Effects of the generator and evaporator temperature differences on a double absorption heat transformer—Different control strategies on utilizing heat sources

International Nuclear Information System (INIS)

Wang, Hanzhi; Li, Huashan; Bu, Xianbiao; Wang, Lingbao

2017-01-01

Highlights: • Effects of the GETD on the DAHT system performance are analyzed. • Three different configurations are compared in detail. • Suggestions on the heat source control strategies are given. - Abstract: The combination of the absorption heat transformer with renewable energy systems, like solar thermal systems, is raising more and more concern. In those combined systems the strategies on utilizing heat sources can affect system thermodynamic performance significantly. Therefore, this study presents a detailed analysis on the effect of the heat source temperature and different heat source flow patterns on the performance of a double absorption heat transformer (DAHT). A detailed comparative study is carried out to clarify the impact of the generator and evaporator temperature differences (GETD) on the coefficient of performance (COP), exergy efficient (ECOP), exergy destruction rates in the individual components and heat transfer areas needed for each component. The results show that the generator, condenser and absorber-evaporator are responsible for most of the exergy destruction rate in the DAHT system; the parallel-flow configuration (the generator temperature is equal to the evaporator temperature) performs better under the high gross temperature lift conditions; in the case of the counter-flow configuration (the generator temperature is relatively higher), better performance can be obtained in both the COP and ECOP under the proper heat source temperature (85 and 95 °C); the fair-flow configuration (higher temperature in the evaporator) is not recommended in this paper due to no advantages found in either thermodynamic performance or system size.

High temperature absorption compression heat pump for industrial waste heat

DEFF Research Database (Denmark)

Reinholdt, Lars; Horntvedt, B.; Nordtvedt, S. R.

2016-01-01

Heat pumps are currently receiving extensive interest because they may be able to support the integration of large shares of fluctuating electricity production based on renewable sources, and they have the potential for the utilization of low temperature waste heat from industry. In most industries......, the needed temperature levels often range from 100°C and up, but until now, it has been quite difficult to find heat pump technologies that reach this level, and thereby opening up the large-scale heat recovery in the industry. Absorption compression heat pumps can reach temperatures above 100°C......, and they have proved themselves a very efficient and reliable technology for applications that have large temperature changes on the heat sink and/or heat source. The concept of Carnot and Lorenz efficiency and its use in the analysis of system integration is shown. A 1.25 MW system having a Carnot efficiency...

Potential of low-temperature nuclear heat applications

International Nuclear Information System (INIS)

1986-12-01

At present, more than one third of the fossil fuel currently used is being consumed to produce space heating and to meet industrial needs in many countries of the world. Imported oil still represents a large portion of this fossil fuel and despite its present relatively low price future market evolutions with consequent upward cost revisions cannot be excluded. Thus the displacement of the fossil fuel by cheaper low-temperature heat produced in nuclear power plants is a matter which deserves careful consideration. Technico-economic studies in many countries have shown that the use of nuclear heat is fully competitive with most of fossil-fuelled plants, the higher investment costs being offset by lower production cost. Another point in favour of heat generation by nuclear source is its indisputable advantage in terms of benefits to the environment. The IAEA activity plans for 1985-86 concentrate on information exchange with specific emphasis on the design criteria, operating experience, safety requirements and specifications of heat-only reactors, co-generation plants and existing power plants backfitted for additional heat applications. The information gained up to 1985 was discussed during the Advisory Group Meeting on the Potential of Low-Temperature Nuclear Heat Applications held in the Federal Institute for Reactor Research, Wuerenlingen, Switzerland in September 1985 and, is included in the present Technical Document

Heat index and adjusted temperature as surrogates for wet bulb globe temperature to screen for occupational heat stress.

Science.gov (United States)

Bernard, Thomas E; Iheanacho, Ivory

2015-01-01

Ambient temperature and relative humidity are readily ava-ilable and thus tempting metrics for heat stress assessment. Two methods of using air temperature and relative humidity to create an index are Heat Index and Adjusted Temperature. The purposes of this article are: (1) to examine how well Heat Index and Adjusted Temperature estimated the wet bulb globe temperature (WBGT) index, and (2) to suggest how Heat Index and Adjusted Temperature can be used to screen for heat stress level. Psychrometric relationships were used to estimate values of actual WBGT for conditions of air temperature, relative humidity, and radiant heat at an air speed of 0.5 m/s. A relationship between Heat Index [°F] and WBGT [°C] was described by WBGT = -0.0034 HI(2) + 0.96 HI - 34. At lower Heat Index values, the equation estimated WBGTs that were ± 2 °C-WBGT around the actual value, and to about ± 0.5 °C-WBGT for Heat Index values > 100 °F. A relationship between Adjusted Temperature [°F] and WBGT [°C] was described by WBGT = 0.45 Tadj - 16. The actual WBGT was between 1 °C-WBGT below the estimated value and 1.4 °C-WBGT above. That is, there was a slight bias toward overestimating WBGT from Adjusted Temperature. Heat stress screening tables were constructed for metabolic rates of 180, 300, and 450 W. The screening decisions were divided into four categories: (1) exposure limit at rest. The authors do not recommend using Heat Index or Adjusted Temperature instead of WBGT, but they may be used to screen for circumstances when a more detailed analysis using WBGT is appropriate. A particular weakness is accounting for radiant heat; and neither air speed nor clothing was considered.

Heat transfer from a high temperature condensable mixture

International Nuclear Information System (INIS)

Chan, S.H.; Cho, D.H.; Condiff, D.W.

1978-01-01

A new development in heat transfer is reported. It is concerned with heat transfer from a gaseous mixture that contains a condensable vapor and is at very high temperature. In the past, heat transfer associated with either a condensable mixture at low temperature or a noncondensable mixture at high temperature has been investigated. The former reduces to the classical problem of fog formation in, say, atmosphere where the rate of condensation is diffusion controlled (molecular or conductive diffusions). In the presence of noncondensable gases, heat transfer to a cooler boundary by this mechanism is known to be drastically reduced. In the latter case, where the high temperature mixture is noncondensable, radiative transfer may become dominant and a vast amount of existing literature exists on this class of problem. A fundamentally different type of problem of relevance to recent advances in open cycle MHD power plants and breeder reactor safety is considered. In the advanced coal-fired power plant using MHD as a topping cycle, a condensable mixture is encountered at temperatures of 2000 to 3000 0 . Condensation of the vaporized slag and seed materials at such a high temperature can take place in the MHD generator channel as well as in the radiant boiler. Similarly, in breeder reactor accident analyses involving hypothetical core disruptive accidents, a UO 2 vapor mixture at 400 0 K or higher is often considered. Since the saturation temperature of UO 2 at one atmosphere is close to 4000 0 K, condensation is also likely at a very high temperature. Accordingly, an objective of the present work is to provide an understanding of heat transfer and condensation mechanics insystems containing a high temperature condensable mixture. The results of the study show that, when a high temperature mixture is in contact with a cooler surface, a thermal boundary layer develops rapidly because of intensive radiative cooling from the mixture

Use of a commercial heat transfer code to predict horizontally oriented spent fuel rod surface temperatures

International Nuclear Information System (INIS)

Wix, S.D.; Koski, J.A.

1993-03-01

Radioactive spent fuel assemblies are a source of hazardous waste that will have to be dealt with in the near future. It is anticipated that the spent fuel assemblies will be transported to disposal sites in spent fuel transportation casks. In order to design a reliable and safe transportation cask, the maximum cladding temperature of the spent fuel rod arrays must be calculated. A comparison between numerical calculations using commercial thermal analysis software packages and experimental data simulating a horizontally oriented spent fuel rod array was performed. Twelve cases were analyzed using air and helium for the fill gas, with three different heat dissipation levels. The numerically predicted temperatures are higher than the experimental data for all levels of heat dissipation with air as the fill gas. The temperature differences are 4 degree C and 23 degree C for the low heat dissipation and high heat dissipation, respectively. The temperature predictions using helium as a fill gas are lower for the low and medium heat dissipation levels, but higher at the high heat dissipation. The temperature differences are 1 degree C and 6 degree C for the low and medium heat dissipation, respectively. For the high heat dissipation level, the temperature predictions are 16 degree C higher than the experimental data. Differences between the predicted and experimental temperatures can be attributed to several factors. These factors include experimental uncertainty in the temperature and heat dissipation measurements, actual convection effects not included in the model, and axial heat flow in the experimental data. This work demonstrates that horizontally oriented spent fuel rod surface temperature predictions can be made using existing commercial software packages. This work also shows that end effects will be increasingly important as the amount of dissipated heat increases

Ambient temperature and added heat wave effects on hospitalizations in California from 1999 to 2009.

Science.gov (United States)

Sherbakov, Toki; Malig, Brian; Guirguis, Kristen; Gershunov, Alexander; Basu, Rupa

2018-01-01

Investigators have examined how heat waves or incremental changes in temperature affect health outcomes, but few have examined both simultaneously. We utilized distributed lag nonlinear models (DLNM) to explore temperature associations and evaluate possible added heat wave effects on hospitalizations in 16 climate zones throughout California from May through October 1999-2009. We define heat waves as a period when daily mean temperatures were above the zone- and month-specific 95th percentile for at least two consecutive days. DLNMs were used to estimate climate zone-specific non-linear temperature and heat wave effects, which were then combined using random effects meta-analysis to produce an overall estimate for each. With higher temperatures, admissions for acute renal failure, appendicitis, dehydration, ischemic stroke, mental health, non-infectious enteritis, and primary diabetes were significantly increased, with added effects from heat waves observed for acute renal failure and dehydration. Higher temperatures also predicted statistically significant decreases in hypertension admissions, respiratory admissions, and respiratory diseases with secondary diagnoses of diabetes, though heat waves independently predicted an added increase in risk for both respiratory types. Our findings provide evidence that both heat wave and temperature exposures can exert effects independently. Copyright © 2017 Elsevier Inc. All rights reserved.

Aggregation of human sperm at higher temperature is due to hyperactivation.

Science.gov (United States)

Keppler, E L; Chan, P J; Patton, W C; King, A

1999-01-01

Chemotaxis of sperm cells to chemicals and hormones, such as progesterone, helps us to understand the concept of sperm transport. Here, the hypothesis was that heat increased sperm hyperactive motility, which caused the sperm to aggregate at the higher temperature. The objectives were (1) to determine the concentration of sperm at both halves of an artificial female reproductive tract made from a hermetically sealed cryopreservation straw filled with culture medium and placed with each end at different temperatures, and (2) to analyze the motility or kinematic parameters and hyperactivation of sperm found at the different temperatures. Cryopreserved-thawed human donor sperm (N = 6) were pooled and processed through 2-layer colloid solution. Analyses of the motile sperm were carried out and the washed sperm were homogeneously mixed and pipetted into several 0.5-mL French cryopreservation straws and heat-sealed. The control substance, consisting of acid-treated sperm, was also placed in several straws. The plastic straws of sperm were placed half at 23 degrees C and half was at either 37 or 40 degrees C. After 4 h, sperm at different sections of the straws were analyzed using the Hamilton Thorn motility analyzer (HTM-C). After 4 h of incubation, the concentration of sperm was doubled at the 40 degrees C heated half of the straw when compared with the other half of the straw at 23 degrees C. There were no differences in sperm concentration in the straw kept half at 37 degrees C and half at 23 degrees C. There were significantly higher percent motility, mean average path velocity, straight line velocity, lateral head displacement, and percent hyperactivation in sperm at the 40 degrees C temperature. The aggregation of sperm at the higher temperature of 40 degrees C may be due to enhanced motility, increased sperm velocities, and a 10-fold increase in hyperactivation at that temperature. The 37 degrees C temperature was not sufficient to attract sperm. Sperm cells

Effect of External Pressure Drop on Loop Heat Pipe Operating Temperature

Science.gov (United States)

Jentung, Ku; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Obenschain, Arthur F. (Technical Monitor)

2002-01-01

This paper discusses the effect of the pressure drop on the operating temperature in a loop heat pipe (LHP). Because the evaporator and the compensation chamber (CC) both contain two-phase fluid, a thermodynamic constraint exists between the temperature difference and the pressure drop for these two components. As the pressure drop increases, so will the temperature difference. The temperature difference in turn causes an increase of the heat leak from the evaporator to the CC, resulting in a higher CC temperature. Furthermore, the heat leak strongly depends on the vapor void fraction inside the evaporator core. Tests were conducted by installing a valve on the vapor line so as to vary the pressure drop, and by charging the LHP with various amounts of fluid. Test results verify that the LHP operating temperature increases with an increasing differential pressure, and the temperature increase is a strong function of the fluid inventory in the loop.

The effect of air velocity on heat stress at increased air temperature

DEFF Research Database (Denmark)

Bjerg, B.; Wang, Xiaoshuai; Zhang, Guoqiang

Increased air velocity is a frequently used method to reduce heat stress of farm animals housed in warm conditions. The main reason why the method works is that higher air velocity increases the convective heat release from the animals. Convective heat release from the animals is strongly related...... to the temperature difference between the surfaces of animals and the surrounding air, and this temperature difference declines when the air temperature approaches the animal body temperature. Consequently it can it by expected that the effect of air velocity decreases at increased air temperature. The literature...... on farm animals in warm conditions includes several thermal indices which incorporate the effect of air velocities. But, surprisingly none of them predicts a decreased influence of air velocity when the air temperature approaches the animal body temperature. This study reviewed published investigations...

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.

Heat treated 9 Cr-1 Mo steel material for high temperature application

Science.gov (United States)

Jablonski, Paul D.; Alman, David; Dogan, Omer; Holcomb, Gordon; Cowen, Christopher

2012-08-21

The invention relates to a composition and heat treatment for a high-temperature, titanium alloyed, 9 Cr-1 Mo steel exhibiting improved creep strength and oxidation resistance at service temperatures up to 650.degree. C. The novel combination of composition and heat treatment produces a heat treated material containing both large primary titanium carbides and small secondary titanium carbides. The primary titanium carbides contribute to creep strength while the secondary titanium carbides act to maintain a higher level of chromium in the finished steel for increased oxidation resistance, and strengthen the steel by impeding the movement of dislocations through the crystal structure. The heat treated material provides improved performance at comparable cost to commonly used high-temperature steels such as ASTM P91 and ASTM P92, and requires heat treatment consisting solely of austenization, rapid cooling, tempering, and final cooling, avoiding the need for any hot-working in the austenite temperature range.

Analysis and research on promising solutions of low temperature district heating without risk of legionella

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Fog, Jette M.

2014-01-01

Most regulations of domestic hot water supply temperature is around 55-60 oC, which potentially requires higher district heating temperature. However, high supply temperature of district heating causes many problems, such as the high heating loss, and obstacles for applying renewable energy...... resources. The most crucial restriction for applying low temperature district heating is the worry about the breakout of legionella, which exists preferably in low temperature hot water systems. Several novel techniques such as electric tracing and flat station were investigated for such dilemma. The pros...... and cons were compared in this paper. Both the energy and economy saving ratios were analysed comparing with high temperature supply scenario. Furthermore, the viability of the applications in different types of buildings for low temperature district heating (LTDH) was also discussed by using dynamic...

Hydride heat pump with heat regenerator

Science.gov (United States)

Jones, Jack A. (Inventor)

1991-01-01

A regenerative hydride heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system. A series of at least four canisters containing a lower temperature performing hydride and a series of at least four canisters containing a higher temperature performing hydride is provided. Each canister contains a heat conductive passageway through which a heat transfer fluid is circulated so that sensible heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

Mask humidity during CPAP: influence of ambient temperature, heated humidification and heated tubing

Directory of Open Access Journals (Sweden)

Nilius G

2018-05-01

Full Text Available Georg Nilius,1,2 Ulrike Domanski,1 Maik Schroeder,1 Holger Woehrle,3,4 Andrea Graml,4 Karl-Josef Franke,1,2 1Helios Klinik Hagen-Ambrock, Department of Pneumology, Hagen, Germany; 2Department of Internal Medicine, Witten-Herdecke University, Witten, Germany; 3Sleep and Ventilation Center Blaubeuren, Respiratory Center Ulm, Ulm, Germany; 4ResMed Science Center, ResMed Germany, Martinsried, Germany Purpose: Mucosal drying during continuous positive airway pressure (CPAP therapy is problematic for many patients. This study assessed the influence of ambient relative humidity (rH and air temperature (T in winter and summer on mask humidity during CPAP, with and without mask leak, and with or without heated humidification ± heated tubing. Methods: CPAP (8 and 12 cmH2O without humidification (no humidity [nH], with heated humidification controlled by ambient temperature and humidity (heated humidity [HH] and HH plus heated tubing climate line (CL, with and without leakage, were compared in 18 subjects with OSA during summer and winter. Results: The absolute humidity (aH and the T inside the mask during CPAP were significantly lower in winter versus summer under all applied conditions. Overall, absolute humidity differences between summer and winter were statistically significant in both HH and CL vs. nH (p < 0.05 in the presence and absence of mouth leak. There were no significant differences in aH between HH and CL. However, in-mask temperature during CL was higher (p < 0.05 and rH lower than during HH. In winter, CPAP with CL was more likely to keep rH constant at 80% than CPAP without humidification or with standard HH. Conclusion: Clinically-relevant reductions in aH were documented during CPAP given under winter conditions. The addition of heated humidification, using a heated tube to avoid condensation is recommended to increase aH, which could be useful in CPAP users complaining of nose and throat symptoms. Keywords: continuous positive

INTENSIFICATION OF HEAT TRANSFER IN A HIGH-TEMPERATURED FLUIDIZED BED

Directory of Open Access Journals (Sweden)

А. O. Redko

2017-10-01

Full Text Available Purpose. This paper highlights experimental research of heat exchange in coarse particles to ensure the performance of ecological characteristics of Heat supply system. Methodology. The test stand has been developed to solve the defined task. It helps to do the research at the temperature of fluidizing bed and pulsating fluidizing bed at the range 800–1000°С. The temperature of the fluidized bed was provided by burning natural gas and wood waste. Sand and chamotte with a particle size of 1.0 to 5.0 mm were used as the layer material. The heat-transfer coefficient from the layer to the surface, immersed in the layer, and the density of the heat flux were measured by a calorimetric method under steady-state conditions. Smooth tubes and transversely finned with different height and rib spacing were investigated. Experiments in a high-temperature pulsating fluidized bed were carried out with pulsating combustion of natural gas in a layer or in a sublattice chamber into which natural gas and air were separately supplied. The frequency of combustion pulsations was provided by the automation system. The flash frequency was regulated in the range from 0.14 to 5 Hz. Findings. It is presented the results of physical modeling to find out the heat-transfer coefficients of smooth and finned tubes in fluidizing bed of coarse particles in the process of wood waste and gaseous fuel combusting. It is proved that the coefficient of heat transfer increases with increasing temperature by 2–2,5 times in the bed which contains particles diameter of 2.5–5 mm is 300–350Vt/(m2 К that is much higher than for layer furnaces. The results of the experiments are presented in the form of a generalized relationship that takes into account the diameter of the particles and the value of the finning coefficient. Heat transfer of finned tubes is 15–20% less then smooth tubes but the density of heat flow referred to the area of a finned tube is 0,12–0,20 МVt/m2 that

2-D temperature distribution and heat flux of PFC in 2011 KSTAR campaign

Energy Technology Data Exchange (ETDEWEB)

Bang, Eunnam, E-mail: bang14@nfri.re.kr; Hong, Suk-Ho; Yu, Yaowei; Kim, Kyungmin; Kim, Hongtack; Kim, Hakkun; Lee, Kunsu; Yang, Hyunglyul

2013-10-15

Highlights: • The heat flux on PFC tiles of 12 s pulse duration and 630 kA plasma current is about 0.02 MW/m{sup 2}. • When the cryopump is operated, the heat flux of CD is higher than without cryopump. • The more H-mode duration is long, the more heat flux on divertor is high. -- Abstract: KSTAR has reached a plasma current up to 630 kA, plasma duration up to 12 s, and has achieved high confinement mode (H-mode) in 2011 campaign. The heat flux of PFC tile was estimated from the temperature increase of PFC since 2010. The heat flux of PFC tiles increases significantly with higher plasma current and longer pulse duration. The time-averaged heat flux of shots in 2010 campaign (with 3 s pulse durations and I{sub p} of 611 kA) is 0.01 MW/m{sup 2} while that in 2011 campaign (with 12 s pulse duration and I{sub p} of 630 kA) is about 0.02 MW/m{sup 2}. The heat flux at divertor is 1.4–2 times higher than that at inboard limiter or passive stabilizer. With the cryopump operation, the heat flux at the central divertor is higher than that without cryopump. The heat flux at divertor is proportional to, of course, the duration of H-mode. Furthermore, a software tool, which visualizes the 2D temperature distribution of PFC tile and estimates the heat flux in real time, is developed.

Experimental investigation of moderately high temperature water source heat pump with non-azeotropic refrigerant mixtures

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shengjun; Wang, Huaixin; Guo, Tao [Department of Thermal Energy and Refrigeration Engineering, School of Mechanical Engineering, Tianjin University, Tianjin 300072 (China)

2010-05-15

Experimental investigations were carried out on non-azeotropic refrigerant mixtures, named M1A (mass fraction of 20%R152a and 80%R245fa), M1B (mass fraction of 37% R152a and 63%R245fa) and M1C (mass fraction of 50%R152a and 50%R245fa), based on a water-to-water heat pump system in the condensing temperature range of 70-90 C with a cycle temperature lift of 45 C. Performance of R245fa was tested for comparison. Unfair factors in experimental comparative evaluation research with the same apparatus were identified and corrected. Experimental cycle performance of the mixtures were tested and compared with improved experimental assessment methodology. The results show that all of the mixtures deliver higher discharge temperature, higher heating capacity, higher COP and higher {epsilon}{sub h,c} than R245fa. M1B presents the most excellent cycle performance and is recommended as working fluid for moderate/high temperature heat pump. (author)

An innovative ORC power plant layout for heat and power generation from medium- to low-temperature geothermal resources

International Nuclear Information System (INIS)

Fiaschi, Daniele; Lifshitz, Adi; Manfrida, Giampaolo; Tempesti, Duccio

2014-01-01

Highlights: • Explotation of medium temperature geothermal resource with ORC–CHP is investigated. • A new CHP configuration to provide higher temperature to thermal user is proposed. • Several organic fluids and wide range of heat demand are studied. • The system produces higher power (almost 55%) in comparison to typical layouts. • Optimal working fluids vary with the characteristics of the heat demand. - Abstract: Medium temperature (up to 170 °C), water dominated geothermal resources are the most widespread in the world. The binary geothermal-ORC power plants are the most suitable energy conversion systems for this kind of resource. Specifically, combined heat and power (CHP) systems have the potential to improve the efficiency in exploiting the geothermal resources by cascading the geothermal fluid heat carrier to successively lower temperature users, thus increasing first and second law efficiency of the entire power plant. However, geothermal CHPs usually extract heat from the geofluid either in parallel or in series to the ORC, and usually provide only low temperature heat, which is seldom suitable for industrial use. In this paper, a new CHP configuration, called Cross Parallel CHP, has been proposed and analyzed. It aims to provide higher temperature heat suitable for industrial use, allowing the exploitation of geothermal resources even in areas where district heating is not needed. The proposed CHP allows the reduction of the irreversibilities in the heat exchangers and the loss to the environment related to the re-injection of geofluid, thus producing higher electric power output while satisfying, at the same time, the heat demand of the thermal utility for a wide range of temperatures and mass flow rates (80–140 °C; 3–13 kg/s). Several organic fluids are investigated and the related optimizing working conditions are found by a built in procedure making use of genetic algorithms. The results show that the optimal working fluids and

Heats pipes for temperature homogenization: A literature review

International Nuclear Information System (INIS)

Blet, Nicolas; Lips, Stéphane; Sartre, Valérie

2017-01-01

Highlights: • This paper is a review based on more than sixty references. • The review is sorted into various application fields. • Quantitative values of thermal gradients are compared with and without heat pipes. • Specificities of mentioned heat pipes are compared to other functions of heat pipes. - Abstract: Heat pipes offer high effective heat transfer in a purely passive way. Other specific properties of heat pipes, like temperature homogenization, can be also reached. In this paper, a literature review is carried out in order to investigate the existing heat pipe systems mainly aiming the reduction of temperature gradients. The review gathering more than sixty references is sorted into various application fields, like thermal management of electronics, of storage vessels or of satellites, for which the management of the temperature uniformity differs by the isothermal surface area, temperature ranges or the targeted precision of the temperature flattening. A summary of heat pipe characteristics for this function of temperature homogenization is then performed to identify their specificities, compared to other applications of heat pipes.

Optimization criteria for low temperature waste heat utilization

International Nuclear Information System (INIS)

Kranebitter, F.

1977-01-01

A special case in this field is the utilization of very low temperature waste heat. The temperature level under consideration in this paper is in the range between the body temperature of human beings and their environment. The waste heat from power generation and industrial processes is also considered. Thermal energy conversion will be mainly accomplished by heat cycles where discharged waste heat is reverse proportional to the upper cycle temperature. Limiting this upper cycle temperature by technological reasons the optimization of the heat cycle will depend on the nature of the cycle itself and specially on the temperature selected for the heat discharge. The waste heat discharge is typical for the different kinds of heat cycles and the paper presents the four most important of them. Feasible heat transfer methods and their economic evaluations are discussed and the distillation processes will be the basis for further considerations. The waste heat utilization for distillation purposes could be realized by three different cycles, the open cycle, the closed cycle and the multy cycle. Resulting problems as deaeration of large water streams and removal of the dissolved gases and their solutions are also discussed. (M.S.)

Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

of Legionella in the DHW (domestic hot water) and assure the comfortable temperature, all substations were installed with supplementary heating devices. Detailed measurements were taken in the substations, including the electricity demand of the supplementary heating devices. To compare the energy and economic......This study investigated the performances of five different substation configurations in single-family houses supplied with ULTDH (ultra-low-temperature district heating). The temperature at the heat plant is 46 degrees C and around 40 degrees C at the substations. To avoid the proliferation...... performance of the substations, separate models were built based on standard assumptions. The relative heat and electricity delivered for preparing DHW were calculated. The results showed that substations with storage tanks and heat pumps have high relative electricity demand, which leads to higher integrated...

Heat exposure in cities: combining the dynamics of temperature and population

Science.gov (United States)

Hu, L.; Wilhelmi, O.; Uejio, C. K.

2017-12-01

Assessment of human exposure to extreme heat requires the distributions of temperature and population. However, both variables are dynamic, thus presenting many challenges in capturing temperature and population patterns spatially and over time in an urban context. This study aims to improve the understanding of spatiotemporal patterns of urban population exposure to heat, taking Chicago, USA as an example. We estimate the hourly, geographically variable, population distribution considering commute of workers and students in a regular weekday and analyze the diurnal air temperature patterns during different meteorological conditions from satellite observations. The results show a relatively larger temperature increase in less urbanized areas during extreme heat events (EHEs), resulting in a spatially homogeneous temperature distribution over Chicago Metropolitan area. A lake cooling effect is weaker during EHEs. Population dynamics due to daily commute determine higher population density in more urbanized areas during daytime. The city-wide analysis reveals that the exposure is more sensitive to the nighttime temperature increases, and EHEs enhance this sensitivity. The high exposure hotspots are identified at the northwest Chicago, Cicero and Oak Park areas, where the influence from Lake Michigan is weakened, while the spatial extent of high outdoor exposure areas varies diurnally. This study's findings have potential to better inform general heat mitigation strategies during hot summer months and facilitate emergency response during EHEs. Availability of remotely-sensed temperature observations as well as the workers and students commute-adjusted population data allows for the adoption of this study's methodology in other major metropolitan areas. A better understanding of space-time patterns of urban population's exposure to heat will further enable local decision makers to mitigate extreme heat health risks and develop more targeted heat preparedness and

Novikov Engine with Fluctuating Heat Bath Temperature

Science.gov (United States)

Schwalbe, Karsten; Hoffmann, Karl Heinz

2018-04-01

The Novikov engine is a model for heat engines that takes the irreversible character of heat fluxes into account. Using this model, the maximum power output as well as the corresponding efficiency of the heat engine can be deduced, leading to the well-known Curzon-Ahlborn efficiency. The classical model assumes constant heat bath temperatures, which is not a reasonable assumption in the case of fluctuating heat sources. Therefore, in this article the influence of stochastic fluctuations of the hot heat bath's temperature on the optimal performance measures is investigated. For this purpose, a Novikov engine with fluctuating heat bath temperature is considered. Doing so, a generalization of the Curzon-Ahlborn efficiency is found. The results can help to quantify how the distribution of fluctuating quantities affects the performance measures of power plants.

Medium Deep High Temperature Heat Storage

Science.gov (United States)

Bär, Kristian; Rühaak, Wolfram; Schulte, Daniel; Welsch, Bastian; Chauhan, Swarup; Homuth, Sebastian; Sass, Ingo

2015-04-01

Heating of buildings requires more than 25 % of the total end energy consumption in Germany. Shallow geothermal systems for indirect use as well as shallow geothermal heat storage systems like aquifer thermal energy storage (ATES) or borehole thermal energy storage (BTES) typically provide low exergy heat. The temperature levels and ranges typically require a coupling with heat pumps. By storing hot water from solar panels or thermal power stations with temperatures of up to 110 °C a medium deep high temperature heat storage (MDHTS) can be operated on relatively high temperature levels of more than 45 °C. Storage depths of 500 m to 1,500 m below surface avoid conflicts with groundwater use for drinking water or other purposes. Permeability is typically also decreasing with greater depth; especially in the crystalline basement therefore conduction becomes the dominant heat transport process. Solar-thermal charging of a MDHTS is a very beneficial option for supplying heat in urban and rural systems. Feasibility and design criteria of different system configurations (depth, distance and number of BHE) are discussed. One system is designed to store and supply heat (300 kW) for an office building. The required boreholes are located in granodioritic bedrock. Resulting from this setup several challenges have to be addressed. The drilling and completion has to be planned carefully under consideration of the geological and tectonical situation at the specific site.

Solar-assisted heat pump – A sustainable system for low-temperature water heating applications

International Nuclear Information System (INIS)

Chaturvedi, S.K.; Gagrani, V.D.; Abdel-Salam, T.M.

2014-01-01

Highlights: • DX-SAHP water heaters systems are economical as well as energy conserving. • The economic analysis is performed using the life cycle cost (LCC) analysis. • LCC can be optimized with respect to the collector area at a specific temperature. • For high load temperature range a two stage heat pump system is more appropriate. - Abstract: Direct expansion solar assisted heat pump systems (DX-SAHP) have been widely used in many applications including water heating. In the DX-SAHP systems the solar collector and the heat pump evaporator are integrated into a single unit in order to transfer the solar energy to the refrigerant. The present work is aimed at studying the use of the DX-SAHP for low temperature water heating applications. The novel aspect of this paper involves a detailed long-term thermo-economic analysis of the energy conservation potential and economic viability of these systems. The thermal performance is simulated using a computer program that incorporates location dependent radiation, collector, economic, heat pump and load data. The economic analysis is performed using the life cycle cost (LCC) method. Results indicate that the DX-SAHP water heaters systems when compared to the conventional electrical water heaters are both economical as well as energy conserving. The analysis also reveals that the minimum value of the system life cycle cost is achieved at optimal values of the solar collector area as well as the compressor displacement capacity. Since the cost of SAHP system presents a barrier to mass scale commercialization, the results of the present study indicating that the SAHP life cycle cost can be minimized by optimizing the collector area would certainly be helpful in lowering, if not eliminating, the economic barrier to these systems. Also, at load temperatures higher than 70 °C, the performance of the single stage heat pump degrades to the extent that its cost and efficiency advantages over the electric only system are

Direct high-temperature ohmic heating of metals as liquid pipes.

Science.gov (United States)

Grosse, A V; Cahill, J A; Liddell, W L; Murphy, W J; Stokes, C S

1968-05-03

When a sufficiently high electric current is passed through a liquid metal, the electromagnetic pressure pinches off the liquid metal and interrupts the flow of current. For the first time the pinch effect has been overcome by use of centrifugal acceleration. By rotation of a pipe of liquid metal, tin or bismuth or their alloys, at sufficiently high speed, it can be heated electrically without intermission of the electric current. One may now heat liquid metallic substances, by resistive (ohmic) heating, to 5000 degrees K and perhaps higher temperatures.

Theoretical overview of heating power and necessary heating supply temperatures in typical Danish single-family houses from the 1900s

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

2016-01-01

in typical Danish single-family houses constructed in the 1900s. The study provides a simplified theoretical overview of typical building constructions and standards for the calculation of design heat loss and design heating power in Denmark in the 1900s. The heating power and heating demand in six typical...... Danish single-family houses constructed in the 1900s were estimated based on simple steady-state calculations. We found that the radiators in existing single-family houses should not necessarilrbe expected to be over-dimensioned compared to current design heat loss. However, there is considerable...... potential for using low-temperature space heating in existing single-family houses in typical operation conditions. Older houses were not always found to require higher heating system temperatures than newer houses. We found that when these houses have gone through reasonable energy renovations, most...

Estimation of Surface Temperature and Heat Flux by Inverse Heat Transfer Methods Using Internal Temperatures Measured While Radiantly Heating a Carbon/Carbon Specimen up to 1920 F

Science.gov (United States)

Pizzo, Michelle; Daryabeigi, Kamran; Glass, David

2015-01-01

The ability to solve the heat conduction equation is needed when designing materials to be used on vehicles exposed to extremely high temperatures; e.g. vehicles used for atmospheric entry or hypersonic flight. When using test and flight data, computational methods such as finite difference schemes may be used to solve for both the direct heat conduction problem, i.e., solving between internal temperature measurements, and the inverse heat conduction problem, i.e., using the direct solution to march forward in space to the surface of the material to estimate both surface temperature and heat flux. The completed research first discusses the methods used in developing a computational code to solve both the direct and inverse heat transfer problems using one dimensional, centered, implicit finite volume schemes and one dimensional, centered, explicit space marching techniques. The developed code assumed the boundary conditions to be specified time varying temperatures and also considered temperature dependent thermal properties. The completed research then discusses the results of analyzing temperature data measured while radiantly heating a carbon/carbon specimen up to 1920 F. The temperature was measured using thermocouple (TC) plugs (small carbon/carbon material specimens) with four embedded TC plugs inserted into the larger carbon/carbon specimen. The purpose of analyzing the test data was to estimate the surface heat flux and temperature values from the internal temperature measurements using direct and inverse heat transfer methods, thus aiding in the thermal and structural design and analysis of high temperature vehicles.

Integration of Space Heating and Hot Water Supply in Low Temperature District Heating

DEFF Research Database (Denmark)

Elmegaard, Brian; Ommen, Torben Schmidt; Markussen, Michael

2014-01-01

pipes, where the water is at the highest temperature. The heat loss may be lowered by decreasing the temperatures in the network for which reason low temperature networks are proposed as a low loss solution for future district heating. However, the heating demand of the consumers involve both domestic......District heating makes it possible to provide heat for many consumers in an efficient manner. In particular, district heating based on combined heat and power production is highly efficient. One disadvantage of district heating is that there is a significant heat loss from the pipes...... to the surrounding ground. In larger networks involving both transmission and distribution systems, the heat loss is most significant from the distribution network. An estimate is that about 80-90 % of the heat loss occurs in the distribution system. In addition, the heat loss is naturally highest from the forward...

Waste Heat Recovery from a High Temperature Diesel Engine

Science.gov (United States)

Adler, Jonas E.

the required heat exchanger volume due to abnormally low engine oil temperatures during the experiment ( 80 °C). Future studies should focus on allowing the engine oil to reach higher operating temperatures which would decrease the heat rejected to the engine oil and reduce the heat duty for the oil coolers resulting in reduced oil cooler volume.

Effect of Temperature Shock and Inventory Surprises on Natural Gas and Heating Oil Futures Returns

Science.gov (United States)

Hu, John Wei-Shan; Lin, Chien-Yu

2014-01-01

The aim of this paper is to examine the impact of temperature shock on both near-month and far-month natural gas and heating oil futures returns by extending the weather and storage models of the previous study. Several notable findings from the empirical studies are presented. First, the expected temperature shock significantly and positively affects both the near-month and far-month natural gas and heating oil futures returns. Next, significant temperature shock has effect on both the conditional mean and volatility of natural gas and heating oil prices. The results indicate that expected inventory surprises significantly and negatively affects the far-month natural gas futures returns. Moreover, volatility of natural gas futures returns is higher on Thursdays and that of near-month heating oil futures returns is higher on Wednesdays than other days. Finally, it is found that storage announcement for natural gas significantly affects near-month and far-month natural gas futures returns. Furthermore, both natural gas and heating oil futures returns are affected more by the weighted average temperature reported by multiple weather reporting stations than that reported by a single weather reporting station. PMID:25133233

Hyperbolic heat conduction, effective temperature, and third law for nonequilibrium systems with heat flux

Science.gov (United States)

Sobolev, S. L.

2018-02-01

Some analogies between different nonequilibrium heat conduction models, particularly random walk, the discrete variable model, and the Boltzmann transport equation with the single relaxation time approximation, have been discussed. We show that, under an assumption of a finite value of the heat carrier velocity, these models lead to the hyperbolic heat conduction equation and the modified Fourier law with relaxation term. Corresponding effective temperature and entropy have been introduced and analyzed. It has been demonstrated that the effective temperature, defined as a geometric mean of the kinetic temperatures of the heat carriers moving in opposite directions, acts as a criterion for thermalization and is a nonlinear function of the kinetic temperature and heat flux. It is shown that, under highly nonequilibrium conditions when the heat flux tends to its maximum possible value, the effective temperature, heat capacity, and local entropy go to zero even at a nonzero equilibrium temperature. This provides a possible generalization of the third law to nonequilibrium situations. Analogies and differences between the proposed effective temperature and some other definitions of a temperature in nonequilibrium state, particularly for active systems, disordered semiconductors under electric field, and adiabatic gas flow, have been shown and discussed. Illustrative examples of the behavior of the effective temperature and entropy during nonequilibrium heat conduction in a monatomic gas and a strong shockwave have been analyzed.

Low-temperature heating systems and public administration

Energy Technology Data Exchange (ETDEWEB)

Boerner, H

1981-06-01

The even temperature distribution and comfortable climate in rooms heated by low-temperature heating systems is mostly due to one of the preconditions of this type of heating system namely, efficient thermal insulation of the rooms. Thermal insulation is already required as part of the pertinent legal regulations but it is also in the interest of the builder-owner as it will, in the long run, greatly reduce the heating cost.

Magnetic heat pumping near room temperature

Science.gov (United States)

Brown, G. V.

