance to other market-available collectors, 3) verify overheat protection, and 4) analyze the economic performance of the HSTC both at the demonstration sites and across a matrix of climate zones and utility markets.

  16. Thermal performance of a passive solar office building in Portugal

    OpenAIRE

    Gonçalves, Helder; Silva, António Rocha e; Rodrigues, Carlos

    2008-01-01

    This paper presents the thermal performance of a Passive Solar Office Building in Portugal in winter and summer 2006 and 2007. This Building, called Solar XXI, pretends to be an example of passive design both for heating and cooling. It contains a direct gain system assisted by a solar thermal system for winter conditions. In summer a ground cooling system (buried pipes) is used to cool the building, together with night cooling strategies. It also integrate in the vertical south envelope a Ph...

  17. Marine Aerosol Properties and Thermal Imager Performance (MAPTIP): Synopsis

    NARCIS (Netherlands)

    Leeuw, G. de; Eijk, A.M.J. van; Jensen, D.R.

    1996-01-01

    The MAPTIP (Marine Aerosol Properties and Thermal Imager Performance) experiment was organised as part of a project to assess atmospheric effects on the performance of electro-optical sensor systems in coastal areas. The main issue was the detection and identification of targets. The experiment took

  18. Marine Aerosol Properties and Thermal Imager Performance (MAPTIP): Synopsis

    NARCIS (Netherlands)

    Leeuw, G. de; Eijk, A.M.J. van; Jensen, D.R.

    1996-01-01

    The MAPTIP (Marine Aerosol Properties and Thermal Imager Performance) experiment was organised as part of a project to assess atmospheric effects on the performance of electro-optical sensor systems in coastal areas. The main issue was the detection and identification of targets. The experiment took

  19. Thermal performance trade-offs for point focusing solar collectors

    Science.gov (United States)

    Wen, L.

    1978-01-01

    Solar thermal conversion performance is assessed in this paper for representative point focusing distributed systems. Trade-off comparisons are made in terms of concentrator quality, solar receiver operating temperature, and power conversion efficiency. Normalized system performance is presented on a unit concentrator area basis for integrated annual electric energy production.

  20. Thermal Performance of the Storage Brick Containing Microencapsulated PCM

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Gyu

    1998-02-15

    The utilization of microencapsulated phase change materials(PCMs) provides several advantages over conventional PCM application. The heat storage system, as well as heat recovery system, can be built to a smaller size than the normal systems for a given thermal cycling capacity. This microencapsulated PCM technique has not yet been commercialized, however. In this work sodium acetate trihydrate(CH{sub 3}COONa {center_dot} 3H{sub 2}O) was selected for the PCM and was encapsulated. This microencapsulated PCM was mixed with cement mortar for utilization as a floor heating system. In this experiment performed here the main purpose was to investigate the thermal performance of a storage brick with microencapsulated PCM concentration. The thermal performance of this storage brick is dependent on PCM concentration, flow rate and cooling temperature of the heat transfer fluid, etc. The results showed that cycle time was shortened as the PCM content was increased and as the mass flow rate was increased. The same effect was obtained when the cooling temperature was decreased. For each thermal storage brick the overall heat transfer coefficient(U-value) was constant for a 0% brick, but was increased with time for the bricks containing microencapsulated PCM. For the same mass flow rate, as the cooling temperature decreased, the amount of heat withdrawn increased, and in particular a critical cooling temperature was found for each thermal storage brick. The average effectiveness of each thermal storage brick was found to be approximately 48%, 51% and 58% respectively.

  1. Thermal Imaging Performance of TIR Onboard the Hayabusa2 Spacecraft

    Science.gov (United States)

    Arai, Takehiko; Nakamura, Tomoki; Tanaka, Satoshi; Demura, Hirohide; Ogawa, Yoshiko; Sakatani, Naoya; Horikawa, Yamato; Senshu, Hiroki; Fukuhara, Tetsuya; Okada, Tatsuaki

    2017-07-01

    The thermal infrared imager (TIR) is a thermal infrared camera onboard the Hayabusa2 spacecraft. TIR will perform thermography of a C-type asteroid, 162173 Ryugu (1999 JU3), and estimate its surface physical properties, such as surface thermal emissivity ɛ , surface roughness, and thermal inertia Γ, through remote in-situ observations in 2018 and 2019. In prelaunch tests of TIR, detector calibrations and evaluations, along with imaging demonstrations, were performed. The present paper introduces the experimental results of a prelaunch test conducted using a large-aperture collimator in conjunction with TIR under atmospheric conditions. A blackbody source, controlled at constant temperature, was measured using TIR in order to construct a calibration curve for obtaining temperatures from observed digital data. As a known thermal emissivity target, a sandblasted black almite plate warmed from the back using a flexible heater was measured by TIR in order to evaluate the accuracy of the calibration curve. As an analog target of a C-type asteroid, carbonaceous chondrites (50 mm × 2 mm in thickness) were also warmed from the back and measured using TIR in order to clarify the imaging performance of TIR. The calibration curve, which was fitted by a specific model of the Planck function, allowed for conversion to the target temperature within an error of 1°C (3σ standard deviation) for the temperature range of 30 to 100°C. The observed temperature of the black almite plate was consistent with the temperature measured using K-type thermocouples, within the accuracy of temperature conversion using the calibration curve when the temperature variation exhibited a random error of 0.3 °C (1σ ) for each pixel at a target temperature of 50°C. TIR can resolve the fine surface structure of meteorites, including cracks and pits with the specified field of view of 0.051°C (328 × 248 pixels). There were spatial distributions with a temperature variation of 3°C at the setting

  2. Thermal Imaging Performance of TIR Onboard the Hayabusa2 Spacecraft

    Science.gov (United States)

    Arai, Takehiko; Nakamura, Tomoki; Tanaka, Satoshi; Demura, Hirohide; Ogawa, Yoshiko; Sakatani, Naoya; Horikawa, Yamato; Senshu, Hiroki; Fukuhara, Tetsuya; Okada, Tatsuaki

    2017-03-01

    The thermal infrared imager (TIR) is a thermal infrared camera onboard the Hayabusa2 spacecraft. TIR will perform thermography of a C-type asteroid, 162173 Ryugu (1999 JU3), and estimate its surface physical properties, such as surface thermal emissivity ɛ , surface roughness, and thermal inertia Γ, through remote in-situ observations in 2018 and 2019. In prelaunch tests of TIR, detector calibrations and evaluations, along with imaging demonstrations, were performed. The present paper introduces the experimental results of a prelaunch test conducted using a large-aperture collimator in conjunction with TIR under atmospheric conditions. A blackbody source, controlled at constant temperature, was measured using TIR in order to construct a calibration curve for obtaining temperatures from observed digital data. As a known thermal emissivity target, a sandblasted black almite plate warmed from the back using a flexible heater was measured by TIR in order to evaluate the accuracy of the calibration curve. As an analog target of a C-type asteroid, carbonaceous chondrites ( 50 mm × 2 mm in thickness) were also warmed from the back and measured using TIR in order to clarify the imaging performance of TIR. The calibration curve, which was fitted by a specific model of the Planck function, allowed for conversion to the target temperature within an error of 1 ∘C ( 3σ standard deviation) for the temperature range of 30 to 100 ∘C. The observed temperature of the black almite plate was consistent with the temperature measured using K-type thermocouples, within the accuracy of temperature conversion using the calibration curve when the temperature variation exhibited a random error of 0.3 ∘C ( 1σ ) for each pixel at a target temperature of 50 ∘C. TIR can resolve the fine surface structure of meteorites, including cracks and pits with the specified field of view of 0.051∘ ( 328 × 248 pixels). There were spatial distributions with a temperature variation of 3

  3. Passive thermal performance increase in cisterns

    Directory of Open Access Journals (Sweden)

    Najmeh Najafi, Arash Alipour, Seyed Mohamad Ali Najafi

    2014-01-01

    Full Text Available Cisterns are ancient building having two main tasks. First task is storing water in raining seasons for using in dry seasons and the second task is decreasing water temperature, which happens because of the air flow above water surface and evaporating water. It can be stated that by increasing fluid flow above the surface, evaporating increase so increasing in heat transfer happens and decreasing of water temperature is the result. This paper has investigated fluid flow around and inside cisterns with FLUENT software results. Increasing in air flow demand to the cistern is the primary purpose of this study, by changing main parameters of cistern geometry like increasing or decreasing of doom hale diameter, inlet and outlet of wind catcher, elevation of wind catcher and also wind speed. This study introduces the best geometry for cisterns according to maximum air flow demand and minimum volume. Considering that, there is a direct relation between heat transfer and airflow rate in cisterns, so in this study, the influence of mentioned parameters are investigated to reach optimum design for the best performance of cisterns.

  4. Thermal resistances of air in cavity walls and their effect upon the thermal insulation performance

    Energy Technology Data Exchange (ETDEWEB)

    Bekkouche, S.M.A.; Cherier, M.K.; Hamdani, M.; Benamrane, N. [Application of Renewable Energies in Arid and Semi Arid Environments /Applied Research Unit on Renewable Energies/ EPST Development Center of Renewable Energies, URAER and B.P. 88, ZI, Gart Taam Ghardaia (Algeria); Benouaz, T. [University of Tlemcen, BP. 119, Tlemcen R.p. 13000 (Algeria); Yaiche, M.R. [Development Center of Renewable Energies, CDER and B.P 62, 16340, Route de l' Observatoire, Bouzareah, Algiers (Algeria)

    2013-07-01

    The optimum thickness in cavity walls in buildings is determined under steady conditions; the heat transfer has been calculated according to ISO 15099:2003. Two forms of masonry units are investigated to conclude the advantage of high thermal emissivity. The paper presents also some results from a study of the thermal insulation performance of air cavities bounded by thin reflective material layer 'eta = 0.05'. The results show that the most economical cavity configuration depends on the thermal emissivity and the insulation material used.

  5. Thermal resistances of air in cavity walls and their effect upon the thermal insulation performance

    Directory of Open Access Journals (Sweden)

    S. M. A. Bekkouche, T. Benouaz, M. K. Cherier, M. Hamdani, M.R. Yaiche, N. Benamrane

    2013-01-01

    Full Text Available The optimum thickness in cavity walls in buildings is determined under steady conditions; the heat transfer has been calculated according to ISO 15099:2003. Two forms of masonry units are investigated to conclude the advantage of high thermal emissivity. The paper presents also some results from a study of the thermal insulation performance of air cavities bounded by thin reflective material layer "ε = 0.05". The results show that the most economical cavity configuration depends on the thermal emissivity and the insulation material used.

  6. Aeolian system dynamics derived from thermal infrared data

    Science.gov (United States)

    Scheidt, Stephen Paul

    Thermal infrared (TIR) remote-sensing and field-based observations were used to study aeolian systems, specifically sand transport pathways, dust emission sources and Saharan atmospheric dust. A method was developed for generating seamless and radiometrically accurate mosaics of thermal infrared data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. Using a combination of high resolution thermal emission spectroscopy results of sand samples and mosaic satellite data, surface emissivity was derived to map surface composition, which led to improvement in the understanding of sand accumulation in the Gran Desierto of northern Sonora, Mexico. These methods were also used to map sand transport pathways in the Sahara Desert, where the interaction between sand saltation and dust emission sources was explored. The characteristics and dynamics of dust sources were studied at White Sands, NM and in the Sahara Desert. At White Sands, an application was developed for studying the response of dust sources to surface soil moisture based on the relationship between soil moisture, apparent thermal inertia and the erosion potential of dust sources. The dynamics of dust sources and the interaction with sand transport pathways were also studied, focusing on the Bodele Depression of Chad and large dust sources in Mali and Mauritania. A dust detection algorithm was developed using ASTER data, and the spectral emissivity of observed atmospheric dust was related to the dust source area in the Sahara. At the Atmospheric Observatory (IZO) in Tenerife, Spain where direct measurement of the Saharan Air Layer could be made, the cycle of dust events occurring in July 2009 were examined. From the observation tower at the IZO, measurements of emitted longwave atmospheric radiance in the TIR wavelength region were made using a Forward Looking Infrared Radiometer (FLIR) handheld camera. The use of the FLIR to study atmospheric dust from the Saharan is a

  7. Thermal Performance Testing of EMU and OSS Liquid Cooling Garments

    Science.gov (United States)

    Rhodes, Richard; Bue, Grant; Hakam, Mary

    2012-01-01

    A test was conducted to evaluate three factors influencing the thermal performance of liquid cooling garments (LCG): (1) the comparable thermal performance of an Oceaneering developed engineering evaluation unit (EEU) prototype LDG, (2) the effect of the thermal comfort undergarment (TCU), and (3) the performance of a torso or upper body only LCG configuration. To evaluate the thermal performance of each configuration a metabolic test was conducted, utilizing suited subjects to generate the metabolic heat. For this study three (3) test subjects of similar health and weight produced a metabolic load on the LDG configuration by either resting (300-600 BTU/hr), walking at a slow pace (1200 BRU/hr), and walking at a brisk pace (2200 BTU/hr), as outlined in Figure 1, the metabolic profile. During the test, oxygen consumption, heart rate, relative humidity, air flow, inlet and outlet air pressure, inlet and outlet air temperature, delta air temperature, water flow (100 lb/hr), inlet water temperature (64 F), delta water temperature, water pressure, core body temperature, skin temperature, and sweat loss data was recorded. Four different test configurations were tested, with one configuration tested twice, as outlined in Table 1. The test was conducted with the suit subjects wearing the Demonstrator Suit, pressurized to vent pressure (approximately 0.5 psig). The demonstrator suit has an integrated ventilation duct system and was used to create a relevant environment with a captured ventilation return, an integrated vent tree, and thermal insulation from the environment.

  8. Performance Analysis of Thermal Energy System with Linear System Method

    Institute of Scientific and Technical Information of China (English)

    Liping LI; Chunfa ZHANG

    2007-01-01

    The paper addresses the system performance of coal-fired power unit with changed auxiliary system or other local heat disturbance. The idea of state space model is imported and the universal formula for the calculation of system performance output is deduced on the system state equation. Two important vector of system are worked out under linear system assumption and transform. The transfer matrix is the characteristics of system itself and is constant for a similar condition, which greatly facilitates the analysis. The concept of thermal disturbance vector is proposed to construct the thermal disturbance input easily. The method can be helpful for analyzing any thermal disturbance input satisfying the assumption and also for supplementing the correction means of performance test. An example of 600MW power unit is presented to demonstrate its availability.

  9. Thermal, dynamic mechanical, and dielectric analyses of some polyurethane biocomposites.

    Science.gov (United States)

    Macocinschi, Doina; Filip, Daniela; Vlad, Stelian; Cristea, Mariana; Musteata, Valentina; Ibanescu, Sorin

    2012-08-01

    Polymer biocomposites based on segmented poly(ester urethane) and extracellular matrix components have been prepared for the development of tissue engineering applications with improved biological characteristics of the materials in contact with blood and tissues for long periods. Thermal, dynamical, and dielectrical analyses were employed to study the molecular dynamics of these materials and the influence of changing the physical network morphology and hydrogen bond interactions accompanied by phase transitions, interfacial effects, and polarization or conductivity. All phenomena that concur in the tested materials are evaluated by cross-examination of the dynamic mechanical characteristic properties (storage modulus, loss modulus, and loss factor) and dielectric properties (relative permittivity, relative loss factor, and loss tangent) as a function of temperature. Comparative aspects were elucidated by calculating the apparent activation energies of multiplex experiments.

  10. Thermal Performance Characterization using Time Series Data - IEA EBC Annex 58 Guidelines

    DEFF Research Database (Denmark)

    Madsen, Henrik; Bacher, Peder; Bauwens, Geert;

    This document presents guidelines for using time series analysis methods, models and tools for estimating the thermal performance of buildings and building components. The thermal performance is measured as estimated parameters of a model, or parameters derived from estimated parameters of a model....... A special focus will be on estimating the Heat Loss Coefficient (HLC) and gA-value. Provided in the guidelines are modelling procedures with which consistent results for estimation of energy performance of buildings and building components can be achieved. These guidelines start with simple (non......-dynamical) steady state models where the parameters are found using classical methods for linear regression. Such steady state techniques provide sub-optimal use of the information embedded in the data and provides information only about the HLC and gA-values. Next the guidelines consider dynamical models. Firstly...

  11. Portable Life Support Subsystem Thermal Hydraulic Performance Analysis

    Science.gov (United States)

    Barnes, Bruce; Pinckney, John; Conger, Bruce

    2010-01-01

    This paper presents the current state of the thermal hydraulic modeling efforts being conducted for the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS). The goal of these efforts is to provide realistic simulations of the PLSS under various modes of operation. The PLSS thermal hydraulic model simulates the thermal, pressure, flow characteristics, and human thermal comfort related to the PLSS performance. This paper presents modeling approaches and assumptions as well as component model descriptions. Results from the models are presented that show PLSS operations at steady-state and transient conditions. Finally, conclusions and recommendations are offered that summarize results, identify PLSS design weaknesses uncovered during review of the analysis results, and propose areas for improvement to increase model fidelity and accuracy.

  12. Feasibility and Performance of the Microwave Thermal Rocket Launcher

    Science.gov (United States)

    Parkin, Kevin L. G.; Culick, Fred E. C.

    2004-03-01

    Beamed-energy launch concepts employing a microwave thermal thruster are feasible in principle, and microwave sources of sufficient power to launch tons into LEO already exist. Microwave thermal thrusters operate on an analogous principle to nuclear thermal thrusters, which have experimentally demonstrated specific impulses exceeding 850 seconds. Assuming such performance, simple application of the rocket equation suggests that payload fractions of 10% are possible for a single stage to orbit (SSTO) microwave thermal rocket. We present an SSTO concept employing a scaled X-33 aeroshell. The flat aeroshell underside is covered by a thin-layer microwave absorbent heat-exchanger that forms part of the thruster. During ascent, the heat-exchanger faces the microwave beam. A simple ascent trajectory analysis incorporating X-33 aerodynamic data predicts a 10% payload fraction for a 1 ton craft of this type. In contrast, the Saturn V had 3 non-reusable stages and achieved a payload fraction of 4%.

  13. Residential building thermal performance energy efficiency in Yangtze River basin

    Institute of Scientific and Technical Information of China (English)

    王厚华; 庄燕燕; 吴伟伟

    2009-01-01

    Using energy consumption software VisualDOE4.0,simulation was carried out on the energy consumption of a typical residential building in Yangtze River basin,with a focus on thermal performance of envelope each component and application of total heating recovery equipment. The effects of thermal performance of building envelope each component on energy efficiency ratio were analyzed. Comprehensive measures schemes of energy saving were designed by the orthogonal experiment. The energy efficiency ratios of different envelopes combination schemes were gained. Finally,the optimize combination scheme was confirmed. With the measurement dates,the correctness of the simulation dates was completely verified.

  14. Duct thermal performance models for large commercial buildings

    Energy Technology Data Exchange (ETDEWEB)

    Wray, Craig P.

    2003-10-01

    Despite the potential for significant energy savings by reducing duct leakage or other thermal losses from duct systems in large commercial buildings, California Title 24 has no provisions to credit energy-efficient duct systems in these buildings. A substantial reason is the lack of readily available simulation tools to demonstrate the energy-saving benefits associated with efficient duct systems in large commercial buildings. The overall goal of the Efficient Distribution Systems (EDS) project within the PIER High Performance Commercial Building Systems Program is to bridge the gaps in current duct thermal performance modeling capabilities, and to expand our understanding of duct thermal performance in California large commercial buildings. As steps toward this goal, our strategy in the EDS project involves two parts: (1) developing a whole-building energy simulation approach for analyzing duct thermal performance in large commercial buildings, and (2) using the tool to identify the energy impacts of duct leakage in California large commercial buildings, in support of future recommendations to address duct performance in the Title 24 Energy Efficiency Standards for Nonresidential Buildings. The specific technical objectives for the EDS project were to: (1) Identify a near-term whole-building energy simulation approach that can be used in the impacts analysis task of this project (see Objective 3), with little or no modification. A secondary objective is to recommend how to proceed with long-term development of an improved compliance tool for Title 24 that addresses duct thermal performance. (2) Develop an Alternative Calculation Method (ACM) change proposal to include a new metric for thermal distribution system efficiency in the reporting requirements for the 2005 Title 24 Standards. The metric will facilitate future comparisons of different system types using a common ''yardstick''. (3) Using the selected near-term simulation approach

  15. Thermal performance modeling of NASA s scientific balloons

    Science.gov (United States)

    Franco, H.; Cathey, H.

    The flight performance of a scientific balloon is highly dependant on the interaction between the balloon and its environment. The balloon is a thermal vehicle. Modeling a scientific balloon's thermal performance has proven to be a difficult analytical task. Most previous thermal models have attempted these analyses by using either a bulk thermal model approach, or by simplified representations of the balloon. These approaches to date have provided reasonable, but not very accurate results. Improvements have been made in recent years using thermal analysis tools developed for the thermal modeling of spacecraft and other sophisticated heat transfer problems. These tools, which now allow for accurate modeling of highly transmissive materials, have been applied to the thermal analysis of NASA's scientific balloons. A research effort has been started that utilizes the "Thermal Desktop" addition to AUTO CAD. This paper will discuss the development of thermal models for both conventional and Ultra Long Duration super-pressure balloons. This research effort has focused on incremental analysis stages of development to assess the accuracy of the tool and the required model resolution to produce usable data. The first stage balloon thermal analyses started with simple spherical balloon models with a limited number of nodes, and expanded the number of nodes to determine required model resolution. These models were then modified to include additional details such as load tapes. The second stage analyses looked at natural shaped Zero Pressure balloons. Load tapes were then added to these shapes, again with the goal of determining the required modeling accuracy by varying the number of gores. The third stage, following the same steps as the Zero Pressure balloon efforts, was directed at modeling super-pressure pumpkin shaped balloons. The results were then used to develop analysis guidelines and an approach for modeling balloons for both simple first order estimates and detailed

  16. Performance of thermal conductivity probes for planetary applications

    Directory of Open Access Journals (Sweden)

    E. S. Hütter

    2012-01-01

    Full Text Available This work aims to contribute to the development of in situ instruments feasible for space application. Commercial as well as custom made thermal sensors, based on the transient hot wire technique and suitable for direct measurement of the effective thermal conductivity of granular media, were tested for application under airless conditions. The investigated media range from compact specimen of well known thermal conductivity used for calibration of the sensors to various granular planetary analogue materials of different shape and grain size. Measurements were performed under gas pressures ranging from 103 hPa down to about 10−5 hPa. It was found that for the inspected granular materials the given pressure decrease results in a decrease of the thermal conductivity by about two orders of magnitude. In order to check the ability of custom-made sensors to measure the thermal conductivity of planetary surface layers, detailed numerical simulations predicting the response of the different sensors have also been performed. Both, measurements and simulations, revealed that for investigations under high vacuum conditions (as they prevail e.g. on the lunar surface the derived thermal conductivity values can significantly depend on the sensor geometry, the axial heat flow and the thermal contact between probe and surrounding material. Therefore in these cases a careful calibration of each particular sensor is necessary in order to obtain reliable thermal conductivity measurements. The custom-made sensors presented in this work can serve as prototypes for payload to be flown on future planetary lander missions, in particular for airless bodies like the Moon, asteroids and comets, but also for Mars.

  17. Air Dispersion Characteristics and Thermal Comparison of Traditional and Fabric Ductwork using Computational Fluid Dynamics

    Science.gov (United States)

    Andreopoulou, Areti

    This thesis research compares the air dispersion and thermal comfort characteristics of conventional diffuser and fabric-based ductwork systems. Heating, ventilation, and air-conditioning (HVAC) systems in buildings produce and regulate airflow traveling through ductwork. The performance characteristics of conventional ductwork are compared with recent advancements in fabric-based ductwork. Using computational fluid dynamics (CFD) analysis, thermal and air distribution flow patterns are compared between the two types of ductwork and preliminary thermal comfort and efficiency conclusions are drawn. Results of the Air Distribution Performance Index (ADPI) for both ducting systems reflect that, under the given test conditions, the fabric duct system is approximately 23% more comfortable than the traditional diffuser system in terms of air speed flow uniformity into the space, while staying within the Effective Draft Temperature comfort zone of -3 to +2°F.

  18. Effect of point defects on the thermal conductivity of UO2: molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Andersson, Anders David Ragnar [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-07-21

    The thermal conductivity of uranium dioxide (UO2) fuel is an important materials property that affects fuel performance since it is a key parameter determining the temperature distribution in the fuel, thus governing, e.g., dimensional changes due to thermal expansion, fission gas release rates, etc. [1] The thermal conductivity of UO2 nuclear fuel is also affected by fission gas, fission products, defects, and microstructural features such as grain boundaries. Here, molecular dynamics (MD) simulations are carried out to determine quantitatively, the effect of irradiation induced point defects on the thermal conductivity of UO2, as a function of defect concentrations, for a range of temperatures, 300 – 1500 K. The results will be used to develop enhanced continuum thermal conductivity models for MARMOT and BISON by INL. These models express the thermal conductivity as a function of microstructure state-variables, thus enabling thermal conductivity models with closer connection to the physical state of the fuel [2].

  19. Dynamic Performance Tuning Supported by Program Specification

    Directory of Open Access Journals (Sweden)

    Eduardo César

    2002-01-01

    Full Text Available Performance analysis and tuning of parallel/distributed applications are very difficult tasks for non-expert programmers. It is necessary to provide tools that automatically carry out these tasks. These can be static tools that carry out the analysis on a post-mortem phase or can tune the application on the fly. Both kind of tools have their target applications. Static automatic analysis tools are suitable for stable application while dynamic tuning tools are more appropriate to applications with dynamic behaviour. In this paper, we describe KappaPi as an example of a static automatic performance analysis tool, and also a general environment based on parallel patterns for developing and dynamically tuning parallel/distributed applications.

  20. Heating performance investigation of a bidirectional partition fluid thermal diode

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Xiande; Xia, Lulu [Institute of Air Conditioning and Refrigeration, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, Jiangsu Province 210016 (China)

    2010-03-15

    A novel thermal diode, bidirectional partition fluid thermal diode (BPFTD) that is fabricated by integrating a thermal insulation partition and a movable control blade into a water tank, is proposed. The bidirectional configuration allows the BPFTD to serve both passive solar heating in winter and passive cooling in summer. BPFTD heating performances are tested with two side-by-side hot boxes and compared experimentally with a water-wall having optimum thickness. Two stages of experiments are conducted. The first stage is to investigate an appropriate position of BPFTD partition, and the second compares the BPFTD with the water-wall. The test results show that the BPFTD has much better heating performances than the water-wall. Analysis indicates that the BPFTD may increase heat supply by around 140% when a single glazing cover without night insulation is used and by around 70% in case of using a double glazing cover without night insulation. (author)

  1. Thermal dynamics on the lattice with exponentially improved accuracy

    CERN Document Server

    Pawlowski, Jan

    2016-01-01

    We present a novel simulation prescription for thermal quantum fields on a lattice that operates directly in imaginary frequency space. By distinguishing initial conditions from quantum dynamics it provides access to correlation functions also outside of the conventional Matsubara frequencies $\\omega_n=2\\pi n T$. In particular it resolves their frequency dependence between $\\omega=0$ and $\\omega_1=2\\pi T$, where the thermal physics $\\omega\\sim T$ of e.g.~transport phenomena is dominantly encoded. Real-time spectral functions are related to these correlators via an integral transform with rational kernel, so their unfolding is exponentially improved compared to Euclidean simulations. We demonstrate this improvement within a $0+1$-dimensional scalar field theory and show that spectral features inaccessible in standard Euclidean simulations are quantitatively captured.

  2. Thermal decomposition dynamics and severity of microalgae residues in torrefaction.

    Science.gov (United States)

    Chen, Wei-Hsin; Huang, Ming-Yueh; Chang, Jo-Shu; Chen, Chun-Yen

    2014-10-01

    To figure out the torrefaction characteristics and weight loss dynamics of microalgae residues, the thermogravimetric analyses of two microalgae (Chlamydomonas sp. JSC4 and Chlorella sorokiniana CY1) residues are carried out. A parameter of torrefaction severity index (TSI) in the range of 0-1, in terms of weight loss ratio between a certain operation and a reference operation, is defined to indicate the degree of biomass thermal degradation due to torrefaction. The TSI profiles of the two residues are similar to each other; therefore, the parameter may be used to describe the torrefaction extents of various biomass materials. The curvature of TSI profile along light torrefaction is slight, elucidating its slight impact on biomass thermal degradation. The sharp curvature along severe torrefaction in the initial pretreatment period reveals that biomass upgraded with high temperature and short duration is more effective than using low temperature with long duration.

  3. Molecular dynamics simulation of thermal stability of nanocrystalline vanadium

    Institute of Scientific and Technical Information of China (English)

    WEI; Mingzhi; XIAO; Shifang; YUAN; Xiaojian; HU; Wangyu

    2006-01-01

    The microstructure and thermal stability of nanocrystalline vanadium with an average grain size ranging from 2.86 to 7.50 nm are calculated by means of the analytic embedded-atom method and molecular dynamics. The grain boundary and nanocrystalline grain atoms are differentiated by the common neighbor analysis method. The results indicate that the fraction of grain boundary increases with the grain size decreasing, and the mean energy of atoms is higher than that of coarse crystals. The thermal-stable temperatures of nanocrystalline vanadium are determined from the evolution of atomic energy, fraction of grain boundary and radial distribution function. It is shown that the stable temperature decreases obviously with the grain size decreasing. In addition the reasons which cause the grain growth of nanocrystalline vanadium are discussed.

  4. Performance of thermal conductivity probes for planetary applications

    Directory of Open Access Journals (Sweden)

    E. S. Hütter

    2012-05-01

    Full Text Available This work aims to contribute to the development of in situ instruments feasible for space application. Commercial as well as custom-made thermal sensors, based on the transient hot wire technique and suitable for direct measurement of the effective thermal conductivity of granular media, were tested for application under airless conditions. In order to check the ability of custom-made sensors to measure the thermal conductivity of planetary surface layers, detailed numerical simulations predicting the response of the different sensors have been performed. These simulations reveal that for investigations under high vacuum conditions (as they prevail, e.g. on the lunar surface, the derived thermal conductivity values can significantly depend on sensor geometry, axial heat flow, and the thermal contact between probe and surrounding material. Therefore, a careful calibration of each particular sensor is necessary in order to obtain reliable thermal conductivity measurements. The custom-made sensors presented in this work can serve as prototypes for payload to be flown on future planetary lander missions, in particular for airless bodies like the Moon, asteroids and comets, but also for Mars.

  5. Dynamic modelling for a submerged freeze microgripper using thermal networks

    Science.gov (United States)

    López-Walle, Beatriz; Gauthier, Michaël; Chaillet, Nicolas

    2010-02-01

    The growing interest in micromanipulation systems requires efficient, reliable and flexible handling strategies. Recent studies have demonstrated that performing manipulations and assembly in liquid surroundings is more advantageous than in dry conditions, especially when objects are below 100 µm in size. The thermally actuated ice microgripper proposed and analysed in this paper is designed to operate in a completely submerged manner in an aqueous medium. The handling principle benefits from the adhesive properties of ice, its thermal control principle is based on the Peltier effect, some features of the prototype and the first micromanipulation tests are summarized. This paper is focused on the modelling of the thermal microhandling system using an electrical analogy. The submerged microgripper is split into different subsystems which are studied in order to identify their thermal network. Then they are interconnected to build the whole thermal network of the submerged microgripper. This model is validated by comparison with experimental measurements. Controlling the temperatures involved in our device will be the purpose of further works.

  6. Anomalous strain effect on the thermal conductivity of borophene: a reactive molecular dynamics study

    Science.gov (United States)

    Mortazavi, Bohayra; Le, Minh-Quy; Rabczuk, Timon; Pereira, Luiz Felipe C.

    2017-09-01

    Borophene, an atomically thin, corrugated, crystalline two-dimensional boron sheet, has been recently synthesized. Here we investigate mechanical properties and lattice thermal conductivity of borophene using reactive molecular dynamics simulations. We performed uniaxial tensile strain simulations at room temperature along in-plane directions, and found 2D elastic moduli of 188 N m-1 and 403 N m-1 along zigzag and armchair directions, respectively. This anisotropy is attributed to the buckling of the borophene structure along the zigzag direction. We also performed non-equilibrium molecular dynamics to calculate the lattice thermal conductivity. Considering its size-dependence, we predict room-temperature lattice thermal conductivities of 75.9 ± 5.0 W m-1 K-1 and 147 ± 7.3 W m-1 K-1, respectively, and estimate effective phonon mean free paths of 16.7 ± 1.7 nm and 21.4 ± 1.0 nm for the zigzag and armchair directions. In this case, the anisotropy is attributed to differences in the density of states of low-frequency phonons, with lower group velocities and possibly shorten phonon lifetimes along the zigzag direction. We also observe that when borophene is strained along the armchair direction there is a significant increase in thermal conductivity along that direction. Meanwhile, when the sample is strained along the zigzag direction there is a much smaller increase in thermal conductivity along that direction. For a strain of 8% along the armchair direction the thermal conductivity increases by a factor of 3.5 (250%), whereas for the same amount of strain along the zigzag direction the increase is only by a factor of 1.2 (20%). Our predictions are in agreement with recent first principles results, at a fraction of the computational cost. The simulations shall serve as a guide for experiments concerning mechanical and thermal properties of borophene and related 2D materials.

  7. Thermal stability of marks gold nanoparticles: A molecular dynamics simulation

    Science.gov (United States)

    Jia, Yanlin; Li, Siqi; Qi, Weihong; Wang, Mingpu; Li, Zhou; Wang, Zhixing

    2017-03-01

    Molecular dynamics (MDs) simulations were used to explore the thermal stability of Au nanoparticles (NPs) with decahedral, cuboctahedral, icosahedral and Marks NPs. According to the calculated cohesive energy and melting temperature, the Marks NPs have a higher cohesive energy and melting temperature compared to these other shapes. The Lindemann index, radial distribution function, deformation parameters, mean square displacement and self-diffusivity have been used to characterize the structure variation during heating. This work may inspire researchers to prepare Marks NPs and apply them in different fields.

  8. Numerical Investigation of the Thermal Management Performance of MEPCM Modules for PV Applications

    Directory of Open Access Journals (Sweden)

    Chao-Yang Huang

    2013-08-01

    Full Text Available The efficiency of photovoltaic modules decreases as the cell temperature increases. It is necessary to have an adequate thermal management mechanism for a photovoltaic module, especially when combined with a building construction system. This study aims to investigate via computational fluid dynamics simulations the heat transfer characteristics and thermal management performance of microencapsulated phase change material modules for photovoltaic applications under temporal variations of daily solar irradiation. The results show that the aspect ratio of the microencapsulated phase change material layer has significant effects on the heat transfer characteristics and the overall thermal performance of the two cases examined with different melting points (26 °C and 34 °C are approximately the same.

  9. Impact and dynamic mechanical thermal properties of textile silk reinforced epoxy resin composites

    Science.gov (United States)

    Yang, K.; Guan, J.

    2016-07-01

    Silk fabric reinforced epoxy resin composites (SFRPs) were prepared using simple techniques of hand lay-up, hot-press and vacuum treatment, and a series of volume fractions of silk reinforcements were achieved. The impact properties and dynamic mechanical properties of SFRPs were investigated using a pendulum impact testing method and dynamic mechanical thermal analysis (DMTA). The results suggest that silk reinforcement could greatly enhance the mechanical performances of SFRPs. The impact strength reached a maximum of 71 kJ/m2 for 60%-silk SFRP, which demonstrated a potential of silk composites for defence and impact- resistant materials.

  10. Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

    Science.gov (United States)

    Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

    2017-03-01

    The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

  11. Dynamic capabilities, Marketing Capability and Organizational Performance

    Directory of Open Access Journals (Sweden)

    Adriana Roseli Wünsch Takahashi

    2017-01-01

    Full Text Available The goal of the study is to investigate the influence of dynamic capabilities on organizational performance and the role of marketing capabilities as a mediator in this relationship in the context of private HEIs in Brazil. As a research method we carried out a survey with 316 IES and data analysis was operationalized with the technique of structural equation modeling. The results indicate that the dynamic capabilities have influence on organizational performance only when mediated by marketing ability. The marketing capability has an important role in the survival, growth and renewal on educational services offerings for HEIs in private sector, and consequently in organizational performance. It is also demonstrated that mediated relationship is more intense for HEI with up to 3,000 students and other organizational profile variables such as amount of courses, the constitution, the type of institution and type of education do not significantly alter the results.

  12. Dynamic modeling of low thermal gradient evaporators and condensers

    Science.gov (United States)

    Mokhtarzadeh, M.

    1980-12-01

    The transient behavior of different types of heat exchangers proposed for ocean thermal energy conversion (OTEC) is discussed. Models are developed for both shell-tube condensers and evaporators and for two phase flow systems. Two numerical techniques for the simulation of distributed parameter systems which arise in heat exchanger modeling are investigated: classic finite difference methods and the more recent delay dissipation (sometimes called sine photography) approach. Frequency response analysis is used to compare the two simulation methods. The resultant heat exchanger models give the dynamic response of ammonia pressure (output of the model) to changes in ammonia vapor flow rate (input). An OTEC power cycle is molded so that different heat exchangers may be plugged in and their transient behavior analyzed. The dynamic stability of the OTEC power plant for all heat exchangers analyzed in this work (falling film, pool boiling and two phase flow system) is confirmed.

  13. Alternative High Performance Polymers for Ablative Thermal Protection Systems

    Science.gov (United States)

    Boghozian, Tane; Stackpoole, Mairead; Gonzales, Greg

    2015-01-01

    Ablative thermal protection systems are commonly used as protection from the intense heat during re-entry of a space vehicle and have been used successfully on many missions including Stardust and Mars Science Laboratory both of which used PICA - a phenolic based ablator. Historically, phenolic resin has served as the ablative polymer for many TPS systems. However, it has limitations in both processing and properties such as char yield, glass transition temperature and char stability. Therefore alternative high performance polymers are being considered including cyanate ester resin, polyimide, and polybenzoxazine. Thermal and mechanical properties of these resin systems were characterized and compared with phenolic resin.

  14. Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study

    Directory of Open Access Journals (Sweden)

    Xiangfei Kong

    2016-01-01

    Full Text Available This study is focused on the preparation and performance of a building energy storage panel (BESP. The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP, which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM was incorporated into expanded perlite (EP through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC, scanning electron microscope (SEM, best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1 the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2 the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3 in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.

  15. Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study.

    Science.gov (United States)

    Kong, Xiangfei; Zhong, Yuliang; Rong, Xian; Min, Chunhua; Qi, Chengying

    2016-01-25

    This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.

  16. Molecular Dynamics Simulation of Thermal Conductivity in Si-Ge Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    HUANG Xiao-Peng; HUAI Xiu-Lan

    2008-01-01

    @@ Thermal conductivity of nanocomposites is calculated by molecular dynamics (MD) simulation. The effect of size on thermal conductivity of nanowire composites and the temperature profiles are studied. The results indicate that the thermal conductivity of nanowire composites could be much lower than alloy value; the thermal conductivity is slightly dependent on temperature except at very low temperature.

  17. THERMAL AND AERODYNAMIC PERFORMANCES OF THE SUPERSONIC MOTION

    Directory of Open Access Journals (Sweden)

    Dejan P Ninković

    2010-01-01

    Full Text Available Generally speaking, Mach number of 4 can be taken as a boundary value for transition from conditions for supersonic, into the area of hypersonic flow, distinguishing two areas: area of supersonic in which the effects of the aerodynamic heating can be neglected and the area of hypersonic, in which the thermal effects become dominant. This paper presents the effects in static and dynamic areas, as well as presentation of G.R.O.M. software for determination of the values of aerodynamic derivatives, which was developed on the basis of linearized theory of supersonic flow. Validation of developed software was carried out through different types of testing, proving its usefulness for engineering practice in the area of supersonic wing aerodynamic loading calculations, even at high Mach numbers, with dominant thermal effects.

  18. Dynamics and thermal sensitivity of ballistic and non-ballistic feeding in salamanders.

    Science.gov (United States)

    Deban, Stephen M; Scales, Jeffrey A

    2016-02-01

    Low temperature reduces the performance of muscle-powered movements, but in movements powered by elastic recoil mechanisms, this effect can be mitigated and performance can be increased. To better understand the morphological basis of high performance and thermal robustness of elastically powered movements, we compared feeding dynamics at a range of temperatures (5-25°C) in two species of terrestrial plethodontid salamanders, Plethodon metcalfi and Ensatina eschscholtzii, which differ in tongue muscle architecture and the mechanism of tongue projection. We found that Ensatina is capable of ballistic projection with a mean muscle mass-specific power of 2100 W kg(-1), revealing an elastic mechanism. Plethodon, in contrast, projected its tongue non-ballistically with a mean power of only 18 W kg(-1), indicating it is muscle powered. Ensatina projected its tongue significantly farther than Plethodon and with dynamics that had significantly lower thermal sensitivity at temperatures below 15°C. These performance differences were correlated with morphological differences, namely elongated collagenous aponeuroses in the projector muscle of Ensatina as compared with Plethodon, which are likely the site of energy storage, and the absence in Ensatina of projector muscle fibers attaching to the tongue skeleton that allows projection to be truly ballistic. These findings demonstrate that, in these otherwise similar species, the presence in one species of elaborated connective tissue in series with myofibers confers not only 10-fold greater absolute performance but also greater thermal robustness of performance. We conclude that changes in muscle and connective tissue architecture are sufficient to alter significantly the mechanics, performance and thermal robustness of musculoskeletal systems.

  19. Thermal performance of evacuated tube heat pipe solar collector

    Science.gov (United States)

    Putra, Nandy; Kristian, M. R.; David, R.; Haliansyah, K.; Ariantara, Bambang

    2016-06-01

    The high fossil energy consumption not only causes the scarcity of energy but also raises problems of global warming. Increasing needs of fossil fuel could be reduced through the utilization of solar energy by using solar collectors. Indonesia has the abundant potential for solar energy, but non-renewable energy sources still dominate energy consumption. With heat pipe as passive heat transfer device, evacuated tube solar collector is expected to heat up water for industrial and home usage without external power supply needed to circulate water inside the solar collector. This research was conducted to determine the performance of heat pipe-based evacuated tube solar collector as solar water heater experimentally. The experiments were carried out using stainless steel screen mesh as a wick material, and water and Al2O3-water 0.1% nanofluid as working fluid, and applying inclination angles of 0°, 15°, 30°, and 45°. To analyze the heat absorbed and transferred by the prototype, water at 30°C was circulated through the condenser. A 150 Watt halogen lamp was used as sun simulator, and the prototype was covered by an insulation box to obtain a steady state condition with a minimum affection of ambient changes. Experimental results show that the usage of Al2O3-water 0.1% nanofluid at 30° inclination angle provides the highest thermal performance, which gives efficiency as high as 0.196 and thermal resistance as low as 5.32 °C/W. The use of nanofluid as working fluid enhances thermal performance due to high thermal conductivity of the working fluid. The increase of the inclination angle plays a role in the drainage of the condensate to the evaporator that leads to higher thermal performance until the optimal inclination angle is reached.

  20. Configuration of the thermal landscape determines thermoregulatory performance of ectotherms.

    Science.gov (United States)

    Sears, Michael W; Angilletta, Michael J; Schuler, Matthew S; Borchert, Jason; Dilliplane, Katherine F; Stegman, Monica; Rusch, Travis W; Mitchell, William A

    2016-09-20

    Although most organisms thermoregulate behaviorally, biologists still cannot easily predict whether mobile animals will thermoregulate in natural environments. Current models fail because they ignore how the spatial distribution of thermal resources constrains thermoregulatory performance over space and time. To overcome this limitation, we modeled the spatially explicit movements of animals constrained by access to thermal resources. Our models predict that ectotherms thermoregulate more accurately when thermal resources are dispersed throughout space than when these resources are clumped. This prediction was supported by thermoregulatory behaviors of lizards in outdoor arenas with known distributions of environmental temperatures. Further, simulations showed how the spatial structure of the landscape qualitatively affects responses of animals to climate. Biologists will need spatially explicit models to predict impacts of climate change on local scales.

