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Magnetocaloric refrigeration is an integral part of technology and is under constant investigation. In this regard, the characterization of the magnetocaloric materials used is of major concern. In this study, we used different approaches to better understand the mechanisms underlying the magnetic and magnetocaloric properties of Rh2S mIn Full-Heusler. A physical model is suggested to explain the magnetic interaction within this material. Utilizing the density functional theory, exchange couplings and magnetic phase stability in Rh2SmIn have been attempted as well in order to understand and clarify the various magnetic interactions in this compound. The magnetic and magnetocaloric properties were examined with Monte Carlo simulation (MCS) based on the Ising model. The transition temperature, magnetic entropy change, and relative cooling power (RCP) were computed and found to be in good agreement with experimental evidence. According to the results, Rh2S mIn is a good candidate to be used in magnetic refrigeration applications at high temperature. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of solar thermoelectric generators integrated with radiative cooling technology (STEG-RC) is presented in this study. Basically, the STEG-RC operates outdoors; therefore, the effects of various weather parameters on the output performance of the STEG-RC are determined. The results reveal that the most efficient way of enhancing the output performance of the STEG-RC is by concentrating solar energy. The radiative cooling power increases linearly with the ambient temperature achieving the maximum cooling power of 135 W/m2 and 232 W/m2 at solar concentration ratios of C = 1 and C = 5, respectively. The maximum output power of 1.5 mW and 459.6 mW at the optimum wind speeds of 3 m/s and 2 m/s are obtained for C = 1 and C = 5, respectively. There were no significant changes in the power output and radiative cooling power when relative humidity was varied. The cooling power is linearly proportional to solar irradiance for both concentrated and unconcentrated cases. [ABSTRACT FROM AUTHOR]

Employing non-equilibrium quantum transport models, we investigate the details and operating conditions of nano-structured Peltier coolers embedded with an energy filtering barrier. Our investigations point out non-trivial aspects of Peltier cooling which include an inevitable trade-off between the cooling power and the coefficient of performance, the coefficient of performance being high at a low voltage bias and subsequently deteriorating with increasing voltage bias. We point out that there is an optimum energy barrier height for nanowire Peltier coolers at which the cooling performance is optimized. However, for bulk Peltier coolers, the cooling performance is enhanced with the height of the energy filtering barrier. Exploring further, we point out that a degradation in cooling performance with respect to bulk is inevitable as a single moded nanowire transitions to a multi-moded one. The results discussed here can provide theoretical insights into optimal design of nano Peltier coolers. [ABSTRACT FROM AUTHOR]

In industrial safety, engulfing pool fires can cause damages and collapse of process vessels with catastrophic consequences. This work investigates the ethoxylation of 1-dodecanol as a case-study with a multiscale approach able to analyse scenarios of runaway triggered by a pool fire engulfing the reactor. The aim is to understand whether and when the cooling power of the external heat exchanger can prevent dangerous temperature build-up in the chemical reactor. [ABSTRACT FROM AUTHOR]

Italy has not yet presented to the scientific community any elastocaloric prototype suitable for refrigeration/air conditioning. The SUSSTAINEBLE project was born from the idea to build a demonstrative elastocaloric prototype for environmental conditioning. The prototype is planned to be rotary and composed by a few bunches of elastocaloric wires crossed by air as heat transfer fluid. Many are the parameters to be investigated before the realization of the device. A numerical practical tool would help to easily optimize the prototype. In this paper a two-dimensional tool of a single bunch of elastocaloric wires based on finite-element method is introduced; it can reproduce step by step the velocity and the pressure field of fluid to predict more accurately the solid-to-fluid heat exchange. The results of a test campaign mostly focused on the optimization of the frequency of the cycle, fluid velocity and the distance between the elastocaloric wires are presented. The results reveal that: (i) 0.12 Hz as frequency; (ii) 7 m s-1 as velocity; (iii) 1.0 mm as optimal wire distance, would better satisfy the trade-off existing in the maximization of temperature span and cooling power per mass unit: 23.7 K and 311.97W kg-1 are the values achieved, respectively. [ABSTRACT FROM AUTHOR]