1976-01-01

It is shown that magnetic heat pumping can be made practical at room temperature by using a ferromagnetic material with a Curie point at or near operating temperature and an appropriate regenerative thermodynamic cycle. Measurements are performed which show that gadolinium is a resonable working material and it is found that the application of a 7-T magnetic field to gadolinium at the Curie point (293 K) causes a heat release of 4 kJ/kg under isothermal conditions or a temperature rise of 14 K under adiabatic conditions. A regeneration technique can be used to lift the load of the lattice and electronic heat capacities off the magnetic system in order to span a reasonable temperature difference and to pump as much entropy per cycle as possible

Performance investigation on a multi-unit heat pump for simultaneous temperature and humidity control

International Nuclear Information System (INIS)

Fan, Hongming; Shao, Shuangquan; Tian, Changqing

2014-01-01

Highlights: • A multi-unit heat pump is proposed for simultaneous temperature and humidity control. • Condensation heat is non, partly or fully recovered for temperature regulation. • Highly integrated heat pump for residential cooling, dehumidification and heating. • High energy saving potential for all-year-round operation in wet and warm regions. - Abstract: A multi-unit heat pump is presented for simultaneous humidity and temperature control to improve the energy efficiency and the thermal comfort. Two parallel connected condensers are employed in the system, locating at the back of the indoor evaporator and the outdoor unit, respectively. The heat pump can operate in four modes, including heating, cooling and dehumidification without and/or with partial or total condensing heat recovery. The experimental investigation shows that the temperature control capacity is from 3.5 kW for cooling to 3.8 kW for heating with the cooling and heating efficiency higher than 3.5 kW kW −1 , and the dehumidification rate is about 2.0 kg h −1 with the efficiency about 2.0 kg h −1 kW −1 . The supply air temperature and humidity can be simultaneously regulated with high accuracy and high efficiency by adjusting the indoor and/or outdoor air volumes. It provides an integrated and effective solution for simultaneous indoor air temperature and humidity control for all-year-round operation in residential buildings

Self-heating, gamma heating and heat loss effects on resistance temperature detector (RTD) accuracy

International Nuclear Information System (INIS)

Qian, T.; Hinds, H.W.; Tonner, P.

1997-01-01

Resistance temperature detectors (RTDs) are extensively used in CANDU nuclear power stations for measuring various process and equipment temperatures. Accuracy of measurement is an important performance parameter of RTDs and has great impact on the thermal power efficiency and safety of the plant. There are a number of factors that contribute to some extent to RTD measurement error. Self-heating, gamma heating and the heat-loss throughout conduction of the thermowell are three of these factors. The degree to which these three affect accuracy of RTDs used for the measurement of reactor inlet header temperature (RIHT) has been analyzed and is presented in this paper. (author)

Performance analysis of ORC power generation system with low-temperature waste heat of aluminum reduction cell

Science.gov (United States)

Wang, Zhiqi; Zhou, Naijun; Jing, Guo

Performance of organic Rankine cycle (ORC) system to recover low-temperature waste heat from aluminum reduction cell was analyzed. The temperature of waste heat is 80°C-200°C and the flow rate is 3×105m3/h. The pinch temperature difference between waste heat and working fluids is 10°C. The results show that there is optimal evaporating temperature for maximum net power under the same pinch point. For heat source temperature range of 80°C-140°C and 150°C-170°C, the working fluid given biggest net power is R227ea and R236fa, respectively. When the temperature is higher than 180°C, R236ea generates the biggest net power. The variation of heat source temperature has important effect on net power. When the temperature decreases 10%, the net power will deviate 30% from the maximum value.

Survey of high-temperature nuclear heat application

International Nuclear Information System (INIS)

Kirch, N.; Schaefer, M.

1984-01-01

Nuclear heat application at high temperatures can be divided into two areas - use of high-temperature steam up to 550 deg. C and use of high-temperature helium up to about 950 deg. C. Techniques of high-temperature steam and heat production and application are being developed in several IAEA Member States. In all these countries the use of steam for other than electricity production is still in a project definition phase. Plans are being discussed about using steam in chemical industries, oil refineries and for new synfuel producing plants. The use of nuclear generated steam for oil recovery from sands and shale is also being considered. High-temperature nuclear process heat production gives new possibilities for the application of nuclear energy - hard coals, lignites, heavy oils, fuels with problems concerning transport, handling and pollution can be converted into gaseous or liquid energy carriers with no loss of their energy contents. The main methods for this conversion are hydrogasification with hydrogen generated by nuclear heated steam reformers and steam gasification. These techniques will allow countries with large coal resources to replace an important part of their natural gas and oil consumption. Even countries with no fossil fuels can benefit from high-temperature nuclear heat - hydrogen production by thermochemical water splitting, nuclear steel making, ammonia production and the chemical heat-pipe system are examples in this direction. (author)

Modelling of temperature in deep boreholes and evaluation of geothermal heat flow at Forsmark and Laxemar

Energy Technology Data Exchange (ETDEWEB)

Sundberg, Jan; Back, Paer-Erik; Laendell, Maerta; Sundberg, Anders (GEO INNOVA AB, Linkoeping (Sweden))

2009-06-15

This report presents modelling of temperature and temperature gradients in boreholes in Laxemar and Forsmark and fitting to measured temperature data. The modelling is performed with an analytical expression including thermal conductivity, thermal diffusivity, heat flow, internal heat generation and climate events in the past. As a result of the fitting procedure it is also possible to evaluate local heat flow values for the two sites. However, since there is no independent evaluation of the heat flow, uncertainties in for example thermal conductivity, diffusivity and the palaeoclimate temperature curve are transferred into uncertainties in the heat flow. Both for Forsmark and Laxemar, reasonably good fits were achieved between models and data on borehole temperatures. However, none of the general models achieved a fit within the 95% confidence intervals of the measurements. This was achieved in some cases for the additional optimised models. Several of the model parameters are uncertain. A good model fit does not automatically imply that 'correct' values have been used for these parameters. Similar model fits can be expected with different sets of parameter values. The palaeoclimatically corrected surface mean heat flow at Forsmark and Laxemar is suggested to be 61 and 56 mW/m2 respectively. If all uncertainties are combined, including data uncertainties, the total uncertainty in the heat flow determination is judged to be within +12% to -14% for both sites. The corrections for palaeoclimate are quite large and verify the need of site-specific climate descriptions. Estimations of the current ground surface temperature have been made by extrapolations from measured temperature logging. The mean extrapolated ground surface temperature in Forsmark and Laxemar is estimated to 6.5 deg and 7.3 deg C respectively. This is approximately 1.7 deg C higher for Forsmark, and 1.6 deg C higher for Laxemar compared to data in the report SKB-TR-06-23. Comparison with

Modelling of temperature in deep boreholes and evaluation of geothermal heat flow at Forsmark and Laxemar

International Nuclear Information System (INIS)

Sundberg, Jan; Back, Paer-Erik; Laendell, Maerta; Sundberg, Anders

2009-05-01

This report presents modelling of temperature and temperature gradients in boreholes in Laxemar and Forsmark and fitting to measured temperature data. The modelling is performed with an analytical expression including thermal conductivity, thermal diffusivity, heat flow, internal heat generation and climate events in the past. As a result of the fitting procedure it is also possible to evaluate local heat flow values for the two sites. However, since there is no independent evaluation of the heat flow, uncertainties in for example thermal conductivity, diffusivity and the palaeoclimate temperature curve are transferred into uncertainties in the heat flow. Both for Forsmark and Laxemar, reasonably good fits were achieved between models and data on borehole temperatures. However, none of the general models achieved a fit within the 95% confidence intervals of the measurements. This was achieved in some cases for the additional optimised models. Several of the model parameters are uncertain. A good model fit does not automatically imply that 'correct' values have been used for these parameters. Similar model fits can be expected with different sets of parameter values. The palaeoclimatically corrected surface mean heat flow at Forsmark and Laxemar is suggested to be 61 and 56 mW/m 2 respectively. If all uncertainties are combined, including data uncertainties, the total uncertainty in the heat flow determination is judged to be within +12% to -14% for both sites. The corrections for palaeoclimate are quite large and verify the need of site-specific climate descriptions. Estimations of the current ground surface temperature have been made by extrapolations from measured temperature logging. The mean extrapolated ground surface temperature in Forsmark and Laxemar is estimated to 6.5 deg and 7.3 deg C respectively. This is approximately 1.7 deg C higher for Forsmark, and 1.6 deg C higher for Laxemar compared to data in the report SKB-TR-06-23. Comparison with air

Impact of heat stress on crop yield—on the importance of considering canopy temperature

International Nuclear Information System (INIS)

Siebert, Stefan; Ewert, Frank; Eyshi Rezaei, Ehsan; Kage, Henning; Graß, Rikard

2014-01-01

Increasing crop productivity while simultaneously reducing the environmental footprint of crop production is considered a major challenge for the coming decades. Even short episodes of heat stress can reduce crop yield considerably causing low resource use efficiency. Studies on the impact of heat stress on crop yields over larger regions generally rely on temperatures measured by standard weather stations at 2 m height. Canopy temperatures measured in this study in field plots of rye were up to 7 °C higher than air temperature measured at typical weather station height with the differences in temperatures controlled by soil moisture contents. Relationships between heat stress and grain number derived from controlled environment studies were only confirmed under field conditions when canopy temperature was used to calculate stress thermal time. By using hourly mean temperatures measured by 78 weather stations located across Germany for the period 1994–2009 it is estimated, that mean yield declines in wheat due to heat stress during flowering were 0.7% when temperatures are measured at 2 m height, but yield declines increase to 22% for temperatures measured at the ground. These results suggest that canopy temperature should be simulated or estimated to reduce uncertainty in assessing heat stress impacts on crop yield. (letter)

District Heating Expansion Potential with Low-Temperature and End-Use Heat Savings

DEFF Research Database (Denmark)

Nielsen, Steffen; Grundahl, Lars

2018-01-01

District heating has the potential to play a key role in the transition towards a renewable energy system. However, the development towards reduced heat demands threatens the feasibility of district heating. Despite this challenge, opportunity exists in the form of fourth generation district...... heating, which operates at lower temperatures and enables better renewable integration. This article investigates this challenge by examining the district heating potential within three scenarios: The first is a reference scenario with current heat demand and temperatures, the second includes heat demand...... costs. The models are applied using an example case of The Northern Region of Denmark. The article concludes that the district heating potential is highest in the reference scenario. When heat savings are introduced, district heating expansions, in most cases, will not be feasible. Introducing low...

Utilization of low-temperature heat sources for heat and power production

DEFF Research Database (Denmark)

Haglind, Fredrik; Elmegaard, Brian

2014-01-01

Low-temperature heat sources are available in many applications, ranging from waste heat from marine diesel engines, industries and refrigeration plants to biomass, geothermal and solar heat sources. There is a great potential for enhancing the utilization of these heat sources by novel...

Students’ Perceived Heat-Health Symptoms Increased with Warmer Classroom Temperatures

Directory of Open Access Journals (Sweden)

Shalin Bidassey-Manilal

2016-06-01

Full Text Available Temperatures in Africa are expected to increase by the end of the century. Heat-related health impacts and perceived health symptoms are potentially a problem, especially in public schools with limited resources. Students (n = 252 aged ~14–18 years from eight high schools completed an hourly heat-health symptom log over 5 days. Data loggers measured indoor classroom temperatures. A high proportion of students felt tired (97.2%, had low concentration (96.8% and felt sleepy (94.1% during at least one hour on any day. There were statistically significant correlations, when controlling for school cluster effect and time of day, between indoor temperatures ≥32 °C and students who felt tired and found it hard to breathe. Consistently higher indoor classroom temperatures were observed in classrooms constructed of prefabricated asbestos sheeting with corrugated iron roof and converted shipping container compared to brick classrooms. Longitudinal studies in multiple seasons and different classroom building types are needed.

Uniformity factor of temperature difference in heat exchanger networks

International Nuclear Information System (INIS)

Chen, Shang; Cui, Guo-min

2016-01-01

Highlights: • A uniformity factor of temperature (UFTD) is proposed to heat exchanger network (HEN). • A novel stage-wise superstructure with inner utilities is presented based on UFTD. • New model and DE method is combined as an optimization method. • Optimal HEN structures with inner utilities can be obtained with new method. - Abstract: A uniformity factor of temperature difference (UFTD) is proposed and set up to guide the optimization of Heat exchanger network (HEN). At first, the factor is presented to evaluate the whole enhancement of HEN by handling the logical mean temperature difference as two-dimensional discrete temperature field in system. Then, the factor is applied to different HENs, of which the comparison indicates that a more uniform discrete temperature field leads to a lower UFTD which correlated with a better whole enhancement to improve the optimization level of HEN. A novel stage-wise superstructure model where inner utility can be generated is presented for further analysis of correlation between UFTD and the efficiency of HEN, and more optimal HEN structures can be obtained as inner utility added. Inner utility appears to violate the thermodynamic law, but it makes the discrete temperature field more uniform and improves the heat transfer efficiency of the whole HEN, which brings much more profit than the side effect of inner utility. In sum, the UFTD can not only evaluate the optimization level of the HEN, but also be an optimization object to design new HEN with higher efficiency of energy utilization and lower total annual cost.

Power generation from low-temperature heat source

Energy Technology Data Exchange (ETDEWEB)

Lakew, Amlaku Abie

2012-07-01

The potential of low-temperature heat sources for power production has been discussed for decades. The diversity and availability of low-temperature heat sources makes it interesting for power production. The thermodynamic power cycle is one of the promising technologies to produce electricity from low-temperature heat sources. There are different working fluids to be used in a thermodynamic power cycle. Working fluid selection is essential for the performance of the power cycle. Over the last years, different working fluid screening criteria have been used. In broad speaking the screening criteria can be grouped as thermodynamic performance, component size requirement, economic performance, safety and environmental impact. Screening of working fluids at different heat source temperatures (80-200 Celsius degrees) using thermodynamic performance (power output and exergy efficiency) and component size (heat exchanger and turbine) is investigated. It is found that the 'best' working fluid depends on the criteria used and heat source temperature level. Transcritical power cycles using carbon dioxide as a working fluid is studied to produce power at 100 Celsius degrees. Carbon dioxide is an environmentally friendly refrigerant. The global warming potential of carbon dioxide is 1. Furthermore, because of its low critical temperature (31 Celsius degrees), carbon dioxide can operate in a transcritical power cycle for lower heat source temperatures. A transcritical configuration avoids the problem of pinching which otherwise would happened in subcritical power cycle. In the process, better temperature matching is achieved and more heat is extracted. Thermodynamic analysis of transcritical cycle is performed; it is found that there is an optimal operating pressure for highest net power output. The pump work is a sizable fraction of the work produced by the turbine. The effect of efficiency deterioration of the pump and the turbine is compared. When the

Rapid self-heating and internal temperature sensing of lithium-ion batteries at low temperatures

International Nuclear Information System (INIS)

Zhang, Guangsheng; Ge, Shanhai; Xu, Terrence; Yang, Xiao-Guang; Tian, Hua; Wang, Chao-Yang

2016-01-01

Highlights: • Self-heating lithium-ion battery (SHLB) structure provided a practical solution to the poor performance at subzero temperatures. • We report an improved SHLB that heats from −20 °C to 0 °C in 12.5 seconds, or 56% more rapidly, while consuming 24% less energy than previously reported. • The nickel foil heating element embedded inside a SHLB cell plays a dominant role in rapid self-heating. • The embedded nickel foil can simultaneously perform as an internal temperature sensor (ITS). • 2-sheet design self-heats faster than 1-sheet design due to more uniform internal temperature distribution. - Abstract: The recently discovered self-heating lithium-ion battery structure provided a practical solution to the poor performance at subzero temperatures that has hampered battery technology for decades. Here we report an improved self-heating lithium-ion battery (SHLB) that heats from −20 °C to 0 °C in 12.5 seconds, or 56% more rapidly, while consuming 24% less energy than that reported previously. We reveal that a nickel foil heating element embedded inside a SHLB cell plays a dominant role in self-heating and we experimentally demonstrate that a 2-sheet design can achieve dramatically accelerated self-heating due to more uniform internal temperature distribution. We also report, for the first time, that this embedded nickel foil can simultaneously perform as an internal temperature sensor (ITS) due to the perfectly linear relationship between the foil’s electrical resistance and temperature.

Challenges in Smart Low-Temperature District Heating Development

DEFF Research Database (Denmark)

Li, Hongwei; Wang, Stephen Jia

2014-01-01

Previous research and development shows that low temperature district heating (LTDH) system is economic feasible for low energy buildings and buildings at sparse areas. Coupling with reduced network temperature and well-designed district heating (DH) networks, LTDH can reduce network heat loss by...

A high-temperature high-pressure calorimeter for determining heats of solution up to 623 K.

Science.gov (United States)

Djamali, Essmaiil; Turner, Peter J; Murray, Richard C; Cobble, James W

2010-07-01

A high-temperature high-pressure isoperibol calorimeter for determining the heats of solution and reaction of very dilute substances in water (10(-4) m) at temperatures up to 623 K is described. The energies of vaporization of water at steam saturation pressure were measured as a function of temperature and the results agree with the corresponding values from steam tables to better than 0.08+/-0.18%. The novelties of the present instrument relative to flow type heat capacity calorimeters are that measurements can be made at orders of magnitude lower concentrations and that measurement of heat of reaction involving solids or gases or in the presence of high concentrations of supporting electrolytes, acids, and bases is possible. Furthermore, the advantage of using enthalpy data over heat capacity data for calculations of the standard state Gibbs free energies of electrolytes is that the experimental heat data of this research need only be integrated once to derive higher temperature free energy data from lower temperatures. The derived heat capacities can be used mathematically to obtain free energies by double integration. However, the resulting errors are much smaller than if experimental aqueous heat capacities were used for the integrations.

Application of Abaqus to analysis of the temperature field in elements heated by moving heat sources

Directory of Open Access Journals (Sweden)

W. Piekarska

2010-10-01

Full Text Available Numerical analysis of thermal phenomena occurring during laser beam heating is presented in this paper. Numerical models of surface andvolumetric heat sources were presented and the influence of different laser beam heat source power distribution on temperature field wasanalyzed. Temperature field was obtained by a numerical solution the transient heat transfer equation with activity of inner heat sources using finite element method. Temperature distribution analysis in welded joint was performed in the ABAQUS/Standard solver. The DFLUXsubroutine was used for implementation of the movable welding heat source model. Temperature-depended thermophysical properties for steelwere assumed in computer simulations. Temperature distribution in laser beam surface heated and butt welded plates was numericallyestimated.

Mapping of low temperature heat sources in Denmark

DEFF Research Database (Denmark)

Bühler, Fabian; Holm, Fridolin Müller; Huang, Baijia

2015-01-01

heat. The total accessible waste heat potential is found to be approximately 266 PJ per year with 58 % of it below 100 °C. In the natural heat category, temperatures below 20 °C originate from ambient air, sea water and shallow geothermal energy, and temperatures up to 100 °C are found for solar...... and deep geothermal energy. The theoretical solar thermal potential alone would be above 500 PJ per year. For the development of advanced thermodynamic cycles for the integration of heat sources in the Danish energy system, several areas of interest are determined. In the maritime transport sector a high......Low temperature heat sources are available in many applications, ranging from waste heat from industrial processes and buildings to geothermal and solar heat sources. Technical advancements, such as heat pumps with novel cycle design and multi-component working fluids, make the utilisation of many...

Effect of radiant heat transfer on the performance of high temperature heat exchanger

International Nuclear Information System (INIS)

Mori, Yasuo; Hijikata, Kunio; Yamada, Yukio

1975-01-01

The development of high temperature gas-cooled reactors is motivated by the consideration of the application of nuclear heat for industrial uses or direct steelmaking and chemical processes. For these purposes, reliable and efficient heat exchangers should be developed. This report analyzes the effect of radiant heat transfer on the performance of high temperature heat exchangers. The heat transfer model is as follows: the channel composed with two parallel adiabatic walls is divided with one parallel plate between the walls. Non-radiative fluid flows in the two separated channels in opposite direction. Heat transfer equations for this system were obtained, and these equations were solved by some approximate method and numerical analysis. The effect of radiation on heat transfer became larger as the radiant heat transfer between two walls was larger. In the heat exchangers of counter flow type, the thermal efficiency is controlled with three parameters, namely radiation-convection parameter, Stanton number and temperature difference. The thermal efficiency was larger with the increase of these parameters. (Iwase, T.)

Helicon plasma ion temperature measurements and observed ion cyclotron heating in proto-MPEX

Science.gov (United States)

Beers, C. J.; Goulding, R. H.; Isler, R. C.; Martin, E. H.; Biewer, T. M.; Caneses, J. F.; Caughman, J. B. O.; Kafle, N.; Rapp, J.

2018-01-01

The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) linear plasma device is a test bed for exploring and developing plasma source concepts to be employed in the future steady-state linear device Material Plasma Exposure eXperiment (MPEX) that will study plasma-material interactions for the nuclear fusion program. The concept foresees using a helicon plasma source supplemented with electron and ion heating systems to reach necessary plasma conditions. In this paper, we discuss ion temperature measurements obtained from Doppler broadening of spectral lines from argon ion test particles. Plasmas produced with helicon heating alone have average ion temperatures downstream of the Helicon antenna in the range of 3 ± 1 eV; ion temperature increases to 10 ± 3 eV are observed with the addition of ion cyclotron heating (ICH). The temperatures are higher at the edge than the center of the plasma either with or without ICH. This type of profile is observed with electrons as well. A one-dimensional RF antenna model is used to show where heating of the plasma is expected.

High temperature heat capacities and electrical conductivities of boron carbides

International Nuclear Information System (INIS)

Matsui, Tsuneo; Arita, Yuri; Naito, Keiji; Imai, Hisashi

1991-01-01

The heat capacities and the electrical conductivities of B x C(x=3, 4, 5) were measured by means of direct heating pulse calorimetry in the temperature range from 300 to 1500 K. The heat capacities of B x C increased with increasing x value. This increase in the heat capacity is probably related to the change of the lattice vibration mode originated from the reduction of the stiffness of the intericosahedral chain accompanied with a change from C-B-C to C-B-B chains. A linear relationship between the logarithm of σT (σ is the electrical conductivity and T is the absolute temperature) of B x C and the reciprocal temperature was observed, indicating the presence of small polaron hopping as the predominant conduction mechanism. The electrical conductivity of B x C also increased with increasing x value (from 4 to 5) due to an increase of the polaron hopping of holes between carbon atoms at geometrically nonequivalent sites, since these nonequivalent sites of carbon atoms were considered to increase in either B 11 C icosahedra or in icosahedral chains with increasing x. The electrical conductivity of B 3 C was higher than that of B 4 C, which is probably due to the precipitation of high-conducting carbon. The thermal conductivity and the thermodynamic quantities of B 4 C were also determined precisely from the heat capacity value. (orig.)

Low Temperature District Heating for Future Energy Systems

DEFF Research Database (Denmark)

Schmidt, Dietrich; Kallert, Anna; Blesl, Markus

2017-01-01

of the building stock. Low temperature district heating (LTDH) can contribute significantly to a more efficient use of energy resources as well as better integration of renewable energy (e.g. geothermal or solar heat), and surplus heat (e.g. industrial waste heat) into the heating sector. LTDH offers prospects......The building sector is responsible for more than one third of the final energy consumption of societies and produces the largest amount of greenhouse gas emissions of all sectors. This is due to the utilisation of combustion processes of mainly fossil fuels to satisfy the heating demand...... for both the demand side (community building structure) and the supply side (network properties or energy sources). Especially in connection with buildings that demand only low temperatures for space heating. The utilisation of lower temperatures reduces losses in pipelines and can increase the overall...

The impact of temperature on mortality in a subtropical city: effects of cold, heat, and heat waves in São Paulo, Brazil

Science.gov (United States)

Son, Ji-Young; Gouveia, Nelson; Bravo, Mercedes A.; de Freitas, Clarice Umbelino; Bell, Michelle L.

2016-01-01

Understanding how weather impacts health is critical, especially under a changing climate; however, relatively few studies have investigated subtropical regions. We examined how mortality in São Paulo, Brazil, is affected by cold, heat, and heat waves over 14.5 years (1996-2010). We used over-dispersed generalized linear modeling to estimate heat- and cold-related mortality, and Bayesian hierarchical modeling to estimate overall effects and modification by heat wave characteristics (intensity, duration, and timing in season). Stratified analyses were performed by cause of death and individual characteristics (sex, age, education, marital status, and place of death). Cold effects on mortality appeared higher than heat effects in this subtropical city with moderate climatic conditions. Heat was associated with respiratory mortality and cold with cardiovascular mortality. Risk of total mortality was 6.1 % (95 % confidence interval 4.7, 7.6 %) higher at the 99th percentile of temperature than the 90th percentile (heat effect) and 8.6 % (6.2, 11.1 %) higher at the 1st compared to the 10th percentile (cold effect). Risks were higher for females and those with no education for heat effect, and males for cold effect. Older persons, widows, and non-hospital deaths had higher mortality risks for heat and cold. Mortality during heat waves was higher than on non-heat wave days for total, cardiovascular, and respiratory mortality. Our findings indicate that mortality in São Paulo is associated with both cold and heat and that some subpopulations are more vulnerable.

The impact of temperature on mortality in a subtropical city: effects of cold, heat, and heat waves in São Paulo, Brazil.

Science.gov (United States)

Son, Ji-Young; Gouveia, Nelson; Bravo, Mercedes A; de Freitas, Clarice Umbelino; Bell, Michelle L

2016-01-01

Understanding how weather impacts health is critical, especially under a changing climate; however, relatively few studies have investigated subtropical regions. We examined how mortality in São Paulo, Brazil, is affected by cold, heat, and heat waves over 14.5 years (1996-2010). We used over-dispersed generalized linear modeling to estimate heat- and cold-related mortality, and Bayesian hierarchical modeling to estimate overall effects and modification by heat wave characteristics (intensity, duration, and timing in season). Stratified analyses were performed by cause of death and individual characteristics (sex, age, education, marital status, and place of death). Cold effects on mortality appeared higher than heat effects in this subtropical city with moderate climatic conditions. Heat was associated with respiratory mortality and cold with cardiovascular mortality. Risk of total mortality was 6.1% (95% confidence interval 4.7, 7.6%) higher at the 99th percentile of temperature than the 90th percentile (heat effect) and 8.6% (6.2, 11.1%) higher at the 1st compared to the 10th percentile (cold effect). Risks were higher for females and those with no education for heat effect, and males for cold effect. Older persons, widows, and non-hospital deaths had higher mortality risks for heat and cold. Mortality during heat waves was higher than on non-heat wave days for total, cardiovascular, and respiratory mortality. Our findings indicate that mortality in São Paulo is associated with both cold and heat and that some subpopulations are more vulnerable.

Cyclic high temperature heat storage using borehole heat exchangers

Science.gov (United States)

Boockmeyer, Anke; Delfs, Jens-Olaf; Bauer, Sebastian

2016-04-01

The transition of the German energy supply towards mainly renewable energy sources like wind or solar power, termed "Energiewende", makes energy storage a requirement in order to compensate their fluctuating production and to ensure a reliable energy and power supply. One option is to store heat in the subsurface using borehole heat exchangers (BHEs). Efficiency of thermal storage is increasing with increasing temperatures, as heat at high temperatures is more easily injected and extracted than at temperatures at ambient levels. This work aims at quantifying achievable storage capacities, storage cycle times, injection and extraction rates as well as thermal and hydraulic effects induced in the subsurface for a BHE storage site in the shallow subsurface. To achieve these aims, simulation of these highly dynamic storage sites is performed. A detailed, high-resolution numerical simulation model was developed, that accounts for all BHE components in geometrical detail and incorporates the governing processes. This model was verified using high quality experimental data and is shown to achieve accurate simulation results with excellent fit to the available experimental data, but also leads to large computational times due to the large numerical meshes required for discretizing the highly transient effects. An approximate numerical model for each type of BHE (single U, double U and coaxial) that reduces the number of elements and the simulation time significantly was therefore developed for use in larger scale simulations. The approximate numerical model still includes all BHE components and represents the temporal and spatial temperature distribution with a deviation of less than 2% from the fully discretized model. Simulation times are reduced by a factor of ~10 for single U-tube BHEs, ~20 for double U-tube BHEs and ~150 for coaxial BHEs. This model is then used to investigate achievable storage capacity, injection and extraction rates as well as induced effects for

Integrated Temperature Sensors based on Heat Diffusion

NARCIS (Netherlands)

Van Vroonhoven, C.P.L.

2015-01-01

This thesis describes the theory, design and implementation of a new class of integrated temperature sensors, based on heat diffusion. In such sensors, temperature is sensed by measuring the time it takes for heat to diffuse through silicon. An on-chip thermal delay can be determined by geometry and

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

High temperature industrial heat pumps

Energy Technology Data Exchange (ETDEWEB)

Berghmans, J. (Louvain Univ., Heverlee (Belgium). Inst. Mechanica)

1990-01-01

The present report intends to describe the state of the art of high temperature industrial heat pumps. A description is given of present systems on the market. In addition the research and development efforts on this subject are described. Compression (open as well as closed cycle) systems, as well as absorption heat pumps (including transformers), are considered. This state of the art description is based upon literature studies performed by a team of researchers from the Katholieke Universiteit Leuven, Belgium. The research team also analysed the economics of heat pumps of different types under the present economic conditions. The heat pumps are compared with conventional heating systems. This analysis was performed in order to evaluate the present condition of the heat pump in the European industry.

Case study of low-temperature heating in an existing single-family house-A test of methods for simulation of heating system temperatures

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

2016-01-01

and the calculated indoor temperatures and radiator return temperatures were compared to temperatures measured in the case house. The results showed that the detail of the simulation model has a large influence on the results obtained. The estimated return temperatures from the radiators varied by up to 16 degrees C...... depending on the assumptions made in the simulation model. The results indicated that a detailed building simulation model can provide a good estimate of the actual heating system operation, provided that actual radiators and realistic indoor temperatures are taken into account in the model. (C) 2016......Low-temperature heating provides an efficient way of heating our buildings. To obtain a high efficiency it is important that the heating systems in the buildings are operated with both low supply and return temperatures. This study set out to investigate how typical assumptions in the modelling...

Human local and total heat losses in different temperature.

Science.gov (United States)

Wang, Lijuan; Yin, Hui; Di, Yuhui; Liu, Yanfeng; Liu, Jiaping

2016-04-01

This study investigates the effects of operative temperature on the local and total heat losses, and the relationship between the heat loss and thermal sensation. 10 local parts of head, neck, chest, abdomen, upper arm, forearm, hand, thigh, leg and foot are selected. In all these parts, convection, radiation, evaporation, respiration, conduction and diffusion heat losses are analyzed when operative temperature is 23, 28, 33 and 37 °C. The local heat losses show that the radiation and convection heat losses are mainly affected by the area of local body, and the heat loss of the thigh is the most in the ten parts. The evaporation heat loss is mainly affected by the distribution of sweat gland, and the heat loss of the chest is the most. The total heat loss of the local body shows that in low temperature, the thigh, leg and chest have much heat loss, while in high temperature, the chest, abdomen, thigh and head have great heat loss, which are useful for clothing design. The heat losses of the whole body show that as the operative temperature increases, the radiation and convection heat losses decrease, the heat losses of conduction, respiration, and diffusion are almost constant, and the evaporation heat loss increases. By comparison, the heat loss ratios of the radiation, convection and sweat evaporation, are in agreement with the previous researches. At last, the formula about the heat loss ratio of convection and radiation is derived. It's useful for thermal comfort evaluation and HVAC (heating, ventilation and air conditioning) design. Copyright © 2016 Elsevier Inc. All rights reserved.

Phenylnaphthalene as a Heat Transfer Fluid for Concentrating Solar Power: High-Temperature Static Experiments

Energy Technology Data Exchange (ETDEWEB)

Bell, Jason R [ORNL; Joseph III, Robert Anthony [ORNL; McFarlane, Joanna [ORNL; Qualls, A L [ORNL

2012-05-01

Concentrating solar power (CSP) may be an alternative to generating electricity from fossil fuels; however, greater thermodynamic efficiency is needed to improve the economics of CSP operation. One way of achieving improved efficiency is to operate the CSP loop at higher temperatures than the current maximum of about 400 C. ORNL has been investigating a synthetic polyaromatic oil for use in a trough type CSP collector, to temperatures up to 500 C. The oil was chosen because of its thermal stability and calculated low vapor and critical pressures. The oil has been synthesized using a Suzuki coupling mechanism and has been tested in static heating experiments. Analysis has been conducted on the oil after heating and suggests that there may be some isomerization taking place at 450 C, but the fluid appears to remain stable above that temperature. Tests were conducted over one week and further tests are planned to investigate stabilities after heating for months and in flow configurations. Thermochemical data and thermophysical predictions indicate that substituted polyaromatic hydrocarbons may be useful for applications that run at higher temperatures than possible with commercial fluids such as Therminol-VP1.

Indoor temperatures for calculating room heat loss and heating capacity of radiant heating systems combined with mechanical ventilation systems

DEFF Research Database (Denmark)

Wu, Xiaozhou; Olesen, Bjarne W.; Fang, Lei

2016-01-01

change rates on the indoor temperatures were performed using the proposed model. When heated surface temperatures and air change rates were from 21.0 to 29.0 degrees C and from 0.5 to 4.0 h-1, the indoor temperatures for calculating the transmission heat loss and ventilation heat loss were between 20...

Comparison of estimated core body temperature measured with the BioHarness and rectal temperature under several heat stress conditions.

Science.gov (United States)

Seo, Yongsuk; DiLeo, Travis; Powell, Jeffrey B; Kim, Jung-Hyun; Roberge, Raymond J; Coca, Aitor

2016-08-01

Monitoring and measuring core body temperature is important to prevent or minimize physiological strain and cognitive dysfunction for workers such as first responders (e.g., firefighters) and military personnel. The purpose of this study is to compare estimated core body temperature (Tco-est), determined by heart rate (HR) data from a wearable chest strap physiology monitor, to standard rectal thermometry (Tre) under different conditions.  Tco-est and Tre measurements were obtained in thermoneutral and heat stress conditions (high temperature and relative humidity) during four different experiments including treadmill exercise, cycling exercise, passive heat stress, and treadmill exercise while wearing personal protective equipment (PPE).  Overall, the mean Tco-est did not differ significantly from Tre across the four conditions. During exercise at low-moderate work rates under heat stress conditions, Tco-est was consistently higher than Tre at all-time points. Tco-est underestimated temperature compared to Tre at rest in heat stress conditions and at a low work rate under heat stress while wearing PPE. The mean differences between the two measurements ranged from -0.1 ± 0.4 to 0.3 ± 0.4°C and Tco-est correlated well with HR (r = 0.795 - 0.849) and mean body temperature (r = 0.637 - 0.861).  These results indicate that, the comparison of Tco-est to Tre may result in over- or underestimation which could possibly lead to heat-related illness during monitoring in certain conditions. Modifications to the current algorithm should be considered to address such issues.

Heat pipes for temperature control

International Nuclear Information System (INIS)

Groll, M.

1978-01-01

Heat pipes have known for years as effective constructional elements for temperature control. With the aid of special techniques (gas, liquid, steam, and voltage control), special operating characteristics can be obtained, e.g. variable heat conduction or diode behaviour. Their main field of application is in spacecraft technology and in nuclear technology in the isothermalisation of irradiation capsules. The different control techniques are presented and critically evaluated on the basis of characteristic properties like heat transfer capacity, volume and mass requirements, complexity of structure and production, reliability, and temperature control characteristics. Advantages and shortcomings of the different concepts are derived and compared. The state of the art of these control techniques is established on the basis of four development levels. Finally, the necessity and direction of further R + D activities are discussed, and suggestions are made for further work. (orig./HP) [de

Conversion of medium and low temperature heat to power

Science.gov (United States)

Fischer, Johann; Wendland, Martin; Lai, Ngoc Anh

2013-04-01

Presently most electricity is produced in power plants which use high temperature heat supplied by coal, oil, gas or nuclear fission and Clausius-Rankine cycles (CRC) with water as working fluid (WF). On the other hand, geo-, solar-, ocean-, and biogenic-heat have medium and low temperatures. At these temperatures, however, the use of other WF and/or other cycles can yield higher efficiencies than those of the water-CRC. For an assessment of the efficiency we model systems which include the heat transfer to and from the WF and the cycle. Optimization criterion is the exergy efficiency defined as the ratio of the net power output to the incoming exergy flow of the heat carrier. First, for a better understanding we discuss some thermodynamic properties of the WFs: 1) the critical point parameters, 2) the shape of the vapour- liquid coexistence curve in the temperature vs entropy (T,s)-diagram which may be either bell-shaped or overhanging [1,2], and 3) the shape of sub- and supercritical isobars for pure fluids and fluid mixtures. Second, we show that the problems of a CRC with water at lower temperatures are 1) the shape of the T,s-diagram and 2) the exergy loss during heat transfer to the WF. The first problem can be overcome by using an organic working fluid in the CRC which then is called organic Rankine cycle (ORC). The second problem is reduced by supercritical organic Rankine cycles (sORC) [1,2], trilateral cycles (TLC) and the more general power-flash cycles (PFC) [2], and organic flash cycles (OFC) [3]. Next, selected results for systems with the above mentioned cycles will be presented. The heat carrier inlet temperatures THC range from 120°C to 350°C.The pure working fluids are water, refrigerants, alkanes, aromates and siloxanes and have to be selected to match with THC. It is found that TLC with water have the highest efficiencies but show very large volume flows at lower temperatures. Moreover, expansion machines for TLC and PFC are still under

Temperature dependent investigation on optically active process of higher-order bands in irradiated silicon

International Nuclear Information System (INIS)

Shi Yi; Nanjing Univ., JS; Wu Fengmei; Nanjing Univ., JS; Zheng Youdou; Nanjing Univ., JS; Suezawa, M.; Imai, M.; Sumino, K.

1996-01-01

Optically active processes of the higher-order bands (HOB) are investigated at different temperatures in fast neutron irradiated silicon using Fourier transform infrared absorption measurement. It is shown that the optically active process is nearly temperature independent below 80 K, the slow decay process remains up to a heating temperature of 180 K. The observations are analyzed in terms of the relaxation behavior of photoexcited carriers governed by fast neutron radiation induced defect clusters. (orig.)

Heat flow and subsurface temperature as evidence for basin-scale ground-water flow, North Slope of Alaska

Science.gov (United States)

Deming, D.; Sass, J.H.; Lachenbruch, A.H.; De Rito, R. F.

1992-01-01

Several high-resolution temperature logs were made in each of 21 drillholes and a total of 601 thermal conductivity measurements were made on drill cuttings and cores. Near-surface heat flow (??20%) is inversely correlated with elevation and ranges from a low of 27 mW/m2 in the foothills of the Brooks Range in the south, to a high of 90 mW/m2 near the north coast. Subsurface temperatures and thermal gradients estimated from corrected BHTs are similarly much higher on the coastal plain than in the foothills province to the south. Significant east-west variation in heat flow and subsurface temperature is also observed; higher heat flow and temperature coincide with higher basement topography. The observed thermal pattern is consistent with forced convection by a topographically driven ground-water flow system. Average ground-water (Darcy) velocity in the postulated flow system is estimated to be of the order of 0.1 m/yr; the effective basin-scale permeability is estimated to be of the order of 10-14 m2. -from Authors

Energy and exergy analysis of low temperature district heating network

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

2012-01-01

is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand...... energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply.......Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network...

Temperature Oscillations in Loop Heat Pipes - A Revisit

Science.gov (United States)

Ku, Jentung

2018-01-01

Three types of temperature oscillation have been observed in the loop heat pipes. The first type is an ultra-high frequency temperature oscillation with a period on the order of seconds or less. This type of temperature oscillation is of little significance in spacecraft thermal control because the amplitude is in the noise level. The second type is a high frequency, low amplitude temperature oscillation with a period on the order of seconds to minutes and an amplitude on the order of one Kelvin. It is caused by the back-and-forth movement of the vapor front near the inlet or outlet of the condenser. The third type is a low frequency, high amplitude oscillation with a period on the order of hours and an amplitude on the order of tens of Kelvin. It is caused by the modulation of the net heat load into the evaporator by the attached large thermal mass which absorbs and releases energy alternately. Several papers on LHP temperature oscillation have been published. This paper presents a further study on the underlying physical processes during the LHP temperature oscillation, with an emphasis on the third type of temperature oscillation. Specifically, equations governing the thermal and hydraulic behaviors of LHP operation will be used to describe interactions among LHP components, heat source, and heat sink. The following sequence of events and their interrelationship will also be explored: 1) maxima and minima of reservoir and thermal mass temperatures; 2) the range of the vapor front movement inside the condenser; 3) rates of change of the reservoir and thermal mass temperatures; 4) the rate of heat absorption and heat release by the thermal mass and the rate of vapor front movement; and 5) inflection points of the reservoir and thermal mass temperatures.