  1. Thermal performance of neighbourhood prototypes built in San Juan, Argentina

    Energy Technology Data Exchange (ETDEWEB)

    Blasco Lucas, I.; Albarracin, O.; Carestia, C. [Universidad Nacional de San Juan (Argentina)

    2000-07-01

    The research work produces a contrasted quantification of the thermal performance of inhabited dwelling houses built in different neighborhoods of San Juan, Argentina. They correspond to five prototypes aimed at families with low and medium income levels, massive spread in their versions with two or three bedrooms. From all of them it can be obtained yearly energy consumption indexes per unit area, under homogeneous conditions respect to minimal thermal comfort levels and inhabitant behaviors. The evolution of their inner temperatures and relative humidity with and without auxiliary thermal conditioning is analyzed. Conclusions assess the deficit level of the studied prototypes contrasted to international standards and the global valuation of the impact on the sectorial annual energy consumption caused by them. (author)

  2. Improved thermal performance of a hydronic radiant panel heating system by the optimization of tube shapes

    Institute of Scientific and Technical Information of China (English)

    Young T. CHAE; Kwang Ho LEE; Jae Sung PARK

    2011-01-01

    The thermal performance enhancement of the hydronic radiant floor heating system by tube shape refinements is investigated in this paper. Both analytical and detailed numerical modelings are carried out to predict the performance of the radiant system. While the simple analytical model briefly investigates the possibility of the effect of the tube shape improvement with the parametric analysis, the commercial computational fluid dynamics (CFD) code (Ansys/CFX) is used to perform the detailed 3D analysis under different tube shape conditions. The fin thickness, the number of fins, and the tube thermal conductivity turn out to have significant effects on the radiant system performance. The potential energy saving impacts of the tube shape refinements are also discussed. The tube shape improvement turns out to increase the floor surface temperature and to decrease the hot water temperature drop across the system, resulting in heating energy savings.

  3. Thermal interpretation of infrared dynamics in de Sitter

    Science.gov (United States)

    Rigopoulos, Gerasimos

    2016-07-01

    The infrared dynamics of a light, minimally coupled scalar field in de Sitter spacetime with Ricci curvature R = 12H2, averaged over horizon sized regions of physical volume VH = (4π/3)(1/H)3, can be interpreted as Brownian motion in a medium with de Sitter temperature TDS = hbarH/2π. We demonstrate this by directly deriving the effective action of scalar field fluctuations with wavelengths larger than the de Sitter curvature radius and generalizing Starobinsky's seminal results on stochastic inflation. The effective action describes stochastic dynamics and the fluctuating force drives the field to an equilibrium characterized by a thermal Gibbs distribution at temperature TDS which corresponds to a de Sitter invariant state. Hence, approach towards this state can be interpreted as thermalization. We show that the stochastic kinetic energy of the coarse-grained description corresponds to the norm of ∂μphi and takes a well defined value per horizon volume ½langle(∇phi)2rangle = - ½TDS/VH. This approach allows for the non-perturbative computation of the de Sitter invariant stress energy tensor langleTμνrangle for an arbitrary scalar potential.

  4. Thermal Interpretation of Infrared Dynamics in de Sitter

    CERN Document Server

    Rigopoulos, Gerasimos

    2016-01-01

    The infrared dynamics of a light, minimally coupled scalar field in de Sitter spacetime with Ricci curvature $R=12H$, averaged over horizon sized regions of physical volume $V_H=\\frac{4\\pi}{3}\\left(\\frac{1}{H}\\right)^3$, can be interpreted as Brownian motion in a medium with de Sitter temperature $T_{DS}=\\frac{\\hbar H}{2\\pi}$. We demonstrate this by employing path integral techniques, deriving the effective action of scalar field fluctuations with wavelengths larger than the de Sitter curvature radius and generalizing Starobinsky's seminal results on stochastic inflation. The effective action describes stochastic dynamics and the fluctuating force drives the field to an equilibrium characterized by a thermal Gibbs distribution at temperature $T_{DS}$ which corresponds to a de Sitter invariant state. Hence, approach towards this state can be interpreted as thermalization. We show that the stochastic kinetic energy of the coarse-grained description corresponds to the norm of $\\partial_\\mu\\phi$ and takes a well ...

  5. A simplified dynamic model for existing buildings using CTF and thermal network models

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xinhua; Wang, Shengwei [Department of Building Services Engineering, The Hong Kong Polytechnic University (China)

    2008-09-15

    An alternative simplified building model is developed to describe existing building system aiming at providing performance benchmark for performance evaluation and diagnosis at building level and performance prediction for air-conditioning system optimal control. This model combines detailed physical models of building envelopes and a thermal network model of building internal mass. The detailed physical models are the CTF (Conduction Transfer Function) models of building envelopes based on the easily available detailed physical properties of exterior walls and roof. The thermal network model is the 2R2C model, and its parameters are estimated and optimized using genetic algorithm with short-term monitored operation data. The parameter optimization of the simplified building internal mass model (2R2C) and the simplified dynamic building model (i.e., CTF+2R2C model) are validated in a high-rising commercial office building under various weather conditions. This CTF+2R2C model is an alternative modeling approach for simulating the overall building dynamic thermal performance when CTF model is chosen to model the building envelope. (author)

  6. Thermal Performance Testing of Glass Microspheres under Cryogenic Vacuum Conditions

    Science.gov (United States)

    Fesmire, J. E.; Augustynowicz, S. D.

    2004-06-01

    A key element of space launch vehicles and systems is thermal insulation for cryogenic tanks and piping. Glass microspheres, or glass bubbles, represent an alternative insulation material for a number of applications. Composite materials and engineered thermal insulation systems are also being developed based on the use of glass bubbles as the main constituent material. Commonly used materials, such as spray-on foam insulation, or SOFI, for vehicle tanks and perlite powder for ground storage tanks, are targeted for replacement with the new-technology systems that use glass bubbles. Complete thermal characterization of the glass bubbles is the first step toward producing the engineering solutions required for the energy-efficient, low-maintenance cryogenic systems of the future. Thermal performance testing of the glass microsphere material was successfully completed at the Cryogenics Test Laboratory of NASA Kennedy Space Center. The test measurements were made at the full temperature difference (typical boundary temperatures of 78 kelvin [K] and 293 K) and included the full cold-vacuum pressure range. The results are reported in apparent thermal conductivity (k-value) and mean heat flux.

  7. Computational Fluid Dynamics and Building Energy Performance Simulation

    DEFF Research Database (Denmark)

    Nielsen, Peter V.; Tryggvason, Tryggvi

    An interconnection between a building energy performance simulation program and a Computational Fluid Dynamics program (CFD) for room air distribution will be introduced for improvement of the predictions of both the energy consumption and the indoor environment. The building energy performance...... simulation program requires a detailed description of the energy flow in the air movement which can be obtained by a CFD program. The paper describes an energy consumption calculation in a large building, where the building energy simulation program is modified by CFD predictions of the flow between three...... program and a building energy performance simulation program will improve both the energy consumption data and the prediction of thermal comfort and air quality in a selected area of the building....

  8. Theoretical investigation of the structural, electronic, dynamical and thermal properties of YSn3 and YPb3

    Science.gov (United States)

    Kılıçarslan, Aynur; Salmankurt, Bahadır; Duman, Sıtkı

    2017-02-01

    We have performed an ab initio study of the structural, electronic, dynamical and thermal properties of the cubic AuCu3-type YSn3 and YPb3 by using the density functional theory, plane-wave pseudopotential method and a linear response scheme, within the generalized gradient approximation. An analysis of the electronic density of states at the Fermi level is found to be governed by the p states of Sn and Pb atoms with some contributions from the d states of Y atoms. The obtained phonon figures indicate that these material are dynamically stable in the cubic structure. Due to the metallic behavior of the compounds, the calculated zone-center phonon modes are triply degenerate. Also the thermal properties have been examined.

  9. Thermodynamic model of a thermal storage air conditioning system with dynamic behavior

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, E; Wen, SY; Shi, L; da Silva, AK

    2013-12-01

    A thermodynamic model was developed to predict transient behavior of a thermal storage system, using phase change materials (PCMs), for a novel electric vehicle climate conditioning application. The main objectives of the paper are to consider the system's dynamic behavior, such as a dynamic air flow rate into the vehicle's cabin, and to characterize the transient heat transfer process between the thermal storage unit and the vehicle's cabin, while still maintaining accurate solution to the complex phase change heat transfer. The system studied consists of a heat transfer fluid circulating between either of the on-board hot and cold thermal storage units, which we refer to as thermal batteries, and a liquid-air heat exchanger that provides heat exchange with the incoming air to the vehicle cabin. Each thermal battery is a shell-and-tube configuration where a heat transfer fluid flows through parallel tubes, which are surrounded by PCM within a larger shell. The system model incorporates computationally inexpensive semianalytic solution to the conjugated laminar forced convection and phase change problem within the battery and accounts for airside heat exchange using the Number of Transfer Units (NTUs) method for the liquid-air heat exchanger. Using this approach, we are able to obtain an accurate solution to the complex heat transfer problem within the battery while also incorporating the impact of the airside heat transfer on the overall system performance. The implemented model was benchmarked against a numerical study for a melting process and against full system experimental data for solidification using paraffin wax as the PCM. Through modeling, we demonstrate the importance of capturing the airside heat exchange impact on system performance, and we investigate system response to dynamic operating conditions, e.g., air recirculation. (C) 2013 Elsevier Ltd. All rights reserved.

  10. Thermal performance of closed two-phase thermosyphon using nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Khandekar, Sameer; Mehta, Balkrishna [Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Joshi, Yogesh M. [Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

    2008-06-15

    Nanofluids, stabilized suspensions of nanoparticles typically <100 nm in conventional fluids, are evolving as potential enhanced heat transfer fluids due to their improved thermal conductivity, increase in single phase heat transfer coefficient and significant increase in critical boiling heat flux. In the present paper, we investigate the overall thermal resistance of closed two-phase thermosyphon using pure water and various water based nanofluids (of Al{sub 2}O{sub 3}, CuO and laponite clay) as working fluids. We observe that all these nanofluids show inferior thermal performance than pure water. Furthermore, we observe that the wettability of all nanofluids on copper substrate, having the same average roughness as that of the thermosyphon container pipe, is better than that of pure water. A scaling analysis is presented which shows that the increase in wettability and entrapment of nanoparticles in the grooves of the surface roughness cause decrease in evaporator side Peclet number that finally leads to poor thermal performance. (author)

  11. Thermal-Hydraulic Performance of Scrubbing Nozzle Used for CFVS

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Chul; Lee, Doo Yong; Jung, Woo Young; Lee, Jong Chan; Kim, Gyu Tae [FNC TECH, Yongin (Korea, Republic of)

    2016-05-15

    A Containment Filtered Venting System (CFVS) is the most interested device to mitigate a threat against containment integrity under the severe accident of nuclear power plant by venting with the filtration of the fission products. FNC technology and partners have been developed the self-priming scrubbing nozzle used for the CFVS which is based on the venturi effect. The thermal-hydraulic performances such as passive scrubbing water suction as well as pressure drop across the nozzle have been tested under various thermal-hydraulic conditions. The two types of test section have been built for testing the thermal-hydraulic performance of the self-priming scrubbing nozzle. Through the visualization loop, the liquid suction performance through the slit, pressure drop across the nozzle are measured. The passive water suction flow through the suction slit at the throat is important parameter to define the scrubbing performance of the self-priming scrubbing nozzle. The water suction flow is increased with the increase of the overhead water level at the same inlet gas flow. It is not so much changed with the change of inlet gas flow at the overhead water level.

  12. Climate change impacts on lake thermal dynamics and ecosystem vulnerabilities

    Science.gov (United States)

    Sahoo, G. B; Forrest, A. L; Schladow, S. G ;; Reuter, J. E; Coats, R.; Dettinger, Michael

    2016-01-01

    Using water column temperature records collected since 1968, we analyzed the impacts of climate change on thermal properties, stability intensity, length of stratification, and deep mixing dynamics of Lake Tahoe using a modified stability index (SI). This new SI is easier to produce and is a more informative measure of deep lake stability than commonly used stability indices. The annual average SI increased at 16.62 kg/m2/decade although the summer (May–October) average SI increased at a higher rate (25.42 kg/m2/decade) during the period 1968–2014. This resulted in the lengthening of the stratification season by approximately 24 d. We simulated the lake thermal structure over a future 100 yr period using a lake hydrodynamic model driven by statistically downscaled outputs of the Geophysical Fluid Dynamics Laboratory Model (GFDL) for two different green house gas emission scenarios (the A2 in which greenhouse-gas emissions increase rapidly throughout the 21st Century, and the B1 in which emissions slow and then level off by the late 21st Century). The results suggest a continuation and intensification of the already observed trends. The length of stratification duration and the annual average lake stability are projected to increase by 38 d and 12 d and 30.25 kg/m2/decade and 8.66 kg/m2/decade, respectively for GFDLA2 and GFDLB1, respectively during 2014–2098. The consequences of this change bear the hallmarks of climate change induced lake warming and possible exacerbation of existing water quality, quantity and ecosystem changes. The developed methodology could be extended and applied to other lakes as a tool to predict changes in stratification and mixing dynamics.

  13. Butterfly micro bilayer thermal energy harvester geometry with improved performances

    Science.gov (United States)

    Trioux, E.; Monfray, S.; Basrour, S.

    2016-11-01

    This paper reports the recent progress of a new technology to scavenge thermal energy, implying a double-step transduction through thermal buckling of a bilayer aluminum nitride / aluminum bridge and piezoelectric transduction. A completely new scavenger design is presented, improving greatly its final performance. The butterfly shape reduces the overall device mechanical rigidity, which leads to a decrease of buckling temperatures compared to previously studied rectangular plates. In a first time we compared performances of rectangular and butterfly plates with an equal thickness of Al and AlN. In a second time, with a thicker Al layer than AlN layer, we will study only butterfly structure in terms of output power and buckling temperatures, and compare it to the previous stack.

  14. Thermal performance of Danish solar combi systems in practice and in theory

    DEFF Research Database (Denmark)

    Andersen, Elsa; Shah, Louise Jivan; Furbo, Simon

    2004-01-01

    An overview of measured thermal performances of Danish solar combi systems in practice is given. The thermal performance varies greatly from system to system. Measured and calculated thermal performances of different solar combi systems are compared and the main reasons for the different thermal ...... as theoretically expected....

  15. Thermal performance modeling of cross-flow heat exchangers

    CERN Document Server

    Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria

    2014-01-01

    This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges

  16. Compound fuzzy model for thermal performance of refrigeration compressors

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The fuzzy method is introduced to the calculation of thermal performance of refrigeration compressors. A compound model combining classical thermodynamic theory and fuzzy theory is presented and compared with a simple fuzzy model without classical thermodynamic fundamentals. Case study of refrigeration compressors shows that the compound fuzzy model and the simple fuzzy model are both more efficient than the classical thermodynamic method. However, the compound fuzzy model is of better precision and adaptability.

  17. Influence of Spacer Grid Outer Strap on Fuel Assembly Thermal Hydraulic Performance

    Directory of Open Access Journals (Sweden)

    Jingwen Yan

    2014-01-01

    Full Text Available The outer strap as a typical structure of a spacer grid enhances the mechanical strength, decreases hang-up susceptibility, and also influences thermal hydraulic performance, for example, pressure loss, mixing performance, and flow distribution. In the present study, a typical grid spacer with different outer strap designs is adopted to investigate the influence of outer strap design on fuel assembly thermal hydraulic performance by using a commercial computational fluid dynamics (CFD code, ANSYS CFX, and a subchannel analysis code, FLICA. To simulate the outer straps’ influence between fuel assemblies downstream, four quarter-bundles from neighboring fuel assemblies are constructed to form the computational domain. The results show that the outer strap design has a major impact on cross-flow between fuel assemblies and temperature distribution within the fuel assembly.

  18. Dynamic Performance of an HVDC Link

    Directory of Open Access Journals (Sweden)

    S. A. ZIDI

    2005-09-01

    Full Text Available This paper presents the results of a simulation study on a 12 pulse HVDC (High Voltage Direct Current using a system in Matlab/Simulink. The object of the study is to investigate the steady state and dynamic performance of the system. First we examine response of current regulator after change in current reference in order to see the behavior of the controllers in controlling the desired current. Next, we present the digital simulation of a test system and show the response to a DC fault in the line and the AC fault at inverter side. The results are evaluated to enhance the recovery of the system from the disturbances for a full range of typical disturbances. The presented approach benefits from Simulink’s advantages in modeling and simulating dynamical systems.

  19. Analytical study of nozzle performance for nuclear thermal rockets

    Science.gov (United States)

    Davidian, Kenneth O.; Kacynski, Kenneth J.

    1991-01-01

    A parametric study has been conducted by the NASA-Lewis Rocket Engine Design Expert System for the convergent-divergent nozzle of the Nuclear Thermal Rocket system, which uses a nuclear reactor to heat hydrogen to high temperature and then expands it through the nozzle. It is established by the study that finite-rate chemical reactions lower performance levels from theoretical levels. Major parametric roles are played by chamber temperature and chamber pressure. A maximum performance of 930 sec is projected at 2700 K, and of 1030 at 3100 K.

  20. Thermal energy storage for a space solar dynamic power system

    Science.gov (United States)

    Faget, N. M.; Fraser, W. M., Jr.; Simon, W. E.

    1985-01-01

    In the past, NASA has employed solar photovoltaic devices for long-duration missions. Thus, the Skylab system has operated with a silicon photovoltaic array and a nickel-cadmium electrochemical system energy storage system. Difficulties regarding the employment of such a system for the larger power requirements of the Space Station are related to a low orbit system efficiency and the large weight of the battery. For this reason the employment of a solar dynamic power system (SDPS) has been considered. The primary components of an SDPS include a concentrating mirror, a heat receiver, a thermal energy storage (TES) system, a thermodynamic heat engine, an alternator, and a heat rejection system. The heat-engine types under consideration are a Brayton cycle engine, an organic Rankine cycle engine, and a free-piston/linear-alternator Stirling cycle engine. Attention is given to a system description, TES integration concepts, and a TES technology assessment.

  1. Dynamic Thermal Model And Control Of A Pem Fuel Cell System

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2013-01-01

    A lumped parameter dynamic model is developed for predicting the stack performance, temperatures of the exit reactant gases and coolant liquid outlet in a proton-exchange membrane fuel cell (PEMFC) system. The air compressor, humidifier and cooling heat exchanger models are integrated to study...... the fuel cell system. A PID temperature control is implemented to study the effect of stack temperature on settling times of other variables such as stack voltage, air flow rate, oxygen excess ratio and net power of the stack. The model allows an assessment of the effect of operating parameters (stack...... power output, cooling water flow rate, air flow rate, and environmental temperature) and parameter interactions on the system thermal performance. The model represents a useful tool to determine the operating temperatures of the various components of the thermal system, and thus to fully assess...

  2. Dynamical and stationary critical behavior of the Ising ferromagnet in a thermal gradient

    Science.gov (United States)

    Muglia, J.; Albano, E. V.

    2012-08-01

    In this paper we present and discuss results of Monte Carlo numerical simulations of the two-dimensional Ising ferromagnet in contact with a heat bath that intrinsically has a thermal gradient. The extremes of the magnet are at temperatures T 1 T c ) by means of a single simulation. By starting the simulations with fully disordered initial configurations with magnetization m ≡ 0 corresponding to T = ∞, which are then suddenly annealed to a preset thermal gradient, we study the short-time critical dynamic behavior of the system. Also, by setting a small initial magnetization m = m 0, we study the critical initial increase of the order parameter. Furthermore, by starting the simulations from fully ordered configurations, which correspond to the ground state at T = 0 and are subsequently quenched to a preset gradient, we study the critical relaxation dynamics of the system. Additionally, we perform stationary measurements ( t → ∞) that are discussed in terms of the standard finite-size scaling theory. We conclude that our numerical simulation results of the Ising magnet in a thermal gradient, which are rationalized in terms of both dynamic and standard scaling arguments, are fully consistent with well established results obtained under equilibrium conditions.

  3. Orion Active Thermal Control System Dynamic Modeling Using Simulink/MATLAB

    Science.gov (United States)

    Wang, Xiao-Yen J.; Yuko, James

    2010-01-01

    This paper presents dynamic modeling of the crew exploration vehicle (Orion) active thermal control system (ATCS) using Simulink (Simulink, developed by The MathWorks). The model includes major components in ATCS, such as heat exchangers and radiator panels. The mathematical models of the heat exchanger and radiator are described first. Four different orbits were used to validate the radiator model. The current model results were compared with an independent Thermal Desktop (TD) (Thermal Desktop, PC/CAD-based thermal model builder, developed in Cullimore & Ring (C&R) Technologies) model results and showed good agreement for all orbits. In addition, the Orion ATCS performance was presented for three orbits and the current model results were compared with three sets of solutions- FloCAD (FloCAD, PC/CAD-based thermal/fluid model builder, developed in C&R Technologies) model results, SINDA/FLUINT (SINDA/FLUINT, a generalized thermal/fluid network-style solver ) model results, and independent Simulink model results. For each case, the fluid temperatures at every component on both the crew module and service module sides were plotted and compared. The overall agreement is reasonable for all orbits, with similar behavior and trends for the system. Some discrepancies exist because the control algorithm might vary from model to model. Finally, the ATCS performance for a 45-hr nominal mission timeline was simulated to demonstrate the capability of the model. The results show that the ATCS performs as expected and approximately 2.3 lb water was consumed in the sublimator within the 45 hr timeline before Orion docked at the International Space Station.

  4. Evaluation of Instrumentation and Dynamic Thermal Ratings for Overhead Lines

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, A. [New York Power Authority, White Plains, NY (United States)

    2013-01-31

    In 2010, a project was initiated through a partnership between the Department of Energy (DOE) and the New York Power Authority (NYPA) to evaluate EPRI's rating technology and instrumentation that can be used to monitor the thermal states of transmission lines and provide the required real-time data for real-time rating calculations. The project included the installation and maintenance of various instruments at three 230 kV line sites in northern New York. The instruments were monitored, and data collection and rating calculations were performed for about a three year period.

  5. The effect of thermal loading on laboratory fume hood performance.

    Science.gov (United States)

    Johnston, J D; Chessin, S J; Chesnovar, B W; Lillquist, D R

    2000-11-01

    A modified version of the ANSI/ASHRAE 110-1995 Method of Testing Performance of Laboratory Fume Hoods was used to evaluate the relationship between thermal loading in a laboratory fume hood and subsequent tracer gas leakage. Three types of laboratory burners were used, alone and in combination, to thermally challenge the hood. Heat output from burners was measured in BTU/hr, which was based on the fuel heat capacity and flow rate. Hood leakage was measured between 2824 and 69,342 BTU/hr. Sulfur hexafluoride (SF6) was released at 23.5 LPM for each level of thermal loading. Duct temperature was also measured during the heating process. Results indicate a linear relationship for both BTU/hr vs. hood leakage and duct temperature vs. hood leakage. Under these test conditions, each increase of 10,000 BTU/hr resulted in an additional 4 ppm SF6 in the manikin's breathing zone (r2 = 0.68). An additional 3.1 ppm SF6 was measured for every 25 degrees F increase in duct temperature (r2 = 0.60). Both BTU/hr and duct temperature models showed p hood leakage than duct temperature. The results of this study indicate that heat output may compromise fume hood performance. This finding is consistent with those of previous studies.

  6. Molecular dynamics prediction of phonon-mediated thermal conductivity of f.c.c. Cu

    Science.gov (United States)

    Evteev, Alexander V.; Momenzadeh, Leila; Levchenko, Elena V.; Belova, Irina V.; Murch, Graeme E.

    2014-03-01

    The phonon-mediated thermal conductivity of f.c.c. Cu is investigated in detail in the temperature range 40-1300 K. The calculations are performed in the framework of equilibrium molecular dynamics making use of the Green-Kubo formalism and one of the most reliable embedded-atom method potentials for Cu. It is found that the temporal decay of the heat current autocorrelation function (HCACF) of the Cu model at low and intermediate temperatures demonstrate a more complex behaviour than the two-stage decay observed previously for the f.c.c. Ar model. After the first stage of decay, it demonstrates a peak in the temperature range 40-800 K. A decomposition model of the HCACF is introduced. In the framework of that model we demonstrate that a classical description of the phonon thermal transport in the Cu model can be used down to around one quarter of the Debye temperature (about 90 K). Also, we find that above 300 K the thermal conductivity of the Cu model varies with temperature more rapidly than ?, following an exponent close to -1.4 in agreement with previous calculations on the Ar model. Phonon thermal conductivity of Cu is found to be about one order of magnitude higher than Ar. The phonon contribution to the total thermal conductivity of Cu can be estimated to be about 0.5% at 1300 K and about 10% at 90 K.

  7. Dynamic characterization for tumor- and deformation-induced thermal contrasts on breast surface: a simulation study

    Science.gov (United States)

    Jiang, Li; Zhan, Wang; Loew, Murray H.

    2009-02-01

    Understanding the complex relationship between the thermal contrasts on the breast surface and the underlying physiological and pathological factors is important for thermogram-based breast cancer detection. Our previous work introduced a combined thermal-elastic modeling method with improved ability to simultaneously characterize both elastic-deformation-induced and tumor-induced thermal contrasts on the breast. In this paper, the technique is further extended to investigate the dynamic behaviors of the breast thermal contrasts during cold stress and thermal recovery procedures in the practice of dynamic thermal imaging. A finite-element method (FEM) has been developed for dynamic thermal and elastic modeling. It is combined with a technique to address the nonlinear elasticity of breast tissues, as would arise in the large deformations caused by gravity. Our simulation results indicate that different sources of the thermal contrasts, such as the presence of a tumor, and elastic deformation, have different transient time courses in dynamic thermal imaging with cold-stress and thermal-recovery. Using appropriate quantifications of the thermal contrasts, we find that the tumor- and deformation-induced thermal contrasts show opposite changes in the initial period of the dynamic courses, whereas the global maxima of the contrast curves are reached at different time points during a cold-stress or thermal-recovery procedure. Moreover, deeper tumors generally lead to smaller peaks but have larger lags in the thermal contrast time course. These findings suggest that dynamic thermal imaging could be useful to differentiate the sources of the thermal contrast on breast surface and hence to enhance tumor detectability.

  8. Thermal dynamic simulation of wall for building energy efficiency under varied climate environment

    Science.gov (United States)

    Wang, Xuejin; Zhang, Yujin; Hong, Jing

    2017-08-01

    Aiming at different kind of walls in five cities of different zoning for thermal design, using thermal instantaneous response factors method, the author develops software to calculation air conditioning cooling load temperature, thermal response factors, and periodic response factors. On the basis of the data, the author gives the net work analysis about the influence of dynamic thermal of wall on air-conditioning load and thermal environment in building of different zoning for thermal design regional, and put forward the strategy how to design thermal insulation and heat preservation wall base on dynamic thermal characteristic of wall under different zoning for thermal design regional. And then provide the theory basis and the technical references for the further study on the heat preservation with the insulation are in the service of energy saving wall design. All-year thermal dynamic load simulating and energy consumption analysis for new energy-saving building is very important in building environment. This software will provide the referable scientific foundation for all-year new thermal dynamic load simulation, energy consumption analysis, building environment systems control, carrying through farther research on thermal particularity and general particularity evaluation for new energy -saving walls building. Based on which, we will not only expediently design system of building energy, but also analyze building energy consumption and carry through scientific energy management. The study will provide the referable scientific foundation for carrying through farther research on thermal particularity and general particularity evaluation for new energy saving walls building.

  9. THE STUDY OF DYNAMIC THERMAL MATHMETICAL MODEL FOR EHV XLPE CABLE

    Directory of Open Access Journals (Sweden)

    Aihong TANG

    2012-01-01

    Full Text Available This paper analyzes the dynamic behavior of the cable, deduces the dynamic mathematical model of XLPE based on the equation of thermal circuit, for the operation supervising of the cable, programs a program, the program can calculate the rated current-carry capacity of the cable and the thermal dynamic process of the cable. The calculation results verify the dynamic mathematical model of the XLPE presented in this paper.

  10. Indoor thermal performance evaluation of Daystar solar collector

    Science.gov (United States)

    Shih, K., Sr.

    1977-01-01

    The test procedures used and results obtained from a test program to obtain thermal performance data on a Daystar Model 21B, S/N 02210, Unit 2, liquid solar collector under simulated conditions are described. The test article is a flat plate solar collector using liquid as a heat transfer medium. The absorber plate is copper and coated with black paint. Between the tempered low iron glass and absorber plate is a polycarbonate trap used to suppress convective heat loss. The collector incorporates a convector heat dump panel to limit temperature excursions during stagnation. The following tests were conducted: (1) collector thermal efficiency; (2) collector time constant; (3) collector incident angle modifier; (4) collector heat loss coefficient; and (5) collector stagnation.

  11. Summer Thermal Performance of Ventilated Roofs with Tiled Coverings

    Science.gov (United States)

    Bortoloni, M.; Bottarelli, M.; Piva, S.

    2017-01-01

    The thermal performance of a ventilated pitched roof with tiled coverings is analysed and compared with unventilated roofs. The analysis is carried out by means of a finite element numerical code, by solving both the fluid and thermal problems in steady-state. A whole one-floor building with a pitched roof is schematized as a 2D computational domain including the air-permeability of tiled covering. Realistic data sets for wind, temperature and solar radiation are used to simulate summer conditions at different times of the day. The results demonstrate that the batten space in pitched roofs is an effective solution for reducing the solar heat gain in summer and thus for achieving better indoor comfort conditions. The efficiency of the ventilation is strictly linked to the external wind conditions and to buoyancy forces occurring due to the heating of the tiles.

  12. Preparation and performance of novel thermal stable composite nanofiltration membrane

    Institute of Scientific and Technical Information of China (English)

    Chunrui WU; Shouhai ZHANG; Fajie YANG; Chun YAN; Xigao JIAN

    2008-01-01

    The novel thermal stable composite nanofiltra-tion membranes were prepared through the interfacial polymerization of piperazine and trimesoyl chloride on the poly (phthalazinone ether) ultrafiltration substrate. The effects of polymerization and testing conditions on membrane performance were studied. The surface morphologies of the substrate and the composite mem-branes were observed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The separation properties of membranes for dyes and salts were tested. The composite membranes show good ther-mal stability. The rejection for Na2SO4 was kept over 96%, 1.0 MPa and 80℃. When tested at 1.0 MPa and 60℃, the rejection of the composite membrane for dyes was kept at the rejection for NaCl was lower than 20%.

  13. Thermal Performance Testing of Order Dependancy of Aerogels Multilayered Insulation

    Science.gov (United States)

    Johnson, Wesley L.; Fesmire, James E.; Demko, J. A.

    2009-01-01

    Robust multilayer insulation systems have long been a goal of many research projects. Such insulation systems must provide some degree of structural support and also mechanical integrity during loss of vacuum scenarios while continuing to provide insulative value to the vessel. Aerogel composite blankets can be the best insulation materials in ambient pressure environments; in high vacuum, the thermal performance of aerogel improves by about one order of magnitude. Standard multilayer insulation (MU) is typically 50% worse at ambient pressure and at soft vacuum, but as much as two or three orders of magnitude better at high vacuum. Different combinations of aerogel and multilayer insulation systems have been tested at Cryogenics Test Laboratory of NASA Kennedy Space Center. Analysis performed at Oak Ridge National Laboratory showed an importance to the relative location of the MU and aerogel blankets. Apparent thermal conductivity testing under cryogenic-vacuum conditions was performed to verify the analytical conclusion. Tests results are shown to be in agreement with the analysis which indicated that the best performance is obtained with aerogel layers located in the middle of the blanket insulation system.

  14. Thermal Protection System Cavity Heating for Simplified and Actual Geometries Using Computational Fluid Dynamics Simulations with Unstructured Grids

    Science.gov (United States)

    McCloud, Peter L.

    2010-01-01

    Thermal Protection System (TPS) Cavity Heating is predicted using Computational Fluid Dynamics (CFD) on unstructured grids for both simplified cavities and actual cavity geometries. Validation was performed using comparisons to wind tunnel experimental results and CFD predictions using structured grids. Full-scale predictions were made for simplified and actual geometry configurations on the Space Shuttle Orbiter in a mission support timeframe.

  15. Numerical analysis on thermal hydraulic performance of a flat plate heat pipe with wick column

    Science.gov (United States)

    Lu, Longsheng; Liao, Huosheng; Liu, Xiaokang; Tang, Yong

    2015-08-01

    A simplified thermal hydraulic model is developed to investigate the influence of wick column on the performance of a flat plate heat pipe (FPHP). The governing equations of the FPHP are solved by using the computational fluid dynamics package FLUENT. The temperature, velocity and pressure fields are obtained. The validity of the model is confirmed by comparing the present solutions with the open literature data. The numerical results show that with the increase of the wick column size, the maximum velocity of the liquid and vapor decreases while the total thermal resistance and capillary heat transfer limit of the FPHP increases gradually. The performance of the FPHP may degrade if the wick column is placed inside the vapor core asymmetrically.

  16. Thermal performance optimization of a flat plate solar air heater using genetic algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Varun; Siddhartha [Department of Mechanical Engineering, National Institute of Technology, Hamirpur 177 005 (H.P.) (India)

    2010-05-15

    Thermal performance of solar air heater is low and different techniques are adopted to increase the performance of solar air heaters, such as: fins, artificial roughness etc. In this paper an attempt has been done to optimize the thermal performance of flat plate solar air heater by considering the different system and operating parameters to obtain maximum thermal performance. Thermal performance is obtained for different Reynolds number, emissivity of the plate, tilt angle and number of glass plates by using genetic algorithm. (author)

  17. Non-equilibrium molecular dynamics simulation of thermal conductivity and thermal diffusion of binary mixtures confined in a nanochannel

    Science.gov (United States)

    Pourali, Meisam; Maghari, Ali

    2014-11-01

    In this paper, direct non-equilibrium molecular dynamics simulation is developed to investigate thermal conductivity and thermal diffusion factors of confined binary mixtures of methane and some n-alkanes in a nanochannel. We used two thermal walls in different temperatures to impose temperature gradient in the system. The mixtures are confined between two parallel atomic walls, normal to temperature gradient. Simulation results show high inhomogeneity and layering in the mixtures. Thermal conductivity of mixtures increases with decreasing the channel width and increases in mixtures with high concentration of methane. Except for very small channels, confinement has minimal effect on thermal diffusion. In very narrow channels, thermal diffusion is small and it reaches a steady state value with increasing the channel width. Local velocity fields for two different channels also show different behaviors. In relatively large channels some convection patterns are observed in mixtures.

  18. Non-equilibrium molecular dynamics simulation of thermal conductivity and thermal diffusion of binary mixtures confined in a nanochannel

    Energy Technology Data Exchange (ETDEWEB)

    Pourali, Meisam; Maghari, Ali, E-mail: maghari@ut.ac.ir

    2014-11-24

    In this paper, direct non-equilibrium molecular dynamics simulation is developed to investigate thermal conductivity and thermal diffusion factors of confined binary mixtures of methane and some n-alkanes in a nanochannel. We used two thermal walls in different temperatures to impose temperature gradient in the system. The mixtures are confined between two parallel atomic walls, normal to temperature gradient. Simulation results show high inhomogeneity and layering in the mixtures. Thermal conductivity of mixtures increases with decreasing the channel width and increases in mixtures with high concentration of methane. Except for very small channels, confinement has minimal effect on thermal diffusion. In very narrow channels, thermal diffusion is small and it reaches a steady state value with increasing the channel width. Local velocity fields for two different channels also show different behaviors. In relatively large channels some convection patterns are observed in mixtures.

  19. Thermal expansion pump for capillary high-performance liquid chromatography.

    Science.gov (United States)

    Tao, Qian; Wu, Qian; Zhang, Xiangmin

    2010-02-01

    A thermal expansion pump (TEP) based on a principle of liquid thermal expansion for capillary high-performance liquid chromatography has been developed. The novel pump is capable of generating a continuous flow at high pressure for constant and stable delivery of binary solvents from nanoliters to microliters per minute without splitting. Theoretical equations for controlling fluidic output of this pump have been established and validated by a series of experiments. Factors affecting flow rate, such as density discrepancy, liquid compressibility, and mass loss in output, were taken into account. An assembly of the pump system employing two groups of thermal expansion pumps (TEPs) working in turns were fabricated, and a controlling strategy for the pump system to maintain a continuous delivery without pressure fluctuation even at switching points was also developed. Both isocratic and gradients of binary solvent delivery by the TEPs were performed. Reproducibility and standard deviation at different flow rates were determined. A capillary high-performance liquid chromatography (micro-HPLC) system consisting of the TEPs, an injection valve, a homemade packed capillary column (20 cm x 100 microm i.d. with 5 microm C18), and a laser-induced fluorescence detector was set up, and sample separations were carried out. Results of RSD = 4% for flow and RSD = 2% for retention times at 500 nL/min were achieved. Such a pump system has almost no moving parts except for the solvent switches. Its overall costs of manufacture and running are very low. It is proven that the TEPs system has great potential and competitive capabilities in capillary liquid chromatography.

  20. Overall Thermal Performance of Flexible Piping Under Simulated Bending Conditions

    Science.gov (United States)

    Fesmire, James E.; Augustynowicz, S. D.; Demko, J. A.; Thompson, Karen (Technical Monitor)

    2001-01-01

    Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal losses than comparable rigid lines. Typical flexible piping construction uses corrugated tubes, inner and outer, with a multilayer insulation (MLI) system in the annular space. Experiments on vacuum insulation systems in a flexible geometry were conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. The effects of bending were simulated by causing the inner tube to be eccentric with the outer tube. The effects of spacers were simulated in a controlled way by inserting spacer tubes for the length of the cylindrical test articles. Two material systems, standard MLI and a layered composite insulation (LCI), were tested under the full range of vacuum levels using a liquid nitrogen boiloff calorimeter to determine the apparent thermal conductivity (k-value). The results indicate that the flexible piping under simulated bending conditions significantly degrades the thermal performance of the insulation system. These data are compared to standard MLI for both straight and flexible piping configurations. The definition of an overall k-value for actual field installations (k(sub oafi)) is described for use in design and analysis of cryogenic piping systems.

  1. Condensing economizers: Thermal performance and particulate removal efficiencies

    Energy Technology Data Exchange (ETDEWEB)

    Butcher, T.A.; Litzke, Wai Lin (Brookhaven National Lab., Upton, NY (United States)); Park, N. (Stony Brook Scientific, Ltd., Morristown, PA (United States))

    1992-02-01

    Condensing economizers can be used to increase the thermal efficiency of boilers and furnaces. This project has involved a study of these specifically for application to coal-water mixture fuels although the results can be extended to other fuels. experimental studies to evaluate thermal performance and removal of particulates across indirect contract economizers have been performed. The test arrangement incorporates oil firing with the injection of flyash into the flue gas to simulate coal combustion products. Water sprays into the combustion products are used to achieve variable flue gas moisture content and a variable amount of condensation in the economizers. The economizers are tubular with flue gas on the outside of the tubes. Tube surfaces are plastic coated to prevent corrosion. The gas temperature and condensation profiles through the economizers have been predicted and overall predicted performance has been compared with test results. Mechanisms for particle removal are discussed and predicted removal efficiencies as a functions of particle diameter are presented. It is is shown that inertial impaction is the dominant mechanism and particle removal efficiencies up to 89% have been realized.

  2. Theoretical and Experimental Thermal Performance Analysis of Complex Thermal Storage Membrane Containing Bio-Based Phase Change Material (PCM)

    Energy Technology Data Exchange (ETDEWEB)

    Kosny, Jan [ORNL; Stovall, Therese K [ORNL; Shrestha, Som S [ORNL; Yarbrough, David W [ORNL

    2010-01-01

    Since 2000, an ORNL research team has been testing different configurations of PCM-enhanced building envelop components to be used in residential and commercial buildings. During 2009, a novel type of thermal storage membrane was evaluated for building envelope applications. Bio-based PCM was encapsulated between two layers of heavy-duty plastic film forming a complex array of small PCM cells. Today, a large group of PCM products are packaged in such complex PCM containers or foils containing arrays of PCM pouches of different shapes and sizes. The transient characteristics of PCM-enhanced building envelope materials depend on the quality and amount of PCM, which is very often difficult to estimate because of the complex geometry of many PCM heat sinks. The only widely used small-scale analysis method used to evaluate the dynamic characteristics of PCM-enhanced building products is the differential scanning calorimeter (DSC). Unfortunately, this method requires relatively uniform, and very small, specimens of the material. However, in numerous building thermal storage applications, PCM products are not uniformly distributed across the surface area, making the results of traditional DSC measurements unrealistic for these products. In addition, most of the PCM-enhanced building products contain blends of PCM with fire retardants and chemical stabilizers. This combination of non-uniform distribution and non-homogenous composition make it nearly impossible to select a representative small specimen suitable for DSC tests. Recognizing these DSC limitations, ORNL developed a new methodology for performing dynamic heat flow analysis of complex PCM-enhanced building materials. An experimental analytical protocol to analyze the dynamic characteristics of PCM thermal storage makes use of larger specimens in a conventional heat-flow meter apparatus, and combines these experimental measurements with three-dimensional (3-D) finite-difference modeling and whole building energy

  3. Theoretical and Experimental Thermal Performance Analysis of Complex Thermal Storage Membrane Containing Bio-Based Phase Change Material (PCM)

    Energy Technology Data Exchange (ETDEWEB)

    Kosny, Jan [ORNL; Stovall, Therese K [ORNL; Shrestha, Som S [ORNL; Yarbrough, David W [ORNL

    2010-12-01

    Since 2000, an ORNL research team has been testing different configurations of PCM-enhanced building envelop components to be used in residential and commercial buildings. During 2009, a novel type of thermal storage membrane was evaluated for building envelope applications. Bio-based PCM was encapsulated between two layers of heavy-duty plastic film forming a complex array of small PCM cells. Today, a large group of PCM products are packaged in such complex PCM containers or foils containing arrays of PCM pouches of different shapes and sizes. The transient characteristics of PCM-enhanced building envelope materials depend on the quality and amount of PCM, which is very often difficult to estimate because of the complex geometry of many PCM heat sinks. The only widely used small-scale analysis method used to evaluate the dynamic characteristics of PCM-enhanced building products is the differential scanning calorimeter (DSC). Unfortunately, this method requires relatively uniform, and very small, specimens of the material. However, in numerous building thermal storage applications, PCM products are not uniformly distributed across the surface area, making the results of traditional DSC measurements unrealistic for these products. In addition, most of the PCM-enhanced building products contain blends of PCM with fire retardants and chemical stabilizers. This combination of non-uniform distribution and non-homogenous composition make it nearly impossible to select a representative small specimen suitable for DSC tests. Recognizing these DSC limitations, ORNL developed a new methodology for performing dynamic heat flow analysis of complex PCM-enhanced building materials. An experimental analytical protocol to analyze the dynamic characteristics of PCM thermal storage makes use of larger specimens in a conventional heat-flow meter apparatus, and combines these experimental measurements with three-dimensional (3-D) finite-difference modeling and whole building energy

  4. Thermal performance of honeywell double covered liquid solar collector

    Science.gov (United States)

    Losey, R.

    1977-01-01

    The test procedures and results obtained during an evaluation test program to determine the outdoor performance characteristics of the Honeywell liquid solar collector are presented. The program was based on the thermal evaluation of a Honeywell double covered liquid solar collection. Initial plans included the simultaneous testing of a single covered Honeywell collector. During the initial testing, the single covered collector failed due to leakage; thus, testing continued on the double covered collector only. To better define the operating characteristics of the collector, several additional data points were obtained beyond those requested.

  5. Thermal performance evaluation of the Semco (liquid) solar collector

    Science.gov (United States)

    1979-01-01

    Procedures used and results obtained during the evaluation test program on a flat plate collector which uses water as the working fluid are discussed. The absorber plate is copper tube soldered to copper fin coated with flat black paint. The glazing consists of two plates of Lo-Iron glass; the insulation is polyurethane foam. The collector weight is 242.5 pounds with overall external dimensions of approximately 48.8 in. x 120.8 in. x 4.1 in. The test program was conducted to obtain thermal performance data before and after 34 days of weather exposure test.

  6. Measured Two-Dimensional Ice-Wedge Polygon Thermal Dynamics

    Science.gov (United States)

    Cable, William; Romanovsky, Vladimir; Busey, Robert

    2016-04-01

    necessarily found in areas of higher MAGT. Active layer thickness does not appear to be correlated to mean annual air temperature but rather is a function of summer air temperature or thawing degree-days. While the refreezing of the active layer initiated at nearly the same time for all locations and polygons, we find differences in the proportion of top-down versus bottom-up freezing and the length of time required to complete the refreezing process. Examination of the daily temperature dynamics using interpolated two-dimensional temperature fields reveal that during the summer, the predominate temperature gradient is vertical while the isotherms tend to follow the topography. However, as the active layer begins to refreeze and snow accumulates, the thermal regime diverges. The fall shows an increased temperature gradient horizontally with landscape positions containing higher soil moisture and/or snow depth (low centers and troughs) cooling more slowly than the adjacent ground (rims and high centers). This two-dimensional effect is greatest as the active layer refreezes and persists until mid-winter, by which time the temperature gradients are again mostly vertical and the isotherms follow the topography. Our findings demonstrate the complexity and two-dimensionality of the temperature dynamics in these landscapes.

