The Heat Is on: An Inquiry-Based Investigation for Specific Heat

Science.gov (United States)

Herrington, Deborah G.

2011-01-01

A substantial number of upper-level science students and practicing physical science teachers demonstrate confusion about thermal equilibrium, heat transfer, heat capacity, and specific heat capacity. The traditional method of instruction, which involves learning the related definitions and equations, using equations to solve heat transfer…

Measurement of low-temperature specific heat

International Nuclear Information System (INIS)

Stewart, G.R.

1983-01-01

The measurement of low-temperature specific heat (LTSH) (0.1 K< T<60 K) has seen a number of breakthroughs both in design concepts and instrumentation in the last 15 years: particularly in small sample calorimetry. This review attempts to provide an overview of both large and small sample calorimetry techniques at temperatures below 60 K, with sufficient references to enable more detailed study. A comprehensive review is made of the most reliable measurements of the LTSH of 84 of the elements to illustrate briefly some of the problems of measurements and analysis, as well as to provide additional references. More detail is devoted to three special areas of low-temperature calorimetry that have seen rapid development recently: (1) measurement of the specific heat of highly radioactive samples, (2) measurement of the specific heat of materials in high magnetic fields (18 T), and (3) measurement of the specific heat of very small (100 μg) samples. The review ends with a brief discussion of the frontier research currently underway on microcalorimetry for nanogram sample weights

Eternity Variables to Simulate Specifications

NARCIS (Netherlands)

Hesselink, WH; Boiten, EA; Moller, B

2002-01-01

Simulation of specifications is introduced as a unification and generalization of refinement mappings, history variables, forward simulations, prophecy variables, and backward simulations. Eternity variables are introduced as a more powerful alternative for prophecy variables and backward

Specific heats of degenerate ideal gases

OpenAIRE

Caruso, Francisco; Oguri, Vitor; Silveira, Felipe

2017-01-01

From arguments based on Heisenberg's uncertainty principle and Pauli's exclusion principle, the molar specific heats of degenerate ideal gases at low temperatures are estimated, giving rise to values consistent with the Nerst-Planck Principle (third law of Thermodynamics). The Bose-Einstein condensation phenomenon based on the behavior of specific heat of massive and non-relativistic boson gases is also presented.

Measurement of specific heat and specific absorption rate by nuclear magnetic resonance

Energy Technology Data Exchange (ETDEWEB)

Gultekin, David H., E-mail: david.gultekin@aya.yale.edu [Department of Electrical Engineering, Yale University, New Haven, CT 06520 (United States); Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY 10065 (United States); Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065 (United States); Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232 (United States); Gore, John C. [Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232 (United States); Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN 37232 (United States); Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232 (United States); Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37232 (United States); Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232 (United States)

2010-05-20

We evaluate a nuclear magnetic resonance (NMR) method of calorimetry for the measurement of specific heat (c{sub p}) and specific absorption rate (SAR) in liquids. The feasibility of NMR calorimetry is demonstrated by experimental measurements of water, ethylene glycol and glycerol using any of three different NMR parameters (chemical shift, spin-spin relaxation rate and equilibrium nuclear magnetization). The method involves heating the sample using a continuous wave laser beam and measuring the temporal variation of the spatially averaged NMR parameter by non-invasive means. The temporal variation of the spatially averaged NMR parameter as a function of thermal power yields the ratio of the heat capacity to the respective nuclear thermal coefficient, from which the specific heat can be determined for the substance. The specific absorption rate is obtained by subjecting the liquid to heating by two types of radiation, radiofrequency (RF) and near-infrared (NIR), and by measuring the change in the nuclear spin phase shift by a gradient echo imaging sequence. These studies suggest NMR may be a useful tool for measurements of the thermal properties of liquids.

Heat-source specification 500 watt(e) RTG

International Nuclear Information System (INIS)

1983-02-01

This specification establishes the requirements for a 90 SrF 2 heat source and its fuel capsule for application in a 500 W(e) thermoelectric generator. The specification covers: fuel composition and quantity; the Hastelloy S fuel capsule material and fabrication; and the quality assurance requirements for the assembled heat source

A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production

Science.gov (United States)

Burton-Johnson, A.; Halpin, J.; Whittaker, J. M.; Graham, F. S.; Watson, S. J.

2017-12-01

We present recently published findings (Burton-Johnson et al., 2017) on the variability of Antarctic sub-glacial heat flux and the impact from upper crustal geology. Our new method reveals that the upper crust contributes up to 70% of the Antarctic Peninsula's subglacial heat flux, and that heat flux values are more variable at smaller spatial resolutions than geophysical methods can resolve. Results indicate a higher heat flux on the east and south of the Peninsula (mean 81 mWm-2) where silicic rocks predominate, than on the west and north (mean 67 mWm-2) where volcanic arc and quartzose sediments are dominant. Whilst the data supports the contribution of HPE-enriched granitic rocks to high heat flux values, sedimentary rocks can be of comparative importance dependent on their provenance and petrography. Models of subglacial heat flux must utilize a heterogeneous upper crust with variable radioactive heat production if they are to accurately predict basal conditions of the ice sheet. Our new methodology and dataset facilitate improved numerical model simulations of ice sheet dynamics. The most significant challenge faced remains accurate determination of crustal structure, particularly the depths of the HPE-enriched sedimentary basins and the sub-glacial geology away from exposed outcrops. Continuing research (particularly detailed geophysical interpretation) will better constrain these unknowns and the effect of upper crustal geology on the Antarctic ice sheet. Burton-Johnson, A., Halpin, J.A., Whittaker, J.M., Graham, F.S., and Watson, S.J., 2017, A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production: Geophysical Research Letters, v. 44, doi: 10.1002/2017GL073596.

Solution of heat equation with variable coefficient using derive

CSIR Research Space (South Africa)

Lebelo, RS

2008-09-01

Full Text Available In this paper, the method of approximating solutions of partial differential equations with variable coefficients is studied. This is done by considering heat flow through a one-dimensional model with variable cross-sections. Two cases...

Instantaneous Metabolic Cost of Walking: Joint-Space Dynamic Model with Subject-Specific Heat Rate.

Directory of Open Access Journals (Sweden)

Dustyn Roberts

Full Text Available A subject-specific model of instantaneous cost of transport (ICOT is introduced from the joint-space formulation of metabolic energy expenditure using the laws of thermodynamics and the principles of multibody system dynamics. Work and heat are formulated in generalized coordinates as functions of joint kinematic and dynamic variables. Generalized heat rates mapped from muscle energetics are estimated from experimental walking metabolic data for the whole body, including upper-body and bilateral data synchronization. Identified subject-specific energetic parameters-mass, height, (estimated maximum oxygen uptake, and (estimated maximum joint torques-are incorporated into the heat rate, as opposed to the traditional in vitro and subject-invariant muscle parameters. The total model metabolic energy expenditure values are within 5.7 ± 4.6% error of the measured values with strong (R2 > 0.90 inter- and intra-subject correlations. The model reliably predicts the characteristic convexity and magnitudes (0.326-0.348 of the experimental total COT (0.311-0.358 across different subjects and speeds. The ICOT as a function of time provides insights into gait energetic causes and effects (e.g., normalized comparison and sensitivity with respect to walking speed and phase-specific COT, which are unavailable from conventional metabolic measurements or muscle models. Using the joint-space variables from commonly measured or simulated data, the models enable real-time and phase-specific evaluations of transient or non-periodic general tasks that use a range of (aerobic energy pathway similar to that of steady-state walking.

Prediction of Liquid Specific Heat Capacity of Food Lipids.

Science.gov (United States)

Zhu, Xiaoyi; Phinney, David M; Paluri, Sravanti; Heldman, Dennis R

2018-04-01

Specific heat capacity (c p ) is a temperature dependent physical property of foods. Lipid-being a macromolecular component of food-provides some fraction of the food's overall heat capacity. Fats/oils are complex chemicals that are generally defined by carbon length and degree of unsaturation. The objective of this investigation was to use advanced specific heat capacity measurement to determine the effect of fatty acid chemical structure on specific heat capacity of food lipids. In this investigation, the specific heat capacity of a series of triacylglycerols were measured to quantify the influence of fatty acid composition on specific heat capacity based on two parameters; the -average carbon number (C) and the average number of double bonds (U). A prediction model for specific heat capacity of food lipids as a function of C, U and temperature (T) has been developed. A multiple linear regression to the three-parameter model (R 2 = 0.87) provided a good fit to the experimental data. The prediction model was evaluated by comparison with previously published specific heat capacity values of vegetable oils. It was found that the model provided a 0.53% error, while three other models from the literature predicted c p values with 0.85% to 1.83% average relative deviation from experimental data. The outcomes from this research confirm that the thermophysical properties of fat present in foods are directly related to the physical chemical properties. The specific heat capacity of food products is widely used in process design. Improvements of current models to predict specific heat capacity of food products will assist in the development of efficient processes and in the control of food quality and safety. Furthermore, the understanding of how changes in chemical structure of macromolecular components of foods effect thermophysical properties may begin to allude to models that are not just empirical, but represent portions of the differences in chemistry. © 2018

Analytical Evalution of Heat Transfer Conductivity with Variable Properties

DEFF Research Database (Denmark)

Rahimi, Masoume; Hosseini, Mohammad Javad; Barari, Amin

2011-01-01

The homotopy analysis method (HAM) as a new technique which is powerful and easy-to-use, is applied to solve heat transfer problems. In this paper, we use HAM for heat transfer conductivity equation with variable properties which may contain highly nonlinear terms. The obtained results are also...

Specific heat in diluted magnetic semiconductor quantum ring

Science.gov (United States)

Babanlı, A. M.; Ibragimov, B. G.

2017-11-01

In the present paper, we have calculated the specific heat and magnetization of a quantum ring of a diluted magnetic semiconductor (DMS) material in the presence of magnetic field. We take into account the effect of Rashba spin-orbital interaction, the exchange interaction and the Zeeman term on the specific heat. We have calculated the energy spectrum of the electrons in diluted magnetic semiconductor quantum ring. Moreover we have calculated the specific heat dependency on the magnetic field and Mn concentration at finite temperature of a diluted magnetic semiconductor quantum ring.

The Specific Heat of Matter at Low Temperatures

CERN Document Server

Tari, A

2003-01-01

Recent discoveries of new materials and improvements in calorimetric techniques have given new impetus to the subject of specific heat. Nevertheless, there is a serious lack of literature on the subject. This invaluable book, which goes some way towards remedying that, is concerned mainly with the specific heat of matter at ordinary temperatures. It discusses the principles that underlie the theory of specific heat and considers a number of theoretical models in some detail. The subject matter ranges from traditional materials to those recently discovered - heavy fermion compounds, high temper

Plasma heating in a variable magnetic field

Energy Technology Data Exchange (ETDEWEB)

Kichigin, G. N., E-mail: king@iszf.irk.ru [Russian Academy of Sciences, Institute of Solar-Terrestrial Physics (Russian Federation)

2013-05-15

The problem of particle acceleration in a periodically variable magnetic field that either takes a zero value or passes through zero is considered. It is shown that, each time the field [0]passes through zero, the particle energy increases abruptly. This process can be regarded as heating in the course of which plasma particles acquire significant energy within one field period. This mechanism of plasma heating takes place in the absence of collisions between plasma particles and is analogous to the mechanism of magnetic pumping in collisional plasma considered by Alfven.

Eternity Variables to Prove Simulation of Specifications

NARCIS (Netherlands)

Hesselink, Wim H.

2005-01-01

Simulations of specifications are introduced as a unification and generalization of refinement mappings, history variables, forward simulations, prophecy variables, and backward simulations. A specification implements another specification if and only if there is a simulation from the first one to

Heat loss mechanisms in a measurement of specific heat capacity of graphite

International Nuclear Information System (INIS)

Shipley, D.R.; Duane, S.

1996-01-01

Absorbed dose to graphite in electron beams with nominal energies in the range 3-20 MeV is determined by measuring the temperature rise in the core of a primary standard graphite calorimeter. This temperature rise is related to absorbed dose by a separate measurement of the specific heat capacity of the graphite core. There is, however, a small but significant amount of heat loss from the sample in the determination of specific heat capacity and corrections for these losses are required. This report discusses the sources of heat loss in the measurements and, where possible, provides estimates for the magnitude of these losses. For those mechanisms which are significant, a more realistic model of the measurement system is analysed and corrections for the losses are provided. (UK)

Retrofitting of heat exchanger networks involving streams with variable heat capacity: Application of single and multi-objective optimization

International Nuclear Information System (INIS)

Sreepathi, Bhargava Krishna; Rangaiah, G.P.

2015-01-01

Heat exchanger network (HEN) retrofitting improves the energy efficiency of the current process by reducing external utilities. In this work, HEN retrofitting involving streams having variable heat capacity is studied. For this, enthalpy values of a stream are fitted to a continuous cubic polynomial instead of a stepwise approach employed in the previous studies [1,2]. The former methodology is closer to reality as enthalpy or heat capacity changes gradually instead of step changes. Using the polynomial fitting formulation, single objective optimization (SOO) and multi-objective optimization (MOO) of a HEN retrofit problem are investigated. The results obtained show an improvement in the utility savings, and MOO provides many Pareto-optimal solutions to choose from. Also, Pareto-optimal solutions involving area addition in existing heat exchangers only (but no new exchangers and no structural modifications) are found and provided for comparison with those involving new exchangers and structural modifications as well. - Highlights: • HEN retrofitting involving streams with variable heat capacities is studied. • A continuous approach to handle variable heat capacity is proposed and tested. • Better and practical solutions are obtained for HEN retrofitting in process plants. • Pareto-optimal solutions provide many alternate choices for HEN retrofitting

Influence of Variable Fluid Properties and Radiative Heat loss on ...

African Journals Online (AJOL)

Consequently, comparative analysis is also performed on the wall shear stress and local heat transfer of the present study with the available results.The results show that the inclusion variable viscosity and thermal conductivity, and radiative heat loss mechanism cause significant effects on the fluid flow velocity, temperature ...

Effects of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux

International Nuclear Information System (INIS)

Seddeek, M.A.; Abdelmeguid, M.S.

2006-01-01

The effect of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux has been studied. The thermal diffusivity is assumed to vary as a linear function of temperature. The governing partial differential equations have been transformed to ordinary differential equations. The exact analytical solution for the velocity and the numerical solution for the temperature field are given. Numerical solutions are obtained for different values of variable thermal diffusivity, radiation, temperature parameter and Prandtl number

Design and Modeling of a Variable Heat Rejection Radiator

Science.gov (United States)

Miller, Jennifer R.; Birur, Gajanana C.; Ganapathi, Gani B.; Sunada, Eric T.; Berisford, Daniel F.; Stephan, Ryan

2011-01-01

Variable Heat Rejection Radiator technology needed for future NASA human rated & robotic missions Primary objective is to enable a single loop architecture for human-rated missions (1) Radiators are typically sized for maximum heat load in the warmest continuous environment resulting in a large panel area (2) Large radiator area results in fluid being susceptible to freezing at low load in cold environment and typically results in a two-loop system (3) Dual loop architecture is approximately 18% heavier than single loop architecture (based on Orion thermal control system mass) (4) Single loop architecture requires adaptability to varying environments and heat loads

Fluctuation-dissipation theorem for frequency-dependent specific heat

DEFF Research Database (Denmark)

Dyre, Jeppe; Nielsen, Johannes K.

1996-01-01

A derivation of the fluctuation-dissipation (FD) theorem for the frequency-dependent specific heat of a system described by a master equation is presented. The FD theorem is illustrated by a number of simple examples, including a system described by a linear Langevin equation, a two-level system......, and a system described by the energy master equation. It is shown that for two quite different models with low-energy cutoffs—a collection of two-level systems and a system described by the energy master equation—the frequency-dependent specific heat in dimensionless units becomes universal at low temperatures......, i.e., independent of both energy distribution and temperature. These two models give almost the same universal frequency-dependent specific heat, which compares favorably to experiments on supercooled alcohols....

Specific heat, polarization and heat conduction in microwave heating systems: A nonequilibrium thermodynamic point of view

International Nuclear Information System (INIS)

Bergese, Paolo

2006-01-01

A microwave (MW) field can induce in a dielectric material an oscillatory polarization. By this mechanism part of the energy carried by the waves is converted into chaotic agitation, and the material heats up. MW heating is a nonequilibrium phenomenon, while conventional heating can generally be considered as quasi-static. Excess (or nonthermal) effects of MWs with respect to conventional heating lie in this difference. Macroscopically, MW heating can be described in the framework of linear nonequilibrium thermodynamics (NET). This approach indicates that in a dielectric material under MW heating the specific heat has a dynamic component linked to the variation of polarization with temperature, and that polarization and heat conduction are intertwined. In particular, linear NET provides a new phenomenological equation for heat conduction that is composed of the classic Fourier's law and an additional term due to polarization relaxation. This term quantitatively describes the excess effect of MWs on thermal conduction

Spatio-Temporal Variability of Urban Heat Island and Urban Mobility

Science.gov (United States)

Kar, B.; Omitaomu, O.

2017-12-01

A 2016 report by the U.S. Census stated that while the rural areas cover 97% of the U.S. landmass, these areas house only 19.7% of the nation's population. Given that the U.S. coastal counties are home to more than 50% of the U.S. population, these urban areas are clustered along the coast that is susceptible to sea level rise induced impacts. In light of increasing climate variability and extreme events, it is pertinent to understand the Urban Heat Island (UHI) effect that results from increasing population density and mobility in the urban areas, and that contributes to increased energy consumption and temperature as well as unmitigated flooding events. For example, in Illinois, warmer summers contribute to heavy precipitation that overwhelms the region's drainage capacity. This study focuses on understanding the spatio-temporal variability of the relationship between population density and mobility distribution, and creation of UHI due to temperature change in selected cities across the U.S. This knowledge will help us understand the role of UHI in energy-water nexus in urban areas, specifically, energy consumption.

A simulation-based analysis of variable flow pumping in ground source heat pump systems with different types of borehole heat exchangers: A case study

International Nuclear Information System (INIS)

Zarrella, Angelo; Emmi, Giuseppe; De Carli, Michele

2017-01-01

Highlights: • The work focuses on the variable flow in ground source heat pump systems. • The constant and variable speed circulation pumps in the ground loop are compared. • The constant temperature difference control across the heat pump is studied. • The variable flow affects the energy performance of the heat pump. • The constant temperature difference control offers an attractive energy saving. - Abstract: A simulation model of ground source heat pump systems has been used to investigate to what extent a variable flow of the heat-carrier fluid of the ground loop affects the energy efficiency of the entire system. The model contemporaneously considers the borehole heat exchangers, the heat pump, the building load, and the control strategies for the circulation pumps of the ground loop. A constant speed of the circulation pumps of the ground loop was compared with a variable flow controlled by means of a constant temperature difference across the heat pump on the ground side considering the load profile of an office building located in North Italy. The analysis was carried out for a single U-tube, double U-tube and coaxial pipe heat exchangers. The control strategies adopted to manage the flow rate of the heat-carrier fluid of the ground loop affect both the heat exchange rate of the borehole field and the heat pump’s long-term energy efficiency. The simulations show considerable differences in the system’s seasonal energy efficiency. The constant speed of the circulation pumps leads to the best results as far as the heat pump’s energy performance was concerned, but this advantage was lost because of the greater amount of electrical energy used by the circulation pumps; this, of course, affects the energy efficiency of the entire system. The optimal solution appears then to be a constant temperature difference in the heat-carrier fluid across the heat pump.

Homotopy Perturbation Method for Thin Film Flow and Heat Transfer over an Unsteady Stretching Sheet with Internal Heating and Variable Heat Flux

Directory of Open Access Journals (Sweden)

I-Chung Liu

2012-01-01

Full Text Available We have analyzed the effects of variable heat flux and internal heat generation on the flow and heat transfer in a thin film on a horizontal sheet in the presence of thermal radiation. Similarity transformations are used to transform the governing equations to a set of coupled nonlinear ordinary differential equations. The obtained differential equations are solved approximately by the homotopy perturbation method (HPM. The effects of various parameters governing the flow and heat transfer in this study are discussed and presented graphically. Comparison of numerical results is made with the earlier published results under limiting cases.

Nuclear combined cycle gas turbines for variable electricity and heat using firebrick heat storage and low-carbon fuels

International Nuclear Information System (INIS)

Forsberg, Charles; Peterson, Per F.; McDaniel, Patrick; Bindra, Hitesh

2017-01-01

The world is transitioning to a low-carbon energy system. Variable electricity and industrial energy demands have been met with storable fossil fuels. The low-carbon energy sources (nuclear, wind and solar) are characterized by high-capital-costs and low-operating costs. High utilization is required to produce economic energy. Wind and solar are non-dispatchable; but, nuclear is the dispatchable energy source. Advanced combined cycle gas turbines with firebrick heat storage coupled to high-temperature reactors may enable economic variable electricity and heat production with constant full-power reactor output. Such systems efficiently couple to fluoride-salt-cooled high-temperature reactors (FHRs) with solid fuel and clean salt coolants, molten salt reactors (MSRs) with fuel dissolved in the salt coolant and salt-cooled fusion machines. Open Brayton combined cycles allow the use of natural gas, hydrogen, other fuels and firebrick heat storage for peak electricity production with incremental heat-to-electricity efficiencies from 66 to 70+% efficient. There are closed Brayton cycle options that use firebrick heat storage but these have not been investigated in any detail. Many of these cycles couple to high-temperature gas-cooled reactors (HTGRs). (author)

Heat pipes with variable thermal conductance property for space applications

Energy Technology Data Exchange (ETDEWEB)

Kravets, V.; Alekseik, Ye.; Alekseik, O.; Khairnasov, S. [National Technical University of Ukraine, Kyiv (Ukraine); Baturkin, V.; Ho, T. [Explorationssysteme RY-ES, Bremen (Germany); Celotti, L. [Active Space Technologies GmbH, Berlin (Germany)

2017-06-15

The activities presented in this paper demonstrate a new approach to provide passive thermal control using heat pipes, as demonstrated on the electronic unit of DLR’s MASCOT lander, which embarked on the NEA sample return mission Hayabusa 2 (JAXA). The focus is on the development and testing of heat pipes with variable thermal conductance in a predetermined temperature range. These heat pipes act as thermal switches. Unlike standard gasloaded heat pipes and thermal-diode heat pipes construction of presented heat pipes does not include any additional elements. Copper heat pipes with metal fibrous wicks were chosen as baseline design. We obtained positive results by choosing the heat carrier and structural parameters of the wick (i.e., pore diameter, porosity, and permeability). The increase in the thermal conductivity of the heat pipes from 0.04 W/K to 2.1 W/K was observed in the temperature range between −20 °C and +55 °C. Moreover, the heat pipes transferred the predetermined power of not less than 10 W within the same temperature range. The heat pipes have been in flight since December 2014, and the supporting telemetry data were obtained in September 2015. The data showed the nominal operation of the thermal control system.

Cooling and Heating Season Impacts of Right-Sizing of Fixed- and Variable-Capacity Heat Pumps With Attic and Indoor Ductwork

Energy Technology Data Exchange (ETDEWEB)

Cummings, James [Building America Partnership for Improved Residential Construction, Cocoa, FL (United States); Withers, Charles [Building America Partnership for Improved Residential Construction, Cocoa, FL (United States); Kono, Jamie [Building America Partnership for Improved Residential Construction, Cocoa, FL (United States)

2015-06-01

A new generation of central, ducted variable-capacity heat pump systems has come on the market, promising very high cooling and heating efficiency. They are controlled differently than standard fixed-capacity systems. Instead of cycling on at full capacity and then cycling off when the thermostat is satisfied, they vary their cooling and heating output over a wide range (approximately 40% - 118% of nominal full capacity), thus staying 'on' for 60% - 100% more hours per day compared to fixed -capacity systems. Experiments in this research examined the performance of 2-ton and 3-ton fixed- and variable-capacity systems and the impacts of system oversizing.

Specific heat of filled skutterudite PrOs4P12

International Nuclear Information System (INIS)

Matsuhira, Kazuyuki; Doi, Yoshihiro; Wakeshima, Makoto; Hinatsu, Yukio; Kihou, Kunihiro; Sekine, Chihiro; Shirotani, Ichimin

2005-01-01

We report the specific heat of filled skutterudite compounds PrOs 4 P 12 and LaOs 4 P 12 down to 1.8K. The specific heat divided by temperature C(T)/T in PrOs 4 P 12 shows a shoulder around 13K. This shoulder is caused by a Schottky anomaly due to a crystalline electric field effect. The electronic specific heat coefficients γ of PrOs 4 P 12 and LaOs 4 P 12 are estimated to be 56.5 and 21.6mJ/K 2 mol, respectively. The value of γ in PrOs 4 P 12 is 2.6 times larger than that in LaOs 4 P 12

Superconductivity and specific heat of titanium base A15 alloys

International Nuclear Information System (INIS)

Junod, A.; Flukiger, R.; Muller, J.

1976-01-01

Experimental data on the superconducting transition temperature, and low temperature specific heat, together with X-ray investigations, are reported for binary and pseudo-binary compounds of Ti with the A15-type structure. A 'true' relative maximum of the coefficient of the electronic specific heat, γ, as well as the superconducting transition temperature, Tsub(c), occurs in the Tisub(3)Irsub(1-x)Ptsub(x) system near x = 0.2. Tisub(3)Irsub(0.8)Ptsub(0.2) shows the lowest Debye temperature, theta 0 , of all A15-type compounds known to date. The anomalous temperature dependence of the lattice specific heat may be reproduced by a model phonon spectrum similar to that of Nb 3 Sn. (author)

Effect of Cattaneo-Christov heat flux on Jeffrey fluid flow with variable thermal conductivity

Science.gov (United States)

Hayat, Tasawar; Javed, Mehwish; Imtiaz, Maria; Alsaedi, Ahmed

2018-03-01

This paper presents the study of Jeffrey fluid flow by a rotating disk with variable thickness. Energy equation is constructed by using Cattaneo-Christov heat flux model with variable thermal conductivity. A system of equations governing the model is obtained by applying boundary layer approximation. Resulting nonlinear partial differential system is transformed to ordinary differential system. Homotopy concept leads to the convergent solutions development. Graphical analysis for velocities and temperature is made to examine the influence of different involved parameters. Thermal relaxation time parameter signifies that temperature for Fourier's heat law is more than Cattaneo-Christov heat flux. A constitutional analysis is made for skin friction coefficient and heat transfer rate. Effects of Prandtl number on temperature distribution and heat transfer rate are scrutinized. It is observed that larger Reynolds number gives illustrious temperature distribution.

Determination and Application of Comprehensive Specific Frictional Resistance in Heating Engineering

Directory of Open Access Journals (Sweden)

Yanan Tian

2018-01-01

Full Text Available In this study, we analyze the deficiencies of specific frictional resistance in heating engineering. Based on economic specific frictional resistance, we put forward the concept of comprehensive specific frictional resistance, which considers the multiple factors of technology, economy, regulation modes, pipe segment differences, and medium pressure. Then, we establish a mathematical model of a heating network across its lifespan in order to develop a method for determining the comprehensive specific frictional resistance. Relevant conclusions can be drawn from the results. As an application, we have planned the heating engineering for Yangyuan County in China, which demonstrates the feasibility and superiority of the method.

Variable viscosity effects on mixed convection heat and mass ...

African Journals Online (AJOL)

An analysis is carried out to study the viscous dissipation and variable viscosity effects on the flow, heat and mass transfer characteristics in a viscous fluid over a semi-infinite vertical porous plate in the presence of chemical reaction. The governing boundary layer equations are written into a dimensionless form by similarity ...

A new hydraulic regulation method on district heating system with distributed variable-speed pumps

International Nuclear Information System (INIS)

Wang, Hai; Wang, Haiying; Zhu, Tong

2017-01-01

Highlights: • A hydraulic regulation method was presented for district heating with distributed variable speed pumps. • Information and automation technologies were utilized to support the proposed method. • A new hydraulic model was developed for distributed variable speed pumps. • A new optimization model was developed based on genetic algorithm. • Two scenarios of a multi-source looped system was illustrated to validate the method. - Abstract: Compared with the hydraulic configuration based on the conventional central circulating pump, a district heating system with distributed variable-speed-pumps configuration can often save 30–50% power consumption on circulating pumps with frequency inverters. However, the hydraulic regulations on distributed variable-speed-pumps configuration could be more complicated than ever while all distributed pumps need to be adjusted to their designated flow rates. Especially in a multi-source looped structure heating network where the distributed pumps have strongly coupled and severe non-linear hydraulic connections with each other, it would be rather difficult to maintain the hydraulic balance during the regulations. In this paper, with the help of the advanced automation and information technologies, a new hydraulic regulation method was proposed to achieve on-site hydraulic balance for the district heating systems with distributed variable-speed-pumps configuration. The proposed method was comprised of a new hydraulic model, which was developed to adapt the distributed variable-speed-pumps configuration, and a calibration model with genetic algorithm. By carrying out the proposed method step by step, the flow rates of all distributed pumps can be progressively adjusted to their designated values. A hypothetic district heating system with 2 heat sources and 10 substations was taken as a case study to illustrate the feasibility of the proposed method. Two scenarios were investigated respectively. In Scenario I, the

Optimum performance analysis of an irreversible Diesel heat engine affected by variable heat capacities of working fluid

International Nuclear Information System (INIS)

Zhao, Yingru; Chen, Jincan

2007-01-01

An irreversible cycle model of the Diesel heat engine is established in which the temperature dependent heat capacities of the working fluid, the irreversibilities resulting from non-isentropic compression and expansion processes and heat leak losses through the cylinder wall are taken into account. The adiabatic equation of ideal gases with temperature dependent heat capacity is strictly deduced without using the additional approximation condition in the relevant literature and is used to analyze the performance of the Diesel heat engine. Expressions for the work output and efficiency of the cycle are derived by introducing the pressure ratio and the compression and expansion efficiencies. The performance characteristic curves of the Diesel heat engine are presented for a set of given parameters. The optimum criteria of some important parameters such as the work output, efficiency, pressure ratio and temperatures of the working fluid are obtained. Moreover, the influence of the compression and expansion efficiencies, variable heat capacities, heat leak and other parameters on the performance of the cycle is discussed in detail. The results obtained may provide a theoretical basis for both optimal design and operation of real Diesel heat engines

Variable viscosity effects on mixed convection heat and mass ...

African Journals Online (AJOL)

DR OKE

the effects of viscous dissipation and variable viscosity on the flow of heat and mass transfer characteristics in a viscous fluid over a semi-infinite vertical porous plate in the ..... been solved by Gauss-. Seidel iteration method and numerical values are carried out after executing the computer program for it. In order to prove.

Experimental Investigation on the Specific Heat of Carbonized Phenolic Resin-Based Ablative Materials

Science.gov (United States)

Zhao, Te; Ye, Hong; Zhang, Lisong; Cai, Qilin

2017-10-01

As typical phenolic resin-based ablative materials, the high silica/phenolic and carbon/phenolic composites are widely used in aerospace field. The specific heat of the carbonized ablators after ablation is an important thermophysical parameter in the process of heat transfer, but it is rarely reported. In this investigation, the carbonized samples of the high silica/phenolic and carbon/phenolic were obtained through carbonization experiments, and the specific heat of the carbonized samples was determined by a 3D DSC from 150 °C to 970 °C. Structural and compositional characterizations were performed to determine the mass fractions of the fiber and the carbonized product of phenolic which are the two constituents of the carbonized samples, while the specific heat of each constituent was also measured by 3D DSC. The masses of the carbonized samples were reduced when heated to a high temperature in the specific heat measurements, due to the thermal degradation of the carbonized product of phenolic resin in the carbonized samples. The raw experimental specific heat of the two carbonized samples and the carbonized product of phenolic resin was modified according to the quality changes of the carbonized samples presented by TGA results. Based on the mass fraction and the specific heat of each constituent, a weighted average method was adopted to obtain the calculated results of the carbonized samples. Due to the unconsolidated property of the fiber samples which impacts the reliability of the DSC measurement, there is a certain deviation between the experimental and calculated results of the carbonized samples. Considering the similarity of composition and structure, the data of quartz glass and graphite were used to substitute the specific heat of the high silica fiber and carbon fiber, respectively, resulting in better agreements with the experimental ones. Furthermore, the accurate specific heat of the high silica fiber and carbon fiber bundles was obtained by

Effect of variable heat input on the heat transfer characteristics in an Organic Rankine Cycle system

Directory of Open Access Journals (Sweden)

Aboaltabooq Mahdi Hatf Kadhum

2016-01-01

Full Text Available This paper analyzes the heat transfer characteristics of an ORC evaporator applied on a diesel engine using measured data from experimental work such as flue gas mass flow rate and flue gas temperature. A mathematical model was developed with regard to the preheater, boiler and the superheater zones of a counter flow evaporator. Each of these zones has been subdivided into a number of cells. The hot source of the ORC cycle was modeled. The study involves the variable heat input's dependence on the ORC system's heat transfer characteristics, with especial emphasis on the evaporator. The results show that the refrigerant's heat transfer coefficient has a higher value for a 100% load from the diesel engine, and decreases with the load decrease. Also, on the exhaust gas side, the heat transfer coefficient decreases with the decrease of the load. The refrigerant's heat transfer coefficient increased normally with the evaporator's tube length in the preheater zone, and then increases rapidly in the boiler zone, followed by a decrease in the superheater zone. The exhaust gases’ heat transfer coefficient increased with the evaporator’ tube length in all zones. The results were compared with result by other authors and were found to be in agreement.

Study of Variable Turbulent Prandtl Number Model for Heat Transfer to Supercritical Fluids in Vertical Tubes

Science.gov (United States)

Tian, Ran; Dai, Xiaoye; Wang, Dabiao; Shi, Lin

2018-06-01

In order to improve the prediction performance of the numerical simulations for heat transfer of supercritical pressure fluids, a variable turbulent Prandtl number (Prt) model for vertical upward flow at supercritical pressures was developed in this study. The effects of Prt on the numerical simulation were analyzed, especially for the heat transfer deterioration conditions. Based on the analyses, the turbulent Prandtl number was modeled as a function of the turbulent viscosity ratio and molecular Prandtl number. The model was evaluated using experimental heat transfer data of CO2, water and Freon. The wall temperatures, including the heat transfer deterioration cases, were more accurately predicted by this model than by traditional numerical calculations with a constant Prt. By analyzing the predicted results with and without the variable Prt model, it was found that the predicted velocity distribution and turbulent mixing characteristics with the variable Prt model are quite different from that predicted by a constant Prt. When heat transfer deterioration occurs, the radial velocity profile deviates from the log-law profile and the restrained turbulent mixing then leads to the deteriorated heat transfer.

Specific heat of Cr-based semimagnetic semiconductors

NARCIS (Netherlands)

Twardowski, A.; Eggenkamp, P.J.T.; Mac, W.; Swagten, H.J.M.; Demianiuk, M.

1993-01-01

Specific heat of ZnCrSe and ZnCrS was measured for 1.5

Diurnal variability of heat fluxes and heat content at a few locations off central east coast of India during April 1989

Digital Repository Service at National Institute of Oceanography (India)

Sadhuram, Y.; Rao, B.P.; Rao, V.S.; Rao, T.V.N.

Diurnal variability of surface wind speed, net heat exchange, sea surface temperature, vertical thermal structure and heat content at three locations, viz., station A (17 degrees 59'N, 83 degrees 53.9'E), station B (17 degrees 00'N, 82 degrees 32...

Efficiency analysis of straight fin with variable heat transfer coefficient and thermal conductivity

International Nuclear Information System (INIS)

Sadri, Somayyeh; Raveshi, Mohammad Reza; Amiri, Shayan

2012-01-01

In this study, one type of applicable analytical method, differential transformation method (DTM), is used to evaluate the efficiency and behavior of a straight fin with variable thermal conductivity and heat transfer coefficient. Fins are widely used to enhance heat transfer between primary surface and the environment in many industrial applications. The performance of such a surface is significantly affected by variable thermal conductivity and heat transfer coefficient, particularly for large temperature differences. General heat transfer equation related to the fin is derived and dimensionalized. The concept of differential transformation is briefly introduced, and then this method is employed to derive solutions of nonlinear equations. Results are evaluated for several cases such as: laminar film boiling or condensation, forced convection, laminar natural convection, turbulent natural convection, nucleate boiling, and radiation. The obtained results from DTM are compared with the numerical solution to verify the accuracy of the proposed method. The effects of design parameters on temperature and efficiency are evaluated by some figures. The major aim of the present study, which is exclusive for this article, is to find the effect of the modes of heat transfer on fin efficiency. It has been shown that for radiation heat transfer, thermal efficiency reaches its maximum value

Electronic specific heat of transition metal carbides

International Nuclear Information System (INIS)

Conte, R.

1964-07-01

The experimental results that make it possible to define the band structure of transition metal carbides having an NaCI structure are still very few. We have measured the electronic specific heat of some of these carbides of varying electronic concentration (TiC, either stoichiometric or non-stoichiometric, TaC and mixed (Ti, Ta) - C). We give the main characteristics (metallography, resistivity, X-rays) of our samples and we describe the low temperature specific heat apparatus which has been built. In one of these we use helium as the exchange gas. The other is set up with a mechanical contact. The two use a germanium probe for thermometer. The measurement of the temperature using this probe is described, as well as the various measurement devices. The results are presented in the form of a rigid band model and show that the density of the states at the Fermi level has a minimum in the neighbourhood of the group IV carbides. (author) [fr

Specific heat of nano-ferrites modified composites

Directory of Open Access Journals (Sweden)

Muntenita Cristian

2017-01-01

Full Text Available The specific heat of nano-ferrites modified composites was studied using differential scanning calorimeter (DSC method in the temperature range of 30 to 150°C. Initially, nano-ferrites were introduced in epoxy systems in order to improve the electromagnetic properties of formed materials. Together with the changes in electromagnetic properties some modifications occur regarding thermal and mechanical properties. The materials were formed by placing 5g or 10g of ferrite into 250g polymer matrix leading to a very low weight ratio of modifying agent. At so low ratios the effect of ferrite presence should be insignificant according to mixing rule. Anyway there is possible to appear some chelation reaction with effects on thermal properties of materials. Three types of epoxy resins had been used as matrix and barium ferrite and strontium ferrite as modifying agents. The thermal analysis was developed on two heatingcooling cycles and the specific heat was evaluated for each segment of the cycle analysis.

Specific heat and magnetization of RMn2(H,D)2

International Nuclear Information System (INIS)

Tarnawski, Z.; Kolwicz-Chodak, L.; Figiel, H.; Kim-Ngan, N.-T.H.; Havela, L.; Miliyanchuk, K.; Sechovsky, V.; Santava, E.; Sebek, J.

2007-01-01

The effect of hydrogen absorption on magnetic and thermodynamic properties of hydrides compounds RMn 2 (H,D) 2 (R = Y, Nd, Tb, Ho, and Er) have been investigated by performing specific heat and magnetization measurements in the temperature range of 2-320 K and in magnetic fields up to 9 T. The phase transition to the antiferromagnetic order accompanying a crystal structure transformation have been revealed by complicated-structure anomalies in specific heat and weak anomalies in magnetization

Heat and Humidity in the City: Neighborhood Heat Index Variability in a Mid-Sized City in the Southeastern United States.

Science.gov (United States)

Hass, Alisa L; Ellis, Kelsey N; Reyes Mason, Lisa; Hathaway, Jon M; Howe, David A

2016-01-11

Daily weather conditions for an entire city are usually represented by a single weather station, often located at a nearby airport. This resolution of atmospheric data fails to recognize the microscale climatic variability associated with land use decisions across and within urban neighborhoods. This study uses heat index, a measure of the combined effects of temperature and humidity, to assess the variability of heat exposure from ten weather stations across four urban neighborhoods and two control locations (downtown and in a nearby nature center) in Knoxville, Tennessee, USA. Results suggest that trees may negate a portion of excess urban heat, but are also associated with greater humidity. As a result, the heat index of locations with more trees is significantly higher than downtown and areas with fewer trees. Trees may also reduce heat stress by shading individuals from incoming radiation, though this is not considered in this study. Greater amounts of impervious surfaces correspond with reduced evapotranspiration and greater runoff, in terms of overall mass balance, leading to a higher temperature, but lower relative humidity. Heat index and relative humidity were found to significantly vary between locations with different tree cover and neighborhood characteristics for the full study time period as well as for the top 10% of heat index days. This work demonstrates the need for high-resolution climate data and the use of additional measures beyond temperature to understand urban neighborhood exposure to extreme heat, and expresses the importance of considering vulnerability differences among residents when analyzing neighborhood-scale impacts.

Heat and Humidity in the City: Neighborhood Heat Index Variability in a Mid-Sized City in the Southeastern United States

Directory of Open Access Journals (Sweden)

Alisa L. Hass

2016-01-01

Full Text Available Daily weather conditions for an entire city are usually represented by a single weather station, often located at a nearby airport. This resolution of atmospheric data fails to recognize the microscale climatic variability associated with land use decisions across and within urban neighborhoods. This study uses heat index, a measure of the combined effects of temperature and humidity, to assess the variability of heat exposure from ten weather stations across four urban neighborhoods and two control locations (downtown and in a nearby nature center in Knoxville, Tennessee, USA. Results suggest that trees may negate a portion of excess urban heat, but are also associated with greater humidity. As a result, the heat index of locations with more trees is significantly higher than downtown and areas with fewer trees. Trees may also reduce heat stress by shading individuals from incoming radiation, though this is not considered in this study. Greater amounts of impervious surfaces correspond with reduced evapotranspiration and greater runoff, in terms of overall mass balance, leading to a higher temperature, but lower relative humidity. Heat index and relative humidity were found to significantly vary between locations with different tree cover and neighborhood characteristics for the full study time period as well as for the top 10% of heat index days. This work demonstrates the need for high-resolution climate data and the use of additional measures beyond temperature to understand urban neighborhood exposure to extreme heat, and expresses the importance of considering vulnerability differences among residents when analyzing neighborhood-scale impacts.

Thermodynamic state, specific heat, and enthalpy function of saturated UO2 vapor between 3,000 K and 5,000 K

International Nuclear Information System (INIS)

Karow, H.U.

1977-02-01

The properties have been determined by means of statistical mechanics. The discussion of the thermodynamic state includes the evaluation of the plasma state and its contribution to the caloric variables-of-state of saturated oxide fuel vapor. Because of the extremely high ion and electron density due to thermal ionization, the ionized component of the fuel vapor does no more represent a perfect kinetic plasma. At temperatures around 5,000 K, UO 2 vapor reaches the collective plasma state and becomes increasingly 'metallic'. - Moreover, the nonuniform molecular equilibrium composition of UO 2 vapor has been taken into account in calculating its caloric functions-of-state. The contribution to specific heat and enthalpy of thermally excited electronic states of the vapor molecules has been derived by means of a Rydberg orbital model of the UO 2 molecule. The resulting enthalpy functions and specific heats for saturated UO 2 vapor of equilibrium composition and that for pure UO 2 gas are compared with the enthalpy and specific heat data of gaseous UO 2 at lower temperatures known from literature. (orig./HP) [de

On the specific heat in a limited medium

International Nuclear Information System (INIS)

Suzuki, A.T.

1980-03-01

The specific heat of solids is studied, following the usual approach in which the solid is considered as an elastic, isotropic and continuum system which bears normal modes of characteristic frequency. (L.C.) [pt

Ocean heat content variability in an ensemble of twentieth century ocean reanalyses

Science.gov (United States)

de Boisséson, Eric; Balmaseda, Magdalena Alonso; Mayer, Michael

2017-08-01

This paper presents a ten-member ensemble of twentieth century Ocean ReAnalyses called ORA-20C. ORA-20C assimilates temperature and salinity profiles and is forced by the ECMWF twentieth century atmospheric reanalysis (ERA-20C) over the 1900-2010 period. This study attempts to identify robust signals of ocean heat content change in ORA-20C and detect contamination by model errors, initial condition uncertainty, surface fluxes and observing system changes. It is shown that ORA-20C trends and variability in the first part of the century result from the surface fluxes and model drift towards a warmer mean state and weak meridional overturning circulation. The impact of the observing system in correcting the mean state causes the deceleration of the warming trend and alters the long-term climate signal. The ensemble spread reflects the long-lasting memory of the initial conditions and the convergence of the system to a solution compatible with surface fluxes, the ocean model and observational constraints. Observations constrain the ocean heat uptake trend in the last decades of the twentieth century, which is similar to trend estimations from the post-satellite era. An ocean heat budget analysis attributes ORA-20C heat content changes to surface fluxes in the first part of the century. The heat flux variability reflects spurious signals stemming from ERA-20C surface fields, which in return result from changes in the atmospheric observing system. The influence of the temperature assimilation increments on the heat budget is growing with time. Increments control the most recent ocean heat uptake signals, highlighting imbalances in forced reanalysis systems in the ocean as well as in the atmosphere.

Cylinder pressure, performance parameters, heat release, specific heats ratio and duration of combustion for spark ignition engine

Energy Technology Data Exchange (ETDEWEB)

Shehata, M.S. [Mechanical Engineering Technology Department, Higher Institute of Technology, Banha University, 4Zagalol Street, Benha, Galubia 1235 Z (Egypt)

2010-12-15

An experimental work were conducted for investigating cylinder pressure, performance parameters, heat release, specific heat ratio and duration of combustion for multi cylinder spark ignition engine (SIE). Ccylinder pressure was measured for gasoline, kerosene and Liquefied Petroleum Gases (LPG) separately as a fuel for SIE. Fast Fourier Transformations (FFT) was used to cylinder pressure data transform from time domain into frequency domain to develop empirical correlation for calculating cylinder pressures at different engine speeds and different fuels. In addition, Inverse Fast Fourier Transformations (IFFT) was used to cylinder pressure reconstruct into time domain. The results gave good agreement between the measured cylinder pressure and the reconstructed cylinder pressure in time domain with different engine speeds and different fuels. The measured cylinder pressure and hydraulic dynamotor were the source of data for calculating engine performance parameters. First law of thermodynamics and single zone heat release model with temperature dependant specific heat ratio {gamma}(T) were the main tools for calculating heat release and heat transfer to cylinder walls. Third order empirical correlation for calculating {gamma}(T) was one of the main gains of the present study. The correlation gave good agreement with other researchers with wide temperatures range. For kerosene, cylinder pressure is higher than for gasoline and LPG due to high volumetric efficiency where kerosene density (mass/volume ratio) is higher than gasoline and LPG. In addition, kerosene heating value is higher than gasoline that contributes in heat release rate and pressure increases. Duration of combustion for different engine speeds was determined using four different methods: (I) Mass fuel burnt, (II) Entropy change, (III) Temperature dependant specific heat ratio {gamma}(T), and (IV) Logarithmic scale of (P and V). The duration of combustion for kerosene is smaller than for gasoline and

Cylinder pressure, performance parameters, heat release, specific heats ratio and duration of combustion for spark ignition engine

International Nuclear Information System (INIS)

Shehata, M.S.

2010-01-01

An experimental work were conducted for investigating cylinder pressure, performance parameters, heat release, specific heat ratio and duration of combustion for multi cylinder spark ignition engine (SIE). Ccylinder pressure was measured for gasoline, kerosene and Liquefied Petroleum Gases (LPG) separately as a fuel for SIE. Fast Fourier Transformations (FFT) was used to cylinder pressure data transform from time domain into frequency domain to develop empirical correlation for calculating cylinder pressures at different engine speeds and different fuels. In addition, Inverse Fast Fourier Transformations (IFFT) was used to cylinder pressure reconstruct into time domain. The results gave good agreement between the measured cylinder pressure and the reconstructed cylinder pressure in time domain with different engine speeds and different fuels. The measured cylinder pressure and hydraulic dynamotor were the sours of data for calculating engine performance parameters. First law of thermodynamics and single zone heat release model with temperature dependant specific heat ratio γ(T) were the main tools for calculating heat release and heat transfer to cylinder walls. Third order empirical correlation for calculating γ(T) was one of the main gains of the present study. The correlation gave good agreement with other researchers with wide temperatures range. For kerosene, cylinder pressure is higher than for gasoline and LPG due to high volumetric efficiency where kerosene density (mass/volume ratio) is higher than gasoline and LPG. In addition, kerosene heating value is higher than gasoline that contributes in heat release rate and pressure increases. Duration of combustion for different engine speeds was determined using four different methods: (I) Mass fuel burnt, (II) Entropy change, (III) Temperature dependant specific heat ratio γ(T), and (IV) Logarithmic scale of (P and V). The duration of combustion for kerosene is smaller than for gasoline and LPG due to high

Specific heat of praseodymium and neodymium

International Nuclear Information System (INIS)

Narayana Murthy, J.V.S.S.; Ramji Rao, R.