HEAT PUMP USING SUBSOIL WATERS AS LOW TEMPERATURE HEAT SOURCE

Directory of Open Access Journals (Sweden)

Denysova Alla

2015-08-01

Full Text Available One of the basic directions of perfection of heat supply systems is the tendency of transition to the low-temperature heating systems based on application of heat pump installations. We consider heat supply system with heat pump installations using subsoil waters. Numerical simulation of thermal processes in the elements of a single-stage and double-stage heat pump systems has been worked out. Values of depths of wells and their quantity, necessary for effective operation of the offered installations, and values of capacity of electric water pumps for subsoil waters unit are calculated. Capacity of compressor electric drive and coefficient of performance of heat pump for the conditions of the city of Odessa are presented.

Decentralized substations for low-temperature district heating with no Legionella risk, and low return temperatures

International Nuclear Information System (INIS)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

To improve energy efficiency and give more access to renewable energy sources, low-temperature district heating (LTDH) is a promising concept to be realized in the future. However, concern about Legionella proliferation restricts applying low-temperature district heating in conventional systems with domestic hot water (DHW) circulation. In this study, a system with decentralized substations was analysed as a solution to this problem. Furthermore, a modification for the decentralized substation system were proposed in order to reduce the average return temperature. Models of conventional system with medium-temperature district heating, decentralized substation system with LTDH, and innovative decentralized substation system with LTDH were built based on the information of a case building. The annual distribution heat loss and the operating costs of the three scenarios were calculated and compared. From the results, realizing LTDH by the decentralized substation unit, 30% of the annual distribution heat loss inside the building can be saved compared to a conventional system with medium-temperature district heating. Replacing the bypass pipe with an in-line supply pipe and a heat pump, the innovative decentralized substation system can reduce distribution heat loss by 39% compared to the conventional system and by 12% compared to the normal decentralized substation system with bypass. - Highlights: • The system of decentralized substations can realize low-temperature district heating without running the risk of Legionella. • Decentralized substations help reduce the distribution heat loss inside the building compared to conventional system. • A new concept that can reduce the return temperature for district heating is proposed and analysed.

CDC WONDER: Daily Air Temperatures and Heat Index

Data.gov (United States)

U.S. Department of Health & Human Services — The Daily Air Temperature and Heat Index data available on CDC WONDER are county-level daily average air temperatures and heat index measures spanning the years...

Energy and exergy analysis of low temperature district heating network

International Nuclear Information System (INIS)

Li, Hongwei; Svendsen, Svend

2012-01-01

Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand. The space heating demand is supplied through floor heating in the bathroom and low temperature radiators in the rest of rooms. The network thermal and hydraulic conditions are simulated under steady state. A district heating network design and simulation code is developed to incorporate the network optimization procedure and the network simultaneous factor. Through the simulation, the overall system energy and exergy efficiencies are calculated and the exergy losses for the major district heating system components are identified. Based on the results, suggestions are given to further reduce the system energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply. -- Highlights: ► Exergy and energy analysis for low and medium temperature district heating systems. ► Different district heating network dimensioning methods are analyzed. ► Major exergy losses are identified in the district heating network and the in-house substations. ► Advantages to apply low temperature district heating are highlighted through exergy analysis. ► The influence of thermal by-pass on system exergy/energy performance is analyzed.

The effect of temperature and heating rate on char properties obtained from solar pyrolysis of beech wood.

Science.gov (United States)

Zeng, Kuo; Minh, Doan Pham; Gauthier, Daniel; Weiss-Hortala, Elsa; Nzihou, Ange; Flamant, Gilles

2015-04-01

Char samples were produced from pyrolysis in a lab-scale solar reactor. The pyrolysis of beech wood was carried out at temperatures ranging from 600 to 2000°C, with heating rates from 5 to 450°C/s. CHNS, scanning electron microscopy analysis, X-ray diffractometry, Brunauer-Emmett-Teller adsorption were employed to investigate the effect of temperature and heating rate on char composition and structure. The results indicated that char structure was more and more ordered with temperature increase and heating rate decrease (higher than 50°C/s). The surface area and pore volume firstly increased with temperature and reached maximum at 1200°C then reduced significantly at 2000°C. Besides, they firstly increased with heating rate and then decreased slightly at heating rate of 450°C/s when final temperature was no lower than 1200°C. Char reactivity measured by TGA analysis was found to correlate with the evolution of char surface area and pore volume with temperature and heating rate. Copyright © 2015 Elsevier Ltd. All rights reserved.

The influence of heat sink temperature on the seasonal efficiency of shallow geothermal heat pumps

Science.gov (United States)

Pełka, Grzegorz; Luboń, Wojciech; Sowiżdżał, Anna; Malik, Daniel

2017-11-01

Geothermal heat pumps, also known as ground source heat pumps (GSHP), are the most efficient heating and cooling technology utilized nowadays. In the AGH-UST Educational and Research Laboratory of Renewable Energy Sources and Energy Saving in Miękinia, shallow geothermal heat is utilized for heating. In the article, the seasonal efficiency of two geothermal heat pump systems are described during the 2014/2015 heating season, defined as the period between 1st October 2014 and 30th April 2015. The first system has 10.9 kW heating capacity (according to European Standard EN 14511 B0W35) and extracts heat from three vertical geothermal loops at a depth of 80m each. During the heating season, tests warmed up the buffer to 40°C. The second system has a 17.03 kW heating capacity and extracts heat from three vertical geothermal loops at a depth of 100 m each, and the temperature of the buffer was 50°C. During the entire heating season, the water temperatures of the buffers was constant. Seasonal performance factors were calculated, defined as the quotient of heat delivered by a heat pump to the system and the sum of electricity consumed by the compressor, source pump, sink pump and controller of heat pumps. The measurements and calculations give the following results: - The first system was supplied with 13 857 kWh/a of heat and consumed 3 388 kWh/a electricity. The SPF was 4.09 and the average temperature of outlet water from heat pump was 40.8°C, and the average temperature of brine flows into the evaporator was 3.7 °C; - The second system was supplied with 12 545 kWh/a of heat and consumed 3 874 kWh/a electricity. The SPF was 3.24 and the average temperature of outlet water from heat pump was 51.6°C, and the average temperature of brine flows into the evaporator was 5.3°C. To summarize, the data shown above presents the real SPF of the two systems. It will be significant in helping to predict the SPF of objects which will be equipped with ground source heat pumps.

MODELING OF TEMPERATURE FIELDS IN A SOLID HEAT ACCUMULLATORS

Directory of Open Access Journals (Sweden)

S. S. Belimenko

2016-10-01

Full Text Available Purpose. Currently, one of the priorities of energy conservation is a cost savings for heating in commercial and residential buildings by the stored thermal energy during the night and its return in the daytime. Economic effect is achieved due to the difference in tariffs for the cost of electricity in the daytime and at night. One of the most common types of devices that allow accumulating and giving the resulting heat are solid heat accumulators. The main purpose of the work: 1 software development for the calculation of the temperature field of a flat solid heat accumulator, working due to the heat energy accumulation in the volume of thermal storage material without phase transition; 2 determination the temperature distribution in its volumes at convective heat transfer. Methodology. To achieve the study objectives a heat transfer theory and Laplace integral transform were used. On its base the problems of determining the temperature fields in the channels of heat accumulators, having different cross-sectional shapes were solved. Findings. Authors have developed the method of calculation and obtained solutions for the determination of temperature fields in channels of the solid heat accumulator in conditions of convective heat transfer. Temperature fields over length and thickness of channels were investigated. Experimental studies on physical models and industrial equipment were conducted. Originality. For the first time the technique of calculating the temperature field in the channels of different cross-section for the solid heat accumulator in the charging and discharging modes was proposed. The calculation results are confirmed by experimental research. Practical value. The proposed technique is used in the design of solid heat accumulators of different power as well as full-scale production of them was organized.

Ground Source Heat Supply in Moscow Oblast: Temperature Potential and Sustainable Depth of Heat Wells

Science.gov (United States)

Vasil'ev, G. P.; Gornov, V. F.; Dmitriev, A. N.; Kolesova, M. V.; Yurchenko, V. A.

2018-01-01

The paper is devoted to a problem of increasing the efficiency of low-potential geothermal heat in heat pump systems of residential buildings the Moscow oblast of Russia, including Moscow. Estimates of a natural geothermal potential in the Moscow oblast (based on climatological data for the period from 1982 to 2011) are presented and a "Typical climatic year of natural soil temperature variations for the geoclimatic conditions of the Moscow oblast, including the city of Moscow" is proposed. Numerical simulation of the influence of geothermal energy potential and the depth of heat wells on the efficiency of ground source heat pump systems for the heat supply of residential buildings is carried out. Analysis of the numerical simulation showed that the operation of a heat pump system in a house heating mode under the geoclimatic conditions of the Moscow oblast leads to a temperature drop of the heat-exchange medium circulating through heat wells to 5-6°C by the end of the first 10 years of operation, and the process stabilizes by the 15th year of operation, and further changes in the heat-exchange medium temperature do not any longer significantly affect the temperature of the heat-exchange medium in the heat well. In this case, the exact dependence of the heat-exchange medium temperature drop on the depth is not revealed. Data on the economically expedient heat well depth for the conditions of the Moscow oblast ensuring a net present value for the whole residential building life cycle are presented. It is found that the heat well depth of 60 m can be considered as an endpoint for the Moscow oblast, and a further heat well deepening is economically impractical.

Determination of Ground Heat Exchangers Temperature Field in Geothermal Heat Pumps

Science.gov (United States)

Zhurmilova, I.; Shtym, A.

2017-11-01

For the heating and cooling supply of buildings and constructions geothermal heat pumps using low-potential ground energy are applied by means of ground exchangers. The process of heat transfer in a system of ground exchangers is a phenomenon of complex heat transfer. The paper presents a mathematical modeling of heat exchange processes, the temperature fields are built which are necessary for the determination of the ground array that ensures an adequate supply of low potential energy excluding the freezing of soil around the pipes in the ground heat exchangers and guaranteeing a reliable operation of geothermal heat pumps.

Comparative technical-economic analysis of the low temperature heating systems

International Nuclear Information System (INIS)

Sharevski, Vasko; Sharevski, Milan

1994-01-01

A method for comparative technical-economic analysis between low temperature heating systems and heating systems with fossil fuel boiler plant, heat pump heating system and electrical heating systems is presented. The single and combined heating systems are analyzed. The technical-economic priority application of the heating system is determined according to the prices of the low temperature heat energy, fossil fuel heat energy, electrical energy, as well as to the coefficient of the annual use of the installed heating capacity, investment expenses, structure of the combined heating system and coefficient of performances of the heat pump. The combined heating system, composed with a low temperature heating subsystem, which is used to cover the base heat demands, and a oil boiler plant heating subsystem, for the top heat demands, have technical-economic justification and wide range of priority application, in comparison with single heating systems. (author)

Development and performance assessment of electrically heating gloves with smart temperature control function.

Science.gov (United States)

Ma, Nini; Lu, Yehu; Xu, Fanfei; Dai, Hongqin

2018-03-27

A pair of lightweight electrically heating gloves (EHG) with smart temperature control function was developed. To evaluate thermoregulation properties of EHG, human trials were conducted in a climate chamber (2.5 °C, 60% RH). The changes in skin temperature of all fingers and opisthenar and the subjective thermal sensation were recorded in 60 min. The effects of two air velocities (i.e., 0.17 m/s and 0.50 m/s) on the cold protective performance of EHG in scenarios of heating and control were also investigated. For heating scenarios, skin temperature and thermal sensation at all fingers and opisthenar were found significantly higher than those in control conditions. Moreover, the air velocity at 0.50 m/s greatly reduced cold protective performance of the gloves. The research findings can be applied to improve thermal comfort and extend working time for persons in cold environments.

Threshold heating temperature for magnetic hyperthermia: Controlling the heat exchange with the blocking temperature of magnetic nanoparticles

Science.gov (United States)

Pimentel, B.; Caraballo-Vivas, R. J.; Checca, N. R.; Zverev, V. I.; Salakhova, R. T.; Makarova, L. A.; Pyatakov, A. P.; Perov, N. S.; Tishin, A. M.; Shtil, A. A.; Rossi, A. L.; Reis, M. S.

2018-04-01

La0.75Sr0.25MnO3 nanoparticles with average diameter close to 20.9 nm were synthesized using a sol-gel method. Measurements showed that the heating process stops at the blocking temperaturesignificantly below the Curie temperature. Measurements of Specific Absorption Rate (SAR) as a function of AC magnetic field revealed a superquadratic power law, indicating that, in addition to usual Néel and Brown relaxation, the hysteresis also plays an important role in the mechanism of heating. The ability to control the threshold heating temperature, a low remanent magnetization and a low field needed to achieve the magnetic saturation are the advantages of this material for therapeutic magnetic hyperthermia.

Modelling of Temperature Profiles and Transport Scaling in Auxiliary Heated Tokamaks

DEFF Research Database (Denmark)

Callen, J.D.; Christiansen, J.P.; Cordey, J.G.

1987-01-01

time , the heating effectiveness η, and the energy offset W(0). Considering both the temperature profile responses and the global transport scaling, the constant heat pinch or excess temperature gradient model is found to best characterize the present JET data. Finally, new methods are proposed......The temperature profiles produced by various heating profiles are calculated from local heat transport models. The models take the heat flux to be the sum of heat diffusion and a non-diffusive heat flow, consistent with local measurements of heat transport. Two models are developed analytically...... in detail: (i) a heat pinch or excess temperature gradient model with constant coefficients; and (ii) a non-linear heat diffusion coefficient (χ) model. Both models predict weak (lesssim20%) temperature profile responses to physically relevant changes in the heat deposition profile – primarily because...

Thermal characteristics of high-temperature R718 heat pumps with turbo compressor thermal vapor recompression

International Nuclear Information System (INIS)

Šarevski, Milan N.; Šarevski, Vasko N.

2017-01-01

Highlights: • High pressure ratio, high speed, transonic R718 centrifugal compressors. • High efficient industrial evaporators/concentrators with turbo thermal vapor recompression. • Utilization of waste heat from industrial thermal and processing systems. • R718 is an ideal refrigerant for the novel high-temperature industrial heat pumps. • Application of single-stage R718 centrifugal compressors. - Abstract: Characteristics of R718 centrifugal compressors are analyzed and range of their applications in industrial high-temperature heat pumps, district heating systems and geothermal green house heating systems are estimated. Implementation of turbo compressor thermal vapor recompression in industrial evaporating/concentrating plants for waste heat utilization results in a high energy efficiency and in other technical, economical and environmental benefits. A novel concept of turbo compression R718 heat pumps is proposed and an assessment of their thermal characteristics is presented for utilization of waste heat from industrial thermal plants and systems (boilers, furnaces, various technological and metallurgical cooling processes, etc.), and for applications in district heating and geothermal green house heating systems. R718 is an ideal refrigerant for the novel high-temperature turbo compression industrial heat pumps. Direct evaporation and condensation are advantages of the proposed system which lead to higher COP, and to simplification of the plant and lower cost.

Design manual. [High temperature heat pump for heat recovery system

Energy Technology Data Exchange (ETDEWEB)

Burch, T.E.; Chancellor, P.D.; Dyer, D.F.; Maples, G.

1980-01-01

The design and performance of a waste heat recovery system which utilizes a high temperature heat pump and which is intended for use in those industries incorporating indirect drying processes are described. It is estimated that use of this heat recovery system in the paper, pulp, and textile industries in the US could save 3.9 x 10/sup 14/ Btu/yr. Information is included on over all and component design for the heat pump system, comparison of prime movers for powering the compressor, control equipment, and system economics. (LCL)

Effect of radiation heat transfer on the performance of high temperature heat exchanger, (2)

International Nuclear Information System (INIS)

Yamada, Yukio; Mori, Yasuo; Hijikata, Kunio.

1977-01-01

In high temperature helium gas-cooled reactors, the nuclear energy can be utilized effectively, and the safety is excellent as compared with conventional reactors. They are advantageous also in view of environmental problems. In this report, the high temperature heat exchanger used for heating steam with the helium from a high temperature gas reactor is modeled, and the case that radiating gas flow between parallel plates is considered. Analysis was made on the case of one channel and constant heat flux and on the model for a counter-flow type heat exchanger with two channels, and the effect of radiation on the heat transfer in laminar flow and turbulent flow regions was clarified theoretically. The basic equations, the method of approximate solution and the results of calculation are explained. When one dimensional radiation was considered, the representative temperature Tr regarding fluid radiation was introduced, and its relation to mean mixing temperature Tm was determined. It was clarified that the large error in the result did not arise even if Tr was taken equally to Tm, especially in case of turbulent flow. The error was practically negligible when the rate of forced convection heat transfer in case of radiating medium flow was taken same as that in the case without radiation. (Kako, I.)

Characterization of Elevated Temperature Properties of Heat Exchanger and Steam Generator Alloys

International Nuclear Information System (INIS)

Wright, J.K.; Carroll, L.J.; Benz, J.K.; Simpson, J.A.; Wright, R.N.; Lloyd, W.R.; Chapman, J.A.

2010-01-01

The Next Generation Nuclear Plant project is considering Alloy 800H and Alloy 617 for steam generator and intermediate heat exchangers. It is envisioned that a steam generator would operate with reactor outlet temperatures from 750 to 800 C, while an intermediate heat exchanger for primary to secondary helium would operate up to an outlet temperature of 950 C. Although both alloys are of interest due in part to their technical maturity, a number of specific properties require further characterization for design of nuclear components. Strain rate sensitivity of both alloys has been characterized and is found to be significant above 600 C. Both alloys also exhibit dynamic strain aging, characterized by serrated flow, over a wide range of temperatures and strain rates. In general dynamic strain aging is observed to begin at higher temperatures and serrated flow persists to higher temperatures in Alloy 617 compared to Alloy 800H. Dynamic strain aging is a concern for these materials since it is observed to result in reduced ductility for many solid solution alloys. The role of dynamic strain aging in the creep-fatigue behavior of Alloy 617 at temperatures of 800 C and above has also been examined in detail. Serrated flow is found to persist in cyclic stress-strain curves up to nearly the cycle to failure in some temperature and strain regimes. Results of those experiments and implications for creep-fatigue testing protocols will be described.

Can high temperature steam electrolysis function with geothermal heat?

International Nuclear Information System (INIS)

Sigurvinsson, J.; Mansilla, C.; Werkoff, F.; Lovera, P.

2007-01-01

It is possible to improve the performance of electrolysis processes by operating at a high temperature. This leads to a reduction in electricity consumption but requires a part of the energy necessary for the dissociation of water to be in the form of thermal energy. Iceland produces low cost electricity and very low cost geothermal heat. However, the temperature of geothermal heat is considerably lower than the temperature required at the electrolyser's inlet, making heat exchangers necessary to recuperate part of the heat contained in the gases at the electrolyser's outlet. A techno-economic optimisation model devoted to a high-temperature electrolysis (HTE) process which includes electrolysers as well as a high temperature heat exchanger network was created. Concerning the heat exchangers, the unit costs used in the model are based on industrial data. For the electrolyser cells, the unit cost scaling law and the physical sub-model we used were formulated using analogies with solid oxide fuel cells. The method was implemented in a software tool, which performs the optimisation using genetic algorithms. The first application of the method is done by taking into account the prices of electricity and geothermal heat in the Icelandic context. It appears that even with a geothermal temperature as low as 230 degrees C, the HTE could compete with alkaline electrolysis. (authors)

High-temperature process heat reactor with solid coolant and radiant heat exchange

International Nuclear Information System (INIS)

Alekseev, A.M.; Bulkin, Yu.M.; Vasil'ev, S.I.

1984-01-01

The high temperature graphite reactor with the solid coolant in which heat transfer is realized by radiant heat exchange is described. Neutron-physical and thermal-technological features of the reactor are considered. The reactor vessel is made of sheet carbon steel in the form of a sealed rectangular annular box. The moderator is a set of graphite blocks mounted as rows of arched laying Between the moderator rows the solid coolant annular layings made of graphite blocks with high temperature nuclear fuel in the form of coated microparticles are placed. The coolant layings are mounted onto ring movable platforms, the continuous rotation of which is realizod by special electric drives. Each part of the graphite coolant laying consecutively passes through the reactor core neutron cut-off zones and technological zone. In the core the graphite is heated up to the temperature of 1350 deg C sufficient for effective radiant heat transfer. In the neutron cut-off zone the chain reaction and further graphite heating are stopped. In the technological zone the graphite transfers the accumulated heat to the walls of technological channels in which the working medium moves. The described reactor is supposed to be used in nuclear-chemical complex for ammonia production by the method of methane steam catalytic conversion

Measured Performance of a Low Temperature Air Source Heat Pump

Energy Technology Data Exchange (ETDEWEB)

R.K. Johnson

2013-09-01

A 4-ton Low Temperature Heat Pump (LTHP) manufactured by Hallowell International was installed in a residence near New Haven, Connecticut and monitored over two winters of operation. After attending to some significant service issues, the heat pump operated as designed. This report should be considered a review of the dual compressor “boosted heat pump” technology. The Low Temperature Heat Pump system operates with four increasing levels of capacity (heat output) as the outdoor temperature drops.

Temperature Assessment of Heating Stage for a Thermoforming Equipment

International Nuclear Information System (INIS)

Mohd Ghazali, F.A.; Ab Rahim, M.F.; Jaafar, A.A.; Ahmad, M.N.

2016-01-01

Thermoforming is a well-known manufacturing process in the productions of various plastic household and industrial solutions. The heating of a plastic sheet allows the plastic to soften and within its forming window temperature the sheet can replicate a required shape when pressed against a mould. Hence, the heating process is an important thermoforming stage that determine uniformity of the material distribution. This article proposed an experimental approach to investigate the thermal characteristics of the heating section of a low cost thermoforming equipment designed for teaching and research purposes. The temperatures of air and a model of a stretched heated plastic sheet were measured and analysed. The experimental data indicates that the spatial temperatures distribution was not localised and the temperature history of the infrared heating agrees well with those given by fast response thermocouples. The findings suggest that the spatial uniformity of temperature can be reasonably evaluated by using the proposed method. (paper)

Temperature distribution in spouted bed and heat transfer

International Nuclear Information System (INIS)

Takeda, Hiroshi; Yamamoto, Yutaka

1976-01-01

Temperature distribution in spouted bed was measured by using brass and graphite spouted beds so as to investigate heat transfer characteristic of spouted bed applied to an apparatus of PyC coating. These spouted beds are batch type and are spouted by air or nitrogen gas of room temperature, and the outer wall of beds are heated by nichrome or graphite heater. Particles used for experiments are alumina spherical particles and the diameter is 0.80 -- 1.12 mm. Temperature condition is in the range of 400 -- 1,400 0 C. In the neighborhood of 400 0 C, the spouting condition is stable, while the spouting condition becomes unstable in the case of above 1,000 0 C. This is caused by abrupt temperature increase of spouting gas. It was found that heat transfer coefficient h sub(w) of our low temperature experiments was closer to the calculated from Malek et al.'s equation, h sub(p) of our experiments was several times greater than the calculated from Uemaki et al.'s equation. On the other hand, h sub(p) of high temperature experiments was compared with an experimental relation for convective heat transfer of fluidized bed, it was found that Nu sub(p) of our experiments was nearly equal to or greater than the calculated from the relation, this would be caused by radiant heat transfer. (auth.)

Heat priming induces trans-generational tolerance to high temperature stress in wheat

Directory of Open Access Journals (Sweden)

Xiao eWang

2016-04-01

Full Text Available Wheat plants are very sensitive to high temperature stress during grain filling. Effects of heat priming applied to the first generation on tolerance of the successive generation to post-anthesis high temperature stress were investigated. Compared with the progeny of non-heat primed plants (NH, the progeny of heat-primed plants (PH possessed higher grain yield, leaf photosynthesis and activities of antioxidant enzymes and lower cell membrane damage under high temperature stress. In the transcriptome profile, 1430 probes showed obvious difference in expression between PH and NH. These genes were related to signal transduction, transcription, energy, defense, and protein destination and storage, respectively. The gene encoding the lysine-specific histone demethylase 1 (LSD1 which was involved in histone demethylation related to epigenetic modification was up-regulated in the PH compared with NH. The proteome analysis indicated that the proteins involved in photosynthesis, energy production and protein destination and storage were up-regulated in the PH compared with NH. In short, thermos-tolerance was induced through heritable epigenetic alternation and signaling transduction, both processes further triggered prompt modifications of defense related responses in anti-oxidation, transcription, energy production, and protein destination and storage in the progeny of the primed plants under high temperature stress. It was concluded that trans-generation thermo-tolerance was induced by heat priming in the first generation, and this might be an effective measure to cope with severe high-temperature stresses during key growth stages in wheat production.

Pressure drop and heat transfer characteristics of a high-temperature printed circuit heat exchanger

International Nuclear Information System (INIS)

Chen, Minghui; Sun, Xiaodong; Christensen, Richard N.; Skavdahl, Isaac; Utgikar, Vivek; Sabharwall, Piyush

2016-01-01

Highlights: • Pressure drop and heat transfer characteristics of a high-temperature printed circuit heat exchanger have been obtained. • Comparisons of experimental data and available correlations have been performed. • New Fanning friction factor and heat transfer correlations for the test PCHE are developed. - Abstract: Printed circuit heat exchanger (PCHE) is one of the leading intermediate heat exchanger (IHX) candidates to be employed in the very-high-temperature gas-cooled reactors (VHTRs) due to its capability for high-temperature, high-pressure applications. In the current study, a reduced-scale zigzag-channel PCHE was fabricated using Alloy 617 plates for the heat exchanger core and Alloy 800H pipes for the headers. The pressure drop and heat transfer characteristics of the PCHE were investigated experimentally in a high-temperature helium test facility (HTHF) at The Ohio State University. The PCHE helium inlet temperatures and pressures were varied up to 464 °C/2.7 MPa for the cold side and 802 °C/2.7 MPa for the hot side, respectively, while the maximum helium mass flow rates on both sides of the PCHE reached 39 kg/h. The corresponding maximum channel Reynolds number was approximately 3558, covering the laminar flow and laminar-to-turbulent flow transition regimes. New pressure drop and heat transfer correlations for the current zigzag channels with rounded bends were developed based on the experimental data. Comparisons between the experimental data and the results obtained from the available PCHE and straight circular pipe correlations were conducted. Compared to the heat transfer performance in straight circular pipes, the zigzag channels provided little advantage in the laminar flow regime but significant advantage near the transition flow regime.

Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating

International Nuclear Information System (INIS)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

This study investigated the performances of five different substation configurations in single-family houses supplied with ULTDH (ultra-low-temperature district heating). The temperature at the heat plant is 46 °C and around 40 °C at the substations. To avoid the proliferation of Legionella in the DHW (domestic hot water) and assure the comfortable temperature, all substations were installed with supplementary heating devices. Detailed measurements were taken in the substations, including the electricity demand of the supplementary heating devices. To compare the energy and economic performance of the substations, separate models were built based on standard assumptions. The relative heat and electricity delivered for preparing DHW were calculated. The results showed that substations with storage tanks and heat pumps have high relative electricity demand, which leads to higher integrated costs considering both heat and electricity for DHW preparation. The substations with in-line electric heaters have low relative electricity usage because very little heat is lost due to the instantaneous DHW preparation. Accordingly, the substations with in-line electric heaters would have the lowest energy cost for DHW preparation. To achieve optimal design and operation for the ULTDH substation, the electricity peak loads of the in-line electric heaters were analysed according to different DHW-heating strategies. - Highlights: • Five different substations supplied with ultra-low-temperature district heating were measured. • The relative heat and electricity delivered for DHW preparation were modelled for different substations. • The levelized cost of the five substations in respect of DHW preparation was calculated. • The feasibility of applying instantaneous electric heater with normal power supply was tested.

Optimal usage of low temperature heat sources to supply district heating by heat pumps

DEFF Research Database (Denmark)

Pieper, Henrik; Ommen, Torben Schmidt; Markussen, Wiebke Brix

2017-01-01

This paper presents a theoretical study on the optimal usage of different low temperature heat sources to supply district heating by heat pumps. The study is based on data for the Copenhagen region. The heat sources were prioritized based on the coefficient of performance calculated for each hour...... and the covered demand of each heat source as well as required peak unit capacity. The results showed that heat pumps using different heat sources yield better performance than a heat pump based on a single one. The performance was influenced by the composition of the different heat sources. It was found that 78......% groundwater, 22% seawater and 0% air resulted in highest COP of 3.33 for the given heat demand. Furthermore, the implementation of rule based short term storage made peak units redundant. The variation in base load capacity showed that heat pumps utilizing the analyzed heat sources could perform very...

Performance of ultra low temperature district heating systems with utility plant and booster heat pumps

DEFF Research Database (Denmark)

Ommen, Torben Schmidt; Thorsen, Jan Eric; Markussen, Wiebke Brix

2017-01-01

The optimal integration of booster heat pumps in ultra low temperature district heating (ULTDH) was investigated and compared to the performance of low temperature district heating. Two possible heat production technologies for the DH networks were analysed, namely extraction combined heat...... temperature and the heat consumption profile. For reference conditions, the optimal return of ULTDH varies between 21 °C and 27 °C. When using a central HP to supply the DH system, the resulting coefficient of system performance (COSP) was in the range of 3.9 (-) to 4.7 (-) for equipment with realistic...... component efficiencies and effectiveness, when including the relevant parameters such as DH system pressure and heat losses. By using ULTDH with booster HPs, performance improvements of 12% for the reference calculations case were found, if the system was supplied by central HPs. Opposite results were found...

Heat treatment on keruing and light red meranti: The effect of heat exposure at different levels of temperature on bending strength properties

Science.gov (United States)

Noh, Nur Ilya Farhana Md; Ahmad, Zakiah

2017-11-01

Heat treatment on timbers is a process of applying heat to modify and equip the timbers with new improvised characteristics. It is environmental friendly compared to the common practice of treating timber by chemical preservatives. Malaysian hardwood timbers namely Keruing and Light Red Meranti which are in green condition were heat treated at temperature 150°C, 170°C, 190°C and 210°C, in a specially designed electronic furnace within one hour duration. The objectives were to determine the effect of heat treatment on bending strength properties of heat treated timbers in terms of Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) and to examine the significance changes at each temperature level. Untreated samples for each species were used as a control sample. The results indicated that the bending strength properties for both species of timbers were affected by the heat exposure. Both MOE and MOR values for heat treated Keruing were increased when subjected to the temperature levels at 150°C, 170°C and 190°C except at 210°C. Heat treated Light Red Meranti shows the same pattern of increment on its MOE and MOR values after exposure to heat at three temperature levels applied and the values dropped at 210°C. However, for both of species, even though there were decrement occurred at 210°C, the value is still higher compared to the control sample. The increments of MOE and MOR values are an indicator that heat treatment had successfully improvised the bending strength properties of these two species of hardwood timber.

Temperature profiles for laser-induced heating of nanocrystals embedded in glass matrices

Science.gov (United States)

Bhatnagar, Promod K.; Nagpal, Swati

2001-05-01

Quantum confined nanostructures are very important because of their application towards optoelectronic devices. Commercial colored glass filters, which have large semiconductor particles, are being used to manufacture nanocrystals by suitable heat treatments. The progress in this area has been hampered by high size dispersion of these dots in the glass matrix which leads to reduction in higher order susceptibility thereby reducing non-linearity. In the present paper attempt has been made to theoretically model the temperature profiles of a laser irradiated CdS doped Borosilicate sample. Laser being used has a beam diameter of 1.5 mm and energy for 10 nsec pulse is 10 mJ. Two different particle radii of 5 nm and 10 nm have been considered. It is found that larger particles reach higher temperatures for the same pulse characteristics. This is because smaller particles have larger surface to volume ratio and hence dissipates out heat faster to the surrounding. Hence bigger particles will reach dissolution temperature faster than smaller particle and particle beyond a certain size should dissolve in the glass matrix when a sample is heat treated by laser. This could lead to a reduction in size dispersion of the nanocrystals. Also photodarkening effect found in semiconductor doped glasses is a big handicap for practical application of these materials in fast optical switching and non-linear optical devices. Photodarkening effect has been established to be a photochemical effect and it is important to study the temperature profiles around a particle since it will effect the impurity migration.

Experimental Study of the Performance of Air Source Heat Pump Systems Assisted by Low-Temperature Solar-Heated Water

Directory of Open Access Journals (Sweden)

Jinshun Wu

2013-01-01

Full Text Available Due to the low temperatures, the heating efficiency of air source heat pump systems during the winter is very low. To address this problem, a low-temperature solar hot water system was added to a basic air source heat pump system. Several parameters were tested and analyzed. The heat collection efficiency of the solar collector was analyzed under low-temperature conditions. The factors that affect the performance of the heat pumps, such as the fluid temperature, pressure, and energy savings, were analyzed for cases where the solar energy auxiliary heat pump and the air source heat pump are used independently. The optimal heating temperature and the changes in the fluid temperature were determined. The influence of the compression ratio and the coefficient of performance (COP were investigated theoretically. The results revealed the parameters that are important to the performance of the system. Several measures for improving the COP of the heat pump units are provided for other applications and future research.

Low-temperature nuclear heat applications: Nuclear power plants for district heating

International Nuclear Information System (INIS)

1987-08-01

The IAEA reflected the needs of its Member States for the exchange of information in the field of nuclear heat application already in the late 1970s. In the early 1980s, some Member States showed their interest in the use of heat from electricity producing nuclear power plants and in the development of nuclear heating plants. Accordingly, a technical committee meeting with a workshop was organized in 1983 to review the status of nuclear heat application which confirmed both the progress made in this field and the renewed interest of Member States in an active exchange of information about this subject. In 1985 an Advisory Group summarized the Potential of Low-Temperature Nuclear Heat Application; the relevant Technical Document reviewing the situation in the IAEA's Member States was issued in 1986 (IAEA-TECDOC-397). Programme plans were made for 1986-88 and the IAEA was asked to promote the exchange of information, with specific emphasis on the design criteria, operating experience, safety requirements and specifications for heat-only reactors, co-generation plants and power plants adapted for heat application. Because of a growing interest of the IAEA's Member States about nuclear heat employment in the district heating domaine, an Advisory Group meeting was organized by the IAEA on ''Low-Temperature Nuclear Heat Application: Nuclear Power Plants for District Heating'' in Prague, Czechoslovakia in June 1986. The information gained up to 1986 and discussed during this meeting is embodied in the present Technical Document. 22 figs, 11 tabs

Temperature-gated thermal rectifier for active heat flow control.

Science.gov (United States)

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

2014-08-13

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

Innovative system for delivery of low temperature district heating

OpenAIRE

Ianakiev, A; Cui, JM; Garbett, S; Filer, A

2017-01-01

An innovative low temperature district heating (LTDH) local network is developed in Nottingham, supported by the REMOURBAN project, part of the H2020 Smart City and Community Lighthouse scheme. It was proposed that a branch emanating from the return pipe of the existing district heating system in Nottingham would be created to use low temperature heating for the first time on such scale in the UK. The development is aimed to extract unused heat from existing district heating system and to mak...

A thermoacoustic engine capable of utilizing multi-temperature heat sources

International Nuclear Information System (INIS)

Qiu Limin; Wang Bo; Sun Daming; Liu Yu; Steiner, Ted

2009-01-01

Low-grade energy is widespread. However, it cannot be utilized with high thermal efficiency directly. Following the principle of thermal energy cascade utilization, a thermoacoustic engine (TE) with a new regenerator that can be driven by multiple heat sources at different temperature levels is proposed. Taking a regenerator that utilizes heat sources at two temperatures as an example, theoretical research has been conducted on a traveling-wave TE with the new regenerator to predict its performance. Experimental verification is also done to demonstrate the benefits of the new regenerator. Results indicate that a TE with the new regenerator utilizing additional heat at a lower temperature experiences an increase in pressure ratio, acoustic power, efficiency, and exergy efficiency with proper heat input at an appropriate temperature at the mid-heater. A regenerator that uses multi-temperature heat sources can provide a means of recovering lower grade heat.

Active ion temperature measurement with heating neutral beam

International Nuclear Information System (INIS)

Miura, Yukitoshi; Matsuda, Toshiaki; Yamamoto, Shin

1987-03-01

When the heating neutral-beam (hydrogen beam) is injected into a deuterium plasma, the density of neutral particles is increased locally. By using this increased neutral particles, the local ion temperature is measured by the active charge-exchange method. The analyzer is the E//B type mass-separated neutral particle energy analyzer and the measured position is about one third outside of the plasma radius. The deuterium energy spectrum is Maxwellian, and the temperature is increased from 350 eV to 900 eV during heating. Since the local hydrogen to deuterium density concentration and the density of the heating neutral-beam as well as the ion temperature can be obtained good S/N ratio, the usefulness of this method during neutral-beam heating is confirmed by this experiment. (author)

Lauric and palmitic acids eutectic mixture as latent heat storage material for low temperature heating applications

International Nuclear Information System (INIS)

Tuncbilek, Kadir; Sari, Ahmet; Tarhan, Sefa; Erguenes, Gazanfer; Kaygusuz, Kamil

2005-01-01

Palmitic acid (PA, 59.8 deg. C) and lauric acid (LA, 42.6 deg. C) are phase change materials (PCM) having quite high melting temperatures which can limit their use in low temperature solar applications such as solar space heating and greenhouse heating. However, their melting temperatures can be tailored to appropriate value by preparing a eutectic mixture of the lauric and the palmitic acids. In the present study, the thermal analysis based on differential scanning calorimetry (DSC) technique shows that the mixture of 69.0 wt% LA and 31 wt% PA forms a eutectic mixture having melting temperature of 35.2 deg. C and the latent heat of fusion of 166.3 J g -1 . This study also considers the experimental determination of the thermal characteristics of the eutectic mixture during the heat charging and discharging processes. Radial and axial temperature distribution, heat transfer coefficient between the heat transfer fluid (HTF) pipe and the PCM, heat recovery rate and heat charging and discharging fractions were experimentally established employing a vertical concentric pipe-in-pipe energy storage system. The changes of these characteristics were evaluated with respect to the effect of inlet HTF temperature and mass flow rate. The DSC thermal analysis and the experimental results indicate that the LA-PA eutectic mixture can be a potential material for low temperature thermal energy storage applications in terms of its thermo-physical and thermal characteristics

Low Temperature District Heating for Future Energy Systems

DEFF Research Database (Denmark)

Ford, Rufus; Pietruschka, Dirk; Sipilä, Kari

participants being VTT Technical Research Centre of Finland (VTT), Technical University of Denmark (DTU), Norwegian University of Science and Technology (NTNU), Stuttgart Technology University of Applied Sciences (HFT) and SSE Enterprise in United Kingdom. The demonstration cases described in the report......This report titled “Case studies and demonstrations” is the subtask D report of the IEA DHC|CHP Annex TS1 project “Low Temperature District Heating for Future Energy Systems” carried out between 2013 and 2016. The project was led by Fraunhofer Institute for Building Physics (IBP) with the other...... include examples on low temperature district heating systems, solar heating in a district heating system, heat pump based heat supply and energy storages for both peak load management and for seasonal heat storage. Some demonstrations have been implemented while others are at planning phase...