  7. Thermal Fluid-Dynamic Study for the thermal control of the new ALICE Central Detectors

    CERN Document Server

    Pelizzari, Andrea

    The Inner Tracking System Detector of the ALICE Experiment at CERN laboratory will be replaced in 2020 with a new Detector. It will have to provide, among others, higher spatial resolution, higher tracking precision and faster data read-out. These goals will be attained thanks to new pixel sensors chips and new electronic components, which will have a high impact in terms of dissipated heat. Therefore, one of the critical aspects for the success of the Upgrade project is the design of the Detector cooling system. This thesis work has been developed at CERN in Geneva in close contact with the group responsible for the Mechanics and Cooling of the Detector. The aim of the thermal fluid dynamic study devised is to deliver to the group a reliable and accurate description of the air flow inside the New Inner Tracking System Detector. After a first part of problem definition and design study, a Computational Fluid Dynamic (CFD) analysis has been developed with the ANSYS Fluent software. The CFD model built in this ...

  8. Analytical study of nozzle performance for nuclear thermal rockets

    Science.gov (United States)

    Davidian, Kenneth O.; Kacynski, Kenneth J.

    1991-01-01

    Nuclear propulsion has been identified as one of the key technologies needed for human exploration of the Moon and Mars. The Nuclear Thermal Rocket (NTR) uses a nuclear reactor to heat hydrogen to a high temperature followed by expansion through a conventional convergent-divergent nozzle. A parametric study of NTR nozzles was performed using the Rocket Engine Design Expert System (REDES) at the NASA Lewis Research Center. The REDES used the JANNAF standard rigorous methodology to determine nozzle performance over a range of chamber temperatures, chamber pressures, thrust levels, and different nozzle configurations. A design condition was set by fixing the propulsion system exit radius at five meters and throat radius was varied to achieve a target thrust level. An adiabatic wall was assumed for the nozzle, and its length was assumed to be 80 percent of a 15 degree cone. The results conclude that although the performance of the NTR, based on infinite reaction rates, looks promising at low chamber pressures, finite rate chemical reactions will cause the actual performance to be considerably lower. Parameters which have a major influence on the delivered specific impulse value include the chamber temperature and the chamber pressures in the high thrust domain. Other parameters, such as 2-D and boundary layer effects, kinetic rates, and number of nozzles, affect the deliverable performance of an NTR nozzle to a lesser degree. For a single nozzle, maximum performance of 930 seconds and 1030 seconds occur at chamber temperatures of 2700 and 3100 K, respectively.

  9. Experimental investigation on the thermal performance of a closed oscillating heat pipe in thermal management

    Science.gov (United States)

    Rao, Zhonghao; Wang, Qingchao; Zhao, Jiateng; Huang, Congliang

    2017-04-01

    To investigate the thermal performance of the closed oscillating heat pipe (OHP) as a passive heat transfer device in thermal management system, the gravitation force, surface tension, cooling section position and inclination angle were discussed with applied heating power ranging from 5 to 65 W. The deionized water was chosen as the working fluid and liquid-filling ratio was 50 ± 5%. The operation of the OHP mainly depends on the phase change of the working fluid. The working fluid within the OHP was constantly evaporated and cooled. The results show that the movement of the working fluid was similar to the forced damped mechanical vibration, it has to overcome the capillary resistance force and the stable oscillation should be that the OHP could successful startup. The oscillation frequency slowed and oscillation amplitude decreased when the inclination angle of the OHP increased. However, the thermal resistance increased. With the increment of the heating power, the average temperature of the evaporation and condensation section would be close. If the heating power was further increased, dry-out phenomenon within the OHP would appeared. With the decrement of the L, the start-up heating power also decreased and stable oscillation would be formed.

  10. Thermal performance of PCM thermal storage unit for a roof integrated solar heating system

    Energy Technology Data Exchange (ETDEWEB)

    Saman, W.; Bruno, F.; Halawa, E. [South Australia Univ., Sustainable Energy Centre, Adelaide, SA (Australia)

    2005-02-01

    The thermal performance of a phase change thermal storage unit is analysed and discussed. The storage unit is a component of a roof integrated solar heating system being developed for space heating of a home. The unit consists of several layers of phase change material (PCM) slabs with a melting temperature of 29 deg C. Warm air delivered by a roof integrated collector is passed through the spaces between the PCM layers to charge the storage unit. The stored heat is utilised to heat ambient air before being admitted to a living space. The study is based on both experimental results and a theoretical two dimensional mathematical model of the PCM employed to analyse the transient thermal behaviour of the storage unit during the charge and discharge periods. The analysis takes into account the effects of sensible heat which exists when the initial temperature of the PCM is well below or above the melting point during melting or freezing. The significance of natural convection occurring inside the PCM on the heat transfer rate during melting which was previously suspected as the cause of faster melting process in one of the experiments is discussed. The results are compared with a previous analysis based on a one dimensional model which neglected the effect of sensible heat. A comparison with experimental results for a specific geometry is also made. (Author)

  11. Experimental investigation on the thermal performance of a closed oscillating heat pipe in thermal management

    Science.gov (United States)

    Rao, Zhonghao; Wang, Qingchao; Zhao, Jiateng; Huang, Congliang

    2017-10-01

    To investigate the thermal performance of the closed oscillating heat pipe (OHP) as a passive heat transfer device in thermal management system, the gravitation force, surface tension, cooling section position and inclination angle were discussed with applied heating power ranging from 5 to 65 W. The deionized water was chosen as the working fluid and liquid-filling ratio was 50 ± 5%. The operation of the OHP mainly depends on the phase change of the working fluid. The working fluid within the OHP was constantly evaporated and cooled. The results show that the movement of the working fluid was similar to the forced damped mechanical vibration, it has to overcome the capillary resistance force and the stable oscillation should be that the OHP could successful startup. The oscillation frequency slowed and oscillation amplitude decreased when the inclination angle of the OHP increased. However, the thermal resistance increased. With the increment of the heating power, the average temperature of the evaporation and condensation section would be close. If the heating power was further increased, dry-out phenomenon within the OHP would appeared. With the decrement of the L, the start-up heating power also decreased and stable oscillation would be formed.

  12. PREDICTING THERMAL PERFORMANCE OF ROOFING SYSTEMS IN SURABAYA

    Directory of Open Access Journals (Sweden)

    MINTOROGO Danny Santoso

    2015-07-01

    Full Text Available Traditional roofing systems in the developing country likes Indonesia are still be dominated by the 30o, 45o, and more pitched angle roofs; the roofing cover materials are widely used to traditional clay roof tiles, then modern concrete roof tiles, and ceramic roof tiles. In the 90’s decay, shop houses are prosperous built with flat concrete roofs dominant. Green roofs and roof ponds are almost rarely built to meet the sustainable environmental issues. Some tested various roof systems in Surabaya were carried out to observe the roof thermal performances. Mathematical equation model from three references are also performed in order to compare with the real project tested. Calculated with equation (Kabre et al., the 30o pitched concrete-roof-tile, 30o clay-roof-tile, 45o pitched concrete-roof-tile are the worst thermal heat flux coming to room respectively. In contrast, the bare soil concrete roof and roof pond system are the least heat flux streamed onto room. Based on predicted calculation without insulation and cross-ventilation attic space, the roof pond and bare soil concrete roof (greenery roof are the appropriate roof systems for the Surabaya’s climate; meanwhile the most un-recommended roof is pitched 30o or 45o angle with concrete-roof tiles roofing systems.

  13. Thermal Performance of a Cryogenic Fluid Management Cubesat Mission

    Science.gov (United States)

    Berg, J. J.; Oliveira, J. M.; Congiardo, J. F.; Walls, L. K.; Putman, P. T.; Haberbusch, M. S.

    2013-01-01

    Development for an in-space demonstration of a CubeS at as a Cryogenic Fluid Management (CFM) test bed is currently underway. The favorable economics of CubeSats make them appealing for technology development activity. While their size limits testing to smaller scales, many of the regimes relevant to CFM can still be achieved. The first demo flight of this concept, CryoCube®-1, will focus on oxygen liquefaction and low-gravity level sensing using Reduced Gravity CryoTracker®. An extensive thermal modeling effort has been underway to both demonstrate concept feasibility and drive the prototype design. The satellite will utilize both a sun- and earth-shield to passively cool its experimental tank below 115 K. An on-board gas generator will create high pressure gaseous oxygen, which will be throttled into a bottle in the experimental node and condensed. The resulting liquid will be used to perform various experiments related to level sensing. Modeling efforts have focused on the spacecraft thermal performance and its effects on condensation in the experimental node. Parametric analyses for both optimal and suboptimal conditions have been considered and are presented herein.

  14. Thermal Performance Evaluation of Walls with Gas Filled Panel Insulation

    Energy Technology Data Exchange (ETDEWEB)

    Shrestha, Som S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Desjarlais, Andre Omer [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Atchley, Jerald Allen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-11-01

    Gas filled insulation panels (GFP) are very light weight and compact (when uninflated) advanced insulation products. GFPs consist of multiple layers of thin, low emittance (low-e) metalized aluminum. When expanded, the internal, low-e aluminum layers form a honeycomb structure. These baffled polymer chambers are enveloped by a sealed barrier and filled with either air or a low-conductivity gas. The sealed exterior aluminum foil barrier films provide thermal resistance, flammability protection, and properties to contain air or a low conductivity inert gas. This product was initially developed with a grant from the U.S. Department of Energy. The unexpanded product is nearly flat for easy storage and transport. Therefore, transportation volume and weight of the GFP to fill unit volume of wall cavity is much smaller compared to that of other conventional insulation products. This feature makes this product appealing to use at Army Contingency Basing, when transportation cost is significant compared to the cost of materials. The objective of this study is to evaluate thermal performance of walls, similar to those used at typical Barracks Hut (B-Hut) hard shelters, when GFPs are used in the wall cavities. Oak Ridge National Laboratory (ORNL) tested performance of the wall in the rotatable guarded hotbox (RGHB) according to the ASTM C 1363 standard test method.

  15. Thermal performance of solar district heating plants in Denmark

    DEFF Research Database (Denmark)

    Furbo, Simon; Perers, Bengt; Bava, Federico

    2014-01-01

    The market for solar heating plants connected to district heating systems is expanding rapidly in Denmark. It is expected that by the end of 2014 the 10 largest solar heating plants in Europe will be located in Denmark. Measurements from 23 Danish solar heating plants, all based on flat plate solar...... collectors mounted on the ground, shows measured yearly thermal performances of the solar heating plants placed in the interval from 313 kWh/m² collector to 493 kWh/m² collector with averages for all plants of 411 kWh/m² collector for 2012 and 450 kWh/m² collector for 2013. Theoretical calculations show...... of the cost/performance ratio for solar collector fields, both with flat plate collectors and with concentrating tracking solar collectors. It is recommended to continue monitoring and analysis of all large solar heating plants to document the reliability of the solar heating plants. It is also recommended...

  16. Standard Guide for Specifying Thermal Performance of Geothermal Power Systems

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This guide covers power plant performance terms and criteria for use in evaluation and comparison of geothermal energy conversion and power generation systems. The special nature of these geothermal systems makes performance criteria commonly used to evaluate conventional fossil fuel-fired systems of limited value. This guide identifies the limitations of the less useful criteria and defines an equitable basis for measuring the quality of differing thermal cycles and plant equipment for geothermal resources. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  17. Thermal Performance Analysis of a Geologic Borehole Repository

    Energy Technology Data Exchange (ETDEWEB)

    Reagin, Lauren [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-08-16

    The Brazilian Nuclear Research Institute (IPEN) proposed a design for the disposal of Disused Sealed Radioactive Sources (DSRS) based on the IAEA Borehole Disposal of Sealed Radioactive Sources (BOSS) design that would allow the entirety of Brazil’s inventory of DSRS to be disposed in a single borehole. The proposed IPEN design allows for 170 waste packages (WPs) containing DSRS (such as Co-60 and Cs-137) to be stacked on top of each other inside the borehole. The primary objective of this work was to evaluate the thermal performance of a conservative approach to the IPEN proposal with the equivalent of two WPs and two different inside configurations using Co-60 as the radioactive heat source. The current WP configuration (heterogeneous) for the IPEN proposal has 60% of the WP volume being occupied by a nuclear radioactive heat source and the remaining 40% as vacant space. The second configuration (homogeneous) considered for this project was a homogeneous case where 100% of the WP volume was occupied by a nuclear radioactive heat source. The computational models for the thermal analyses of the WP configurations with the Co-60 heat source considered three different cooling mechanisms (conduction, radiation, and convection) and the effect of mesh size on the results from the thermal analysis. The results of the analyses yielded maximum temperatures inside the WPs for both of the WP configurations and various mesh sizes. The heterogeneous WP considered the cooling mechanisms of conduction, convection, and radiation. The temperature results from the heterogeneous WP analysis suggest that the model is cooled predominantly by conduction with effect of radiation and natural convection on cooling being negligible. From the thermal analysis comparing the two WP configurations, the results suggest that either WP configuration could be used for the design. The mesh sensitivity results verify the meshes used and results obtained from the thermal analyses were close to being

  18. Thermal Performance Analysis of a Geologic Borehole Repository

    Energy Technology Data Exchange (ETDEWEB)

    Reagin, Lauren [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-08-16

    The Brazilian Nuclear Research Institute (IPEN) proposed a design for the disposal of Disused Sealed Radioactive Sources (DSRS) based on the IAEA Borehole Disposal of Sealed Radioactive Sources (BOSS) design that would allow the entirety of Brazil’s inventory of DSRS to be disposed in a single borehole. The proposed IPEN design allows for 170 waste packages (WPs) containing DSRS (such as Co-60 and Cs-137) to be stacked on top of each other inside the borehole. The primary objective of this work was to evaluate the thermal performance of a conservative approach to the IPEN proposal with the equivalent of two WPs and two different inside configurations using Co-60 as the radioactive heat source. The current WP configuration (heterogeneous) for the IPEN proposal has 60% of the WP volume being occupied by a nuclear radioactive heat source and the remaining 40% as vacant space. The second configuration (homogeneous) considered for this project was a homogeneous case where 100% of the WP volume was occupied by a nuclear radioactive heat source. The computational models for the thermal analyses of the WP configurations with the Co-60 heat source considered three different cooling mechanisms (conduction, radiation, and convection) and the effect of mesh size on the results from the thermal analysis. The results of the analyses yielded maximum temperatures inside the WPs for both of the WP configurations and various mesh sizes. The heterogeneous WP considered the cooling mechanisms of conduction, convection, and radiation. The temperature results from the heterogeneous WP analysis suggest that the model is cooled predominantly by conduction with effect of radiation and natural convection on cooling being negligible. From the thermal analysis comparing the two WP configurations, the results suggest that either WP configuration could be used for the design. The mesh sensitivity results verify the meshes used, and results obtained from the thermal analyses were close to

  19. Correlation between dynamic wetting behavior and chemical components of thermally modified wood

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wang; Zhu, Yuan; Cao, Jinzhen, E-mail: caoj@bjfu.edu.cn; Sun, Wenjing

    2015-01-01

    Highlights: • We studied the dynamic wetting behavior of thermally modified wood by wetting models. • We found lower wetting speed of water droplets on thermally modified wood surface. • Dynamic wetting behavior and surface chemical components show a strong correlation. - Abstract: In order to investigate the dynamic wetting behavior of thermally modified wood, Cathay poplar (Populus cathayana Rehd.) and Scots pine (Pinus sylvestris L.) samples were thermally modified in an oven at 160, 180, 200, 220 or 240 °C for 4 h in this study. The dynamic contact angles and droplet volumes of water droplets on modified and unmodified wood surfaces were measured by sessile drop method, and their changing rates (expression index: K value and wetting slope) calculated by wetting models were illustrated for mapping the dynamic wetting process. The surface chemical components were also measured by X-ray photoelectron spectroscopy analysis (XPS), thus the relationship between dynamic wetting behavior and chemical components of thermally modified wood were determined. The results indicated that thermal modification was capable of decreasing the dynamic wettability of wood, expressed in lowing spread and penetration speed of water droplets on wood surfaces. This change was more obvious with the increased heating temperature. The K values varied linearly with the chemical components parameter (mass loss, O/C ratio, and C{sub 1}/C{sub 2} ratio), indicating a strong correlation between dynamic wetting behavior and chemical components of thermally modified wood.

  20. Free Molecular Heat Transfer Programs for Setup and Dynamic Updating the Conductors in Thermal Desktop

    Science.gov (United States)

    Malroy, Eric T.

    2007-01-01

    The programs, arrays and logic structure were developed to enable the dynamic update of conductors in thermal desktop. The MatLab program FMHTPRE.m processes the Thermal Desktop conductors and sets up the arrays. The user needs to manually copy portions of the output to different input regions in Thermal Desktop. Also, Fortran subroutines are provided that perform the actual updates to the conductors. The subroutines are setup for helium gas, but the equations can be modified for other gases. The maximum number of free molecular conductors allowed is 10,000 for a given radiation task. Additional radiation tasks for FMHT can be generated to account for more conductors. Modifications to the Fortran subroutines may be warranted, when the mode of heat transfer is in the mixed or continuum mode. The FMHT Thermal Desktop model should be activated by using the "Case Set Manager" once the model is setup. Careful setup of the model is needed to avoid excessive solve times.

  1. Influence of Transient Thermal Response of Solid Wall on Bubble Dynamics in Pool Boiling

    Directory of Open Access Journals (Sweden)

    Liang Zhang

    2014-09-01

    Full Text Available Numerical simulation of single bubble pool boiling process including transient thermal response of solid wall is performed using the ghost fluid method and the level set method for the sharp interface representation. The results show that non-physical initial condition in the numerical simulation deeply affects the process of bubble growth, and then multi-cycle simulation is necessary to eliminate its influence. It is shown by the present results that two nucleate criteria, i.e. constant waiting time and constant nucleate superheat, for determining the appearance time for the subsequent bubble lead to the same quasi-steady process of bubble growth if they are matched with each other. A periodically expanding and receding thermal “hollow” can be observed inside solid wall underneath the growing bubble. The recovery of the temperature on the nucleate site and the thermal boundary layer near the heating surface is influenced by transient heat conduction inside solid wall, which can affect evidently bubble thermal dynamics and heat transfer.

  2. Influence of Transient Thermal Response of Solid Wall on Bubble Dynamics in Pool Boiling

    Directory of Open Access Journals (Sweden)

    Liang Zhang

    2014-12-01

    Full Text Available Numerical simulation of single bubble pool boiling process including transient thermal response of solid wall is performed using the ghost fluid method and the level set method for the sharp interface representation. The results show that non-physical initial condition in the numerical simulation deeply affects the process of bubble growth, and then multicycle simulation is necessary to eliminate its influence. It is shown by the present results that two nucleate criteria, i.e. constant waiting time and constant nucleate superheat, for determining the appearance time for the subsequent bubble lead to the same quasi-steady process of bubble growth if they are matched with each other. A periodically expanding and receding thermal “hollow” can be observed inside solid wall underneath the growing bubble. The recovery of the temperature on the nucleate site and the thermal boundary layer near the heating surface is influenced by transient heat conduction inside solid wall, which can affect evidently bubble thermal dynamics and heat transfer.

  3. Performance Evaluation of Modern Building Thermal Envelope Designs in the Semi-Arid Continental Climate of Tehran

    Directory of Open Access Journals (Sweden)

    Shaghayegh Mohammad

    2013-10-01

    Full Text Available In this paper we evaluate the thermal performance of a range of modern wall constructions used in the residential buildings of Tehran in order to find the most appropriate alternative to the traditional un-fired clay and brick materials, which are increasingly being replaced in favor of more slender wall constructions employing hollow clay, autoclaved aerated concrete or light expanded clay aggregate blocks. The importance of improving the building envelope through estimating the potential for energy saving due to the application of the most energy-efficient wall type is presented and the wall constructions currently erected in Tehran are introduced along with their dynamic and steady-state thermal properties. The application of a dynamic simulation tool is explained and the output of the thermal simulation model is compared with the dynamic thermal properties of the wall constructions to assess their performance in summer and in winter. Finally, the best and worst wall type in terms of their cyclic thermal performance and their ability to moderate outdoor conditions is identified through comparison of the predicted indoor temperature and a target comfort temperature.

  4. Thermal effects in the dynamics of disordered elastic systems

    Energy Technology Data Exchange (ETDEWEB)

    Bustingorry, S.; Kolton, A.B. [Centro Atomico Bariloche, 8400 S.C. de Bariloche (Argentina); Rosso, A. [CNRS, LPTMS, Univ. Paris-Sud, UMR 8626, Orsay Cedex F-91405 (France); Krauth, W. [CNRS-Laboratoire de Physique Statistique, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Giamarchi, T. [DPMC-MaNEP, University of Geneva, 24 Quai Ernest Ansermet, 1211 Geneva 4 (Switzerland)], E-mail: Thierry.Giamarchi@physics.unige.ch

    2009-03-01

    Many seemingly different macroscopic systems (magnets, ferroelectrics, CDW, vortices, etc.) can be described as generic disordered elastic systems. Understanding their static and dynamics thus poses challenging problems both from the point of view of fundamental physics and of practical applications. Despite important progress many questions remain open. In particular the temperature has drastic effects on the way these systems respond to an external force. We address here the important question of the thermal effect close to depinning, and whether these effects can be understood in the analogy with standard critical phenomena, analogy so useful to understand the zero temperature case. We show that close to the depinning force temperature leads to a rounding of the depinning transition and compute the corresponding exponent. In addition, using a novel algorithm it is possible to study precisely the behavior close to depinning, and to show that the commonly accepted analogy of the depinning with a critical phenomenon does not fully hold, since no divergent lengthscale exists in the steady state properties of the line below the depinning threshold.

  5. Computational simulations of thermally activated magnetisation dynamics at high frequencies

    CERN Document Server

    Hannay, J D

    2001-01-01

    short time scale breakdown of the Arrhenius-Neel law for a single magnetic moment is demonstrated and explained in terms of the dynamics of the precessional motion. The variation in response as a function of the damping parameter is found to be an important factor determining the remanent magnetisation for a given pulse width. The effects of interactions between moments are described, including the apparent increase in effective damping. It is shown that interactions between grains can be described in terms of thermally excited spin waves. The most important device for today's large scale information storage is the magnetic hard disk drive. This is because it can store vast amounts of data and also provides the fastest way of accessing this valuable information. A current state of the art commercially available hard disk has data rates in excess of 1 GHz which means the magnetic bits are required to reverse in less than one nanosecond. The areal density is greater than 10 Gbits/in sup 2 which requires extreme...

  6. A dynamically adaptive lattice Boltzmann method for thermal convection problems

    Directory of Open Access Journals (Sweden)

    Feldhusen Kai

    2016-12-01

    Full Text Available Utilizing the Boussinesq approximation, a double-population incompressible thermal lattice Boltzmann method (LBM for forced and natural convection in two and three space dimensions is developed and validated. A block-structured dynamic adaptive mesh refinement (AMR procedure tailored for the LBM is applied to enable computationally efficient simulations of moderate to high Rayleigh number flows which are characterized by a large scale disparity in boundary layers and free stream flow. As test cases, the analytically accessible problem of a two-dimensional (2D forced convection flow through two porous plates and the non-Cartesian configuration of a heated rotating cylinder are considered. The objective of the latter is to advance the boundary conditions for an accurate treatment of curved boundaries and to demonstrate the effect on the solution. The effectiveness of the overall approach is demonstrated for the natural convection benchmark of a 2D cavity with differentially heated walls at Rayleigh numbers from 103 up to 108. To demonstrate the benefit of the employed AMR procedure for three-dimensional (3D problems, results from the natural convection in a cubic cavity at Rayleigh numbers from 103 up to 105 are compared with benchmark results.

  7. International Space Station power module thermal control system hydraulic performance

    Energy Technology Data Exchange (ETDEWEB)

    Goldberg, V. [Boeing North American, Inc., Canoga Park, CA (United States). Rocketdyne Div.

    1997-12-31

    The International Space Station (ISS) uses four photovoltaic power modules (PVMs) to provide electric power for the US On-Orbit Segment. The PVMs consist of photovoltaic arrays (PVAs), orbit replaceable units (ORUs), photovoltaic radiators (PVRs), and a thermal control system (TCS). The PVM TCS function is to maintain selected PVM components within their specified operating ranges. The TCS consists of the pump flow control subassembly (PFCS), piping system, including serpentine tubing for individual component heat exchangers, headers/manifolds, fluid disconnect couplings (FQDCs), and radiator (PVR). This paper describes the major design requirements for the TCS and the results of the system hydraulic performance predictions in regard to these requirements and system component sizing. The system performance assessments were conducted using the PVM TCS fluid network hydraulic model developed for predicting system/component pressure losses and flow distribution. Hardy-Cross method of iteration was used to model the fluid network configuration. Assessments of the system hydraulic performance were conducted based on an evaluation of uncertainties associated with the manufacturing and design tolerances. Based on results of the analysis, it was concluded that all design requirements regarding system performance could be met. The hydraulic performance range, enveloping possible system operating parameter variations was determined.

  8. Summer and Winter Effect of Innovative Cool Roof Tiles on the Dynamic Thermal Behavior of Buildings

    Directory of Open Access Journals (Sweden)

    Anna Laura Pisello

    2014-04-01

    Full Text Available Cool roofs represent an acknowledged passive cooling technique to reduce building energy consumption for cooling and to mitigate urban heat island effects. This paper concerns the evaluation of the dynamic effect of new cool roof clay tiles on building thermal performance in summer and winter conditions. To this end, these properties have been analyzed on traditional roof brick tiles through an indoor and outdoor two-year long continuous monitoring campaign set up in a residential building located in central Italy. The analysis and the cooperation with industrial companies producing brick tiles and reflective coatings allowed the production of a new tile with notable “cool roof” properties through the traditional industrial manufacturing path of such tiles. Notable results show that during summer the high reflection tiles are able to decrease the average external roof surface temperature by more than 10 °C and the indoor operative temperature by more than 3 °C. During winter the average external surface temperature is lower with high reflection tiles by about 1 °C. Singular optic-thermal phenomena are registered while evaluating the dynamics of the cool roof effect. Interesting findings show how the sloped cool roof application could suggest further considerations about the dynamic effect of cool roofs.

  9. Thermal Performance of Cryogenic Multilayer Insulation at Various Layer Spacings

    Science.gov (United States)

    Johnson, Wesley Louis

    2010-01-01

    Multilayer insulation (MLI) has been shown to be the best performing cryogenic insulation system at high vacuum (less that 10 (exp 3) torr), and is widely used on spaceflight vehicles. Over the past 50 years, many investigations into MLI have yielded a general understanding of the many variables that are associated with MLI. MLI has been shown to be a function of variables such as warm boundary temperature, the number of reflector layers, and the spacer material in between reflectors, the interstitial gas pressure and the interstitial gas. Since the conduction between reflectors increases with the thickness of the spacer material, yet the radiation heat transfer is inversely proportional to the number of layers, it stands to reason that the thermal performance of MLI is a function of the number of layers per thickness, or layer density. Empirical equations that were derived based on some of the early tests showed that the conduction term was proportional to the layer density to a power. This power depended on the material combination and was determined by empirical test data. Many authors have graphically shown such optimal layer density, but none have provided any data at such low densities, or any method of determining this density. Keller, Cunnington, and Glassford showed MLI thermal performance as a function of layer density of high layer densities, but they didn't show a minimal layer density or any data below the supposed optimal layer density. However, it was recently discovered that by manipulating the derived empirical equations and taking a derivative with respect to layer density yields a solution for on optimal layer density. Various manufacturers have begun manufacturing MLI at densities below the optimal density. They began this based on the theory that increasing the distance between layers lowered the conductive heat transfer and they had no limitations on volume. By modifying the circumference of these blankets, the layer density can easily be

  10. Thermal Performance Evaluation of Friction Stir Welded and Bolted Cold Plates with Al/Cu Interface

    Science.gov (United States)

    Lakshminarayanan, A. K.; Suresh, M.; Sibi Varshan, M.

    2015-05-01

    An attempt is made to design and fabricate a cold plate with aluminum-copper dissimilar interface joined by friction stir welding. Optimum welding conditions for obtaining sound-quality corner and T joints with an aluminum-copper interface were established. Welded cross sections of the friction stir welded cold plate were analyzed to understand the bonding characteristics. Computational fluid dynamics (CFD) was used to evaluate the fluid-flow characteristics and thermal resistance of friction stir welded cold plate and the resulted are compared with the conventional bolted cold plate configuration. For CFD modeling of a cold plate with a dissimilar interface, a new methodology is proposed. From the CFD analysis and experimental results, it is observed that friction stir welded cold plate offered better thermal performance compared to the bolted cold plate and it is due to the metallurgical bonding at the aluminum-copper interface with the dispersion of copper particles.

  11. 3D modeling and simulation of the thermal performance of solid cyclotron targets

    Energy Technology Data Exchange (ETDEWEB)

    Avila-Rodriguez, M.A.; Sader, J.A.; McQuarrie, S.A. [Alberta Univ., Edmonton PET Centre, Cross Cancer Institute, AB (Canada); McQuarrie, S.A. [Alberta Univ., Faculty of Medicine and Dentistry, Div. of Oncologic Imaging, Edmonton, AB (Canada)

    2007-07-01

    COMSOL Multiphysics was used to model and simulate the thermal performance of solid targets irradiated with charged particles. Parametric solutions for beam power densities in the range from 1.5 10{sup 5} to 1.5 10{sup 6} W/m{sup 2} and cooling water flow velocities from 0.2 to 4.0 m/s were obtained for different plate materials. Results showed that materials with a high thermal conductivity to heat capacity ratio behave better in cooling dynamic systems requiring fast dissipation of heat. Results also showed that water flow rates greater than 2.6 L/min do not noticeably improve the heat dissipation of solid targets irradiated with charged particles. (authors)

  12. Performance of thermal distribution systems in large commercial buildings

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tengfang [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States); Carrie, Remi F. [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States); Dickerhoff, Darryl J. [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States); Fisk, William J. [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States); McWilliams, Jennifer [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States); Wang, Duo [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States); Modera, Mark P. [Lawrence Berkeley National Lab. (LBNL), Univ. of California, Berkeley, CA (United States)

    2001-12-08

    This paper presents major findings of a field study on the performance of five thermal distribution systems in four large commercial buildings. The five systems studied are typical single-duct or dual-duct constant air volume (CAV) systems and variable air volume (VAV) systems, each of which serves an office building or a retail building with floor area over 2000 m2. The air leakage from ducts is reported in terms of effective leakage area (ELA) at 25 Pa reference pressure, the ASHRAE-defined duct leakage class CL, and air leakage ratios. The specific ELAs ranged from 0.7 to 12.9 cm2/m2 of duct surface area, and from 0.1 to 7.7 cm2/m2 of floor area served. The ASHRAE-defined duct leakage classes ranged from 34 to 606 for the five systems and systems sections tested. The air leakage ratios were estimated to be up to approximately one-third of the fan-supplied airflow in the constant air volume systems. The specific ELAs and leakage classes indicated that air leakage in large commercial duct systems varied significantly from system to system, and from system section to system section even within the same thermal distribution system. Overall, the duct systems measured were much leakier than the ductwork specified as “unsealed ducts” by ASHRAE. On the other hand, thermal losses from supply ducts induced by conduction (including convection and radiation) were significant, on the scale that was comparable to the losses induced by air leakage in the duct systems. Furthermore, the energy losses induced by leakage and conduction suggested that there exist significant energy savings potentials from duct sealing and duct insulation practice in large commercial buildings.

  13. A performance analysis of solar chimney thermal power systems

    Directory of Open Access Journals (Sweden)

    Al-Dabbas Awwad Mohammed

    2011-01-01

    Full Text Available The objective of this study was to evaluate the solar chimney performance theoretically (techno-economic. A mathematical model was developed to estimate the following parameter: Power output, Pressure drop across the turbine, the max chimney height, Airflow temperature, and the overall efficiency of solar chimney. The mathematical model was validated with experimental data from the prototype in Manzanares power. It can be concluded that the differential pressure of collector-chimney transition section in the system, is increase with the increase of solar radiation intensity. The specific system costs are between 2000 Eur/kW and 5000 Eur/kW depending on the system size, system concept and storage size. Hence, a 50 MWe solar thermal power plant will cost 100-250 Eur million. At very good sites, today’s solar thermal power plants can generate electricity in the range of 0.15 Eur/kWh, and series production could soon bring down these costs below 0.10 Eur /kWh.

  14. GCFR Coupled Neutronic and Thermal-Fluid-Dynamics Analyses for a Core Containing Minor Actinides

    Directory of Open Access Journals (Sweden)

    Diego Castelliti

    2009-01-01

    Full Text Available Problems about future energy availability, climate changes, and air quality seem to play an important role in energy production. While current reactor generations provide a guaranteed and economical energy production, new nuclear power plant generation would increase the ways and purposes in which nuclear energy can be used. To explore these new technological applications, several governments, industries, and research communities decided to contribute to the next reactor generation, called “Generation IV.” Among the six Gen-IV reactor designs, the Gas Cooled Fast Reactor (GCFR uses a direct-cycle helium turbine for electricity generation and for a CO2-free thermochemical production of hydrogen. Additionally, the use of a fast spectrum allows actinides transmutation, minimizing the production of long-lived radioactive waste in an integrated fuel cycle. This paper presents an analysis of GCFR fuel cycle optimization and of a thermal-hydraulic of a GCFR-prototype under steady-state and transient conditions. The fuel cycle optimization was performed to assess the capability of the GCFR to transmute MAs, while the thermal-hydraulic analysis was performed to investigate the reactor and the safety systems behavior during a LOFA. Preliminary results show that limited quantities of MA are not affecting significantly the thermal-fluid-dynamics behavior of a GCFR core.

  15. Dynamic Exergy Analysis for the Thermal Storage Optimization of the Building Envelope

    Directory of Open Access Journals (Sweden)

    Valentina Bonetti

    2017-01-01

    Full Text Available As a measure of energy “quality”, exergy is meaningful for comparing the potential for thermal storage. Systems containing the same amount of energy could have considerably different capabilities in matching a demand profile, and exergy measures this difference. Exergy stored in the envelope of buildings is central in sustainability because the environment could be an unlimited source of energy if its interaction with the envelope is optimised for maintaining the indoor conditions within comfort ranges. Since the occurring phenomena are highly fluctuating, a dynamic exergy analysis is required; however, dynamic exergy modelling is complex and has not hitherto been implemented in building simulation tools. Simplified energy and exergy assessments are presented for a case study in which thermal storage determines the performance of seven different wall types for utilising nocturnal ventilation as a passive cooling strategy. Hourly temperatures within the walls are obtained with the ESP-r software in free-floating operation and are used to assess the envelope exergy storage capacity. The results for the most suitable wall types were different between the exergy analysis and the more traditional energy performance indicators. The exergy method is an effective technique for selecting the construction type that results in the most favourable free-floating conditions through the analysed passive strategy.

  16. Dynamic Web Pages: Performance Impact on Web Servers.

    Science.gov (United States)

    Kothari, Bhupesh; Claypool, Mark

    2001-01-01

    Discussion of Web servers and requests for dynamic pages focuses on experimentally measuring and analyzing the performance of the three dynamic Web page generation technologies: CGI, FastCGI, and Servlets. Develops a multivariate linear regression model and predicts Web server performance under some typical dynamic requests. (Author/LRW)

  17. Parametric study of solar thermal rocket nozzle performance

    Science.gov (United States)

    Pearson, J. Boise; Landrum, D. Brian; Hawk, Clark W.

    1995-01-01

    This paper details a numerical investigation of performance losses in low-thrust solar thermal rocket nozzles. The effects of nozzle geometry on three types of losses were studied; finite rate dissociation-recombination kinetic losses, two dimensional axisymmetric divergence losses, and compressible viscous boundary layer losses. Short nozzle lengths and supersonic flow produce short residence times in the nozzle and a nearly frozen flow, resulting in large kinetic losses. Variations in geometry have a minimal effect on kinetic losses. Divergence losses are relatively small, and careful shaping of the nozzle can nearly eliminate them. The boundary layer in these small nozzles can grow to a major fraction of nozzle radius, and cause large losses. These losses are attributed to viscous drag on the nozzle walls and flow blockage by the boundary layer, especially in the throat region. Careful shaping of the nozzle can produce a significant reduction in viscous losses.

  18. THERMAL PERFORMANCE OF RADIOACTIVE MATERIAL PACKAGES IN TRANSPORT CONFIGURATION

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, N.

    2010-03-04

    Drum type packages are routinely used to transport radioactive material (RAM) in the U.S. Department of Energy (DOE) complex. These packages are designed to meet the federal regulations described in 10 CFR Part 71. The packages are transported in specially designed vehicles like Safe Secure Transport (SST) for safety and security. In the transport vehicles, the packages are placed close to each other to maximize the number of units in the vehicle. Since the RAM contents in the packagings produce decay heat, it is important that they are spaced sufficiently apart to prevent overheating of the containment vessel (CV) seals and the impact limiter to ensure the structural integrity of the package. This paper presents a simple methodology to assess thermal performance of a typical 9975 packaging in a transport configuration.

  19. Evaluating thermal performance of a single slope solar still

    Science.gov (United States)

    Badran, Omar O.; Abu-Khader, Mazen M.

    2007-08-01

    The distillation is one of the important methods of getting clean water from brackish and sea water using the free energy supply from the sun. An experimental work is conducted on a single slope solar still. The thermal performance of the single slope solar still is examined and evaluated through implementing the following effective parameters: (a) different insulation thicknesses of 1, 2.5 and 5 cm; (b) water depth of 2 and 3.5 cm; (c) solar intensity; (d) Overall heat loss coefficient (e) effective absorbtivity and transmissivity; and (f) ambient, water and vapor temperatures. Different effective parameters should be taken into account to increase the still productivity. A mathematical model is presented and compared with experimental results. The model gives a good match with experimental values.

  20. Thermal performance evaluation of the Calmac (liquid) solar collector

    Science.gov (United States)

    Usher, H.

    1978-01-01

    The procedures used and the results obtained during the evaluation test program on the S. N. 1, (liquid) solar collector are presented. The flat plate collector uses water as the working fluid. The absorber plate is aluminum with plastic tubes coated with urethane black. The glazing consists of .040 in fiberglass reinforced polyester. The collector weight is 78.5 pounds with overall external dimensions of approximately 50.3in. x 98.3in. x 3.8in. The following information is given: thermal performance data under simulated conditions, structural behavior under static loading, and the effects of long term exposure to natural weathering. These tests were conducted using the MSFC Solar Simulator.

  1. LARGO hot water system thermal performance test report

    Science.gov (United States)

    1978-01-01

    The thermal performance tests and results on the LARGO Solar Hot Water System under natural environmental conditions is presented. Some objectives of these evaluations are to determine the amount of energy collected, the amount of energy delivered to the household as contributed by solar power supplied to operate the system and auxiliary power to maintain tank temperature at proper level, overall system efficiency and to determine temperature distribution within the tank. The Solar Hot Water system is termed a Dump-type because of the draining system for freeze protection. The solar collector is a single glazed flat plate. An 82-gallon domestic water heater is provided as the energy storage vessel. Water is circulated through the collector and water heater by a 5.3 GPM capacity pump, and control of the pump motor is achieved by a differential temperature controller.

  2. Spared nerve injury rats exhibit thermal hyperalgesia on an automated operant dynamic thermal escape Task

    OpenAIRE

    Chialvo Dante R; Calvo Oscar; Baliki Marwan; Apkarian A Vania

    2005-01-01

    Abstract Well-established methods are available to measure thermal and mechanical sensitivity in awake behaving rats. However, they require experimenter manipulations and tend to emphasize reflexive behaviors. Here we introduce a new behavioral test, with which we examine thermal sensitivity of rats with neuropathic injury. We contrast thermal hyperalgesia between spared nerve injury and chronic constriction injury rats. This device is a fully automated thermal sensitivity assessment tool des...

  3. Experiment Investigation on Electrical and Thermal Performances of a Semitransparent Photovoltaic/Thermal System with Water Cooling

    Directory of Open Access Journals (Sweden)

    Guiqiang Li

    2014-01-01

    Full Text Available Different from the semitransparent building integrated photovoltaic/thermal (BIPV/T system with air cooling, the semitransparent BIPV/T system with water cooling is rare, especially based on the silicon solar cells. In this paper, a semitransparent photovoltaic/thermal system (SPV/T with water cooling was set up, which not only would provide the electrical power and hot water, but also could attain the natural illumination for the building. The PV efficiency, thermal efficiency, and exergy analysis were all adopted to illustrate the performance of SPV/T system. The results showed that the PV efficiency and the thermal efficiency were about 11.5% and 39.5%, respectively, on the typical sunny day. Furthermore, the PV and thermal efficiencies fit curves were made to demonstrate the SPV/T performance more comprehensively. The performance analysis indicated that the SPV/T system has a good application prospect for building.

  4. Design Issues for Low Power Integrated Thermal Flow Sensors with Ultra-Wide Dynamic Range and Low Insertion Loss

    Directory of Open Access Journals (Sweden)

    Paolo Bruschi

    2012-04-01

    Full Text Available Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several critical issues have still to be solved. In this work, a systematic approach to the design of integrated thermal flow sensors, with specification of resolution, dynamic range, power consumption and pressure insertion loss is proposed. All the critical components of the sensors, namely thermal microstructure, package and read-out interface are examined, showing their impact on the sensor performance and indicating effective optimization strategies. The proposed design procedures are supported by experiments performed using a recently developed test chip,including several different sensing structures and a flexible electronic interface.

  5. Driver performance-based assessment of thermal display degradation effects

    Science.gov (United States)

    Ruffner, John W.; Massimi, Michael S.; Choi, Yoon S.; Ferrett, Donald A.

    1998-07-01

    The Driver's Vision Enhancer (DVE) is a thermal sensor and display combination currently being procured for use in U.S. Army combat and tactical wheeled vehicles. During the DVE production process, a given number of sensor or display pixels may either vary from the desired luminance values (nonuniform) or be inactive (nonresponsive). The amount and distribution of pixel luminance nonuniformity (NU) and nonresponsivity (NR) allowable in production DVEs is a significant cost factor. No driver performance-based criteria exist for determining the maximum amount of allowable NU and NR. For safety reasons, these characteristics are specified conservatively. This paper describes an experiment to assess the effects of different levels of display NU and NR on Army drivers' ability to identify scene features and obstacles using a simulated DVE display and videotaped driving scenarios. Baseline, NU, and NR display conditions were simulated using real-time image processing techniques and a computer graphics workstation. The results indicate that there is a small, but statistically insignificant decrease in identification performance with the NU conditions tested. The pattern of the performance-based results is consistent with drivers' subjective assessments of display adequacy. The implications of the results for specifying NU and NR criteria for the DVE display are discussed.

  6. Development of fuel performance and thermal hydraulic technology

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Youn Ho; Song, K. N.; Kim, H. K. and others

    2000-03-01

    Space grid in LWR fuel assembly is a key structural component to support fuel rods and to enhance heat transfer from fuel rod to the coolant. Therefore, the original spacer grid has been developed. In addition, new phenomena in fuel behavior occurs at the high burnup, so that models to analyze those new phenomena were developed. Results of this project can be summarized as follows. - Seven different spacer grid candidates have been invented and submitted for domestic and US patents. Spacer grid test specimen(3x3 array and 5x5 array) were fabricated for each candidate and the mechanical tests were performed. - Basic technologies in the mechanical and thermal hydraulic behavior in the spacer grid development are studied and relevant test facilities were established - Fuel performance analysis models and programs were developed for the high burnup pellet and cladding, and fuel performance data base were compiled - Procedures of fuel characterization and in-/out of-pile tests were prepared - Conceptual design of fuel rod for integral PWR was carried out. (author)

  7. Thermal Performance Analysis of Solar Collectors Installed for Combisystem in the Apartment Building

    Science.gov (United States)

    Žandeckis, A.; Timma, L.; Blumberga, D.; Rochas, C.; Rošā, M.

    2012-01-01

    The paper focuses on the application of wood pellet and solar combisystem for space heating and hot water preparation at apartment buildings under the climate of Northern Europe. A pilot project has been implemented in the city of Sigulda (N 57° 09.410 E 024° 52.194), Latvia. The system was designed and optimised using TRNSYS - a dynamic simulation tool. The pilot project was continuously monitored. To the analysis the heat transfer fluid flow rate and the influence of the inlet temperature on the performance of solar collectors were subjected. The thermal performance of a solar collector loop was studied using a direct method. A multiple regression analysis was carried out using STATGRAPHICS Centurion 16.1.15 with the aim to identify the operational and weather parameters of the system which cause the strongest influence on the collector's performance. The parameters to be used for the system's optimisation have been evaluated.

  8. Electro-thermal pilot in the Athabasca oil sands : theory versus performance

    Energy Technology Data Exchange (ETDEWEB)

    McGee, B.C.W. [E-T Energy, Calgary, AB (Canada)

    2008-07-01

    This paper provided details of a proof of concept test of E-T Energy's electro-thermal dynamic stripping process (ET-DSP). The technology combined features of electro-thermal heating with heat transfer by convection. Water was injected into the ends of an electrode where power density was most intense. Injected water carried heat away from the electrode into the reservoir. The tests were preceded by a mathematical model designed to quantify performance metrics including the amount of water usage for produced oil, energy input requirements, greenhouse gas (GHG) emissions, drilling performance, and operating costs. Field tests included a monitoring phase with new progressive cavity pumps (PCPs). Results of the tests and modelling studies showed that recovery factors were achieved with less energy use than thought possible. An energy oil ratio of 61.52 kWh per barrel was achieved for the production of bitumen from X05 was equivalent to a steam oil ratio of 0.49. Increases in temperature were achieved within 30 days. It was concluded that the ET-DSP process provided an efficient in situ thermal recovery technology for the production of bitumens. Recovery factors were demonstrated at 75 per cent or more. The process also provided rapid and uniform heating without the need for injection and displacing reservoir fluids. The process produced bitumens that were sand-free, with virtually no emulsions. 8 refs., 3 tabs., 10 figs.

