Controlling Thermal Conduction by Graded Materials

Science.gov (United States)

Ji, Qin; Huang, Ji-Ping

2018-04-01

Manipulating thermal conductivities are fundamentally important for controlling the conduction of heat at will. Thermal cloaks and concentrators, which have been extensively studied recently, are actually graded materials designed according to coordinate transformation approaches, and their effective thermal conductivity is equal to that of the host medium outside the cloak or concentrator. Here we attempt to investigate a more general problem: what is the effective thermal conductivity of graded materials? In particular, we perform a first-principles approach to the analytic exact results of effective thermal conductivities of materials possessing either power-law or linear gradation profiles. On the other hand, by solving Laplace’s equation, we derive a differential equation for calculating the effective thermal conductivity of a material whose thermal conductivity varies along the radius with arbitrary gradation profiles. The two methods agree with each other for both external and internal heat sources, as confirmed by simulation and experiment. This work provides different methods for designing new thermal metamaterials (including thermal cloaks and concentrators), in order to control or manipulate the transfer of heat. Support by the National Natural Science Foundation of China under Grant No. 11725521, by the Science and Technology Commission of Shanghai Municipality under Grant No. 16ZR1445100

Experimental study of the influence of anticipated control on human thermal sensation and thermal comfort.

Science.gov (United States)

Zhou, X; Ouyang, Q; Zhu, Y; Feng, C; Zhang, X

2014-04-01

To investigate whether occupants' anticipated control of their thermal environment can influence their thermal comfort and to explain why the acceptable temperature range in naturally ventilated environments is greater than that in air-conditioned environments, a series of experiments were conducted in a climate chamber in which the thermal environment remained the same but the psychological environment varied. The results of the experiments show that the ability to control the environment can improve occupants' thermal sensation and thermal comfort. Specifically, occupants' anticipated control decreased their thermal sensation vote (TSV) by 0.4-0.5 and improved their thermal comfort vote (TCV) by 0.3-0.4 in neutral-warm environment. This improvement was due exclusively to psychological factors. In addition, having to pay the cost of cooling had no significant influence on the occupants' thermal sensation and thermal comfort in this experiment. Thus, having the ability to control the thermal environment can improve occupants' comfort even if there is a monetary cost involved. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Controlled Thermal Expansion Alloys

Data.gov (United States)

National Aeronautics and Space Administration — There has always been a need for controlled thermal expansion alloys suitable for mounting optics and detectors in spacecraft applications.  These alloys help...

Thermal oxidation for air toxics control

International Nuclear Information System (INIS)

Pennington, R.L.

1991-01-01

The Administration projects annual expenditures of $1.1 billion by 1995, increasing to $6.7 billion by 2005, in order to comply with the new Clean Air Act Title III hazardous air pollutant requirements. The Title III requirements include 189 hazardous air pollutants which must be reduced or eliminated by 2003. Twenty of the 189 listed pollutants account for approximately 75 percent of all hazardous air pollutant emissions. Ninety percent of these 20 pollutants can be effectively controlled through one or mote of the thermal oxidation technologies. This paper reports that the advantages and disadvantages of each thermal oxidation technology vary substantially and must be reviewed for each application in order to establish the most effective thermal oxidation solution. Effective thermal oxidation will meet MACT (maximum achievable control technology) emission standards

Proportional and Integral Thermal Control System for Large Scale Heating Tests

Science.gov (United States)

Fleischer, Van Tran

2015-01-01

The National Aeronautics and Space Administration Armstrong Flight Research Center (Edwards, California) Flight Loads Laboratory is a unique national laboratory that supports thermal, mechanical, thermal/mechanical, and structural dynamics research and testing. A Proportional Integral thermal control system was designed and implemented to support thermal tests. A thermal control algorithm supporting a quartz lamp heater was developed based on the Proportional Integral control concept and a linearized heating process. The thermal control equations were derived and expressed in terms of power levels, integral gain, proportional gain, and differences between thermal setpoints and skin temperatures. Besides the derived equations, user's predefined thermal test information generated in the form of thermal maps was used to implement the thermal control system capabilities. Graphite heater closed-loop thermal control and graphite heater open-loop power level were added later to fulfill the demand for higher temperature tests. Verification and validation tests were performed to ensure that the thermal control system requirements were achieved. This thermal control system has successfully supported many milestone thermal and thermal/mechanical tests for almost a decade with temperatures ranging from 50 F to 3000 F and temperature rise rates from -10 F/s to 70 F/s for a variety of test articles having unique thermal profiles and test setups.

Controlling Thermal Expansion: A Metal-Organic Frameworks Route.

Science.gov (United States)

Balestra, Salvador R G; Bueno-Perez, Rocio; Hamad, Said; Dubbeldam, David; Ruiz-Salvador, A Rabdel; Calero, Sofia

2016-11-22

Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal-organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host-guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion.

Controlling Thermal Expansion: A Metal–Organic Frameworks Route

Science.gov (United States)

2016-01-01

Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal–organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host–guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion. PMID:28190918

Temperature-gated thermal rectifier for active heat flow control.

Science.gov (United States)

Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

2014-08-13

Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.

New flexible thermal control material for long-life satellite

International Nuclear Information System (INIS)

Sasaki, Shigekuni; Hasuda, Yoshinori; Ichino, Toshihiro

1986-01-01

Flexible thermal control materials are light weight, cheap and excellent in the practical applicability, and are expected to be applied to future long life, large capacity satellites. However, the flexible thermal control materials used at present have the defect that either the space environment withstanding capability or the thermal control performance is poor. Therefore, the authors examined the flexible thermal control materials which are excellent in both these properties, and have developed the thermal control material PEI-OSR using polyether imide films as the substrate. In this study, while comparing with the FEP Teflon with silver vapor deposition, which has been used so far for short life satellites, the long term reliability of the PEI-OSR supposing the use for seven years was examined. As the results, the FEP Teflon with silver vapor deposition caused cracking and separation by irradiation and heat cycle test, and became unusable, but the PEI-OSR did not change its flexibility at all. Also the thermal control performance of the PEI-OSR after the test equivalent to seven years was superior to the initial performance of the Kaptone with aluminum vapor deposition, which has excellent space environment endurance, thus it was clarified that the PEI-OSR is the most excellent for this purpose. (Kako, I.)

Transient thermal camouflage and heat signature control

Science.gov (United States)

Yang, Tian-Zhi; Su, Yishu; Xu, Weikai; Yang, Xiao-Dong

2016-09-01

Thermal metamaterials have been proposed to manipulate heat flux as a new way to cloak or camouflage objects in the infrared world. To date, however, thermal metamaterials only operate in the steady-state and exhibit detectable, transient heat signatures. In this letter, the theoretical basis for a thermal camouflaging technique with controlled transient diffusion is presented. This technique renders an object invisible in real time. More importantly, the thermal camouflaging device instantaneously generates a pre-designed heat signature and behaves as a perfect thermal illusion device. A metamaterial coating with homogeneous and isotropic thermal conductivity, density, and volumetric heat capacity was fabricated and very good camouflaging performance was achieved.

Embedded Thermal Control for Subsystems for Next Generation Spacecraft Applications

Science.gov (United States)

Didion, Jeffrey R.

2015-01-01

Thermal Fluids and Analysis Workshop, Silver Spring MD NCTS 21070-15. NASA, the Defense Department and commercial interests are actively engaged in developing miniaturized spacecraft systems and scientific instruments to leverage smaller cheaper spacecraft form factors such as CubeSats. This paper outlines research and development efforts among Goddard Space Flight Center personnel and its several partners to develop innovative embedded thermal control subsystems. Embedded thermal control subsystems is a cross cutting enabling technology integrating advanced manufacturing techniques to develop multifunctional intelligent structures to reduce Size, Weight and Power (SWaP) consumption of both the thermal control subsystem and overall spacecraft. Embedded thermal control subsystems permit heat acquisition and rejection at higher temperatures than state of the art systems by employing both advanced heat transfer equipment (integrated heat exchangers) and high heat transfer phenomena. The Goddard Space Flight Center Thermal Engineering Branch has active investigations seeking to characterize advanced thermal control systems for near term spacecraft missions. The embedded thermal control subsystem development effort consists of fundamental research as well as development of breadboard and prototype hardware and spaceflight validation efforts. This paper will outline relevant fundamental investigations of micro-scale heat transfer and electrically driven liquid film boiling. The hardware development efforts focus upon silicon based high heat flux applications (electronic chips, power electronics etc.) and multifunctional structures. Flight validation efforts include variable gravity campaigns and a proposed CubeSat based flight demonstration of a breadboard embedded thermal control system. The CubeSat investigation is technology demonstration will characterize in long-term low earth orbit a breadboard embedded thermal subsystem and its individual components to develop

The Calipso Thermal Control Subsystem

Science.gov (United States)

Gasbarre, Joseph F.; Ousley, Wes; Valentini, Marc; Thomas, Jason; Dejoie, Joel

2007-01-01

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is a joint NASA-CNES mission to study the Earth s cloud and aerosol layers. The satellite is composed of a primary payload (built by Ball Aerospace) and a spacecraft platform bus (PROTEUS, built by Alcatel Alenia Space). The thermal control subsystem (TCS) for the CALIPSO satellite is a passive design utilizing radiators, multi-layer insulation (MLI) blankets, and both operational and survival surface heaters. The most temperature sensitive component within the satellite is the laser system. During thermal vacuum testing of the integrated satellite, the laser system s operational heaters were found to be inadequate in maintaining the lasers required set point. In response, a solution utilizing the laser system s survival heaters to augment the operational heaters was developed with collaboration between NASA, CNES, Ball Aerospace, and Alcatel-Alenia. The CALIPSO satellite launched from Vandenberg Air Force Base in California on April 26th, 2006. Evaluation of both the platform and payload thermal control systems show they are performing as expected and maintaining the critical elements of the satellite within acceptable limits.

A thermal manikin with human thermoregulatory control: implementation and validation.

Science.gov (United States)

Foda, Ehab; Sirén, Kai

2012-09-01

Tens of different sorts of thermal manikins are employed worldwide, mainly in the evaluation of clothing thermal insulation and thermal environments. They are regulated thermally using simplified control modes. This paper reports on the implementation and validation of a new thermoregulatory control mode for thermal manikins. The new control mode is based on a multi-segmental Pierce (MSP) model. In this study, the MSP control mode was implemented, using the LabVIEW platform, onto the control system of the thermal manikin 'Therminator'. The MSP mode was then used to estimate the segmental equivalent temperature (t(eq)) along with constant surface temperature (CST) mode under two asymmetric thermal conditions. Furthermore, subjective tests under the same two conditions were carried out using 17 human subjects. The estimated segmental t(eq) from the experiments with the two modes and from the subjective assessment were compared in order to validate the use of the MSP mode for the estimation of t(eq). The results showed that the t(eq) values estimated by the MSP mode were closer to the subjective mean votes under the two test conditions for most body segments and compared favourably with values estimated by the CST mode.

Thermally and magnetically controlled superconducting rectifiers

International Nuclear Information System (INIS)

Mulder, G.B.J.; TenKate, H.H.J.; Krooshoop, H.J.G.; Van de Klundert, L.J.M.

1989-01-01

The switches of a superconducting rectifier can be controlled either magnetically or thermally. The main purpose of this paper is to point out the differences between both methods of switching and discuss the consequences for the operation of the rectifier. The discussion is illustrated by the experimental results of a rectifier which was tested with magnetically as well as thermally controlled switches. It has an input current of 30 A, an output current of more than 1 kA and an operating frequency of a few Hertz. A superconducting magnet connected to this rectifier can be energized at a rate exceeding 1 MJ/hour and an efficiency of about 97%

Emission and thermal performance upgrade through advanced control backfit

Energy Technology Data Exchange (ETDEWEB)

Banerjee, A.K. [Stone & Webster Engineering Corporation, Boston, MA (United States)

1994-12-31

Reducing emission and improving thermal performance of currently operating power plants is a high priority. A majority of these power plants are over 20 years old with old control systems. Upgrading the existing control systems with the latest technology has many benefits, the most cost beneficial are the reduction of emission and improving thermal performance. The payback period is usually less than two years. Virginia Power is installing Stone & Webster`s NO{sub x} Emissions Advisor and Advanced Steam Temperature Control systems on Possum Point Units 3 and 4 to achieve near term NO{sub x} reductions while maintaining high thermal performance. Testing has demonstrated NO{sub x} reductions of greater than 20 percent through the application of NO{sub x} Emissions Advisor on these units. The Advanced Steam Temperature Control system which has been operational at Virginia Power`s Mt. Storm Unit 1 has demonstrated a signification improvement in unit thermal performance and controllability. These control systems are being combined at Units 3 and 4 to reduce NO{sub x} emissions and achieve improved unit thermal performance and control response with the existing combustion hardware. Installation has been initiated and is expected to be completed by the spring of 1995. Possum Point Power Station Units 3 and 4 are pulverized coal, tangentially fired boilers producing 107 and 232 MW and have a distributed control system and a PC based performance monitoring system. The installation of the advanced control and automation system will utilize existing control equipment requiring the addition of several PCs and PLC.

Phase change thermal control materials, method and apparatus

Science.gov (United States)

Buckley, Theresa M. (Inventor)

2001-01-01

An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The apparatus may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the apparatus also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Power Admission Control with Predictive Thermal Management in Smart Buildings

DEFF Research Database (Denmark)

Yao, Jianguo; Costanzo, Giuseppe Tommaso; Zhu, Guchuan

2015-01-01

This paper presents a control scheme for thermal management in smart buildings based on predictive power admission control. This approach combines model predictive control with budget-schedulability analysis in order to reduce peak power consumption as well as ensure thermal comfort. First...

The CALIPSO Integrated Thermal Control Subsystem

Science.gov (United States)

Gasbarre, Joseph F.; Ousley, Wes; Valentini, Marc; Thomas, Jason; Dejoie, Joel

2007-01-01

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is a joint NASA-CNES mission to study the Earth's cloud and aerosol layers. The satellite is composed of a primary payload (built by Ball Aerospace) and a spacecraft platform bus (PROTEUS, built by Alcatel Alenia Space). The thermal control subsystem (TCS) for the CALIPSO satellite is a passive design utilizing radiators, multi-layer insulation (MLI) blankets, and both operational and survival surface heaters. The most temperature sensitive component within the satellite is the laser system. During thermal vacuum testing of the integrated satellite, the laser system's operational heaters were found to be inadequate in maintaining the lasers required set point. In response, a solution utilizing the laser system's survival heaters to augment the operational heaters was developed with collaboration between NASA, CNES, Ball Aerospace, and Alcatel-Alenia. The CALIPSO satellite launched from Vandenberg Air Force Base in California on April 26th, 2006. Evaluation of both the platform and payload thermal control systems show they are performing as expected and maintaining the critical elements of the satellite within acceptable limits.

Modelling and Control of Thermal System

Directory of Open Access Journals (Sweden)

Vratislav Hladky

2014-01-01

Full Text Available Work presented here deals with the modelling of thermal processes in a thermal system consisting of direct and indirect heat exchangers. The overal thermal properties of the medium and the system itself such as liquid mixing or heat capacity are shortly analysed and their features required for modelling are reasoned and therefore simplified or neglected. Special attention is given to modelling heat losses radiated into the surroundings through the walls as they are the main issue of the effective work with the heat systems. Final part of the paper proposes several ways of controlling the individual parts’ temperatures as well as the temperature of the system considering heating elements or flowage rate as actuators.

Controlling Thermal Expansion: A Metal?Organic Frameworks Route

OpenAIRE

Balestra, Salvador R. G.; Bueno-Perez, Rocio; Hamad, Said; Dubbeldam, David; Ruiz-Salvador, A. Rabdel; Calero, Sofia

2016-01-01

Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal?organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model m...

Gas Analysis and Control Methods for Thermal Batteries

Science.gov (United States)

2013-09-01

when using highly efficient microporous thermal insulation packages. An easily implemented method of H2 gas removal from vendor thermal batteries is... microporous thermal insulation packages (1, 4, 5) or reduce volume requirements significantly. More rigorous gas control methods combined with...measured from the DCM pressures and known internal volumes of the 3 GHS that were measured using the ideal gas law with a 10-cc internal volume SS

Thermal battery for portable climate control

International Nuclear Information System (INIS)

Narayanan, Shankar; Li, Xiansen; Yang, Sungwoo; Kim, Hyunho; Umans, Ari; McKay, Ian S.; Wang, Evelyn N.

2015-01-01

Highlights: • ATB is adsorptive thermal battery delivering both heating and cooling via storage. • The novel design promotes transport and maximizes ATB performance. • A general theoretical framework is developed to analyze ATB performance. • NaX–water is used as the adsorbent–refrigerant pair as a specific case study. • The effect of key geometric parameters and operating conditions are presented. - Abstract: Current technologies that provide climate control in the transportation sector are quite inefficient. In gasoline-powered vehicles, the use of air-conditioning is known to result in higher emissions of greenhouse gases and pollutants apart from decreasing the gas-mileage. On the other hand, for electric vehicles (EVs), a drain in the onboard electric battery due to the operation of heating and cooling system results in a substantial decrease in the driving range. As an alternative to the conventional climate control system, we are developing an adsorption-based thermal battery (ATB), which is capable of storing thermal energy, and delivering both heating and cooling on demand, while requiring minimal electric power supply. Analogous to an electrical battery, the ATB can be charged for reuse. Furthermore, it promises to be compact, lightweight, and deliver high performance, which is desirable for mobile applications. In this study, we describe the design and operation of the ATB-based climate control system. We present a general theoretical framework to determine the maximum achievable heating and cooling performance using the ATB. The framework is then applied to study the feasibility of ATB integration in EVs, wherein we analyze the use of NaX zeolite–water as the adsorbent–refrigerant pair. In order to deliver the necessary heating and cooling performance, exceeding 2.5 kW h thermal capacity for EVs, the analysis determines the optimal design and operating conditions. While the use of the ATB in EVs can potentially enhance its driving

The Earth Observing System AM Spacecraft - Thermal Control Subsystem

Science.gov (United States)

Chalmers, D.; Fredley, J.; Scott, C.

1993-01-01

Mission requirements for the EOS-AM Spacecraft intended to monitor global changes of the entire earth system are considered. The spacecraft is based on an instrument set containing the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER), Clouds and Earth's Radiant Energy System (CERES), Multiangle Imaging Spectro-Radiometer (MISR), Moderate-Resolution Imaging Spectrometer (MODIS), and Measurements of Pollution in the Troposphere (MOPITT). Emphasis is placed on the design, analysis, development, and verification plans for the unique EOS-AM Thermal Control Subsystem (TCS) aimed at providing the required environments for all the onboard equipment in a densely packed layout. The TCS design maximizes the use of proven thermal design techniques and materials, in conjunction with a capillary pumped two-phase heat transport system for instrument thermal control.

Controllable laser thermal cleavage of sapphire wafers

Science.gov (United States)

Xu, Jiayu; Hu, Hong; Zhuang, Changhui; Ma, Guodong; Han, Junlong; Lei, Yulin

2018-03-01

Laser processing of substrates for light-emitting diodes (LEDs) offers advantages over other processing techniques and is therefore an active research area in both industrial and academic sectors. The processing of sapphire wafers is problematic because sapphire is a hard and brittle material. Semiconductor laser scribing processing suffers certain disadvantages that have yet to be overcome, thereby necessitating further investigation. In this work, a platform for controllable laser thermal cleavage was constructed. A sapphire LED wafer was modeled using the finite element method to simulate the thermal and stress distributions under different conditions. A guide groove cut by laser ablation before the cleavage process was observed to guide the crack extension and avoid deviation. The surface and cross section of sapphire wafers processed using controllable laser thermal cleavage were characterized by scanning electron microscopy and optical microscopy, and their morphology was compared to that of wafers processed using stealth dicing. The differences in luminous efficiency between substrates prepared using these two processing methods are explained.

Power Control and Monitoring Requirements for Thermal Vacuum/Thermal Balance Testing of the MAP Observatory

Science.gov (United States)

Johnson, Chris; Hinkle, R. Kenneth (Technical Monitor)

2002-01-01

The specific heater control requirements for the thermal vacuum and thermal balance testing of the Microwave Anisotropy Probe (MAP) Observatory at the Goddard Space Flight Center (GSFC) in Greenbelt, Maryland are described. The testing was conducted in the 10m wide x 18.3m high Space Environment Simulator (SES) Thermal Vacuum Facility. The MAP thermal testing required accurate quantification of spacecraft and fixture power levels while minimizing heater electrical emissions. The special requirements of the MAP test necessitated construction of five (5) new heater racks.

Controlling thermal chaos in the mantle by positive feedback from radiative thermal conductivity

Directory of Open Access Journals (Sweden)

F. Dubuffet

2002-01-01

Full Text Available The thermal conductivity of mantle materials has two components, the lattice component klat from phonons and the radiative component krad due to photons. These two contributions of variable thermal conductivity have a nonlinear dependence in the temperature, thus endowing the temperature equation in mantle convection with a strongly nonlinear character. The temperature derivatives of these two mechanisms have different signs, with ∂klat /∂T negative and dkrad /dT positive. This offers the possibility for the radiative conductivity to control the chaotic boundary layer instabilities developed in the deep mantle. We have parameterized the weight factor between krad and klat with a dimensionless parameter f , where f = 1 corresponds to the reference conductivity model. We have carried out two-dimensional, time-dependent calculations for variable thermal conductivity but constant viscosity in an aspect-ratio 6 box for surface Rayleigh numbers between 106 and 5 × 106. The averaged Péclet numbers of these flows lie between 200 and 2000. Along the boundary in f separating the chaotic and steady-state solutions, the number decreases and the Nusselt number increases with internal heating, illustrating the feedback between internal heating and radiative thermal conductivity. For purely basal heating situation, the time-dependent chaotic flows become stabilized for values of f of between 1.5 and 2. The bottom thermal boundary layer thickens and the surface heat flow increases with larger amounts of radiative conductivity. For magnitudes of internal heating characteristic of a chondritic mantle, much larger values of f , exceeding 10, are required to quench the bottom boundary layer instabilities. By isolating the individual conductive mechanisms, we have ascertained that the lattice conductivity is partly responsible for inducing boundary layer instabilities, while the radiative conductivity and purely depth-dependent conductivity exert a stabilizing

Process control and monitoring system: Thermal Power Plant Gacko

International Nuclear Information System (INIS)

Jeremovic, Dragan; Skoko, Maksim; Gjokanovic, Zdravko

2004-01-01

DCS Ovation system, manufactured by Westinghouse, USA, is described in this paper. Emphasize on concept of realization and basic characteristic in Thermal Power Plant Gacko is given in this paper. The most important, noticed by now, comparative effects and performances of new monitoring and control system according to classical monitoring and control system of 300 MW units Thermal Power Plant Gacko in Gacko, are given in the conclusion. (Author)

Automatic Thermal Control System with Temperature Difference or Derivation Feedback

Directory of Open Access Journals (Sweden)

Darina Matiskova

2016-02-01

Full Text Available Automatic thermal control systems seem to be non-linear systems with thermal inertias and time delay. A controller is also non-linear because its information and power signals are limited. The application of methods that are available to on-linear systems together with computer simulation and mathematical modelling creates a possibility to acquire important information about the researched system. This paper provides a new look at the heated system model and also designs the structure of the thermal system with temperature derivation feedback. The designed system was simulated by using a special software in Turbo Pascal. Time responses of this system are compared to responses of a conventional thermal system. The thermal system with temperature derivation feedback provides better transients, better quality of regulation and better dynamical properties.

Preterm infant thermal care: differing thermal environments produced by air versus skin servo-control incubators.

Science.gov (United States)

Thomas, K A; Burr, R

1999-06-01

Incubator thermal environments produced by skin versus air servo-control were compared. Infant abdominal skin and incubator air temperatures were recorded from 18 infants in skin servo-control and 14 infants in air servo-control (26- to 29-week gestational age, 14 +/- 2 days postnatal age) for 24 hours. Differences in incubator and infant temperature, neutral thermal environment (NTE) maintenance, and infant and incubator circadian rhythm were examined using analysis of variance and scatterplots. Skin servo-control resulted in more variable air temperature, yet more stable infant temperature, and more time within the NTE. Circadian rhythm of both infant and incubator temperature differed by control mode and the relationship between incubator and infant temperature rhythms was a function of control mode. The differences between incubator control modes extend beyond temperature stability and maintenance of NTE. Circadian rhythm of incubator and infant temperatures is influenced by incubator control.

Transient stress control of aeroengine disks based on active thermal management

International Nuclear Information System (INIS)

Ding, Shuiting; Wang, Ziyao; Li, Guo; Liu, Chuankai; Yang, Liu

2016-01-01

Highlights: • The essence of cooling in turbine system is a process of thermal management. • Active thermal management is proposed to control transient stress of disks. • The correlation between thermal load and transient stress of disks is built. • Stress level can be declined by actively adjusting the thermal load distribution. • Artificial temperature gradient can be used to counteract stress from rotating. - Abstract: The physical essence of cooling in the turbine system is a process of thermal management. In order to overcome the limits of passive thermal management based on thermal protection, the concept of active thermal management based on thermal load redistribution has been proposed. On this basis, this paper focuses on a near real aeroengine disk during a transient process and studies the stress control mechanism of active thermal management in transient conditions by a semi-analytical method. Active thermal management is conducted by imposing extra heating energy on the disk hub, which is represented by the coefficient of extra heat flow η. The results show that the transient stress level can be effectively controlled by actively adjusting the thermal load distribution. The decline ratio of the peak equivalent stress of the disk hub can be 9.0% for active thermal management load condition (η = 0.2) compared with passive condition (η = 0), even at a rotation speed of 10,000 r/min. The reason may be that the temperature distribution of the disk turns into an artificial V-shape because of the extra heating energy on the hub, and the resulting thermal stresses induced by the negative temperature gradients counteract parts of the stress from rotating.

Pump and Flow Control Subassembly of Thermal Control Subsystem for Photovoltaic Power Module

Science.gov (United States)

Motil, Brian; Santen, Mark A.

1993-01-01

The pump and flow control subassembly (PFCS) is an orbital replacement unit (ORU) on the Space Station Freedom photovoltaic power module (PVM). The PFCS pumps liquid ammonia at a constant rate of approximately 1170 kg/hr while providing temperature control by flow regulation between the radiator and the bypass loop. Also, housed within the ORU is an accumulator to compensate for fluid volumetric changes as well as the electronics and firmware for monitoring and control of the photovoltaic thermal control system (PVTCS). Major electronic functions include signal conditioning, data interfacing and motor control. This paper will provide a description of each major component within the PFCS along with performance test data. In addition, this paper will discuss the flow control algorithm and describe how the nickel hydrogen batteries and associated power electronics will be thermally controlled through regulation of coolant flow to the radiator.

Negative thermal expansion in functional materials: controllable thermal expansion by chemical modifications.

Science.gov (United States)

Chen, Jun; Hu, Lei; Deng, Jinxia; Xing, Xianran

2015-06-07

Negative thermal expansion (NTE) is an intriguing physical property of solids, which is a consequence of a complex interplay among the lattice, phonons, and electrons. Interestingly, a large number of NTE materials have been found in various types of functional materials. In the last two decades good progress has been achieved to discover new phenomena and mechanisms of NTE. In the present review article, NTE is reviewed in functional materials of ferroelectrics, magnetics, multiferroics, superconductors, temperature-induced electron configuration change and so on. Zero thermal expansion (ZTE) of functional materials is emphasized due to the importance for practical applications. The NTE functional materials present a general physical picture to reveal a strong coupling role between physical properties and NTE. There is a general nature of NTE for both ferroelectrics and magnetics, in which NTE is determined by either ferroelectric order or magnetic one. In NTE functional materials, a multi-way to control thermal expansion can be established through the coupling roles of ferroelectricity-NTE, magnetism-NTE, change of electron configuration-NTE, open-framework-NTE, and so on. Chemical modification has been proved to be an effective method to control thermal expansion. Finally, challenges and questions are discussed for the development of NTE materials. There remains a challenge to discover a "perfect" NTE material for each specific application for chemists. The future studies on NTE functional materials will definitely promote the development of NTE materials.

Performance of silvered Teflon (trademark) thermal control blankets on spacecraft

Science.gov (United States)

Pippin, Gary; Stuckey, Wayne; Hemminger, Carol

1993-01-01

Silverized Teflon (Ag/FEP) is a widely used passive thermal control material for space applications. The material has a very low alpha/e ratio (less than 0.1) for low operating temperatures and is fabricated with various FEP thicknesses (as the Teflon thickness increases, the emittance increases). It is low outgassing and, because of its flexibility, can be applied around complex, curved shapes. Ag/FEP has achieved multiyear lifetimes under a variety of exposure conditions. This has been demonstrated by the Long Duration Exposure Facility (LDEF), Solar Max, Spacecraft Charging at High Altitudes (SCATHA), and other flight experiments. Ag/FEP material has been held in place on spacecraft by a variety of methods: mechanical clamping, direct adhesive bonding of tapes and sheets, and by Velcro(TM) tape adhesively bonded to back surfaces. On LDEF, for example, 5-mil blankets held by Velcro(TM) and clamping were used for thermal control over 3- by 4-ft areas on each of 17 trays. Adhesively bonded 2- and 5-mil sheets were used on other LDEF experiments, both for thermal control and as tape to hold other thermal control blankets in place. Performance data over extended time periods are available from a number of flights. The observed effects on optical properties, mechanical properties, and surface chemistry will be summarized in this paper. This leads to a discussion of performance life estimates and other design lessons for Ag/FEP thermal control material.

CubeSat Form Factor Thermal Control Louvers

Data.gov (United States)

National Aeronautics and Space Administration — As small spacecraft become a part of NASA’s repertoire of missions, one reoccurring theme is an increased need for thermal control as power budgets increase and...

Study on the effect of shape-stabilized phase change materials on spacecraft thermal control in extreme thermal environment

International Nuclear Information System (INIS)

Wu, Wan-fan; Liu, Na; Cheng, Wen-long; Liu, Yi

2013-01-01

Highlights: ► A shape-stabilized PCM is used to protect the spacecraft attacked by high energy. ► Taking a satellite as example, it proves the solution given in the work is feasible. ► Low thermal conductivity makes the material above its thermal stability limit. ► It provides guidance on how to choose the shape-stabilized PCM for similar problems. - Abstract: In space, the emergencies such as short-term high heat flux is prone to cause spacecraft thermal control system faults, resulting in temperature anomalies of electronic equipment of the spacecraft and even failures in them. In order to protect the spacecraft attacked by the high energy, a new guard method is proposed. A shape-stabilized phase change material (PCM), which has high thermal conductivity and does not require being tightly packaged, is proposed to be used on the spacecraft. To prove the feasibility of using the material on spacecraft attacked by high energy, the thermal responses for spacecraft with shape-stabilized PCM are investigated in situations of normal and short-term high heat flux, in contrast to that with conventional thermal control system. The results indicate that the shape-stabilized PCM can effectively absorb the heat to prevent the thermal control system faults when the spacecraft’s outer heat flux changes dramatically and has no negative effect on spacecraft in normal heat flux. Additionally the effect of thermal conductivity of PCM on its application effectiveness is discussed

Mapping Thermal Habitat of Ectotherms Based on Behavioral Thermoregulation in a Controlled Thermal Environment

Science.gov (United States)

Fei, T.; Skidmore, A.; Liu, Y.

2012-07-01

Thermal environment is especially important to ectotherm because a lot of physiological functions rely on the body temperature such as thermoregulation. The so-called behavioural thermoregulation function made use of the heterogeneity of the thermal properties within an individual's habitat to sustain the animal's physiological processes. This function links the spatial utilization and distribution of individual ectotherm with the thermal properties of habitat (thermal habitat). In this study we modelled the relationship between the two by a spatial explicit model that simulates the movements of a lizard in a controlled environment. The model incorporates a lizard's transient body temperatures with a cellular automaton algorithm as a way to link the physiology knowledge of the animal with the spatial utilization of its microhabitat. On a larger spatial scale, 'thermal roughness' of the habitat was defined and used to predict the habitat occupancy of the target species. The results showed the habitat occupancy can be modelled by the cellular automaton based algorithm at a smaller scale, and can be modelled by the thermal roughness index at a larger scale.

Advances in thermal control and performance of the MMT M1 mirror

Science.gov (United States)

Gibson, J. D.; Williams, G. G.; Callahan, S.; Comisso, B.; Ortiz, R.; Williams, J. T.

2010-07-01

Strategies for thermal control of the 6.5-meter diameter borosilicate honeycomb primary (M1) mirror at the MMT Observatory have included: 1) direct control of ventilation system chiller setpoints by the telescope operator, 2) semiautomated control of chiller setpoints, using a fixed offset from the ambient temperature, and 3) most recently, an automated temperature controller for conditioned air. Details of this automated controller, including the integration of multiple chillers, heat exchangers, and temperature/dew point sensors, are presented here. Constraints and sanity checks for thermal control are also discussed, including: 1) mirror and hardware safety, 2) aluminum coating preservation, and 3) optimization of M1 thermal conditions for science acquisition by minimizing both air-to-glass temperature differences, which cause mirror seeing, and internal glass temperature gradients, which cause wavefront errors. Consideration is given to special operating conditions, such as high dew and frost points. Precise temperature control of conditioned ventilation air as delivered to the M1 mirror cell is also discussed. The performance of the new automated controller is assessed and compared to previous control strategies. Finally, suggestions are made for further refinement of the M1 mirror thermal control system and related algorithms.

Data on the interaction between thermal comfort and building control research.

Science.gov (United States)

Park, June Young; Nagy, Zoltan

2018-04-01

This dataset contains bibliography information regarding thermal comfort and building control research. In addition, the instruction of a data-driven literature survey method guides readers to reproduce their own literature survey on related bibliography datasets. Based on specific search terms, all relevant bibliographic datasets are downloaded. We explain the keyword co-occurrences of historical developments and recent trends, and the citation network which represents the interaction between thermal comfort and building control research. Results and discussions are described in the research article entitled "Comprehensive analysis of the relationship between thermal comfort and building control research - A data-driven literature review" (Park and Nagy, 2018).

Sensitivity of control times in function of core parameters and oscillations control in thermal nuclear systems

International Nuclear Information System (INIS)

Amorim, E.S. do; D'Oliveira, A.B.; Galvao, O.B.; Oyama, K.

1981-03-01

Sensitivity of control times to variation of a thermal reactor core parameters is defined by suitable changes in the power coefficient, core size and fuel enrichment. A control strategy is developed based on control theory concepts and on considerations of the physics of the problem. Digital diffusion theory simulation is described which tends to verify the control concepts considered, face dumped oscillations introduced in one thermal nuclear power system. The effectivity of the control actions, in terms of eliminating oscillations, provided guidelines for the working-group engaged in the analysis of the control rods and its optimal performance. (Author) [pt

Plasma effects on the passive external thermal control coating of Space Station Freedom

Science.gov (United States)

Carruth, Ralph, Jr.; Vaughn, Jason A.; Holt, James M.; Werp, Richard; Sudduth, Richard D.

1992-01-01

The current baseline chromic acid anodized thermal control coating on 6061-T6 aluminum meteoroid debris (M/D) shields for SSF has been evaluated. The degradation of the solar absorptance, alpha, and the thermal emittance, epsilon, of chromic acid anodized aluminum due to dielectric breakdown in plasma was measured to predict the on-orbit lifetime of the SSF M/D shields. The lifetime of the thermal control coating was based on the surface temperatures achieved with degradation of the thermal control properties, alpha and epsilon. The temperatures of each M/D shield from first element launch (FEL) through FEL+15 years were analyzed. It is shown that the baseline thermal control coating cannot withstand the -140 V potential between the conductive structure of the SSF and the current plasma environment.

Choosing Actuators for Automatic Control Systems of Thermal Power Plants

Energy Technology Data Exchange (ETDEWEB)

Gorbunov, A. I., E-mail: gor@tornado.nsk.ru [JSC “Tornado Modular Systems” (Russian Federation); Serdyukov, O. V. [Siberian Branch of the Russian Academy of Sciences, Institute of Automation and Electrometry (Russian Federation)

2015-03-15

Two types of actuators for automatic control systems of thermal power plants are analyzed: (i) pulse-controlled actuator and (ii) analog-controlled actuator with positioning function. The actuators are compared in terms of control circuit, control accuracy, reliability, and cost.

Fuzzy logic-based advanced on–off control for thermal comfort in residential buildings

International Nuclear Information System (INIS)

Kang, Chang-Soon; Hyun, Chang-Ho; Park, Mignon

2015-01-01

Highlights: • Fuzzy logic-based advanced on–off control is proposed. • An anticipative control mechanism is implemented by using fuzzy theory. • Novel thermal analysis program including solar irradiation as a factor is developed. • The proposed controller solves over-heating and under-heating thermal problems. • Solar energy compensation method is applied to compensate for the solar energy. - Abstract: In this paper, an advanced on–off control method based on fuzzy logic is proposed for maintaining thermal comfort in residential buildings. Due to the time-lag of the control systems and the late building thermal response, an anticipative control mechanism is required to reduce energy loss and thermal discomfort. The proposed controller is implemented based on an on–off controller combined with a fuzzy algorithm. On–off control was chosen over other conventional control methods because of its structural simplicity. However, because conventional on–off control has a fixed operating range and a limited ability for improvements in control performance, fuzzy theory can be applied to overcome these limitations. Furthermore, a fuzzy-based solar energy compensation algorithm can be applied to the proposed controller to compensate for the energy gained from solar radiation according to the time of day. Simulations were conducted to compare the proposed controller with a conventional on–off controller under identical external conditions such as outdoor temperature and solar energy; these simulations were carried out by using a previously reported thermal analysis program that was modified to consider such external conditions. In addition, experiments were conducted in a residential building called Green Home Plus, in which hydronic radiant floor heating is used; in these experiments, the proposed system performed better than a system employing conventional on–off control methods

0-π phase-controllable thermal Josephson junction

Science.gov (United States)

Fornieri, Antonio; Timossi, Giuliano; Virtanen, Pauli; Solinas, Paolo; Giazotto, Francesco

2017-05-01

Two superconductors coupled by a weak link support an equilibrium Josephson electrical current that depends on the phase difference ϕ between the superconducting condensates. Yet, when a temperature gradient is imposed across the junction, the Josephson effect manifests itself through a coherent component of the heat current that flows opposite to the thermal gradient for |ϕ| heat currents can be inverted by adding a π shift to ϕ. In the static electrical case, this effect has been obtained in a few systems, for example via a ferromagnetic coupling or a non-equilibrium distribution in the weak link. These structures opened new possibilities for superconducting quantum logic and ultralow-power superconducting computers. Here, we report the first experimental realization of a thermal Josephson junction whose phase bias can be controlled from 0 to π. This is obtained thanks to a superconducting quantum interferometer that allows full control of the direction of the coherent energy transfer through the junction. This possibility, in conjunction with the completely superconducting nature of our system, provides temperature modulations with an unprecedented amplitude of ∼100 mK and transfer coefficients exceeding 1 K per flux quantum at 25 mK. Then, this quantum structure represents a fundamental step towards the realization of caloritronic logic components such as thermal transistors, switches and memory devices. These elements, combined with heat interferometers and diodes, would complete the thermal conversion of the most important phase-coherent electronic devices and benefit cryogenic microcircuits requiring energy management, such as quantum computing architectures and radiation sensors.

Using geophysical techniques to control in situ thermal remediation

International Nuclear Information System (INIS)

Boyd, S.; Daily, W.; Ramirez, A.; Wilt, M.; Goldman, R.; Kayes, D.; Kenneally, K.; Udell, K.; Hunter, R.

1994-01-01

Monitoring the thermal and hydrologic processes that occur during thermal environmental remediation programs in near real-time provides essential information for controlling the process. Geophysical techniques played a crucial role in process control as well as for characterization during the recent Dynamic Underground Stripping Project demonstration in which several thousand gallons of gasoline were removed from heterogeneous soils both above and below the water table. Dynamic Underground Stripping combines steam injection and electrical heating for thermal enhancement with ground water pumping and vacuum extraction for contaminant removal. These processes produce rapid changes in the subsurface properties including changes in temperature fluid saturation, pressure and chemistry. Subsurface imaging methods are used to map the heated zones and control the thermal process. Temperature measurements made in wells throughout the field reveal details of the complex heating phenomena. Electrical resistance tomography (ERT) provides near real-time detailed images of the heated zones between boreholes both during electrical heating and steam injection. Borehole induction logs show close correlation with lithostratigraphy and, by identifying the more permeable gravel zones, can be used to predict steam movement. They are also useful in understanding the physical changes in the field and in interpreting the ERT images. Tiltmeters provide additional information regarding the shape of the steamed zones in plan view. They were used to track the growth of the steam front from individual injectors

Optimal control theory applied to fusion plasma thermal stabilization

International Nuclear Information System (INIS)

Sager, G.; Miley, G.; Maya, I.

1985-01-01

Many authors have investigated stability characteristics and performance of various burn control schemes. The work presented here represents the first application of optimal control theory to the problem of fusion plasma thermal stabilization. The objectives of this initial investigation were to develop analysis methods, demonstrate tractability, and present some preliminary results of optimal control theory in burn control research

Desiccant wheel thermal performance modeling for indoor humidity optimal control

International Nuclear Information System (INIS)

Wang, Nan; Zhang, Jiangfeng; Xia, Xiaohua

2013-01-01

Highlights: • An optimal humidity control model is formulated to control the indoor humidity. • MPC strategy is used to implement the optimal operation solution. • Practical applications of the MPC strategy is illustrated by the case study. - Abstract: Thermal comfort is an important concern in the energy efficiency improvement of commercial buildings. Thermal comfort research focuses mostly on temperature control, but humidity control is an important aspect to maintain indoor comfort too. In this paper, an optimal humidity control model (OHCM) is presented. Model predictive control (MPC) strategy is applied to implement the optimal operation of the desiccant wheel during working hours of a commercial building. The OHCM is revised to apply the MPC strategy. A case is studied to illustrate the practical applications of the MPC strategy

Full control and manipulation of heat signatures: cloaking, camouflage and thermal metamaterials.

Science.gov (United States)

Han, Tiancheng; Bai, Xue; Thong, John T L; Li, Baowen; Qiu, Cheng-Wei

2014-03-19

Thermal camouflage and cloaking can transform an actual heat signature into a pre-controlled one. A viable recipe for controlling and manipulating heat signatures using thermal metamaterials to empower cloaking and camouflage in heat conduction is demonstrated. The thermal signature of the object is thus metamorphosed and perceived as multiple targets with different geometries and compositions, with the original object cloaked. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Feedback control of thermal instability by compression and decompression

International Nuclear Information System (INIS)

Okamoto, M.; Hirano, K.; Amano, T.; Ohnishi, M.

1983-01-01

Active feedback control of the fusion output power by means of plasma compression-decompression is considered with the purpose of achieving steady-state plasma ignition in a tokamak. A simple but realistic feedback control system is modelled and zero-dimensional energy balance equations are solved numerically by taking into account the errors in the measurements, a procedure that is necessary for the feedback control. It is shown that the control can stabilize the thermal runaway completely and maintain steady-state operation without any significant change in major radius or thermal output power. Linear stability is analysed for a general type of scaling law, and the dependence of the stability conditions on the scaling law is studied. The possibility of load-following operation is considered. Finally, a one-dimensional analysis is applied to the large-aspect-ratio case. (author)

A Morphing Radiator for High-Turndown Thermal Control of Crewed Space Exploration Vehicles

Science.gov (United States)

Cognata, Thomas J.; Hardtl, Darren; Sheth, Rubik; Dinsmore, Craig

2015-01-01

Spacecraft designed for missions beyond low earth orbit (LEO) face a difficult thermal control challenge, particularly in the case of crewed vehicles where the thermal control system (TCS) must maintain a relatively constant internal environment temperature despite a vastly varying external thermal environment and despite heat rejection needs that are contrary to the potential of the environment. A thermal control system is in other words required to reject a higher heat load to warm environments and a lower heat load to cold environments, necessitating a quite high turndown ratio. A modern thermal control system is capable of a turndown ratio of on the order of 12:1, but for crew safety and environment compatibility these are massive multi-loop fluid systems. This paper discusses the analysis of a unique radiator design which employs the behavior of shape memory alloys (SMA) to vary the turndown of, and thus enable, a single-loop vehicle thermal control system for space exploration vehicles. This design, a morphing radiator, varies its shape in response to facesheet temperature to control view of space and primary surface emissivity. Because temperature dependence is inherent to SMA behavior, the design requires no accommodation for control, instrumentation, nor power supply in order to operate. Thermal and radiation modeling of the morphing radiator predict a turndown ranging from 11.9:1 to 35:1 independent of TCS configuration. Stress and deformation analyses predict the desired morphing behavior of the concept. A system level mass analysis shows that by enabling a single loop architecture this design could reduce the TCS mass by between 139 kg and 225 kg. The concept is demonstrated in proof-of-concept benchtop tests.

Development of Tailorable Electrically Conductive Thermal Control Material Systems

Science.gov (United States)

Deshpande, M. S.; Harada, Y.

1997-01-01

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and have been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties as well as mechanical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has added to already existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The objective of this program was to develop two types of passive electrically conductive TCMS. The first was a highly absorbing/emitting black surface and the second was a low (alpha(sub s)/epsilon(sub N)) type white surface. The surface resistance goals for the black absorber was 10(exp 4) to 10(exp 9) Omega/square, and for the white surfaces it was 10(exp 6) to 10(exp 10) Omega/square. Several material system concepts were suggested and evaluated for space environment stability and electrical performance characterization. Our efforts in designing and evaluating these material systems have resulted in several developments. New concepts, pigments and binders have been developed to provide new engineering quality TCMS. Some of these have already found application on space hardware, some are waiting to be recognized by thermal designers, and some require further detailed studies to become state-of-the-art for future space hardware and space structures. Our studies on baseline state-of-the-art materials and

Control of thermal therapies with moving power deposition field

International Nuclear Information System (INIS)

Arora, Dhiraj; Minor, Mark A; Skliar, Mikhail; Roemer, Robert B

2006-01-01

A thermal therapy feedback control approach to control thermal dose using a moving power deposition field is developed and evaluated using simulations. A normal tissue safety objective is incorporated in the controller design by imposing constraints on temperature elevations at selected normal tissue locations. The proposed control technique consists of two stages. The first stage uses a model-based sliding mode controller that dynamically generates an 'ideal' power deposition profile which is generally unrealizable with available heating modalities. Subsequently, in order to approximately realize this spatially distributed idealized power deposition, a constrained quadratic optimizer is implemented to compute intensities and dwell times for a set of pre-selected power deposition fields created by a scanned focused transducer. The dwell times for various power deposition profiles are dynamically generated online as opposed to the commonly employed a priori-decided heating strategies. Dynamic intensity and trajectory generation safeguards the treatment outcome against modelling uncertainties and unknown disturbances. The controller is designed to enforce simultaneous activation of multiple normal tissue temperature constraints by rapidly switching between various power deposition profiles. The hypothesis behind the controller design is that the simultaneous activation of multiple constraints substantially reduces treatment time without compromising normal tissue safety. The controller performance and robustness with respect to parameter uncertainties is evaluated using simulations. The results demonstrate that the proposed controller can successfully deliver the desired thermal dose to the target while maintaining the temperatures at the user-specified normal tissue locations at or below the maximum allowable values. Although demonstrated for the case of a scanned focused ultrasound transducer, the developed approach can be extended to other heating modalities with

Variable Emissive Smart Radiator for Dynamic Thermal Control

Data.gov (United States)

National Aeronautics and Space Administration — Trending towards reduced power and mass budget on satellites with a longer mission life, there is a need for a reliable thermal control system that is more efficient...