The role of fluid temperature and form on endurance performance in the heat.

Science.gov (United States)

Tan, P M S; Lee, J K W

2015-06-01

Exercising in the heat often results in an excessive increase in body core temperature, which can be detrimental to health and endurance performance. Research in recent years has shifted toward the optimum temperature at which drinks should be ingested. The ingestion of cold drinks can reduce body core temperature before exercise but less so during exercise. Temperature of drinks does not seem to have an effect on the rate of gastric emptying and intestinal absorption. Manipulating the specific heat capacity of a solution can further induce a greater heat sink. Ingestion of ice slurry exploits the additional energy required to convert the solution from ice to water (enthalpy of fusion). Body core temperature is occasionally observed to be higher at the point of exhaustion with the ingestion of ice slurry. There is growing evidence to suggest that ingesting ice slurry is an effective and practical strategy to prevent excessive rise of body core temperature and improve endurance performance. This information is especially important when only a fixed amount of fluid is allowed to be carried, often seen in some ultra-endurance events and military operations. Future studies should evaluate the efficacy of ice slurry in various exercise and environmental conditions. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Comparison of LCA results of low temperature heat plant using electric heat pump, absorption heat pump and gas-fired boiler

International Nuclear Information System (INIS)

Nitkiewicz, Anna; Sekret, Robert

2014-01-01

Highlights: • Usage of geothermal heat pump can bring environmental benefits. • The lowest environmental impact for whole life cycle is obtained for absorption heat pump. • The value of heat pump COP has a significant influence on environmental impact. • In case of coal based power generation the damage to human health is significant. - Abstract: This study compares the life cycle impacts of three heating plant systems which differ in their source of energy and the type of system. The following heating systems are considered: electric water-water heat pump, absorption water-water heat pump and natural gas fired boiler. The heat source for heat pump systems is low temperature geothermal source with temperature below 20 °C and spontaneous outflow 24 m 3 /h. It is assumed that the heat pumps and boiler are working in monovalent system. The analysis was carried out for heat networks temperature characteristic at 50/40 °C which is changing with outdoor temperature during heating season. The environmental life cycle impact is evaluated within life cycle assessment methodological framework. The method used for life cycle assessment is eco-indicator ‘99. The functional unit is defined as heating plant system with given amount of heat to be delivered to meet local heat demand in assumed average season. The data describing heating plant system is derived from literature and energy analysis of these systems. The data describing the preceding life cycle phases: extraction of raw materials and fuels, production of heating devices and their transportation is taken from Ecoinvent 2.0 life cycle inventory database. The results were analyzed on three levels of indicators: single score indicator, damage category indicators and impact category indicator. The indicators were calculated for characterization, normalization and weighting phases as well. SimaPro 7.3.2 is the software used to model the systems’ life cycle. The study shows that heating plants using a low

Calculation of the fuel temperature field under heat release and heat conductance transient conditions

International Nuclear Information System (INIS)

Kazakov, E.K.; Chernukhina, G.M.

1974-01-01

Results of calculation of the temperature distribution in an annular fuel element at transient thermal conductivity and heat release values are given. The calculation has been carried out by the mesh technique with the third-order boundary conditions for the inner surface assumed and with heat fluxes and temperatures at the zone boundaries to be equal. Three variants of solving the problem of a stationary temperature field are considered for failed fuel elements with clad flaking or cracks. The results obtained show the nonuniformity of the fuel element temperature field to depend strongly on the perturbation parameter at transient thermal conductivity and heat release values. In case of can flaking at a short length, the core temperature rises quickly after flaking. While evaluating superheating, one should take into account the symmetry of can flaking [ru

Temperature distribution of the energy consumed as heat in Canada

International Nuclear Information System (INIS)

Puttagunta, V.R.

1974-10-01

The amount of energy consumed as heat (excluding thermal generation of electricity) in Canada is estimated from statistical data available on the total consumption of energy for the years 1958 to 2000. Based on some actual plant data and other statistical information this energy consumption is sub-divided into four temperature categories: high (>260 degrees C), intermediate (140-260 degrees C), low (100-140 degrees C), and space heating (<100 degrees C). The results of this analysis show that approximately half of all the energy consumed in Canada has an end use as heat. Less than 10 percent of the energy consumed as heat is in the high temperature category, 12 to 14 percent is in the intermediate temperature range, 21 to 27 percent is in the low temperature range, and 50 to 58 percent is used for space heating. Over 90 percent of the energy consumed as heat in Canada is within the temperature capability of the CANDU-PHW reactor. (author)

Heat exchangers and recuperators for high temperature waste gases

Science.gov (United States)

Meunier, H.

General considerations on high temperature waste heat recovery are presented. Internal heat recovery through combustion air preheating and external heat recovery are addressed. Heat transfer and pressure drop in heat exchanger design are discussed.

The relationship between radiant heat, air temperature and thermal comfort at rest and exercise.

Science.gov (United States)

Guéritée, Julien; Tipton, Michael J

2015-02-01

The aims of the present work were to investigate the relationships between radiant heat load, air velocity and body temperatures with or without coincidental exercise to determine the physiological mechanisms that drive thermal comfort and thermoregulatory behaviour. Seven male volunteers wearing swimming trunks in 18°C, 22°C or 26°C air were exposed to increasing air velocities up to 3 m s(-1) and self-adjusted the intensity of the direct radiant heat received on the front of the body to just maintain overall thermal comfort, at rest or when cycling (60 W, 60 rpm). During the 30 min of the experiments, skin and rectal temperatures were continuously recorded. We hypothesized that mean body temperature should be maintained stable and the intensity of the radiant heat and the mean skin temperatures would be lower when cycling. In all conditions, mean body temperature was lower when facing winds of 3 m s(-1) than during the first 5 min, without wind. When facing winds, in all but the 26°C air, the radiant heat was statistically higher at rest than when exercising. In 26°C air mean skin temperature was lower at rest than when exercising. No other significant difference was observed. In all air temperatures, high correlation coefficients were observed between the air velocity and the radiant heat load. Other factors that we did not measure may have contributed to the constant overall thermal comfort status despite dropping mean skin and body temperatures. It is suggested that the allowance to behaviourally adjust the thermal environment increases the tolerance of cold discomfort. Copyright © 2014 Elsevier Inc. All rights reserved.

Effect of heat-treatment on elevated temperature fatigue-crack growth behavior of two heats of Alloy 718

International Nuclear Information System (INIS)

Mills, W.J.; James, L.A.

1978-05-01

The room temperature and elevated temperature fatigue-crack growth behavior of two heats of Alloy 718 was characterized within a linear-elastic fracture mechanics framework. Two different heat-treatments were used: the ''conventional'' (ASTM A637) treatment, and a ''modified'' heat-treatment designed to improve the toughness of Alloy 718 base metal and weldments. Heat-to-heat variations in the fatigue-crack propagation behavior were observed in the conventionally-treated material. On the other hand, no heat-to-heat variations were observed in the modified condition. Furthermore, both heats of Alloy 718 exhibited superior fatigue-crack growth resistance when given the modified heat-treatment. Electron fractographic examination of Alloy 718 fatigue fracture surfaces revealed that the operative crack growth mechanisms were dependent on heat-treatment, temperature, and ΔK level

Effect of tunnel cross section on gas temperatures and heat fluxes in case of large heat release rate

International Nuclear Information System (INIS)

Fan, Chuan Gang; Li, Ying Zhen; Ingason, Haukur; Lönnermark, Anders

2016-01-01

Highlights: • The effect of tunnel cross section together with ventilation velocity was studied. • Ceiling temperature varies clearly with tunnel height, but little with tunnel width. • Downstream temperature decreases with increasing tunnel dimensions. • HRR is an important factor that influences decay rate of excess gas temperature. • An equation considering both tunnel dimensions and HRR was developed. - Abstract: Tests with liquid and solid fuels in model tunnels (1:20) were performed and analysed in order to study the effect of tunnel cross section (width and height) together with ventilation velocity on ceiling gas temperatures and heat fluxes. The model tunnel was 10 m long with varying width (0.3 m, 0.45 m and 0.6 m) and height (0.25 m and 0.4 m). Test results show that the maximum temperature under the ceiling is a weak function of heat release rate (HRR) and ventilation velocity for cases with HRR more than 100 MW at full scale. It clearly varies with the tunnel height and is a weak function of the tunnel width. With a lower tunnel height, the ceiling is closer to the base of continuous flame zone and the temperatures become higher. Overall, the gas temperature beneath the ceiling decreases with the increasing tunnel dimensions, and increases with the increasing longitudinal ventilation velocity. The HRR is also an important factor that influences the decay rate of excess gas temperature, and a dimensionless HRR integrating HRR and other two key parameters, tunnel cross-sectional area and distance between fuel centre and tunnel ceiling, was introduced to account for the effect. An equation for the decay rate of excess gas temperature, considering both the tunnel dimensions and HRR, was developed. Moreover, a larger tunnel cross-sectional area will lead to a smaller heat flux.

Exergetic evaluation of heat pump booster configurations in a low temperature district heating network

DEFF Research Database (Denmark)

Ommen, Torben Schmidt; Elmegaard, Brian

2012-01-01

In order to minimise losses in a district heating network, one approach is to lower the temperature difference between working media and soil. Considering only direct heat exchange, the minimum forward temperature level is determined by the demand side, as energy services are required at a certai...

Preliminary estimations on the heat recovery method for hydrogen production by the high temperature steam electrolysis

International Nuclear Information System (INIS)

Koh, Jae Hwa; Yoon, Duck Joo

2009-01-01

As a part of the project 'development of hydrogen production technologies by high temperature electrolysis using very high temperature reactor', we have developed an electrolyzer model for high temperature steam electrolysis (HTSE) system and carried out some preliminary estimations on the effects of heat recovery on the HTSE hydrogen production system. To produce massive hydrogen by using nuclear energy, the HTSE process is one of the promising technologies with sulfur-iodine and hybrid sulfur process. The HTSE produces hydrogen through electrochemical reaction within the solid oxide electrolysis cell (SOEC), which is a reverse reaction of solid oxide fuel cell (SOFC). The HTSE system generally operates in the temperature range of 700∼900 .deg. C. Advantages of HTSE hydrogen production are (a) clean hydrogen production from water without carbon oxide emission, (b) synergy effect due to using the current SOFC technology and (c) higher thermal efficiency of system when it is coupled nuclear reactor. Since the HTSE system operates over 700 .deg. C, the use of heat recovery is an important consideration for higher efficiency. In this paper, four different heat recovery configurations for the HTSE system have been investigated and estimated

Inverse heat transfer problem in digital temperature control in plate fin and tube heat exchangers

Science.gov (United States)

Taler, Dawid; Sury, Adam

2011-12-01

The aim of the paper is a steady-state inverse heat transfer problem for plate-fin and tube heat exchangers. The objective of the process control is to adjust the number of fan revolutions per minute so that the water temperature at the heat exchanger outlet is equal to a preset value. Two control techniques were developed. The first is based on the presented mathematical model of the heat exchanger while the second is a digital proportional-integral-derivative (PID) control. The first procedure is very stable. The digital PID controller becomes unstable if the water volumetric flow rate changes significantly. The developed techniques were implemented in digital control system of the water exit temperature in a plate fin and tube heat exchanger. The measured exit temperature of the water was very close to the set value of the temperature if the first method was used. The experiments showed that the PID controller works also well but becomes frequently unstable.

Analysis of the Potential of Low-Temperature Heat Pump Energy Sources

Directory of Open Access Journals (Sweden)

Pavel Neuberger

2017-11-01

Full Text Available The paper deals with an analysis of temperatures of ground masses in the proximities of linear and slinky-type HGHE (horizontal ground heat exchanger. It evaluates and compares the potentials of HGHEs and ambient air. The reason and aim of the verification was to gain knowledge of the temperature course of the monitored low-temperature heat pump energy sources during heating periods and periods of stagnation and to analyse the knowledge in terms of the potential to use those sources for heat pumps. The study was conducted in the years 2012–2015 during three heating periods and three periods of HGHEs stagnation. The results revealed that linear HGHE had the highest temperature potential of the observed low-temperature heat pump energy sources. The average daily temperatures of the ground mass surrounding the linear HGHE were the highest ranging from 7.08 °C to 9.20 °C during the heating periods, and having the lowest temperature variation range of 12.62–15.14 K, the relative frequency of the average daily temperatures of the ground mass being the highest at 22.64% in the temperature range containing the mode of all monitored temperatures in a recorded interval of [4.10, 6.00] °C. Ambient air had lower temperature potential than the monitored HGHEs.

Temperature distributions of a conductively heated filament

International Nuclear Information System (INIS)

Tamura, Koji; Ohba, Hironori; Shibata, Takemasa

1999-07-01

Temperature distributions of a heated filament were measured. A W-Re(5%) filament (0.25 mm in diameter, 24.7 mm in length) was conductively heated by currents between 5A and 7A with a DC power supply, and the surface of the filament was imaged with a charge coupled device (CCD) camera through a monochromatic filter. The spectral radiation intensity at the filament center region was almost uniform. Since the temperature distribution was also uniform and the energy loss by thermal conduction was negligible, temperature in this region was determined from the energy balance between applied power and radiation loss. Temperature distribution of the filament was determined based on the Planck's law of radiation from the spectral radiation intensity ratio of the filament surface using obtained temperature as a reference. It was found that temperature distribution of a filament was easily measured by this method. (author)

High temperature superconducting current lead test facility with heat pipe intercepts

International Nuclear Information System (INIS)

Blumenfeld, P.E.; Prenger, C.; Roth, E.W.; Stewart, J.A.

1998-01-01

A high temperature superconducting (HTS) current lead test facility using heat pipe thermal intercepts is under development at the Superconducting Technology Center at Los Alamos National Laboratory. The facility can be configured for tests at currents up to 1,000 A. Mechanical cryocoolers provide refrigeration to the leads. Electrical isolation is maintained by intercepting thermal energy from the leads through cryogenic heat pipes. HST lead warm end temperature is variable from 65 K to over 90 K by controlling heat pipe evaporator temperature. Cold end temperature is variable up to 30 K. Performance predictions in terms of heat pipe evaporator temperature as a function of lead current are presented for the initial facility configuration, which supports testing up to 200 A. Measurements are to include temperature and voltage gradient in the conventional and HTS lead sections, temperature and heat transfer rate in the heat pipes. as well as optimum and off-optimum performance of the conventional lead sections

Temperature distribution of a simplified rotor due to a uniform heat source

Science.gov (United States)

Welzenbach, Sarah; Fischer, Tim; Meier, Felix; Werner, Ewald; kyzy, Sonun Ulan; Munz, Oliver

2018-03-01

In gas turbines, high combustion efficiency as well as operational safety are required. Thus, labyrinth seal systems with honeycomb liners are commonly used. In the case of rubbing events in the seal system, the components can be damaged due to cyclic thermal and mechanical loads. Temperature differences occurring at labyrinth seal fins during rubbing events can be determined by considering a single heat source acting periodically on the surface of a rotating cylinder. Existing literature analysing the temperature distribution on rotating cylindrical bodies due to a stationary heat source is reviewed. The temperature distribution on the circumference of a simplified labyrinth seal fin is calculated using an available and easy to implement analytical approach. A finite element model of the simplified labyrinth seal fin is created and the numerical results are compared to the analytical results. The temperature distributions calculated by the analytical and the numerical approaches coincide for low sliding velocities, while there are discrepancies of the calculated maximum temperatures for higher sliding velocities. The use of the analytical approach allows the conservative estimation of the maximum temperatures arising in labyrinth seal fins during rubbing events. At the same time, high calculation costs can be avoided.

Heating and Domestic Hot Water Systems in Buildings Supplied by Low-Temperature District Heating

DEFF Research Database (Denmark)

Brand, Marek

solutions simply redirect the bypassed water back to the DH network without additional cooling, but bypassed water can instead be redirected to floor heating in the bathroom to be further cooled and thus reduce heat loss from the DH network while improving comfort for occupants and still ensure fast DHW...... increased risk of Legionella if the DH substation and DHW system are designed for the low-temperature supply conditions. To ensure the fast provision of DHW during non-heating periods, the supply service pipe should be kept warm, preferably with the bypass solution redirecting the bypass flow to bathroom...... temperature. To accord with the literature, the modelling of internal heat gains reflected the improved efficiency of equipment by reduction of value from 5W/m2 to 4.2W/m2, also modelled as intermittent heat gains based on a realistic week schedule. Furthermore, the indoor set-point temperature was increased...

Comparison of shell-and-tube with plate heat exchangers for the use in low-temperature organic Rankine cycles

International Nuclear Information System (INIS)

Walraven, Daniël; Laenen, Ben; D’haeseleer, William

2014-01-01

Highlights: • Binary cycles for low-temperature heat sources are investigated. • Shell-and-tube and plate heat exchangers are modeled. • System optimization of the cycle variables and heat exchanger geometry. • ORCs with plate heat exchangers obtain in most cases higher efficiencies. - Abstract: Organic Rankine cycles (ORCs) can be used for electricity production from low-temperature heat sources. These ORCs are often designed based on experience, but this experience will not always lead to the most optimal configuration. The ultimate goal is to design ORCs by performing a system optimization. In such an optimization, the configuration of the components and the cycle parameters (temperatures, pressures, mass flow rate) are optimized together to obtain the optimal configuration of power plant and components. In this paper, the configuration of plate heat exchangers or shell-and-tube heat exchangers is optimized together with the cycle configuration. In this way every heat exchanger has the optimum allocation of heat exchanger surface, pressure drop and pinch-point-temperature difference for the given boundary conditions. ORCs with plate heat exchangers perform mostly better than ORCs with shell-and-tube heat exchangers, but one disadvantage of plate heat exchangers is that the geometry of both sides is the same, which can result in an inefficient heat exchanger. It is also shown that especially the cooling-fluid inlet temperature and mass flow have a strong influence on the performance of the power plant

Exergy and Energy Analysis of Low Temperature District Heating Network

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

is in line with a pilot project that is carrying out in Denmark with network supply/return temperature at 55oC/25 oC. The consumer domestic hot water (DHW) demand is supplied with a special designed district heating (DH) storage tank. The space heating (SH) demand is supplied with a low temperature radiator......Low temperature district heating (LTDH) with reduced network supply and return temperature provides better match of the low quality building thermal demand and the low quality waste heat supply. In this paper, an exemplary LTDH network was designed for 30 low energy demand residential houses, which....... The network thermal and hydraulic conditions were simulated under steady state with an in-house district heating network design and simulation code. Through simulation, the overall system energetic and exergetic efficiencies were calculated and the exergy losses for the major district heating system...

Residential CO{sub 2} heat pump system for combined space heating and hot water heating

Energy Technology Data Exchange (ETDEWEB)

Stene, Joern

2004-02-01

Carbon dioxide (CO{sub 2}, R-744) has been identified as a promising alternative to conventional working fluids in a number of applications due to its favourable environmental and thermophysical properties. Previous work on residential CO{sub 2} heat pumps has been dealing with systems for either space heating or hot water heating, and it was therefore considered interesting to carry out a theoretical and experimental study of residential CO{sub 2} heat pump systems for combined space heating and hot water heating - o-called integrated CO{sub 2} heat pump systems. The scope of this thesis is limited to brine-to-water and water-to-water heat pumps connected to low-temperature hydronic space heating systems. The main conclusions are: (1) Under certain conditions residential CO{sub 2} heat pump systems for combined space heating and hot water heating may achieve the same or higher seasonal performance factor (SPF) than the most energy efficient state-of-the-art brine-to-water heat pumps. (2) In contrary to conventional heat pump systems for combined space heating and DHW heating, the integrated CO{sub 2} heat pump system achieves the highest COP in the combined heating mode and the DHW heating mode, and the lowest COP in the space heating mode. Hence, the larger the annual DHW heating demand, the higher the SPF of the integrated CO{sub 2} heat pump system. (3) The lower the return temperature in the space heating system and the lower the DHW storage temperature, the higher the COP of the integrated CO{sub 2} heat pump. A low return temperature in the space heating system also results in a moderate DHW heating capacity ratio, which means that a relatively large part of the annual space heating demand can be covered by operation in the combined heating mode, where the COP is considerably higher than in the space heating mode. (4) During operation in the combined heating mode and the DHW heating mode, the COP of the integrated CO{sub 2} heat pump is heavily influenced by

Research on suitable heating conditions during local PWHT. Pt. 1. Influence of heating conditions on temperature distribution

International Nuclear Information System (INIS)

Tanaka, Jinkichi; Horii, Yukihiko; Sato, Masanobu; Murakawa, Hidekazu; Wang Jianhua

1999-01-01

To improve weld joint properties a heat treatment so called post weld heat treatment (PWHT) is often implemented for steel weldment. Generally, the PWHT is conducted in a furnace at a factory. But in site welds such as the girth joint of pipe, a local PWHT is applied using electric heater and so on. In the local PWHT steep temperature gradient occurs depending on the heating condition and it leads to rise of the thermal stress in addition to the welding residual stress. However, heating condition is not always defined the same in some standards. Therefore, suitable heat conditions for the local PWHT were studied supposing the power plant and so on experimentally and theoretically. Temperature distribution and thermal strains under different heating conditions were measured during the local PWHT using carbon steel pipes of 340 mm in diameter and 53 mm in wall thickness. The temperature gradient, thermal strain were also analyzed using Finite Element Method (FEM) as axis-symmetric model. Further, the influences of pipe size and heat transfer coefficient on the temperature distribution were analyzed and suitable heating source widths for various pipe sizes were proposed from the viewpoint of temperature distribution. (orig.)

Survival rate and expression of Heat-shock protein 70 and Frost genes after temperature stress in Drosophila melanogaster lines that are selected for recovery time from temperature coma.

Science.gov (United States)

Udaka, Hiroko; Ueda, Chiaki; Goto, Shin G

2010-12-01

In this study, we investigated the physiological mechanisms underlying temperature tolerance using Drosophila melanogaster lines with rapid, intermediate, or slow recovery from heat or chill coma that were established by artificial selection or by free recombination without selection. Specifically, we focused on the relationships among their recovery from heat or chill coma, survival after severe heat or cold, and survival enhanced by rapid cold hardening (RCH) or heat hardening. The recovery time from heat coma was not related to the survival rate after severe heat. The line with rapid recovery from chill coma showed a higher survival rate after severe cold exposure, and therefore the same mechanisms are likely to underlie these phenotypes. The recovery time from chill coma and survival rate after severe cold were unrelated to RCH-enhanced survival. We also examined the expression of two genes, Heat-shock protein 70 (Hsp70) and Frost, in these lines to understand the contribution of these stress-inducible genes to intraspecific variation in recovery from temperature coma. The line showing rapid recovery from heat coma did not exhibit higher expression of Hsp70 and Frost. In addition, Hsp70 and Frost transcription levels were not correlated with the recovery time from chill coma. Thus, Hsp70 and Frost transcriptional regulation was not involved in the intraspecific variation in recovery from temperature coma. Copyright © 2010 Elsevier Ltd. All rights reserved.

Surface temperature and surface heat flux determination of the inverse heat conduction problem for a slab

International Nuclear Information System (INIS)

Kuroyanagi, Toshiyuki

1983-07-01

Based on an idea that surface conditions should be a reflection of interior temperature and interior heat flux variation as inverse as interior conditions has been determined completely by the surface temperature and/on surface heat flux as boundary conditions, a method is presented for determining the surface temperature and the surface heat flux of a solid when the temperature and heat flux at an interior point are a prescribed function of time. The method is developed by the integration of Duhumels' integral which has unknown temperature or unknown heat flux in its integrand. Specific forms of surface condition determination are developed for a sample inverse problem: slab. Ducussing the effect of a degree of avairable informations at an interior point due to damped system and the effect of variation of surface conditions on those formulations, it is shown that those formulations are capable of representing the unknown surface conditions except for small time interval followed by discontinuous change of surface conditions. The small un-resolved time interval is demonstrated by a numerical example. An evaluation method of heat flux at an interior point, which is requested by those formulations, is discussed. (author)

Impact of ambient air temperature and heat load variation on the performance of air-cooled heat exchangers in propane cycles in LNG plants – Analytical approach

International Nuclear Information System (INIS)

Fahmy, M.F.M.; Nabih, H.I.

2016-01-01

Highlights: • An analytical method regulated the air flow rate in an air-cooled heat exchanger. • Performance of an ACHE in a propane cycle in an LNG plant was evaluated. • Summer inlet air temperature had higher impact on ACHE air flow rate requirement. - Abstract: An analytical method is presented to evaluate the air flow rate required in an air-cooled heat exchanger used in a propane pre-cooling cycle operating in an LNG (liquefied natural gas) plant. With variable ambient air inlet temperature, the air flow rate is to be increased or decreased so as to assure and maintain good performance of the operating air-cooled heat exchanger at the designed parameters and specifications. This analytical approach accounts for the variations in both heat load and ambient air inlet temperature. The ambient air inlet temperature is modeled analytically by simplified periodic relations. Thus, a complete analytical method is described so as to manage the problem of determining and accordingly regulate, either manually or automatically, the flow rate of air across the finned tubes of the air-cooled heat exchanger and thus, controls the process fluid outlet temperature required for the air-cooled heat exchangers for both cases of constant and varying heat loads and ambient air inlet temperatures. Numerical results are obtained showing the performance of the air-cooled heat exchanger of a propane cycle which cools both NG (natural gas) and MR (mixed refrigerant) streams in the LNG plant located at Damietta, Egypt. The inlet air temperature variation in the summer time has a considerable effect on the required air mass flow rate, while its influence becomes relatively less pronounced in winter.

NSSEFF Designing New Higher Temperature Superconductors

Science.gov (United States)

2017-04-13

AFRL-AFOSR-VA-TR-2017-0083 NSSEFF - DESIGINING NEW HIGHER TEMPERATURE SUPERCONDUCTORS Meigan Aronson THE RESEARCH FOUNDATION OF STATE UNIVERSITY OF...2015 4. TITLE AND SUBTITLE NSSEFF - DESIGINING NEW HIGHER TEMPERATURE SUPERCONDUCTORS 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-10-1-0191 5c...materials, identifying the most promising candidates. 15. SUBJECT TERMS TEMPERATURE, SUPERCONDUCTOR 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

Effect of temperature during ion sputtering on the surface segregation rate of antimony in an iron-antimony alloy at higher temperatures

International Nuclear Information System (INIS)

Oku, M.; Hirokawa, K.; Kimura, H.; Suzuki, S.

1986-01-01

The surface segregation of antimony in an iron-0.23 at% antimony alloy was studied by XPS. The segregation rate in the temperature range between 800 and 900 K depends on the temperature during sputtering with argon ion of kinetic energy of 1 keV. The sputtering at room temperature or 473 K gives higher values of the segregation rate than those at 673 K. Both cases give the activation energy of 170 kJmol -1 for the surface segregation rate. The segregation of antimony is not observed after the sample is heated at 1000 K. (author)

Measurement of a surface heat flux and temperature

Science.gov (United States)

Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

1994-04-01

The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The

Industrial waste heat utilization for low temperature district heating

International Nuclear Information System (INIS)

Fang, Hao; Xia, Jianjun; Zhu, Kan; Su, Yingbo; Jiang, Yi

2013-01-01

Large quantities of low grade waste heat are discharged into the environment, mostly via water evaporation, during industrial processes. Putting this industrial waste heat to productive use can reduce fossil fuel usage as well as CO 2 emissions and water dissipation. The purpose of this paper is to propose a holistic approach to the integrated and efficient utilization of low-grade industrial waste heat. Recovering industrial waste heat for use in district heating (DH) can increase the efficiency of the industrial sector and the DH system, in a cost-efficient way defined by the index of investment vs. carbon reduction (ICR). Furthermore, low temperature DH network greatly benefits the recovery rate of industrial waste heat. Based on data analysis and in-situ investigations, this paper discusses the potential for the implementation of such an approach in northern China, where conventional heat sources for DH are insufficient. The universal design approach to industrial-waste-heat based DH is proposed. Through a demonstration project, this approach is introduced in detail. This study finds three advantages to this approach: (1) improvement of the thermal energy efficiency of industrial factories; (2) more cost-efficient than the traditional heating mode; and (3) CO 2 and pollutant emission reduction as well as water conservation. -- Highlights: •We review situation of industrial waste heat recovery with a global perspective. •We present a way to analyze the potential to utilize industrial waste heat for DH. •Northern China has huge potential for using low-grade industrial waste heat for DH. •A demonstration project is introduced using the universal approach we propose. •It proves huge benefits for factories, heat-supply companies and the society

Decentralized substations for low-temperature district heating with no Legionella risk, and low return temperatures

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

. From the results, realizing LTDH by the decentralized substation unit, 30% of the annual distribution heat loss inside the building can be saved compared to a conventional system with medium-temperature district heating. Replacing the bypass pipe with an in-line supply pipe and a heat pump...... with domestic hot water (DHW) circulation. In this study, a system with decentralized substations was analysed as a solution to this problem. Furthermore, a modification for the decentralized substation system were proposed in order to reduce the average return temperature. Models of conventional system...... with medium-temperature district heating, decentralized substation system with LTDH, and innovative decentralized substation system with LTDH were built based on the information of a case building. The annual distribution heat loss and the operating costs of the three scenarios were calculated and compared...

Calculation of Vertical Temperature Gradients in Heated Rooms

DEFF Research Database (Denmark)

Overby, H.; Steen-Thøde, Mogens

This paper deals with a simple model which predicts the vertical temperature gradient in a heated room. The gradient is calculated from a dimensionless temperature profile which is determined by two room air temperatures only, the mean temperature in the occupied zone and the mean temperature...

The ADAM and EVE project: Heat transfer at ambient temperature

International Nuclear Information System (INIS)

Boltendahl, U.; Harth, R.

1980-01-01

In the nuclear research plant at Juelich a new heating system is at present being developed as part of the Nuclear Long-distance Heating Project. Helium is heated up in a high-temperature reactor. The heat chemically converts a gas mixture in a reformer plant (EVE). The gases 'charged' with energy can be transported through tubes over any distance required at ambient temperatures. In a methanisation plant (ADAM) the gases react with one another, releasing the energy in the form of heat which can be used for heating air or water. (orig.) [de

Basic thermo-fluid dynamic problems in high temperature heat exchangers

International Nuclear Information System (INIS)

McEligot, D.M.

1986-01-01

The authors consider high temperature heat exchangers to be ones where the heat transfer coefficients cannot be predicted confidently by classical analyses for pure forced convection with constant fluid properties. Alternatively, one could consider heat exchangers operating above some arbitrary temperature, say 1000F or 600C perhaps, to be at high temperature conditions. In that case, most common working fluids will be superheated vapors or gases. While some liquid metal heat exchangers are designed to operate in this range, the heat transfer coefficients of liquid metals are usually sufficiently high that the dominant thermal resistance would be due to the second fluid. This paper concentrates on convective heat transfer with gases. Typical applications include modular gas cooled nuclear reactors, proposed nuclear propulsion systems and space power plants, and superheaters in Rankine steam cycles

Heat Transfer and Cooling Techniques at Low Temperature

CERN Document Server

Baudouy, B

2014-07-17

The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.

Heat Transfer and Cooling Techniques at Low Temperature

Energy Technology Data Exchange (ETDEWEB)

Baudouy, B [Saclay (France)

2014-07-01

The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.

Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation

Science.gov (United States)

Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.

2012-01-01

Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.

Analysis of microwave heating of materials with temperature-dependent properties

International Nuclear Information System (INIS)

Ayappa, K.G.; Davis, H.T.; Davis, E.A.; Gordon, J.

1991-01-01

In this paper transient temperature profiles in multilayer slabs are predicted, by simultaneously solving Maxwell's equations with the heat conduction equation, using Galerkin-finite elements. It is assumed that the medium is homogeneous and has temperature-dependent dielectric and thermal properties. The method is illustrated with applications involving the heating of food and polymers with microwaves. The temperature dependence of dielectric properties affects the heating appreciably, as is shown by comparison with a constant property model

Mask humidity during CPAP: influence of ambient temperature, heated humidification and heated tubing.

Science.gov (United States)

Nilius, Georg; Domanski, Ulrike; Schroeder, Maik; Woehrle, Holger; Graml, Andrea; Franke, Karl-Josef

2018-01-01

Mucosal drying during continuous positive airway pressure (CPAP) therapy is problematic for many patients. This study assessed the influence of ambient relative humidity (rH) and air temperature (T) in winter and summer on mask humidity during CPAP, with and without mask leak, and with or without heated humidification ± heated tubing. CPAP (8 and 12 cmH 2 O) without humidification (no humidity [nH]), with heated humidification controlled by ambient temperature and humidity (heated humidity [HH]) and HH plus heated tubing climate line (CL), with and without leakage, were compared in 18 subjects with OSA during summer and winter. The absolute humidity (aH) and the T inside the mask during CPAP were significantly lower in winter versus summer under all applied conditions. Overall, absolute humidity differences between summer and winter were statistically significant in both HH and CL vs. nH ( p humidification or with standard HH. Clinically-relevant reductions in aH were documented during CPAP given under winter conditions. The addition of heated humidification, using a heated tube to avoid condensation is recommended to increase aH, which could be useful in CPAP users complaining of nose and throat symptoms.

Measured Performance of a Low Temperature Air Source Heat Pump

Energy Technology Data Exchange (ETDEWEB)

Johnson, R. K. [Johnson Research LLC, Pueblo West, CO (United States)

2013-09-01

A 4-ton Low Temperature Heat Pump (LTHP) manufactured by Hallowell International was installed in a residence near New Haven, Connecticut and monitored over two winters of operation. After attending to some significant service issues, the heat pump operated as designed. This report should be considered a review of the dual compressor 'boosted heat pump' technology. The Low Temperature Heat Pumpsystem operates with four increasing levels of capacity (heat output) as the outdoor temperature drops. The system was shown to select capacity correctly, supplying the appropriate amount of heat to the house across the full range of outdoor temperatures. The system's Coefficient of Performance (Seasonal COP, or SCOP) over two entire winters was calculated, based on measured data, to be 3.29over the first winter and 2.68 over the second winter. A second seasonal efficiency calculation by a different method yielded a SCOP of 2.78 for the first winter and 2.83 for the second winter. This second seasonal efficiency calculation was determined by comparing measured heat pump energy use to the in situ energy use with resistance heat alone. This method is the ratio of the slopes of thedaily energy use load lines.

Optimization of Temperature Schedule Parameters on Heat Supply in Power-and-Heat Supply Systems

Directory of Open Access Journals (Sweden)

V. A. Sednin

2009-01-01

Full Text Available The paper considers problems concerning optimization of a temperature schedule in the district heating systems with steam-turbine thermal power stations having average initial steam parameters. It has been shown in the paper that upkeeping of an optimum network water temperature permits to increase an energy efficiency of heat supply due to additional systematic saving of fuel. 

Discharging process of a finned heat pipe–assisted thermal energy storage system with high temperature phase change material

International Nuclear Information System (INIS)

Tiari, Saeed; Qiu, Songgang; Mahdavi, Mahboobe

2016-01-01

Highlights: • The discharging process of a latent heat thermal energy storage system is studied. • The thermal energy storage system is assisted by finned heat pipes. • The influences of heat pipe spacing and fins geometrical features are studied. • Smaller heat pipe spacing enhances the solidification rate. • Better heat pipe and fin arrangements are determined. - Abstract: This paper presents the results of a numerical study conducted to investigate the discharging process of a latent heat thermal energy storage system assisted by finned heat pipes. A two-dimensional finite volume based numerical model along with enthalpy-porosity technique is employed to simulate the phase change of storage media during the discharging mode. The thermal energy storage system in this study consists of a square container, finned heat pipes, and potassium nitrate (KNO 3 ) as the phase change material. The charging process of the same thermal energy storage system was reported in an early paper by the authors. This paper reports the results of discharging process of the thermal energy storage system. The influences of heat pipe spacing, fin geometry and quantities as well as the effects of natural convection heat transfer on the thermal performance of the storage system were studied. The results indicate that the phase change material solidification process is hardly affected by the natural convection. Decreasing the heat pipe spacing results in faster discharging process and higher container base wall temperature. Increasing the fins length does not change the discharging time but yields higher base wall temperature. Using more fins also accelerates the discharging process and increases the container base wall temperature.

Low Temperature District Heating Consumer Unit with Micro Heat Pump for Domestic Hot Water Preparation

DEFF Research Database (Denmark)

Zvingilaite, Erika; Ommen, Torben Schmidt; Elmegaard, Brian

2012-01-01

In this paper we present and analyse the feasibility of a district heating (DH) consumer unit with micro heat pump for domestic hot water (DHW) preparation in a low temperature (40 °C) DH network. We propose a micro booster heat pump of high efficiency (COP equal to 5,3) in a consumer DH unit...... in order to boost the temperature of the district heating water for heating the DHW. The paper presents the main designs of the suggested system and different alternative micro booster heat pump concepts. Energy efficiency and thermodynamic performance of these concepts are calculated and compared....... The results show that the proposed system has the highest efficiency. Furthermore, we compare thermodynamic and economic performance of the suggested heat pump-based concept with different solutions, using electric water heater. The micro booster heat pump system has the highest annualised investment (390 EUR...

The relationship among CPU utilization, temperature, and thermal power for waste heat utilization

International Nuclear Information System (INIS)

Haywood, Anna M.; Sherbeck, Jon; Phelan, Patrick; Varsamopoulos, Georgios; Gupta, Sandeep K.S.

2015-01-01

Highlights: • This work graphs a triad relationship among CPU utilization, temperature and power. • Using a custom-built cold plate, we were able capture CPU-generated high quality heat. • The work undertakes a radical approach using mineral oil to directly cool CPUs. • We found that it is possible to use CPU waste energy to power an absorption chiller. - Abstract: This work addresses significant datacenter issues of growth in numbers of computer servers and subsequent electricity expenditure by proposing, analyzing and testing a unique idea of recycling the highest quality waste heat generated by datacenter servers. The aim was to provide a renewable and sustainable energy source for use in cooling the datacenter. The work incorporates novel approaches in waste heat usage, graphing CPU temperature, power and utilization simultaneously, and a mineral oil experimental design and implementation. The work presented investigates and illustrates the quantity and quality of heat that can be captured from a variably tasked liquid-cooled microprocessor on a datacenter server blade. It undertakes a radical approach using mineral oil. The trials examine the feasibility of using the thermal energy from a CPU to drive a cooling process. Results indicate that 123 servers encapsulated in mineral oil can power a 10-ton chiller with a design point of 50.2 kW th . Compared with water-cooling experiments, the mineral oil experiment mitigated the temperature drop between the heat source and discharge line by up to 81%. In addition, due to this reduction in temperature drop, the heat quality in the oil discharge line was up to 12.3 °C higher on average than for water-cooled experiments. Furthermore, mineral oil cooling holds the potential to eliminate the 50% cooling expenditure which initially motivated this project

Investigation of second grade fluid through temperature dependent thermal conductivity and non-Fourier heat flux

Science.gov (United States)

Hayat, T.; Ahmad, Salman; Khan, M. Ijaz; Alsaedi, A.; Waqas, M.