1983-01-01

The elements of the dynamical matrix of an ideal deep lattice, with nearest neighbour central interactions, have been obtained in a homogeneously strained state. The dispersion relations along the [0001] direction, on this model, have been presented for Pr and Nd. The frequency distribution function g(ω) is obtained and the lattice specific heat is calculated for Pr and Nd and the temperature variation of the equivalent Debye temperature is presented. (author)

Specific heat of amorphous 3He films and confined liquid 3He

International Nuclear Information System (INIS)

Golov, A.; Pobell, F.

1995-01-01

We have measured the heat capacities of 3 He films and liquid 3 He in porous Vycor glass at 10 to 600 mK. With increasing the film thickness front 1 to 3 atomic layers , the specific heat evolves gradually from that typical to solid to that of liquid 3 He. At about 2 atomic layers, however, its low-temperature part is nearly temperature-independent; we interpret this as a result of gradual freezing of spins in an amorphous solid 3 He film with decreasing the temperature. The contribution of liquid 3 He in the center of the Vycor pores can be described as the specific heat of bulk liquid 3 He at corresponding pressures in the range 0 to 28 bar. The thickness of amorphous solid on the pore walls increases with external pressure roughly linearly. Preplating the walls with 4 He allows to determine the positions of 3 He atoms contributing to the surface specific heat at 10 to 50 mK. In addition, the contribution from the specific heat of 3 He- 4 He mixing at 100 to 600 mK is discussed as a function of pressure and amount of 4 He

On the low-temperature specific heat of icosahedral and decagonal quasicrystals

International Nuclear Information System (INIS)

Chernikov, M.A.

2005-01-01

Calorimetric experiments on icosahedral (Al-Re-Pd, Al-Mn-Pd) and decagonal (Al-Cu-Co, Al-Ni-Co) quasicrystals are described. For quasicrystals of both classes, the coefficient γ of the linear term to the specific heat falls into the range of 0.1-0.6 mJ/g-atom K 2 indicating a low density of energy states at Fermi level. For icosahedral Al-Mn-Pd, the cubic-in-temperature term to the specific heat is distinctly larger than the estimated contribution of long-wave acoustic excitations. On the contrary, the magnitude of the cubic-in-temperature term to the specific heat of decagonal Al-Ni-Co is in agreement,within the experimental accuracy, with the Debye acoustic contribution from the results of low-temperature measurements of the elastic modules [ru

A study of variable thrust, variable specific impulse trajectories for solar system exploration

Science.gov (United States)

Sakai, Tadashi

A study has been performed to determine the advantages and disadvantages of variable thrust and variable Isp (specific impulse) trajectories for solar system exploration. There have been several numerical research efforts for variable thrust, variable Isp, power-limited trajectory optimization problems. All of these results conclude that variable thrust, variable Isp (variable specific impulse, or VSI) engines are superior to constant thrust, constant Isp (constant specific impulse; or CSI) engines. However, most of these research efforts assume a mission from Earth to Mars, and some of them further assume that these planets are circular and coplanar. Hence they still lack the generality. This research has been conducted to answer the following questions: (1) Is a VSI engine always better than a CSI engine or a high thrust engine for any mission to any planet with any time of flight considering lower propellant mass as the sole criterion? (2) If a planetary swing-by is used for a VSI trajectory, is the fuel savings of a VSI swing-by trajectory better than that of a CSI swing-by or high thrust swing-by trajectory? To support this research, an unique, new computer-based interplanetary trajectory calculation program has been created. This program utilizes a calculus of variations algorithm to perform overall optimization of thrust, Isp, and thrust vector direction along a trajectory that minimizes fuel consumption for interplanetary travel. It is assumed that the propulsion system is power-limited, and thus the compromise between thrust and Isp is a variable to be optimized along the flight path. This program is capable of optimizing not only variable thrust trajectories but also constant thrust trajectories in 3-D space using a planetary ephemeris database. It is also capable of conducting planetary swing-bys. Using this program, various Earth-originating trajectories have been investigated and the optimized results have been compared to traditional CSI and high

Influence of variable heat transfer coefficient of fireworks and crackers on thermal explosion critical ambient temperature and time to ignition

Directory of Open Access Journals (Sweden)

Guo Zerong

2016-01-01

Full Text Available To study the effect of variable heat transfer coefficient of fireworks and crackers on thermal explosion critical ambient temperature and time to ignition, considering the heat transfer coefficient as the power function of temperature, mathematical thermal explosion steady state and unsteady-state model of finite cylindrical fireworks and crackers with complex shell structures are established based on two-dimensional steady state thermal explosion theory. The influence of variable heat transfer coefficient on thermal explosion critical ambient temperature and time to ignition are analyzed. When heat transfer coefficient is changing with temperature and in the condition of natural convection heat transfer, critical ambient temperature lessen, thermal explosion time to ignition shorten. If ambient temperature is close to critical ambient temperature, the influence of variable heat transfer coefficient on time to ignition become large. For firework with inner barrel in example analysis, the critical ambient temperature of propellant is 463.88 K and the time to ignition is 4054.9s at 466 K, 0.26 K and 450.8s less than without considering the change of heat transfer coefficient respectively. The calculation results show that the influence of variable heat transfer coefficient on thermal explosion time to ignition is greater in this example. Therefore, the effect of variable heat transfer coefficient should be considered into thermal safety evaluation of fireworks to reduce potential safety hazard.

Climate change projections of heat stress in Europe: From meteorological variables to impacts on productivity

Science.gov (United States)

Casanueva, Ana; Kotlarski, Sven; Liniger, Mark A.

2017-04-01

Future climate change is likely to have important impacts in many socio-economic sectors. In particular, higher summer temperatures or more prolonged heat waves may be responsible for health problems and productivity losses related to heat stress, especially affecting people exposed to such situations (e.g. working under outside settings or in non-acclimatized workplaces). Heat stress on the body under work load and consequently their productivity loss can be described through heat stress indices that are based on multiple meteorological parameters such as temperature, humidity, wind and radiation. Exploring the changes of these variables under a warmer climate is of prime importance for the Impacts, Adaptation and Vulnerability communities. In particular, the H2020 project HEAT-SHIELD aims at analyzing the impact of climate change on heat stress in strategic industries in Europe (manufacturing, construction, transportation, tourism and agriculture) within an inter-sectoral framework (climate scientists, biometeorologists, physiologists and stakeholders). In the present work we explore present and future heat stress over Europe using an ensemble of the state-of-the-art RCMs from the EURO-CORDEX initiative. Since RCMs cannot be directly used in impact studies due to their partly substantial biases, a standard bias correction method (empirical quantile mapping) is applied to correct the individual variables that are then used to derive heat stress indices. The objectives of this study are twofold, 1) to test the ability of the separately bias corrected variables to reproduce the main characteristics of heat stress indices in present climate conditions and 2) to explore climate change projections of heat stress indices. We use the wet bulb globe temperature (WBGT) as primary heat stress index, considering two different versions for indoor (or in the shade, based on temperature and humidity conditions) and outdoor settings (including also wind and radiation). The WBGT

Sex specific effects of heat induced hormesis in Hsf-deficient Drosophila melanogaster

DEFF Research Database (Denmark)

Sørensen, J G; Kristensen, Torsten Nygård; Kristensen, K V

2007-01-01

In insects mild heat stress early in life has been reported to increase life span and heat resistance later in life, a phenomenon termed hormesis. Here, we test if the induction of the heat shock response by mild heat stress is mediating hormesis in longevity and heat resistance at older age...... line, seemingly mediated by the production of heat shock proteins (Hsps). The results indicate that heat inducible Hsps are important for heat induced hormesis in longevity and heat stress resistance. However, the results also suggest that other processes are involved and that different mechanisms...... might have marked sex specific impact...

Development, manufacturing and testing of a gas-loaded variable conductance methanol heat pipe

Science.gov (United States)

Vanbuggenum, R. I. J.; Daniels, D. H. W.

1987-02-01

The experimental technology required to measure the performance of moderate temperature heat pipes is presented. The heat pipe manufacturing process is described. The hydrodynamic characteristics of the porous structure inside the heat pipe envelope were examined using a specially developed test rig, based upon a steady-state evaporation test. A fully automated test facility was developed and validated by testing constant conductance and variable conductance heat pipes (VCHP). Theoretical performance predictions are illustrated in terms of pressure, depicted in 3D-plots, and compared with the test results of the heat pipe performance tests. The design of the VCHP was directed towards the verification of the VCHP mathematical model. The VCHP design is validated and ready for the final testing and model verification.

Application of EoEP principle with variable heat transfer coefficient in minimizing entropy production in heat exchangers

International Nuclear Information System (INIS)

Balkan, F.

2005-01-01

A more realistic application of the entropy minimization principle EoEP is presented. This principle dictates uniform local entropy generations along the heat exchanger in order to minimize the total entropy generation rate due only to heat transfer. For a certain heat duty and area of an existing exchanger, this is done by changing the temperatures of one fluid while the temperatures of the other fluid are held constant. Since the heat duty is fixed, the change in the temperatures of the fluid after the change, however, may sometimes cause a drastic change in its flow rate. This may cause considerable changes in the overall heat transfer coefficient (U) and, consequently, in the entropy generation rate. Depending on the choice of the fluid for changing, the new entropy generation rates may be higher or lower than those based on constant U as is the case in papers recently published. So, the classical application of the EoEP principle needs to be modified to achieve more realistic entropy generation rates. In this study, the principle of EoEP with variable U is applied to some cases of heat exchange, and a simple method is presented as a criterion for the proper choice of the fluid to be changed

Low temperature specific heat of Lu-Cu-Y metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Mohammed, K.A.; Lanchester, P.C.

1987-02-01

The specific heat of a series of amorphous metallic alloys of the form Lu/sub x/Cu/sub 0.37/Y/sub 0.36/ (x=0, 0.1, 0.3 and 0.4) has been measured between 2 and 50 K, primarily in order to be able to determine the non-magnetic contributions to the specific heat in magnetic Re-Cu-Y amorphous alloys. The data at low temperature fit the simple form C/sub p/=..gamma..T+..beta..T/sup 3/ from which values of ..gamma.. and theta/sub D/(0) have been determined. Consideration is given to the error that arises if Y is used rather than Lu or La in forming non-magnetic rare earth intermetallics for purposes of determining the non-magnetic contributions to the specific heat of magnetic samples. A simple procedure is described that allows a useful improvement in accuracy in estimating non-magnetic contributions below 20 K if Y is used. The method may also be useful if only a restricted range of compositions using Lu is possible.

q-deformed Einstein's model to describe specific heat of solid

Science.gov (United States)

Guha, Atanu; Das, Prasanta Kumar

2018-04-01

Realistic phenomena can be described more appropriately using generalized canonical ensemble, with proper parameter sets involved. We have generalized the Einstein's theory for specific heat of solid in Tsallis statistics, where the temperature fluctuation is introduced into the theory via the fluctuation parameter q. At low temperature the Einstein's curve of the specific heat in the nonextensive Tsallis scenario exactly lies on the experimental data points. Consequently this q-modified Einstein's curve is found to be overlapping with the one predicted by Debye. Considering only the temperature fluctuation effect(even without considering more than one mode of vibration is being triggered) we found that the CV vs T curve is as good as obtained by considering the different modes of vibration as suggested by Debye. Generalizing the Einstein's theory in Tsallis statistics we found that a unique value of the Einstein temperature θE along with a temperature dependent deformation parameter q(T) , can well describe the phenomena of specific heat of solid i.e. the theory is equivalent to Debye's theory with a temperature dependent θD.

Determination of Specific Heat Capacity on Composite Shape-Stabilized Phase Change Materials and Asphalt Mixtures by Heat Exchange System.

Science.gov (United States)

Ma, Biao; Zhou, Xue-Yan; Liu, Jiang; You, Zhanping; Wei, Kun; Huang, Xiao-Feng

2016-05-19

Previous research has shown that composite shape-stabilized phase change material (CPCM) has a remarkable capacity for thermal storage and stabilization, and it can be directly applied to highway construction without leakage. However, recent studies on temperature changing behaviors of CPCM and asphalt mixture cannot intuitively reflect the thermoregulation mechanism and efficiency of CPCM on asphalt mixture. The objective of this paper is to determine the specific heat capacity of CPCM and asphalt mixtures mixed with CPCM using the heat exchange system and the data acquisition system. Studies have shown that the temperature-rise curve of 5 °C CPCM has an obvious temperature plateau, while an asphalt mixture mixed with 5 °C CPCM does not; with increasing temperature, the specific heat capacities of both 5 °C CPCM and asphalt mixture first increase and then decrease, while the variation rate of 5 °C CPCM is larger than that of the asphalt mixture, and the maximum specific heat capacity of 5 °C CPCM appears around the initial phase change temperature. It is concluded that the temperature intervals of 5 °C CPCM are -18 °C-7 °C, 7 °C-25 °C and 25 °C-44 °C, respectively, and that of the asphalt mixture are -18 °C~10 °C, -10 °C~5 °C and 5 °C~28 °C. A low dosage of 5 °C CPCM has little influence on the specific heat capacity of asphalt mixture. Finally, the functions of specific heat capacities and temperature for CPCM and asphalt mixture mixed with CPCM were recommended by the sectional regression method.

Negative specific heat with trapped ultracold quantum gases

Science.gov (United States)

Strzys, M. P.; Anglin, J. R.

2014-01-01

The second law of thermodynamics normally prescribes that heat tends to disperse, but in certain cases it instead implies that heat will spontaneously concentrate. The spontaneous formation of stars out of cold cosmic nebulae, without which the universe would be dark and dead, is an example of this phenomenon. Here we show that the counter-intuitive thermodynamics of spontaneous heat concentration can be studied experimentally with trapped quantum gases, by using optical lattice potentials to realize weakly coupled arrays of simple dynamical subsystems, so that under the standard assumptions of statistical mechanics, the behavior of the whole system can be predicted from ensemble properties of the isolated components. A naive application of the standard statistical mechanical formalism then identifies the subsystem excitations as heat in this case, but predicts them to share the peculiar property of self-gravitating protostars, of having negative micro-canonical specific heat. Numerical solution of real-time evolution equations confirms the spontaneous concentration of heat in such arrays, with initially dispersed energy condensing quickly into dense ‘droplets’. Analysis of the nonlinear dynamics in adiabatic terms allows it to be related to familiar modulational instabilities. The model thus provides an example of a dictionary mesoscopic system, in which the same non-trivial phenomenon can be understood in both thermodynamical and mechanical terms.

Economies of scale in the Korean district heating system: A variable cost function approach

International Nuclear Information System (INIS)

Park, Sun-Young; Lee, Kyoung-Sil; Yoo, Seung-Hoon

2016-01-01

This paper aims to investigate the cost efficiency of South Korea’s district heating (DH) system by using a variable cost function and cost-share equation. We employ a seemingly unrelated regression model, with quarterly time-series data from the Korea District Heating Corporation (KDHC)—a public utility that covers about 59% of the DH system market in South Korea—over the 1987–2011 period. The explanatory variables are price of labor, price of material, capital cost, and production level. The results indicate that economies of scale are present and statistically significant. Thus, expansion of its DH business would allow KDHC to obtain substantial economies of scale. According to our forecasts vis-à-vis scale economies, the KDHC will enjoy cost efficiency for some time yet. To ensure a socially efficient supply of DH, it is recommended that the KDHC expand its business proactively. With regard to informing policy or regulations, our empirical results could play a significant role in decision-making processes. - Highlights: • We examine economies of scale in the South Korean district heating sector. • We focus on Korea District Heating Corporation (KDHC), a public utility. • We estimate a translog cost function, using a variable cost function. • We found economies of scale to be present and statistically significant. • KDHC will enjoy cost efficiency and expanding its supply is socially efficient.

Specific heat of the simple-cubic Ising model

NARCIS (Netherlands)

Feng, X.; Blöte, H.W.J.

2010-01-01

We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions

Development of Field Angle Resolved Specific Heat Measurement System for Unconventional Superconductors

International Nuclear Information System (INIS)

Kitamura, Yasuhiro; Matsubara, Takeshi; Machida, Yo; Izawa, Koichi; Onuki, Yoshichika; Salce, Bernard; Flouquet, Jacques

2015-01-01

We developed a measurement system for field angle resolved specific heat under multiple extreme conditions at low temperature down to 50 mK, in magnetic field up to 7 T, and under high pressure up to 10 GPa. We demonstrated the performance of our developed system by measuring field angle dependence of specific heat of pressure induced unconventional superconductor CeIrSi 3

Influence of kondo effect on the specific heat jump of anisotropic superconductors

Science.gov (United States)

Yoksan, S.

1986-01-01

A calculation for the specific heat jump of an anisotropic superconductor with Kondo impurities is presented. The impurities are treated within the Matsuura - Ichinose - Nagaoka framework and the anisotropy effect is described by the factorizable model of Markowitz and Kadanoff. We give explicit expressions for the change in specific heat jump due to anisotropy and impurities which can be tested experimentally.

Influence of Kondo effect on the specific heat jump of anisotropic superconductors

International Nuclear Information System (INIS)

Yoksan, S.

1986-01-01

A calculation for the specific heat jump of an anisotropic superconductor with Kondo impurities is presented. The impurities are treated within the Matsuura - Ichinose - Nagaoka framework and the anisotropy effect is described by the factorizable model of Markowitz and Kadanoff. Explicit expressions are given for the change in specific heat jump due to anisotropy and impurities which can be tested experimentally. (author)

Heat flux measurements of Tb{sub 3}M series (M=Co, Rh and Ru): Specific heat and magnetocaloric properties

Energy Technology Data Exchange (ETDEWEB)

Monteiro, J.C.B., E-mail: jolmiui@gmail.com [Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Campinas, SP 13083-859 (Brazil); Lombardi, G.A. [Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Campinas, SP 13083-859 (Brazil); Reis, R.D. dos [Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden (Germany); Freitas, H.E.; Cardoso, L.P.; Mansanares, A.M.; Gandra, F.G. [Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin, Campinas, SP 13083-859 (Brazil)

2016-12-15

We report on the magnetic properties and magnetocaloric effect (MCE) for the Tb{sub 3}M series, with M=Co, Rh and Ru, obtained using a heat flux technique. The specific heat of Tb{sub 3}Co and Tb{sub 3}Rh are very similar, with a first order type transition occurring around 6 K below the magnetic ordering temperature without any corresponding feature on the magnetization. The slightly enhanced electronic specific heat, the Debye temperature around 150 K and the presence of the magnetic specific heat well above the ordering temperature are also characteristic of many other compounds of the R{sub 3}M family (R=Rare Earth). The specific heat for Tb{sub 3}Ru, however, presents two peaks at 37 K and 74 K. The magnetization shows that below the first peak the system presents an antiferromagnetic behavior and is paramagnetic above 74 K. We obtained a magnetocaloric effect for M=Co and Rh, −∆S=12 J/kg K, but for Tb{sub 3}Ru it is less than 3 J/kg K (μ{sub 0}∆H=5 T). We believe that the experimental results show that the MCE is directly related with the process of hybridization of the (R)5d-(M)d electrons that occurs in the R{sub 3}M materials.

Specific heat studies of lanthanum and yttrium sesquicarbides

International Nuclear Information System (INIS)

Cort, B.; Stewart, G.R.; Giorgi, A.L.

1984-01-01

The specific heats of the sesquicarbides LaC/sub 1.35/ and La/sub 0.9/Th/sub 0.1/C/sub 1.6/ (prepared by arc melting) and YC/sub 1.35/ (prepared by a high-pressure technique) have been measured for the first time. No bulk specific heat anomaly appears in either lanthanum compounds, even though (1) inductively measured superconducting transition temperatures are respectively high (11.0 K for LaC/sub 1.35/ and 12.7 K for La/sub 0.9/Th/sub 0.1/C/sub 1.6/) and (2) YC/sub 1.35/ is a bulk superconductor with a T/sub c/ = 10.5 K and Y/sub 0.7/Th/sub 0.3/C/sub 1.58/ (also prepared by high pressure) was previously reported to be a bulk superconductor with a T/sub c/ = 17.1 K. The apparent correlation with preparation technique is discussed

Origin of two maxima in specific heat in enthalpy relaxation under thermal history composed of cooling, annealing, and heating.

Science.gov (United States)

Sakatsuji, Waki; Konishi, Takashi; Miyamoto, Yoshihisa

2016-12-01

The origin of two maxima in specific heat observed at the higher and the lower temperatures in the glass-transition region in the heating process has been studied for polymethyl methacrylate and polyvinyl chloride using differential scanning calorimetry, and the calculation was done using the phenomenological model equation under a thermal history of the typical annealing experiment composed of cooling, annealing, and heating. The higher maximum is observed above the glass-transition temperature, and it remains almost unchanged independent of annealing time t_{a}, while the lower one is observed above an annealing temperature T_{a} and shifts toward the higher one, increasing its magnitude with t_{a}. The analysis by the phenomenological model equation proposed in order to interpret the memory effect in the glassy state clarifies that under a typical annealing history, two maxima in specific heat essentially appear. The shift of the lower maximum toward higher temperatures from above T_{a} is caused by an increase in the amount of relaxation during annealing with t_{a}. The annealing temperature and the amount of relaxation during annealing play a major role in the determination of the number of maxima in the specific heat.

Measurement and Model Validation of Nanofluid Specific Heat Capacity with Differential Scanning Calorimetry

Directory of Open Access Journals (Sweden)

Harry O'Hanley

2012-01-01

Full Text Available Nanofluids are being considered for heat transfer applications; therefore it is important to know their thermophysical properties accurately. In this paper we focused on nanofluid specific heat capacity. Currently, there exist two models to predict a nanofluid specific heat capacity as a function of nanoparticle concentration and material. Model I is a straight volume-weighted average; Model II is based on the assumption of thermal equilibrium between the particles and the surrounding fluid. These two models give significantly different predictions for a given system. Using differential scanning calorimetry (DSC, a robust experimental methodology for measuring the heat capacity of fluids, the specific heat capacities of water-based silica, alumina, and copper oxide nanofluids were measured. Nanoparticle concentrations were varied between 5 wt% and 50 wt%. Test results were found to be in excellent agreement with Model II, while the predictions of Model I deviated very significantly from the data. Therefore, Model II is recommended for nanofluids.

Specific heat of ZnCoSe semimagnetic semiconductor

NARCIS (Netherlands)

Twardowski, A.; Swagten, H.J.M.; Jonge, de W.J.M.; Demianiuk, M.

1990-01-01

The magnetic specific heat of ZnCoSe data are reported in the temperature range 1.5

Investigation of enthalpy and specific heat of the gallium-indium-tin eutectic alloy

International Nuclear Information System (INIS)

Roshchupkin, V.V.; Migaj, L.L.; Fordeeva, L.K.; Perlova, N.L.

1978-01-01

Enthalpy and specific heat of the fusible (melting point is 10.6 deg C) eutectic alloy (67% Ga - 20.5% In - 12.5% Sn according to mass) are determined by the mixing method. The determination was carried out in vacuum at the residual pressure of >= 1x10 -5 torr in the temperature range from 59.3 to 437.0 deg C. It is established that temperature dependence of alloy enthalpy is described by the equation: Hsub(t) - Hsub(0degC)=1.014+0.0879t-0.0000129 t 2 , where (Hsub(t) - Hsub(0degC)) is enthalpy, cal/g; t-temperature, deg C. Mean-square dispersion is +-0.6%. Temperature dependence of alloy specific heat in the temperature range under study was determined by differentiation of the equation obtained for enthalpy: Csub(p)=0.0879-0.000026t, where Csub(p)-specific heat, cal/gx deg. It is supposed that temperature increase makes it possible to decrease slightly specific heat

Cappuccino and Specific Heat Versus Heat of Vaporization

Science.gov (United States)

Hidden, Frits; Boomsma, Jorn; Schins, Anton; van den Berg, Ed

2012-02-01

A cappuccino is prepared by adding about 50 mL frothing, foaming milk to a cup of espresso. Whole milk is best for foaming and the ideal milk temperature when adding it to the espresso is 65 °C. The espresso itself may be warmer than that. During the heating the milk should not burn, as that would spoil the taste. The best way is to heat the milk slowly while stirring to froth the milk and create foam. But modern cappuccino machines in restaurants do not have time for slow heating. Could we heat the milk by just adding hot water?

Analyzing variables for district heating collaborations between energy utilities and industries

International Nuclear Information System (INIS)

Thollander, P.; Svensson, I.L.; Trygg, L.

2010-01-01

One vital means of raising energy efficiency is to introduce district heating in industry. The aim of this paper is to study factors which promote and inhibit district heating collaborations between industries and utilities. The human factors involved showed to affect district heating collaborations more than anything else does. Particularly risk, imperfect and asymmetric information, credibility and trust, inertia and values are adequate variables when explaining the establishment or failure of industry-energy utility collaborations, while heterogeneity, access to capital and hidden costs appear to be of lower importance. A key conclusion from this study is that in an industry-energy utility collaboration, it is essential to nurture the business relationship. In summary, successful collaboration depends more on the individuals and organizations involved in the relationship between the two parties than on the technology used in the collaboration.

Symmetric Anderson impurity model: Magnetic susceptibility, specific heat and Wilson ratio

Science.gov (United States)

Zalom, Peter; Pokorný, Vladislav; Janiš, Václav

2018-05-01

We extend the spin-polarized effective-interaction approximation of the parquet renormalization scheme from Refs. [1,2] applied on the symmetric Anderson model by adding the low-temperature asymptotics of the total energy and the specific heat. We calculate numerically the Wilson ratio and determine analytically its asymptotic value in the strong-coupling limit. We demonstrate in this way that the exponentially small Kondo scale from the strong-coupling regime emerges in qualitatively the same way in the spectral function, magnetic susceptibility and the specific heat.

Urban Heat Wave Hazard Assessment

Science.gov (United States)

Quattrochi, Dale A.; Jedlovec, Gary; Meyer, Paul J.; LaFontaine, Frank J.; Crane, Dakota L.

2016-01-01

Heat waves are the largest cause of environment-related deaths globally. On average, over 6,000 people in the United States alone are hospitalized each summer due to excessive heat. Key elements leading to these disasters are elevated humidity and the urban heat island effect, which act together to increase apparent temperature and amplify the effects of a heat wave. Urban demographics and socioeconomic factors also play a role in determining individual risk. Currently, advisories of impending heat waves are often too generalized, with limited or no spatial variability over urban regions. This frequently contributes to a lack of specific response on behalf of the population. A goal of this project is to develop a product that has the potential to provide more specific heat wave guidance invoking greater awareness and action.

Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems

Science.gov (United States)

Tarau, Calin; Anderson, William G.; Walker, Kara

2009-01-01

In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the converter stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, and also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) has been designed to allow multiple stops and restarts of the Stirling convertor in an Advanced Stirling Radioisotope Generator (ASRG). When the Stirling convertor is turned off, the VCHP will activate when the temperatures rises 30 C above the setpoint temperature. A prototype VCHP with sodium as the working fluid was fabricated and tested in both gravity aided and against gravity conditions for a nominal heater head temperature of 790 C. The results show very good agreement with the predictions and validate the model. The gas front was located at the exit of the reservoir when heater head temperature was 790 C while cooling was ON, simulating an operating Advanced Stirling Converter (ASC). When cooling stopped, the temperature increased by 30 C, allowing the gas front to move past the radiator, which transferred the heat to the case. After resuming the cooling flow, the front returned at the initial location turning OFF the VCHP. The against gravity working conditions showed a colder reservoir and faster transients.

VS2DRTI: Simulating Heat and Reactive Solute Transport in Variably Saturated Porous Media.

Science.gov (United States)

Healy, Richard W; Haile, Sosina S; Parkhurst, David L; Charlton, Scott R

2018-01-29

Variably saturated groundwater flow, heat transport, and solute transport are important processes in environmental phenomena, such as the natural evolution of water chemistry of aquifers and streams, the storage of radioactive waste in a geologic repository, the contamination of water resources from acid-rock drainage, and the geologic sequestration of carbon dioxide. Up to now, our ability to simulate these processes simultaneously with fully coupled reactive transport models has been limited to complex and often difficult-to-use models. To address the need for a simple and easy-to-use model, the VS2DRTI software package has been developed for simulating water flow, heat transport, and reactive solute transport through variably saturated porous media. The underlying numerical model, VS2DRT, was created by coupling the flow and transport capabilities of the VS2DT and VS2DH models with the equilibrium and kinetic reaction capabilities of PhreeqcRM. Flow capabilities include two-dimensional, constant-density, variably saturated flow; transport capabilities include both heat and multicomponent solute transport; and the reaction capabilities are a complete implementation of geochemical reactions of PHREEQC. The graphical user interface includes a preprocessor for building simulations and a postprocessor for visual display of simulation results. To demonstrate the simulation of multiple processes, the model is applied to a hypothetical example of injection of heated waste water to an aquifer with temperature-dependent cation exchange. VS2DRTI is freely available public domain software. © 2018, National Ground Water Association.

Monoclonal antibodies specific to heat-treated porcine blood.

Science.gov (United States)

Raja Nhari, Raja Mohd Hafidz; Hamid, Muhajir; Rasli, Nurmunirah Mohamad; Omar, Abdul Rahman; El Sheikha, Aly Farag; Mustafa, Shuhaimi

2016-05-01

Porcine blood is potentially being utilized in food as a binder, gelling agent, emulsifier or colorant. However, for certain communities, the usage of animal blood in food is strictly prohibited owing to religious concerns and health reasons. This study reports the development of monoclonal antibodies (MAbs) against heat-treated soluble proteins (HSPs) of autoclaved porcine blood; characterization of MAbs against blood, non-blood and plasma from different animal species using qualitative indirect non-competitive enzyme-linked immunosorbent assay (ELISA); and immunoblotting of antigenic components in HSPs of porcine blood. Fifteen MAbs are specific to heat-treated and raw porcine blood and not cross-reacted with other animal blood and non-blood proteins (meat and non-meat). Twelve MAbs are specific to porcine plasma, while three MAbs specific to porcine plasma are cross-reacted with chicken plasma. Immunoblotting revealed antigenic protein bands (∼60, ∼85-100 and ∼250 kDa) in porcine blood and plasma recognized by the MAbs. Selection of MAbs that recognized 60 kDa HSPs of porcine blood and plasma as novel monoclonal antibodies would be useful for detection of porcine plasma in processed food using the immunoassay method. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Specific microRNAs Regulate Heat Stress Responses in Caenorhabditis elegans

DEFF Research Database (Denmark)

Nehammer, Camilla; Podolska, Agnieszka; Mackowiak, Sebastian D

2015-01-01

have identified additional functions for already known players (mir-71 and mir-239) as well as identifying mir-80 and the mir-229 mir-64-66 cluster as important regulators of the heat stress response in C. elegans. These findings uncover an additional layer of complexity to the regulation of stress...... to heat stress in Caenorhabditis elegans and show that a discrete subset of miRNAs is thermoregulated. Using in-depth phenotypic analyses of miRNA deletion mutant strains we reveal multiple developmental and post-developmental survival and behavioral functions for specific miRNAs during heat stress. We...

Experimental determination of nanofluid specific heat with SiO2 nanoparticles in different base fluids

Science.gov (United States)

Akilu, S.; Baheta, A. T.; Sharma, K. V.; Said, M. A.

2017-09-01

Nanostructured ceramic materials have recently attracted attention as promising heat transfer fluid additives owing to their outstanding heat storage capacities. In this paper, experimental measurements of the specific heats of SiO2-Glycerol, SiO2-Ethylene Glycol, and SiO2-Glycerol/Ethylene Glycol mixture 60:40 ratio (by mass) nanofluids with different volume concentrations of 1.0-4.0% have been carried out using differential scanning calorimeter at temperatures of 25 °C and 50 °C. Experimental results indicate lower specific heat capacities are found with SiO2 nanofluids compared to their respective base fluids. The specific heat was decreasing with the increase of concentration, and this decrement depends on upon the type of the base fluid. It is observed that temperature has a positive impact on the specific heat capacity. Furthermore, the experimental values were compared with the theoretical model predictions, and a satisfactory agreement was established.

Elastic modulus, thermal expansion, and specific heat at a phase transition

International Nuclear Information System (INIS)

Testardi, L.R.

1975-01-01

The interrelation of the elastic modulus, thermal-expansion coefficient, and specific heat of a transformed phase relative to the untransformed phase is calculated assuming a particular but useful form of the thermodynamic potential. For second-order phase transitions where this potential applies, measurements of modulus, expansion, and specific heat can yield the general (longitudinal as well as shear) first- and second-order stress (or strain) dependences of the transition temperature and of the order parameter at absolute zero. An exemplary application to one type of phase transition is given

Specific heat measurement set-up for quench condensed thin superconducting films.

Science.gov (United States)

Poran, Shachaf; Molina-Ruiz, Manel; Gérardin, Anne; Frydman, Aviad; Bourgeois, Olivier

2014-05-01

We present a set-up designed for the measurement of specific heat of very thin or ultra-thin quench condensed superconducting films. In an ultra-high vacuum chamber, materials of interest can be thermally evaporated directly on a silicon membrane regulated in temperature from 1.4 K to 10 K. On this membrane, a heater and a thermometer are lithographically fabricated, allowing the measurement of heat capacity of the quench condensed layers. This apparatus permits the simultaneous thermal and electrical characterization of successively deposited layers in situ without exposing the deposited materials to room temperature or atmospheric conditions, both being irreversibly harmful to the samples. This system can be used to study specific heat signatures of phase transitions through the superconductor to insulator transition of quench condensed films.

Specific heat capacities of different clayey samples obtained by differential scanning calorimetry

International Nuclear Information System (INIS)

Fernandez, A.M.

2012-01-01

Document available in extended abstract form only. The thermo-physical properties allow to calculate heat flows and to determine the thermal behaviour of the materials. Temperature influences the rates of the physical, chemical and biological reactions and processes in the soil or a material. Variations in temperature and water content in thermal, hydraulic, mechanical and geochemical processes affect the thermal properties such as density, specific heat, thermal conductivity and thermal diffusivity. Therefore, mathematical models that describe the dependence of the thermal properties on temperature and concentration are of interest to be used in computational programs applied to the modelling of coupled thermo-mechanical-hydraulic and chemical (THMC) processes. In this work, the specific heat capacity of different clayey international reference materials was determined. Differential Scanning Calorimetry (DSC) was used for such purpose. DSC is the main tool for determining the specific heat capacities of materials as a function of temperature. The specific heat capacity, c p (J/Kg.K), is a measurement of the amount of heat required to raise the temperature of a unit mass of a substance by one unit of temperature. A change in temperature, caused by a gain or a loss of heat from a material, depends on the specific heat capacity of the material. Thus, the specific heat capacity is a key and characteristic property of a material and/or substance, which should be determine accurately. The specific heat capacity is an intensive property and, unlike the thermal conductivity and thermal diffusivity, is independent of the dry density of the material. C p of the solid samples was determined by using a SETSYS Evolution 16 thermal analyser coupled to a differential scanning calorimeter (TG-DSC-DTA) from SETARAM Instrumentation. The thermal analyser system can use a heating rate from 0.01 to 100 C/min under a dynamic argon atmosphere and temperatures ranging from ambient to

3D numerical simulation of fluid–solid coupled heat transfer with variable property in a LBE-helium heat exchanger

Energy Technology Data Exchange (ETDEWEB)

Chen, Fei, E-mail: chenfei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); North China University of Water Resources and Electric Power, 36 Beihuan Road, Zhengzhou, Henan 450011 (China); Cai, Jun, E-mail: caijun@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Li, Xunfeng, E-mail: lixunfeng@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Huai, Xiulan, E-mail: hxl@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Wang, Yongwei, E-mail: wangyongwei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China)

2014-07-01

Highlights: • Heat transfer in heat exchanger can be improved by increasing helium's flow rate. • The outlet temperature of helium decreases with increasing helium's flow rate. • Balance is necessary between good heat transfer and high helium outlet temperature. - Abstract: LBE-helium experimental loop of ADS (LELA) and LBE-helium heat exchanger have been designed and constructed with the supporting of the “ADS Transmutation System” project of Chinese Academy of Sciences. In order to investigate the flow and heat transfer characteristics between LBE and helium, 3D numerical simulation of fluid–solid coupled heat transfer with variable property in the LBE-helium heat exchanger is conducted in the present study. The effects of mass-flow-rates of helium and LBE in the shell-side and tube-side on the heat transfer performance are addressed. It is found that the heat transfer performance can be significantly improved by increasing helium mass-flow-rate in the shell-side. In order to easily and quickly obtain the outlet temperatures of helium and LBE, a concept of modified effectiveness is introduced and correlated as the function of tube-side to shell-side heat capacity rate ratio. The results show that the outlet temperature of helium decreases with increasing helium mass-flow-rate. Therefore, considering the utilization of high-temperature helium in the future, for example power generation, there should be a tradeoff between good heat transfer performance and high outlet helium temperature when confirming helium mass-flow-rate.

Measurement of the specific heat capacity of graphite

Energy Technology Data Exchange (ETDEWEB)

Picard, S.; Burns, D.T.; Roger, P

2006-01-15

With the objective of implementing graphite calorimetry at the BIPM to measure absorbed dose, an experimental assembly has recently been constructed to measure the specific heat capacity of graphite. A status description of the apparatus and results from the first measurements are given. The outcome is discussed and the experimental uncertainty is reviewed. (authors)

Measurement of the specific heat capacity of graphite

International Nuclear Information System (INIS)

Picard, S.; Burns, D.T.; Roger, P.

2006-01-01

With the objective of implementing graphite calorimetry at the BIPM to measure absorbed dose, an experimental assembly has recently been constructed to measure the specific heat capacity of graphite. A status description of the apparatus and results from the first measurements are given. The outcome is discussed and the experimental uncertainty is reviewed. (authors)

Specific-heat measurements on dilute 3He-4He mixtures

International Nuclear Information System (INIS)

Zeeuw, H.C.M. van der.

1985-01-01

The author measured the specific heat of dilute 3 He- 4 He mixtures in the concentration range from X = 1 x 10 -3 to X = 3 x 10 -3 and in the temperature range from 100 mK to 600 mK. This has been done by means of a thermal relaxation method. This method provides some interesting features and is applied, to our knowledge, for the first time to dilute 3 He- 4 He mixtures. To reach the required temperature range for our experiments a 4 He circulating 3 He- 4 He dilution refrigerator has been constructed. The results confirm the deviation of the 3 He contribution to the specific heat from the ideal Fermi gas behaviour. (Auth.)

Phonon spectrum of YBCO obtained by specific heat inversion method for real data

CERN Document Server

Tao Wen; Dai Xian Xi; Dai Ji Xin; Evenson, W E

2003-01-01

In this paper, the phonon spectrum of YBCO is obtained from experimental specific heat data by an exact inversion formula with a parameter for eliminating divergences. The results can be compared to those of neutron inelastic scattering, which can only be carried out in a few laboratories. Some key points of specific heat-phonon spectrum inversion (SPI) theory and a method of asymptotic behaviour control are discussed. An improved unique existence theorem is presented, and a universal function set for numerical calculation of SPI is calculated with high accuracy, which makes the inversion method applicable and convenient in practice. This is the first time specific heat-phonon SPI has been realized for a concrete system.

Effect of water content on specific heat capacity of porcine septum cartilage

Science.gov (United States)

Chae, Yongseok; Lavernia, Enrique J.; Wong, Brian J.

2002-06-01

The effect of water content on specific heat capacity was examined using temperature modulated Differential Scanning Calorimetry (TMDSC). This research was motivated in part by the development laser cartilage reshaping operations, which use photothermal heating to accelerate stress relaxation and shape change. Deposition of thermal energy leads to mechanical stress relaxation and redistribution of cartilage internal stresses, which may lead to a permanent shape change. The specific heat of cartilage specimens (dia: 3 mm and thickness 1-2 mm) was measured using a heating rate of 2 degree(s)C/min for conventional DSC and 2 degree(s)C/min with an amplitude 0.38-0.45 degree(s)C and a period 60-100 sec for TMDSC. The amount of water in cartilaginous tissue was determined using thermogravimetry analysis (TGA) under ambient conditions. In order to correlate changes in heat flow with alterations in cartilage mechanical behavior, dynamic mechanical temperature analysis (DMTA) was used to estimate the specific transition temperatures where stress relaxation occurs. With decreasing water content, we identified a phase transition that shifted to a higher temperature after 35-45% water content was measured. The phase transition energy increased from 0.12 J/g to 1.68 J/g after a 45% weight loss. This study is a preliminary investigation focused on understanding the mechanism of the stress relaxation of cartilage during heating. The energy requirement of such a transition estimated using TMDSC and temperature range, where cartilage shape changes likely occur, was estimated.

Improved flexibility with large-scale variable renewable power in cities through optimal demand side management and power-to-heat conversion

International Nuclear Information System (INIS)

Salpakari, Jyri; Mikkola, Jani; Lund, Peter D.

2016-01-01

Highlights: • New models for optimal control of shiftable loads and power-to-heat conversion. • Full technical and economic potential with optimal controls. • Detailed time series of shiftable loads based on empirical data. • Case study of Helsinki (Finland) with over 90% share of district heating. • Positive net present values in cost-optimal operation. - Abstract: Solar and wind power are potential carbon-free energy solutions for urban areas, but they are also subject to large variability. At the same time, urban areas offer promising flexibility solutions for balancing variable renewable power. This paper presents models for optimal control of power-to-heat conversion to heating systems and shiftable loads in cities to incorporate large variable renewable power schemes. The power-to-heat systems comprise heat pumps, electric boilers, and thermal storage. The control strategies comprise optimal matching of load and production, and cost-optimal market participation with investment analysis. All analyses are based on hourly data. The models are applied to a case study in Helsinki, Finland. For a scheme providing ca. 50% of all electricity in the city through self-consumption of variable renewables, power-to-heat with thermal storage could absorb all the surplus production. A significant reduction in the net load magnitude was obtained with shiftable loads. Investments to both power-to-heat and load shifting with electric heating and commercial refrigeration have a positive net present value if the resources are controlled cost-optimally.

The low temperature specific heat of Lu-Cu-Y metallic glasses

International Nuclear Information System (INIS)

Mohammed, K.A.; Lanchester, P.C.

1987-01-01

The specific heat of a series of amorphous metallic alloys of the form Lu x Cu 0.37 Y 0.36 (x=0, 0.1, 0.3 and 0.4) has been measured between 2 and 50 K, primarily in order to be able to determine the non-magnetic contributions to the specific heat in magnetic Re-Cu-Y amorphous alloys. The data at low temperature fit the simple form C p =γT+βT 3 from which values of γ and θ D (0) have been determined. Consideration is given to the error that arises if Y is used rather than Lu or La in forming non-magnetic rare earth intermetallics for purposes of determining the non-magnetic contributions to the specific heat of magnetic samples. A simple procedure is described that allows a useful improvement in accuracy in estimating non-magnetic contributions below 20 K if Y is used. The method may also be useful if only a restricted range of compositions using Lu is possible. (orig.)

Exergoeconomic performance optimization of an endoreversible intercooled regenerative Brayton combined heat and power plant coupled to variable-temperature heat reservoirs

Energy Technology Data Exchange (ETDEWEB)

Yang, Bo; Chen, Lingen; Sun, Fengrui [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)

2012-07-01

An endoreversible intercooled regenerative Brayton combined heat and power (CHP) plant model coupled to variable-temperature heat reservoirs is established. The exergoeconomic performance of the CHP plant is investigated using finite time thermodynamics. The analytical formulae about dimensionless profit rate and exergy efficiency of the CHP plant with the heat resistance losses in the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator are deduced. By taking the maximum profit rate as the objective, the heat conductance allocation among the five heat exchangers and the choice of intercooling pressure ratio are optimized by numerical examples, the characteristic of the optimal dimensionless profit rate versus corresponding exergy efficiency is investigated. When the optimization is performed further with respect to the total pressure ratio, a double-maximum profit rate is obtained. The effects of the design parameters on the double-maximum dimensionless profit rate and corresponding exergy efficiency, optimal total pressure ratio and optimal intercooling pressure ratio are analyzed in detail, and it is found that there exist an optimal consumer-side temperature and an optimal thermal capacitance rate matching between the working fluid and the heat reservoir, respectively, corresponding to a thrice-maximum dimensionless profit rate.

Enhanced specific heat capacity of molten salt-based nanomaterials: Effects of nanoparticle dispersion and solvent material

International Nuclear Information System (INIS)

Jo, Byeongnam; Banerjee, Debjyoti

2014-01-01

This study investigated the effect of nanoparticle dispersion on the specific heat capacity for carbonate salt mixtures doped with graphite nanoparticles. The effect of the solvent material was also examined. Binary carbonate salt mixtures consisting of lithium carbonate and potassium carbonate were used as the base material for the graphite nanomaterial. The different dispersion uniformity of the nanoparticles was created by employing two distinct synthesis protocols for the nanomaterial. Different scanning calorimetry was employed to measure the specific heat capacity in both solid and liquid phases. The results showed that doping the molten salt mixture with the graphite nanoparticles significantly raised the specific heat capacity, even in minute concentrations of graphite nanoparticles. Moreover, greater enhancement in the specific heat capacity was observed from the nanomaterial samples with more homogeneous dispersion of the nanoparticles. A molecular dynamics simulation was also performed for the nanomaterials used in the specific heat capacity measurements to explain the possible mechanisms for the enhanced specific heat capacity, including the compressed layering and the species concentration of liquid solvent molecules

Temperature and air-fuel ratio dependent specific heat ratio functions for lean burned and unburned mixture

International Nuclear Information System (INIS)

Ceviz, M.A.; Kaymaz, I.

2005-01-01

The most important thermodynamic property used in heat release calculations for engines is the specific heat ratio. The functions proposed in the literature for the specific heat ratio are temperature dependent and apply at or near stoichiometric air-fuel ratios. However, the specific heat ratio is also influenced by the gas composition in the engine cylinder and especially becomes important for lean combustion engines. In this study, temperature and air-fuel ratio dependent specific heat ratio functions were derived to minimize the error by using an equilibrium combustion model for burned and unburned mixtures separately. After the error analysis between the equilibrium combustion model and the derived functions is presented, the results of the global specific heat ratio function, as varying with mass fraction burned, were compared with the proposed functions in the literature. The results of the study showed that the derived functions are more feasible at lean operating conditions of a spark ignition engine

Pseudogap and the specific heat of high Tc superconductors: a Hubbard model in a n-pole approximation

Science.gov (United States)

Calegari, E. J.; Lausmann, A. C.; Magalhaes, S. G.; Chaves, C. M.; Troper, A.

2015-03-01

In this work the specific heat of a two-dimensional Hubbard model, suitable to discuss high-Tc superconductors (HTSC), is studied taking into account hopping to first (t) and second (t2) nearest neighbors. Experimental results for the specific heat of HTSC's, for instance, the YBCO and LSCO, indicate a close relation between the pseudogap and the specific heat. In the present work, we investigate the specific heat by the Green's function method within a n-pole approximation. The specific heat is calculated on the pseudogap and on the superconducting regions. In the present scenario, the pseudogap emerges when the antiferromagnetic (AF) fluctuations become sufficiently strong. The specific heat jump coefficient Δγ decreases when the total occupation per site (nT) reaches a given value. Such behavior of Δγ indicates the presence of a pseudogap in the regime of high occupation.

Experimental study of heat transfer to the N2O4 dissociating coolant in the circular tube with variable heat load on the wall

International Nuclear Information System (INIS)

Golovnya, V.N.; Kolykhan, L.I.

1983-01-01

The results of the experimental study of heat transfer to N 2 O 4 dissociating coolant with a sinusoidal law of heat flux density variation by length are presented. The heat transfer process has been studied at subcritical and supercritical parameters and different substance aggregation states. Maximum error of heat transfer coefficient determination don't exceed 15%. The esimation of the effect of variable heat load on heat transfer has been condUcted by comparison of experimental data on the Nusselt number change along the tube length with that calculated using conventional relations for the conditions of uniform heat release. It is shown that heat transfer is enhanced in the region of heat load qsub(c) growth while its intensity is decreased in the region of heat flux reduction. The quantitative effect of qsub(c) variation on heat transfer can be regarded for by the method of superpositions

Using heat to characterize streambed water flux variability in four stream reaches

Science.gov (United States)

Essaid, H.I.; Zamora, C.M.; McCarthy, K.A.; Vogel, J.R.; Wilson, J.T.