Peak load shifting control using different cold thermal energy storage facilities in commercial buildings: A review

International Nuclear Information System (INIS)

Sun, Yongjun; Wang, Shengwei; Xiao, Fu; Gao, Diance

2013-01-01

Highlights: • Little study reviews the load shifting control using different facilities. • This study reviews load shifting control using building thermal mass. • This study reviews load shifting control using thermal energy storage systems. • This study reviews load shifting control using phase change material. • Efforts for developing more applicable load shifting control are addressed. - Abstract: For decades, load shifting control, one of most effective peak demand management methods, has attracted increasing attentions from both researchers and engineers. Different load shifting control strategies have been developed when diverse cold thermal energy storage facilities are used in commercial buildings. The facilities include building thermal mass (BTM), thermal energy storage system (TES) and phase change material (PCM). Little study has systematically reviewed these load shifting control strategies and therefore this study presents a comprehensive review of peak load shifting control strategies using these thermal energy storage facilities in commercial buildings. The research and applications of the load shifting control strategies are presented and discussed. The further efforts needed for developing more applicable load shifting control strategies using the facilities are also addressed

PID temperature controller in pig nursery: spatial characterization of thermal environment

Science.gov (United States)

de Souza Granja Barros, Juliana; Rossi, Luiz Antonio; Menezes de Souza, Zigomar

2018-05-01

The use of enhanced technologies of temperature control can improve the thermal conditions in environments of livestock facilities. The objective of this study was to evaluate the spatial distribution of the thermal environment variables in a pig nursery with a heating system with two temperature control technologies based on the geostatistical analysis. The following systems were evaluated: overhead electrical resistance with Proportional, Integral, and Derivative (PID) controller and overhead electrical resistance with a thermostat. We evaluated the climatic variables: dry bulb temperature (Tbs), air relative humidity (RH), temperature and humidity index (THI), and enthalpy in the winter, at 7:00, 12:00, and 18:00 h. The spatial distribution of these variables was mapped by kriging. The results showed that the resistance heating system with PID controllers improved the thermal comfort conditions in the pig nursery in the coldest hours, maintaining the spatial distribution of the air temperature more homogeneous in the pen. During the hottest weather, neither system provided comfort.

PID temperature controller in pig nursery: spatial characterization of thermal environment

Science.gov (United States)

de Souza Granja Barros, Juliana; Rossi, Luiz Antonio; Menezes de Souza, Zigomar

2017-11-01

The use of enhanced technologies of temperature control can improve the thermal conditions in environments of livestock facilities. The objective of this study was to evaluate the spatial distribution of the thermal environment variables in a pig nursery with a heating system with two temperature control technologies based on the geostatistical analysis. The following systems were evaluated: overhead electrical resistance with Proportional, Integral, and Derivative (PID) controller and overhead electrical resistance with a thermostat. We evaluated the climatic variables: dry bulb temperature (Tbs), air relative humidity (RH), temperature and humidity index (THI), and enthalpy in the winter, at 7:00, 12:00, and 18:00 h. The spatial distribution of these variables was mapped by kriging. The results showed that the resistance heating system with PID controllers improved the thermal comfort conditions in the pig nursery in the coldest hours, maintaining the spatial distribution of the air temperature more homogeneous in the pen. During the hottest weather, neither system provided comfort.

PID temperature controller in pig nursery: spatial characterization of thermal environment.

Science.gov (United States)

de Souza Granja Barros, Juliana; Rossi, Luiz Antonio; Menezes de Souza, Zigomar

2017-11-28

The use of enhanced technologies of temperature control can improve the thermal conditions in environments of livestock facilities. The objective of this study was to evaluate the spatial distribution of the thermal environment variables in a pig nursery with a heating system with two temperature control technologies based on the geostatistical analysis. The following systems were evaluated: overhead electrical resistance with Proportional, Integral, and Derivative (PID) controller and overhead electrical resistance with a thermostat. We evaluated the climatic variables: dry bulb temperature (Tbs), air relative humidity (RH), temperature and humidity index (THI), and enthalpy in the winter, at 7:00, 12:00, and 18:00 h. The spatial distribution of these variables was mapped by kriging. The results showed that the resistance heating system with PID controllers improved the thermal comfort conditions in the pig nursery in the coldest hours, maintaining the spatial distribution of the air temperature more homogeneous in the pen. During the hottest weather, neither system provided comfort.

Different Approaches to Control of TISO Thermal System

Directory of Open Access Journals (Sweden)

Jaroslava KRÁLOVÁ

2009-06-01

Full Text Available The contribution is aimed on problematic of multivariable control. Multivariable system can be controlled by multivariable controller or we can use decentralized control. Control of thermal system with two inputs and one output is shown in the paper. The goal of paper is to find what sort of results we can get by classical approaches and by more sophisticated strategies. Two discrete-time PID controllers are selected as a representative of classical approach and split-range with discrete-time PID controller is selected as a representative of more sophisticated strategy. Control strategies are compared in the view of control quality and costs, information and knowledge required by control design and application.

Modeling and analysis of a robust thermal control system based on forced convection thermal switches

Science.gov (United States)

Williams, Andrew D.; Palo, Scott E.

2006-05-01

There is a critical need, not just in the Department of Defense (DOD) but the entire space industry, to reduce the development time and overall cost of satellite missions. To that end, the DOD is actively pursuing the capability to reduce the deployment time of a new system from years to weeks or even days. The goal is to provide the advantages space affords not just to the strategic planner but also to the battlefield commanders. One of the most challenging aspects of this problem is the satellite's thermal control system (TCS). Traditionally the TCS must be vigorously designed, analyzed, tested, and optimized from the ground up for every satellite mission. This "reinvention of the wheel" is costly and time intensive. The next generation satellite TCS must be modular and scalable in order to cover a wide range of applications, orbits, and mission requirements. To meet these requirements a robust thermal control system utilizing forced convection thermal switches was investigated. The problem was investigated in two separate stages. The first focused on the overall design of the bus. The second stage focused on the overarching bus architecture and the design impacts of employing a thermal switch based TCS design. For the hot case, the fan provided additional cooling to increase the heat transfer rate of the subsystem. During the cold case, the result was a significant reduction in survival heater power.

PID temperature controller in pig nursery: improvements in performance, thermal comfort, and electricity use.

Science.gov (United States)

de Souza Granja Barros, Juliana; Rossi, Luiz Antonio; Sartor, Karina

2016-08-01

The use of smarter temperature control technologies in heating systems can optimize the use of electric power and performance of piglets. Two control technologies of a resistive heating system were assessed in a pig nursery: a PID (proportional, integral, and derivative) controller and a thermostat. The systems were evaluated regarding thermal environment, piglet performance, and use of electric power for 99 days. The heating system with PID controller improved the thermal environment conditions and was significantly (P PID-controlled heating system is more efficient in electricity use and provides better conditions for thermal comfort and animal performance than heating with thermostat.

Kinetically controlled thermal response of beta2-microglobulin amyloid fibrils.

Science.gov (United States)

Sasahara, Kenji; Naiki, Hironobu; Goto, Yuji

2005-09-23

Calorimetric measurements were carried out using a differential scanning calorimeter in the temperature range from 10 to 120 degrees C for characterizing the thermal response of beta2-microglobulin amyloid fibrils. The thermograms of amyloid fibril solution showed a remarkably large decrease in heat capacity that was essentially released upon the thermal unfolding of the fibrils, in which the magnitude of negative heat capacity change was not explicable in terms of the current accessible surface area model of protein structural thermodynamics. The heat capacity-temperature curve of amyloid fibrils prior to the fibril unfolding exhibited an unusual dependence on the fibril concentration and the heating rate. Particularly, the heat needed to induce the thermal response was found to be linearly dependent on the heating rate, indicating that its thermal response is under a kinetic control and precluding the interpretation in terms of equilibrium thermodynamics. Furthermore, amyloid fibrils of amyloid beta peptides also exhibited a heating rate-dependent exothermic process before the fibril unfolding, indicating that the kinetically controlled thermal response may be a common phenomenon to amyloid fibrils. We suggest that the heating rate-dependent negative change in heat capacity is coupled to the association of amyloid fibrils with characteristic hydration pattern.

Weld Nugget Temperature Control in Thermal Stir Welding

Science.gov (United States)

Ding, R. Jeffrey (Inventor)

2014-01-01

A control system for a thermal stir welding system is provided. The control system includes a sensor and a controller. The sensor is coupled to the welding system's containment plate assembly and generates signals indicative of temperature of a region adjacent and parallel to the welding system's stir rod. The controller is coupled to the sensor and generates at least one control signal using the sensor signals indicative of temperature. The controller is also coupled to the welding system such that at least one of rotational speed of the stir rod, heat supplied by the welding system's induction heater, and feed speed of the welding system's weld material feeder are controlled based on the control signal(s).

Nuclear thermal rocket engine operation and control

International Nuclear Information System (INIS)

Gunn, S.V.; Savoie, M.T.; Hundal, R.

1993-06-01

The operation of a typical Rover/Nerva-derived nuclear thermal rocket (NTR) engine is characterized and the control requirements of the NTR are defined. A rationale for the selection of a candidate diverse redundant NTR engine control system is presented and the projected component operating requirements are related to the state of the art of candidate components and subsystems. The projected operational capabilities of the candidate system are delineated for the startup, full-thrust, shutdown, and decay heat removal phases of the engine operation. 9 refs

Film-Evaporation MEMS Tunable Array for Picosat Propulsion and Thermal Control

Science.gov (United States)

Alexeenko, Alina; Cardiff, Eric; Martinez, Andres; Petro, Andrew

2015-01-01

The Film-Evaporation MEMS Tunable Array (FEMTA) concept for propulsion and thermal control of picosats exploits microscale surface tension effect in conjunction with temperature- dependent vapor pressure to realize compact, tunable and low-power thermal valving system. The FEMTA is intended to be a self-contained propulsion unit requiring only a low-voltage DC power source to operate. The microfabricated thermal valving and very-high-integration level enables fast high-capacity cooling and high-resolution, low-power micropropulsion for picosats that is superior to existing smallsat micropropulsion and thermal management alternatives.

Joint excitation and reactive power control in thermal power plant

Directory of Open Access Journals (Sweden)

Dragosavac Jasna

2013-01-01

Full Text Available The coordinated voltage and reactive power controller, designed for the thermal power plant, is presented in the paper. A brief explanation of the need for such device is given and justification for commissioning of such equipment is outlined. After short description of the theoretical background of the proposed control design, the achieved features of the commissioned equipment are fully given. Achieved performances are illustrated by recorded reactive power and bus voltage responses after commissioning of the described equipment into the largest thermal power plant in Serbia. As it can be seen in presented records, all design targets are met.

Simulation of thermal environment in a three-layer vinyl greenhouse by natural ventilation control

Science.gov (United States)

Jin, Tea-Hwan; Shin, Ki-Yeol; Yoon, Si-Won; Im, Yong-Hoon; Chang, Ki-Chang

2017-11-01

A high energy, efficient, harmonious, ecological greenhouse has been highlighted by advanced future agricultural technology recently. This greenhouse is essential for expanding the production cycle toward growth conditions through combined thermal environmental control. However, it has a negative effect on farming income via huge energy supply expenses. Because not only production income, but operating costs related to thermal load for thermal environment control is important in farming income, it needs studies such as a harmonious ecological greenhouse using natural ventilation control. This study is simulated for energy consumption and thermal environmental conditions in a three-layered greenhouse by natural ventilation using window opening. A virtual 3D model of a three-layered greenhouse was designed based on the real one in the Gangneung area. This 3D model was used to calculate a thermal environment state such as indoor temperature, relative humidity, and thermal load in the case of a window opening rate from 0 to 100%. There was also a heat exchange operated for heating or cooling controlled by various setting temperatures. The results show that the cooling load can be reduced by natural ventilation control in the summer season, and the heat exchange capacity for heating can also be simulated for growth conditions in the winter season.

Simulation of thermal environment in a three-layer vinyl greenhouse by natural ventilation control

Directory of Open Access Journals (Sweden)

Jin Tea-Hwan

2017-01-01

Full Text Available A high energy, efficient, harmonious, ecological greenhouse has been highlighted by advanced future agricultural technology recently. This greenhouse is essential for expanding the production cycle toward growth conditions through combined thermal environmental control. However, it has a negative effect on farming income via huge energy supply expenses. Because not only production income, but operating costs related to thermal load for thermal environment control is important in farming income, it needs studies such as a harmonious ecological greenhouse using natural ventilation control. This study is simulated for energy consumption and thermal environmental conditions in a three-layered greenhouse by natural ventilation using window opening. A virtual 3D model of a three-layered greenhouse was designed based on the real one in the Gangneung area. This 3D model was used to calculate a thermal environment state such as indoor temperature, relative humidity, and thermal load in the case of a window opening rate from 0 to 100%. There was also a heat exchange operated for heating or cooling controlled by various setting temperatures. The results show that the cooling load can be reduced by natural ventilation control in the summer season, and the heat exchange capacity for heating can also be simulated for growth conditions in the winter season.

Automatic control of human thermal comfort with a liquid-cooled garment

Science.gov (United States)

Kuznetz, L. H.

1977-01-01

Water cooling in a liquid-cooled garment is used to maintain the thermal comfort of crewmembers during extravehicular activity. The feasibility of a simple control that will operate automatically to maintain the thermal comfort is established. Data on three test subjects are included to support the conclusion that heat balance can be maintained well within allowable medical limits. The controller concept was also successfully demonstrated for ground-based applications and shows potential for any tasks involving the use of liquid-cooled garments.

Control of surface thermal scratch of strip in tandem cold rolling

Science.gov (United States)

Chen, Jinshan; Li, Changsheng

2014-07-01

The thermal scratch seriously affects the surface quality of the cold rolled stainless steel strip. Some researchers have carried out qualitative and theoretical studies in this field. However, there is currently a lack of research on effective forecast and control of thermal scratch defects in practical production, especially in tandem cold rolling. In order to establish precise mathematical model of oil film thickness in deformation zone, the lubrication in cold rolling process of SUS410L stainless steel strip is studied, and major factors affecting oil film thickness are also analyzed. According to the principle of statistics, mathematical model of critical oil film thickness in deformation zone for thermal scratch is built, with fitting and regression analytical method, and then based on temperature comparison method, the criterion for deciding thermal scratch defects is put forward. Storing and calling data through SQL Server 2010, a software on thermal scratch defects control is developed through Microsoft Visual Studio 2008 by MFC technique for stainless steel in tandem cold rolling, and then it is put into practical production. Statistics indicate that the hit rate of thermal scratch is as high as 92.38%, and the occurrence rate of thermal scratch is decreased by 89.13%. Owing to the application of the software, the rolling speed is increased by approximately 9.3%. The software developed provides an effective solution to the problem of thermal scratch defects in tandem cold rolling, and helps to promote products surface quality of stainless steel strips in practical production.

Optimization of Thermal Object Nonlinear Control Systems by Energy Efficiency Criterion.

Science.gov (United States)

Velichkin, Vladimir A.; Zavyalov, Vladimir A.

2018-03-01

This article presents the results of thermal object functioning control analysis (heat exchanger, dryer, heat treatment chamber, etc.). The results were used to determine a mathematical model of the generalized thermal control object. The appropriate optimality criterion was chosen to make the control more energy-efficient. The mathematical programming task was formulated based on the chosen optimality criterion, control object mathematical model and technological constraints. The “maximum energy efficiency” criterion helped avoid solving a system of nonlinear differential equations and solve the formulated problem of mathematical programming in an analytical way. It should be noted that in the case under review the search for optimal control and optimal trajectory reduces to solving an algebraic system of equations. In addition, it is shown that the optimal trajectory does not depend on the dynamic characteristics of the control object.

Ultraviolet and visible BRDF data on spacecraft thermal control and optical baffle materials

Science.gov (United States)

Viehmann, W.; Predmore, R. E.

1987-01-01

Bidirectional scattering functions of numerous optical baffle materials and of spacecraft thermal control coatings and surfaces are presented. Measurements were made at 254 nm and at 633 nm. The coatings and surfaces include high-reflectance white paints, low-reflectance optical blacks, thermal control blankets, and various conversion coatings on aluminum.

Thermal Storage Power Balancing with Model Predictive Control

DEFF Research Database (Denmark)

Halvgaard, Rasmus; Poulsen, Niels Kjølstad; Madsen, Henrik

2013-01-01

The method described in this paper balances power production and consumption with a large number of thermal loads. Linear controllers are used for the loads to track a temperature set point, while Model Predictive Control (MPC) and model estimation of the load behavior are used for coordination....... The total power consumption of all loads is controlled indirectly through a real-time price. The MPC incorporates forecasts of the power production and disturbances that influence the loads, e.g. time-varying weather forecasts, in order to react ahead of time. A simulation scenario demonstrates...

Experimental results of thermally controlled superconducting switches for high frequency operation

International Nuclear Information System (INIS)

Mulder, G.B.J.; IerAvest, D.; Tenkate, H.H.J.; Krooshoop, H.J.G.; Van de Klundert, L.

1988-01-01

The aim of this study is to develop thermally controlled switches which are to be used in superconducting rectifiers operating at a few hertz and 1 kA. Usually, the operating frequency of thermally controlled rectifiers is limited to about 0.1 Hz due to the thermal recovery times of the switches. The thermal switches have to satisfy two conditions which are specific for the application in a superconducting rectifier: a) they have to operate in the repetitive mode so beside short activation times, fast recovery times of the switches are equally important, b) the power required to effect and maintain the normal state of the switches should be low since it will determine the rectifier efficiency. To what extent these obviously conflicting demands can be satisfied depends on the material and geometry of the switch. This paper presents a theoretical model of the thermal behaviour of a switch. The calculations are compared with experimental results of several switches having recovery times between 40 and 200 ms. Also, the feasibility of such switches for application in superconducting rectifiers operating at a few hertz with an acceptable efficiency is demonstrated

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.

Occupant feedback based model predictive control for thermal comfort and energy optimization: A chamber experimental evaluation

International Nuclear Information System (INIS)

Chen, Xiao; Wang, Qian; Srebric, Jelena

2016-01-01

Highlights: • This study evaluates an occupant-feedback driven Model Predictive Controller (MPC). • The MPC adjusts indoor temperature based on a dynamic thermal sensation (DTS) model. • A chamber model for predicting chamber air temperature is developed and validated. • Experiments show that MPC using DTS performs better than using Predicted Mean Vote. - Abstract: In current centralized building climate control, occupants do not have much opportunity to intervene the automated control system. This study explores the benefit of using thermal comfort feedback from occupants in the model predictive control (MPC) design based on a novel dynamic thermal sensation (DTS) model. This DTS model based MPC was evaluated in chamber experiments. A hierarchical structure for thermal control was adopted in the chamber experiments. At the high level, an MPC controller calculates the optimal supply air temperature of the chamber heating, ventilation, and air conditioning (HVAC) system, using the feedback of occupants’ votes on thermal sensation. At the low level, the actual supply air temperature is controlled by the chiller/heater using a PI control to achieve the optimal set point. This DTS-based MPC was also compared to an MPC designed based on the Predicted Mean Vote (PMV) model for thermal sensation. The experiment results demonstrated that the DTS-based MPC using occupant feedback allows significant energy saving while maintaining occupant thermal comfort compared to the PMV-based MPC.

Performance Assessment of Low-Temperature Thermal Storage with Electromagnetic Control

Directory of Open Access Journals (Sweden)

Ya-Wei Lee

2014-08-01

Full Text Available This study presents electromagnetic-controlled thermal storage (ECTS that can be directly implemented in strategies of low-temperature waste heat recovery for energy-consuming equipment. A magnetic nanofluid (MNF prepared from fine iron ferrite ferromagnetic particles is recommended as a latent heat medium (LHM. During electromagnetic induction, local flow fluctuations are generated and thermal convection in the MNF can be enhanced. The achieved results demonstrated that ECTS has a wide operational range and an optimum storage efficiency of 84.46%. Thus, a self-perturbation mode used to enhance thermal energy transportation can be designed for numerous waste heat management applications.

A thermal control system for long-term survival of scientific instruments on lunar surface

Energy Technology Data Exchange (ETDEWEB)

Ogawa, K., E-mail: ogawa@astrobio.k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba (Japan); Iijima, Y.; Tanaka, S. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa (Japan); Sakatani, N. [The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa (Japan); Otake, H. [JAXA Space Exploration Center, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa (Japan)

2014-03-15

A thermal control system is being developed for scientific instruments placed on the lunar surface. This thermal control system, Lunar Mission Survival Module (MSM), was designed for scientific instruments that are planned to be operated for over a year in the future Japanese lunar landing mission SELENE-2. For the long-term operations, the lunar surface is a severe environment because the soil (regolith) temperature varies widely from nighttime −200 degC to daytime 100 degC approximately in which space electronics can hardly survive. The MSM has a tent of multi-layered insulators and performs a “regolith mound”. Temperature of internal devices is less variable just like in the lunar underground layers. The insulators retain heat in the regolith soil in the daylight, and it can keep the device warm in the night. We conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. Thermal vacuum tests were also conducted by using a thermal evaluation model in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The numerical and experimental results indicated a sufficient survivability potential of the concept of our thermal control system.

A thermal control system for long-term survival of scientific instruments on lunar surface.

Science.gov (United States)

Ogawa, K; Iijima, Y; Sakatani, N; Otake, H; Tanaka, S

2014-03-01

A thermal control system is being developed for scientific instruments placed on the lunar surface. This thermal control system, Lunar Mission Survival Module (MSM), was designed for scientific instruments that are planned to be operated for over a year in the future Japanese lunar landing mission SELENE-2. For the long-term operations, the lunar surface is a severe environment because the soil (regolith) temperature varies widely from nighttime -200 degC to daytime 100 degC approximately in which space electronics can hardly survive. The MSM has a tent of multi-layered insulators and performs a "regolith mound". Temperature of internal devices is less variable just like in the lunar underground layers. The insulators retain heat in the regolith soil in the daylight, and it can keep the device warm in the night. We conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. Thermal vacuum tests were also conducted by using a thermal evaluation model in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The numerical and experimental results indicated a sufficient survivability potential of the concept of our thermal control system.

A thermal control system for long-term survival of scientific instruments on lunar surface

International Nuclear Information System (INIS)

Ogawa, K.; Iijima, Y.; Tanaka, S.; Sakatani, N.; Otake, H.

2014-01-01

A thermal control system is being developed for scientific instruments placed on the lunar surface. This thermal control system, Lunar Mission Survival Module (MSM), was designed for scientific instruments that are planned to be operated for over a year in the future Japanese lunar landing mission SELENE-2. For the long-term operations, the lunar surface is a severe environment because the soil (regolith) temperature varies widely from nighttime −200 degC to daytime 100 degC approximately in which space electronics can hardly survive. The MSM has a tent of multi-layered insulators and performs a “regolith mound”. Temperature of internal devices is less variable just like in the lunar underground layers. The insulators retain heat in the regolith soil in the daylight, and it can keep the device warm in the night. We conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. Thermal vacuum tests were also conducted by using a thermal evaluation model in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The numerical and experimental results indicated a sufficient survivability potential of the concept of our thermal control system

An automatic energy-saving and thermal monitoring/controlling system for a pond

Directory of Open Access Journals (Sweden)

Cheng Ching-Chien

2017-01-01

Full Text Available Because of low temperatures and oxygen in cold water, fish will die when cold currents arrive. This will cause tremendous loss of money. In order reduce the cooling of the pond, an automatic thermal detecting and cold-roofing system using a wind-proofing device, heaters, and thermal detectors is proposed. To reduce heat loss due to thermal convection above the pond surface, a motor-driven wind-proofing device automatically controlled by a PLC controller is adopted. Here, the wind-proofing device, thermal detectors, and heating system are connected to the PLC controller. The PLC will also be connected to the PC interface. The temperature thresholds used to trigger the heater and the wind proofing device can be set at the PC interface. Two options for manipulating the heating and the automatic heating can be selected. The related wind-proofing area and the number of heaters will be determined according to the current temperature. Moreover, the PLC can be wirelessly connected to the server PC in the control room. The pond keeper can monitor everything online and control the pond water's temperature. With this, the problem of fish dying in a cold wave can be solved. Consequently, to reduce the electrical exhaust when heating up the pond water, green energy, solar energy and wind energy, is used.

Robust multi-model predictive control of multi-zone thermal plate system

Directory of Open Access Journals (Sweden)

Poom Jatunitanon

2018-02-01

Full Text Available A modern controller was designed by using the mathematical model of a multi–zone thermal plate system. An important requirement for this type of controller is that it must be able to keep the temperature set-point of each thermal zone. The mathematical model used in the design was determined through a system identification process. The results showed that when the operating condition is changed, the performance of the controller may be reduced as a result of the system parameter uncertainties. This paper proposes a weighting technique of combining the robust model predictive controller for each operating condition into a single robust multi-model predictive control. Simulation and experimental results showed that the proposed method performed better than the conventional multi-model predictive control in rise time of transient response, when used in a system designed to work over a wide range of operating conditions.

A Multi-Environment Thermal Control System With Freeze-Tolerant Radiator

Science.gov (United States)

Chen, Weibo; Fogg, David; Mancini, Nick; Steele, John; Quinn, Gregory; Bue, Grant; Littibridge, Sean

2013-01-01

Future space exploration missions require advanced thermal control systems (TCS) to dissipate heat from spacecraft, rovers, or habitats operating in environments that can vary from extremely hot to extremely cold. A lightweight, reliable TCS is being developed to effectively control cabin and equipment temperatures under widely varying heat loads and ambient temperatures. The system uses freeze-tolerant radiators, which eliminate the need for a secondary circulation loop or heat pipe systems. Each radiator has a self-regulating variable thermal conductance to its ambient environment. The TCS uses a nontoxic, water-based working fluid that is compatible with existing lightweight aluminum heat exchangers. The TCS is lightweight, compact, and requires very little pumping power. The critical characteristics of the core enabling technologies were demonstrated. Functional testing with condenser tubes demonstrated the key operating characteristics required for a reliable, freeze-tolerant TCS, namely (1) self-regulating thermal conductance with short transient responses to varying thermal loads, (2) repeatable performance through freeze-thaw cycles, and (3) fast start-up from a fully frozen state. Preliminary coolant tests demonstrated that the corrosion inhibitor in the water-based coolant can reduce the corrosion rate on aluminum by an order of magnitude. Performance comparison with state-of-the-art designs shows significant mass and power saving benefits of this technology.

Passive Set-Point Thermal Control Skin for Spacecraft, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Current manned and unmanned spacecraft require sophisticated thermal control technologies to keep systems at temperatures within their proper operating ranges....

Towards the control of car underhood thermal conditions

International Nuclear Information System (INIS)

Khaled, Mahmoud; Harambat, Fabien; Peerhossaini, Hassan

2011-01-01

The present paper reports an experimental study of the aerothermal phenomena in the vehicle underhood compartment as investigated by measuring temperature, convective heat flux, and radiative heat flux. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France. The underhood space is instrumented by 120 surface and air thermocouples and 20 fluxmeters. Measurements are performed for three thermal functioning conditions while the engine is in operation and the front wheels are positioned on the test facility with power-absorption-controlled rollers. In the thermal analysis, particular attention is given to measuring absorbed convective heat fluxes at component surfaces. It is shown that, in some components, the outside air entering the engine compartment (for cooling certain components) can in fact heat other components. This problem arises from the underhood architecture, specifically the positioning of some components downstream of warmer components in the same airflow. Optimized thermal management suggests placing these components further upstream or isolating them from the hot stream by deflectors. Given style constraints, however, the use of air deflectors is more suitable than underhood architectural changes. Much of the present paper is devoted to heat flux analysis of the specific thermal behaviours in the underhood compartment (especially the absorption of convective heat fluxes) and to a description of a new control approach exploiting air deflectors to optimize underhood aerothermal management. - Research highlights: → We present a physical analysis of particular underhood aerothermal behaviors. → In this analysis, convective heat flux absorption should be noted. → A new optimization procedure based on this physical analysis is proposed. → It entails airflow redistribution in the underhood through deflectors. → The new procedures are simple and easy to implement in the car underhood.

Laboratory electron exposure of TSS-1 thermal control coating

Science.gov (United States)

Vaughn, J. A.; Mccollum, M.; Carruth, M. R., Jr.

1995-01-01

RM400, a conductive thermal control coating, was developed for use on the exterior shell of the tethered satellite. Testing was performed by the Engineering Physics Division to quantify effects of the space environment on this coating and its conductive and optical properties. Included in this testing was exposure of RM400 to electrons with energies ranging from 0.1 to 1 keV, to simulate electrons accelerated from the ambient space plasma when the tethered satellite is fully deployed. During this testing, the coating was found to luminesce, and a prolonged exposure of the coating to high-energy electrons caused the coating to darken. This report describes the tests done to quantify the degradation of the thermal control properties caused by electron exposure and to measure the luminescence as a function of electron energy and current density to the satellite.

Effect of Personal Control over Thermal Environment in a Laboratorium Setting

DEFF Research Database (Denmark)

Kulve, M. te; Boerstra, A. C.; Toftum, Jørn

Field studies have demonstrated that personal control over the indoor climate may increase comfort and could reduce SBS symptoms. A laboratory study was performed to investigate if being in control over the thermal environment influences comfort, symptoms and performance. The central hypothesis...... was that human responses to a thermal indoor environment depend on the availability of control opportunities. This was tested in a field lab where subjects had a personal desk fan with a stepless controller at their workplace. Two conditions were tested: one (the first) with individual control and one without......, but with identical indoor climate exposure as recorded during the first session. During both experimental conditions, 23 subjects were exposed for 120 min to an operative temperature of 28 °C and they were provided with a personal desk fan. During the first exposure subjects were allowed to adjust air velocity (and...

A Tunable Mid-Infrared Solid-State Laser with a Compact Thermal Control System

Directory of Open Access Journals (Sweden)

Deyang Yu

2018-05-01

Full Text Available Tunable mid-infrared lasers are widely used in laser spectroscopy, gas sensing and many other related areas. In order to solve heat dissipation problems and improve the environmental temperature adaptability of solid-state laser sources, a tunable all-fiber laser pumped optical parametric oscillator (OPO was established, and a compact thermal control system based on thermoelectric coolers, an automatic temperature control circuit, cooling fins, fans and heat pipes was integrated and designed for the laser. This system is compact, light and air-cooling which satisfies the demand for miniaturization of lasers. A mathematical model and method was established to estimate the cooling capacity of this thermal control system under different ambient environments. A finite-element model was built and simulated to analyze the thermal transfer process. Experiments in room and high temperature environments were carried out and showed that the substrate temperature of a pump module could be maintained at a stable value with controlled precision to 0.2 degrees, while the output power stability of the laser was within ±1%. The experimental results indicate that this compact air-cooling thermal control system could effectively solve the heat dissipation problem of mid-infrared solid-state lasers with a one hundred watts level pump module in room and high temperature environments.

Predictive Optimal Control of Active and Passive Building Thermal Storage Inventory

Energy Technology Data Exchange (ETDEWEB)

Gregor P. Henze; Moncef Krarti

2005-09-30

Cooling of commercial buildings contributes significantly to the peak demand placed on an electrical utility grid. Time-of-use electricity rates encourage shifting of electrical loads to off-peak periods at night and weekends. Buildings can respond to these pricing signals by shifting cooling-related thermal loads either by precooling the building's massive structure or the use of active thermal energy storage systems such as ice storage. While these two thermal batteries have been engaged separately in the past, this project investigated the merits of harnessing both storage media concurrently in the context of predictive optimal control. To pursue the analysis, modeling, and simulation research of Phase 1, two separate simulation environments were developed. Based on the new dynamic building simulation program EnergyPlus, a utility rate module, two thermal energy storage models were added. Also, a sequential optimization approach to the cost minimization problem using direct search, gradient-based, and dynamic programming methods was incorporated. The objective function was the total utility bill including the cost of reheat and a time-of-use electricity rate either with or without demand charges. An alternative simulation environment based on TRNSYS and Matlab was developed to allow for comparison and cross-validation with EnergyPlus. The initial evaluation of the theoretical potential of the combined optimal control assumed perfect weather prediction and match between the building model and the actual building counterpart. The analysis showed that the combined utilization leads to cost savings that is significantly greater than either storage but less than the sum of the individual savings. The findings reveal that the cooling-related on-peak electrical demand of commercial buildings can be considerably reduced. A subsequent analysis of the impact of forecasting uncertainty in the required short-term weather forecasts determined that it takes only very

Thermal analysis of hybrid single-phase, two-phase and heat pump thermal control system (TCS) for future spacecraft

International Nuclear Information System (INIS)

Lee, S.H.; Mudawar, I.; Hasan, Mohammad M.

2016-01-01

Highlights: • Hybrid Thermal Control System (H-TCS) is proposed for future spacecraft. • Thermodynamic performance of H-TCS is examined for different space missions. • Operational modes including single-phase, two-phase and heat pump are explored. • R134a is deemed most appropriate working fluid. - Abstract: An urgent need presently exists to develop a new class of versatile spacecraft capable of conducting different types of missions and enduring varying gravitational and temperature environments, including Lunar, Martian and Near Earth Object (NEOs). This study concerns the spacecraft's Thermal Control System (TCS), which tackles heat acquisition, especially from crew and avionics, heat transport, and ultimate heat rejection by radiation. The primary goal of the study is to explore the design and thermal performance of a Hybrid Thermal Control System (H-TCS) that would satisfy the diverse thermal requirements of the different space missions. The H-TCS must endure both ‘cold’ and ‘hot’ environments, reduce weight and size, and enhance thermodynamic performance. Four different operational modes are considered: single-phase, two-phase, basic heat pump and heat pump with liquid-side, suction-side heat exchanger. A thermodynamic trade study is conducted for six different working fluids to assess important performance parameters including mass flow rate of the working fluid, maximum pressure, radiator area, compressor/pump work, and coefficient of performance (COP). R134a is determined to be most suitable based on its ability to provide a balanced compromise between reducing flow rate and maintaining low system pressure, and a moderate coefficient of performance (COP); this fluid is also both nontoxic and nonflammable, and features zero ozone depletion potential (ODP) and low global warming potential (GWP). It is shown how specific mission stages dictate which mode of operation is most suitable, and this information is used to size the radiator for the

Modelling and Design of Active Thermal Controls for Power Electronics of Motor Drive Applications

DEFF Research Database (Denmark)

Vernica, Ionut; Blaabjerg, Frede; Ma, Ke

2017-01-01

of active thermal control methods for the power devices of a motor drive application. The motor drive system together with the thermal cycling of the power devices have been modelled, and adverse temperature swings could be noticed during the start-up and deceleration periods of the motor. Based...... on the electrical response of the system, the junction temperature of the semiconductor devices is estimated, and consequently three active thermal control methods are proposed and practically designed with respect to the following parameters: switching frequency, deceleration slope and modulation technique....... Finally, experimental results are provided in order to validate the effectiveness of the proposed control methods....

Thermal performance analysis of reciprocating compressor with stepless capacity control system

International Nuclear Information System (INIS)

Bin, Tang; Yuanyang, Zhao; Liansheng, Li; Guangbin, Liu; Le, Wang; Qichao, Yang; Haiping, Xu; Feng, Zhu; Wenhui, Meng

2013-01-01

On the basic principle of stepless capacity control system for large reciprocating compressor, the thermal cycle was analyzed. The equations for the process of suction, reverse flow, compression, discharge and expansion of clearance gas were established. According to these equations, p–V diagrams at various situations were simulated. An experimental platform was setup and the compressor with designed stepless capacity control system run well. The experimental results show that the capacity of compressor can be regulated steplessly, and the motor power is reduced proportionally with respect to the reduction of capacity. During the suction process, both the flow resistance of valve and the pressure fluctuation in cylinder can be reduced by opening the suction valves with the actuators. The simulated and experimental results showed good coincidence. The clearance volume and valve clearance Mach number had a negative influence on the thermal performance of compressor with stepless capacity control system. -- Highlights: ► Flow resistance of valve can be reduced and pressure fluctuation can be reduced. ► Equivalent Mach number of reverse flow is much higher than that of suction process. ► Response of stepless capacity control system is important for regulation accuracy. ► Clearance and valve clearance Mach number have influence on thermal performance

Enhanced thermal expansion control rod drive lines for improving passive safety of fast reactors

International Nuclear Information System (INIS)

Edelmann, M.; Baumann, W.; Kuechle, M.; Kussmaul, G.; Vaeth, W.; Bertram, A.

1992-01-01

The paper presents a device for increasing the thermal expansion effect of control rod drive lines on negative reactivity feedback in fast reactors. The enhanced thermal expansion of this device can be utilized for both passive rod drop and forced insertion of absorbers in unprotected transients, e.g. ULOF. In this way the reactor is automatically brought into a permanently subcritical state and temperatures are kept well below the boiling point of the coolant. A prototype of such a device called ATHENa (German: Shut-down by THermal Expansion of Na) is presently under construction and will be tested. The paper presents the principle, design features and thermal properties of ATHENs as well as results of reactor dynamics calculations of ULOF's for EFR with enhanced thermal expansion control rod drive lines. (author)

A Hybrid Power Control Concept for PV Inverters with Reduced Thermal Loading

DEFF Research Database (Denmark)

Yang, Yongheng; Wang, Huai; Blaabjerg, Frede

2014-01-01

on a single-phase PV inverter under yearly operation is presented with analyses of the thermal loading, lifetime, and annual energy yield. It has revealed the trade-off factors to select the power limit and also verified the feasibility and the effectiveness of the proposed control concept.......This letter proposes a hybrid power control concept for grid-connected Photovoltaic (PV) inverters. The control strategy is based on either a Maximum Power Point Tracking (MPPT) control or a Constant Power Generation (CPG) control depending on the instantaneous available power from the PV panels....... The essence of the proposed concept lies in the selection of an appropriate power limit for the CPG control to achieve an improved thermal performance and an increased utilization factor of PV inverters,and thus to cater for a higher penetration level of PV systems with intermittent nature. A case study...

Development of a Microelectromechanical System for Small Satellite Thermal Control

National Research Council Canada - National Science Library

Beasley, Matthew

2004-01-01

.... This new direction requires a similar evolution in thermal control. Previous techniques such as heat pipes and conventional radiators have large masses themselves and are not scaleable to fit these smaller designs...

Automatic thermal control switches. [for use in Space Shuttle borne Get Away Special container

Science.gov (United States)

Wing, L. D.

1982-01-01

Two automatic, flexible connection thermal control switches have been designed and tested in a thermal vacuum facility and in the Get Away Special (GAS) container flown on the third Shuttle flight. The switches are complementary in that one switch passes heat when the plate on which it is mounted exceeds some selected temperature and the other switch will pass heat only when the mounting plate temperature is below the selected value. Both switches are driven and controlled by phase-change capsule motors and require no other power source or thermal sensors.

The performance of thermal control coatings on LDEF and implications to future spacecraft

Science.gov (United States)

Wilkes, Donald R.; Miller, Edgar R.; Mell, Richard J.; Lemaster, Paul S.; Zwiener, James M.

1993-01-01

The stability of thermal control coatings over the lifetime of a satellite or space platform is crucial to the success of the mission. With the increasing size, complexity, and duration of future missions, the stability of these materials becomes even more important. The Long Duration Exposure Facility (LDEF) offered an excellent testbed to study the stability and interaction of thermal control coatings in the low-Earth orbit (LEO) space environment. Several experiments on LDEF exposed thermal control coatings to the space environment. This paper provides an overview of the different materials flown and their stability during the extended LDEF mission. The exposure conditions, exposure environment, and measurements of materials properties (both in-space and postflight) are described. The relevance of the results and the implications to the design and operation of future space vehicles are also discussed.

The Neural-fuzzy Thermal Error Compensation Controller on CNC Machining Center

Science.gov (United States)

Tseng, Pai-Chung; Chen, Shen-Len

The geometric errors and structural thermal deformation are factors that influence the machining accuracy of Computer Numerical Control (CNC) machining center. Therefore, researchers pay attention to thermal error compensation technologies on CNC machine tools. Some real-time error compensation techniques have been successfully demonstrated in both laboratories and industrial sites. The compensation results still need to be enhanced. In this research, the neural-fuzzy theory has been conducted to derive a thermal prediction model. An IC-type thermometer has been used to detect the heat sources temperature variation. The thermal drifts are online measured by a touch-triggered probe with a standard bar. A thermal prediction model is then derived by neural-fuzzy theory based on the temperature variation and the thermal drifts. A Graphic User Interface (GUI) system is also built to conduct the user friendly operation interface with Insprise C++ Builder. The experimental results show that the thermal prediction model developed by neural-fuzzy theory methodology can improve machining accuracy from 80µm to 3µm. Comparison with the multi-variable linear regression analysis the compensation accuracy is increased from ±10µm to ±3µm.

Prediction and control of the coefficient of thermal expansion of concrete

International Nuclear Information System (INIS)

Ziegeldorf, S.; Kleiser, K.; Hilsdorf, H.K.

1979-01-01

Prediction and control of the coefficient of thermal expansion of concrete. In this report various procedures for the prediction of the coefficient of thermal expansion of concrete are summarized. The values predicted with these procedures are compared to experimental data. In the experimental investigation the coefficient of thermal expansion of various types of aggregates and types of concrete both in a dry and a moist state in the temperature range RT/180 0 C have been measured. The most significant result obtained is that for equal volume fractions the thermal properties of coarse aggregates have a more pronounced effect upon thermal expansion of concrete than those of fine aggregates. In the analysis an attempt has been made to estimate the thermal expansion of concrete from the properties of the concrete components by means of a finite element procedure. On the basis of the experimental data and of the analysis of internal temperature stresses in the concrete a simple relationship for the determination of the coefficient of thermal expansion of concrete has been deduced. In this relationship different thermal properties of coarse and fine aggregates may be taken into account. Compared to other methods this relationship yields, both for dry and for moist concrete, values which are in good agreement with the experimental data. (orig.) [de

Minimum scale controlled topology optimization and experimental test of a micro thermal actuator

DEFF Research Database (Denmark)

Heo, S.; Yoon, Gil Ho; Kim, Y.Y.

2008-01-01

This paper is concerned with the optimal topology design, fabrication and test of a micro thermal actuator. Because the minimum scale was controlled during the design optimization process, the production yield rate of the actuator was improved considerably; alternatively, the optimization design ...... tested. The test showed that control over the minimum length scale in the design process greatly improves the yield rate and reduces the performance deviation....... without scale control resulted in a very low yield rate. Using the minimum scale controlling topology design method developed earlier by the authors, micro thermal actuators were designed and fabricated through a MEMS process. Moreover, both their performance and production yield were experimentally...

Thermal control system. [removing waste heat from industrial process spacecraft

Science.gov (United States)

Hewitt, D. R. (Inventor)

1983-01-01

The temperature of an exothermic process plant carried aboard an Earth orbiting spacecraft is regulated using a number of curved radiator panels accurately positioned in a circular arrangement to form an open receptacle. A module containing the process is insertable into the receptacle. Heat exchangers having broad exterior surfaces extending axially above the circumference of the module fit within arcuate spacings between adjacent radiator panels. Banks of variable conductance heat pipes partially embedded within and thermally coupled to the radiator panels extend across the spacings and are thermally coupled to broad exterior surfaces of the heat exchangers by flanges. Temperature sensors monitor the temperature of process fluid flowing from the module through the heat exchanges. Thermal conduction between the heat exchangers and the radiator panels is regulated by heating a control fluid within the heat pipes to vary the effective thermal length of the heat pipes in inverse proportion to changes in the temperature of the process fluid.

Parameter optimization of thermal-model-oriented control law for PEM fuel cell stack via novel genetic algorithm

International Nuclear Information System (INIS)

Li Xi; Deng Zhonghua; Wei Dong; Xu Chunshan; Cao Guangyi

2011-01-01

Highlights: →We build up the thermal expressions of PEMFC stack. → The expressions are converted into the affine state space control-oriented model for the VSC strategy. → The NGA is developed to optimize the parameter of thermal-model-oriented control law. → Numerical results demonstrate the effectiveness and rationality of the method proposed. - Abstract: It is critical to understand and manage the thermal effects in optimizing the performance and durability of proton exchange membrane fuel cell (PEMFC) stack. And building up the control-oriented thermal model of PEMFC stack is necessary. The thermal model, a set of differential equations, is established according to the conservation equations of mass and energy, which can be used to reflect truly the actual temperature response of PEMFC stack, however, the expressions of the model are too complicated to be used in the design of control. For this reason, the expressions are converted into the affine state space control-oriented model in detail for the variable structure control (VSC) strategy. Meanwhile, the accurate model must be established for the VSC and the parameters of VSC laws should be optimized. Consequently, a novel genetic algorithm (NGA) is developed to optimize the parameter of thermal-model-oriented control law for PEMFC stack. Finally, numerical test results demonstrate the effectiveness and rationality of the method proposed in this paper. It lays the foundation for the realization of online thermal management of PEMFC stack based on VSC.

Model Predictive Control of Hybrid Thermal Energy Systems in Transport Refrigeration

DEFF Research Database (Denmark)

Shafiei, Seyed Ehsan; Alleyne, Andrew

2015-01-01

A predictive control scheme is designed to control a transport refrigeration system, such as a delivery truck, that includes a vapor compression cycle configured in parallel with a thermal energy storage (TES) unit. A novel approach to TES utilization is introduced and is based on the current...

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...

Thermally controlled comb generation and soliton modelocking in microresonators.

Science.gov (United States)

Joshi, Chaitanya; Jang, Jae K; Luke, Kevin; Ji, Xingchen; Miller, Steven A; Klenner, Alexander; Okawachi, Yoshitomo; Lipson, Michal; Gaeta, Alexander L

2016-06-01

We report, to the best of our knowledge, the first demonstration of thermally controlled soliton mode-locked frequency comb generation in microresonators. By controlling the electric current through heaters integrated with silicon nitride microresonators, we demonstrate a systematic and repeatable pathway to single- and multi-soliton mode-locked states without adjusting the pump laser wavelength. Such an approach could greatly simplify the generation of mode-locked frequency combs and facilitate applications such as chip-based dual-comb spectroscopy.

Controllable magnetic thermal rectification in a SMM dimmer with the Dzyaloshinskii-Moriya interaction

Science.gov (United States)

Xu, Ai-Hua; Liu, Juan; Luo, Bo

2016-10-01

Using the quantum master equation, we studied the thermally driven magnonic spin current in a single-molecule magnet (SMM) dimer with the Dzyaloshinskii-Moriya interaction (DMI). Due to the asymmetric DMI, one can observe the thermal rectifying effect in the case of the spatial symmetry coupling with the thermal reservoirs. The properties of the thermal rectification can be controlled by tuning the angle and intensity of the magnetic field. Specially, when the DM vector and magnetic field point at the specific angles, the thermal rectifying effect disappears. And this phenomenon does not depend on the intensities of DMI and magnetic field, the temperature bias and the magnetic anisotropies of the SMM.

Combined Contamination and Space Environmental Effects on Solar Cells and Thermal Control Surfaces

Science.gov (United States)

Dever, Joyce A.; Bruckner, Eric J.; Scheiman, David A.; Stidham, Curtis R.