2018-06-01

Here we investigated stagnation point flow of second grade fluid over a stretchable cylinder. Heat transfer is characterized by non-Fourier law of heat flux and thermal stratification. Temperature dependent thermal conductivity and activation energy are also accounted. Transformations procedure is applying to transform the governing PDE's into ODE's. Obtained system of ODE's are solved analytically by HAM. Influence of flow variables on velocity, temperature, concentration, skin friction and Sherwood number are analyzed. Obtained outcome shows that velocity enhanced through curvature parameter, viscoelastic parameter and velocities ratio variable. Temperature decays for larger Prandtl number, thermal stratification, thermal relaxation and curvature parameter. Sherwood number and concentration field show opposite behavior for higher estimation of activation energy, reaction rate, curvature parameter and Schmidt number.

Heat pipes and heat pipe exchangers for heat recovery systems

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, L L; Grakovich, L P; Kiselev, V G; Kurustalev, D K; Matveev, Yu

1984-01-01

Heat pipes and heat pipe exchangers are of great importance in power engineering as a means of recovering waste heat of industrial enterprises, solar energy, geothermal waters and deep soil. Heat pipes are highly effective heat transfer units for transferring thermal energy over large distance (tens of meters) with low temperature drops. Their heat transfer characteristics and reliable working for more than 10-15 yr permit the design of new systems with higher heat engineering parameters.

Development and Validation of a Simulation Model for the Temperature Field during High-Frequency Heating of Wood

Directory of Open Access Journals (Sweden)

Haojie Chai

2018-06-01

Full Text Available In the process of applying high-frequency heating technology to wood drying, controlling the material temperature affects both drying speed and drying quality. Therefore, research on the heat transfer mechanism of high-frequency heating of wood is of great significance. To study the heat transfer mechanism of high-frequency heating, the finite element method was used to establish and solve the wood high-frequency heating model, and experimental verification was carried out. With a decrease in moisture content, the heating rate decreased, then increased, and then decreased again. There was no obvious linear relationship between the moisture content and heating rate; the simulation accuracy of the heating rate was higher in the early and later drying stages and slightly lower near the fiber saturation point. For the central section temperature distribution, the simulation and actual measurement results matched poorly in the early drying stage because the model did not fully consider the differences in the moisture content distribution of the actual test materials. In the later drying stage, the moisture content distribution of the test materials became uniform, which was consistent with the model assumptions. Considering the changes in heating rate and temperature distribution, the accuracy of the model is good under the fiber saturation point, and it can be used to predict the high-frequency heating process of wood.

Influence of Gas-Liquid Interface on Temperature Wave of Pulsating Heat Pipe

Directory of Open Access Journals (Sweden)

Ying Zhang

2018-01-01

Full Text Available The influence of the interface on the amplitude and phase of the temperature wave and the relationship between the attenuation of the temperature wave and the gas-liquid two-phase physical parameters are studied during the operation of the pulsating heat pipe. The numerical simulation shows that the existence of the phase interface changes the direction of the temperature gradient during the propagation of the temperature wave, which increases the additional “thermal resistance.” The relative size of the gas-liquid two-phase thermal conductivity affects the propagation direction of heat flow at phase interface directly. The blockage of the gas plug causes hysteresis in the phase of the temperature wave, the relative size of the gas-liquid two-phase temperature coefficient will gradually increase the phase of the temperature wave, and the time when the heat flow reaches the peak value is also advanced. The attenuation of the temperature wave is almost irrelevant to the absolute value of the density, heat capacity, and thermal conductivity of the gas-liquid two phases, and the ratio of the thermal conductivity of the gas-liquid two phases is related. When the temperature of the heat pipe was changed, the difference of heat storage ability between gas and liquid will lead to the phenomenon of heat reflux and becomes more pronounced with the increases of the temperature wave.

Effect of heat source shape on the thermal field in the pebble bed core of High Temperature Gas-cooled Reactor (HTGR)

Energy Technology Data Exchange (ETDEWEB)

Chen, Leisheng; Lee, Jaeyoung [Handong Global University, Pohang (Korea, Republic of)

2015-10-15

In this study, in order to minimize the error brought by non-uniform heat flux, the spherical heaters are employed as heat source; subsequently, thermal field and heat transfer characteristics of the pebbles are investigated. The thermal field of the pebble surface in PBR is measured with heat source in different shapes. The HTGR design concept exhibits excellent safety features due to the low power density and the large amount of graphite present in the core which gives a large thermal inertia in an accident such as loss of coolant. However, the possible appearance of hot spots in the pebble bed cores of HTGR may affect the integrity of the pebbles, which has drawn the attention of many scientists to investigate the thermal field and to predict the maximum temperature locations in the pebbles using CFD method, Lee et.al has also done some experimental work on measuring the surface temperature of the pebbles as well as visualizing flow patterns of the coolant gas, and it was found that the temperature near the contacting points between pebbles was not higher than the flow stagnation points due to the higher thermal conductivity of the pebble. Certain error of temperature measurement might occur because of not very uniform heat flux in the pebbles since heater in cylindrical shape was utilized as heat source in previous experiment. More uniform heat flux and more complicated thermal profile are found in the result obtained using spherical heaters. The result shows that the temperature in contact point is higher than that in the top point, which is different from the previous results. The complex thermal phenomena observed in the lower-half side-sphere can be explained by the flow pattern near the surface.

The Integration Of Process Heat Applications To High Temperature Gas Reactors

International Nuclear Information System (INIS)

McKellar, Michael G.

2011-01-01

A high temperature gas reactor, HTGR, can produce industrial process steam, high-temperature heat-transfer gases, and/or electricity. In conventional industrial processes, these products are generated by the combustion of fossil fuels such as coal and natural gas, resulting in significant emissions of greenhouse gases such as carbon dioxide. Heat or electricity produced in an HTGR could be used to supply process heat or electricity to conventional processes without generating any greenhouse gases. Process heat from a reactor needs to be transported by a gas to the industrial process. Two such gases were considered in this study: helium and steam. For this analysis, it was assumed that steam was delivered at 17 MPa and 540 C and helium was delivered at 7 MPa and at a variety of temperatures. The temperature of the gas returning from the industrial process and going to the HTGR must be within certain temperature ranges to maintain the correct reactor inlet temperature for a particular reactor outlet temperature. The returning gas may be below the reactor inlet temperature, ROT, but not above. The optimal return temperature produces the maximum process heat gas flow rate. For steam, the delivered pressure sets an optimal reactor outlet temperature based on the condensation temperature of the steam. ROTs greater than 769.7 C produce no additional advantage for the production of steam.

High-temperature industrial process heat: technology assessment and introduction rationale

Energy Technology Data Exchange (ETDEWEB)

1978-03-03

Three specific topics of interest to DOE are addressed: to establish the significance and identify the role of high-temperature process heat in the nation's energy economy; to identify the role of solar thermal power in these high-temperature industrial applications in terms of possible markets and economic potential; and to recommend programmatic approaches for these solar thermal high-temperature process heat activities, including proposed content for initial Request for Proposals (RFPs) to accomplish such activities. The scope of the work required to accomplish these three purposes included the following: review of US industrial energy requirements, survey of current DOE low-temperature Agricultural and Industrial Process Heat Program, examination of high-temperature solar thermal electric systems already developed or under development by DOE and industry, and coordination with the high-energy user segments of industry (i.e., cement, chemical and petroleum) to find additional markets for some or all of the systems or components being developed in the DOE solar thermal electric program. Statistical data are presented identifying energy allocations to process heat and defining DOE's involvement. Three current fossil fuel process heat system examples are provided and the corresponding solar potential is identified.

Numerical model of a thermoelectric generator with compact plate-fin heat exchanger for high temperature PEM fuel cell exhaust heat recovery

DEFF Research Database (Denmark)

Xin, Gao; Andreasen, Søren Juhl; Chen, Min

2012-01-01

on a finite-element approach. On each discretized segment, fluid properties, heat transfer process and TEG performance are locally calculated for higher model precision. To benefit both the system design and fabrication, the way to model TEG modules is herein reconsidered; a database of commercialized compact......This paper presents a numerical model of an exhaust heat recovery system for a high temperature polymer electrolyte membrane fuel cell (HTPEMFC) stack. The system is designed as thermoelectric generators (TEGs) sandwiched in the walls of a compact plate-fin heat exchanger. Its model is based...... plate-fin heat exchangers is adopted. Then the model is validated against experimental data and the main variables are identified by means of a sensitivity analysis. Finally, the system configuration is optimized for recovering heat from the exhaust gas. The results exhibit the crucial importance...

High-Temperature Test of 800HT Printed Circuit Heat Exchanger in HELP

International Nuclear Information System (INIS)

Kim, Chan Soo; Hong, Sung-Deok; Kim, Min Hwan; Shim, Jaesool

2014-01-01

Korea Atomic Energy Research Institute has developed high-temperature Printed Circuit Heat Exchangers (PCHE) for a Very High Temperature gas-cooled Reactor and operated a very high temperature Helium Experimental LooP (HELP) to verify the performance of the high temperature heat exchanger at the component level environment. PCHE is one of the candidates for the intermediate heat exchanger in a VHTR, because its design temperature and pressure are larger than any other compact heat exchanger types. High temperature PCHEs in HELP consist of an alloy617 PCHE and an 800HT PCHE. This study presents the high temperature test of an 800HT PCHE in HELP. The experimental data include the pressure drops, the overall heat transfer coefficients, and the surface temperature distributions under various operating conditions. The experimental data are compared with the thermo-hydraulic analysis from COMSOL. In addition, the single channel tests are performed to quantify the friction factor under normal nitrogen and helium inlet conditions. (author)

Heat pump using dual heat sources of air and water. Performance with heat sources arranged in parallel; Mizu kuki ryonetsugen heat pump no kenkyu. Netsugen heiretsu unten ni okeru seino

Energy Technology Data Exchange (ETDEWEB)

Ito, S; Miura, N; Sato, S [Kanagawa Institute of Technology, Kanagawa (Japan); Uchikawa, Y; Hamada, K [Kubota Corp., Osaka (Japan)

1996-10-27

A heat pump system using water and air as heat sources was built and evaluated for its performance. In this system, evaporators may be operated singly or as connected in parallel or series, and, for each case, the quantity of heat acquired may be measured and system performance may be quantitatively evaluated. The findings follow. When the two heat sources are equal in temperature in the single-evaporator operation, the evaporation temperature is about 7{degree}C higher on the water side than on the air side, and the performance coefficient is about 0.7 higher. When the air heat source temperature is 25{degree}C in the parallel operation, like quantities of heat are obtained from both heat sources, and collection of heat from the water increases with a decrease in the air heat source temperature but, with an increase, collection from the air increases. When the air heat source temperature decreases, the evaporation temperature decreases in the single-evaporator working on the air and in the parallel operation but it levels off in the single-evaporator working on the water alone. When the water heat source temperature decreases, evaporation temperature drop is sharper in the single-evaporator working on the water than in the parallel operation, which suggests the transfer from the parallel operation to the single-evaporator working on the air. In the single-evaporator operation on the water heat source, the evaporation temperature linearly decreases with an increase in superheating. 1 ref., 10 figs.

Soil temperature distribution around a U-tube heat exchanger in a multi-function ground source heat pump system

International Nuclear Information System (INIS)

Li Shuhong; Yang Weihua; Zhang Xiaosong

2009-01-01

The imbalance of heat extracted from the earth by the underground heat exchangers in winter and ejected into it in summer is expected to affect the long term performance of conventional ground source heat pump (GSHP) in territories with a cold winter and a warm summer such as the middle and downstream areas of the Yangtze River in China. This paper presents a new multi-function ground source heat pump (MFGSHP) system which supplies hot water as well as space cooling/heating to mitigate the soil imbalance of the extracted and ejected heat by a ground source heat pump system. The heat transfer characteristic is studied and the soil temperature around the underground heat exchangers are simulated under a typical climatic condition of the Yangtze River. A three-dimensional model was constructed with the commercial computational fluid dynamics software FLUENT based on the inner heat source theory. Temperature distribution and variation trend of a tube cluster of the underground heat exchanger are simulated for the long term performance. The results show that the soil temperature around the underground tube keeps increasing due to the surplus heat ejected into the earth in summer, which deteriorates the system performance and may lead to the eventual system deterioration. The simulation shows that MFGSHP can effectively alleviate the temperature rise by balancing the heat ejected to/extracted from underground by the conventional ground source heat pump system. The new system also improves the energy efficiency.

SCEPTIC, Pressure Drop, Flow Rate, Heat Transfer, Temperature in Reactor Heat Exchanger

International Nuclear Information System (INIS)

Kattchee, N.; Reynolds, W.C.

1975-01-01

1 - Nature of physical problem solved: SCEPTIC is a program for calculating pressure drop, flow rates, heat transfer rates, and temperature in heat exchangers such as fuel elements of typical gas or liquid cooled nuclear reactors. The effects of turbulent and heat interchange between flow passages are considered. 2 - Method of solution: The computation procedure amounts to a nodal of lumped parameter type of calculation. The axial mesh size is automatically selected to assure that a prescribed accuracy of results is obtained. 3 - Restrictions on the complexity of the problem: Maximum number of subchannels is 25, maximum number of heated surfaces is 46

Innovative system for delivery of low temperature district heating

Directory of Open Access Journals (Sweden)

Anton Ivanov Ianakiev

2017-01-01

Full Text Available An innovative Low Temperature District Heating (LTDH local network is developed in Nottingham, supported by REMOURBAN project, part of the H2020 Smart City and Community Lighthouse scheme. It was proposed that a branch emanating from the return pipe of the of the existing district heating system in Nottingham would be created to use low temperature heating for the first time in UK. The development is aimed to extract wasted (unused heat from existing district heating system and make it more efficient and profitable. Four maisonette blocks of 94 low-raised flats, at Nottingham demo site of the REMOURBAN project will be connected to this new LTDH system. The scheme will provide a primary supply of heat and hot water at approximately 50oC to 60oC. Innovated solutions have been put forward to overcome certain barriers, such as legionella related risks and peak loads during extreme heating seasons and occasional maintenance.

Suppression of the sonic heat transfer limit in high-temperature heat pipes

Science.gov (United States)

Dobran, Flavio

1989-08-01

The design of high-performance heat pipes requires optimization of heat transfer surfaces and liquid and vapor flow channels to suppress the heat transfer operating limits. In the paper an analytical model of the vapor flow in high-temperature heat pipes is presented, showing that the axial heat transport capacity limited by the sonic heat transfer limit depends on the working fluid, vapor flow area, manner of liquid evaporation into the vapor core of the evaporator, and lengths of the evaporator and adiabatic regions. Limited comparisons of the model predictions with data of the sonic heat transfer limits are shown to be very reasonable, giving credibility to the proposed analytical approach to determine the effect of various parameters on the axial heat transport capacity. Large axial heat transfer rates can be achieved with large vapor flow cross-sectional areas, small lengths of evaporator and adiabatic regions or a vapor flow area increase in these regions, and liquid evaporation in the evaporator normal to the main flow.

Thermodynamic modelling of a recompression CO_2 power cycle for low temperature waste heat recovery

International Nuclear Information System (INIS)

Banik, Shubham; Ray, Satyaki; De, Sudipta

2016-01-01

Highlights: • Thermodynamic model for recompression T-CO_2 is developed. • Energetic and exergetic analysis compared with S-CO_2 and Reg. Brayton cycle. • Maximum efficiency of 13.6% is obtained for T-CO_2 cycle. • Optimum recompression ratio of 0.48 is obtained for minimum irreversibility. • Reg. Brayton has better efficiency, T-CO_2 offers minimum irreversibility. - Abstract: Due to the rising prices of conventional fossil fuels, increasing the overall thermal efficiency of a power plant is essential. One way of doing this is waste heat recovery. This recovery is most difficult for low temperature waste heat, below 240 °C, which also covers majority of the waste heat source. Carbon dioxide, with its low critical temperature and pressure, offers an advantage over ozone-depleting refrigerants used in Organic Rankine Cycles (ORCs) and hence is most suitable for the purpose. This paper introduces parametric optimization of a transcritical carbon dioxide (T-CO_2) power cycle which recompresses part of the total mass flow of working fluid before entering the precooler, thereby showing potential for higher cycle efficiency. Thermodynamic model for a recompression T-CO_2 power cycle has been developed with waste heat source of 2000 kW and at a temperature of 200 °C. Results obtained from this model are analysed to estimate effects on energetic and exergetic performances of the power cycle with varying pressure and mass recompression ratio. Higher pressure ratio always improves thermodynamic performance of the cycle – both energetic and exergetic. Higher recompression ratio also increases exergetic efficiency of the cycle. However, it increases energy efficiency, only if precooler inlet temperature remains constant. Maximum thermal efficiency of the T-CO_2 cycle with a recompression ratio of 0.26 has been found to be 13.6%. To minimize total irreversibility of the cycle, an optimum ratio of 0.48 was found to be suitable.

Heat Transport upon River-Water Infiltration investigated by Fiber-Optic High-Resolution Temperature Profiling

Science.gov (United States)

Vogt, T.; Schirmer, M.; Cirpka, O. A.

2010-12-01

Infiltrating river water is of high relevance for drinking water supply by river bank filtration as well as for riparian groundwater ecology. Quantifying flow patterns and velocities, however, is hampered by temporal and spatial variations of exchange fluxes. In recent years, heat has become a popular natural tracer to estimate exchange rates between rivers and groundwater. Nevertheless, field investigations are often limited by insufficient sensors spacing or simplifying assumptions such as one-dimensional flow. Our interest lies in a detailed local survey of river water infiltration at a restored river section at the losing river Thur in northeast Switzerland. Here, we measured three high-resolution temperature profiles along an assumed flow path by means of distributed temperature sensing (DTS) using fiber optic cables wrapped around poles. Moreover, piezometers were equipped with standard temperature sensors for a comparison to the DTS data. Diurnal temperature oscillations were tracked in the river bed and the riparian groundwater and analyzed by means of dynamic harmonic regression and subsequent modeling of heat transport with sinusoidal boundary conditions to quantify seepage velocities and thermal diffusivities. Compared to the standard temperature sensors, the DTS data give a higher vertical resolution, facilitating the detection of process- and structure-dependent patterns of the spatiotemporal temperature field. This advantage overcompensates the scatter in the data due to instrument noise. In particular, we could demonstrate the impact of heat conduction through the unsaturated zone on the riparian groundwater by the high resolution temperature profiles.

Depression of the Superfluid Transition Temperature in 4He by a Heat Flow

International Nuclear Information System (INIS)

Yin Liang; Qi Xin; Lin Peng

2014-01-01

The depression of the superfluid transition temperature T λ in 4 He by a heat flow Q is studied. A small sealed cell with a capillary is introduced and a stable and flat superfluid transition temperature plateau is easily obtained by controlling the temperature of the variable-temperature platform and the bottom chamber of the sealed cell. Owing to the depression effect of the superfluid transition temperature by the heat flow, the heat flow through the capillary is changed by the temperature control to obtain multiple temperature plateaus of different heat flows. The thermometer self-heating effect, the residual heat leak of the 4.2 K environment, the temperature difference on the He II liquid column, the Kapiza thermal resistance between the liquid helium and the copper surface of the sealed cell, the temperature gradient of the sealed cell, the static pressure of the He II liquid column and other factors have influence on the depression effect and the influence is analyzed in detail. Twenty experiments of the depression of the superfluid transition temperature in 4 He by heat flow are made with four sealed cells in one year. The formula of the superfluid transition temperature pressured by the heat flow is T λ (Q) = −0.00000103Q + 2.1769108, and covers the range 229 ≤ Q ≤ 6462 μW/cm 2

The effects of heated and room-temperature abdominal lavage solutions on core body temperature in dogs undergoing celiotomy.

Science.gov (United States)

Nawrocki, Michael A; McLaughlin, Ron; Hendrix, P K

2005-01-01

To document the magnitude of temperature elevation obtained with heated lavage solutions during abdominal lavage, 18 dogs were lavaged with sterile isotonic saline intraoperatively (i.e., during a celiotomy). In nine dogs, room-temperature saline was used. In the remaining nine dogs, saline heated to 43+/-2 degrees C (110+/-4 degrees F) was used. Esophageal, rectal, and tympanic temperatures were recorded every 60 seconds for 15 minutes after initiation of the lavage. Temperature levels decreased in dogs lavaged with room-temperature saline. Temperature levels increased significantly in dogs lavaged with heated saline after 2 to 6 minutes of lavage, and temperatures continued to increase throughout the 15-minute lavage period.

Simultaneous determination of reference free-stream temperature and convective heat transfer coefficients

International Nuclear Information System (INIS)

Jeong, Gi Ho; Song, Ki Bum; Kim, Kui Soon

2001-01-01

This paper deals with the development of a new method that can obtain heat transfer coefficient and reference free stream temperature simultaneously. The method is based on transient heat transfer experiments using two narrow-band TLCs. The method is validated through error analysis in terms of the random uncertainties in the measured temperatures. It is shown how the uncertainties in heat transfer coefficient and free stream temperature can be reduced. The general method described in this paper is applicable to many heat transfer models with unknown free stream temperature

Secondary heat exchanger design and comparison for advanced high temperature reactor

International Nuclear Information System (INIS)

Sabharwall, P.; Kim, E. S.; Siahpush, A.; McKellar, M.; Patterson, M.

2012-01-01

Next generation nuclear reactors such as the advanced high temperature reactor (AHTR) are designed to increase energy efficiency in the production of electricity and provide high temperature heat for industrial processes. The efficient transfer of energy for industrial applications depends on the ability to incorporate effective heat exchangers between the nuclear heat transport system and the industrial process heat transport system. This study considers two different types of heat exchangers - helical coiled heat exchanger and printed circuit heat exchanger - as possible options for the AHTR secondary heat exchangers with distributed load analysis and comparison. Comparison is provided for all different cases along with challenges and recommendations. (authors)

Entropy Generation of Desalination Powered by Variable Temperature Waste Heat

Directory of Open Access Journals (Sweden)

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.

Effects of phonon dimensionality in the specific heat of multiwall carbon nanotubes at low temperatures

International Nuclear Information System (INIS)

Jorge, Guillermo A; Bekeris, V; Acha, C; Escobar, M M; Goyanes, S; Zilli, D; Cukierman, A L; Candal, R J

2009-01-01

We have measured the specific heat at constant pressure, C p , of three different samples of multiwall carbon nanotubes (MWNT). For all samples, C p departs from a graphitic behavior at T p measurements show a temperature threshold from a linear regime for intermediate temperature to a higher-order power law for low temperatures. Moreover, it was found that this crossover only depends on the internal structure of the individual MWNT and not on the spatial order of the MWNT within a bundle.

Control of surface temperature of an aluminum alloy billet by air flow during a heating process at elevated temperature

Energy Technology Data Exchange (ETDEWEB)

Choi, Young [KITECH, Cheonan (Korea, Republic of); Park, Joon Hong [Dong-A University, Busan (Korea, Republic of)

2016-06-15

The procedure of semi-solid forming is composed of heating a billet, forming, compression holding and ejecting step. There are several methods to heat a billet during semi-solid forming process such as electric heating and induction heating. Usually in semi-solid forming process, induction heating has been adopted to achieve more uniform temperature of semi-solid material. Although induction heating is better method than any others, however, there is still difference of temperature between internal part and surface part of semi-solid material. Worse yet, in case of high liquid fraction of semi-solid material, liquid of the billet will flow down though solid of the billet still remains, which is very difficult to handle. In the present study, induction heating of the billet during thixoforging process with forced surface cooling has been performed to obtain more uniform distribution of temperature, microstructure and shape of the billet. Distribution of temperature of the billets was measured and compared with that of conventional distribution of temperature. Microscopic and macroscopic aspects of the billets were discussed according to location of the measuring points. By this new induction heating method, not only temperature distributions over the whole billet become uniform, but also control of temperature distribution between inside and outside part of the billet is possible as user's experimental intentions,.

ITER-W monoblocks under high pulse number transient heat loads at high temperature

International Nuclear Information System (INIS)

Loewenhoff, Th.; Linke, J.; Pintsuk, G.; Pitts, R.A.; Riccardi, B.

2015-01-01

In the context of using a full-tungsten (W) divertor for ITER, thermal shock resistance has become even more important as an issue that may potentially influence the long term performance. To address this issue a unique series of experiments has been performed on ITER-W monoblock mock ups in three EU high heat flux facilities: GLADIS (neutral beam), JUDITH 2 (electron beam) and Magnum-PSI (plasma beam). This paper discusses the JUDITH 2 experiments. Two different base temperatures, 1200 °C and 1500 °C, were chosen superimposed by ∼18,000/100,000 transient events (Δt = 0.48 ms) of 0.2 and 0.6 GW/m 2 . Results showed a stronger surface deterioration at higher base temperature, quantified by an increase in roughening. This is intensified if the same test is done after preloading (exposure to high temperature without transients), especially at higher base temperature when the material recrystallizes

Elevated-temperature tensile properties of three heats of commercially heat-treated Alloy 718

International Nuclear Information System (INIS)

Booker, M.K.; Booker, B.L.P.

1980-03-01

Three heats of commercially heat-treated alloy 718 were tensile tested over the temperature range from room temperature to 816 degree C and at nominal strain rates from 6.7 x 10 -6 to 6.7 x 10 -3 /s. We examined data for yield strength, ultimate tensile strength, uniform elongation, total elongation, and reduction in area and also inspected tensile stress-strain behavior. Yield and ultimate tensile strengths for commercially heat-treated alloy 718 decrease very gradually with temperature from room temperature up to about 600 degree C for a strain rate of 6.7 x 10 -5 /s or to about 700 degree C for a strain rate of 6.7 x 10 -4 /s. Above these temperatures the strength drops off fairly rapidly. Reduction in area and total elongation data show minimum around 700 degree C, with each ductility measure falling to 10% or less at the minimum. This minimum is more pranced and occurs at lower temperatures as strain rate decreases. Up to about 600 degree C the ductility is typically around 30%. As the temperature reaches 816 degree C the ductility again increases to perhaps 60%. The uniform elongation (plastic strain at peak load) decreases only slightly with temperature to about 500 degree C then drops off rapidly and monotonically with temperature, reaching values less than 1% at 816 degree C. At the highest test temperatures the load maximum may result, not from necking of the specimen, but from overaging of the precipitation-hardened microstructure. Stress-strain curves showed serrated deformations in the temperature range from 316 to 649 degree C, although they occur only for the faster strain rates at the supper end of this temperature range. The serrations can be quite large, involving load drops of perhaps 40 to 80 MPa. The serrations typically begin within the first 2% of deformation and continue until fracture, although exceptions were noted. 16 refs., 14 figs., 3 tabs

A study on heat resistance of high temperature resistant coating

Energy Technology Data Exchange (ETDEWEB)

Zhang, Liping; Wang, Xueying; Zhang, Qibin; Qin, Yanlong; Lin, Zhu [Research Institute of Engineering Technology of CNPC, Tianjin (China)

2005-04-15

A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes,the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper

A study on heat resistance of high temperature resistant coating

International Nuclear Information System (INIS)

Zhang, Liping; Wang, Xueying; Zhang, Qibin; Qin, Yanlong; Lin, Zhu

2005-01-01

A high temperature resistant coating has been developed, which is mainly for heavy oil production pipes deserved the serious corrosion. The coating has excellent physical and mechanical performance and corrosion resistance at room and high temperature. In order to simulate the underground working condition of heavy oil pipes,the heat resistance of the high temperature resistant coating has been studied. The development and a study on the heat resistance of the DHT high temperature resistance coating have been introduced in this paper

Modelling of Ammonia Heat Pump Desuperheaters

DEFF Research Database (Denmark)

Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix

2015-01-01

This paper presents a study of modelling desuperheating in ammonia heat pumps. Focus is on the temperature profile of the superheated refrigerant. Typically, the surface area of a heat exchanger is estimated using the Log Mean Temperature Difference (LMTD) method. The assumption of this method...... is that the specific heat is constant throughout the temperature glide of the refrigerant in the heat exchanger. However, considering ammonia as refrigerant, the LMTD method does not give accurate results due to significant variations of the specific heat. By comparing the actual temperature profiles from a one....... The area of the heat exchanger can be increased or the condensation temperature can be raised to achieve the same temperature difference for the discretized model as for the LMTD. This would affect the compressor work, hence the COP of the system. Furthermore, for higher condenser pressure, and thus higher...

Preliminary study on high temperature heat exchanger for nuclear steel making

Energy Technology Data Exchange (ETDEWEB)

Nakada, T; Ohtomo, A; Yamada, R; Suzuki, K; Narita, Y [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

1975-05-01

Both in the high temperature heat exchanger and in the steam reformer, there remain several technical problems to be solved before nuclear steel making is actualized. The loop for use with basic studies of those problems was planned by the Iron and Steel Institute of Japan (ISIJ), and its actual design, construction and co-ordination of tests were undertaken by IHI on behalf of ISIJ. The primary coolant used in the loop was helium having a pressure of approx. 12 kg/cm/sup 2/g and a temperature of approx. 1100/sup 0/C at the inlet of the high temperature heat exchanger, i.e., the test section. Steam, hydrogen, and carbon monoxide were used as secondary coolants. Of the technical problems regarding the high temperature heat exchanger for nuclear steel making, which were selected and studied using the loop, the following items are discussed: (1) heat exchange performance using helium and steam; (2) hydrogen permeation of heat resisting alloys; (3) creep and carburization of heat resisting alloys; amd (4) hydrogen absorption performance of the titanium sponge.

Thermal power generation during heat cycle near room temperature

Science.gov (United States)

Shibata, Takayuki; Fukuzumi, Yuya; Kobayashi, Wataru; Moritomo, Yutaka

2018-01-01

We demonstrate that a sodium-ion secondary battery (SIB)-type thermocell consisting of two types of Prussian blue analogue (PBA) with different electrochemical thermoelectric coefficients (S EC ≡ ∂V/∂T V and T are the redox potential and temperature, respectively) produces electrical energy during heat cycles. The device produces an electrical energy of 2.3 meV/PBA per heat cycle between 295 K (= T L) and 323 K (= T H). The ideal thermal efficiency (η = 1.0%), which is evaluated using the heat capacity (C = 4.16 meV/K) of ideal Na2Co[Fe(CN)6], reaches 11% of the Carnot efficiency (ηth = 8.7%). Our SIB-type thermocell is a promising thermoelectric device that harvests waste heat near room temperature.

Impact of aspect ratio and solar heating on street canyon air temperature

International Nuclear Information System (INIS)

Memon, R.A.; Lal, K.

2011-01-01

The results obtained from RNG (Re-Normalization Group) version of k-and turbulence model are reported in this study. The model is adopted to elucidate the impact of different building aspect ratios (i.e., ratio of building-height-to-street-canyon-width) and solar heating on temperatures in street canyon. The validation of Navier-Stokes and energy an sport equations showed that the model prediction for air-temperature and ambient wind provides reasonable accuracy. The model was applied on AR (Aspect Ratios) one to eight and surface temperature difference (delta and theta/sub s-a/)) of 2 -8. Notably, air-temperatures were higher in high AR street canyons in particular on the leeward side of the street canyon. Further investigation showed that the difference between the air-temperature 'high and low AR street canyons (AR) was positive and high with higher delta and theta/sub s-a/) conversely, the AR become negative and low gradually with lower values of delta and theta(/sub s-a/). These results could be very beneficial for the city and regional planners, civil engineers Id HVAC experts who design street canyons and strive for human thermal comfort with minimum possible energy requirements. (author)

Impact of Aspect Ratio and Solar Heating on Street Conyn Air Temperature

Directory of Open Access Journals (Sweden)

Rizwan Ahmed Memon

2011-01-01

Full Text Available The results obtained from RNG (Re-Normalization Group version of k-? turbulence model are reported in this study. The model is adopted to elucidate the impact of different building aspect ratios (i.e., ratio of building-height-to-street-canyon-width and solar heating on temperatures in street canyon. The validation of Navier-Stokes and energy transport equations showed that the model prediction for air-temperature and ambient wind provides reasonable accuracy. The model was applied on AR (Aspect Ratios one to eight and surface temperature difference (??s-a of 2 -8. Notably, air-temperatures were higher in high AR street canyons in particular on the leeward side of the street canyon. Further investigation showed that the difference between the air-temperature of high and low AR street canyons ( AR was positive and high with higher ??s-a. Conversely, the AR become negative and low gradually with lower values of ??s-a. These results could be very beneficial for the city and regional planners, civil engineers and HVAC experts who design street canyons and strive for human thermal comfort with minimum possible energy requirements.

Heat Transfer Measurement and Modeling in Rigid High-Temperature Reusable Surface Insulation Tiles

Science.gov (United States)

Daryabeigi, Kamran; Knutson, Jeffrey R.; Cunnington, George R.

2011-01-01

Heat transfer in rigid reusable surface insulations was investigated. Steady-state thermal conductivity measurements in a vacuum were used to determine the combined contribution of radiation and solid conduction components of heat transfer. Thermal conductivity measurements at higher pressures were then used to estimate the effective insulation characteristic length for gas conduction modeling. The thermal conductivity of the insulation can then be estimated at any temperature and pressure in any gaseous media. The methodology was validated by comparing estimated thermal conductivities with published data on a rigid high-temperature silica reusable surface insulation tile. The methodology was also applied to the alumina enhanced thermal barrier tiles. Thermal contact resistance for thermal conductivity measurements on rigid tiles was also investigated. A technique was developed to effectively eliminate thermal contact resistance on the rigid tile s cold-side surface for the thermal conductivity measurements.

Influence of ambient temperatures on performance of a CO2 heat pump water heating system

International Nuclear Information System (INIS)

Yokoyama, Ryohei; Shimizu, Takeshi; Ito, Koichi; Takemura, Kazuhisa

2007-01-01

In residential applications, an air-to-water CO 2 heat pump is used in combination with a domestic hot water storage tank, and the performance of this system is affected significantly not only by instantaneous ambient air and city water temperatures but also by hourly changes of domestic hot water consumption and temperature distribution in the storage tank. In this paper, the performance of a CO 2 heat pump water heating system is analyzed by numerical simulation. A simulation model is created based on thermodynamic equations, and the values of model parameters are estimated based on measured data for existing devices. The calculated performance is compared with the measured one, and the simulation model is validated. The system performance is clarified in consideration of seasonal changes of ambient air and city water temperatures

A Numerical Study on the Heat Transfer Characteristics of a Solar Thermal Receiver with High-temperature Heat Pipes

International Nuclear Information System (INIS)

Park, Young Hark; Jung, Eui Guk; Boo, Joon Hong

2007-01-01

A numerical analysis was conducted to predict the heat transfer characteristics of a solar receiver which is subject to very high heat fluxes and temperatures for solar thermal applications. The concentration ratio of the solar receiver ranges from 200 to 1000 and the concentrated heat is required to be transported to a certain distance for specific applications. The study deals with a solar receiver incorporating high-temperature sodium heat pipe as well as typical one that employs a molten-salt circulation loop. The isothermal characteristics in the receiver section is of major concern. The diameter of the solar thermal receiver was 120 mm and the length was 400 mm. For the molten-salt circulation type receiver, 48 axial channels of the same dimensions were attached to the outer wall of the receiver with even spacing in the circumferential direction. The molten salt fed through the channels by forced convection using a special pump. For the heat pipe receiver, the channels are changed to high-temperature sodium heat pipes. Commercial softwares were employed to deal with the radiative heat transfer inside the receiver cavity and the convection heat transfer along the channels. The numerical results are compared and analyzed from the view point of high-temperature solar receiver

Air source absorption heat pump in district heating: Applicability analysis and improvement options

International Nuclear Information System (INIS)

Wu, Wei; Shi, Wenxing; Li, Xianting; Wang, Baolong

2015-01-01

Highlights: • Applicability of air source absorption heat pump (ASAHP) district heating is studied. • Return temperature and energy saving rate (ESR) in various conditions are optimized. • ASAHP is more suitable for shorter distance or lower temperature district heating. • Two options can reduce the primary return temperature and improve the applicability. • The maximum ESR is improved from 13.6% to 20.4–25.6% by compression-assisted ASAHP. - Abstract: The low-temperature district heating system based on the air source absorption heat pump (ASAHP) was assessed to have great energy saving potential. However, this system may require smaller temperature drop leading to higher pump consumption for long-distance distribution. Therefore, the applicability of ASAHP-based district heating system is analyzed for different primary return temperatures, pipeline distances, pipeline resistances, supplied water temperatures, application regions, and working fluids. The energy saving rate (ESR) under different conditions are calculated, considering both the ASAHP efficiency and the distribution consumption. Results show that ASAHP system is more suitable for short-distance district heating, while for longer-distance heating, lower supplied hot water temperature is preferred. In addition, the advantages of NH 3 /H 2 O are inferior to those of NH 3 /LiNO 3 , and the advantages for warmer regions and lower pipeline resistance are more obvious. The primary return temperatures are optimized to obtain maximum ESRs, after which the suitable distances under different acceptable ESRs are summarized. To improve the applicability of ASAHP, the integration of cascaded heat exchanger (CHX) and compression-assisted ASAHP (CASAHP) are proposed, which can reduce the primary return temperature. The integration of CHX can effectively improve the applicability of ASAHP under higher supplied water temperatures. As for the utilization of CASAHP, higher compression ratio (CR) is better in

Future changes of temperature and heat waves in Ontario, Canada

Science.gov (United States)

Li, Zhong; Huang, Guohe; Huang, Wendy; Lin, Qianguo; Liao, Renfei; Fan, Yurui

2018-05-01

Apparent changes in the temperature patterns in recent years brought many challenges to the province of Ontario, Canada. As the need for adapting to climate change challenges increases, the development of reliable climate projections becomes a crucial task. In this study, a regional climate modeling system, Providing Regional Climates for Impacts Studies (PRECIS), is used to simulate the temperature patterns in Ontario. Three PRECIS runs with a resolution of 25 km × 25 km are carried out to simulate the present (1961-1990) temperature variations. There is a good match between the simulated and observed data, which validates the performance of PRECIS in reproducing temperature changes in Ontario. Future changes of daily maximum, mean, and minimum temperatures during the period 2071-2100 are then projected under the IPCC SRES A2 and B2 emission scenarios using PRECIS. Spatial variations of annual mean temperature, mean diurnal range, and temperature seasonality are generated. Furthermore, heat waves defined based on the exceedance of local climatology and their temporal and spatial characteristics are analyzed. The results indicate that the highest temperature and the most intensive heat waves are most likely to occur at the Toronto-Windsor corridor in Southern Ontario. The Northern Ontario, in spite of the relatively low projected temperature, would be under the risk of long-lasting heat waves, and thus needs effective measures to enhance its climate resilience in the future. This study can assist the decision makers in better understanding the future temperature changes in Ontario and provide decision support for mitigating heat-related loss.

Application of 'SPICE' to predict temperature distribution in heat pipes

Energy Technology Data Exchange (ETDEWEB)

Li, H M; Liu, Y; Damodaran, M [Nanyang Technological Univ., Singapore (SG). School of Mechanical and Production Engineering

1991-11-01

This article presents a new alternative approach to predict temperature distribution in heat pipes. In this method, temperature distribution in a heat pipe, modelled as an analogous electrical circuit, is predicted by applying SPICE, a general-purpose circuit simulation program. SPICE is used to simulate electrical circuit designs before the prototype is assembled. Useful predictions are obtained for heat pipes with and without adiabatic sections and for heat pipes with various evaporator and condenser lengths. Comparison of the predicted results with experiments demonstrates fairly good agreement. It is also shown how interdisciplinary developments could be used appropriately. (author).