  9. Theory analysis and system identification methods on thermal dynamics characteristics of ballscrews

    Institute of Scientific and Technical Information of China (English)

    Junyong XIA; Youmin HU; Bo WU; Tielin SHI

    2008-01-01

    Empirical model of machine tools on thermal error has been widely researched, which can compensate for thermal error to some extent but not suitable for ther-mal dynamic errors produced by dynamic heat sources. The thermoelastic phenomenon of unidimensional heat transfer of ballscrews influenced by changeable heat sources is analyzed based on the theory of heat transfer. Two methods for system identification (the least square system identification and BP artificial neural network (ANN) system identification) are put forward to establish a dynamic characteristic model of thermal deformation of ballscrews. The model of thermal error of the X axis in a feed system of DM4600 vertical miller is established with a fine identification effect. Comparing the results of the two identification methods, the BP ANN system identification is more precise than the least square system identification.

  10. Static and dynamic thermal infrared signatures measured during the FESTER experiment: first results

    Science.gov (United States)

    Gunter, W. H.; February, F.; Seiffer, D. P.; Eisele, C.

    2016-10-01

    The First European South African Experiment (FESTER) was conducted over about a 10 month period at the Institute of Maritime Technology (IMT) in False Bay, South Africa. One of the principal goals was recording of static and dynamic thermal infrared signatures under different environmental conditions for both validations of existing thermal equilibrium signature prediction codes, but also to aid development of dynamic thermal signature models. A small scientific work boat (called Sea Lab) was used as the principal target and sensor platform. Painted metal plates of different thicknesses were also used as infrared targets on-board Sea Lab to study static/dynamic thermal signatures and were also fitted with pyrgeometers, pyrometers and iButton temperature sensors/loggers. First results focused on the variable of thermal signatures as function of environmental conditions and the accuracy of calculated source temperatures (from measured radiometric temperatures) compared to the physical temperature measurements of the plates.

  11. Mako airborne thermal infrared imaging spectrometer: performance update

    Science.gov (United States)

    Hall, Jeffrey L.; Boucher, Richard H.; Buckland, Kerry N.; Gutierrez, David J.; Keim, Eric R.; Tratt, David M.; Warren, David W.

    2016-09-01

    The Aerospace Corporation's sensitive Mako thermal infrared imaging spectrometer, which operates between 7.6 and 13.2 microns at a spectral sampling of 44 nm, and flies in a DeHavilland DHC-6 Twin Otter, has undergone significant changes over the past year that have greatly increased its performance. A comprehensive overhaul of its electronics has enabled frame rates up to 3255 Hz and noise reductions bringing it close to background-limited. A replacement diffraction grating whose peak efficiency was tuned to shorter wavelength, coupled with new AR coatings on certain key optics, has improved the performance at the short wavelength end by a factor of 3, resulting in better sensitivity for methane detection, for example. The faster frame rate has expanded the variety of different scan schemes that are possible, including multi-look scans in which even sizeable target areas can be scanned multiple times during a single overpass. Off-nadir scanning to +/-56.4° degrees has also been demonstrated, providing an area scan rate of 33 km2/minute for a 2-meter ground sampling distance (GSD) at nadir. The sensor achieves a Noise Equivalent Spectral Radiance (NESR) of better than 0.6 microflicks (μf, 10-6 W/sr/cm2/μm) in each of the 128 spectral channels for a typical airborne dataset in which 4 frames are co-added. An additional improvement is the integration of a new commercial 3D stabilization mount which is significantly better at compensating for aircraft motions and thereby maintains scan performance under quite turbulent flying conditions. The new sensor performance and capabilities are illustrated.

  12. Dynamics and control designs for internal thermally coupled distillation columns with different purities, Part 1: Open loop dynamic behaviors

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The open loop dynamic behaviors of internal thermally coupled distillation column with four different purities (low-,moderate-, high- and very high-purity) are studied. These dynamic behaviors are characterized by strong asymmetric non-linearity, high sensitivity to operation conditions change and distinct inverse response. With the increase of purity, these dynamic behaviors are intensified and become more complex, which easily lead to the mismatch between linear model and plant and also change the relationship between manipulated and controlled variables.

  13. Development of a test device to characterize thermal protective performance of fabrics against hot steam and thermal radiation

    Science.gov (United States)

    Su, Yun; Li, Jun

    2016-12-01

    Steam burns severely threaten the life of firefighters in the course of their fire-ground activities. The aim of this paper was to characterize thermal protective performance of flame-retardant fabrics exposed to hot steam and low-level thermal radiation. An improved testing apparatus based on ASTM F2731-11 was developed in order to simulate the routine fire-ground conditions by controlling steam pressure, flow rate and temperature of steam box. The thermal protective performance of single-layer and multi-layer fabric system with/without an air gap was studied based on the calibrated tester. It was indicated that the new testing apparatus effectively evaluated thermal properties of fabric in hot steam and thermal radiation. Hot steam significantly exacerbated the skin burn injuries while the condensed water on the skin’s surface contributed to cool down the skin tissues during the cooling. Also, the absorbed thermal energy during the exposure and the cooling was mainly determined by the fabric’s configuration, the air gap size, the exposure time and the existence of hot steam. The research provides a effective method to characterize the thermal protection of fabric in complex conditions, which will help in optimization of thermal protection performance of clothing and reduction of steam burn.

  14. High Temperature Thermal Properties of Columnar Yttria Stabilized Zirconia Thermal Barrier Coating Performed by Suspension Plasma Spraying

    Science.gov (United States)

    Bernard, B.; Schick, V.; Remy, B.; Quet, A.; Bianchi, L.

    2016-09-01

    Performance enhancement of gas turbines is a main issue for the aircraft industry. Over many years, a large part of the effort has been focused on the development of more insulating Thermal Barrier Coatings (TBCs). In this study, Yttria Stabilized Zirconia (YSZ) columnar structures are processed by Suspension Plasma Spraying (SPS). These structures have already demonstrated abilities to get improved thermal lifetime, similarly to standard YSZ TBCs performed by EB-PVD. Thermal diffusivity measurements coupled with differential scanning calorimetry analysis are performed from room temperature up to 1100 °C, first, on HastelloyX substrates and then, on bilayers including a SPS YSZ coating. Results show an effective thermal conductivity for YSZ performed by SPS lower than 1 W.m-1K-1 whereas EB- PVD YSZ coatings exhibit a value of 1.5 W.m-1K-1.

  15. Dynamical Screening Effect on $\\alpha$-$\\alpha$ Resonant Scattering and Thermal Nuclear Scattering Rate

    CERN Document Server

    Yao, Xiaojun; Müller, Berndt

    2016-01-01

    We study the dynamical screening effect in the QED plasma on the $\\alpha$-$\\alpha$ scattering at the $^8$Be resonance. Dynamical screening leads to an imaginary part of the potential which results in a thermal width for the resonance and dominates over the previously considered static screening effect. As a result, both the resonance energy and width increase with the plasma temperature. Furthermore, dynamical screening can have a huge impact on the $\\alpha$-$\\alpha$ thermal nuclear scattering rate. For example, when the temperature is around $10$ keV, the rate is suppressed by a factor of about $900$. We expect similar thermal suppressions of nuclear reaction rates to occur in nuclear reactions dominated by an above threshold resonance with a thermal energy. Dynamical screening effects on nuclear reactions can be relevant to cosmology and astrophysics.

  16. A review on the flexural mode of graphene: lattice dynamics, thermal conduction, thermal expansion, elasticity and nanomechanical resonance.

    Science.gov (United States)

    Jiang, Jin-Wu; Wang, Bing-Shen; Wang, Jian-Sheng; Park, Harold S

    2015-03-04

    Single-layer graphene is so flexible that its flexural mode (also called the ZA mode, bending mode, or out-of-plane transverse acoustic mode) is important for its thermal and mechanical properties. Accordingly, this review focuses on exploring the relationship between the flexural mode and thermal and mechanical properties of graphene. We first survey the lattice dynamic properties of the flexural mode, where the rigid translational and rotational invariances play a crucial role. After that, we outline contributions from the flexural mode in four different physical properties or phenomena of graphene-its thermal conductivity, thermal expansion, Young's modulus and nanomechanical resonance. We explain how graphene's superior thermal conductivity is mainly due to its three acoustic phonon modes at room temperature, including the flexural mode. Its coefficient of thermal expansion is negative in a wide temperature range resulting from the particular vibration morphology of the flexural mode. We then describe how the Young's modulus of graphene can be extracted from its thermal fluctuations, which are dominated by the flexural mode. Finally, we discuss the effects of the flexural mode on graphene nanomechanical resonators, while also discussing how the essential properties of the resonators, including mass sensitivity and quality factor, can be enhanced.

  17. Full-size solar dynamic heat receiver thermal-vacuum tests

    Science.gov (United States)

    Sedgwick, L. M.; Kaufmann, K. J.; McLallin, K. L.; Kerslake, T. W.

    The testing of a full-size, 102 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test period.

  18. Test of Cable Products in Respect of Thermal and Dynamic Stability

    Directory of Open Access Journals (Sweden)

    M. A. Коrotkevich

    2010-01-01

    Full Text Available The paper considers conditions for selection of  power supply of the unit which is used for testing samples of cable products by thermal and dynamic stability currents. It has been shown that while conducting testing by thermal and dynamic stability currents at nominal cable voltage it is more justifiable to use a percussive energy accumulator, and in the case when the voltage is low an inductive energy accumulator is used.

  19. Review on thermal insulation performance in various type of concrete

    Science.gov (United States)

    Shahedan, Noor Fifinatasha; Abdullah, Mohd Mustafa Al Bakri; Mahmed, Norsuria; Kusbiantoro, Andri; Binhussain, Mohammed; Zailan, Siti Norsaffirah

    2017-04-01

    Thermal insulation concrete building plays an important role in environment sustainability especially energy saving buildings. Buildings are one of the largest consumers of energy worldwide. Therefore, significant energy saving can be realized by buildings with proper materials, design and operation. Thermal insulation systems are nowadays mostly applied for such building envelopes where the materials of load bearing structure such as concrete do not have a substantial thermal insulation capability. Thermal insulation in concrete are materials or combinations of materials that are used to provide resistance to heat flow, should have low conductivity for building application in order to represence of a temperature gradient, has an important effect on the heat exchange between the building interior and the ambiance. The aim of this paper is to review the thermal properties include thermal conductivity and specific heat on various types of concrete.

  20. Fuel Cycle Performance of Thermal Spectrum Small Modular Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Worrall, Andrew [ORNL; Todosow, Michael [Brookhaven National Laboratory (BNL)

    2016-01-01

    Small modular reactors may offer potential benefits, such as enhanced operational flexibility. However, it is vital to understand the holistic impact of small modular reactors on the nuclear fuel cycle and fuel cycle performance. The focus of this paper is on the fuel cycle impacts of light water small modular reactors in a once-through fuel cycle with low-enriched uranium fuel. A key objective of this paper is to describe preliminary reactor core physics and fuel cycle analyses conducted in support of the U.S. Department of Energy Office of Nuclear Energy Fuel Cycle Options Campaign. Challenges with small modular reactors include: increased neutron leakage, fewer assemblies in the core (and therefore fewer degrees of freedom in the core design), complex enrichment and burnable absorber loadings, full power operation with inserted control rods, the potential for frequent load-following operation, and shortened core height. Each of these will impact the achievable discharge burn-up in the reactor and the fuel cycle performance. This paper summarizes the results of an expert elicitation focused on developing a list of the factors relevant to small modular reactor fuel, core, and operation that will impact fuel cycle performance. Preliminary scoping analyses were performed using a regulatory-grade reactor core simulator. The hypothetical light water small modular reactor considered in these preliminary scoping studies is a cartridge type one-batch core with 4.9% enrichment. Some core parameters, such as the size of the reactor and general assembly layout, are similar to an example small modular reactor concept from industry. The high-level issues identified and preliminary scoping calculations in this paper are intended to inform on potential fuel cycle impacts of one-batch thermal spectrum SMRs. In particular, this paper highlights the impact of increased neutron leakage and reduced number of batches on the achievable burn-up of the reactor. Fuel cycle performance

  1. 动力电池热失控方法研究%Research on Thermal Runaway Method of Dynamic Battery

    Institute of Scientific and Technical Information of China (English)

    秦李伟; 赵久志; 吴国辉; 吴飞驰

    2016-01-01

    通过电阻丝加热和针刺方法使动力电池内短路,研究动力电池的热失控方法。试验结果表明:不同试验方法触发电池内短路引发的热失控对相邻电池的影响不同,针刺方法比电阻丝加热更适合于动力电池热失控验证,电阻丝加热产生的热量增大了动力电池发生热失控的机率。%Two methods of the internal short circuit of the dynamic lithium-ion battery were carried out to research the thermal runaway of the dynamic lithium-ion battery.The results show that the thermal runaway of the dynamic lithium-ion battery performs differently at the different test methods. The nail penetration is more suitable for the dynamic lithium-ion battery than the heating by the resistive wire and the heating of the battery will generate more heat,witch make the thermal runaway of the dynamic lithium-ion battery easier.

  2. Dynamic response analysis of an aircraft structure under thermal-acoustic loads

    Science.gov (United States)

    Cheng, H.; Li, H. B.; Zhang, W.; Wu, Z. Q.; Liu, B. R.

    2016-09-01

    Future hypersonic aircraft will be exposed to extreme combined environments includes large magnitude thermal and acoustic loads. It presents a significant challenge for the integrity of these vehicles. Thermal-acoustic test is used to test structures for dynamic response and sonic fatigue due to combined loads. In this research, the numerical simulation process for the thermal acoustic test is presented, and the effects of thermal loads on vibro-acoustic response are investigated. To simulate the radiation heating system, Monte Carlo theory and thermal network theory was used to calculate the temperature distribution. Considering the thermal stress, the high temperature modal parameters are obtained with structural finite element methods. Based on acoustic finite element, modal-based vibro-acoustic analysis is carried out to compute structural responses. These researches are very vital to optimum thermal-acoustic test and structure designs for future hypersonic vehicles structure

  3. Molecular structure-property correlations from optical nonlinearity and thermal-relaxation dynamics.

    Science.gov (United States)

    Bhattacharyya, Indrajit; Priyadarshi, Shekhar; Goswami, Debabrata

    2009-02-01

    We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560 nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560 nm thermal lens pump and 780 nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

  4. Thermal wave dynamics in rivers impacted by hydropeaking

    Science.gov (United States)

    Toffolon, M.; Siviglia, A.; Zolezzi, G.

    2009-04-01

    Release of hypolimnetic water from reservoir for hydropower generation production generates hydro- and thermo-peaking waves which propagate downstream. The resulting thermal regime alteration causes detrimental impacts on habitats and ecosystems due to both direct (e.g. spatial-temporal patterns of maximum and minimum temperature) and indirect (e.g. affecting timing of lifecycle stages, growth rates restriction or alterations) effects. In order to reduce such effects, mitigation procedure must be studied and implemented. The phenomenon is studied using the one-dimensional model governed by the Saint Venant equations coupled with an equation imposing thermal energy conservation. The difference between the propagation celerity of the hydrodynamic wave and that of the thermal wave identifies two different phases: (I) where the hydrodynamic wave strongly interacts with the thermal wave; and (II) where the hydrodynamic wave separates from the thermal wave. The diffusive approximation for the hydrodynamic model is assumed to hold while the hydropeaking initial condition is schematized as a square wave characterized by a peak value over a base flow. The resulting problem is solved assuming constant coefficients, i.e. the celerity is taken as a constant function of the two uniform states computed with the peak and base discharges. The resulting flow field is used to evaluate the propagation of an initial square thermal wave, assuming that the tail and the head travel downstream with different celerities in phase I and with the same celerity, equal to the velocity of the base flow, in phase II. Comparison between the proposed analytical solution and numerical solutions of the fully hydro-thermal problem are in good agreement, showing its applicability in predicting the thermal field occurring under hydropeaking conditions. The proposed model can be employed to study the spatial-temporal patterns of maximum and minimum temperature maximum that arise downstream of hydropower

  5. Physiological performance of warm-adapted marine ectotherms: Thermal limits of mitochondrial energy transduction efficiency.

    Science.gov (United States)

    Martinez, Eloy; Hendricks, Eric; Menze, Michael A; Torres, Joseph J

    2016-01-01

    Thermal regimes in aquatic systems have profound implications for the physiology of ectotherms. In particular, the effect of elevated temperatures on mitochondrial energy transduction in tropical and subtropical teleosts may have profound consequences on organismal performance and population viability. Upper and lower whole-organism critical temperatures for teleosts suggest that subtropical and tropical species are not susceptible to the warming trends associated with climate change, but sub-lethal effects on energy transduction efficiency and population dynamics remain unclear. The goal of the present study was to compare the thermal sensitivity of processes associated with mitochondrial energy transduction in liver mitochondria from the striped mojarra (Eugerres plumieri), the whitemouth croaker (Micropogonias furnieri) and the palometa (Trachinotus goodei), to those of the subtropical pinfish (Lagodon rhomboides) and the blue runner (Caranx crysos). Mitochondrial function was assayed at temperatures ranging from 10 to 40°C and results obtained for both tropical and subtropical species showed a reduction in the energy transduction efficiency of the oxidative phosphorylation (OXPHOS) system in most species studied at temperatures below whole-organism critical temperature thresholds. Our results show a loss of coupling between O2 consumption and ATP production before the onset of the critical thermal maxima, indicating that elevated temperature may severely impact the yield of ATP production per carbon unit oxidized. As warming trends are projected for tropical regions, increasing water temperatures in tropical estuaries and coral reefs could impact long-term growth and reproductive performance in tropical organisms, which are already close to their upper thermal limit.

  6. Coupled analysis of core thermal hydraulics and fuel performance to evaluate a thermally induced fuel failure in an SFR subassembly

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sun Rock; Chang, Doo Soo; Kim, Sang Ji [KAERI, Daejeon (Korea, Republic of)

    2012-10-15

    A limiting factor analysis in a core thermal design is highly important to assure the safe and reliable operation of a reactor system. In a sodium cooled fast reactor (SFR), the coolant thermal conductivity is about hundreds of times larger than the thermal conductivity of water. Moreover, the coolant boiling temperature in an SFR is around 900 .deg. C, which is much higher than that of the water coolant in a PWR. Considering typical operating temperatures, an SFR has about a 300 .deg. C thermal margin to its boiling point. Therefore, instead of DNBR (Departure from Nucleate Boiling Ratio) in a PWR, the core thermal design of SFRs requires assuring proper fuel performance and safety, where the design limits are highly related to the temperature distribution and material behavior under various operating conditions. Typical limiting factors in SFRs are the thermal component of the plastic hoop strain, radial primary hoop stress, and cumulative damage factor during normal operation. However, the previous fuel performance codes only evaluate a single fuel pin performance, which neglects the radial peaking factors and reveals too conservative results. In this work, the multi physics analysis is performed using both thermalhydraulic and fuel performance codes.

  7. Effect of thermal acclimation on thermal preference, resistance and locomotor performance of hatchling soft-shelled turtle

    Directory of Open Access Journals (Sweden)

    Mei-Xian WU,Ling-Jun HU, Wei DANG, Hong-Liang LU, Wei-Guo DU

    2013-12-01

    Full Text Available The significant influence of thermal acclimation on physiological and behavioral performance has been documented in many ectothermic animals, but such studies are still limited in turtle species. We acclimated hatchling soft-shelled turtles Pelodiscus sinensis under three thermal conditions (10, 20 and 30 °C for 4 weeks, and then measured selected body temperature (Tsel, critical thermal minimum (CTMin and maximum (CTMax, and locomotor performance at different body temperatures. Thermal acclimation significantly affected thermal preference and resistance of P. sinensis hatchlings. Hatchling turtles acclimated to 10 °C selected relatively lower body temperatures and were less resistant to high temperatures than those acclimated to 20 °C and 30 °C. The turtles’ resistance to low temperatures increased with a decreasing acclimation temperature. The thermal resistance range (i.e. the difference between CTMax and CTMin, TRR was widest in turtles acclimated to 20 °C, and narrowest in those acclimated to 10 °C. The locomotor performance of turtles was affected by both body temperature and acclimation temperature. Hatchling turtles acclimated to relatively higher temperatures swam faster than did those acclimated to lower temperatures. Accordingly, hatchling turtles acclimated to a particular temperature may not enhance the performance at that temperature. Instead, hatchlings acclimated to relatively warm temperatures have a better performance, supporting the “hotter is better” hypothesis [Current Zoology 59 (6 : 718–724, 2013 ].

  8. Hydrogen recombination kinetics and nuclear thermal rocket performance prediction

    Science.gov (United States)

    Wetzel, Kyle K.; Solomon, Wayne C.

    1994-07-01

    The rate constants for the hydrogen three-body collisional recombination reaction with atomic and molecular hydrogen acting as third bodies have been determined by numerous investigators during the past 30 yr, but these rates exhibit significant scatter. The discrepancies in the rate constants determined by different investigators are as great as two orders of magnitude in the temperature range of interest for nuclear thermal rocket (NTR) operation, namely, 2000-3300 K. The impact of this scatter on our ability to predict the specific impulse (I(sub sp)) delivered by a 30-klbf NTR has been determined for chamber pressures and temperatures from, respectively, 20-1000 psia and 2700-3300 K. The variation in I(sub sp) produced by using the different rate constants is as great as 10%, or 100 s. This variation also obscures the influence of chamber pressure on I(sub sp); using fast kinetics, low pressures yield significantly improved performance, while using slow or nominal kinetics, the pressure dependence of I(sub sp) is negligible. Because the flow composition freezes at very small area ratios, optimization of the nozzle contour in the near-throat region maximizes recombination. Vibrational relaxation is found to produce negligible losses in I(sub sp).

  9. Thermal performance of integration of solar collectors and building envelopes

    Institute of Scientific and Technical Information of China (English)

    于国清; 龚小辉; 曹双华

    2009-01-01

    The integration of building with solar collector was studied. The theoretical model of integration of building envelopes and flat plate solar collectors was set up and the thermal performance of integration was studied in winter and summer,and compared to envelopes without solar collectors. The results show that the solar collection efficiency is raised in the integration of building envelopes and solar collectors with the air layer doors closed. This is true whether in winter or summer. The increment is higher as the inlet water temperature increases or the ambient temperature is low. In winter,the heat loss is significantly reduced through integration of the building envelopes and solar collectors with the closed air layer doors. The integration with the open air layer door is worse than that without collectors. In summer,the heat gains of the integration of envelopes and solar collectors are more obviously reduced than envelopes without collectors,the integration with the open air layer door is a little better than the closed one,but the difference is very small.

  10. Geometric thermal phase diagrams for studying the thermal dynamic stability of hollow gold nanoballs at different temperatures.

    Science.gov (United States)

    Jiang, Luyun; Sun, Wei; Gao, Yajun; Zhao, Jianwei

    2014-04-14

    Thermal stability is one of the main concerns for the synthesis of hollow nanoparticles. In this work, molecular dynamics simulation gave an insight into the atomic reconstruction and energy evolution during the collapse of hollow gold nanoballs, based on which a mechanism was proposed. The stability was found to depend on temperature, its wall thickness and aspect ratio to a great extent. The relationship among these three factors was revealed in geometric thermal phase diagrams (GTPDs). The GTPDs were studied theoretically, and the boundary between different stability regions can be fitted and calculated. Therefore, the GTPDs at different temperatures can be deduced and used as a guide for hollow structure synthesis.

  11. Parametric Characterization on the Thermal Performance of a Closed Loop Pulsating Heat Pipe

    Directory of Open Access Journals (Sweden)

    sreenivasa Rao

    2016-01-01

    Full Text Available Recently closed loop pulsating heat pipes have been receiving much attention because of their potential applications in high heat flux micro-electronic systems. They work by self thermal driven oscillation without any mechanical parts. Though they are simple in structure, understanding of the heat transfer mechanism is highly complex having a strong thermo- hydro dynamic coupling governing their performance. In this paper, an experimental study on a closed loop PHP with a single turn has been conducted there by providing vital information regarding parameter dependence on its performance. The PHP is made of brass tube having an internal diameter of 2 mm and outer diameter of 3 mm. The parametric characterization has been done for the variation in internal diameter, fill ratio, working fluid and orientation of the device. The working fluids Acetone, Methanol, Ethanol and Propanol are considered for experimentation with volumetric filling ratios of 50%, 60%, 70% and 80%. Input heat power of 7 to 12 W is varied at the evaporator section. The CLPHP is also verified for its thermal performance at 00, 300 and 600 orientations. The transient and steady state experiments are conducted and operating temperatures are measured using K- type thermocouples. The results highlighted that the thermal performance of a PHPis strongly influenced by change in fill ratios, orientation and heat input. 80% fill ratio yields an effective heat transfer rate for a horizontal mode of operation. Appreciable fluid movement and better heat transfer rate are observed for the 300 orientation of PHP operation. Acetone exhibits better heat transport capability compared to other working fluids in all orientations.

  12. Predicting performance of coatings under thermal insulation at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Lasarte, C. (Pequiven, S.A., Maracaibo (Venezuela). Petroquimica de Venezuela); Rincon, O.T. De; Montiel, A. (Univ. del Zulia, Maracaibo (Venezuela). Centro de Estudios de Corrosion)

    1994-10-01

    A probe was designed to evaluate coatings used under thermal insulation for temperatures of 30 to 150 C. This article describes the results obtained with various combinations of coatings (aluminum silicone, inorganic zinc, and aluminum metallizing) and thermal insulators (mineral wool, fiber glass, and calcium silicate), which were recommended in NACE Publication 6H189.

  13. Effect of water-ice phase change on thermal performance of building materials

    Science.gov (United States)

    Kočí, Václav; Černý, Robert

    2016-07-01

    The effect of water ice-phase change on thermal performance of integrated building material is investigated in this paper. As a characteristic construction, simple external wall made of aerated autoclaved concrete was assumed which was exposed to dynamic climatic condition of Šerák, Czech Republic. The computational modelling of hygrothermal performance was carried out using computer codes HEMOT and SIFEL that work on the basis of finite element method. The effect of phase change was taken into account by fixed-domain method, when experimentally determined effective specific heat capacity was used as a material parameter. It comprises also the effect of heat consumption and heat release that accompany the water-ice phase change. Comparing to the results with specific heat capacity, the effect of phase change on thermal performance could be quantified. The results showed that temperature fields can differ more than 6 °C. Additionally, the amount energy transported through the wall may be higher up to 4 %. This confirmed, that the effect water-ice phase change should be included in all the relevant energy calculations.

  14. Comparison between steady-state and dynamic test methods of thermal performance of parabolic trough solar collectors%抛物面槽式太阳能集热器热性能稳态与动态测试方法的比较

    Institute of Scientific and Technical Information of China (English)

    徐立; 原郭丰; 孙飞虎

    2013-01-01

    抛物面槽式太阳能集热器热性能测试主要可以分为稳态和动态测试2种方法,依据二者所采用的物理模型,比较它们的应用范围,并且分析各自的优缺点.基于北京延庆实验平台测得的天气和集热器运行数据,运用最小二乘法进行模型的多元回归,得到稳态测试模型和动态测试模型的判定系数分别为0.58和0.96.研究表明:对于稳态测试方法,虽然物理参数少,但测试条件要求极高,只能在特定的实验装置上进行,不适合于实际运行方式下的槽式集热器;而动态测试方法充分考虑集热器的光学响应和热容特性,因此很大程度上降低了测试条件,使现场规模化槽式集热器热性能测试成为可能,是未来标准测试方法的发展趋势.%Test for thermal performance of paraboloidal trough solar collectors can be chiefly divided into two kinds as steady-state test and the dynamic one.Based on the physical models employed,their application ranges were compared and their advantages and disadvantages were analyzed.By means of multiple regression of the data on the weather and operation of test platform at Yanqing district,Beijing with least squares method,the determination coefficients for the steady-state and dynamic models were 0.58 and 0.96,respectively.The investigation result showed that,although the mathematical model of the steadystate method would include less physical parameters,the requirements of test conditions would be extremely strict,meaning that this method could only be used on a particular experimental setup and it would be not applicable to paraboloidal trough solar collectors operated in actual practice.As for the dynamic method,however,the optical response and thermal capacitance of collectors were carefully considered,and consequently the test requirements were dramatically lowered,making the on-site test for determining thermal performance of utility-scale paraboloidal tough solar collectors possible

  15. Environmental and Thermal Performance of District Heating Pipes

    Energy Technology Data Exchange (ETDEWEB)

    Froeling, Morgan

    2002-06-01

    The introduction of district heating has reduced the environmental impact from local heat production in urban areas. However, in order to fit into a sustainable society, district heating must be continuously developed according to the increasing demands on activities in a society moving towards sustainability. Our technical improvements must result in environmental improvements. This thesis focuses on the environmental performance of the distribution system - the district heating pipes. The purpose of this research is to understand how the distribution system can be improved. The information presented in this thesis can be used to identify possibilities for improving the environmental performance of different life cycle phases of the distribution system as well as a baseline when evaluating new technical developments. The heat losses during use of the pipes are of large importance for the environmental impact of district heating pipes. Such heat losses can be modelled if the mass transfer parameters for gases in the polyurethane insulation and the polyethylene casing are known. The diffusion coefficients, the permeability coefficients and the solubility coefficients and their temperature dependence have been determined for cyclopentane, carbon dioxide, nitrogen, and oxygen. The same parameters have been studied for the blowing agent alternative HFC-365mfc at room temperature. The long-term thermal performance of district heating pipes has been modelled using effective permeabilities for the pipe construction. Environmental consequences of heat losses during the use phase of district heating pipes have been compared with the impacts from production of the pipes and from construction of the district heating network. The use of the district heating pipes is the most important of the studied life cycle phases. Thus, it is very important to minimise heat losses from the pipes. The heat losses will for some district heating pipes increase notably during use due to foam

  16. Performance assessment of low pressure nuclear thermal propulsion

    Science.gov (United States)

    Gerrish, Harrold P., Jr.; Doughty, Glen E.

    1993-01-01

    An increase in Isp for nuclear thermal propulsion systems is desirable for reducing the propellant requirements and cost of future applications, such as the Mars Transfer Vehicle. Several previous design studies have suggested that the Isp could be increased substantially with hydrogen dissociation/recombination. Hydrogen molecules (H2), at high temperatures and low pressures, will dissociate to monatomic hydrogen (H). The reverse process (i.e., formation of H2 from H) is exothermic. The exothermic energy in a nozzle increases the kinetic energy and therefore, increases the Isp. The low pressure nuclear thermal propulsion system (LPNTP) system is expected to maximize the hydrogen dissociation/recombination and Isp by operating at high chamber temperatures and low chamber pressures. The process involves hydrogen flow through a high temperature, low pressure fission reactor, and out a nozzle. The high temperature (approximately 3000 K) of the hydrogen in the reactor is limited by the temperature limits of the reactor material. The minimum chamber pressure is about 1 atm because lower pressures decrease the engines thrust to weight ratio below acceptable limits. This study assumes that hydrogen leaves the reactor and enters the nozzle at the 3000 K equilibrium dissociation level. Hydrogen dissociation in the reactor does not affect LPNTP performance like dissociation in traditional chemical propulsion systems, because energy from the reactor resupplies energy lost due to hydrogen dissociation. Recombination takes place in the nozzle due primarily to a drop in temperature as the Mach number increases. However, as the Mach number increases beyond the nozzle throat, the static pressure and density of the flow decreases and minimizes the recombination. The ideal LPNTP Isp at 3000 K and 10 psia is 1160 seconds due to the added energy from fast recombination rates. The actual Isp depends on the finite kinetic reaction rates which affect the amount of monatomic hydrogen

  17. Static Versus Dynamic Stretching Effect on Agility Performance

    OpenAIRE

    Troumbley, Patrick

    2010-01-01

    The purpose of this study was to compare effects of static and dynamic stretching on explosive agility movements, and to examine the effect of the interaction of dynamic and static stretching prior to explosive agility movements. Fourteen men and 10 women performed the different warm-up protocols, including no warm-up (NWU), static stretching (SS), dynamic stretching (DS), and dynamic stretching with static stretching (DS+SS). The T-Drill was used to assess agility. The results indicated n...

  18. Rumination and Performance in Dynamic, Team Sport

    Directory of Open Access Journals (Sweden)

    Michael eRoy

    2016-01-01

    Full Text Available People high in rumination are good at tasks that require persistence whereas people low in rumination are good at tasks that require flexibility. Here we examine real world implications of these differences in dynamic, team sport. In two studies, we found that professional male football (soccer players from Germany and female field hockey players on the US national team were lower in rumination than were non-athletes. Further, low levels of rumination were associated with a longer career at a higher level in football players. Results indicate that athletes in dynamic, team sport might benefit from the flexibility associated with being low in rumination.

  19. Molecular dynamics simulation of thermal conductivity of GaN/AlN quantum dot superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Takahiro [Graduate School of Engineering, Kyushu University, 6-1, Kasuga-Koen, Kasuga, Fukuoka 816-8580 (Japan); Kangawa, Yoshihiro; Kakimoto, Koichi [Research Institute for Applied Mechanics, Kyushu University, 6-1, Kasuga-Koen, Kasuga, Fukuoka 816-8580 (Japan)

    2007-06-15

    We calculated thermal conductivity of GaN/AlN quantum dot superlattices by molecular dynamics simulation. The results of investigation of the effect of quantum dots on thermal conductivity as a function of superlattice period are presented in this paper. An empirical potential function of Stillinger-Weber potential was used for simulations. Thermal conductivity was obtained by Green-Kubo's equation. The results show that the values of thermal conductivity parallel to the wetting layers decreased due to the effect of quantum dots. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Energy Performance of a Novel System Combining Natural Ventilation with Diffuse Ceiling Inlet and Thermally Activated Building Systems (TABS)

    DEFF Research Database (Denmark)

    Yu, Tao

    saving potential and the steady-state and dynamic energy performance of this system. The presented work utilizes building simulation method to investigate the energy saving potential of this novel system. Afterwards, an experimental set-up is built in the laboratory to simulate a real office environment....... Both steady-state and dynamic measurements are carried out in the experimental chamber to investigate the energy performance of the system and the thermal comfort in the test room. Overall, this integrated system has high energy saving potential without any compromise of thermal comfort even in extreme...... winter period. Since natural ventilation is of great importance in the system, this system is recommended for use in a temperate climate with high natural ventilation potential....

  1. Load Responsive MLI: Thermal Insulation with High In-Atmosphere and On-Orbit Performance Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Lightweight, high performance thermal insulation is critical to NASA's next generation Exploration spacecraft. Zero or low cryogenic propellant boiloff is required...

  2. Performance of modified greenhouse dryer with thermal energy storage

    Directory of Open Access Journals (Sweden)

    Om Prakash

    2016-11-01

    Full Text Available In this attempt, the main goal is to do annual performance, environomical analysis, energy analysis and exergy analysis of the modified greenhouse dryer (MGD operating under active mode (AM and passive mode (PM. Thermal storage is being applied on the ground of MGD. It is applied in three different ways namely barren floor, floor covered with black PVC sheet (PVC and Black Coated. Experimental study of dryers in no-load conditions reveals that floor covered with a black PVC sheet is more conducive for drying purpose than other floors. The MGD under AM is found to be more effective as compared to PM for tomato and capsicum, which are high moisture content crops. For medium moisture content crop (potato chips, both dryers show relatively similar drying performance. Crops dried inside the greenhouse dryer are found to be more nutrient than open sun dried crops. The payback period of the modified greenhouse dryer under passive mode is found to be 1.11 years. However, for the active mode of the modified greenhouse dryer is only 1.89 years. The embodied energy of the passive mode of the dryer is a 480.277 kWh and 628.73 kWh for the active mode of the dryer. The CO2 emissions per annum for passive and active mode greenhouse dryers are found to be 13.45 kg and 17.6 kg respectively. The energy payback time, carbon mitigation and carbon credit have been calculated based type of crop dried. The range of exergy efficiency is 29%–86% in MGD under PM and 30%–78% in the MGD under AM. The variation of Heat utilization factor (HUF for MGD under PM is 0.12–0.38 and 0.26–0.53 for MGD under AM. The range of co-efficient of performances (COP for MGD under PM is 0.55–0.87 and 0.58–0.73 for MGD under AM.

  3. Dynamic responses in hollow concrete cylinders under hazardous thermal loads

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.L.D.; Ahmed, G.N. (Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering)

    1991-10-01

    Prediction of the structural integrity of high temperature nuclear reactors under hostile thermal environments is of considerable concern in safety assessments of reactors. A mathematical model, simulating the coupled heat and mass transfer in concrete structures exposed to extremely high temperatures, has been developed and numerically solved. With the prediction of the pore pressure, temperature, and moisture redistribution, the effect of various rates of thermal loads on the concrete response is investigated. The rate of moisture clog penetration into the concrete cylinder and hence the locations of the maximum pore pressure peaks developed under different rates of the severe thermal loads are determined. Thus, the possibilities of concrete spallings occurring under these conditions are studied and predicted. (author).

  4. Dynamics of charged particles in an adiabatic thermal beam equilibrium

    Directory of Open Access Journals (Sweden)

    Haofei Wei

    2011-02-01

    Full Text Available Charged-particle motion is studied in the self-electric and self-magnetic fields of a well-matched, intense charged-particle beam and an applied periodic solenoidal magnetic focusing field. The beam is assumed to be in a state of adiabatic thermal equilibrium. The phase space is analyzed and compared with that of the well-known Kapchinskij-Vladimirskij (KV-type beam equilibrium. It is found that the widths of nonlinear resonances in the adiabatic thermal beam equilibrium are narrower than those in the KV-type beam equilibrium. Numerical evidence is presented, indicating almost complete elimination of chaotic particle motion in the adiabatic thermal beam equilibrium.

  5. Correlation between dynamic wetting behavior and chemical components of thermally modified wood

    Science.gov (United States)

    Wang, Wang; Zhu, Yuan; Cao, Jinzhen; Sun, Wenjing

    2015-01-01

    In order to investigate the dynamic wetting behavior of thermally modified wood, Cathay poplar (Populus cathayana Rehd.) and Scots pine (Pinus sylvestris L.) samples were thermally modified in an oven at 160, 180, 200, 220 or 240 °C for 4 h in this study. The dynamic contact angles and droplet volumes of water droplets on modified and unmodified wood surfaces were measured by sessile drop method, and their changing rates (expression index: K value and wetting slope) calculated by wetting models were illustrated for mapping the dynamic wetting process. The surface chemical components were also measured by X-ray photoelectron spectroscopy analysis (XPS), thus the relationship between dynamic wetting behavior and chemical components of thermally modified wood were determined. The results indicated that thermal modification was capable of decreasing the dynamic wettability of wood, expressed in lowing spread and penetration speed of water droplets on wood surfaces. This change was more obvious with the increased heating temperature. The K values varied linearly with the chemical components parameter (mass loss, O/C ratio, and C1/C2 ratio), indicating a strong correlation between dynamic wetting behavior and chemical components of thermally modified wood.

  6. The thermal-wave model: A Schroedinger-like equation for charged particle beam dynamics

    Science.gov (United States)

    Fedele, Renato; Miele, G.

    1994-01-01

    We review some results on longitudinal beam dynamics obtained in the framework of the Thermal Wave Model (TWM). In this model, which has recently shown the capability to describe both longitudinal and transverse dynamics of charged particle beams, the beam dynamics is ruled by Schroedinger-like equations for the beam wave functions, whose squared modulus is proportional to the beam density profile. Remarkably, the role of the Planck constant is played by a diffractive constant epsilon, the emittance, which has a thermal nature.

  7. Thermalization and out-of-equilibrium dynamics in open quantum many-body systems

    Energy Technology Data Exchange (ETDEWEB)

    Buchhold, Michael

    2015-06-30

    modes, which are the consequence of exactly energy conserving dynamics and lead to an algebraic decay ∝τ{sup -η{sub D}} with η{sub D}=0.58. The presence of these dynamical slow modes is not contained in the equilibrium Matsubara formalism, while they emerge naturally in the non-equilibrium formalism developed in this thesis. In order to initialize a one-dimensional quantum fluid out of equilibrium, we consider an interaction quench in a model of interacting, dispersive fermions. In this scenario, the fermionic interaction is suddenly changed at time t=0, such that for t>0 the system is not in an eigenstate and therefore undergoes a non-trivial time evolution. For the quadratic theory, the stationary state in the limit t→∞ is a non-thermal, or prethermal, state, described by a generalized Gibbs ensemble (GGE). The GGE takes into account for the conservation of all integrals of motion, formed by the eigenmodes of the Hamiltonian. On the other hand, in the presence of non-linearities, the final state for t→∞ is a thermal state with a finite temperature T>0. The spatio-temporal, dynamical thermalization process can be decomposed into three regimes: A prequench regime on the largest distances, which is determined by the initial state, a prethermal plateau for intermediate distances, which is determined by the metastable fixed point of the quadratic theory and a thermal region on the shortest distances. The latter spreads sub-ballistically ∝ t{sup α} in space with 0<α<1 depending on the quench. Until complete thermalization (i.e. for times t<∞), the thermal region contains more energy than the prethermal and prequench region, which is expressed in a larger temperature T{sub t}>T{sub ∞}, decreasing towards its final value T{sub ∞}. As the system has achieved local detailed balance in the thermalized region, energy transport to the non-thermal region can only be performed by the macroscopic dynamical slow modes and the decay of the temperature T{sub t

  8. Molecular dynamics study of the lattice thermal conductivity of Kr/Ar superlattice nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen Yunfei; Li Deyu; Yang Juekuan; Wu Yonghua; Lukes, J.R.; Majumdar, Arun

    2004-06-15

    The nonequilibrium molecular dynamics (NEMD) method has been used to calculate the lattice thermal conductivities of Ar and Kr/Ar nanostructures in order to study the effects of interface scattering, boundary scattering, and elastic strain on lattice thermal conductivity. Results show that interface scattering poses significant resistance to phonon transport in superlattices and superlattice nanowires. The thermal conductivity of the Kr/Ar superlattice nanowire is only about ((1)/(3)) of that for pure Ar nanowires with the same cross-sectional area and total length due to the additional interfacial thermal resistance. It is found that nanowire boundary scattering provides significant resistance to phonon transport. As the cross-sectional area increases, the nanowire boundary scattering decreases, which leads to increased nanowire thermal conductivity. The ratio of the interfacial thermal resistance to the total effective thermal resistance increases from 30% for the superlattice nanowire to 42% for the superlattice film. Period length is another important factor affecting the effective thermal conductivity of the nanostructures. Increasing the period length will lead to increased acoustic mismatch between the adjacent layers, and hence increased interfacial thermal resistance. However, if the total length of the superlattice nanowire is fixed, reducing the period length will lead to decreased effective thermal conductivity due to the increased number of interfaces. Finally, it is found that the interfacial thermal resistance decreases as the reference temperature increases, which might be due to the inelastic interface scattering.

  9. The Adaptive Thermal Comfort model may not always predict thermal effects on performance

    DEFF Research Database (Denmark)

    Wyon, David Peter; Wargocki, Pawel

    2014-01-01

    A letter to the editor is presented in response to the article "Progress in thermal comfort research over the last twenty years," by R.J. de Dear and colleagues.......A letter to the editor is presented in response to the article "Progress in thermal comfort research over the last twenty years," by R.J. de Dear and colleagues....

  10. Thermal performance of marketed SDHW systems under laboratory conditions

    DEFF Research Database (Denmark)

    Furbo, Simon; Andersen, Elsa; Fan, Jianhua

    A test facility for solar domestic hot water systems, SDHW systems was established at the Technical University of Denmark in 1992. During the period 1992-2012 21 marketed SDHW systems, 16 systems from Danish manufacturers and 5 systems from manufacturers from abroad, have been tested in the test...... comfort, avoiding simple errors, using the low flow principle and heat stores with a high degree of thermal stratification and by using components with good thermal characteristics....

  11. Indoor temperatures for optimum thermal comfort and human performance

    DEFF Research Database (Denmark)

    de Dear, R.; Arens, E. A.; Candido, C.;

    2014-01-01

    A response by R. J. de Dear et al to a letter to the editor in response to their article "Progress in thermal comfort research over the last 20 years," published in a 2013 issue.......A response by R. J. de Dear et al to a letter to the editor in response to their article "Progress in thermal comfort research over the last 20 years," published in a 2013 issue....