1994-01-01

For spacecraft in low Earth orbit (LEO), contamination can occur from thruster fuel, sputter contamination products and from products of silicone degradation. This paper describes laboratory testing in which solar cell materials and thermal control surfaces were exposed to simulated spacecraft environmental effects including contamination, atomic oxygen, ultraviolet radiation and thermal cycling. The objective of these experiments was to determine how the interaction of the natural LEO environmental effects with contaminated spacecraft surfaces impacts the performance of these materials. Optical properties of samples were measured and solar cell performance data was obtained. In general, exposure to contamination by thruster fuel resulted in degradation of solar absorptance for fused silica and various thermal control surfaces and degradation of solar cell performance. Fused silica samples which were subsequently exposed to an atomic oxygen/vacuum ultraviolet radiation environment showed reversal of this degradation. These results imply that solar cells and thermal control surfaces which are susceptible to thruster fuel contamination and which also receive atomic oxygen exposure may not undergo significant performance degradation. Materials which were exposed to only vacuum ultraviolet radiation subsequent to contamination showed slight additional degradation in solar absorptance.

Optically-controlled long-term storage and release of thermal energy in phase-change materials

OpenAIRE

Han, Grace G. D.; Li, Huashan; Grossman, Jeffrey C.

2017-01-01

Thermal energy storage offers enormous potential for a wide range of energy technologies. Phase-change materials offer state-of-the-art thermal storage due to high latent heat. However, spontaneous heat loss from thermally charged phase-change materials to cooler surroundings occurs due to the absence of a significant energy barrier for the liquid–solid transition. This prevents control over the thermal storage, and developing effective methods to address this problem has remained an elusive ...

DACS II - A distributed thermal/mechanical loads data acquisition and control system

Science.gov (United States)

Zamanzadeh, Behzad; Trover, William F.; Anderson, Karl F.

1987-01-01

A distributed data acquisition and control system has been developed for the NASA Flight Loads Research Facility. The DACS II system is composed of seven computer systems and four array processors configured as a main computer system, three satellite computer systems, and 13 analog input/output systems interconnected through three independent data networks. Up to three independent heating and loading tests can be run concurrently on different test articles or the entire system can be used on a single large test such as a full scale hypersonic aircraft. Thermal tests can include up to 512 independent adaptive closed loop control channels. The control system can apply up to 20 MW of heating to a test specimen while simultaneously applying independent mechanical loads. Each thermal control loop is capable of heating a structure at rates of up to 150 F per second over a temperature range of -300 to +2500 F. Up to 64 independent mechanical load profiles can be commanded along with thermal control. Up to 1280 analog inputs monitor temperature, load, displacement and strain on the test specimens with real time data displayed on up to 15 terminals as color plots and tabular data displays. System setup and operation is accomplished with interactive menu-driver displays with extensive facilities to assist the users in all phases of system operation.

Simulation study of multi-step model algorithmic control of the nuclear reactor thermal power tracking system

International Nuclear Information System (INIS)

Shi Xiaoping; Xu Tianshu

2001-01-01

The classical control method is usually hard to ensure the thermal power tracking accuracy, because the nuclear reactor system is a complex nonlinear system with uncertain parameters and disturbances. A sort of non-parameter model is constructed with the open-loop impulse response of the system. Furthermore, a sort of thermal power tracking digital control law is presented using the multi-step model algorithmic control principle. The control method presented had good tracking performance and robustness. It can work despite the existence of unmeasurable disturbances. The simulation experiment testifies the correctness and effectiveness of the method. The high accuracy matching between the thermal power and the referenced load is achieved

Instrumentation and control systems for monitoring and data acquisition for thermal recovery process

Energy Technology Data Exchange (ETDEWEB)

Aparicio, J.; Hernandez, E.; Perozo, H. [PDVSA Intevep, S.A. (Venezuela)

2011-07-01

Thermal recovery methods are often applied to enhance oil recovery in heavy oil reservoirs, one of its challenges is to control the displacement of the thermal front. Methods are thus implemented to obtain data on the temperatures in the wells at any given time and to monitor other variables so that the behaviour of the thermal front can be predicted. The aim of this paper is to present a new control and instrumentation scheme to measure all of the variables. A software was created using Labview a graphs-based programming language software and PostgreSQL, a database management system. Using this software, sensors can be added or removed at any time; trends can be immediately visualized; and quality of the information is ensured since there is no human intervention in the data collection or processing. This paper presented a software which improves monitoring of all of the variables affecting the behaviour of the thermal front.

Hybrid model predictive control of a residential HVAC system with on-site thermal energy generation and storage

International Nuclear Information System (INIS)

Fiorentini, Massimo; Wall, Josh; Ma, Zhenjun; Braslavsky, Julio H.; Cooper, Paul

2017-01-01

Highlights: • A comprehensive approach to managing thermal energy in residential buildings. • Solar-assisted HVAC system with on-site energy generation and storage. • Mixed logic-dynamical building model identified using experimental data. • Design and implementation of a logic-dynamical model predictive control strategy. • MPC applied to the Net-Zero Energy house winner of the Solar Decathlon China 2013. - Abstract: This paper describes the development, implementation and experimental investigation of a Hybrid Model Predictive Control (HMPC) strategy to control solar-assisted heating, ventilation and air-conditioning (HVAC) systems with on-site thermal energy generation and storage. A comprehensive approach to the thermal energy management of a residential building is presented to optimise the scheduling of the available thermal energy resources to meet a comfort objective. The system has a hybrid nature with both continuous variables and discrete, logic-driven operating modes. The proposed control strategy is organized in two hierarchical levels. At the high-level, an HMPC controller with a 24-h prediction horizon and a 1-h control step is used to select the operating mode of the HVAC system. At the low-level, each operating mode is optimised using a 1-h rolling prediction horizon with a 5-min control step. The proposed control strategy has been practically implemented on the Building Management and Control System (BMCS) of a Net Zero-Energy Solar Decathlon house. This house features a sophisticated HVAC system comprising of an air-based photovoltaic thermal (PVT) collector and a phase change material (PCM) thermal storage integrated with the air-handling unit (AHU) of a ducted reverse-cycle heat pump system. The simulation and experimental results demonstrated the high performance achievable using an HMPC approach to optimising complex multimode HVAC systems in residential buildings, illustrating efficient selection of the appropriate operating modes

Evaluation of Surface Modification as a Lunar Dust Mitigation Strategy for Thermal Control Surfaces

Science.gov (United States)

Gaier, James R.; Waters, Deborah L.; Misconin, Robert M.; Banks, Bruce A.; Crowder, Mark

2011-01-01

Three surface treatments were evaluated for their ability to lower the adhesion between lunar simulant dust and AZ93, AlFEP, and AgFEP thermal control surfaces under simulated lunar conditions. Samples were dusted in situ and exposed to a standardized puff of nitrogen gas. Thermal performance before dusting, after dusting, and after part of the dust was removed by the puff of gas, were compared to perform the assessment. None of the surface treatments was found to significantly affect the adhesion of lunar simulants to AZ93 thermal control paint. Oxygen ion beam texturing also did not lower the adhesion of lunar simulant dust to AlFEP or AgFEP. But a workfunction matching coating and a proprietary Ball Aerospace surface treatment were both found to significantly lower the adhesion of lunar simulants to AlFEP and AgFEP. Based on these results, it is recommended that all these two techniques be further explored as dust mitigation coatings for AlFEP and AgFEP thermal control surfaces.

A Robust Model Predictive Control for efficient thermal management of internal combustion engines

International Nuclear Information System (INIS)

Pizzonia, Francesco; Castiglione, Teresa; Bova, Sergio

2016-01-01

Highlights: • A Robust Model Predictive Control for ICE thermal management was developed. • The proposed control is effective in decreasing the warm-up time. • The control system reduces coolant flow rate under fully warmed conditions. • The control strategy operates the cooling system around onset of nucleate boiling. • Little on-line computational effort is required. - Abstract: Optimal thermal management of modern internal combustion engines (ICE) is one of the key factors for reducing fuel consumption and CO_2 emissions. These are measured by using standardized driving cycles, like the New European Driving Cycle (NEDC), during which the engine does not reach thermal steady state; engine efficiency and emissions are therefore penalized. Several techniques for improving ICE thermal efficiency were proposed, which range from the use of empirical look-up tables to pulsed pump operation. A systematic approach to the problem is however still missing and this paper aims to bridge this gap. The paper proposes a Robust Model Predictive Control of the coolant flow rate, which makes use of a zero-dimensional model of the cooling system of an ICE. The control methodology incorporates explicitly the model uncertainties and achieves the synthesis of a state-feedback control law that minimizes the “worst case” objective function while taking into account the system constraints, as proposed by Kothare et al. (1996). The proposed control strategy is to adjust the coolant flow rate by means of an electric pump, in order to bring the cooling system to operate around the onset of nucleate boiling: across it during warm-up and above it (nucleate or saturated boiling) under fully warmed conditions. The computationally heavy optimization is carried out off-line, while during the operation of the engine the control parameters are simply picked-up on-line from look-up tables. Owing to the little computational effort required, the resulting control strategy is suitable for

Alternatives for thermal legionella control; Alternatieven thermische legionellabestrijding

Energy Technology Data Exchange (ETDEWEB)

Van Lieshout, M.

2008-03-15

One supplier considers his system a breakthrough in legionella control. Another claims decisively that his system provides the only affordable and effective solution. It is clear that manufacturers have their own way of finding alternatives in those cases where thermal control for complex existing installations prove not to be effective. (mk) [Dutch] De ene leverancier noemt zijn systeem een doorbraak in de legionellabestrijding. Een ander beweert met grote stelligheid dat zijn systeem de enige betaalbare en effectieve oplossing is. Duidelijk is dat fabrikanten op hun eigen manier een oplossing zoeken naar alternatieven, daar waar het thermisch beheer voor complexe bestaande installaties niet effectief blijk te zijn.

Implementation of Active Thermal Control (ATC) for the Soil Moisture Active and Passive (SMAP) Radiometer

Science.gov (United States)

Mikhaylov, Rebecca; Kwack, Eug; French, Richard; Dawson, Douglas; Hoffman, Pamela

2014-01-01

NASA's Earth Observing Soil Moisture Active and Passive (SMAP) Mission is scheduled to launch in November 2014 into a 685 kilometer near-polar, sun-synchronous orbit. SMAP will provide comprehensive global mapping measurements of soil moisture and freeze/thaw state in order to enhance understanding of the processes that link the water, energy, and carbon cycles. The primary objectives of SMAP are to improve worldwide weather and flood forecasting, enhance climate prediction, and refine drought and agriculture monitoring during its three year mission. The SMAP instrument architecture incorporates an L-band radar and an L-band radiometer which share a common feed horn and parabolic mesh reflector. The instrument rotates about the nadir axis at approximately 15 revolutions per minute, thereby providing a conically scanning wide swath antenna beam that is capable of achieving global coverage within three days. In order to make the necessary precise surface emission measurements from space, the electronics and hardware associated with the radiometer must meet tight short-term (instantaneous and orbital) and long-term (monthly and mission) thermal stabilities. Maintaining these tight thermal stabilities is quite challenging because the sensitive electronics are located on a fast spinning platform that can either be in full sunlight or total eclipse, thus exposing them to a highly transient environment. A passive design approach was first adopted early in the design cycle as a low-cost solution. With careful thermal design efforts to cocoon and protect all sensitive components, all stability requirements were met passively. Active thermal control (ATC) was later added after the instrument Preliminary Design Review (PDR) to mitigate the threat of undetected gain glitches, not for thermal-stability reasons. Gain glitches are common problems with radiometers during missions, and one simple way to avoid gain glitches is to use the in-flight set point programmability that ATC

Spatial and temporal control of thermal waves by using DMDs for interference based crack detection

Science.gov (United States)

Thiel, Erik; Kreutzbruck, Marc; Ziegler, Mathias

2016-02-01

Active Thermography is a well-established non-destructive testing method and used to detect cracks, voids or material inhomogeneities. It is based on applying thermal energy to a samples' surface whereas inner defects alter the nonstationary heat flow. Conventional excitation of a sample is hereby done spatially, either planar (e.g. using a lamp) or local (e.g. using a focused laser) and temporally, either pulsed or periodical. In this work we combine a high power laser with a Digital Micromirror Device (DMD) allowing us to merge all degrees of freedom to a spatially and temporally controlled heat source. This enables us to exploit the possibilities of coherent thermal wave shaping. Exciting periodically while controlling at the same time phase and amplitude of the illumination source induces - via absorption at the sample's surface - a defined thermal wave propagation through a sample. That means thermal waves can be controlled almost like acoustical or optical waves. However, in contrast to optical or acoustical waves, thermal waves are highly damped due to the diffusive character of the thermal heat flow and therefore limited in penetration depth in relation to the achievable resolution. Nevertheless, the coherence length of thermal waves can be chosen in the mmrange for modulation frequencies below 10 Hz which is perfectly met by DMD technology. This approach gives us the opportunity to transfer known technologies from wave shaping techniques to thermography methods. We will present experiments on spatial and temporal wave shaping, demonstrating interference based crack detection.

Thermal Control Subsystem Design for the Avionics of a Space Station Payload

Science.gov (United States)

Moran, Matthew E.

1996-01-01

A case study of the thermal control subsystem development for a space based payload is presented from the concept stage through preliminary design. This payload, the Space Acceleration Measurement System 2 (SAMS-2), will measure the acceleration environment at select locations within the International Space Station. Its thermal control subsystem must maintain component temperatures within an acceptable range over a 10 year life span, while restricting accessible surfaces to touch temperature limits and insuring fail safe conditions in the event of loss of cooling. In addition to these primary design objectives, system level requirements and constraints are imposed on the payload, many of which are driven by multidisciplinary issues. Blending these issues into the overall system design required concurrent design sessions with the project team, iterative conceptual design layouts, thermal analysis and modeling, and hardware testing. Multiple tradeoff studies were also performed to investigate the many options which surfaced during the development cycle.

Simplified Building Thermal Model Used for Optimal Control of Radiant Cooling System

Directory of Open Access Journals (Sweden)

Lei He

2016-01-01

Full Text Available MPC has the ability to optimize the system operation parameters for energy conservation. Recently, it has been used in HVAC systems for saving energy, but there are very few applications in radiant cooling systems. To implement MPC in buildings with radiant terminals, the predictions of cooling load and thermal environment are indispensable. In this paper, a simplified thermal model is proposed for predicting cooling load and thermal environment in buildings with radiant floor. In this thermal model, the black-box model is introduced to derive the incident solar radiation, while the genetic algorithm is utilized to identify the parameters of the thermal model. In order to further validate this simplified thermal model, simulated results from TRNSYS are compared with those from this model and the deviation is evaluated based on coefficient of variation of root mean square (CV. The results show that the simplified model can predict the operative temperature with a CV lower than 1% and predict cooling loads with a CV lower than 10%. For the purpose of supervisory control in HVAC systems, this simplified RC thermal model has an acceptable accuracy and can be used for further MPC in buildings with radiation terminals.

Engineering aspects of a thermal control subsystem for the 25 kW power module

Science.gov (United States)

Schroeder, P. E.

1979-01-01

The paper presents the key trade study results, analysis results, and the recommended thermal control approach for the 25 kW power module defined by NASA. Power conversion inefficiencies and component heat dissipation results in a minimum heat rejection requirement of 9 kW to maintain the power module equipment at desired temperature levels. Additionally, some cooling capacity should be provided for user payloads in the sortie and free-flying modes. The baseline thermal control subsystem includes a dual-loop-pumped Freon-21 coolant with the heat rejected from deployable existing orbiter radiators. Thermal analysis included an assessment of spacecraft orientations, radiator shapes and locations, and comparison of hybrid heat pipe and all liquid panels.

Passive Films for CubeSat Solar Array and Radiator Thermal Control

Data.gov (United States)

National Aeronautics and Space Administration — Trending towards reduced power and mass budget on satellites with a longer mission life, there is a need for a reliable thermal control system that is more efficient...

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

Fabrication and performance evaluation of flexible heat pipes for potential thermal control of foldable electronics

International Nuclear Information System (INIS)

Yang, Chao; Chang, Chao; Song, Chengyi; Shang, Wen; Wu, Jianbo; Tao, Peng; Deng, Tao

2016-01-01

Highlights: • A flexible and high-performance heat pipe is fabricated. • Bending effect on thermal performance of flexible heat pipes is evaluated. • Theoretical analysis is carried out to reveal the change of thermal resistance with bending. • Thermal control of foldable electronics with flexible heat pipes is demonstrated. - Abstract: In this work, we report the fabrication and thermal performance evaluation of flexible heat pipes prepared by using a fluororubber tube as the connector in the adiabatic section and using strong base treated hydrophilic copper meshes as the wick structure. Deionized water was chosen as working fluid and three different filling ratios (10%, 20%, and 30%) of working fluid were loaded into the heat pipe to investigate its impact on thermal performance. The fabricated heat pipes can be easily bended from 0"o to 180"o in the horizontal operation mode and demonstrated consistently low thermal resistances after repeated bending. It was found that with optimized amount of working fluid, the thermal resistance of flexible heat pipes increased with larger bending angles. Theoretical analysis reveals that bending disturbs the normal vapor flow from evaporator to condenser in the heat pipe, thus leads to increased liquid–vapor interfacial thermal resistance in the evaporator section. The flexible heat pipes have been successfully applied for thermal control of foldable electronic devices showing superior uniform heat-transfer performance.

Investigation of phase-change coatings for variable thermal control of spacecraft

Science.gov (United States)

Kelliher, W. C.; Young, P. R.

1972-01-01

An investigation was conducted to determine the feasibility of producing a spacecraft coating system that could vary the ratio of its solar absorptance to thermal emittance to adjust automatically for changes in the thermal balance of a spacecraft. This study resulted in a new concept called the phase-change effect which uses the change that occurs in the optical properties of many materials during the phase transition from a crystalline solid to an amorphous material. A series of two-component model coatings was developed which, when placed on a highly reflecting substrate, exhibited a sharp decrease in solar absorptance within a narrow temperature range. A variable thermal control coating can have a significant amount of temperature regulation with the phase-change effect. Data are presented on several crystallite-polymer formulations, their physical and optical properties, and associated phase-change temperatures. Aspects pertaining to their use in a space environment and an example of the degree of thermal regulation attainable with these coatings is also given.

Pumped Fluid Loop Heat Rejection and Recovery Systems for Thermal Control of the Mars Science Laboratory

Science.gov (United States)

Bhandari, Pradeep; Birur, Gajanana; Prina, Mauro; Ramirez, Brenda; Paris, Anthony; Novak, Keith; Pauken, Michael

2006-01-01

This viewgraph presentation reviews the heat rejection and heat recovery system for thermal control of the Mars Science Laboratory (MSL). The MSL mission will use mechanically pumped fluid loop based architecture for thermal control of the spacecraft and rover. The architecture is designed to harness waste heat from an Multi Mission Radioisotope Thermo-electric Generator (MMRTG) during Mars surface operations for thermal control during cold conditions and also reject heat during the cruise aspect of the mission. There are several test that are being conducted that will insure the safety of this concept. This architecture can be used during any future interplanetary missions utilizing radioisotope power systems for power generation.

Two-Dimension Sorting and Selection Algorithm featuring Thermal Balancing Control for Modular Multilevel Converters

DEFF Research Database (Denmark)

Sangwongwanich, Ariya; Máthé, Lászlo; Teodorescu, Remus

2016-01-01

With the aim to solve the unbalanced thermal behavior in the modular multilevel converter, introduced by mismatch in the submodule parameters, a thermal balancing control strategy is proposed here. The proposed solution ensures a balanced junction temperature for the power devices, while the bala...

CO2 Insulation for Thermal Control of the Mars Science Laboratory

Science.gov (United States)

Bhandari, Pradeep; Karlmann, Paul; Anderson, Kevin; Novak, Keith

2011-01-01

The National Aeronautics and Space Administration (NASA) is sending a large (>850 kg) rover as part of the Mars Science Laboratory (MSL) mission to Mars in 2011. The rover's primary power source is a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) that generates roughly 2000 W of heat, which is converted to approximately 110 W of electrical power for use by the rover electronics, science instruments, and mechanism-actuators. The large rover size and extreme thermal environments (cold and hot) for which the rover is designed for led to a sophisticated thermal control system to keep it within allowable temperature limits. The pre-existing Martian atmosphere of low thermal conductivity CO2 gas (8 Torr) is used to thermally protect the rover and its components from the extremely cold Martian environment (temperatures as low as -130 deg C). Conventional vacuum based insulation like Multi Layer Insulation (MLI) is not effective in a gaseous atmosphere, so engineered gaps between the warm rover internal components and the cold rover external structure were employed to implement this thermal isolation. Large gaps would lead to more thermal isolation, but would also require more of the precious volume available within the rover. Therefore, a balance of the degree of thermal isolation achieved vs. the volume of rover utilized is required to reach an acceptable design. The temperature differences between the controlled components and the rover structure vary from location to location so each gap has to be evaluated on a case-by-case basis to arrive at an optimal thickness. For every configuration and temperature difference, there is a critical thickness below which the heat transfer mechanism is dominated by simple gaseous thermal conduction. For larger gaps, the mechanism is dominated by natural convection. In general, convection leads to a poorer level of thermal isolation as compared to conduction. All these considerations play important roles in the

Investigation of thermal management materials for automotive electronic control units

International Nuclear Information System (INIS)

Mallik, Sabuj; Ekere, Ndy; Best, Chris; Bhatti, Raj

2011-01-01

Today's electronics packages are smaller and more powerful than ever before. This leads to ever increasing thermal challenges for the systems designer. The automotive electronic control unit (ECU) package faces the same challenge of thermal management as the industry in general. This is coupled with the latest European Union legislation (Euro 6 standard) which forced the ECU manufacturers to completely re-design their ECU platform with improved hardware and software capability. This will result in increased power densities and therefore, the ability to dissipate heat will be a key factor. A higher thermal conductivity (TC) material for the ECU housing (than the currently used Aluminium) could improve heat dissipation from the ECU. This paper critically reviews the state-of-the-art in thermal management materials which may be applicable to an automotive ECU. This review shows that of the different materials currently available, the Al/SiC composites in particular have very good potential for automotive ECU application. In terms of metal composites processing, the liquid metal infiltration process is recommended as it has a lower processing cost and it also has the ability to produce near net-shape materials.

Thermal stability analysis and auxiliary power feedback control for the tokamak engineering test breeder (TETB-II)

International Nuclear Information System (INIS)

Sheng Guangzhao

1993-01-01

The thermal stability of TETB-II is analyzed using different methods, viz., POPCON, linear stability analysis and the time evolution calculation of plasma parameters. A thermal instability of the TETB-II is predicted. Auxiliary power feedback control for thermal stability appears feasible and efficient

Evaluation of thermal control coatings for use on solar dynamic radiators in low earth orbit

Science.gov (United States)

Dever, Joyce A.; Rodriguez, Elvin; Slemp, Wayne S.; Stoyack, Joseph E.

1991-01-01

Thermal control coatings with high thermal emittance and low solar absorptance are needed for Space Station Freedom (SSF) solar dynamic power module radiator (SDR) surfaces for efficient heat rejection. Additionally, these coatings must be durable to low earth orbital (LEO) environmental effects of atomic oxygen, ultraviolet radiation and deep thermal cycles which occur as a result of start-up and shut-down of the solar dynamic power system. Eleven candidate coatings were characterized for their solar absorptance and emittance before and after exposure to ultraviolet (UV) radiation (200 to 400 nm), vacuum UV (VUV) radiation (100 to 200 nm) and atomic oxygen. Results indicated that the most durable and best performing coatings were white paint thermal control coatings Z-93, zinc oxide pigment in potassium silicate binder, and YB-71, zinc orthotitanate pigment in potassium silicate binder. Optical micrographs of these materials exposed to the individual environmental effects of atomic oxygen and vacuum thermal cycling showed that no surface cracking occurred.

Effect of energy-regenerative braking on electric vehicle battery thermal management and control method based on simulation investigation

International Nuclear Information System (INIS)

Huang, Jingying; Qin, Datong; Peng, Zhiyuan

2015-01-01

Highlights: • A two-degree-of-freedom lumped thermal model is developed for battery. • The battery thermal model is integrated with vehicle driving model. • Real-time battery thermal responses is obtained. • Active control of current by regenerative braking ratio adjustment is proposed. • More energy is recovered with smaller battery temperature rise. - Abstract: Battery thermal management is important for the safety and reliability of electric vehicle. Based on the parameters obtained from battery hybrid pulse power characterization test, a two-degree-of-freedom lumped thermal model is established. The battery model is then integrated with vehicle driving model to simulate real-time battery thermal responses. An active control method is proposed to reduce heat generation due to regenerative braking. The proposed control method not only subjects to the braking safety regulation, but also adjusts the regenerative braking ratio through a fuzzy controller. By comparing with other regenerative braking scenarios, the effectiveness of the proposed strategy has been validated. According to the results, the proposed control strategy suppresses battery temperature rise by modifying the charge current due to regenerative braking. The overlarge components of current are filtered out whereas the small ones are magnified. Therefore, with smaller battery temperature rise, more energy is recovered. Compared to the traditional passive heat dissipating, the proposed active methodology is feasible and provides a novel solution for electric vehicle battery thermal management.

Load Frequency Control of AC Microgrid Interconnected Thermal Power System

Science.gov (United States)

Lal, Deepak Kumar; Barisal, Ajit Kumar

2017-08-01

In this paper, a microgrid (MG) power generation system is interconnected with a single area reheat thermal power system for load frequency control study. A new meta-heuristic optimization algorithm i.e. Moth-Flame Optimization (MFO) algorithm is applied to evaluate optimal gains of the fuzzy based proportional, integral and derivative (PID) controllers. The system dynamic performance is studied by comparing the results with MFO optimized classical PI/PID controllers. Also the system performance is investigated with fuzzy PID controller optimized by recently developed grey wolf optimizer (GWO) algorithm, which has proven its superiority over other previously developed algorithm in many interconnected power systems.

Microkelvin thermal control system for the laser interferometer space antenna mission and beyond

Science.gov (United States)

Higuchi, Sei

2009-10-01

The Laser Interferometer Space Antenna (LISA) mission aims to detect directly gravitational waves from massive black holes and galactic binaries. Through detecting gravitational waves, we can study blackholes and the origin of the universe, which is inaccessible from the electromagnetic wave spectrum. It will open a new window to the universe. LISA is essentially a Michelson interferometer placed in space with a third spacecraft added. Gravitational waves are time-varying strain in space-time, which is detectable as a fractional change in a proper distance. LISA will monitor fractional changes in the interferometer arms of a nominally 5 million km. The fractional change in the arm length can be as small as 1 x 10-21 m/(m · Hz ) even for powerful sources. LISA makes use of the gravitational reference sensors (GRS) for drag-free control and will achieve the required sensitivity through management of specific acceleration noise. The total acceleration disturbance to each proof mass, which floats at the center of each GRS, is required to be below 3 x 10-15 m/(s2 · Hz ). Thermal variations due to, for example, solar irradiation, or temperature gradients across the proof mass housing, are expected to be significant disturbance source to the LISA sensitivity requirements. Even a small temperature gradient can produce distortions in the housing structure, which results in a mass attraction force. In this thesis, I focus on developing a thermal control system that aims to achieve the temperature stability of 10 muK / Hz over 0.1 mHz to 1 Hz. We have chosen glass-bead thermistors as the temperature sensor for feedback temperature control of the GRS. First, we created a temperature sensor design program in MATLAB that provides an optimal values of resistances in the thermistor bridge circuit for the given application. The spectral stability of the sensor achieves as low as 20 muK/ Hz at 1 mHz with a DC excitation source. The LISA thermal requirement is met by employing AC

Indirect thermal control for improved reliability of Modular Multilevel Converter by utilizing circulating current

DEFF Research Database (Denmark)

Dowlatabadi, Mohammadkazem Bakhshizadeh; Ma, Ke; Loh, Poh Chiang

2015-01-01

semiconductor devices are comprehensively investigated. Also a novel control strategy by utilizing the circulating current is proposed to enhance the reliability performance of MMC in order to limit the amplitude of thermal cycles. It is concluded that the circulating current may change the losses and thermal...

Improvement of environmental aspects of thermal power plant operation by advanced control concepts

Directory of Open Access Journals (Sweden)

Mikulandrić Robert

2012-01-01

Full Text Available The necessity of the reduction of greenhouse gas emissions, as formulated in the Kyoto Protocol, imposes the need for improving environmental aspects of existing thermal power plants operation. Improvements can be reached either by efficiency increment or by implementation of emission reduction measures. Investments in refurbishment of existing plant components or in plant upgrading by flue gas desulphurization, by primary and secondary measures of nitrogen oxides reduction, or by biomass co-firing, are usually accompanied by modernisation of thermal power plant instrumentation and control system including sensors, equipment diagnostics and advanced controls. Impact of advanced control solutions implementation depends on technical characteristics and status of existing instrumentation and control systems as well as on design characteristics and actual conditions of installed plant components. Evaluation of adequacy of implementation of advanced control concepts is especially important in Western Balkan region where thermal power plants portfolio is rather diversified in terms of size, type and commissioning year and where generally poor maintenance and lack of investments in power generation sector resulted in high greenhouse gases emissions and low efficiency of plants in operation. This paper is intended to present possibilities of implementation of advanced control concepts, and particularly those based on artificial intelligence, in selected thermal power plants in order to increase plant efficiency and to lower pollutants emissions and to comply with environmental quality standards prescribed in large combustion plant directive. [Acknowledgements. This paper has been created within WBalkICT - Supporting Common RTD actions in WBCs for developing Low Cost and Low Risk ICT based solutions for TPPs Energy Efficiency increasing, SEE-ERA.NET plus project in cooperation among partners from IPA SA - Romania, University of Zagreb - Croatia and Vinca

A Module For Thermal Pest Control In Stored Raw Materials Used In ...

African Journals Online (AJOL)

Pests are heterogeneous both in space and time, creating gradients and patterns depending on the prevailing environmental variables. Pest control efforts have utilized manipulations of these variables. This project is ona module for thermal control of pests using the hitherto waste steam from the indusries. The module is an ...

Evaluations of Silica Aerogel-Based Flexible Blanket as Passive Thermal Control Element for Spacecraft Applications

Science.gov (United States)

Hasan, Mohammed Adnan; Rashmi, S.; Esther, A. Carmel Mary; Bhavanisankar, Prudhivi Yashwantkumar; Sherikar, Baburao N.; Sridhara, N.; Dey, Arjun

2018-03-01

The feasibility of utilizing commercially available silica aerogel-based flexible composite blankets as passive thermal control element in applications such as extraterrestrial environments is investigated. Differential scanning calorimetry showed that aerogel blanket was thermally stable over - 150 to 126 °C. The outgassing behavior, e.g., total mass loss, collected volatile condensable materials, water vapor regained and recovered mass loss, was within acceptable range recommended for the space applications. ASTM tension and tear tests confirmed the material's mechanical integrity. The thermo-optical properties remained nearly unaltered in simulated space environmental tests such as relative humidity, thermal cycling and thermo-vacuum tests and confirmed the space worthiness of the aerogel. Aluminized Kapton stitched or anchored to the blanket could be used to control the optical transparency of the aerogel. These outcomes highlight the potential of commercial aerogel composite blankets as passive thermal control element in spacecraft. Structural and chemical characterization of the material was also done using scanning electron microscopy, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy.

Process-based quality for thermal spray via feedback control

Science.gov (United States)

Dykhuizen, R. C.; Neiser, R. A.

2006-09-01

Quality control of a thermal spray system manufacturing process is difficult due to the many input variables that need to be controlled. Great care must be taken to ensure that the process remains constant to obtain a consistent quality of the parts. Control is greatly complicated by the fact that measurement of particle velocities and temperatures is a noisy stochastic process. This article illustrates the application of quality control concepts to a wire flame spray process. A central feature of the real-time control system is an automatic feedback control scheme that provides fine adjustments to ensure that uncontrolled variations are accommodated. It is shown how the control vectors can be constructed from simple process maps to independently control particle velocity and temperature. This control scheme is shown to perform well in a real production environment. We also demonstrate that slight variations in the feed wire curvature can greatly influence the process. Finally, the geometry of the spray system and sensor must remain constant for the best reproducibility.

Quality control of thermal spray coatings in diesel engines; Qualitaetskontrolle an thermisch gespritzten Beschichtungen in Dieselmotoren

Energy Technology Data Exchange (ETDEWEB)

Carstensen, Jesper Vejloe [MAN Diesel and Turbo, Copenhagen (Denmark). Material Technology and Research Dept.; Lindegren, Maria [Struers A/S, Ballerup (Denmark). Application Dept.

2013-06-01

Thermal spraying is a method, which is suitable for coating of large components. The coatings can e.g. improve the wear, friction and/or corrosion properties of components so that they can withstand the increased loads. The quality of the coatings is essential to ensure reliable operation of the components. However, quality control of thermally sprayed coatings is indeed nontrivial and sample preparation is a key issue. This paper shows examples of thermal spray coated components in large diesel engines and provides insight into the methods used in preparing samples for quality control. (orig.)

System Level Analysis of a Water PCM HX Integrated into Orion's Thermal Control System

Science.gov (United States)

Navarro, Moses; Hansen, Scott; Seth, Rubik; Ungar, Eugene

2015-01-01

In a cyclical heat load environment such as low Lunar orbit, a spacecraft's radiators are not sized to reject the full heat load requirement. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a "topper" to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HXs do not use a consumable, thereby leading to reduced launch mass and volume requirements. In continued pursuit of water PCM HX development an Orion system level analysis was performed using Thermal Desktop for a water PCM HX integrated into Orion's thermal control system in a 100km Lunar orbit. The study verified of the thermal model by using a wax PCM and analyzed 1) placing the PCM on the Internal Thermal Control System (ITCS) versus the External Thermal Control System (ETCS) 2) use of 30/70 PGW verses 50/50 PGW and 3) increasing the radiator area in order to reduce PCM freeze times. The analysis showed that for the assumed operating and boundary conditions utilizing a water PCM HX on Orion is not a viable option for any case. Additionally, it was found that the radiator area would have to be increased by at least 40% in order to support a viable water-based PCM HX.

Thermal-Hydraulic Analysis Tasks for ANAV NPPs in Support of Plant Operation and Control

Directory of Open Access Journals (Sweden)

L. Batet

2007-11-01

Full Text Available Thermal-hydraulic analysis tasks aimed at supporting plant operation and control of nuclear power plants are an important issue for the Asociación Nuclear Ascó-Vandellòs (ANAV. ANAV is the consortium that runs the Ascó power plants (2 units and the Vandellòs-II power plant. The reactors are Westinghouse-design, 3-loop PWRs with an approximate electrical power of 1000 MW. The Technical University of Catalonia (UPC thermal-hydraulic analysis team has jointly worked together with ANAV engineers at different levels in the analysis and improvement of these reactors. This article is an illustration of the usefulness of computational analysis for operational support. The contents presented were operational between 1985 and 2001 and subsequently changed slightly following various organizational adjustments. The paper has two different parts. In the first part, it describes the specific aspects of thermal-hydraulic analysis tasks related to operation and control and, in the second part, it briefly presents the results of three examples of analyses that were performed. All the presented examples are related to actual situations in which the scenarios were studied by analysts using thermal-hydraulic codes and prepared nodalizations. The paper also includes a qualitative evaluation of the benefits obtained by ANAV through thermal-hydraulic analyses aimed at supporting operation and plant control.

Building-Related Symptoms, Energy, and Thermal Control in the Workplace: Personal and Open Plan Offices

Directory of Open Access Journals (Sweden)

Sally S. Shahzad

2016-04-01

Full Text Available This study compared building-related symptoms in personal and open plan offices, where high and low levels of control over the thermal environment were provided, respectively. The individualized approach in Norway provided every user with a personal office, where they had control over an openable window, door, blinds, and thermostat. In contrast, the open plan case studies in the United Kingdom provided control over openable windows and blinds only for limited occupants seated around the perimeter of the building, with users seated away from the windows having no means of environmental control. Air conditioning was deployed in the Norwegian case study buildings, while displacement ventilation and natural ventilation were utilized in the British examples. Field studies of thermal comfort were applied with questionnaires, environmental measurements, and interviews. Users’ health was better in the Norwegian model (28%, while the British model was much more energy efficient (up to 10 times. The follow-up interviews confirmed the effect of lack of thermal control on users’ health. A balanced appraisal was made of energy performance and users’ health between the two buildings.

Thermal Equilibrium Dynamic Control Based on DPWM Dual-Mode Modulation of High Power NPC Three-Level Inverter

Directory of Open Access Journals (Sweden)

Shi-Zhou Xu

2016-01-01

Full Text Available In some special applications of NPC three-level inverters, such as mine hoist, there exist special conditions of overloading during the whole hoisting process and large overload in starting stage, during which the power-loss calculation of power devices and thermal control are important factors affecting the thermal stability of inverters. The principles of SVPWM and DPWM were described in this paper firstly, based on which the dynamic power losses of the two modulations of hoist in single period were calculated. Secondly, a thermal equilibrium dynamic control based on DPMW dual-mode modulation was proposed, which can switch the modulation dynamically according to the change of dynamic power loss to realize dynamic control of power loss and thermal equilibrium of inverter. Finally, simulation and experiment prove the effectiveness of the proposed strategy.

James Webb Space Telescope Core 2 Test - Cryogenic Thermal Balance Test of the Observatorys Core Area Thermal Control Hardware

Science.gov (United States)

Cleveland, Paul; Parrish, Keith; Thomson, Shaun; Marsh, James; Comber, Brian

2016-01-01

The James Webb Space Telescope (JWST), successor to the Hubble Space Telescope, will be the largest astronomical telescope ever sent into space. To observe the very first light of the early universe, JWST requires a large deployed 6.5-meter primary mirror cryogenically cooled to less than 50 Kelvin. Three scientific instruments are further cooled via a large radiator system to less than 40 Kelvin. A fourth scientific instrument is cooled to less than 7 Kelvin using a combination pulse-tube Joule-Thomson mechanical cooler. Passive cryogenic cooling enables the large scale of the telescope which must be highly folded for launch on an Ariane 5 launch vehicle and deployed once on orbit during its journey to the second Earth-Sun Lagrange point. Passive cooling of the observatory is enabled by the deployment of a large tennis court sized five layer Sunshield combined with the use of a network of high efficiency radiators. A high purity aluminum heat strap system connects the three instrument's detector systems to the radiator systems to dissipate less than a single watt of parasitic and instrument dissipated heat. JWST's large scale features, while enabling passive cooling, also prevent the typical flight configuration fully-deployed thermal balance test that is the keystone of most space missions' thermal verification plans. This paper describes the JWST Core 2 Test, which is a cryogenic thermal balance test of a full size, high fidelity engineering model of the Observatory's 'Core' area thermal control hardware. The 'Core' area is the key mechanical and cryogenic interface area between all Observatory elements. The 'Core' area thermal control hardware allows for temperature transition of 300K to approximately 50 K by attenuating heat from the room temperature IEC (instrument electronics) and the Spacecraft Bus. Since the flight hardware is not available for test, the Core 2 test uses high fidelity and flight-like reproductions.

Dendrimer-assisted controlled growth of carbon nanotubes for enhanced thermal interface conductance

International Nuclear Information System (INIS)

Amama, Placidus B; Cola, Baratunde A; Sands, Timothy D; Xu, Xianfan; Fisher, Timothy S

2007-01-01

Multi-walled carbon nanotubes (MWCNTs) with systematically varied diameter distributions and defect densities were reproducibly grown from a modified catalyst structure templated in an amine-terminated fourth-generation poly(amidoamine) (PAMAM) dendrimer by microwave plasma-enhanced chemical vapor deposition. Thermal interface resistances of the vertically oriented MWCNT arrays as determined by a photoacoustic technique reveal a strong correlation with the quality as assessed by Raman spectroscopy. This study contributes not only to the development of an active catalyst via a wet chemical route for structure-controlled MWCNT growth, but also to the development of efficient and low-cost MWCNT-based thermal interface materials with thermal interface resistances ≤10 mm 2 K W -1

Development of a thermal control algorithm using artificial neural network models for improved thermal comfort and energy efficiency in accommodation buildings

International Nuclear Information System (INIS)

Moon, Jin Woo; Jung, Sung Kwon

2016-01-01

Highlights: • An ANN model for predicting optimal start moment of the cooling system was developed. • An ANN model for predicting the amount of cooling energy consumption was developed. • An optimal control algorithm was developed employing two ANN models. • The algorithm showed the advanced thermal comfort and energy efficiency. - Abstract: The aim of this study was to develop a control algorithm to demonstrate the improved thermal comfort and building energy efficiency of accommodation buildings in the cooling season. For this, two artificial neural network (ANN)-based predictive and adaptive models were developed and employed in the algorithm. One model predicted the cooling energy consumption during the unoccupied period for different setback temperatures and the other predicted the time required for restoring current indoor temperature to the normal set-point temperature. Using numerical simulation methods, the prediction accuracy of the two ANN models and the performance of the algorithm were tested. Through the test result analysis, the two ANN models showed their prediction accuracy with an acceptable error rate when applied in the control algorithm. In addition, the two ANN models based algorithm can be used to provide a more comfortable and energy efficient indoor thermal environment than the two conventional control methods, which respectively employed a fixed set-point temperature for the entire day and a setback temperature during the unoccupied period. Therefore, the operating range was 23–26 °C during the occupied period and 25–28 °C during the unoccupied period. Based on the analysis, it can be concluded that the optimal algorithm with two predictive and adaptive ANN models can be used to design a more comfortable and energy efficient indoor thermal environment for accommodation buildings in a comprehensive manner.

Hybrid Heat Pipes for High Heat Flux Spacecraft Thermal Control, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Grooved aluminum/ammonia Constant Conductance Heat Pipes (CCHPs) are the standard for thermal control in zero-gravity. Unfortunately, they are limited in terms of...

Control of propagation characteristics of spin wave pulses via elastic and thermal effects

Energy Technology Data Exchange (ETDEWEB)

Gómez-Arista, Ivan [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Kolokoltsev, O., E-mail: oleg.kolokoltsev@ccadet.unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Acevedo, A.; Qureshi, N. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Ordóñez-Romero, César L. [Instituto de Física, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico)

2017-05-01

A study of the magnetoelastic (ME) and thermal effects governing the phase (φ) and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides is presented. The ME effects were studied in a flexural configuration, under punctual mechanical force (F). Thermally induced ME and demagnetization phenomena were controlled by optically injected thermal power P{sub th}. It was determined that in an unclamped Ga:YIG waveguide, the force F that induces the phase shift Δφ=π, decreases by a quadratic law in the range from 1 mN to nN, and the P{sub th} at which Δφ=π decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. For nano-volume waveguides the ME control energy (E{sub me}) can be of order of aJ, and the thermal control energy (ΔE{sub th}) can be as small as 50 fJ. The response time of these effects lies in the ns time scale. Both the mechanical and the thermo-magnetic forces provide an effective control of MSSW pulse amplitude, in addition to its phase shift. The thermo-magnetic effect allows one to realize variable delays of a MSSW pulse. - Highlights: • The Magneto-elastic (ME) and optically induced thermal effects governing the phase and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides are presented. • A mechanical force that causes phase shift Δφ=π for spin waves in the waveguides decreases by a quadratic law in the range from 1 mN to nN, and the optical power that induces the phase shift Δφ=π, decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. • The response time of these effects can lie in the ns time scale.

The study of thermal processes in control systems of heat consumption of buildings

Science.gov (United States)

Tsynaeva, E.; A, Tsynaeva

2017-11-01

The article discusses the main thermal processes in the automated control systems for heat consumption (ACSHC) of buildings, schematic diagrams of these systems, mathematical models used for description of thermal processes in ACSHC. Conducted verification represented by mathematical models. It was found that the efficiency of the operation of ACSHC depend from the external and internal factors. Numerical study of dynamic modes of operation of ACSHC.

Optically-controlled long-term storage and release of thermal energy in phase-change materials.

Science.gov (United States)

Han, Grace G D; Li, Huashan; Grossman, Jeffrey C

2017-11-13

Thermal energy storage offers enormous potential for a wide range of energy technologies. Phase-change materials offer state-of-the-art thermal storage due to high latent heat. However, spontaneous heat loss from thermally charged phase-change materials to cooler surroundings occurs due to the absence of a significant energy barrier for the liquid-solid transition. This prevents control over the thermal storage, and developing effective methods to address this problem has remained an elusive goal. Herein, we report a combination of photo-switching dopants and organic phase-change materials as a way to introduce an activation energy barrier for phase-change materials solidification and to conserve thermal energy in the materials, allowing them to be triggered optically to release their stored latent heat. This approach enables the retention of thermal energy (about 200 J g -1 ) in the materials for at least 10 h at temperatures lower than the original crystallization point, unlocking opportunities for portable thermal energy storage systems.

Thermoelectric Exhaust Heat Recovery with Heat Pipe-Based Thermal Control

Science.gov (United States)

Brito, F. P.; Martins, Jorge; Hançer, Esra; Antunes, Nuno; Gonçalves, L. M.

2015-06-01

Heat pipe (HP)-based heat exchangers can be used for very low resistance heat transfer between a hot and a cold source. Their operating temperature depends solely on the boiling point of their working fluid, so it is possible to control the heat transfer temperature if the pressure of the HP can be adjusted. This is the case of the variable conductance HPs (VCHP). This solution makes VCHPs ideal for the passive control of thermoelectric generator (TEG) temperature levels. The present work assesses, both theoretically and experimentally, the merit of the aforementioned approach. A thermal and electrical model of a TEG with VCHP assist is proposed. Experimental results obtained with a proof of concept prototype attached to a small single-cylinder engine are presented and used to validate the model. It was found that the HP heat exchanger indeed enables the TEG to operate at a constant, optimal temperature in a passive and safe way, and with a minimal overall thermal resistance, under part load, it effectively reduces the active module area without deprecating the temperature level of the active modules.

Mineralogical control on thermal damage and the presence of a thermal Kaiser effect during temperature-cycling experiments

Science.gov (United States)

Browning, J.; Daoud, A.; Meredith, P. G.; Mitchell, T. M.

2017-12-01

Volcanic and geothermal systems are in part controlled by the mechanical and thermal stresses acting on them and so it is important to understand the response of volcanic rocks to thermo-mechanical loading. One such response is the well-known `Kaiser stress-memory' effect observed under cyclic mechanical loading. By contrast, the presence of an analogous `Kaiser temperature-memory effect' during cyclic thermal loading has received little attention. We have therefore explored the possibility of a Kaiser temperature-memory effect using three igneous rocks of different composition, grain size and origin; Slaufrudalur Granophyre (SGP), Nea Kameni Andesite (NKA) and Seljadalur Basalt (SB). We present results from a series of thermal stressing experiments in which acoustic emissions (AE) were recorded contemporaneously with changing temperature. Samples of each rock were subjected to both a single heating and cooling cycle to a maximum temperature of 900 °C and multiple heating/cooling cycles to peak temperatures of 350°C, 500°C, 700°C and 900 °C (all at a constant rate of 1°C/min on heating and a natural cooling rate of memory effect in SGP, but not in either NKA and SB. We further find that the vast majority of thermal crack damage is generated upon cooling in the finer grained materials (NKA and SB), but that substantial thermal crack damage is generated during heating in the coarser grained SGP. The total amount of crack damage generated due to heating or cooling is dependent on the mineral composition and, most importantly, the grain size and arrangement, as well as the maximum temperature to which the rock is exposed. Knowledge of thermal stress history and the presence of a Kaiser temperature-memory effect is potentially important in understanding magma chamber dynamics, where the cyclic nature of mechanical and thermal inflation and deflation can lead to sequential accumulation of damage, potentially leading to critical rupture.