Quantum Heat Engine and Negative Boltzmann Temperature

International Nuclear Information System (INIS)

Xi Jing-Yi; Quan Hai-Tao

2017-01-01

To clarify the ambiguity on negative Boltzmann temperature in literature, we study the Carnot and the Otto cycle with one of the heat reservoirs at the negative Boltzmann temperature based on a canonical ensemble description. The work extraction, entropy production and the efficiency of these cycles are explored. Conditions for constructing and properties of these thermodynamic cycles are elucidated. We find that the apparent “violation” of the second law of thermodynamics in these cycles are due to the fact that the traditional definition of thermodynamic efficiency is inappropriate in this situation. When properly understanding the efficiency and the adiabatic processes, in which the system crosses over “absolute ZERO” in a limit sense, the Carnot cycle with one of the heat reservoirs at a negative Boltzmann temperature can be understood straightforwardly, and it contradicts neither the second nor the third law of thermodynamics. Hence, negative Boltzmann temperature is a consistent concept in thermodynamics. We use a two-level system and an Ising spin system to illustrate our central results. (paper)

Space heating with ultra-low-temperature district heating - a case study of four single-family houses from the 1980s

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

2017-01-01

. These benefits can be maximized if district heating temperatures are lowered as much as possible. In this paper we report on a project where 18 Danish single-family houses from the 1980s were supplied by ultra-low temperature district heating with a supply temperature as low as 45 degrees C for the main part...... of the year. The houses were heated by the existing hydraulic radiator systems, while domestic hot water was prepared by use of district heating and electric boosting. This paper evaluated the heating system temperatures that were necessary in order to maintain thermal comfort in four of the houses. First...... the four houses were modelled in the building simulation tool IDA ICE. The simulation models included the actual radiator sizes and the models were used to simulate the expected thermal comfort in the houses and resulting district heating return temperatures. Secondly measurements of the actual district...

Interaction of chemical reactions and radiant heat transfer with temperature turbulent pulsations and its effect on heat traner in high-temperature gas flows

International Nuclear Information System (INIS)

Petukhov, B.S.; Zal'tsman, I.G.; Shikov, V.K.

1980-01-01

Methods of taking account of mutual effect of chemical transformations, radiation and turbulence in the calculations of heat transfer in gas flows are considered. Exponential functions of medium parameters are used to describe chemical sources and optical properties of media. It is shown using as an example the dissociation reaction C 2 reversible 2C that the effect of temperature and composition pulsations on recombination rates is negligibly small. It is also shown on the example of turbulent flow of hot molecular gas in a flat channel with cold walls that at moderate temperatures the effect of temperature pulsations on heat radiation flow can be significant (30-40%). The calculational results also show that there is a region in a turbulent boundary layer where the radiation greatly affects the coefficient of turbulent heat transfer

Heat exchanger for transfering heat produced in a high temperature reactor to an intermediate circuit gas

International Nuclear Information System (INIS)

Barchewitz, E.; Baumgaertner, H.

1985-01-01

The invention is concerned with improving the arrangement of a heat exchanger designed to transfer heat from the coolant gas circuit of a high temperature reactor to a gas which is to be used for a process heat plant. In the plant the material stresses are to be kept low at high differential pressures and temperatures. According to the invention the tube bundles designed as boxes are fixed within the heat exchanger closure by means of supply pipes having got loops. For conducting the hot gas the heat exchanger has got a central pipe leading out of the reactor vessel through the pod closure and having got only one point of fixation, lying in this closure. Additional advantageous designs are mentioned. (orig./PW)

The Heat Flux Analysis in an Annulus Narrows Gap With Initial Temperature Variations Using HeaTiNG-01 Test Section

International Nuclear Information System (INIS)

Mulya Juarsa; Efrizon Umar; Andhang Widi Harto

2009-01-01

An experiment to understand the complexity of boiling phenomena on a narrow gap, which has occurs in severe accident at TMI-2 NPP is necessary to be done in aimed to increase the understanding of accident management. The goal of research is to obtain a heat flux and critical heat flux (CHF) value during boiling heat transfer process in a narrow gap annulus. The method of research is experimental using HeaTiNG-01 test section. The experiment has been done with heating-up heated rod until a certain initial temperature, for this experiment, three initial temperature variations was decided at 650°C, 750°C dan 850°C. Then, a cooling process in heated rod by saturated water was recorded based on temperature data changes. Temperature data was used to calculate a value of heat flux and wall superheat temperature, until the results could be defined in boiling curve. The result of this research shows that, although the initial temperature of heated rod was different, the value of CHF is almost similar with CHF average 253.7 kW/m 2 with the changes of only 4.7%. The event of boiling in a narrow gap is not included pool boiling category based on the comparison of film boiling area of the experiment to Bromley correlations. (author)

Low temperature waste heat brought into the greenhouse. Scientific investigations of favourable experience in Austria. Niedertemperatur-Abwaerme ins Gewaechshaus gebracht. Wissenschaftliche Untersuchung positiver Erfahrungen in Oesterreich

Energy Technology Data Exchange (ETDEWEB)

Schrottmaier; Nadlinger, M. (Bundesanstalt fuer Landtechnik, Wieselburg (Austria))

1986-01-01

In the Indinger garden centre at Brunn, the low temperature ground and rack heating (heating the soil by hoses laid 2-5 cm deep in the ballast bed) is compared with conventional heating. Loss of heat of ground heating downwards was prevented by insulating under the hoses with styropor. At low outside temperatures, vegetation heating in the ground and on the table for decorative plants is not sufficient by itself, a thermal insulation umbrella must be used or the peak demand must be met by the old heating system. The lower the air temperature, compared to the pot temperature, the greater is the energy saving. The air and pot temperature must be controlled independently of one another. For the same energy consumption, the pot temperature was 2 K higher. The success in growing things was excellent. (orig.).

Heat source reconstruction from noisy temperature fields using an optimised derivative Gaussian filter

Science.gov (United States)

Delpueyo, D.; Balandraud, X.; Grédiac, M.

2013-09-01

The aim of this paper is to present a post-processing technique based on a derivative Gaussian filter to reconstruct heat source fields from temperature fields measured by infrared thermography. Heat sources can be deduced from temperature variations thanks to the heat diffusion equation. Filtering and differentiating are key-issues which are closely related here because the temperature fields which are processed are unavoidably noisy. We focus here only on the diffusion term because it is the most difficult term to estimate in the procedure, the reason being that it involves spatial second derivatives (a Laplacian for isotropic materials). This quantity can be reasonably estimated using a convolution of the temperature variation fields with second derivatives of a Gaussian function. The study is first based on synthetic temperature variation fields corrupted by added noise. The filter is optimised in order to reconstruct at best the heat source fields. The influence of both the dimension and the level of a localised heat source is discussed. Obtained results are also compared with another type of processing based on an averaging filter. The second part of this study presents an application to experimental temperature fields measured with an infrared camera on a thin plate in aluminium alloy. Heat sources are generated with an electric heating patch glued on the specimen surface. Heat source fields reconstructed from measured temperature fields are compared with the imposed heat sources. Obtained results illustrate the relevancy of the derivative Gaussian filter to reliably extract heat sources from noisy temperature fields for the experimental thermomechanics of materials.

Temperature distribution and heat radiation of patterned surfaces at short wavelengths

Science.gov (United States)

Emig, Thorsten

2017-05-01

We analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape.

Pressurized Recuperator For Heat Recovery In Industrial High Temperature Processes

Directory of Open Access Journals (Sweden)

Gil S.

2015-09-01

Full Text Available Recuperators and regenerators are important devices for heat recovery systems in technological lines of industrial processes and should have high air preheating temperature, low flow resistance and a long service life. The use of heat recovery systems is particularly important in high-temperature industrial processes (especially in metallurgy where large amounts of thermal energy are lost to the environment. The article presents the process design for a high efficiency recuperator intended to work at high operating parameters: air pressure up to 1.2 MPa and temperature of heating up to 900°C. The results of thermal and gas-dynamic calculations were based on an algorithm developed for determination of the recuperation process parameters. The proposed technical solution of the recuperator and determined recuperation parameters ensure its operation under maximum temperature conditions.

The TX-model - a quantitative heat loss analysis of district heating pipes by means of IR surface temperature measurements

Energy Technology Data Exchange (ETDEWEB)

Zinki, Heimo [ZW Energiteknik, Nykoeping (Sweden)

1996-11-01

The aim of this study was to investigate the possibility of analysing the temperature profile at the ground surface above buried district heating pipes in such a way that would enable the quantitative determination of heat loss from the pair of pipes. In practical applications, it is supposed that this temperature profile is generated by means of advanced IR-thermography. For this purpose, the principle of the TX - model has been developed, based on the fact that the heat losses from pipes buried in the ground have a temperature signature on the ground surface. Qualitative analysis of this temperature signature is very well known and in practical use for detecting leaks from pipes. These techniques primarily make use of relative changes of the temperature pattern along the pipe. In the quantitative heat loss analysis, however, it is presumed that the temperature profile across the pipes is related to the pipe heat loss per unit length. The basic idea is that the integral of the temperature profile perpendicular to the pipe, called TX, is a function of the heat loss, but is also affected by other parameters such as burial depth, heat diffusivity, wind, precipitation and so on. In order to analyse the parameters influencing the TX- factor, a simulation model for the energy balance at the ground surface has been developed. This model includes the heat flow from the pipe to the surface and the heat exchange at the surface with the environment due to convection, latent heat change, solar and long wave radiation. The simulation gives the surprising result that the TX factor is by and large unaffected during the course of a day even when the sun is shining, as long as other climate conditions are relatively stable (low wind, no rain, no shadows). The results from the simulations were verified at different sites in Denmark, Finland, Sweden and USA through a co-operative research program organised and partially financed by the IEA District Heating Programme, Task III, and

Promising materials for HTGR high temperature heat exchangers

International Nuclear Information System (INIS)

Kuznetsov, E.V.; Tokareva, T.B.; Ryabchenkov, A.V.; Novichkova, O.V.; Starostin, Yu.D.

1989-01-01

The service conditions for high-temperature heat-exchangers with helium coolant of HTGRs and requirements imposed on materials for their production are discussed. The choice of nickel-base alloys with solid-solution hardening for long-term service at high temperatures is grounded. Results of study on properties and structure of types Ni-25Cr-5W-5Mo and Ni-20Cr-20W alloy in the temperature range of 900 deg. - 1,000 deg. C are given. The ageing of Ni-25Cr-5W-5Mo alloy at 900 deg. - 950 deg. C results in decreased corrosion-mechanical properties and is caused by the change of structural metal stability. Alloy with 20% tungsten retains a high stability of both structure and properties after prolonged exposure in helium at above temperatures. The alloy has also increased resistance to delayed fracture and low-cycle fatigue at high temperatures. The developed alloy of type Ni-20Cr-20W with microalloying is recommended for production of tubes for HTGR high-temperature heat-exchangers with helium coolant. (author). 3 refs, 8 figs

Critical heat flux analysis on change of plate temperature and cooling water flow rate for rectangular narrow gap with bilateral-heated cases

International Nuclear Information System (INIS)

M Hadi Kusuma; Mulya Juarsa; Anhar Riza Antariksawan

2013-01-01

Boiling heat transfer phenomena on rectangular narrow gap was related to the safety of nuclear reactors. Research done in order to study the safety of nuclear reactors in particular relating to boiling heat transfer and useful on the improvement of next-generation reactor designs. The research focused on calculation of the heat flux during the cooling process in rectangular narrow gap size 1.0 mm. with initial temperatures 200°C. 400°C, and 600°C, also the flow rates of cooling water 0,1 liters/second. 0,2 liters/second. and 0,3 liters/second. Experiments carried out by injecting water at a certain flow rate with the water temperature 85°C. Transient temperature measurement data recorded by the data acquisition system. Transient temperature measurement data is used to calculate the flux of heat gain is then used to obtain the heat transfer coefficient. This research aimed to obtain the correlation between critical heat flux and heat transfer coefficient to changes in temperatures and water flow rates for bilaterally-heated cases on rectangular narrow gap. The results obtained for a constant cooling water flow rate, critical heat flux will increase when hot plate temperature also increased. While on a constant hot plate temperature, coefficient heat transfer will increase when cooling water flow rate also increased. Thus it can be said that the cooling water flow rate and temperature of the hot plate has a significant effect on the critical heat flux and heat transfer coefficient resulted in quenching process of vertical rectangular narrow gap with double-heated cases. (author)

The effect of humidified heated breathing circuit on core body temperature in perioperative hypothermia during thyroid surgery.

Science.gov (United States)

Park, Hue Jung; Moon, Ho Sik; Moon, Se Ho; Do Jeong, Hyeon; Jeon, Young Jae; Do Han, Keung; Koh, Hyun Jung

2017-01-01

Purpose: During general anesthesia, human body easily reaches a hypothermic state, which is mainly caused by heat redistribution. Most studies suggested that humidified heated breathing circuits (HHBC) have little influence on maintenance of the core temperature during early phase of anesthesia. This study was aimed at examining heat preservation effect with HHBC in case of undergoing surgery with less exposure of surgical fields and short surgical duration. Methods: Patients aged 19 to 70 yr - old, ASA-PS I or II who were scheduled for elective thyroidectomy were assigned and divided to the group using HHBC (G1) and the group using conventional circuit (G2) by random allocation. During operation, core, skin, and room temperatures were measured every 5minutes by specific thermometer. Results: G1 was decreased by a lesser extent than G2 in core temperature, apparently higher at 30 and 60 minutes after induction. Skin and room temperatures showed no differences between the two groups (p>0.05). Consequently, we confirmed HHBC efficiently prevented a decrease in core temperature during early period in small operation which has difficulty in preparing warming devices or environments were not usually considered. Conclusions: This study showed that HHBC influences heat redistribution in early period of operation and can lessen the magnitude of the decrease in core body temperature. Therefore, it can be applied efficiently for other active warming devices in mild hypothermia.

Solar radiative heating of fiber-optic cables used to monitor temperatures in water

Science.gov (United States)

Neilson, Bethany T.; Hatch, Christine E.; Ban, Heng; Tyler, Scott W.

2010-08-01

In recent years, applications of distributed temperature sensing (DTS) have increased in number and diversity. Because fiber-optic cables used for DTS are typically sheathed in dark UV-resistant materials, the question arises as to how shortwave solar radiation penetrating a water column influences the accuracy of absolute DTS-derived temperatures in aquatic applications. To quantify these effects, we completed a modeling effort that accounts for the effects of radiation and convection on a submersed cable to predict when solar heating may be important. Results indicate that for cables installed at shallow depths in clear, low-velocity water bodies, measurable heating of the cable is likely during peak solar radiation. However, at higher velocities, increased turbidity and/or greater depths, the effects of solar heating are immeasurable. A field study illustrated the effects of solar radiation by installing two types of fiber-optic cable at multiple water depths (from 0.05 to 0.8 m) in the center and along the sidewall of a trapezoidal canal. Thermistors were installed at similar depths and shielded from solar radiation to record absolute water temperatures. During peak radiation, thermistor data showed small temperature differences (˜0.003°C-0.04°C) between depths suggesting minor thermal stratification in the canal center. DTS data from cables at these same depths show differences of 0.01°C-0.17°C. The DTS differences cannot be explained by stratification alone and are likely evidence of additional heating from solar radiation. Sidewall thermistor strings also recorded stratification. However, corresponding DTS data suggested that bed conduction overwhelmed the effects of solar radiation.

Phase change based cooling for high burst mode heat loads with temperature regulation above the phase change temperature

Science.gov (United States)

The United States of America as represented by the United States Department of Energy

2009-12-15

An apparatus and method for transferring thermal energy from a heat load is disclosed. In particular, use of a phase change material and specific flow designs enables cooling with temperature regulation well above the fusion temperature of the phase change material for medium and high heat loads from devices operated intermittently (in burst mode). Exemplary heat loads include burst mode lasers and laser diodes, flight avionics, and high power space instruments. Thermal energy is transferred from the heat load to liquid phase change material from a phase change material reservoir. The liquid phase change material is split into two flows. Thermal energy is transferred from the first flow via a phase change material heat sink. The second flow bypasses the phase change material heat sink and joins with liquid phase change material exiting from the phase change material heat sink. The combined liquid phase change material is returned to the liquid phase change material reservoir. The ratio of bypass flow to flow into the phase change material heat sink can be varied to adjust the temperature of the liquid phase change material returned to the liquid phase change material reservoir. Varying the flowrate and temperature of the liquid phase change material presented to the heat load determines the magnitude of thermal energy transferred from the heat load.

Theoretical simulation of the dual-heat-flux method in deep body temperature measurements.

Science.gov (United States)

Huang, Ming; Chen, Wenxi

2010-01-01

Deep body temperature reveals individual physiological states, and is important in patient monitoring and chronobiological studies. An innovative dual-heat-flux method has been shown experimentally to be competitive with the conventional zero-heat-flow method in its performance, in terms of measurement accuracy and step response to changes in the deep temperature. We have utilized a finite element method to model and simulate the dynamic process of a dual-heat-flux probe in deep body temperature measurements to validate the fundamental principles of the dual-heat-flux method theoretically, and to acquire a detailed quantitative description of the thermal profile of the dual-heat-flux probe. The simulation results show that the estimated deep body temperature is influenced by the ambient temperature (linearly, at a maximum rate of 0.03 °C/°C) and the blood perfusion rate. The corresponding depth of the estimated temperature in the skin and subcutaneous tissue layer is consistent when using the dual-heat-flux probe. Insights in improving the performance of the dual-heat-flux method were discussed for further studies of dual-heat-flux probes, taking into account structural and geometric considerations.

Heat transfer coefficient: Medivance Arctic Sun Temperature Management System vs. water immersion.

Science.gov (United States)

English, M J; Hemmerling, T M

2008-07-01

To improve heat transfer, the Medivance Arctic Sun Temperature Management System (Medivance, Inc., Louisville, CO, USA) features an adhesive, water-conditioned, highly conductive hydrogel pad for intimate skin contact. This study measured and compared the heat transfer coefficient (h), i.e. heat transfer efficiency, of this pad (hPAD), in a heated model and in nine volunteers' thighs; and of 10 degrees C water (hWATER) in 33 head-out immersions by 11 volunteers. Volunteer studies had ethical approval and written informed consent. Calibrated heat flux transducers measured heat flux (W m-2). Temperature gradient (DeltaT) was measured between skin and pad or water temperatures. Temperature gradient was changed through the pad's water temperature controller or by skin cooling on immersion. The heat transfer coefficient is the slope of W m-2/DeltaT: its unit is W m-2 degrees C-1. Average with (95% CI) was: model, hPAD = 110.4 (107.8-113.1), R2 = 0.99, n = 45; volunteers, hPAD = 109.8 (95.5-124.1), R2 = 0.83, n = 51; and water immersion, hWATER = 107.1 (98.1-116), R2 = 0.86, n = 94. The heat transfer coefficient for the pad was the same in the model and volunteers, and equivalent to hWATER. Therefore, for the same DeltaT and heat transfer area, the Arctic Sun's heat transfer rate would equal water immersion. This has important implications for body cooling/rewarming rates.

Numerical analysis of steady state and transient analysis of high temperature ceramic plate-fin heat exchanger

International Nuclear Information System (INIS)

Nagarajan, Vijaisri; Chen, Yitung; Wang, Qiuwang; Ma, Ting

2014-01-01

Highlights: • Rip saw fin design is considered to be the best because it has thin fins and has higher heat transfer coefficient. • Minimum principal stress and maximum safety factor are obtained for the inverted bolt fin design. • Maximum principal stress and minimum safety factor are obtained for triangular fin design. • Thermal stress has significant impact than mechanical stress. • High principal stress is found at the startup and shutdown stage. - Abstract: In this study three-dimensional model of ceramic plate-fin high temperature heat exchanger with different fin designs and arrangements is analyzed numerically using ANSYS FLUENT and ANSYS structural module. The ability of ceramics to withstand high temperature and corrosion makes silicon carbide (SiC) suitable candidate material to be used in high temperature heat exchanger. The operating temperature of heat exchanger is 950 °C and the operating pressure is 1.5 MPa. The working fluids are helium, sulfur trioxide, sulfur dioxide, oxygen and the water vapor. Fluid flow and heat transfer analysis are carried out for steady and transient state in FLUENT. The obtained thermal and pressure load for the steady and transient state from ANSYS FLUENT are imported to ANSYS structural module to obtain the principal stress and the factor of safety. Different arrangements of rectangular fins, triangular fins, inverted bolt fins and ripsaw fins are studied. From the results it is found that the minimum stress and the maximum safety factor are obtained for inverted bolt fins. The triangular fins have the maximum principal stress and minimum factor of safety. However, the fluid flow and heat transfer analysis show inverted bolt fins and triangular fins produce higher pressure drop and friction factor. The steady state maximum principal stress is 10.08 MPa, 9.90 MPa and 11.43 MPa for straight, staggered and top and bottom ripsaw fin arrangement. The corresponding safety factors are 21.80, 21.95 and 19

Exergy efficiency analysis of ORC (Organic Rankine Cycle) and ORC-based combined cycles driven by low-temperature waste heat

International Nuclear Information System (INIS)

Sun, Wenqiang; Yue, Xiaoyu; Wang, Yanhui

2017-01-01

Highlights: • ORC-ARC and ORC-ERC driven by low-temperature waste heat are investigated. • Thermodynamic models of basic ORC, ORC-ARC, and ORC-ERC are developed. • Exergy efficiencies of ORC, ORC-ARC, and ORC-ERC are parametrically simulated. • Suitable application conditions of ORC-ARC and ORC-ERC are reported. - Abstract: There is large amount of waste heat resources in industrial processes. However, most low-temperature waste heat is directly discharged into the environment. With the advantages of being energy-efficient, enabling investment-savings and being environmentally friendly, the Organic Rankine Cycle (ORC) plays an important role in recycling energy from low-temperature waste heat. In this study, the ORC system driven by industrial low-temperature waste heat was analyzed and optimized. The impacts of the operational parameters, including evaporation temperature, condensation temperature, and degree of superheat, on the thermodynamic performances of ORC system were conducted, with R113 used as the working fluid. In addition, the ORC-based cycles, combined with the Absorption Refrigeration Cycle (ARC) and the Ejector Refrigeration Cycle (ERC), were investigated to recover waste heat from low-temperature flue gas. The uncoupled ORC-ARC and ORC-ERC systems can generate both power and cooling for external uses. The exergy efficiency of both systems decreases with the increase of the evaporation temperature of the ORC. The net power output, the refrigerating capacity and the resultant exergy efficiency of the uncoupled ORC-ARC are all higher than those of the ORC-ERC for the evaporation temperature of the basic ORC >153 °C, in the investigated application. Finally, suitable application conditions over other temperature ranges are also given.

Temperature response functions (G-functions) for single pile heat exchangers

International Nuclear Information System (INIS)

Loveridge, Fleur; Powrie, William

2013-01-01

Foundation piles used as heat exchangers as part of a ground energy system have the potential to reduce energy use and carbon dioxide emissions from new buildings. However, current design approaches for pile heat exchangers are based on methods developed for boreholes which have a different geometry, with a much larger aspect (length to diameter) ratio. Current methods also neglect the transient behaviour of the pile concrete, instead assuming a steady state resistance for design purposes. As piles have a much larger volume of concrete than boreholes, this neglects the significant potential for heat storage within the pile. To overcome these shortcomings this paper presents new pile temperature response functions (G-functions) which are designed to reflect typical geometries of pile heat exchangers and include the transient response of the pile concrete. Owing to the larger number of pile sizes and pipe configurations which are possible with pile heat exchangers it is not feasible to developed a single unified G-function and instead upper and lower bound solutions are provided for different aspects ratios. - Highlights: • We present new temperature response functions for pile heat exchangers. • The functions include transient heat transfer within the pile concrete. • Application of the functions reduces the resulting calculated temperature ranges. • Greater energy efficiency is possible by accounting for heat storage in the pile

Effect of re-heating on the hot electron temperature

International Nuclear Information System (INIS)

Estabrook, K.; Rosen, M.

1980-01-01

Resonant absorption is the direct conversion of the transverse laser light to longitudinal electron plasma waves (epw) at the critical density [10 21 (1.06 μm/lambda 0 ) 2 cm -3 ]. The oscillating longitudinal electric field of the epw heats the electrons by accelerating them down the density gradient to a temperature of approximately 21T/sub e/ 0 25 ([I(W/cm 2 )/10 16 ](lambda 0 /1.06 μm) 2 ) 0 4 . This section extends the previous work by studying the effects of magnetic fields and collisions (albedo) which return the heated electrons for further heating. A magnetic field increases their temperature and collisions do not

Design and manufacture of ceramic heat pipes for high temperature applications

International Nuclear Information System (INIS)

Meisel, Peter; Jobst, Matthias; Lippmann, Wolfgang; Hurtado, Antonio

2015-01-01

Heat exchangers based on ceramic heat pipes were designed for use under highly abrasive and corrosive atmospheres at temperatures in the range of 800–1200 °C for high-temperature power-engineering applications. The presented heat pipes are gravity assisted and based on a multi-layer concept comprising a ceramic cladding and an inner metal tube that contains sodium as the working fluid. Hermetical encapsulation of the working fluid was achieved by electron-beam welding of the inner metal tube. Subsequently, closure of the surrounding ceramic tube was performed by laser brazing technology using a glass solder. Temperature resistance and functionality of the manufactured ceramic thermosyphons could be confirmed experimentally in a hot combustion gas atmosphere at temperatures up to 1100 °C. The ceramic tubes used had an outer diameter of 22 mm and a total length of 770 mm. The measured axial heat transfer of the ceramic gravity assisted heat pipes at the stationary operating point with cold/hot gas temperature of 100 °C/900 °C was 400 W. The result of the calculation using the created mathematical model amounted to 459 W. - Highlights: • Heat-pipe design consists of a ceramic shell and an inner metallic tube. • Laser brazing technology is suitable to seal ceramic heat-pipes. • Thermal characteristic of double wall thermosyphon was modelled using FEM code. • Experimental investigations demonstrated functionality of double wall thermosyphons

Experimental investigation on heating performance of heat pump for electric vehicles at −20 °C ambient temperature

International Nuclear Information System (INIS)

Qin, Fei; Xue, Qingfeng; Albarracin Velez, Giovanny Marcelo; Zhang, Guiying; Zou, Huiming; Tian, Changqing

2015-01-01

Highlights: • An ASHP system with refrigerant injection for EVs is designed, for cold regions. • The heat performances of the system are tested at −20 °C ambient temperature. • The system cycle process with refrigerant injection are analyzed on lgP-H diagrams. • The effects of refrigerant injection, dryness, and in-car inlet state are discussed. • The new system can improve heating and own better application prospect. - Abstract: Since the performance of conventional air source heat pump (ASHP) for electric vehicles (EVs) is apt to decline sharply in low ambient temperature, it will consume more electricity of the cell, and affect driving mileage in cold regions. Aiming at developing high efficiency heating system for EVs in cold regions, an ASHP system applying refrigerant injection for EVs is designed, as well as the test bench is built to investigate its performance. According to the operation condition of EVs, heating performances are tested on different in-car inlet air temperature and various fresh air ratios under −20 °C ambient temperature. The system cycle process with refrigerant injection, as well as the influences of refrigerant injection and dryness are also analyzed and discussed. The results show that the heating capacity of the ASHP with refrigerant injection can be increased up to 31%, and in comparison with the conventional heat pump system its heating performance is better when in-car inlet temperature is above −10 °C. Therefore, ASHP with refrigerant injection has great potentiality to be applied for the EVs in cold regions

Space heating with ultra-low-temperature district heating - A case study of four single-family houses from the 1980s

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

. These benefits can be maximized if district heating temperatures are lowered as much as possible. In this paper we report on a project where 18 Danish single-family houses from the 1980s were supplied by ultra-low-temperature district heating with a supply temperature as low as 45 °C for the main part...... the four houses were modelled in the building simulation tool IDA ICE. The simulation models included the actual radiator sizes and the models were used to simulate the expected thermal comfort in the houses and resulting district heating return temperatures. Secondly measurements of the actual district...... heating return temperatures in the houses were analysed for different times of the year. The study found that existing Danish single-family houses from the 1980s can be heated with supply temperatures as low as 45 °C for the main part of the year. Both simulation models and test measurements showed...

Heat pump using dual heat sources of air and water. Performance in cooling mode; Mizu kuki ryonetsugen heat pump no kenkyu. Reibo unten ni okeru seino

Energy Technology Data Exchange (ETDEWEB)

Ito, S; Miura, N [Kanagawa Institute of Technology, Kanagawa (Japan); Uchikawa, Y [Kubota Corp., Osaka (Japan)

1997-11-25

When a heat pump is used for cooling purpose, it is possible to utilize different kinds of waste water as high-heat sources. However, these heat sources would have their temperatures vary with seasons and time in a day. Therefore, a discussion was given on performance of a heat pump when water and air heat sources are used for condensers during cooling operation independently, in series and in parallel, respectively. The air condenser shows an equivalent COP as compared with the water condenser when air temperature is lower by about 8 degC than water temperature. At the same heat source temperature, the COP for the water condenser indicated a value higher by about 0.6 than the case of the air condenser. A method to use condensers in parallel experiences little contribution from the air heat source, and performance of the heat pump decreases below the case of using the water heat source independently when the air heat source temperature becomes higher than that of the water heat source. In the case of series use in which a water condenser is installed in front and an air condenser in rear, its effect is exhibited when temperature in the air heat source is lower than that in the water heat source. Better performance was shown than in operating the water heat source independently. 2 refs., 9 figs.

Effects of phonon dimensionality in the specific heat of multiwall carbon nanotubes at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Jorge, Guillermo A; Bekeris, V; Acha, C [Laboratorio de Bajas Temperaturas, Departamento de Fisica, FCEyN-UBA, Pab. 1, Ciudad Universitaria (1428), Buenos Aires (Argentina); Escobar, M M; Goyanes, S [Laboratorio de Polimeros y Materiales Compuestos, Departamento de Fisica, FCEyN-UBA, Pab. 1, Ciudad Universitaria (1428), Buenos Aires (Argentina); Zilli, D; Cukierman, A L [PINMATE, Departamento de Industrias, FCEyN-UBA, Pab. Industrias, Ciudad Universitaria (1428), Buenos Aires (Argentina); Candal, R J, E-mail: gjorge@df.uba.a [Instituto de Fisicoquimica de Materiales, Ambiente y EnergIa, CONICET-UBA, Ciudad Universitaria (1428) Buenos Aires (Argentina)

2009-05-01

We have measured the specific heat at constant pressure, C{sub p}, of three different samples of multiwall carbon nanotubes (MWNT). For all samples, C{sub p} departs from a graphitic behavior at T < 120 K. C{sub p} measurements show a temperature threshold from a linear regime for intermediate temperature to a higher-order power law for low temperatures. Moreover, it was found that this crossover only depends on the internal structure of the individual MWNT and not on the spatial order of the MWNT within a bundle.

Summer outdoor temperature and occupational heat-related illnesses in Quebec (Canada)

International Nuclear Information System (INIS)

Adam-Poupart, Ariane; Smargiassi, Audrey; Busque, Marc-Antoine; Duguay, Patrice; Fournier, Michel; Zayed, Joseph; Labrèche, France

2014-01-01

Background: Predicted rise in global mean temperature and intensification of heat waves associated with climate change present an increasing challenge for occupational health and safety. Although important scientific knowledge has been gathered on the health effects of heat, very few studies have focused on quantifying the association between outdoor heat and mortality or morbidity among workers. Objective: To quantify the association between occupational heat-related illnesses and exposure to summer outdoor temperatures. Methods: We modeled 259 heat-related illnesses compensated by the Workers' Compensation Board of Quebec between May and September, from 1998 to 2010, with maximum daily summer outdoor temperatures in 16 health regions of Quebec (Canada) using generalized linear models with negative binomial distributions, and estimated the pooled effect sizes for all regions combined, by sex and age groups, and for different time lags with random-effect models for meta-analyses. Results: The mean daily compensation count was 0.13 for all regions of Quebec combined. The relationship between daily counts of compensations and maximum daily temperatures was log-linear; the pooled incidence rate ratio (IRR) of daily heat-related compensations per 1 °C increase in daily maximum temperatures was 1.419 (95% CI 1.326 to 1.520). Associations were similar for men and women and by age groups. Increases in daily maximum temperatures at lags 1 and 2 and for two and three-day lag averages were also associated with increases in daily counts of compensations (IRRs of 1.206 to 1.471 for every 1 °C increase in temperature). Conclusion: This study is the first to quantify the association between occupational heat-related illnesses and exposure to summer temperatures in Canada. The model (risk function) developed in this study could be useful to improve the assessment of future impacts of predicted summer outdoor temperatures on workers and vulnerable groups, particularly in

Summer outdoor temperature and occupational heat-related illnesses in Quebec (Canada)

Energy Technology Data Exchange (ETDEWEB)

Adam-Poupart, Ariane [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Smargiassi, Audrey [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Institut national de santé publique du Québec (INSPQ), Montreal, QC (Canada); Busque, Marc-Antoine; Duguay, Patrice [Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montreal, QC (Canada); Fournier, Michel [Direction de santé publique, Agence de la santé et des services sociaux de Montréal, Montreal, QC (Canada); Zayed, Joseph [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montreal, QC (Canada); Labrèche, France, E-mail: labreche.france@irsst.qc.ca [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montreal, QC (Canada)

2014-10-15

Background: Predicted rise in global mean temperature and intensification of heat waves associated with climate change present an increasing challenge for occupational health and safety. Although important scientific knowledge has been gathered on the health effects of heat, very few studies have focused on quantifying the association between outdoor heat and mortality or morbidity among workers. Objective: To quantify the association between occupational heat-related illnesses and exposure to summer outdoor temperatures. Methods: We modeled 259 heat-related illnesses compensated by the Workers' Compensation Board of Quebec between May and September, from 1998 to 2010, with maximum daily summer outdoor temperatures in 16 health regions of Quebec (Canada) using generalized linear models with negative binomial distributions, and estimated the pooled effect sizes for all regions combined, by sex and age groups, and for different time lags with random-effect models for meta-analyses. Results: The mean daily compensation count was 0.13 for all regions of Quebec combined. The relationship between daily counts of compensations and maximum daily temperatures was log-linear; the pooled incidence rate ratio (IRR) of daily heat-related compensations per 1 °C increase in daily maximum temperatures was 1.419 (95% CI 1.326 to 1.520). Associations were similar for men and women and by age groups. Increases in daily maximum temperatures at lags 1 and 2 and for two and three-day lag averages were also associated with increases in daily counts of compensations (IRRs of 1.206 to 1.471 for every 1 °C increase in temperature). Conclusion: This study is the first to quantify the association between occupational heat-related illnesses and exposure to summer temperatures in Canada. The model (risk function) developed in this study could be useful to improve the assessment of future impacts of predicted summer outdoor temperatures on workers and vulnerable groups, particularly in

Multi-boiling Heat Transfer Analysis of a Convective Straight Fin with Temperature-Dependent Thermal Properties and Internal Heat Generation

Directory of Open Access Journals (Sweden)

Gbeminiyi Sobamowo

2017-10-01

Full Text Available In this study, by using the finite volume method, the heat transfer in a convective straight fin with temperature-dependent thermal properties and an internal heat generation under multi-boiling heat transfer modes are analyzed. In this regard, the local heat transfer coefficient is considered to vary within a power-law function of temperature. In the present study, the coexistence of all the boiling modes is taken into consideration. The developed heat transfer models and the corresponding numerical solutions are used to investigate the effects of various thermo-geometric parameters on the thermal performance of the longitudinal rectangular fin. The results shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin and the internal heat generation within the fin. The obtained results can provide a platform for improvements in the design of the fin in the heat transfer equipment.

Heat Capacity of Room-Temperature Ionic Liquids: A Critical Review

Science.gov (United States)

Paulechka, Yauheni U.

2010-09-01

Experimental data on heat capacity of room-temperature ionic liquids in the liquid state were compiled and critically evaluated. The compilation contains data for 102 aprotic ionic liquids from 63 literature references and covers the period of time from 1998 through the end of February 2010. Parameters of correlating equations for temperature dependence of the heat capacities were developed.

The influence of river water temperature annual variation to the moderator heat exchangers heat flux

International Nuclear Information System (INIS)

Nita, I. P.

2015-01-01

The Main Moderator heat exchangers are the most important consumers supplied by Recirculated Cooling Water (RCW) System. In order to determine an appropriate operating configuration of the RCW system it is needed to determine the flowrate required by the Main Moderator consumers, in real time. From operating experience, the required RCW flowrate necessary to be supplied to the main moderator heat exchangers is much lower than design flowrate. In installation, there are no flow elements that could measure especially that flow. However, there are two control valves which regulate the flow to the main moderator heaters; they control the outlet temperature of the moderator to 69"oC. That leads to the requirement of calculating the flowrate function of the outside temperature for all possible temperatures during a calendar year. One considered all possible temperatures during an operating year, and more, going beyond design point, up to 36"oC, temperature that can occur during quick transients after forth RCW pump starting. The calculation was made to verify the capacity of heat exchanger to remove the designed 100 MW(t) in the new condition of reducing moderator temperature outlet from 77 to 69°C. The obtained model was validated using field temperatures and flow measurements and the conclusion was the model can accurately predict how the RCW system operates in all year operation conditions. (authors)

Flue gas heat recovery operating below the dew point and its utilisation for low temperature heating installations

Energy Technology Data Exchange (ETDEWEB)

Wilsdorf, J.

1986-11-01

This paper deals at first with the characteristics of two principal systems for the flue gas heat recovery by reducing the temperature below the dew point. With test results on experimental plants are shown the typical differences between surface and direct contact heat exchange. A second part informs about experiences from the application for low temperature heating installations, especially about thermodynamics condensate quality and technical design. The possible increasing of the efficiency ranges between 10 to 20 per cent.

Temperature dependence of heat sensitization and thermotolerance induction with ethanol

International Nuclear Information System (INIS)

Henle, K.J.; Nagle, W.A.; Moss, A.J.

1987-01-01

Cytoxicity of 1 M ethanol was strongly temperature dependent; survival curves between 34 0 and 39 0 C were similar to heat survival curves between 40 and 45 0 without ethanol. Ethanol was non-toxic at 22 0 ; at 34.5 0 and 35.5 0 ethanol survival curves were biphasic. The major effect of 1 M ethanol was an effective temperature shift of 6.4 Celsius degrees, although temperatures between 34 0 and 36 0 caused additional sensitization reminiscent of the stepdown heating phenomenon. Induction of thermotolerance with equitoxic ethanol exposures at 35.5 0 and 37 0 or with heat alone (10 min, 45 0 ) resulted in tolerance development with similar kinetics; in contrast, ethanol exposures at 22 0 did not induce any tolerance development with similar kinetics; in contrast, ethanol exposures at 22 0 did not induce any tolerance to hyperthermia. These data provide a rationale for conflicting reports in the literature regarding thermotolerance induction by ethanol and suggest that ethanol causes ''heat'' stress at temperatures that are generally considered to be physiological. This interpretation predicts that the use of ethanol and other organic solvents in high concentrations will cause effects at 37 0 that normally occur only at hyperthermic temperatures, including membrane perturbations and HSP synthesis, and that ''physiological'' temperatures must be precisely controlled under those conditions

Heat experiment design to estimate temperature dependent thermal properties

International Nuclear Information System (INIS)

Romanovski, M

2008-01-01

Experimental conditions are studied to optimize transient experiments for estimating temperature dependent thermal conductivity and volumetric heat capacity. A mathematical model of a specimen is the one-dimensional heat equation with boundary conditions of the second kind. Thermal properties are assumed to vary nonlinearly with temperature. Experimental conditions refer to the thermal loading scheme, sampling times and sensor location. A numerical model of experimental configurations is studied to elicit the optimal conditions. The numerical solution of the design problem is formulated on a regularization scheme with a stabilizer minimization without a regularization parameter. An explicit design criterion is used to reveal the optimal sensor location, heating duration and flux magnitude. Results obtained indicate that even the strongly nonlinear experimental design problem admits the aggregation of its solution and has a strictly defined optimal measurement scheme. Additional region of temperature measurements with allowable identification error is revealed.