  12. Design of the Building Envelope: A Novel Multi-Objective Approach for the Optimization of Energy Performance and Thermal Comfort

    Directory of Open Access Journals (Sweden)

    Fabrizio Ascione

    2015-08-01

    Full Text Available According to the increasing worldwide attention to energy and the environmental performance of the building sector, building energy demand should be minimized by considering all energy uses. In this regard, the development of building components characterized by proper values of thermal transmittance, thermal capacity, and radiative properties is a key strategy to reduce the annual energy need for the microclimatic control. However, the design of the thermal characteristics of the building envelope is an arduous task, especially in temperate climates where the energy demands for space heating and cooling are balanced. This study presents a novel methodology for optimizing the thermo-physical properties of the building envelope and its coatings, in terms of thermal resistance, capacity, and radiative characteristics of exposed surfaces. A multi-objective approach is adopted in order to optimize energy performance and thermal comfort. The optimization problem is solved by means of a Genetic Algorithm implemented in MATLAB®, which is coupled with EnergyPlus for performing dynamic energy simulations. For demonstration, the methodology is applied to a residential building for two different Mediterranean climates: Naples and Istanbul. The results show that for Naples, because of the higher incidence of cooling demand, cool external coatings imply significant energy savings, whereas the insulation of walls should be high but not excessive (no more than 13–14 cm. The importance of high-reflective coating is clear also in colder Mediterranean climates, like Istanbul, although the optimal thicknesses of thermal insulation are higher (around 16–18 cm. In both climates, the thermal envelope should have a significant mass, obtainable by adopting dense and/or thick masonry layers. Globally, a careful design of the thermal envelope is always necessary in order to achieve high-efficiency buildings.

  13. Molecular Dynamics Simulations of the Thermal Conductivity of Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Osman, M.; Srivastava, Deepak; Govindan,T. R. (Technical Monitor)

    2000-01-01

    Carbon nanotubes (CNT) have very attractive electronic, mechanical. and thermal properties. Recently, measurements of thermal conductivity in single wall CNT mats showed estimated thermal conductivity magnitudes ranging from 17.5 to 58 W/cm-K at room temperature. which are better than bulk graphite. The cylinderical symmetry of CNT leads to large thermal conductivity along the tube axis, additionally, unlike graphite. CNTs can be made into ropes that can be used as heat conducting pipes for nanoscale applications. The thermal conductivity of several single wall carbon nanotubes has been calculated over temperature range from l00 K to 600 K using non-equilibrium molecular dynamics using Tersoff-Brenner potential for C-C interactions. Thermal conductivity of single wall CNTs shows a peaking behavior as a function of temperature. Dependence of the peak position on the chirality and radius of the tube will be discussed and explained in this presentation.

  14. Molecular Dynamics Simulations of the Thermal Conductivity of Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Osman, M.; Srivastava, Deepak; Govindan,T. R. (Technical Monitor)

    2000-01-01

    Carbon nanotubes (CNT) have very attractive electronic, mechanical. and thermal properties. Recently, measurements of thermal conductivity in single wall CNT mats showed estimated thermal conductivity magnitudes ranging from 17.5 to 58 W/cm-K at room temperature. which are better than bulk graphite. The cylinderical symmetry of CNT leads to large thermal conductivity along the tube axis, additionally, unlike graphite. CNTs can be made into ropes that can be used as heat conducting pipes for nanoscale applications. The thermal conductivity of several single wall carbon nanotubes has been calculated over temperature range from l00 K to 600 K using non-equilibrium molecular dynamics using Tersoff-Brenner potential for C-C interactions. Thermal conductivity of single wall CNTs shows a peaking behavior as a function of temperature. Dependence of the peak position on the chirality and radius of the tube will be discussed and explained in this presentation.

  15. High Performance Interactive System Dynamics Visualization

    Energy Technology Data Exchange (ETDEWEB)

    Bush, Brian W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Brunhart-Lupo, Nicholas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gruchalla, Kenny M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Duckworth, Jonathan C [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-14

    This brochure describes a system dynamics simulation (SD) framework that supports an end-to-end analysis workflow that is optimized for deployment on ESIF facilities(Peregrine and the Insight Center). It includes (I) parallel and distributed simulation of SD models, (ii) real-time 3D visualization of running simulations, and (iii) comprehensive database-oriented persistence of simulation metadata, inputs, and outputs.

  16. High Performance Interactive System Dynamics Visualization

    Energy Technology Data Exchange (ETDEWEB)

    Bush, Brian W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Brunhart-Lupo, Nicholas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gruchalla, Kenny M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Duckworth, Jonathan C [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-14

    This presentation describes a system dynamics simulation (SD) framework that supports an end-to-end analysis workflow that is optimized for deployment on ESIF facilities(Peregrine and the Insight Center). It includes (I) parallel and distributed simulation of SD models, (ii) real-time 3D visualization of running simulations, and (iii) comprehensive database-oriented persistence of simulation metadata, inputs, and outputs.

  17. Metaconcrete: designed aggregates to enhance dynamic performance

    Science.gov (United States)

    Mitchell, Stephanie J.; Pandolfi, Anna; Ortiz, Michael

    2014-04-01

    We propose a new type of concrete for the attenuation of elastic waves induced by dynamic excitation. In this metamaterial, which we call metaconcrete, the stone, sand, and gravel aggregates of standard concrete are replaced with spherical inclusions consisting of a heavy metal core coated with a soft outer layer. These engineered aggregates can be tuned so that particular frequencies of a propagating blast wave will activate resonant oscillations of the heavy mass within the inclusions. The resonant behavior causes the system to exhibit negative effective mass, and this interaction between the wave motion and the resonant aggregates results in the attenuation of the applied dynamic loading. We introduce the concept of negative mass by deriving the effective momentum mass for the system and we define the geometrical and material parameters for the design of resonant aggregates. We develop finite element models for the analysis of metaconcrete behavior, defining a section of slab containing a periodic arrangement of inclusions. By computing the energy histories for the system when subject to a blast load, we show that there is a transfer of energy between the inclusions and the surrounding mortar. The inclusions are able to absorb a significant portion of the applied energy, resulting in a reduction in the amount of stress carried by the mortar phase and greatly improving the ability of the material to resist damage under explosive dynamic loading.

  18. Neutronic and Thermal-hydraulic Modelling of High Performance Light Water Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Seppaelae, Malla [VTT Technical Research Centre of Finland, P.O.Box 1000, FI02044 VTT (Finland)

    2008-07-01

    High Performance Light Water Reactor (HPLWR), which is studied in EU project 'HPLWR2', uses water at supercritical pressures as coolant and moderator to achieve higher core outlet temperature and thus higher efficiency compared to present reactors. At VTT Technical Research Centre of Finland, functionality of the thermal-hydraulics in the coupled reactor dynamics code TRAB3D/ SMABRE was extended to supercritical pressures for the analyses of HPLWR. Input models for neutronics and thermal-hydraulics were made for TRAB3D/ SMABRE according to the latest HPLWR design. A preliminary analysis was performed in which the capability of SMABRE in the transition from supercritical pressures to subcritical pressures was demonstrated. Parameterized two-group cross sections for TRAB3D neutronics were received from Hungarian Academy of Sciences KFKI Atomic Energy Research Institute together with a subroutine for handling them. PSG, a new Monte Carlo transport code developed at VTT, was also used to generate two-group constants for HPLWR and comparisons were made with the KFKI cross sections and MCNP calculations. (author)

  19. Thermal Performance of Ventilated Double Skin Façades with Venetian Blinds

    Directory of Open Access Journals (Sweden)

    Jordi Parra

    2015-05-01

    Full Text Available Venetian blinds (VB are shading devices of widespread use in residential and corporate buildings. They can reflect or transmit light into buildings and at the same time allow daylighting and exterior views. They can also efficiently block radiative heat from entering the building, and if combined with a heat dissipation system such as forced ventilation, they can improve the thermal performance of double skin façades (DSF. Computational Fluid Dynamics (CFD has proven to be a useful tool for modeling flow and heat transfer in DSF, including conduction, convection and radiation heat transfer phenomena. The aim of this work is to evaluate, by means of CFD, the influence of several optical, construction and operation parameters of a DSF (such as optical properties of the materials, geometrical relations of the VB or flow stream conditions in terms of energy savings, measured as a reduction of the solar load entering the building. Results obtained show that parameters such as the proximity of the VB to the exterior skin of the façade or a differentiated surface treatment for the exterior and interior faces of the VB louvers can notably affect the thermal performance of the DSF and hence the heat gains experienced by the building.

  20. Quantitatively analyzing phonon spectral contribution of thermal conductivity based on nonequilibrium molecular dynamics simulations. I. From space Fourier transform

    Science.gov (United States)

    Zhou, Yanguang; Zhang, Xiaoliang; Hu, Ming

    2015-11-01

    Probing detailed spectral dependence of phonon transport properties in bulk materials is critical to improve the function and performance of structures and devices in a diverse spectrum of technologies. Currently, such information can only be provided by the phonon spectral energy density (SED) or equivalently, time domain normal mode analysis (TDNMA) methods in the framework of equilibrium molecular dynamics simulations (EMD), but has not been realized in nonequilibrium molecular dynamics simulations (NEMD) so far. In this paper we generate a scheme directly based on NEMD and lattice dynamics theory, called the time domain direct decomposition method (TDDDM), to predict the phonon mode specific thermal conductivity. Two benchmark cases of Lennard-Jones (LJ) argon and Stillinger-Weber (SW) Si are studied by TDDDM to characterize contributions of individual phonon modes to overall thermal conductivity and the results are compared with that predicted using SED and TDNMA. Similar trends are found for both cases, which indicate that our TDDDM approach captures the major phonon properties in NEMD run. The biggest advantage of TDDDM is that it can be used to investigate the size effect of individual phonon modes in NEMD simulations, which cannot be tackled by SED and TDNMA in EMD simulations currently. We found that the phonon modes with mean free path larger than the system size are truncated in NEMD and contribute little to the overall thermal conductivity. The TDDDM provides direct physical origin for the well-known strong size effects in thermal conductivity prediction by NEMD. Moreover, the well-known common sense of the zero thermal conductivity contribution from the Γ point is rigorously proved by TDDDM. Since TDDDM inherently possesses the nature of both NEMD simulations and lattice dynamics, we anticipate that TDDDM is particularly useful for offering a deep understanding of phonon behaviors in nanostructures or under strong confinement, especially when the

  1. Dynamic Heat Storage and Cooling Capacity of a Concrete Deck with PCM and Thermally Activated Building System

    DEFF Research Database (Denmark)

    Pomianowski, Michal Zbigniew; Heiselberg, Per; Jensen, Rasmus Lund

    2012-01-01

    the performance of the new deck with PCM concrete is the thermal properties of such a new material, as the PCM concrete is yet to be well defined. The results presented in the paper include models in which the PCM concrete material properties, such as thermal conductivity, and specific heat capacity were first......This paper presents a heat storage and cooling concept that utilizes a phase change material (PCM) and a thermally activated building system (TABS) implemented in a hollow core concrete deck. Numerical calculations of the dynamic heat storage capacity of the hollow core concrete deck element...... with and without microencapsulated PCM are presented. The new concrete deck with microencapsulated PCM is the standard deck on which an additional layer of the PCM concrete was added and, at the same time, the latent heat storage was introduced to the construction. The challenge of numerically simulating...

  2. Nanocomposite of photocurable epoxy-acrylate resin and carbon nanotubes: dynamic-mechanical, thermal and tribological properties

    Directory of Open Access Journals (Sweden)

    Marcos Nunes dos Santos

    2013-04-01

    Full Text Available In this study, the thermal, dynamic-mechanical and tribological behavior of nanocomposites of a photocurable epoxy-acrylate resin and multiwalled carbon nanotubes (MWCNT are investigated. A route consisting of a combination of sonication, mechanical and magnetic stirring is used to disperse 0.25-0.75 wt. (% MWCNT into the resin. Two photocuring cycles using 12 hours and 24 hours of UV-A radiation are studied. The storage modulus, the loss modulus and the tan delta are obtained by dynamic mechanical analysis. Thermal stability is investigated by thermogravimetry, morphology by transmission electronic microscopy (TEM and tribological performance using a pin-on-disk apparatus. The results indicate an increase in stiffness and higher ability to dissipate energy, as well as a shift in the glass transition temperature for the nanocomposites. The addition of nanofillers also decreased friction coefficient and wear rate of the nanocomposites but did not change the observed wear mechanisms.

  3. Thermal performance of a photographic laboratory process: Solar Hot Water System

    Science.gov (United States)

    Walker, J. A.; Jensen, R. N.

    1982-01-01

    The thermal performance of a solar process hot water system is described. The system was designed to supply 22,000 liters (5,500 gallons) per day of 66 C (150 F) process water for photographic processing. The 328 sq m (3,528 sq. ft.) solar field has supplied 58% of the thermal energy for the system. Techniques used for analyzing various thermal values are given. Load and performance factors and the resulting solar contribution are discussed.

  4. Thermal adaptation of conformational dynamics in ribonuclease H.

    Directory of Open Access Journals (Sweden)

    Kate A Stafford

    Full Text Available The relationship between inherent internal conformational processes and enzymatic activity or thermodynamic stability of proteins has proven difficult to characterize. The study of homologous proteins with differing thermostabilities offers an especially useful approach for understanding the functional aspects of conformational dynamics. In particular, ribonuclease HI (RNase H, an 18 kD globular protein that hydrolyzes the RNA strand of RNA:DNA hybrid substrates, has been extensively studied by NMR spectroscopy to characterize the differences in dynamics between homologs from the mesophilic organism E. coli and the thermophilic organism T. thermophilus. Herein, molecular dynamics simulations are reported for five homologous RNase H proteins of varying thermostabilities and enzymatic activities from organisms of markedly different preferred growth temperatures. For the E. coli and T. thermophilus proteins, strong agreement is obtained between simulated and experimental values for NMR order parameters and for dynamically averaged chemical shifts, suggesting that these simulations can be a productive platform for predicting the effects of individual amino acid residues on dynamic behavior. Analyses of the simulations reveal that a single residue differentiates between two different and otherwise conserved dynamic processes in a region of the protein known to form part of the substrate-binding interface. Additional key residues within these two categories are identified through the temperature-dependence of these conformational processes.

  5. Application of computational fluid dynamics methods to improve thermal hydraulic code analysis

    Science.gov (United States)

    Sentell, Dennis Shannon, Jr.

    A computational fluid dynamics code is used to model the primary natural circulation loop of a proposed small modular reactor for comparison to experimental data and best-estimate thermal-hydraulic code results. Recent advances in computational fluid dynamics code modeling capabilities make them attractive alternatives to the current conservative approach of coupled best-estimate thermal hydraulic codes and uncertainty evaluations. The results from a computational fluid dynamics analysis are benchmarked against the experimental test results of a 1:3 length, 1:254 volume, full pressure and full temperature scale small modular reactor during steady-state power operations and during a depressurization transient. A comparative evaluation of the experimental data, the thermal hydraulic code results and the computational fluid dynamics code results provides an opportunity to validate the best-estimate thermal hydraulic code's treatment of a natural circulation loop and provide insights into expanded use of the computational fluid dynamics code in future designs and operations. Additionally, a sensitivity analysis is conducted to determine those physical phenomena most impactful on operations of the proposed reactor's natural circulation loop. The combination of the comparative evaluation and sensitivity analysis provides the resources for increased confidence in model developments for natural circulation loops and provides for reliability improvements of the thermal hydraulic code.

  6. Thermal stress, human performance, and physical employment standards.

    Science.gov (United States)

    Cheung, Stephen S; Lee, Jason K W; Oksa, Juha

    2016-06-01

    Many physically demanding occupations in both developed and developing economies involve exposure to extreme thermal environments that can affect work capacity and ultimately health. Thermal extremes may be present in either an outdoor or an indoor work environment, and can be due to a combination of the natural or artificial ambient environment, the rate of metabolic heat generation from physical work, processes specific to the workplace (e.g., steel manufacturing), or through the requirement for protective clothing impairing heat dissipation. Together, thermal exposure can elicit acute impairment of work capacity and also chronic effects on health, greatly contributing to worker health risk and reduced productivity. Surprisingly, in most occupations even in developed economies, there are rarely any standards regarding enforced heat or cold safety for workers. Furthermore, specific physical employment standards or accommodations for thermal stressors are rare, with workers commonly tested under near-perfect conditions. This review surveys the major occupational impact of thermal extremes and existing employment standards, proposing guidelines for improvement and areas for future research.

  7. Metaconcrete: Engineered aggregates for enhanced dynamic performance

    Science.gov (United States)

    Mitchell, Stephanie J.

    This work presents the development and investigation of a new type of concrete for the attenuation of waves induced by dynamic excitation. Recent progress in the field of metamaterials science has led to a range of novel composites which display unusual properties when interacting with electromagnetic, acoustic, and elastic waves. A new structural metamaterial with enhanced properties for dynamic loading applications is presented, which is named metaconcrete. In this new composite material the standard stone and gravel aggregates of regular concrete are replaced with spherical engineered inclusions. Each metaconcrete aggregate has a layered structure, consisting of a heavy core and a thin compliant outer coating. This structure allows for resonance at or near the eigenfrequencies of the inclusions, and the aggregates can be tuned so that resonant oscillations will be activated by particular frequencies of an applied dynamic loading. The activation of resonance within the aggregates causes the overall system to exhibit negative effective mass, which leads to attenuation of the applied wave motion. To investigate the behavior of metaconcrete slabs under a variety of different loading conditions a finite element slab model containing a periodic array of aggregates is utilized. The frequency dependent nature of metaconcrete is investigated by considering the transmission of wave energy through a slab, which indicates the presence of large attenuation bands near the resonant frequencies of the aggregates. Applying a blast wave loading to both an elastic slab and a slab model that incorporates the fracture characteristics of the mortar matrix reveals that a significant portion of the supplied energy can be absorbed by aggregates which are activated by the chosen blast wave profile. The transfer of energy from the mortar matrix to the metaconcrete aggregates leads to a significant reduction in the maximum longitudinal stress, greatly improving the ability of the material

  8. Thermal Performance of Composite Flexible Blanket Insulations for Hypersonic Aerospace Vehicles

    Science.gov (United States)

    Kourtides, Demetrius A.

    1993-01-01

    This paper describes the thermal performance of a Composite Flexible Blanket Insulation (C.F.B.I.) considered for potential use as a thermal protection system or thermal insulation for future hypersonic vehicles such as the National Aerospace Plane (N.A.S.P.). Thermophysical properties for these insulations were also measured including the thermal conductivity at various temperatures and pressures and the emissivity of the fabrics used in the flexible insulations. The thermal response of these materials subjected to aeroconvective heating from a plasma arc is also described. Materials tested included two surface variations of the insulations, and similar insulations coated with a Protective Ceramic Coating (P.C.C.). Surface and backface temperatures were measured in the flexible insulations and on Fibrous Refractory Composite Insulation (F.R.C.I.) used as a calibration model. The uncoated flexible insulations exhibited good thermal performance up to 35 W/sq cm. The use of a P.C.C. to protect these insulations at higher heating rates is described. The results from a computerized thermal analysis model describing thermal response of those materials subjected to the plasma arc conditions are included. Thermal and optical properties were determined including thermal conductivity for the rigid and flexible insulations and emissivity for the insulation fabrics. These properties were utilized to calculate the thermal performance of the rigid and flexible insulations at the maximum heating rate.

  9. Lattice dynamics and thermal transport in multiferroic CuCrO2

    Science.gov (United States)

    Bansal, Dipanshu; Niedziela, Jennifer L.; May, Andrew F.; Said, Ayman; Ehlers, Georg; Abernathy, Douglas L.; Huq, Ashfia; Kirkham, Melanie; Zhou, Haidong; Delaire, Olivier

    2017-02-01

    Inelastic neutron and x-ray scattering measurements of phonons and spin waves were performed in the delafossite compound CuCrO2 over a wide range of temperature, and complemented with first-principles lattice dynamics simulations. The phonon dispersions and density of states are well reproduced by our density functional calculations, and reveal a strong anisotropy of Cu vibrations, which exhibit low-frequency modes of large amplitude parallel to the basal plane of the layered delafossite structure. The low frequency in-plane modes also show a systematic temperature dependence of neutron and x-ray scattering intensities. In addition, we find that spin fluctuations persist above 300 K, far above the Néel temperature for long-range antiferromagnetic order, TN≃24 K . Our modeling of the thermal conductivity, based on our phonon measurements and simulations, reveals a significant anisotropy and indicates that spin fluctuations above TN constitute an important source of phonon scattering, considerably suppressing the thermal conductivity compared to that of the isostructural but nonmagnetic compound CuAlO2.

  10. Assessment of structural, thermal, and mechanical properties of portlandite through molecular dynamics simulations

    Science.gov (United States)

    Hajilar, Shahin; Shafei, Behrouz

    2016-12-01

    The structural, thermal, and mechanical properties of portlandite, the primary solid phase of ordinary hydrated cement paste, are investigated using the molecular dynamics method. To understand the effects of temperature on the structural properties of portlandite, the coefficients of thermal expansion of portlandite are determined in the current study and validated with what reported from the experimental tests. The atomic structure of portlandite equilibrated at various temperatures is then subjected to uniaxial tensile strains in the three orthogonal directions and the stress-strain curves are developed. Based on the obtained results, the effect of the direction of straining on the mechanical properties of portlandite is investigated in detail. Structural damage analysis is performed to reveal the failure mechanisms in different directions. The energies of the fractured surfaces are calculated in different directions and compared to those of the ideal surfaces available in the literature. The key mechanical properties, including tensile strength, Young's modulus, and fracture strain, are extracted from the stress-strain curves. The sensitivity of the obtained mechanical properties to temperature and strain rate is then explored in a systematic way. This leads to valuable information on how the structural and mechanical properties of portlandite are affected under various exposure conditions and loading rates.

  11. Determination of the Optimal Fourier Number on the Dynamic Thermal Transmission

    Science.gov (United States)

    Bruzgevičius, P.; Burlingis, A.; Norvaišienė, R.

    2016-12-01

    This article represents the result of experimental research on transient heat transfer in a multilayered (heterogeneous) wall. Our non-steady thermal transmission simulation is based on a finite-difference calculation method. The value of a Fourier number shows the similarity of thermal variation in conditional layers of an enclosure. Most scientists recommend using no more than a value of 0.5 for the Fourier number when performing calculations on dynamic (transient) heat transfer. The value of the Fourier number is determined in order to acquire reliable calculation results with optimal accuracy. To compare the results of simulation with experimental research, a transient heat transfer calculation spreadsheet was created. Our research has shown that a Fourier number of around 0.5 or even 0.32 is not sufficient ({≈ }17 % of oscillation amplitude) for calculations of transient heat transfer in a multilayered wall. The least distorted calculation results were obtained when the multilayered enclosure was divided into conditional layers with almost equal Fourier number values and when the value of the Fourier number was around 1/6, i.e., approximately 0.17. Statistical deviation analysis using the Statistical Analysis System was applied to assess the accuracy of the spreadsheet calculation and was developed on the basis of our established methodology. The mean and median absolute error as well as their confidence intervals has been estimated by the two methods with optimal accuracy ({F}_{oMDF}= 0.177 and F_{oEPS}= 0.1633 values).

  12. Nonequlibrium dynamics of scalar fields in a thermal bath

    Energy Technology Data Exchange (ETDEWEB)

    Anisimov, A.; Buchmueller, W.; Drewes, M.; Mendizabal, S.

    2008-12-15

    We study the approach to equilibrium for a scalar field which is coupled to a large thermal bath. Our analysis of the initial value problem is based on Kadanoff-Baym equations which are shown to be equivalent to a stochastic Langevin equation. The interaction with the thermal bath generates a temperature-dependent spectral density, either through decay and inverse decay processes or via Landau damping. In equilibrium, energy density and pressure are determined by the Bose-Einstein distribution function evaluated at a complex quasi-particle pole. The time evolution of the statistical propagator is compared with solutions of the Boltzmann equations for particles as well as quasi-particles. The dependence on initial conditions and the range of validity of the Boltzmann approximation are determined. (orig.)

  13. Thermal performance of a flat polymer heat pipe heat spreader under high acceleration

    Science.gov (United States)

    Oshman, Christopher; Li, Qian; Liew, Li-Anne; Yang, Ronggui; Lee, Y. C.; Bright, Victor M.; Sharar, Darin J.; Jankowski, Nicholas R.; Morgan, Brian C.

    2012-04-01

    This paper presents the fabrication and application of a micro-scale hybrid wicking structure in a flat polymer-based heat pipe heat spreader, which improves the heat transfer performance under high adverse acceleration. The hybrid wicking structure which enhances evaporation and condensation heat transfer under adverse acceleration consists of 100 µm high, 200 µm wide square electroplated copper micro-pillars with 31 µm wide grooves for liquid flow and a woven copper mesh with 51 µm diameter wires and 76 µm spacing. The interior vapor chamber of the heat pipe heat spreader was 30×30×1.0 mm3. The casing of the heat spreader is a 100 µm thick liquid crystal polymer which contains a two-dimensional array of copper-filled vias to reduce the overall thermal resistance. The device performance was assessed under 0-10 g acceleration with 20, 30 and 40 W power input on an evaporator area of 8×8 mm2. The effective thermal conductivity of the device was determined to range from 1653 W (m K)-1 at 0 g to 541 W (m K)-1 at 10 g using finite element analysis in conjunction with a copper reference sample. In all cases, the effective thermal conductivity remained higher than that of the copper reference sample. This work illustrates the possibility of fabricating flexible, polymer-based heat pipe heat spreaders compatible with standardized printed circuit board technologies that are capable of efficiently extracting heat at relatively high dynamic acceleration levels.

  14. Performance evaluation of a thermal Doppler Michelson interferometer system.

    Science.gov (United States)

    Mani, Reza; Dobbie, Steven; Scott, Alan; Shepherd, Gordon; Gault, William; Brown, Stephen

    2005-11-20

    The thermal Doppler Michelson interferometer is the primary element of a proposed limb-viewing satellite instrument called SWIFT (Stratospheric Wind Interferometer for Transport studies). SWIFT is intended to measure stratospheric wind velocities in the altitude range of 15-45 km. SWIFT also uses narrowband tandem etalon filters made of germanium to select a line out of the thermal spectrum. The instrument uses the same technique of phase-stepping interferometry employed by the Wind Imaging Interferometer onboard the Upper Atmosphere Research Satellite. A thermal emission line of ozone near 9 microm is used to detect the Doppler shift due to winds. A test bed was set up for this instrument that included the Michelson interferometer and the etalon filters. For the test bed work, we investigate the behavior of individual components and their combination and report the results.

  15. CTS TEP thermal anomalies: Heat pipe system performance

    Science.gov (United States)

    Marcus, B. D.

    1977-01-01

    A part of the investigation is summarized of the thermal anomalies of the transmitter experiment package (TEP) on the Communications Technology Satellite (CTS) which were observed on four occasions in 1977. Specifically, the possible failure modes of the variable conductance heat pipe system (VCHPS) used for principal thermal control of the high-power traveling wave tube in the TEP are considered. Further, the investigation examines how those malfunctions may have given rise to the TEP thermal anomalies. Using CTS flight data information, ground test results, analysis conclusions, and other relevant information, the investigation concentrated on artery depriming as the most likely VCHPS failure mode. Included in the study as possible depriming mechanisms were freezing of the working fluid, Marangoni flow, and gas evolution within the arteries. The report concludes that while depriming of the heat pipe arteries is consistent with the bulk of the observed data, the factors which cause the arteries to deprime have yet to be identified.

  16. ATS-6 engineering performance report. Volume:Program and systems summaries: Mechanical and thermal details

    Science.gov (United States)

    Wales, R. O. (Editor)

    1981-01-01

    The overall mission and spacecraft systems, testing, and operations are summarized. The mechanical subsystems are reviewed, encompassing mechanical design requirements; separation and deployment mechanisms; design and performance evaluation; and the television camera reflector monitor. Thermal control and contamination are discussed in terms of thermal control subsystems, design validation, subsystems performance, the advanced flight experiment, and the quartz-crystal microbalance contamination monitor.

  17. Effects of Thermal Treatment on the Dynamic Mechanical Properties of Coal Measures Sandstone

    Science.gov (United States)

    Li, Ming; Mao, Xianbiao; Cao, Lili; Pu, Hai; Mao, Rongrong; Lu, Aihong

    2016-09-01

    Many projects such as the underground gasification of coal seams and coal-bed methane mining (exploitation) widely involve the dynamic problems of coal measures sandstone achieved via thermal treatment. This study examines the dynamic mechanical properties of coal measures sandstone after thermal treatment by means of an MTS653 high-temperature furnace and Split Hopkinson pressure bar test system. Experimental results indicate that 500 °C is a transition point for the dynamic mechanical parameters of coal measures sandstone. The dynamic elastic modulus and peak strength increase linearly from 25 to 500 °C while the dynamic peak strain decreases linearly over the same temperature range. The dynamic elastic modulus and peak strength drop quickly from 500 to 800 °C, with a significant increase in the dynamic peak strain over the same temperature range. The rock mechanics are closely linked to material composition and mesoscopic structure. Analysis by X-ray diffraction and scanning electron microscopy indicate that the molecules inside the sandstone increase in density due to the thermal expansion of the material particles, which effectively improves the deformation resistance and carrying capacity of the sandstone and reduces the likelihood of axial deformation. With heat treatment that exceeds 500 °C, the dynamic mechanical properties rapidly weaken due to the decomposition of kaolinite; additionally, hot cracking of the mineral particles within the materials arises from coal sandstone internal porosity, and other defects gradually appear.

  18. Lunar Eclipse Observations Reveal Anomalous Thermal Performance of Apollo Reflectors

    CERN Document Server

    Murphy, T W; Johnson, N H; Goodrow, S D

    2013-01-01

    Laser ranging measurements during the total lunar eclipse on 2010 December 21 verify previously suspected thermal lensing in the retroreflectors left on the lunar surface by the Apollo astronauts. Signal levels during the eclipse far exceeded those historically seen at full moon, and varied over an order of magnitude as the eclipse progressed. These variations can be understood via a straightforward thermal scenario involving solar absorption by a ~50% covering of dust that has accumulated on the front surfaces of the reflectors. The same mechanism can explain the long-term degradation of signal from the reflectors as well as the acute signal deficit observed near full moon.

  19. Lunar eclipse observations reveal anomalous thermal performance of Apollo reflectors

    Science.gov (United States)

    Murphy, T. W.; McMillan, R. J.; Johnson, N. H.; Goodrow, S. D.

    2014-03-01

    Laser ranging measurements during the total lunar eclipse on 2010 December 21 verify previously suspected thermal lensing in the retroreflectors left on the lunar surface by the Apollo astronauts. Signal levels during the eclipse far exceeded those historically seen at full moon, and varied over an order of magnitude as the eclipse progressed. These variations can be understood via a straightforward thermal scenario involving solar absorption by a ∼50% covering of dust that has accumulated on the front surfaces of the reflectors. The same mechanism can explain the long-term degradation of signal from the reflectors as well as the acute signal deficit observed near full moon.

  20. Influence of the Thermal Inertia in the European Simplified Procedures for the Assessment of Buildings’ Energy Performance

    Directory of Open Access Journals (Sweden)

    Luca Evangelisti

    2014-07-01

    Full Text Available This study aims to highlight the importance of thermal inertia in buildings. Nowadays, it is possible to use energy analysis software to simulate the building energy performance. Considering Italian standards, these analyses are based on the UNI TS 11300 that defines the procedures for the national implementation of the UNI EN ISO 13790. These standards require an energy analysis under steady-state condition, underestimating the thermal inertia of the building. In order to understand the inertial behavior of walls, a cubic Test-Cell was modelled through the dynamic calculation code TRNSYS and three different wall types were tested. Different stratigraphies, characterized by the same thermal transmittance value, composed by massive elements and insulating layers in different order, were simulated. Through TRNSYS, it was possible to define maximum surface temperatures and to calculate thermal lag between maximum values, both external and internal. Moreover, the attenuation between external surface temperatures and internal ones during summer (July was calculated. Finally, the comparison between Test-Cell’s annual energy demands, performed by using a commercial code based on the Italian standard UNITS 11300 and the dynamic code, TRNSYS, was carried out.

  1. Thermal fluctuations in amphipol A8-35 particles: a neutron scattering and molecular dynamics study.

    Science.gov (United States)

    Tehei, Moeava; Perlmutter, Jason D; Giusti, Fabrice; Sachs, Jonathan N; Zaccai, Giuseppe; Popot, Jean-Luc

    2014-10-01

    Amphipols are a class of polymeric surfactants that can stabilize membrane proteins in aqueous solutions as compared to detergents. A8-35, the best-characterized amphipol to date, is composed of a polyacrylate backbone with ~35% of the carboxylates free, ~25% grafted with octyl side-chains, and ~40% with isopropyl ones. In aqueous solutions, A8-35 self-organizes into globular particles with a molecular mass of ~40 kDa. The thermal dynamics of A8-35 particles was measured by neutron scattering in the 10-picosecond, 18-picosecond, and 1-nanosecond time-scales on natural abundance and deuterium-labeled molecules, which permitted to separate backbone and side-chain motions. A parallel analysis was performed on molecular dynamics trajectories (Perlmutter et al., Langmuir 27:10523-10537, 2011). Experimental results and simulations converge, from their respective time-scales, to show that A8-35 particles feature a more fluid hydrophobic core, predominantly containing the octyl chains, and a more rigid solvent-exposed surface, made up predominantly of the hydrophilic polymer backbone. The fluidity of the core is comparable to that of the lipid environment around proteins in the center of biological membranes, as also measured by neutron scattering. The biological activity of proteins depends sensitively on molecular dynamics, which itself is strongly dependent on the immediate macromolecular environment. In this context, the characterization of A8-35 particle dynamics constitutes a step toward understanding the effect of amphipols on membrane protein stability and function.

  2. Dynamic Buffering Performance of the Honeycomb Paperboard Filled with Polyurethane

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong; XIE Weihong; CHEN Li

    2014-01-01

    A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material’s dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffering area of the composite material.

  3. Thermal vibration of a single-walled carbon nanotube predicted by semiquantum molecular dynamics.

    Science.gov (United States)

    Liu, Rumeng; Wang, Lifeng

    2015-02-21

    Quantum effects should be considered in the thermal vibrations of carbon nanotubes (CNTs). To this end, molecular dynamics based on modified Langevin dynamics, which accounts for quantum statistics by introducing a quantum heat bath, is used to simulate the thermal vibration of a cantilevered single-walled CNT (SWCNT). A nonlocal elastic Timoshenko beam model with quantum effects (TBQN), which can take the effect of microstructure into consideration, has been established to explain the resulting power spectral density of the SWCNT. The root of mean squared (RMS) amplitude of the thermal vibration of the SWCNT obtained from semiquantum molecular dynamics (SQMD) is lower than that obtained from classical molecular dynamics, especially at very low temperature and high-order modes. The natural frequencies of the SWCNT obtained from the Timoshenko beam model are closer to those obtained from molecular dynamics if the nonlocal effect is taken into consideration. However, the nonlocal Timoshenko beam model with the law of energy equipartition (TBCN) can only predict the RMS amplitude of the SWCNT obtained from classical molecular dynamics without considering quantum effects. The RMS amplitude of the SWCNT obtained from SQMD and that obtained from TBQN coincide very well. These results indicate that quantum effects are important for the thermal vibration of the SWCNT in the case of high-order modes, short length and low temperature.

  4. Shock initiated thermal and chemical responses of HMX crystal from ReaxFF molecular dynamics simulation.

    Science.gov (United States)

    Zhou, Tingting; Song, Huajie; Liu, Yi; Huang, Fenglei

    2014-07-21

    To gain an atomistic-level understanding of the thermal and chemical responses of condensed energetic materials under thermal shock, we developed a thermal shock reactive dynamics (TS-RD) computational protocol using molecular dynamics simulation coupled with ReaxFF force field. β-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) was selected as a a target explosive due to its wide usage in the military and industry. The results show that a thermal shock initiated by a large temperature gradient between the "hot" region and the "cold" region results in thermal expansion of the particles and induces a thermal-mechanical wave propagating back and forth in the system with an averaged velocity of 3.32 km s(-1). Heat propagating along the direction of thermal shock leads to a temperature increment of the system and thus chemical reaction initiation. Applying a continuum reactive heat conduction model combined with the temperature distribution obtained from the RD simulation, a heat conduction coefficient is derived as 0.80 W m(-1) K(-1). The chemical reaction mechanisms during thermal shock were analyzed, showing that the reaction is triggered by N-NO2 bond breaking followed by HONO elimination and ring fission. The propagation rates of the reaction front and reaction center are obtained to be 0.069 and 0.038 km s(-1), based on the time and spatial distribution of NO2. The pressure effect on the thermal shock was also investigated by employing uniaxial compression before the thermal shock. We find that compression significantly accelerates thermal-mechanical wave propagation and heat conduction, resulting in higher temperature and more excited molecules and thus earlier initiation and faster propagation of chemical reactions.

  5. Smoothed dissipative particle dynamics model for mesoscopic multiphase flows in the presence of thermal fluctuations

    Science.gov (United States)

    Lei, Huan; Baker, Nathan A.; Wu, Lei; Schenter, Gregory K.; Mundy, Christopher J.; Tartakovsky, Alexandre M.

    2016-08-01

    Thermal fluctuations cause perturbations of fluid-fluid interfaces and highly nonlinear hydrodynamics in multiphase flows. In this work, we develop a multiphase smoothed dissipative particle dynamics (SDPD) model. This model accounts for both bulk hydrodynamics and interfacial fluctuations. Interfacial surface tension is modeled by imposing a pairwise force between SDPD particles. We show that the relationship between the model parameters and surface tension, previously derived under the assumption of zero thermal fluctuation, is accurate for fluid systems at low temperature but overestimates the surface tension for intermediate and large thermal fluctuations. To analyze the effect of thermal fluctuations on surface tension, we construct a coarse-grained Euler lattice model based on the mean field theory and derive a semianalytical formula to directly relate the surface tension to model parameters for a wide range of temperatures and model resolutions. We demonstrate that the present method correctly models dynamic processes, such as bubble coalescence and capillary spectra across the interface.

  6. Smoothed dissipative particle dynamics model for mesoscopic multiphase flows in the presence of thermal fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Huan; Baker, Nathan A.; Wu, Lei; Schenter, Gregory K.; Mundy, Christopher J.; Tartakovsky, Alexandre M.

    2016-08-05

    Thermal fluctuations cause perturbations of fluid-fluid interfaces and highly nonlinear hydrodynamics in multiphase flows. In this work, we develop a novel multiphase smoothed dissipative particle dynamics model. This model accounts for both bulk hydrodynamics and interfacial fluctuations. Interfacial surface tension is modeled by imposing a pairwise force between SDPD particles. We show that the relationship between the model parameters and surface tension, previously derived under the assumption of zero thermal fluctuation, is accurate for fluid systems at low temperature but overestimates the surface tension for intermediate and large thermal fluctuations. To analyze the effect of thermal fluctuations on surface tension, we construct a coarse-grained Euler lattice model based on the mean field theory and derive a semi-analytical formula to directly relate the surface tension to model parameters for a wide range of temperatures and model resolutions. We demonstrate that the present method correctly models the dynamic processes, such as bubble coalescence and capillary spectra across the interface.

  7. Dynamic measurement of coal thermal properties and elemental composition of volatile matter during coal pyrolysis

    Directory of Open Access Journals (Sweden)

    Rohan Stanger

    2014-01-01

    Full Text Available A new technique that allows dynamic measurement of thermal properties, expansion and the elemental chemistry of the volatile matter being evolved as coal is pyrolysed is described. The thermal and other properties are measured dynamically as a function of temperature of the coal without the need for equilibration at temperature. In particular, the technique allows for continuous elemental characterisation of tars as they are evolved during pyrolysis and afterwards as a function of boiling point. The technique is demonstrated by measuring the properties of maceral concentrates from a coal. The variation in heats of reaction, thermal conductivity and expansion as a function of maceral composition is described. Combined with the elemental analysis, the results aid in the interpretation of the chemical processes contributing to the physical and thermal behaviour of the coal during pyrolysis. Potential applications in cokemaking studies are discussed.

  8. Transient modelling of loss and thermal dynamics in power semiconductor devices

    DEFF Research Database (Denmark)

    Ma, Ke; Yang, Yongheng; Blaabjerg, Frede

    2014-01-01

    on the proposed models, the bandwidths of the loss or thermal response to major disturbances in the converter system can be analytically mapped, enabling more advanced tools to investigate the transient characteristics of loss and thermal dynamics in the power electronics devices.......The dynamical behavior of temperature is becoming a critical design consideration for the power electronics, because they are referred as “thermal cycling” which is the root cause of fatigues in the power electronics devices, and thus is closely related to the reliability of the converter....... It is well understood that the loading of power devices are disturbed by many factors of the converter system like grid, control, environment, etc., which emerge at various time-constants. However, the corresponding thermal response to these disturbances is still unclear, especially the transient behaviors...

  9. Predicting micro thermal habitat of lizards in a dynamic thermal environment

    NARCIS (Netherlands)

    Fei, T.; Skidmore, A.K.; Venus, V.; Wang, T.; Toxopeus, A.G.; Bian, B.M.; Liu, Y.

    2012-01-01

    Understanding behavioural thermoregulation and its consequences is a central topic in ecology. In this study, a spatial explicit model was developed to simulate the movement and thermal habitat use of lizards in a controlled environment. The model incorporates a lizard's transient body temperatures

  10. Thermal conductance of carbon nanotube contacts: Molecular dynamics simulations and general description of the contact conductance

    Science.gov (United States)

    Salaway, Richard N.; Zhigilei, Leonid V.

    2016-07-01

    The contact conductance of carbon nanotube (CNT) junctions is the key factor that controls the collective heat transfer through CNT networks or CNT-based materials. An improved understanding of the dependence of the intertube conductance on the contact structure and local environment is needed for predictive computational modeling or theoretical description of the effective thermal conductivity of CNT materials. To investigate the effect of local structure on the thermal conductance across CNT-CNT contact regions, nonequilibrium molecular dynamics (MD) simulations are performed for different intertube contact configurations (parallel fully or partially overlapping CNTs and CNTs crossing each other at different angles) and local structural environments characteristic of CNT network materials. The results of MD simulations predict a stronger CNT length dependence present over a broader range of lengths than has been previously reported and suggest that the effect of neighboring junctions on the conductance of CNT-CNT junctions is weak and only present when the CNTs that make up the junctions are within the range of direct van der Waals interaction with each other. A detailed analysis of the results obtained for a diverse range of intertube contact configurations reveals a nonlinear dependence of the conductance on the contact area (or number of interatomic intertube interactions) and suggests larger contributions to the conductance from areas of the contact where the density of interatomic intertube interactions is smaller. An empirical relation accounting for these observations and expressing the conductance of an arbitrary contact configuration through the total number of interatomic intertube interactions and the average number of interatomic intertube interactions per atom in the contact region is proposed. The empirical relation is found to provide a good quantitative description of the contact conductance for various CNT configurations investigated in the MD

  11. Thermal conductivity predictions of herringbone graphite nanofibers using molecular dynamics simulations.

    Science.gov (United States)

    Khadem, Masoud H; Wemhoff, Aaron P

    2013-02-28

    Non-equilibrium molecular dynamics (NEMD) simulations are used to investigate the thermal conductivity of herringbone graphite nanofibers (GNFs) at room temperature by breaking down the axial and transverse conductivity values into intralayer and interlayer components. The optimized Tersoff potential is used to account for intralayer carbon-carbon interactions while the Lennard-Jones potential is used to model the interlayer carbon-carbon interactions. The intralayer thermal conductivity of the graphene layers near room temperature is calculated for different crease angles and number of layers using NEMD with a constant applied heat flux. The edge effect on a layer's thermal conductivity is investigated by computing the thermal conductivity values in both zigzag and armchair directions of the heat flow. The interlayer thermal conductivity is also predicted by imposing hot and cold Nosé-Hoover thermostats on two layers. The limiting case of a 90° crease angle is used to compare the results with those of single-layer graphene and few-layer graphene. The axial and transverse thermal conductivities are then calculated using standard trigonometric conversions of the calculated intralayer and interlayer thermal conductivities, along with calculations of few-layer graphene without a crease. The results show a large influence of the crease angle on the intralayer thermal conductivity, and the saturation of thermal conductivity occurs when number of layers is more than three. The axial thermal conductivity, transverse thermal conductivity in the crease direction, and transverse thermal conductivity normal to the crease for the case of a five-layer herringbone GNF with a 45° crease angle are calculated to be 27 W∕m K, 263 W∕m K, and 1500 W∕m K, respectively, where the axial thermal conductivity is in good agreement with experimental measurements.