Closed-Loop, Non-Venting Thermal Control for Mars EVA Suits, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — NASA seeks new thermal control technology for EVA suits on Mars. The system must be closed-loop and non-venting, have negligible impact on the Martian environment,...

Building envelope regulations on thermal comfort in glass facade buildings and energy-saving potential for PMV-based comfort control

Energy Technology Data Exchange (ETDEWEB)

Hwang, Ruey-Lung; Shu, Shiu-Ya [Department of Architecture, National United University, 1, Lien-Da, Kung-Ching Li, Miaoli, 36003 (China)

2011-04-15

This paper presents an investigation of the effect of building envelope regulation on thermal comfort and on the energy-saving potential for PMV-based comfort control in glass facade buildings. Occurrences and severity of overheating, based on the PMV-PPD model contained in ISO 7730, were used for the thermal comfort assessment. Parametric study simulations for an actual building with a large glass facade were carried out to predict the changes in thermal comfort levels in a space due to different glazing types, depths of overhang and glazing areas, which are the key parameters of the building envelope regulation index, named ENVLOAD, in Taiwan. The result demonstrates that the ENVLOAD has significant effect on thermal comfort. Additionally, comparative simulations between PMV-based comfort control and conventional thermostatic control were performed to investigate the changes in the energy-saving potential of a thermal comfort-controlled space due to changes of its ENVLOAD. The results demonstrate that the energy-saving potential in a PMV-based controlled space increases with low ENVLOAD conditions. (author)

Learning control for batch thermal sterilization of canned foods.

Science.gov (United States)

Syafiie, S; Tadeo, F; Villafin, M; Alonso, A A

2011-01-01

A control technique based on Reinforcement Learning is proposed for the thermal sterilization of canned foods. The proposed controller has the objective of ensuring a given degree of sterilization during Heating (by providing a minimum temperature inside the cans during a given time) and then a smooth Cooling, avoiding sudden pressure variations. For this, three automatic control valves are manipulated by the controller: a valve that regulates the admission of steam during Heating, and a valve that regulate the admission of air, together with a bleeder valve, during Cooling. As dynamical models of this kind of processes are too complex and involve many uncertainties, controllers based on learning are proposed. Thus, based on the control objectives and the constraints on input and output variables, the proposed controllers learn the most adequate control actions by looking up a certain matrix that contains the state-action mapping, starting from a preselected state-action space. This state-action matrix is constantly updated based on the performance obtained with the applied control actions. Experimental results at laboratory scale show the advantages of the proposed technique for this kind of processes. Copyright © 2010 ISA. Published by Elsevier Ltd. All rights reserved.

Studies on black anodic coatings for spacecraft thermal control applications

Energy Technology Data Exchange (ETDEWEB)

Uma Rani, R.; Subba Rao, Y.; Sharma, A.K. [ISRO Satellite Centre, Bangalore (India). Thermal Systems Group

2011-10-15

An inorganic black colouring process using nickel sulphate and sodium sulphide was investigated on anodized aluminium alloy 6061 to provide a flat absorber black coating for spacecraft thermal control applications. Influence of colouring process parameters (concentration, pH) on the physico-optical properties of black anodic film was investigated. The nature of black anodic film was evaluated by the measurement of film thickness, micro hardness and scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy studies confirmed the presence of nickel and sulphur in the black anodic coating. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion resistance of the coating. The environmental tests, namely, humidity, corrosion resistance, thermal cycling and thermo vacuum performance tests were used to evaluate the space worthiness of the coating. Optical properties of the film were measured before and after each environmental test to ascertain its stability in harsh space environment. The black anodic films provide higher thermal emittance ({proportional_to} 0.90) and solar absorptance ({proportional_to} 0.96) and their high stability during the environmental tests indicated their suitability for space and allied applications. (orig.)

Thermal equilibrium control by frequent bang-bang modulation.

Science.gov (United States)

Yang, Cheng-Xi; Wang, Xiang-Bin

2010-05-01

In this paper, we investigate the non-Markovian heat transfer between a weakly damped harmonic oscillator (system) and a thermal bath. When the system is initially in a thermal state and not correlated with the environment, the mean energy of the system always first increases, then oscillates, and finally reaches equilibrium with the bath, no matter what the initial temperature of the system is. Moreover, the heat transfer between the system and the bath can be controlled by fast bang-bang modulation. This modulation does work on the system, and temporarily inverts the direction of heat flow. In this case, the common sense that heat always transfers from hot to cold does not hold any more. At the long time scale, a new dynamic equilibrium is established between the system and the bath. At this equilibrium, the energy of the system can be either higher or lower than its normal equilibrium value. A comprehensive analysis of the relationship between the dynamic equilibrium and the parameters of the modulation as well as the environment is presented.

Thermal control surfaces on the MSFC LDEF experiments

International Nuclear Information System (INIS)

Wilkes, D.R.; Whitaker, A.F.; Zwiener, J.M.; Linton, R.C.; Shular, D.; Peters, P.N.; Gregory, J.C.

1992-01-01

There were five Marshall Space Flight Center (MSFC) experiments on the LDEF. Each of those experiments carried thermal control surfaces either as test samples or as operational surfaces. These materials experienced varying degrees of mechanical and optical damage. Some materials were virtually unchanged by the extended exposure while others suffered extensive degradation. The synergistic effects due to the constituents of the space environment are evident in the diversity of these material changes. The sample complement for the MSFC experiments is described along with results of the continuing analyses efforts

Thermal treating of acrylic matrices as a tool for controlling drug release.

Science.gov (United States)

Hasanzadeh, Davood; Ghaffari, Solmaz; Monajjemzadeh, Farnaz; Al-Hallak, M H D-Kamal; Soltani, Ghazal; Azarmi, Shirzad

2009-12-01

The purpose of the present study was to investigate the effect of thermal-treating on the release of ibuprofen from the granules prepared using aqueous dispersions of Eudragit. To accomplish this goal, different formulations were prepared using wet granulation method containing two different types of Eudragit aqueous dispersions, RS30D, RL30D and Avicel as filler. Tablets were prepared using direct compression method. The prepared tablets were thermally treated at 50 and 70 degrees C for 24 h. The drug release from tablets was assessed before and after thermal-treating. The results of release study showed that, thermally-treating the tablets at the temperatures higher than glass transition temperature (Tg) of the polymer can decrease the drug release from matrices. For mechanistic evaluation of the effect of thermal-treating, powder X-ray diffraction (XPD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), Fourier transform infrared (FT-IR) and helium pycnometer have been employed. The SEM graphs showed that the tablets have smoother surface with less porosity after thermal-treating. FT-IR spectra showed no change in the spectrum of thermally-treated tablet compared to control. In DSC graphs, no crystalline change was seen in the heat-treated samples of ibuprofen tablets, but decreased and widened peak size were related to the probable formation of solid solution of ibuprofen in Eudragit matrix. The results of helium pycnometer showed a significant decrease in the total porosity of some heat-treated samples. This study revealed the importance of thermal treating on the drug release from sustained release tablets containing Eudragit polymer.

Assessment of the Use of Nanofluids in Spacecraft Active Thermal Control Systems

Science.gov (United States)

Ungar, Eugene K.; Erickson, Lisa R.

2011-01-01

The addition of metallic nanoparticles to a base heat transfer fluid can dramatically increase its thermal conductivity. These nanofluids have been shown to have advantages in some heat transport systems. Their enhanced properties can allow lower system volumetric flow rates and can reduce the required pumping power. Nanofluids have been suggested for use as working fluids for spacecraft Active Thermal Control Systems (ATCSs). However, there are no studies showing the end-to-end effect of nanofluids on the design and performance of spacecraft ATCSs. In the present work, a parametric study is performed to assess the use of nanofluids in a spacecraft ATCSs. The design parameters of the current Orion capsule and the tabulated thermophysical properties of nanofluids are used to assess the possible benefits of nanofluids and how their incorporation affects the overall design of a spacecraft ATCS. The study shows that the unique system and component-level design parameters of spacecraft ATCSs render them best suited for pure working fluids. The addition of nanoparticles to typical spacecraft thermal control working fluids actually results in an increase in the system mass and required pumping power.

Optical Coating Performance and Thermal Structure Design for Heat Reflectors of JWST Electronic Control Unit

Science.gov (United States)

Quijada, Manuel A.; Threat, Felix; Garrison, Matt; Perrygo, Chuck; Bousquet, Robert; Rashford, Robert

2008-01-01

The James Webb Space Telescope (JWST) consists of an infrared-optimized Optical Telescope Element (OTE) that is cooled down to 40 degrees Kelvin. A second adjacent component to the OTE is the Integrated Science Instrument Module, or ISIM. This module includes the electronic compartment, which provides the mounting surfaces and ambient thermally controlled environment for the instrument control electronics. Dissipating the 200 watts generated from the ISIM structure away from the OTE is of paramount importance so that the spacecraft's own heat does not interfere with the infrared light detected from distant cosmic sources. This technical challenge is overcome by a thermal subsystem unit that provides passive cooling to the ISIM control electronics. The proposed design of this thermal radiator consists of a lightweight structure made out of composite materials and low-emittance metal coatings. In this paper, we will present characterizations of the coating emittance, bidirectional reflectance, and mechanical structure design that will affect the performance of this passive cooling system.

Assessing thermal comfort and energy efficiency in buildings by statistical quality control for autocorrelated data

International Nuclear Information System (INIS)

Barbeito, Inés; Zaragoza, Sonia; Tarrío-Saavedra, Javier; Naya, Salvador

2017-01-01

Highlights: • Intelligent web platform development for energy efficiency management in buildings. • Controlling and supervising thermal comfort and energy consumption in buildings. • Statistical quality control procedure to deal with autocorrelated data. • Open source alternative using R software. - Abstract: In this paper, a case study of performing a reliable statistical procedure to evaluate the quality of HVAC systems in buildings using data retrieved from an ad hoc big data web energy platform is presented. The proposed methodology based on statistical quality control (SQC) is used to analyze the real state of thermal comfort and energy efficiency of the offices of the company FRIDAMA (Spain) in a reliable way. Non-conformities or alarms, and the actual assignable causes of these out of control states are detected. The capability to meet specification requirements is also analyzed. Tools and packages implemented in the open-source R software are employed to apply the different procedures. First, this study proposes to fit ARIMA time series models to CTQ variables. Then, the application of Shewhart and EWMA control charts to the time series residuals is proposed to control and monitor thermal comfort and energy consumption in buildings. Once thermal comfort and consumption variability are estimated, the implementation of capability indexes for autocorrelated variables is proposed to calculate the degree to which standards specifications are met. According with case study results, the proposed methodology has detected real anomalies in HVAC installation, helping to detect assignable causes and to make appropriate decisions. One of the goals is to perform and describe step by step this statistical procedure in order to be replicated by practitioners in a better way.

Optimal control of building storage systems using both ice storage and thermal mass – Part I: Simulation environment

International Nuclear Information System (INIS)

Hajiah, Ali; Krarti, Moncef

2012-01-01

Highlights: ► A simulation environment is described to account for both passive and active thermal energy storage (TES) systems. ► Laboratory testing results have been used to validate the predictions from the simulation environment. ► Optimal control strategies for TES systems have been developed as part of the simulation environment. - Abstract: This paper presents a simulation environment that can evaluate the benefits of using simultaneously building thermal capacitance and ice storage system to reduce total operating costs including energy and demand charges while maintaining adequate occupant comfort conditions within commercial buildings. The building thermal storage is controlled through pre-cooling strategies by setting space indoor air temperatures. The ice storage system is controlled by charging the ice tank and operating the chiller during low electrical charge periods and melting the ice during on-peak periods. Optimal controls for both building thermal storage and ice storage are developed to minimize energy charges, demand charges, or combined energy and demand charges. The results obtained from the simulation environment are validated using laboratory testing for an optimal controller.

Biology and thermal requirements to Trichogramma spp. selection for Ecdytolopha aurantiana control

International Nuclear Information System (INIS)

Molina, Rosa M.S.; Parra, Jose R.P.

2005-01-01

The purpose of this work was to evaluate the potential of Trichogramma atopovirilia Oatman and Platner, 1983 and T. pretiosum Riley, 1879 as agents of control of Ecdytolopha aurantiana (Lima, 1927) (Lepidoptera: Tortricidae), an important Citrus pest in Sao Paulo State (South-East Brazil). In order to provide subsidies to programs of biological control with these parasitoids, studies of biology in different temperatures, thermal requirements and parasitism capacity were carried out. The temperatures (18, 20, 22, 25, 28, 30, and 32 deg C) did not affect the sex ratio, however, female longevity of both species was higher at 22 and 25 deg C. The temperature of 25 deg C tended to be more suitable to both emergency rate and female longevity. The egg-adult period for both Trichogramma species was inversely proportional to temperature. The thermal requirements of the two species were very close, about 108 DD (degree days). Neither the natural rearing host, E. aurantiana, nor the alternative host Anagasta kuehniella (Zeller, 1879) (Lepidoptera, Pyralidae), affected the number of parasitized eggs per Trichogramma female. The parasitism rate and the number of emerged adults per egg on E. aurantiana eggs were higher than on A. kuehniella eggs. However, the emergency rate was higher when the parasitoids were reared on A. kuehniella eggs. Both Trichogramma species could be tested in the field for citrus fruit borer control. The thermal requirements and the parasitism capacity also could be good parameters for selection of Trichogramma species/strains. (author)

Simulation, optimization and control of a thermal cracking furnace

International Nuclear Information System (INIS)

Masoumi, M.E.; Sadrameli, S.M.; Towfighi, J.; Niaei, A.

2006-01-01

The ethylene production process is one of the most important aspect of a petrochemical plant and the cracking furnace is the heart of the process. Since, ethylene is one of the raw materials in the chemical industry and the market situation of not only the feed and the product, but also the utility is rapidly changing, the optimal operation and control of the plant is important. A mathematical model, which describes the static and dynamic operations of a pilot plant furnace, was developed. The static simulation was used to predict the steady-state profiles of temperature, pressure and products yield. The dynamic simulation of the process was used to predict the transient behavior of thermal cracking reactor. Using a dynamic programming technique, an optimal temperature profile was developed along the reactor. Performances of temperature control loop were tested for different controller parameters and disturbances. The results of the simulation were tested experimentally in a computer control pilot plant

Comfort and performance impact of personal control over thermal environment in summer

DEFF Research Database (Denmark)

Boerstra, Atze C.; te Kulve, Marije; Toftum, Jørn

2015-01-01

Field studies suggest that the availability of adjustable thermostats, operable windows and other controls has a positive impact on comfort, the incidence of building related symptoms and productivity. This laboratory study was designed to further investigate how having or not having control over...... the thermal environment affects human responses to the indoor environment.The study was conducted in summer in a field laboratory that was kept at 28°C. A total of 23 subjects were exposed twice for about 2.5h. During the first session (A) subjects were able to fine-tune their local thermal environment at any...... recorded during the first session. Thus, each subject was exposed to two customized conditions with identical exposure, only different from a psychological point of view.During the two sessions identical questionnaires and performance tests were used to evaluate subjects' comfort, SBS symptom incidence...

Controlling Heat Transport and Flow Structures in Thermal Turbulence Using Ratchet Surfaces

Science.gov (United States)

Jiang, Hechuan; Zhu, Xiaojue; Mathai, Varghese; Verzicco, Roberto; Lohse, Detlef; Sun, Chao

2018-01-01

In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchetlike roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the large scale circulation roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through a quantitative analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. The current work has important implications for passive and active flow control in engineering, biofluid dynamics, and geophysical flows.

Thermal cycling fatigue of organic thermal interface materials using a thermal-displacement measurement technique

Science.gov (United States)

Steill, Jason Scott

The long term reliability of polymer-based thermal interface materials (TIM) is essential for modern electronic packages which require robust thermal management. The challenge for today's materials scientists and engineers is to maximize the heat flow from integrated circuits through a TIM and out the heat sink. Thermal cycling of the electronic package and non-uniformity in the heat flux with respect to the plan area can lead to void formation and delamination which re-introduces inefficient heat transfer. Measurement and understanding at the nano-scale is essential for TIM development. Finding and documenting the evolution of the defects is dependent upon a full understanding of the thermal probes response to changing environmental conditions and the effects of probe usage. The response of the thermal-displacement measurement technique was dominated by changes to the environment. Accurate measurement of the thermal performance was hindered by the inability to create a model system and control the operating conditions. This research highlights the need for continued study into the probe's thermal and mechanical response using tightly controlled test conditions.

Tropical Cyclone Report, 1988

Science.gov (United States)

1988-01-01

Cmdr. David Gray; National Weather Service 5. Cooperation with the Naval Environmental Pacific Region for the startup of 24-hour operatiois at Ponape...0.1 27.7 TOTAL CASES 3 1 1 4 12 27 54 56 30 25 7 1 221 * (GRAY, 1979) TABLE 4-3 ANNUAL VARIATION C SOTR MUSHER TROPICAL CYCLOUZ BY O(EN BASIN SOUTH

Electrically conductive, black thermal control coatings for spacecraft applications. III - Plasma-deposited ceramic matrix

Science.gov (United States)

Hribar, V. F.; Bauer, J. L.; O'Donnell, T. P.

1987-01-01

Five black, electrically-conductive thermal control coatings have been formulated and tested for application on the Galileo spacecraft. The coatings consist of both organic and inorganic systems applied on titanium, aluminum, and glass/epoxy composite surfaces. The coatings were tested under simulated space environment conditions. Coated specimens were subjected to thermal radiation, convective and combustive heating, and cryogenic conditions over a temperature range between -196 C and 538 C. Mechanical, physical, thermal, electrical, and thermooptical properties are presented for one of these coatings. This paper describes the preparation, characteristics, and spraying of iron titanate on titanium and aluminum, and presents performance results.

Safe, Non-Corrosive Dielectric Fluid for Stagnating Radiator Thermal Control System, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Paragon proposes to develop a single-loop, non-toxic, stagnating active pumped loop thermal control design for NASA's Orion or Lunar Surface Access Module (LSAM)...

Thermal margin control

International Nuclear Information System (INIS)

Musick, C.R.

1976-01-01

A monitoring system is described for providing warning and/or trip signals indicative of the approach of the operating conditions of a nuclear steam supply system to a departure from nucleate boiling or coolant temperature saturation. The invention is characterized by calculation of the thermal limit locus in response to signals which accurately represent reactor cold leg temperature and core power, the core power signal being adjusted to compensate for the effects of both radial and axial peaking factor. 37 claims, 3 figures

Thermal control for the MFTF magnet

International Nuclear Information System (INIS)

Vansant, J.H.; Russ, R.M.

1980-01-01

The external dimensions of the Yin-Yang magnet of the Mirror Fusion Test Facility will be 7.8 by 8.5 by 8.5 m, and it will weigh approximately 300 tons. More than 8000 liters of circulating liquid helium will be required to maintain the nearly 50 km of superconductor at below 5.0 K while the latter carries almost 6000 A in a magnetic field of up to nearly 7.7 T. This paper describes several features of the thermal control plans for the Yin-Yang: (1) the proposed cooldown and warmup schedules for the MFTF and the procedure for regenerating external cooling surfaces (2) the design of an external quench resistor based on an estimate of the superconductor's maximum temperature and (3) the use of a computer model of liquid helium circulation in choosing pipe size for the liquid helium lines

Fuzzy control of the iron ore pellets thermal treatment on a conveying car

Directory of Open Access Journals (Sweden)

В’ячеслав Йосипович Лобов

2017-07-01

Full Text Available The purpose of this article is to solve the problem of fuzzy control of iron ore pellets thermal treatment on a conveyor roasting machine, to build an automated control system of conveyor roasting machine and perform simulation and to present the results of research. According to the structural scheme of the fuzzy control an automated control system is proposed for being modelled. This is done by using the software MATLAB. The use of atomic emission spectroscopy determines the percentage of the major elements in iron ore pellets considering the main process parameters. This article uses an automated system of fuzzy control of iron ore pellets firing on a conveyor roasting machine with the introduction of atomic emission spectroscopy of the pellets. Development and practical implementation of fuzzy control will improve their quality by taking into account the basic parameters of thermal treatment of pellets such as speed of movement of the grate trucks, gas flow rate, the height of the layer of pellets and the venting speed of the pellets layer with gas-air flow, humidity, average diameter, the basicity and the iron composition in the pellets. The expediency of the developed method of using automated fuzzy control system of iron ore pellets firing on a conveyor roasting car has been proved. The system with fuzzy controller provides a reduction on average 2 m3/h, which is 0,3% of natural gas consumption as compared to the existing systems. This provides more uniform gas permeability of the layer of pellets, which leads to filtration rate increase of the gas flow and to heat exchange intensification in the layer of pellets. It makes it possible to introduce the atomic emission spectroscopy of non-burned pellets and to increase the productivity of conveyor roasting machine by 2,5%. At the same time the resistance of technological equipment (pallets increases, due to more uniform distribution of the thermal field

Vision-aided Monitoring and Control of Thermal Spray, Spray Forming, and Welding Processes

Science.gov (United States)

Agapakis, John E.; Bolstad, Jon

1993-01-01

Vision is one of the most powerful forms of non-contact sensing for monitoring and control of manufacturing processes. However, processes involving an arc plasma or flame such as welding or thermal spraying pose particularly challenging problems to conventional vision sensing and processing techniques. The arc or plasma is not typically limited to a single spectral region and thus cannot be easily filtered out optically. This paper presents an innovative vision sensing system that uses intense stroboscopic illumination to overpower the arc light and produce a video image that is free of arc light or glare and dedicated image processing and analysis schemes that can enhance the video images or extract features of interest and produce quantitative process measures which can be used for process monitoring and control. Results of two SBIR programs sponsored by NASA and DOE and focusing on the application of this innovative vision sensing and processing technology to thermal spraying and welding process monitoring and control are discussed.

A Numerical Proof of Concept for Thermal Flow Control

Directory of Open Access Journals (Sweden)

V. Dragan

2017-02-01

Full Text Available In this paper computational fluid dynamics is used to provide a proof of concept for controlled flow separation using thermal wall interactions with the velocity boundary layer. A 3D case study is presented, using a transition modeling Shear Stress Transport turbulence model. The highly loaded single slot flap airfoil was chosen to be representative for a light aircraft and the flow conditions were modeled after a typical landing speed. In the baseline case, adiabatic walls were considered while in the separation control case, the top surface of the flaps was heated to 500 K. This heating lead to flow separation on the flaps and a significant alteration of the flow pattern across all the elements of the wing. The findings indicate that this control method has potential, with implications in both aeronautical as well as sports and civil engineering applications.

Construction and experimental verification of a novel flexible thermal control system configuration for the autonomous on-orbit services of space missions

International Nuclear Information System (INIS)

Guo, Wei; Li, Yunhua; Li, Yun-Ze; Wang, Sheng-Nan; Zhong, Ming-Liang; Wang, Ji-Xiang; Zhang, Jia-Xun

2017-01-01

Highlights: • A novel flexible thermal control system (F-TCS) for spacecraft on-orbit services is proposed. • Systemic construction and reconfiguration operating mechanism are highlighted. • Thermal-hydraulic performances of the F-TCS are investigated both numerically and experimentally. • The F-TCS has the vast potential for spacecrafts autonomous thermal management. - Abstract: This paper proposed a novel flexible thermal control system (F-TCS) configuration for realizing thermal management for spacecrafts autonomous on-orbit service (A-OOS) demands. With a dual-ring topology which composes of a heat collecting bus, a heat dissipating bus, connection brunches and inter-platform service interfaces, the F-TCS may realize not only self-reconfiguration operations but also providing heat dissipation resources for other spacecrafts or cabins. The F-TCS hydraulic and thermal dynamics were modeled, a verification testbed was also established to validate the F-TCS thermal control performance. Focused on investigating the self-reconfiguration and thermal control cooperative operations, several typical A-OOS cases were imposed on the F-TCS, numerical simulations and experimental validations were respectively implemented. Both results demonstrated that the meticulously designed F-TCS is capable of offering self-topological reconfiguration with fast time response and robust temperature control performances, high systemic heat transfer efficiency is also recommended from the point of view of energy saving. The F-TCS is suggested as a promising solution for A-OOS owing to its higher reliability and promising autonomous maintenance potential which is suitable for future spacecrafts thermal management requirements.

System Level Analysis of a Water PCM HX Integrated Into Orion's Thermal Control System Abstract

Science.gov (United States)

Navarro, Moses; Hansen, Scott; Ungar, Eugene; Sheth, Rubik

2015-01-01

In a cyclical heat load environment such as low Lunar orbit, a spacecraft's radiators are not sized to reject the full heat load requirement. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a "topper" to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HXs do not use a consumable, thereby leading to reduced launch mass and volume requirements. In continued pursuit of water PCM HX development an Orion system level analysis was performed using Thermal Desktop for a water PCM HX integrated into Orion's thermal control system and in a 100km Lunar orbit. The study analyzed 1) placing the PCM on the Internal Thermal Control System (ITCS) versus the External Thermal Control System (ETCS) 2) use of 30/70 PGW verses 50/50 PGW and 3) increasing the radiator area in order to reduce PCM freeze times. The analysis showed that for the assumed operating and boundary conditions utilizing a water PCM HX on Orion is not a viable option. Additionally, it was found that the radiator area would have to be increased over 20% in order to have a viable water-based PCM HX.

Electromagnetic and thermal analysis of electromagnet for SMART control element drive mechanism

International Nuclear Information System (INIS)

Huh, H.; Kim, J. H.; Park, J. S.; Kim, Y. W.; Kim, J. I.

1999-01-01

A numerical electromagnetic and thermal analysis was performed for the electromagnet which is installed in the control element drive mechanism(CEDM) of the integral reactor SMART. A model for the electromagnetic analysis of the electromagnet was developed and theoretical bases for the model were established. Design parameters related to thrust force were identified, and the optimum design point was determined by analyzing the trend of the magnetic saturation with finite element method. Also It is important that the temperature of the electomagnet windings be maintained within the allowable limit of the insulation, since the electromagnet of CEDM is always supplied with current during the reactor operation. So the thermal analysis of the winding insulation which is composed of polyimide and air were performed by finite element method. The electromagnetic and thermal properties obtained here will be used as input for the optimization analysis of the electromagnet

A numerical and experimental investigation of the thermal control performance of a spaceborne compressor assembly

Science.gov (United States)

Oh, Hyun-Ung; Lee, Min-Kyu; Shin, Somin; Hong, Joo-Sung

2011-09-01

Spaceborne pulse tube type cryocoolers are widely used for providing cryogenic temperatures for sensitive infrared, gamma-ray and X-ray detectors. Thermal control for the compressor of the cryocooler is one of the important technologies for the cooling performance, mission life time, and jitter stability of the cooler. The thermal design of the compressor assembly proposed in this study is basically composed of a heat pipe, a radiator, and a heater. In the present work, a method for heat pipe implementation is proposed and investigated to ensure the jitter stability of the compressor under the condition that one heat pipe is not working. An optimal design of the radiator that uses ribs for effective use by minimizing the temperature gradient on the radiator and reducing its weight is introduced. The effectiveness of the thermal design of the compressor assembly is demonstrated by on-orbit thermal analysis using the correlated thermal model obtained from the thermal balance test that is performed under a space simulating environment.

International Space Station Active Thermal Control Sub-System On-Orbit Pump Performance and Reliability Using Liquid Ammonia as a Coolant

Science.gov (United States)

Morton, Richard D.; Jurick, Matthew; Roman, Ruben; Adamson, Gary; Bui, Chinh T.; Laliberte, Yvon J.

2011-01-01

The International Space Station (ISS) contains two Active Thermal Control Sub-systems (ATCS) that function by using a liquid ammonia cooling system collecting waste heat and rejecting it using radiators. These subsystems consist of a number of heat exchangers, cold plates, radiators, the Pump and Flow Control Subassembly (PFCS), and the Pump Module (PM), all of which are Orbital Replaceable Units (ORU's). The PFCS provides the motive force to circulate the ammonia coolant in the Photovoltaic Thermal Control Subsystem (PVTCS) and has been in operation since December, 2000. The Pump Module (PM) circulates liquid ammonia coolant within the External Active Thermal Control Subsystem (EATCS) cooling the ISS internal coolant (water) loops collecting waste heat and rejecting it through the ISS radiators. These PM loops have been in operation since December, 2006. This paper will discuss the original reliability analysis approach of the PFCS and Pump Module, comparing them against the current operational performance data for the ISS External Thermal Control Loops.

Predictive control of thermal state of blast furnace

Science.gov (United States)

Barbasova, T. A.; Filimonova, A. A.

2018-05-01

The work describes the structure of the model for predictive control of the thermal state of a blast furnace. The proposed model contains the following input parameters: coke rate; theoretical combustion temperature, comprising: natural gas consumption, blasting temperature, humidity, oxygen, blast furnace cooling water; blast furnace gas utilization rate. The output parameter is the cast iron temperature. The results for determining the cast iron temperature were obtained following the identification using the Hammerstein-Wiener model. The result of solving the cast iron temperature stabilization problem was provided for the calculated values of process parameters of the target area of the respective blast furnace operation mode.

A Modified Thermal Treatment Method for the Up-Scalable Synthesis of Size-Controlled Nanocrystalline Titania

Directory of Open Access Journals (Sweden)

Aysar Sabah Keiteb

2016-10-01

Full Text Available Considering the increasing demand for titania nanoparticles with controlled quality for various applications, the present work reports the up-scalable synthesis of size-controlled titanium dioxide nanocrystals with a simple and convenient thermal treatment route. Titanium dioxide nanocrystals with tetragonal structure were synthesized directly from an aqueous solution containing titanium (IV isopropoxide as the main reactant, polyvinyl pyrrolidone (PVP as the capping agent, and deionized water as a solvent. With the elimination of the drying process in a thermal treatment method, an attempt was made to decrease the synthesis time. The mixture directly underwent calcination to form titanium dioxide (TiO2 nanocrystalline powder, which was confirmed by FT-IR, energy dispersive X-ray spectroscopy (EDX, and X-ray diffraction (XRD analysis. The control over the size and optical properties of nanocrystals was achieved via variation in calcination temperatures. The obtained average sizes from XRD spectra and transmission electron microscopy (TEM images showed exponential variation with increasing calcination temperature. The optical properties showed a decrease in the band gap energy with increasing calcination temperature due to the enlargement of the nanoparticle size. These results prove that direct calcination of reactant solution is a convenient thermal treatment route for the potential large-scale production of size-controlled Titania nanoparticles.

Thermal stability of hydrocarbons in nature: Limits, evidence, characteristics, and possible controls

Science.gov (United States)

Price, L.C.

1993-01-01

Numerous petroleum-geochemical analyses of deeply buried, high-rank, fine-grained rocks from ultra-deep wellbores by different investigators demonstrate that C15+ hydrocarbons (HCs) persist in moderate to high concentrations at vitrinite reflectance (R0) values of 2.0-5.0% and persist in measurable concentrations up to R0 = 7.0-8.0%, at which point the thermal deadline for C15+ HC's is finally approached. Qualitative analyses have been carried out on 1. (1) high-rank gas condensates which have been exposed to the HC-thermal-destructive phase, 2. (2) bitumens from high-temperature aqueous-pyrolysis experiments in the HC-thermal-destructive phase, and 3. (3) bitumens from high-rank, fine-grained rocks near the HC-thermal-destructive phase. These analyses clearly demonstrate that well-defined compositional suites are established in the saturated, aromatic, and sulfur-bearing aromatic HCs in and near the HC-thermal-destructive phase. On the other hand, accepted petroleum-geochemical paradigms place rigid limits on HC thermal stability: C15+ HCs begin thermal cracking at R0 values of 0.9% and are completely thermally destroyed by R0 = 1.35%; C2-C4 HC gases are thermally destroyed by R0 = 2.0% and methane is thermally destroyed by R0 = 4.0%. Furthermore, published data and observations in many HC basins worldwide support these models; for example, 1. (1) sharp basinal zonations of gas and oil deposits vs. maturation rank in HC basins and 2. (2) decreasing C15+ HC concentrations in some fine-grained rocks at ranks of R0 ??? 0.9%. The fact that observed data (C15+ HCs thermally stable to R0 = 7.0-8.0%) is so far removed from predicted behavior (C15+) HCs expected to be thermally destroyed by R0 = 1.35%) may be due to 1. (1) a lack of recognition of some important possible controlling parameters of organic matter (OM) metamorphism and too much importance given to other assumed controlling parameters; and 2. (2) assigning HC distribution patterns in petroleum basins to HC

Controlling thermal deformation by using composite materials having variable fiber volume fraction

International Nuclear Information System (INIS)

Bouremana, M.; Tounsi, A.; Kaci, A.; Mechab, I.

2009-01-01

In application, many thin structural components such as beams, plates and shells experience a through-thickness temperature variation. This temperature variation can produce both an in-plane expansion and an out-of-plane (bending) curvature. Given that these thin components interact with or connect to other components, we often wish to minimize the thermal deformation or match the thermal deformation of another component. This is accomplished by using a composite whose fibers have a negative axial thermal expansion coefficient. By varying the fiber volume fraction within a symmetric laminated beam to create a functionally graded material (FGM), certain thermal deformations can be controlled or tailored. Specifically, a beam can be designed which does not curve under a steady-state through-thickness temperature variation. Continuous gradation of the fiber volume fraction in the FGM layer is modelled in the form of a mth power polynomial of the coordinate axis in thickness direction of the beam. The beam results are independent of the actual temperature values, within the limitations of steady-state heat transfer and constant material properties. The influence of volume fiber fraction distributions are studied to match or eliminate an in-plane expansion coefficient, or to match a desired axial stiffness. Combining two fiber types to create a hybrid FGM can offer desirable increase in axial and bending stiffness while still retaining the useful thermal deformation behavior.

Fundamental limitations of non-thermal plasma processing for internal combustion engine NOx control

International Nuclear Information System (INIS)

Penetrante, B.M.

1993-01-01

This paper discusses the physics and chemistry of non-thermal plasma processing for post-combustion NO x control in internal combustion engines. A comparison of electron beam and electrical discharge processing is made regarding their power consumption, radical production, NO x removal mechanisms, and by product formation. Can non-thermal deNO x operate efficiently without additives or catalysts? How much electrical power does it cost to operate? What are the by-products of the process? This paper addresses these fundamental issues based on an analysis of the electron-molecule processes and chemical kinetics

Project W-320 SAR and process control thermal analyses

International Nuclear Information System (INIS)

Sathyanarayana, K.

1997-01-01

This report summarizes the results of thermal hydraulic computer modeling supporting Project W-320 for process control and SAR documentation. Parametric analyses were performed for the maximum steady state waste temperature. The parameters included heat load distribution, tank heat load, fluffing factor and thermal conductivity. Uncertainties in the fluffing factor and heat load distribution had the largest effect on maximum waste temperature. Safety analyses were performed for off normal events including loss of ventilation, loss of evaporation and loss of secondary chiller. The loss of both the primary and secondary ventilation was found to be the most limiting event with saturation temperature in the bottom waste reaching in just over 30 days. An evaluation was performed for the potential lowering of the supernatant level in tank 241-AY-102. The evaluation included a loss of ventilation and steam bump analysis. The reduced supernatant level decreased the time to reach saturation temperature in the waste for the loss of ventilation by about one week. However, the consequence of a steam bump were dramatically reduced

Improvement of chemical control in the water-steam cycle of thermal power plants

International Nuclear Information System (INIS)

Rajakovic-Ognjanovic, Vladana N.; Zivojinovic, Dragana Z.; Grgur, Branimir N.; Rajakovic, Ljubinka V.

2011-01-01

A more effective chemical control in the water-steam cycle (WSC) of thermal power plants (TPP) is proposed in this paper. Minimization of corrosion effects by the production of ultra pure water and its strict control is the basis of all the investigated processes. The research involved the analysis of water samples in the WSC through key water quality parameters and by the most convenient analytical tools. The necessity for the stricter chemical control is demonstrated through a concrete example of the TPP Nikola Tesla, Serbia. After a thorough analysis of the chemical control system of the WSC, diagnostic and control parameters were chosen for continuous systematic measurements. Sodium and chloride ions were recognized as the ions which indicate the corrosion potential of the water and give insight into the proper production and maintenance of water within the WSC. Chemical transformations of crucial corrosion elements, iron and silica, were considered and related to their quantitative values. - Research highlights: → The more effective chemical control in the water-steam cycle of thermal power plant Nikola Tesla, Serbia. → In chemical control the diagnostic and control parameters were optimized and introduced for the systematic measurements in the water-steam cycle. → Sodium and chloride ions were recognized as ions which indicate corrosion potential of water and give insight to proper function of production and maintenance of water within water-team cycle. → Chemical transformations of crucial corrosion elements, iron and silica are considered and related with their quantitative values.

Microgrid Control Strategy Utlizing Thermal Energy Storage With Renewable Solar And Wind Power Generation

Science.gov (United States)

2016-06-01

iii Approved for public release; distribution is unlimited MICROGRID CONTROL STRATEGY UTLIZING THERMAL ENERGY STORAGE WITH RENEWABLE SOLAR AND WIND... control tracks increasing power generation in the morning. The batteries require a large amount of electrical power to charge every morning, as charge ...is 37 lost throughout the night. This causes the solar panels to output their maximum power generation. The MPPT control records when power

A control-oriented model for combined building climate comfort and aquifer thermal energy storage system

NARCIS (Netherlands)

Rostampour Samarin, Vahab; Bloemendal, J.M.; Jaxa-Rozen, M.; Keviczky, T.

2016-01-01

This paper presents a control-oriented model for combined building climate comfort and aquifer thermal energy storage (ATES) system. In particular, we first provide a description of building operational systems together with control framework variables. We then focus on the derivation of an

International Space Station Passive Thermal Control System Analysis, Top Ten Lessons-Learned

Science.gov (United States)

Iovine, John

2011-01-01

The International Space Station (ISS) has been on-orbit for over 10 years, and there have been numerous technical challenges along the way from design to assembly to on-orbit anomalies and repairs. The Passive Thermal Control System (PTCS) management team has been a key player in successfully dealing with these challenges. The PTCS team performs thermal analysis in support of design and verification, launch and assembly constraints, integration, sustaining engineering, failure response, and model validation. This analysis is a significant body of work and provides a unique opportunity to compile a wealth of real world engineering and analysis knowledge and the corresponding lessons-learned. The analysis lessons encompass the full life cycle of flight hardware from design to on-orbit performance and sustaining engineering. These lessons can provide significant insight for new projects and programs. Key areas to be presented include thermal model fidelity, verification methods, analysis uncertainty, and operations support.

Control performances of a piezoactuator direct drive valve system at high temperatures with thermal insulation

Science.gov (United States)

Han, Yung-Min; Han, Chulhee; Kim, Wan Ho; Seong, Ho Yong; Choi, Seung-Bok

2016-09-01

This technical note presents control performances of a piezoactuator direct drive valve (PDDV) operated at high temperature environment. After briefly discussing operating principle and mechanical dimensions of the proposed PDDV, an appropriate size of the PDDV is manufactured. As a first step, the temperature effect on the valve performance is experimentally investigated by measuring the spool displacement at various temperatures. Subsequently, the PDDV is thermally insulated using aerogel and installed in a large-size heat chamber in which the pneumatic-hydraulic cylinders and sensors are equipped. A proportional-integral-derivative feedback controller is then designed and implemented to control the spool displacement of the valve system. In this work, the spool displacement is chosen as a control variable since it is directly related to the flow rate of the valve system. Three different sinusoidal displacements with different frequencies of 1, 10 and 50 Hz are used as reference spool displacement and tracking controls are undertaken up to 150 °C. It is shown that the proposed PDDV with the thermal insulation can provide favorable control responses without significant tracking errors at high temperatures.

Artificial Neural Network based control for PV/T panel to track optimum thermal and electrical power

International Nuclear Information System (INIS)

Ben Ammar, Majed; Chaabene, Maher; Chtourou, Zied

2013-01-01

Highlights: ► We establish a state model of PV/T panel. ► We study the effect of mass flow rate on PV/T efficiency. ► A real time PV/T control algorithm is proposed. ► A model based optimal thermal and electrical power operation point is tracked. - Abstract: As solar energy is intermittent, many algorithms and electronics have been developed to track the maximum power generation from photovoltaic and thermal panels. Following technological advances, these panels are gathered into one unit: PV/T system. PV/T delivers simultaneously two kinds of power: electrical power and thermal power. Nevertheless, no control systems have been developed in order to track maximum power generation from PV/T system. This paper suggests a PV/T control algorithm based on Artificial Neural Network (ANN) to detect the optimal power operating point (OPOP) by considering PV/T model behavior. The OPOP computes the optimum mass flow rate of PV/T for a considered irradiation and ambient temperature. Simulation results demonstrate great concordance between OPOP model based calculation and ANN outputs.

LTCS (Laser Thermal Control System) Test Supporting the Improvement of DeCoM (Deepak Condenser Model)

Science.gov (United States)

Patel, Deepak

2014-01-01

Thermal and Fluids Analysis Workshop, Cleveland OH. NCTS 19701-14. On Dec 2013 a Loop Heat Pipe (LHP) test was performed as part of the integral Laser Thermal Control System (LTCS). During the balance portion of this testing it was noticed that the LHP was not going to be able to maintain temperature on the operational thermal mass. The test was stopped. After multiple meetings with the LTCS designers, LHP experts (in house and external) it was concluded that gravity was preventing the control heaters to maintain control on the reservoir. A heater was installed onto the liquid return line as part of the fix. After implementing the fix on the liquid return line, the test on May 2014 proved that the system works in vertical orientation using the liquid line heater. Through this testing, the correlation of the Deepak Condenser Model (DeCoM) was possible. This paper describes how well DeCoM predicts the condenser behavior in comparison to the test results of LTCS test.

Stable and self-adaptive performance of mechanically pumped CO2 two-phase loops for AMS-02 tracker thermal control in vacuum

International Nuclear Information System (INIS)

Zhang, Z.; Sun, X.-H.; Tong, G.-N.; Huang, Z.-C.; He, Z.-H.; Pauw, A.; Es, J. van; Battiston, R.; Borsini, S.; Laudi, E.; Verlaat, B.; Gargiulo, C.

2011-01-01

A mechanically pumped CO 2 two-phase loop cooling system was developed for the temperature control of the silicon tracker of AMS-02, a cosmic particle detector to work in the International Space Station. The cooling system (called TTCS, or Tracker Thermal Control System), consists of two evaporators in parallel to collect heat from the tracker's front-end electronics, two radiators in parallel to emit the heat into space, and a centrifugal pump that circulates the CO 2 fluid that carries the heat to the radiators, and an accumulator that controls the pressure, and thus the temperature of the evaporators. Thermal vacuum tests were performed to check and qualify the system operation in simulated space thermal environment. In this paper, we reported the test results which show that the TTCS exhibited excellent temperature control ability, including temperature homogeneity and stability, and self-adaptive ability to the various external heat flux to the radiators. Highlights: → The active-pumped CO 2 two-phase cooling loop passed the thermal vacuum test. → It provides high temperature homogeneity and stability thermal boundaries. → Its working temperature is controllable in vacuum environment. → It possesses self-adaptive ability to imbalanced external heat fluxes.

A Controlled Agitation Process for Improving Quality of Canned Green Beans during Agitation Thermal Processing.

Science.gov (United States)

Singh, Anika; Pratap Singh, Anubhav; Ramaswamy, Hosahalli S

2016-06-01

This work introduces the concept of a controlled agitation thermal process to reduce quality damage in liquid-particulate products during agitation thermal processing. Reciprocating agitation thermal processing (RA-TP) was used as the agitation thermal process. In order to reduce the impact of agitation, a new concept of "stopping agitations after sufficient development of cold-spot temperature" was proposed. Green beans were processed in No. 2 (307×409) cans filled with liquids of various consistency (0% to 2% CMC) at various frequencies (1 to 3 Hz) of RA-TP using a full-factorial design and heat penetration results were collected. Corresponding operator's process time to impart a 10-min process lethality (Fo ) and agitation time (AT) were calculated using heat penetration results. Accordingly, products were processed again by stopping agitations as per 3 agitation regimes, namely; full time agitation, equilibration time agitation, and partial time agitation. Processed products were photographed and tested for visual quality, color, texture, breakage of green beans, turbidity, and percentage of insoluble solids in can liquid. Results showed that stopping agitations after sufficient development of cold-spot temperatures is an effective way of reducing product damages caused by agitation (for example, breakage of beans and its leaching into liquid). Agitations till one-log temperature difference gave best color, texture and visual product quality for low-viscosity liquid-particulate mixture and extended agitations till equilibration time was best for high-viscosity products. Thus, it was shown that a controlled agitation thermal process is more effective in obtaining high product quality as compared to a regular agitation thermal process. © 2016 Institute of Food Technologists®

Bottom-up nanoarchitecture of semiconductor nano-building blocks by controllable in situ SEM-FIB thermal soldering method

KAUST Repository

Zhang, Xuan; Zheng, Xiujun; Zhang, Hong; Zhang, Junli; Fu, Jiecai; Zhang, Qiang; Peng, Chaoyi; Bai, Feiming; Zhang, Xixiang; Peng, Yong

2017-01-01

Here we demonstrate that the building blocks of semiconductor WO3 nanowires can be controllably soldered together by a novel nano-soldering technique of in situ SEM-FIB thermal soldering, in which the soldering temperature can precisely remain in an optimal range to avoid a strong thermal diffusion.

Bottom-up nanoarchitecture of semiconductor nano-building blocks by controllable in situ SEM-FIB thermal soldering method

KAUST Repository

Zhang, Xuan

2017-08-10

Here we demonstrate that the building blocks of semiconductor WO3 nanowires can be controllably soldered together by a novel nano-soldering technique of in situ SEM-FIB thermal soldering, in which the soldering temperature can precisely remain in an optimal range to avoid a strong thermal diffusion.

Thermal weapon sights with integrated fire control computers: algorithms and experiences

Science.gov (United States)

Rothe, Hendrik; Graswald, Markus; Breiter, Rainer

2008-04-01

The HuntIR long range thermal weapon sight of AIM is deployed in various out of area missions since 2004 as a part of the German Future Infantryman system (IdZ). In 2007 AIM fielded RangIR as upgrade with integrated laser Range finder (LRF), digital magnetic compass (DMC) and fire control unit (FCU). RangIR fills the capability gaps of day/night fire control for grenade machine guns (GMG) and the enhanced system of the IdZ. Due to proven expertise and proprietary methods in fire control, fast access to military trials for optimisation loops and similar hardware platforms, AIM and the University of the Federal Armed Forces Hamburg (HSU) decided to team for the development of suitable fire control algorithms. The pronounced ballistic trajectory of the 40mm GMG requires most accurate FCU-solutions specifically for air burst ammunition (ABM) and is most sensitive to faint effects like levelling or firing up/downhill. This weapon was therefore selected to validate the quality of the FCU hard- and software under relevant military conditions. For exterior ballistics the modified point mass model according to STANAG 4355 is used. The differential equations of motions are solved numerically, the two point boundary value problem is solved iteratively. Computing time varies according to the precision needed and is typical in the range from 0.1 - 0.5 seconds. RangIR provided outstanding hit accuracy including ABM fuze timing in various trials of the German Army and allied partners in 2007 and is now ready for series production. This paper deals mainly with the fundamentals of the fire control algorithms and shows how to implement them in combination with any DSP-equipped thermal weapon sights (TWS) in a variety of light supporting weapon systems.