The effect of heating temperature on cytotoxicity and α-mangostin yield: Mangosteen pericarp juice and mangosteen extract

Science.gov (United States)

Mulia, Kamarza; Hasanah, Fitria; Krisanti, Elsa A.

2018-03-01

The pericarp of mangosteen (Garcinia mangostana L.) contains bioactive xanthones, with α-mangostin being the major component, has been known to possess antitumor, antiviral, and other pharmacological activities. In this study, the effect of elevated temperature during the preparation step of fresh mangosteen pericarp juice and mangosteen extract, on their α-mangostin yield and cytotoxicities was investigated. The cytotoxicity activity of fresh juice and mangosteen extract was investigated using the brine shrimp test. Heating the fresh pericarp mangosteen in water at 65°C for 30 minutes prior to blending produced a juice with higher α-mangostin yield and cytotoxicity compared to the traditional way of blending the juice at room temperature. Increasing α-mangostin yield of 9%-w/w due to heating was also observed when mangosteen extract was heated at 65°C, consistent with the increased cytotoxicity in terms of LC50 value. It is concluded that the effect of temperature on α-mangostin yield was in line with the temperature effect on cytotoxicity activity in all samples of pericarp juice and mangosteen extract in ethyl acetate fraction.

System efficiency for two-step metal oxide solar thermochemical hydrogen production – Part 2: Impact of gas heat recuperation and separation temperatures

KAUST Repository

Ehrhart, Brian D.

2016-09-22

The solar-to-hydrogen (STH) efficiency is calculated for various operating conditions for a two-step metal oxide solar thermochemical hydrogen production cycle using cerium(IV) oxide. An inert sweep gas was considered as the O2 removal method. Gas and solid heat recuperation effectiveness values were varied between 0 and 100% in order to determine the limits of the effect of these parameters. The temperature at which the inert gas is separated from oxygen for an open-loop and recycled system is varied. The hydrogen and water separation temperature was also varied and the effect on STH efficiency quantified. This study shows that gas heat recuperation is critical for high efficiency cycles, especially at conditions that require high steam and inert gas flowrates. A key area for future study is identified to be the development of ceramic heat exchangers for high temperature gas-gas heat exchange. Solid heat recuperation is more important at lower oxidation temperatures that favor temperature-swing redox processing, and the relative impact of this heat recuperation is muted if the heat can be used elsewhere in the system. A high separation temperature for the recycled inert gas has been shown to be beneficial, especially for cases of lower gas heat recuperation and increased inert gas flowrates. A higher water/hydrogen separation temperature is beneficial for most gas heat recuperation effectiveness values, though the overall impact on optimal system efficiency is relatively small for the values considered. © 2016 Hydrogen Energy Publications LLC.

Heat production and body temperature during cooling and rewarming in overweight and lean men.

Science.gov (United States)

Claessens-van Ooijen, Anne M J; Westerterp, Klaas R; Wouters, Loek; Schoffelen, Paul F M; van Steenhoven, Anton A; van Marken Lichtenbelt, Wouter D

2006-11-01

To compare overweight and lean subjects with respect to thermogenesis and physiological insulation in response to mild cold and rewarming. Ten overweight men (mean BMI, 29.2 +/- 2.8 kg/m(2)) and 10 lean men (mean BMI, 21.1 +/- 2.0 kg/m(2)) were exposed to cold air for 1 hour, followed by 1 hour of rewarming. Body composition was determined by hydrodensitometry and deuterium dilution. Heat production and body temperatures were measured continuously by indirect calorimetry and thermistors, respectively. Muscle activity was recorded using electromyography. In both groups, heat production increased significantly during cooling (lean, p = 0.004; overweight, p = 0.006). The increase was larger in the lean group compared with the overweight group (p = 0.04). During rewarming, heat production returned to baseline in the overweight group and stayed higher compared with baseline in the lean group (p = 0.003). The difference in heat production between rewarming and baseline was larger in the lean (p = 0.01) than in the overweight subjects. Weighted body temperature of both groups decreased during cold exposure (lean, p = 0.002; overweight, p < 0.001) and did not return to baseline during rewarming. Overweight subjects showed a blunted mild cold-induced thermogenesis. The insulative cold response was not different among the groups. The energy-efficient response of the overweight subjects can have consequences for energy balance in the long term. The results support the concept of a dynamic heat regulation model instead of temperature regulation around a fixed set point.

Clinical observation on thermophysics in radiofrequency heating

International Nuclear Information System (INIS)

Qi Chao; Li Dingjiu; Guo Baozhong; Shi Yonggang; Yang Daoke

2002-01-01

Objective: To study the physical characters of NRL-001 heating machine. Methods: 151 patients with deep-seated tumors were heated by NRL-001 heating machine in the recent one year. NRL-001 heating machine with two pairs of perpendicular electrodes intercross the two magnetic fields at the center. thermocouples were placed in rectum, ear, esophageal lumen, tumor mass and peritoneal cavity for temperature measurement. The accuracy of the measurement system was evaluated by comparing the rectal mercury thermometer reading with the machine measured value right after the completion of heating. Results: The deviation between the values read by rectal mercury thermometer and the machine was 0.1-0.7 degree C. Intra-tumoral measurement in a patient with lung carcinoma revealed that the temperature within the tumor was 2.0 degree C higher than that in the esophagus. When the peritoneal cavity was heated after perfusion with hot normal saline, the temperature in peritoneal cavity was 0.5 degree C higher than that in the rectum which became even with heating time. Temperature homogeneity was obtained after 50 minutes and abdominal massage was able to shorten this interval. Conclusions: The temperature measurement system of NRL-001 heating machine, having acceptable discrepancies from the mercury thermometer, is reliable. The temperature in the ear, esophagus and rectum can be trusted when treating esophageal or peritoneo-pelvic lesions. Temperature in the esophagus is 2.0 degree C lower than that in lung tumor. Temperature measured in the heated region is about 2.0 degree C higher than that over the whole body. Intra-tumoral temperature measurement is highly recommended if possible. Peritoneo-pelvic heating after peritoneal perfusion is feasible, with the temperature homogeneity obtained as heating time is prolonged, thereby heating time over 120 min is recommended. Temperature measurement is, in fact, necessary for every session of hyperthermia

Recovery Temperature, Transition, and Heat Transfer Measurements at Mach 5

Science.gov (United States)

Brinich, Paul F.

1961-01-01

Schlieren, recovery temperature, and heat-transfer measurements were made on a hollow cylinder and a cone with axes alined parallel to the stream. Both the cone and cylinder were equipped with various bluntnesses, and the tests covered a Reynolds number range up to 20 x 10(exp 6) at a free-stream Mach number of 4.95 and wall to free-stream temperature ratios from 1.8 to 5.2 (adiabatic). A substantial transition delay due to bluntness was found for both the cylinder and the cone. For the present tests (Mach 4.95), transition was delayed by a factor of 3 on the cylinder and about 2 on the cone, these delays being somewhat larger than those observed in earlier tests at Mach 3.1. Heat-transfer tests on the cylinder showed only slight effects of wall temperature level on transition location; this is to be contrasted to the large transition delays observed on conical-type bodies at low surface temperatures at Mach 3.1. The schlieren and the peak-recovery-temperature methods of detecting transition were compared with the heat-transfer results. The comparison showed that the first two methods identified a transition point which occurred just beyond the end of the laminar run as seen in the heat-transfer data.

Thermodynamic analysis into a heat exchanger for absorption at high temperatures

International Nuclear Information System (INIS)

Márquez-Nolasco, A.; Huicochea, A.; Torres-Merino, J.; Siqueiros, J.; Hernández, J.A.

2016-01-01

Highlights: • Energy and exergy analyses for split absorber inside an AHT were developed. • The coefficient of operation for energy and exergy were improved above 30%. • A split absorber can reduce the irreversibility up to 28%. - Abstract: The residual heat or renewable energy can be used to activate a thermodynamic cycle inside a heat transformer by absorption (AHT), in order to obtain heat with a higher temperature in whole equipment. The performance of the AHT is mainly influenced by the absorber, since the useful heat is obtained here at different operating conditions. According to this study, a split absorber can improve the performance of the AHT because of the existing absorption processes in accordance with the first and second law of thermodynamics. The proposal is to divide the heat transfer area in equal sections, where the steam supplied is equal and the strong working solution is increased for all sections, in order to diminish the irreversibility in the absorber. With respect to the basic absorber, the best results are found when the absorber has two sections, because COP can be improved from 0.307 to 0.415, while the ECOP from 0.118 to 0.160, besides the irreversibility can reduce up to almost 28%.

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.

Temperature dependency of the thermal conductivity of porous heat storage media

Science.gov (United States)

Hailemariam, Henok; Wuttke, Frank

2018-04-01

Analyzing the variation of thermal conductivity with temperature is vital in the design and assessment of the efficiency of sensible heat storage systems. In this study, the temperature variation of the thermal conductivity of a commercial cement-based porous heat storage material named - Füllbinder L is analyzed in saturated condition in the temperature range between 20 to 70°C (water based storage) with a steady state thermal conductivity and diffusivity meter. A considerable decrease in the thermal conductivity of the saturated sensible heat storage material upon increase in temperature is obtained, resulting in a significant loss of system efficiency and slower loading/un-loading rates, which when unaccounted for can lead to the under-designing of such systems. Furthermore, a new empirical prediction model for the estimation of thermal conductivity of cement-based porous sensible heat storage materials and naturally occurring crystalline rock formations as a function of temperature is proposed. The results of the model prediction are compared with the experimental results with satisfactory results.

Heat generation and heating limits for the IRUS LLRW disposal facility

International Nuclear Information System (INIS)

Donders, R.E.; Caron, F.

1995-10-01

Heat generation from radioactive decay and chemical degradation must be considered when implementing low-level radioactive waste (LLRW) disposal. This is particularly important when considering the management of spent radioisotope sources. Heating considerations and temperature calculations for the proposed IRUS (Intrusion Resistant Underground Structure) near-surface disposal facility are presented. Heat transfer calculations were performed using a finite element code with realistic but somewhat conservative heat transfer parameters and environmental boundary conditions. The softening-temperature of the bitumen waste-form (38 deg C) was found to be the factor that limits the heat generation rate in the facility. This limits the IRUS heat rate, assuming a uniform source term, to 0.34 W/m 3 . If a reduced general heat-limit is considered, then some higher-heat packages can be accepted with restrictions placed on their location within the facility. For most LLRW, heat generation from radioactive decay and degradation are a small fraction of the IRUS heating limits. However, heating restrictions will impact on the disposal of higher-activity radioactive sources. High activity 60 Co sources will require decay-storage periods of about 70 years, and some 137 Cs will need to bed disposed of in facilities designed for higher-heat waste. (author). 21 refs., 8 tabs., 2 figs

Expieriences On Low-Temperature District Heating In Lystrup – Denmark

DEFF Research Database (Denmark)

Thorsen, Jan Eric; Christiansen, Christian Holm; Brand, Marek

2011-01-01

by implementing Low-temperature district heating systems. Demonstration cases in EnergyFlexHouse and Boligforeningen Ringgården” EUDP 2011. A key challenge for optimum and competitive district heating (DH) system operation is reducing heat loss in networks. Today building regulations in most countries demand...

Experimental Study on Compression/Absorption High-Temperature Hybrid Heat Pump with Natural Refrigerant Mixture

Energy Technology Data Exchange (ETDEWEB)

Kim, Ji Young; Park, Seong Ryong; Baik, Young Jin; Chang, Ki Chang; Ra, Ho Sang; Kim, Min Sung [Korea Institute of Energy Research, Daejeon (Korea, Republic of); Kim, Yong Chan [Korea University, Seoul (Korea, Republic of)

2011-12-15

This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than 90 .deg. C when the heat source and sink temperatures were 50 .deg. C. Experiments with various NH{sub 3}/H{sub 2}O mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific NH{sub 3} concentration.

Sensing disks for slug-type calorimeters have higher temperature stability

Science.gov (United States)

1967-01-01

Graphite sensing disk for slug-type radiation calorimeters exhibits better performance at high temperatures than copper and nickel disks. The graphite is heat-soaked to stabilize its emittance and the thermocouple is protected from the graphite so repeated temperature cycling does not change its sensitivity.

Investigation of ammonia/water hybrid absorption/compression heat pumps for heat supply temperatures above 100 °C

DEFF Research Database (Denmark)

Jensen, Jonas Kjær; Reinholdt, Lars; Markussen, Wiebke Brix

2014-01-01

The hybrid absorption/compression heat pump (HACHP) using ammonia-water as working fluid is a promising technology for development of a high temperature industrial heat pump. This is due to two properties inherent to the use of zeotropic mixtures: non-isothermal phase change and reduced vapour...... using these components. A technically and economically feasible solution is defined as one that satisfies constraints on the coefficient of performance (COP), low and high pressure, compressor discharge temperature and volumetric heat capacity. The ammonia mass fraction of the rich solution...

CARS Temperature Measurements in a Combustion-Heated Supersonic Jet

Science.gov (United States)

Tedder, S. A.; Danehy, P. M.; Magnotti, G.; Cutler, A. D.

2009-01-01

Measurements were made in a combustion-heated supersonic axi-symmetric free jet from a nozzle with a diameter of 6.35 cm using dual-pump Coherent Anti-Stokes Raman Spectroscopy (CARS). The resulting mean and standard deviation temperature maps are presented. The temperature results show that the gas temperature on the centerline remains constant for approximately 5 nozzle diameters. As the heated gas mixes with the ambient air further downstream the mean temperature decreases. The standard deviation map shows evidence of the increase of turbulence in the shear layer as the jet proceeds downstream and mixes with the ambient air. The challenges of collecting data in a harsh environment are discussed along with influences to the data. The yield of the data collected is presented and possible improvements to the yield is presented are discussed.

Effects of temperature on heat pain adaptation and habituation in men and women.

Science.gov (United States)

Hashmi, Javeria A; Davis, Karen D

2010-12-01

We recently reported that women report greater pain adaptation and habituation to moderately painful heat stimuli than men (Hashmi and Davis [16]); but slightly lower temperatures were needed to evoke moderate pain in the women. Hardy et al (1962) and LaMotte (1979) suggested that pain adaptation is most prominent at modest noxious heat temperatures and may occur at temperatures close to pain thresholds. Thus, as a follow-up to our previous study, we examined the role of absolute temperature in pain adaptation and habituation in men and women and assessed whether pain threshold impacts these findings. We hypothesised that pain adaptation and habituation would be more prominent at low and moderate temperatures, and that higher temperatures would induce pain adaptation and habituation in women but not in men. We further hypothesized that pain adaptation would not be correlated with pain thresholds. To test this, we obtained continuous ratings of pain evoked by 44.5-47.5°C stimuli applied to the dorsal foot of men and women. Each run consisted of three 30s stimuli at the same temperature with a 60s inter-stimulus interval. Women showed within-stimulus adaptation of total pain at all temperatures, but men showed significant adaptation to temperatures less than 47°C. There were no sex differences in inter-stimulus habituation and both men and women reported habituation to temperatures less than 46°C. Pain thresholds did not correlate with pain adaptation. These data highlight the temperature-sensitivity and sex differences of pain adaptation and habituation. Copyright © 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

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

Gas Temperature and Radiative Heat Transfer in Oxy-fuel Flames

DEFF Research Database (Denmark)

Bäckström, Daniel; Johansson, Robert; Andersson, Klas

This work presents measurements of the gas temperature, including fluctuations, and its influence on the radiative heat transfer in oxy-fuel flames. The measurements were carried out in the Chalmers 100 kW oxy-fuel test unit. The in-furnace gas temperature was measured by a suction pyrometer...... on the radiative heat transfer shows no effect of turbulence-radiation interaction. However, by comparing with temperature fluctuations in other flames it can be seen that the fluctuations measured here are relatively small. Further research is needed to clarify to which extent the applied methods can account...

Preliminary study on high temperature heat exchanger for nuclear steel making

Energy Technology Data Exchange (ETDEWEB)

Mori, Y [Tokyo Inst. of Tech. (Japan); Ikegami, H

1975-03-01

In the high temperature heat exchanger as well as the steam reformer, several technical problems should be solved before realizing a nuclear plant complex for iron and steel making. Research has been carried out on heat exchanger between helium and steam, hydrogen permeation through super alloys, hydrogen removal using a titanium sponge, and creep and carburization performance of super alloys. The primary coolant used is helium having a pressure of approximately 12 kg/cm/sup 2/G and a temperature of approximately 1100/sup 0/C measured at the inlet of the high temperature heat exchanger, i.e., the test section. Steam, hydrogen and carbon monoxide are used as secondary coolants.

Energetic and Exergetic Analysis of Low and Medium Temperature District Heating Network Integration

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

In this paper, energetic and exergetic approaches were applied to an exemplary low temperature district heating (LTDH) network with supply/return water temperature at 55oC/25 oC. The small LTDH network is annexed to a large medium temperature district heating (MTDH) network. The LTDH network can ...... will reduce the amount of water supply from the MTDH network and improve the system energy conversion efficiency. Through the simulation, the system energetic and exergetic efficiencies based on the two network integration approaches were calculated and evaluated.......In this paper, energetic and exergetic approaches were applied to an exemplary low temperature district heating (LTDH) network with supply/return water temperature at 55oC/25 oC. The small LTDH network is annexed to a large medium temperature district heating (MTDH) network. The LTDH network can...... be supplied through upgrading the return water from the MTDH network with a small centralized heat pump. Alternatively, the supply and return water from the MTDH network can be mixed with a shunt at the junction point to supply the LTDH network. Comparing with the second approach, the heat pump system...

Performance analysis of double organic Rankine cycle for discontinuous low temperature waste heat recovery

International Nuclear Information System (INIS)

Wang Dongxiang; Ling Xiang; Peng Hao

2012-01-01

This research proposes a double organic Rankine cycle for discontinuous waste heat recovery. The optimal operation conditions of several working fluids have been calculated by a procedure employing MATLAB and REFPROP. The influence of outlet temperature of heat source on the net power output, thermal efficiency, power consumption, mass flow rate, expander outlet temperature, cycle irreversibility and exergy efficiency at a given pinch point temperature difference (PPTD) has been analyzed. Pinch point analysis has also been employed to obtain a thermodynamic understanding of the ORC performance. Of all the working fluids investigated, some performances between each working fluid are rather similar. For a fixed low temperature heat source, the optimal operation condition should be mainly determined by the heat carrier of the heat source, and working fluids have limited influence. Lower outlet temperature of heat source does not always mean more efficient energy use. Acetone exhibits the least exergy destruction, while R245fa possesses the maximal exergy efficiency at a fixed PPTD. Wet fluids exhibit lower thermal efficiency than the others with the increasing of PPTD at a fixed outlet temperature of heat source. Dry and isentropic fluids offer attractive performance. - Highlights: ► We propose a double organic Rankine cycle for discontinuous waste heat recovery. ► Performance of organic Rankine cycle (ORC) is analyzed by pinch point analysis. ► The heat carrier of the heat source determines ORC optimal operation condition. ► Design of ORC heat exchangers prefers lower pinch point temperature difference.

Exergy analysis for stationary flow systems with several heat exchange temperatures

Energy Technology Data Exchange (ETDEWEB)

Lampinen, M J; Heikkinen, M A [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Energy Engineering

1995-07-01

A thermodynamic theory of exergy analysis for a stationary flow system having several heat inputs and outputs at different temperature levels is presented. As a new result a relevant reference temperature of the surroundings is derived for each case. Also a general formula which combines exergy analysis with a modified Carnot efficiency is derived. The results are illustrated by numerical examples for mechanical multi-circuit heat pump cycles, for a Brayton process and for an absorption heat pump. (Author)

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

Temperature field distribution of coal seam in heat injection

OpenAIRE

Zhang Zhizhen; Peng Weihong; Shang Xiaoji; Wang Kun; Li Heng; Ma Wenming

2017-01-01

In this article, we present a natural boundary element method (NBEM) to solve the steady heat flow problem with heat sources in a coal seam. The boundary integral equation is derived to obtain the temperature filed distribution of the coal seam under the different injecting conditions.

Thermoeconomic Evaluation of Modular Organic Rankine Cycles for Waste Heat Recovery over a Broad Range of Heat Source Temperatures and Capacities

Directory of Open Access Journals (Sweden)

Markus Preißinger

2017-02-01

Full Text Available Industrial waste heat recovery by means of an Organic Rankine Cycle (ORC can contribute to the reduction of CO2 emissions from industries. Before market penetration, high efficiency modular concepts have to be developed to achieve appropriate economic value for industrial decision makers. This paper aims to investigate modularly designed ORC systems from a thermoeconomic point of view. The main goal is a recommendation for a suitable chemical class of working fluids, preferable ORC design and a range of heat source temperatures and thermal capacities in which modular ORCs can be economically feasible. For this purpose, a thermoeconomic model has been developed which is based on size and complexity parameters of the ORC components. Special emphasis has been laid on the turbine model. The paper reveals that alkylbenzenes lead to higher exergetic efficiencies compared to alkanes and siloxanes. However, based on the thermoeconomic model, the payback periods of the chemical classes are almost identical. With the ORC design, the developed model and the boundary conditions of this study, hexamethyldisiloxane is a suitable working fluid and leads to a payback period of less than 5 years for a heat source temperature of 400 to 600 °C and a mass flow rate of the gaseous waste heat stream of more than 4 kg/s.

Investigation of heat flux processes governing the increase of groundwater temperatures beneath cities

Science.gov (United States)

Bayer, P.; Menberg, K.; Zhu, K.; Blum, P.

2012-12-01

In the subsurface of many cities there are widespread and persistent thermal anomalies. These so-called subsurface urban heat islands (UHIs), which also stimulate warming of urban aquifers, are triggered by various processes. 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 Central European cities, such as Berlin, Cologne (Germany) and Zurich (Switzerland) 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 combination of various heat sources results in an extensive temperature increase. In many cases, the maximum temperature elevation is found close to the city center. Regional groundwater temperature differences between the city center 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 the

Temperature distribution due to the heat generation in nuclear reactor shielding

International Nuclear Information System (INIS)

Torres, L.M.R.

1985-01-01

A study is performed for calculating nuclear heating due to the interaction of neutrons and gamma-rays with matter. Modifications were implemented in the ANISN and DOT 3.5 codes, that solve the transport equation using the discrete ordinate method, in one two-dimensions respectively, to include nuclear heating calculations in these codes. In order to determine the temperature distribution, using the finite difference method, a numerical model was developed for solving the heat conduction equation in one-dimension, in plane, cylindrical and spherical geometries, and in two-dimensions, X-Y and R-Z geometries. Based on these models, computer programs were developed for calculating the temperature distribution. Tests and applications of the implemented modifications were performed in problems of nuclear heating and temperature distribution due to radiation energy deposition in fission and fusion reactor shields. (Author) [pt

The Heat Is On! Using Particle Models to Change Students' Conceptions of Heat and Temperature

Science.gov (United States)

Hitt, Austin Manning; Townsend, J. Scott

2015-01-01

Elementary, middle-level, and high school science teachers commonly find their students have misconceptions about heat and temperature. Unfortunately, student misconceptions are difficult to modify or change and can prevent students from learning the accurate scientific explanation. In order to improve our students' understanding of heat and…

Thermal analysis of heat and power plant with high temperature reactor and intermediate steam cycle

Directory of Open Access Journals (Sweden)

Fic Adam

2015-03-01

Full Text Available Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle, which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle. The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.

Regenerative adsorbent heat pump

Science.gov (United States)

Jones, Jack A. (Inventor)

1991-01-01

A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

Modelling temperature-dependent heat production over decades in High Arctic coal waste rock piles

DEFF Research Database (Denmark)

Hollesen, Jørgen; Elberling, Bo; Jansson, P.E.

2011-01-01

Subsurface heat production from oxidation of pyrite is an important process that may increase subsurface temperatures within coal waste rock piles and increase the release of acid mine drainage, AMD. Waste rock piles in the Arctic are especially vulnerable to changes in subsurface temperatures...... such as heat production from coal oxidation may be equally important....... as the release of AMD normally is limited by permafrost. Here we show that temperatures within a 20 year old heat-producing waste rock pile in Svalbard (78°N) can be modelled by the one-dimensional heat and water flow model (CoupModel) with a new temperature-dependent heat-production module that includes both...

Effects of heat treatment temperature on morphology and properties of opal crystal

International Nuclear Information System (INIS)

Duan Tao; China Academy of Engineering Physics, Mianyang; Peng Tongjiang; Chen Jiming; Tang Yongjian

2008-01-01

The monodispersed SiO 2 microspheres were synthesized by reactant mixed equally. The colloid crystal templates were assemblied by vertical sedimentation method in ethanol at certain temperatures, and the effects of the heat treatment temperature on the morphology and the properties of opal colloid crystals were investigated. SEM, TCr-DSC results indicate SiO 2 colloid templates should be heat treated at 700-800 degree C, enhancing the conglutination and mechanistic intensity of opal templates. UV-Vis analysis result indicates that the heat treatment process can remove the photonic band gap location of the opal colloid crystals, and with the heat treatment temperature increasing gradually, blue shift occurs and the gap narrows. (authors)

Integrated multiscale simulation of combined heat and power based district heating system

International Nuclear Information System (INIS)

Li, Peifeng; Nord, Natasa; Ertesvåg, Ivar Ståle; Ge, Zhihua; Yang, Zhiping; Yang, Yongping

2015-01-01

Highlights: • Simulation of power plant, district heating network and heat users in detail and integrated. • Coupled calculation and analysis of the heat and pressure losses of the district heating network. • District heating is not preferable for very low heat load due to relatively high heat loss. • Lower design supply temperatures of the district heating network give higher system efficiency. - Abstract: Many studies have been carried out separately on combined heat and power and district heating. However, little work has been done considering the heat source, the district heating network and the heat users simultaneously, especially when it comes to the heating system with large-scale combined heat and power plant. For the purpose of energy conservation, it is very important to know well the system performance of the integrated heating system from the very primary fuel input to the terminal heat users. This paper set up a model of 300 MW electric power rated air-cooled combined heat and power plant using Ebsilon software, which was validated according to the design data from the turbine manufacturer. Then, the model of heating network and heat users were developed based on the fundamental theories of fluid mechanics and heat transfer. Finally the combined heat and power based district heating system was obtained and the system performances within multiscale scope of the system were analyzed using the developed Ebsilon model. Topics with regard to the heat loss, the pressure drop, the pump power consumption and the supply temperatures of the district heating network were discussed. Besides, the operational issues of the integrated system were also researched. Several useful conclusions were drawn. It was found that a lower design primary supply temperature of the district heating network would give a higher seasonal energy efficiency of the integrated system throughout the whole heating season. Moreover, it was not always right to relate low design

Heating tar sands formations to visbreaking temperatures

Science.gov (United States)

Karanikas, John Michael [Houston, TX; Colmenares, Tulio Rafael [Houston, TX; Zhang, Etuan [Houston, TX; Marino, Marian [Houston, TX; Roes, Augustinus Wilhelmus Maria [Houston, TX; Ryan, Robert Charles [Houston, TX; Beer, Gary Lee [Houston, TX; Dombrowski, Robert James [Houston, TX; Jaiswal, Namit [Houston, TX

2009-12-22

Methods for treating a tar sands formation are described herein. Methods may include heating at least a section of a hydrocarbon layer in the formation from a plurality of heaters located in the formation. The heat may be controlled so that at least a majority of the section reaches an average temperature of between 200.degree. C. and 240.degree. C., which results in visbreaking of at least some hydrocarbons in the section. At least some visbroken hydrocarbon fluids may be produced from the formation.

Liquid metal heat exchanger for efficient heating of soils and geologic formations

Science.gov (United States)

DeVault, Robert C [Knoxville, TN; Wesolowski, David J [Kingston, TN

2010-02-23

Apparatus for efficient heating of subterranean earth includes a well-casing that has an inner wall and an outer wall. A heater is disposed within the inner wall and is operable within a preselected operating temperature range. A heat transfer metal is disposed within the outer wall and without the inner wall, and is characterized by a melting point temperature lower than the preselected operating temperature range and a boiling point temperature higher than the preselected operating temperature range.

Heat Exchangers for Utilization of the Heat of High-Temperature Geothermal Brines

Science.gov (United States)

Alkhasov, A. B.; Alkhasova, D. A.

2018-03-01

The basic component of two-circuit geothermal systems is the heat exchanger. When used in geothermal power systems, conventional shell-and-tube and plate heat exchangers cause problems related to the cleaning of the latter from salt-deposition and corrosion products. Their lifetime does not exceed, as a rule, 1 year. To utilize the heat of high-temperature geothermal brines, a heat exchanger of the "tube-in-tube" type is proposed. A heat exchanger of this design has been operated for several years in Ternair geothermal steam field; in this heat exchanger, the thermal potential of the saline thermal water is transferred to the fresh water of the secondary circuit of the heating system for apartment houses. The reduction in the weight and size characteristics of the heat exchangers is a topical problem that can be solved with the help of heat transfer enhancers. To enhance the heat transfer process in the heat exchanger, longitudinal ribbing of the heat exchange surface is proposed. The increase in the heat exchange surface from the heat carrier side by ribbing results in an increase in the amount of the heat transferred from the heating agent. The heat exchanger is easy to manufacture and is assembled out of components comprised of two concentrically positioned tubes of a definite length, 3-6 m, serially connected with each other. The method for calculation of the impact of the number and the size of the longitudinal ribs on the heat transfer in the well heat exchanger is presented and a criterion for the selection of the optimal number and design parameters of the ribs is formulated. To prevent the corrosion and salt deposition in the heat exchanger, the use of an effective OEDFK (oxyethylidenediphosphonic acid) agent is proposed. This agent has a long-lasting corrosion-inhibiting and antiscaling effect, which is explained by the formation of a strongly adhesive chelate layer difficult to wash off the surface. The passivating OEDFK layer is restored by periodical

Modeling and simulation of control system response to temperature disturbances in a coupled heat exchangers-AHTR system

International Nuclear Information System (INIS)

Skavdahl, I.; Utgikar, V.P.; Christensen, R.; Sabharwall, P.; Chen, M.; Sun, X.

2016-01-01

Highlights: • Control architecture defined for nuclear reactor-coupled heat exchangers system. • MATLAB code developed for simulation of system response for various temperature disturbances in the system. • Control system effective in maintaining controlled variables at desired set points. • New equilibrium steady state established using controllers. • Adaptive control system capable of switching manipulated variables based on system constraints. - Abstract: An effective control strategy is essential for maintaining optimum operational efficiency of the Advanced High Temperature Reactor (AHTR)-intermediate heat exchanger (IHX)-secondary heat exchanger (SHX) system for power conversion or process heat applications. A control system design is presented in this paper for the control of the coupled intermediate and secondary heat exchangers. The cold side outlet temperature of the SHX (T_c_o) and the hot side outlet temperature of the IHX (T_h_o_2) were identified as the controlled variables that were maintained at their set points by manipulating the flow rates of heat exchange media. Transfer functions describing the relationships between the controlled variables and the manipulated and load variables were developed and the system response to various temperature disturbances was simulated using a custom-developed MATLAB program. It was found that a step disturbance of ±10 °C in the process loop changed the thermal duty by ±650 kW, equal to 6.5% of the initial duty. Similar disturbances in the primary loop had a higher impact on the system. The control system design included a provision for the switching of manipulated variables to limit the adjustment in the magnitudes of the primary manipulated variables. Simulation results indicate that the controlled variables are maintained successfully at their desired points by the control system.

Modeling and simulation of control system response to temperature disturbances in a coupled heat exchangers-AHTR system

Energy Technology Data Exchange (ETDEWEB)

Skavdahl, I. [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Utgikar, V.P., E-mail: vutgikar@uidaho.edu [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Christensen, R. [Nuclear Engineering Program, University of Idaho, Idaho Falls, ID 83402 (United States); Sabharwall, P. [Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Chen, M.; Sun, X. [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States)

2016-04-15

Highlights: • Control architecture defined for nuclear reactor-coupled heat exchangers system. • MATLAB code developed for simulation of system response for various temperature disturbances in the system. • Control system effective in maintaining controlled variables at desired set points. • New equilibrium steady state established using controllers. • Adaptive control system capable of switching manipulated variables based on system constraints. - Abstract: An effective control strategy is essential for maintaining optimum operational efficiency of the Advanced High Temperature Reactor (AHTR)-intermediate heat exchanger (IHX)-secondary heat exchanger (SHX) system for power conversion or process heat applications. A control system design is presented in this paper for the control of the coupled intermediate and secondary heat exchangers. The cold side outlet temperature of the SHX (T{sub co}) and the hot side outlet temperature of the IHX (T{sub ho2}) were identified as the controlled variables that were maintained at their set points by manipulating the flow rates of heat exchange media. Transfer functions describing the relationships between the controlled variables and the manipulated and load variables were developed and the system response to various temperature disturbances was simulated using a custom-developed MATLAB program. It was found that a step disturbance of ±10 °C in the process loop changed the thermal duty by ±650 kW, equal to 6.5% of the initial duty. Similar disturbances in the primary loop had a higher impact on the system. The control system design included a provision for the switching of manipulated variables to limit the adjustment in the magnitudes of the primary manipulated variables. Simulation results indicate that the controlled variables are maintained successfully at their desired points by the control system.

Influence of heating temperature on bainite transformation proceeding in chromium-nickel-molybdenum steels

International Nuclear Information System (INIS)

Kaletin, Yu.M.; Kaletin, A.Yu.

1983-01-01

The purpose of the present paper is to investigate the effect of heating and cooling from austenization temperature on development of bainite transformation in 37KhN3MFA and 18Kh2N4MA structural alloyed steels. The metallographical analysis of specimens has revealed that first crystals of bainite under slow heating up to 770-790 deg C appear at the temperature of about 500 deg C and at 475 deg C there has been much bainite over the whole cross section of the specimen. It is revealed that an increase of heating temperature and cooling rate replace the starting point of bainite transformation upwards. The strongest displacement of the point Bsub(S) into hogh-temperature range takes place after heating steel with the initial bainite structure in intercritical temperature range

Integrated heat transport simulation of high ion temperature plasma of LHD

International Nuclear Information System (INIS)

Murakami, S.; Yamaguchi, H.; Sakai, A.

2014-10-01

A first dynamical simulation of high ion temperature plasma with carbon pellet injection of LHD is performed by the integrated simulation GNET-TD + TASK3D. NBI heating deposition of time evolving plasma is evaluated by the 5D drift kinetic equation solver, GNET-TD and the heat transport of multi-ion species plasma (e, H, He, C) is studied by the integrated transport simulation code, TASK3D. Achievement of high ion temperature plasma is attributed to the 1) increase of heating power per ion due to the temporal increase of effective charge, 2) reduction of effective neoclassical transport with impurities, 3) reduction of turbulence transport. The reduction of turbulence transport is most significant contribution to achieve the high ion temperature and the reduction of the turbulent transport from the L-mode plasma (normal hydrogen plasma) is evaluated to be a factor about five by using integrated heat transport simulation code. Applying the Z effective dependent turbulent reduction model we obtain a similar time behavior of ion temperature after the C pellet injection with the experimental results. (author)

Heat transfer study on convective–radiative semi-spherical fins with temperature-dependent properties and heat generation using efficient computational methods

International Nuclear Information System (INIS)

Atouei, S.A.; Hosseinzadeh, Kh.; Hatami, M.; Ghasemi, Seiyed E.; Sahebi, S.A.R.; Ganji, D.D.

2015-01-01

In this study, heat transfer and temperature distribution equations for semi-spherical convective–radiative porous fins are presented. Temperature-dependent heat generation, convection and radiation effects are considered and after deriving the governing equation, Least Square Method (LSM), Collocation Method (CM) and fourth order Runge-Kutta method (NUM) are applied for predicting the temperature distribution in the described fins. Results reveal that LSM has excellent agreement with numerical method, so can be suitable analytical method for solving the problem. Also, the effect of some physical parameters which are appeared in the mathematical formulation on fin surface temperature is investigated to show the effect of radiation and heat generation in a solid fin temperature. - Highlights: • Thermal analysis of a semi-spherical fin is investigated. • Collocation and Least Square Methods are applied on the problem. • Convection, radiation and heat generation is considered. • Physical results are compared to numerical outcomes.

Effect of Heat Flux on the Specimen Temperature of an LBE Capsule

International Nuclear Information System (INIS)

Kang, Y. H.; Park, S. J.; Cho, M. S.; Choo, K. N.; Lee, Y. S.

2011-01-01

For application of high-temperature irradiation tests in the HANARO reactor for Gen IV reactor material development, a number of newly designed LBE capsules have been investigated at KAERI since 2008. Recent study on heat transfer experiment of an LBE capsule with a single heater has shown that the specimen temperature of the mock-up increased linearly with an increase of heat input. The work highlighted only the heat transfer capability of an LBE capsule with a single heater as a simulated specimen in a liquid metal medium. Hence, a new LBE capsule with multi specimen sets has been designed and fabricated for the heat transfer experiment of an LBE capsule of 11M-01K. In this paper, a series of thermal analyses and heat transfer experiments for a newly designed LBE capsule was implemented to study the effect of an increase in the value of heat input and its influence on temperature distribution in the capsule mock-up

Simulation and experimental study of solar-absorption heat transformer integrating with two-stage high temperature vapor compression heat pump

Directory of Open Access Journals (Sweden)

Nattaporn Chaiyat

2014-11-01

Full Text Available In this study, simulation and experiment studies of a 10 kW solar H2O–LiBr absorption heat transformer (AHT integrating with a two-stage vapor compression heat pump (VCHP were carried out. The whole system was named as compression/absorption heat transformer (CAHT. The VCHP was used to recover rejected heat at the AHT condenser which was transferred back to the AHT evaporator at a higher temperature. The AHT unit took solar heat from a set of flat-plate solar collectors in parallel connection. R-134a and R-123 were refrigerants in the VCHP cycle. From the simulation, the total cycle coefficient (COP of the solar-CAHT was 0.71 compared with 0.49 of the normal solar-AHT. From the experiment, the total cycle COPs of the solar-CAHT and the solar-AHT were 0.62 and 0.39, respectively. The experimental results were lower than those of the simulated models due to the oversize of the experimental compressor. The annual expense of the solar-CAHT was found to be 5113 USD which was lower than 5418 USD of the solar-AHT. So it could be concluded that the modified unit was beneficial than the normal unit in terms of energy efficiency and economic expense.