  12. Performance Evaluation of HP/ORC (Heat Pump/Organic Rankine Cycle) System with Optimal Control of Sensible Thermal Storage

    DEFF Research Database (Denmark)

    Do Carmo, Carolina Madeira Ramos; Nielsen, Mads Pagh; Elmegaard, Brian

    2016-01-01

    energy in periods of no thermal energy demand and reverses the heat pump cycle to supply electrical power. A dynamic model based on empirical data of this system is used to determine the annual performance. Furthermore, this work assesses the benefits of different control strategies that address...... of the users. Results show that real load control logic can lessen the adverse effects of cycling in the compressor of the system as well as increase the thermal demand (up to 33%) and the electrical demand (max. 8.4%) covered by renewable energy (solar). However, the extension of these improvements is highly......In energy systems with high share of renewable energy sources, like wind and solar power, it is paramount to deal with their intrinsic variability. The interaction between electric and thermal energy (heating and cooling) demands represent a potential area for balancing supply and demand that could...

  13. Dynamic thermal expansivity of liquids near the glass transition

    DEFF Research Database (Denmark)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage Emil;

    2012-01-01

    Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704) in the ......Based on previous works on polymers by Bauer et al. [ Phys. Rev. E 61 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704...

  14. Performance Analysis and Modeling of Thermally Sprayed Resistive Heaters

    Science.gov (United States)

    Lamarre, Jean-Michel; Marcoux, Pierre; Perrault, Michel; Abbott, Richard C.; Legoux, Jean-Gabriel

    2013-08-01

    Many processes and systems require hot surfaces. These are usually heated using electrical elements located in their vicinity. However, this solution is subject to intrinsic limitations associated with heating element geometry and physical location. Thermally spraying electrical elements directly on surfaces can overcome these limitations by tailoring the geometry of the heating element to the application. Moreover, the element heat transfer is maximized by minimizing the distance between the heater and the surface to be heated. This article is aimed at modeling and characterizing resistive heaters sprayed on metallic substrates. Heaters were fabricated by using a plasma-sprayed alumina dielectric insulator and a wire flame-sprayed iron-based alloy resistive element. Samples were energized and kept at a constant temperature of 425 °C for up to 4 months. SEM cross-sectional observations revealed the formation of cracks at very specific locations in the alumina layer after thermal use. Finite-element modeling shows that these cracks originate from high local thermal stresses and can be predicted according to the considered geometry. The simulation model was refined using experimental parameters obtained by several techniques such as emissivity and time-dependent temperature profile (infra-red camera), resistivity (four-probe technique), thermal diffusivity (laser flash method), and mechanical properties (micro and nanoindentation). The influence of the alumina thickness and the substrate material on crack formation was evaluated.

  15. High-Performance Home Technologies: Solar Thermal & Photovoltaic Systems

    Energy Technology Data Exchange (ETDEWEB)

    Baechler, M.; Gilbride, T.; Ruiz, K.; Steward, H.; Love, P.

    2007-06-01

    This document is the sixth volume of the Building America Best Practices Series. It presents information that is useful throughout the United States for enhancing the energy efficiency practices in the specific climate zones that are presented in the first five Best Practices volumes. It provides an introduction to current photovoltaic and solar thermal building practices. Information about window selection and shading is included.

  16. Seismology of the Sun : Inference of Thermal, Dynamic and Magnetic Field Structures of the Interior

    CERN Document Server

    Hiremath, K M

    2012-01-01

    Recent overwhelming evidences show that the sun strongly influences the Earth's climate and environment. Moreover existence of life on this Earth mainly depends upon the sun's energy. Hence, understanding of physics of the sun, especially the thermal, dynamic and magnetic field structures of its interior, is very important. Recently, from the ground and space based observations, it is discovered that sun oscillates near 5 min periodicity in millions of modes. This discovery heralded a new era in solar physics and a separate branch called helioseismology or seismology of the sun has started. Before the advent of helioseismology, sun's thermal structure of the interior was understood from the evolutionary solution of stellar structure equations that mimicked the present age, mass and radius of the sun. Whereas solution of MHD equations yielded internal dynamics and magnetic field structure of the sun's interior. In this presentation, I review the thermal, dynamic and magnetic field structures of the sun's inter...

  17. Preparation and performance of thermal insulation energy saving coating materials for exterior wall.

    Science.gov (United States)

    Wang, Fei; Liang, Jinsheng; Tang, Qingguo; Chen, Gong; Chen, Yalei

    2014-05-01

    Nano zinc oxide with a high refractive index has good thermal reflection performance, hollow glass microspheres have good thermal reflection and insulation performance, and sepiolite nanofibers with many nanostructural pores have good thermal insulation performance. The dispensability of nano zinc oxide in coating materials was improved by optimizing surface silane coupling agent modification process, leading to the good thermal reflection performance. The thermal insulation performance was improved by hollow glass microspheres and sepiolite nanofibers. On this basis, the thermal insulation coating materials were prepared by exploring the effect of amount, complex mode, and other factors of the above three kinds of functional fillers on the thermal reflection and insulation performance of coating materials. The results showed that the surface modification effect of nano zinc oxide was the best when the silane coupling agent addition was 6%. The reflection and insulation performance of the coatings were the best when the additions of modified nano zinc oxide, hollow glass microspheres, and sepiolite nanofibers were 3%, 4%, and 4%, respectively. Compared with the control coating materials, the thermal insulation effect was improved obviously, which was evaluated by the -13.5 degrees C increase of maximum temperature difference between the upper and the lower surfaces.

  18. Millisecond dynamics of thermal expansion of mechanically controllable break junction electrodes studied in the tunneling regime

    Science.gov (United States)

    Kolesnychenko, O. Yu.; Toonen, A. J.; Shklyarevskii, O. I.; van Kempen, H.

    2001-10-01

    The thermal expansion dynamics of W, Pt-Ir, and Au mechanically controllable break junction electrodes was studied in the millisecond range. By measuring a transient tunnel current as a function of time, we found that, at low temperatures, the electrode elongation Δs˜t1/2 due to the large values of thermal diffusivity of metals. The magnitude of Δs varies in direct proportion to the power P dissipated in the electrodes.

  19. Computational Fluid Dynamics Analysis of Viscosity Influence on Thermal In-Package Liquid Food Process

    OpenAIRE

    Augusto, PED; Cristianini, M

    2010-01-01

    Food processes must ensure safety and high-quality products for a growing demand consumer creating needs for its better unit operations knowledge. Computational fluid dynamics (CFD) have been widely used to better understand food thermal processes, one of the safest and most frequently used methods for food preservation. Fluid heating in enclosures is a complex phenomenon, which must be better understood. Although the relative convection importance at thermal liquid food process was recently ...

  20. Effects of vacuum thermal cycling on mechanical and physical properties of high performance carbon/bismaleimide composite

    Energy Technology Data Exchange (ETDEWEB)

    Yu Qi [State Key Laboratory of Fine Chemicals and School of Chemical Engineering, Dalian University of Technology, Dalian Liaoning 116024 (China); Liaoning Key Laboratory of Advanced Polymer Matrix Composites and College of Aerospace Engineering, Shenyang Aerospace University, Shenyang Liaoning 110136 (China); Chen Ping, E-mail: chenping_898@126.com [State Key Laboratory of Fine Chemicals and School of Chemical Engineering, Dalian University of Technology, Dalian Liaoning 116024 (China) and Liaoning Key Laboratory of Advanced Polymer Matrix Composites and College of Aerospace Engineering, Shenyang Aerospace University, Shenyang Liaoning 110136 (China); Gao Yu; Mu Jujie; Chen Yongwu; Lu Chun [Liaoning Key Laboratory of Advanced Polymer Matrix Composites and College of Aerospace Engineering, Shenyang Aerospace University, Shenyang Liaoning 110136 (China); Liu Dong [State Key Laboratory of Fine Chemicals and School of Chemical Engineering, Dalian University of Technology, Dalian Liaoning 116024 (China)

    2011-11-01

    Highlights: {yields} The level of cross-links was improved to a certain extent. {yields} The thermal stability was firstly improved and then decreased. {yields} The transverse and longitudinal CTE were both determined by the degree of interfacial debonding. {yields} The mass loss ratio increases firstly and then reaches a plateau value. {yields} The surface morphology was altered and the surface roughness increased firstly and then decreased. {yields} The transverse tensile strength was reduced. {yields} The flexural strength increased firstly and then decreased to a plateau value. {yields} The ILSS increased firstly and then decreased to a plateau value. - Abstract: The aim of this article was to investigate the effects of vacuum thermal cycling on mechanical and physical properties of high performance carbon/bismaleimide (BMI) composites used in aerospace. The changes in dynamic mechanical properties and thermal stability were characterized by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. The changes in linear coefficient of thermal expansion (CTE) were measured in directions perpendicular and parallel to the fiber direction, respectively. The outgassing behavior of the composites were examined. The evolution of surface morphology and surface roughness were observed by atomic force microscopy (AFM). Changes in mechanical properties including transverse tensile strength, flexural strength and interlaminar shear strength (ILSS) were measured. The results indicated that the vacuum thermal cycling could improve the crosslinking degree and the thermal stability of resin matrix to a certain extent, and induce matrix outgassing and thermal stress, thereby leading to the mass loss and the interfacial debonding of the composite. The degradation in transverse tensile strength was caused by joint effects of the matrix outgassing and the interfacial debonding, while the changes in flexural strength and ILSS were affected by a competing

  1. The ORC method. Effective modelling of thermal performance of multilayer building components

    Energy Technology Data Exchange (ETDEWEB)

    Akander, Jan

    2000-02-01

    The ORC Method (Optimised RC-networks) provides a means of modelling one- or multidimensional heat transfer in building components, in this context within building simulation environments. The methodology is shown, primarily applied to heat transfer in multilayer building components. For multilayer building components, the analytical thermal performance is known, given layer thickness and material properties. The aim of the ORC Method is to optimise the values of the thermal resistances and heat capacities of an RC-model such as to give model performance a good agreement with the analytical performance, for a wide range of frequencies. The optimisation procedure is made in the frequency domain, where the over-all deviation between model and analytical frequency response, in terms of admittance and dynamic transmittance, is minimised. It is shown that ORC's are effective in terms of accuracy and computational time in comparison to finite difference models when used in building simulations, in this case with IDA/ICE. An ORC configuration of five mass nodes has been found to model building components in Nordic countries well, within the application of thermal comfort and energy requirement simulations. Simple RC-networks, such as the surface heat capacity and the simple R-C-configuration are not appropriate for detailed building simulation. However, these can be used as basis for defining the effective heat capacity of a building component. An approximate method is suggested on how to determine the effective heat capacity without the use of complex numbers. This entity can be calculated on basis of layer thickness and material properties with the help of two time constants. The approximate method can give inaccuracies corresponding to 20%. In-situ measurements have been carried out in an experimental building with the purpose of establishing the effective heat capacity of external building components that are subjected to normal thermal conditions. The auxiliary

  2. Assessment of thermal performance for the design of a passively-cooled plutonium storage vault

    Science.gov (United States)

    Sanders, Joseph Conway

    A passively-cooled plutonium storage vault, rather than one with a safety-qualified, forced-flow cooling system, could save as much as 100 million over the project lifetime. Either configuration must maintain the temperature of the stored plutonium metal, with its significant internal heat generation, below 239 sp circF. Alpha-phase metal, if allowed to exceed this temperature, will transition to beta-phase metal and undergo a volumetric expansion which could rupture the storage container system. An investigation was performed to determine whether a passively-cooled vault is feasible. Significant temperature drops occurred in two regions, both were gas-filled vertical annuli with heat flux boundary conditions on the inner surfaces and fixed temperature boundary conditions on the outer surfaces. The thermal resistance method was employed to evaluate radial heat transfer across each annulus, coupling natural convection, radiation, and conduction. Correlations from Thomas et al and Kulacki et al were used to evaluate the degree of natural convective enhancement. For the helium-filled region between the plutonium metal rod and the container with a characteristic length of 3.9 centimeters and an aspect ratio of 5.6, the Rayleigh number was 800 when the effect of radiation was removed. This resulted in a Nusselt number of 1.8. For the air-filled region between twelve vertically arranged containers and the storage tube with a characteristic length of 5.8 centimeters and an aspect ratio of 78, the Rayleigh number was 5times10sp5. This resulted in a Nusselt number of approximately 4.5, neglecting the effect of radiation. FIDAP 7.62\\copyright$ (Fluid Dynamics Analysis Package) was used to perform multi-dimensional finite element analyses of these regions employing both buoyant and radiative effects. Both simplified and more geometrically complex models were employed, all of which compared favorably to the results using the thermal resistance method. The results of the

  3. High-Frequency Dynamic Analysis of Plates in Thermal Environments Based on Energy Finite Element Method

    Directory of Open Access Journals (Sweden)

    Di Wang

    2015-01-01

    Full Text Available The energy density governing equation to analyze the high-frequency dynamic behavior of plates in thermal environments is derived in this paper, in which the thermal effects are considered to change the membrane stress state and temperature dependent material properties of plates. Then the thermal effects on the energy reflection and transmission coefficients are dealt with hereof. Based on the above, an EFEM (energy finite element method based approximate approach for the energy analysis of coupled plates under nonuniform thermal environments is proposed. The approach could be conducted by three steps: (1 thermal analysis, (2 thermal stress analysis, and (3 forming element matrixes, joint matrixes, and the whole EFEM formulation for the energy analysis. The same mesh model is used for all the three steps. The comparison between EFEM results and classical modal superposition method results of simply supported plates in various uniform thermal environments and coupled plates in nonuniform thermal environments demonstrated that the derived energy governing equation and the proposed approach described well the smooth time- and locally space-averaged energy density. It is found that the distributions and levels of energy density are affected by thermal effects, and the variation trends are related to exciting frequency.

  4. Thermal vibration of a single-layered graphene with initial stress predicted by semiquantum molecular dynamics

    Science.gov (United States)

    Liu, Rumeng; Wang, Lifeng; Jiang, Jingnong

    2016-09-01

    Thermal vibration of a rectangular single-layered graphene sheet (RSLGS) with initial stress is investigated by a semiquantum molecular dynamics (SQMD) method on the basis of modified Langevin dynamics. The quantum effect in the thermal vibration of RSLGS is accounted by introducing a quantum thermal bath. The spectrum of the thermal vibration of RSLGSs is obtained both by SQMD and classical molecular dynamics (CMD). The RSLGS vibrates with the same frequencies via both the SQMD simulation and the CMD simulation. The root of mean squared (rms) amplitude obtained via the CMD is greater than that obtained via the SQMD. The energy in high order mode is frozen at very low temperature if quantum effect is taken into consideration. An elastic plate model with initial stress considering quantum effects is established to describe the thermal vibration of the RSLGS. The rms amplitude of RSLGS calculated by plate model with the law of energy equipartition and that obtained from the CMD coincide very well. The plate model considering the quantum effects provides accurate prediction of the rms amplitude of the RSLGS obtained from the SQMD. These results indicate that quantum effects cannot be neglected in the thermal vibration of the RSLGS at low temperature case.

  5. On a computational model of building thermal dynamic response

    Science.gov (United States)

    Jarošová, Petra; Vala, Jiří

    2016-07-01

    Development and exploitation of advanced materials, structures and technologies in civil engineering, both for buildings with carefully controlled interior temperature and for common residential houses, together with new European and national directives and technical standards, stimulate the development of rather complex and robust, but sufficiently simple and inexpensive computational tools, supporting their design and optimization of energy consumption. This paper demonstrates the possibility of consideration of such seemingly contradictory requirements, using the simplified non-stationary thermal model of a building, motivated by the analogy with the analysis of electric circuits; certain semi-analytical forms of solutions come from the method of lines.

  6. Heavy Quark Coupled Channel Dynamics from Thermal Shifts

    CERN Document Server

    Arriola, Enrique Ruiz; Megias, Eugenio

    2016-01-01

    QCD at finite temperature below the phase transition should be determined in terms of colour singlet states such as hadrons and strings. We show how quark-hadron duality allows extracting sensible information concerning heavy quark and string breaking coupled channel dynamics from Polyakov loop correlators.

  7. Multiphase flow dynamics 2 thermal and mechanical interactions

    CERN Document Server

    Kolev, Nikolay I

    2007-01-01

    The industrial use of multi-phase systems requires analytical and numerical strategies for predicting their behavior. This book contains theory, methods and practical experience for describing complex transient multi-phase processes. It provides a systematic presentation of the theory and practice of numerical multi-phase fluid dynamics.

  8. Thermally driven molecular linear motors - A molecular dynamics study

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard Lawrence

    2009-01-01

    We conduct molecular dynamics simulations of a molecular linear motor consisting of coaxial carbon nanotubes with a long outer carbon nanotube confining and guiding the motion of an inner short, capsule-like nanotube. The simulations indicate that the motion of the capsule can be controlled...

  9. Exploring streamwater mixing dynamics via handheld thermal infrared imagery

    NARCIS (Netherlands)

    Antonelli, Marta; Klaus, Julian; Smettem, Keith; Teuling, Ryan; Pfister, Laurent

    2017-01-01

    Stream confluences are important hotspots of aquatic ecological processes. Water mixing dynamics at stream confluences influence physio-chemical characteristics of the stream as well as sediment mobilisation and pollutant dispersal. In this study, we investigated the potential for handheld

  10. Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions (Invited paper)

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.

    2008-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

  11. Synchronized molecular-dynamics simulation for the thermal lubrication of a polymeric liquid between parallel plates

    CERN Document Server

    Yasuda, Shugo

    2015-01-01

    The Synchronized Molecular-Dynamics simulation which was recently proposed by authors [Phys. Rev. X {\\bf 4}, 041011 (2014)] is applied to the analysis of polymer lubrication between parallel plates. The rheological properties, conformational change of polymer chains, and temperature rise due to the viscous heating are investigated with changing the values of thermal conductivity of the polymeric liquid. It is found that at a small applied shear stress on the plate, the temperature of polymeric liquid only slightly increases in inverse proportion to the thermal conductivity and the apparent viscosity of polymeric liquid is not much affected by changing the thermal conductivity. However, at a large shear stress, the transitional behaviors of the polymeric liquid occur due to the interplay of the shear deformation and viscous heating by changing the thermal conductivity. This transition is characterized by the Nahme-Griffith number $Na$ which is defined as the ratio of the viscous heating to the thermal conducti...

  12. Computational fluid dynamics evaluation of liquid food thermal process in a brick shaped package

    Directory of Open Access Journals (Sweden)

    Pedro Esteves Duarte Augusto

    2012-03-01

    Full Text Available Food processes must ensure safety and high-quality products for a growing demand consumer creating the need for better knowledge of its unit operations. The Computational Fluid Dynamics (CFD has been widely used for better understanding the food thermal processes, and it is one of the safest and most frequently used methods for food preservation. However, there is no single study in the literature describing thermal process of liquid foods in a brick shaped package. The present study evaluated such process and the influence of its orientation on the process lethality. It demonstrated the potential of using CFD to evaluate thermal processes of liquid foods and the importance of rheological characterization and convection in thermal processing of liquid foods. It also showed that packaging orientation does not result in different sterilization values during thermal process of the evaluated fluids in the brick shaped package.

  13. Thermal Hydraulic Computational Fluid Dynamics Simulations and Experimental Investigation of Deformed Fuel Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Mays, Brian [AREVA Federal Services, Lynchburg, VA (United States); Jackson, R. Brian [TerraPower, Bellevue, WA (United States)

    2017-03-08

    The project, Toward a Longer Life Core: Thermal Hydraulic CFD Simulations and Experimental Investigation of Deformed Fuel Assemblies, DOE Project code DE-NE0008321, was a verification and validation project for flow and heat transfer through wire wrapped simulated liquid metal fuel assemblies that included both experiments and computational fluid dynamics simulations of those experiments. This project was a two year collaboration between AREVA, TerraPower, Argonne National Laboratory and Texas A&M University. Experiments were performed by AREVA and Texas A&M University. Numerical simulations of these experiments were performed by TerraPower and Argonne National Lab. Project management was performed by AREVA Federal Services. The first of a kind project resulted in the production of both local point temperature measurements and local flow mixing experiment data paired with numerical simulation benchmarking of the experiments. The project experiments included the largest wire-wrapped pin assembly Mass Index of Refraction (MIR) experiment in the world, the first known wire-wrapped assembly experiment with deformed duct geometries and the largest numerical simulations ever produced for wire-wrapped bundles.

  14. Size Effect of Lattice Thermal Conductivity Across Nanoscale Thin Films by Molecular Dynamics Simulations

    Institute of Scientific and Technical Information of China (English)

    FENG Xiao-Li; LI Zhi-Xin; GUO Zeng-Yuan

    2001-01-01

    Thermal conductivity in the normal direction of ultra-thin dielectric films is predicted by molecular dynamics calculations for argon crystal. For film thicknesses of about 2-10nm within which real measurements cannot yet be implemented, the size dependence of lattice thermal conductivity is captured and a remarkable thermal conductivity drop is found as compared with bulk experimental data. This size effect demonstrates that phonon-boundary scattering in thin films may also be very significant at high temperatures even above the Debye temperature. The influence of different potential models is examined according to the comparison between results from the Lennard-Jones potential and a soft-sphere potential.

  15. Turbomachinery Flow Physics and Dynamic Performance

    CERN Document Server

    Schobeiri, Meinhard T

    2012-01-01

    With this second revised and extended edition, the readers have a solid source of information for designing state-of-the art turbomachinery components and systems at hand.   Based on fundamental principles of turbomachinery thermo-fluid mechanics, numerous CFD based calculation methods are being developed to simulate the complex 3-dimensional, highly unsteady turbulent flow within turbine or compressor stages. The objective of this book is to present the fundamental principles of turbomachinery fluid-thermodynamic design process of turbine and compressor components, power generation and aircraft gas turbines in a unified and compact manner. The book provides senior undergraduate students, graduate students and engineers in the turbomachinery industry with a solid background of turbomachinery flow physics and performance fundamentals that are essential for understanding turbomachinery performance and flow complexes.   While maintaining the unifying character of the book structure in this second revised and e...

  16. Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory

    Science.gov (United States)

    Rietze, Clemens; Titov, Evgenii; Lindner, Steven; Saalfrank, Peter

    2017-08-01

    The thermal Z\\to E (back-)isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G* including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model—Z\\to E isomerization in azobenzene—a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the Z\\to E (back-)isomerization of azobenzenes under solvent-free conditions.

  17. Diffusion in a soft confining environment: Dynamic effects of thermal fluctuations

    Science.gov (United States)

    Palmieri, Benoit; Safran, Samuel

    2013-03-01

    A dynamical model of a soft, thermally fluctuating two-dimensional tube is used to study the effect of thermal fluctuations of a confining environment on diffusive transport. The tube fluctuations in both space and time are driven by Brownian motion and suppressed by surface tension and the rigidity of the surrounding environment. The dynamical fluctuations modify the concentration profile boundary condition at the tube surface. They decrease the diffusive transport rate through the tube for two important cases: uniform tube fluctuations (wave vector, q = 0 mode) for finite tube lengths and fluctuations of any wave vector for infinitely long tubes.

  18. Dynamic structure factor in single- and two-species thermal GBL lattice gas

    Science.gov (United States)

    Dubbeldam, D.; Hoekstra, A. G.; Sloot, P. M. A.

    2000-07-01

    The two-dimensional 19-bits GBL lattice gas model conserves energy in a non-trivial way, allowing temperature, temperature gradients, and heat conduction. We describe the thermodynamics of the model, its equilibrium properties, and confirm the change of sound speed with energy density at fixed density with simulation results. The sound speed, the sound damping, and the thermal diffusivity are extracted from the dynamic structure factor and shown for various energy densities at fixed density. We have extended the 19 bits GBL model with multiple-species (miscible fluid model) and have measured the dynamic structure factor for this two-component thermal lattice gas model.

  19. Thermal Activation Analyses of Dynamic Fracture Toughness of High Strength Low Alloy Steels

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A formula is derived for determining the influence of temperatureand loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. lt is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.

  20. Heater induced thermal effects on the LTP dynamics

    CERN Document Server

    Gibert, Ferran; Lobo, Alberto; Díaz-Aguiló, Marc; Mateos, Ignacio; Karnesis, Nikolaos; Sanjuán, Josep; Gesa, Lluís; lloro, Ivan; Martín, Víctor

    2013-01-01

    The STOC (Science and Technology Operations Centre) simulator of the LPF (LISA PathFinder) mission is intended to provide a validation tool for the mission operations tele-commanding chain, as well as for a deeper understanding of the underlying physical processes happening in the LTP (LISA Technology Package). Amongst the different physical effects that will appear onboard, temperature fluctuations in the Electrode Housing (EH) could generate disturbances on the interferometer (IFO) readouts, therefore they must be known and controlled. In this article we report on the latest progress in the analysis at IEEC of the LTP response to thermal signals injected by means of heaters. More specifically, we determine the transfer functions relating heat input signals to forces on the Test Masses (TMs) in the LTP frequency band, from 1 mHz to 30 mHz. A complete thermal model of the entire LPF spacecraft plus payload, elaborated and maintained at European Space Technology Center (ESTEC), was used to obtain temperature d...

  1. Numerical investigation of thermal performance of heat loss of parabolic trough receiver

    Institute of Scientific and Technical Information of China (English)

    Modibo; Kane; TRAORE

    2010-01-01

    Based on the analysis of computation methods and heat transfer processes of the parabolic trough receiver running in steady state, a two-dimensional empirical model was developed to investigate the thermal performance of heat loss of parabolic trough receivers under steady state equilibrium. A numerical simulation was conducted for the parabolic trough receiver involved in a literature. Comparisons between numerical and experimental results show that the empirical model is accurate enough and can be used to investigate the thermal performance of heat loss of parabolic trough receivers. The thermal performance of heat loss of UVAC3 and the new-generation UVAC2008 was investigated respectively. The simulation results show that selective coatings and annular pressure influence the thermal performance of heat loss of parabolic trough receivers greatly, wind velocity influences the thermal performance of thermal loss of parabolic trough receivers only a little in contrast with the emittance of selective coatings and air pressure in annular space. And the thermal performance of thermal loss of the new-generation parabolic trough receiver has been improved in a large amount.

  2. An empirical analysis of thermal protective performance of fabrics used in protective clothing.

    Science.gov (United States)

    Mandal, Sumit; Song, Guowen

    2014-10-01

    Fabric-based protective clothing is widely used for occupational safety of firefighters/industrial workers. The aim of this paper is to study thermal protective performance provided by fabric systems and to propose an effective model for predicting the thermal protective performance under various thermal exposures. Different fabric systems that are commonly used to manufacture thermal protective clothing were selected. Laboratory simulations of the various thermal exposures were created to evaluate the protective performance of the selected fabric systems in terms of time required to generate second-degree burns. Through the characterization of selected fabric systems in a particular thermal exposure, various factors affecting the performances were statistically analyzed. The key factors for a particular thermal exposure were recognized based on the t-test analysis. Using these key factors, the performance predictive multiple linear regression and artificial neural network (ANN) models were developed and compared. The identified best-fit ANN models provide a basic tool to study thermal protective performance of a fabric.

  3. The Effect of Thermal Exfoliation Temperature on the Structure and Supercapacitive Performance of Graphene Nanosheets

    Institute of Scientific and Technical Information of China (English)

    Haiyang Xian; Tongjiang Peng; Hongjuan Sun; Jiande Wang

    2015-01-01

    Graphene nanosheets (GSs) were prepared from graphite oxide by thermal exfoliation method. The effect of thermal exfoliation temperature on the structure and supercapacitive performance of GSs has been investigated. The results show that the GSs with pore sizes center around 4.0 nm. With an increase of thermal reduction temperature, the number of stacking layers and the structure disorder degree increase, while the oxygen-containing groups content, BET surface area, and electrical resistivity of GSs decrease. The results indicate that 673 K is the preferable thermal exfoliation temperature to acquire good supercapacitive performance. In this case, the GSs have the best supercapacitive performance (233.1 F g-1) in a 6 mol L-1 KOH electrolyte. The prepared GSs at the preferable thermal exfoliation temperature have good rate performance and cycle stability.

  4. CFD investigations of data centers’ thermal performance for different configurations of CRACs units and aisles separation

    Directory of Open Access Journals (Sweden)

    S.A. Nada

    2016-06-01

    Full Text Available The thermal performance of data centers is numerically studied for different configurations of computer room air conditioning (CRAC units and physical separations of cold and hot aisles. Temperature distribution, air flow characteristics and thermal management of data centers racks array are predicted and evaluated for the different arrangements. Measureable performance indices: supply/return heat index (SHI/RHI, return temperature index (RTI and return cooling index (RCI are used to measure the thermal management effectiveness of data center racks. The results showed that: (i hot air recirculation, cold air bypass and the measurable performance indices of the racks strongly depend on the racks location in the racks array, (ii the CRACs units layout affects the thermal managements of the racks array especially the sides and middle racks in the array, and (iii using cold aisle containments enhances the thermal performance of the data center.

  5. Thermal Performance and Reliability Characterization of Bonded Interface Materials (BIMs): Preprint

    Energy Technology Data Exchange (ETDEWEB)

    DeVoto, D.; Paret, P.; Mihalic, M.; Narumanchi, S.; Bar-Cohen, A.; Matin, K.

    2014-08-01

    Thermal interface materials are an important enabler for low thermal resistance and reliable electronics packaging for a wide array of applications. There is a trend towards bonded interface materials (BIMs) because of their potential for low thermal resistivity (< 1 mm2K/W). However, BIMs induce thermomechanical stresses in the package and can be prone to failures and integrity risks. Deteriorated interfaces can result in high thermal resistance in the package and degradation and/or failure of the electronics. DARPA's Thermal Management Technologies program has addressed this challenge, supporting the development of mechanically-compliant, low resistivity nano-thermal interface (NTI) materials. In this work, we describe the testing procedure and report the results of NREL's thermal performance and reliability characterization of an initial sample of four different NTI-BIMs.

  6. Performance Evaluation and Modeling of Erosion Resistant Turbine Engine Thermal Barrier Coatings

    Science.gov (United States)

    Miller, Robert A.; Zhu, Dongming; Kuczmarski, Maria

    2008-01-01

    The erosion resistant turbine thermal barrier coating system is critical to the rotorcraft engine performance and durability. The objective of this work was to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and thermal gradient environments, thus validating a new thermal barrier coating turbine blade technology for future rotorcraft applications. A high velocity burner rig based erosion test approach was established and a new series of rare earth oxide- and TiO2/Ta2O5- alloyed, ZrO2-based low conductivity thermal barrier coatings were designed and processed. The low conductivity thermal barrier coating systems demonstrated significant improvements in the erosion resistance. A comprehensive model based on accumulated strain damage low cycle fatigue is formulated for blade erosion life prediction. The work is currently aiming at the simulated engine erosion testing of advanced thermal barrier coated turbine blades to establish and validate the coating life prediction models.

  7. The Effect of Booster-Mirror Reflector on the Thermal Performance of a Truncated Pyramid Solar Thermal Cooker

    Directory of Open Access Journals (Sweden)

    I. L. Mohammed

    2014-05-01

    Full Text Available In this paper, the results and analysis of the performance of a truncated pyramid solar thermal cooker under two conditions are presented: booster-mirror reflector covered with black cloth, and booster-mirror reflector exposed to solar radiation. Results of the thermal performance tests show respective stagnation absorber plate temperatures of 145 oC and 137 oC. First/Second Figures of Merit are 0.120/0.346 and 0.125/0.400 respectively. The total heating times of 5.2 kg of water when reflector is covered with black cloth and when exposed to solar radiation are respectively 195 and 190 minutes. There is a nominal time reduction of 5 minutes in favour of the case when reflector is exposed to solar radiation, but in reality the time reduction could be as high as 30.5 minutes. In a similar vein, the difference in pot wall temperatures for corresponding water temperatures during sensible heating could be about 6 oC higher, and at boiling point this could be up to 11.6 oC. Thus, the overall thermal performance of the cooker when reflector is exposed to solar radiation is superior to its thermal performance when reflector is covered with black cloth. This superiority is manifested in improved values of the First and Second Figures of Merit, reduction in the overall heating and boiling times, and higher values of pot wall temperatures.

  8. Dynamic thermal expansivity of liquids near the glass transition.

    Science.gov (United States)

    Niss, Kristine; Gundermann, Ditte; Christensen, Tage; Dyre, Jeppe C

    2012-04-01

    Based on previous works on polymers by Bauer et al. [Phys. Rev. E 61, 1755 (2000)], this paper describes a capacitative method for measuring the dynamical expansion coefficient of a viscous liquid. Data are presented for the glass-forming liquid tetramethyl tetraphenyl trisiloxane (DC704) in the ultraviscous regime. Compared to the method of Bauer et al., the dynamical range has been extended by making time-domain experiments and by making very small and fast temperature steps. The modeling of the experiment presented in this paper includes the situation in which the capacitor is not full because the liquid contracts when cooling from room temperature down to around the glass-transition temperature, which is relevant when measuring on a molecular liquid rather than a polymer.

  9. Architectural designs and thermal performances of school sports-halls

    Energy Technology Data Exchange (ETDEWEB)

    El-Kadi, Abd El-Wahab M. Adel [Military Technical Coll., Architectural Dept., Cairo (Egypt); Fanny, Mona A. [Building Research Center, Building Physics Dept., Cairo (Egypt)

    2003-11-01

    The school playground is an essential part of any school building because of its important role in the overall teaching process. The study presents the current design of most of the governmental school playgrounds in Cairo and shows how existing playgrounds sustain this function and describes the inherent shortcomings of that design. Constructing a sports hall on the roof of the building is one of the solutions presented to overcome existing deficiencies. The paper presents the schematics of the concept along with the schematic diagrams for the interior of the hall. The study investigates the thermal criteria of the sport hall and how it serves the intended activity. Evaluation of the heat gain and thermal load of the structure-taking into account occupants, lighting and appliances, is carried out. The study also introduces the use of mechanical ventilation with the contributions of different heat-gain sources and considers the number of fans and fan velocity at the reference height and at the height of pupils, are calculated, to get the indoor air velocity for verifying the suitable heat-stress index and the thermal comfort. Model verification will be accomplished with a building under construction. The concepts presented in this paper would better serve the needs of schools, without harming the environment. (Author)

  10. Ballistic performance of porous-ceramic, thermal protection systems

    Science.gov (United States)

    Miller, Joshua E.; Bohl, William E.; Christiansen, Eric C.; Davis, Bruce A.; Foreman, Cory D.

    2012-03-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These systems insulate reentry critical components of a spacecraft against the intense thermal environments of atmospheric reentry. Additionally, these materials are highly exposed to space environment hazards like solid particle impacts. This paper discusses impact studies up to 10 km/s on 8 lb/ft3 alumina-fiber-enhanced-thermal-barrier (AETB8) tiles coated with a toughened-unipiece-fibrousinsulation/ reaction-cured-glass layer (TUFI/RCG). A semi-empirical, first principles impact model that describes projectile dispersion is described that provides excellent agreement with observations over a broad range of impact velocities, obliquities and projectile materials. Model extensions to look at the implications of greater than 10 GPa equation of state is also discussed. Predicted penetration probabilities for a vehicle visiting the International Space Station is 60% lower for orbital debris and 95% lower for meteoroids with this model compared to an energy scaled approach.

  11. Flightweight radiantly and actively cooled panel: Thermal and structural performance

    Science.gov (United States)

    Shore, C. P.; Nowak, R. J.; Kelly, H. N.

    1982-01-01

    A 2- by 4-ft flightweight panel was subjected to thermal/structural tests representative of design flight conditions for a Mach 6.7 transport and to off-design conditions simulating flight maneuvers and cooling system failures. The panel utilized Rene 41 heat shields backed by a thin layer of insulation to radiate away most of the 12 Btu/ft2-sec incident heating. A solution of ethylene glycol in water circulating through tubes in an aluminum-honeycomb-sandwich panel absorbed the remainder of the incident heating (0.8 Btu/sq ft-sec). The panel successfully withstood (1) 46.7 hr of radiant heating which included 53 thermal cycles and 5000 cycles of uniaxial inplane loading of + or - 1200 lfb/in; (2) simulated 2g-maneuver heating conditions and simulated cooling system failures without excessive temperatures on the structural panel; and (3) the extensive thermal/structural tests and the aerothermal tests reported in NASA TP-1595 without significant damage to the structural panel, coolant leaks, or hot-gas ingress to the structural panel.

  12. Dynamics of liquid solidification thermal resistance of contact layer

    CERN Document Server

    Lipnicki, Zygmunt

    2017-01-01

    This monograph comprehensively describes phenomena of heat flow during phase change as well as the dynamics of liquid solidification, i.e. the development of a solidified layer. The book provides the reader with basic knowledge for practical designs, as well as with equations which describe processes of energy transformation. The target audience primarily comprises researchers and experts in the field of heat flow, but the book may also be beneficial for both practicing engineers and graduate students.

  13. Design Of High Performance CMOS Dynamic Latch Comparator

    Directory of Open Access Journals (Sweden)

    G.Saroja

    2016-10-01

    Full Text Available High performance analog to digital converters (ADC, memory sense amplifiers, and Radio Frequency identification applications, data receivers with less area and power efficient designs has attracted a broad range of dynamic comparators. This paper presents an ameliorate design for a dynamic latch based comparator in attaining high performance. The comparators accuracyis mainly defined by two factors they are speed and power consumption. The latch based comparator has two different stages encompassing of a dynamic differential input gain stage and an output latch.The output node in the differential gain stage of proposed comparator requires lesser time to regain higher charge potential. The proposed comparator hasbeen designed and simulated using 130nm CMOS 1P2M technology by using mentor graphics tools with a supply voltage of 1V. Proposed dynamic latch comparator iscompared with existing conventional dynamic latch comparator and with other comparators and the results are discussed in detail.

  14. Thermal structure and dynamics of Saturn's northern springtime disturbance

    Science.gov (United States)

    Fletcher, L.N.; Hesman, B.E.; Irwin, P.G.J.; Baines, K.H.; Momary, T.W.; Sanchez-Lavega, A.; Flasar, F.M.; Read, P.L.; Orton, G.S.; Simon-Miller, A.; Hueso, R.; Bjoraker, G.L.; Mamoutkine, A.; Del, Rio-Gaztelurrutia; Gomez, J.M.; Buratti, B.; Clark, R.N.; Nicholson, P.D.; Sotin, C.

    2011-01-01

    Saturn's slow seasonal evolution was disrupted in 2010-2011 by the eruption of a bright storm in its northern spring hemisphere. Thermal infrared spectroscopy showed that within a month, the resulting planetary-scale disturbance had generated intense perturbations of atmospheric temperatures, winds, and composition between 20?? and 50??N over an entire hemisphere (140,000 kilometers). The tropospheric storm cell produced effects that penetrated hundreds of kilometers into Saturn's stratosphere (to the 1-millibar region). Stratospheric subsidence at the edges of the disturbance produced "beacons" of infrared emission and longitudinal temperature contrasts of 16 kelvin. The disturbance substantially altered atmospheric circulation, transporting material vertically over great distances, modifying stratospheric zonal jets, exciting wave activity and turbulence, and generating a new cold anticyclonic oval in the center of the disturbance at 41??N.

  15. Decoherence and thermalization dynamics of a quantum oscillator

    CERN Document Server

    Dodonov, V V; De Souza-Silva, A L

    2000-01-01

    We introduce the quantitative measures characterizing the rates of decoherence and thermalization of quantum systems. We study the time evolution of these measures in the case of a quantum harmonic oscillator whose relaxation is described in the framework of the standard master equation, for various initial states (coherent, `cat', squeezed and number). We establish the conditions under which the true decoherence measure can be approximated by the linear entropy $1-{Tr}\\hat\\rho^2$. We show that at low temperatures and for highly excited initial states the decoherence process consists of three distinct stages with quite different time scales. In particular, the `cat' states preserve 50% of the initial coherence for a long time interval which increases logarithmically with increase of the initial energy.

  16. Evaluation of Strategies to Improve the Thermal Performance of Steel Frames in Curtain Wall Systems

    Directory of Open Access Journals (Sweden)

    Ji Hyun Oh

    2016-12-01

    Full Text Available Recently, metal curtain wall systems have been widely used in high-rise buildings due to many advantages, including being lightweight, rapid construction, and aesthetic features. Since the metal frame may lead to lower energy performance, thermal discomfort, and condensation risk due to the high thermal conductivity, its thermal performance can be important for the improvement of the overall thermal performance of the curtain wall system, as well as the energy efficiency of the building envelope. This study aims to evaluate variety of design strategies to improve the thermal performance of steel curtain wall frames. Five base cases and three further steps were selected for two different head profile shapes based on a state-of-the art technology review, and their thermal transmittances were calculated through simulations according to the ISO 12631 standard which is an international standard for calculating thermal transmittance of curtain wall system. Measured results that were obtained from hot-box tests were compared with the calculated results to validate the simulation method of this study. The shape of the head profile did not strongly influence the overall thermal transmittance, and the choice of strategies for the rabbet space was more important. More effective strategies could be decided according to the steps for variation development. This result can serve as a guideline for the design of high-performance curtain wall frames.

  17. Modelling of PEM Fuel Cell Performance: Steady-State and Dynamic Experimental Validation

    Directory of Open Access Journals (Sweden)

    Idoia San Martín

    2014-02-01

    Full Text Available This paper reports on the modelling of a commercial 1.2 kW proton exchange membrane fuel cell (PEMFC, based on interrelated electrical and thermal models. The electrical model proposed is based on the integration of the thermodynamic and electrochemical phenomena taking place in the FC whilst the thermal model is established from the FC thermal energy balance. The combination of both models makes it possible to predict the FC voltage, based on the current demanded and the ambient temperature. Furthermore, an experimental characterization is conducted and the parameters for the models associated with the FC electrical and thermal performance are obtained. The models are implemented in Matlab Simulink and validated in a number of operating environments, for steady-state and dynamic modes alike. In turn, the FC models are validated in an actual microgrid operating environment, through the series connection of 4 PEMFC. The simulations of the models precisely and accurately reproduce the FC electrical and thermal performance.

  18. Thermal Performance of Hollow Clay Brick with Low Emissivity Treatment in Surface Enclosures

    OpenAIRE

    Roberto Fioretti; Paolo Principi

    2014-01-01

    External walls made with hollow clay brick or block are widely used for their thermal, acoustic and structural properties. However, the performance of the bricks frequently does not conform with the minimum legal requirements or the values required for high efficiency buildings, and for this reason, they need to be integrated with layers of thermal insulation. In this paper, the thermal behavior of hollow clay block with low emissivity treatment on the internal cavity surfaces has been invest...

  19. Thermal preference, thermal tolerance and the thermal dependence of digestive performance in two Phrynocephalus lizards (Agamidae), with a review of species studied

    Institute of Scientific and Technical Information of China (English)

    Yanfu QU; Hong LI; Jianfang GAO; Xuefeng XU; Xiang JI

    2011-01-01

    We reported data on thermal preference,thermal tolerance and the thermal dependence of digestive performance for two Phrynocephalus lizards (P.frontalis and P.versicolor),and compared data among lizards so far studied worldwide.Mean values for selected body temperature (Tsel) and critical thermal maximum (CTMax) were greater in P.versicolor,whereas mean values for critical thermal minimum (CTMin) did not differ between the two species.The two lizards differed in food intake,but not in food passage time,apparent digestive coefficient (ADC) and assimilation efficiency (AE),across the experimental temperatures.Four general conclusions can be drawn from published data.Firstly,thermal preference and thermal tolerance differ among lizards differing in distribution,temporal activity pattern and habitat use.Lizards in thermally more variable regions are better able to tolerate low and high temperatures.Diurnal lizards generally select higher body temperatures than nocturnal lizards,and lizards using habitats with direct sun exposure generally selected higher body temperatures and are better able to tolerate high temperatures.Secondly,CTMax is positively correlated with Tsel.Lizards more likely exposed to extremely high temperatures while active select higher body temperatures than those using shaded habitats.Thirdly,the effects of body temperature on food intake,food passage time,ADC and AE differ among lizards,but it seems to be common among lizards that ADC and AE are less thermally sensitive than food intake and food passage time.Lastly,ADC is dependent on the type of food ingested,with insectivorous lizards digesting food more efficiently than herbivorous lizards [Current Zoology 57 (6):684-700,2011].

  20. Effect of Material Inhomogeneity on Thermal Performance of a Rheocast Aluminum Heatsink for Electronics Cooling

    Science.gov (United States)

    Payandeh, M.; Belov, I.; Jarfors, A. E. W.; Wessén, M.

    2016-06-01

    The relation between microstructural inhomogeneity and thermal conductivity of a rheocast component manufactured from two different aluminum alloys was investigated. The formation of two different primary α-Al particles was observed and related to multistage solidification process during slurry preparation and die cavity filling process. The microstructural inhomogeneity of the component was quantified as the fraction of α 1-Al particles in the primary Al phase. A high fraction of coarse solute-lean α 1-Al particles in the primary Al phase caused a higher thermal conductivity of the component in the near-to-gate region. A variation in thermal conductivity through the rheocast component of 10% was discovered. The effect of an inhomogeneous temperature-dependent thermal conductivity on the thermal performance of a large rheocast heatsink for electronics cooling in an operation environment was studied by means of simulation. Design guidelines were developed to account for the thermal performance of heatsinks with inhomogeneous thermal conductivity, as caused by the rheocasting process. Under the modeling assumptions, the simulation results showed over 2.5% improvement in heatsink thermal resistance when the higher conductivity near-to-gate region was located at the top of the heatsink. Assuming homogeneous thermo-physical properties in a rheocast heatsink may lead to greater than 3.5% error in the estimation of maximum thermal resistance of the heatsink. The variation in thermal conductivity within a large rheocast heatsink was found to be important for obtaining of a robust component design.