Evaluating local and overall thermal comfort in buildings using thermal manikins

Energy Technology Data Exchange (ETDEWEB)

Foda, E.

2012-07-01

Evaluation methods of human thermal comfort that are based on whole-body heat balance with its surroundings may not be adequate for evaluations in non-uniform thermal conditions. Under these conditions, the human body's segments may experience a wide range of room physical parameters and the evaluation of the local (segmental) thermal comfort becomes necessary. In this work, subjective measurements of skin temperature were carried out to investigate the human body's local responses due to a step change in the room temperature; and the variability in the body's local temperatures under different indoor conditions and exposures as well as the physiological steady state local temperatures. Then, a multi-segmental model of human thermoregulation was developed based on these findings to predict the local skin temperatures of individuals' body segments with a good accuracy. The model predictability of skin temperature was verified for steady state and dynamic conditions using measured data at uniform neutral, cold and warm as well as different asymmetric thermal conditions. The model showed very good predictability with average absolute deviation ranged from 0.3-0.8 K. The model was then implemented onto the control system of the thermal manikin 'THERMINATOR' to adjust the segmental skin temperature set-points based on the indoor conditions. This new control for the manikin was experimentally validated for the prediction of local and overall thermal comfort using the equivalent temperature measure. THERMINATOR with the new control mode was then employed in the evaluation of localized floor-heating system variants towards maximum energy efficiency. This aimed at illustrating a design strategy using the thermal manikin to find the optimum geometry and surface area of a floor-heater for a single seated person. Furthermore, a psychological comfort model that is based on local skin temperature was adapted for the use with the model of human

Outdoor thermal comfort.

Science.gov (United States)

Nikolopoulou, Marialena

2011-06-01

A review of the various approaches in understanding outdoor thermal comfort is presented. The emphasis on field surveys from around the world, particularly across Europe, enables us to understand thermal perception and evaluate outdoor thermal comfort conditions. The consistent low correlations between objective microclimatic variables, subjective thermal sensation and comfort outdoors, internationally, suggest that thermophysiology alone does not adequate describe these relationships. Focusing on the concept of adaptation, it tries to explain how this influences outdoor comfort, enabling us to inhabit and get satisfaction from outdoor spaces throughout the year. Beyond acclimatization and behavioral adaptation, through adjustments in clothing and changes to the metabolic heat, psychological adaptation plays a critical role to ensure thermal comfort and satisfaction with the outdoor environment. Such parameters include recent experiences and expectations; personal choice and perceived control, more important than whether that control is actually exercised; and the need for positive environmental stimulation suggesting that thermal neutrality is not a pre-requisite for thermal comfort. Ultimately, enhancing environmental diversity can influence thermal perception and experience of open spaces.

Quantifying demand flexibility of power-to-heat and thermal energy storage in the control of building heating systems

DEFF Research Database (Denmark)

Finck, Christian; Li, Rongling; Kramer, Rick

2018-01-01

restricted by power-to-heat conversion such as heat pumps and thermal energy storage possibilities of a building. To quantify building demand flexibility, it is essential to capture the dynamic response of the building energy system with thermal energy storage. To identify the maximum flexibility a building......’s energy system can provide, optimal control is required. In this paper, optimal control serves to determine in detail demand flexibility of an office building equipped with heat pump, electric heater, and thermal energy storage tanks. The demand flexibility is quantified using different performance...... of TES and power-to-heat in any case of charging, discharging or idle mode. A simulation case study is performed showing that a water tank, a phase change material tank, and a thermochemical material tank integrated with building heating system can be designed to provide flexibility with optimal control....

Thermally-controlled centrifuge for isotopic separation

International Nuclear Information System (INIS)

Cenedese, A.; Cunsolo, D.

1976-01-01

Among the various methods proposed to obtain lighter component enrichment in the isotopic separation of uranium, ultracentrifugation is becoming more and more interesting today, as this process becomes a useful alternate method to gaseous diffusion. The ultracentrifuge main gas-dynamic features are investigated in the present study. In particular, the field inside the centrifuge has been subdivided into three axial zones: an internal central zone, characterized by an essentially axial flow; two external zones, near the two caps of the centrifuge; two intermediate zones, of a length of the order of the radius. For the analytical solution the linearized Navier-Stokes equations have been considered. The central zone flow is solved by separating the independent variables; the corresponding eigenvalue problem has been solved numerically. A series of eigensolutions which satisfy boundary conditions at the walls of the cylinder has been calculated. An integral method for the superimposition of the above mentioned eigensolutions is proposed in order to satisfy the conditions at the tops for thermally-controlled centrifuges. (author)

Thermal modeling and temperature control of a PEM fuel cell system for forklift applications

DEFF Research Database (Denmark)

Liso, Vincenzo; Nielsen, Mads Pagh; Kær, Søren Knudsen

2014-01-01

Temperature changes in PEM fuel cell stacks are considerably higher during load variations and have a negative impact as they generate thermal stresses and stack degradation. Cell hydration is also of vital importance in fuel cells and it is strongly dependent on operating temperature....... A combination of high temperature and reduced humidity increases the degradation rate. Stack thermal management and control are, thus, crucial issues in PEM fuel cell systems especially in automotive applications such as forklifts. In this paper we present a control–oriented dynamic model of a liquid–cooled PEM...... fuel cell system for studying temperature variations over fast load changes. A temperature dependent cell polarization and hydration model integrated with the compressor, humidifier and cooling system are simulated in dynamic condition. A feedback PID control was implemented for stack cooling...

Software for Automated Generation of Reduced Thermal Models for Spacecraft Thermal Control, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Thermal analysis is increasingly used in thermal engineering of spacecrafts in every stage, including design, test, and ground-operation simulation. Current...

Thermal and structural limitations for impurity-control components in FED/INTOR

International Nuclear Information System (INIS)

Majumdar, S.; Cha, Y.; Mattas, R.; Abdou, M.; Cramer, B.; Haines, J.

1983-02-01

The successful operation of the impurity-control system of the FED/INTOR will depend to a large extent on the ability of its various components to withstand the imposed thermal and mechanical loads. The present paper explores the thermal and stress analyses aspects of the limiter and divertor operation of the FED/INTOR in its reference configuration. Three basic limitations governing the design of the limiter and the divertor are the maximum allowable metal temperature, the maximum allowable stress intensity and the allowable fatigue life of the structural material. Other important design limitations stemming from sputtering, evaporation, melting during disruptions, etc. are not considered in the present paper. The materials considered in the present analysis are a copper and a vanadium alloy for the structural material and graphite, beryllium, beryllium oxide, tungsten and silicon carbide for the coating or tile material

Dynamic Thermal Model And Control Of A Pem Fuel Cell System

DEFF Research Database (Denmark)

Liso, Vincenzo; Nielsen, Mads Pagh

2013-01-01

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......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...

Novel variable structure control for the temperature of PEM fuel cell stack based on the dynamic thermal affine model

International Nuclear Information System (INIS)

Li Xi; Deng Zhonghua; Wei Dong; Xu Chunshan; Cao Guangyi

2011-01-01

Highlights: → The affine state space control-oriented model is designed and realized for the variant structure control (VSC) strategy. → The VSC with rapid-smooth reaching law and rapid-convergent sliding mode is presented for the PEMFC stack temperature. → Numerical results show that the method can control the operating temperature to reach the target value satisfactorily. - Abstract: Dynamic thermal management of proton exchange membrane fuel cell stack (PEMFC) is a very important aspect, which plays an important role on electro-reaction. Its variation also has a significant influence on the performance and lifespan of PEMFC stack. The temperature of stack should be controlled efficiently, which has great impacts on the performance of PEMFC due to the thermal variation. Based on the control-oriented dynamic thermal affine model identified by optimization algorithm, a novel variable structures control (VSC) with rapid-smooth reaching law (RSRL) and rapid-convergent sliding mode (FCSM) is presented for the temperature control system of PEMFC stack. Numerical test results show that the method can control the operating temperature to reach the target value satisfactorily, which proves the effectiveness and robustness of the algorithm.

Josephson Thermal Memory

Science.gov (United States)

Guarcello, Claudio; Solinas, Paolo; Braggio, Alessandro; Di Ventra, Massimiliano; Giazotto, Francesco

2018-01-01

We propose a superconducting thermal memory device that exploits the thermal hysteresis in a flux-controlled temperature-biased superconducting quantum-interference device (SQUID). This system reveals a flux-controllable temperature bistability, which can be used to define two well-distinguishable thermal logic states. We discuss a suitable writing-reading procedure for these memory states. The time of the memory writing operation is expected to be on the order of approximately 0.2 ns for a Nb-based SQUID in thermal contact with a phonon bath at 4.2 K. We suggest a noninvasive readout scheme for the memory states based on the measurement of the effective resonance frequency of a tank circuit inductively coupled to the SQUID. The proposed device paves the way for a practical implementation of thermal logic and computation. The advantage of this proposal is that it represents also an example of harvesting thermal energy in superconducting circuits.

Advanced Durable Flexible Ultra Low Outgassing Thermal Control Coatings for NASA Science Missions, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This Phase I program proposes to synthesize novel nanoengineered ultra low out gassing elastomers and formulate high temperature capable flexible thermal control...

Thermal protection system gap analysis using a loosely coupled fluid-structural thermal numerical method

Science.gov (United States)

Huang, Jie; Li, Piao; Yao, Weixing

2018-05-01

A loosely coupled fluid-structural thermal numerical method is introduced for the thermal protection system (TPS) gap thermal control analysis in this paper. The aerodynamic heating and structural thermal are analyzed by computational fluid dynamics (CFD) and numerical heat transfer (NHT) methods respectively. An interpolation algorithm based on the control surface is adopted for the data exchanges on the coupled surface. In order to verify the analysis precision of the loosely coupled method, a circular tube example was analyzed, and the wall temperature agrees well with the test result. TPS gap thermal control performance was studied by the loosely coupled method successfully. The gap heat flux is mainly distributed in the small region at the top of the gap which is the high temperature region. Besides, TPS gap temperature and the power of the active cooling system (CCS) calculated by the traditional uncoupled method are higher than that calculated by the coupled method obviously. The reason is that the uncoupled method doesn't consider the coupled effect between the aerodynamic heating and structural thermal, however the coupled method considers it, so TPS gap thermal control performance can be analyzed more accurately by the coupled method.

Near-real-time feedback control system for liver thermal ablations based on self-referenced temperature imaging

International Nuclear Information System (INIS)

Keserci, Bilgin M.; Kokuryo, Daisuke; Suzuki, Kyohei; Kumamoto, Etsuko; Okada, Atsuya; Khankan, Azzam A.; Kuroda, Kagayaki

2006-01-01

Our challenge was to design and implement a dedicated temperature imaging feedback control system to guide and assist in a thermal liver ablation procedure in a double-donut 0.5T open MR scanner. This system has near-real-time feedback capability based on a newly developed 'self-referenced' temperature imaging method using 'moving-slab' and complex-field-fitting techniques. Two phantom validation studies and one ex vivo experiment were performed to compare the newly developed self-referenced method with the conventional subtraction method and evaluate the ability of the feedback control system in the same MR scanner. The near-real-time feedback system was achieved by integrating the following primary functions: (1) imaging of the moving organ temperature; (2) on-line needle tip tracking; (3) automatic turn-on/off the heating devices; (4) a Windows operating system-based novel user-interfaces. In the first part of the validation studies, microwave heating was applied in an agar phantom using a fast spoiled gradient recalled echo in a steady state sequence. In the second part of the validation and ex vivo study, target visualization, treatment planning and monitoring, and temperature and thermal dose visualization with the graphical user interface of the thermal ablation software were demonstrated. Furthermore, MR imaging with the 'self-referenced' temperature imaging method has the ability to localize the hot spot in the heated region and measure temperature elevation during the experiment. In conclusion, we have demonstrated an interactively controllable feedback control system that offers a new method for the guidance of liver thermal ablation procedures, as well as improving the ability to assist ablation procedures in an open MR scanner

Solar-energy conversion system provides electrical power and thermal control for life-support systems

Science.gov (United States)

Davis, B. K.

1974-01-01

System utilizes Freon cycle and includes boiler turbogenerator with heat exchanger, regenerator and thermal-control heat exchangers, low-pressure and boiler-feed pumps, and condenser. Exchanger may be of interest to engineers and scientists investigating new energy sources.

Magnetic graphene enabled tunable microwave absorber via thermal control

Science.gov (United States)

Quan, L.; Qin, F. X.; Li, Y. H.; Estevez, D.; Fu, G. J.; Wang, H.; Peng, H.-X.

2018-06-01

By synthesizing nitrogen-doped graphene (NG) via a facile thermal annealing method, a fine control of the amount and location of doped nitrogen as well as the oxygen-containing functional groups is achieved with varying annealing temperature. The favorable magnetic properties have been achieved for N-doped rGO samples obtained at two temperatures of all NG samples, i.e., 500 °C and 900 °C with saturation magnetization of 0.63 emu g‑1 and 0.67 emu g‑1 at 2 K, respectively. This is attributed to the optimized competition of the N-doping and reduction process at 500 °C and the dominated reduction process at 900 °C. NG obtained at 300 °C affords the best overall absorbing performance: when the absorber thickness is 3.0 mm, the maximum absorption was ‑24.6 dB at 8.51 GHz, and the absorption bandwidth was 4.89 GHz (7.55–12.44 GHz) below ‑10 dB. It owes its large absorbing intensity to the good impedance match and significant dielectric loss. The broad absorption bandwidth benefits from local fluctuations of dielectric responses contributed by competing mechanisms. Despite the significant contribution from materials loss to the absorption, the one quarter-wavelength model is found to be responsible for the reflection loss peak positions. Of particular significance is that an appropriate set of electromagnetic parameters associated with reasonable reduction is readily accessible by convenient control of annealing temperature to modulate the microwave absorbing features of graphene. Thus, NG prepared by thermal annealing promises to be a highly efficient microwave absorbent.

Life support and internal thermal control system design for the Space Station Freedom

Science.gov (United States)

Humphries, R.; Mitchell, K.; Reuter, J.; Carrasquillo, R.; Beverly, B.

1991-01-01

A Review of the Space Station Freedom Environmental Control and Life Support System (ECLSS) as well as the Internal Thermal Control System (ITCS) design, including recent changes resulting from an activity to restructure the program, is provided. The development state of the original Space Station Freedom ECLSS through the restructured configuration is considered and the selection of regenerative subsystems for oxygen and water reclamation is addressed. A survey of the present ground development and verification program is given.

Thermal insulation

International Nuclear Information System (INIS)

Aspden, G.J.; Howard, R.S.

1988-01-01

The patent concerns high temperature thermal insulation of large vessels, such as the primary vessel of a liquid metal cooled nuclear reactor. The thermal insulation consists of multilayered thermal insulation modules, and each module comprises a number of metal sheet layers sandwiched between a back and front plate. The layers are linked together by straps and clips to control the thickness of the module. (U.K.)

Metabolic Heat Regenerated Temperature Swing Adsorption for CO2, Thermal and Humidity Control, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — MTSA technology specifically addresses the thermal, CO2 and humidity control challenges faced by Portable Life Support Systems (PLSS) to be used in NASA's...

Teaching Thermal Hydraulics & Numerical Methods: An Introductory Control Volume Primer

Energy Technology Data Exchange (ETDEWEB)

D. S. Lucas

2004-10-01

A graduate level course for Thermal Hydraulics (T/H) was taught through Idaho State University in the spring of 2004. A numerical approach was taken for the content of this course since the students were employed at the Idaho National Laboratory and had been users of T/H codes. The majority of the students had expressed an interest in learning about the Courant Limit, mass error, semi-implicit and implicit numerical integration schemes in the context of a computer code. Since no introductory text was found the author developed notes taught from his own research and courses taught for Westinghouse on the subject. The course started with a primer on control volume methods and the construction of a Homogeneous Equilibrium Model (HEM) (T/H) code. The primer was valuable for giving the students the basics behind such codes and their evolution to more complex codes for Thermal Hydraulics and Computational Fluid Dynamics (CFD). The course covered additional material including the Finite Element Method and non-equilibrium (T/H). The control volume primer and the construction of a three-equation (mass, momentum and energy) HEM code are the subject of this paper . The Fortran version of the code covered in this paper is elementary compared to its descendants. The steam tables used are less accurate than the available commercial version written in C Coupled to a Graphical User Interface (GUI). The Fortran version and input files can be downloaded at www.microfusionlab.com.

Experimental and economic study of a greenhouse thermal control system using aquifer water

Energy Technology Data Exchange (ETDEWEB)

Sethi, V.P. [Department of Mechanical Engineering, Punjab Agricultural University, Ludhiana 141 008, Punjab (India)]. E-mail: vpsethi68@yahoo.co.in; Sharma, S.K. [Energy Research Centre, Punjab University, Chandigarh 160 017, Punjab (India)

2007-01-15

Underground aquifer water is used for thermal control (heating as well as cooling) of a greenhouse in which chilli and capsicum are grown. Year round performance of the designed system is experimentally evaluated and presented. The designed system utilizes the constant temperature aquifer water available on the ground surface at around 24 deg. C (year round) in the agricultural field through deep tubewell used for irrigation purposes for heating a greenhouse in winter nights and cooling in summer days. Experimental performance of the designed system is tested during a full winter as well as for summer conditions. To enhance the efficiency of the system and to improve relative humidity during extreme summer conditions, a simple evaporative cooling process is also added within the same designed system. The experimental results show that the average greenhouse room air temperature is maintained 7-9 deg. C above ambient during winter nights and 6-7 deg. C below ambient in summer days besides decreasing the daily temperature fluctuations inside the greenhouse. Improvement in the average relative humidity during extreme summer conditions is also observed. Technoeconomic analysis of the greenhouse integrated to the designed aquifer coupled cavity flow heat exchanger system (ACCFHES) is also conducted based on the yield of capsicum and chilli crops and compared with those of the greenhouse without any thermal control system and the open field condition yields. An economic comparison of the ACCFHES has also been made with other existing thermal control technologies such as the earth air heat exchanger system, ground air collector, evaporative cooling using foggers and a fan and pad system.

Control system design of the CERN/CMS tracker thermal screen

CERN Document Server

Carrone, E

2003-01-01

The Tracker is one of the CMS (Compact Muon Solenoid experiment) subdetectors to be installed at the LHC (Large Hadron Collider) accelerator, scheduled to start data taking in 2007 at CERN (European Organization for Nuclear Research). The tracker will be operated at a temperature of -10 degree C in order to reduce the radiation damage on the silicon detectors; hence, an insulated environment has to be provided by means of a screen that introduces a thermal separation between the Tracker and the neighboring detection systems. The control system design includes a formal description of the process by means of a thermodynamic model; then, the electrical equivalence is derived. The transfer function is inferred by the ratio of the voltage on the outer skin and the voltage input, i.e. the ratio of the temperature outside the tracker and the heat generated (which is the controlled variable). A PID (Proportional Integral Derivative) controller has been designed using MatLab. The results achieved so far prove that thi...

Influence of controlled atmosphere on thermal inactivation of Escherichia coli ATCC 25922 in almond powder.

Science.gov (United States)

Cheng, Teng; Li, Rui; Kou, Xiaoxi; Wang, Shaojin

2017-06-01

Heat controlled atmosphere (CA) treatments hold potential to pasteurize Salmonella enteritidis PT 30 in almonds. Nonpathogenic Escherichia coli ATCC 25922 was used as a surrogate species of pathogenic Salmonella for validation of thermal pasteurization to meet critical safety requirements. A controlled atmosphere/heating block system (CA-HBS) was used to rapidly determine thermal inactivation of E. coli ATCC 25922. D- and z-values of E. coli ATCC 25922 inoculated in almond powder were determined at four temperatures between 65 °C and 80 °C under different gas concentrations and heating rates. The results showed that D- and z-values of E. coli under CA treatment were significantly (P < 0.05) lower than those under regular atmosphere (RA) treatment at 4 given temperatures. Relatively higher CO 2 concentrations (20%) and lower O 2 concentrations (2%) were more effective to reduce thermal inactivation time. There were no significant differences in D-values of E. coli when heating rates were above 1 °C/min both in RA and CA treatments. But D-values significantly (P < 0.05) increased under RA treatment and decreased under CA treatment at lower heating rates. Combination of rapid heat and CA treatments could be a promising method for thermal inactivation of S. enteritidis PT 30 in almond powder. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal hydraulics of the impurity control system for FED/INTOR

International Nuclear Information System (INIS)

Cha, Y.S.; Mattas, R.F.; Abdou, M.A.; Haines, J.R.

1983-01-01

This paper addresses two important aspects of thermal hydraulics related to the design of the impurity control system (limiter and divertor) of the Fusion Engineering Device (FED) and the International Tokamak Reactor (INTOR). The first part of the paper is devoted to the determination of temperature distributions in various combinations of the coating/structural materials proposed for the limiter/divertor of FED and INTOR. The second part of the paper describes the analysis of the tangential motion of the melt layer under the influence of magnetic force during plasma disruption. The results of both analysis provide inputs to the determination of the life time of the limiter (or divertor) which is the most critical problem for the impurity control system as far as engineering and materials consideration is concerned

Thermal energy storage devices, systems, and thermal energy storage device monitoring methods

Science.gov (United States)

Tugurlan, Maria; Tuffner, Francis K; Chassin, David P.

2016-09-13

Thermal energy storage devices, systems, and thermal energy storage device monitoring methods are described. According to one aspect, a thermal energy storage device includes a reservoir configured to hold a thermal energy storage medium, a temperature control system configured to adjust a temperature of the thermal energy storage medium, and a state observation system configured to provide information regarding an energy state of the thermal energy storage device at a plurality of different moments in time.

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. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Development of process data capturing, analysis and controlling for thermal spray techniques - SprayTracker

Science.gov (United States)

Kelber, C.; Marke, S.; Trommler, U.; Rupprecht, C.; Weis, S.

2017-03-01

Thermal spraying processes are becoming increasingly important in high-technology areas, such as automotive engineering and medical technology. The method offers the advantage of a local layer application with different materials and high deposition rates. Challenges in the application of thermal spraying result from the complex interaction of different influencing variables, which can be attributed to the properties of different materials, operating equipment supply, electrical parameters, flow mechanics, plasma physics and automation. In addition, spraying systems are subject to constant wear. Due to the process specification and the high demands on the produced coatings, innovative quality assurance tools are necessary. A central aspect, which has not yet been considered, is the data management in relation to the present measured variables, in particular the spraying system, the handling system, working safety devices and additional measuring sensors. Both the recording of all process-characterizing variables, their linking and evaluation as well as the use of the data for the active process control presuppose a novel, innovative control system (hardware and software) that was to be developed within the scope of the research project. In addition, new measurement methods and sensors are to be developed and qualified in order to improve the process reliability of thermal spraying.

Controlling heat transport and flow structures in thermal turbulence using ratchet surfaces

Science.gov (United States)

Sun, Chao; Jiang, Hechuan; Zhu, Xiaojue; Mathai, Varghese; Verzicco, Roberto; Lohse, Detlef

2017-11-01

In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchet-like roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the Large Scale Circulation Roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. This work is financially supported by the Natural Science Foundation of China under Grant No. 11672156, the Dutch Foundation for Fundamental Research on Matter (FOM), the Dutch Technology Foundation (STW) and a VIDI Grant.

Controllable isotope fractionation with thermal ionisation mass-spectrometers

International Nuclear Information System (INIS)

Hebeda, E.H.

1980-01-01

Isotopic ratios measured with thermal ionisation mass-spectrometers are biased by fractionation effects. A sample must therefore be analyzed according to the same procedures as applied for the analysis of the standard reference material. A comparison of the behaviour of the sample with that of the standard can then be used as a criterion whether the analytical results are acceptable or not. In this way it is possible to obtain reproducibilities similar to those for elements acceptable or not. In this way it is possible to obtain reproducibilities similar to those for elements where the fractionation can be determined by an internal standard. This procedure of controlled fractionation is demonstrated by means of the 88 Sr/ 86 Sr ratios measured on geological samples and the SRM 987 standard. (orig.)

An adaptive control application in a large thermal combined power plant

International Nuclear Information System (INIS)

Kocaarslan, Ilhan; Cam, Ertugrul

2007-01-01

In this paper, an adaptive controller was applied to a 765 MW large thermal power plant to decrease operating costs, increase quality of generated electricity and satisfy environmental concerns. Since power plants may present several operating problems such as disturbances and severe effects at operating points, design of their controllers needs to be carried out adequately. For these reasons, first, a reduced mathematical model was developed under Computer Aided Analysis and Design Package for Control (CADACS), so that the results of the experimental model have briefly been discussed. Second, conventional PID and adaptive controllers were designed and implemented under the real-time environment of the CADACS software. Additionally, the design of the adaptive model-reference and conventional PID controllers used in the power plant for real-time control were theoretically presented. All processes were realized in real-time. Due to safety restrictions, a direct connection to the sensors and actuators of the plant was not allowed. Instead a coupling to the control system was realized. This offers, in addition, the usage of the supervisory functions of an industrial process computer system. Application of the controllers indicated that the proposed adaptive controller has better performances for rise and settling times of electrical power, and enthalpy outputs than the conventional PID controller does

Control of Several Emissions during Olive Pomace Thermal Degradation

Directory of Open Access Journals (Sweden)

Teresa Miranda

2014-10-01

Full Text Available Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25–750 °C and a heating rate of 20 °C·min−1. The following species were analysed: aromatic compounds (benzene and toluene, sulphur emissions (sulphur dioxide, 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor.

Phase 1 engineering and technical data report for the thermal control extravehicular life support system

Science.gov (United States)

1975-01-01

A shuttle EVLSS Thermal Control System (TCS) is defined. Thirteen heat rejection subsystems, thirteen water management subsystems, nine humidity control subsystems, three pressure control schemes and five temperature control schemes are evaluated. Sixteen integrated TCS systems are studied, and an optimum system is selected based on quantitative weighting of weight, volume, cost, complexity and other factors. The selected sybsystem contains a sublimator for heat rejection, a bubble expansion tank for water management, and a slurper and rotary separator for humidity control. Design of the selected subsystem prototype hardware is presented.

Neuro-Fuzzy Computational Technique to Control Load Frequency in Hydro-Thermal Interconnected Power System

Science.gov (United States)

Prakash, S.; Sinha, S. K.

2015-09-01

In this research work, two areas hydro-thermal power system connected through tie-lines is considered. The perturbation of frequencies at the areas and resulting tie line power flows arise due to unpredictable load variations that cause mismatch between the generated and demanded powers. Due to rising and falling power demand, the real and reactive power balance is harmed; hence frequency and voltage get deviated from nominal value. This necessitates designing of an accurate and fast controller to maintain the system parameters at nominal value. The main purpose of system generation control is to balance the system generation against the load and losses so that the desired frequency and power interchange between neighboring systems are maintained. The intelligent controllers like fuzzy logic, artificial neural network (ANN) and hybrid fuzzy neural network approaches are used for automatic generation control for the two area interconnected power systems. Area 1 consists of thermal reheat power plant whereas area 2 consists of hydro power plant with electric governor. Performance evaluation is carried out by using intelligent (ANFIS, ANN and fuzzy) control and conventional PI and PID control approaches. To enhance the performance of controller sliding surface i.e. variable structure control is included. The model of interconnected power system has been developed with all five types of said controllers and simulated using MATLAB/SIMULINK package. The performance of the intelligent controllers has been compared with the conventional PI and PID controllers for the interconnected power system. A comparison of ANFIS, ANN, Fuzzy and PI, PID based approaches shows the superiority of proposed ANFIS over ANN, fuzzy and PI, PID. Thus the hybrid fuzzy neural network controller has better dynamic response i.e., quick in operation, reduced error magnitude and minimized frequency transients.

Mechanisms Controlling Species Responses to Climate Change: Thermal Tolerances and Shifting Range Limits. (Invited)

Science.gov (United States)

Sage, R. F.; Bykova, O.; Coiner, H.

2010-12-01

One of the main effects of anthropogenic climate change will be widespread shifts in species distribution, with the common assumption that they will migrate to higher elevation and latitude. While this assumption is supported by migration patterns following climate warming in the past 20,000 years, it has not been rigorously evaluated in terms of physiological mechanism, despite the implication that migration in response to climate warming is controlled by some form of thermal adaptation. We have been evaluating the degree to which species range limits are controlled by physiological patterns of thermal tolerance in bioinvaders of North America. Bioinvaders presumably have few biotic controls over their distribution and thus are more likely to fully exploit their thermal niche. In cheatgrass (Bromus tectorum), the minimum lethal temperature in winter is -32C, which corresponds to the mean winter minimum temperature at its northern range limit. In red brome (Bromus rubens), the minimum lethal temperature is also near -32C, which is well below the minimum winter temperature near -20C that corresponds to its northern distribution limit. In kudzu (Pueraria lobata), the minimum lethal temperature is near -20C, which corresponds to the midwinter minimum at its northern distribution limit; however, overwintering kudzu tissues are insulated by soil and snow cover, and thus do not experience lethal temperatures at kudzu's northern range limit. These results demonstrate that some invasive species can exploit the potential range defined by their low temperature tolerance and thus can be predicted by mechanistic models to migrate to higher latitudes with moderation of winter cold. The distribution of other invaders such as kudzu and red brome are not controlled by tolerance of midwinter cold. Developing mechanistic models of their distributions, and how these might change with climate warming, will require extensive physiological study.

Instrumentation and Control Systems for Sodium thermal hydraulic Experiment Loop for Finned-tube sodium-to-Air heat exchanger (SELFA)

Energy Technology Data Exchange (ETDEWEB)

Kim, Byeong Yeon; Kim, Hyung Mo; Cho, Youn Gil; Kim, Jong Man; Ko, Yung Joo; Kang, Byeong Su; Jung, Min Hwan; Jeong, Ji Young [KAERI, Daejeon (Korea, Republic of)

2016-05-15

A forced-draft sodium-to-air heat exchanger (FHX) is a part of decay heat removal system (DHRS) in Prototype Gen-IV Sodium-cooled fast reactor (PGSFR), which is being developed at Korea Atomic Energy Research Institute (KAERI). Sodium thermal hydraulic Experiment Loop for Finned-tube sodium-to-Air heat exchanger (SELFA) is a test facility for verification and validation of the design code for a forced-draft sodium-to-air heat exchanger (FHX). In this paper, we have provided design and fabrication features for the instrumentation and control systems of SELFA. In general, the instrumentation systems and control systems are coupled for measurement and control of process variables. Instrumentation systems have been designed for investigating thermal-hydraulic characteristics of FHX and control systems have been designed to control the main components (e.g. electromagnetic pumps, heaters, valves etc.) required for test in SELFA. In this paper, we have provided configurations of instrumentation and control systems for Sodium thermal hydraulic Experiment Loop for Finned-tube sodium-to-Air heat exchanger (SELFA). The instrumentation and control systems of SELFA have been implemented based on the expected operation ranges and lesson learned from operational experience of 'Sodium integral effect test loop for safety simulation and assessment-1' (STELLA-1)

Thermal-mechanical deformation modelling of soft tissues for thermal ablation.

Science.gov (United States)

Li, Xin; Zhong, Yongmin; Jazar, Reza; Subic, Aleksandar

2014-01-01

Modeling of thermal-induced mechanical behaviors of soft tissues is of great importance for thermal ablation. This paper presents a method by integrating the heating process with thermal-induced mechanical deformations of soft tissues for simulation and analysis of the thermal ablation process. This method combines bio-heat transfer theories, constitutive elastic material law under thermal loads as well as non-rigid motion dynamics to predict and analyze thermal-mechanical deformations of soft tissues. The 3D governing equations of thermal-mechanical soft tissue deformation are discretized by using the finite difference scheme and are subsequently solved by numerical algorithms. Experimental results show that the proposed method can effectively predict the thermal-induced mechanical behaviors of soft tissues, and can be used for the thermal ablation therapy to effectively control the delivered heat energy for cancer treatment.

Effect of personal control over thermal environment in a laboratory setting; Effect van klimaatbeinvloeding in een laboratoriumsetting

Energy Technology Data Exchange (ETDEWEB)

Te Kulve, M.; ; Loomans, M.G.L.C.; Hensen, J.L.M. [Technische Universiteit Eindhoven TUE, Eindhoven (Netherlands); Boerstra, A.C. [BBA Binnenmilieu, Rotterdam (Netherlands); Toftum, J. [Technical University of Denmark DTU, Kongens Lyngby (Denmark)

2013-07-15

A laboratory study was performed to investigate if being in control over the thermal environment influences comfort, symptoms and performance. Two conditions were tested: the first with individual control and the second without, but with identical indoor climate exposure as recorded during the first session. For the investigated case, the availability of control opportunities does not directly influence human perception to the thermal environment, symptoms or performance. However, personal preferences for the air velocity of the fan makes a lot of difference [Dutch] Onderzoeken in kantoorgebouwen hebben aangetoond dat het hebben van persoonlijke controle over het binnenklimaat een positieve invloed heeft op comfort en productiviteit. Is dit effect toe te schrijven aan het verschil in behoefte van werknemers, of is alleen het gevoel van het hebben van controle al voldoende om een positieve invloed te hebben? Dit laboratoriumonderzoek richtte zich op die vraag. Het onderzoek maakt deel uit van het promotieonderzoek 'Persoonlijke Beinvloeding van het Binnenklimaat in kantoorgebouwen'.

Internal Thermal Control System Hose Heat Transfer Fluid Thermal Expansion Evaluation Test Report

Science.gov (United States)

Wieland, P. O.; Hawk, H. D.

2001-01-01

During assembly of the International Space Station, the Internal Thermal Control Systems in adjacent modules are connected by jumper hoses referred to as integrated hose assemblies (IHAs). A test of an IHA has been performed at the Marshall Space Flight Center to determine whether the pressure in an IHA filled with heat transfer fluid would exceed the maximum design pressure when subjected to elevated temperatures (up to 60 C (140 F)) that may be experienced during storage or transportation. The results of the test show that the pressure in the IHA remains below 227 kPa (33 psia) (well below the 689 kPa (100 psia) maximum design pressure) even at a temperature of 71 C (160 F), with no indication of leakage or damage to the hose. Therefore, based on the results of this test, the IHA can safely be filled with coolant prior to launch. The test and results are documented in this Technical Memorandum.

Applications of sand control technology in thermal recovery systems

Energy Technology Data Exchange (ETDEWEB)

Rensvold, R F

1982-01-01

The ever-increasing application of thermal methods to recover low gravity crude oil has warranted the review of existing sand control techniques relative to their compatibility with high temperature environments. The advantages and limitations of a large number of materials are considered. Carrying fluids, granular pack solids, clay stabilizers, and resin-coated pack sands are discussed. Resins used for in situ sand consolidation processes also are reviewed, and their suitability for application in a high temperature steam environment is evaluated. The effects of highly deviated boreholes on the placement of pressure packs also are considered. Full scale gravel pack model studies have provided valuable clues to the procedures and materials that help to create optimum pressure packs. 58 references.

From thermal boredom to thermal pleasure: a brief literature review

Directory of Open Access Journals (Sweden)

Christhina Candido

Full Text Available The most recent review of the ASHRAE Standard 55 (2010 incorporates the dialectic between static and adaptive approaches to thermal comfort by proposing different recommendations for airconditioned and naturally ventilated buildings. Particularly in naturally ventilated buildings, this standard aligns with three important topics in research field of thermal comfort during the last decades: (i air movement enhancement versus draft, (ii control availability and its impact on occupants' satisfaction, and (iii the search for thermal pleasure. This paper presents the rationale behind these three research topics and discusses its positive influence when moving from thermal comfort towards thermal pleasure.

Improvement of existing coal fired thermal power plants performance by control systems modifications

International Nuclear Information System (INIS)

Mikulandrić, Robert; Lončar, Dražen; Cvetinović, Dejan; Spiridon, Gabriel

2013-01-01

This paper presents possibilities of implementation of advanced combustion control concepts in selected Western Balkan thermal power plant, and particularly those based on artificial intelligence as part of primary measures for nitrogen oxide reduction in order to optimise combustion and to increase plant efficiency. Both considered goals comply with environmental quality standards prescribed in large combustion plant directive. Due to specific characterisation of Western Balkan power sector these goals should be reached by low cost and easily implementable solution. Advanced self-learning controller has been developed and the effects of advanced control concept on combustion process have been analysed using artificial neural-network based parameter prediction model

Blackness coefficients, effective diffusion parameters, and control rod worths for thermal reactors - Methods

Energy Technology Data Exchange (ETDEWEB)

Bretscher, M M [Argonne National Laboratory, Argonne, IL 60439 (United States)

1985-07-01

Simple diffusion theory cannot be used to evaluate control rod worths in thermal neutron reactors because of the strongly absorbing character of the control material. However, reliable control rod worths can be obtained within the framework of diffusion theory if the control material is characterized by a set of mesh-dependent effective diffusion parameters. For thin slab absorbers the effective diffusion parameters can be expressed as functions of a suitably-defined pair of 'blackness coefficients'. Methods for calculating these blackness coefficients in the P1, P3, and P5 approximations, with and without scattering, are presented. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method, based on reaction rate ratios, is discussed. (author)

Optimal controls of building storage systems using both ice storage and thermal mass – Part II: Parametric analysis

International Nuclear Information System (INIS)

Hajiah, Ali; Krarti, Moncef

2012-01-01

Highlights: ► A detailed analysis is presented to assess the performance of thermal energy storage (TES) systems. ► Utility rates have been found to be significant in assessing the operation of TES systems. ► Optimal control strategies for TES systems can save up to 40% of total energy cost of office buildings. - Abstract: This paper presents the results of a series of parametric analysis to investigate the factors that affect the effectiveness of using simultaneously building thermal capacitance and ice storage system to reduce total operating costs (including energy and demand costs) while maintaining adequate occupant comfort conditions in buildings. The analysis is based on a validated model-based simulation environment and includes several parameters including the optimization cost function, base chiller size, and ice storage tank capacity, and weather conditions. It found that the combined use of building thermal mass and active thermal energy storage system can save up to 40% of the total energy costs when integrated optimal control are considered to operate commercial buildings.

Shape memory thermal conduction switch

Science.gov (United States)

Vaidyanathan, Rajan (Inventor); Krishnan, Vinu (Inventor); Notardonato, William U. (Inventor)

2010-01-01

A thermal conduction switch includes a thermally-conductive first member having a first thermal contacting structure for securing the first member as a stationary member to a thermally regulated body or a body requiring thermal regulation. A movable thermally-conductive second member has a second thermal contacting surface. A thermally conductive coupler is interposed between the first member and the second member for thermally coupling the first member to the second member. At least one control spring is coupled between the first member and the second member. The control spring includes a NiTiFe comprising shape memory (SM) material that provides a phase change temperature <273 K, a transformation range <40 K, and a hysteresis of <10 K. A bias spring is between the first member and the second member. At the phase change the switch provides a distance change (displacement) between first and second member by at least 1 mm, such as 2 to 4 mm.

Environmental emissions control programs at Lambton TGS [Thermal Generating Station

International Nuclear Information System (INIS)

Kalvins, A.K.

1992-01-01

Ontario Hydro's air emissions control programs at Lambton thermal generating station, both committed and planned, are reviewed, and their potential impacts on emissions, effluents and wastes are discussed. Control technologies examined include flue gas conditioning, wet limestone scrubbing, combustion process modifications, urea injection, and selective catalytic reduction. The implementation of these technologies has the potential to create new solid and liquid waste disposal problems, the full extent of which is often not realized at the process selection stage. For example, selective noncatalytic reduction using urea injection can lead to increased CO emissions, escape of unreacted ammonia from the stack at levels of 5-50 ppM, increase in N 2 O emissions, contamination of fly ash, gypsum and waste water with ammonia, and an increase in CO 2 emissions of less than 0.4% due to increased power consumption. Optimum performance of the air emissions control systems, with minimum negative impact on the environment, requires consideration of the impact of these systems on all waste streams. 11 refs., 3 figs., 1 tab

Thermal elastic shock and its effect on TOPEX spacecraft attitude control

Science.gov (United States)

Zimbelman, Darrell F.

1991-01-01

Thermal elastic shock (TES) is a twice per orbit impulsive disturbance torque experienced by low-Earth orbiting spacecraft. The fundamental equations used to model the TES disturbance torque for typical spacecraft appendages (e.g., solar arrays and antenna booms) are derived in detail. In particular, the attitude-pointing performance of the TOPEX spacecraft, when subjected to the TES disturbance, is analyzed using a three-axis nonlinear time-domain simulation. Results indicate that the TOPEX spacecraft could exceed its roll-axis attitude-control requirement during penumbral transitions, and remain in violation for approximately 150 sec each orbit until the umbra collapses. A localized active-control system is proposed as a solution to minimize and/or eliminate the degrading effects of the TES disturbance.

Control of thermal deformation in dielectric mirrors using mechanical design and atomic layer deposition.

Science.gov (United States)

Gabriel, Nicholas T; Kim, Sangho S; Talghader, Joseph J

2009-07-01

A mechanical design technique for optical coatings that simultaneously controls thermal deformation and optical reflectivity is reported. The method requires measurement of the refractive index and thermal stress of single films prior to the design. Atomic layer deposition was used for deposition because of the high repeatability of the film constants. An Al2O3/HfO2 distributed Bragg reflector was deposited with a predicted peak reflectivity of 87.9% at 542.4 nm and predicted edge deformation of -360 nm/K on a 10 cm silicon substrate. The measured peak reflectivity was 85.7% at 541.7 nm with an edge deformation of -346 nm/K.

Robust Engineered Thermal Control Material Systems for Crew Exploration Vehicle (CEV) and Prometheus Needs, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — identified needs for the thermal control and ESD functions of the Prometheus Program's hardware for the heat rejection system for the planned nuclear system. These...

Low-Cost Radiator for Fission Power Thermal Control

Science.gov (United States)

Maxwell, Taylor; Tarau, Calin; Anderson, William; Hartenstine, John; Stern, Theodore; Walmsley, Nicholas; Briggs, Maxwell

2014-01-01

NASA Glenn Research Center (GRC) is developing fission power system technology for future Lunar surface power applications. The systems are envisioned in the 10 to 100kW(sub e) range and have an anticipated design life of 8 to 15 years with no maintenance. NASA GRC is currently setting up a 55 kW(sub e) non-nuclear system ground test in thermal-vacuum to validate technologies required to transfer reactor heat, convert the heat into electricity, reject waste heat, process the electrical output, and demonstrate overall system performance. Reducing the radiator mass, size, and cost is essential to the success of the program. To meet these goals, Advanced Cooling Technologies, Inc. (ACT) and Vanguard Space Technologies, Inc. (VST) are developing a single facesheet radiator with heat pipes directly bonded to the facesheet. The facesheet material is a graphite fiber reinforced composite (GFRC) and the heat pipes are titanium/water. By directly bonding a single facesheet to the heat pipes, several heavy and expensive components can be eliminated from the traditional radiator design such as, POC(TradeMark) foam saddles, aluminum honeycomb, and a second facesheet. A two-heat pipe radiator prototype, based on the single facesheet direct-bond concept, was fabricated and tested to verify the ability of the direct-bond joint to withstand coefficient of thermal expansion (CTE) induced stresses during thermal cycling. The thermal gradients along the bonds were measured before and after thermal cycle tests to determine if the performance degraded. Overall, the results indicated that the initial uniformity of the adhesive was poor along one of the heat pipes. However, both direct bond joints showed no measureable amount of degradation after being thermally cycled at both moderate and aggressive conditions.

Methane Lunar Surface Thermal Control Test

Science.gov (United States)

Plachta, David W.; Sutherlin, Steven G.; Johnson, Wesley L.; Feller, Jeffrey R.; Jurns, John M.

2012-01-01

NASA is considering propulsion system concepts for future missions including human return to the lunar surface. Studies have identified cryogenic methane (LCH4) and oxygen (LO2) as a desirable propellant combination for the lunar surface ascent propulsion system, and they point to a surface stay requirement of 180 days. To meet this requirement, a test article was prepared with state-of-the-art insulation and tested in simulated lunar mission environments at NASA GRC. The primary goals were to validate design and models of the key thermal control technologies to store unvented methane for long durations, with a low-density high-performing Multi-layer Insulation (MLI) system to protect the propellant tanks from the environmental heat of low Earth orbit (LEO), Earth to Moon transit, lunar surface, and with the LCH4 initially densified. The data and accompanying analysis shows this storage design would have fallen well short of the unvented 180 day storage requirement, due to the MLI density being much higher than intended, its substructure collapse, and blanket separation during depressurization. Despite the performance issue, insight into analytical models and MLI construction was gained. Such modeling is important for the effective design of flight vehicle concepts, such as in-space cryogenic depots or in-space cryogenic propulsion stages.

Emission Control Technologies for Thermal Power Plants

Science.gov (United States)

Nihalani, S. A.; Mishra, Y.; Juremalani, J.

2018-03-01

Coal thermal power plants are one of the primary sources of artificial air emissions, particularly in a country like India. Ministry of Environment and Forests has proposed draft regulation for emission standards in coal-fired power plants. This includes significant reduction in sulphur-dioxide, oxides of nitrogen, particulate matter and mercury emissions. The first step is to evaluate the technologies which represent the best selection for each power plant based on its configuration, fuel properties, performance requirements, and other site-specific factors. This paper will describe various technology options including: Flue Gas Desulfurization System, Spray Dryer Absorber (SDA), Circulating Dry Scrubber (CDS), Limestone-based Wet FGD, Low NOX burners, Selective Non Catalytic Reduction, Electrostatic Precipitator, Bag House Dust Collector, all of which have been evaluated and installed extensively to reduce SO2, NOx, PM and other emissions. Each control technology has its advantages and disadvantages. For each of the technologies considered, major features, potential operating and maintenance cost impacts, as well as key factors that contribute to the selection of one technology over another are discussed here.

Thermal conductivity and thermal rectification in unzipped carbon nanotubes

International Nuclear Information System (INIS)

Ni Xiaoxi; Li Baowen; Zhang Gang

2011-01-01

We study the thermal transport in completely unzipped carbon nanotubes, which are called graphene nanoribbons, partially unzipped carbon nanotubes, which can be seen as carbon-nanotube-graphene-nanoribbon junctions, and carbon nanotubes by using molecular dynamics simulations. It is found that the thermal conductivity of a graphene nanoribbon is much less than that of its perfect carbon nanotube counterparts because of the localized phonon modes at the boundary. A partially unzipped carbon nanotube has the lowest thermal conductivity due to additional localized modes at the junction region. More strikingly, a significant thermal rectification effect is observed in both partially unzipped armchair and zigzag carbon nanotubes. Our results suggest that carbon-nanotube-graphene-nanoribbon junctions can be used in thermal energy control.