2008-01-01

Estimates of streambed water flux are needed for the interpretation of streambed chemistry and reactions. Continuous temperature and head monitoring in stream reaches within four agricultural watersheds (Leary Weber Ditch, IN; Maple Creek, NE; DR2 Drain, WA; and Merced River, CA) allowed heat to be used as a tracer to study the temporal and spatial variability of fluxes through the streambed. Synoptic methods (seepage meter and differential discharge measurements) were compared with estimates obtained by using heat as a tracer. Water flux was estimated by modeling one-dimensional vertical flow of water and heat using the model VS2DH. Flux was influenced by physical heterogeneity of the stream channel and temporal variability in stream and ground-water levels. During most of the study period (April-December 2004), flux was upward through the streambeds. At the IN, NE, and CA sites, high-stage events resulted in rapid reversal of flow direction inducing short-term surface-water flow into the streambed. During late summer at the IN site, regional ground-water levels dropped, leading to surface-water loss to ground water that resulted in drying of the ditch. Synoptic measurements of flux generally supported the model flux estimates. Water flow through the streambed was roughly an order of magnitude larger in the humid basins (IN and NE) than in the arid basins (WA and CA). Downward flux, in response to sudden high streamflows, and seasonal variability in flux was most pronounced in the humid basins and in high conductivity zones in the streambed. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Pseudogap and the specific heat of high Tc superconductors: a Hubbard model in a n-pole approximation

International Nuclear Information System (INIS)

Calegari, E J; Lausmann, A C; Magalhaes, S G; Chaves, C M; Troper, A

2015-01-01

In this work the specific heat of a two-dimensional Hubbard model, suitable to discuss high-T c superconductors (HTSC), is studied taking into account hopping to first (t) and second (t 2 ) nearest neighbors. Experimental results for the specific heat of HTSC's, for instance, the YBCO and LSCO, indicate a close relation between the pseudogap and the specific heat. In the present work, we investigate the specific heat by the Green's function method within a n-pole approximation. The specific heat is calculated on the pseudogap and on the superconducting regions. In the present scenario, the pseudogap emerges when the antiferromagnetic (AF) fluctuations become sufficiently strong. The specific heat jump coefficient Δγ decreases when the total occupation per site (n T ) reaches a given value. Such behavior of Δγ indicates the presence of a pseudogap in the regime of high occupation

Beam Energy Scan of Specific Heat Through Temperature Fluctuations in Heavy Ion Collisions

Science.gov (United States)

Basu, Sumit; Nandi, Basanta K.; Chatterjee, Sandeep; Chatterjee, Rupa; Nayak, Tapan

2016-01-01

Temperature fluctuations may have two distinct origins, first, quantum fluctuations that are initial state fluctuations, and second, thermodynamical fluctuations. We discuss a method of extracting the thermodynamic temperature from the mean transverse momentum of pions, by using controllable parameters such as centrality of the system, and range of the transverse momenta. Event-by-event fluctuations in global temperature over a large phase space provide the specific heat of the system. We present Beam Energy Scan of specific heat from data, AMPT and HRG model prediction. Experimental results from NA49, STAR, PHENIX, PHOBOS and ALICE are combined to obtain the specific heat as a function of beam energy. These results are compared to calculations from AMPT event generator, HRG model and lattice calculations, respectively.

Theoretical analysis for the specific heat and thermal parameters of solid C60

Science.gov (United States)

Soto, J. R.; Calles, A.; Castro, J. J.

1997-08-01

We present the results of a theoretical analysis for the thermal parameters and phonon contribution to the specific heat in solid C60. The phonon contribution to the specific heat is calculated through the solution of the corresponding dynamical matrix, for different points in the Brillouin zone, and the construccion of the partial and generalized phonon density of states. The force constants are obtained from a first principle calculation, using a SCF Hartree-Fock wave function from the Gaussian 92 program. The thermal parameters reported are the effective temperatures and vibrational amplitudes as a function of temperature. Using this model we present a parametization scheme in order to reproduce the general behaviour of the experimental specific heat for these materials.

Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data

Science.gov (United States)

Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.

2006-01-01

Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.

Analysis of transient and hysteresis behavior of cross-flow heat exchangers under variable fluid mass flow rate for data center cooling applications

International Nuclear Information System (INIS)

Gao, Tianyi; Murray, Bruce; Sammakia, Bahgat

2015-01-01

Effective thermal management of data centers is an important aspect of reducing the energy required for the reliable operation of data processing and communications equipment. Liquid and hybrid (air/liquid) cooling approaches are becoming more widely used in today's large and complex data center facilities. Examples of these approaches include rear door heat exchangers, in-row and overhead coolers and direct liquid cooled servers. Heat exchangers are primary components of liquid and hybrid cooling systems, and the effectiveness of a heat exchanger strongly influences the thermal performance of a cooling system. Characterizing and modeling the dynamic behavior of heat exchangers is important for the design of cooling systems, especially for control strategies to improve energy efficiency. In this study, a dynamic thermal model is solved numerically in order to predict the transient response of an unmixed–unmixed crossflow heat exchanger, of the type that is widely used in data center cooling equipment. The transient response to step and ramp changes in the mass flow rate of both the hot and cold fluid is investigated. Five model parameters are varied over specific ranges to characterize the transient performance. The parameter range investigated is based on available heat exchanger data. The thermal response to the magnitude, time period and initial and final conditions of the transient input functions is studied in detail. Also, the hysteresis associated with the fluid mass flow rate variation is investigated. The modeling results and performance data are used to analyze specific dynamic performance of heat exchangers used in practical data center cooling applications. - Highlights: • The transient performance of a crossflow heat exchanger was modeled and studied. • This study provides design information for data center thermal management. • The time constant metric was used to study the impacts of many variable inputs. • The hysteresis behavior

Experimental Analysis of Variable Capacity Heat Pump Systems equipped with a liquid-cooled frequency inverter

OpenAIRE

Ebraheem, Thair

2013-01-01

Using an inverter-driven compressor in variable capacity heat pump systems has a main drawback, which is the extra loss in the inverter. The present experimental study aims to recover the inverter losses by using brine-cooled and water-cooled inverters, thereby improving the total efficiency of the heat pump system. In order to achieve this goal, a test rig with the air-cooled, water-cooled and brine-cooled inverters is designed and built, and a comparative analysis of the recovered heat, inv...

High-field specific heats of A15 V3Si and Nb3Sn

International Nuclear Information System (INIS)

Stewart, G.R.; Brandt, B.L.

1984-01-01

In order to further understand the anomalous behavior of the specific heat of Nb 3 Sn in an 18-T magnetic field discovered by Stewart, Cort, and Webb [Phys. Rev. B 24, 3841 (1981)], we have performed specific-heat measurements on a different sample of Nb 3 Sn at lower fields both in the normal and mixed states, as well as measurement to 19 T on both transforming and nontransforming V 3 Si. The high-field data for V 3 Si indicate that this material behaves quite normally, and that γ/sup trans/ 3 Sn, however, remains anomalous, with both the same ''kink'' in the normal-state field data as observed by Stewart, Cort, and Webb (although at a slightly higher temperature) and unusual mixed-state behavior. The mixed-state specific heat of the V 3 Si samples is as expected, based on earlier work on the mixed-state specific heat of V and Nb

High-field specific heats of A15 V3Si and Nb3Sn

Science.gov (United States)

Stewart, G. R.; Brandt, B. L.

1984-04-01

In order to further understand the anomalous behavior of the specific heat of Nb3Sn in an 18-T magnetic field discovered by Stewart, Cort, and Webb [Phys. Rev. B 24, 3841 (1981)], we have performed specific-heat measurements on a different sample of Nb3Sn at lower fields both in the normal and mixed states, as well as measurement to 19 T on both transforming and nontransforming V3Si. The high-field data for V3Si indicate that this material behaves quite normally, and that γtransJunod and Muller [Solid State Commun. 36, 721 (1980)]. Nb3Sn, however, remains anomalous, with both the same "kink" in the normal-state field data as observed by Stewart, Cort, and Webb (although at a slightly higher temperature) and unusual mixed-state behavior. The mixed-state specific heat of the V3Si samples is as expected, based on earlier work on the mixed-state specific heat of V and Nb.

Low temperature specific heat anomalies in melanins and tumor melanosomes

Energy Technology Data Exchange (ETDEWEB)

Mizutani, U [Carnegie--Mellon Univ., Pittsburgh; Massalski, T B; McGinness, J E; Corry, P M

1976-02-12

Human malignant melanoma cells obtained at autopsy were used. Data indicate that melanins exhibit a large linear term (50-200 erg g/sup -1/K/sup -2/) and that they seem to undergo a phase transition as indicated by the heat capacity near 1.9/sup 0/K. A table is presented to show low temperature specific heat data for melanin samples. The measurements include two anomalies, a transition and an unusually high linear contribution. (HLW)

Specific heat of FeSe: Two gaps with different anisotropy in superconducting state

Science.gov (United States)

Muratov, A. V.; Sadakov, A. V.; Gavrilkin, S. Yu.; Prishchepa, A. R.; Epifanova, G. S.; Chareev, D. A.; Pudalov, V. M.

2018-05-01

We present detailed study of specific heat of FeSe single crystals with critical temperature Tc = 8.45 K at 0.4 - 200 K in magnetic fields 0 - 9 T. Analysis of the electronic specific heat at low temperatures shows the coexistence of isotropic s-wave gap and strongly anisotropic extended s-wave gap without nodes. It was found two possibilities of superconducting gap parameters which give equally description of experimental data: (i) two gaps with approximately equal amplitudes and weight contribution to specific heat: isotropic Δ1 = 1.7 meV (2Δ1 /kBTc =4.7) and anisotropic gap with the amplitude Δ2max = 1.8 meV (2 Δ2max /kBTc =4.9 and anisotropy parameter m = 0.85); (ii) two gaps with substantially different values: isotropic large gap Δ1 = 1.65 meV (2Δ1 /kBTc = 4.52) and anisotropic small gap Δ2max = 0.75 meV (2Δ2max /kBTc = 2) with anisotropy parameter m = 0.71 . These results are confirmed by the field behavior of the residual electronic specific heat γr.

Effect of variable thermal conductivity and specific heat capacity on the calculation of the critical metal hydride thickness for Ti1.1CrMn

DEFF Research Database (Denmark)

Mazzucco, Andrea; Rokni, Masoud

2014-01-01

model is applied to the metal hydride system, with Ti 1.1 CrMn as the absorbing alloy, to predict the weight fraction of absorbed hydrogen and solid bed temperat ure . Dependencies of thermal conductivity and specific heat capacity upon pressure and hydrogen content respectively , are accounted for...

Parametric Sensitivity Study of Operating and Design Variables in Wellbore Heat Exchangers

International Nuclear Information System (INIS)

Nalla, G.; Shook, G.M.; Mines, G.L.; Bloomfield, K.K.

2004-01-01

This report documents the results of an extensive sensitivity study conducted by the Idaho National Engineering and Environmental Laboratory. This study investigated the effects of various operating and design parameters on wellbore heat exchanger performance to determine conditions for optimal thermal energy extraction and evaluate the potential for using a wellbore heat exchanger model for power generation. Variables studied included operational parameters such as circulation rates, wellbore geometries and working fluid properties, and regional properties including basal heat flux and formation rock type. Energy extraction is strongly affected by fluid residence time, heat transfer contact area, and formation thermal properties. Water appears to be the most appropriate working fluid. Aside from minimal tubing insulation, tubing properties are second order effects. On the basis of the sensitivity study, a best case model was simulated and the results compared against existing low-temperature power generation plants. Even assuming ideal work conversion to electric power, a wellbore heat exchange model cannot generate 200 kW (682.4e+3 BTU/h) at the onset of pseudosteady state. Using realistic conversion efficiency, the method is unlikely to generate 50 kW (170.6e+3 BTU/h)

Specific Heat Capacity of Alloy 690 for Simulating Neutron Irradiation

International Nuclear Information System (INIS)

Park, Dae Gyu; Kim, Hee Moon; Song, Woong Sub; Baik, Seung Je; Joo, Young Sun; Ahn, Sang Bok; Park, Jin Seok; Lee, Won Jae; Ryu, Woo Seok

2011-01-01

The KAERI(Korea Atomic Energy Research Institute) is developing new type of nuclear reactor, so called 'SMART'(System Integrated Modular Advanced Reactor) which has many features of small power and system integrated modular type. Alloy 690 was selected as the candidate material for the heat exchanger tube of the steam generator of SMART. The SMART R and D is now facing the stage of engineering verification and approval of standard design to apply to DEMO reactors. Therefore, the material performance under the relevant environment is required to be evaluated. The important material performance issues are mechanical properties i.e. (fracture toughness, tensile and hardness) and thermal properties i.e. (thermal diffusivity, specific heat capacity and thermal conductivity) for which the engineering database is necessary to design a steam generator. However, the neutron post irradiation characteristics of the alloy 690 are barely known. As a result, PIE(Post Irradiation Examination) of thermal properties are planed and performed successfully. But specific heat capacity measurement is not performed because of not having proper test system for irradiated materials. Therefore in order to verify the effect of neutron irradiation for alloy 690, simulation method is adopted. In general, high energy neutron bombardment in material bring about lattice defects i.e. void, pore and dislocation. Dominant factor to impact to heat capacity is mainly dislocation in material. Therefore, simulation of neutron irradiation is devised by material rolling method in order to make artificial dislocation in alloy 690 as same effect of neutron irradiation. After preparing test specimens, heat capacity measurements are performed and results are compared with rolled materials and un-rolled materials to verify the effect of neutron irradiation simulation. Main interest of simulation is that heat capacity value is changed by neutron irradiation

Negative specific heat, phase transition and particles spilling from a potential well

International Nuclear Information System (INIS)

Rao, J.; Liu, Q.H.; Liu, T.G.; Li, L.X.

2008-01-01

For a finite number of noninteracting particles in a box with a potential well in the center, the microcanonical kinetic energy in dependence on the total energy as it is negative can be classified into three categories. The first exhibits a monotonical rise and the specific heat is positive. The second shows a diminishing sawtooth wave with a global rise. The last corresponds to the extreme case and takes the regular sawtooth wave form. The sawtooth wave portion associates periodically a kinetic energy fall in spite of an increase of the total energy; and we attribute to such a fall the negative specific heat. The phase transition can be defined when the relatively dense particle state in the well and relatively dilute particle state in the rest volume of the box coexist, and the appearance of the negative specific heat is sufficient but not necessary for the onset of the phase transition

Detection of Second Order Melting Transitions in the HTSC's by Specific Heat Measurements?

Science.gov (United States)

Pierson, Stephen W.; Valls, Oriol T.

1997-03-01

The finite magnetic field phase transition in the high-temperature superconductors from the solid vortex lattice to the liquid has been under intense study recently. Detection of this melting is difficult but has been seen in magnetization and resistivity measurements. It has also been reported recently in specific heat measurements. In particular, in one case, evidence for a second order melting phase transition has been presented based on specific heat measurements.(M. Roulin, A. Junod, and E. Walker. Science 273), 1210 (1996). However, we present evidence that the feature in the specific heat data can be explained using a theory derived using the lowest-Landau-level approximation(Z. Tes)anović and A. V. Andreev, Phys. Rev. B 49, 4064 (1994) that does not invoke flux lattice melting arguments.

Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source

Science.gov (United States)

Tarau, Calin; Schwendeman, Carl; Anderson, William G.; Cornell, Peggy A.; Schifer, Nicholas A.

2013-01-01

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental

Specific heat of ceramic and single crystal MgB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Junod, A.; Wang, Y.; Bouquet, F.; Sheikin, I.; Toulemonde, P.; Eskildsen, M.R.; Eisterer, M.; Weber, H.W.; Lee, S.; Tajima, S

2003-05-15

The two-gap structure of MgB{sub 2} gives rise to unusual thermodynamic properties which depart markedly from the single-gap BCS model, both in their temperature- and field-dependence. We report measurements of the specific heat up to 16 T on ceramic and single crystal samples, which demonstrate these effects in bulk. The low-temperature mixed-state specific heat reveals a field-dependent anisotropy, and points to the existence of unusually large vortices, in agreement with local density-of-states measurements by scanning tunneling spectroscopy. It is finally shown that a suitable irradiation process nearly doubles H{sub c2} in the bulk.

Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

Science.gov (United States)

Afshari, Ebrahim; Ziaei-Rad, Masoud; Jahantigh, Nabi

2016-06-01

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

A computational procedure for finding multiple solutions of convective heat transfer equations

International Nuclear Information System (INIS)

Mishra, S; DebRoy, T

2005-01-01

In recent years numerical solutions of the convective heat transfer equations have provided significant insight into the complex materials processing operations. However, these computational methods suffer from two major shortcomings. First, these procedures are designed to calculate temperature fields and cooling rates as output and the unidirectional structure of these solutions preclude specification of these variables as input even when their desired values are known. Second, and more important, these procedures cannot determine multiple pathways or multiple sets of input variables to achieve a particular output from the convective heat transfer equations. Here we propose a new method that overcomes the aforementioned shortcomings of the commonly used solutions of the convective heat transfer equations. The procedure combines the conventional numerical solution methods with a real number based genetic algorithm (GA) to achieve bi-directionality, i.e. the ability to calculate the required input variables to achieve a specific output such as temperature field or cooling rate. More important, the ability of the GA to find a population of solutions enables this procedure to search for and find multiple sets of input variables, all of which can lead to the desired specific output. The proposed computational procedure has been applied to convective heat transfer in a liquid layer locally heated on its free surface by an electric arc, where various sets of input variables are computed to achieve a specific fusion zone geometry defined by an equilibrium temperature. Good agreement is achieved between the model predictions and the independent experimental results, indicating significant promise for the application of this procedure in finding multiple solutions of convective heat transfer equations

Experience gained in the process of the variable mass heat flow control implemented in the district heat supply system of the city of Gyor

Energy Technology Data Exchange (ETDEWEB)

Nagy, F.; Milanovich, L.; Lelek, J.; Kekk, I. [District Heating LTD. of Gyor (Hungary)

1996-11-01

The district heating system of the city of Gyor is fed from a hot water boiler plant. The total heat demand for 23,000 residential homes and several public facilities is 260 MW. The variable mass flow control was implemented in 1991 through 1992. Design, preparatory job and the majority of implementation was carried out without external involvement. The paper presents historical background and brief project presentation which is followed by comparative presentation of the variable mass flow control and constant mass flow control. This comparative survey has been conducted on the basis of operating data for 1993 and those for 1988. In the conclusion the gained experience is summarized.

The real gas dynamics of the fluids of high specific heat

International Nuclear Information System (INIS)

Meier, G.E.A.

1987-01-01

The gas dynamics of real fluids show several new effects beyond the gas dynamics of ideal substances. Many of these effects rely on phase changes in the flow fields and can be explained with the help of more complicated thermal and caloric state equations of the real fluids. Complete adiabatic liquefaction and evaporation are possible for those substances whose specific heat exceeds a limit of about twenty gas constants. These fluids consisting of great molecules have so much internal energy storage capacity in their numerous vibrational degrees of freedom that the heat of evaporation can be supplied or also stored in the case of condensation. So liquefaction shock waves, which transform a gas completely or partly into a liquid, are possible. The shock front becomes thereby the surface of a liquid. Partial liquefaction with droplet condensation occurs in weaker shock waves. On the other hand a superheated liquid with high specific heat can be changed into a gas or mixture state in expansion waves or flows. (orig.)

Specific heat of holmium and YNi2B2C. Criticalbehaviour and superconducting properties

International Nuclear Information System (INIS)

Bekkali, Abdelhakim

2010-01-01

Object of the thesis is the study of the specific heat of holmium and YNi 2 B 2 C in the temperature ranges from 50 to 200 KI respectively from 380 mK to 20 K in magnetic fields up to 9 T. In the present thesis the criticalbehaviour of YNi 2 B 2 C and properties of the superconducting state of tne non-magnetic rare-earth nickel borocarbide YNi 2 B 2 C are studied by means of a self-developed measurement apparatur of the specific heat using the quasi-adiabatic heating-pulse method as well as of holmium by means of the relaxation method. In this thesis reliable statements about the critical exponents on monocrystalline holmium could be made. The study on holmium proves that the critical behaviour of the specific heats cannot be described in the framework of the predictions of the chiral universality classes. By means of measurements of the specific heat in this thesis could be confirmed that YNi 2 B 2 C is a multiband superconductor. The positive curvature of the boundary line below T c in the phase diagram yields a first hint to the many-band character of YNI 2 B 2 C. In the zero-field the electronic specific heat in the superconducting state c es (T) can be not explained in the framework of the pure BCS theory. At low temperatures a residual contribution by normally conducting electrons could be detected, which hints to a not completely opened energy gap. A possible explanation would be that a band (or several bands) with low charge-carrier concentration not contribute to the superconductivity. This result agrees with de Haas-van Alphen measurements on isostructural superconducting LuNi 2 B 2 C monocrystals, which suggest the many-band character of the superconductivity as well as a vanishing energy gap in one band. The fluctuation behaviour of the specific heat of YNi 2 B 2 C in the neighbourhood of the superconducting-normally conducting transition agrees well with that of the 3D-XY model. [de

Measurements of thermal diffusivity, specific heat capacity and thermal conductivity with LFA 447 apparatus

DEFF Research Database (Denmark)

Zajas, Jan Jakub; Heiselberg, Per

The LFA 447 can be successfully used for measurements of thermal diffusivity, specific heat and thermal conductivity of various samples. It is especially useful when determining the properties of materials on a very small scale. The matrix measurement mode allows for determining the local...... that the heat losses from both samples during the measurement are similar. Finally, the leveling of the samples is very important. Very small discrepancies can cause a massive error in the derivation of specific heat capacity and, as a result, thermal conductivity....

The specific heat of Cu-Al-Ni shape memory alloys

International Nuclear Information System (INIS)

Ruiz-Larrea, I.; Lopez-Echarri, A.; Bocanegra, E.H.; No, M.L.; San Juan, J.M.

2006-01-01

The specific heat of Cu 81.8 Al 13.7 Ni 4.5 (AK10) shape memory alloy has been studied by means of conventional DSC and adiabatic calorimetry techniques. The transformation temperatures and the shape of the calorimetric curves obtained by adiabatic calorimetry do not show any noticeable dependence on the temperature measurement rates, contrarily to what is observed by other calorimetric techniques. The dynamical character of the various experimental methods together with the influence of the latent heat associated to the first order character of these phase transitions are discussed. The specific heat of AK10 has been measured from 50 to 350 K which covers the phase transformation temperature range. The forward and reverse martensitic transformation peaks were found at 299.5 and 304.6 K, showing a thermal hysteresis of 5.1 deg. C. The C p accuracy can be estimated in 0.1% of C p and permits a reliable assignment of the following values to the phase transition thermodynamic functions: ΔH = 7.4 ± 0.2 J/g and ΔS = 0.025 ± 0.001 J/gK

Daily affect variability and context-specific alcohol consumption.

Science.gov (United States)

Mohr, Cynthia D; Arpin, Sarah; McCabe, Cameron T

2015-11-01

Research explored the effects of variability in negative and positive affect on alcohol consumption, specifying daily fluctuation in affect as a critical form of emotion dysregulation. Using daily process methodology allows for a more objective calculation of affect variability relative to traditional self-reports. The present study models within-person negative and positive affect variabilities as predictors of context-specific consumption (i.e. solitary vs. social drinking), controlling for mean levels of affect. A community sample of moderate-to-heavy drinkers (n = 47; 49% women) from a US metropolitan area reported on affect and alcohol consumption thrice daily for 30 days via a handheld electronic interviewer. Within-person affect variability was calculated using daily standard deviations in positive and negative affect. Within person, greater negative and positive variabilities are related to greater daily solitary and social consumption. Across study days, mean levels of negative and positive affect variabilities related to greater social consumption between persons; yet, aggregated negative affect variability was related to less solitary consumption. Results affirm affect variability as a unique predictor of alcohol consumption, independent of mean affect levels. Yet, it is important to differentiate social context of consumption, as well as type of affect variability, particularly at the between-person level. These distinctions help clarify inconsistencies in the self-medication literature regarding associations between average levels of affect and consumption. Importantly, consistent within-person relationships for both variabilities support arguments that both negative and positive affect variabilities are detrimental and reflect an inability to regulate emotional experience. © 2015 Australasian Professional Society on Alcohol and other Drugs.

Ordering effects on structure and specific heat of nonstoichiometric titanium carbide

International Nuclear Information System (INIS)

Lipatnikov, V.N.; Gusev, A.I.

1999-01-01

The experimental results on the change in the crystal structure and specific heat of the nonstoichiometric titanium carbide TiC y (0.5 2 C phases with cubic and trigonal symmetry and the rhombic ordered Ti 3 C 2 phase are formed in the titanium carbide at the temperature below 1000 K by the phase transitions mechanism. The temperatures and heats of the order-disorder phase transitions are determined [ru

Non Debye approximation on specific heat of solids

Science.gov (United States)

Bhattacharjee, Ruma; Das, Anamika; Sarkar, A.

2018-05-01

A simple non Debye frequency spectrum is proposed. The normalized frequency spectrum is compared to that of Debye spectrum. The proposed spectrum, provides a good account of low frequency phonon density of states, which gives a linear temperature variation at low temperature in contrast to Debye T3 law. It has been analyzed that the proposed model provides a good account of excess specific heat for nanostructure solid.

Specific heat and magnetism of a UIrGe single crystal

Czech Academy of Sciences Publication Activity Database

Sechovský, V.; Vejpravová, J.; Andreev, Alexander V.; Honda, F.; Prokeš, K.; Šantavá, Eva

359-361, - (2005), s. 1126-1128 ISSN 0921-4526 Institutional research plan: CEZ:AV0Z10100520 Keywords : uranium intermetallics * antiferromagnetism * magnetic anisotropy * specific heat Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.796, year: 2005

Investigate the effect of anisotropic order parameter on the specific heat of anisotropic two-band superconductors

International Nuclear Information System (INIS)

Udomsamuthirun, P.; Peamsuwan, R.; Kumvongsa, C.

2009-01-01

The effect of anisotropic order parameter on the specific heat of anisotropic two-band superconductors in BCS weak-coupling limit is investigated. An analytical specific heat jump and the numerical specific heat are shown by using anisotropic order parameters, and the electron-phonon interaction and non-electron-phonon interaction. The two models of anisotropic order parameters are used for numerical calculation that we find little effect on the numerical results. The specific heat jump of MgB 2 , Lu 2 Fe 3 Si 5 and Nb 3 Sn superconductors can fit well with both of them. By comparing the experimental data with overall range of temperature, the best fit is Nb 3 Sn, MgB 2 , and Lu 2 Fe 3 Si 5 superconductors.

Specification of steam generator, condenser and regenerative heat exchanger materials for nuclear applications

International Nuclear Information System (INIS)

Jovasevic, J.V.; Stefanovic, V.M.; Spasic, Z.LJ.

1977-01-01

The basic standards specifications of materials for nuclear applications are selected. Seamless Ni-Cr-Fe alloy Tubes (Inconel-600) for steam generators, condensers and other heat exchangers can be employed instead of austenitic stainless steal or copper alloys tubes; supplementary requirements for these materials are given. Specifications of Ni-Cr-Fe alloy plate, sheet and strip for steam generator lower sub-assembly, U-bend seamless copper-alloy tubes for heat exchanger and condensers are also presented. At the end, steam generator channel head material is proposed in the specification for carbon-steel castings suitable for welding

Incorporation of gene-specific variability improves expression analysis using high-density DNA microarrays

Directory of Open Access Journals (Sweden)

Spitznagel Edward

2003-11-01

Full Text Available Abstract Background The assessment of data reproducibility is essential for application of microarray technology to exploration of biological pathways and disease states. Technical variability in data analysis largely depends on signal intensity. Within that context, the reproducibility of individual probe sets has not been hitherto addressed. Results We used an extraordinarily large replicate data set derived from human placental trophoblast to analyze probe-specific contribution to variability of gene expression. We found that signal variability, in addition to being signal-intensity dependant, is probe set-specific. Importantly, we developed a novel method to quantify the contribution of this probe set-specific variability. Furthermore, we devised a formula that incorporates a priori-computed, replicate-based information on probe set- and intensity-specific variability in determination of expression changes even without technical replicates. Conclusion The strategy of incorporating probe set-specific variability is superior to analysis based on arbitrary fold-change thresholds. We recommend its incorporation to any computation of gene expression changes using high-density DNA microarrays. A Java application implementing our T-score is available at http://www.sadovsky.wustl.edu/tscore.html.

Specific heat study of quasi-one-dimensional antiferromagnetic model for an organic polymer chain

International Nuclear Information System (INIS)

Qu Shaohua; Zhu Lin

2008-01-01

The specific heat of an infinite one-dimensional polymer chain bearing periodically arranged side radicals connected to the even sites is studied by means of quantum transfer-matrix method based on a Ising-Heisenberg model. In the absence of the exchange interactions between side radicals and the main chain, the curves of specific heat show a round peak due to the antiferromagnetic excitations for the all antiferromagnetic interactions along the polymer chain. Considering the exchange interactions between the side radicals and the main chain, the curves of the specific heat show double-peak structure for ferromagnetic interactions between the radicals and main chain, indicating that a competition between ferromagnetic and antiferromagnetic interactions and the possibility of the occurrence of the stable ferrimagnetic state along the polymer chain

Characterization of dynamic thermal control schemes and heat transfer pathways for incorporating variable emissivity electrochromic materials into a space suit heat rejection system

Science.gov (United States)

Massina, Christopher James

The feasibility of conducting long duration human spaceflight missions is largely dependent on the provision of consumables such as oxygen, water, and food. In addition to meeting crew metabolic needs, water sublimation has long served as the primary heat rejection mechanism in space suits during extravehicular activity (EVA). During a single eight hour EVA, approximately 3.6 kg (8 lbm) of water is lost from the current suit. Reducing the amount of expended water during EVA is a long standing goal of space suit life support systems designers; but to date, no alternate thermal control mechanism has demonstrated the ability to completely eliminate the loss. One proposed concept is to convert the majority of a space suit's surface area into a radiator such that the local environment can be used as a radiative thermal sink for rejecting heat without mass loss. Due to natural variations in both internal (metabolic) loads and external (environmental) sink temperatures, radiative transport must be actively modulated in order to maintain an acceptable thermal balance. Here, variable emissivity electrochromic devices are examined as the primary mechanism for enabling variable heat rejection. This dissertation focuses on theoretical and empirical evaluations performed to determine the feasibility of using a full suit, variable emissivity radiator architecture for space suit thermal control. Operational envelopes are described that show where a given environment and/or metabolic load combination may or may not be supported by the evaluated thermal architecture. Key integration considerations and guidelines include determining allowable thermal environments, defining skin-to-radiator heat transfer properties, and evaluating required electrochromic performance properties. Analysis also considered the impacts of dynamic environmental changes and the architecture's extensibility to EVA on the Martian surface. At the conclusion of this work, the full suit, variable emissivity

Specific heat measurements of TiB2 and 6LiF from 0.5 to 30 K

International Nuclear Information System (INIS)

Lang, Brian E.; Donaldson, Marcus H.; Woodfield, Brian F.; Burger, Arnold; Roy, Utupal N.; Lamberti, Vincent; Bell, Zane W.

2005-01-01

The specific heats of TiB 2 and 6 LiF have been measured from 0.5 to 30 K as part of a larger project in the construction of a neutron spectrometer. For this application, the measured specific heats were used to extrapolate the specific heats down to 0.1 K with lattice, electronic, and Schottky equations for the respective samples. The resultant specific heat values at 0.1 K for TiB 2 and 6 LiF are 4.08 x 10 -4 ± 0.27 x 10 -4 J/K/mol and 9.19 x 10 -9 ± 0.15 x 10 -9 J/K/mol, respectively

The heat engine cycle, the heat removal cycle, and ergonomics of the control room displays

International Nuclear Information System (INIS)

Beltracchi, L.

1986-01-01

This paper discusses and illustrates the ergonomics of an integrated display, which will allow operators to monitor the heat engine cycle during normal operation of the plant, and the heat removal cycle during emergency operation of the plant. A computer-based iconic display is discussed as an overview to monitor these cycles. Specific emphasis is placed upon the process variables and process functions within each cycle, and the action of control systems and engineered safeguard systems within each cycle. This paper contains examples of display formats for the heat engine cycle and the heat removal cycle in a pressurized water reactor

Performance analysis for an irreversible variable temperature heat reservoir closed intercooled regenerated Brayton cycle

International Nuclear Information System (INIS)

Wang Wenhua; Chen Lingen; Sun Fengrui; Wu Chih

2003-01-01

In this paper, the theory of finite time thermodynamics is used in the performance analysis of an irreversible closed intercooled regenerated Brayton cycle coupled to variable temperature heat reservoirs. The analytical formulae for dimensionless power and efficiency, as functions of the total pressure ratio, the intercooling pressure ratio, the component (regenerator, intercooler, hot and cold side heat exchangers) effectivenesses, the compressor and turbine efficiencies and the thermal capacity rates of the working fluid and the heat reservoirs, the pressure recovery coefficients, the heat reservoir inlet temperature ratio, and the cooling fluid in the intercooler and the cold side heat reservoir inlet temperature ratio, are derived. The intercooling pressure ratio is optimized for optimal power and optimal efficiency, respectively. The effects of component (regenerator, intercooler and hot and cold side heat exchangers) effectivenesses, the compressor and turbine efficiencies, the pressure recovery coefficients, the heat reservoir inlet temperature ratio and the cooling fluid in the intercooler and the cold side heat reservoir inlet temperature ratio on optimal power and its corresponding intercooling pressure ratio, as well as optimal efficiency and its corresponding intercooling pressure ratio are analyzed by detailed numerical examples. When the heat transfers between the working fluid and the heat reservoirs are executed ideally, the pressure drop losses are small enough to be neglected and the thermal capacity rates of the heat reservoirs are infinite, the results of this paper replicate those obtained in recent literature

Viscous and Joule heating effects on MHD free convection flow with variable plate temperature

International Nuclear Information System (INIS)

Hossain, M.A.

1990-09-01

A steady two-dimensional laminar boundary layer flow of a viscous incompressible and electrically conducting fluid past a vertical heated plate with variable temperature in the presence of a transverse uniform magnetic field has been investigated by bringing the effect of viscous and Joules heating. The non-dimensional boundary layer equations are solved using the implicit finite difference method along with Newton's approximation for small Prandtl number chosen as typical of coolant liquid metals at operating temperature. (author). 10 refs, 2 figs, 1 tab

Specific heat studies of pure Nb3Sn single crystals at low temperature

International Nuclear Information System (INIS)

Escudero, R; Morales, F; Bernes, S

2009-01-01

Specific heat measurements performed on high purity vapor-grown Nb 3 Sn crystals show clear features related to both the martensitic and superconducting transitions. Our measurements indicate that the martensitic anomaly does not display hysteresis, meaning that the martensitic transition could be a weak first-order or a second-order thermodynamic transition. Careful measurements of the two transition temperatures display an inverse correlation between them. At low temperature, specific heat measurements show the existence of a single superconducting energy gap feature.

MHD effects on heat transfer over stretching sheet embedded in porous medium with variable viscosity, viscous dissipation and heat source/sink

Directory of Open Access Journals (Sweden)

Hunegnaw Dessie

2014-09-01

Full Text Available In this analysis, MHD boundary layer flow and heat transfer of a fluid with variable viscosity through a porous medium towards a stretching sheet by taking in to the effects of viscous dissipation in presence of heat source/sink is considered. The symmetry groups admitted by the corresponding boundary value problem are obtained by using Lie’s scaling group of transformations. These transformations are used to convert the partial differential equations of the governing equations into self-similar non-linear ordinary differential equations. Numerical solutions of these equations are obtained by Runge-Kutta fourth order with shooting method. Numerical results obtained for different parameters such as viscosity variation parameter A, permeability parameter k1, heat source/sink parameter λ, magnetic field parameter M, Prandtl number Pr, and Eckert number Ec are drawn graphically and effects of different flow parameters on velocity and temperature profiles are discussed. The skin-friction coefficient -f″(0 and heat transfer coefficient −θ′(0 are presented in tables.

Cooling and Heating Season Impacts of Right-Sizing of Fixed- and Variable-Capacity Heat Pumps With Attic and Indoor Ductwork

Energy Technology Data Exchange (ETDEWEB)

Cummings, James [Building America Partnership for Improved Residential Construction, Cocoa, FL (United States); Withers, Charles [Building America Partnership for Improved Residential Construction, Cocoa, FL (United States); Kono, Jamie [Building America Partnership for Improved Residential Construction, Cocoa, FL (United States)

2015-06-24

A new generation of full variable-capacity air-conditioning (A/C) and heat pump units has come on the market that promises to deliver very high cooling and heating efficiency. The units are controlled differently than standard single-capacity (fixed-capacity) systems. Instead of cycling on at full capacity and cycling off when the thermostat is satisfied, the new units can vary their capacity over a wide range (approximately 40%–118% of nominal full capacity) and stay on for 60%–100% more hours per day than the fixed-capacity systems depending on load-to-capacity ratios. Two-stage systems were not evaluated in this research effort.

Low-temperature specific heat and thermal conductivity of silica aerogels

DEFF Research Database (Denmark)

Sleator, T.; Bernasconi, A.; Posselt, D.

1991-01-01

Specific-heat and thermal-conductivity measurements were made on a series of base-catalyzed silica aerogels at temperatures between 0.05 and 20 K. Evidence for a crossover between regimes of characteristically different excitations was observed. The data analysis indicates a "bump" in the density...

Silver oxides. II. Specific heats of silver oxide and silver peroxide. [20 to 99 C

Energy Technology Data Exchange (ETDEWEB)

Jirsa, F

1949-01-01

Specific heats were determined in a water calorimeter over the temperature range 20 through 99 C. The specific heat of Ag/sub 2/O is given as 0.0803 +- 0.001 cal/g-C, and that of Ag/sub 2/O/sub 2/ is given as 0.0869 +- 0.0005 cal/g-C.

Impacts of Realistic Urban Heating, Part I: Spatial Variability of Mean Flow, Turbulent Exchange and Pollutant Dispersion

Science.gov (United States)

Nazarian, Negin; Martilli, Alberto; Kleissl, Jan

2018-03-01

As urbanization progresses, more realistic methods are required to analyze the urban microclimate. However, given the complexity and computational cost of numerical models, the effects of realistic representations should be evaluated to identify the level of detail required for an accurate analysis. We consider the realistic representation of surface heating in an idealized three-dimensional urban configuration, and evaluate the spatial variability of flow statistics (mean flow and turbulent fluxes) in urban streets. Large-eddy simulations coupled with an urban energy balance model are employed, and the heating distribution of urban surfaces is parametrized using sets of horizontal and vertical Richardson numbers, characterizing thermal stratification and heating orientation with respect to the wind direction. For all studied conditions, the thermal field is strongly affected by the orientation of heating with respect to the airflow. The modification of airflow by the horizontal heating is also pronounced for strongly unstable conditions. The formation of the canyon vortices is affected by the three-dimensional heating distribution in both spanwise and streamwise street canyons, such that the secondary vortex is seen adjacent to the windward wall. For the dispersion field, however, the overall heating of urban surfaces, and more importantly, the vertical temperature gradient, dominate the distribution of concentration and the removal of pollutants from the building canyon. Accordingly, the spatial variability of concentration is not significantly affected by the detailed heating distribution. The analysis is extended to assess the effects of three-dimensional surface heating on turbulent transfer. Quadrant analysis reveals that the differential heating also affects the dominance of ejection and sweep events and the efficiency of turbulent transfer (exuberance) within the street canyon and at the roof level, while the vertical variation of these parameters is less

Physical Properties and Specific Heat Capacity of Tamarind (Tamarindus indica Seed

Directory of Open Access Journals (Sweden)

A. Dauda

2017-04-01

Full Text Available This study investigated the effect of moisture content on physical properties and specific heat capacity of Tamarindus indica seed. Physical properties investigated were axial dimensions, one thousand seed weight, bulk and true densities, porosity, roundness and sphericity, surface area, angle of repose and static coefficient of friction. The thermal property determined was the specific heat. These properties of Tamarindus indica seed were investigated within the moisture content range of 7.55 - 10.47% (d.b. The length, width and thickness increased from 9.979 to 10.634mm, 8.909 to 10.089mm and 5.039 to 5.658mm, respectively in the above moisture range. One thousand seed weight, surface area, seed volume, true density and porosity, increased from 388.4 to 394.8g, 86.916 to 87.58cm2, 0.353 to 0.366cm3, 1217.5 to 1287.00kg/m3 and 28.22 to 33.87%, respectively, as moisture content increased in the above range, while bulk density decreased from 873.9 to 851.4kg/m3. Roundness and sphericity, and angle of repose also increased from 41 to 42.4% and 73.7 to 76.3% and 36.1 to 38.93o, respectively. Specific heat capacity values increased linearly from 589.00J/kgK to 638.61 J/kgK in the above moisture range.

Transport properties and specific heat of UTe and USb

International Nuclear Information System (INIS)

Ochiai, A.; Suzuki, Y.; Shikama, T.; Suzuki, K.; Hotta, E.; Haga, Y.; Suzuki, T.

1994-01-01

Uranium monochalcogenides and monopnictides crystallize in the NaCl-type structure and exhibit ferromagnetic and antiferromagnetic order, respectively. These series reveal interesting properties such as Kondo behavior of UTe. However, such interesting properties are much sample dependent. We grew single crystals of USb and UTe with high purity using the Bridgman technique, and measured transport properties and specific heat. ((orig.))

Two-Dimensional Variable Property Conjugate Heat Transfer Simulation of Nanofluids in Microchannels

International Nuclear Information System (INIS)

Ramiar, A.; Ranjbar, A.A.

2013-01-01

Laminar two-dimensional forced convective heat transfer of CuO-water and Al 2 O 3 -water nanofluids in a horizontal microchannel has been studied numerically, considering axial conduction effects in both solid and liquid regions and variable thermal conductivity and dynamic viscosity. The results show that using nanoparticles with higher thermal conductivities will intensify enhancement of heat transfer characteristics and slightly increases shear stress on the wall. The obtained results show more steep changes in Nusselt number for lower diameters and also higher values of Nusselt number by decreasing the diameter of nanoparticles. Also, by utilizing conduction number as the criterion, it was concluded from the results that adding nanoparticles will intensify the axial conduction effect in the geometry considered.

Specific heats of lunar surface materials from 90 to 350 degrees Kelvin

Science.gov (United States)

Robie, R.A.; Hemingway, B.S.; Wilson, W.H.

1970-01-01

The specific heats of lunar samples 10057 and 10084 returned by the Apollo 11 mission have been measured between 90 and 350 degrees Kelvin by use of an adiabatic calorimeter. The samples are representative of type A vesicular basalt-like rocks and of finely divided lunar soil. The specific heat of these materials changes smoothly from about 0.06 calorie per gram per degree at 90 degrees Kelvin to about 0.2 calorie per gram per degree at 350 degrees Kelvin. The thermal parameter ??=(k??C)-1/2 for the lunar surface will accordingly vary by a factor of about 2 between lunar noon and midnight.

Determination of the thermal conductivity and specific heat capacity of neem seeds by inverse problem method

Directory of Open Access Journals (Sweden)

S.N. Nnamchi

2010-01-01

Full Text Available Determination of the thermal conductivity and the specific heat capacity of neem seeds (Azadirachta indica A. Juss usingthe inverse method is the main subject of this work. One-dimensional formulation of heat conduction problem in a spherewas used. Finite difference method was adopted for the solution of the heat conduction problem. The thermal conductivityand the specific heat capacity were determined by least square method in conjunction with Levenberg-Marquardt algorithm.The results obtained compare favourably with those obtained experimentally. These results are useful in the analysis ofneem seeds drying and leaching processes.

On Thermally Interacting Multiple Boreholes with Variable Heating Strength: Comparison between Analytical and Numerical Approaches

Directory of Open Access Journals (Sweden)

Marc A. Rosen

2012-08-01

Full Text Available The temperature response in the soil surrounding multiple boreholes is evaluated analytically and numerically. The assumption of constant heat flux along the borehole wall is examined by coupling the problem to the heat transfer problem inside the borehole and presenting a model with variable heat flux along the borehole length. In the analytical approach, a line source of heat with a finite length is used to model the conduction of heat in the soil surrounding the boreholes. In the numerical method, a finite volume method in a three dimensional meshed domain is used. In order to determine the heat flux boundary condition, the analytical quasi-three-dimensional solution to the heat transfer problem of the U-tube configuration inside the borehole is used. This solution takes into account the variation in heating strength along the borehole length due to the temperature variation of the fluid running in the U-tube. Thus, critical depths at which thermal interaction occurs can be determined. Finally, in order to examine the validity of the numerical method, a comparison is made with the results of line source method.

A Plasma Diagnostic Set for the Study of a Variable Specific Impulse Magnetoplasma Rocket

Science.gov (United States)

Squire, J. P.; Chang-Diaz, F. R.; Bengtson Bussell, R., Jr.; Jacobson, V. T.; Wootton, A. J.; Bering, E. A.; Jack, T.; Rabeau, A.

1997-11-01

The Advanced Space Propulsion Laboratory (ASPL) is developing a Variable Specific Impulse Magnetoplasma Rocket (VASIMR) using an RF heated magnetic mirror operated asymmetrically. We will describe the initial set of plasma diagnostics and data acquisition system being developed and installed on the VASIMR experiment. A U.T. Austin team is installing two fast reciprocating probes: a quadruple Langmuir and a Mach probe. These measure electron density and temperature profiles, electrostatic plasma fluctuations, and plasma flow profiles. The University of Houston is developing an array of 20 highly directional Retarding Potential Analyzers (RPA) for measuring ion energy distribution function profiles in the rocket plume, giving a measurement of total thrust. We have also developed a CAMAC based data acquisition system using LabView running on a Power Macintosh communicating through a 2 MB/s serial highway. We will present data from initial plasma operations and discuss future diagnostic development.

Arctic Sea Ice Basal Melt Onset Variability and Associated Ocean Surface Heating

Science.gov (United States)

Merrick, R. A.; Hutchings, J. K.

2015-12-01

The interannual and regional variability in Arctic sea ice melt has previously been characterized only in terms of surface melting. A focus on the variability in the onset of basal melt is additionally required to understand Arctic melt patterns. Monitoring basal melt provides a glimpse into the importance of ocean heating to sea ice melt. This warming is predominantly through seawater exposure due to lead opening and the associated solar warming at the ocean's surface. We present the temporal variability in basal melt onset observed by ice mass balance buoys throughout the Arctic Ocean since 2003, providing a different perspective than the satellite microwave data used to measure the onset of surface melt. We found that melt onset varies greatly, even for buoys deployed within 100km of each other. Therefore large volumes of data are necessary to accurately estimate the variability of basal melt onset. Once the variability of basal melt onset has been identified, we can investigate how this range has been changing as a response to atmospheric and oceanic warming, changes in ice morphology as well as the intensification of the ice albedo feedback.

On the importance of specific heats as regards efficiency increases for highly dilute IC engines

International Nuclear Information System (INIS)

Caton, Jerald A.