  1. Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation.

    Science.gov (United States)

    Zhang, Chao; Hao, Xiao-Li; Wang, Cui-Xia; Wei, Ning; Rabczuk, Timon

    2017-01-25

    Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12-16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications.

  2. Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation

    Science.gov (United States)

    Zhang, Chao; Hao, Xiao-Li; Wang, Cui-Xia; Wei, Ning; Rabczuk, Timon

    2017-01-01

    Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12–16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications. PMID:28120921

  3. Equilibrium Limit of Boundary Scattering in Carbon Nanostructures: Molecular Dynamics Calculations of Thermal Transport

    Science.gov (United States)

    Haskins, Justin; Kinaci, Alper; Sevik, Cem; Cagin, Tahir

    2012-01-01

    It is widely known that graphene and many of its derivative nanostructures have exceedingly high reported thermal conductivities (up to 4000 W/mK at 300 K). Such attractive thermal properties beg the use of these structures in practical devices; however, to implement these materials while preserving transport quality, the influence of structure on thermal conductivity should be thoroughly understood. For graphene nanostructures, having average phonon mean free paths on the order of one micron, a primary concern is how size influences the potential for heat conduction. To investigate this, we employ a novel technique to evaluate the lattice thermal conductivity from the Green-Kubo relations and equilibrium molecular dynamics in systems where phonon-boundary scattering dominates heat flow. Specifically, the thermal conductivities of graphene nanoribbons and carbon nanotubes are calculated in sizes up to 3 microns, and the relative influence of boundary scattering on thermal transport is determined to be dominant at sizes less than 1 micron, after which the thermal transport largely depends on the quality of the nanostructure interface. The method is also extended to carbon nanostructures (fullerenes) where phonon confinement, as opposed to boundary scattering, dominates, and general trends related to the influence of curvature on thermal transport in these materials are discussed.

  4. Study on the Performance of a Ground Source Heat Pump System Assisted by Solar Thermal Storage

    Directory of Open Access Journals (Sweden)

    Yu Jin Nam

    2015-11-01

    Full Text Available A ground source heat pump system (GSHPS utilizes a relatively stable underground temperature to achieve energy-saving for heating and cooling in buildings. However, continuous long-term operation will reduce the soil temperature in winter, resulting in a decline in system performance. In this research, in order to improve the system performance of a GSHPS, a ground heat pump system integrated with solar thermal storage was developed. This solar-assisted ground heat pump system (SAGHPS can both maintain the balance of the soil temperature effectively and achieve higher system performance than the conventional system. In this paper, in order to examine the characteristics of the system, a dynamic simulation was conducted under various conditions. The results of our case study provide specific operation data such as heat exchange rate, heat source temperature, and heat pump COP. As a result, the heat pump COP of SAGHPS was 4.7%, 9.3% higher than that of the GSHPS.

  5. A thermal and electrical dynamic mathematical model for squirrel cage induction motors; Modelamento matematico dinamico termico e eletrico de motores de inducao

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, Ronaldo Martins de

    1996-01-01

    A thermal and electrical dynamic mathematical model for squirrel cage induction motors is presented. The electrical model is described by Park equation and the torque equation, while the thermal model is described by a system of four first order differential equations that represent the motor heat transfer process. The model presented can be used to determine thermal and electrical performance for any operation condition. However, it is suitable mainly for machines operating under continuously transient condition. The presented mathematical model also incorporate variation of rotor winding electrical parameters due to skin effect. (author)

  6. Comparison of thermal and hydraulic performances of eccentric and concentric annular-fins of heat exchanger tubes

    Science.gov (United States)

    Benmachiche, Abdelmoumène Hakim; Tahrour, Farouk; Aissaoui, Faris; Aksas, Mounir; Bougriou, Cherif

    2017-08-01

    The present study is an experimental and 3-D computational fluid dynamics. It is used to compare between the heat transfer characteristics and pressure drops of eccentric and concentric annular-finned tube bundles. The RNG k-ɛ turbulence model of fluent is used to determine the optimum tube position in the circular fin that gives the highest thermal and hydraulic performances for both staggered and aligned arrangements. Then, experiments and numerical simulations were performed to examine the effects of bundle configurations, the Reynolds number (ranging from 5500 to 29,700) and the tube location inside the heat exchangers. A satisfactory qualitative and quantitative agreement was obtained between the numerical and experimental results. For both aligned and staggered heat exchangers, the thermal characteristics of the eccentric annular-finned tube are greater than that of the concentric ones. This gain is associated with reduction in pressure drop.

  7. Comparison of thermal and hydraulic performances of eccentric and concentric annular-fins of heat exchanger tubes

    Science.gov (United States)

    Benmachiche, Abdelmoumène Hakim; Tahrour, Farouk; Aissaoui, Faris; Aksas, Mounir; Bougriou, Cherif

    2017-02-01

    The present study is an experimental and 3-D computational fluid dynamics. It is used to compare between the heat transfer characteristics and pressure drops of eccentric and concentric annular-finned tube bundles. The RNG k-ɛ turbulence model of fluent is used to determine the optimum tube position in the circular fin that gives the highest thermal and hydraulic performances for both staggered and aligned arrangements. Then, experiments and numerical simulations were performed to examine the effects of bundle configurations, the Reynolds number (ranging from 5500 to 29,700) and the tube location inside the heat exchangers. A satisfactory qualitative and quantitative agreement was obtained between the numerical and experimental results. For both aligned and staggered heat exchangers, the thermal characteristics of the eccentric annular-finned tube are greater than that of the concentric ones. This gain is associated with reduction in pressure drop.

  8. Millikelvin thermal and electrical performance of lossy transmission line filters

    Energy Technology Data Exchange (ETDEWEB)

    Slichter, Daniel; Naaman, Ofer; Siddiqi, Irfan

    2009-03-11

    We report on the scattering parameters and Johnson noise emission of low-pass stripline filters employing a magnetically loaded silicone dielectric down to 25 mK. The transmission characteristic of a device with f-3dB=1.3 GHz remains essentially unchanged upon cooling. Another device with f-edB=0.4 GHz, measured in its stopband, exhibits a steady state noise power emission consistent with a temperature difference of a few mK relative to a well-anchored cryogenic microwave attenuator at temperatures down to 25 mK, thus presenting a matched thermal load.

  9. EVOLUTION OF ANTENNA PERFORMANCE FOR APPLICATIONS IN THERMAL MEDICNE.

    Science.gov (United States)

    Stauffer, P R; Maccarini, P F

    2011-01-01

    This presentation provides an overview of electromagnetic heating technology that has proven useful in clinical applications of hyperthermia therapy for cancer. Several RF and microwave antenna designs are illustrated which highlight the evolution of technology from simple waveguide antennas to spatially and temporally adjustable multiple antenna phased arrays for deep heating, conformal arrays for superficial heating, and compatible approaches for radiometric and magnetic resonance image based non-invasive thermal monitoring. Examples of heating capabilities for several recently developed applicators demonstrate highly adjustable power deposition that has not been possible in the past.

  10. Molecular dynamics simulations of the lattice thermal conductivity of thermoelectric material CuInTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wei, J. [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong (Hong Kong); Liu, H.J., E-mail: phlhj@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Cheng, L.; Zhang, J.; Jiang, P.H.; Liang, J.H.; Fan, D.D.; Shi, J. [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2017-05-10

    Highlights: • A simple but effective Morse potential is constructed to accurately describe the interatomic interactions of CuInTe{sub 2}. • The lattice thermal conductivity of CuInTe{sub 2} predicted by MD agrees well with those measured experimentally, as well as those calculated from phonon BTE. • Introducing Cd impurity or Cu vacancy can effectively reduce the lattice thermal conductivity of CuInTe{sub 2} and thus further enhance its thermoelectric performance. - Abstract: The lattice thermal conductivity of thermoelectric material CuInTe{sub 2} is predicted using classical molecular dynamics simulations, where a simple but effective Morse-type interatomic potential is constructed by fitting first-principles total energy calculations. In a broad temperature range from 300 to 900 K, our simulated results agree well with those measured experimentally, as well as those obtained from phonon Boltzmann transport equation. By introducing the Cd impurity or Cu vacancy, the thermal conductivity of CuInTe{sub 2} can be effectively reduced to further enhance the thermoelectric performance of this chalcopyrite compound.

  11. Thermal cleanups using dynamic underground stripping and hydrous pyrolysis oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Aines, R D; Knauss, K; Leif, R; Newmark, R L

    1999-05-01

    In the early 1990s, in collaboration with the School of Engineering at the University of California, Berkeley, Lawrence Livermore National Laboratory developed dynamic underground stripping (DUS), a method for treating subsurface contaminants with heat that is much faster and more effective than traditional treatment methods. more recently, Livermore scientists developed hydrous pyrolysis/oxidation (HPO), which introduces both heat and oxygen to the subsurface to convert contaminants in the ground to such benign products as carbon dioxide, chloride ion, and water. This process has effectively destroyed all contaminants it encountered in laboratory tests. With dynamic underground stripping, the contaminants are vaporized and vacuumed out of the ground, leaving them still to be destroyed elsewhere. Hydrous pyrolysis/oxidation technology takes the cleanup process one step further by eliminating the treatment, handling, and disposal requirements and destroying the contamination in the ground. When used in combination, HPO is especially useful in the final polishing of a site containing significant free-product contaminant, once the majority of the contaminant has been removed.

  12. Characterization of Shape Memory Polymer Estane by Means of Dynamic Mechanical Thermal Analysis Technique

    Directory of Open Access Journals (Sweden)

    Rasa Kazakevičiūtė-Makovska

    2014-01-01

    Full Text Available Commercially available shape memory polymer (SMP Estane (designation: ETE75DT3 NAT022 is investigated by means of dynamic mechanical thermal analysis (DMTA technique in torsion mode using the Modular Compact Rheometer MCR-301 (Anton Paar GmbH. Amplitude sweep tests have been run below and above the glass transition temperature to establish the linear viscoelastic range (LVR in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTA data. Temperature sweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduli and the storage and loss compliances as well as the viscosities. These tests have been carried out in heating mode with different rates and at different strain amplitudes. The short- and long-term behavior of SMP Estane have been studied by frequency sweep tests performed at different temperatures and data have been transformed into time-domain properties by applying time-temperature superposition principles. All these DMTA data provide the experimental basis for the study of relaxation processes, property-structure relationships, and the shape memory effect in this little-known SMP.

  13. Numerical simulation of the effects of nanofluid on a heat pipe thermal performance

    DEFF Research Database (Denmark)

    Gavtash, Barzin; Hussain, Khalid; Layeghi, Mohammad;

    2014-01-01

    This research aims at modeling and simulating the effects of nanofluids on cylindrical heat pipes thermal performance using the ANSYS-FLUENT CFD commercial software. The heat pipe outer wall temperature distribution, thermal resistance, liquid pressure and axial velocity in presence of suspended ...

  14. Performance results of a solar greenhouse combining electrical and thermal energy production

    NARCIS (Netherlands)

    Sonneveld, P.J.; Swinkels, G.L.A.M.; Campen, J.B.; Tuijl, van B.A.J.; Janssen, H.J.J.; Bot, G.P.A.

    2010-01-01

    Performance results are given of a new type of greenhouse, which combines reflection of near infrared radiation (NIR) with electrical power generation using hybrid photovoltaic cell/thermal collector modules. Besides the generation of electrical and thermal energy, the reflection of the NIR will res

  15. MAPTIP - Marine Aerosol Properties and Thermal Imager Performance : Summary and initial results

    NARCIS (Netherlands)

    Eijk, A.M.J. van; Leeuw, G. de; Jensen, D.R.

    1995-01-01

    The marine aerosol properties and thermal imager performance trial (MAPTIP) was conducted by NATO AC/243 Panel 04/RSG.8 and 04/RSG.5 in the Dutch coastal waters during the fall of 1993. The main objectives of the trial were (1) to assess marine boundary layer effects on thermal imaging systems and (

  16. Performance results of a solar greenhouse combining electrical and thermal energy production

    NARCIS (Netherlands)

    Sonneveld, P.J.; Swinkels, G.L.A.M.; Campen, J.B.; Tuijl, van B.A.J.; Janssen, H.J.J.; Bot, G.P.A.

    2010-01-01

    Performance results are given of a new type of greenhouse, which combines reflection of near infrared radiation (NIR) with electrical power generation using hybrid photovoltaic cell/thermal collector modules. Besides the generation of electrical and thermal energy, the reflection of the NIR will

  17. Comparison of Electrical and Thermal Performances of Glazed and Unglazed PVT Collectors

    Directory of Open Access Journals (Sweden)

    Jin-Hee Kim

    2012-01-01

    Full Text Available Photovoltaic-thermal (PVT collectors combine photovoltaic modules and solar thermal collectors, forming a single device that receives solar radiation and produces electricity and heat simultaneously. PVT collectors can produce more energy per unit surface area than side-by-side PV modules and solar thermal collectors. There are two types of liquid-type flat-plate PVT collectors, depending on the existence of glass cover over PV module: glass-covered (glazed PVT collectors, which produce relatively more thermal energy but have lower electrical yield, and uncovered (unglazed PVT collectors, which have relatively lower thermal energy with somewhat higher electrical performance. In this paper, the experimental performance of two types of liquid-type PVT collectors, glazed and unglazed, was analyzed. The electrical and thermal performances of the PVT collectors were measured in outdoor conditions, and the results were compared. The results show that the thermal efficiency of the glazed PVT collector is higher than that of the unglazed PVT collector, but the unglazed collector had higher electrical efficiency than the glazed collector. The overall energy performance of the collectors was compared by combining the values of the average thermal and electrical efficiency.

  18. Dynamic Capability and Its Effects on Firm Performance

    Directory of Open Access Journals (Sweden)

    Kuo-Wei Lin

    2012-01-01

    Full Text Available Problem statement: The study has been mainly attempted as an extension to previous studies made on dynamic capabilities and their necessity in organizational firms for goals accomplishments. Approach: The literature review illustrates the effects of dynamic capabilities on product innovation, firm performance and environmental dynamism. The researches of different authors and theorists on the subject of dynamic capability have been consulted and analysed to present a research study through this study. Results: The study has provided with a detailed understanding of the dynamic capability strategies that have been found to be highly significant in successful organizational performance. The development of different propositions also reflect the increasing importance of dynamic capabilities in organizations that managers are integrating in their strategic management practices all the more from before. Conclusion: This study reveals that the availability of dynamic capabilities imply that a firm may be protected from the negative impacts through planned strategic measures intended to encounter challenges and uncertainties and yet perform to the utmost level and succeed in achieving organizational goals and objectives.

  19. Molecular Dynamics Study of a Thermal Expansion Coefficient: Ti Bulk with an Elastic Minimum Image Method

    Institute of Scientific and Technical Information of China (English)

    Yakup Hundur; Rainer Hippler; Ziya B. Güven(c)

    2006-01-01

    @@ Linear thermal expansion coefficient (TEC) of Ti bulk is investigated by means of molecular dynamics simulation.The elastic minimum image convention of periodic boundary conditions is introduced to allow the bulk to adjust its size according to the new fixed temperature. The TEC and the specific heat of Ti are compared to the available theoretical and experimental data.

  20. Dynamic properties of silica aerogels as deduced from specific-heat and thermal-conductivity measurements

    DEFF Research Database (Denmark)

    Bernasconi, A.; Sleator, T.; Posselt, D.;

    1992-01-01

    The specific heat C(p) and the thermal conductivity lambda of a series of base-catalyzed silica aerogels have been measured at temperatures between 0.05 and 20 K. The results confirm that the different length-scale regions observed in the aerogel structure are reflected in the dynamic behavior...

  1. Dynamic Thermal Model and Temperature Control of Proton Exchange Membrane Fuel Cell Stack

    Institute of Scientific and Technical Information of China (English)

    邵庆龙; 卫东; 曹广益; 朱新坚

    2005-01-01

    A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.

  2. Three-DOF dynamic model with lubricant contact for thermal fly-height control nanotechnology

    NARCIS (Netherlands)

    Vakis, Antonis I.; Hadjicostis, Christoforos N.; Polycarpou, Andreas A.

    2012-01-01

    A three-degree-of-freedom dynamic contact model with friction and lubricant contact is introduced for thermal fly-height control of a near-contact flying slider. The proposed model addresses the issue of contact with a molecularly thin lubricant layer and includes a third degree-of-freedom, roll. Ne

  3. SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature

    CERN Document Server

    Rimmer, Robert; Preble, Joseph P; Reece, Charles E

    2005-01-01

    In September 2003, in the wake of Hurricane Isabel, JLab was without power for four days after a tree fell on the main power lines feeding the site. This was long enough to lose insulating vacuum in the cryomodules and cryogenic systems resulting in the whole accelerator warming up and the total loss of the liquid helium inventory. This thermal cycle stressed many of the cryomodule components causing several cavities to become inoperable due to helium to vacuum leaks. At the same time the thermal cycle released years of adsorbed gas from the cold surfaces. Over the next days and weeks this gas was pumped away, the insulating vacuum was restored and the machine was cooled back down and re-commissioned. In a testament to the robustness of SRF technology, only a small loss in energy capability was apparent, although individual cavities had quite different field-emission characteristics compared to before the event. In Summer 2004 a section of the machine was again cycled to room temperature during the long maint...

  4. Far-field characterization of the thermal dynamics in lasing microspheres

    CERN Document Server

    Ramirez, J M; Capuj, N E; Berencen, Y; Pitanti, A; Garrido, B; Tredicucci, A

    2015-01-01

    This work reports the dynamical thermal behavior of lasing microspheres placed on a dielectric substrate while they are homogeneously heated-up by the top-pump laser used to excite the active medium. The lasing modes are collected in the far-field and their temporal spectral traces show characteristic lifetimes of about 2 ms. The latter values scale with the microsphere radius and are independent of the pump power in the studied range. Finite-Element Method simulations reproduce the experimental results, revealing that the thermal dynamics is dominated by the heat dissipated towards the substrate through the medium surrounding the contact point. The characteristic system scale regarding thermal transport is of few hundreds of nanometers, thus enabling an effective toy model for investigating heat conduction in non-continuum gaseous media and near-field radiative energy transfer.

  5. Interplay of classical and quantum dynamics in a thermal ensemble of atoms

    CERN Document Server

    Laskar, Arif Warsi; Mukherjee, Arunabh; Ghosh, Saikat

    2016-01-01

    In a thermal ensemble of atoms driven by coherent fields, how does evolution of quantum superposition compete with classical dynamics of optical pumping and atomic diffusion? Is it optical pumping that first prepares a thermal ensemble, with coherent superposition developing subsequently or is it the other way round: coherently superposed atoms driven to steady state via optical pumping? Using a stroboscopic probing technique, here we experimentally explore these questions. A 100 ns pulse is used to probe an experimentally simulated, closed three-level, lambda-like configuration in rubidium atoms, driven by strong coherent control and incoherent fields. Temporal evolution of probe transmission shows an initial overshoot with turn-on of control, resulting in a scenario akin to lasing without inversion (LWI). The corresponding rise time is dictated by coherent dynamics, with a distinct experimental signature of half-cycle Rabi flop in a thermal ensemble of atoms. Our results indicate that, in fact, optical pump...

  6. Analysing the temporal dynamics of model performance for hydrological models

    NARCIS (Netherlands)

    Reusser, D.E.; Blume, T.; Schaefli, B.; Zehe, E.

    2009-01-01

    The temporal dynamics of hydrological model performance gives insights into errors that cannot be obtained from global performance measures assigning a single number to the fit of a simulated time series to an observed reference series. These errors can include errors in data, model parameters, or m

  7. Incentives and Their Dynamics in Public Sector Performance Management Systems

    Science.gov (United States)

    Heinrich, Carolyn J.; Marschke, Gerald

    2010-01-01

    We use the principal-agent model as a focal theoretical frame for synthesizing what we know, both theoretically and empirically, about the design and dynamics of the implementation of performance management systems in the public sector. In this context, we review the growing body of evidence about how performance measurement and incentive systems…

  8. Maintenance performance improvement with System Dynamics: A Corrective Maintenance showcase

    NARCIS (Netherlands)

    Deenen, R.E.M.; Van Daalen, C.E.; Koene, E.G.C.

    2008-01-01

    This paper presents a case study of an analysis of a Corrective Maintenance process to realize performance improvement. The Corrective Maintenance process is supported by SAP, which has indicated the performance realisation problem. System Dynamics is used in a Group Model Building process to

  9. Computational Fluid Dynamics and Building Energy Performance Simulation

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm; Tryggvason, T.

    1998-01-01

    An interconnection between a building energy performance simulation program and a Computational Fluid Dynamics program (CFD) for room air distribution will be introduced for improvement of the predictions of both the energy consumption and the indoor environment. The building energy performance...

  10. Simple method of calculating the transient thermal performance of composite material and its applicable condition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Degree of mixing of composite material is defined and the condition of using the effective thermal diffusivity for calculating the transient thermal performance of composite material is studied. The analytical result shows that for a prescribed precision of temperature, there is a condition under which the transient temperature distribution in composite material can be calculated by using the effective thermal diffusivity. As illustration, for the composite material whose temperatures of both ends are constant, the condition is presented and the factors affecting the relative error of calculated temperature of composite materials by using effective thermal diffusivity are discussed.

  11. Stationary DIANE equipment Description and performance of the thermal neutron source

    Science.gov (United States)

    Cluzeau, S.; Le Tourneur, P.

    1994-05-01

    A new neutron radiography facility using a GENIE 46 generator is now operating at SODERN (France). In contrast to the first mobile DIANE system working at IABG (Germany), this new version uses a stationary thermal neutron source. With this second equipment the performance has been significantly improved. Thanks to computer simulations and experimental thermal neutron cartography, progress has been made on neutron moderation/thermalization (combination of lead and HD polyethylene), extraction geometry, neutron and photon collimation. The results in terms of gamma ray and thermal neutron contents in the beam are reported.

  12. Dynamic Service Selection in Workflows Using Performance Data

    Directory of Open Access Journals (Sweden)

    David W. Walker

    2007-01-01

    Full Text Available An approach to dynamic workflow management and optimisation using near-realtime performance data is presented. Strategies are discussed for choosing an optimal service (based on user-specified criteria from several semantically equivalent Web services. Such an approach may involve finding "similar" services, by first pruning the set of discovered services based on service metadata, and subsequently selecting an optimal service based on performance data. The current implementation of the prototype workflow framework is described, and demonstrated with a simple workflow. Performance results are presented that show the performance benefits of dynamic service selection. A statistical analysis based on the first order statistic is used to investigate the likely improvement in service response time arising from dynamic service selection.

  13. A dynamic performance evaluation method based on SD-BSC

    Institute of Scientific and Technical Information of China (English)

    TENG Chun-xian; PAN Xiao-dong; HU Xian-wu

    2007-01-01

    Taking into consideration the disadvantage of Balanced Scorecard (BSC) not being able to reflect time delay, nonlinear problems of causal relationship and being lack of effective simulation, we combined it with the characteristics of the System Dynamics (SD). Basing on the background of manufacturing enterprises,through SD integrating with the BSC we established a new performance evaluation method-SD-BSC method to overcome the disadvantage of BSC. A performance evaluation model of SD-BSC is provided and the simulation results are analyzed which show different production policies will lead to different customer's satisfaction degrees. The SD-BSC dynamic performance evaluation method can reflect dynamic, complex causal feedback relationship and time delay, so it compensates for the disadvantage of traditional financial performance evaluation method, and at the same time makes the BSC perfect.

  14. Relativistic stellar jets: dynamics and non-thermal radiation

    Directory of Open Access Journals (Sweden)

    Bosch-Ramon Valentí

    2013-12-01

    Full Text Available Relativistic stellar jets, produced in binary systems called microquasars, propagate through media with different spatial scales releasing their energy in the form of work and radiation from radio to gamma rays. There are several medium-interaction scenarios that these jets can face. In particular, in relativistic stellar jets the presence of a star is an unavoidable element whose importance deserves to be studied. In the case of highmass stars, their powerful winds are likely to interact dynamically with the jet, but also low-mass stars in the post-main sequence phase can present dense winds that will act as an obstacle for the jet propagation. In this work, we present a semi-qualitative discussion on the importance of the star for the evolution of relativistic stellar jets.

  15. A dynamic experimental study on the evaporative cooling performance of porous building materials

    Science.gov (United States)

    Zhang, Yu; Zhang, Lei; Meng, Qinglin; Feng, Yanshan; Chen, Yuanrui

    2017-08-01

    Conventional outdoor dynamic and indoor steady-state experiments have certain limitations in regard to investigating the evaporative cooling performance of porous building materials. The present study investigated the evaporative cooling performance of a porous building material using a special wind tunnel apparatus. First, the composition and control principles of the wind tunnel environment control system were elucidated. Then, the meteorological environment on a typical summer day in Guangzhou was reproduced in the wind tunnel and the evaporation process and thermal parameters of specimens composed of a porous building material were continuously measured. Finally, the experimental results were analysed to evaluate the accuracy of the wind tunnel environment control system, the heat budget of the external surface of the specimens and the total thermal resistance of the specimens and its uncertainty. The analysis results indicated that the normalized root-mean-square error between the measured value of each environmental parameter in the wind tunnel test section and the corresponding value input into the environment control system was internal surface of the specimen. Compared to the dry specimen, the total thermal resistance of the wet specimen was approximately doubled, indicating that the evaporation process of the porous building material could significantly improve the thermal insulation performance of the specimen.

  16. Dynamic contact with friction of an ultra-low flying head-disk interface with thermal protrusion

    NARCIS (Netherlands)

    Vakis, A.I.; Lee, S.-C.; Polycarpou, A.A.

    2009-01-01

    A dynamic two-degree-of-freedom contact with friction model of the head-disk interface (HDI) is presented accounting for slider thermal protrusion and its influence on the HDI dynamics. Using this model, which includes roughness, the applied power to the thermal protrusion is calculated that leads t

  17. Investigation of thermal conductivity of nitride mixed crystals and superlattices by molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Takahiro [Graduate School of Engineering, Kyushu University (Japan); Kangawa, Yoshihiro; Kakimoto, Koichi [Research Institute for Applied Mechanics, Kyushu University, 6-1, Kasuga-Koen, Kasuga 816-8580 (Japan)

    2006-06-15

    The thermal conductivities of Al{sub x}Ga{sub 1-x}N and In{sub x}Ga{sub 1-x}N mixed crystal and AlN/GaN superlattices were investigated by molecular dynamics simulation. We used Stillinger-Weber potentials, and Green-Kubo's formula was employed to calculate thermal conductivity. The results showed that the value of thermal conductivity of Al{sub 0.5}Ga{sub 0.5}N was about 1/20 smaller than that of GaN. It was also found that the thermal conductivity of AlN/GaN superlattices along the c-axis, which is parallel to the growth direction, was much less than that of bulk GaN. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Tuning the thermal conductivity of silicon carbide by twin boundary: a molecular dynamics study

    Science.gov (United States)

    Liu, Qunfeng; Luo, Hao; Wang, Liang; Shen, Shengping

    2017-02-01

    Silicon carbide (SiC) is a semiconductor with excellent mechanical and physical properties. We study the thermal transport in SiC by using non-equilibrium molecular dynamics simulations. The work is focused on the effects of twin boundaries and temperature on the thermal conductivity of 3C-SiC. We find that compared to perfect SiC, twinned SiC has a markedly reduced thermal conductivity when the twin boundary spacing is less than 100 nm. The Si-Si twin boundary is more effective to phonon scattering than the C-C twin boundary. We also find that the phonon scattering effect of twin boundary decreases with increasing temperature. Our findings provide insights into the thermal management of SiC-based electronic devices and thermoelectric applications.

  19. Thermal Performance of Hollow Clay Brick with Low Emissivity Treatment in Surface Enclosures

    Directory of Open Access Journals (Sweden)

    Roberto Fioretti

    2014-10-01

    Full Text Available External walls made with hollow clay brick or block are widely used for their thermal, acoustic and structural properties. However, the performance of the bricks frequently does not conform with the minimum legal requirements or the values required for high efficiency buildings, and for this reason, they need to be integrated with layers of thermal insulation. In this paper, the thermal behavior of hollow clay block with low emissivity treatment on the internal cavity surfaces has been investigated. The purpose of this application is to obtain a reduction in the thermal conductivity of the block by lowering the radiative heat exchange in the enclosures. The aims of this paper are to indicate a methodology for evaluating the thermal performance of the brick and to provide information about the benefits that should be obtained. Theoretical evaluations are carried out on several bricks (12 geometries simulated with two different thermal conductivities of the clay, using a finite elements model. The heat exchange procedure is implemented in accordance with the standard, so as to obtain standardized values of the thermal characteristics of the block. Several values of emissivity are hypothesized, related to different kinds of coating. Finally, the values of the thermal transmittance of walls built with the evaluated blocks have been calculated and compared. The results show how coating the internal surface of the cavity provides a reduction in the thermal conductivity of the block, of between 26% and 45%, for a surface emissivity of 0.1.

  20. A Facile Approach to Evaluate Thermal Insulation Performance of Paper Cups

    Directory of Open Access Journals (Sweden)

    Yudi Kuang

    2015-01-01

    Full Text Available Paper cups are ubiquitous in daily life for serving water, soup, coffee, tea, and milk due to their convenience, biodegradability, recyclability, and sustainability. The thermal insulation performance of paper cups is of significance because they are used to supply hot food or drinks. Using an effective thermal conductivity to accurately evaluate the thermal insulation performance of paper cups is complex due to the inclusion of complicated components and a multilayer structure. Moreover, an effective thermal conductivity is unsuitable for evaluating thermal insulation performance of paper cups in the case of fluctuating temperature. In this work, we propose a facile approach to precisely analyze the thermal insulation performance of paper cups in a particular range of temperature by using an evaluation model based on the MISO (Multiple-Input Single-Output technical theory, which includes a characterization parameter (temperature factor and a measurement apparatus. A series of experiments was conducted according to this evaluation model, and the results show that this evaluation model enables accurate characterization of the thermal insulation performance of paper cups and provides an efficient theoretical basis for selecting paper materials for paper cups.

  1. Thermal design and performance of the balloon-borne large aperture submillimeter telescope for polarimetry BLASTPol

    CERN Document Server

    Soler, J D; Angilè, F E; Benton, S J; Devlin, M J; Dober, B; Fissel, L M; Fukui, Y; Galitzki, N; Gandilo, N N; Klein, J; Korotkov, A L; Matthews, T G; Moncelsi, L; Mroczkowski, A; Netterfield, C B; Novak, G; Nutter, D; Pascale, E; Poidevin, F; Savini, G; Scott, D; Shariff, J A; Thomas, N E; Truch, M D; Tucker, C E; Tucker, G S; Ward-Thompson, D

    2014-01-01

    We present the thermal model of the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). This instrument was successfully flown in two circumpolar flights from McMurdo, Antarctica in 2010 and 2012. During these two flights, BLASTPol obtained unprecedented information about the magnetic field in molecular clouds through the measurement of the polarized thermal emission of interstellar dust grains. The thermal design of the experiment addresses the stability and control of the payload necessary for this kind of measurement. We describe the thermal modeling of the payload including the sun-shielding strategy. We present the in-flight thermal performance of the instrument and compare the predictions of the model with the temperatures registered during the flight. We describe the difficulties of modeling the thermal behavior of the balloon-borne platform and establish landmarks that can be used in the design of future balloon-borne instruments.

  2. Thermal Performance Analysis of Reinforced Concrete Floor Structure with Radiant Floor Heating System in Apartment Housing

    Directory of Open Access Journals (Sweden)

    Young-Sun Jeong

    2015-01-01

    Full Text Available The use of the resilient materials in the radiant floor heating systems of reinforced concrete floor in apartment housing is closely related to the reduction of the floor impact sound and the heating energy loss. This study examined the thermal conductivity of expanded polystyrene (EPS foam used for the resilient material in South Korea and analysed the thermal transfer of reinforced concrete floor structure according to the thermal conductivity of the resilient materials. 82 EPS specimens were used to measure the thermal conductivity. The measured apparent density of EPS resilient materials ranged between 9.5 and 63.0 kg/m3, and the thermal conductivity ranged between 0.030 and 0.046 W/(m·K. As the density of resilient materials made of expanded polystyrene foam increases, the thermal conductivity tends to proportionately decrease. To set up reasonable thermal insulation requirements for radiant heating floor systems, the thermal properties of floor structure according to thermal insulation materials must be determined. Heat transfer simulations were performed to analyze the surface temperature, heat loss, and heat flow of floor structure with radiant heating system. As the thermal conductivity of EPS resilient material increased 1.6 times, the heat loss was of 3.4% increase.

  3. Thermal performance of back-up current-limiting fuses

    Energy Technology Data Exchange (ETDEWEB)

    Torres, E.; Mazon, A.J.; Fernandez, E.; Zamora, I. [Department of Electrical Engineering, University of the Basque Country (UPV/EHU), Alameda de Urquijo, s/n, Bilbao 48013, Bizkaia (Spain); Perez, J.C. [MESA - Schneider Electric, Gatica 48110 (Spain)

    2010-12-15

    The design and development of current-limiting power fuses requires considerable time and expense on testing to verify that the maximum temperature limits under the rated current established in international standards are not exceeded. This paper presents a new methodology that reproduces the thermal behaviour of high voltage current-limiting fuses under currents up to the rated value and so, it reduces the need for testing as prototypes, more similar to the final design, can be obtained. Firstly, the methodology solves the transient heating process of the fuse to obtain the values of the power dissipated and the heat transfer coefficient, corresponding to the steady state condition. Once these values have been calculated, the temperature distribution at the surface of the complete fuse is obtained. The validity of the method proposed has been verified by comparison of the numerical values calculated with those obtained by testing real fuses. (author)

  4. Research on Dynamic Performance of Power Shift Clutch

    Directory of Open Access Journals (Sweden)

    Wang Li

    2016-01-01

    Full Text Available Smooth shift and low shift shock are needed to improve power shift quality and comfort of construction vehicle. And higher dynamic performance of power shift clutch is needed. In this paper, the dynamic mathematical model and simulation model of the clutch engagement process were established, the factors affecting the shift quality were analyzed qualitatively and quantitatively. The simulation model of the transmission system was established based on the software AMESim, the corresponding vehicle tests were performed, and the shifting quality was improved by changing key parameters. Analysis results illustrate that the proposed mathematical model and simulation model are correct and effective and can be used to predict and evaluate construction vehicle shift-feel, which are the theoretical basis for analysis and research on the static and dynamic characteristics of the dynamic shifting process in the future.

  5. Managing Performance Analysis with Dynamic Statistical Projection Pursuit

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, J.S.; Reed, D.A.

    2000-05-22

    Computer systems and applications are growing more complex. Consequently, performance analysis has become more difficult due to the complex, transient interrelationships among runtime components. To diagnose these types of performance issues, developers must use detailed instrumentation to capture a large number of performance metrics. Unfortunately, this instrumentation may actually influence the performance analysis, leading the developer to an ambiguous conclusion. In this paper, we introduce a technique for focusing a performance analysis on interesting performance metrics. This technique, called dynamic statistical projection pursuit, identifies interesting performance metrics that the monitoring system should capture across some number of processors. By reducing the number of performance metrics, projection pursuit can limit the impact of instrumentation on the performance of the target system and can reduce the volume of performance data.

  6. Performance Testing of Thermal Cutting Systems for Sweet Pepper Harvesting Robot in Greenhouse Horticulture

    Science.gov (United States)

    Bachche, Shivaji; Oka, Koichi

    2013-03-01

    This paper proposes design of end-effector and prototype of thermal cutting system for harvesting sweet peppers. The design consists of two parallel gripper bars mounted on a frame connected by specially designed notch plate and operated by servo motor. Based on voltage and current, two different types of thermal cutting system prototypes; electric arc and temperature arc respectively were developed and tested for performance. In electric arc, a special electric device was developed to obtain high voltage to perform cutting operation. At higher voltage, electrodes generate thermal arc which helps to cut stem of sweet pepper. In temperature arc, nichrome wire was mounted between two electrodes and current was provided directly to electrodes which results in generation of high temperature arc between two electrodes that help to perform cutting operation. In both prototypes, diameters of basic elements were varied and the effect of this variation on cutting operation was investigated. The temperature arc thermal system was found significantly suitable for cutting operation than electric arc thermal system. In temperature arc thermal cutting system, 0.5 mm nichrome wire shows significant results by accomplishing harvesting operation in 1.5 seconds. Also, thermal cutting system found suitable to increase shelf life of fruits by avoiding virus and fungal transformation during cutting process and sealing the fruit stem. The harvested sweet peppers by thermal cutting system can be preserved at normal room temperature for more than 15 days without any contamination.

  7. Optimization of power cable thermal performance using finite-element generated gradient

    Energy Technology Data Exchange (ETDEWEB)

    Al-Saud, M.S.; El-Kady, M.A.; Findlay, R.D. [McMaster Univ., Hamilton, ON (Canada). Dept. of Electrical and Computer Engineering

    2007-07-01

    This paper addressed the issue of optimizing the performance of underground power cables used in modern power transmission and distribution grids. The objective was to reduce operating cost through optimized cable performance under a range of loading conditions, soil parameters and ambient conditions. The thermal performance of an underground cable depends on its design, operation and environmental parameters. The cable ampacity is influenced by cable insulation and structure; thermal conductivity of the surrounding soil; ambient temperature and cable loading. This paper proposed a new method for calculating cable thermal field and ampacity using a concept of perturbed finite element which involves the use of derived sensitivity coefficients associated with different cable parameters. The model provides the optimal solution subject to user-defined constraints. The design problem of choosing the optimal parameter values of the thermal circuit parameters, including the thermal conductivities, boundary conditions and heat generation, was formulated using a multi-dimensional gradient optimization method. The technique takes into account all thermal circuit parameters. The model represents a generalization of the nonlinear programming formulation to include practical cases of the cable design objective functions which may include the thermal parameters and the cable temperatures (ampacity) subjected to upper and lower bounds on the design parameters, linear system of equations constrains, or nonlinear constrains. In order to obtain a reliable cable design, this optimization analysis included the ampacity sensitivity profiles of the soil temperature fluctuations with respect to the thermal circuit parameters. 9 refs., 9 figs.

  8. Thermal Impact of Fasteners in High-Performance Wood-Framed Walls

    Energy Technology Data Exchange (ETDEWEB)

    Dane Christensen

    2011-01-01

    This paper discusses high-performance wood-framed walls that use much less than 40% of the energy consumed by similar homes built to minimum code, and evaluates the thermal impact of fasteners used to construct these walls.

  9. The influence of weather on the thermal performance of solar heating systems

    DEFF Research Database (Denmark)

    Andersen, Elsa; Furbo, Simon; Shah, Louise Jivan

    2003-01-01

    The influence of weather on the thermal performance of solar combi systems, solar domestic hot water systems and solar heating plants is investigated. The investigation is based on weather data from the Danish Design Reference Year, DRY and weather data measured for a period from 1990 until 2002....... The investigation is based on calculations with validated models. Solar heating systems with different solar collector types, heat storage volumes and solar fractions are included in the investigation. The yearly solar radiation varies with approximately 20 % in the period from 1990 until 2002. The calculations...... show that the thermal performance of the investigated systems varies due to the weather variation. The variation of the yearly thermal performance of a solar heating plant is about 40 % while the variation of the yearly thermal performance of a solar domestic hot water system is about 30...

  10. Study of lattice thermal conductivity of alpha-zirconium by molecular dynamics simulation

    Institute of Scientific and Technical Information of China (English)

    Wu Tian-Yu; Lai Wen-Sheng; Fu Bao-Qin

    2013-01-01

    The non-equilibrium molecular dynamics method is adapted to calculate the phonon thermal conductivity of alphazirconium.By exchanging velocities of atoms in different regions,the stable heat flux and the temperature gradient are established to calculate the thermal conductivity.The phonon thermal conductivities under different conditions,such as different heat exchange frequencies,different temperatures,different crystallographic orientations,and crossing grain boundary (GB),are studied in detail with considering the finite size effect.It turns out that the phonon thermal conductivity decreases with the increase of temperature,and displays anisotropies along different crystallographic orientations.The phonon thermal conductivity in [0001] direction (close-packed plane) is largest,while the values in other two directions of [2(1)(1)0] and [01 (1)0] are relatively close.In the region near GB,there is a sharp temperature drop,and the phonon thermal conductivity is about one-tenth of that of the single crystal at 550 K,suggesting that the GB may act as a thermal barrier in the crystal.

  11. Phonon thermal transport in silicene-germanene superlattice: a molecular dynamics study

    Science.gov (United States)

    Wang, Xinyu; Hong, Yang; Chan, Paddy K. L.; Zhang, Jingchao

    2017-06-01

    Two-dimensional (2D) hybrid materials have drawn enormous attention in thermoelectric applications. In this work, we apply a molecular dynamics (MD) simulation to investigate the phonon thermal transport in silicene-germanene superlattice. A non-monotonic thermal conductivity of silicene-germanene superlattice with period length is revealed, which is due to the coherent-incoherent phonon conversion and phonon confinement mechanisms. We also calculate the thermal conductivity of a Si-Ge random mixing monolayer, showing a U-shaped trend. Because of the phonon mode localizations at Ge concentration of 80%, thermal conductivity varies dramatically at low doping regions. By changing the total length (L total), the infinite-length thermal conductivities of pure silicene, pure germanene, silicene-germanene superlattice, and Si-Ge random mixing monolayer are extracted as 16.08, 15.95, 5.60 and 4.47 W/m-K, respectively. The thermal boundary conductance (TBC) of the silicene-germanene is also evaluated, showing a small thermal rectification. At L total = 274.7 nm, the TBC of silicene to germanene is 620.49 MW/m2-K, while that of germanene to silicene is 528.76 MW/m2-K.

  12. Dynamic weakening of fault gouge affected by thermal conductivity of host specimen: implications for the high-velocity weakening mechanisms

    Science.gov (United States)

    Yao, Lu; Ma, Shengli; Shimamoto, Toshihiko; Niemeijer, André

    2015-04-01

    Since many high-velocity weakening mechanisms are thermal in origin, we study the effects of thermal conductivity of host specimen on fault gouge friction behavior at seismic slip rates. By using host specimens made of brass, stainless steel, Ti-Al-V alloy and gabbro with thermal conductivities of 123, 15, 5.8 and 3.25 W/m/K, respectively, the experiments in this study produce completely different temperature conditions within the same gouge under the same slip rates and normal stresses. Fault gouges used in the experiments are a natural illite- and quartz-rich gouge from Longmenshan fault zone and pure periclase (MgO) nanopowder. High-velocity weakening of gouges were more pronounced with decreasing thermal conductivity of the specimens. Particularly, almost no dynamic weakening was observed in the tests performed with brass host specimens, while tests with specimens of gabbro and Ti-Al-V alloy exhibits quite similar dramatic weakening behaviors. Such differences in gouge frictional behavior cannot be explained by original flash heating model, since asperity contacts within the slip zone and experimental conditions are still same, even though host specimens are different. Microstructure observations under scanning and transmission electron microscopes reveal that slip zone materials tend to change from individual ultrafine nanograins to larger sintered grains or aggregates, with decreasing thermal conductivities of host specimens. Calculated temperature together with observed microstructure indicate that bulk temperature rise may be also play an important role in fault weakening, as predicted by a recent theoretical analysis of the role of flash heating within the gouge zone [Proctor et al., 2014]. Current results demonstrate the importance of frictional heating in causing the dynamic weakening of gouge, and the powder lubrication hypothesis is not consistent with our experimental data.

  13. Thermal dynamics of silver clusters grown on rippled silica surfaces

    Science.gov (United States)

    Bhatnagar, Mukul; Ranjan, Mukesh; Jolley, Kenny; Lloyd, Adam; Smith, Roger; Mukherjee, Subroto

    2017-02-01

    Silver nanoparticles have been deposited on silicon rippled patterned templates at an angle of incidence of 70° to the surface normal. The templates are produced by oblique incidence argon ion bombardment and as the fluence increases, the periods and heights of the structures increase. Structures with periods of 20 nm, 35 nm and 45 nm have been produced. Moderate temperature vacuum annealing shows the phenomenon of cluster coalescence following the contour of the more exposed faces of the ripple for the case of 35 nm and 45 nm but not at 20 nm where the silver aggregates into larger randomly distributed clusters. In order to understand this effect, the morphological changes of silver nanoparticles deposited on an asymmetric rippled silica surface are investigated through the use of molecular dynamics simulations for different deposition angles of incidence between 0° and 70° and annealing temperatures between 500 K and 900 K. Near to normal incidence, clusters are observed to migrate over the entire surface but for deposition at 70°, a similar patterning is observed as in the experiment. The random distribution of clusters for the periodicity ≈ of 20 nm is linked to the geometry of the silica surface which has a lower ripple height than the longer wavelength structures. Calculations carried out on a surface with such a lower ripple height also demonstrate a similar effect.