Adaptive multiparameter control: application to a Rapid Thermal Processing process; Commande Adaptative Multivariable: Application a un Procede de Traitement Thermique Rapide

Energy Technology Data Exchange (ETDEWEB)

Morales Mago, S J

1995-12-20

In this work the problem of temperature uniformity control in rapid thermal processing is addressed by means of multivariable adaptive control. Rapid Thermal Processing (RTP) is a set of techniques proposed for semiconductor fabrication processes such as annealing, oxidation, chemical vapour deposition and others. The product quality depends on two mains issues: precise trajectory following and spatial temperature uniformity. RTP is a fabrication technique that requires a sophisticated real-time multivariable control system to achieve acceptable results. Modelling of the thermal behaviour of the process leads to very complex mathematical models. These are the reasons why adaptive control techniques are chosen. A multivariable linear discrete time model of the highly non-linear process is identified on-line, using an identification scheme which includes supervisory actions. This identified model, combined with a multivariable predictive control law allows to prevent the controller from systems variations. The control laws are obtained by minimization of a quadratic cost function or by pole placement. In some of these control laws, a partial state reference model was included. This reference model allows to incorporate an appropriate tracking capability into the control law. Experimental results of the application of the involved multivariable adaptive control laws on a RTP system are presented. (author) refs

Teaching Thermal Hydraulics and Numerical Methods: An Introductory Control Volume Primer

International Nuclear Information System (INIS)

D. S. Lucas

2004-01-01

A graduate level course for Thermal Hydraulics (T/H) was taught through Idaho State University in the spring of 2004. A numerical approach was taken for the content of this course since the students were employed at the Idaho National Laboratory and had been users of T/H codes. The majority of the students had expressed an interest in learning about the Courant Limit, mass error, semi-implicit and implicit numerical integration schemes in the context of a computer code. Since no introductory text was found the author developed notes taught from his own research and courses taught for Westinghouse on the subject. The course started with a primer on control volume methods and the construction of a Homogeneous Equilibrium Model (HEM) (T/H) code. The primer was valuable for giving the students the basics behind such codes and their evolution to more complex codes for Thermal Hydraulics and Computational Fluid Dynamics (CFD). The course covered additional material including the Finite Element Method and non-equilibrium (T/H). The control volume primer and the construction of a three-equation (mass, momentum and energy) HEM code are the subject of this paper . The Fortran version of the code covered in this paper is elementary compared to its descendants. The steam tables used are less accurate than the available commercial version written in C Coupled to a Graphical User Interface (GUI). The Fortran version and input files can be downloaded at www.microfusionlab.com

Junction temperature measurements via thermo-sensitive electrical parameters and their application to condition monitoring and active thermal control of power converters

DEFF Research Database (Denmark)

Baker, Nick; Liserre, Marco; Dupont, L.

2013-01-01

implementation of active thermal control to reduce losses and increase lifetime can be performed given an accurate knowledge of temperature. Temperature measurements via thermo-sensitive electrical parameters (TSEP) are one way to carry out immediate temperature readings on fully packaged devices. However...... scale implementation of these methods are discussed. Their potential use in the aforementioned goals in condition monitoring and active thermal control is also described....

A review of human thermal comfort experiments in controlled and semi-controlled environments

NARCIS (Netherlands)

Craenendonck, Van Stijn; Lauriks, Leen; Vuye, Cedric; Kampen, Jarl

2018-01-01

There are three main methods to improve thermal comfort in existing buildings: modeling, experiments and measurements. Regarding experiments, no standardized procedure exists. This article provides an answer to the question: “What is the most common practice for human thermal comfort experiments in

Scaling behavior of the thermal conductivity of width-modulated nanowires and nanofilms for heat transfer control at the nanoscale.

Science.gov (United States)

Zianni, Xanthippi; Jean, Valentin; Termentzidis, Konstantinos; Lacroix, David

2014-11-21

We report on scaling behavior of the thermal conductivity of width-modulated nanowires and nanofilms that have been studied with the phonon Monte Carlo technique. It has been found that the reduction of the thermal conductivity scales with the nanostructure transmissivity, a property entirely determined by the modulation geometry, irrespectively of the material choice. Tuning of the thermal conductivity is possible by the nanostructure width-modulation without strict limitations for the modulation profile. In addition, a very significant constriction thermal resistance due to width-discontinuity has been identified, in analogy to the contact thermal resistance between two dissimilar materials. The constriction thermal resistance also scales with the modulated nanostructure transmissivity. Our conclusions are generic indicating that a wide range of materials can be used for the modulated nanostructures. Direct heat flow control can be provided by designing the nanostructure width-modulation.

Two-Phase Flow Research on the ISS for Thermal Control Applications

Science.gov (United States)

Motil, Brian J.

2013-01-01

With the era of full utilization of the ISS now upon us, this presentation will discuss some of the highest-priority areas for two-phase flow systems with thermal control applications. These priorities are guided by recommendations of a 2011 NRC Decadal Survey report, Recapturing a Future for Space Exploration, Life and Physical Sciences for a New Era as well as an internal NASA exercise in response to the NRC report conducted in early 2012. Many of these proposals are already in various stages of development, while others are still conceptual.

Shuttle Orbiter Active Thermal Control Subsystem design and flight experience

Science.gov (United States)

Bond, Timothy A.; Metcalf, Jordan L.; Asuncion, Carmelo

1991-01-01

The paper examines the design of the Space Shuttle Orbiter Active Thermal Control Subsystem (ATCS) constructed for providing the vehicle and payload cooling during all phases of a mission and during ground turnaround operations. The operation of the Shuttle ATCS and some of the problems encountered during the first 39 flights of the Shuttle program are described, with special attention given to the major problems encountered with the degradation of the Freon flow rate on the Orbiter Columbia, the Flash Evaporator Subsystem mission anomalies which occurred on STS-26 and STS-34, and problems encountered with the Ammonia Boiler Subsystem. The causes and the resolutions of these problems are discussed.

Stochastic control and real options valuation of thermal storage-enabled demand response from flexible district energy systems

International Nuclear Information System (INIS)

Kitapbayev, Yerkin; Moriarty, John; Mancarella, Pierluigi

2015-01-01

Highlights: • We calculate the real option value of flexibility from CHP-thermal storage. • Stochastic optimal feedback control problem is solved under uncertain market prices. • Efficient real-time numerical solutions combine simulation, regression and recursion. • Clear, interpretable feedback control maps are produced for each hour of the day. • We give a realistic UK case study using projected market gas and electricity prices. - Abstract: In district energy systems powered by Combined Heat and Power (CHP) plants, thermal storage can significantly increase CHP flexibility to respond to real time market signals and therefore improve the business case of such demand response schemes in a Smart Grid environment. However, main challenges remain as to what is the optimal way to control inter-temporal storage operation in the presence of uncertain market prices, and then how to value the investment into storage as flexibility enabler. In this outlook, the aim of this paper is to propose a model for optimal and dynamic control and long term valuation of CHP-thermal storage in the presence of uncertain market prices. The proposed model is formulated as a stochastic control problem and numerically solved through Least Squares Monte Carlo regression analysis, with integrated investment and operational timescale analysis equivalent to real options valuation models encountered in finance. Outputs are represented by clear and interpretable feedback control strategy maps for each hour of the day, thus suitable for real time demand response under uncertainty. Numerical applications to a realistic UK case study with projected market gas and electricity prices exemplify the proposed approach and quantify the robustness of the selected storage solutions

Discrimination of thermal diffusivity

NARCIS (Netherlands)

Bergmann Tiest, W.M.; Kappers, A.M.L.

2009-01-01

Materials such as wood or metal which are at equal temperatures are perceived to be of different ‘coldness’ due to differences in thermal properties, such as the thermal diffusivity. The thermal diffusivity of a material is a parameter that controls the rate with which heat is extracted from the

Using cooperative control to manage uncertainties for Aquifer Thermal Energy Storage (ATES)

Science.gov (United States)

Jaxa-Rozen, Marc; Rostampour, Vahab; Kwakkel, Jan; Bloemendal, Martin

2017-04-01

Aquifer Thermal Energy Storage (ATES) technology can lead to major reductions in energy demand for heating and cooling in buildings. ATES systems rely on shallow aquifers to seasonally store thermal energy and have become popular in the Netherlands, where a combination of easily accessible aquifers and strict energy regulations makes the technology especially relevant. However, this rapid adoption has made their management in dense urban areas more challenging. For instance, thermal interferences between neighboring systems can degrade storage efficiency. Policies for the permitting and spatial layout of ATES thus tend to be conservative to ensure the performance of individual systems, but this limits the space available for new systems - leading to a trade-off between individual system performance, and the overall energy savings obtained from ATES in a given area. Furthermore, recent studies show that operational uncertainties contribute to poor outcomes under current planning practices; systems in the Netherlands typically use less than half of their permitted water volume. This further reduces energy savings compared to expectations and also leads to an over-allocation of subsurface space. In this context, this work investigates the potential of a more flexible approach for ATES planning and operation, under which neighboring systems coordinate their operation. This is illustrated with a three-building idealized case, using a model predictive control approach for two control schemes: a decoupled formulation, and a centralized scheme that aims to avoid interferences between neighboring systems (assuming perfect information exchange). These control schemes are compared across a range of scenarios for spatial layout, building energy demand, and climate, using a coupled agent-based/geohydrological simulation. The simulation indicates that centralized operation could significantly improve the spatial layout efficiency of ATES systems, by allowing systems to be placed

Thermal Interaction of Closely Spaced Persons

DEFF Research Database (Denmark)

Brohus, Henrik; Nielsen, Peter V.; Tøgersen, Michael

2011-01-01

This paper presents results from a pilot study on the thermal interaction of closely spaced persons in a large enclosure. The surface temperature at different densities of persons is evaluated using a high resolution thermo vision camera in a controlled thermal environment. The corresponding ther...... thermal sensation is evaluated using questionnaires for the various densities. The results indicate that it may be acceptable to consider persons standalone, in a thermal sense, disregarding thermal interaction at usual densities in the design of large enclosures.......This paper presents results from a pilot study on the thermal interaction of closely spaced persons in a large enclosure. The surface temperature at different densities of persons is evaluated using a high resolution thermo vision camera in a controlled thermal environment. The corresponding...

Effects of thermal treatment on mineralogy and heavy metal behavior in iron oxide stabilized air pollution control residues

DEFF Research Database (Denmark)

Sørensen, Mette Abildgaard; Bender-Koch, C.; Starckpoole, M. M.

2000-01-01

Stabilization of air pollution control residues by coprecipitation with ferrous iron and subsequent thermal treatment (at 600 and 900 °C) has been examined as a means to reduce heavy metal leaching and to improve product stability. Changes in mineralogy and metal binding were analyzed using various...... analytical and environmental techniques. Ferrihydrite was formed initially but transformed upon thermal treatment to more stable and crystalline iron oxides (maghemite and hematite). For some metals leaching studies showed more substantial binding after thermal treatment, while other metals either....... Thermal treatment of the stabilized residues produced structures with an inherently better iron oxide stability. However, the concentration of metals in the leachate generally increased as a consequence of the decreased solubility of metals in the more stable iron oxide structure....

Microcontact printing of polydopamine on thermally expandable hydrogels for controlled cell adhesion and delivery of geometrically defined microtissues.

Science.gov (United States)

Lee, Yu Bin; Kim, Se-Jeong; Kim, Eum Mi; Byun, Hayeon; Chang, Hyung-Kwan; Park, Jungyul; Choi, Yu Suk; Shin, Heungsoo

2017-10-01

Scaffold-free harvest of microtissue with a defined structure has received a great deal of interest in cell-based assay and regenerative medicine. In this study, we developed thermally expandable hydrogels with spatially controlled cell adhesive patterns for rapid harvest of geometrically controlled microtissue. We patterned polydopamine (PD) on to the hydrogel via microcontact printing (μCP), in linear shapes with widths of 50, 100 and 200μm. The hydrogels facilitated formation of spatially controlled strip-like microtissue of human dermal fibroblasts (HDFBs). It was possible to harvest and translocate microtissues with controlled widths of 61.4±14.7, 104.3±15.6, and 186.6±22.3μm from the hydrogel to glass substrates by conformal contact upon expansion of the hydrogel in response to a temperature change from 37 to 4°C, preserving high viability, extracellular matrix, and junction proteins. Microtissues were readily translocated in vivo to the subcutaneous tissue of mouse. The microtissues were further utilized as a simple assay model for monitoring of contraction in response to ROCK1 inhibitor. Collectively, micro-sized patterning of PD on the thermally expandable hydrogels via μCP holds promise for the development of microtissue harvesting systems that can be employed to ex vivo tissue assay and cell-based therapy. Harvest of artificial tissue with controlled cellular arrangement independently from external materials has been widely studied in cell-based assay and regenerative medicine. In this study, we developed scaffold-free harvest system of microtissues with anisotropic arrangement and controlled width by exploiting thermally expandable hydrogels with cell-adhesive patterns of polydopamine formed by simple microcontact printing. Cultured strips of human dermal fibroblasts on the hydrogels were rapidly delivered to various targets ranging from flat coverglass to mice subcutaneous tissue by thermal expansion of the hydrogel at 4°C for 10min. These

A predictive model for smart control of a domestic heat pump and thermal storage

NARCIS (Netherlands)

van Leeuwen, Richard Pieter; Gebhardt, I.; de Wit, J.B.; Smit, Gerardus Johannes Maria

The purpose of this paper is to develop and validate a predictive model of a thermal storage which is charged by a heat pump and used for domestic hot water supply. The model is used for smart grid control purposes and requires measurement signals of flow and temperature at the inlet and outlet of

Thermal modelling using discrete vasculature for thermal therapy: a review

Science.gov (United States)

Kok, H.P.; Gellermann, J.; van den Berg, C.A.T.; Stauffer, P.R.; Hand, J.W.; Crezee, J.

2013-01-01

Reliable temperature information during clinical hyperthermia and thermal ablation is essential for adequate treatment control, but conventional temperature measurements do not provide 3D temperature information. Treatment planning is a very useful tool to improve treatment quality and substantial progress has been made over the last decade. Thermal modelling is a very important and challenging aspect of hyperthermia treatment planning. Various thermal models have been developed for this purpose, with varying complexity. Since blood perfusion is such an important factor in thermal redistribution of energy in in vivo tissue, thermal simulations are most accurately performed by modelling discrete vasculature. This review describes the progress in thermal modelling with discrete vasculature for the purpose of hyperthermia treatment planning and thermal ablation. There has been significant progress in thermal modelling with discrete vasculature. Recent developments have made real-time simulations possible, which can provide feedback during treatment for improved therapy. Future clinical application of thermal modelling with discrete vasculature in hyperthermia treatment planning is expected to further improve treatment quality. PMID:23738700

Studies on preparation and adaptive thermal control performance of novel PTC (positive temperature coefficient) materials with controllable Curie temperatures

International Nuclear Information System (INIS)

Cheng, Wen-long; Yuan, Shuai; Song, Jia-liang

2014-01-01

PTC (positive temperature coefficient) material is a kind of thermo-sensitive material. In this study, a series of novel PTC materials adapted to thermal control of electron devices are prepared. By adding different low-melting-point blend matrixes into GP (graphite powder)/LDPE (low density polyethylene) composite, the Curie temperatures are adjusted to 9 °C, 25 °C, 34 °C and 41 °C, and the resistance–temperature coefficients are enhanced to 1.57/°C–2.15/°C. These PTC materials remain solid in the temperature region of PTC effect, which makes it possible to be used as heating element to achieve adaptive temperature control. In addition, the adaptive thermal control performances of this kind of materials are investigated both experimentally and theoretically. The result shows that the adaptive effect becomes more significant while the resistance–temperature coefficient increases. A critical heating power defined as the initial heating power which makes the equilibrium temperature reach terminal temperature is presented. The adaptive temperature control will be effective only if the initial power is below this value. The critical heating power is determined by the Curie temperature and resistance–temperature coefficient of PTC materials, and a higher Curie temperature or resistance–temperature coefficient will lead to a larger critical heating power. - Highlights: • A series of novel PTC (positive temperature coefficient) materials were prepared. • The Curie point of PTC material can be adjusted by choosing different blend matrixes. • The resistance–temperature coefficient of PTC materials is enhanced to 2.15/°C. • The material has good adaptive temperature control ability with no auxiliary method. • A mathematical model is established to analyze the performance and applicability

Thermal Equilibrium Dynamic Control Based on DPWM Dual-Mode Modulation of High Power NPC Three-Level Inverter

OpenAIRE

Xu, Shi-Zhou; He, Feng-You

2016-01-01

In some special applications of NPC three-level inverters, such as mine hoist, there exist special conditions of overloading during the whole hoisting process and large overload in starting stage, during which the power-loss calculation of power devices and thermal control are important factors affecting the thermal stability of inverters. The principles of SVPWM and DPWM were described in this paper firstly, based on which the dynamic power losses of the two modulations of hoist in single pe...

Controlled growth of gold nanoparticles in zeolite L via ion-exchange reactions and thermal reduction processes

KAUST Repository

Zeng, Shangjing; Ding, Shuang; Li, Shangyu; Wang, Runwei; Zhang, Zongtao

2014-01-01

The growth of gold nanoparticles in zeolite can be controlled using ion-exchange reactions and thermal reduction processes. We produce a number of different sizes of the gold nanoparticles with the particle size increasing with increased temperature

Meat products: main pathogens and non-thermal control strategies

Directory of Open Access Journals (Sweden)

Norma Heredia

2014-12-01

Full Text Available Meat is a rich nutrient matrix that allows the proper environment for diverse microorganisms’ proliferation, deteriorative and pathogen. E. coli O157 and non-O157, Salmonella spp. and Listeria monocytogenes are among the pathogen ones. On other hand, the growing demand for “fresh-like” products with high sanitary, organoleptic and nutritional quality had drive the development of alternative technologies to traditional or thermal, to satisfy consumers’ demand. In the last decades new food preservation techniques with no effect on nutritional or organoleptic characteristics had been developed, maintaining or improving microbiological stability and quality. This work is review of the most common pathogen microorganisms in meat and meat products, and the emerging technologies like high hydrostatic pressure, radiation, intelligent and active packages, and the use of natutal compounds for their control.

Vibration, buckling and smart control of microtubules using piezoelectric nanoshells under electric voltage in thermal environment

Energy Technology Data Exchange (ETDEWEB)

Farajpour, A., E-mail: ariobarzan.oderj@gmail.com; Rastgoo, A.; Mohammadi, M.

2017-03-15

Piezoelectric nanomaterials such as zinc oxide (ZnO) are of low toxicity and have many biomedical applications including optical imaging, drug delivery, biosensing and harvesting biomechanical energy using hybrid nanogenerators. In this paper, the vibration, buckling and smart control of microtubules (MTs) embedded in an elastic medium in thermal environment using a piezoelectric nanoshell (PNS) are investigated. The MT and PNS are considered to be coupled by a filament network. The PNS is subjected to thermal loads and an external electric voltage which operates to control the mechanical behavior of the MT. Using the nonlocal continuum mechanics, the governing differential equations are derived. An exact solution is presented for simply supported boundary conditions. The differential quadrature method is also used to solve the governing equations for other boundary conditions. A detailed parametric study is conducted to investigate the effects of the elastic constants of surrounding medium and internal filament matrix, scale coefficient, electric voltage, the radius-to-thickness ratio of PNSs and temperature change on the smart control of MTs. It is found that the applied electric voltage can be used as an effective controlling parameter for the vibration and buckling of MTs.

Demonstration of Passive Fuel Cell Thermal Management Technology

Science.gov (United States)

Burke, Kenneth A.; Jakupca, Ian; Colozza, Anthony; Wynne, Robert; Miller, Michael; Meyer, Al; Smith, William

2012-01-01

The NASA Glenn Research Center is developing advanced passive thermal management technology to reduce the mass and improve the reliability of space fuel cell systems for the NASA Exploration program. The passive thermal management system relies on heat conduction within highly thermally conductive cooling plates to move the heat from the central portion of the cell stack out to the edges of the fuel cell stack. Using the passive approach eliminates the need for a coolant pump and other cooling loop components within the fuel cell system which reduces mass and improves overall system reliability. Previous development demonstrated the performance of suitable highly thermally conductive cooling plates and integrated heat exchanger technology to collect the heat from the cooling plates (Ref. 1). The next step in the development of this passive thermal approach was the demonstration of the control of the heat removal process and the demonstration of the passive thermal control technology in actual fuel cell stacks. Tests were run with a simulated fuel cell stack passive thermal management system outfitted with passive cooling plates, an integrated heat exchanger and two types of cooling flow control valves. The tests were run to demonstrate the controllability of the passive thermal control approach. Finally, successful demonstrations of passive thermal control technology were conducted with fuel cell stacks from two fuel cell stack vendors.

Method and device for thermal control of biological and chemical reactions using magnetic particles or magnetic beads and variable magnetic fields

OpenAIRE

Zilch, C.; Gerdes, W.; Bauer, J.; Holschuh, K.

2009-01-01

The invention relates to a method for the thermal control of at least one temperature-dependent enzymatic reaction in the presence of magnetic particles, particularly nanoparticles, or magnetic beads, in vitro by heating the magnetic beads or magnetic particles to at least one defined target temperature using alternating magnetic fields. The thermally controllable enzymatic reaction carried out with the method according to the invention is preferably a PCR reaction or another reaction for elo...

Thermal fluctuation based study of aqueous deficient dry eyes by non-invasive thermal imaging.

Science.gov (United States)

Azharuddin, Mohammad; Bera, Sumanta Kr; Datta, Himadri; Dasgupta, Anjan Kr

2014-03-01

In this paper we have studied the thermal fluctuation patterns occurring at the ocular surface of the left and right eyes for aqueous deficient dry eye (ADDE) patients and control subjects by thermal imaging. We conducted our experiment on 42 patients (84 eyes) with aqueous deficient dry eyes and compared with 36 healthy volunteers (72 eyes) without any history of ocular surface disorder. Schirmer's test, Tear Break-up Time, tear Meniscus height and fluorescein staining tests were conducted. Ocular surface temperature measurement was done, using an FL-IR thermal camera and thermal fluctuation in left and right eyes was calculated and analyzed using MATLAB. The time series containing the sum of squares of the temperature fluctuation on the ocular surface were compared for aqueous deficient dry eye and control subjects. Significant statistical difference between the fluctuation patterns for control and ADDE was observed (p eyes are significantly correlated in controls but not in ADDE subjects. The possible origin of such correlation in control and lack of correlation in the ADDE subjects is discussed in the text. Copyright © 2014 Elsevier Ltd. All rights reserved.

Automatic Generation Control Study in Two Area Reheat Thermal Power System

Science.gov (United States)

Pritam, Anita; Sahu, Sibakanta; Rout, Sushil Dev; Ganthia, Sibani; Prasad Ganthia, Bibhu

2017-08-01

Due to industrial pollution our living environment destroyed. An electric grid system has may vital equipment like generator, motor, transformers and loads. There is always be an imbalance between sending end and receiving end system which cause system unstable. So this error and fault causing problem should be solved and corrected as soon as possible else it creates faults and system error and fall of efficiency of the whole power system. The main problem developed from this fault is deviation of frequency cause instability to the power system and may cause permanent damage to the system. Therefore this mechanism studied in this paper make the system stable and balance by regulating frequency at both sending and receiving end power system using automatic generation control using various controllers taking a two area reheat thermal power system into account.

Vapor Chamber with Phase Change Material-based Wick Structure for Thermal Control of Manned Spacecraft, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — In response to NASA SBIR solicitation H3.01 "Thermal Control for Future Human Exploration", Advanced Cooling Technologies, Inc. (ACT) is proposing a novel Phase...

Heat pipe thermal control of slender optics probes

International Nuclear Information System (INIS)

Prenger, F.C.

1979-01-01

The thermal design for a stereographic viewing system is presented. The design incorporates an annular heat pipe and thermal isolation techniques. Test results are compared with design predictions for a prototype configuration. Test data obtained during heat pipe startup showing temperature gradients along the evaporator wall are presented. Correlations relating maximum wall temperature differences to a liquid Reynolds number were obtained at low power levels. These results are compared with Nusselt's Falling Film theory

Guide to Setting Thermal Comfort Criteria and Minimizing Energy Use in Delivering Thermal Comfort

Energy Technology Data Exchange (ETDEWEB)

Regnier, Cindy [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2012-08-01

Historically thermal comfort in buildings has been controlled by simple dry bulb temperature settings. As we move into more sophisticated low energy building systems that make use of alternate systems such as natural ventilation, mixed mode system and radiant thermal conditioning strategies, a more complete understanding of human comfort is needed for both design and control. This guide will support building designers, owners, operators and other stakeholders in defining quantifiable thermal comfort parameters?these can be used to support design, energy analysis and the evaluation of the thermal comfort benefits of design strategies. This guide also contains information that building owners and operators will find helpful for understanding the core concepts of thermal comfort. Whether for one building, or for a portfolio of buildings, this guide will also assist owners and designers in how to identify the mechanisms of thermal comfort and space conditioning strategies most important for their building and climate, and provide guidance towards low energy design options and operations that can successfully address thermal comfort. An example of low energy design options for thermal comfort is presented in some detail for cooling, while the fundamentals to follow a similar approach for heating are presented.

Thermal Design and Thermal Behaviour of Radio Telescopes and their Enclosures

CERN Document Server

Greve, Albert

2010-01-01

Radio telescopes as well as communication antennas operate under the influence of gravity, temperature and wind. Among those, temperature influences may degrade the performance of a radio telescope through transient changes of the focus, pointing, path length and sensitivity, often in an unpredictable way. Thermal Design and Thermal Behaviour of Radio Telescopes and their Enclosures reviews the design and construction principles of radio telescopes in view of thermal aspects and heat transfer with the variable thermal environment; it explains supporting thermal model calculations and the application and efficiency of thermal protection and temperature control; it presents many measurements illustrating the thermal behaviour of telescopes in the environment of their observatory sites. The book benefits scientists and radio/communication engineers, telescope designers and construction firms as well as telescope operators, observatory staff, but also the observing astronomer who is directly confronted with the t...

Bayesian networks modeling for thermal error of numerical control machine tools

Institute of Scientific and Technical Information of China (English)

Xin-hua YAO; Jian-zhong FU; Zi-chen CHEN

2008-01-01

The interaction between the heat source location,its intensity,thermal expansion coefficient,the machine system configuration and the running environment creates complex thermal behavior of a machine tool,and also makes thermal error prediction difficult.To address this issue,a novel prediction method for machine tool thermal error based on Bayesian networks (BNs) was presented.The method described causal relationships of factors inducing thermal deformation by graph theory and estimated the thermal error by Bayesian statistical techniques.Due to the effective combination of domain knowledge and sampled data,the BN method could adapt to the change of running state of machine,and obtain satisfactory prediction accuracy.Ex-periments on spindle thermal deformation were conducted to evaluate the modeling performance.Experimental results indicate that the BN method performs far better than the least squares(LS)analysis in terms of modeling estimation accuracy.

Simulator with integrated HW and SW for prediction of thermal comfort to provide feedback to the climate control system

Science.gov (United States)

Pokorný, Jan; Kopečková, Barbora; Fišer, Jan; JÍcha, Miroslav

2018-06-01

The aim of the paper is to assemble a simulator for evaluation of thermal comfort in car cabins in order to give a feedback to the HVAC (heating, ventilation and air conditioning) system. The HW (hardware) part of simulator is formed by thermal manikin Newton and RH (relative humidity), velocity and temperature probes. The SW (software) part consists of the Thermal Comfort Analyser (using ISO 14505-2) and Virtual Testing Stand of Car Cabin defining the heat loads of car cabin. Simulator can provide recommendation for the climate control how to improve thermal comfort in cabin by distribution and directing of air flow, and also by amount of ventilation power to keep optimal temperature inside a cabin. The methods of evaluation of thermal comfort were verified by tests with 10 test subjects for summer (summer clothing, ambient air temperature 30 °C, HVAC setup: +24 °C auto) and winter conditions (winter clothing, ambient air temperature -5 °C, HVAC setup: +18 °C auto). The tests confirmed the validity of the thermal comfort evaluation using the thermal manikin and ISO 14505-2.

Thermal-stress analysis of HTGR fuel and control rod fuel blocks in in-block carbonization and annealing furnace

International Nuclear Information System (INIS)

Gwaltney, R.C.; McAfee, W.J.

1977-01-01

A new method for performing thermal stress analyses in structures with multiple penetrations was applied to these analyses. This method couples the development of an equivalent thermal conductivity for the blocks, a technique that has been used extensively for modeling the thermal characteristics of reactor cores, with the use of the equivalent solid plate method for stress analysis. Using this equivalent thermal conductivity, which models as one material the heat transfer characteristics of the fuel, coolant, and graphite two-dimensional, steady-state thermal analyses of the fuel and control rod fuel blocks were performed to establish all temperature boundaries required for the stress analyses. In applying the equivalent solid plate method, the region of penetrations being modeled was replaced by a pseudo material having the same dimensions but whose materials properties were adjusted to account for the penetration. The peak stresses and strains were determined by applying stress and strain intensification factors to the calculated distributions. The condition studied was where the blocks were located near the center of the furnace. In this position, the axial surface of the block is heated near one end and cooled near the other. The approximate axial surface temperatures ranged from 1521 0 C at both the heated and the cooled ends to a peak of 1800 0 C near the center. Five specific cases were analyzed: plane (two-dimensional thermal, plane stress strain) analyses of each end of a standard fuel block (2 cases), plane analyses of each end of a control rod fuel block (2 cases), and a two-dimensional analysis of a fuel block treated as an axisymmetric cylind

Thermal Emission Control via Bandgap Engineering in Aperiodically Designed Nanophotonic Devices

Directory of Open Access Journals (Sweden)

Enrique Maciá

2015-05-01

Full Text Available Aperiodic photonic crystals can open up novel routes for more efficient photon management due to increased degrees of freedom in their design along with the unique properties brought about by the long-range aperiodic order as compared to their periodic counterparts. In this work we first describe the fundamental notions underlying the idea of thermal emission/absorption control on the basis of the systematic use of aperiodic multilayer designs in photonic quasicrystals. Then, we illustrate the potential applications of this approach in order to enhance the performance of daytime radiative coolers and solar thermoelectric energy generators.

The relationship between bioclimatic thermal stress and subjective thermal sensation in pedestrian spaces

Science.gov (United States)

Pearlmutter, David; Jiao, Dixin; Garb, Yaakov

2014-12-01

Outdoor thermal comfort has important implications for urban planning and energy consumption in the built environment. To better understand the relation of subjective thermal experience to bioclimatic thermal stress in such contexts, this study compares micrometeorological and perceptual data from urban spaces in the hot-arid Negev region of Israel. Pedestrians reported on their thermal sensation in these spaces, whereas radiation and convection-related data were used to compute the Index of Thermal Stress (ITS) and physiologically equivalent temperature (PET). The former is a straightforward characterization of energy exchanges between the human body and its surroundings, without any conversion to an "equivalent temperature." Although the relation of ITS to subjective thermal sensation has been analyzed in the past under controlled indoor conditions, this paper offers the first analysis of this relation in an outdoor setting. ITS alone can account for nearly 60 % of the variance in pedestrians' thermal sensation under outdoor conditions, somewhat more than PET. A series of regressions with individual contextual variables and ITS identified those factors which accounted for additional variance in thermal sensation, whereas multivariate analyses indicated the considerable predictive power ( R-square = 0.74) of models including multiple contextual variables in addition to ITS. Our findings indicate that pedestrians experiencing variable outdoor conditions have a greater tolerance for incremental changes in thermal stress than has been shown previously under controlled indoor conditions, with a tapering of responses at high values of ITS. However, the thresholds of ITS corresponding to thermal "neutrality" and thermal "acceptability" are quite consistent regardless of context.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets.

Science.gov (United States)

Chang, Nan; Lu, Shukuan; Qin, Dui; Xu, Tianqi; Han, Meng; Wang, Supin; Wan, Mingxi

2018-07-01

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration. Copyright © 2018. Published by Elsevier B.V.

Thermal management of space stations

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

Thermal management aims at making full use of energy resources available in the space station to reduce energy consumption, waste heat rejection and the weight of the station. It is an extension of the thermal control. This discussion introduces the concept and development of thermal management, presents the aspects of thermal management and further extends its application to subsystems of the space station.

PID-controller with predictor and auto-tuning algorithm: study of efficiency for thermal plants

Science.gov (United States)

Kuzishchin, V. F.; Merzlikina, E. I.; Hoang, Van Va

2017-09-01

The problem of efficiency estimation of an automatic control system (ACS) with a Smith predictor and PID-algorithm for thermal plants is considered. In order to use the predictor, it is proposed to include an auto-tuning module (ATC) into the controller; the module calculates parameters for a second-order plant module with a time delay. The study was conducted using programmable logical controllers (PLC), one of which performed control, ATC, and predictor functions. A simulation model was used as a control plant, and there were two variants of the model: one of them was built on the basis of a separate PLC, and the other was a physical model of a thermal plant in the form of an electrical heater. Analysis of the efficiency of the ACS with the predictor was carried out for several variants of the second order plant model with time delay, and the analysis was performed on the basis of the comparison of transient processes in the system when the set point was changed and when a disturbance influenced the control plant. The recommendations are given on correction of the PID-algorithm parameters when the predictor is used by means of using the correcting coefficient k for the PID parameters. It is shown that, when the set point is changed, the use of the predictor is effective taking into account the parameters correction with k = 2. When the disturbances influence the plant, the use of the predictor is doubtful, because the transient process is too long. The reason for this is that, in the neighborhood of the zero frequency, the amplitude-frequency characteristic (AFC) of the system with the predictor has an ascent in comparison with the AFC of the system without the predictor.

Aquifer Thermal Energy Storage for Seasonal Thermal Energy Balance

Science.gov (United States)

Rostampour, Vahab; Bloemendal, Martin; Keviczky, Tamas

2017-04-01

Aquifer Thermal Energy Storage (ATES) systems allow storing large quantities of thermal energy in subsurface aquifers enabling significant energy savings and greenhouse gas reductions. This is achieved by injection and extraction of water into and from saturated underground aquifers, simultaneously. An ATES system consists of two wells and operates in a seasonal mode. One well is used for the storage of cold water, the other one for the storage of heat. In warm seasons, cold water is extracted from the cold well to provide cooling to a building. The temperature of the extracted cold water increases as it passes through the building climate control systems and then gets simultaneously, injected back into the warm well. This procedure is reversed during cold seasons where the flow direction is reversed such that the warmer water is extracted from the warm well to provide heating to a building. From the perspective of building climate comfort systems, an ATES system is considered as a seasonal storage system that can be a heat source or sink, or as a storage for thermal energy. This leads to an interesting and challenging optimal control problem of the building climate comfort system that can be used to develop a seasonal-based energy management strategy. In [1] we develop a control-oriented model to predict thermal energy balance in a building climate control system integrated with ATES. Such a model however cannot cope with off-nominal but realistic situations such as when the wells are completely depleted, or the start-up phase of newly installed wells, etc., leading to direct usage of aquifer ambient temperature. Building upon our previous work in [1], we here extend the mathematical model for ATES system to handle the above mentioned more realistic situations. Using our improved models, one can more precisely predict system behavior and apply optimal control strategies to manage the building climate comfort along with energy savings and greenhouse gas reductions

Transf ormation thermotics and the manipulation of thermal energy

Institute of Scientific and Technical Information of China (English)

Xiangfan Xu; Baowen Li

2017-01-01

Thermal energy has been proposed to have ever greater potential for human beings if the heat carriers, pho-nons can be controlled in micron-scale as easy as its counterpart, electrons in solid. However, it is a challenge to control phonons due to its relatively short wavelength, which is in the order of a few nanometers to a few tens of nanometers. Alternatively, in macroscopical scale, functional thermal materials are used to control thermal energy. The transfor-mation of macroscopical thermal diffusion equation is proposed to obtain the asymmetrical thermal conductivity in real space. This new type of thermal functional materials helps to control heat flow and to realize thermal cloak and thermal camouflage. In this review, we summarize the recent advances in constructing thermal functional materials (also called thermal metamaterials). In SecⅠ, we discussed the history of functional materials and the principles of constructing thermal functional materials , special focus was given to the thermal cloak, followed by the realization of thermal cloak in SecⅡ.Thermal camouflage, based on the realization of thermal cloak, was discussed in SecⅢ, which is proposed to have great potentials in military usage. We stressed both the principle and practical based challenges in thermal cloak and thermal camouflage in SecⅣ, in which outlooks were also given. It is worth noting that thermal transports consist of thermal conduction, thermal convection and thermal radiation. Recent progresses on thermal functional materials are based on the transformation of thermotics, i.e. spacial distortion of thermal conducting path, leaving thermal convection and thermal radiation untouched. We hope, though this review paper, to encourage more researchers in China to engage in this field, and to accelerate the practical usage of thermal cloak and thermal camouflage.

Thermal comfort in urban transitional spaces

Energy Technology Data Exchange (ETDEWEB)

Chungyoon Chun [Yonsei University, Seoul (Korea). College of Human Ecology, Department of Housing and Interior Design; Tamura, A. [Yokohama National University (Japan). Department of Architecture and Building Science

2005-05-15

This paper deals with thermal comfort in urban transitional spaces. This topic investigates thermal comfort during walking activities through transitional spaces-urban corridors, shopping streets, and open-ended passageways. The study involves a field study and a laboratory study with a sequenced walk through an environmental control chamber. Subjects in both studies wore the same clothing ensembles, walked the same speed, and evaluated their thermal comfort at 20 designated point in the field and in specific rooms in the control chamber. Air temperature, relative humidity, and air velocity were measured concurrently as the thermal comfort votes completed. Findings revealed that the previously experienced temperatures determined thermal comfort at the following point in the sequence. Because thermal comfort at a point can be influenced widely by relative placement of temperatures in sequence, thermal comfort in transitional spaces can be adapted very widely compared to comfort inside of buildings. Thermal comfort along the experimental courses was evaluated by averaging the temperature of a course. (author)

Thermal stress management of a solid oxide fuel cell using neural network predictive control

International Nuclear Information System (INIS)

Hajimolana, S.A.; Tonekabonimoghadam, S.M.; Hussain, M.A.; Chakrabarti, M.H.; Jayakumar, N.S.; Hashim, M.A.

2013-01-01

In SOFC (solid oxide fuel cell) systems operating at high temperatures, temperature fluctuation induces a thermal stress in the electrodes and electrolyte ceramics; therefore, the cell temperature distribution is recommended to be kept as constant as possible. In the present work, a mathematical model based on first principles is presented to avert such temperature fluctuations. The fuel cell running on ammonia is divided into five subsystems and factors such as mass/energy/momentum transfer, diffusion through porous media, electrochemical reactions, and polarization losses inside the subsystems are presented. Dynamic cell-tube temperature responses of the cell to step changes in conditions of the feed streams is investigated. The results of simulation indicate that the transient response of the SOFC is mainly influenced by the temperature dynamics. It is also shown that the inlet stream temperatures are associated with the highest long term start-up time (467 s) among other parameters in terms of step changes. In contrast the step change in fuel velocity has the lowest influence on the start-up time (about 190 s from initial steady state to the new steady state) among other parameters. A NNPC (neural network predictive controller) is then implemented for thermal stress management by controlling the cell tube temperature to avoid performance degradation by manipulating the temperature of the inlet air stream. The regulatory performance of the NNPC is compared with a PI (proportional–integral) controller. The performance of the control system confirms that NNPC is a non-linear-model-based strategy which can assure less oscillating control responses with shorter settling times in comparison to the PI controller. - Highlights: • Effect of the operating parameters on the fuel cell temperature is analysed. • A neural network predictive controller (NNPC) is implemented. • The performance of NNPC is compared with the PI controller. • A detailed model is used for

Tunable thermal link

Science.gov (United States)

Chang, Chih-Wei; Majumdar, Arunava; Zettl, Alexander K.

2014-07-15

Disclosed is a device whereby the thermal conductance of a multiwalled nanostructure such as a multiwalled carbon nanotube (MWCNT) can be controllably and reversibly tuned by sliding one or more outer shells with respect to the inner core. As one example, the thermal conductance of an MWCNT dropped to 15% of the original value after extending the length of the MWCNT by 190 nm. The thermal conductivity returned when the tube was contracted. The device may comprise numbers of multiwalled nanotubes or other graphitic layers connected to a heat source and a heat drain and various means for tuning the overall thermal conductance for applications in structure heat management, heat flow in nanoscale or microscale devices and thermal logic devices.

Thermal stability control system of photo-elastic interferometer in the PEM-FTs

Science.gov (United States)

Zhang, M. J.; Jing, N.; Li, K. W.; Wang, Z. B.

2018-01-01

A drifting model for the resonant frequency and retardation amplitude of a photo-elastic modulator (PEM) in the photo-elastic modulated Fourier transform spectrometer (PEM-FTs) is presented. A multi-parameter broadband-matching driving control method is proposed to improve the thermal stability of the PEM interferometer. The automatically frequency-modulated technology of the driving signal based on digital phase-locked technology is used to track the PEM's changing resonant frequency. Simultaneously the maximum optical-path-difference of a laser's interferogram is measured to adjust the amplitude of the PEM's driving signal so that the spectral resolution is stable. In the experiment, the multi-parameter broadband-matching control method is applied to the driving control system of the PEM-FTs. Control of resonant frequency and retardation amplitude stabilizes the maximum optical-path-difference to approximately 236 μm and results in a spectral resolution of 42 cm-1. This corresponds to a relative error smaller than 2.16% (4.28 standard deviation). The experiment shows that the method can effectively stabilize the spectral resolution of the PEM-FTs.

Solar energy thermally powered electrical generating system

Science.gov (United States)

Owens, William R. (Inventor)

1989-01-01

A thermally powered electrical generating system for use in a space vehicle is disclosed. The rate of storage in a thermal energy storage medium is controlled by varying the rate of generation and dissipation of electrical energy in a thermally powered electrical generating system which is powered from heat stored in the thermal energy storage medium without exceeding a maximum quantity of heat. A control system (10) varies the rate at which electrical energy is generated by the electrical generating system and the rate at which electrical energy is consumed by a variable parasitic electrical load to cause storage of an amount of thermal energy in the thermal energy storage system at the end of a period of insolation which is sufficient to satisfy the scheduled demand for electrical power to be generated during the next period of eclipse. The control system is based upon Kalman filter theory.

Voltage tunability of thermal conductivity in ferroelectric materials

Science.gov (United States)

Ihlefeld, Jon; Hopkins, Patrick Edward

2016-02-09

A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

Experimental and Numerical Studies of Controlling Thermal Cracks in Mass Concrete Foundation by Circulating Water

Directory of Open Access Journals (Sweden)

Wenchao Liu

2016-04-01

Full Text Available This paper summarizes an engineering experience of solving the problem of thermal cracking in mass concrete by using a large project, Zhongguancun No.1 (Beijing, China, as an example. A new method is presented for controlling temperature cracks in the mass concrete of a foundation. The method involves controlled cycles of water circulating between the surface of mass concrete foundation and the atmospheric environment. The temperature gradient between the surface and the core of the mass concrete is controlled at a relatively stable state. Water collected from the well-points used for dewatering and from rainfall is used as the source for circulating water. Mass concrete of a foundation slab is experimentally investigated through field temperature monitoring. Numerical analyses are performed by developing a finite element model of the foundation with and without water circulation. The calculation parameters are proposed based on the experiment, and finite element analysis software MIDAS/CIVIL is used to calculate the 3D temperature field of the mass concrete during the entire process of heat of hydration. The numerical results are in good agreement with the measured results. The proposed method provides an alternative practical basis for preventing thermal cracks in mass concrete.

Thermal morphing anisogrid smart space structures: thermal isolation design and linearity evaluation

Science.gov (United States)

Phoenix, Austin A.

2017-04-01

To meet the requirements for the next generation of space missions, a paradigm shift is required from current structures that are static, heavy and stiff, toward innovative structures that are adaptive, lightweight, versatile, and intelligent. A novel morphing structure, the thermally actuated anisogrid morphing boom, can be used to meet the design requirements by making the primary structure actively adapt to the on-orbit environment. The anisogrid structure is able to achieve high precision morphing control through the intelligent application of thermal gradients. This active primary structure improves structural and thermal stability performance, reduces mass, and enables new mission architectures. This effort attempts to address limits to the author's previous work by incorporating the impact of thermal coupling that was initially neglected. This paper introduces a thermally isolated version of the thermal morphing anisogrid structure in order to address the thermal losses between active members. To evaluate the isolation design the stiffness and thermal conductivity of these isolating interfaces need to be addressed. This paper investigates the performance of the thermal morphing system under a variety of structural and thermal isolation interface properties.

Simulator with integrated HW and SW for prediction of thermal comfort to provide feedback to the climate control system

Directory of Open Access Journals (Sweden)

Pokorný Jan

2018-01-01

Full Text Available The aim of the paper is to assemble a simulator for evaluation of thermal comfort in car cabins in order to give a feedback to the HVAC (heating, ventilation and air conditioning system. The HW (hardware part of simulator is formed by thermal manikin Newton and RH (relative humidity, velocity and temperature probes. The SW (software part consists of the Thermal Comfort Analyser (using ISO 14505-2 and Virtual Testing Stand of Car Cabin defining the heat loads of car cabin. Simulator can provide recommendation for the climate control how to improve thermal comfort in cabin by distribution and directing of air flow, and also by amount of ventilation power to keep optimal temperature inside a cabin. The methods of evaluation of thermal comfort were verified by tests with 10 test subjects for summer (summer clothing, ambient air temperature 30 °C, HVAC setup: +24 °C auto and winter conditions (winter clothing, ambient air temperature -5 °C, HVAC setup: +18 °C auto. The tests confirmed the validity of the thermal comfort evaluation using the thermal manikin and ISO 14505-2.

Experience of Implementing a Distributed Control System for Thermal and Mechanical and Electrical Equipment at the South-West CHP

Energy Technology Data Exchange (ETDEWEB)

Babkin, K. V., E-mail: babkin@uztec.ru; Tsvetkov, M. S.; Kostyuk, R. I.; Chugin, A. V. [SC “South-West CHP” (Russian Federation); Bilenko, V. A.; Molchanov, K. A.; Fedunov, V. V. [JSC “Interautomatika” (Russian Federation)

2015-01-15

Results of implementing an SPPA-T3000-based unified distributed control system for thermal and mechanical and electrical equipment at the South-West CHP are discussed. Hardware solutions for integration with local control systems, control of electrical equipment in compliance with the standards IEC 61850, Modbus RTU, and communication between the plant control system and the System Operator of the Unified Power System are described.

Experience of Implementing a Distributed Control System for Thermal and Mechanical and Electrical Equipment at the South-West CHP

International Nuclear Information System (INIS)

Babkin, K. V.; Tsvetkov, M. S.; Kostyuk, R. I.; Chugin, A. V.; Bilenko, V. A.; Molchanov, K. A.; Fedunov, V. V.