2014-01-01

Highlights: • Importance of specific heats towards increasing engine efficiency was quantified. • Decreases of specific heats contribute 3.5–6.3% (abs) to the efficiency. • Dilute engines benefit from decreases of specific heats due to lower temperatures. - Abstract: Engineering and scientific efforts continue with the development of advanced, IC engines using highly dilute mixtures, and relatively high compression ratios. Such engines are known to provide opportunities for low emissions as well as high efficiencies. The main features of these engines include higher compression ratios, lean operation, use of EGR, and shorter burn durations. First, this study reviews the quantitative contributions of each of these features as determined by an engine cycle simulation. Second, this study provides the quantitative contributions to the increased efficiency in terms of fundamental thermodynamic considerations. An automotive engine operated at 2000 rpm was selected for this study. For the conditions examined, the net indicated thermal efficiency increased from 37.0% (conventional engine) to 53.9% (high efficiency engine) – for an incremental increase of 16.9% (absolute). The contribution of increases of the ratio of specific heats towards the final thermal efficiency is quantified. This aspect has been well known, but has not been quantified for actual engines. For the various conditions examined, 21–35% of the total efficiency improvement was estimated to be due to the increase of the ratio of specific heats

Pulsatile flow of blood and heat transfer with variable viscosity under magnetic and vibration environment

International Nuclear Information System (INIS)

Shit, G.C.; Majee, Sreeparna

2015-01-01

Unsteady flow of blood and heat transfer characteristics in the neighborhood of an overlapping constricted artery have been investigated in the presence of magnetic field and whole body vibration. The laminar flow of blood is taken to be incompressible and Newtonian fluid with variable viscosity depending upon temperature with an aim to provide resemblance to the real situation in the physiological system. The unsteady flow mechanism in the constricted artery is subjected to a pulsatile pressure gradient arising from systematic functioning of the heart and from the periodic body acceleration. The numerical computation has been performed using finite difference method by developing Crank–Nicolson scheme. The results show that the volumetric flow rate, skin-friction and the rate of heat transfer at the wall are significantly altered in the downstream of the constricted region. The axial velocity profile, temperature and flow rate increases with increase in temperature dependent viscosity, while the opposite trend is observed in the case of skin-friction and flow impedance. - Highlights: • We have investigated the pulsatile MHD flow of blood and heat transfer in arteries. • The influence of periodic body acceleration has been taken into account. • The temperature dependent viscosity of blood is considered. • The variable viscosity has an increasing effect on blood flow and heat transfer. • The overall temperature distribution enhances in the presence of magnetic field

Pulsatile flow of blood and heat transfer with variable viscosity under magnetic and vibration environment

Energy Technology Data Exchange (ETDEWEB)

Shit, G.C., E-mail: gopal_iitkgp@yahoo.co.in; Majee, Sreeparna

2015-08-15

Unsteady flow of blood and heat transfer characteristics in the neighborhood of an overlapping constricted artery have been investigated in the presence of magnetic field and whole body vibration. The laminar flow of blood is taken to be incompressible and Newtonian fluid with variable viscosity depending upon temperature with an aim to provide resemblance to the real situation in the physiological system. The unsteady flow mechanism in the constricted artery is subjected to a pulsatile pressure gradient arising from systematic functioning of the heart and from the periodic body acceleration. The numerical computation has been performed using finite difference method by developing Crank–Nicolson scheme. The results show that the volumetric flow rate, skin-friction and the rate of heat transfer at the wall are significantly altered in the downstream of the constricted region. The axial velocity profile, temperature and flow rate increases with increase in temperature dependent viscosity, while the opposite trend is observed in the case of skin-friction and flow impedance. - Highlights: • We have investigated the pulsatile MHD flow of blood and heat transfer in arteries. • The influence of periodic body acceleration has been taken into account. • The temperature dependent viscosity of blood is considered. • The variable viscosity has an increasing effect on blood flow and heat transfer. • The overall temperature distribution enhances in the presence of magnetic field.

Development of variable width ribbon heating elements for liquid metal and gas-cooled fast breeder reactor fuel rod simulators

International Nuclear Information System (INIS)

McCulloch, R.W.; Lovell, R.T.; Post, D.W.; Snyder, S.D.

1980-01-01

Variable width ribbon heating elements have been fabricated which provide a chopped cosine, variable heat flux profile for fuel rod simulators used in test loops by the Breeder Reactor Program Thermal Hydraulic Out-of-Reactor Safety test facility and the Gas-Cooled Fast Breeder Reactor Core Flow Test Loop. Thermal, mechanical, and electrical design considerations result in the derivation of an analytical expression for the ribbon contours. From this, the ribbons are machined and wound on numerically controlled equipment. Postprocessing and inspection results in a wound, variable width ribbon with the precise dimensional, electrical, and mechanical properties needed for use in fuel pin simulators

Technical Subtopic 2.1: Modeling Variable Refrigerant Flow Heat Pump and Heat Recovery Equipment in EnergyPlus

Energy Technology Data Exchange (ETDEWEB)

Raustad, Richard; Nigusse, Bereket; Domitrovic, Ron

2013-09-30

The University of Central Florida/Florida Solar Energy Center, in cooperation with the Electric Power Research Institute and several variable-refrigerant-flow heat pump (VRF HP) manufacturers, provided a detailed computer model for a VRF HP system in the United States Department of Energy's (U.S. DOE) EnergyPlus? building energy simulation tool. Detailed laboratory testing and field demonstrations were performed to measure equipment performance and compare this performance to both the manufacturer's data and that predicted by the use of this new model through computer simulation. The project goal was to investigate the complex interactions of VRF HP systems from an HVAC system perspective, and explore the operational characteristics of this HVAC system type within a laboratory and real world building environment. Detailed laboratory testing of this advanced HVAC system provided invaluable performance information which does not currently exist in the form required for proper analysis and modeling. This information will also be useful for developing and/or supporting test standards for VRF HP systems. Field testing VRF HP systems also provided performance and operational information pertaining to installation, system configuration, and operational controls. Information collected from both laboratory and field tests were then used to create and validate the VRF HP system computer model which, in turn, provides architects, engineers, and building owners the confidence necessary to accurately and reliably perform building energy simulations. This new VRF HP model is available in the current public release version of DOE?s EnergyPlus software and can be used to investigate building energy use in both new and existing building stock. The general laboratory testing did not use the AHRI Standard 1230 test procedure and instead used an approach designed to measure the field installed full-load operating performance. This projects test methodology used the air

Specific heat of V3GaH/sub x/

International Nuclear Information System (INIS)

Cort, B.; Stewart, G.R.; Huang, S.Z.; Meng, R.L.; Chu, C.W.

1981-01-01

Specific-heat measurements have been made on V 3 GaH/sub x/ for x = 0, 0.2, 1.4, and 1.9 in the temperature range 1.2--20 K. In addition to increased lattice parameter and depressed transition temperature with increased hydrogen concentrations, the Debye temperature increases and the electronic density of states drops, both dramatically. Decreased electron-phonon coupling is also indicated with hydrogenation

Long-term variability of heat waves in Argentina and recurrence probability of the severe 2008 heat wave in Buenos Aires

Czech Academy of Sciences Publication Activity Database

Rusticucci, M.; Kyselý, Jan; Almeira, G.; Lhotka, Ondřej

2016-01-01

Roč. 124, č. 3 (2016), s. 679-689 ISSN 0177-798X R&D Projects: GA MŠk 7AMB15AR001 Institutional support: RVO:68378289 Keywords : heat waves * long-term variability * climate extremes Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.640, year: 2016 http://link.springer.com/article/10.1007%2Fs00704-015-1445-7

An advanced straight tube heat exchanger in which a fluid flows at variable and elevated temperatures

International Nuclear Information System (INIS)

Mauget, C.; Benoit, G.; Stalport, G.

1993-01-01

Straight tube heat exchangers are used as steam generators in nuclear reactors such as in fast neutron nuclear power plants; elevated and highly variable temperatures induce very high thermal expansion constraints in these long straight tubes. In order to avoid the expansion problems, an expansion bellow is disposed between the heat exchanger and the collector tubular plate in such a way that the bundle differential expansions may be absorbed

Low-temperature specific-heat and thermal-conductivity of silica aerogels

DEFF Research Database (Denmark)

Bernasconi, A.; Sleator, T.; Posselt, D.

1992-01-01

Specific heat, C(p), and thermal conductivity, lambda, have been measured on a series of base-catalyzed silica aerogels at temperatures between 0.05 and 20 K. Results for both C(p)(T) and lambda(T) confirm that the different length-scale regions observed in the aerogel structure are reflected...

Numerical analysis of unsteady 3D flow of Carreau nanofluid with variable thermal conductivity and heat source/sink

Science.gov (United States)

Irfan, M.; Khan, M.; Khan, W. A.

Inspired by modern deeds of nanotechnology and nanoscience and their abundant applications in the field of science and engineering, we establish a mathematical relation for unsteady 3D forced convective flow of Carreau nanofluid over a bidirectional stretched surface. Heat transfer phenomena of Carreau nanofluid is inspected through the variable thermal conductivity and heat generation/absorption impact. Furthermore, this research paper presents a more convincing approach for heat and mass transfer phenomenon of nanoliquid by utilizing new mass flux condition. Practically, zero mass flux condition is more adequate because in this approach we assume nanoparticle amends itself accordingly on the boundaries. Now the features of Buongiorno's relation for Carreau nanofluid can be applied in a more efficient way. An appropriate transformation is vacant to alter the PDEs into ODEs and then tackled numerically by employing bvp4c scheme. The numerous consequence of scheming parameters on the Carreau nanoliquid velocity components, temperature and concentration fields are portrayed graphically and deliberated in detail. The numerical outcomes for local skin friction and the wall temperature gradient for nanoliquid are intended and vacant through tables. The outcomes conveyed here manifest that impact of Brownian motion parameter Nb on the rate of heat transfer for nanoliquids becomes negligible for the recently recommended revised relation. Addationally, for authentication of the present relation, the achieved results are distinguished with earlier research works in specific cases and marvelous agreement has been noted.

Theoretical approach to the phonon modes and specific heat of germanium nanowires

Energy Technology Data Exchange (ETDEWEB)

Trejo, A.; López-Palacios, L.; Vázquez-Medina, R.; Cruz-Irisson, M., E-mail: irisson@ipn.mx

2014-11-15

The phonon modes and specific heat of Ge nanowires were computed using a first principles density functional theory scheme with a generalized gradient approximation and finite-displacement supercell algorithms. The nanowires were modeled in three different directions: [001], [111], and [110], using the supercell technique. All surface dangling bonds were saturated with Hydrogen atoms. The results show that the specific heat of the GeNWs at room temperature increases as the nanowire diameter decreases, regardless the orientation due to the phonon confinement and surface passivation. Also the phonon confinement effects could be observed since the highest optical phonon modes in the Ge vibration interval shifted to a lower frequency compared to their bulk counterparts.

Numerical study of an innovative design of a finned double-pipe heat exchanger with variable fin-tip thickness

International Nuclear Information System (INIS)

Syed, K.S.; Ishaq, Muhammad; Iqbal, Zafar; Hassan, Ahmad

2015-01-01

Highlights: • Variable fin tip angle significantly effect the velocity and temperature distribution. • Significant gain in the thermal performance with decrease in the friction factor. • Variable fin tip angle must be considered an important parameter in designing finned annulus. - Abstract: The analysis of fully developed laminar convective heat transfer in an innovate design of a finned double-pipe heat exchanger (DPHE) with longitudinal fins of variable thickness of the tip subjected to the constant heat transfer rate boundary conditions is investigated here. The tip thickness is controlled by the ratio of tip to base angles as a parameter whose values varying from 0 to 1 correspond to the fin shapes varying from the triangular to the rectangular cross-section. Upto the knowledge of the authors, this parameter is being introduced for the first time in the literature. Discontinuous Galerkin finite element method (DG-FEM) has been employed in the present work. The overall performance of the proposed DPHE has been investigated by considering the friction factor, the Nusselt number and the j-factor. Upto 178% gain in the Nusselt number and 89% gain in the j-factor have been achieved relative to the rectangular cross-section. Such gains relative to the triangular cross-section are respectively 9.5% and 19%. The results indicate that the newly introduced parameter the ratio of tip to base angles has proved to play significant role in the design of a double-pipe heat exchanger in reducing the cost, weight and frictional loss, in improving the heat transfer rate and making the exchanger energy-efficient. Therefore, it must be considered as an important design parameter for heat exchanger design

Changes in cause-specific mortality during heat waves in central Spain, 1975-2008

Science.gov (United States)

Miron, Isidro Juan; Linares, Cristina; Montero, Juan Carlos; Criado-Alvarez, Juan Jose; Díaz, Julio

2015-09-01

The relationship between heat waves and mortality has been widely described, but there are few studies using long daily data on specific-cause mortality. This study is undertaken in central Spain and analysing natural causes, circulatory and respiratory causes of mortality from 1975 to 2008. Time-series analysis was performed using ARIMA models, including data on specific-cause mortality and maximum and mean daily temperature and mean daily air pressure. The length of heat waves and their chronological number were analysed. Data were stratified in three decadal stages: 1975-1985, 1986-1996 and 1997-2008. Heat-related mortality was triggered by a threshold temperature of 37 °C. For each degree that the daily maximum temperature exceeded 37 °C, the percentage increase in mortality due to circulatory causes was 19.3 % (17.3-21.3) in 1975-1985, 30.3 % (28.3-32.3) in 1986-1996 and 7.3 % (6.2-8.4) in 1997-2008. The increase in respiratory cause ranged from 12.4 % (7.8-17.0) in the first period, to 16.3 % (14.1-18.4) in the second and 13.7 % (11.5-15.9) in the last. Each day of heat-wave duration explained 5.3 % (2.6-8.0) increase in respiratory mortality in the first period and 2.3 % (1.6-3.0) in the last. Decadal scale differences exist for specific-causes mortality induced by extreme heat. The impact on heat-related mortality by natural and circulatory causes increases between the first and the second period and falls significantly in the last. For respiratory causes, the increase is no reduced in the last period. These results are of particular importance for the estimation of future impacts of climate change on health.

Low-temperature specific heat of YMn sub 2 in the paramagnetic and antiferromagnetic phases

Energy Technology Data Exchange (ETDEWEB)

Fisher, R.A.; Emerson, J.P.; Phillips, N.E. (Lawrence Berkeley Lab., CA (United States)); Ballou, R.; Lelievre-Berna, E. (Centre National de la Recherche Scientifique (CNRS), 38 - Grenoble (France). Lab. Louis Neel)

1992-07-01

The low-temperature specific heat of YMn{sub 2} has been measured at applied pressures of 0 to 7.7 kbar. A paramagnetic state is stabilized for moderate values of the applied pressure (of the order of 1.6 kbar). A large linear term in the specific heat, which decreases regularly with increasing pressure, is observed in this phase. It is ascribed to giant spin fluctuations associated with a magnetic-non magnetic instability and a strong geometrical spin frustration.

Specific heat of MgB_2 after irradiation

OpenAIRE

Wang, Yuxing; Bouquet, Frederic; Sheikin, Ilya; Toulemonde, Pierre; Revaz, Bernard; Eisterer, Michael; Weber, Harald W.; Hinderer, Joerg; Junod, Alain

2002-01-01

We studied the effect of disorder on the superconducting properties of polycrystalline MgB_2 by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2 Delta 0 / k_B T_c = 1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T_c and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutr...

Characterization of Machine Variability and Progressive Heat Treatment in Selective Laser Melting of Inconel 718

Science.gov (United States)

Prater, Tracie; Tilson, Will; Jones, Zack

2015-01-01

The absence of an economy of scale in spaceflight hardware makes additive manufacturing an immensely attractive option for propulsion components. As additive manufacturing techniques are increasingly adopted by government and industry to produce propulsion hardware in human-rated systems, significant development efforts are needed to establish these methods as reliable alternatives to conventional subtractive manufacturing. One of the critical challenges facing powder bed fusion techniques in this application is variability between machines used to perform builds. Even with implementation of robust process controls, it is possible for two machines operating at identical parameters with equivalent base materials to produce specimens with slightly different material properties. The machine variability study presented here evaluates 60 specimens of identical geometry built using the same parameters. 30 samples were produced on machine 1 (M1) and the other 30 samples were built on machine 2 (M2). Each of the 30-sample sets were further subdivided into three subsets (with 10 specimens in each subset) to assess the effect of progressive heat treatment on machine variability. The three categories for post-processing were: stress relief, stress relief followed by hot isostatic press (HIP), and stress relief followed by HIP followed by heat treatment per AMS 5664. Each specimen (a round, smooth tensile) was mechanically tested per ASTM E8. Two formal statistical techniques, hypothesis testing for equivalency of means and one-way analysis of variance (ANOVA), were applied to characterize the impact of machine variability and heat treatment on six material properties: tensile stress, yield stress, modulus of elasticity, fracture elongation, and reduction of area. This work represents the type of development effort that is critical as NASA, academia, and the industrial base work collaboratively to establish a path to certification for additively manufactured parts. For future

Magnetic ordering and specific heat analysis of TmPtSn

Czech Academy of Sciences Publication Activity Database

Vejpravová, J.; Svoboda, P.; Šebek, Josef; Janeček, M.; Komatsubara, T.

2003-01-01

Roč. 328, - (2003), s. 142-144 ISSN 0921-4526 R&D Projects: GA ČR GA106/02/0943 Grant - others:GA UK(CZ) 165/01; VACUUM PRAHA(CZ) 2002 Keywords : rare-earth intermetallic compounds * magnetic ordering * specific heat Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.908, year: 2003

Specific heat of 4He and 3He--4He mixtures at their lambda transition

International Nuclear Information System (INIS)

Gasparini, F.M.; Moldover, M.R.

1975-01-01

We have measured the specific heat near the lambda transition of pure 4 He and of five 3 He-- 4 He mixtures up to a mole fraction of 0.39 3 He in 4 He. Our data for 4 He confirm the results of Ahlers revealing an asymmetry in the exponents above and below T/sub lambda/ when the specific heat is represented by a simple-power-law temperature dependence. Our results for these exponents (α = 0.012 plus-or-minus 0.002 and α' = -0.012 plus-or-minus 0.004) differ somewhat from Ahlers's. Our results can be reconciled with the requirement of scaling (α = α') only by supposing substantial contributions to C/sub p/ are made by singular correction terms to a simple power law. The measured specific heat of the mixtures richest in 3 He appears to be finite, continuous, and cusped at the lambda line. These qualitative features have been termed ''renormalization'' by Fisher. An analysis of our mixture data with a power-law temperature dependence does not yield a fully renormalized exponent, but rather an effective exponent. Derivatives at the lambda line were used to calculate the specific heat along paths of constant pressure and constant relative chemical potential.This specific heat behaves very much like C/sub p/ of pure 4 He, this behavior supporting the idea of universality for the specific-heat exponents. It is also true that the same asymmetry in the branches above and below T/sub lambda/ which is []bserved in pure 4 He is retained in the mixtures. The persistence of the asymmetry of C/subp//sub phi/ as one moves along the lambda line towards increasing 3 He concentration (at the saturated vapor pressure of the mixtures) is analogous to the persistence of the asymmetry of C/subp/ as one moves along the lambda line towards increasing pressure in pure 4 He

Analysis of Cattaneo-Christov heat and mass fluxes in the squeezed flow embedded in porous medium with variable mass diffusivity

Directory of Open Access Journals (Sweden)

M. Farooq

Full Text Available This research article investigates the squeezing flow of Newtonian fluid with variable viscosity over a stretchable sheet inserted in Darcy porous medium. Cattaneo-Christov double diffusion models are implemented to scrutinize the characteristics of heat and mass transfer via variable thermal conductivity and variable mass diffusivity. These models are the modification of conventional laws of Fourier’s and Fick’s via thermal and solutal relaxation times respectively. The homotopy analysis Method (HAM is being utilized to provide the solution of highly nonlinear system of coupled partial differential equations after converted into dimensionless governing equations. The behavior of flow parameters on velocity, concentration, and temperature distributions are sketched and analyzed physically. The result indicates that both concentration and temperature distributions decay for higher solutal and thermal relaxation parameters respectively. Keywords: Squeezing flow, Porous medium, Variable viscosity, Cattaneo-Christov heat and mass flux models, Variable thermal conductivity, Variable mass diffusivity

Quantifying Livestock Heat Stress Impacts in the Sahel

Science.gov (United States)

Broman, D.; Rajagopalan, B.; Hopson, T. M.

2014-12-01

Livestock heat stress, especially in regions of the developing world with limited adaptive capacity, has a largely unquantified impact on food supply. Though dominated by ambient air temperature, relative humidity, wind speed, and solar radiation all affect heat stress, which can decrease livestock growth, milk production, reproduction rates, and mortality. Indices like the thermal-humidity index (THI) are used to quantify the heat stress experienced from climate variables. Livestock experience differing impacts at different index critical thresholds that are empirically determined and specific to species and breed. This lack of understanding has been highlighted in several studies with a limited knowledge of the critical thresholds of heat stress in native livestock breeds, as well as the current and future impact of heat stress,. As adaptation and mitigation strategies to climate change depend on a solid quantitative foundation, this knowledge gap has limited such efforts. To address the lack of study, we have investigated heat stress impacts in the pastoral system of Sub-Saharan West Africa. We used a stochastic weather generator to quantify both the historic and future variability of heat stress. This approach models temperature, relative humidity, and precipitation, the climate variables controlling heat stress. Incorporating large-scale climate as covariates into this framework provides a better historical fit and allows us to include future CMIP5 GCM projections to examine the climate change impacts on heat stress. Health and production data allow us to examine the influence of this variability on livestock directly, and are considered in conjunction with the confounding impacts of fodder and water access. This understanding provides useful information to decision makers looking to mitigate the impacts of climate change and can provide useful seasonal forecasts of heat stress risk. A comparison of the current and future heat stress conditions based on

Measurement of the specific heats of Santowax 'R', para-, meta- and ortho-terphenyl, diphenyl and dowtherm 'A'

International Nuclear Information System (INIS)

Bowring, R.W.; Garton, D.A.; Norris, H.F.

1960-12-01

New absolute measurements have been made of the specific heats of Santowax 'R1, the terphenyl isomers, diphenyl and Dowtherm 'A'. An adiabatic calorimeter was used in which the sample was heated electrically while a surrounding jacket was maintained at the same temperature as the calorimeter. The specific heats of all materials tested were found to increase linearly with temperature, the slope being substantially the same for all the pure materials except para-terphenyl. The specific heat of Santowax 'R' was about 1/2% less than the weighted mean of its components. The probable accuracy of the measurements was ± 2% and this was confirmed by comparison with diphenyl ether. A summary of results is given in Table 1 and Figure 10. (author)

Technical specifications for the provision of heat and steam sources for INPP and Visaginas. Final report

International Nuclear Information System (INIS)

2003-01-01

In October 1999, the National Energy Strategy was approved by the Lithuanian Parliament. The National Energy Strategy included the decision to close Unit-1 of INPP before 2005. Later is has been decided to close Unit 2 before the end of 2009 as well. The closure and decommissioning will have heavy impact on the heat supply for the city of Visaginas. Unit 1 and Unit 2 of INPP supplies hot water and steam to INPP for process purposes and for space heating of residential and commercial buildings. When Unit 1 is permanently shut down, reliable heat and steam sources independent of the power plants own heat and steam generation facilities are required for safety reasons in the event of shutdown of the remaining unit for maintenance or in an emergency. These steam and heat sources must be operational before single unit operation is envisaged. Provision of a reliable independent heat and steam source is therefore urgent. After both reactors are shut down permanently, a steam source will be needed at the plant for radioactive waste storage and disposal. INPP and DEA has performed a feasibility study for the provision of a reliable heat source for Ignalina Nuclear Power Plant and Visaginas, and the modernisation of Visaginas district heating system. The objective of this project is to prepare technical specifications for the provision of new heat and steam sources for INPP and Visaginas, and for rehabilitation of the heat transmission pipeline between INPP, the back-up boiler station and Visaginas City. The results of the study are presented in detail in the reports and technical specifications: 1. Transient analysis for Visaginas DH system, 2. Non-destructive testing of boiler stations, pump stations and transmission lines, 3. Conceptual design, 4. Technical specifications, Package 1 to 6. The study has suggested: 1. Construction of new steam boiler station, 2. Construction of new heat only boiler station, 3. Renovation of existing back-up heat only boiler station, 4

Variable electricity and steam from salt, helium and sodium cooled base-load reactors with gas turbines and heat storage - 15115

International Nuclear Information System (INIS)

Forsberg, C.; McDaniel, P.; Zohuri, B.

2015-01-01

Advances in utility natural-gas-fired air-Brayton combed cycle technology is creating the option of coupling salt-, helium-, and sodium-cooled nuclear reactors to Nuclear air-Brayton Combined Cycle (NACC) power systems. NACC may enable a zero-carbon electricity grid and improve nuclear power economics by enabling variable electricity output with base-load nuclear reactor operations. Variable electricity output enables selling more electricity at times of high prices that increases plant revenue. Peak power is achieved using stored heat or auxiliary fuel (natural gas, bio-fuels, hydrogen). A typical NACC cycle includes air compression, heating compressed air using nuclear heat and a heat exchanger, sending air through a turbine to produce electricity, reheating compressed air, sending air through a second turbine, and exhausting to a heat recovery steam generator (HRSG). In the HRSG, warm air produces steam that is used to produce added electricity. For peak power production, auxiliary heat (natural gas, stored heat) is added before the air enters the second turbine to raise air temperatures and power output. Like all combined cycle plants, water cooling requirements are dramatically reduced relative to other power cycles because much of the heat rejection is in the form of hot air. (authors)

Site-specific variability of loess and palaeosols (Ruma, Vojvodina, northern Serbia)

NARCIS (Netherlands)

Vandenberghe, J.; Markovic, S.B.; Jovanovic, M.; Hambach, U.

2013-01-01

The study of temporal variations in soil intensity has mostly been limited to specific sites. However, it is important for correctly interpreting the stratigraphy and palaeoclimatic significance of loess and palaeosols series to understand the reasons for the spatial variability. More specifically,

Short-term variability of surface heat budget of the east central Arabian Sea during November, 1992

Digital Repository Service at National Institute of Oceanography (India)

Subrahmanyam, B.; Murty, V.S.N.; Rao, L.V.G.

The analysis of surface meteorological data collected from the east central Arabian Sea during 10-28 November, 1992 revealed considerable variability in the meteorological parameters and heat budget components on both daily and diurnal time scales...

Diurnal and vertical variability of the sensible heat and carbon dioxide budgets in the atmospheric surface layer

International Nuclear Information System (INIS)

Casso-Torralba, P.; Rosa Soler, M.; Vila-Guerau de Arellano, J.; Bosveld, F.; Vermeulen, A.; Werner, C.; Moors, E.

2008-08-01

The diurnal and vertical variability of heat and carbon dioxide (CO2) in the atmospheric surface layer are studied by analyzing measurements from a 213 m tower in Cabauw (Netherlands). Observations of thermodynamic variables and CO2 mixing ratio as well as vertical profiles of the turbulent fluxes are used to retrieve the contribution of the budget terms in the scalar conservation equation. On the basis of the daytime evolution of turbulent fluxes, we calculate the budget terms by assuming that turbulent fluxes follow a linear profile with height. This assumption is carefully tested and the deviation from linearity is quantified. The budget calculation allows us to assess the importance of advection of heat and CO2 during day hours for three selected days. It is found that, under nonadvective conditions, the diurnal variability of temperature and CO2 is well reproduced from the flux divergence measurements. Consequently, the vertical transport due to the turbulent flux plays a major role in the daytime evolution of both scalars and the advection is a relatively small contribution. During the analyzed days with a strong contribution of advection of either heat or carbon dioxide, the flux divergence is still an important contribution to the budget. For heat, the quantification of the advection contribution is in close agreement with results from a numerical model. For carbon dioxide, we qualitatively corroborate the results with a Lagrangian transport model. Our estimation of advection is compared with traditional estimations based on the Net Ecosystem-atmosphere Exchange (NEE)

Experimental study of R134a/R410A cascade cycle for variable refrigerant flow heat pump systems

International Nuclear Information System (INIS)

Kim, Jeong Hun; Lee, Jae Wan; Park, Warn Gyu; Choi, Hwan Jong; Lee, Sang Hun; Oh, Sai Kee

2015-01-01

Cascade cycle is widely applied to heat pumps operating at low ambient temperature to overcome problems such as low heating capacity and Coefficient of performance (COP) deterioration A number of researches have been conducted on cascade cycle heat pumps, but most of those studies were focused on system optimization to determine optimal intermediate temperature in air-to-water heat pumps. However, experimental optimization in regard to air and water heating simultaneously using a cascade cycle has been an understudied area. Therefore, we focused on experimental analysis for a cascade system with Variable refrigerant flow (VRF) heat pumps. Experiments were conducted under a variety of operating conditions, such as ambient and water inlet temperature. COP increased up to 16% when water inlet temperature decreased. COP of VRF heat pumps with cascade cycle is three-times higher compared with conventional boilers as well as 17% higher compared to single heat pumps

The DNA electronic specific heat at low temperature: The role of aperiodicity

Energy Technology Data Exchange (ETDEWEB)

Sarmento, R.G. [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Mendes, G.A. [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Albuquerque, E.L., E-mail: eudenilson@gmail.com [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Fulco, U.L. [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Vasconcelos, M.S. [Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Ujsághy, O. [Department of Theoretical Physics and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budapest University of Technology and Economics, Budafoki út 8, H-1521 Budapest (Hungary); Freire, V.N. [Departamento de Física, Universidade Federal do Ceará, 60455-760, Fortaleza, CE (Brazil); Caetano, E.W.S. [Instituto Federal de Educação, Ciência e Tecnologia do Ceará, 60040-531, Fortaleza, CE (Brazil)

2012-07-16

The electronic specific heat spectra at constant volume (C{sub V}) of a long-range correlated extended ladder model, mimicking a DNA molecule, is theoretically analyzed for a stacked array of a double-stranded structure made up from the nucleotides guanine G, adenine A, cytosine C and thymine T. The role of the aperiodicity on C{sub V} is discussed, considering two different nucleotide arrangements with increasing disorder, namely the Fibonacci and the Rudin–Shapiro quasiperiodic structures. Comparisons are made for different values of the band fillings, considering also a finite segment of natural DNA, as part of the human chromosome Ch22. -- Highlights: ► Quasiperiodic sequence to mimic the DNA nucleotides arrangement. ► Electronic tight-binding Hamiltonian model. ► Electronic density of states. ► Electronic specific heat spectra.

Specific heat and magnetization of a ZrB12 single crystal: characterization of a type II/1 superconductor

OpenAIRE

Wang, Yuxing; Lortz, Rolf; Paderno, Yuriy; Filippov, Vladimir; Abe, Satoko; Tutsch, Ulrich; Junod, Alain

2005-01-01

We measured the specific heat, the magnetization, and the magnetoresistance of a single crystal of ZrB12, which is superconducting below Tc ~ 6 K. The specific heat in zero field shows a BCS-type superconducting transition. The normal- to superconducting-state transition changes from first order (with a latent heat) to second order (without latent heat) with increasing magnetic field, indicating that the pure compound is a low-kappa, type-II/1 superconductor in the classification of Auer and ...

Determination of the specific heat petroleum derivates; Determinacao do calor especifico de derivados ultrapesados de petroleo

Energy Technology Data Exchange (ETDEWEB)

Ballesteros Hernandez, Julie A.; Zuniga Linan, Lamia; Jardini, Andre; Maciel, Maria Regina Wolf; Maciel Filho, Rubens Maciel [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Faculdade de Engenharia Quimica; Medina, Lilian Carmen [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)

2008-07-01

In the development of the specific mathematical modeling for heavy and ultra heavy petroleum fractions in a molecular distiller is very important the definition of physical and chemical parameters as density and specific heat of the mixture, the enthalpy of vaporization, among others, since they are used in the energy balance. Information on these properties and their variation with temperature are found in the open literature for mixture with few components (simple mixtures). However, for multicomponent solutions consisting of complex mixtures such as oil and its heavy and ultraheavy fractions, available data are few, or are limited to low temperatures. The specific heat is an important property in the energy balance. This property can be measured by Differential Scanning Calorimetry (DSC), which gives results with great sensitivity and accuracy. This paper presents the variation of specific heat with the temperature of ultra-heavy oil fractions in the range from 80 deg to 350 deg C . Through the study of this variation, the equation nowadays used can be adjusted, in order to determine the specific heat. New values of the constants are determined, so that the equation can be used for these complex products, optimizing the estimative of Cp and so no experimental data are always necessary for simulations. (author)

Fractional derivatives of constant and variable orders applied to anomalous relaxation models in heat transfer problems

Directory of Open Access Journals (Sweden)

Yang Xiao-Jun

2017-01-01

Full Text Available In this paper, we address a class of the fractional derivatives of constant and variable orders for the first time. Fractional-order relaxation equations of constants and variable orders in the sense of Caputo type are modeled from mathematical view of point. The comparative results of the anomalous relaxation among the various fractional derivatives are also given. They are very efficient in description of the complex phenomenon arising in heat transfer.

Unsteady Flow of Reactive Viscous, Heat Generating/Absorbing Fluid with Soret and Variable Thermal Conductivity

Directory of Open Access Journals (Sweden)

I. J. Uwanta

2014-01-01

Full Text Available This study investigates the unsteady natural convection and mass transfer flow of viscous reactive, heat generating/absorbing fluid in a vertical channel formed by two infinite parallel porous plates having temperature dependent thermal conductivity. The motion of the fluid is induced due to natural convection caused by the reactive property as well as the heat generating/absorbing nature of the fluid. The solutions for unsteady state temperature, concentration, and velocity fields are obtained using semi-implicit finite difference schemes. Perturbation techniques are used to get steady state expressions of velocity, concentration, temperature, skin friction, Nusselt number, and Sherwood number. The effects of various flow parameters such as suction/injection (γ, heat source/sinks (S, Soret number (Sr, variable thermal conductivity δ, Frank-Kamenetskii parameter λ, Prandtl number (Pr, and nondimensional time t on the dynamics are analyzed. The skin friction, heat transfer coefficients, and Sherwood number are graphically presented for a range of values of the said parameters.

Specific heat measurements in KCN:KCL mixed crystals

International Nuclear Information System (INIS)

Ghivelder, L.

1983-01-01

An adiabatic calorimeter to perform specific heat measurements of small samples (approximatelly 150 mg) was built. The measurements were taken from 6 to 120 K, iN KCN:KCL mixed crystals, in order to observe the evolution of the antiferroelectric phase transition - that occurs at 83 K in KCN pure. From the experimental results the values of the phase transition critical temperature are found, for some particular concentrations of the mixture, and it was detected that this phase transition disappears with only 10% of Cl - . This result is explained in terms of a change of the potential wells in the crystal. (Author) [pt

Variability of the ocean heat content during the last millennium – an assessment with the ECHO-g Model

Directory of Open Access Journals (Sweden)

P. Ortega

2013-03-01

Full Text Available Studies addressing climate variability during the last millennium generally focus on variables with a direct influence on climate variability, like the fast thermal response to varying radiative forcing, or the large-scale changes in atmospheric dynamics (e.g. North Atlantic Oscillation. The ocean responds to these variations by slowly integrating in depth the upper heat flux changes, thus producing a delayed influence on ocean heat content (OHC that can later impact low frequency SST (sea surface temperature variability through reemergence processes. In this study, both the externally and internally driven variations of the OHC during the last millennium are investigated using a set of fully coupled simulations with the ECHO-G (coupled climate model ECHAMA4 and ocean model HOPE-G atmosphere–ocean general circulation model (AOGCM. When compared to observations for the last 55 yr, the model tends to overestimate the global trends and underestimate the decadal OHC variability. Extending the analysis back to the last one thousand years, the main impact of the radiative forcing is an OHC increase at high latitudes, explained to some extent by a reduction in cloud cover and the subsequent increase of short-wave radiation at the surface. This OHC response is dominated by the effect of volcanism in the preindustrial era, and by the fast increase of GHGs during the last 150 yr. Likewise, salient impacts from internal climate variability are observed at regional scales. For instance, upper temperature in the equatorial Pacific is controlled by ENSO (El Niño Southern Oscillation variability from interannual to multidecadal timescales. Also, both the Pacific Decadal Oscillation (PDO and the Atlantic Multidecadal Oscillation (AMO modulate intermittently the interdecadal OHC variability in the North Pacific and Mid Atlantic, respectively. The NAO, through its influence on North Atlantic surface heat fluxes and convection, also plays an important role on

Single-crystal Brillouin spectroscopy with CO{sub 2} laser heating and variable q

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jin S.; Bass, Jay D. [Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Zhu, Gaohua [Materials Research Department, Toyota Research Institute of North America, Ann Arbor, Michigan 48105 (United States)

2015-06-15

We describe a Brillouin spectroscopy system integrated with CO{sub 2} laser-heating and Raman spectroscopic capabilities. Temperature is determined by measurements of the grey-body thermal radiation emitted by the hot sample, with the system response calibrated relative to a standard tungsten ribbon lamp. High-pressure laser-heating Brillouin scattering measurements of acoustic velocities on liquid water and ice compressed in a diamond-anvil cell were performed at temperatures up to 2500 ± 150 K at high pressure. Single-crystal laser-heating Brillouin measurements were made on the (111) plane of San Carlos olivine at ∼13 GPa, 1300 ± 200 K. The pressure as measured by ruby fluorescence is shown to be within ±0.5 GPa of the pressure on the olivine sample during laser heating when KCl and KBr are used as pressure-transmitting media. In addition, the system is designed for continuously variable scattering angles from forward scattering (near 0° scattering angle) up to near back scattering (∼141°). This novel setup allows us to probe a wide range of wave vectors q for investigation of phonon dispersion on, for example, crystals with large unit cells (on the scale of hundreds of nm)

Country-Specific Effects of Climate Variability on Human Migration

Science.gov (United States)

Gray, Clark; Wise, Erika

2016-01-01

Involuntary human migration is among the social outcomes of greatest concern in the current era of global climate change. Responding to this concern, a growing number of studies have investigated the consequences of short to medium-term climate variability for human migration using demographic and econometric approaches. These studies have provided important insights, but at the same time have been significantly limited by lack of expertise in the use of climate data, access to cross-national data on migration, and attention to model specification. To address these limitations, we link data on internal and international migration over a 6-year period from 9,812 origin households in Kenya, Uganda, Nigeria, Burkina Faso and Senegal to high-resolution gridded climate data from both station and satellite sources. Analyses of these data using several plausible specifications reveal that climate variability has country-specific effects on migration: Migration tends to increase with temperature anomalies in Uganda, tends to decrease with temperature anomalies in Kenya and Burkina Faso, and shows no consistent relationship with temperature in Nigeria and Senegal. Consistent with previous studies, precipitation shows weak and inconsistent relationships with migration across countries. These results challenge generalizing narratives that foresee a consistent migratory response to climate change across the globe. PMID:27092012

Country-Specific Effects of Climate Variability on Human Migration.

Science.gov (United States)

Gray, Clark; Wise, Erika

2016-04-01

Involuntary human migration is among the social outcomes of greatest concern in the current era of global climate change. Responding to this concern, a growing number of studies have investigated the consequences of short to medium-term climate variability for human migration using demographic and econometric approaches. These studies have provided important insights, but at the same time have been significantly limited by lack of expertise in the use of climate data, access to cross-national data on migration, and attention to model specification. To address these limitations, we link data on internal and international migration over a 6-year period from 9,812 origin households in Kenya, Uganda, Nigeria, Burkina Faso and Senegal to high-resolution gridded climate data from both station and satellite sources. Analyses of these data using several plausible specifications reveal that climate variability has country-specific effects on migration: Migration tends to increase with temperature anomalies in Uganda, tends to decrease with temperature anomalies in Kenya and Burkina Faso, and shows no consistent relationship with temperature in Nigeria and Senegal. Consistent with previous studies, precipitation shows weak and inconsistent relationships with migration across countries. These results challenge generalizing narratives that foresee a consistent migratory response to climate change across the globe.

Performance analysis and comparison of an Atkinson cycle coupled to variable temperature heat reservoirs under maximum power and maximum power density conditions

International Nuclear Information System (INIS)

Wang, P.-Y.; Hou, S.-S.

2005-01-01

In this paper, performance analysis and comparison based on the maximum power and maximum power density conditions have been conducted for an Atkinson cycle coupled to variable temperature heat reservoirs. The Atkinson cycle is internally reversible but externally irreversible, since there is external irreversibility of heat transfer during the processes of constant volume heat addition and constant pressure heat rejection. This study is based purely on classical thermodynamic analysis methodology. It should be especially emphasized that all the results and conclusions are based on classical thermodynamics. The power density, defined as the ratio of power output to maximum specific volume in the cycle, is taken as the optimization objective because it considers the effects of engine size as related to investment cost. The results show that an engine design based on maximum power density with constant effectiveness of the hot and cold side heat exchangers or constant inlet temperature ratio of the heat reservoirs will have smaller size but higher efficiency, compression ratio, expansion ratio and maximum temperature than one based on maximum power. From the view points of engine size and thermal efficiency, an engine design based on maximum power density is better than one based on maximum power conditions. However, due to the higher compression ratio and maximum temperature in the cycle, an engine design based on maximum power density conditions requires tougher materials for engine construction than one based on maximum power conditions

Climate variability of heat wave and projection of warming scenario in Taiwan

Science.gov (United States)

Lin, C. Y.; Chien, Y. Y.; Su, C. J.

2017-12-01

This study examined the climate variability of heat wave (HW) according to air temperature and relative humidity to determine trends of variation and stress threshold in three major cities of Taiwan, Taipei (TP), Taichung (TC) and Kaohsiung (KH), during in the past four decades (1971-2010). According to data available, the wet-bulb globe temperature (WBGT) heat stress for the three studied cities was also calculated for the past (2003-2012) and simulated under the projected warming scenario for the end of this century (2075-2099) using ECHAM5/MPIOM-WRF (ECW) dynamic downscaling 5-km resolution Analysis showed that past decade (2001-2010) saw increase not only in number of HW days in all three cities but also the duration of each HW event in TP and KH. Simulation results revealed that ECW captures well the characteristics of data distribution in these three cities during 2003-2012. Under the A1B projection, ECW yielded higher WBGT in all three cities for 2075-2099. The WBGT in TP indicated that the heat stress for 50% of the days in July and August by 2075-2099 will be at danger level (WBGT ³ 31 °C). Even the median WBGT in TC and KH (30.91°C and 30.88°C, respectively), are close to 31°C. Hence, the heat stress in all three cities will either exceed or approach the danger level by the end of this century. Such projection under the global warming trend would necessitate adaptation and mitigation, and the huge impact of dangerous heat stress on public health merits urgent attention for Taiwan.

Quantifying the influence of land-use and surface characteristics on spatial variability in the urban heat island

Science.gov (United States)

Hart, Melissa A.; Sailor, David J.

2009-03-01

The urban thermal environment varies not only from its rural surroundings but also within the urban area due to intra-urban differences in land-use and surface characteristics. Understanding the causes of this intra-urban variability is a first step in improving urban planning and development. Toward this end, a method for quantifying causes of spatial variability in the urban heat island has been developed. This paper presents the method as applied to a specific test case of Portland, Oregon. Vehicle temperature traverses were used to determine spatial differences in summertime ~2 m air temperature across the metropolitan area in the afternoon. A tree-structured regression model was used to quantify the land-use and surface characteristics that have the greatest influence on daytime UHI intensity. The most important urban characteristic separating warmer from cooler regions of the Portland metropolitan area was canopy cover. Roadway area density was also an important determinant of local UHI magnitudes. Specifically, the air above major arterial roads was found to be warmer on weekdays than weekends, possibly due to increased anthropogenic activity from the vehicle sector on weekdays. In general, warmer regions of the city were associated with industrial and commercial land-use. The downtown core, whilst warmer than the rural surroundings, was not the warmest part of the Portland metropolitan area. This is thought to be due in large part to local shading effects in the urban canyons.

Specific heat of the Ising linear chain in a Random field

International Nuclear Information System (INIS)

Silva, P.R.; Sa Barreto, F.C. de

1984-01-01

Starting from correlation identities for the Ising model the effect of a random field on the one dimension version of the model is studied. Explicit results for the magnetization, the two-particle correlation function and the specific heat are obtained for an uncorrelated distribution of the random fields. (Author) [pt

An analysis of boundary-effects in obtaining the frequency dependent specific heat by effusivity measurements

DEFF Research Database (Denmark)

Christensen, Tage Emil; Behrens, Claus

The frequency dependent specific heat is a significant response function characterizing the glass transition. Contrary to the dielectric response it is not easily measured over many decades. The introduction of the 3-omega method, where the temperature oscillations at a planar oscillatoric heat g...

Estimating heat-to-heat variation from a statistician's point of view

International Nuclear Information System (INIS)

Hebble, T.L.

1976-01-01

Heat-to-heat variability is the change in results that occurs when the same tests under the same conditions are applied to samples from different heats of the same material. Heat-to-heat variability reflects, among other things, difference in chemistry and in processing history. Published Japanese tensile and creep tests on types 304 and 316 stainless steel tube are used to illustrate the analysis of variance technique as a tool for isolating heat-to-heat variation. The importance of the underlying model and the role of replication are indicated. Finally, confidence intervals and tolerance limits are computed from numerical estimates of heat-to-heat variation. 17 tables

A new experimental method to determine specific heat capacity of inhomogeneous concrete material with incorporated microencapsulated-PCM

DEFF Research Database (Denmark)

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

2014-01-01

PCM. This paper describes the development of the new material and the experimental set-up to determine the specific heat capacity of the PCM concrete material. Moreover, various methods are proposed and compared to calculate the specific heat capacity of the PCM concrete. Finally, it is hoped......The study presented in this paper focuses on an experimental investigation of the specific heat capacity as a function of the temperature Cp (T) of concrete mixed with various amounts of phase change material (PCM). The tested specimens are prepared by directly mixing concrete and microencapsulated...... that this work can be used as an inspiration and guidance to perform measurements on the various composite materials containing PCM....

Hyperfine coupling in gadolinium-praseodymium alloys by specific heat measurements

International Nuclear Information System (INIS)

Michel, J.

1969-01-01

We have studied the hyperfine coupling in gadolinium-praseodymium alloys by specific heat measurements down to 0.3 K. In the first part we describe the apparatus used to perform our measurements. The second part is devoted to some theoretical considerations. We have studied in detail the case of praseodymium which is an exception in the rare earth series. The third part shows the results we have obtained. (author) [fr

Causes of intraseasonal diabatic heating variability over and near the Tibetan Plateau in boreal summer

Science.gov (United States)

Yang, Shuangyan; Li, Tim

2017-10-01

The structure and evolution features of the first two leading modes of the intraseasonal diabatic heating variability over the Tibetan Plateau (TP) during northern summer are investigated using reanalysis and observational data. Both of the leading modes present a dominant 10-30-day intraseasonal oscillation (ISO). The first mode is characterized by a perturbation center over the southern TP (STP), which remains quasi-stationary and is closely related to the low-latitude ISO. The associated low-latitude ISO is originated from the tropical western Pacific (WP) and propagates westward/northwestward toward northwestern India along the mean monsoon trough. The westward propagation near the South China Sea is mainly attributed to anomalous meridional vorticity advection and the advection of the planetary vorticity by ISO flow. The stationary feature of the perturbation over the STP is ascribed to the topographical features around the STP. The intraseasonal heating variability over the STP is attributed to the alternation of anticyclonic and cyclonic flow associated with the westward-propagating ISO perturbation originated from the tropical WP. The second leading mode is characterized by an east-west asymmetric structure over the TP. The intraseasonal diabatic heating anomaly propagates clockwise from the northwestern to eastern TP, while a heating anomaly with an opposite sign propagates from the southeastern to western TP. The mid-latitude Rossby wave trains play an essential role in forming the dipole structure. The wave trains propagate southeastward before reaching the TP and then eastward as they cross the TP. The source of anomalous water vapor over the TP is originated from lower latitudes. The upper- and lower-level wave trains are well coupled over the TP, exhibiting a baroclinic structure.

Generic Guide Specification for Geothermal Heat Pump Systems

Energy Technology Data Exchange (ETDEWEB)

Thomas, WKT

2000-04-12

The attached Geothermal (Ground-Source) Heat Pump (GHP) Guide Specifications have been developed by Oak Ridge National Laboratory (ORNL) with the intent to assist federal agency sites and engineers in the preparation of construction specifications for GHP projects. These specifications have been developed in the industry-standard Construction Specification Institute (CSI) format and cover several of the most popular members of the family of GHP systems. These guide specifications are applicable to projects whether the financing is with conventional appropriations, arranged by GHP specialty ESCOs under the U.S. Department of Energy's Technology-Specific GHP Super ESPCs, arranged by utilities under Utility Energy Service Contracts (UESCs) or arranged by generalist ESCOs under the various regional ESPCs. These specifications can provide several benefits to the end user that will help ensure successful GHP system installations. GHP guide specifications will help to streamline the specification development, review, and approval process because the architecture and engineering (AE) firm will be working from the familiar CSI format instead of developing the specifications from other sources. The guide specifications help to provide uniformity, standardization, and consistency in both the construction specifications and system installations across multiple federal sites. This standardization can provide future benefits to the federal sites in respect to both maintenance and operations. GHP guide specifications can help to ensure that the agency is getting its money's worth from the GHP system by preventing the use of marginal or inferior components and equipment. The agency and its AE do not have to start from scratch when developing specifications and can use the specification as a template and/or a checklist in developing both the design and the contract documents. The guide specifications can save project costs by reducing the engineering effort required

Design of a High Temperature Radiator for the Variable Specific Impulse Magnetoplasma Rocket

Science.gov (United States)

Sheth, Rubik B.; Ungar, Eugene K.; Chambliss, Joe P.