  14. Dynamic Heat Generation Modeling and Thermal Management of Electromechanical Actuators

    Science.gov (United States)

    2012-07-01

    calculated by counting the teeth on each gear and measuring the linear displacement of the actuator rod for one full revolution of the rotor. b...Maxwell 2D. Values of rotor angle, torque angle, and current amplitude are varied as multiple simulation runs are performed. Many of the motor modeling...behavior during highly transient moments. The torque angle should be varied from 0 to π radians to capture the full character of the inductances

  15. Hydrocarbon Fuel Thermal Performance Modeling based on Systematic Measurement and Comprehensive Chromatographic Analysis

    Science.gov (United States)

    2016-07-31

    distribution unlimited Hydrocarbon Fuel Thermal Performance Modeling based on Systematic Measurement and Comprehensive Chromatographic Analysis Matthew...Technical Note 3. DATES COVERED (From - To) 04 January 2016 - 31 July 2016 4. TITLE AND SUBTITLE Hydrocarbon Fuel Thermal Performance Modeling based on...Systematic Measurement and Comprehensive Chromatographic Analysis 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  16. Indoor test for thermal performance of the Sunmaster evacuated tube (liquid) solar collector

    Science.gov (United States)

    1979-01-01

    The test procedures used to obtain the thermal performance data for a solar collector under simulated conditions are presented. Tests included a stagnation test, a time constant test, a thermal efficiency test, an incident angle modifier test, and a hot fill test. All tests were performed at ambient conditions and the transient effect and the incident angle effect on the collector were determined. The solar collector is a water working fluid type.

  17. Molecular Dynamics Simulation of Thermal Transport in UO2 Containing Uranium, Oxygen, and Fission-product Defects

    Science.gov (United States)

    Liu, X.-Y.; Cooper, M. W. D.; McClellan, K. J.; Lashley, J. C.; Byler, D. D.; Bell, B. D. C.; Grimes, R. W.; Stanek, C. R.; Andersson, D. A.

    2016-10-01

    Uranium dioxide (UO2 ) is the most commonly used fuel in light-water nuclear reactors and thermal conductivity controls the removal of heat produced by fission, thereby governing fuel temperature during normal and accident conditions. The use of fuel performance codes by the industry to predict operational behavior is widespread. A primary source of uncertainty in these codes is thermal conductivity, and optimized fuel utilization may be possible if existing empirical models are replaced with models that incorporate explicit thermal-conductivity-degradation mechanisms during fuel burn up. This approach is able to represent the degradation of thermal conductivity due to each individual defect type, rather than the overall burn-up measure typically used, which is not an accurate representation of the chemical or microstructure state of the fuel that actually governs thermal conductivity and other properties. To generate a mechanistic thermal conductivity model, molecular dynamics (MD) simulations of UO2 thermal conductivity including representative uranium and oxygen defects and fission products are carried out. These calculations employ a standard Buckingham-type interatomic potential and a potential that combines the many-body embedded-atom-method potential with Morse-Buckingham pair potentials. Potential parameters for UO2 +x and ZrO2 are developed for the latter potential. Physical insights from the resonant phonon-spin-scattering mechanism due to spins on the magnetic uranium ions are introduced into the treatment of the MD results, with the corresponding relaxation time derived from existing experimental data. High defect scattering is predicted for Xe atoms compared to that of La and Zr ions. Uranium defects reduce the thermal conductivity more than oxygen defects. For each defect and fission product, scattering parameters are derived for application in both a Callaway model and the corresponding high-temperature model typically used in fuel-performance codes

  18. Review on thermal performance of phase change energy storage building envelope

    Institute of Scientific and Technical Information of China (English)

    WANG Xin; ZHANG YinPing; XlAO Wei; ZENG RuoLang; ZHANG QunLi; DI HongFa

    2009-01-01

    Improving the thermal performance of building envelope is an important way to save building energy consumption. The phase change energy storage building envelope is helpful to effective use of renewable energy, reducing building operational energy consumption, increasing building thermal comfort, and reducing environment pollution and greenhouse gas emission. This paper presents the concept of ideal energy-saving building envelope, which is used to guide the building envelope material selection and thermal performance design. This paper reviews some available researches on phase change building material and phase change energy storage building envelope. At last, this paper presents some current problems needed further research.

  19. Dynamic Simulation of the Green Roofs Impact on Building Energy Performance, Case Study of Antananarivo, Madagascar

    Directory of Open Access Journals (Sweden)

    Hery Tiana Rakotondramiarana

    2015-05-01

    Full Text Available Green roofs improve building energy performance and constitute an alternative to sustainable buildings. A green roof model is dynamically coupled with a building thermal model to assess its energy performance that takes into account the indoor air temperature dynamic changes. Under the climate conditions in Antananarivo, we compared green and conventional roofs. The present study shows that green roofs protect the roof structure under extreme temperature and large temperature fluctuations. For the case of Antananarivo, the amplitude of the temperature fluctuations at the top face of the support is reduced by 28 °C when using green roof. The impact of the green roof on indoor air temperature and energy demand is investigated. The vegetation decreases the maximum indoor air temperature and improves the building thermal comfort during summer days. It has no effect on the minimum indoor air temperature, but additional soil thickness can increase it. In addition, a global sensitivity analysis, which is carried out on the proposed model without considering any specific weather data, allows us to identify the most influential parameters on the energy demand. It has been found that green roofs have almost insignificant thermal impact in insulated buildings; however, their potential prevails over the building envelope and weather characteristics in the case of non-insulated building.

  20. Differential thermal performance curves in response to different habitats in the parasitoid Venturia canescens

    Science.gov (United States)

    Foray, Vincent; Gibert, Patricia; Desouhant, Emmanuel

    2011-08-01

    Environmental variability is expected to be important in shaping performance curves, reaction norms of phenotypic traits related to fitness. Models predict that the breadth of performance curves should increase with environmental variability at the expense of maximal performance. In this study, we compared the thermal performance curves of two sympatric populations of the parasitoid Venturia canescens that were observed under contrasting thermal regimes in their respective preferred habitats and differing in their modes of reproduction. Our results confirm the large effect of developmental temperature on phenotypic traits of insects and demonstrate that thelytokous and arrhenotokous wasps respond differently to temperature during development, in agreement with model predictions. For traits related to fecundity, thelytokous parasitoids, which usually occur in stable thermal conditions, exhibit specialist performance curves, maximising their reproductive success under a restricted range of temperature. In contrast, arrhenotokous parasitoids, which occur in variable climates, exhibit generalist performance curves, in keeping with the hypothesis "jack of all temperatures, master of none".

  1. Thermal dynamics-based mechanism for intense laser-induced material surface vaporization

    Indian Academy of Sciences (India)

    N Kumar; S Dash; A K Tyagi; Baldev Raj

    2008-09-01

    Laser material processing involving welding, ablation and cutting involves interaction of intense laser pulses of nanosecond duration with a condensed phase. Such interaction involving high brightness radiative flux causes multitude of non-linear events involving thermal phase transition at soild–liquid–gas interfaces. A theoretical perspective involving thermal dynamics of the vaporization process and consequent non-linear multiple thermal phase transitions under the action of laser plasma is the subject matter of the present work. The computational calculations were carried out where titanium (Ti) was treated as a condensed medium. The solution to the partial differential equations governing the thermal dynamics and the underlying phase transition event in the multiphase system is based on non-stationary Eulerian variables. The Mach number depicts significant fluctuations due to thermal instabilities associated with the laser beam flux and intensity. A conclusive amalgamation has been established which relates material surface temperature profile to laser intensity, laser flux and the pressure in the plasma cloud.

  2. Molecular Dynamics Studies on Ballistic Thermal Resistance of Graphene Nano-Junctions

    Science.gov (United States)

    Yao, Wen-Jun; Cao, Bing-Yang

    2015-05-01

    Ballistic thermal resistance of graphene nano-junctions is investigated using non-equilibrium molecular dynamics simulation. The simulation system is consisted of two symmetrical trapezoidal or rectangular graphene nano-ribbons (GNRs) and a connecting nanoscale constriction in between. From the simulated temperature profile, a big temperature jump resulted from the constriction is found, which is proportional to the heat current and corresponds to a local ballistic thermal resistance. Fixing the constriction width and the length of GNRs, this ballistic thermal resistance is independent of the width of the GNRs bottom layer, i.e., the convex angle. But interestingly, this thermal resistance has obvious size effect. It is inversely proportional to the constriction width and will disappear with the constriction being wider. Moreover, based on the phonon dynamics theory, a theoretical model of the ballistic thermal resistance in two-dimensional nano-systems is developed, which gives a good explanation on microcosmic level and agrees well with the simulation result quantitatively and qualitatively. Supported by the National Natural Science Foundation of China under Grant Nos. 51322603, 51136001, 51356001, Science Fund for Creative Research Groups (No. 51321002), the Program for New Century Excellent Talents in University, Tsinghua University Initiative Scientific Research Program, the Tsinghua National Laboratory for Information Science and Technology of China

  3. Thermal Performance of Building Roof with Infrared Reflective Coatings

    Institute of Scientific and Technical Information of China (English)

    SHEN Hui; TAN Hong-wei; KATSUO MIKI; LIU Xiao-yu

    2009-01-01

    This paper investigated the applicability and effects of infrared reflective coating on energy con-sumption of factory building in hot summer and warm winter zone. It first resorted to theoretical calculation, which demonstrated the beneficial effects of infrared reflective coating on reducing building energy consumption. Then it analyzed a field measurement done on two identical rooms respectively with ordinary coated roof and in-frared reflective coated roof from November 2006 to October 2007, on a 24h basis. The measured data include exterior and interior roof surface temperature, indoor air temperature, and indoor globe temperature. The relat-ed weather data is from a weather station near the measured area. The continuous measurement has been accom-plished in southern China, and the measured data indicate that roof surface temperature and heat gain are signifi-cantly decreased in summer while slight negative effects in winter are induced by adopting infrared reflective coating. Thus it is simple and applicable to reduce building energy consumption in this area by applying infrared reflective coating. Regress equation between reduced roof thermal property, such as surface temperature and heat gain, and reduction in absorbed solar radiation shows their highly linear relationship. Based on the mea-sured data, it is estimated that the reduced power consumption is 3.45 kWh/m2·month in June.

  4. Distributed multicast routing algorithm with dynamic performance in multimedia networks

    Institute of Scientific and Technical Information of China (English)

    Zhu Baoping; Zhang Kun

    2009-01-01

    Tbe delay and DVBMT problem is known to be NP-complete. In this paper, an efficient distributed dynamic multicast muting algorithm was proposed to produce muting trees with delay and delay variation constraints. The pro-posed algorithm is fully distributed, and supports the dynamic reorganizing of the muhicast tree in response to changes for the destination. Simulations demonstrate that our algorithm is better in terms of tree delay and muting success ratio as compared with other existing algorithms, and performs excellently in delay variation performance under lower time complexity, which ensures it to support the requirements of real-time multimedia communications more effectively.

  5. Thermal-hydraulic performance of convective boiling jet array impingement

    Science.gov (United States)

    Jenkins, R.; De Brún, C.; Kempers, R.; Lupoi, R.; Robinson, A. J.

    2016-09-01

    Jet impingement boiling is investigated with regard to heat transfer and pressure drop performance using a novel laser sintered 3D printed jet impingement manifold design. Water was the working fluid at atmospheric pressure with inlet subcooling of 7oC. The convective boiling performance of the impinging jet system was investigated for a flat copper target surface for 2700≤Re≤5400. The results indicate that the heat transfer performance of the impinging jet is independent of Reynolds number for fully developed boiling. Also, the investigation of nozzle to plate spacing shows that low spacing delays the onset of nucleate boiling causing a superheat overshoot that is not observed with larger gaps. However, no sensitivity to the gap spacing was measured once boiling was fully developed. The assessment of the pressure drop performance showed that the design effectively transfers heat with low pumping power requirements. In particular, owing to the insensitivity of the heat transfer to flow rate during fully developed boiling, the coefficient of performance of jet impingement boiling in the fully developed boiling regime deteriorates with increased flow rate due to the increase in pumping power flux.

  6. Incorporating Artificial Neural Networks in the dynamic thermal-hydraulic model of a controlled cryogenic circuit

    Science.gov (United States)

    Carli, S.; Bonifetto, R.; Savoldi, L.; Zanino, R.

    2015-09-01

    A model based on Artificial Neural Networks (ANNs) is developed for the heated line portion of a cryogenic circuit, where supercritical helium (SHe) flows and that also includes a cold circulator, valves, pipes/cryolines and heat exchangers between the main loop and a saturated liquid helium (LHe) bath. The heated line mimics the heat load coming from the superconducting magnets to their cryogenic cooling circuits during the operation of a tokamak fusion reactor. An ANN is trained, using the output from simulations of the circuit performed with the 4C thermal-hydraulic (TH) code, to reproduce the dynamic behavior of the heated line, including for the first time also scenarios where different types of controls act on the circuit. The ANN is then implemented in the 4C circuit model as a new component, which substitutes the original 4C heated line model. For different operational scenarios and control strategies, a good agreement is shown between the simplified ANN model results and the original 4C results, as well as with experimental data from the HELIOS facility confirming the suitability of this new approach which, extended to an entire magnet systems, can lead to real-time control of the cooling loops and fast assessment of control strategies for heat load smoothing to the cryoplant.

  7. Thermal Stability of Modified Insulation Paper Cellulose Based on Molecular Dynamics Simulation

    Directory of Open Access Journals (Sweden)

    Chao Tang

    2017-03-01

    Full Text Available In this paper, polysiloxane is used to modify insulation paper cellulose, and molecular dynamics methods are used to evaluate the glass transition temperature and mechanical properties of the paper before and after the modification. Analysis of the static mechanical performance of the model shows that, with increasing temperature, the elastic modulus of both the modified and unmodified cellulose models decreases gradually. However, the elastic modulus of the modified model is greater than that of the unmodified model. Using the specific volume method and calculation of the mean square displacement of the models, the glass transition temperature of the modified cellulose model is found to be 48 K higher than that of the unmodified model. Finally, the changes in the mechanical properties and glass transition temperature of the model are analyzed by energy and free volume theory. The glass transition temperatures of the unmodified and modified cellulose models are approximately 400 K and 450 K, respectively. These results are consistent with the conclusions obtained from the specific volume method and the calculation of the mean square displacement. It can be concluded that the modification of insulation paper cellulose with polysiloxane will effectively improve its thermal stability.

  8. Thermal Performance Comparison of Glass Microsphere and Perlite Insulation Systems for Liquid Hydrogen Storage Tanks

    Science.gov (United States)

    Sass, J. P.; Fesmire, J. E.; Nagy, Z. F.; Sojourner, S. J.; Morris, D. L.; Augustynowicz, S. D.

    2008-03-01

    A technology demonstration test project was conducted by the Cryogenics Test Laboratory at the Kennedy Space Center (KSC) to provide comparative thermal performance data for glass microspheres, referred to as bubbles, and perlite insulation for liquid hydrogen tank applications. Two identical 1/15th scale versions of the 3,200,000 liter spherical liquid hydrogen tanks at Launch Complex 39 at KSC were custom designed and built to serve as test articles for this test project. Evaporative (boil-off) calorimeter test protocols, including liquid nitrogen and liquid hydrogen, were established to provide tank test conditions characteristic of the large storage tanks that support the Space Shuttle launch operations. This paper provides comparative thermal performance test results for bubbles and perlite for a wide range of conditions. Thermal performance as a function of cryogenic commodity (nitrogen and hydrogen), vacuum pressure, insulation fill level, tank liquid level, and thermal cycles will be presented.

  9. Performance of thermal-sprayed zinc anodes treated with humectants in cathodic protection systems

    Energy Technology Data Exchange (ETDEWEB)

    Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Russell, James H.; Bennett, John E. (JE Bennett Consulting Inc.); Milius, John K. (Corrosion Restoration Tech.); Cryer, Curtis B. (Oregon Dept. of Transportation); Soltesz, Steven M. (Oregon Dept. of Transportation)

    2001-01-01

    Thermal-sprayed Zn anodes are used for impressed current cathodic protection (ICCP) systems in Oregon's reinforced concrete coastal bridges to minimize corrosion damage. Thermal-sprayed Zn performs well as an ICCP anode but the voltage requirement can increase with increasing electrochemical age. It also performs well as a galvanic (GCP) anode but current output can decrease with increasing electrochemical age. Past research has shown that increasing moisture at the Zn anode-concrete interface improves the operation of the thermal-sprayed Zn anode. Humectants, hygroscopic materials that are applied to the surface of the Zn-anode, can increase the moisture at the zinc-concrete interface, thereby improving the performance and extending the anode service life. Results are given for humectant-treated (LiBr and LiNO3) thermal-sprayed Zn anodes used in the laboratory electrochemical aging studies and in field studies on the Yaquina Bay Bridge, Oregon, USA.

  10. Thermal performance of heat pipe with different micro-groove structures

    Institute of Scientific and Technical Information of China (English)

    白鹏飞; 汤勇; 唐彪; 陆龙生

    2008-01-01

    Four kinds of micro heat pipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture of micro heat pipe with groove wick structure. The results show that these micro heat pipes have excellent performance in heat transfer; the equivalent thermal conductivity coefficient is two orders of magnitude compared with that of copper; the number and aspect ratio of grooves have a prominent effect on the performance of such thermal transfer. The optimum number of grooves is lower than 60 and the best aspect ratio is near to 1.5. The temperature and thermal transport rate are almost directly proportional relationship, but this relationship will be broken up suddenly when the critical heat flux is reached.

  11. Observation of nonlinear thermal optical dynamics in a chalcogenide nanobeam cavity

    CERN Document Server

    Sun, Yue; Choi, Duk-Yong; Sukhorukov, Andrey A

    2016-01-01

    We present a theoretical and experimental analysis of nonlinear thermo-optic effects in suspended chalcogenide glass nanobeam cavities. We measure the power dependent resonance peaks and characterise the dynamic nonlinear thermo-optic response of the cavity under modulated light input. Several distinct nonlinear characteristics are identified, including a modified spectral response containing periodic fringes, a critical wavelength jump and saturated time delay for modulation frequency faster than the thermal characteristic time. We reveal that the coupling to a parasitic Fabry-Perot cavity enables isolated thermal equilibrium states resulting in the discontinuous thermo-optic critical point.

  12. Laser-induced thermal dynamics and temperature localization phenomenon in tissues and cells doped with nanoshells

    Science.gov (United States)

    Yakunin, Alexander N.; Avetisyan, Yury A.; Tuchin, Valery V.

    2012-03-01

    Paper presents and discusses the features of laser-induced thermal dynamics of the gold nanoshells, which is associated with their relatively large size and layered structure. Unlike bulk nanoparticles the existence of a novel thermal phenomenon - hoop-shaped narrow hot zone on the nanoshell surface - is found. It is caused by spatial-temporal inhomogeneities of light field diffracted by a nanoshell and corresponding absorption of laser radiation. The numerical solution of time-dependent heat conduction equation accounting for corresponding spatially inhomogeneous distribution of heating sources is presented.

  13. Quantum Performance of Thermal Machines over Many Cycles

    Science.gov (United States)

    Watanabe, Gentaro; Venkatesh, B. Prasanna; Talkner, Peter; del Campo, Adolfo

    2017-02-01

    The performance of quantum heat engines is generally based on the analysis of a single cycle. We challenge this approach by showing that the total work performed by a quantum engine need not be proportional to the number of cycles. Furthermore, optimizing the engine over multiple cycles leads to the identification of scenarios with a quantum enhancement. We demonstrate our findings with a quantum Otto engine based on a two-level system as the working substance that supplies power to an external oscillator.

  14. Photo-thermal quartz tuning fork excitation for dynamic mode atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Bontempi, Alexia; Teyssieux, Damien; Thiery, Laurent; Hermelin, Damien; Vairac, Pascal [FEMTO-ST Institute UMR 6174, Université de Franche-Comté, CNRS, ENSMM, UTBM, 32 Avenue de l' Observatoire, F-25044 Besançon (France); Friedt, Jean-Michel [SENSeOR SAS, Besançon (France)

    2014-10-13

    A photo-thermal excitation of a Quartz Tuning Fork (QTF) for topographic studies is introduced. The non-invasive photo-thermal excitation presents practical advantages compared to QTF mechanical and electrical excitations, including the absence of the anti-resonance and its associated phase rotation. Comparison between our theoretical model and experiments validate that the optical transduction mechanism is a photo-thermal rather than photo-thermoacoustic phenomenon. Topographic maps in the context of near-field microscopy distance control have been achieved to demonstrate the performance of the system.

  15. Intentional thought dynamics during exercise performed until volitional exhaustion.

    Science.gov (United States)

    Balagué, Natàlia; Hristovski, Robert; Garcia, Sergi; Aragonés, Daniel; Razon, Selen; Tenenbaum, Gershon

    2015-01-01

    Using a non-linear approach, intentional dynamics of thoughts were examined during constant cycling performed until volitional exhaustion. Participants (n = 12) completed two sessions at 80% Wmax. Their (1) intrinsic thought dynamics (i.e., no-imposed thoughts condition) and (2) intentional thought dynamics (i.e., imposed task-unrelated thoughts condition; TUT) were recorded and then classified into four categories: internal and external TUT (TUT-I, TUT-E) and external and internal task-related thoughts (TRT-E, TRT-I). The probability estimates for maintaining each thought category stable, the rate of switching from one category to another, and the entropy dynamics along the testing procedure were assessed and compared through time phase. Friedman ANOVA tests revealed a significant effect of effort increase on thought contents only in the imposed TUT test. While TUT-I probabilities decreased significantly (P < .001) as effort increased, TRT-I probabilities increased (P < .05). Moreover, the entropy to the entire thought dynamics increased at the outset of task performance and decreased upon approaching volitional exhaustion (P < .001). As time spent in constant effort increased, and volitional exhaustion approached, task relatedness (TUT, TRT), direction (internal, external), and entropy of thought contents changed unintentionally providing further evidence for a nonlinear dynamics of attention focus.

  16. A CFD model for analysis of performance, water and thermal distribution, and mechanical related failure in PEM fuel cells

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2016-07-01

    Full Text Available This paper presents a comprehensive three–dimensional, multi–phase, non-isothermal model of a Proton Exchange Membrane (PEM fuel cell that incorporates significant physical processes and key parameters affecting the fuel cell performance. The model construction involves equations derivation, boundary conditions setting, and solution algorithm flow chart. Equations in gas flow channels, gas diffusion layers (GDLs, catalyst layers (CLs, and membrane as well as equations governing cell potential and hygro-thermal stresses are described. The algorithm flow chart starts from input of the desired cell current density, initialization, iteration of the equations solution, and finalizations by calculating the cell potential. In order to analyze performance, water and thermal distribution, and mechanical related failure in the cell, the equations are solved using a computational fluid dynamic (CFD code. Performance analysis includes a performance curve which plots the cell potential (Volt against nominal current density (A/cm2 as well as losses. Velocity vectors of gas and liquid water, liquid water saturation, and water content profile are calculated. Thermal distribution is then calculated together with hygro-thermal stresses and deformation. The CFD model was executed under boundary conditions of 20°C room temperature, 35% relative humidity, and 1 MPA pressure on the lower surface. Parameters values of membrane electrode assembly (MEA and other base conditions are selected. A cell with dimension of 1 mm x 1 mm x 50 mm is used as the object of analysis. The nominal current density of 1.4 A/cm2 is given as the input of the CFD calculation. The results show that the model represents well the performance curve obtained through experiment. Moreover, it can be concluded that the model can help in understanding complex process in the cell which is hard to be studied experimentally, and also provides computer aided tool for design and optimization of PEM

  17. Thermal conductivity of tungsten: Effects of plasma-related structural defects from molecular-dynamics simulations

    Science.gov (United States)

    Hu, Lin; Wirth, Brian D.; Maroudas, Dimitrios

    2017-08-01

    We report results on the lattice thermal conductivities of tungsten single crystals containing nanoscale-sized pores or voids and helium (He) nanobubbles as a function of void/bubble size and gas pressure in the He bubbles based on molecular-dynamics simulations. For reference, we calculated lattice thermal conductivities of perfect tungsten single crystals along different crystallographic directions at room temperature and found them to be about 10% of the overall thermal conductivity of tungsten with a weak dependence on the heat flux direction. The presence of nanoscale voids in the crystal causes a significant reduction in its lattice thermal conductivity, which decreases with increasing void size. Filling the voids with He to form He nanobubbles and increasing the bubble pressure leads to further significant reduction of the tungsten lattice thermal conductivity, down to ˜20% of that of the perfect crystal. The anisotropy in heat conduction remains weak for tungsten single crystals containing nanoscale-sized voids and He nanobubbles throughout the pressure range examined. Analysis of the pressure and atomic displacement fields in the crystalline region that surrounds the He nanobubbles reveals that the significant reduction of tungsten lattice thermal conductivity in this region is due to phonon scattering from the nanobubbles, as well as lattice deformation around the nanobubbles and formation of lattice imperfections at higher bubble pressure.

  18. Dynamic indoor thermal comfort model identification based on neural computing PMV index

    Science.gov (United States)

    Sahari, K. S. Mohamed; Jalal, M. F. Abdul; Homod, R. Z.; Eng, Y. K.

    2013-06-01

    This paper focuses on modelling and simulation of building dynamic thermal comfort control for non-linear HVAC system. Thermal comfort in general refers to temperature and also humidity. However in reality, temperature or humidity is just one of the factors affecting the thermal comfort but not the main measures. Besides, as HVAC control system has the characteristic of time delay, large inertia, and highly nonlinear behaviour, it is difficult to determine the thermal comfort sensation accurately if we use traditional Fanger's PMV index. Hence, Artificial Neural Network (ANN) has been introduced due to its ability to approximate any nonlinear mapping. Using ANN to train, we can get the input-output mapping of HVAC control system or in other word; we can propose a practical approach to identify thermal comfort of a building. Simulations were carried out to validate and verify the proposed method. Results show that the proposed ANN method can track down the desired thermal sensation for a specified condition space.

  19. Comparison of thermal performance between test cells with different coverage systems for experimental typical day of heat in Brazilian Southeastern

    Directory of Open Access Journals (Sweden)

    Grace Tiberio Cardoso

    2014-09-01

    Full Text Available This article shows experimentally the thermal performance of two test cells with different coverage systems, Light Green Roof (LGR and ceramic roof by analyzing internal surface temperatures (IST in the ceiling and dry bulb temperatures (DBT. The objective was to evaluate the spatial distribution of temperatures in buildings according to spatial and temporal Dynamic Climatology approaches. An experimental, typical day for heat conditions was determined. The data of the main climatic variables provided by an automatic weather station and temperatures inside the test cells were collected using thermocouples installed such that the entire space is included. The results led to the conclusion that the LGR has a balanced IST and DBT spatial distribution compared with ceramic roofs. Nevertheless, the analysis of the thermal performance is only one of the variables that must be considered when developing a construction proposal that is adapted to the context. The manner in which the thermocouples were placed inside the test cells also showed the importance of specifying the location of the sensors in experimental studies on the behavior and thermal performance of buildings.

  20. Toward a dynamical theory of body movement in musical performance.

    Science.gov (United States)

    Demos, Alexander P; Chaffin, Roger; Kant, Vivek

    2014-01-01

    Musicians sway expressively as they play in ways that seem clearly related to the music, but quantifying the relationship has been difficult. We suggest that a complex systems framework and its accompanying tools for analyzing non-linear dynamical systems can help identify the motor synergies involved. Synergies are temporary assemblies of parts that come together to accomplish specific goals. We assume that the goal of the performer is to convey musical structure and expression to the audience and to other performers. We provide examples of how dynamical systems tools, such as recurrence quantification analysis (RQA), can be used to examine performers' movements and relate them to the musical structure and to the musician's expressive intentions. We show how detrended fluctuation analysis (DFA) can be used to identify synergies and discover how they are affected by the performer's expressive intentions.

  1. The dynamics of shared leadership: building trust and enhancing performance.

    Science.gov (United States)

    Drescher, Marcus A; Korsgaard, M Audrey; Welpe, Isabell M; Picot, Arnold; Wigand, Rolf T

    2014-09-01

    In this study, we examined how the dynamics of shared leadership are related to group performance. We propose that, over time, the expansion of shared leadership within groups is related to growth in group trust. In turn, growth in group trust is related to performance improvement. Longitudinal data from 142 groups engaged in a strategic simulation game over a 4-month period provide support for positive changes in trust mediating the relationship between positive changes in shared leadership and positive changes in performance. Our findings contribute to the literature on shared leadership and group dynamics by demonstrating how the growth in shared leadership contributes to the emergence of trust and a positive performance trend over time.

  2. Improvement of energy performances of existing buildings by application of solar thermal systems

    Directory of Open Access Journals (Sweden)

    Krstić-Furundžić Aleksandra

    2009-01-01

    Full Text Available Improvement of energy performances of the existing buildings in the suburban settlement Konjarnik in Belgrade, by the application of solar thermal systems is the topic presented in this paper. Hypothetical models of building improvements are created to allow the benefits of applying solar thermal collectors to residential buildings in Belgrade climate conditions to be estimated. This case study presents different design variants of solar thermal collectors integrated into a multifamily building envelope. The following aspects of solar thermal systems integration are analyzed in the paper: energy, architectural, ecological and economic. The results show that in Belgrade climatic conditions significant energy savings and reduction of CO2 emissions can be obtained with the application of solar thermal collectors.

  3. Optimization of the thermal performance of multi-layer silicon microchannel heat sinks

    Directory of Open Access Journals (Sweden)

    Xu Shanglong

    2016-01-01

    Full Text Available The objective is to optimize the configuration sizes and thermal performance of a multilayer silicon microchannel heat sink by the thermal resistance network model. The effect of structural parameter on the thermal resistance is analyzed by numercal simulation. Taking the thermal resistance as an objective function, a nonlinear and multi-constrained optimization model are proposed for the silicon microchannel heat sink in electronic chips cooling. The sequential quadratic programming (SQP method is used to do the optimization design of the configuration sizes of the microchannel. For the heat sink with the size of 20mm×20mm and the power of 400 W, the optimized microchannel number, layer, height and width are 40 and 2, 2.2mm and 0.2mm, respectively, and its corresponding total thermal resistance for whole microchannel heat sink is 0.0424 K/W.

  4. Predicting the thermal/structural performance of the atmospheric trace molecules spectroscopy /ATMOS/ Fourier transform spectrometer

    Science.gov (United States)

    Miller, J. M.

    1980-01-01

    ATMOS is a Fourier transform spectrometer to measure atmospheric trace molecules over a spectral range of 2-16 microns. Assessment of the system performance of ATMOS includes evaluations of optical system errors induced by thermal and structural effects. In order to assess the optical system errors induced from thermal and structural effects, error budgets are assembled during system engineering tasks and line of sight and wavefront deformations predictions (using operational thermal and vibration environments and computer models) are subsequently compared to the error budgets. This paper discusses the thermal/structural error budgets, modelling and analysis methods used to predict thermal/structural induced errors and the comparisons that show that predictions are within the error budgets.

  5. The thermal performance of shelter modelling: Improvement of temporary structures

    OpenAIRE

    Obyn, Sophie; Van Moeseke, Geoffrey; Virgo, Vincent; 4th International Conference on Mobile, Adaptable and Rapidly Assembled Structures, MARAS 2014

    2014-01-01

    There exist many disasters, whether natural or caused by human factors. In emergency situations, it is important to provide shelters to protect the population and the support against their environment and to give them some privacy. Unfortunately, contexts and exposure constraints in which these items are used can be very different which implies that their performance can be reduced with a direct impact on occupant comfort. Furthermore, given the very large scale of emergency camps, the intake...

  6. Thermal performance of a new solar air heater

    Energy Technology Data Exchange (ETDEWEB)

    Tiris, C.; Ozbalta, N. [Ege Univ., Izmir (Turkey). Solar Energy Institute; Tiris, M.; Dincer, I. [TUBITAK-Marmara Research Center, Kocaeli (Turkey)

    1995-05-01

    A solar air heater, part of a food drying system using solar energy as a renewable energy source for heat, was developed and tested for several agricultural products (i.e., sultana grapes, green beans, sweet peppers, chili peppers). Drying processes were conducted in the chamber with forced natural air heated partly by solar energy. Solar air heater performances were discussed along with estimates of energy efficiency of the system. The obtained results indicate that the present system is efficiency and effective.

  7. A thermal-mechanical constitutive model for b-HMX single crystal and cohesive interface under dynamic high pressure loading

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Due to the significant thermal-mechanical effects during hot spot formation in PBX explosives,a thermodynamic constitutive model has been constructed for HMX anisotropic single crystal subjected to dynamic impact loading. The crystal plasticity model based on dislocation dynamics theory was employed to describe the anisotropic plastic behavior along the preferential slip systems. A modified equation of state (EOS) was introduced into the constitutive equations through the decomposing stress tensor and the nonlinear elasticity for materials was taken into account. The one-dimensional strain impact simulations for HMX single crystal and quasi-bicrystal were performed respectively,in which the cohesive elements were inserted over the interface areas for the latter. The predicted particle velocities for the single crystal sample agreed well with the experimental results in the literature. Furthermore,the effects of crystal orientations,interface,misorientations on localized strain,stress and temperature distributions were predicted and discussed.

  8. Comparison of the Green-Kubo and homogeneous non-equilibrium molecular dynamics methods for calculating thermal conductivity

    Science.gov (United States)

    Dongre, B.; Wang, T.; Madsen, G. K. H.

    2017-07-01

    Different molecular dynamics methods like the direct method, the Green-Kubo (GK) method and homogeneous non-equilibrium molecular dynamics (HNEMD) method have been widely used to calculate lattice thermal conductivity ({κ }{\\ell }). While the first two methods have been used and compared quite extensively, there is a lack of comparison of these methods with the HNEMD method. Focusing on the underlying computational parameters, we present a detailed comparison of the GK and HNEMD methods for both bulk and vacancy Si using the Stillinger-Weber potential. For the bulk calculations, we find both methods to perform well and yield {κ }{\\ell } within acceptable uncertainties. In case of the vacancy calculations, HNEMD method has a slight advantage over the GK method as it becomes computationally cheaper for lower {κ }{\\ell } values. This study could promote the application of HNEMD method in {κ }{\\ell } calculations involving other lattice defects like nanovoids, dislocations, interfaces.

  9. Performance of a proton exchange membrane fuel cell stack with thermally conductive pyrolytic graphite sheets for thermal management

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Chih-Yung; Lin, Yu-Sheng; Lu, Chien-Heng [Department of Aeronautics and Astronautics, National Cheng-Kung University, Tainan 70101 (China)

    2009-04-15

    This work experimentally investigates the effects of the pyrolytic graphite sheets (PGS) on the performance and thermal management of a proton exchange membrane fuel cell (PEMFC) stack. These PGS with the features of light weight and high thermal conductivity serve as heat spreaders in the fuel cell stack for the first time to reduce the volume and weight of cooling systems, and homogenizes the temperature in the reaction areas. A PEMFC stack with an active area of 100 cm{sup 2} and 10 cells in series is constructed and used in this research. Five PGS of thickness 0.1 mm are cut into the shape of flow channels and bound to the central five cathode gas channel plates. Four thermocouples are embedded on the cathode gas channel plates to estimate the temperature variation in the stack. It is shown that the maximum power of the stack increase more than 15% with PGS attached. PGS improve the stack performance and alleviate the flooding problem at low cathode flow rates significantly. Results of this study demonstrate the feasibility of application of PGS to the thermal management of a small-to-medium-sized fuel cell stack. (author)

  10. A review of thermal performance improving methods of lithium ion battery: Electrode modification and thermal management system

    Science.gov (United States)

    Zhao, Rui; Zhang, Sijie; Liu, Jie; Gu, Junjie

    2015-12-01

    Lithium ion (Li-ion) battery has emerged as an important power source for portable devices and electric vehicles due to its superiority over other energy storage technologies. A mild temperature variation as well as a proper operating temperature range are essential for a Li-ion battery to perform soundly and have a long service life. In this review paper, the heat generation and dissipation of Li-ion battery are firstly analyzed based on the energy conservation equations, followed by an examination of the hazardous effects of an above normal operating temperature. Then, advanced techniques in respect of electrode modification and systematic battery thermal management are inspected in detail as solutions in terms of reducing internal heat production and accelerating external heat dissipation, respectively. Specifically, variable parameters like electrode thickness and particle size of active material, along with optimization methods such as coating, doping, and adding conductive media are discussed in the electrode modification section, while the current development in air cooling, liquid cooling, heat pipe cooling, and phase change material cooling systems are reviewed in the thermal management part as different ways to improve the thermal performance of Li-ion batteries.

  11. Improving lean team performance: leadership and workfloor dynamics

    NARCIS (Netherlands)

    Dun, van Desirée Hermina

    2015-01-01

    This Ph.D. thesis reports four different studies that were undertaken to identify and examine the content of human dynamics that may account for sustainable lean team performance, at multiple organizational levels: higher-level leaders (including top- and middle managers), team leaders, and team mem

  12. Dynamic Incentive Effects of Relative Performance Pay: A Field Experiment

    NARCIS (Netherlands)

    J. Delfgaauw (Josse); A.J. Dur (Robert); J.A. Non (Arjan); W.J.M.I. Verbeke (Willem)

    2010-01-01

    textabstractWe conduct a field experiment among 189 stores of a retail chain to study dynamic incentive effects of relative performance pay. Employees in the randomly selected treatment stores could win a bonus by outperforming three comparable stores from the control group over the course of four w

  13. Analysing the performance of dynamic multi-objective optimisation algorithms

    CSIR Research Space (South Africa)

    Helbig, M

    2013-06-01

    Full Text Available Congress on Evolutionary Computation, 20-23 June 2013, Cancún, México Analysing the Performance of Dynamic Multi-objective Optimisation Algorithms Marde Helbig CSIR: Meraka Institute, Brummeria, South Africa; and University of Pretoria Computer...

  14. Improving lean team performance: leadership and workfloor dynamics

    NARCIS (Netherlands)

    van Dun, Desirée Hermina

    2015-01-01

    This Ph.D. thesis reports four different studies that were undertaken to identify and examine the content of human dynamics that may account for sustainable lean team performance, at multiple organizational levels: higher-level leaders (including top- and middle managers), team leaders, and team mem

  15. Thermal performance study and evaluation of comfort temperatures in vernacular buildings of North-East India

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Manoj Kumar; Atreya, S.K. [Instrument Design and Development Centre, Indian Institute of Technology Delhi, New Delhi 110016 (India); Mahapatra, Sadhan [Department of Energy, Tezpur University, Tezpur 784028, Assam (India)

    2010-02-15

    Solar passive techniques are being used in vernacular buildings throughout the world. Researchers have done extensive study on thermal performance of vernacular buildings in the different parts of the world. Vernacular architecture of North-Eastern India represents the principle of climate-responsive architecture, which still lacks experimental validation and quantitative analysis. Thermal comfort not only makes the occupants comfortable but also governs energy consumption in the building. Detailed field studies on thermal performances of typical traditional vernacular dwellings in different bioclimatic zones have been undertaken. This field study includes detailed survey of 150 vernacular dwellings, field tests and thermal sensation vote of 300 occupants on ASHRAE thermal sensation scale. Field test includes measurement of temperature, humidity, illumination level and building design parameters. Thermal performances of these vernacular dwellings were evaluated for winter, pre-summer, summer/monsoon and pre-winter months of the year 2008. This evaluation is based on 'adaptive approach', which is the outcome of the field studies and is now part of ASHRAE standard 55/2004 for predicting comfortable temperature of naturally ventilated buildings. This study also tried to find out the range of comfort temperature in these vernacular buildings for different season of the year. It has been found that these vernacular dwellings perform quite satisfactorily except in the winter months and the occupants feel comfortable in a wider range of temperature. (author)

  16. Effects of Absorber Emissivity on Thermal Performance of a Solar Cavity Receiver

    Directory of Open Access Journals (Sweden)

    Jiabin Fang

    2014-01-01

    Full Text Available Solar cavity receiver is a key component to realize the light-heat conversion in tower-type solar power system. It usually has an aperture for concentrated sunlight coming in, and the heat loss is unavoidable because of this aperture. Generally, in order to improve the thermal efficiency, a layer of coating having high absorptivity for sunlight would be covered on the surface of the absorber tubes inside the cavity receiver. As a result, it is necessary to investigate the effects of the emissivity of absorber tubes on the thermal performance of the receiver. In the present work, the thermal performances of the receiver with different absorber emissivity were numerically simulated. The results showed that the thermal efficiency increases and the total heat loss decreases with increasing emissivity of absorber tubes. However, the thermal efficiency increases by only 1.6% when the emissivity of tubes varies from 0.2 to 0.8. Therefore, the change of absorber emissivity has slight effect on the thermal performance of the receiver. The reason for variation tendency of performance curves was also carefully analyzed. It was found that the temperature reduction of the cavity walls causes the decrease of the radiative heat loss and the convective heat loss.

  17. Vacuum Insulation Panels: Analysis of the Thermal Performance of Both Single Panel and Multilayer Boards

    Directory of Open Access Journals (Sweden)

    Alfonso Capozzoli

    2015-03-01

    Full Text Available The requirements for improvement in the energy efficiency of buildings, mandatory in many EU countries, entail a high level of thermal insulation of the building envelope. In recent years, super-insulation materials with very low thermal conductivity have been developed. These materials provide satisfactory thermal insulation, but allow the total thickness of the envelope components to be kept below a certain thickness. Nevertheless, in order to penetrate the building construction market, some barriers have to be overcome. One of the main issues is that testing procedures and useful data that are able to give a reliable picture of their performance when applied to real buildings have to be provided. Vacuum Insulation Panels (VIPs are one of the most promising high performing technologies. The overall, effective, performance of a panel under actual working conditions is influenced by thermal bridging, due to the edge of the panel envelope and to the type of joint. In this paper, a study on the critical issues related to the laboratory measurement of the equivalent thermal conductivity of VIPs and their performance degradation due to vacuum loss has been carried out utilizing guarded heat flux meter apparatus. A numerical analysis has also been developed to study thermal bridging effect when VIP panels are adopted to create multilayer boards for building applications.

  18. Thermal buffering performance of composite phase change materials applied in low-temperature protective garments

    Science.gov (United States)

    Yang, Kai; Jiao, Mingli; Yu, Yuanyuan; Zhu, Xueying; Liu, Rangtong; Cao, Jian

    2017-07-01

    Phase change material (PCM) is increasingly being applied in the manufacturing of functional thermo-regulated textiles and garments. This paper investigated the thermal buffering performance of different composite PCMs which are suitable for the application in functional low-temperature protective garments. First, according to the criteria selecting PCM for functional textiles/garments, three kinds of pure PCM were selected as samples, which were n-hexadecane, n-octadecane and n-eicosane. To get the adjustable phase change temperature range and higher phase change enthalpy, three kinds of composite PCM were prepared using the above pure PCM. To evaluate the thermal buffering performance of different composite PCM samples, the simulated low-temperature experiments were performed in the climate chamber, and the skin temperature variation curves in three different low temperature conditions were obtained. Finally composite PCM samples’ thermal buffering time, thermal buffering capacity and thermal buffering efficiency were calculated. Results show that the comprehensive thermal buffering performance of n-octadecane and n-eicosane composite PCM is the best.

  19. Interring Gas Dynamic Analysis of Piston in a Diesel Engine considering the Thermal Effect

    Directory of Open Access Journals (Sweden)

    Wanyou Li

    2015-01-01

    Full Text Available Understanding the interaction between ring dynamics and gas transport in ring pack systems is crucial and needs to be imperatively studied. The present work features detailed interring gas dynamics of piston ring pack behavior in internal combustion engines. The model is developed for a ring pack with four rings. The dynamics of ring pack are simulated. Due to the fact that small changes in geometry of the grooves and lands would have a significant impact on the interring gas dynamics, the thermal deformation of piston has been considered during the ring pack motion analysis in this study. In order to get the temperature distribution of piston head more quickly and accurately, an efficient method utilizing the concept of inverse heat conduction is presented. Moreover, a sensitive analysis based on the analysis of partial regression coefficients is presented to investigate the effect of groove parameters on blowby.

  20. Comparison of the Thermal Performance of Radiative and Convective Terminals

    DEFF Research Database (Denmark)

    Le Dreau, Jerome; Heiselberg, Per

    2012-01-01

    of interest to compare the energy efficiency of the two types of terminals for heating and cooling buildings. Convective terminals (i.e. air conditioning systems) have been widely used in buildings, but the level of comfort is not always acceptable due to high air velocity. On the other hand radiant terminals...... can provide a better indoor climate, and be more energy efficient because they can make use of low-grade sources. The output of this conceptual approach is a better understanding of the advantages and drawbacks of the two technologies under different conditions. The analysis has been performed...