2015-01-01

Results of implementing an SPPA-T3000-based unified distributed control system for thermal and mechanical and electrical equipment at the South-West CHP are discussed. Hardware solutions for integration with local control systems, control of electrical equipment in compliance with the standards IEC 61850, Modbus RTU, and communication between the plant control system and the System Operator of the Unified Power System are described

Selective microrobot control using a thermally responsive microclamper for microparticle manipulation

International Nuclear Information System (INIS)

Go, Gwangjun; Choi, Hyunchul; Ko, Seong Young; Park, Jong-Oh; Park, Sukho; Jeong, Semi

2016-01-01

Microparticle manipulation using a microrobot in an enclosed environment, such as a lab-on-a-chip, has been actively studied because an electromagnetic actuated microrobot can have accurate motility and wireless controllability. In most studies on electromagnetic actuated microrobots, only a single microrobot has been used to manipulate cells or microparticles. However, the use of a single microrobot can pose several limitations when performing multiple roles in microparticle manipulation. To overcome the limitations associated with using a single microrobot, we propose a new method for the control of multiple microrobots. Multiple microrobots can be controlled independently by an electromagnetic actuation system and multiple microclampers combined with microheaters. To select a specific microrobot among multiple microrobots, we propose a microclamper composed of a clamper structure using thermally responsive hydrogel and a microheater for controlling the microclamper. A fundamental test of the proposed microparticle manipulation system is performed by selecting a specific microrobot among multiple microrobots. Through the independent locomotion of multiple microrobots with U- and V-shaped tips, heterogeneous microparticle manipulation is demonstrated in the creation of a two-dimensional structure. In the future, our proposed multiple-microrobot system can be applied to tasks that are difficult to perform using a single microrobot, such as cell manipulation, cargo delivery, tissue assembly, and cloning. (paper)

High temperature glass thermal control structure and coating. [for application to spacecraft reusable heat shielding

Science.gov (United States)

Stewart, D. A.; Goldstein, H. E.; Leiser, D. B. (Inventor)

1983-01-01

A high temperature stable and solar radiation stable thermal control coating is described which is useful either as such, applied directly to a member to be protected, or applied as a coating on a re-usable surface insulation (RSI). It has a base coat layer and an overlay glass layer. The base coat layer has a high emittance, and the overlay layer is formed from discrete, but sintered together glass particles to give the overlay layer a high scattering coefficient. The resulting two-layer space and thermal control coating has an absorptivity-to-emissivity ratio of less than or equal to 0.4 at room temperature, with an emittance of 0.8 at 1200 F. It is capable of exposure to either solar radiation or temperatures as high as 2000 F without significant degradation. When used as a coating on a silica substrate to give an RSI structure, the coatings of this invention show significantly less reduction in emittance after long term convective heating and less residual strain than prior art coatings for RSI structures.

Active Participation of Air Conditioners in Power System Frequency Control Considering Users’ Thermal Comfort

Directory of Open Access Journals (Sweden)

Rongxiang Zhang

2015-09-01

Full Text Available Air conditioners have great potential to participate in power system frequency control. This paper proposes a control strategy to facilitate the active participation of air conditioners. For each air conditioner, a decentralized control law is designed to adjust its temperature set point in response to the system frequency deviation. The decentralized control law accounts for the user’s thermal comfort that is evaluated by a fuzzy algorithm. The aggregation of air conditioners’ response is conducted by using the Monte Carlo simulation method. A structure preserving model is applied to the multi-bus power system, in which air conditioners are aggregated at certain load buses. An inner-outer iteration scheme is adopted to solve power system dynamics. An experiment is conducted on a test air conditioner to examine the performance of the proposed decentralized control law. Simulation results on a test power system verify the effectiveness of the proposed strategy for air conditioners participating in frequency control.

Thermal comfort assessment in civil aircraft cabins

OpenAIRE

Pang Liping; Qin Yue; Liu Dong; Liu Meng

2014-01-01

Aircraft passengers are more and demanding in terms of thermal comfort. But it is not yet easy for aircraft crew to control the environment control system (ECS) that satisfies the thermal comfort for most passengers due to a number of causes. This paper adopts a corrected predicted mean vote (PMV) model and an adaptive model to assess the thermal comfort conditions for 31 investigated flights and draws the conclusion that there does exist an uncomfortable thermal phenomenon in civil aircraft ...

Neural computing thermal comfort index PMV for the indoor environment intelligent control system

Science.gov (United States)

Liu, Chang; Chen, Yifei

2013-03-01

Providing indoor thermal comfort and saving energy are two main goals of indoor environmental control system. An intelligent comfort control system by combining the intelligent control and minimum power control strategies for the indoor environment is presented in this paper. In the system, for realizing the comfort control, the predicted mean vote (PMV) is designed as the control goal, and with chastening formulas of PMV, it is controlled to optimize for improving indoor comfort lever by considering six comfort related variables. On the other hand, a RBF neural network based on genetic algorithm is designed to calculate PMV for better performance and overcoming the nonlinear feature of the PMV calculation better. The formulas given in the paper are presented for calculating the expected output values basing on the input samples, and the RBF network model is trained depending on input samples and the expected output values. The simulation result is proved that the design of the intelligent calculation method is valid. Moreover, this method has a lot of advancements such as high precision, fast dynamic response and good system performance are reached, it can be used in practice with requested calculating error.

Controlled growth of gold nanoparticles in zeolite L via ion-exchange reactions and thermal reduction processes

KAUST Repository

Zeng, Shangjing

2014-09-01

The growth of gold nanoparticles in zeolite can be controlled using ion-exchange reactions and thermal reduction processes. We produce a number of different sizes of the gold nanoparticles with the particle size increasing with increased temperature of the final heat treatment. © 2014 Elsevier B.V.

Modern techniques for the emissions control in thermal electric stations; Tecnicas modernas para el control de emisiones en centrales termoelectricas

Energy Technology Data Exchange (ETDEWEB)

Romo Millares, C. A. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1995-12-31

This paper presents the techniques and the control equipment for emissions in thermal stations that have the highest possibilities of being considered in the immediate future in the national energy panorama and the established frame for the environmental normativity. The pollutant compounds subject to revision are the nitrogen and sulfur oxides and unburned particles. [Espanol] Se presentan las tecnicas y equipos de control de emisiones para centrales termoelectricas que tienen mayores posibilidades de ser consideradas en el futuro inmediato dentro del panorama energetico nacional y el marco establecido por la normatividad ambiental. Los compuestos contaminantes sujetos a revision son los oxidos de nitrogeno y azufre y las particulas inquemadas.

Modern techniques for the emissions control in thermal electric stations; Tecnicas modernas para el control de emisiones en centrales termoelectricas

Energy Technology Data Exchange (ETDEWEB)

Romo Millares, C A [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1996-12-31

This paper presents the techniques and the control equipment for emissions in thermal stations that have the highest possibilities of being considered in the immediate future in the national energy panorama and the established frame for the environmental normativity. The pollutant compounds subject to revision are the nitrogen and sulfur oxides and unburned particles. [Espanol] Se presentan las tecnicas y equipos de control de emisiones para centrales termoelectricas que tienen mayores posibilidades de ser consideradas en el futuro inmediato dentro del panorama energetico nacional y el marco establecido por la normatividad ambiental. Los compuestos contaminantes sujetos a revision son los oxidos de nitrogeno y azufre y las particulas inquemadas.

Low order modelling and closed-loop thermal control of a ventilated plate subject to a heat source disturbance

International Nuclear Information System (INIS)

Videcoq, E; Girault, M; Petit, D

2012-01-01

A multi-input multi-output (MIMO) thermal control problem in real-time is investigated. An aluminum slab is heated on one side by a radiative heat source and cooled on the other side by a fan panel. Starting from a nominal steady state configuration of heat source power and ventilation level, the objective is to control temperature at 4 chosen locations on the rear side when the thermal system is subject to a perturbation: the heat source power. The 4 actuators are the ventilation levels of 4 fans. The hypothesis of small inputs and temperature responses deviations is made, resulting in the assumption of a linear control problem. The originality of this work is twofold: (i) instead of a (large-sized) classical heat transfer model built from spatial discretization of local partial differential equations governing physics over the system domain, a low order model is identified from experimental data using the Modal Identification Method, (ii) this low order model is used to perform state feedback control in real time through a Linear Quadratic Gaussian (LQG) compensator.

Applications of Fuzzy adaptive PID control in the thermal power plant denitration liquid ammonia evaporation

Directory of Open Access Journals (Sweden)

Li Jing

2016-01-01

Full Text Available For the control of the liquid level of liquid ammonia in thermal power plant’s ammonia vaporization room, traditional PID controller parameter tuning is difficult to adapt to complex control systems, the setting of the traditional PID controller parameters is difficult to adapt to the complex control system. For the disadvantage of bad parameter setting, poor performance and so on the fuzzy adaptive PID control is proposed. Fuzzy adaptive PID control combines the advantages of traditional PID technology and fuzzy control. By using the fuzzy controller to intelligent control the object, the performance of the PID controller is further improved, and the control precision of the system is improved[1]. The simulation results show that the fuzzy adaptive PID controller not only has the advantages of high accuracy of PID controller, but also has the characteristics of fast and strong adaptability of fuzzy controller. It realizes the optimization of PID parameters which are in the optimal state, and the maximum increase production efficiency, so that are more suitable for nonlinear dynamic system.

Investigation on Active Thermal Control Method with Pool Boiling Heat Transfer at Low Pressure

Science.gov (United States)

Sun, Chuang; Guo, Dong; Wang, Zhengyu; Sun, Fengxian

2018-06-01

In order to maintain a desirable temperature level of electronic equipment at low pressure, the thermal control performance with pool boiling heat transfer of water was examined based on experimental measurement. The total setup was designed and performed to accomplish the experiment with the pressure range from 4.5 kPa to 20 kPa and the heat flux between 6 kW/m2 and 20 kW/m2. The chosen material of the heat surface was aluminium alloy and the test cavity had the capability of varying the direction for the heat surface from vertical to horizontal directions. Through this study, the steady and transient temperature of the heat surface at different pressures and directions were obtained. Although the temperature non-uniformity of the heat surface from the centre to the edge could reach 10°C for the aluminium alloy due to the varying pressures, the whole temperature results successfully satisfied with the thermal control requirements for electronic equipment, and the temperature control effect of the vertically oriented direction was better than that of the horizontally oriented direction. Moreover, the behaviour of bubbles generating and detaching from the heat surface was recorded by a high-resolution camera, so as to understand the pool boiling heat transfer mechanism at low-load heat flux. These pictures showed that the bubbles departure diameter becomes larger, and departure frequency was slower at low pressure, in contrast to 1.0 atm.

Thermal analysis of an HVAC system with TRV controlled hydronic radiator

DEFF Research Database (Denmark)

Tahersima, Fatemeh; Stoustrup, Jakob; Rasmussen, Henrik

2010-01-01

A model for an HVAC system is derived in this paper. The HVAC system consists of a room and a hydronic radiator with temperature regulating valve (TRV) which has a step motor to adjust the valve opening. The heating system and the room are simulated as a unit entity for thermal analysis and contr......A model for an HVAC system is derived in this paper. The HVAC system consists of a room and a hydronic radiator with temperature regulating valve (TRV) which has a step motor to adjust the valve opening. The heating system and the room are simulated as a unit entity for thermal analysis...... and controller design. A discrete-element model with interconnected small scaled elements is proposed for the radiator. This models the radiator more precisely than that of a lumped model in terms of transfer delay and radiator gain. This precise modeling gives us an intuition into a regular unwanted phenomenon...... which occurs in low demand situations. When flow is very low in radiator and the supply water temperature and the pressure drop across the valve is constant, oscillation in room temperature occurs. One reason could be the large gain of radiator in low demand conditions compared to the high demand...

Thermal control modeling approach for GRAPE (GRAntecan PolarimEter)

Science.gov (United States)

Di Varano, I.; Woche, M.; Strassmeier, K. G.

2016-08-01

GRAPE is the polarimeter planned to be installed on the main Cassegrain focus of GTC (Gran Telescopio Canarias), having an equivalent entrance pupil of 10.4 m, located at the Observatorio del Roque de los Muchachos (ORM) , in La Palma, Canary Islands. It's meant to deliver full Stokes (IQUV) polarimetry covering the spectral range 0.420-1.6 μ, in order to feed the HORS instrument (High Optical Resolution Spectrograph), mounted on the Nasmyth platform, which has a FWHM resolving power of about 25,000 (5 pixel) designed for the wavelength range of 380-800 nm. Two calcite blocks and a BK-7 prism arranged in a Foster configuration are splitting the Ø12.5mm collimated beam into the ordinary and extraordinary components. The entire subunit from the Foster prisms down to the input fibers is rotated by steps of 45 degrees in order to retrieve Q, U components. By inserting a quarter wave retarder plate before the entrance to the Foster unit circular polarization is measured too. The current paper consist of two main parts: at first CFD simulations are introduced, which have been run compliant to the specifications derived by the environmental conditions and the transient thermal gradients taking into account the presence of the electronic cabinets installed, which are triggering the boundary conditions for the outer structure of the instrument; then a thermal control model is proposed based on heat exchangers to stabilize the inner temperature when compensation via passive insulation is not enough. The tools that have been adopted to reach for such goal are Ansys Multiphysics, in particular CFX package and Python scripts.

Comparative performance analysis of the artificial-intelligence-based thermal control algorithms for the double-skin building

International Nuclear Information System (INIS)

Moon, Jin Woo

2015-01-01

This study aimed at developing artificial-intelligence-(AI)-theory-based optimal control algorithms for improving the indoor temperature conditions and heating energy efficiency of the double-skin buildings. For this, one conventional rule-based and four AI-based algorithms were developed, including artificial neural network (ANN), fuzzy logic (FL), and adaptive neuro fuzzy inference systems (ANFIS), for operating the surface openings of the double skin and the heating system. A numerical computer simulation method incorporating the matrix laboratory (MATLAB) and the transient systems simulation (TRNSYS) software was used for the comparative performance tests. The analysis results revealed that advanced thermal-environment comfort and stability can be provided by the AI-based algorithms. In particular, the FL and ANFIS algorithms were superior to the ANN algorithm in terms of providing better thermal conditions. The ANN-based algorithm, however, proved its potential to be the most energy-efficient and stable strategy among the four AI-based algorithms. It can be concluded that the optimal algorithm can be differently determined according to the major focus of the strategy. If comfortable thermal condition is the principal interest, then the FL or ANFIS algorithm could be the proper solution, and if energy saving for space heating and system operation stability is the main concerns, then the ANN-based algorithm may be applicable. - Highlights: • Integrated control algorithms were developed for the heating system and surface openings. • AI theories were applied to the control algorithms. • ANN, FL, and ANFIS were the applied AI theories. • Comparative performance tests were conducted using computer simulation. • AI algorithms presented superior temperature environment.

Tailored functional materials with controlled thermal expansion and excellent thermal conductivity

International Nuclear Information System (INIS)

Korb, G.; Sebo, P.

1997-01-01

Engineering materials are mainly used for structures. Therefore high-strength, stiffness and sufficient toughness are of prime importance. For a long time engineers thought first in terms of metals. Material scientists developed alloys tailored to the needs of industry. Ceramics are known to be brittle and therefore not suitable in the first place for structural application under stress. Polymers with their low modulus became attractive when reinforced with high-strength fibres. Composites processed by polymer, metal or ceramic matrices and high-strength reinforcements have been introduced into many sectors of industry. Engineering materials for structural applications fulfil a function: they withstand high stresses, temperatures, fatigue, creep etc. But usually we do not call them functional materials. Functional materials serve applications apart from classical engineering fields. Electricity conducting materials, semi conductors, memory alloys and many others are called functional materials. Because of the fact that the basic physical properties cannot be changed in single-phase materials, the combination of two and more materials with different properties lead to components with new and tailored properties. A few techniques for preparation are described as powder metallurgy, infiltration of prepegs and compaction of precoated fibres/particles. The lecture is focusing on carbon fibre/particle reinforced Metal Matrix Materials. The achievable properties, in particular the thermal conductivity originating from the base materials is depending on the orientation of the fibres and interfacial contacts in the composite. The carefully controlled expansion behaviour is the most important property to use the material as a heat sink in electronic assemblies. (author)

Thermal crosstalk in heated microcantilever arrays

International Nuclear Information System (INIS)

Kim, Hoe Joon; Dai, Zhenting; King, William P

2013-01-01

We report on a detailed characterization and analysis of thermal crosstalk in a heated microcantilever array. The fabricated heated cantilever array consists of five identical independently controlled heated cantilevers. The temperature of each cantilever can be controlled over a large temperature range, up to 900 °C, by means of an integrated solid-state resistive heater. We analyze thermal crosstalk in steady and transient operating conditions when the heated cantilever array is either in contact with a substrate or freely suspended in air. The thermal conductance between neighboring cantilevers is as high as 0.61 µW °C −1 , resulting in non-negligible temperature increases in neighboring cantilevers, depending upon the operating conditions. By understanding and accounting for thermal crosstalk, it is possible to improve temperature control and temperature measurements with heated microcantilever arrays. (paper)

Formation of polyhedral ceria nanoparticles with enhanced catalytic CO oxidation activity in thermal plasma via a hydrogen mediated shape control mechanism

International Nuclear Information System (INIS)

Zheng Jie; Zhang Yaohua; Song Xubo; Li Xingguo

2011-01-01

Ceria nanoparticles with well defined facets are prepared in argon–hydrogen thermal plasma followed by controlled oxidation. With increasing hydrogen fraction in the plasma, a clear sphere-to-polyhedron shape transition is observed. The heat released during the hydrogenation of cerium, which significantly enhances the species mobility on the surface, favors the growth of well defined facets. The polyhedron ceria nanoparticles, though lower in specific surface area, exhibit superior catalytic performance for CO oxidation over the round particles, which is attributed to the higher density of the reactive {200} and {220} facets on the surface. The hydrogen mediated shape control mechanism provides new insights into the shape control of nanoparticles during thermal plasma processing.

Gas Control and Thermal Modeling Methods for Pressed Pellet and Fast Rise Thin-Film Thermal Batteries

Science.gov (United States)

2015-09-01

high operating battery case temperatures. Acceptable hermetic seals for thermal batteries ordinarily use laser welding , tungsten inert gas ( TIG ...20 Fig. 16 Sierra TABS Internal Plotter – Final pre- processing step for Low Cost Competent Munition (LCCM) thermal battery (battery shown drawn to...of experimental and DOE statistical methods. Such studies could be used to identify 2 electrochemical and thermodynamic processes that occur

Growth of large aluminum nitride single crystals with thermal-gradient control

Science.gov (United States)

Bondokov, Robert T; Rao, Shailaja P; Gibb, Shawn Robert; Schowalter, Leo J

2015-05-12

In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.

Thermal comfort assessment in civil aircraft cabins

Directory of Open Access Journals (Sweden)

Pang Liping

2014-04-01

Full Text Available Aircraft passengers are more and demanding in terms of thermal comfort. But it is not yet easy for aircraft crew to control the environment control system (ECS that satisfies the thermal comfort for most passengers due to a number of causes. This paper adopts a corrected predicted mean vote (PMV model and an adaptive model to assess the thermal comfort conditions for 31 investigated flights and draws the conclusion that there does exist an uncomfortable thermal phenomenon in civil aircraft cabins, especially in some short-haul continental flights. It is necessary to develop an easy way to predict the thermal sensation of passengers and to direct the crew to control ECS. Due to the assessment consistency of the corrected PMV model and the adaptive model, the adaptive model of thermal neutrality temperature can be used as a method to predict the cabin optimal operative temperature. Because only the mean outdoor effective temperature ET∗ of a departure city is an input variable for the adaptive model, this method can be easily understood and implemented by the crew and can satisfy 80–90% of the thermal acceptability levels of passengers.

Study of fuzzy adaptive PID controller on thermal frequency stabilizing laser with double longitudinal modes

Science.gov (United States)

Mo, Qingkai; Zhang, Tao; Yan, Yining

2016-10-01

There are contradictions among speediness, anti-disturbance performance, and steady-state accuracy caused by traditional PID controller in the existing light source systems of thermal frequency stabilizing laser with double longitudinal modes. In this paper, a new kind of fuzzy adaptive PID controller was designed by combining fuzzy PID control technology and expert system to make frequency stabilizing system obtain the optimal performance. The experiments show that the frequency stability of the designed PID controller is similar to the existing PID controller (the magnitude of frequency stability is less than 10-9 in constant temperature and 10-7 in open air). But the preheating time is shortened obviously (from 10 minutes to 5 minutes) and the anti-disturbance capability is improved significantly (the recovery time needed after strong interference is reduced from 1 minute to 10 seconds).

Fossilization processes in siliceous thermal springs: trends in preservation along thermal gradients

Science.gov (United States)

Cady, S. L.; Farmer, J. D.

1996-01-01

To enhance our ability to extract palaeobiological and palaeoenvironmental information from ancient thermal spring deposits, we have studied the processes responsible for the development and preservation of stromatolites in modern subaerial thermal spring systems in Yellowstone National Park (USA). We investigated specimens collected from silica-depositing thermal springs along the thermal gradient using petrographic techniques and scanning electron microscopy. Although it is known that thermophilic cyanobacteria control the morphogenesis of thermal spring stromatolites below 73 degrees C, we have found that biofilms which contain filamentous thermophiles contribute to the microstructural development of subaerial geyserites that occur along the inner rims of thermal spring pools and geyser effluents. Biofilms intermittently colonize the surfaces of subaerial geyserites and provide a favoured substrate for opaline silica precipitation. We have also found that the preservation of biotically produced microfabrics of thermal spring sinters reflects dynamic balances between rates of population growth, decomposition of organic matter, silica deposition and early diagenesis. Major trends in preservation of thermophilic organisms along the thermal gradient are defined by differences in the mode of fossilization, including replacement, encrustation and permineralization.

Research of thermal dynamic characteristics for variable load single screw refrigeration compressor with different capacity control mechanism

International Nuclear Information System (INIS)

Wang, Zengli; Wang, Zhenbo; Wang, Jun; Jiang, Wenchun; Feng, Quanke

2017-01-01

Highlights: • Theoretical models of SSRC under part-load condition have been established. • The experiment of SSRC performance under part-load condition was conducted. • Thermal dynamic characteristic of SSRC under part-load condition was gained. • Economy and reliability of SSRC under part-load condition was analyzed. - Abstract: In the single screw refrigeration compressor (SSRC), the capacity control mechanism is normally employed to meet the actual required cooling capacity under different load conditions. In this paper, theoretical calculation models describing the working process of the SSRC with the single slide valve capacity control mechanism (SVCCM) and SSRC with the frequency conversion regulating mechanism (FCRM) are established to research the thermal dynamic characteristics for variable load SSRC under part-load conditions. Experimental investigation on a SSRC under part-load conditions is also carried out to verify the theoretical calculation models. By using these validated models, the thermodynamic performances and dynamic characteristics of the SSRC with different capacity control mechanism under part-load conditions have been analyzed and compared. Through the comparison, the economical efficiency and reliability of the SSRC with different capacity control mechanism were obtained. All of these works can provide the basis for the later optimization design for the variable load single screw refrigeration compressor.

Multi-Evaporator Miniature Loop Heat Pipe for Small Spacecraft Thermal Control. Part 1; New Technologies and Validation Approach

Science.gov (United States)

Ku, Jentung; Ottenstein, Laura; Douglas, Donya; Hoang, Triem

2010-01-01

Under NASA s New Millennium Program Space Technology 8 (ST 8) Project, four experiments Thermal Loop, Dependable Microprocessor, SAILMAST, and UltraFlex - were conducted to advance the maturity of individual technologies from proof of concept to prototype demonstration in a relevant environment , i.e. from a technology readiness level (TRL) of 3 to a level of 6. This paper presents the new technologies and validation approach of the Thermal Loop experiment. The Thermal Loop is an advanced thermal control system consisting of a miniature loop heat pipe (MLHP) with multiple evaporators and multiple condensers designed for future small system applications requiring low mass, low power, and compactness. The MLHP retains all features of state-of-the-art loop heat pipes (LHPs) and offers additional advantages to enhance the functionality, performance, versatility, and reliability of the system. Details of the thermal loop concept, technical advances, benefits, objectives, level 1 requirements, and performance characteristics are described. Also included in the paper are descriptions of the test articles and mathematical modeling used for the technology validation. An MLHP breadboard was built and tested in the laboratory and thermal vacuum environments for TRL 4 and TRL 5 validations, and an MLHP proto-flight unit was built and tested in a thermal vacuum chamber for the TRL 6 validation. In addition, an analytical model was developed to simulate the steady state and transient behaviors of the MLHP during various validation tests. Capabilities and limitations of the analytical model are also addressed.

Handbook for replacement of process control systems in thermal power plants; Handbok - Utbytesbehov i kontrollsystem foer vaermekraftverk

Energy Technology Data Exchange (ETDEWEB)

Tuszynski, J. [Sydkraft Konsult AB, Malmoe (Sweden); Eriksson, Tage [Vattenfall Energisystem AB, Stockholm (Sweden)

1996-12-01

Modernization of control equipment in more complex power plants, such as thermal power plants, requires special attention due to the almost complete change-over to new computerised technology. The introduction of new technology gives rise to great changes in both the process control systems and in operation and maintenance routines. The change-over to computerised technology also causes lack of spare parts and service for older equipment. The older technology becomes obsolete due to the great advantages that comes with new technology. Therefore, the lifetime of control equipment is not only coupled to traditional ageing and wear, such as oxidation and fatigue of material, but also to the fact that the old equipment is getting out of date. It becomes more and more common that this out-of-date factor, rather than ageing, sets the limit for the useful life of the equipment. The Handbook for replacement of process control systems in thermal power plants is thought to be a first help for engineers and managers who has the responsibility for process control modernization. The Handbook points out the factors that determines the service life of the control equipment. It also suggests what information is required in order to take a decision on modernization. The Handbook at its present form constitutes a first approach that leaves room for an extension later on. Any request to expand the Handbook should be put forward to Vaermeforsk or its partners

The thermal comfort, the indoor environment control, and the energy consumption in three types of operating rooms

NARCIS (Netherlands)

Melhado, M.D.A.; Beyer, P.O.; Hensen, J.L.M.; Siqueira, L.F.G.

2005-01-01

This research investigated the influence of three layouts of operating rooms on the indoor environment control, on thermal comfort and on energy consumption. It was used the EnergyPlus software. The parameters of the environment were described in accordance with standards. The three layouts had

Thermal degradation of ethanolic biodiesel: Physicochemical and thermal properties evaluation

International Nuclear Information System (INIS)

Silva, Wellington Costa; Castro, Maria Priscila Pessanha; Perez, Victor Haber; Machado, Francisco A.; Mota, Leonardo; Sthel, Marcelo Silva

2016-01-01

The aim of this paper was to study the thermal degradation of soybean biodiesel attained by ethanolic route. The soybean biodiesel samples were subjected to heating treatment at 150 °C for 24 h in a closed oven under controlled atmosphere. During the experiments, samples were withdrawn at intervals of 3, 6, 9, 12, 15 and 24 h for physicochemical and thermophysical properties analysis. The biodiesel degradation was validated by Thermogravimetric analysis since their profiles for control and treated biodiesel were different. Also, "1H NMR confirmed this result due to a significant reduction at the signals related to the "1H located near to the double bonds in the unsaturated ethyl esters in agreement with an iodine index reduction and viscosity increase observed during degradation. Nevertheless, degraded biodiesel, under study conditions, preserved its thermophysical properties. These results may be relevant to qualify the produced biodiesel quality and collect physicochemical and thermophysical data important for applications in combustion studies including project of fuel injection systems. - Highlights: • Soybean biodiesel from ethanolic route was subjected to thermal degradation to verify its stability. • Thermal degradation of biodiesel was correlated with physicochemical properties. • Thermal effusivity, diffusivity and conductivity were estimate by photothermal techniques.

Distributed Control of Heat Conduction in Thermal Inductive Materials with 2D Geometrical Isomorphism

Directory of Open Access Journals (Sweden)

Chia-Yu Chou

2014-09-01

Full Text Available In a previous study we provided analytical and experimental evidence that some materials are able to store entropy-flow, of which the heat-conduction behaves as standing waves in a bounded region small enough in practice. In this paper we continue to develop distributed control of heat conduction in these thermal-inductive materials. The control objective is to achieve subtle temperature distribution in space and simultaneously to suppress its transient overshoots in time. This technology concerns safe and accurate heating/cooling treatments in medical operations, polymer processing, and other prevailing modern day practices. Serving for distributed feedback, spatiotemporal H ∞ /μ control is developed by expansion of the conventional 1D-H ∞ /μ control to a 2D version. Therein 2D geometrical isomorphism is constructed with the Laplace-Galerkin transform, which extends the small-gain theorem into the mode-frequency domain, wherein 2D transfer-function controllers are synthesized with graphical methods. Finally, 2D digital-signal processing is programmed to implement 2D transfer-function controllers, possibly of spatial fraction-orders, into DSP-engine embedded microcontrollers.

Thermal Analysis of TRIO-CINEMA Mission

Directory of Open Access Journals (Sweden)

Jaegun Yoo

2012-03-01

Full Text Available Thermal analysis and control design are prerequisite essential to design the satellite. In the space environment, it makes satellite survive from extreme hot and cold conditions. In recent years CubeSat mission is developed for many kinds of purpose. Triplet Ionospheric Observatory (TRIO–CubeSat for Ion, Neutral, Electron, MAgnetic fields (CINEMA is required to weigh less than 3 kg and operate on minimal 3 W power. In this paper we describe the thermal analysis and control design for TRIO-CINEMA mission. For this thermal analysis, we made a thermal model of the CubeSat with finite element method and NX6.0 TMG software is used to simulate this analysis model. Based on this result, passive thermal control method has been applied to thermal design of CINEMA. In order to get the better conduction between solar panel and chassis, we choose aluminum 6061-T6 for the material property of standoff. We can increase the average temperature of top and bottom solar panels from -70°C to -40°C and decrease the average temperature of the magnetometer from +93°C to -4°C using black paint on the surface of the chassis, inside of top & bottom solar panels, and magnetometer.

Efficient thermal management for multiprocessor systems

OpenAIRE

Coşkun, Ayşe Kıvılcım

2009-01-01

High temperatures and large thermal variations on the die create severe challenges in system reliability, performance, leakage power, and cooling costs. Designing for worst-case thermal conditions is highly costly and time-consuming. Therefore, dynamic thermal management methods are needed to maintain safe temperature levels during execution. Conventional management techniques sacrifice performance to control temperature and only consider the hot spots, neglecting the effects of thermal varia...

Analysis of the Effects of Thermal Environment on Optical Systems for Navigation Guidance and Control in Supersonic Aircraft Based on Empirical Equations.

Science.gov (United States)

Cheng, Xuemin; Yang, Yikang; Hao, Qun

2016-10-17

The thermal environment is an important factor in the design of optical systems. This study investigated the thermal analysis technology of optical systems for navigation guidance and control in supersonic aircraft by developing empirical equations for the front temperature gradient and rear thermal diffusion distance, and for basic factors such as flying parameters and the structure of the optical system. Finite element analysis (FEA) was used to study the relationship between flying and front dome parameters and the system temperature field. Systematic deduction was then conducted based on the effects of the temperature field on the physical geometry and ray tracing performance of the front dome and rear optical lenses, by deriving the relational expressions between the system temperature field and the spot size and positioning precision of the rear optical lens. The optical systems used for navigation guidance and control in supersonic aircraft when the flight speed is in the range of 1-5 Ma were analysed using the derived equations. Using this new method it was possible to control the precision within 10% when considering the light spot received by the four-quadrant detector, and computation time was reduced compared with the traditional method of separately analysing the temperature field of the front dome and rear optical lens using FEA. Thus, the method can effectively increase the efficiency of parameter analysis and computation in an airborne optical system, facilitating the systematic, effective and integrated thermal analysis of airborne optical systems for navigation guidance and control.

Thermal stress control using waste steel fibers in massive concretes

Science.gov (United States)

Sarabi, Sahar; Bakhshi, Hossein; Sarkardeh, Hamed; Nikoo, Hamed Safaye

2017-11-01

One of the important subjects in massive concrete structures is the control of the generated heat of hydration and consequently the potential of cracking due to the thermal stress expansion. In the present study, using the waste turnery steel fibers in the massive concretes, the amount of used cement was reduced without changing the compressive strength. By substituting a part of the cement with waste steel fibers, the costs and the generated hydration heat were reduced and the tensile strength was increased. The results showed that by using 0.5% turnery waste steel fibers and consequently, reducing to 32% the cement content, the hydration heat reduced to 23.4% without changing the compressive strength. Moreover, the maximum heat gradient reduced from 18.5% in the plain concrete sample to 12% in the fiber-reinforced concrete sample.

A self-driven temperature and flow rate co-adjustment mechanism based on Shape-Memory-Alloy (SMA) assembly for an adaptive thermal control coldplate module with on-orbit service characteristics

International Nuclear Information System (INIS)

Guo, Wei; Li, Yunhua; Li, Yun-Ze; Zhong, Ming-Liang; Wang, Sheng-Nan; Wang, Ji-Xiang; Zhang, Jia-Xun

2017-01-01

Highlights: • A self-driven temperature and flow rate co-adjustment mechanism based on SMA assembly is proposed. • An adaptive thermal control coldplate module (TCCM) is introduced. • A testbed is set up to investigate the TCCM adaptive thermal management performances. • The TCCM has the potential for spacecrafts on-orbit services. - Abstract: An adaptive thermal control coldplate module (TCCM) was proposed in this paper to fulfill the requirements of modular thermal control systems for spacecrafts on-orbit services. The TCCM could provide flow rate and temperature co-adjustment by using Shape-Memory-Alloy (SMA) assembly which possesses self-driven abilities. In this paper, the adaptive thermal management mechanism of the TCCM integrated with a single phase mechanically pumped fluid loop (SPMPFL) is described in detail, a verification testbed was established to examine the TCCM dynamic characteristics. Various working conditions such as inlet temperature, flow rate and thermal load disturbances were imposed on the TCCM to inspect its startup and transient performance. It was observed that the TCCM may present robust temperature control results with low overshoot (maximum 16.8%) and small temperature control error (minimum 0.18%), fast time response (minimum 600 s) was also revealed. The results demonstrated that the well-designed TCCM provided effective autonomous flow-rate and temperature co-adjustment operations, which may be a promising candidate for realizing modular level adaptive thermal management for spacecrafts on-orbit services.

Negative thermal expansion materials

International Nuclear Information System (INIS)

Evans, J.S.O.

1997-01-01

The recent discovery of negative thermal expansion over an unprecedented temperature range in ZrW 2 O 8 (which contracts continuously on warming from below 2 K to above 1000 K) has stimulated considerable interest in this unusual phenomenon. Negative and low thermal expansion materials have a number of important potential uses in ceramic, optical and electronic applications. We have now found negative thermal expansion in a large new family of materials with the general formula A 2 (MO 4 ) 3 . Chemical substitution dramatically influences the thermal expansion properties of these materials allowing the production of ceramics with negative, positive or zero coefficients of thermal expansion, with the potential to control other important materials properties such as refractive index and dielectric constant. The mechanism of negative thermal expansion and the phase transitions exhibited by this important new class of low-expansion materials will be discussed. (orig.)

Phase change material thermal capacitor clothing

Science.gov (United States)

Buckley, Theresa M. (Inventor)

2005-01-01

An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The apparatus may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the apparatus also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Optimizing Compliance and Thermal Conductivity of Plasma Sprayed Thermal Barrier Coatings via Controlled Powders and Processing Strategies

Science.gov (United States)

Tan, Yang; Srinivasan, Vasudevan; Nakamura, Toshio; Sampath, Sanjay; Bertrand, Pierre; Bertrand, Ghislaine

2012-09-01

The properties and performance of plasma-sprayed thermal barrier coatings (TBCs) are strongly dependent on the microstructural defects, which are affected by starting powder morphology and processing conditions. Of particular interest is the use of hollow powders which not only allow for efficient melting of zirconia ceramics but also produce lower conductivity and more compliant coatings. Typical industrial hollow spray powders have an assortment of densities resulting in masking potential advantages of the hollow morphology. In this study, we have conducted process mapping strategies using a novel uniform shell thickness hollow powder to control the defect microstructure and properties. Correlations among coating properties, microstructure, and processing reveal feasibility to produce highly compliant and low conductivity TBC through a combination of optimized feedstock and processing conditions. The results are presented through the framework of process maps establishing correlations among process, microstructure, and properties and providing opportunities for optimization of TBCs.

Thermal performance of a double pane window with a solar control coating for warm climate of Mexico

International Nuclear Information System (INIS)

Xamán, J.; Jiménez-Xamán, C.; Álvarez, G.; Zavala-Guillén, I.; Hernández-Pérez, I.; Aguilar, J.O.

2016-01-01

Highlights: • Pseudo-transient thermal performance of a double pane window (DPW) was determined. • The DPW was analyzed each 5 s by a period from 8:00 to 18:00 h. • 57,600 computational runs were necessary and the additive correction multigrid was implemented. • Solar control coating (SCC) in a DPW reduces 1073.79 W/m 2 with respect to the DPW without SCC. • SCC is highly recommended in a DPW because it reduces a 53.88% of the amount of energy gained. - Abstract: The pseudo-transient thermal performance (each 5 s) of a double pane window without and with a solar control coating was determined numerically. The study considers warm climatic conditions (Mexico) and a period from 8:00 to 18:00 h. The effect of varying the indoor air temperature (15–30 °C); and the incident solar radiation and the outdoor air temperature as functions of time is analyzed. The simulations were done with a self-developed ForTran program and it was verified with results from the literature. To obtain the results, 57,600 computational runs were necessary. From the results, the double pane window with a solar control coating allows a smaller heat flux to enter into a room than the corresponding without a solar control coating. The solar control coating in double glass window reduces the amount of 1073.79 W h/m 2 with respect to the case without a solar control coating, which represents a reduction of 53.88% of the heat gain.

Thermal Distribution System | Energy Systems Integration Facility | NREL

Science.gov (United States)

Thermal Distribution System Thermal Distribution System The Energy Systems Integration Facility's . Photo of the roof of the Energy Systems Integration Facility. The thermal distribution bus allows low as 10% of its full load level). The 60-ton chiller cools water with continuous thermal control

Analysis of the Effects of Thermal Environment on Optical Systems for Navigation Guidance and Control in Supersonic Aircraft Based on Empirical Equations

Directory of Open Access Journals (Sweden)

Xuemin Cheng

2016-10-01

Full Text Available The thermal environment is an important factor in the design of optical systems. This study investigated the thermal analysis technology of optical systems for navigation guidance and control in supersonic aircraft by developing empirical equations for the front temperature gradient and rear thermal diffusion distance, and for basic factors such as flying parameters and the structure of the optical system. Finite element analysis (FEA was used to study the relationship between flying and front dome parameters and the system temperature field. Systematic deduction was then conducted based on the effects of the temperature field on the physical geometry and ray tracing performance of the front dome and rear optical lenses, by deriving the relational expressions between the system temperature field and the spot size and positioning precision of the rear optical lens. The optical systems used for navigation guidance and control in supersonic aircraft when the flight speed is in the range of 1–5 Ma were analysed using the derived equations. Using this new method it was possible to control the precision within 10% when considering the light spot received by the four-quadrant detector, and computation time was reduced compared with the traditional method of separately analysing the temperature field of the front dome and rear optical lens using FEA. Thus, the method can effectively increase the efficiency of parameter analysis and computation in an airborne optical system, facilitating the systematic, effective and integrated thermal analysis of airborne optical systems for navigation guidance and control.

Enhancement of the efficiency of the automatic control system to control the thermal load of steam boilers fired with fuels of several types

Science.gov (United States)

Ismatkhodzhaev, S. K.; Kuzishchin, V. F.

2017-05-01

An automatic control system to control the thermal load (ACS) in a drum-type boiler under random fluctuations in the blast-furnace and coke-oven gas consumption rates and to control action on the natural gas consumption is considered. The system provides for use of a compensator by the basic disturbance, the blast-furnace gas consumption rate. To enhance the performance of the system, it is proposed to use more accurate mathematical second-order delay models of the channels of the object under control in combination with calculation by frequency methods of the controller parameters as well as determination of the structure and parameters of the compensator considering the statistical characteristics of the disturbances and using simulation. The statistical characteristics of the random blast-furnace gas consumption signal based on experimental data are provided. The random signal is presented in the form of the low-frequency (LF) and high-frequency (HF) components. The models of the correlation functions and spectral densities are developed. The article presents the results of calculating the optimal settings of the control loop with the controlled variable in the form of the "heat" signal with the restricted frequency variation index using three variants of the control performance criteria, viz., the linear and quadratic integral indices under step disturbance and the control error variance under random disturbance by the blastfurnace gas consumption rate. It is recommended to select a compensator designed in the form of series connection of two parts, one of which corresponds to the operator inverse to the transfer function of the PI controller, i.e., in the form of a really differentiating element. This facilitates the realization of the second part of the compensator by the invariance condition similar to transmitting the compensating signal to the object input. The results of simulation under random disturbance by the blast-furnace gas consumption are reported

Highly directional transurethral ultrasound applicators with rotational control for MRI-guided prostatic thermal therapy

Energy Technology Data Exchange (ETDEWEB)

Ross, Anthony B [Thermal Therapy Research Group, UCSF Radiation Oncology, San Francisco, CA (United States); Diederich, Chris J [Thermal Therapy Research Group, UCSF Radiation Oncology, San Francisco, CA (United States); Nau, William H [Thermal Therapy Research Group, UCSF Radiation Oncology, San Francisco, CA (United States); Gill, Harcharan [Department of Urology, Stanford University, Stanford, CA (United States); Bouley, Donna M [Department of Comparative Medicine, Stanford University, Stanford, CA (United States); Daniel, Bruce [Department of Radiology, Stanford University, Stanford, CA (United States); Rieke, Viola [Department of Radiology, Stanford University, Stanford, CA (United States); Butts, R Kim [Department of Radiology, Stanford University, Stanford, CA (United States); Sommer, Graham [Department of Radiology, Stanford University, Stanford, CA (United States)

2004-01-21

Transurethral ultrasound applicators with highly directional energy deposition and rotational control were investigated for precise treatment of benign prostatic hyperplasia (BPH) and adenocarcinoma of the prostate (CaP). Two types of catheter-based applicators were fabricated, using either sectored tubular (3.5 mm OD x 10 mm) or planar transducers (3.5 mm x 10 mm). They were constructed to be MRI compatible, minimally invasive and allow for manual rotation of the transducer array within a 10 mm cooling balloon. In vivo evaluations of the applicators were performed in canine prostates (n 3) using MRI guidance (0.5 T interventional magnet). MR temperature imaging (MRTI) utilizing the proton resonance frequency shift method was used to acquire multiple-slice temperature overlays in real time for monitoring and guiding the thermal treatments. Post-treatment T1-weighted contrast-enhanced imaging and triphenyl tetrazolium chloride stained tissue sections were used to define regions of tissue coagulation. Single sonications with the tubular applicator ) produced coagulated zones covering a wedge of the prostate extending from 1-2 mm outside the urethra to the outer boundary of the gland (16 mm radial coagulation). Single sonications with the planar applicator (15-20 W, 10 min, {approx}8 MHz) generated thermal lesions of {approx}30 extending to the prostate boundary. Multiple sequential sonications (sweeping) of a planar applicator (12 W with eight rotations of 30 each) demonstrated controllable coagulation of a 270 contiguous section of the prostate extending to the capsule boundary. The feasibility of using highly directional transurethral ultrasound applicators with rotational capabilities to selectively coagulate regions of the prostate while monitoring and controlling the treatments with MRTI was demonstrated in this study.

Efficacy of thermal treatment and copper-silver ionization for controlling Legionella pneumophila in high-volume hot water plumbing systems in hospitals.

Science.gov (United States)

Mietzner, S; Schwille, R C; Farley, A; Wald, E R; Ge, J H; States, S J; Libert, T; Wadowsky, R M; Miuetzner, S

1997-12-01

Thermal treatment and copper-silver ionization are often used for controlling Legionella pneumophila in high-volume hospital plumbing systems, although the comparative efficacies of these measures in high-volume systems are unknown. Thermal treatment of a hot water circuit was accomplished by flushing hot water (> 60 degrees C) through distal fixtures for 10 minutes. Copper-silver ionization was conducted in three circuits by installing units into return lines immediately upstream from hot water tanks. Recovery rates of L. pneumophila were monitored by culturing swab samples from faucets. Concentrations of copper and silver in water samples were determined by atomic absorption spectrophotometry. Four heat-flush treatments failed to provide long-term control of L. pneumophila. In contrast, ionization treatment reduced the rate of recovery of L. pneumophila from 108 faucets from 72% to 2% within 1 month and maintained effective control for at least 22 months. Only three samples (1.9%) of hot water from faucets exceeded Environmental Protection Agency standards for silver, and none exceeded the standards for copper. Of 24 samples obtained from hot water tanks, 42% and 50% exceeded the silver and copper standards, respectively. Copper-silver ionization effectively controls L. pneumophila in high-volume plumbing systems and is superior to thermal treatment; however, high concentrations of copper and silver can accumulate at the bottom of hot water tanks.

Thermal management of batteries

Science.gov (United States)

Gibbard, H. F.; Chen, C.-C.

Control of the internal temperature during high rate discharge or charge can be a major design problem for large, high energy density battery systems. A systematic approach to the thermal management of such systems is described for different load profiles based on: thermodynamic calculations of internal heat generation; calorimetric measurements of heat flux; analytical and finite difference calculations of the internal temperature distribution; appropriate system designs for heat removal and temperature control. Examples are presented of thermal studies on large lead-acid batteries for electrical utility load levelling and nickel-zinc and lithium-iron sulphide batteries for electric vehicle propulsion.

Tuning the thermal diffusivity of silver based nanofluids by controlling nanoparticle aggregation

International Nuclear Information System (INIS)

Agresti, Filippo; Barison, Simona; Battiston, Simone; Pagura, Cesare; Fabrizio, Monica; Colla, Laura; Fedele, Laura

2013-01-01

With the aim of preparing stable nanofluids for heat exchange applications and to study the effect of surfactant on the aggregation of nanoparticles and thermal diffusivity, stable silver colloids were synthesized in water by a green method, reducing AgNO 3 with fructose in the presence of poly-vinylpyrollidone (PVP) of various molecular weights. A silver nanopowder was precipitated from the colloids and re-dispersed at 4 vol% in deionized water. The Ag colloids were characterized by UV–visible spectroscopy, combined dynamic light scattering and ζ-potential measurements, and laser flash thermal diffusivity. The Ag nanopowders were characterized by scanning electron microscopy and thermal gravimetric analysis. It was found that the molecular weight of PVP strongly affects the ζ-potential and the aggregation of nanoparticles, thereby affecting the thermal diffusivity of the obtained colloids. In particular, it was observed that on increasing the molecular weight of PVP the absolute value of the ζ-potential is reduced, leading to increased aggregation of nanoparticles. A clear relation was identified between thermal diffusivity and aggregation, showing higher thermal diffusivity for nanofluids having higher aggregation. A maximum improvement of thermal diffusivity by about 12% was found for nanofluids prepared with PVP having higher molecular weight. (paper)

Ultra-low thermal expansion realized in giant negative thermal expansion materials through self-compensation

Science.gov (United States)

Shen, Fei-Ran; Kuang, Hao; Hu, Feng-Xia; Wu, Hui; Huang, Qing-Zhen; Liang, Fei-Xiang; Qiao, Kai-Ming; Li, Jia; Wang, Jing; Liu, Yao; Zhang, Lei; He, Min; Zhang, Ying; Zuo, Wen-Liang; Sun, Ji-Rong; Shen, Bao-Gen

2017-10-01

Materials with zero thermal expansion (ZTE) or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE) materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn-Co-Ge-In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10-6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.