2012-01-01

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR), currently under development by Ad Astra Rocket Company (Webster, TX), is a unique propulsion system that could change the way space propulsion is performed. VASIMR's efficiency, when compared to that of a conventional chemical rocket, reduces the propellant needed for exploration missions by a factor of 10. Currently plans include flight tests of a 200 kW VASIMR system, titled VF-200, on the International Space Station (ISS). The VF-200 will consist of two 100 kW thruster units packaged together in one engine bus. Each thruster core generates 27 kW of waste heat during its 15 minute firing time. The rocket core will be maintained between 283 and 573 K by a pumped thermal control loop. The design of a high temperature radiator is a unique challenge for the vehicle design. This paper will discuss the path taken to develop a steady state and transient-based radiator design. The paper will describe the radiator design option selected for the VASIMR thermal control system for use on ISS, and how the system relates to future exploration vehicles.

Heat content variability in the tropical Indian Ocean during second pre-INDOEX campaign (boreal winter 1996-1997)

Digital Repository Service at National Institute of Oceanography (India)

Rao, E.P.R.; RameshBabu, V.; Rao, L.V.G.

Surface meteorological data and upper ocean temperature profiles are obtained on-board ORV Sagar Kanya (cruise 120) during the second pre-INDOEX Campaign (December 1996-January 1997) for evaluating the north-south variability of surface heat fluxes...

Diurnal variability of upper ocean temperature and heat budget in the southern Bay of Bengal during October-November, 1998 (BOBMEX-Pilot)

Digital Repository Service at National Institute of Oceanography (India)

Murty, V.S.N.; RameshBabu, V.; Rao, L.V.G.; Prabhu, C.V.; Tilvi, V.

°N locations along 87°E during October -- November, 1998 under BOBMEX-Pilot programme. These data have been analysed to examine the diurnal variability of upper oceanic heat budget and to estimate the eddy diffusivity coefficient of heat in the upper...

Performance evaluation of cryogenic counter-flow heat exchangers with longitudinal conduction, heat in-leak and property variations

Science.gov (United States)

Jiang, Q. F.; Zhuang, M.; Zhu, Z. G.; Y Zhang, Q.; Sheng, L. H.

2017-12-01

Counter-flow plate-fin heat exchangers are commonly utilized in cryogenic applications due to their high effectiveness and compact size. For cryogenic heat exchangers in helium liquefaction/refrigeration systems, conventional design theory is no longer applicable and they are usually sensitive to longitudinal heat conduction, heat in-leak from surroundings and variable fluid properties. Governing equations based on distributed parameter method are developed to evaluate performance deterioration caused by these effects. The numerical model could also be applied in many other recuperators with different structures and, hence, available experimental data are used to validate it. For a specific case of the multi-stream heat exchanger in the EAST helium refrigerator, quantitative effects of these heat losses are further discussed, in comparison with design results obtained by the common commercial software. The numerical model could be useful to evaluate and rate the heat exchanger performance under the actual cryogenic environment.

Heart rate variability during exertional heat stress: effects of heat production and treatment.

Science.gov (United States)

Flouris, Andreas D; Bravi, Andrea; Wright-Beatty, Heather E; Green, Geoffrey; Seely, Andrew J; Kenny, Glen P

2014-04-01

We assessed the efficacy of different treatments (i.e., treatment with ice water immersion vs. natural recovery) and the effect of exercise intensities (i.e., low vs. high) for restoring heart rate variability (HRV) indices during recovery from exertional heat stress (EHS). Nine healthy adults (26 ± 3 years, 174.2 ± 3.8 cm, 74.6 ± 4.3 kg, 17.9 ± 2.8 % body fat, 57 ± 2 mL·kg·(-1) min(-1) peak oxygen uptake) completed four EHS sessions incorporating either walking (4.0-4.5 km·h(-1), 2 % incline) or jogging (~7.0 km·h(-1), 2 % incline) on a treadmill in a hot-dry environment (40 °C, 20-30 % relative humidity) while wearing a non-permeable rain poncho for a slow or fast rate of rectal temperature (T re) increase, respectively. Upon reaching a T re of 39.5 °C, participants recovered until T re returned to 38 °C either passively or with whole-body immersion in 2 °C water. A comprehensive panel of 93 HRV measures were computed from the time, frequency, time-frequency, scale-invariant, entropy and non-linear domains. Exertional heat stress significantly affected 60/93 HRV measures analysed. Analyses during recovery demonstrated that there were no significant differences between HRV measures that had been influenced by EHS at the end of passive recovery vs. whole-body cooling treatment (p > 0.05). Nevertheless, the cooling treatment required statistically significantly less time to reduce T re (p whole-body immersion in 2 °C water results in faster cooling, there were no observed differences in restoration of autonomic heart rate modulation as measured by HRV indices with whole-body cold-water immersion compared to passive recovery in thermoneutral conditions.

MHD natural convection from a heated vertical wavy surface with variable viscosity and thermal conductivity

International Nuclear Information System (INIS)

Choudhury, M.; Hazarika, G.C.; Sibanda, P.

2013-01-01

We investigate the effects of temperature dependent viscosity and thermal conductivity on natural convection flow of a viscous incompressible electrically conducting fluid along a vertical wavy surface. The flow is permeated by uniform transverse magnetic field. The fluid viscosity and thermal conductivity are assumed to vary as inverse linear functions of temperature. The coupled non-linear systems of partial differential equations are solved using the finite difference method. The effects of variable viscosity parameter, variable thermal conductivity parameter and magnetic parameter on the flow field and the heat transfer characteristics are discussed and shown graphically. (author)

On calculation of difference in specific heats at constant pressure and constant volume using an empiric Nernst-Lindeman equation

International Nuclear Information System (INIS)

Leont'ev, K.L.

1981-01-01

Known theoretical and empirical formulae are considered for the difference in specific heats at constant pressure and volume. On the basis of the Grunaiser law on the ratio of specific heat to thermal expansion and on the basis of the correlation proposed by the author, between this ratio and average velocity of elastic waves obtained in a new expression for the difference in specific heats and determined are conditions at which empiric Nernst-Lindeman equation can be considered to be strict. Results of calculations for metals with fcc lattice are presented

Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

Energy Technology Data Exchange (ETDEWEB)

Hatami, M., E-mail: m.hatami@tue.nl [Esfarayen University of Technology, Mechanical Engineering Department, Esfarayen, North Khorasan (Iran, Islamic Republic of); Jing, Dengwei; Song, Dongxing [International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi' an 710049 (China); Sheikholeslami, M.; Ganji, D.D. [Department of Mechanical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

2015-12-15

In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number. - Highlights: • Heat and mass transfer of nanofluids between parallel plates investigated. • A variable magnetic field is applied on the plates. • Governing equations are solved analytically. • Effects of physical parameters are discussed on the Nusselt number.

Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

International Nuclear Information System (INIS)

Hatami, M.; Jing, Dengwei; Song, Dongxing; Sheikholeslami, M.; Ganji, D.D.

2015-01-01

In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number. - Highlights: • Heat and mass transfer of nanofluids between parallel plates investigated. • A variable magnetic field is applied on the plates. • Governing equations are solved analytically. • Effects of physical parameters are discussed on the Nusselt number

HEATING-7, Multidimensional Finite-Difference Heat Conduction Analysis

International Nuclear Information System (INIS)

2000-01-01

1 - Description of program or function: HEATING 7.2i and 7.3 are the most recent developments in a series of heat-transfer codes and obsolete all previous versions distributed by RSICC as SCA-1/HEATING5 and PSR-199/HEATING 6. Note that Unix and PC versions of HEATING7 are available in the CCC-545/SCALE 4.4 package. HEATING can solve steady-state and/or transient heat conduction problems in one-, two-, or three-dimensional Cartesian, cylindrical, or spherical coordinates. A model may include multiple materials, and the thermal conductivity, density, and specific heat of each material may be both time- and temperature-dependent. The thermal conductivity may also be anisotropic. Materials may undergo change of phase. Thermal properties of materials may be input or may be extracted from a material properties library. Heat- generation rates may be dependent on time, temperature, and position, and boundary temperatures may be time- and position-dependent. The boundary conditions, which may be surface-to-environment or surface-to-surface, may be specified temperatures or any combination of prescribed heat flux, forced convection, natural convection, and radiation. The boundary condition parameters may be time- and/or temperature-dependent. General gray body radiation problems may be modeled with user-defined factors for radiant exchange. The mesh spacing may be variable along each axis. HEATING uses a run-time memory allocation scheme to avoid having to recompile to match memory requirements for each specific problem. HEATING utilizes free-form input. In June 1997 HEATING 7.3 was added to the HEATING 7.2i packages, and the Unix and PC versions of both 7.2i and 7.3 were merged into one package. HEATING 7.3 is being released as a beta-test version; therefore, it does not entirely replace HEATING 7.2i. There is no published documentation for HEATING 7.3; but a listing of input specifications, which reflects changes for 7.3, is included in the PSR-199 documentation. For 3-D

Evaluating Moisture Control of Variable-Capacity Heat Pumps in Mechanically Ventilated, Low-Load Homes in Climate Zone 2A

Energy Technology Data Exchange (ETDEWEB)

Eric Martin, Chuck Withers, Janet McIlvaine, Dave Chasar, and David Beal

2018-03-29

Low-load homes can present a challenge when selecting appropriate space-conditioning equipment. Conventional, fixed-capacity heating and cooling equipment is often oversized for small homes, causing increased first costs and operating costs. This report evaluates the performance of variable-capacity comfort systems, with a focus on inverter-driven, variable-capacity systems, as well as proposed system enhancements.

Comparative Analysis of Upper Ocean Heat Content Variability from Ensemble Operational Ocean Analyses

Science.gov (United States)

Xue, Yan; Balmaseda, Magdalena A.; Boyer, Tim; Ferry, Nicolas; Good, Simon; Ishikawa, Ichiro; Rienecker, Michele; Rosati, Tony; Yin, Yonghong; Kumar, Arun

2012-01-01

Upper ocean heat content (HC) is one of the key indicators of climate variability on many time-scales extending from seasonal to interannual to long-term climate trends. For example, HC in the tropical Pacific provides information on thermocline anomalies that is critical for the longlead forecast skill of ENSO. Since HC variability is also associated with SST variability, a better understanding and monitoring of HC variability can help us understand and forecast SST variability associated with ENSO and other modes such as Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), Tropical Atlantic Variability (TAV) and Atlantic Multidecadal Oscillation (AMO). An accurate ocean initialization of HC anomalies in coupled climate models could also contribute to skill in decadal climate prediction. Errors, and/or uncertainties, in the estimation of HC variability can be affected by many factors including uncertainties in surface forcings, ocean model biases, and deficiencies in data assimilation schemes. Changes in observing systems can also leave an imprint on the estimated variability. The availability of multiple operational ocean analyses (ORA) that are routinely produced by operational and research centers around the world provides an opportunity to assess uncertainties in HC analyses, to help identify gaps in observing systems as they impact the quality of ORAs and therefore climate model forecasts. A comparison of ORAs also gives an opportunity to identify deficiencies in data assimilation schemes, and can be used as a basis for development of real-time multi-model ensemble HC monitoring products. The OceanObs09 Conference called for an intercomparison of ORAs and use of ORAs for global ocean monitoring. As a follow up, we intercompared HC variations from ten ORAs -- two objective analyses based on in-situ data only and eight model analyses based on ocean data assimilation systems. The mean, annual cycle, interannual variability and longterm trend of HC have

Radial Pressure Pulse and Heart Rate Variability in Heat- and Cold-Stressed Humans

Directory of Open Access Journals (Sweden)

Chin-Ming Huang

2011-01-01

Full Text Available This study aims to explore the effects of heat and cold stress on the radial pressure pulse (RPP and heart rate variability (HRV. The subjects immersed their left hand into 45°C and 7°C water for 2 minutes. Sixty healthy subjects (age 25±4 yr; 29 men and 31 women were enrolled in this study. All subjects underwent the supine temperature measurements of the bilateral forearms, brachial arterial blood pressure, HRV and RPP with a pulse analyzer in normothermic conditions, and thermal stresses. The power spectral low-frequency (LF and high-frequency (HF components of HRV decreased in the heat test and increased in the cold test. The heat stress significantly reduced radial augmentation index (AIr (P<.05, but the cold stress significantly increased AIr (P<.01. The spectral energy of RPP did not show any statistical difference in 0∼10 Hz region under both conditions, but in the region of 10∼50 Hz, there was a significant increase (P<.01 in the heat test and a significant decrease in the cold test (P<.01. The changes in AIr induced by heat and cold stress were significantly negatively correlated with the spectral energy in the region of 10∼50 Hz (SE10−50 Hz but not in the region of 0∼10 Hz (SE0−10 Hz. The results demonstrated that the SE10−50 Hz, which only possessed a small percentage in total pulse energy, presented more physiological characteristics than the SE0−10 Hz under the thermal stresses.

Radial Pressure Pulse and Heart Rate Variability in Heat- and Cold-Stressed Humans

Science.gov (United States)

Huang, Chin-Ming; Chang, Hsien-Cheh; Kao, Shung-Te; Li, Tsai-Chung; Wei, Ching-Chuan; Chen, Chiachung; Liao, Yin-Tzu; Chen, Fun-Jou

2011-01-01

This study aims to explore the effects of heat and cold stress on the radial pressure pulse (RPP) and heart rate variability (HRV). The subjects immersed their left hand into 45°C and 7°C water for 2 minutes. Sixty healthy subjects (age 25 ± 4 yr; 29 men and 31 women) were enrolled in this study. All subjects underwent the supine temperature measurements of the bilateral forearms, brachial arterial blood pressure, HRV and RPP with a pulse analyzer in normothermic conditions, and thermal stresses. The power spectral low-frequency (LF) and high-frequency (HF) components of HRV decreased in the heat test and increased in the cold test. The heat stress significantly reduced radial augmentation index (AIr) (P < .05), but the cold stress significantly increased AIr (P < .01). The spectral energy of RPP did not show any statistical difference in 0 ~ 10 Hz region under both conditions, but in the region of 10 ~ 50 Hz, there was a significant increase (P < .01) in the heat test and a significant decrease in the cold test (P < .01). The changes in AIr induced by heat and cold stress were significantly negatively correlated with the spectral energy in the region of 10 ~ 50 Hz (SE10−50 Hz) but not in the region of 0 ~ 10 Hz (SE0−10 Hz). The results demonstrated that the SE10−50 Hz, which only possessed a small percentage in total pulse energy, presented more physiological characteristics than the SE0−10 Hz under the thermal stresses. PMID:21113292

Stage- and sex-specific heat tolerance in the yellow dung fly Scathophaga stercoraria

OpenAIRE

Blanckenhorn Wolf U.; Gautier Roland; Nick Marcel; Puniamoorthy Nalini; Schäfer Martin A.

2014-01-01

Thermal tolerance varies at all hierarchical levels of biological organization: among species populations individuals and even within individuals. Age or developmental stage and sex specific thermal effects have received relatively little attention in the literature despite being crucial for understanding thermal adaptation in nature and responses to global warming. We document stage and sex specific heat tolerance in the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) a...

The analysis of the specific heat of RFe2Si2 compounds

Czech Academy of Sciences Publication Activity Database

Svoboda, P.; Vejpravová, J.; Honda, F.; Šantavá, E.; Schneeweiss, Oldřich; Komatsubara, T.

2003-01-01

Roč. 328, 1-2 (2003), s. 139-141 ISSN 0921-4526 R&D Projects: GA ČR GA106/02/0943 Institutional research plan: CEZ:AV0Z2041904 Keywords : specific heat * magnetic properties * intermetallics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.908, year: 2003

Renormalisation-group specific heat of the square lattice Potts ferromagnet

International Nuclear Information System (INIS)

Martin, H.O.; Tsallis, C.

1982-01-01

The free and internal energies and specific heat of the q-state Potts ferromagnet are discussed. A real space renormalisation group approach is presented which recovers a considerable amount of exact particular results for all dimensionalities (hypercubic lattices). The square lattice case is calculated in detail by using self-dual clusters (which provide the exact critical point for all q). Comparison with Onsager results (q=2) is satisfactory; the general tendencies for q different 2 (1 [pt

Specific heat jump at T/sub c/ of proximity effect sandwiches containing nonmagnetic localized states

International Nuclear Information System (INIS)

Maneeratankul, S.; Tang, I.M.

1987-01-01

The decrease in the transition temperature and the jump in the specific heat at T/sub c/ of proximity effect sandwiches containing nonmagnetic Anderson impurities in the normal layer are studied. The effects of the resonant scattering by the impurities are treated in the same manner as that used by Kaiser in his study of the effects of resonant scattering on the properties of bulk superconductors. Numerical calculations of the decrease in T/sub c/ and the jump in the specific heat at T/sub c/ as a function of the thickness of the normal layer are presented

Effect of high energy electron beam (10 MeV) on specific heat capacity of low-density polyethylene/hydroxyapatite nano-composite

Energy Technology Data Exchange (ETDEWEB)

Soltani, Z., E-mail: zhr_soltani@yahoo.com [Health Physics and Radiation Dosimetry Research Laboratory, Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Ziaie, F. [Radiation Application Research School, Nuclear Science & Technology Research Institute, Tehran (Iran, Islamic Republic of); Ghaffari, M. [Polymer Group, Golestan University, Golestan (Iran, Islamic Republic of); Beigzadeh, A.M. [Radiation Application Research School, Nuclear Science & Technology Research Institute, Tehran (Iran, Islamic Republic of)

2017-02-01

In the present work, thermal properties of low density polyethylene (LDPE) and its nano composites are investigated. For this purpose LDPE reinforced with different weight percents of hydroxyapatite (HAP) powder which was synthesized via hydrolysis method are produced. The samples were irradiated with 10 MeV electron beam at doses of 75 to 250 kGy. Specific heat capacity measurement have been carried out at different temperatures, i.e. 25, 50, 75 and 100 °C using modulated temperature differential scanning calorimetry (MTDSC) apparatus and the effect of three parameters include of temperature, irradiation dose and the amount of HAP nano particles as additives on the specific heat capacity of PE/HAP have been investigated precisely. The MTDSC results indicate that the specific heat capacity have decreased by addition of nano sized HAP as reinforcement for LDPE. On the other hand, the effect of radiation dose is reduction in the specific heat capacity in all materials including LDPE and its nano composites. The HAP nano particles along with cross-link junctions due to radiation restrain the movement of the polymer chains in the vicinity of each particle and improve the immobility of polymer chains and consequently lead to reduction in specific heat capacity. Also, the obtained results confirm that the radiation effect on the specific heat capacity is more efficient than the reinforcing effect of nano-sized hydroxyapatite.

Physiological and performance adaptations to an in-season soccer camp in the heat: Associations with heart rate and heart rate variability

DEFF Research Database (Denmark)

Buchheit, M; Voss, S C; Nybo, Lars

2011-01-01

The aim of the present study was to examine the associations between adaptive responses to an in-season soccer training camp in the heat and changes in submaximal exercising heart rate (HRex, 5-min run at 9 ¿km/h), postexercise HR recovery (HRR) and HR variability (HRV). Fifteen well-trained but ......The aim of the present study was to examine the associations between adaptive responses to an in-season soccer training camp in the heat and changes in submaximal exercising heart rate (HRex, 5-min run at 9 ¿km/h), postexercise HR recovery (HRR) and HR variability (HRV). Fifteen well......-trained but non-heat-acclimatized male adult players performed a training week in Qatar (34.6¿±¿1.9°C wet bulb globe temperature). HRex, HRR, HRV (i.e. the standard deviation of instantaneous beat-to-beat R-R interval variability measured from Poincaré plots SD1, a vagal-related index), creatine kinase (CK...... at the beginning and at the end of the training week. Throughout the intervention, HRex and HRV showed decreasing (P¿...

Two-dimensional nonlinear transient heat transfer analysis of variable section pin fins

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, P. [Department of Mechanical Engineering, School of Engineering, Persian Gulf University, Boushehr 75168 (Iran); Rahideh, H. [Department of Chemical Engineering, School of Engineering, Persian Gulf University, Boushehr 75168 (Iran)

2009-04-15

The two-dimensional nonlinear transient heat transfer analysis of variable cross section pin-fins is studied using the incremental differential quadrature method (IDQM) as a simple, accurate, and computationally efficient numerical tool. The formulations are general so that it can easily be used for arbitrary continuously varying cross section pin fins with the spatial-temperature dependent thermal parameters. On all external surfaces of the pin fin, the convective-radiative condition is considered. The effects of two different types of boundary conditions at the base of pin fin are investigated: time and spatial dependent temperature, and the convection heat transfer. The thermal conductivity of the pin fin is assumed to vary as a linear function of the temperature. The accuracy of the method is demonstrated by comparing its results with those generated by finite difference method. It is shown that using few grid points, results in excellent agreements with those of FDM are obtained. Less computational efforts of the method with respect to finite difference method is shown. (author)

Experimental studies of parameters affecting the heat generation in friction stir welding process

Directory of Open Access Journals (Sweden)

Mijajlović Miroslav M.

2012-01-01

Full Text Available Heat generation is a complex process of transformation of a specific type of energy into heat. During friction stir welding, one part of mechanical energy delivered to the welding tool is consumed in the welding process, another is used for deformational processes etc., and the rest of the energy is transformed into heat. The analytical procedure for the estimation of heat generated during friction stir welding is very complex because it includes a significant number of variables and parameters, and many of them cannot be fully mathematically explained. Because of that, the analytical model for the estimation of heat generated during friction stir welding defines variables and parameters that dominantly affect heat generation. These parameters are numerous and some of them, e. g. loads, friction coefficient, torque, temperature, are estimated experimentally. Due to the complex geometry of the friction stir welding process and requirements of the measuring equipment, adequate measuring configurations and specific constructional solutions that provide adequate measuring positions are necessary. This paper gives an overview of the process of heat generation during friction stir welding, the most influencing parameters on heat generation, constructional solutions for the measuring equipment needed for these experimental researches and examples of measured values.

Investigation of the variation of the specific heat capacity of local soil samples from the Niger delta, Nigeria with moisture content

International Nuclear Information System (INIS)

Ofoegbu, C.O.; Adjepong, S.K.

1987-11-01

Results of an investigation of the variation, with moisture content, of the specific heat capacity of samples of three texturally different types of soil (clayey, sandy and sandy loam) obtained from the Niger delta area of Nigeria, are presented. The results show that the specific heat capacities of the soils studied, increase with moisture content. This increase is found to be linear for the entire range of moisture contents considered (0-25%), in the case of the sandy loam soil while for the clayey and sandy soils the specific heat capacity is found to increase linearly with moisture content up to about 15% after which the increase becomes parabolic. The rate of increase of specific heat capacity with moisture content appears to be highest in the clayey soil and lowest in the sandy soil. It is thought that the differences in the rates of increase of specific heat capacity with moisture content, observed for the soils, reflect the soils' water-retention capacities. (author) 3 refs, 5 figs

Effects of variable thermal conductivity on Stokes' flow of a thermoelectric fluid with fractional order of heat transfer

International Nuclear Information System (INIS)

Ezzat, M.A.; El-Bary, A.A.

2016-01-01

In this study, the constitutive relation for the heat flux vector is derived to be the Fourier's law of heat conduction with a variable thermal conductivity and time-fractional order. The Stokes' flow of unsteady incompressible thermoelectric fluid due to a moving plate in the presence of a transverse magnetic field is molded. Stokes' first problem is solved by applying Laplace transform with respect to time variable and evaluating the inverse transform integrals by using a numerical approach. Numerical results for the temperature and the velocity distributions are given and illustrated graphically for given problem. The results indicate that the thermal conductivity and time-fractional order play a major role in the temperature and velocity distributions. (authors)

Development of variable-width ribbon heating elements for liquid-metal and gas-cooled fast breeder reactor fuel-pin simulators

International Nuclear Information System (INIS)

McCulloch, R.W.; Post, D.W.; Lovell, R.T.; Snyder, S.D.

1981-04-01

Variable-width ribbon heating elements that provide a chopped-cosine variable heat flux profile have been fabricated for fuel pin simulators used in test loops by the Breeder Reactor Program Thermal-Hydraulic Out-of-Reactor Safety test facility and the Gas-Cooled Fast Breeder Reactor-Core Flow Test Loop. Thermal, mechanical, and electrical design considerations are used to derive an analytical expression that precisely describes ribbon contour in terms of the major fabrication parameters. These parameters are used to generate numerical control tapes that control ribbon cutting and winding machines. Infrared scanning techniques are developed to determine the optimum transient thermal profile of the coils and relate this profile to that generated by the coils in completed fuel pin simulators

Residential Cold Climate Heat Pump (CCHP) w/Variable Speed Technology

Energy Technology Data Exchange (ETDEWEB)

Messmer, Craig S. [Unico, Inc., Arnold, MO (United States)

2016-09-30

This report summarizes the results of a three year program awarded to Unico, Inc. to commercialize a residential cold climate heat pump. Several designs were investigated. Compressors were selected using analysis from Oakridge National Laboratories followed by prototype construction and lab testing in a specially built environmental chamber capable of reaching -30°F. The initial design utilized two variable speed compressors in series with very good capacity results and acceptable efficiency at very cold temperatures. The design was then modified to reduce cost and complexity by redesigning the system using three dual-stage compressors: two in parallel followed by one in series. Extensive testing found significant challenge with oil management, reliability, weight and cost which prevented the system from being fully commercialized. Further analysis of other conceptual designs indicated that these challenges could be overcome in the future.

The effect of Ca doping on specific heat of YCoO{sub 3} cobaltate

Energy Technology Data Exchange (ETDEWEB)

Thakur, Rasna, E-mail: rasnathakur@yahoo.com; Thakur, Rajesh K., E-mail: thakur.rajesh2009@gmail.com; Gaur, N. K., E-mail: srl-nkgaur@yahoo.co.in [Department of Physics, Barkatullah University, Bhopal, 462026 (India)

2016-05-06

We have investigated the thermodynamic properties of Y{sub 1-x}Ca{sub x}CoO{sub 3} (0.0≤x≤0.1) perovskites by means of a modified rigid ion model (MRIM). The variations of specific heat at wide temperatures 1 K ≤ T ≤ 1000 K are reported. Also, the effect of lattice distortions on the elastic and thermal properties of pure and Ca doped cobaltates has been studied by an atomistic approach. Besides, we have reported bulk modulus (B), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ{sub D}), Gruneisen parameter (γ) and specific heat (C). It is found that the present model has a promise to predict the thermodynamic properties of other perovskites as well.

Laboratory Activity: Specific Heat by Change in Internal Energy of Silly Putty

Science.gov (United States)

Koser, John

2011-01-01

Students in introductory physics courses often don't study thermodynamics or thermodynamic events. If any thermal physics is taught in introductory courses (e.g., Physics 101 for Liberal Arts Majors), it usually involves the concepts of specific heat and various temperature scales. Seldom are the first and second laws of thermodynamics taught in…

Overview PWR-Blowdown Heat Transfer Separate-Effects Program

International Nuclear Information System (INIS)

White, J.D.

1978-01-01

The ORNL Pressurized Water Reactor Blowdown Heat Transfer Program (PWR-BDHT) is a separate-effects experimental study of thermal-hydraulic phenomena occurring during the first 20 sec of a hypothetical LOCA. Specific objectives include the determination, for a wide range of parameters, of time to CHF and the following variables for both pre- and post-CHF: heat fluxes, ΔT (temperature difference between pin surface and fluid), heat transfer coefficients, and local fluid properties. A summary of the most interesting results from the program obtained during the past year is presented. These results are in the area of: (1) RELAP verification, (2) electric pin calibration, (3) time to critical heat flux (CHF), (4) heat transfer coefficient comparisons, and (5) nuclear fuel pin simulation

Overall conductance and heat transfer area minimization of refrigerators and heat pumps with finite heat reservoirs

International Nuclear Information System (INIS)

Sarkar, J.; Bhattacharyya, Souvik

2007-01-01

In the present study, the overall conductance and the overall heat transfer area per unit capacity of refrigeration and heat pump systems have been minimized analytically considering both internal and external irreversibilities with variable temperature (finite capacity) heat reservoirs. Hot and cold side refrigerant temperatures, conductance and heat transfer area ratios have been optimized to attain this goal. The results have been verified with the more elaborate numerical optimization results obtained for ammonia based vapour compression refrigeration and heat pump systems working with variable temperature reservoirs. It is observed that the analytical results for optimum refrigerant temperatures, minimum overall conductance and heat transfer area deviate marginally from the numerically optimized results (within 1%), if one assumes a constant heat rejection temperature. The deviation of minimum overall conductance and heat transfer area is more (about 20%), if one considers both the desuperheating and condensation regions separately. However, in the absence of complex and elaborate numerical models, the simple analytical results obtained here can be used as reasonably accurate preliminary guidelines for optimization of refrigeration and heat pump systems

Quantifying variety-specific heat resistance and the potential for adaptation to climate change.

Science.gov (United States)

Tack, Jesse; Barkley, Andrew; Rife, Trevor W; Poland, Jesse A; Nalley, Lawton Lanier

2016-08-01

The impact of climate change on crop yields has become widely measured; however, the linkages for winter wheat are less studied due to dramatic weather changes during the long growing season that are difficult to model. Recent research suggests significant reductions under warming. A potential adaptation strategy involves the development of heat resistant varieties by breeders, combined with alternative variety selection by producers. However, the impact of heat on specific wheat varieties remains relatively unstudied due to limited data and the complex genetic basis of heat tolerance. Here, we provide a novel econometric approach that combines field-trial data with a genetic cluster mapping to group wheat varieties and estimate a separate extreme heat impact (temperatures over 34 °C) across 24 clusters spanning 197 varieties. We find a wide range of heterogeneous heat resistance and a trade-off between average yield and resistance. Results suggest that recently released varieties are less heat resistant than older varieties, a pattern that also holds for on-farm varieties. Currently released - but not yet adopted - varieties do not offer improved resistance relative to varieties currently grown on farm. Our findings suggest that warming impacts could be significantly reduced through advances in wheat breeding and/or adoption decisions by producers. However, current adaptation-through-adoption potential is limited under a 1 °C warming scenario as increased heat resistance cannot be achieved without a reduction in average yields. © 2015 John Wiley & Sons Ltd.

Lattice specific heat and local density of states of Ni-based dilute ...

Indian Academy of Sciences (India)

The required perfect lattice phonons of Ni are calculated using a general 4 Th neighbour force model derived by Birge- neau et al [14], on the basis of Born Von Karman fit to the measured dispersion curves in neutron scattering experiments. A comparison of calculated and experi- mental lattice specific heat provides us an ...

Specific-heat measurements in superconducting indium-thallium alloys and the pseudopotential form factor

International Nuclear Information System (INIS)

Munukutla, L.V.; Cappelletti, R.L.

1980-01-01

Normal-state specific heats between 1 and 4.4 K and superconducting transition temperatures of pure indium and In-Tl alloys have been measured. Excellent agreement with previous results was found. N/sub bs/(0) was extracted using our γ values and Dynes's lambda values and shows a large variation. The measured variation of lambda 2 > was also obtained from Dynes's results and found to be nearly linear in spite of the large variation of N/sub bs/(0). This is shown to be a consequence of the fact that the ratio of the calculated average screened pseudopotential form factor to electron density of states, 2 /sub s/>/N/sub bs/(0), is nearly constant across the alloy series for each element. No anomaly was found in the specific heat of In/sub 0.69/Tl/sub 0.31/ at the expected martensitic transition temperature

Experimental Study of a Novel Direct-Expansion Variable Frequency Finned Solar/Air-Assisted Heat Pump Water Heater

Directory of Open Access Journals (Sweden)

Jing Qin

2018-01-01

Full Text Available A novel direct expansion variable frequency finned solar/air-assisted heat pump water heater was fabricated and tested in the enthalpy difference lab with a solar simulator. A solar/air source evaporator-collector with an automatic lifting glass cover plate was installed on the system. The system could be operated in three modes, namely, air, solar, and dual modes. The effects of the ambient temperature, solar irradiation, compressor frequency, and operating mode on the performance of this system were studied in this paper. The experimental results show that the ambient temperature, solar irradiation, and operating mode almost have no effect on the energy consumption of the compressor. When the ambient temperature and the solar irradiation were increased, the COP was found to increase with decreasing heating time. Also, when the compressor frequency was increased, an increase in the energy consumption of the compressor and the heat gain of the evaporator were noted with a decrease in the heating time.

Lattice specific heat for the RMIn5 (R=Gd, La, Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction

International Nuclear Information System (INIS)

Facio, Jorge I.; Betancourth, D.; Cejas Bolecek, N.R.; Jorge, G.A.; Pedrazzini, Pablo; Correa, V.F.; Cornaglia, Pablo S.; Vildosola, V.; García, D.J.

2016-01-01

We analyze theoretically a common experimental process used to obtain the magnetic contribution to the specific heat of a given magnetic material. In the procedure, the specific heat of a non-magnetic analog is measured and used to subtract the non-magnetic contributions, which are generally dominated by the lattice degrees of freedom in a wide range of temperatures. We calculate the lattice contribution to the specific heat for the magnetic compounds GdMIn 5 (M=Co, Rh) and for the non-magnetic YMIn 5 and LaMIn 5 (M=Co, Rh), using density functional theory based methods. We find that the best non-magnetic analog for the subtraction depends on the magnetic material and on the range of temperatures. While the phonon specific heat contribution of YRhIn 5 is an excellent approximation to the one of GdCoIn 5 in the full temperature range, for GdRhIn 5 we find a better agreement with LaCoIn 5 , in both cases, as a result of an optimum compensation effect between masses and volumes. We present measurements of the specific heat of the compounds GdMIn 5 (M=Co, Rh) up to room temperature where it surpasses the value expected from the Dulong–Petit law. We obtain a good agreement between theory and experiment when we include anharmonic effects in the calculations.

Specific heat of heavy-fermion CePd2Si2 in high magnetic fields

International Nuclear Information System (INIS)

Sheikin, I.; Wang, Y.; Bouquet, F.; Junod, A.; Lejay, P.

2002-01-01

We report specific heat measurements on the heavy-fermion compound CePd 2 Si 2 in magnetic fields up to 16 T and in the temperature range 1.4-16 K. A sharp peak in the specific heat signals the antiferromagnetic transition at T N ∼ 9.3 K in zero field. The transition is found to shift to lower temperatures when a magnetic field is applied along the crystallographic a-axis, while a field applied parallel to the tetragonal c-axis does not affect the transition. The magnetic contribution to the specific heat below T N is well described by a sum of a linear electronic term and an antiferromagnetic spin-wave contribution. Just below T N , an additional positive curvature, especially at high fields, arises most probably due to thermal fluctuations. The field dependence of the coefficient of the low-temperature linear term, γ 0 , extracted from the fits shows a maximum at about 6 T, at the point where an anomaly was detected in susceptibility measurements. The relative field dependences of both T N and the magnetic entropy at T N scale as [1-(B/B 0 ) 2 ] for B parallel a, suggesting the disappearance of antiferromagnetism at B 0 ∼42 T. The expected suppression of the antiferromagnetic transition temperature to zero makes the existence of a magnetic quantum critical point possible. (author). Letter-to-the-editor

Building America Case Study: Impact of Improved Duct Insulation on Fixed-Capacity (SEER 13) and Variable-Capacity (SEER 22) Heat Pumps, Cocoa, Florida

Energy Technology Data Exchange (ETDEWEB)

2017-04-01

A new generation of central, ducted variable-capacity heat pump systems has come on the market, promising very high cooling and heating efficiency. Instead of cycling on at full capacity and then cycling off when the thermostat is satisfied, they vary their cooling and heating output over a wide range (approximately 40 to 118% of nominal full capacity); thus, staying 'on' for 60% to 100% more hours per day compared to fixed-capacity systems. Current Phase 4 experiments in an instrumented lab home with simulated occupancy evaluate the impact of duct R-value enhancement on the overall operating efficiency of the variable-capacity system compared to the fixed-capacity system.

A broad set of different llama antibodies specific for a 16 kDa heat shock protein of Mycobacterium tuberculosis.

Directory of Open Access Journals (Sweden)

Anke K Trilling

Full Text Available BACKGROUND: Recombinant antibodies are powerful tools in engineering of novel diagnostics. Due to the small size and stable nature of llama antibody domains selected antibodies can serve as a detection reagent in multiplexed and sensitive assays for M. tuberculosis. METHODOLOGY/PRINCIPAL FINDINGS: Antibodies for Mycobacterium tuberculosis (M. tb recognition were raised in Alpaca, and, by phage display, recombinant variable domains of heavy-chain antibodies (VHH binding to M. tuberculosis antigens were isolated. Two phage display selection strategies were followed: one direct selection using semi-purified protein antigen, and a depletion strategy with lysates, aiming to avoid cross-reaction to other mycobacteria. Both panning methods selected a set of binders with widely differing complementarity determining regions. Selected recombinant VHHs were produced in E. coli and shown to bind immobilized lysate in direct Enzymelinked Immunosorbent Assay (ELISA tests and soluble antigen by surface plasmon resonance (SPR analysis. All tested VHHs were specific for tuberculosis-causing mycobacteria (M. tuberculosis, M. bovis and exclusively recognized an immunodominant 16 kDa heat shock protein (hsp. The highest affinity VHH had a dissociation constant (KD of 4 × 10(-10 M. CONCLUSIONS/SIGNIFICANCE: A broad set of different llama antibodies specific for 16 kDa heat shock protein of M. tuberculosis is available. This protein is highly stable and abundant in M. tuberculosis. The VHH that detect this protein are applied in a robust SPR sensor for identification of tuberculosis-causing mycobacteria.

Increment of specific heat capacity of solar salt with SiO2 nanoparticles.

Science.gov (United States)

Andreu-Cabedo, Patricia; Mondragon, Rosa; Hernandez, Leonor; Martinez-Cuenca, Raul; Cabedo, Luis; Julia, J Enrique

2014-01-01

Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable. 65.: Thermal properties of condensed matter; 65.20.-w: Thermal properties of liquids; 65.20.Jk: Studies of thermodynamic properties of specific liquids.

Measurement of the enthalpy and specific heat of a Be2C-graphite-UC2 reactor fuel material to 19800K

International Nuclear Information System (INIS)

Roth, E.P.

1980-01-01

The enthalpy and specific heat of a Be 2 C-graphite-UC 2 composite nuclear fuel material were measured over the temperature range 300 to 1980 0 K using differential scanning calorimetry and liquid argon vaporization calorimetry. The fuel material measured was developed at Sandia National Laboratories for use in pulsed test reactors. The material is a hot-pressed composite consisting of 40 vol % Be 2 C, 49.5 vol % graphite, 3.5 vol % UC 2 and 7.0 vol % void. The specific heat was measured with the differential scanning calorimeter over the temperature range 300 to 950 0 K while the enthalpy was measured over the range 1185 to 1980 0 K with the liquid argon vaporization calorimeter. The normal spectral emittance at a wavelength of 6.5 x 10 -5 cm was measured over the experimental temperature range. The combined experimental enthalpy data were fit using a spline routine and differentiated to give the specific heat. Comparison of the measured specific heat of the composite to the specific heat calculated by summing the contributions of the individual components indicates that the specific heat of the Be 2 C component differs significantly from literature values and is approximately 0.6 cal/g-K (2.5 x 10 3 J/Kg-K) for temperatures above 1000 0 K

Summary of some feasibility studies for site-specific solar industrial process heat

Energy Technology Data Exchange (ETDEWEB)

None

1982-01-01

Some feasibility studies for several different site specific solar industrial process heat applications are summarized. The followng applications are examined. Leather Tanning; Concrete Production: Lumber and Paper Processing; Milk Processing; Molding, Curing or Drying; Automobile Manufacture; and Food Processing and Preparation. For each application, site and process data, system design, and performance and cost estimates are summarized.

Magnon specific heat and free energy of Heisenberg ferromagnetic single-walled nanotubes: Green's function approach

Energy Technology Data Exchange (ETDEWEB)

Mi, Bin-Zhou, E-mail: mbzfjerry2008@126.com [Department of Basic Curriculum, North China Institute of Science and Technology, Beijing 101601 (China); Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083 (China); Zhai, Liang-Jun [The School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001 (China); Hua, Ling-Ling [Department of Basic Curriculum, North China Institute of Science and Technology, Beijing 101601 (China)

2016-01-15

The effect of magnetic spin correlation on the thermodynamic properties of Heisenberg ferromagnetic single-walled nanotubes are comprehensively investigated by use of the double-time Green's function method. The influence of temperature, spin quantum number, diameter of the tube, anisotropy strength and external magnetic field to internal energy, free energy, and magnon specific heat are carefully calculated. Compared to the mean field approximation, the consideration of the magnetic correlation effect significantly improves the internal energy values at finite temperature, while it does not so near zero temperature, and this effect is related to the diameter of the tube, anisotropy strength, and spin quantum number. The magnetic correlation effect lowers the internal energy at finite temperature. As a natural consequence of the reduction of the internal energy, the specific heat is reduced, and the free energy is elevated. - Highlights: • Magnon specific heat and free energy of Heisenberg ferromagnetic single-walled nanotubes (HFM-SWNTs) are investigated. • The magnetic correlations effect has a considerable contribution to the thermodynamics properties of HFM-SWNTs. • Magnetic correlation effects are always to lower the internal energy at finite temperature. • At Curie point, magnetic correlation energy is much less than zero. • The peak values of magnon specific heat curves rise and shift right towards higher temperatures with the diameter of tubes, the anisotropy strength, and the spin quantum number rising.

Highly macroscopically degenerated single-point ground states as source of specific heat capacity anomalies in magnetic frustrated systems

Science.gov (United States)

Jurčišinová, E.; Jurčišin, M.

2018-04-01

Anomalies of the specific heat capacity are investigated in the framework of the exactly solvable antiferromagnetic spin- 1 / 2 Ising model in the external magnetic field on the geometrically frustrated tetrahedron recursive lattice. It is shown that the Schottky-type anomaly in the behavior of the specific heat capacity is related to the existence of unique highly macroscopically degenerated single-point ground states which are formed on the borders between neighboring plateau-like ground states. It is also shown that the very existence of these single-point ground states with large residual entropies predicts the appearance of another anomaly in the behavior of the specific heat capacity for low temperatures, namely, the field-induced double-peak structure, which exists, and should be observed experimentally, along with the Schottky-type anomaly in various frustrated magnetic system.

Quantifying the energy impact of a variable flow pump in a ground-coupled heat pump system

Energy Technology Data Exchange (ETDEWEB)

Iolova, K.; Bernier, M.A. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. de Genie Mecanique; Nichols, L. [Dessau-Soprin, Montreal, PQ (Canada)

2006-07-01

The thermal behaviour of an energy-efficient public high school building was modelled using the TRNSYS multi-zone building simulation program. The architectural elements such as windows, external and internal walls, roofs, and slabs were described in detail. The two-storey Ecole du Tournant high school near Montreal is the most efficient in Quebec and the second in Canada. It consumes 79.2 per cent less source energy than a typical high school built in accordance with the Model National Energy Code of Canada for Buildings. This presentation described the case study and quantified the energy impact of replacing a constant speed pump with a pump driven by a variable frequency drive in a ground-coupled heat pump (GCHP) system that was installed in the high school. Performance data collected from an on-site energy management system showed that the annual energy consumption of the heat pumps is 33 per cent (63700 kWh) of the total energy consumption of the school while the circulating pump consumes 7.1 per cent (13702 kWh). This performance data was used to validate the energy simulations which were performed using TRNSYS 15. Simulations with variable-flow pumping showed that pumping energy consumption was reduced by about 82 per cent while the total energy used by the circulating pump and heat pumps was reduced by 18.5 per cent. 11 refs., 2 tabs., 13 figs.

Specific heat of MgB2 after irradiation

International Nuclear Information System (INIS)

Wang Yuxing; Bouquet, Frederic; Sheikin, Ilya; Toulemonde, Pierre; Revaz, Bernard; Eisterer, Michael; Weber, Harald W; Hinderer, Joerg; Junod, Alain

2003-01-01

We studied the effect of disorder on the superconducting properties of polycrystalline MgB 2 by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2Δ 0 /k B T c =1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T c and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutrons, a substantial bulk increase of dH c2 /dT at T c can be obtained without sacrificing more than a few degrees in T c . The upper critical field of the sample after irradiation exceeds 28 T at T→0

Specific heat of rare earth cobaltates RCoO{sub 3} (R = La, Pr and Nd)

Energy Technology Data Exchange (ETDEWEB)

Thakur, Rasna, E-mail: rasnathakur@yahoo.com [Department of Physics, Barkatullah University, Bhopal 462026 (India); Srivastava, Archana [Department of Physics, Sri Sathya Sai College for Women, Bhopal 462024 (India); Thakur, Rajesh K.; Gaur, N.K. [Department of Physics, Barkatullah University, Bhopal 462026 (India)

2012-03-05

Highlights: Black-Right-Pointing-Pointer We have reported the temperature dependence (5 K {<=} T {<=} 1000 K) of the lattice contribution to the specific heat of rhombohedral LaCoO{sub 3} and orthocobaltates RCoO{sub 3} (R = Pr and Nd). Black-Right-Pointing-Pointer The strong electron phonon interactions are present in these compounds and lattice distortions can affect them substantially. Black-Right-Pointing-Pointer Thus Rigid Ion Model (RIM) is used for the first time to study the cohesive and thermal properties of the cobaltates RCoO{sub 3} with rare earth cation (R = La, Pr and Nd). Black-Right-Pointing-Pointer The values of specific heat calculated by us have shown remarkably good agreement with corresponding experimental data. Black-Right-Pointing-Pointer In addition, the results on the temperature dependence of cohesive energy ({phi}), molecular force constant (f), Reststrahlen frequency ({upsilon}), Debye temperature ({theta}{sub D}) and Gruneisen parameter ({gamma}) are also reported. - Abstract: We have reported the temperature dependence (5 K {<=} T {<=} 1000 K) of the lattice contribution to the specific heat of rhombohedral LaCoO{sub 3} and orthocobaltates RCoO{sub 3} (R = Pr and Nd). The strong electron phonon interactions are present in these compounds and lattice distortions can affect them substantially. Thus Rigid Ion Model (RIM) is used for the first time to study the cohesive and thermal properties of the cobaltates RCoO{sub 3} with rare earth cation (R = La, Pr and Nd). The values of specific heat calculated by us have shown remarkably good agreement with corresponding experimental data. In addition, the results on the temperature dependence of cohesive energy ({phi}), molecular force constant (f), Reststrahlen frequency ({upsilon}), Debye temperature ({theta}{sub D}) and Gruneisen parameter ({gamma}) are also reported.

Technical specification improvements to containment heat removal and emergency core cooling systems: Final report

International Nuclear Information System (INIS)

Sullivan, W.P.; Ha, C.; Pentzien, D.C.; Visweswaran, S.

1988-07-01

This report presents the results of an analysis for technical specification improvements to the emergency core cooling systems (ECCS) and containment heat removal systems (EPRI Research Project 2142-3). The objective of this project is to further develop a reliability- and risk-based methodology to provide improvements by considering groups of surveillance test intervals and allowed out-of-service times jointly. This was done for the technical specifications for the ECCS, containment heat removal equipment, and supporting systems of a boiling water reactor plant. The project (1) developed a methodology for optimizing groups of surveillance test intervals and allowed out-of-service times jointly, (2) applied the methodology in a case study of a specific operating plant, Hatch-2, and (3) evaluated benefits of the application. The results of the case study demonstrate that beneficial technical specification improvements can be realized with application of the methodology. By tightening a small group of sensitive surveillance test intervals (STIs) and allowed out-of-service times (AOTs), a larger group of less sensitive STIs and AOTs can be extended resulting in an overall plant operating cost improvement without reducing the plant safety. The reliability- and risk-based methodology and results from this project can be effectively applied for technical specification improvements at other operating plants

Ocean heat content variability and change in an ensemble of ocean reanalyses

Science.gov (United States)

Palmer, M. D.; Roberts, C. D.; Balmaseda, M.; Chang, Y.-S.; Chepurin, G.; Ferry, N.; Fujii, Y.; Good, S. A.; Guinehut, S.; Haines, K.; Hernandez, F.; Köhl, A.; Lee, T.; Martin, M. J.; Masina, S.; Masuda, S.; Peterson, K. A.; Storto, A.; Toyoda, T.; Valdivieso, M.; Vernieres, G.; Wang, O.; Xue, Y.