Identifying the optimal supply temperature in district heating networks - A modelling approach

DEFF Research Database (Denmark)

Mohammadi, Soma; Bojesen, Carsten

2014-01-01

of this study is to develop a model for thermo-hydraulic calculation of low temperature DH system. The modelling is performed with emphasis on transient heat transfer in pipe networks. The pseudo-dynamic approach is adopted to model the District Heating Network [DHN] behaviour which estimates the temperature...... dynamically while the flow and pressure are calculated on the basis of steady state conditions. The implicit finite element method is applied to simulate the transient temperature behaviour in the network. Pipe network heat losses, pressure drop in the network and return temperature to the plant...... are calculated in the developed model. The model will serve eventually as a basis to find out the optimal supply temperature in an existing DHN in later work. The modelling results are used as decision support for existing DHN; proposing possible modifications to operate at optimal supply temperature....

Temperature ranges of the application of air-to-air heat recovery ventilator in supermarkets in winter, China

Energy Technology Data Exchange (ETDEWEB)

Kang, Yanming; Wang, Youjun; Zhong, Ke [School of Environmental Science and Engineering, Donghua University, Shanghai 201620 (China); Liu, Jiaping [School of Architecture, Xi' an University of Architecture and Technology, Xi' an 710055 (China)

2010-12-15

Energy consumption is an important issue in China. In heating, ventilation and air conditioning (HVAC) systems, more and more commercial buildings use air-to-air heat recovery ventilators as energy saving units for recovering heat from the exhaust air in ventilation systems in current years. In the present paper, critical temperatures of air-to-air heat recovery systems for supermarkets in winter are recommended and discussed for the four cities in different climate zones of China. The analysis shows that the temperature of fresh air in winter can be categorized into three regions, i.e., recovery region, transition region and impermissible recovery region. The results also indicate that the latent heat recovery is not suitable for ventilation energy savings in supermarkets in winter. Meanwhile, the applicability of sensible heat recovery in supermarkets depends on outdoor climate and fresh air flow rate. If a variable rotational speed fan is used to introduce fresh air into the building, heat recovery does always function as planned in winter for all the selected cities except Guangzhou, and most values of the COP are much higher than 2.5. Otherwise, there is the risk of negative impact on building energy savings in all cities except Harbin. (author)

Mathematical Simulation of Temperature Profiles within Microwave Heated Wood Made for Wood-Based Nano composites

International Nuclear Information System (INIS)

Li, X.; He, X.; Lv, J.; Wu, Y.; Luo, Y.; Chen, H.

2013-01-01

High intensive microwave pretreatment is a new method to modify wood for the fabrication of wood-based nano composites. Based on the physical law on heat transfer, a mathematical model to describe the temperature profiles within wood heated by high intensive microwave was established and simulated in this research. The results showed that the temperature profiles within wood were related to microwave heating methods; The temperature inside wood firstly increased and then gradually decreased along the direction of microwave transmission when the unilateral microwave heating was applied, and the temperature difference along the thickness direction of wood was very significant; The temperature with wood firstly increased and then gradually decreased from the wood surface to interior when the bilateral microwave heating was applied. Compared with the unilateral microwave heating, bilateral microwave heating is a better microwave heating method for the more uniform wood microwave pretreatment.

Numerical investigation of heat transfer in high-temperature gas-cooled reactors

Energy Technology Data Exchange (ETDEWEB)

Chen, g.; Anghaie, S. [Univ. of Florida, Gainesville, FL (United States)

1995-09-01

This paper proposes a computational model for analysis of flow and heat transfer in high-temperature gas-cooled reactors. The formulation of the problem is based on using the axisymmetric, thin layer Navier-Stokes equations. A hybrid implicit-explicit method based on finite volume approach is used to numerically solve the governing equations. A fast converging scheme is developed to accelerate the Gauss-Siedel iterative method for problems involving the wall heat flux boundary condition. Several cases are simulated and results of temperature and pressure distribution in the core are presented. Results of a parametric analysis for the assessment of the impact of power density on the convective heat transfer rate and wall temperature are discussed. A comparative analysis is conducted to identify the Nusselt number correlation that best fits the physical conditions of the high-temperature gas-cooled reactors.

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.

Very High Temperature Test of Alloy617 Compact Heat Exchanger in Helium Experimental Loop

Energy Technology Data Exchange (ETDEWEB)

Kim, Chan Soo; Park, Byung-Ha; Kim, Eung-Seon [KAERI, Daejeon (Korea, Republic of)

2016-05-15

The Intermediate Heat eXchanger (IHX) is a key-challenged high temperature component which determines the efficiency and the economy of VHTR system. Heat generated in the VHTR fuel block is transferred from the VHTR to the intermediate loop through IHX. In the present, the shell-helical tube heat exchanger is generally used as IHX of the helium cooled reactor. Recently, a Printed Circuit Heat Exchanger (PCHE) is one of the candidates for the IHX in a VHTR because its operation temperature and pressure are larger than any other compact heat exchanger types. These test results show that there is no problem in operation of HELP at the very high temperature experimental condition and the alloy617 compact heat exchanger can be operated in the very high temperature condition above 850℃. In the future, the high temperature structural analysis will be studied to estimate the thermal stress during transient and thermal shock condition. The conditions and evaluation standard for the alloy 617 diffusion bonding will be minutely studied to fabricate the large-scale PCHE for the high temperature condition.

Improvement of high temperature fatigue lifetime in AZ91 magnesium alloy by heat treatment

International Nuclear Information System (INIS)

Mokhtarishirazabad, Mehdi; Azadi, Mohammad; Hossein Farrahi, Gholam; Winter, Gerhard; Eichlseder, Wilfred

2013-01-01

In the present paper, an improvement in high temperature fatigue properties of the AZ91 magnesium alloy with rare earth elements has been obtained by a typical heat treatment, denoted by T6. For this objective, out-of-phase thermo-mechanical fatigue, room temperature and high temperature low cycle fatigue tests are performed to compare lifetimes. Several rare earth elements are initially added to the AZ91 alloy during a gravity casting process in permanent molds. Also, the type of the heat treatment is examined. Results of specimens with only the solution (the T4 heat treatment) and the solution with the ageing process (the T6 heat treatment) are compared under isothermal fatigue loadings. Microstructural investigations are carried out, before and after fatigue experiments to demonstrate the heat treatment effect. Results showed that both low cycle fatigue and thermo-mechanical fatigue of the alloy at high temperatures increases tremendously after the T6 heat treatment. This behavior attributes to the variation of the ductility, which was a result of microstructural changes during the heat treatment and the varying temperature in fatigue tests

Improvement of high temperature fatigue lifetime in AZ91 magnesium alloy by heat treatment

Energy Technology Data Exchange (ETDEWEB)

Mokhtarishirazabad, Mehdi [School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Azadi, Mohammad, E-mail: m_azadi@ip-co.com [Fatigue and Wear Workgroup, Irankhodro Powertrain Company (IPCO), Tehran (Iran, Islamic Republic of); Hossein Farrahi, Gholam [School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Winter, Gerhard; Eichlseder, Wilfred [Chair of Mechanical Engineering, University of Leoben, Leoben (Austria)

2013-12-20

In the present paper, an improvement in high temperature fatigue properties of the AZ91 magnesium alloy with rare earth elements has been obtained by a typical heat treatment, denoted by T6. For this objective, out-of-phase thermo-mechanical fatigue, room temperature and high temperature low cycle fatigue tests are performed to compare lifetimes. Several rare earth elements are initially added to the AZ91 alloy during a gravity casting process in permanent molds. Also, the type of the heat treatment is examined. Results of specimens with only the solution (the T4 heat treatment) and the solution with the ageing process (the T6 heat treatment) are compared under isothermal fatigue loadings. Microstructural investigations are carried out, before and after fatigue experiments to demonstrate the heat treatment effect. Results showed that both low cycle fatigue and thermo-mechanical fatigue of the alloy at high temperatures increases tremendously after the T6 heat treatment. This behavior attributes to the variation of the ductility, which was a result of microstructural changes during the heat treatment and the varying temperature in fatigue tests.

Heat exchangers for high-temperature thermodynamic cycles

International Nuclear Information System (INIS)

Fraas, A.P.

1975-01-01

The special requirements of heat exchangers for high temperature thermodynamic cycles are outlined and discussed with particular emphasis on cost and thermal stress problems. Typical approaches that have been taken to a comprehensive solution intended to meet all of the many boundary conditions are then considered by examining seven typical designs including liquid-to-liquid heat exchangers for nuclear plants, a heater for a closed cycle gas turbine coupled to a fluidized bed coal combustion chamber, steam generators for nuclear plants, a fossil fuel-fired potassium boiler, and a potassium condenser-steam generator. (auth)

High temperature heat pipe experiments in low earth orbit

International Nuclear Information System (INIS)

Woloshun, K.; Merrigan, M.A.; Sena, J.T.; Critchley, E.

1993-01-01

Although high temperature, liquid metal heat pipe radiators have become a standard component on most high power space power system designs, there is no experimental data on the operation of these heat pipes in a zero gravity or micro-gravity environment. Experiments to benchmark the transient and steady state performance of prototypical heat pipe space radiator elements are in preparation for testing in low earth orbit. It is anticipated that these heat pipes will be tested aborad the Space Shuttle in 1995. Three heat pipes will be tested in a cargo bay Get Away Special (GAS) canister. The heat pipes are SST/potassium, each with a different wick structure; homogeneous, arterial, and annular gap, the heat pipes have been designed, fabricated, and ground tested. In this paper, the heat pipe designs are specified, and transient and steady-state ground test data are presented

Effect of foam on temperature prediction and heat recovery potential from biological wastewater treatment.

Science.gov (United States)

Corbala-Robles, L; Volcke, E I P; Samijn, A; Ronsse, F; Pieters, J G

2016-05-15

Heat is an important resource in wastewater treatment plants (WWTPs) which can be recovered. A prerequisite to determine the theoretical heat recovery potential is an accurate heat balance model for temperature prediction. The insulating effect of foam present on the basin surface and its influence on temperature prediction were assessed in this study. Experiments were carried out to characterize the foam layer and its insulating properties. A refined dynamic temperature prediction model, taking into account the effect of foam, was set up. Simulation studies for a WWTP treating highly concentrated (manure) wastewater revealed that the foam layer had a significant effect on temperature prediction (3.8 ± 0.7 K over the year) and thus on the theoretical heat recovery potential (30% reduction when foam is not considered). Seasonal effects on the individual heat losses and heat gains were assessed. Additionally, the effects of the critical basin temperature above which heat is recovered, foam thickness, surface evaporation rate reduction and the non-absorbed solar radiation on the theoretical heat recovery potential were evaluated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Improving thermal performance of an existing UK district heat network: a case for temperature optimization

DEFF Research Database (Denmark)

Tunzi, Michele; Boukhanouf, Rabah; Li, Hongwei

2018-01-01

This paper presents results of a research study into improving energy performance of small-scale district heat network through water supply and return temperature optimization technique. The case study involves establishing the baseline heat demand of the estate’s buildings, benchmarking...... the existing heat network operating parameters, and defining the optimum supply and return temperature. A stepwise temperature optimization technique of plate radiators heat emitters was applied to control the buildings indoor thermal comfort using night set back temperature strategy of 21/18 °C....... It was established that the heat network return temperature could be lowered from the current measured average of 55 °C to 35.6 °C, resulting in overall reduction of heat distribution losses and fuel consumption of 10% and 9% respectively. Hence, the study demonstrates the potential of operating existing heat...

Pulmonary artery and intestinal temperatures during heat stress and cooling

DEFF Research Database (Denmark)

Pearson, James; Ganio, Matthew S; Seifert, Thomas

2012-01-01

In humans, whole body heating and cooling are used to address physiological questions where core temperature is central to the investigated hypotheses. Core temperature can be measured in various locations throughout the human body. The measurement of intestinal temperature is increasingly used...

Energy balance of droplets impinging onto a wall heated above the Leidenfrost temperature

International Nuclear Information System (INIS)

Dunand, P.; Castanet, G.; Gradeck, M.; Maillet, D.; Lemoine, F.

2013-01-01

Highlights: • Measurement techniques are combined to characterize the heat lost due to liquid vaporization. • The wall heat flux is estimated by infrared thermography associated with inverse heat conduction. • The liquid heating is characterized by the two-color Laser-Induced Fluorescence thermometry. • Results reveal how the heat fluxes vary with the droplet sizes and the Weber number. -- Abstract: This work is an experimental study aiming at characterizing the heat transfers induced by the impingement of water droplets (diameter 80–180 μm) on a thin nickel plate heated by electromagnetic induction. The temperature of the rear face of the nickel sample is measured by means of an infrared camera and the heat removed from the wall due to the presence of the droplets is estimated using a semi-analytical inverse heat conduction model. In parallel, the temperature of the droplets is measured using the two-color Laser-Induced Fluorescence thermometry (2cLIF) which has been extended to imagery for the purpose of these experiments. The measurements of the variation in the droplet temperature occurring during an impact allow determining the sensible heat removed by the liquid. Measurements are performed at wall conditions well above the Leidenfrost temperature. Different values of the Weber numbers corresponding to the bouncing and splashing regimes are tested. Comparisons between the heat flux removed from the wall and the sensible heat gained by the liquid allows estimating the heat flux related to liquid evaporation. Results reveal that the respective level of the droplet sensible heat and the heat lost due to liquid vaporization can vary significantly with the droplet sizes and the Weber number

Heat transfer analysis of underground U-type heat exchanger of ground source heat pump system.

Science.gov (United States)

Pei, Guihong; Zhang, Liyin

2016-01-01

Ground source heat pumps is a building energy conservation technique. The underground buried pipe heat exchanging system of a ground source heat pump (GSHP) is the basis for the normal operation of an entire heat pump system. Computational-fluid-dynamics (CFD) numerical simulation software, ANSYS-FLUENT17.0 have been performed the calculations under the working conditions of a continuous and intermittent operation over 7 days on a GSHP with a single-well, single-U and double-U heat exchanger and the impact of single-U and double-U buried heat pipes on the surrounding rock-soil temperature field and the impact of intermittent operation and continuous operation on the outlet water temperature. The influence on the rock-soil temperature is approximately 13 % higher for the double-U heat exchanger than that of the single-U heat exchanger. The extracted energy of the intermittent operation is 36.44 kw·h higher than that of the continuous mode, although the running time is lower than that of continuous mode, over the course of 7 days. The thermal interference loss and quantity of heat exchanged for unit well depths at steady-state condition of 2.5 De, 3 De, 4 De, 4.5 De, 5 De, 5.5 De and 6 De of sidetube spacing are detailed in this work. The simulation results of seven working conditions are compared. It is recommended that the side-tube spacing of double-U underground pipes shall be greater than or equal to five times of outer diameter (borehole diameter: 180 mm).

Maximum Efficiency of Thermoelectric Heat Conversion in High-Temperature Power Devices

Directory of Open Access Journals (Sweden)

V. I. Khvesyuk

2016-01-01

Full Text Available Modern trends in development of aircraft engineering go with development of vehicles of the fifth generation. The features of aircrafts of the fifth generation are motivation to use new high-performance systems of onboard power supply. The operating temperature of the outer walls of engines is of 800–1000 K. This corresponds to radiation heat flux of 10 kW/m2 . The thermal energy including radiation of the engine wall may potentially be converted into electricity. The main objective of this paper is to analyze if it is possible to use a high efficiency thermoelectric conversion of heat into electricity. The paper considers issues such as working processes, choice of materials, and optimization of thermoelectric conversion. It presents the analysis results of operating conditions of thermoelectric generator (TEG used in advanced hightemperature power devices. A high-temperature heat source is a favorable factor for the thermoelectric conversion of heat. It is shown that for existing thermoelectric materials a theoretical conversion efficiency can reach the level of 15–20% at temperatures up to 1500 K and available values of Ioffe parameter being ZT = 2–3 (Z is figure of merit, T is temperature. To ensure temperature regime and high efficiency thermoelectric conversion simultaneously it is necessary to have a certain match between TEG power, temperature of hot and cold surfaces, and heat transfer coefficient of the cooling system. The paper discusses a concept of radiation absorber on the TEG hot surface. The analysis has demonstrated a number of potentialities for highly efficient conversion through using the TEG in high-temperature power devices. This work has been implemented under support of the Ministry of Education and Science of the Russian Federation; project No. 1145 (the programme “Organization of Research Engineering Activities”.

Experimental demonstration of a tailored-width microchannel heat exchanger configuration for uniform wall temperature

International Nuclear Information System (INIS)

Riera, S; Barrau, J; Rosell, J I; Omri, M; Fréchette, L G

2013-01-01

In this work, an experimental study of a novel microfabricated heat sink configuration that tends to uniform the wall temperature, even with increasing flow temperature, is presented. The design consists of a series of microchannel sections with stepwise varying width. This scheme counteracts the flow temperature increase by reducing the local thermal resistance along the flow path. A test apparatus with uniform heat flux and distributed wall temperature measurements was developed for microchannel heat exchanger characterisation. The energy balance is checked and the temperature distribution is analysed for each test. The results show that the wall temperature decreases slightly along the flow path while the fluid temperature increases, highlighting the strong impact of this approach. For a flow rate of 16 ml/s, the mean thermal resistance of the heat sink is 2,35·10 −5 m 2 ·K/W which enhances the results compared to the millimeter scale channels nearly three-fold. For the same flow rate and a heat flux of 50 W/cm 2 , the temperature uniformity, expressed as the standard deviation of the wall temperature, is around 6 °C

Modeling of Heating During Food Processing

Science.gov (United States)

Zheleva, Ivanka; Kamburova, Veselka

Heat transfer processes are important for almost all aspects of food preparation and play a key role in determining food safety. Whether it is cooking, baking, boiling, frying, grilling, blanching, drying, sterilizing, or freezing, heat transfer is part of the processing of almost every food. Heat transfer is a dynamic process in which thermal energy is transferred from one body with higher temperature to another body with lower temperature. Temperature difference between the source of heat and the receiver of heat is the driving force in heat transfer.

Heat stress in urban areas. Indoor and outdoor temperatures in different urban structure types and subjectively reported well-being during a heat wave in the city of Leipzig

Energy Technology Data Exchange (ETDEWEB)

Franck, Ulrich; Roeder, Stefan; Schlink, Uwe [Helmholtz Centre for Environmental Research - UFZ, Leipzig (Germany). Core Facility Studies; Krueger, Michael [Leipzig Univ. (Germany). Inst. of Geography; Schwarz, Nina [Helmholtz Centre for Environmental Research - UFZ, Leipzig (Germany). Dept. of Computational Landscape Ecology; Grossmann, Katrin [Helmholtz Centre for Environmental Research - UFZ, Leipzig (Germany). Dept. of Urban and Environmental Sociology

2013-04-15

Climate projections for Leipzig suggest elevated minimum and maximum temperatures as well as more frequent days with high temperatures. Hence, climate change is threatening human well-being and health. People spend the majority of their time indoors. Therefore, indoor temperatures (especially during the night) are of special importance with respect to well-being and health. Indoor air temperature depends on outdoor air temperatures, but is for example modified by type of urban structure, housing area, and may be also influenced by differences in the behavior of the inhabitants. Especially in cities, outdoor air temperatures depend on urban structure e.g. housing density, building arrangement, unpaved areas, types of urban structures, urban green, and other factors. Hence, the questions arise how types of urban structures are related to inner-urban temperature differences and how outdoor air temperatures influence indoor temperatures in dependence on urban housing conditions. This work is a part of a pilot study conducted during the summer 2010 which gathered data from remote sensing, mobile measurements, stationary measurements of air temperatures and relative humidity in areas with different housing structures, and of indoor as well as outdoor temperatures in occupied apartments. Household-survey data reported the subjective perception of heat stress. The study resulted in rather complex relationships between type of housing areas, indoor and outdoor temperatures, morning and evening temperatures, indoor and outdoor temperatures as well as subjective heat perception. Green spaces and types of residential areas are related to air temperatures. More green resulted in lower temperatures. Temperatures have a tendency to increase with increasing story number and are significantly higher in the top floor. An indoor heat island effect corresponding to the outdoor effect could be shown for the homes: Distance to city center is a predicting variable for both outdoor and

Heat stress in urban areas: Indoor and outdoor temperatures in different urban structure types and subjectively reported well-being during a heat wave in the city of Leipzig

Directory of Open Access Journals (Sweden)

Ulrich Franck

2013-04-01

Full Text Available Climate projections for Leipzig suggest elevated minimum and maximum temperatures as well as more frequent days with high temperatures. Hence, climate change is threatening human well-being and health. People spend the majority of their time indoors. Therefore, indoor temperatures (especially during the night are of special importance with respect to well-being and health. Indoor air temperature depends on outdoor air temperatures, but is for example modified by type of urban structure, housing area, and may be also influenced by differences in the behavior of the inhabitants. Especially in cities, outdoor air temperatures depend on urban structure e.g. housing density, building arrangement, unpaved areas, types of urban structures, urban green, and other factors. Hence, the questions arise how types of urban structures are related to inner-urban temperature differences and how outdoor air temperatures influence indoor temperatures in dependence on urban housing conditions. This work is a part of a pilot study conducted during the summer 2010 which gathered data from remote sensing, mobile measurements, stationary measurements of air temperatures and relative humidity in areas with different housing structures, and of indoor as well as outdoor temperatures in occupied apartments. Household-survey data reported the subjective perception of heat stress. The study resulted in rather complex relationships between type of housing areas, indoor and outdoor temperatures, morning and evening temperatures, indoor and outdoor temperatures as well as subjective heat perception. Green spaces and types of residential areas are related to air temperatures. More green resulted in lower temperatures. Temperatures have a tendency to increase with increasing story number and are significantly higher in the top floor. An indoor heat island effect corresponding to the outdoor effect could be shown for the homes: Distance to city center is a predicting variable for

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

Numerical Simulation of Pulsation Flow in the Vapour Channel of Short Low Temperature Heat Pipes at High Heat Loads

Science.gov (United States)

Seryakov, A. V.; Konkin, A. V.

2017-11-01

The results of the numerical simulation of pulsations in the Laval-liked vapour channel of short low-temperature range heat pipes (HPs) are presented. The numerical results confirmed the experimentally obtained increase of the frequency of pulsations in the vapour channel of short HPs with increasing overheat of the porous evaporator relative to the boiling point of the working fluid. The occurrence of pressure pulsations inside the vapour channel in a short HPs is a complex phenomenon associated with the boiling beginning in the capillary-porous evaporator at high heat loads, and appearance the excess amount of vapour above it, leading to the increase in pressure P to a value at which the boiling point TB of the working fluid becomes higher than the evaporator temperature Tev. Vapour clot spreads through the vapour channel and condense, and then a rarefaction wave return from condenser in the evaporator, the boiling in which is resumed and the next cycle of the pulsations is repeated. Numerical simulation was performed using finite element method implemented in the commercial program ANSYS Multiphisics 14.5 in the two-dimensional setting of axis symmetric moist vapour flow with third kind boundary conditions.

Novel immobilization process of a thermophilic catalase: efficient purification by heat treatment and subsequent immobilization at high temperature.

Science.gov (United States)

Xu, Juan; Luo, Hui; López, Claudia; Xiao, Jing; Chang, Yanhong

2015-10-01

The main goal of the present work is to investigate a novel process of purification and immobilization of a thermophilic catalase at high temperatures. The catalase, originated from Bacillus sp., was overexpressed in a recombinant Escherichia coli BL21(DE3)/pET28-CATHis and efficiently purified by heat treatment, achieving a threefold purification. The purified catalase was then immobilized onto an epoxy support at different temperatures (25, 40, and 55 °C). The immobilizate obtained at higher temperatures reached its maximum activity in a shorter time than that obtained at lower temperatures. Furthermore, immobilization at higher temperatures required a lower ionic strength than immobilization at lower temperatures. The characteristics of immobilized enzymes prepared at different temperatures were investigated. The high-temperature immobilizate (55 °C) showed the highest thermal stability, followed by the 40 °C immobilizate. And the high-temperature immobilizate (55 °C) had slightly higher operational stability than the 25 °C immobilizate. All of the immobilized catalase preparations showed higher stability than the free enzyme at alkaline pH 10.0, while the alkali resistance of the 25 °C immobilizate was slightly better than that of the 40 and 55 °C immobilizates.

Renewable-based low-temperature district heating for existing buildings in various stages of refurbishment

DEFF Research Database (Denmark)

Brand, Marek; Svendsen, Svend

2013-01-01

Denmark is aiming for a fossil-free heating sector for buildings by 2035. Judging by the national heating plan, this will be achieved mainly by a further spread of DH (district heating) based on the renewable heat sources. To make the most cost-effective use of these sources, the DH supply...... and, for 98% of the year, to below 60 °C. However for the temperatures below 60 °C a low-temperature DH substation is required for DHW (domestic hot water) heating. This research shows that renewable sources of heat can be integrated into the DH system without problems and contribute to the fossil...... temperature should be as low as possible. We used IDA–ICE software to simulate a typical Danish single-family house from the 1970s connected to DH at three different stages of envelope and space heating system refurbishment. We wanted to investigate how low the DH supply temperature can be without reducing...

Numerical simulation of seasonal heat storage in a contaminated shallow aquifer - Temperature influence on flow, transport and reaction processes

Science.gov (United States)

Popp, Steffi; Beyer, Christof; Dahmke, Andreas; Bauer, Sebastian

2015-04-01

taken into account for the numerical simulations. Hence, the simulations are performed with the code OpenGeoSys, which is especially suited for simulating coupled thermal, hydraulic and geochemical processes. The scenario simulations show an increase in the source zone emission of TCE at higher temperatures, which is primarily due to the focusing of the groundwater flow in the area of higher temperatures within the source zone and to a lesser part to an increase in TCE solubility. On the other hand, a widening of the contaminant plume and enlargement of the area for TCE biodegradation is induced, which leads to an increase in biodegradation of the chlorinated hydrocarbons. In combination almost no change in the overall ratio of degraded to emitted TCE is found, which shows that the seasonal heat storage is not negatively influencing the present TCE contamination under these assumptions. The results of this work serve to support the risk assessment for the interaction between heat storage and contaminations in the shallow subsurface and show positive interactions as well as possible conflicts.

Thermochemical heat storage for high temperature applications. A review

Energy Technology Data Exchange (ETDEWEB)

Felderhoff, Michael [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany); Urbanczyk, Robert; Peil, Stefan [Institut fuer Energie- und Umwelttechnik e.V. (IUTA), Duisburg (Germany)

2013-07-01

Heat storage for high temperature applications can be performed by several heat storage techniques. Very promising heat storage methods are based on thermochemical gas solid reactions. Most known systems are metal oxide/steam (metal hydroxides), carbon dioxide (metal carbonates), and metal/hydrogen (metal hydrides) systems. These heat storage materials posses high gravimetric and volumetric heat storage densities and because of separation of the reaction products and their storage in different locations heat losses can be avoided. The reported volumetric heat storage densities are 615, 1340 and 1513 [ kWh m{sup -3}] for calcium hydroxide Ca(OH){sub 2}, calcium carbonate CaCO{sub 3} and magnesium iron hydride Mg{sub 2}FeH{sub 6} respectively. Additional demands for gas storage decrease the heat storage density, but metal hydride systems can use available hydrogen storage possibilities for example caverns, pipelines and chemical plants. (orig.)

Pre-anthesis high temperature acclimation alleviates the negative effects of postanthesis heat stress on stem stored carbohydrates remobilization and grain starch accumulation in wheat

DEFF Research Database (Denmark)

Wang, Xiao; Cai, Jian; Liu, Fulai

2012-01-01

The potential role of pre-anthesis high temperature acclimation in alleviating the negative effects of post-anthesis heat stress on stem stored carbohydrate remobilization and grain starch accumulation in wheat was investigated. The treatments included no heat-stress (CC), heat stress at pre...... had much higher starch content, and caused less modified B-type starch granule size indicators than the CH plants. Our results indicated that, compared with the non-acclimated plants, the pre-anthesis high temperature acclimation effectively enhanced carbohydrate remobilization from stems to grains...

Heating patterns during cancer heat therapy as a function of blood flow

International Nuclear Information System (INIS)

Mendecki, J.; Friedenthal, E.; Botstein, C.; Sterzer, F.; Paglione, R.W.

1984-01-01

Heating patterns as a function of regional blood flow were evaluated in healthy tissues with different vascular characteristics as well as in a variety of tumors submitted to microwave and RF-induced hyperthermia. Generally, faster heating and slower cooling was demonstrated for tumors. Definite correlation was found between the power needed to heat given tissue volume to a specific temperature and the ability of this tissue to dissipate heat via vascular flow. The measurements show that during the early phase of heating of tumors temperature rises slowly up to about 40 0 C. indicating good heat exchanges but that at this level rapid increase of temperature occurs for relatively small increments of power input. It is suggested that blood flow in malignant tissue remains competent and responsive to low grade heating, but that at higher temperature levels, in contrast to normal tissue, tumor blood flow rapidly decreases indicating compromised vascular system. Implication for treatment protocols are discussed

Temperature-dependent electrochemical heat generation in a commercial lithium-ion battery

Science.gov (United States)

Bandhauer, Todd M.; Garimella, Srinivas; Fuller, Thomas F.

2014-02-01

Lithium-ion batteries suffer from inherent thermal limitations (i.e., capacity fade and thermal runaway); thus, it is critical to understand heat generation experienced in the batteries under normal operation. In the current study, reversible and irreversible electrochemical heat generation rates were measured experimentally on a small commercially available C/LiFePO4 lithium-ion battery designed for high-rate applications. The battery was tested over a wide range of temperatures (10-60 °C) and discharge and charge rates (∼C/4-5C) to elucidate their effects. Two samples were tested in a specially designed wind tunnel to maintain constant battery surface temperature within a maximum variation of ±0.88 °C. A data normalization technique was employed to account for the observed capacity fade, which was largest at the highest rates. The heat rate was shown to increase with both increasing rate and decreasing temperature, and the reversible heat rate was shown to be significant even at the highest rate and temperature (7.4% at 5C and 55 °C). Results from cycling the battery using a dynamic power profile also showed that constant-current data predict the dynamic performance data well. In addition, the reversible heat rate in the dynamic simulation was shown to be significant, especially for charge-depleting HEV applications.

Heat transfer and temperature distribution in fuel

International Nuclear Information System (INIS)

Katanic-Popovic, J.; Stevanovic, M.

1966-01-01

This paper describes methods and procedures for determining the integral, mean and effective heat conductivity and temperature distribution in fuel, with the experimental solutions for measuring these parameters. A procedure for measuring the integral conductivity by measuring the power generated in the fuel is given [sr

Inverse heat transfer analysis of a functionally graded fin to estimate time-dependent base heat flux and temperature distributions

International Nuclear Information System (INIS)

Lee, Haw-Long; Chang, Win-Jin; Chen, Wen-Lih; Yang, Yu-Ching

2012-01-01

Highlights: ► Time-dependent base heat flux of a functionally graded fin is inversely estimated. ► An inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied. ► The distributions of temperature in the fin are determined as well. ► The influence of measurement error and measurement location upon the precision of the estimated results is also investigated. - Abstract: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to estimate the unknown time-dependent base heat flux of a functionally graded fin from the knowledge of temperature measurements taken within the fin. Subsequently, the distributions of temperature in the fin can be determined as well. It is assumed that no prior information is available on the functional form of the unknown base heat flux; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors and measurement location upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent base heat flux and temperature distributions can be obtained for the test case considered in this study.

Temperatures and heating energy in New Zealand houses from a nationally representative study - HEEP

Energy Technology Data Exchange (ETDEWEB)

French, L.J.; Camilleri, M.J.; Isaacs, N.P.; Pollard, A.R. [BRANZ Ltd., Private Bag 50 908, Porirua City (New Zealand)

2007-07-15

The household energy end-use project (HEEP) has collected energy and temperature data from a randomly selected, nationally representative sample of about 400 houses throughout New Zealand. This database has been used to explore the drivers of indoor temperatures and heating energy. Initial analysis of the winter living room temperatures shows that heating type, climate and house age are the key drivers. On average, houses heated by solid fuel are the warmest, with houses heated by portable LPG and electric heaters the coldest. Over the three winter months, living rooms are below 20 {sup o}C for 83% of the time - and the living room is typically the warmest room. Central heating is in only 5% of houses. Solid fuel is the dominant heating fuel in houses. The lack of air conditioning means that summer temperatures are affected by passive influences (e.g. house design, construction). Summer temperatures are strongly influenced by the house age and the local climate - together these variables explain 69% of the variation in daytime (9 a.m. to 5 p.m.) living room temperatures. In both summer and winter newer (post-1978) houses are warmer - this is beneficial in winter, but the high temperatures in summer are potentially uncomfortable. (author)

Twin solution calorimeter determines heats of formation of alloys at high temperatures

Science.gov (United States)

Darby, J. B., Jr.; Kleb, R.; Kleppa, O. J.

1968-01-01

Calvert-type, twin liquid metal solution calorimeter determines the heats of formation of transition metal alloys at high temperatures. The twin differential calorimeter measures the small heat effects generated over extended periods of time, has maximum operating temperature of 1073 degrees K and an automatic data recording system.

Heat-flow and subsurface temperature history at the site of Saraya (eastern Senegal)

Science.gov (United States)

Lucazeau, F.; Rolandone, F.

2012-08-01

New temperature measurements from eight boreholes in the West African Craton (WAC) reveal superficial perturbations down to 100 m below the alteration zone. These perturbations are both related to a recent increase in the surface air temperature (SAT) and to the site effects caused by fluid circulations and/or the lower conduction in the alterites. The ground surface temperature (GST), inverted from the boreholes temperatures, increased slowly in the past (~0.4 °C from 1700 to 1940) and then, more importantly, in recent years (~1.5 °C from 1940 to 2010). This recent trend is consistent with the increase of the SAT recorded at two nearby meteorological stations (Tambacounda and Kedougou), and more generally in the Sahel with a coeval rainfall decrease. Site effects are superimposed to the climatic effect and interpreted by advective (circulation of fluids) or conductive (lower conductivity of laterite and of high-porosity sand) perturbations. We used a 1-D finite differences thermal model and a Monte-Carlo procedure to find the best estimates of these site perturbations: all the eight borehole temperature logs can be interpreted with the same basal heat-flow and the same surface temperature history, but with some realistic changes of thermal conductivity and/or fluid velocity. The GST trend observed in Senegal can be confirmed by two previous borehole measurements made in 1983 in other locations of West Africa, the first one in an arid zone of northern Mali and the second one in a sub-humid zone in southern Mali. Finally, the background heat-flow is low (31±2 mW m-2), which makes this part of the WAC more similar with the observations in the southern part (33±8 mW m-2) rather than with those in the northern part and in the Pan-African domains where the surface heat-flow is 15-20 mW m-2 higher.

Design and evaluation of heat utilization systems for the high temperature engineering test reactor

International Nuclear Information System (INIS)

2001-08-01

in the prioritized selection of hydrogen production through thermochemical water splitting, followed by the conversion of coal into higher quality fuels. These processes are to be demonstrated by out-of-pile tests prior to coupling to the HTTR. The main findings and conclusions for each of the systems evaluated within this CRP are as follows: reforming of methane for hydrogen production and synthesis Steam reforming of methane for the production of hydrogen is planned to be the initial heat utilization process demonstrated with the HTTR; large resources consisting of a mixture of CO 2 and natural gas exist worldwide which have the capability to be converted into usable synthesis gas; gas turbine for electricity production by the use of the gas turbine was determined to be a priority application (of similar status as steam reforming of methane) for demonstration with the HTTR; thermochemical water splitting for hydrogen production, iodine-sulfur (IS) process is considered one of the most attractive for thermochemical water splitting to achieve hydrogen; significant investigation has been undertaken by Member States into the processes for conversion of coal into higher quality, more convenient to use; gasification of coal using external heat from the HTGR can have a 150 to 180% yield compared to conventional conversion processes; heavy oil recovery Investigation within the scope of this CRP into the feasibility of using the HTGR in the recovery of heavy oil concluded that HTGRs are capable of producing the high temperature and high pressure steam necessary for this process and could be used as the need arises with current technology

The Effects of the Heat and Moisture Exchanger on Humidity, Airway Temperature, and Core Body Temperature

National Research Council Canada - National Science Library

Delventhal, Mary

1999-01-01

Findings from several studies have demonstrated that the use of a heat and moisture exchanger increases airway humidity, which in turn increases mean airway temperature and prevents decreases in core body temperature...

Heat capacity measurements on ThO2 by temperature modulated differential scanning calorimetry (TMDSC)

International Nuclear Information System (INIS)

Venkatakrishnan, R.; Nagarajan, K.; Vasudeva Rao, P.R.

2001-01-01

Heat capacity measurements were carried out on ThO 2 in the temperature range 330-820 K by using temperature modulated DSC. An underlying heating rate of 5 K. min -1 , a temperature modulation with an amplitude of 0.398K and a period of 150s were used for these measurements. The heat capacity values are within ± 2-4% of the literature data. (author)

High-temperature gas-cooled reactors and process heat

International Nuclear Information System (INIS)

Kasten, P.R.

1980-01-01

High-Temperature Gas-Cooled Reactors (HTGRs) are fueled with ceramic-coated microspheres of uranium and thorium oxides/carbides embedded in graphite blocks which are cooled with helium. Promising areas of HTGR application are in cogeneration, energy transport using Heat Transfer Salt, recovery of oils from oil shale, steam reforming of methane for chemical production, coal gasification, and in energy transfer using chemical heat jpipes in the long term. Further, HTGRs could be used as the energy source for hydrogen production through thermochemical water splitting in the long term. The potential market for Process Heat HTGRs is 100-200 large units by about the year 2020

Heat or Cold: Which One Exerts Greater Deleterious Effects on Health in a Basin Climate City? Impact of Ambient Temperature on Mortality in Chengdu, China.

Science.gov (United States)

Cui, Yan; Yin, Fei; Deng, Ying; Volinn, Ernest; Chen, Fei; Ji, Kui; Zeng, Jing; Zhao, Xing; Li, Xiaosong

2016-12-10

Background : Although studies from many countries have estimated the impact of ambient temperature on mortality, few have compared the relative impacts of heat and cold on health, especially in basin climate cities. We aimed to quantify the impact of ambient temperature on mortality, and to compare the contributions of heat and cold in a large basin climate city, i.e., Chengdu (Sichuan Province, China); Methods : We estimated the temperature-mortality association with a distributed lag non-linear model (DLNM) with a maximum lag-time of 21 days while controlling for long time trends and day of week. We calculated the mortality risk attributable to heat and cold, which were defined as temperatures above and below an "optimum temperature" that corresponded to the point of minimum mortality. In addition, we explored effects of individual characteristics; Results : The analysis provides estimates of the overall mortality burden attributable to temperature, and then computes the components attributable to heat and cold. Overall, the total fraction of deaths caused by both heat and cold was 10.93% (95%CI: 7.99%-13.65%). Taken separately, cold was responsible for most of the burden (estimate 9.96%, 95%CI: 6.90%-12.81%), while the fraction attributable to heat was relatively small (estimate 0.97%, 95%CI: 0.46%-2.35%). The attributable risk (AR) of respiratory diseases was higher (19.69%, 95%CI: 14.45%-24.24%) than that of cardiovascular diseases (11.40%, 95%CI: 6.29%-16.01%); Conclusions : In Chengdu, temperature was responsible for a substantial fraction of deaths, with cold responsible for a higher proportion of deaths than heat. Respiratory diseases exert a larger effect on death than other diseases especially on cold days. There is potential to reduce respiratory-associated mortality especially among the aged population in basin climate cities when the temperature deviates beneath the optimum. The result may help to comprehensively assess the impact of ambient