Ultra-low thermal expansion realized in giant negative thermal expansion materials through self-compensation

Directory of Open Access Journals (Sweden)

Fei-Ran Shen

2017-10-01

Full Text Available Materials with zero thermal expansion (ZTE or precisely tailored thermal expansion are in urgent demand of modern industries. However, the overwhelming majority of materials show positive thermal expansion. To develop ZTE or negative thermal expansion (NTE materials as compensators has become an important challenge. Here, we present the evidence for the realization of ultra-low thermal expansion in Mn–Co–Ge–In particles. The bulk with the Ni2In-type hexagonal structure undergoes giant NTE owing to a martensitic magnetostructural transition. The major finding is that the thermal expansion behavior can be totally controlled by modulating the crystallinity degree and phase transition from atomic scale. Self-compensation effect leads to ultra-low thermal expansion with a linear expansion coefficient as small as +0.68 × 10−6/K over a wide temperature range around room temperature. The present study opens an avenue to reach ZTE particularly from the large class of giant NTE materials based on phase transition.

Optical control of spin-dependent thermal transport in a quantum ring

Science.gov (United States)

Abdullah, Nzar Rauf

2018-05-01

We report on calculation of spin-dependent thermal transport through a quantum ring with the Rashba spin-orbit interaction. The quantum ring is connected to two electron reservoirs with different temperatures. Tuning the Rashba coupling constant, degenerate energy states are formed leading to a suppression of the heat and thermoelectric currents. In addition, the quantum ring is coupled to a photon cavity with a single photon mode and linearly polarized photon field. In a resonance regime, when the photon energy is approximately equal to the energy spacing between two lowest degenerate states of the ring, the polarized photon field can significantly control the heat and thermoelectric currents in the system. The roles of the number of photon initially in the cavity, and electron-photon coupling strength on spin-dependent heat and thermoelectric currents are presented.

Determination of residual boron in thermally treated controlled-porosity glasses, by colorimetry, spectrography and isotachophoresis

International Nuclear Information System (INIS)

Dawidowicz, A.L.; Matusewicz, J.; Wysocka-Lisek, J.

1989-01-01

Controlled-porosity glasses (CPGs) are often applied as sorbents in chromatography. Besides having high thermal, chemical and mechanical resistance they are characterized by a very narrow pore-size distribution and the choice of mean pore diameter and porosity covers a wide range. In spite of these advantages, their range of use in chromatography is restricted because of their strong adsorption properties, which are connected with the presence of residual boron atoms in the porous CPG skeleton. The boron concentration on the CPG surface can be increased by proper thermal treatment. When CPGs are heated in the range 400-800 0 the residual boron atoms in the network diffuse from the bulk to the surface. The paper discusses the boron content in porous glasses of different mean pore diameters and the determination of the enrichment of boron on the GPG surface, by three independent methods: colorimetry, spectrography and isotachophoresis. (author)

Thermally controlled coupling of a rolled-up microtube integrated with a waveguide on a silicon electronic-photonic integrated circuit.

Science.gov (United States)

Zhong, Qiuhang; Tian, Zhaobing; Veerasubramanian, Venkat; Dastjerdi, M Hadi Tavakoli; Mi, Zetian; Plant, David V

2014-05-01

We report on the first experimental demonstration of the thermal control of coupling strength between a rolled-up microtube and a waveguide on a silicon electronic-photonic integrated circuit. The microtubes are fabricated by selectively releasing a coherently strained GaAs/InGaAs heterostructure bilayer. The fabricated microtubes are then integrated with silicon waveguides using an abruptly tapered fiber probe. By tuning the gap between the microtube and the waveguide using localized heaters, the microtube-waveguide evanescent coupling is effectively controlled. With heating, the extinction ratio of a microtube whispering-gallery mode changes over an 18 dB range, while the resonant wavelength remains approximately unchanged. Utilizing this dynamic thermal tuning effect, we realize coupling modulation of the microtube integrated with the silicon waveguide at 2 kHz with a heater voltage swing of 0-6 V.

Thermal comfort: research and practice.

Science.gov (United States)

van Hoof, Joost; Mazej, Mitja; Hensen, Jan L M

2010-01-01

Thermal comfort--the state of mind, which expresses satisfaction with the thermal environment--is an important aspect of the building design process as modern man spends most of the day indoors. This paper reviews the developments in indoor thermal comfort research and practice since the second half of the 1990s, and groups these developments around two main themes; (i) thermal comfort models and standards, and (ii) advances in computerization. Within the first theme, the PMV-model (Predicted Mean Vote), created by Fanger in the late 1960s is discussed in the light of the emergence of models of adaptive thermal comfort. The adaptive models are based on adaptive opportunities of occupants and are related to options of personal control of the indoor climate and psychology and performance. Both models have been considered in the latest round of thermal comfort standard revisions. The second theme focuses on the ever increasing role played by computerization in thermal comfort research and practice, including sophisticated multi-segmental modeling and building performance simulation, transient thermal conditions and interactions, thermal manikins.

Manipulating the Flow of Thermal Noise in Quantum Devices

Science.gov (United States)

Barzanjeh, Shabir; Aquilina, Matteo; Xuereb, André

2018-02-01

There has been significant interest recently in using complex quantum systems to create effective nonreciprocal dynamics. Proposals have been put forward for the realization of artificial magnetic fields for photons and phonons; experimental progress is fast making these proposals a reality. Much work has concentrated on the use of such systems for controlling the flow of signals, e.g., to create isolators or directional amplifiers for optical signals. In this Letter, we build on this work but move in a different direction. We develop the theory of and discuss a potential realization for the controllable flow of thermal noise in quantum systems. We demonstrate theoretically that the unidirectional flow of thermal noise is possible within quantum cascaded systems. Viewing an optomechanical platform as a cascaded system we show here that one can ultimately control the direction of the flow of thermal noise. By appropriately engineering the mechanical resonator, which acts as an artificial reservoir, the flow of thermal noise can be constrained to a desired direction, yielding a thermal rectifier. The proposed quantum thermal noise rectifier could potentially be used to develop devices such as a thermal modulator, a thermal router, and a thermal amplifier for nanoelectronic devices and superconducting circuits.

Thermally controlled femtosecond pulse shaping using metasurface based optical filters

Science.gov (United States)

Rahimi, Eesa; Şendur, Kürşat

2018-02-01

Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP) band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse's spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360°. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.

Thermally controlled femtosecond pulse shaping using metasurface based optical filters

Directory of Open Access Journals (Sweden)

Rahimi Eesa

2018-02-01

Full Text Available Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse’s spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360°. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.

Active Control of Thermal Convection in a Rectangular Loop by Changing its Spatial Orientation

Science.gov (United States)

Bratsun, Dmitry A.; Krasnyakov, Ivan V.; Zyuzgin, Alexey V.

2018-02-01

The problem of the automatic control of the fluid flow in a rectangular convective loop heated from below is studied theoretically and experimentally. The control is performed by using a feedback subsystem which changes the convection regimes by introducing small discrete changes in the spatial orientation of the loop with respect to gravity. We focus on effects that arise when the feedback controller operates with an unavoidable time delay, which is cause by the thermal inertia of the medium. The mathematical model of the phenomenon is developed. The dynamic regimes of the convection in the thermosyphon loop under control are studied. It is shown that the proposed control method can successfully stabilize not only a no-motion state of the fluid, but also time-dependent modes of convection including the irregular fluid flow at high values of the Rayleigh number. It is shown that the excessive gain of the proportional feedback can result in oscillations in the loop orientation exciting the unsteady convection modes. The comparison of the experimental data obtained for dielectric oil and dodecane with theory is given, and their good agreement is demonstrated.

House thermal model parameter estimation method for Model Predictive Control applications

NARCIS (Netherlands)

van Leeuwen, Richard Pieter; de Wit, J.B.; Fink, J.; Smit, Gerardus Johannes Maria

In this paper we investigate thermal network models with different model orders applied to various Dutch low-energy house types with high and low interior thermal mass and containing floor heating. Parameter estimations are performed by using data from TRNSYS simulations. The paper discusses results

Structurally Efficient Three-dimensional Metamaterials with Controllable Thermal Expansion

Science.gov (United States)

Xu, Hang; Pasini, Damiano

2016-01-01

The coefficient of thermal expansion (CTE) of architected materials, as opposed to that of conventional solids, can be tuned to zero by intentionally altering the geometry of their structural layout. Existing material architectures, however, achieve CTE tunability only with a sacrifice in structural efficiency, i.e. a drop in both their stiffness to mass ratio and strength to mass ratio. In this work, we elucidate how to resolve the trade-off between CTE tunability and structural efficiency and present a lightweight bi-material architecture that not only is stiffer and stronger than other 3D architected materials, but also has a highly tunable CTE. Via a combination of physical experiments on 3D fabricated prototypes and numeric simulations, we demonstrate how two distinct mechanisms of thermal expansion appearing in a tetrahedron, can be exploited in an Octet lattice to generate a large range of CTE values, including negative, zero, or positive, with no loss in structural efficiency. The novelty and simplicity of the proposed design as well as the ease in fabrication, make this bi-material architecture well-suited for a wide range of applications, including satellite antennas, space optical systems, precision instruments, thermal actuators, and MEMS. PMID:27721437

Total control of chromium in tanneries - thermal decomposition of filtration cake from enzymatic hydrolysis of chrome shavings.

Science.gov (United States)

Kocurek, P; Kolomazník, K; Bařinová, M; Hendrych, J

2017-04-01

This paper deals with the problem of chromium recovery from chrome-tanned waste and thus with reducing the environmental impact of the leather industry. Chrome-tanned waste was transformed by alkaline enzymatic hydrolysis promoted by magnesium oxide into practically chromium-free, commercially applicable collagen hydrolysate and filtration cake containing a high portion of chromium. The crude and magnesium-deprived chromium cakes were subjected to a process of thermal decomposition at 650°C under oxygen-free conditions to reduce the amount of this waste and to study the effect of magnesium removal on the resulting products. Oxygen-free conditions were applied in order to prevent the oxidation of trivalent chromium into the hazardous hexavalent form. Thermal decomposition products from both crude and magnesium-deprived chrome cakes were characterized by high chromium content over 50%, which occurred as eskolaite (Cr 2 O 3 ) and magnesiochromite (MgCr 2 O 4 ) crystal phases, respectively. Thermal decomposition decreased the amount of chrome cake dry feed by 90%. Based on the performed experiments, a scheme for the total control of chromium in the leather industry was designed.

Semi-transparent solar energy thermal storage device

Science.gov (United States)

McClelland, John F.

1985-06-18

A visually transmitting solar energy absorbing thermal storage module includes a thermal storage liquid containment chamber defined by an interior solar absorber panel, an exterior transparent panel having a heat mirror surface substantially covering the exterior surface thereof and associated top, bottom and side walls, Evaporation of the thermal storage liquid is controlled by a low vapor pressure liquid layer that floats on and seals the top surface of the liquid. Porous filter plugs are placed in filler holes of the module. An algicide and a chelating compound are added to the liquid to control biological and chemical activity while retaining visual clarity. A plurality of modules may be supported in stacked relation by a support frame to form a thermal storage wall structure.

Nanoscale thermal transport. II. 2003-2012

Science.gov (United States)

Cahill, David G.; Braun, Paul V.; Chen, Gang; Clarke, David R.; Fan, Shanhui; Goodson, Kenneth E.; Keblinski, Pawel; King, William P.; Mahan, Gerald D.; Majumdar, Arun; Maris, Humphrey J.; Phillpot, Simon R.; Pop, Eric; Shi, Li

2014-03-01

A diverse spectrum of technology drivers such as improved thermal barriers, higher efficiency thermoelectric energy conversion, phase-change memory, heat-assisted magnetic recording, thermal management of nanoscale electronics, and nanoparticles for thermal medical therapies are motivating studies of the applied physics of thermal transport at the nanoscale. This review emphasizes developments in experiment, theory, and computation in the past ten years and summarizes the present status of the field. Interfaces become increasingly important on small length scales. Research during the past decade has extended studies of interfaces between simple metals and inorganic crystals to interfaces with molecular materials and liquids with systematic control of interface chemistry and physics. At separations on the order of ˜ 1 nm , the science of radiative transport through nanoscale gaps overlaps with thermal conduction by the coupling of electronic and vibrational excitations across weakly bonded or rough interfaces between materials. Major advances in the physics of phonons include first principles calculation of the phonon lifetimes of simple crystals and application of the predicted scattering rates in parameter-free calculations of the thermal conductivity. Progress in the control of thermal transport at the nanoscale is critical to continued advances in the density of information that can be stored in phase change memory devices and new generations of magnetic storage that will use highly localized heat sources to reduce the coercivity of magnetic media. Ultralow thermal conductivity—thermal conductivity below the conventionally predicted minimum thermal conductivity—has been observed in nanolaminates and disordered crystals with strong anisotropy. Advances in metrology by time-domain thermoreflectance have made measurements of the thermal conductivity of a thin layer with micron-scale spatial resolution relatively routine. Scanning thermal microscopy and thermal

Thermal analysis control of in-mould and ladle inoculated grey cast irons

Directory of Open Access Journals (Sweden)

Mihai Chisamera

2009-05-01

Full Text Available The effect of addition of 0.05wt.% to 0.25 wt.% Ca, Zr, Al-FeSi alloy on in-ladle and in-mould inoculation of grey cast irons was investigated. In the present paper, the conclusions drawn are based on thermal analysis. For the solidification pattern, some specific cooling curves characteristics, such as the degree of undercooling at the beginning of eutectic solidifi cation and at the end of solidifi cation, as well as the recalescence level, are identifi ed to be more infl uenced by the inoculation technique. The degree of eutectic undercooling of the electrically melted base iron having 0.025% S, 0.003% Al and 3.5% Ce is excessively high (39–40℃, generating a relatively high need for inoculation. Under these conditions, the in-mould inoculation has a more signifi cant effect compared to ladle inoculation, especially at lower inoculant usage (less than 0.20 wt.%. Generally, the efficiency of 0.05wt.%–0.15wt.% of alloy for in-mould inoculation is comparable to, or better than, that of 0.15wt.%–0.25wt.% addition in ladle inoculation procedures. In order to secure stable and controlled processes, representative thermal analysis parameters could be used, especially in thin wall grey iron castings production.

Study of the thermal comfort, of the energy consumption and of the indoor environment control in surgery rooms

NARCIS (Netherlands)

Melhado, M.D.A.; Beyer, P.O.; Hensen, J.L.M.; Siqueira, L.F.G.

2005-01-01

In this research were investigated the influence of different layouts of operating rooms on thermal comfort, on the indoor environment control and on energy consumption. The layouts studied were: Case 1 (a surgery room and a hallway); Case 2 (a surgery room and two hallways); and Case 3 (a surgery

Exploitation Strategies of Cabin and Galley Thermal Dynamics

OpenAIRE

Schlabe, Daniel; Zimmer, Dirk; Pollok, Alexander

2017-01-01

The thermal inertia of aircraft cabins and galleys is significant for commercial aircraft. The aircraft cabin is controlled by the Environment Control System (ECS) to reach, among other targets, a prescribed temperature. By allowing a temperature band of ± 2 K instead of a fixed temperature, it is possible to use this thermal dynamic of the cabin as energy storage. This storage can then be used to reduce electrical peak power, increase efficiency of the ECS, reduce thermal cooling peak power...

Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: In vivo evaluation under MR guidance

International Nuclear Information System (INIS)

Kinsey, Adam M.; Diederich, Chris J.; Rieke, Viola; Nau, William H.; Pauly, Kim Butts; Bouley, Donna; Sommer, Graham

2008-01-01

The purpose of this study was to explore the feasibility and performance of a multi-sectored tubular array transurethral ultrasound applicator for prostate thermal therapy, with potential to provide dynamic angular and length control of heating under MR guidance without mechanical movement of the applicator. Test configurations were fabricated, incorporating a linear array of two multi-sectored tubular transducers (7.8-8.4 MHz, 3 mm OD, 6 mm length), with three 120 deg. independent active sectors per tube. A flexible delivery catheter facilitated water cooling (100 ml min -1 ) within an expandable urethral balloon (35 mm longx10 mm diameter). An integrated positioning hub allows for rotating and translating the transducer assembly within the urethral balloon for final targeting prior to therapy delivery. Rotational beam plots indicate ∼90 deg. - 100 deg. acoustic output patterns from each 120 deg. transducer sector, negligible coupling between sectors, and acoustic efficiencies between 41% and 53%. Experiments were performed within in vivo canine prostate (n=3), with real-time MR temperature monitoring in either the axial or coronal planes to facilitate control of the heating profiles and provide thermal dosimetry for performance assessment. Gross inspection of serial sections of treated prostate, exposed to TTC (triphenyl tetrazolium chloride) tissue viability stain, allowed for direct assessment of the extent of thermal coagulation. These devices created large contiguous thermal lesions (defined by 52 deg. C maximum temperature, t 43 =240 min thermal dose contours, and TTC tissue sections) that extended radially from the applicator toward the border of the prostate (∼15 mm) during a short power application (∼8-16 W per active sector, 8-15 min), with ∼200 deg. or 360 deg. sector coagulation demonstrated depending upon the activation scheme. Analysis of transient temperature profiles indicated progression of lethal temperature and thermal dose contours

Adaptable Single Active Loop Thermal Control System (TCS) for Future Space Missions

Science.gov (United States)

Mudawar, Issam; Lee, Seunghyun; Hasan, Mohammad

2015-01-01

This presentation will examine the development of a thermal control system (TCS) for future space missions utilizing a single active cooling loop. The system architecture enables the TCS to be reconfigured during the various mission phases to respond, not only to varying heat load, but to heat rejection temperature as well. The system will consist of an accumulator, pump, cold plates (evaporators), condenser radiator, and compressor, in addition to control, bypass and throttling valves. For cold environments, the heat will be rejected by radiation, during which the compressor will be bypassed, reducing the system to a simple pumped loop that, depending on heat load, can operate in either a single-phase liquid mode or two-phase mode. For warmer environments, the pump will be bypassed, enabling the TCS to operate as a heat pump. This presentation will focus on recent findings concerning two-phase flow regimes, pressure drop, and heat transfer coefficient trends in the cabin and avionics micro-channel heat exchangers when using the heat pump mode. Also discussed will be practical implications of using micro-channel evaporators for the heat pump.

Thermal modelling using discrete vasculature for thermal therapy: A review

NARCIS (Netherlands)

Kok, H. Petra; Gellermann, Johanna; van den Berg, Cornelis A. T.; Stauffer, Paul R.; Hand, Jeffrey W.; Crezee, Johannes

2013-01-01

Reliable temperature information during clinical hyperthermia and thermal ablation is essential for adequate treatment control, but conventional temperature measurements do not provide 3D temperature information. Treatment planning is a very useful tool to improve treatment quality, and substantial

Proceedings of the Twenty-First Water Reactor Safety Information Meeting: Volume 1, Plenary session; Advanced reactor research; advanced control system technology; advanced instrumentation and control hardware; human factors research; probabilistic risk assessment topics; thermal hydraulics; thermal hydraulic research for advanced passive LWRs

International Nuclear Information System (INIS)

Monteleone, S.

1994-04-01

This three-volume report contains 90 papers out of the 102 that were presented at the Twenty-First Water Reactor Safety Information Meeting held at the Bethesda Marriott Hotel, Bethesda, Maryland, during the week of October 25--27, 1993. The papers are printed in the order of their presentation in each session and describe progress and results of programs in nuclear safety research conducted in this country and abroad. Foreign participation in the meeting included papers presented by researchers from France, Germany, Japan, Russia, Switzerland, Taiwan, and United Kingdom. The titles of the papers and the names of the authors have been updated and may differ from those that appeared in the final program of the meeting. Individual papers have been cataloged separately. This document, Volume 1 covers the following topics: Advanced Reactor Research; Advanced Instrumentation and Control Hardware; Advanced Control System Technology; Human Factors Research; Probabilistic Risk Assessment Topics; Thermal Hydraulics; and Thermal Hydraulic Research for Advanced Passive Light Water Reactors

Proceedings of the Twenty-First Water Reactor Safety Information Meeting: Volume 1, Plenary session; Advanced reactor research; advanced control system technology; advanced instrumentation and control hardware; human factors research; probabilistic risk assessment topics; thermal hydraulics; thermal hydraulic research for advanced passive LWRs

Energy Technology Data Exchange (ETDEWEB)

Monteleone, S. [Brookhaven National Lab., Upton, NY (United States)] [comp.

1994-04-01

This three-volume report contains 90 papers out of the 102 that were presented at the Twenty-First Water Reactor Safety Information Meeting held at the Bethesda Marriott Hotel, Bethesda, Maryland, during the week of October 25--27, 1993. The papers are printed in the order of their presentation in each session and describe progress and results of programs in nuclear safety research conducted in this country and abroad. Foreign participation in the meeting included papers presented by researchers from France, Germany, Japan, Russia, Switzerland, Taiwan, and United Kingdom. The titles of the papers and the names of the authors have been updated and may differ from those that appeared in the final program of the meeting. Individual papers have been cataloged separately. This document, Volume 1 covers the following topics: Advanced Reactor Research; Advanced Instrumentation and Control Hardware; Advanced Control System Technology; Human Factors Research; Probabilistic Risk Assessment Topics; Thermal Hydraulics; and Thermal Hydraulic Research for Advanced Passive Light Water Reactors.

Technological challenges in thermal plasma production

International Nuclear Information System (INIS)

Ramakrishnan, S.

1995-01-01

Thermal plasmas, generated by electric arc discharges, are used in a variety of industrial applications. The electric arc is a constricted electrical discharge with a high temperature in the range 6000-25,000 K. These characteristics are useful in plasma cutting, spraying, welding and specific areas of material processing. The thermal plasma technology is an enabling process technology and its status in the market depends upon its advantages over competing technologies. A few technological challenges to enhance the status of plasma technology are to improve the utilisation of the unique characteristics of the electric arc and to provide enhanced control of the process. In particular, new solutions are required for increasing the plasma-material interaction, controlling the electrode roots and controlling the thermal power generated by the arcing process. In this paper, the advantages of plasma technology, its constraints and future challenges for technology developments are highlighted. 36 refs., 14 figs

Technical and economic aspects of operation of thermal and hydro power systems

Energy Technology Data Exchange (ETDEWEB)

Bakken, Bjoern Harald

1997-12-31

This thesis studies system operation and operational costs of primary and secondary control in hydro and thermal power systems. The cost of providing primary control reserves in thermal power systems is estimated to 1-3% of total production cost. Hydro power units, on the other hand, provide a very cheap primary reserve compared to thermal units. The HVDC (High Voltage Direct Current) connection can be used for primary control in either direction but the thesis only considers substitution of reserves in the thermal system with reserves from the hydro system. Since the HVDC connection is easy to control, the transient characteristics are considerably improved, and one can substitute an amount of thermal spinning reserve corresponding to the available HVDC capacity with little disturbance in any system. A more realistic alternative, at present, is to sell secondary control reserves across the HVDC connections. Keeping spinning reserve for automatic secondary control in a thermal power system is estimated to cost 3-5% of total production cost. Secondary control reserves probably cannot compete with the value of the peak load export, but one should seriously consider using part of the HVDC capacity as secondary control reserve for the thermal system during off-peak hours with. The author discusses the concept of automatic secondary control both theoretically and by simulations and finds that there are no special technical difficulties in introducing automatic secondary control in the Nordel (an organization for Nordic power cooperation) system. 78 refs., 4 figs., 23 tabs.

Technical and economic aspects of operation of thermal and hydro power systems

Energy Technology Data Exchange (ETDEWEB)

Bakken, Bjoern Harald

1998-12-31

This thesis studies system operation and operational costs of primary and secondary control in hydro and thermal power systems. The cost of providing primary control reserves in thermal power systems is estimated to 1-3% of total production cost. Hydro power units, on the other hand, provide a very cheap primary reserve compared to thermal units. The HVDC (High Voltage Direct Current) connection can be used for primary control in either direction but the thesis only considers substitution of reserves in the thermal system with reserves from the hydro system. Since the HVDC connection is easy to control, the transient characteristics are considerably improved, and one can substitute an amount of thermal spinning reserve corresponding to the available HVDC capacity with little disturbance in any system. A more realistic alternative, at present, is to sell secondary control reserves across the HVDC connections. Keeping spinning reserve for automatic secondary control in a thermal power system is estimated to cost 3-5% of total production cost. Secondary control reserves probably cannot compete with the value of the peak load export, but one should seriously consider using part of the HVDC capacity as secondary control reserve for the thermal system during off-peak hours with. The author discusses the concept of automatic secondary control both theoretically and by simulations and finds that there are no special technical difficulties in introducing automatic secondary control in the Nordel (an organization for Nordic power cooperation) system. 78 refs., 4 figs., 23 tabs.

Technical and economic aspects of operation of thermal and hydro power systems

International Nuclear Information System (INIS)

Bakken, Bjoern Harald.

1997-01-01

This thesis studies system operation and operational costs of primary and secondary control in hydro and thermal power systems. The cost of providing primary control reserves in thermal power systems is estimated to 1-3% of total production cost. Hydro power units, on the other hand, provide a very cheap primary reserve compared to thermal units. The HVDC (High Voltage Direct Current) connection can be used for primary control in either direction but the thesis only considers substitution of reserves in the thermal system with reserves from the hydro system. Since the HVDC connection is easy to control, the transient characteristics are considerably improved, and one can substitute an amount of thermal spinning reserve corresponding to the available HVDC capacity with little disturbance in any system. A more realistic alternative, at present, is to sell secondary control reserves across the HVDC connections. Keeping spinning reserve for automatic secondary control in a thermal power system is estimated to cost 3-5% of total production cost. Secondary control reserves probably cannot compete with the value of the peak load export, but one should seriously consider using part of the HVDC capacity as secondary control reserve for the thermal system during off-peak hours with. The author discusses the concept of automatic secondary control both theoretically and by simulations and finds that there are no special technical difficulties in introducing automatic secondary control in the Nordel (an organization for Nordic power cooperation) system. 78 refs., 4 figs., 23 tabs

Thermal Plasma decomposition of fluoriated greenhouse gases

Energy Technology Data Exchange (ETDEWEB)

Choi, Soo Seok; Watanabe, Takayuki [Tokyo Institute of Technology, Yokohama (Japan); Park, Dong Wha [Inha University, Incheon (Korea, Republic of)

2012-02-15

Fluorinated compounds mainly used in the semiconductor industry are potent greenhouse gases. Recently, thermal plasma gas scrubbers have been gradually replacing conventional burn-wet type gas scrubbers which are based on the combustion of fossil fuels because high conversion efficiency and control of byproduct generation are achievable in chemically reactive high temperature thermal plasma. Chemical equilibrium composition at high temperature and numerical analysis on a complex thermal flow in the thermal plasma decomposition system are used to predict the process of thermal decomposition of fluorinated gas. In order to increase economic feasibility of the thermal plasma decomposition process, increase of thermal efficiency of the plasma torch and enhancement of gas mixing between the thermal plasma jet and waste gas are discussed. In addition, noble thermal plasma systems to be applied in the thermal plasma gas treatment are introduced in the present paper.

A Nanostructured Composites Thermal Switch Controls Internal and External Short Circuit in Lithium Ion Batteries

Science.gov (United States)

McDonald, Robert C.; VanBlarcom, Shelly L.; Kwasnik, Katherine E.

2013-01-01

A document discusses a thin layer of composite material, made from nano scale particles of nickel and Teflon, placed within a battery cell as a layer within the anode and/or the cathode. There it conducts electrons at room temperature, then switches to an insulator at an elevated temperature to prevent thermal runaway caused by internal short circuits. The material layer controls excess currents from metal-to-metal or metal-to-carbon shorts that might result from cell crush or a manufacturing defect

Simple thermal to thermal face verification method based on local texture descriptors

Science.gov (United States)

Grudzien, A.; Palka, Norbert; Kowalski, M.

2017-08-01

Biometrics is a science that studies and analyzes physical structure of a human body and behaviour of people. Biometrics found many applications ranging from border control systems, forensics systems for criminal investigations to systems for access control. Unique identifiers, also referred to as modalities are used to distinguish individuals. One of the most common and natural human identifiers is a face. As a result of decades of investigations, face recognition achieved high level of maturity, however recognition in visible spectrum is still challenging due to illumination aspects or new ways of spoofing. One of the alternatives is recognition of face in different parts of light spectrum, e.g. in infrared spectrum. Thermal infrared offer new possibilities for human recognition due to its specific properties as well as mature equipment. In this paper we present the scheme of subject's verification methodology by using facial images in thermal range. The study is focused on the local feature extraction methods and on the similarity metrics. We present comparison of two local texture-based descriptors for thermal 1-to-1 face recognition.

Research on seasonal indoor thermal environment and residents' control behavior of cooling and heating systems in Korea

Energy Technology Data Exchange (ETDEWEB)

Bae, Chihye; Chun, Chungyoon [Department of Housing and Interior Design, College of Human Ecology, Graduate School, Yonsei University, Seoul (Korea)

2009-11-15

Indoor thermal environments and residents' control behavior of cooling and heating systems were investigated in Seoul, Korea and compared with the results of previous studies. Twenty-four houses in summer, six houses in autumn and 36 houses in winter were used in this study. The measurement of temperature, humidity and air conditioner usage behavior was carried out. The clo-value, thermal comfort, sensation and basic data of the houses were also investigated. The indoor thermal environment in the summer had a high temperature and a high humidity ratio compare to standard comfort zone. Most of the indoor thermal environments at the time of starting the air conditioner in the summer were out of the comfort zone. Some of the data recorded while the air conditioner was stopped were in the comfort zone, but in many cases the temperature was relatively higher than comfort zone. Most indoor climate distributions in the winter were in the comfort zone and the indoor climate in autumn coincided well with the criteria of the comfort zone. Compared with results of previous studies in these 25 years, indoor ambient average temperature in winter has increased and the comfort temperature has increased in the heating period and decreased in the cooling period. This result indicates that the development of an HVAC system has created an expectation of comfort for residents and has shifted their thermal comfort zone warmer in winter and cooler in summer. (author)

Application of non-thermal plasmas to pollution control

International Nuclear Information System (INIS)

Penetrante, B.M.; Vogtlin, G.E.; Bardsley, J.N.; Vitello, P.A.; Wallman, P.H.

1993-06-01

Non-thermal plasma techniques can be used to destroy many types of hazardous molecules. They are particularly efficient when the toxic materials are present in very small concentrations. This paper discusses three particular applications of non-thermal plasmas: (1) decomposition of hydrogen sulfide (H 2 S), (2) removal of trichloroethylene (TCE), and (3) removal of nitrogen oxides (NO x ). Emphasis is placed on the energy cost for implementing the decomposition or removal of these pollutants. Some of the factors affecting the energy cost are discussed. The authors discuss in detail their work at LLNL on pulsed plasma processing for the treatment of NO x in diesel engine exhaust. The results suggest that their plasma reactor can remove up to 70% of NO with relatively high initial concentrations (up to 500 ppM) at a power consumption cost of 2.5% for an engine with an output of 14 kW and an exhaust gas flow rate of 1,200 liters per minute

Application of non-thermal plasmas to pollution control

International Nuclear Information System (INIS)

Penetrante, B.M.; Vogtlin, G.E.; Bardsley, J.N.; Vitello, P.A.; Wallman, P.H.

1993-01-01

Non-thermal plasma techniques can be used to destroy many types of hazardous molecules. They are particularly efficient when the toxic materials are present in very small concentrations. This paper discusses three particular applications of non-thermal plasmas: (1) decomposition of hydrogen sulfide (H 2 S), (2) removal of trichloroethylene (TCE), and (3) removal of nitric oxides (NO x ) Emphasis is placed on the energy cost for implementing the decomposition or removal of these pollutants. Some of the factors affecting the energy cost are discussed. We discuss in detail our work at LLNL on pulsed plasma processing for the treatment of NO x in diesel engine exhaust. Our results suggest that our plasma reactor can remove up to 70% of NO x with relatively high initial concentrations (up to 500 ppM) at a power consumption cost of 2.5% for an engine with an output of 14 kill and an exhaust gas flow rate of 1200 liters per minute

Entropy generation method to quantify thermal comfort

Science.gov (United States)

Boregowda, S. C.; Tiwari, S. N.; Chaturvedi, S. K.

2001-01-01

is needed in the future to fully establish the validity of the OTCI formula and the model. One of the practical applications of this index is that could it be integrated in thermal control systems to develop human-centered environmental control systems for potential use in aircraft, mass transit vehicles, intelligent building systems, and space vehicles.

Laser weld process monitoring and control using chromatic filtering of thermal radiation from a weld pool

International Nuclear Information System (INIS)

Kim, Cheol Jung; Kim, Min Suk; Baik, Sung Hoon; Chung, Chin Man

2000-06-01

The application of high power Nd: YAG lasers for precision welding in industry has been growing quite fast these days in diverse areas such as the automobile, the electronics and the aerospace industries. These diverse applications also require the new developments for the precise control and the reliable process monitoring. Due to the hostile environment in laser welding, a remote monitoring is required. The present development relates in general to weld process monitoring techniques, and more particularly to improved methods and apparatus for real-time monitoring of thermal radiation of a weld pool to monitor a size variation and a focus shift of the weld pool for weld process control, utilizing the chromatic aberration of focusing lens or lenses. The monitoring technique of the size variation and the focus shift of a weld pool is developed by using the chromatic filtering of the thermal radiation from a weld pool. The monitoring of weld pool size variation can also be used to monitor the weld depth in a laser welding. Furthermore, the monitoring of the size variation of a weld pool is independent of the focus shift of a weld pool and the monitoring of the focus shift of a weld pool is independent of the size variation of a weld pool

Design, fabrication, and application of a directional thermal processing system for controlled devitrification of metallic glasses

Science.gov (United States)

Meyer, Megan Anne Lamb

The potential of using metallic glass as a pathway to obtaining novel morphologies and metastable phases has been garnering attention since their discovery. Several rapid solidification techniques; such as gas atomization, melt spinning, laser melting, and splat quenching produce amorphous alloys. A directional thermal processing system (DTPS) was designed, fabricated and characterized for the use of zone processing or gradient-zone processing of materials. Melt-spun CuZr metallic glass alloy was subjected to the DTPS and the relaxation and crystallization responses of the metallic glass were characterized. A range of processing parameters were developed and analyzed that would allow for devitrification to occur. The relaxation and crystallization responses were compared with traditional heat treatment methods of metallic glasses. The new processing method accessed equilibrium and non-equilibrium phases of the alloy and the structures were found to be controllable and sensitive to processing conditions. Crystallized fraction, crystallization onset temperature, and structural relaxation were controlled through adjusting the processing conditions, such as the hot zone temperature and sample velocity. Reaction rates computed from isothermal (TTT) transformation data were not found to be reliable, suggesting that the reaction kinetics are not additive. This new processing method allows for future studying of the thermal history effects of metallic glasses.

Serial grey-box model of a stratified thermal tank for hierarchical control of a solar plant

Energy Technology Data Exchange (ETDEWEB)

Arahal, Manuel R. [Universidad de Sevilla, Dpto. de Ingenieria de Sistemas y Automatica, Camino de los Descubrimientos s/n, 41092 Sevilla (Spain); Cirre, Cristina M. [Convenio Universidad de Almeria-Plataforma Solar de Almeria, Ctra. Senes s/n, 04200 Tabernas, Almeria (Spain); Berenguel, Manuel [Universidad de Almeria, Dpto. Lenguajes y Computacion, Ctra. Sacramento s/n, 04120, Almeria (Spain)

2008-05-15

The ACUREX collector field together with a thermal storage tank and a power conversion system forms the Small Solar Power Systems plant of the Plataforma Solar de Almeria, a facility that has been used for research for the last 25 years. A simulator of the collector field produced by the last author has been available to and used as a test-bed for control strategies. Up to now, however, there is not a model for the whole plant. Such model is needed for hierarchical control schemes also proposed by the authors. In this paper a model of the thermal storage tank is derived using the Simultaneous Perturbation Stochastic Approximation technique to adjust the parameters of a serial grey-box model structure. The benefits of the proposed approach are discussed in the context of the intended use, requiring a model capable of simulating the behavior of the storage tank with low computational load and low error over medium to large horizons. The model is tested against real data in a variety of situations showing its performance in terms of simulation error in the temperature profile and in the usable energy stored in the tank. The results obtained demonstrate the viability of the proposed approach. (author)

Laser weld process monitoring and control using chromatic filtering of thermal radiation from a weld pool

Energy Technology Data Exchange (ETDEWEB)

Kim, Cheol Jung; Kim, Min Suk; Baik, Sung Hoon; Chung, Chin Man

2000-06-01

The application of high power Nd: YAG lasers for precision welding in industry has been growing quite fast these days in diverse areas such as the automobile, the electronics and the aerospace industries. These diverse applications also require the new developments for the precise control and the reliable process monitoring. Due to the hostile environment in laser welding, a remote monitoring is required. The present development relates in general to weld process monitoring techniques, and more particularly to improved methods and apparatus for real-time monitoring of thermal radiation of a weld pool to monitor a size variation and a focus shift of the weld pool for weld process control, utilizing the chromatic aberration of focusing lens or lenses. The monitoring technique of the size variation and the focus shift of a weld pool is developed by using the chromatic filtering of the thermal radiation from a weld pool. The monitoring of weld pool size variation can also be used to monitor the weld depth in a laser welding. Furthermore, the monitoring of the size variation of a weld pool is independent of the focus shift of a weld pool and the monitoring of the focus shift of a weld pool is independent of the size variation of a weld pool.

ISS qualified thermal carrier equipment

Science.gov (United States)

Deuser, Mark S.; Vellinger, John C.; Jennings, Wm. M.

2000-01-01

Biotechnology is undergoing a period of rapid and sustained growth, a trend which is expected to continue as the general population ages and as new medical treatments and products are conceived. As pharmaceutical and biomedical companies continue to search for improved methods of production and, for answers to basic research questions, they will seek out new avenues of research. Space processing on the International Space Station (ISS) offers such an opportunity! Space is rapidly becoming an industrial laboratory for biotechnology research and processing. Space bioprocessing offers exciting possibilities for developing new pharmaceuticals and medical treatments, which can be used to benefit mankind on Earth. It also represents a new economic frontier for the private sector. For over eight years, the thermal carrier development team at SHOT has been working with government and commercial sector scientists who are conducting microgravity experiments that require thermal control. SHOT realized several years ago that the hardware currently being used for microgravity thermal control was becoming obsolete. It is likely that the government, academic, and industrial bioscience community members could utilize SHOT's hardware as a replacement to their current microgravity thermal carrier equipment. Moreover, SHOT is aware of several international scientists interested in utilizing our space qualified thermal carrier. SHOT's economic financing concept could be extremely beneficial to the international participant, while providing a source of geographic return for their particular region. Beginning in 2000, flight qualified thermal carriers are expected to be available to both the private and government sectors. .

NSGA-II based optimal control scheme of wind thermal power system for improvement of frequency regulation characteristics

Directory of Open Access Journals (Sweden)

S. Chaine

2015-09-01

Full Text Available This work presents a methodology to optimize the controller parameters of doubly fed induction generator modeled for frequency regulation in interconnected two-area wind power integrated thermal power system. The gains of integral controller of automatic generation control loop and the proportional and derivative controllers of doubly fed induction generator inertial control loop are optimized in a coordinated manner by employing the multi-objective non-dominated sorting genetic algorithm-II. To reduce the numbers of optimization parameters, a sensitivity analysis is done to determine that the above mentioned three controller parameters are the most sensitive among the rest others. Non-dominated sorting genetic algorithm-II has depicted better efficiency of optimization compared to the linear programming, genetic algorithm, particle swarm optimization, and cuckoo search algorithm. The performance of the designed optimal controller exhibits robust performance even with the variation in penetration levels of wind energy, disturbances, parameter and operating conditions in the system.

Biology and thermal requirements to Trichogramma spp. selection for Ecdytolopha aurantiana control; Selecao de Trichogramma spp., para o controle de Ecdytolopha aurantiana, com base na biologia e exigencias termicas

Energy Technology Data Exchange (ETDEWEB)

Molina, Rosa M.S.; Parra, Jose R.P. [Escola Superior de Agricultura Luiz de Queiroz (ESALQ/USP), Piracicaba, SP (Brazil). Dept. de Entomologia, Fitopatologia e Zoologia Agricola], e-mail: rmsmolina@ig.com.br, e-mail: jrpparra@esalq.usp.br; Fronza, Vanoli [Empresa de Pesquisa Agropecuaria de Minas Gerais (EPAMIG), Uberaba, MG (Brazil)], e-mail: vanoli@epamig.br

2005-03-15

The purpose of this work was to evaluate the potential of Trichogramma atopovirilia Oatman and Platner, 1983 and T. pretiosum Riley, 1879 as agents of control of Ecdytolopha aurantiana (Lima, 1927) (Lepidoptera: Tortricidae), an important Citrus pest in Sao Paulo State (South-East Brazil). In order to provide subsidies to programs of biological control with these parasitoids, studies of biology in different temperatures, thermal requirements and parasitism capacity were carried out. The temperatures (18, 20, 22, 25, 28, 30, and 32 deg C) did not affect the sex ratio, however, female longevity of both species was higher at 22 and 25 deg C. The temperature of 25 deg C tended to be more suitable to both emergency rate and female longevity. The egg-adult period for both Trichogramma species was inversely proportional to temperature. The thermal requirements of the two species were very close, about 108 DD (degree days). Neither the natural rearing host, E. aurantiana, nor the alternative host Anagasta kuehniella (Zeller, 1879) (Lepidoptera, Pyralidae), affected the number of parasitized eggs per Trichogramma female. The parasitism rate and the number of emerged adults per egg on E. aurantiana eggs were higher than on A. kuehniella eggs. However, the emergency rate was higher when the parasitoids were reared on A. kuehniella eggs. Both Trichogramma species could be tested in the field for citrus fruit borer control. The thermal requirements and the parasitism capacity also could be good parameters for selection of Trichogramma species/strains. (author)

Extensive feedwater quality control and monitoring concept for preventing chemistry-related failures of boiler tubes in a subcritical thermal power plant

International Nuclear Information System (INIS)

Vidojkovic, Sonja; Onjia, Antonije; Matovic, Branko; Grahovac, Nebojsa; Maksimovic, Vesna; Nastasovic, Aleksandra

2013-01-01

Prevention and minimizing corrosion processes on steam generating equipment is highly important in the thermal power industry. The maintenance of feedwater quality at a level corresponding to the standards of technological designing, followed by timely respond to the fluctuation of measured parameters, has a decisive role in corrosion prevention. In this study, the comprehensive chemical control of feedwater quality in 210 MW Thermal Power Plant (TPP) was carried out in order to evaluate its potentiality to assure reliable function of the boiler and discover possible irregularity that might be responsible for frequent boiler tube failures. Sensitive on-line and off-line analytical instruments were used for measuring key and diagnostic parameters considered to be crucial for boiler safety and performances. Obtained results provided evidences for exceeded levels of oxygen, silica, sodium, chloride, sulfate, copper, and conductivity what distinctly demonstrated necessity of feedwater control improvement. Consequently, more effective feedwater quality monitoring concept was recommended. In this paper, the explanation of presumable root causes of corrosive contaminants was given including basic directions for their maintenance in proscribed limits. -- Highlights: • Feedwater quality monitoring practice in a thermal power plant has been evaluated. • The more efficient feedwater quality control have been applied. • Analysis of feedwater quality parameters has been performed. • Exceeded levels of corrosive contaminants were found. • Recommendations for their maintenance at proscribed values were given

The simulation of transients in thermal plant. Part II: Applications

International Nuclear Information System (INIS)

Morini, G.L.; Piva, S.

2008-01-01

This paper deals with the simulation of the transients of thermal plant with control systems. In the companion paper forming part I of this article [G.L. Morini, S. Piva, The simulation of transients in thermal plant. Part I: Mathematical model, Applied Thermal Engineering 27 (2007) 2138-2144] it has been described how a 'thermal-library' of customised blocks can be built and used, in an intuitive way, to study the transients of any kind of thermal plant. Each component of plant such as valves, boilers, and pumps, is represented by a single block. In this paper, the 'thermal-library' approach is demonstrated by the analysis of the dynamic behaviour of a central heating plant of a typical apartment house during a sinusoidal variation of the external temperature. A comparison of the behaviour of such a plant with three way valve working either in flow rate or in temperature control, is presented and discussed. Finally, the results show the delaying effect of the thermal capacity of the building on the performance of the control system

Thermal expansion of granite rocks

International Nuclear Information System (INIS)

Stephansson, O.

1978-04-01

The thermal expansion of rocks is strongly controlled by the thermal expansion of the minerals. The theoretical thermal expansion of the Stripa Granite is gound to be 21 . 10 -6 [deg C] -1 at 25 deg C and 38 . 10 -6 [deg C] -1 at 400 deg C. The difference in expansion for the rock forming minerals causes micro cracking at heating. The expansion due to micro cracks is found to be of the same order as the mineral expansion. Most of the micro cracks will close at pressures of the order of 10 - 20 MPa. The thermal expansion of a rock mass including the effect of joints is determined in the pilot heater test in the Stripa Mine

Analysis of the sensitivity and sample-furnace thermal-lag of a differential thermal analyzer

International Nuclear Information System (INIS)

Roura, P.; Farjas, J.

2005-01-01

The heat exchange between the horizontal furnace of a differential thermal analyzer (DTA) and the sample is analyzed with the aim of understanding the parameters governing the thermal signal. The resistance due to radiation and conduction through the gas has been calculated and compared to the experimental values of the thermal-lag between the sample and furnace and apparatus sensitivity. The overall evolution of these parameters with the temperature and their relative values are well understood by considering the temperature differences that arise between the sample and holder. Two RC thermal models are used for describing the apparatus performance at different temperature ranges. Finally, the possibility of improving the signal quality through the control of the leak resistances is stressed

Effects of Heating on Teflon(Registered Trademark) FEP Thermal Control Material from the Hubble Space Telescope

Science.gov (United States)

deGroh, Kim; Gaier, James R.; Hall, Rachelle L.; Norris, Mary Jo; Espe, Matthew P.; Cato, Daveen R.

1999-01-01

Metallized Teflon(Registered Trademark) FEP (fluorinated ethylene propylene) thermal control material on the Hubble Space Telescope (HST) is degrading in the space environment. Teflon(Registered Trademark) FEP thermal control blankets (space-facing FEP) retrieved during the first servicing mission (SM1) were found to be embrittled on solar facing surfaces and contained microscopic cracks. During the second servicing mission (SM2) astronauts noticed that the FEP outer layer of the multi-layer insulation (MLI) covering the telescope was cracked in many locations around the telescope. Large cracks were observed on the light shield, forward shell and equipment bays. A tightly curled piece of cracked FEP from the light shield was retrieved during SM2 and was severely embrittled, as witnessed by ground testing. A Failure Review Board (FRB) was organized to determine the mechanism causing the MLI degradation. Density, x-ray crystallinity and solid state nuclear magnetic resonance (NMR) analyses of FEP retrieved during SM1 were inconsistent with results of FEP retrieved during SM2. Because the retrieved SM2 material curled while in space, it experienced a higher temperature extreme during thermal cycling, estimated at 200 C, than the SM1 material, estimated at 50 C. An investigation on the effects of heating pristine and FEP exposed on HST was therefore conducted. Samples of pristine. SM1, and SM2 FEP were heated to 200 C and evaluated for changes in density and morphology. Elevated temperature exposure was found to have a major impact on the density of the retrieved materials. Characterization of polymer morphology of as-received and heated FEP samples by NMR provided results that were consistent with the density results. These findings have provided insight to the damage mechanisms of FEP in the space environment.

Flexible composite material with phase change thermal storage

Science.gov (United States)

Buckley, Theresa M. (Inventor)