2017-08-01

Accurate knowledge of the location and magnitude of ocean heat content (OHC) variability and change is essential for understanding the processes that govern decadal variations in surface temperature, quantifying changes in the planetary energy budget, and developing constraints on the transient climate response to external forcings. We present an overview of the temporal and spatial characteristics of OHC variability and change as represented by an ensemble of dynamical and statistical ocean reanalyses (ORAs). Spatial maps of the 0-300 m layer show large regions of the Pacific and Indian Oceans where the interannual variability of the ensemble mean exceeds ensemble spread, indicating that OHC variations are well-constrained by the available observations over the period 1993-2009. At deeper levels, the ORAs are less well-constrained by observations with the largest differences across the ensemble mostly associated with areas of high eddy kinetic energy, such as the Southern Ocean and boundary current regions. Spatial patterns of OHC change for the period 1997-2009 show good agreement in the upper 300 m and are characterized by a strong dipole pattern in the Pacific Ocean. There is less agreement in the patterns of change at deeper levels, potentially linked to differences in the representation of ocean dynamics, such as water mass formation processes. However, the Atlantic and Southern Oceans are regions in which many ORAs show widespread warming below 700 m over the period 1997-2009. Annual time series of global and hemispheric OHC change for 0-700 m show the largest spread for the data sparse Southern Hemisphere and a number of ORAs seem to be subject to large initialization `shock' over the first few years. In agreement with previous studies, a number of ORAs exhibit enhanced ocean heat uptake below 300 and 700 m during the mid-1990s or early 2000s. The ORA ensemble mean (±1 standard deviation) of rolling 5-year trends in full-depth OHC shows a relatively steady

Low-temperature specific heat of the quasi-two-dimensional charge-density wave compound KMo6O17

Science.gov (United States)

Wang, Junfeng; Xiong, Rui; Yin, Di; Li, Changzhen; Tang, Zheng; Wang, Ququan; Shi, Jing; Wang, Yue; Wen, Haihu

2006-05-01

Low temperature specific heat (Cp) of quasi-two-dimensional charge-density wave (CDW) compound KMo6O17 has been studied by a relaxation method from 2to48K under zero and 12T magnetic fields. The results show that no specific heat anomaly is found at 16K under both zero and 12T magnetic fields, although an anomaly is clearly observed in the resistivity and magnetoresistance measurements. From the data between 2 and 4K , the density of states at Fermi level is estimated as 0.2eV-1permolecule and the Debye temperature is extracted to be 418K . A bump appearing in Cp/T3 is found between 4 and 48K centered around 12.5-15K , indicating that the phason excitations contribute to the total specific heat similarly as in quasi-one-dimensional CDW conductors. Using a modified Debye model, a pinning frequency of 0.73THz for KMo6O17 is estimated from the phason contribution.

A study on specific heat capacities of Li-ion cell components and their influence on thermal management

Science.gov (United States)

Loges, André; Herberger, Sabrina; Seegert, Philipp; Wetzel, Thomas

2016-12-01

Thermal models of Li-ion cells on various geometrical scales and with various complexity have been developed in the past to account for the temperature dependent behaviour of Li-ion cells. These models require accurate data on thermal material properties to offer reliable validation and interpretation of the results. In this context a thorough study on the specific heat capacities of Li-ion cells starting from raw materials and electrode coatings to representative unit cells of jelly rolls/electrode stacks with lumped values was conducted. The specific heat capacity is reported as a function of temperature and state of charge (SOC). Seven Li-ion cells from different manufactures with different cell chemistry, application and design were considered and generally applicable correlations were developed. A 2D thermal model of an automotive Li-ion cell for plug-in hybrid electric vehicle (PHEV) application illustrates the influence of specific heat capacity on the effectivity of cooling concepts and the temperature development of Li-ion cells.

Single Chain Variable Fragments Produced in Escherichia coli against Heat-Labile and Heat-Stable Toxins from Enterotoxigenic E. coli.

Directory of Open Access Journals (Sweden)

Christiane Y Ozaki

Full Text Available Diarrhea is a prevalent pathological condition frequently associated to the colonization of the small intestine by enterotoxigenic Escherichia coli (ETEC strains, known to be endemic in developing countries. These strains can produce two enterotoxins associated with the manifestation of clinical symptoms that can be used to detect these pathogens. Although several detection tests have been developed, minimally equipped laboratories are still in need of simple and cost-effective methods. With the aim to contribute to the development of such diagnostic approaches, we describe here two mouse hybridoma-derived single chain fragment variable (scFv that were produced in E. coli against enterotoxins of ETEC strains.Recombinant scFv were developed against ETEC heat-labile toxin (LT and heat-stable toxin (ST, from previously isolated hybridoma clones. This work reports their design, construction, molecular and functional characterization against LT and ST toxins. Both antibody fragments were able to recognize the cell-interacting toxins by immunofluorescence, the purified toxins by ELISA and also LT-, ST- and LT/ST-producing ETEC strains.The developed recombinant scFvs against LT and ST constitute promising starting point for simple and cost-effective ETEC diagnosis.

Multidimensional Heat Conduction

DEFF Research Database (Denmark)

Rode, Carsten

1998-01-01

Analytical theory of multidimensional heat conduction. General heat conduction equation in three dimensions. Steay state, analytical solutions. The Laplace equation. Method of separation of variables. Principle of superposition. Shape factors. Transient, multidimensional heat conduction....

Environmental interaction, additive and non-additive genetic variability is involved in the expression of tissue and whole-plant heat tolerance in upland cotton (Gossypium hirsutum. L

Directory of Open Access Journals (Sweden)

Hafeez-ur-Rahman

2006-01-01

Full Text Available Heat tolerance is measured at tissue level by cellular membrane thermostability (CMT and at the whole plant level by the heat tolerance index (HTI. Eight upland cotton cultivars and 15 crosses were used to determine the type and extent of genetic variability associated with the expression of these traits between and within environments. Heat stress and non-stress conditions were used as the CMT environments and years for HTI. The wide variation in heterotic expression and combining ability effects observed for CMT and HTI suggest multigenic inheritance of these traits. Significant genetic variability across environments was evident but the traits were not highly heritable because of substantial environmental interaction. The available genetic variability included both additive and non-additive components, but the proportion of additive genetic variability was high for HTI. The parental cultivars CRIS-19 and CIM-448 were good donor parents for high CMT under heat-stressed conditions, and MNH-552 and N-Karishma under non-stressed conditions. Cultivar FH-634 was a good donor parent for HTI. The results show two types of general combining ability (GCA inheritance among high CMT parents: positive GCA inheritance expressed by CRIS-19 in the presence of heat stress and MNH-552 and N-Karishma in the absence of heat stress; and negative GCA inheritance expressed by FH-900 in the presence of heat stress. It was also evident that genes controlling high CMT in cultivar CRIS-19 were different from those present in the MNH-552, N-Karishma and FH-900 cultivars. Similarly, among high HTI parents, FH-634 showed positive and CIM-443 negative GCA inheritance. No significant relationship due to genetic causes existed between tissue and whole plant heat tolerance, diminishing the likelihood of simultaneous improvement and selection of the two traits.

Monte Carlo study of internal energy and specific heat of a nano-graphene bilayer in a longitudinal magnetic field

Energy Technology Data Exchange (ETDEWEB)

Luo, Xiao-hong; Wang, Wei, E-mail: ww9803@126.com; Chen, Dong-dong; Xu, Si-yuan

2016-06-15

The thermodynamic properties of a nano-graphene bilayer, consisting of the upper layer A of spin-3/2 with antiferromagnetic intralayer exchange coupling and the bottom layer B of spin-5/2 with ferromagnetic intralayer exchange coupling, have been studied by the use of Monte Carlo simulation. We find a number of characteristic phenomena. The effects of the exchange coupling, the single-ion anisotropy and the longitudinal magnetic field on the internal energy, the specific heat and the blocking temperature of the mixed-spin bilayer system have been investigated in detail. The internal energy and the specific heat profiles are clarified. In particular, we have found that the specific heat curve may show two peaks phenomenon for appropriate values of the system parameters.

Combined effect of thermal dispersion and variable viscosity of non-darcy convection heat transfer in a fluidsaturated porous medium

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; El-Amin, Ammaarah A.; Gorla, Rama Subba Reddy

2013-01-01

In this paper, the effects of thermal dispersion and variable viscosity on the non-Darcy free, mixed, and forced convection heat transfer along a vertical flat plate embedded in a fluid-saturated porous medium are investigated. Forchheimer extension

Low-temperature specific heat measurements on the NdCoxFe1-xO3 system

International Nuclear Information System (INIS)

Bartolome, F.; Kuz'min, M.D.; Bartolome, J.; Blasco, J.; Garcia, J.

1995-01-01

Low-temperature specific heat measurements have been carried out on the NdCo x Fe 1-x O 3 perovskite system (x=0, 0.25, 0.5, 0.9, 1). Magnetic ordering of Nd 3+ ions have been observed in NdCoO 3 (at 1.20 K) and NdFeO 3 (at 1.05 K). The studied dilutions, unlike the pure Fe or Co compounds, do not show a magnetic order of the Nd ions due to the stronger molecular field caused by decompensation of the internal field upon the introduction of the (Co 3+ ) magnetic vacancies in the antiferromagnetically ordered Fe subsystem. The specific heat curve of the system at x=0.9 resembles spin-glass behaviour. ((orig.))

Energy saving analyses on the reconstruction project in district heating system with distributed variable speed pumps

International Nuclear Information System (INIS)

Sheng, Xianjie; Lin, Duanmu

2016-01-01

Highlights: • The mathematical model of economic frictional factor based on DVFSP DHS is established. • Influence factors of economic frictional factor are analyzed. • Energy saving in a DVFSP district heating system is presented and analyzed. - Abstract: Optimization of the district heating (DH) piping network is of vital importance to the economics of the whole DH system. The application of distributed variable frequency speed pump (DVFSP) in the district heating network has been considered as a technology improvement that has a potential in saving energy compared to the conventional central circulating pump (CCCP) district heating system (DHS). Economic frictional factor is a common design parameter used in DH pipe network design. In this paper, the mathematical model of economic frictional factor based on DVFSP DHS is established, and influence factors are analyzed, providing a reference for engineering designs for the system. According to the analysis results, it is studied that the energy efficiency in the DH system with the DVFSP is compared with the one in the DH system with conventional central circulating pump (CCCP) using a case based on a district heating network in Dalian, China. The results of the study on the case show that the average electrical energy saved is 49.41% of the one saved by the DH system with conventional central circulating pump in the primary network.

Phonon-induced anomalous specific heat of a model nanocrystal by computer simulation

International Nuclear Information System (INIS)

Wang, J.; Wolf, D.; Phillpot, S.R.; Gleiter, H.

1994-10-01

The authors construct a simple model of a nanocrystalline material in which all the grains are the same size and shape, and in which all the grain boundaries are crystallographically identical. The authors show that the model nanocrystal has a low-temperature specific-heat anomaly similar to that seen in experiment, which arises from the presence of low-frequency phonons localized at the grain boundaries

Calculation of cracking under pulsed heat loads in tungsten manufactured according to ITER specifications

International Nuclear Information System (INIS)

Arakcheev, A.S.; Skovorodin, D.I.; Burdakov, A.V.; Shoshin, A.A.; Polosatkin, S.V.; Vasilyev, A.A.; Postupaev, V.V.; Vyacheslavov, L.N.; Kasatov, A.A.; Huber, A.; Mertens, Ph; Wirtz, M.; Linsmeier, Ch; Kreter, A.; Löwenhoff, Th; Begrambekov, L.; Grunin, A.; Sadovskiy, Ya

2015-01-01

A mathematical model of surface cracking under pulsed heat load was developed. The model correctly describes a smooth brittle–ductile transition. The elastic deformation is described in a thin-heated-layer approximation. The plastic deformation is described with the Hollomon equation. The time dependence of the deformation and stresses is described for one heating–cooling cycle for a material without initial plastic deformation. The model can be applied to tungsten manufactured according to ITER specifications. The model shows that the stability of stress-relieved tungsten deteriorates when the base temperature increases. This proved to be a result of the close ultimate tensile and yield strengths. For a heat load of arbitrary magnitude a stability criterion was obtained in the form of condition on the relation of the ultimate tensile and yield strengths.

Design Analysis of a High Temperature Radiator for the Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

Science.gov (United States)

Sheth, Rubik B.; Ungar, Eugene K.; Chambliss, Joe P.; Cassady, Leonard D.

2011-01-01

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR), currently under development by Ad Astra Rocket Company, is a unique propulsion system that can potentially change the way space propulsion is performed. VASIMR's efficiency, when compared to that of a conventional chemical rocket, reduce propellant needed for exploration missions by a factor of 10. Currently plans include flight tests of a 200 kW VASIMR system, titled VF-200, on the International Space Station. The VF-200 will consist of two 100 kW thruster units packaged together in one engine bus. Each thruster unit has a unique heat rejection requirement of about 27 kW over a firing time of 15 minutes. In order to control rocket core temperatures, peak operating temperatures of about 300 C are expected within the thermal control loop. Design of a high temperature radiator is a unique challenge for the vehicle design. This paper will discuss the path taken to develop a steady state and transient based radiator design. The paper will describe radiator design options for the VASIMR thermal control system for use on ISS as well as future exploration vehicles.

Evaluation of specific heat for superfluid helium between 0 - 2.1 K based on nonlinear theory

International Nuclear Information System (INIS)

Sasaki, Shosuke

2009-01-01

The specific heat of liquid helium was calculated theoretically in the Landau theory. The results deviate from experimental data in the temperature region of 1.3 - 2.1 K. Many theorists subsequently improved the results of the Landau theory by applying temperature dependence of the elementary excitation energy. As well known, many-body system has a total energy of Galilean covariant form. Therefore, the total energy of liquid helium has a nonlinear form for the number distribution function. The function form can be determined using the excitation energy at zero temperature and the latent heat per helium atom at zero temperature. The nonlinear form produces new temperature dependence for the excitation energy from Bose condensate. We evaluate the specific heat using iteration method. The calculation results of the second iteration show good agreement with the experimental data in the temperature region of 0 - 2.1 K, where we have only used the elementary excitation energy at 1.1 K.

Numerical renormalization group calculation of impurity internal energy and specific heat of quantum impurity models

Science.gov (United States)

Merker, L.; Costi, T. A.

2012-08-01

We introduce a method to obtain the specific heat of quantum impurity models via a direct calculation of the impurity internal energy requiring only the evaluation of local quantities within a single numerical renormalization group (NRG) calculation for the total system. For the Anderson impurity model we show that the impurity internal energy can be expressed as a sum of purely local static correlation functions and a term that involves also the impurity Green function. The temperature dependence of the latter can be neglected in many cases, thereby allowing the impurity specific heat Cimp to be calculated accurately from local static correlation functions; specifically via Cimp=(∂Eionic)/(∂T)+(1)/(2)(∂Ehyb)/(∂T), where Eionic and Ehyb are the energies of the (embedded) impurity and the hybridization energy, respectively. The term involving the Green function can also be evaluated in cases where its temperature dependence is non-negligible, adding an extra term to Cimp. For the nondegenerate Anderson impurity model, we show by comparison with exact Bethe ansatz calculations that the results recover accurately both the Kondo induced peak in the specific heat at low temperatures as well as the high-temperature peak due to the resonant level. The approach applies to multiorbital and multichannel Anderson impurity models with arbitrary local Coulomb interactions. An application to the Ohmic two-state system and the anisotropic Kondo model is also given, with comparisons to Bethe ansatz calculations. The approach could also be of interest within other impurity solvers, for example, within quantum Monte Carlo techniques.

Specific heat of the 38-K superconductor MgB_2 in the normal and superconducting state: bulk evidence for a double gap

OpenAIRE

Junod, Alain; Wang, Yuxing; Bouquet, Frederic; Toulemonde, Pierre

2001-01-01

The specific heat of two polycrystalline samples of MgB_2 is presented and analyzed (2 - 300 K, 0 - 16 T), together with magnetic properties. The main characteristics are a low density of states at the Fermi level, high phonon frequencies, and an anomalous temperature- and field- dependence of the specific heat at T < T_c. A two-gap model with a gap ratio of 3:1 fits the specific heat in zero field. The smaller gap is washed out by a field of 0.5 T.

Neutron diffraction, specific heat and magnetic susceptibility of Ni3(PO4)2

International Nuclear Information System (INIS)

Escobal, J.; Pizarro, J.L.; Mesa, J.L.; Rojo, J.M.; Bazan, B.; Arriortua, M.I.; Rojo, T.

2005-01-01

The Ni 3 (PO 4 ) 2 phosphate was synthesized by the ceramic method in air atmosphere. The crystal structure consists of a three-dimensional skeleton constructed from Ni 3 O 14 edge-sharing octahedra, which are interconnected by (PO 4 ) 3- oxoanions with tetrahedral geometry. The magnetic behavior was studied on powdered sample by using susceptibility, specific heat and neutron diffraction data. The nickel(II) orthophosphate exhibits a three-dimensional magnetic ordering at approximately 17.1 K. However, its complex crystal structure hampers any parametrization of the J-exchange parameter. The specific heat measurements of Ni 3 (PO 4 ) 2 exhibit a three-dimensional magnetic ordering (λ-type) peak at 17.1 K. Measurements above T N suggest the presence of a small short-range order in this phase. The total magnetic entropy was found to be 28.1 KJ/mol at 50 K. The magnetic structure of the nickel(II) phosphate exhibits ferromagnetic interactions inside the Ni 3 O 14 trimers which are antiferromagnetically coupled between them, giving rise to a purely antiferromagnetic structure

Unusual specific heat of almost dry L-cysteine and L-cystine amino acids.

Science.gov (United States)

Ishikawa, M S; Lima, T A; Ferreira, F F; Martinho, H S

2015-03-01

A detailed quantitative analysis of the specific heat in the 0.5- to 200-K temperature range for almost dry L-cysteine and its dimer, L-cystine, amino acids is presented. We report the occurrence of a sharp first-order transition at ∼76 K for L-cysteine associated with the thiol group ordering which was successfully modeled with the two-dimensional Ising model. We demonstrated that quantum rotors, two-level systems (TLS), Einstein oscillators, and acoustic phonons (the Debye model) are essential ingredients to correctly describe the overall experimental data. Our analysis pointed out the absence of the TLS contribution to the low temperature specific heat of L-cysteine. This result was similar to that found in other noncrystalline amorphous materials, e.g., amorphous silicon, low density amorphous water, and ultrastable glasses. L-cystine presented an unusual nonlinear acoustic dispersion relation ω(q)=vq0.95 and a Maxwell-Boltzmann-type distribution of tunneling barriers. The presence of Einstein oscillators with ΘE∼70 K was common in both systems and adequately modeled the boson peak contributions.

Pressure dependence of thermal conductivity and specific heat in CeRh2Si2 measured by an extended thermal relaxation method

Science.gov (United States)

Nishigori, Shijo; Seida, Osamu

2018-05-01

We have developed a new technique for measuring thermal conductivity and specific heat under pressure by improving a thermal relaxation method. In this technique, a cylindrical sample with a small disc heater is embedded in the pressure-transmitting medium, then temperature variations of the sample and heater were directly measured by thermocouples during a heating and cooling process. Thermal conductivity and specific heat are estimated by comparing the experimental data with temperature variations simulated by a finite element method. The obtained thermal conductivity and specific heat of the test sample CeRh2Si2 exhibit a small enhancement and a clear peak arising from antiferromagnetic transition, respectively. The observation of these typical behaviors for magnetic compounds indicate that the technique is valid for the study on thermal properties under pressure.

Lattice specific heat for the RMIn{sub 5} (R=Gd, La, Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction

Energy Technology Data Exchange (ETDEWEB)

Facio, Jorge I., E-mail: jorge.facio@cab.cnea.gov.ar [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Betancourth, D.; Cejas Bolecek, N.R. [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Jorge, G.A. [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Pedrazzini, Pablo; Correa, V.F.; Cornaglia, Pablo S. [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Vildosola, V. [Centro Atómico Constituyentes, CNEA, 1650 San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); García, D.J. [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina)

2016-06-01

We analyze theoretically a common experimental process used to obtain the magnetic contribution to the specific heat of a given magnetic material. In the procedure, the specific heat of a non-magnetic analog is measured and used to subtract the non-magnetic contributions, which are generally dominated by the lattice degrees of freedom in a wide range of temperatures. We calculate the lattice contribution to the specific heat for the magnetic compounds GdMIn{sub 5} (M=Co, Rh) and for the non-magnetic YMIn{sub 5} and LaMIn{sub 5} (M=Co, Rh), using density functional theory based methods. We find that the best non-magnetic analog for the subtraction depends on the magnetic material and on the range of temperatures. While the phonon specific heat contribution of YRhIn{sub 5} is an excellent approximation to the one of GdCoIn{sub 5} in the full temperature range, for GdRhIn{sub 5} we find a better agreement with LaCoIn{sub 5}, in both cases, as a result of an optimum compensation effect between masses and volumes. We present measurements of the specific heat of the compounds GdMIn{sub 5} (M=Co, Rh) up to room temperature where it surpasses the value expected from the Dulong–Petit law. We obtain a good agreement between theory and experiment when we include anharmonic effects in the calculations.

Communication: High pressure specific heat spectroscopy reveals simple relaxation behavior of glass forming molecular liquid

DEFF Research Database (Denmark)

Roed, Lisa Anita; Niss, Kristine; Jakobsen, Bo

2015-01-01

The frequency dependent specific heat has been measured under pressure for the molecular glass forming liquid 5-polyphenyl-4-ether in the viscous regime close to the glass transition. The temperature and pressure dependences of the characteristic time scale associated with the specific heat...... is compared to the equivalent time scale from dielectric spectroscopy performed under identical conditions. It is shown that the ratio between the two time scales is independent of both temperature and pressure. This observation is non-trivial and demonstrates the existence of specially simple molecular...... liquids in which different physical relaxation processes are both as function of temperature and pressure/density governed by the same underlying “inner clock.” Furthermore, the results are discussed in terms of the recent conjecture that van der Waals liquids, like the measuredliquid, comply...

Susceptibility and specific heat of the Heisenberg antiferromagnet on the Kagome lattice

International Nuclear Information System (INIS)

Bernhard, B.H.; Canals, B.; Lacroix, C.

2001-01-01

The dynamic susceptibility of the S=((1)/(2)) Heisenberg antiferromagnet is calculated on the Kagome lattice by means of a Green's function decoupling scheme. The spin-spin correlation functions decrease exponentially with distance. The specific heat exhibits a single-peak structure with a T 2 dependence at low temperature and the correct high-temperature behaviour. The calculated total change in entropy indicates a ground-state entropy of 0.46 ln 2

Thermal resistance of a convectively cooled plate with applied heat flux and variable internal heat generation

International Nuclear Information System (INIS)

Venkataraman, N.S.; Cardoso, H.P.; Oliveira Filho, O.B. de

1981-01-01

The conductive heat transfer in a rectangular plate with nonuniform internal heat generation, with one end convectively cooled and a part of the opposite end subjected to external heat flux is considered. The remaining part of this end as well as the other two sides are thermally insulated. The governing differential equation is solved by a finite difference scheme. The variation of the thermal resistance with Biot modulus, the plate geometry, the internal heat generation parameter and the type of profile of internal heat generation is discussed. (author) [pt

Specific heat and magnetic susceptibility vs long range order in V3Ga

International Nuclear Information System (INIS)

Junod, A.; Fluekiger, R.; Treyvaud, A.; Muller, J.

1976-01-01

A new technique of studying the magnetic susceptibility together with the specific heat and the superconducting transition of typical A15-type compounds in different ordering states enables us to consistently isolate the spin paramagnetism. Satisfactory results are obtained for V 3 Ga and these are compared with data on V 3 Au and Nb 3 (Au-Pt). (author)

Identifying Changes in the Probability of High Temperature, High Humidity Heat Wave Events

Science.gov (United States)

Ballard, T.; Diffenbaugh, N. S.

2016-12-01

Understanding how heat waves will respond to climate change is critical for adequate planning and adaptation. While temperature is the primary determinant of heat wave severity, humidity has been shown to play a key role in heat wave intensity with direct links to human health and safety. Here we investigate the individual contributions of temperature and specific humidity to extreme heat wave conditions in recent decades. Using global NCEP-DOE Reanalysis II daily data, we identify regional variability in the joint probability distribution of humidity and temperature. We also identify a statistically significant positive trend in humidity over the eastern U.S. during heat wave events, leading to an increased probability of high humidity, high temperature events. The extent to which we can expect this trend to continue under climate change is complicated due to variability between CMIP5 models, in particular among projections of humidity. However, our results support the notion that heat wave dynamics are characterized by more than high temperatures alone, and understanding and quantifying the various components of the heat wave system is crucial for forecasting future impacts.

Specific heat of Ginzburg-Landau fields in the n-1 expansion

International Nuclear Information System (INIS)

Bray, A.J.

1975-01-01

The n -1 expansion for the specific heat C/subv/ of the n-component Ginzburg-Landau model is discussed in terms of an n -1 expansion for the irreducible polarization. In the low-temperature limit, each successive term of the latter expansion diverges more strongly than the last, invalidating a truncation of this series at any finite order in 1/n. The most divergent terms in each order are identified and summed. The results provide justification for the usual truncated expansions for C/subv/

Heat-treatment and heat-to-heat variations in the fracture toughness of Alloy 718

International Nuclear Information System (INIS)

Mills, W.J.

1981-07-01

The effect of heat-treatment and heat-to-heat variations on the J Ic fracture toughness response of Alloy 718 was examined at room and elevated temperatures using the multiple-specimen R-curve technique. Six heats of alloy 718 were tested in the conventional and modified heat-treated conditions. The fracture toughness response for the modified superalloy was found to be superior to that exhibited by the conventional material. Heat-to-heat variations in the J Ic response of Alloy 718 were observed in both heat-treated conditions; the modified treatment exhibited much larger variability. The J Ic and corresponding K Ic fracture toughness values were analyzed statistically to establish minimum expected toughness, values for use in design and safety analyses. 26 refs., 10 figs., 9 tabs

Measurement of condensation heat transfer coefficients in a steam chamber using a variable conductance heat pipe

International Nuclear Information System (INIS)

Robinson, J.A.; Windebank, S.R.

1988-01-01

Condensation heat transfer coefficients have been measured in a pressurised chamber containing a mixture of saturated steam and air. They were determined as a function of the air-steam ratio in nominally stagnant conditions. The effect of pressure is assessed and preliminary measurements with a forced convective component of velocity are presented. A novel measurement technique was adopted, namely to use a vertical heat pipe whose conductance could easily be varied. It transported heat from an evaporator located inside the chamber to a condenser section outside, at which the heat flow was measured. Heat flux at the evaporator could then be determined and a condensation heat transfer coefficient derived. The range of coefficients covered was from 150 W/m 2 0 K at high air-steam ratios to 20,000 W/m 2 0 K in pure steam. Results show that increasing either total pressure or velocity enhances condensation heat transfer over the range of air/steam ratios considered. (author)

Optimizing the District Heating Primary Network from the Perspective of Economic-Specific Pressure Loss

Directory of Open Access Journals (Sweden)

Haichao Wang

2017-07-01

Full Text Available A district heating (DH system is one of the most important components of infrastructures in cold areas. Proper DH network design should balance the initial investment and the heat distribution cost of the DH network. Currently, this design is often based on a recommended value for specific pressure loss (R = ∆P/L in the main lines. This will result in a feasible network design, but probably not be optimal in most cases. The paper develops a novel optimization model to facilitate the design by considering the initial investment in the pipes and the heat distribution costs. The model will generate all possible network scenarios consisting of different series of diameters for each pipe in the flow direction of the network. Then, the annuity on the initial investment, the heat distribution cost, and the total annual cost will be calculated for each network scenario, taking into account the uncertainties of the material prices and the yearly operating time levels. The model is applied to a sample DH network and the results indicate that the model works quite well, clearly identifying the optimal network design and demonstrating that the heat distribution cost is more important than the initial investment in DH network design.

Mixed convection heat transfer simulation in a rectangular channel with a variable speed rotational cylinder

Science.gov (United States)

Khan, Md Imran; Billah, Md. Mamun; Rahman, Mohammed Mizanur; Hasan, Mohammad Nasim

2017-12-01

Numerical simulation of steady two-dimensional heat transfer in a rectangular channel with a centered variable speed cylinder has been performed in this paper. In this setup, an isoflux heater is placed at the bottom wall of the channel while the upper wall is kept isothermal with a low temperature. The cylinder's peripheral speed to maximum inlet fluid velocity ratio (ξ) is varied from 0.5 to 1.5 for both clockwise and anticlockwise rotational cases. Air has been considered as working fluid while other system parameters such as Grashof and Reynolds numbers are varied. The effects of rotational speed, Grashof and Reynolds numbers on the streamline pattern, isothermal lines, local and average Nusselt number are analyzed and presented. It is observed the cylinder's rotational direction and speed has a significant effect on the flow pattern, temperature distribution as well as heat transfer characteristics.

Flow and Heat Transfer of Bingham Plastic Fluid over a Rotating Disk with Variable Thickness

Science.gov (United States)

Liu, Chunyan; Pan, Mingyang; Zheng, Liancun; Ming, Chunying; Zhang, Xinxin

2016-11-01

This paper studies the steady flow and heat transfer of Bingham plastic fluid over a rotating disk of finite radius with variable thickness radially in boundary layer. The boundary layer flow is caused by the rotating disk when the extra stress is greater than the yield stress of the Bingham fluid. The analyses of the velocity and temperature field related to the variable thickness disk have not been investigated in current literatures. The governing equations are first simplified into ordinary differential equations owing to the generalized von Kármán transformation for seeking solutions easily. Then semi-similarity approximate analytical solutions are obtained by using the homotopy analysis method for different physical parameters. It is found that the Bingham number clearly influences the velocity field distribution, and the skin friction coefficient Cfr is nonlinear growth with respect to the shape parameter m. Additionally, the effects of the involved parameters (i.e. shape parameter m, variable thickness parameter β, Reynolds number Rev, and Prandtl number Pr) on velocity and temperature distribution are investigated and analyzed in detail.

Quantification of the heat wave effect on mortality in nine French cities during summer 2006.

Science.gov (United States)

Pascal, Mathilde; Le Tertre, Alain; Saoudi, Abdessattar

2012-02-23

July 2006 was the first major heat wave in France after the creation of a heat prevention plan. Understanding its impacts on health will help improving the efficiency of this plan. We assessed the mortality impact of the heat wave, and investigated the influence of the heat prevention plan. The study focused on nine French cities. A Poisson regression model was used to analyze the correlation between temperature, air quality and mortality. An additional spline of time was introduced to capture an additional heat wave effect. Heat-action days defined by the prevention plan were introduced as a dummy variable. 411 extra deaths were observed in the nine cities during the 2006 heat wave. Unlike the 2003 heat wave, no additional heat wave effect was observed in 2006. The maximum daily relative risk of mortality varied from 1.45 in Strasbourg (IC 95% [1.01-2.08]) to 1.04 in Lille (IC 95% [0.92-1.18]). The impact on mortality of the implementation of heat-action days was non-significant and highly variable depending on the cities, with a combined excess of relative risk of -3.3% (IC 95% [-10.3%; 4.4%]). Although no specific heat wave effect was observed, warm temperatures and air pollution were still responsible for a significant excess mortality in France. The absence of a specific heat wave effect may be partly explained by the prevention plan. It may also indicate that higher temperatures are required to observe a mortality outburst.

The Role of the Process and Design Variables in Improving the Performance of Heat Exchanger Tube Expansion

Directory of Open Access Journals (Sweden)

Changwan Han

2018-05-01

Full Text Available In the expansion process of a fin-tube heat exchanger, the process variables and shape of the expansion ball affect the deformation of the tube’s inner grooves, the adhesion, and the expansion force. These factors influence the efficiency of heat transfer and the lifetime of the expansion equipment. Therefore, this study analyzed the influential variables of the tube expansion process as well as the expansion ball design through experiments and simulations. A new method was proposed to determine the severity of adhesion in the tube’s inner grooves using the expansion force rate. Expansion experiments with Al tubes show that the expansion force decreases when using a lubricant with high viscosity and when the lubricant remains on the expansion ball for a longer duration. Finite element analysis was also performed to examine the expansion of Cu tubes, which showed that the expansion force was higher when using expansion ball shapes that have higher contact area between the ball and tube surface. The radius of curvature of the expansion ball also influenced the expansion force. However, increasing the ratio of the radial force to the expansion force increased the deformation of the tube’s inner grooves.

Influence on Heat Transfer Coefficient of Heat Exchanger by Velocity and Heat Transfer Temperature Difference

Directory of Open Access Journals (Sweden)

WANG Fang

2017-04-01

Full Text Available Aimed to insufficient heat transfer of heat exchanger, research the influence on the heat transfer coefficient impacted by velocity and heat transfer temperature difference of tube heat exchanger. According to the different heat transfer temperature difference and gas velocity，the experimental data were divided into group. Using the control variable method，the above two factors were analyzed separately. K一△T and k一:fitting curve were clone to obtain empirical function. The entire heat exchanger is as the study object，using numerical simulation methods，porous media，k一￡model，second order upwind mode，and pressure一velocity coupling with SIMPLE algorithm，the entire heat exchanger temperature field and the heat transfer coefficient distribution were given. Finally the trend of the heat transfer coefficient effected by the above two factors was gotten.

Lunar Base Heat Pump

Science.gov (United States)

Walker, D.; Fischbach, D.; Tetreault, R.

1996-01-01

The objective of this project was to investigate the feasibility of constructing a heat pump suitable for use as a heat rejection device in applications such as a lunar base. In this situation, direct heat rejection through the use of radiators is not possible at a temperature suitable for lde support systems. Initial analysis of a heat pump of this type called for a temperature lift of approximately 378 deg. K, which is considerably higher than is commonly called for in HVAC and refrigeration applications where heat pumps are most often employed. Also because of the variation of the rejection temperature (from 100 to 381 deg. K), extreme flexibility in the configuration and operation of the heat pump is required. A three-stage compression cycle using a refrigerant such as CFC-11 or HCFC-123 was formulated with operation possible with one, two or three stages of compression. Also, to meet the redundancy requirements, compression was divided up over multiple compressors in each stage. A control scheme was devised that allowed these multiple compressors to be operated as required so that the heat pump could perform with variable heat loads and rejection conditions. A prototype heat pump was designed and constructed to investigate the key elements of the high-lift heat pump concept. Control software was written and implemented in the prototype to allow fully automatic operation. The heat pump was capable of operation over a wide range of rejection temperatures and cooling loads, while maintaining cooling water temperature well within the required specification of 40 deg. C +/- 1.7 deg. C. This performance was verified through testing.

Flux line lattice melting transition in YBa2Cu3O6.94 observed in specific heat experiments

International Nuclear Information System (INIS)

Roulin, M.; Junod, A.; Walker, E.

1996-01-01

When a magnetic field penetrates a type II superconductor, it forms a lattice of thin quantized filaments called magnetic vortices. Resistance, magnetization, and neutron diffraction experiments have shown that the vortex lattice of high-temperature superconductors can melt along a line in the field-temperature plane. The calorimetric signature of melting on this line was observed in a high-accuracy adiabatic specific heat experiment performed on YBa 2 Cu 3 O 6.94 . The specific heat of the vortex liquid was greater than that of the vortex solid. 17 refs., 3 figs

Variability in creep and rupture test results in a single heat of type 304 stainless steel. R and D report LR:75:4213-01:3

International Nuclear Information System (INIS)

Leyda, W.E.; Schultz, C.C.

1975-09-01

Results of uniaxial creep and rupture tests, from a single heat of type 304 stainless steel, are examined to determine the reasons for their greater-than-expected variability. The test results were obtained as part of a program to develop and verify high temperature structural design methods for liquid metal fast breeder reactor system components. A single heat of material (heat 9T2796) is being used throughout the program, by all investigators and in several product forms, to minimize the problem of heat-to-heat variations in elevated temperature behavior. The same laboratory reanneal was specified for each product form to reduce differences in behavior among the several being used. The data discussed was obtained from the 5/8-inch diameter, hot-rolled bar product form. The laboratory reanneal was performed after finish machining to minimize specimen-to-specimen differences. In spite of these efforts to reduce data variability, significant scatter was observed in both short-time and long-time deformation response, and also in time-to-rupture results

A form of MHD universal equations of unsteady incompressible fluid flow with variable elctroconductivity on heated moving plate

Directory of Open Access Journals (Sweden)

Boričić Zoran

2005-01-01

Full Text Available This paper deals with laminar, unsteady flow of viscous, incompressible and electro conductive fluid caused by variable motion of flat plate. Fluid electro conductivity is variable. Velocity of the plate is time function. Plate moves in its own plane and in "still" fluid. Present external magnetic filed is perpendicular to the plate. Plate temperature is a function of longitudinal coordinate and time. Viscous dissipation, Joule heat, Hole and polarization effects are neglected. For obtaining of universal equations system general similarity method is used as well as impulse and energy equation of described problem.

Performance analysis of air source heat pump system for office building

Energy Technology Data Exchange (ETDEWEB)

Han, Dong Won; KIm, Yong Chan [Korea University, Seoul (Korea, Republic of); Chang, Young Soo [School of Mechanical System Engineering, Kookmin University, Seoul (Korea, Republic of)

2016-11-15

In this study, the performance of an air source heat pump system installed in a commercial building is analyzed using the developed heat pump performance model and building load simulation data of several regions in Korea. The performance test of an air source heat pump system with a variable speed compressor is tested to develop model that considers changes in the performance characteristics of the heat pump system under various operating conditions. The heat pump system is installed in an environmental chamber, and the experimental equipment is set up according to the manufacturer' specifications as well as the AHRI 1230 test specifications. The performance test conditions of the heat pump system are selected using a central composite design method, in which 29 points for each cooling and heating mode are selected. The developed performance model based on experimental data predicts experimental values with an error of ±5 %. Building cooling and heating loads in three regions in Korea are analyzed using TRNSYS software, which includes standard building and weather data from Seoul, Daejeon and Busan in Korea. The effects of outdoor air temperature and part load ratio on the performance and regional monthly average power consumption of the heat pump system are analyzed.

Specific heat and magnetism of LuFe.sub.6./sub.Al.sub.6./sub..

Czech Academy of Sciences Publication Activity Database

Svoboda, P.; Andreev, Alexander V.; Šantavá, Eva; Šebek, Josef

2008-01-01

Roč. 113, č. 1 (2008), s. 307-310 ISSN 0587-4246. [CSMAG'07. Košice, 09.07.2007-12.07.2007] Institutional research plan: CEZ:AV0Z10100520 Keywords : specific heat * LuFe 6 Al 6 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.321, year: 2008

The New S-RAM Air Variable Compressor/Expander for Heat Pump and Waste Heat to Power Application

Energy Technology Data Exchange (ETDEWEB)

Dehoff, Ryan R [ORNL; Jestings, Lee [S-RAM Dynamics; Conde, Ricardo [S-RAM Dynamics

2016-05-23

S-RAM Dynamics (S-RAM) has designed an innovative heat pump system targeted for commercial and industrial applications. This new heat pump system is more efficient than anything currently on the market and utilizes air as the refrigerant instead of hydrofluorocarbon (HFC) refrigerants, leading to lower operating costs, minimal environmental costs or concerns, and lower maintenance costs. The heat pumps will be manufactured in the United States. This project was aimed at determining the feasibility of utilizing additive manufacturing to make the heat exchanger device for the new heat pump system. ORNL and S-RAM Dynamics collaborated on determining the prototype performance and subsequently printing of the prototype using additive manufacturing. Complex heat exchanger designs were fabricated using the Arcam electron beam melting (EBM) powder bed technology using Ti-6Al-4V material. An ultrasonic welding system was utilized in order to remove the powder from the small openings of the heat exchanger. The majority of powder in the small chambers was removed, however, the amount of powder remaining in the heat exchanger was a function of geometry. Therefore, only certain geometries of heat exchangers could be fabricated. SRAM Dynamics evaluated a preliminary heat exchanger design. Although the results of the additive manufacturing of the heat exchanger were not optimum, a less complex geometry was demonstrated. A sleeve valve was used as a demonstration piece, as engine designs from S-RAM Dynamics require the engine to have a very high density. Preliminary designs of this geometry were successfully fabricated using the EBM technology.

Application of the modulated temperature differential scanning calorimetry technique for the determination of the specific heat of copper nanofluids

International Nuclear Information System (INIS)

De Robertis, E.; Cosme, E.H.H.; Neves, R.S.; Kuznetsov, A.Yu.; Campos, A.P.C.; Landi, S.M.; Achete, C.A.

2012-01-01

The purpose of this work is to investigate the applicability of the modulated temperature differential scanning calorimetry technique to measure specific heat of copper nanofluids by using the ASTM E2719 standard procedure, which is generally applied to thermally stable solids and liquids. The one-step method of preparation of copper nanofluid samples is described. The synthesized nanoparticles were separated from the base fluid and examined by X-ray diffraction and transmission electron microscopy in order to evaluate their structure, morphology and chemical nature. The presence of copper nanoparticles in the base fluid alters the characteristics of crystallization and melting processes and reduces the specific heat values of nanofluids in the whole studied temperature range. - Highlights: ► Copper nanofluids prepared by one-step method. ► Methodology of synthesis improved nanofluid stability. ► Specific heat determinations using modulated temperature differential scanning calorimetry. ► Good agreement between theoretical and experimental values.

Specific heat characteristics of Ce70Ga8.5Cu18.5Ni3 metallic glass at low temperatures

Science.gov (United States)

Liu, Rentao; Zhong, Langxiang; Zhang, Bo

2018-03-01

Specific heat behaviors have been studied in Ce70Ga8.5Cu18.5Ni3 bulk metallic glass (BMG) from 2 K to 50 K. The low-temperature specific heat of the Ce-based metallic glass is a combined action of the Fermi liquids term, Debye oscillator term, and Einstein oscillator term as well as excess term. We also observed an intense boson peak around 15 K and attributed it to a harmonic localized Einstein mode influenced by the dense-packed atomic cluster structure. It is also demonstrated that Ce70Ga8.5Cu18.5Ni3 BMG belongs to the strongly correlated heavy-fermion system with a great electron specific heat coefficient and a high Wilson ratio. It exhibits a typical Fermi-Liquid feature when the temperature is above 10 K, while it exhibits a Non-Fermi-Liquid feature when the temperature is below 3.5 K.

The Effect of Forging Variables on the Supersolvus Heat-Treatment Response of Powder-Metallurgy Nickel-Base Superalloys

Science.gov (United States)

2014-12-01

AFRL-RX-WP-JA-2015-0160 THE EFFECT OF FORGING VARIABLES ON THE SUPERSOLVUS HEAT-TREATMENT RESPONSE OF POWDER - METALLURGY NICKEL-BASE SUPERALLOYS... POWDER - METALLURGY NICKEL- BASE SUPERALLOYS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR...treatment (SSHT) of two powder - metallurgy , gamma–gamma prime superalloys, IN-100 and LSHR, was established. For this purpose, isothermal, hot

Competing pseudogap and impurity effects on the normal-state specific heat properties of cuprate superconductors

Science.gov (United States)

Dzhumanov, S.; Karimboev, E. X.

2014-07-01

In this paper, we show that the pseudogap in the excitation spectra of high-Tc cuprates together with the impurity phase and charge inhomogeneity plays key roles in determining the essential features of their anomalous specific heat properties observed above Tc. We consider the doped cuprate superconductor as a multi-carrier model system (which consists of intrinsic and extrinsic polarons and pre-formed bosonic Cooper pairs) and study the competing pseudogap and impurity effects on the normal-state electronic specific heat of high-Tc cuprates taking into account charge inhomogeneities. We argue that unconventional electron-phonon interactions are responsible for the precursor Cooper pairing in the polaronic band below a mean-field temperature T∗ and the existence of a pseudogap above Tc in the cuprates. The electronic specific heat Ce(T) of doped cuprates below T∗ is calculated taking into account three contributions coming from the excited components of Cooper pairs, the ideal Bose-gas of incoherent Cooper pairs and the unpaired carriers in the impurity band. Above T∗, two contributions to Ce(T) coming from the unpaired intrinsic and extrinsic polarons are calculated within the two-component degenerate Fermi-gas model. By comparing our results with the experimental Ce(T) data obtained for La- and Y-based cuprates, we find that the observed behaviors of Ce(T) (below and above T∗) are similar to the calculated results for Ce(T) and the BCS-type jumps of Ce(T) at T∗ may be depressed by the impurity effects and may become more or less pronounced BCS-type anomalies in Ce(T) .

Space and time variability of heating requirements for greenhouse tomato production in the Euro-Mediterranean area.

Science.gov (United States)

Mariani, Luigi; Cola, Gabriele; Bulgari, Roberta; Ferrante, Antonio; Martinetti, Livia

2016-08-15

The Euro-Mediterranean area is the seat of a relevant greenhouse activity, meeting the needs of important markets. A quantitative assessment of greenhouse energy consumption and of its variability in space and time is an important decision support tool for both greenhouse-sector policies and farmers. A mathematical model of greenhouse energy balance was developed and parameterized for a state-of-the-art greenhouse to evaluate the heating requirements for vegetables growing. Tomato was adopted as reference crop, due to its high energy requirement for fruit setting and ripening and its economic relevance. In order to gain a proper description of the Euro-Mediterranean area, 56 greenhouse areas located within the ranges 28°N-72°N and 11°W-55°E were analyzed over the period 1973-2014. Moreover, the two 1973-1987 and 1988-2014 sub-periods were separately studied to describe climate change effects on energy consumption. Results account for the spatial variability of energy needs for tomato growing, highlighting the strong influence of latitude on the magnitude of heat requirements. The comparison between the two selected sub-periods shows a decrease of energy demand in the current warm phase, more relevant for high latitudes. Finally, suggestions to reduce energy consumptions are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

Specific heat of MgB{sub 2} after irradiation

Energy Technology Data Exchange (ETDEWEB)

Wang Yuxing [Universite de Geneve, Departement de physique de la matiere condensee, 24 quai Ernest-Ansermet, CH-1211 Geneva (Switzerland); Bouquet, Frederic [Universite de Geneve, Departement de physique de la matiere condensee, 24 quai Ernest-Ansermet, CH-1211 Geneva (Switzerland); Sheikin, Ilya [Universite de Geneve, Departement de physique de la matiere condensee, 24 quai Ernest-Ansermet, CH-1211 Geneva (Switzerland); Toulemonde, Pierre [Universite de Geneve, Departement de physique de la matiere condensee, 24 quai Ernest-Ansermet, CH-1211 Geneva (Switzerland); Revaz, Bernard [Universite de Geneve, Departement de physique de la matiere condensee, 24 quai Ernest-Ansermet, CH-1211 Geneva (Switzerland); Eisterer, Michael [Atominstitut der Oesterreichischen Universitaeten, A-1020 Vienna (Austria); Weber, Harald W [Atominstitut der Oesterreichischen Universitaeten, A-1020 Vienna (Austria); Hinderer, Joerg [GHMFL, Max-Planck Institute Grenoble, BP 166, F-38042, Grenoble (France); Junod, Alain [Universite de Geneve, Departement de physique de la matiere condensee, 24 quai Ernest-Ansermet, CH-1211 Geneva (Switzerland)

2003-02-19

We studied the effect of disorder on the superconducting properties of polycrystalline MgB{sub 2} by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2{delta}{sub 0}/k{sub B}T{sub c}=1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T{sub c} and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutrons, a substantial bulk increase of dH{sub c2}/dT at T{sub c} can be obtained without sacrificing more than a few degrees in T{sub c}. The upper critical field of the sample after irradiation exceeds 28 T at T{yields}0.

Analysis of the phonon surface specific heat using Green function techniques

International Nuclear Information System (INIS)

Silva Carrico, A. da; Albuquerque, E.L. de

1981-01-01

Green functions are derived for the displacement associated with acoustic vibrations in isotropic elastic media and used to evaluate the surface specific heat in the harmonic approximation. Only the low-temperature limit case is considered since, provided K sub(B) T/h is very small, the dispersion relation for the three acoustic branches can be replaced by its long-wavelenght form. The contributions of surface elastic waves of the Rayleigh and Love types are pointed out and their features discussed. The nature of the result and their relations to previous work in this field is also presented and discussed. (Author) [pt

Analysis of the phonon surface specific heat using Green function techniques

International Nuclear Information System (INIS)

Carrico, A.S.; Albuquerque, E.L.

1980-01-01

Green functions are derived for the displacement associated with acoustic vibrations in isotropic elastic media and used to evaluate the surface specific heat in the harmonic approximation. We consider only the low-temperature limit case since, provided K B 1/h is very samll, we can replace the dispersion relation for the three acoustic branches by its long-wavelenghts form. The contributions of surface elastic waves ot the Rayleigh and Love types are pointed out and their features discussed. The nature of the result and their relations to previous work in this field is also presented and discussed. (author) [pt

New terrestrial heat flow measurements on the Nazca Plate

Energy Technology Data Exchange (ETDEWEB)

Anderson, R N [Columbia Univ., Palisades, NY; Langseth, M G; Vacquier, V; Francheteau, J

1976-03-01

Sixty-seven new heat flow measurements on the Nazca Plate are reported, and the thermal regimes of three specific areas on the plate are examined. The Nazca Ridge is an aseismic ridge which may have been generated as an ''island trail'' from the Easter Island ''hot spot'' and/or may be a fossil transform fault. The Nazca Ridge has lower heat flow than the surrounding sea floor implying that the ridge might have low ''effective'' thermal conductivity causing heat to preferentially flow or refract to surrounding ocean crust which has higher conductivity, or, the low heat flow values may be caused by hydrothermal circulation on the ridge. The Carnegie Plateau is an elevated region south of the Carnegie Ridge on the northeastern Nazca Plate with high heat flow and shallow topography consistent with an age of less than 20 m.y. B.P. The central Nazca Plate is an area of highly variable heat flow which is possibly related to thin sediment and to rough regional topography.

Research supporting potential modification of the NASA specification for dry heat microbial reduction of spacecraft hardware

Science.gov (United States)

Spry, James A.; Beaudet, Robert; Schubert, Wayne

Dry heat microbial reduction (DHMR) is the primary method currently used to reduce the microbial load of spacecraft and component parts to comply with planetary protection re-quirements. However, manufacturing processes often involve heating flight hardware to high temperatures for purposes other than planetary protection DHMR. At present, the specifica-tion in NASA document NPR8020.12, describing the process lethality on B. atrophaeus (ATCC 9372) bacterial spores, does not allow for additional planetary protection bioburden reduction credit for processing outside a narrow temperature, time and humidity window. Our results from a comprehensive multi-year laboratory research effort have generated en-hanced data sets on four aspects of the current specification: time and temperature effects in combination, the effect that humidity has on spore lethality, and the lethality for spores with exceptionally high thermal resistance (so called "hardies"). This paper describes potential modifications to the specification, based on the data set gener-ated in the referenced studies. The proposed modifications are intended to broaden the scope of the current specification while still maintaining confidence in a conservative interpretation of the lethality of the DHMR process on microorganisms.

Effects of variable properties on MHD heat and mass transfer flow near a stagnation point towards a stretching sheet in a porous medium with thermal radiation

International Nuclear Information System (INIS)

Salem, A. M.; Fathy, Rania

2012-01-01

The effect of variable viscosity and thermal conductivity on steady magnetohydrodynamic (MHD) heat and mass transfer flow of viscous and incompressible fluid near a stagnation point towards a permeable stretching sheet embedded in a porous medium are presented, taking into account thermal radiation and internal heat genberation/absorbtion. The stretching velocity and the ambient fluid velocity are assumed to vary linearly with the distance from the stagnation point. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing fundamental equations are first transformed into a system of ordinary differential equations using a scaling group of transformations and are solved numerically by using the fourth-order Rung—Kutta method with the shooting technique. A comparison with previously published work has been carried out and the results are found to be in good agreement. The results are analyzed for the effect of different physical parameters, such as the variable viscosity and thermal conductivity, the ratio of free stream velocity to stretching velocity, the magnetic field, the porosity, the radiation and suction/injection on the flow, and the heat and mass transfer characteristics. The results indicate that the inclusion of variable viscosity and thermal conductivity into the fluids of light and medium molecular weight is able to change the boundary-layer behavior for all values of the velocity ratio parameter λ except for λ = 1. In addition, the imposition of fluid suction increases both the rate of heat and mass transfer, whereas fluid injection shows the opposite effect. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Variability of Jovian ion winds: an upper limit for enhanced Joule heating

Directory of Open Access Journals (Sweden)

M. B. Lystrup

2007-05-01

Full Text Available It has been proposed that short-timescale fluctuations about the mean electric field can significantly increase the upper atmospheric energy inputs at Jupiter, which may help to explain the high observed thermospheric temperatures. We present data from the first attempt to detect such variations in the Jovian ionosphere. Line-of-sight ionospheric velocity profiles in the Southern Jovian auroral/polar region are shown, derived from the Doppler shifting of H₃⁺ infrared emission spectra. These data were recently obtained from the high-resolution CSHELL spectrometer at the NASA Infrared Telescope Facility. We find that there is no variability within this data set on timescales of the order of one minute and spatial scales of 640 km, putting upper limits on the timescales of fluctuations that would be needed to enhance Joule heating.

Application study of the heat pipe to the passive decay heat removal system of the modular HTR

International Nuclear Information System (INIS)

Ohashi, K.; Okamoto, F.; Hayakawa, H.; Hayashi, T.

2001-01-01

To investigate the applicability of the heat pipe to the decay hat removal (DHR) system of the modular HTRs, preliminary study of the Heat Pipe DHR System was performed. The results show that the Heat Pipe DHR System is applicable to the modular HTRs and its heat removal capability is sufficient. Especially by applying the variable conductance heat pipe, the possibility of a fully passive DHR system with lower heat loss during normal operation is suggested. The experiments to obtain the fundamental characteristics data of the variable conductance heat pipe were carried out. The experimental results show very clear features of self-control characteristics. The experimental results and the experimental analysis results are also shown. (author)

Specific heat and electric conductivity of zirconium alloy with 2,5 mass% niobium in the range of phase transitions

International Nuclear Information System (INIS)

Roshchupkin, V.V.; Pokrasin, M.A.; Chernov, A.I.; Semashko, N.A.

1996-01-01

Experimental investigation of specific heat and electric resistance of zirconium alloy with 2.5 mass% niobium in the range of phase transitions was conducted, using adiabatic calorimeter of original design, characterized by high sensitivity, efficiency and high accuracy. It was revealed that temperature dependence of specific heat was characterized by anomalous growth at 590 deg C, related with (α+β Nb )→(α+β Zr )-transition, and at 810 deg -related with (α+β Zr )→β Zr - transition. Temperature dependence of electric resistance was specific in the region of α+β Zr →β Zr phase transition. It was established that revealed anomalies were connected with high oxygen absorption at high temperatures. 11 refs., 1 fig., 1 tab

Specific heat of heavy-fermion CePd{sub 2}Si{sub 2} in high magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Sheikin, I. [University of Geneva, DPMC, Geneva (Switzerland)]. E-mail: Ilya.Sheikin@physics.unige.ch; Wang, Y.; Bouquet, F.; Junod, A. [University of Geneva, DPMC, Geneva (Switzerland); Lejay, P. [CRTBT, CNRS, Grenoble (France)

2002-07-22

We report specific heat measurements on the heavy-fermion compound CePd{sub 2}Si{sub 2} in magnetic fields up to 16 T and in the temperature range 1.4-16 K. A sharp peak in the specific heat signals the antiferromagnetic transition at T{sub N} {approx} 9.3 K in zero field. The transition is found to shift to lower temperatures when a magnetic field is applied along the crystallographic a-axis, while a field applied parallel to the tetragonal c-axis does not affect the transition. The magnetic contribution to the specific heat below T{sub N} is well described by a sum of a linear electronic term and an antiferromagnetic spin-wave contribution. Just below T{sub N}, an additional positive curvature, especially at high fields, arises most probably due to thermal fluctuations. The field dependence of the coefficient of the low-temperature linear term, {gamma}{sub 0}, extracted from the fits shows a maximum at about 6 T, at the point where an anomaly was detected in susceptibility measurements. The relative field dependences of both T{sub N} and the magnetic entropy at T{sub N} scale as [1-(B/B{sub 0}){sup 2}] for B parallel a, suggesting the disappearance of antiferromagnetism at B{sub 0}{approx}42 T. The expected suppression of the antiferromagnetic transition temperature to zero makes the existence of a magnetic quantum critical point possible. (author). Letter-to-the-editor.

Electronic contributions to the transport properties and specific heat of solid UO2: an empirical, self-consistent analysis

International Nuclear Information System (INIS)

Hyland, G.J.; Ralph, J.

1982-07-01

From an empirical, self-consistent analysis of new high temperature data on the thermo-electric Seebeck coefficient and d.c. electrical conductivity, the value of the free energy controlling the equilibrium of the thermally induced reaction, 2U 4+ reversible U 3+ + U 5+ is determined (treating the U 3+ and U 5+ as small polarons) and used to calculate the contribution of the process to the high temperature thermal conductivity and specific heat of UO 2 . It is found that the transport properties can be completely accounted for in this way, but not the anomalous rise in specific heat - the origin of which remains obscure. (U.K.)

Specific heat of superconducting metallic glasses at low temperatures; Spezifische Waerme von supraleitenden metallischen Glaesern bei tiefen Temperaturen

Energy Technology Data Exchange (ETDEWEB)

Reifenberger, Andreas

2017-11-15

In the framework of this thesis we performed, for the first time, an in-depth investigation of the thermodynamic properties of superconducting bulk metallic glasses (BMGs) by means of specific heat measurements in the temperature range between 25 mK and 300 K. To determine the specific heat we used a setup based on the well-established relaxation method. Furthermore we developed a novel micro-fabricated platform to measure superconducting, mg-sized samples down to T=5 mK. The platform temperature is measured by a metallic paramagnetic Ag:Er sensor that is inductively coupled to the input coil of a dc-SQUID by means of a micro-structured gradiometric meander coil. Thereby, we reached a temperature resolution of less than 30 nK/√(Hz) and a very low addenda heat capacity below 200 pJ/K at 50 mK. Connecting the obtained results with thermal conductivity data we were able to consistently model the various degrees of freedom in these BMGs and their interaction mechanisms: For temperatures T>2 K, we find pronounced low temperature anomalies in the phononic specific heat, which are attributed to localized harmonic vibration modes. In the superconducting state close to T{sub C}, where interactions of atomic tunneling systems with quasi-particles need to be taken into account, both measurements agree well with BCS-theory predictions. Far below T{sub C} we find good agreement between the data and the standard tunneling model predictions.

Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

Science.gov (United States)

Willa, K.; Diao, Z.; Campanini, D.; Welp, U.; Divan, R.; Hudl, M.; Islam, Z.; Kwok, W.-K.; Rydh, A.

2017-12-01

Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-δ crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

Experimental study on density, thermal conductivity, specific heat, and viscosity of water-ethylene glycol mixture dispersed with carbon nanotubes

Directory of Open Access Journals (Sweden)

Ganeshkumar Jayabalan

2017-01-01

Full Text Available This article presents the effect of adding multi wall carbon nanotubes (MWCNT in water – ethylene glycol mixture on density and various thermophysical properties such as thermal conductivity, specific heat and viscosity. Density of nanofluids was measured using standard volumetric flask method and the data showed a good agreement with the mixing theory. The maximum thermal conductivity enhancement of 11 % was noticed for the nanofluids with 0.9 wt. %. Due to lower specific heat of the MWCNT, the specific heat of the nanofluids decreased in proportion with the MWCNT concentration. The rheological analysis showed that the transition region from shear thinning to Newtonian extended to the higher shear stress range compared to that of base fluids. Viscosity ratio of the nanofluids augmented anomalously with respect to increase in temperature and about 2.25 fold increase was observed in the temperature range of 30 – 40 ˚C. The modified model of Maron and Pierce predicted the viscosity of the nanofluids with the inclusion of effect of aspect ratio of MWCNT and nanoparticle aggregates.

The radiation and variable viscosity effects on electrically conducting fluid over a vertically moving plate subjected to suction and heat flux

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, P., E-mail: malekzadeh@pgu.ac.i [Department of Mechanical Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Center of Excellence for Computational Mechanics, Shiraz University, Shiraz (Iran, Islamic Republic of); Moghimi, M.A. [Department of Mechanical Engineering, School of Engineering, Shaid Bahonar University, Kerman (Iran, Islamic Republic of); Nickaeen, M. [K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)

2011-05-15

Research highlights: {yields} A new application of the differential quadrature method in thermo-fluid fields. {yields} Moving vertical plate with suction and heat flux is considered. {yields} Fluid with variable viscosity subjected to thermal radiation is studied. -- Abstract: In this paper, firstly, the applicability of the differential quadrature method (DQM) as an efficient and accurate numerical method for solving the problem of variable viscosity and thermally radiative unsteady magneto-hydrodynamic (MHD) flow over a moving vertical plate with suction and heat flux is investigated. The spatial as well as the temporal domains are discretized using the DQM. The fast rate of convergence of the method is demonstrated and for the cases that a solution is available, comparison is done. Then, effects of the temperature dependence of viscosity and different fluid parameters on the velocity and temperature of transient MHD flow subjected to the above mentioned boundary condition are studied.

Combined effect of thermal dispersion and variable viscosity of non-darcy convection heat transfer in a fluidsaturated porous medium

KAUST Repository

El-Amin, Mohamed

2013-01-01

In this paper, the effects of thermal dispersion and variable viscosity on the non-Darcy free, mixed, and forced convection heat transfer along a vertical flat plate embedded in a fluid-saturated porous medium are investigated. Forchheimer extension is employed in the flow equation to express the non-Darcy model. The fluid viscosity varies as an inverse linear function of temperature. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. Similarity solutions of the governing equations, for an isothermally heated plate, are obtained. Effects of the physical parameters, which govern the problem, on the rate of heat transfer in terms of Nusselt number, the slip velocity, and the boundary layer thickness, for the two cases Darcy and non-Darcy, are shown on graphs or entered in tables. © 2013 by Begell House, Inc.

Novel specific heat and magnetoresistance behavior of Tb0.5Ho0.5Mn2Si2

Science.gov (United States)

Pandey, Swati; Siruguri, V.; Rawat, R.

2018-04-01

In this report, we study temperature dependent heat capacity and electrical resistance of Tb1-xHoxMn2Si2 (x = 0.5). Two successive low temperature magnetic transitions T1 (˜15 K) and T2 (˜25 K) are observed from both measurements. Anomalous rise in heat capacity at low temperatures is ascribed to the nuclear Schottky effect. Sommerfeld coefficient (γ), Debye temperature (θD) and density of states at Fermi level N(EF) is calculated from the zero field specific heat data. We observe 4f contribution to heat capacity from T1 to 100K, which is attributed to crystal field effect. In the electrical transport study, application of the magnetic field shows a substantial change around the ordering temperature of rare earth moment resulting in large positive magnetoresistance of about 20% with field change of 6T.

The Effect of Moisture Content and Temperature on the Specific Heat Capacity of Nut and Kernel of Two Iranian Pistachio Varieties

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A.R Salari Kia

2014-04-01

Full Text Available Pistachio has a special ranking among Iranian agricultural products. Iran is known as the largest producer and exporter of pistachio in the world. Agricultural products are imposed under different thermal treatments during storage and processing. Designing all these processes requires thermal parameters of the products such as specific heat capacity. Regarding the importance of pistachio processing as an exportable product, in this study the specific heat capacity of nut and kernel of two varieties of Iranian pistachio (Kalle-Ghochi and Badami were investigated at four levels of moisture content (initial moisture content (5%, 15%, 25% and 40% w.b. and three levels of temperature (40, 50 and 60°C. In both varieties, the differences between the data were significant at the 1% of probability; however, the effect of moisture content was greater than that of temperature. The results indicated that the specific heat capacity of both nuts and kernels increase logarithmically with increase of moisture content and also increase linearly with increase of temperature. This parameter has altered for nut and kernel of Kalle-Ghochi and Badami varieties within the range of 1.039-2.936 kJ kg-1 K-1, 1.236-3.320 kJ kg-1 K-1, 0.887-2.773 kJ kg-1 K-1 and 0.811-2.914 kJ kg-1 K-1, respectively. Moreover, for any given level of temperature, the specific heat capacity of kernels was higher than that of nuts. Finally, regression models with high R2 values were developed to predict the specific heat capacity of pistachio varieties as a function of moisture content and temperature

Study of vibrational modes and specific heat of wurtzite phase of BN

Energy Technology Data Exchange (ETDEWEB)

Singh, Daljit, E-mail: daljit.jt@gmail.com; Sinha, M. M. [Department of Physics, SLIET, Longowal (India)

2016-05-06

In these days of nanotechnology the materials like BN is of utmost importance as in hexagonal phase it is among hardest materials. The phonon mode study of the materials is most important factor to find structural and thermodynamcal properties. To study the phonons de launey angular force (DAF) constant model is best suited as it involves many particle interactions. Therefore in this presentation we have studied the lattice dynamical properties and specific heat of BN in wurtzite phase using DAF model. The obtained results are in excellent agreement with existing results.

Study of vibrational modes and specific heat of wurtzite phase of BN

International Nuclear Information System (INIS)

Singh, Daljit; Sinha, M. M.

2016-01-01

In these days of nanotechnology the materials like BN is of utmost importance as in hexagonal phase it is among hardest materials. The phonon mode study of the materials is most important factor to find structural and thermodynamcal properties. To study the phonons de launey angular force (DAF) constant model is best suited as it involves many particle interactions. Therefore in this presentation we have studied the lattice dynamical properties and specific heat of BN in wurtzite phase using DAF model. The obtained results are in excellent agreement with existing results.

The role of electron heating physics in images and variability of the Galactic Centre black hole Sagittarius A*

Science.gov (United States)

Chael, Andrew; Rowan, Michael; Narayan, Ramesh; Johnson, Michael; Sironi, Lorenzo

2018-05-01

The accretion flow around the Galactic Centre black hole Sagittarius A* (Sgr A*) is expected to have an electron temperature that is distinct from the ion temperature, due to weak Coulomb coupling in the low-density plasma. We present four two-temperature general relativistic radiative magnetohydrodynamic (GRRMHD) simulations of Sgr A* performed with the code KORAL. These simulations use different electron heating prescriptions, motivated by different models of the underlying plasma microphysics. We compare the Landau-damped turbulent cascade model used in previous work with a new prescription we introduce based on the results of particle-in-cell simulations of magnetic reconnection. With the turbulent heating model, electrons are preferentially heated in the polar outflow, whereas with the reconnection model electrons are heated by nearly the same fraction everywhere in the accretion flow. The spectra of the two models are similar around the submillimetre synchrotron peak, but the models heated by magnetic reconnection produce variability more consistent with the level observed from Sgr A*. All models produce 230 GHz images with distinct black hole shadows which are consistent with the image size measured by the Event Horizon Telescope, but only the turbulent heating produces an anisotropic `disc-jet' structure where the image is dominated by a polar outflow or jet at frequencies below the synchrotron peak. None of our models can reproduce the observed radio spectral slope, the large near-infrared and X-ray flares, or the near-infrared spectral index, all of which suggest non-thermal electrons are needed to fully explain the emission from Sgr A*.

Magnetic susceptibility, specific heat and magnetic structure of CuNi2(PO4)2

International Nuclear Information System (INIS)

Escobal, Jaione; Pizarro, Jose L.; Mesa, Jose L.; Larranaga, Aitor; Fernandez, Jesus Rodriguez; Arriortua, Maria I.; Rojo, Teofilo

2006-01-01

The CuNi 2 (PO 4 ) 2 phosphate has been synthesized by the ceramic method at 800 deg. C in air. The crystal structure consists of a three-dimensional skeleton constructed from MO 4 (M II =Cu and Ni) planar squares and M 2 O 8 dimers with square pyramidal geometry, which are interconnected by (PO 4 ) 3- oxoanions with tetrahedral geometry. The magnetic behavior has been studied on powdered sample by using susceptibility, specific heat and neutron diffraction data. The bimetallic copper(II)-nickel(II) orthophosphate exhibits a three-dimensional magnetic ordering at, approximately, 29.8 K. However, its complex crystal structure hampers any parametrization of the J-exchange parameter. The specific heat measurements exhibit a three-dimensional magnetic ordering (λ-type) peak at 29.5 K. The magnetic structure of this phosphate shows ferromagnetic interactions inside the Ni 2 O 8 dimers, whereas the sublattice of Cu(II) ions presents antiferromagnetic couplings along the y-axis. The change of the sign in the magnetic unit-cell, due to the [1/2, 0, 1/2] propagation vector determines a purely antiferromagnetic structure. - Graphical abstract: Magnetic structure of CuNi2(PO4)2

Component Cooling Heat Exchanger Heat Transfer Capability Operability Monitoring

International Nuclear Information System (INIS)

Mihalina, M.; Djetelic, N.

2010-01-01

The ultimate heat sink (UHS) is of highest importance for nuclear power plant safe and reliable operation. The most important component in line from safety-related heat sources to the ultimate heat sink water body is a component cooling heat exchanger (CC Heat Exchanger). The Component Cooling Heat Exchanger has a safety-related function to transfer the heat from the Component Cooling (CC) water system to the Service Water (SW) system. SW systems throughout the world have been the root of many plant problems because the water source, usually river, lake, sea or cooling pond, are conductive to corrosion, erosion, biofouling, debris intrusion, silt, sediment deposits, etc. At Krsko NPP, these problems usually cumulate in the summer period from July to August, with higher Sava River (service water system) temperatures. Therefore it was necessary to continuously evaluate the CC Heat Exchanger operation and confirm that the system would perform its intended function in accordance with the plant's design basis, given as a minimum heat transfer rate in the heat exchanger design specification sheet. The Essential Service Water system at Krsko NPP is an open cycle cooling system which transfers heat from safety and non-safety-related systems and components to the ultimate heat sink the Sava River. The system is continuously in operation in all modes of plant operation, including plant shutdown and refueling. However, due to the Sava River impurities and our limited abilities of the water treatment, the system is subject to fouling, sedimentation buildup, corrosion and scale formation, which could negatively impact its performance being unable to satisfy its safety related post accident heat removal function. Low temperature difference and high fluid flows make it difficult to evaluate the CC Heat Exchanger due to its specific design. The important effects noted are measurement uncertainties, nonspecific construction, high heat transfer capacity, and operational specifics (e

Climate Variability and Industrial-Suburban Heat Environment in a Mediterranean Area

Directory of Open Access Journals (Sweden)

Giuseppina A. Giorgio

2017-05-01

Full Text Available The Urban Heat Island (UHI phenomenon prevalently concerns industrialized countries. It consists of a significant increase in temperatures, especially in industrialized and urbanized areas, in particular, during extreme warm periods like summer. This paper explores the climate variability of temperatures in two stations located in Matera city (Southern Italy, evaluating the increase in temperatures from 1988 to 2015. Moreover, the Corine Land Covers (1990–2000–2006–2012 were used in order to investigate the effect of land use on temperatures. The results obtained confirm the prevalence of UHI phenomena for industrialized areas, highlighting the proposal that the spreading of settlements may further drive these effects on the microclimate. In particular, the presence of industrial structures, even in rural areas, shows a clear increase in summer maximum temperatures. This does not occur in the period before 2000, probably due to the absence of the industrial settlement. On the contrary, from 2000 to 2015, changes are not relevant, but the maximum temperatures have always been higher than in the suburban area (station localized in green zone during daylight hours.

Crystal-field and clustering effects in the specific heat of Dy in Pd

International Nuclear Information System (INIS)

Devine, R.A.B.; Jacques, P.; Poirier, M.

1975-01-01

Recent results of specific-heat measurements on dilute alloys of Dy in Pd are reanalyzed. Assuming the ionic ground state found from paramagnetic-resonance measurements, the Schottky-anomaly and cluster contributions are segregated and the crystal-field splitting of the ground and first-excited states is found to be in reasonable agreement with theoretical predictions. The nature of the cluster contribution is discussed and an upper limit to the range of the Ruderman-Kittel-Kasuya-Yosida interaction deduced

An examination of the estimation method for the specific heat of TRU dioxides: evaluation with PuO2

International Nuclear Information System (INIS)

Serizawa, H.; Arai, Y.

2000-01-01

This work set out to study the estimation method of the specific heat, C p , for the dioxides of the transuranic elements. C p was evaluated as a sum of three terms, contributions of phonon vibration, C ph , dilation, C d , and Schottky specific heat, C s , C ph and C d were calculated using the Debye temperature and Grueneisen constant obtained by high-temperature X-ray diffractometry. The method was applied to PuO 2 . The estimated C p was in good accordance with the reported one measured using a calorimeter. The error in the estimation was small compared to that which arises from using the conventional method based on C p (298) and the melting temperature. (orig.)

Frictional Heating with Time-Dependent Specific Power of Friction

Directory of Open Access Journals (Sweden)

Topczewska Katarzyna

2017-06-01

Full Text Available In this paper analytical solutions of the thermal problems of friction were received. The appropriate boundary-value problems of heat conduction were formulated and solved for a homogeneous semi–space (a brake disc heated on its free surface by frictional heat fluxes with different and time-dependent intensities. Solutions were obtained in dimensionless form using Duhamel's theorem. Based on received solutions, evolution and spatial distribution of the dimensionless temperature were analyzed using numerical methods. The numerical results allowed to determine influence of the time distribution of friction power on the spatio-temporal temperature distribution in brake disc.

Specific heat and magnetic properties of single-crystalline ZnxDyyCrzSe4 spinels

International Nuclear Information System (INIS)

Jendrzejewska, Izabela; Groń, Tadeusz; Maciążek, Ewa; Duda, Henryk; Kubisztal, Marian; Ślebarski, Andrzej; Pietrasik, Ewa; Fijałkowski, Marcin

2016-01-01

The crystal structure, magnetic isotherm, magnetic susceptibility, electrical conductivity and specific heat measurements for single-crystalline Zn x Dy y Cr z Se 4 (where x+y+z≈3) spinels are presented. A semiconducting behavior with the activation energy of 0.53 eV, an antiferromagnetic order with a Néel temperature T N =22 K and a strong ferromagnetic exchange evidenced by a positive Curie–Weiss temperature θ=79, 71 and 70 K with increasing Dy-content in the sequence 0.05, 0.13 and 0.19 were established. Below T N the magnetic field dependence of magnetization, M(H), shows two peaks at critical fields H c1 and H c2 . The values of H c1 decrease slightly with temperature, especially for the larger Dy-content, while the values of H c2 drop rapidly with temperature. The magnetic contribution to the specific heat displays a sharp peak at T N , which is strongly shifted to much lower temperatures in the applied magnetic fields. Similar behavior was found for the temperature dependence of the specific heat C(T) plotted as C(T)/T vs. T. The value of the magnetic and phonon contribution to the entropy at T N and at H=0 is only ∼4.8, ∼4.4 and ∼4.2 J mol −1 K −1 /Cr 3+ for y=0.05, 0.13 and 0.19, respectively, much lower than the average magnetic contribution S m =(z/2)Rln(2S+1)=12.33 J mol −1 K −1 /Cr 3+ calculated for Cr 3+ ion with S=3/2, as the dysprosium one is paramagnetic. - Highlights: • Dy-substitution does not affect the Cr 3+ 3d 3 electronic configuration and AFM order. • The larger Dy-content, the smaller FM short-range interactions. • The magnetic and phonon contribution to the entropy decreases as Dy-content increases.

Effects of variable properties on MHD heat and mass transfer flow near a stagnation point towards a stretching sheet in a porous medium with thermal radiation

Science.gov (United States)

M. Salem, A.; Rania, Fathy

2012-05-01

The effect of variable viscosity and thermal conductivity on steady magnetohydrodynamic (MHD) heat and mass transfer flow of viscous and incompressible fluid near a stagnation point towards a permeable stretching sheet embedded in a porous medium are presented, taking into account thermal radiation and internal heat genberation/absorbtion. The stretching velocity and the ambient fluid velocity are assumed to vary linearly with the distance from the stagnation point. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing fundamental equations are first transformed into a system of ordinary differential equations using a scaling group of transformations and are solved numerically by using the fourth-order Rung—Kutta method with the shooting technique. A comparison with previously published work has been carried out and the results are found to be in good agreement. The results are analyzed for the effect of different physical parameters, such as the variable viscosity and thermal conductivity, the ratio of free stream velocity to stretching velocity, the magnetic field, the porosity, the radiation and suction/injection on the flow, and the heat and mass transfer characteristics. The results indicate that the inclusion of variable viscosity and thermal conductivity into the fluids of light and medium molecular weight is able to change the boundary-layer behavior for all values of the velocity ratio parameter λ except for λ = 1. In addition, the imposition of fluid suction increases both the rate of heat and mass transfer, whereas fluid injection shows the opposite effect.

Specific heat of NiCl26NH3 between 0.3 and 4.2K

International Nuclear Information System (INIS)

Sano, W.

1979-01-01

A careful specific heat measurements of nickel hexammine cloride, at liquid helium temperatures, revealed two maxima of magnetic origin in agreement with one of the works available in the literature. An inequivalency of Ni ions, resulting from a structural change at high temperatures, is considered as the new explanation of the magnetic ordering. (Author) [pt

Analysis and optimization of the heat transfer coefficient of a finned heat exchanger submitted to natural convection; Analise e otimizacao do coeficiente de transferencia de calor de um trocador aletado submetido a conveccao natural

Energy Technology Data Exchange (ETDEWEB)

Rocha, Alan Carlos Bueno da

1997-07-01

A heat transfer (condenser) of a domestic freezer was tested in a vertical channel in order to study the influence of the chimney effect in the optimization of the heat transfer coefficient. The variation of the opening of the channel, position and the heating power of the heat exchanger in the heat transfer coefficient was considered. The influence of the surface emissivity on the heat transfer by thermal radiation was studied with the heat exchanger testes without paint and with black paint. The air velocity entering the channel was measured with a hot wire anemometer. In order to evaluate the chimney effect, the heat exchanger was testes in a open ambient. This situation simulates its operational conditions when installed on the freezer system. The variables collected in the experimental procedures was gathered in the form of dimensionless parameters as Nusselt, Rayleigh, Grashof and Prandtl numbers, and dimensional parameters of the convection. The results showed that the highest heat transfer value occurred when both a specific position and a specific channel opening were used. The experiments pointed out that the radiation contribution must be considered in heat transfer calculations. The conclusions showed that different channel openings can improve the heat transfer coefficient in this heat transfer exchanger. (author)

Boundary Layer Flow and Heat Transfer with Variable Fluid Properties on a Moving Flat Plate in a Parallel Free Stream

Directory of Open Access Journals (Sweden)

Norfifah Bachok

2012-01-01

Full Text Available The steady boundary layer flow and heat transfer of a viscous fluid on a moving flat plate in a parallel free stream with variable fluid properties are studied. Two special cases, namely, constant fluid properties and variable fluid viscosity, are considered. The transformed boundary layer equations are solved numerically by a finite-difference scheme known as Keller-box method. Numerical results for the flow and the thermal fields for both cases are obtained for various values of the free stream parameter and the Prandtl number. It is found that dual solutions exist for both cases when the fluid and the plate move in the opposite directions. Moreover, fluid with constant properties shows drag reduction characteristics compared to fluid with variable viscosity.

Generic and sequence-variant specific molecular assays for the detection of the highly variable Grapevine leafroll-associated virus 3.

Science.gov (United States)

Chooi, Kar Mun; Cohen, Daniel; Pearson, Michael N

2013-04-01

Grapevine leafroll-associated virus 3 (GLRaV-3) is an economically important virus, which is found in all grapevine growing regions worldwide. Its accurate detection in nursery and field samples is of high importance for certification schemes and disease management programmes. To reduce false negatives that can be caused by sequence variability, a new universal primer pair was designed against a divergent sequence data set, targeting the open reading frame 4 (heat shock protein 70 homologue gene), and optimised for conventional one-step RT-PCR and one-step SYBR Green real-time RT-PCR assays. In addition, primer pairs for the simultaneous detection of specific GLRaV-3 variants from groups 1, 2, 6 (specifically NZ-1) and the outlier NZ2 variant, and the generic detection of variants from groups 1 to 5 were designed and optimised as a conventional one-step multiplex RT-PCR assay using the plant nad5 gene as an internal control (i.e. one-step hexaplex RT-PCR). Results showed that the generic and variant specific assays detected in vitro RNA transcripts from a range of 1×10(1)-1×10(8) copies of amplicon per μl diluted in healthy total RNA from Vitis vinifera cv. Cabernet Sauvignon. Furthermore, the assays were employed effectively to screen 157 germplasm and 159 commercial field samples. Thus results demonstrate that the GLRaV-3 generic and variant-specific assays are prospective tools that will be beneficial for certification schemes and disease management programmes, as well as biological and epidemiological studies of the divergent GLRaV-3 populations. Copyright © 2013 Elsevier B.V. All rights reserved.

Compact Representation for Specific Heat of Interacting Fermion Systems in Terms of Fully Renormalized Matsubara Green Function

OpenAIRE

Miyake, Kazumasa; Tsuruta, Atsushi

2015-01-01

On the basis of the Luttinger-Ward formalism for the thermodynamic potential, the specific heat of single-component interacting fermion systems with fixed chemical potential is compactly expressed in terms of the fully renormalized Matsubara Green function.

Design specifications to ensure flow-induced vibration and fretting-wear performance in CANDU steam generators and heat exchangers

International Nuclear Information System (INIS)

Janzen, V.P.; Han, Y.; Pettigrew, M.J.

2009-01-01

Preventing flow-induced vibration and fretting-wear problems in steam generators and heat exchangers requires design specifications that bring together specific guidelines, analysis methods, requirements and appropriate performance criteria. This paper outlines the steps required to generate and support such design specifications for CANDU nuclear steam generators and heat exchangers, and relates them to typical steam-generator design features and computer modeling capabilities. It also describes current issues that are driving changes to flow-induced vibration and fretting-wear specifications that can be applied to the design process for component refurbishment, replacement or new designs. These issues include recent experimental or field evidence for new excitation mechanisms, e.g., the possibility of in-plane fluidelastic instability of U-tubes, the demand for longer reactor and component lifetimes, the need for better predictions of dynamic properties and vibration response, e.g., two-phase random-turbulence excitation, and requirements to consider system 'excursions' or abnormal scenarios, e.g., a main steam line break in the case of steam generators. The paper describes steps being taken to resolve these issues. (author)

Thermoluminescence glow curve for UV induced ZrO2:Ti phosphor with variable concentration of dopant and various heating rate

Directory of Open Access Journals (Sweden)

Neha Tiwari

2014-10-01

Full Text Available The present paper reports the synthesis and characterization of Ti doped ZrO2 nanophosphors. The effects of variable concentration of titanium on thermoluminescence (TL behaviour are studied. The samples were prepared by combustion a synthesis technique which is suitable for less time taking techniques also for large scale production for nano phosphors. The starting material used for sample preparation are Zr(NO33 and Ti(NO33 and urea used as a fuel. The prepared sample was characterized by X-ray diffraction technique (XRD with variable concentration of Ti (0.05–0.5 mol% there is no any phase change found with increase the concentration of Ti. Sample shows cubic structure and the particle size calculated by Scherer's formula. The surface morphology of prepared phosphor was determined by field emission gun scanning electron microscopy (FEGSEM technique for optimized concentration of dopant. The good connectivity with grains and the semi-sphere like structure was found by FEGSEM. The functional group analysis was determined by Fourier transform infrared (FTIR spectroscopic techniques. The prepared phosphor examined by thermoluminescence technique. For recording TL glow curve every time 2 mg phosphor was irradiated by UV 254 nm source and fixed the heating rate at 5 °C s−1. Sample shows well resolved peak at 167 °C with a shoulder peak at 376 °C. The higher temperature peak shows the well stability and less fading in prepared phosphor. Also the effect of Ti concentration at fixed UV exposure time was studied. The effect of UV exposure time and dose versus intensity plot was studied. Sample shows linear response with dose and broaden peak with high temperature shows the more stability and less fading in TL glow curve. The linear dose response, high stability and less fading phenomenon shows the sample may be useful for thermoluminescence dosimetry application. Trapping parameters are calculated for every recorded glow curve. The

Entropy Generation of Desalination Powered by Variable Temperature Waste Heat

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David M. Warsinger

2015-10-01

Full Text Available Powering desalination by waste heat is often proposed to mitigate energy consumption and environmental impact; however, thorough technology comparisons are lacking in the literature. This work numerically models the efficiency of six representative desalination technologies powered by waste heat at 50, 70, 90, and 120 °C, where applicable. Entropy generation and Second Law efficiency analysis are applied for the systems and their components. The technologies considered are thermal desalination by multistage flash (MSF, multiple effect distillation (MED, multistage vacuum membrane distillation (MSVMD, humidification-dehumidification (HDH, and organic Rankine cycles (ORCs paired with mechanical technologies of reverse osmosis (RO and mechanical vapor compression (MVC. The most efficient technology was RO, followed by MED. Performances among MSF, MSVMD, and MVC were similar but the relative performance varied with waste heat temperature or system size. Entropy generation in thermal technologies increases at lower waste heat temperatures largely in the feed or brine portions of the various heat exchangers used. This occurs largely because lower temperatures reduce recovery, increasing the relative flow rates of feed and brine. However, HDH (without extractions had the reverse trend, only being competitive at lower temperatures. For the mechanical technologies, the energy efficiency only varies with temperature because of the significant losses from the ORC.

Anomalous Schottky specific heat and structural distortion in ferromagnetic PrAl2.

Science.gov (United States)

Pathak, Arjun K; Paudyal, D; Mudryk, Y; Gschneidner, K A; Pecharsky, V K

2013-05-03

Unique from other rare earth dialuminides, PrAl(2) undergoes a cubic to tetragonal distortion below T = 30 K in a zero magnetic field, but the system recovers its cubic symmetry upon the application of an external magnetic field of 10 kOe via a lifting of the 4f crystal field splitting. The nuclear Schottky specific heat in PrAl(2) is anomalously high compared to that of pure Pr metal. First principles calculations reveal that the 4f crystal field splitting in the tetragonally distorted phase of PrAl(2) underpins the observed unusual low temperature phenomena.

Fine-scale spatial variability of heat-related mortality in Philadelphia County, USA, from 1983-2008: a case-series analysis

Directory of Open Access Journals (Sweden)

Hondula David M

2012-03-01

Full Text Available Abstract Background High temperature and humidity conditions are associated with short-term elevations in the mortality rate in many United States cities. Previous research has quantified this relationship in an aggregate manner over large metropolitan areas, but within these areas the response may differ based on local-scale variability in climate, population characteristics, and socio-economic factors. Methods We compared the mortality response for 48 Zip Code Tabulation Areas (ZCTAs comprising Philadelphia County, PA to determine if certain areas are associated with elevated risk during high heat stress conditions. A randomization test was used to identify mortality exceedances for various apparent temperature thresholds at both the city and local scale. We then sought to identify the environmental, demographic, and social factors associated with high-risk areas via principal components regression. Results Citywide mortality increases by 9.3% on days following those with apparent temperatures over 34°C observed at 7:00 p.m. local time. During these conditions, elevated mortality rates were found for 10 of the 48 ZCTAs concentrated in the west-central portion of the County. Factors related to high heat mortality risk included proximity to locally high surface temperatures, low socioeconomic status, high density residential zoning, and age. Conclusions Within the larger Philadelphia metropolitan area, there exists statistically significant fine-scale spatial variability in the mortality response to high apparent temperatures. Future heat warning systems and mitigation and intervention measures could target these high risk areas to reduce the burden of extreme weather on summertime morbidity and mortality.

A point of view on Otto cycle approach specific for an undergraduate thermodynamics course in CMU

Science.gov (United States)

Memet, F.; Preda, A.

2015-11-01

This paper refers to the description of the way in which can be presented to future marine engineers the analyzis of the performance of an Otto cycle, in a manner which is beyond the classic approach of the course of thermodynamics in Constanta Maritime University. The conventional course of thermodynamics is dealing with the topic of performance analysis of the cycle of the internal combustion engine with isochoric combustion for the situation in which the working medium is treated as such a perfect gas. This type of approach is viable only when are considered relatively small temperature differences. But this is the situation when specific heats are seen as constant. Instead, the practical experience has shown that small temperature differences are not viable, resulting the need for variable specific heat evaluation. The presentation bellow is available for the adiabatic exponent written as a liniar function depending on temperature. In the section of this paper dedicated to methods and materials, the situation in which the specific heat is taken as constant is not neglected, additionaly being given the algorithm for variable specific heat.For the both cases it is given the way in which it is assessed the work output. The calculus is based on the cycle shown in temperature- entropy diagram, in which are also indicated the irreversible adiabatic compression and expansion. The experience achieved after understanding this theory will allow to future professionals to deal successfully with the design practice of internal combustion engines.

Integration of aerial imaging and variable-rate technology for site-specific aerial herbicide application

Science.gov (United States)

As remote sensing and variable rate technology are becoming more available for aerial applicators, practical methodologies on effective integration of these technologies are needed for site-specific aerial applications of crop production and protection materials. The objectives of this study were to...

Crystal-field study of magnetization and specific heat properties of frustrated pyrochlore Pr2Zr2O7

International Nuclear Information System (INIS)

Alam, J.; Jana, Y.M.; Biswas, A. Ali

2016-01-01

The experimental results of temperature dependent dc magnetic susceptibility, field dependent isothermal magnetization, magnetic specific heat and entropy of the pyrochlore Pr 2 Zr 2 O 7 are simulated and analyzed using appropriate D 3d crystal-field (CF) and anisotropic molecular field tensors at Pr-sites in the self-consistent mean-field approach involving four magnetically non-equivalent rare-earth spins on the tetrahedral unit of the pyrochlore structure. CF level pattern and wave-functions of the ground 3 H 4 multiplet of the Pr 3+ ions are obtained considering intermediate coupling between different Russell-Saunders terms of the 4f 2 electronic configurations of Pr-ion and J-mixing effects. CF analysis shows that the CF ground-state of the Pr 3+ ion in Pr 2 Zr 2 O 7 is a well-isolated doublet, with significant admixtures of terms coming from |M J =±4〉 and |M J =±1〉, and the Pr-spins are effectively Ising-like along the local <111> axes. Magnetic specific heat in zero-field is simulated by considering a temperature dependence of the exchange splitting of the ground doublet. - Highlights: • Full CF diagonalization using intermediate coupling and J-mixing. • Pr-spins are Ising-like along local [111] axis. • Magnetic specific heat is due to temperature dependence exchange splitting of ground CF doublet.

Diurnal variability of heat fluxes over the coastal waters off Visakhapatnam during post-monsoon and winter seasons

Digital Repository Service at National Institute of Oceanography (India)

Ramu, Ch V.; Bharathi, G.; Sadhuram, Y.; Prasad, K.V.S.R.

by De Cosmo et al.9 are used in this computation. τ = ρa CD U2 (3) QSH = ρa Cp CH (Ts-Ta) U (4) QLH = ρa L CE (es-ea) U (5) where ρa is the density of air (kg/m3), Cp is the specific heat of air at constant pressure, CH is the Stanton number..., Energy budget studies, water-loss Investigations: Lake Hefner studies, U.S. Geol. Surv. CIRC., 229, (1952) 71-88. 9 DeCosmo J, Katsaros K B, Smith S D, Anderson R J, Oost W A, Bumke K & Chadwick H M, Air-sea exchange of water vapor and sensible heat...

Low temperature specific heat of the spin-density-wave compound (TMTSF)2PF6

DEFF Research Database (Denmark)

Odin, J.; Lasjaunias, J.C.; Biljakovic, K.

1994-01-01

We report on specific heat measurements of the SDW compound (TMTSF)2PF6 between 2 and 25 K, performed by two different techniques. We discuss the two successive transitions which occur in this T-range : the SDW ordering transition at T = 12.1 K, and a glass transition around-3-3.5 K. The latter i...... is very dependent on the kinetics of measurements, and has all characteristic features of freezing of supercooled liquids....

Landau-Placzek ratio for heat density dynamics and its application to heat capacity of liquids.

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Bryk, Taras; Ruocco, Giancarlo; Scopigno, Tullio

2013-01-21

Exact relation for contributions to heat capacity of liquids is obtained from hydrodynamic theory. It is shown from analysis of the long-wavelength limit of heat density autocorrelation functions that the heat capacity of simple liquids is represented as a sum of two contributions due to "phonon-like" collective excitations and heat relaxation. The ratio of both contributions being the analogy of Landau-Placzek ratio for heat processes depends on the specific heats ratio. The theory of heat density autocorrelation functions in liquids is verified by computer simulations. Molecular dynamics simulations for six liquids having the ratio of specific heats γ in the range 1.1-2.3, were used for evaluation of the heat density autocorrelation functions and predicted Landau-Placzek ratio for heat processes. The dependence of contributions from collective excitations and heat relaxation process to specific heat on γ is shown to be in excellent agreement with the theory.

Specific phosphorylation of histone demethylase KDM3A determines target gene expression in response to heat shock.

Directory of Open Access Journals (Sweden)

Mo-bin Cheng

2014-12-01

Full Text Available Histone lysine (K residues, which are modified by methyl- and acetyl-transferases, diversely regulate RNA synthesis. Unlike the ubiquitously activating effect of histone K acetylation, the effects of histone K methylation vary with the number of methyl groups added and with the position of these groups in the histone tails. Histone K demethylases (KDMs counteract the activity of methyl-transferases and remove methyl group(s from specific K residues in histones. KDM3A (also known as JHDM2A or JMJD1A is an H3K9me2/1 demethylase. KDM3A performs diverse functions via the regulation of its associated genes, which are involved in spermatogenesis, metabolism, and cell differentiation. However, the mechanism by which the activity of KDM3A is regulated is largely unknown. Here, we demonstrated that mitogen- and stress-activated protein kinase 1 (MSK1 specifically phosphorylates KDM3A at Ser264 (p-KDM3A, which is enriched in the regulatory regions of gene loci in the human genome. p-KDM3A directly interacts with and is recruited by the transcription factor Stat1 to activate p-KDM3A target genes under heat shock conditions. The demethylation of H3K9me2 at the Stat1 binding site specifically depends on the co-expression of p-KDM3A in the heat-shocked cells. In contrast to heat shock, IFN-γ treatment does not phosphorylate KDM3A via MSK1, thereby abrogating its downstream effects. To our knowledge, this is the first evidence that a KDM can be modified via phosphorylation to determine its specific binding to target genes in response to thermal stress.

Effects of thermal property variations on the liquid flow and heat transfer in microchannel heat sinks

Energy Technology Data Exchange (ETDEWEB)

Li, Zhigang [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Huai, Xiulan; Tao, Yujia; Chen, Huanzhuo [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080 (China)

2007-12-15

Three-dimensional conjugate numerical simulations using the inlet, average and variable thermal properties respectively were performed for the laminar water flow and heat transfer in rectangular microchannels with D{sub h} of 0.333 mm at Re of 101-1775. Both average and variable properties are adopted in data reduction. The calculated local and average characteristics of flow and heat transfer are compared among different methods, and with the experiments, correlations and simplified theoretical solution data from published literatures. Compared with the inlet property method, both average and variable property methods have significantly lower f{sub app}, but higher convective heat transfer coefficient h{sub z} and Nu{sub z}. Compared with the average property method, the variable property method has higher f{sub app}Re{sub ave} and lower h{sub z} at the beginning, but lower f{sub app}Re{sub ave} and higher h{sub z} at the later section of the channel. The calculated Nu{sub ave} agree well with the Sieder-Tate correlation and the recently reported experiment, validating the traditional macroscale theory in predicting the flow and heat transfer characteristics in the dimension and Re range of the present work. (author)

Specific heat of the chiral-soliton-lattice phase in Yb(Ni0.94Cu0.06)3Al9

Science.gov (United States)

Ninomiya, Hiroki; Sato, Takaaki; Inoue, Katsuya; Ohara, Shigeo

2018-05-01

We have studied the monoaxial-chiral helimagnet YbNi3Al9 and its-substituted analogue Yb(Ni0.94Cu0.06)3Al9. These compounds belong to a chiral space group R32. In Yb(Ni0.94Cu0.06)3Al9 with the magnetic ordering temperature TM = 6.4 K , only when the magnetic field is applied perpendicular to the helical axis, the chiral soliton lattice is observed below Hc = 10 kOe . YbNi3Al9 with TM = 3.4 K exhibits a metamagnetic transition at Hc = 1 kOe in 2 K. To study the formation of chiral helimagnetic state and chiral soliton lattice, we have measured the specific heat in magnetic fields applied parallel and perpendicular to the helical axis. In zero field, with decreasing temperature, specific heat shows λ-type phase transition from paramagnetic state to chiral helimagnetic one. At the temperature where the chiral soliton lattice emerges, we have found that the specific heat shows a sharp peak. In addition, at around the crossover between paramagnetic state and forced-ferromagnetic one, a broad maximum has been observed. We have determined the magnetic phase diagrams of YbNi3Al9 and Yb(Ni0.94Cu0.06)3Al9.

On a specific feature of heat transfer to organic coolants

International Nuclear Information System (INIS)

Kafengauz, N.L.; Gladkikh, V.A.

1986-01-01

Heat transfer to organic coolants, which is accompanied by solid carbon deposit formation, is experimentally studied. Polished and rough steel tubes with 3 mm outside diameter and 0.5 mm wall thickness, heated by electric current, were used as fuel elements. Results of experiments with kerosene T-1 are presented under the following regime parameters: pressure - 45 b; flow rate - 3.75 m/s; temperature - 25-40 deg C; fuel element temperature - 400-900 deg C. In experiments on fuel elements with natural roughness deposit formation caused a smooth increase of the wall temperature. In fuel elements with polished surface, deposit formation caused during the first minutes the reduction of the wall temperature and after that it increased. Intensity of solid deposit formation in fuel elements with polished and rough surface was the same. Similar results were observed not only in experiments with kerosene T-1, but with other organic fluids as well: with toluene, n-heptane, diisopropylcyclohexane etc. The results obtained can be explained in the following way. Solid deposits on a smooth surface create roughness which improves heat exchange and reduces, respectively, the heating surface temperature. But deposits possess weak heat conductivity and create additional thermal resistance, which aggravates heat exchange. Interaction of these two factors causes the complicated time dependence of wall temperature

Momentum, sensible heat and CO2 correlation coefficient variability: what can we learn from 20 years of continuous eddy covariance measurements?

Science.gov (United States)

Hurdebise, Quentin; Heinesch, Bernard; De Ligne, Anne; Vincke, Caroline; Aubinet, Marc

2017-04-01

Long-term data series of carbon dioxide and other gas exchanges between terrestrial ecosystems and atmosphere become more and more numerous. Long-term analyses of such exchanges require a good understanding of measurement conditions during the investigated period. Independently of climate drivers, measurements may indeed be influenced by measurement conditions themselves subjected to long-term variability due to vegetation growth or set-up changes. The present research refers to the Vielsalm Terrestrial Observatory (VTO) an ICOS candidate site located in a mixed forest (beech, silver fir, Douglas fir, Norway spruce) in the Belgian Ardenne. Fluxes of momentum, carbon dioxide and sensible heat have been continuously measured there by eddy covariance for more than 20 years. During this period, changes in canopy height and measurement height occurred. The correlation coefficients (for momemtum, sensible heat and CO2) and the normalized standard deviations measured for the past 20 years at the Vielsalm Terrestrial Observatory (VTO) were analysed in order to define how the fluxes, independently of climate conditions, were affected by the surrounding environment evolution, including tree growth, forest thinning and tower height change. A relationship between canopy aerodynamic distance and the momentum correlation coefficient was found which is characteristic of the roughness sublayer, and suggests that momentum transport processes were affected by z-d. In contrast, no relationship was found for sensible heat and CO2 correlation coefficients, suggesting that the z-d variability observed did not affect their turbulent transport. There were strong differences in these coefficients, however, between two wind sectors, characterized by contrasted stands (height differences, homogeneity) and different hypotheses were raised to explain it. This study highlighted the importance of taking the surrounding environment variability into account in order to ensure the spatio

Pressure dependence of the specific heat of heavy-fermion YbCu4.5

International Nuclear Information System (INIS)

Amato, A.; Fisher, R.A.; Phillips, N.E.; Jaccard, D.; Walker, E.

1990-03-01

The specific heat of a polycrystalline sample of YbCu 4.5 has been measured between 0.3 and 20K at pressures to 8.2 kbar. Unlike cerium-based heavy-fermion compounds, an increase of C/T is observed with increasing pressure, with the linear term enhanced by about 16% at 8.2 kbar. Above 7K, (∂C/∂P) T is negative. The nuclear contribution observed at P = 0 is increased by roughly a factor of two at 8.2 kbar. 7 refs., 3 figs

Low-temperature specific heat of the β-pyrochlore oxide superconductors under high pressure

Science.gov (United States)

Isono, T.; Iguchi, D.; Machida, Y.; Izawa, K.; Salce, B.; Flouquet, J.; Ogusu, H.; Yamaura, J.; Hiroi, Z.

2011-01-01

We report the results of the low-temperature specific heat measurements of the single crystalline β-pyrochlore oxide superconductors AOs 2O 6 (A=K, Rb, and Cs) under high pressure up to 13 GPa. We find that superconducting transition temperature ( Tc) monotonically increases for CsOs 2O 6 and RbOs 2O 6, while the one for KOs 2O 6 decreases by applying the pressure. With further increasing the pressure, Tc is suddenly suppressed at the same lattice volume for all compounds, concomitant with the first-order structural phase transition.

Transgenerational effects of mild heat in Arabidopsis thaliana show strong genotype specificity that is explained by climate at origin.

Science.gov (United States)

Groot, Maartje P; Kubisch, Alexander; Ouborg, N Joop; Pagel, Jörn; Schmid, Karl J; Vergeer, Philippine; Lampei, Christian

2017-08-01

Transgenerational environmental effects can trigger strong phenotypic variation. However, it is unclear how cues from different preceding generations interact. Also, little is known about the genetic variation for these life history traits. Here, we present the effects of grandparental and parental mild heat, and their combination, on four traits of the third-generation phenotype of 14 Arabidopsis thaliana genotypes. We tested for correlations of these effects with climate and constructed a conceptual model to identify the environmental conditions that favour the parental effect on flowering time. We observed strong evidence for genotype-specific transgenerational effects. On average, A. thaliana accustomed to mild heat produced more seeds after two generations. Parental effects overruled grandparental effects in all traits except reproductive biomass. Flowering was generally accelerated by all transgenerational effects. Notably, the parental effect triggered earliest flowering in genotypes adapted to dry summers. Accordingly, this parental effect was favoured in the model when early summer heat terminated the growing season and environments were correlated across generations. Our results suggest that A. thaliana can partly accustom to mild heat over two generations and genotype-specific parental effects show non-random evolutionary divergence across populations that may support climate change adaptation in the Mediterranean. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

ENSO Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific.

Science.gov (United States)

Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng

2015-12-18

Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other.

Heat transfer model for quenching by submerging

International Nuclear Information System (INIS)

Passarella, D N; Varas, F; MartIn, E B

2011-01-01

In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.

Heat transfer model for quenching by submerging

Energy Technology Data Exchange (ETDEWEB)

Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)

2011-05-01

In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.

Visualized study on specific points on demand curves and flow patterns in a single-side heated narrow rectangular channel

International Nuclear Information System (INIS)

Wang Junfeng; Huang Yanping; Wang Yanlin

2011-01-01

Highlights: → Specific points on the demand curve and flow patterns are visually studied. → Bubbly, churn, and annular flows were observed. → Onset of flow instability and bubbly-churn transition occurs at the same time. → The evolution of specific points and flow pattern transitions were examined. - Abstract: A simultaneous visualization and measurement study on some specific points on demand curves, such as onset of nucleate boiling (ONB), onset of significant void (OSV), onset of flow instability (OFI), and two-phase flow patterns in a single-side heated narrow rectangular channel, having a width of 40 mm and a gap of 3 mm, was carried out. New experimental approaches were adopted to identify OSV and OFI in a narrow rectangular channel. Under experimental conditions, the ONB could be predicted well by the Sato and Matsumura model. The OSV model of Bowring can reasonably predict the OSV if the single-side heated condition is considered. The OFI was close to the saturated boiling point and could be described accurately by Kennedy's correlation. The two-phase flow patterns observed in this experiment could be classified into bubbly, churn, and annular flow. Slug flow was never observed. The OFI always occurred when the bubbles at the channel exit began to coalesce, which corresponded to the beginning of the bubbly-churn transition in flow patterns. Finally, the evolution of specific points and flow pattern transitions were examined in a single-side heated narrow rectangular channel.

Temperature and Thermal Expansion Analysis of the Cooling Roller Based on the Variable Heat Flux Boundary Condition

Science.gov (United States)

Li, Yongkang; Yang, Yang; He, Changyan

2018-06-01

Planar flow casting (PFC) is a primary method for preparing an amorphous ribbon. The qualities of the amorphous ribbon are significantly influenced by the temperature and thermal expansion of the cooling roller. This study proposes a new approach to analyze the three-dimensional temperature and thermal expansion of the cooling roller using variable heat flux that acted on the cooling roller as a boundary condition. First, a simplified two-dimensional model of the PFC is developed to simulate the distribution of the heat flux in the circumferential direction with the software FLUENT. The resulting heat flux is extended to be three-dimensional in the ribbon's width direction. Then, the extended heat flux is imported as the boundary condition by the CFX Expression Language, and the transient temperature of the cooling roller is analyzed in the CFX software. Next, the transient thermal expansion of the cooling roller is simulated through the thermal-structural coupling method. Simulation results show that the roller's temperature and expansion are unevenly distributed, reach the peak value in the middle width direction, and the quasi-steady state of the maximum temperature and thermal expansion are achieved after approximately 50 s and 150 s of casting, respectively. The minimum values of the temperature and expansion are achieved when the roller has a thickness of 45 mm. Finally, the reliability of the approach proposed is verified by measuring the roller's thermal expansion on the spot. This study provides theoretical guidance for the roller's thermal expansion prediction and the gap adjustment in the PFC.

Investigation of Heat Transfer Enhancement or Deterioration of Variable Properties Al2O3-EG-water Nanofluid in Buoyancy Driven Convection

Directory of Open Access Journals (Sweden)

H. Khorasanizadeh

2014-01-01

Full Text Available In this study, the natural convection heat transfer of variable properties Al2O3-EG-water nanofluid in a differentially heated rectangular cavity has been investigated numerically. The governing equations, for a Newtonian fluid, have been solved numerically with a finite volume approach. The influences of the pertinent parameters such as Ra in the range of 103-107 and volume fraction of nanoparticles from 0 to 0.04 on heat transfer characteristics have been studied. The results verified by making overall comparison with some existing experimental results have shown that for Ra=103, for which conduction heat transfer is dominant, the average Nusselt number increases as volume fraction of nanoparticles increases, but for higher Ra numbers in contradiction with the constant properties cases it decreases. This reduction, which is associated with increased viscosity, is more severe at Ra of 104 compared to higher Ra numbers such that the least deterioration in heat transfer occurs for Ra=107. This is due to the fact that as Ra increases, the Brownian motion enhances; thus conductivity improves and becomes more important than viscosity increase. An scale analysis, performed to clarify the contradictory reports in the literature on the natural convection heat transfer enhancement or deterioration of nanofluids, showed that different kinds of evaluating the base fluid Rayleigh number has led to such a difference.

Debye–Einstein approximation approach to calculate the lattice specific heat and related parameters for a Si nanowire

Directory of Open Access Journals (Sweden)

A. KH. Alassafee

2017-11-01

Full Text Available The modified Debye–Einstein approximation model is used to calculate nanoscale size-dependent values of Gruneisen parameters and lattice specific heat capacity for Si nanowires. All parameters forming the model, including Debye temperatures, bulk moduli, the lattice thermal expansion and the lattice volume, are calculated according to their nanoscale size dependence. Values for lattice volume Gruneisen parameters increase with the decrease of the nanowires’ diameter, while all other parameters decrease. The nanosize dependence of lattice thermal parameters agree with other reported theoretical results. Keywords: Lattice specific heat capacity, Gruneisen parameter, Debye–Einstein model, Si nanowires

Combined role of heat and water stresses on wheat, maize and rice inter-annual variability and trend from 1980 to 2010.

Science.gov (United States)

Zampieri, M.; Ceglar, A., , Dr; Dentener, F., , Dr; van den Berg, M., , Dr; Toreti, A., , Dr

2017-12-01

Heat waves and drought are often considered the most damaging climatic stressors for wheat and maize. In this study, based on data derived from observations, we characterize and attribute the effects of these climate extremes on wheat and maize yield anomalies (at global and national scales) with respect to the mean trend from 1980 to 2010. Using a combination of up-to-date heat wave and drought indexes (i.e. the Heat Magnitude Day, HMD, and the Standardized Precipitation Evapotranspiration Index, SPEI), we have developed a composite indicator (i.e. the Combined Stress Index, CSI) that is able to capture the spatio-temporal characteristics of the underlying physical processes in the different agro-climatic regions of the world. At the global level, our diagnostic explains the 42% and the 50% of the inter-annual wheat and maize production variabilities, respectively. The relative importance of heat stress and drought in determining the yield anomalies depends on the region. Compared to maize, and in contrast to common perception, water excess affects wheat production more than drought in several countries. The index definition can be modified in order to quantify the role of combined heat and water stress events occurrence in determining the recorded yield trends as well. Climate change is increasingly limiting maize yields in several countries, especially in Europe and China. A comparable opposite signal, albeit less statistically significant, is found for the USA, which is the main world producer. As for rice, we provide a statistical evidence pointing out to the importance of considering the interactions with the horizontal surface waters fluxes carried out by the rivers. In fact, compared to wheat and maize, the CSI statistical skills in explaining rice production variability are quite reduced. This issue is particularly relevant in paddy fields and flooded lowlands where rice is mainly grown. Therefore, we have modified the procedure including a proxy for the

Industrial excess heat for district heating in Denmark

DEFF Research Database (Denmark)

Bühler, Fabian; Petrovic, Stefan; Karlsson, Kenneth Bernard

2017-01-01

analyses excess heat sources from the industrial sector and how they could be used for district heating. This method first allocates excess heat to single production units by introducing and validating a new approach. Spatial analysis of the heat sources and consumers are then performed to evaluate...... the potential for using them for district heating. In this way the theoretical potential of using the excess heat for covering the heating demand of buildings is determined. Through the use of industry specific temperature profiles the heat usable directly or via heat pumps is further found. A sensitivity...... analysis investigates the impact of future energy efficiency measures in the industry, buildings and the district heating grid on the national potential. The results show that for the case study of Denmark, 1.36 TWh of district heat could be provided annually with industrial excess heat from thermal...

Specific heat measurements of CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z}

Energy Technology Data Exchange (ETDEWEB)

Motoyama, G. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)]. E-mail: motoyama@sci.u-hyogo.ac.jp; Watanabe, M. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Maeda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Oda, Y. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Ueda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Kohara, T. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

2007-03-15

We have measured the specific heat of a series of polycrystalline CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples whose compositions vary slightly from the stoichiometric composition. We observed two peaks derived from magnetic anomalies on the specific heat measurements of the Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples. One of the peaks relates to the antiferromagnetic phase transition at T{sub N}=2.2K. The other is a large peak at 2.7K observed for the sample that showed a ferromagnetic anomaly at 3.0K on the temperature dependence of the magnetization. Heat treatment had different effects between these anomalies.

Physiological-metabolic variables of heat stress in cows grazing in silvopastoral systems and in one treeless prairie.

Directory of Open Access Journals (Sweden)

Wilson Andrés Berragán-Hernández

2015-06-01

Full Text Available The aim of this work was to analyze changes of physiological and metabolic parameters as indicators of heat stress of cows in pasture systems. The research was carried out from 2011 to 2012 at the Turipaná Agricultural Research Center of Corpoica located in the Caribbean region in Cereté–Colombia. Environmental temperature (T and relative humidity (H were determined, as well as and rectal temperature (RT, skin temperature (ST, respiratory frequency (RF and the acid-basic status of animals. The variables were measured in the morning (6:00 h and in the afternoon (13:00 h. Significant Statistical differences were observed (p<0.05 in environmental temperature treatments (T with 7% and 6% less temperature in p-Arbus-Arbor y p-Arbor, respectively, compared with grass treatment. There was a significant hour effect on T and H (p<0.05 and a significant treatment-hour interaction on T (p<0.05. TP and FR showed a significant treatment-hour interaction per hour (6:00/13:00 h. The results show a positive effect of shadow from trees on the physiological variables. The negative effects observed on the physiological variables of unshaded treatments impacted in a minimal way the metabolic variables suggesting homeostatic responses in the animals under the evaluated stressful environmental conditions.

Variability in cell response of Cronobacter sakazakii after mild-heat treatments and its impact on food safety

Directory of Open Access Journals (Sweden)

Julio eParra-Flores

2016-04-01

Full Text Available Cronobacter spp. have been responsible for severe infections in infants associated with consumption of powdered infant formula (PIF and follow-up formulae (FUF. Despite several risk assessments described in published studies, few approaches have considered the tremendous variability in cell response that small micropopulations or single cells can have in infant formula during storage, preparation or post process/preparation before the feeding of infants. Stochastic approaches can better describe microbial single cell response than deterministic models as we prove in this study. A large variability of lag phase was observed in single cell and micropopulations of ≤50 cells. This variability increased as the heat shock increased and growth temperature decreased. Obviously, variability of growth of individual Cronobacter sakazakii cell is affected by inoculum size, growth temperature and the probability of cells able to grow at the conditions imposed by the experimental conditions should be taken into account, especially when errors in bottle-preparation practices, such as improper holding temperatures or manipulation, may lead to growth of the pathogen to a critical cell level. The mean probability of illness from initial inoculum size of 1 cell were below 0.2 in all the cases and for inoculum size of 50 cells the mean probability of illness were, in most of the cases, was above 0.7.

Seasonal variability of cyclone heat potential in the Bay of Bengal

Digital Repository Service at National Institute of Oceanography (India)

Sadhuram, Y.; Rao, B.P.; Rao, D.P.; Shastri, P.N.M.; Subrahmanyam, M.V.

when it moved over the region of high heat potential (>90 kJ/cm 2 ) in the western Gulf of Mexico (Goni et al., 1996; Shay et al., 2000). Monitoring of warm core eddies and regions of high heat potential have become important to predict... bordered by Burma, Thailand, Sumatra and Andaman–Nicobar ridge. Heat storage of the Andaman Sea had been reported by Ramesh Babu and Sastry (1981), using IIOE Data set (1960–1965). Unfortunately, this region had not been covered for several decades after...

Heat savings and heat generation technologies: Modelling of residential investment behaviour with local health costs

International Nuclear Information System (INIS)

Zvingilaite, Erika; Klinge Jacobsen, Henrik

2015-01-01

The trade-off between investing in energy savings and investing in individual heating technologies with high investment and low variable costs in single family houses is modelled for a number of building and consumer categories in Denmark. For each group the private economic cost of providing heating comfort is minimised. The private solution may deviate from the socio-economical optimal solution and we suggest changes to policy to incentivise the individuals to make choices more in line with the socio-economic optimal mix of energy savings and technologies. The households can combine their primary heating source with secondary heating e.g. a woodstove. This choice results in increased indoor air pollution with fine particles causing health effects. We integrate health cost due to use of woodstoves into household optimisation of heating expenditures. The results show that due to a combination of low costs of primary fuel and low environmental performance of woodstoves today, included health costs lead to decreased use of secondary heating. Overall the interdependence of heat generation technology- and heat saving-choice is significant. The total optimal level of heat savings for private consumers decrease by 66% when all have the option to shift to the technology with lowest variable costs. - Highlights: • Heat saving investment and heat technology choice are interdependent. • Health damage costs should be included in private heating choice optimisation. • Flexibility in heating technology choice reduce the optimal level of saving investments. • Models of private and socioeconomic optimal heating produce different technology mix. • Rebound effects are moderate but varies greatly among consumer categories

Investigations of Intelligent Solar Heating Systems for Single Family House

DEFF Research Database (Denmark)

Andersen, Elsa; Chen, Ziqian; Fan, Jianhua

2014-01-01

Three differently designed intelligent solar heating systems are investigated experimentally in a test facility. The systems provide all the needed yearly heating demand in single family houses. The systems are based on highly stratified tanks with variable auxiliary heated volumes. The tank is a......, the control strategy of intelligent solar heating systems is investigated and the yearly auxiliary energy use of the systems and the electricity price for supplying the consumers with domestic hot water and space heating are calculated....... systems.The system will be equipped with an intelligent control system where the control of the electrical heating element(s)/heat pump is based on forecasts of the variable electricity price, the heating demand and the solar energy production.By means of numerical models of the systems made in Trnsys......Three differently designed intelligent solar heating systems are investigated experimentally in a test facility. The systems provide all the needed yearly heating demand in single family houses. The systems are based on highly stratified tanks with variable auxiliary heated volumes. The tank...

All varieties of encoding variability are not created equal: Separating variable processing from variable tasks

Science.gov (United States)

Huff, Mark J.; Bodner, Glen E.

2014-01-01

Whether encoding variability facilitates memory is shown to depend on whether item-specific and relational processing are both performed across study blocks, and whether study items are weakly versus strongly related. Variable-processing groups studied a word list once using an item-specific task and once using a relational task. Variable-task groups’ two different study tasks recruited the same type of processing each block. Repeated-task groups performed the same study task each block. Recall and recognition were greatest in the variable-processing group, but only with weakly related lists. A variable-processing benefit was also found when task-based processing and list-type processing were complementary (e.g., item-specific processing of a related list) rather than redundant (e.g., relational processing of a related list). That performing both item-specific and relational processing across trials, or within a trial, yields encoding-variability benefits may help reconcile decades of contradictory findings in this area. PMID:25018583

Thermomechanical and calorimetric behaviours of supported glass-forming films: A study based on thermodynamics with internal variables

International Nuclear Information System (INIS)

Lion, Alexander; Engelhard, Marco; Johlitz, Michael

2012-01-01

In order to understand the temperature-dependent response behaviour of thin thermoviscoelastic films which are deposited on relative stiff but thermally deformable substrates it is important to consider the lateral geometric constraints. They are generated by differences in the thermal expansion properties between the substrate and the film and provoke internal stresses. Since glass-forming materials exhibit distinct temperature history-dependent thermal expansion and calorimetric properties, primarily in the vicinity of the glass transition, the situation is rather complicated. In this article, a recently developed three-dimensional model of thermodynamics with internal variables is applied and adapted to simulate this type of behaviour. Explicit relations are obtained for the specific heat of the film, the normal strain and the lateral stresses. Numerical simulations demonstrate that the magnitude of the internal stress at temperatures below the glass transition depends strongly on the cooling rate. It is also shown that the specific heat of the supported film is principally different from the isobaric specific heat of the bulk material: the glassy limit of the specific heat of the film is reduced but the glass transition temperature is almost uninfluenced. The simulated behaviour is in accordance with experimental observations from literature. - Highlights: ► For the specific heat, stress and strain of the film, explicit equations were derived. ► The constraints of the substrate reduce the glassy limit of specific heat of the film. ► Glass transition temperatures of free bulk material and supported film are equal. ► Simulations are in good agreement with experimental observations from literature.

Self-similar Lagrangian hydrodynamics of beam-heated solar flare atmospheres

International Nuclear Information System (INIS)

Brown, J.C.; Emslie, A.G.

1989-01-01

The one-dimensional hydrodynamic problem in Lagrangian coordinates (Y, t) is considered for which the specific energy input Q has a power-law dependence on both Y and t, and the initial density distribution is rho(0) which is directly proportional to Y exp gamma. In regimes where the contributions of radiation, conduction, quiescent heating, and gravitational terms in the energy equation are negligible compared to those arising from Q, the problem has a self-similar solution, with the hydrodynamic variables depending only on a single independent variable which is a combination of Y, t, and the dimensional constants of the problem. It is then shown that the problem of solar flare chromospheric heating due to collisional interaction of a beam of electrons (or protons) with a power-law energy spectrum can be approximated by such forms of Q(Y, t) and rho(0)(Y), and that other terms are negligible compared to Q over a restricted regime early in the flare. 29 refs

Competition in the household heat product markets in Finland

International Nuclear Information System (INIS)

Linden, Mikael; Peltola-Ojala, Paeivi

2005-01-01

In the article the market of household heat products is defined independently. The market consists mainly of electricity, district heating, light fuel oil, and wood. Geographically household heat product markets are limited to the area which is covered by the local district heating network. We test indirectly whether this market definition is valid, i.e. do different household heat products act as substitutes to each other. However, the substitution may quite often be limited since the local district heat supplier is the only supplier on the area and also electricity companies have high market shares in the area they are located. The amount of competitors even in these enlarged markets is low. Also the local district heating network gives a technological potential to non-competitive product specific pricing. Thus, a relevant case exists where the district heating company can determine the price of its product without constraints from other firms and heat products. We test empirically whether the local prices of district heating are affected by the local heat product market shares of district heating companies. We use panel data which consists of 75 district heating companies in years 1996 - 2002. The data includes market share, joint production, district heating tariffs, production scale, and raw material input cost variables. The results obtained from different estimations indicate clearly that competitive case is not the prevailing one in the Finnish district heating pricing. The market shares of district heating companies had a positive effect on the district heating prices. The result also does not support the hypothesis that different household heat products belong to same heat product markets. (Author)

Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

Energy Technology Data Exchange (ETDEWEB)

Willa, K. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Diao, Z. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden; Laboratory of Mathematics, Physics and Electrical Engineering, Halmstad University, P.O. Box 823, SE-301 18 Halmstad, Sweden; Campanini, D. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden; Welp, U. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Divan, R. [Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Hudl, M. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden; Islam, Z. [X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Kwok, W. -K. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Rydh, A. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden

2017-12-01

Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-delta crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

A Numerical Procedure for Flow Distribution and Pressure Drops for U and Z Type Configurations Plate Heat Exchangers with Variable Coefficients

International Nuclear Information System (INIS)

López, R; Lecuona, A; Ventas, R; Vereda, C

2012-01-01

In Plate Heat Exchangers it is important to determine the flow distribution and pressure drops, because they affect directly the performance of a heat exchanger. This work proposes an incompressible, one-dimensional, steady state, discrete model allowing for variable overall momentum coefficients to determine these magnitudes. The model consists on a modified version of the Bajura and Jones model for dividing and combining flow manifolds. The numerical procedure is based on the finite differences approximation approach proposed by Datta and Majumdar. A linear overall momentum coefficient distribution is used in the dividing manifold, but the model is not limited to linear distributions. Comparisons are made with experimental, numerical and analytical data, yielding good results.

Fuzzy multivariable control of domestic heat pumps

International Nuclear Information System (INIS)

Underwood, C.P.

2015-01-01

Poor control has been identified as one of the reasons why recent field trials of domestic heat pumps in the UK have produced disappointing results. Most of the technology in use today uses a thermostatically-controlled fixed speed compressor with a mechanical expansion device. This article investigates improved control of these heat pumps through the design and evaluation of a new multivariable fuzzy logic control system utilising a variable speed compressor drive with capacity control linked through to evaporator superheat control. A new dynamic thermal model of a domestic heat pump validated using experimental data forms the basis of the work. The proposed control system is evaluated using median and extreme daily heating demand profiles for a typical UK house compared with a basic thermostatically-controlled alternative. Results show good tracking of the heating temperature and superheat control variables, reduced cycling and an improvement in performance averaging 20%. - Highlights: • A new dynamic model of a domestic heat pump is developed and validated. • A new multivariable fuzzy logic heat pump control system is developed/reported. • The fuzzy controller regulates both plant capacity and evaporator superheat degree. • Thermal buffer storage is also considered as well as compressor cycling. • The new controller shows good variable tracking and a reduction in energy of 20%.

CASKETSS-HEAT: a finite difference computer program for nonlinear heat conduction problems

International Nuclear Information System (INIS)

Ikushima, Takeshi

1988-12-01

A heat conduction program CASKETSS-HEAT has been developed. CASKETSS-HEAT is a finite difference computer program used for the solution of multi-dimensional nonlinear heat conduction problems. Main features of CASKETSS-HEAT are as follows. (1) One, two and three-dimensional geometries for heat conduction calculation are available. (2) Convection and radiation heat transfer of boundry can be specified. (3) Phase change and chemical change can be treated. (4) Finned surface heat transfer can be treated easily. (5) Data memory allocation in the program is variable according to problem size. (6) The program is a compatible heat transfer analysis program to the stress analysis program SAP4 and SAP5. (7) Pre- and post-processing for input data generation and graphic representation of calculation results are available. In the paper, brief illustration of calculation method, input data and sample calculation are presented. (author)

Regenerative heat sources for heating networks

International Nuclear Information System (INIS)

Huenges, Ernst; Sperber, Evelyn; Eggers, Jan-Bleicke; Noll, Florian; Kallert, Anna Maria; Reuss, Manfred

2015-01-01

The ambitious goal, the German Federal Government has set itself, to reduce the emissions of greenhouse gases by 80% to 95% by the year 2050. As there are currently more than half of German energy consumption for the production of heat is required, big contributions to climate protection can be expected from this area if more renewable heat sources are used. Renewable heat sources such as bioenergy, solar thermal and geothermal energy in particular can be provided as compared to fossil fuels with significantly lower specific CO 2 emissions. Objectives in the heating market and scenarios for the transformation of the heat sector have been elaborated in the BMU Lead Study 2011. The main pillar of this scenario is the reduction of final energy consumption for heat by the energy-efficient renovation of existing buildings and further increasing demands on the energetic quality of new buildings. To cover the remaining energy demand, a focus is on the expansion of heating networks based on renewable energies. [de

A soft sensor for bioprocess control based on sequential filtering of metabolic heat signals.

Science.gov (United States)

Paulsson, Dan; Gustavsson, Robert; Mandenius, Carl-Fredrik

2014-09-26

Soft sensors are the combination of robust on-line sensor signals with mathematical models for deriving additional process information. Here, we apply this principle to a microbial recombinant protein production process in a bioreactor by exploiting bio-calorimetric methodology. Temperature sensor signals from the cooling system of the bioreactor were used for estimating the metabolic heat of the microbial culture and from that the specific growth rate and active biomass concentration were derived. By applying sequential digital signal filtering, the soft sensor was made more robust for industrial practice with cultures generating low metabolic heat in environments with high noise level. The estimated specific growth rate signal obtained from the three stage sequential filter allowed controlled feeding of substrate during the fed-batch phase of the production process. The biomass and growth rate estimates from the soft sensor were also compared with an alternative sensor probe and a capacitance on-line sensor, for the same variables. The comparison showed similar or better sensitivity and lower variability for the metabolic heat soft sensor suggesting that using permanent temperature sensors of a bioreactor is a realistic and inexpensive alternative for monitoring and control. However, both alternatives are easy to implement in a soft sensor, alone or in parallel.

A Soft Sensor for Bioprocess Control Based on Sequential Filtering of Metabolic Heat Signals

Directory of Open Access Journals (Sweden)

Dan Paulsson

2014-09-01

Full Text Available Soft sensors are the combination of robust on-line sensor signals with mathematical models for deriving additional process information. Here, we apply this principle to a microbial recombinant protein production process in a bioreactor by exploiting bio-calorimetric methodology. Temperature sensor signals from the cooling system of the bioreactor were used for estimating the metabolic heat of the microbial culture and from that the specific growth rate and active biomass concentration were derived. By applying sequential digital signal filtering, the soft sensor was made more robust for industrial practice with cultures generating low metabolic heat in environments with high noise level. The estimated specific growth rate signal obtained from the three stage sequential filter allowed controlled feeding of substrate during the fed-batch phase of the production process. The biomass and growth rate estimates from the soft sensor were also compared with an alternative sensor probe and a capacitance on-line sensor, for the same variables. The comparison showed similar or better sensitivity and lower variability for the metabolic heat soft sensor suggesting that using permanent temperature sensors of a bioreactor is a realistic and inexpensive alternative for monitoring and control. However, both alternatives are easy to implement in a soft sensor, alone or in parallel.

Evaluation of high specific-heat ceramic for regenerator use at temperatures between 2-30 K

Science.gov (United States)

Lawless, W. N.

1979-01-01

Specific heat, thermal conductivity (both in the range 2-30 K), and microhardness data were measured on the ceramics labelled LS-8, LS-8A, and LS-8A doped with CsI, SnCl2, and AgCl. A work hardened sample of LS-8A was also studied in an effort to determine the feasibility of using these types of LS-8 materials to replace Pb spheres in the regenerator of the JPL cryocooler. The LS-8A materials are all more than an order of magnitude harder than Pb, and the dopants do not significantly improve the hardness. However, the SnCl2 dopant has a remarkable effect in improving the specific heat and thermal conductivity of LS-8A. The SnCl2 doping level which maximized the regenerator enthalpy change in going from an unloaded to a loaded condition was found to be 0.2 percent SnCl2 in LS-8A. It was also found that the enthalpy change for a regenerator employing the LS-8A material is more than three times larger than for the Pb spheres case. The use of rods, rather than spheres, of optimally doped LS-8A in regenerators is discussed.

Pulse induction heating

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, A S; Kachanov, B Y; Kogan, B V

1993-12-31

Induction heating and three types of pulse processes were studied. It was found that in pulse processes the frequency and pulse duration of heat treatments do not remain constant. High frequency pulse heat treatments can be used on sprayed coatings; such treatments will result in stronger surfaces with no cracks. For induction hardening, the rate of specific power was 1 to 1.5 kW/sq.cm, for forging it was 0.2 to 0.3 kW/sq.cm and for melting it was 0.05 to 0.1 kW/sq.cm. The application of pulse heating will result in higher rates of specific power.

Numerical Modeling of Fin and Tube Heat Exchanger for Waste Heat Recovery

DEFF Research Database (Denmark)

Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph

In the present work, multiphysics numerical modeling is carried out to predict the performance of a liquid-gas fin and tube heat exchanger design. Three-dimensional (3D) steady-state numerical model using commercial software COMSOL based on finite element method (FEM) is developed. The study...... associates conjugate heat transfer phenomenon with the turbulent flow to describe the variable temperature and velocity profile. The performance of heat exchanger design is investigated in terms of overall heat transfer coefficient, Nusselt number, Colburn j-factor, flow resistance factor, and efficiency...... between fin and tube. The present numerical model predicts the performance of the heat exchanger design, therefore, can be applied to existing waste heat recovery systems to improve the overall performance with optimized design and process-dependent parameters....

Urban heat islands in the subsurface of German cities

Science.gov (United States)

Menberg, K.; Blum, P.; Zhu, K.; Bayer, P.

2012-04-01

In the subsurface of many cities there are widespread and persistent thermal anomalies (subsurface urban heat islands) that result in a warming of urban aquifers. The reasons for this heating are manifold. Possible heat sources are basements of buildings, leakage of sewage systems, buried district heating networks, re-injection of cooling water and solar irradiation on paved surfaces. In the current study, the reported groundwater temperatures in several German cities, such as Berlin, Munich, Cologne and Karlsruhe, are compared. Available data sets are supplemented by temperature measurements and depth profiles in observation wells. Trend analyses are conducted with time series of groundwater temperatures, and three-dimensional groundwater temperature maps are provided. In all investigated cities, pronounced positive temperature anomalies are present. The distribution of groundwater temperatures appears to be spatially and temporally highly variable. Apparently, the increased heat input into the urban subsurface is controlled by very local and site-specific parameters. In the long-run, the superposition of various heat sources results in an extensive temperature increase. In many cases, the maximum temperature elevation is found close to the city centre. Regional groundwater temperature differences between the city centre and the rural background are up to 5 °C, with local hot spots of even more pronounced anomalies. Particular heat sources, like cooling water injections or case-specific underground constructions, can cause local temperatures > 20°C in the subsurface. Examination of the long-term variations in isotherm maps shows that temperatures have increased by about 1°C in the city, as well as in the rural background areas over the last decades. This increase could be reproduced with trend analysis of temperature data gathered from several groundwater wells. Comparison between groundwater and air temperatures in Karlsruhe, for example, also indicates a

A modified variable physical properties model, for analyzing nanofluids flow and heat transfer over nonlinearly stretching sheet

Directory of Open Access Journals (Sweden)

Pooria Akbarzadeh

2017-07-01

Full Text Available In this paper, the problem of laminar nanofluid flow which results from the nonlinear stretching of a flat sheet is investigated numerically. In this paper, a modified variable physical properties model for analyzing nanofluids flow and heat transfer is introduced. In this model, the effective viscosity, density, and thermal conductivity of the solid-liquid mixture (nanofluids which are commonly utilized in the homogenous single-phase model, are locally combined with the prevalent single-phase model. A numerical similarity solution is considered which depends on the local Prandtl number, local Brownian motion number, local Lewis number, and local thermophoresis number. The results are compared to the prevalent single-phase model. This comparison depicts that the prevalent single-phase model has a considerable deviation for predicting the behavior of nanofluids flow especially in dimensionless temperature and nanoparticle volume fraction. In addition the effect of the governing parameters such as Prandtl number, the Brownian motion number, the thermophoresis parameter, the Lewis number, and etc. on the velocity, temperature, and volume fraction distribution and the dimensionless heat and mass transfer rates are examined.

Heat Transfer Analysis of Localized Heat-Treatment for Grade 91 Steel

Science.gov (United States)

Walker, Jacob D.

Many of the projects utilizing Grade 91 steel are large in scale, therefore it is necessary to assemble on site. The assembly of the major pieces requires welding in the assembly; this drastically changes the superior mechanical properties of Grade 91 steel that it was specifically developed for. Therefore, because of the adverse effects of welding on the mechanical properties of Grade 91, it is necessary to do a localized post weld heat treatment. As with most metallic materials grade 91 steel requires a very specific heat treatment process. This process includes a specific temperature and duration at that temperature to achieve the heat treatment desired. Extensive research has been done to determine the proper temperatures and duration to provide the proper microstructure for the superior mechanical properties that are inherent to Grade 91 steel. The welded sections are typically large structures that require local heat treatments and cannot be placed in an oven. The locations of these structures vary from indoors in a controlled environment to outdoors with unpredictable environments. These environments can be controlled somewhat, however in large part the surrounding conditions are unchangeable. Therefore, there is a need to develop methods to accurately apply the surrounding conditions and geometries to a theoretical model in order to provide the proper requirements for the local heat treatment procedure. Within this requirement is the requirement to define unknowns used in the heat transfer equations so that accurate models can be produced and accurate results predicted. This study investigates experimentally and numerically the heat transfer and temperature fields of Grade 91 piping in a local heat treatment. The objective of this thesis research is to determine all of the needed heat transfer coefficients. The appropriate heat transfer coefficients are determined through the inverse heat conduction method utilizing a ceramic heat blanket. This will be done

Thermo-economic optimization of Regenerative Organic Rankine Cycle for waste heat recovery applications

International Nuclear Information System (INIS)

Imran, Muhammad; Park, Byung Sik; Kim, Hyouck Ju; Lee, Dong Hyun; Usman, Muhammad; Heo, Manki

2014-01-01

Highlights: • Thermo-economic optimization of regenerative ORC is performed. • Optimization is performed using multi objective genetic algorithm. • Objective function is maximum cycle efficiency and minimum specific investment. • Evaporation pressure, pinch point and superheat are decision variables. • Sensitivity analysis is performed to investigate effect of decision variables. - Abstract: Organic Rankine Cycle (ORC) is low grade and waste heat conversion technology. The current article deal with the thermo-economic optimization of basic ORC and regenerative ORC for waste heat recovery applications under constant heat source condition. Thermal efficiency and specific investment cost of basic ORC, single stage regenerative and double stage regenerative ORC has been optimized by using Non-dominated Sorting Genetic Algorithm-II (NSGA-II). Maximum thermal efficiency and minimum specific investment cost were selected as objective functions and relative increase in thermal efficiency and cost has been analyzed taking the basic ORC as base case. The constraint set consist of evaporation pressure, superheat, pinch point temperature difference in evaporator and condenser. The optimization was performed for five different working fluids. The optimization result show that R245fa is best working under considered conditions and basic ORC has low specific investment cost and thermal efficiency compared to regenerative ORC. R245fa is low boiling organic fluid, which has high degree of thermal stability and compatible with common construction materials of ORC. The average increase in thermal efficiency from basic ORC to single stage regenerative ORC was 1.01% with an additional cost of 187 $/kW while from basic ORC to double stage regenerative ORC was 1.45% with an average increase in cost of 297 $/kW. The sensitivity analysis was also performed to investigate the effect of operating conditions which show that evaporation pressure has promising effect on thermal

Flexible use of electricity in heat-only district heating plants

Directory of Open Access Journals (Sweden)

Erik Trømborg

2017-01-01

Full Text Available European energy systems are in a period of significant transition, with the increasing shares of variable renewable energy (VRE and less flexible fossil-based generation units as predominant factors. The supply-side changes are expected to cause large short-term electricity price volatility. More frequent periods of low electricity prices may mean that electric use in flexible heating systems will become more profitable, and such flexible heating systems may, in turn, improve the integration of increasing shares of VRE. The objective of this study is to analyze the likely future of Nordic electricity price levels and variations and how the expected prices might affect the use of electricity and thermal storage in heat-only district heating plants. We apply the North European energy market model Balmorel to provide scenarios for future hourly electricity prices in years with normal, high, and low inflow levels to the hydro power system. The simulation tool energyPRO is subsequently applied to quantify how these electricity price scenarios affect the hourly use of thermal storage and individual boilers in heat-only district heating plants located in Norway. The two studied example plants use wood chips or heat pump as base load representing common technologies for district heating in Norway. The Balmorel results show that annual differences in inflow is still a decisive factor for Norwegian and Nordic electricity prices in year 2030 and that short-term (daily price variability is expected to increase. In the plant-level simulations, we find that tank storage, which is currently installed in only a few district heating plants in Norway, is a profitable flexibility option that will significantly reduce the use of fossil peak load in both biomass and heat-pump-based systems. Installation of an electric boiler in addition to tank storage is profitable in the heat pump system due to the limited capacity of the heat pump. Electricity will hence, to a

A cost-effective evaluation of biomass district heating in rural communities

International Nuclear Information System (INIS)

Hendricks, Aaron M.; Wagner, John E.; Volk, Timothy A.; Newman, David H.; Brown, Tristan R.

2016-01-01

Highlights: • Develop a cost-effective model using secondary data examining delivering heat through Biomass District Heating (BDH). • Eight of ten rural villages studied could cost-effectively deliver heat through BDH below the 2013 price of heating oil. • 80% of the annual cost of BDH was attributable to capital expenses. • Erratic fuel oil prices substantially impact future feasibility. • Village level feasibility is highly-influenced by the presence of large heat demanders. - Abstract: The economic feasibility of Biomass District Heating (BDH) networks in rural villages is largely unknown. A cost-effective evaluation tool is developed to examine the feasibility of BDH in rural communities using secondary data sources. The approach is unique in that it accounts for all the major capital expenses: energy center, distribution network, and energy transfer stations, as well as biomass procurement. BDH would deliver heat below #2 fuel oil in eight of the ten rural study villages examined, saving nearly $500,000 per year in heating expenses while demanding less than 5% of the forest residues sustainably available regionally. Capital costs comprised over 80% of total costs, illuminating the importance of reaching a sufficient heat density. Reducing capital costs by 1% lowers total cost by $93,000 per year. Extending capital payment period length five years or lowering interest rates has the next highest influence decreasing delivered heat price 0.49% and 0.35% for each 1% change, respectively. This highlights that specific building heat is a strong determinant of feasibility given the relative influence of high-demanding users on the overall village heat-density. Finally, we use a stochastic analysis projecting future #2 fuel oil prices, incorporating historical variability, to determine the probability of future BDH feasibility. Although future oil prices drop below the BDH feasibility threshold, the villages retain a 22–53% probability of feasibility after

Method to reduce non-specific tissue heating of small animals in solenoid coils.

Science.gov (United States)

Kumar, Ananda; Attaluri, Anilchandra; Mallipudi, Rajiv; Cornejo, Christine; Bordelon, David; Armour, Michael; Morua, Katherine; Deweese, Theodore L; Ivkov, Robert

2013-01-01

Solenoid coils that generate time-varying or alternating magnetic fields (AMFs) are used in biomedical devices for research, imaging and therapy. Interactions of AMF and tissue produce eddy currents that deposit power within tissue, thus limiting effectiveness and safety. We aim to develop methods that minimise excess heating of mice exposed to AMFs for cancer therapy experiments. Numerical and experimental data were obtained to characterise thermal management properties of water using a continuous, custom water jacket in a four-turn simple solenoid. Theoretical data were obtained with method-of-moments (MoM) numerical field calculations and finite element method (FEM) thermal simulations. Experimental data were obtained from gel phantoms and mice exposed to AMFs having amplitude >50 kA/m and frequency of 160 kHz. Water has a high specific heat and thermal conductivity, is diamagnetic, polar, and nearly transparent to magnetic fields. We report at least a two-fold reduction of temperature increase from gel phantom and animal models when a continuous layer of circulating water was placed between the sample and solenoid, compared with no water. Thermal simulations indicate the superior efficiency in thermal management by the developed continuous single chamber cooling system over a double chamber non-continuous system. Further reductions of heating were obtained by regulating water temperature and flow for active cooling. These results demonstrate the potential value of a contiguous layer of circulating water to permit sustained exposure to high intensity alternating magnetic fields at this frequency for research using small animal models exposed to AMFs.

Effect of the design variables on the energy performance and size parameters of a heat transformer based on the system acetone/H[sub 2]/2-propanol

Energy Technology Data Exchange (ETDEWEB)

Gandia, L M; Montes, M [Ente Vasco de la Energia, Bilbao (Spain). Div. de Investigacion y Recursos

1992-12-01

A high-temperature chemical heat pump based on the system acetone/H[sub 2]/2-propanol for waste heat recovery was studied. Two reversible catalytic chemical reactions are involved in this system. The waste heat (at 333-353K) is recovered by means of the endothermic liquid-phase dehydrogenation of 2-propanol, and is upgraded at high temperature (453-473K) by the reverse reaction, the exothermic gaseous-phase hydrogenation of acetone. In this process, a fraction of the recovered waste heat is removed at low temperature (303K), to carry out the separation by vapour rectification between acetone and 2-propanol. A mathematical model was developed, that permits the study of the effect of the heat pump operating conditions on the coefficient of performance (COP), exergetic efficiency and size parameters. This model allows the optimal range for the system control variables to be estimated. Under these conditions, the energy and size parameters have been calculated on a basis of 0.32 MW upgraded heat. (author)

Non intrusive measurement of the convective heat transfer coefficient

Energy Technology Data Exchange (ETDEWEB)

Rebay, M.; Mebarki, G.; Padet, J. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Arfaoui, A. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM; Maad, B.R. [Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM

2010-07-01

The efficiency of cooling methods in thermal systems such as radiators and heat exchangers must be improved in order to enhance performance. The evaluation of the heat transfer coefficients between a solid and a fluid is necessary for the control and the dimensioning of thermal systems. In this study, the pulsed photothermal method was used to measure the convective heat transfer coefficient on a solid-fluid interface, notably between an air flow and a heated slab mounted on a PVC flat plate. This configuration simulated the electronic air-cooling inside enclosures and racks. The influence of the deflector's inclination angle on the enhancement of heat transfer was investigated using 2 newly developed identification models. The first model was based on a constant heat transfer coefficient during the pulsed experiment, while the second, improved model was based on a variable heat transfer coefficient. The heat transfer coefficient was deduced from the evolution of the transient temperature induced by a sudden deposit of a luminous energy on the front face of the slab. Temperature evolutions were derived by infrared thermography, a camera for cartography and a detector for precise measurement in specific locations. The results show the improvement of measurement accuracies when using a model that considers the temporal evolution of the convective heat transfer coefficient. The deflection of air flow on the upper surface of the heated slab demonstrated better cooling of the slab by the deflection of air flow. 11 refs., 1 tab., 8 figs.

Interannual variability of sea surface temperature and circulation in ...

African Journals Online (AJOL)

Local surface heat flux exchanges driven by the anomalous shortwave radiation dominated the interannual SST variability in the Tanzanian shelf region, with some contribution by the advection of heat anomalies from the North-East Madagascar Current. Farther offshore, the interannual variability of the SST was dominated ...

Heat-balance integral method for heat transfer in superfluid helium

Directory of Open Access Journals (Sweden)

Baudouy Bertrand

2009-01-01

Full Text Available The heat-balance integral method is used to solve the non-linear heat diffusion equation in static turbulent superfluid helium (He II. Although this is an approximate method, it has proven that it gives solutions with fairly good accuracy in non-linear fluid dynamics and heat transfer. Using this method, it has been possible to develop predictive solutions that reproduce analytical solution and experimental data. We present the solutions of the clamped heat flux case and the clamped temperature case in a semi-infinite using independent variable transformation to take account of temperature dependency of the thermophysical properties. Good accuracy is obtained using the Kirchhoff transform whereas the method fails with the Goodman transform for larger temperature range.

Cryogenic heat transfer

CERN Document Server

Barron, Randall F

2016-01-01

Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.

Specific heat of S=1 quasi-1D antiferromagnet NDMAP in magnetic fields