We investigate the fundamental limit of radiative cooling of objects on the Earth's surfaces under general conditions including nonradiative heat transfer. We deduce the lowest steady-state temperature attainable and highest net radiative cooling power density available as a function of temperature. We present the exact spectral emissivity that can reach such limiting values, and show that the previously used 8–13 μm atmospheric window is highly inappropriate in low-temperature cases. The critical need for materials with simultaneously optimized optical and thermal properties is also identified. These results provide a reference against which radiative coolers can be benchmarked. [ABSTRACT FROM AUTHOR]

• We proposed a simulation method to calculate the cooling performance of a radiative cooler. • The principle and progress of humidity effect on radiative cooling are analyzed. • With increasing total water vapor column, the cooling power decrease and the deceleration is attenuating. • We designed experiment and measured the cooling performance of several surfaces in different weather. • The simulated and experimental results match well. The sub-ambient clear sky daytime radiative cooling has been achieved recently by applying advanced nanofabrication technologies, which attracted significant research attention in this area. However, there are also several researches which reported that radiative coolers with excellent thermal radiative spectrum failed to achieve sub-ambient radiative cooling. To elucidate the difference, in this work, we perform a detailed investigation of ambient conditions, in particular, water vapor density, on the performance of radiative coolers. We first present the details of how to estimate the performance of radiative coolers under different water vapor concentration and simulate the transmittance and emitted radiation of atmosphere as well as the cooling performance of the ideal selective emitter, which finds the cooling power decreases by 86.6 W/m2 with increasing total water vapor column. Furthermore, the cooling performance of an integrated photonic solar reflector and thermal emitter with atmospheric profiles in California and Hong Kong were calculated and compared with experiment result. To verify our calculation, nighttime on-site cooling performance of a reference film (Al foil) and two selective emitters (DESR-M and double-layer coating) was measured in several ambient conditions. Our research reveals how the ambient humidity affects the radiative cooling performance by both theoretical and experimental analysis and is important for the further application development of radiative coolers. [ABSTRACT FROM AUTHOR]

Highlights • 2D numerical model of a device with an active electrocaloric regenerator is presented. • Material hysteresis greatly impacts the efficiency of the cooling device. • A system for energy recovery can increase the device efficiency by ten times. • The electrocaloric cooling device has a maximum specific cooling power of 16 W kg−1. Abstract This paper reports on the research and development of a cooling device with an active electrocaloric regenerator (AER) based on the bulk ceramic material (1-x)Pb(Mg 1/3 Nb 2/3)O 3 –xPbTiO 3 (PMN-100xPT). For the purposes of the study a 2D transient numerical model of the AER was developed. This model makes it possible to investigate the cooling characteristics of a device with an AER while considering the effect of the hysteresis of the electrocaloric material and the effect of the electric-energy recovery related to the polarization/depolarization process. The results of the numerical analyses show that the degree of electric energy recovery has a major impact on the efficiency of the device. By considering an idealised system for electric-energy recovery the energy efficiency (expressed by the coefficient of performance) of the device could be increased by up to ten times. A validation of the numerical model was performed through the design, construction and experiments on an improved AER cooling device. The results revealed a maximum specific cooling power of 16 W kg−1 and a maximum temperature span of 3.1 K for the new device. [ABSTRACT FROM AUTHOR]

Highlights • We propose using gratings for a radiative cooling application. • Considered gratings have emission peaks in the atmosphere transparency window. • Association of gratings with multi-layers complete emission spectrum. • A radiative cooling power density up to 80 W.m − 2 at night is produced. • A simplified structure for fabrication is shown. Abstract We propose in this article a method to conceive radiative coolers that are reflective in the solar spectrum and emissive in the transparency window of the atmosphere (8–13 µm). We choose an approach combining thermal control capacities of gratings and multi-layers. It is the first time that simple gratings are used for radiative cooling applications. We use optimized BN, SiC and SiO 2 gratings, which have emissivity peaks in the transparency window. We place under these gratings a metal/dielectric multi-layer structure to obtain a near perfect reflectivity in the solar spectrum and to enhance the emissivity in the transparency window. The optimized structures produce a good radiative cooling power density up to 80 W.m − 2 at night and a mean daytime radiative cooling power density of 55 W.m − 2 , with local atmospherical and solar conditions in Poitiers. [ABSTRACT FROM AUTHOR]

In this article, a scaling analysis of heat and mass transfer processes in an adsorption packed bed is presented. New scaling parameters that characterize the performance of the adsorption cooling bed are derived and their importance are discussed. In addition, a numerical study is performed to illustrate the roles played by the newly derived scaling parameters. It is found that the presence of heat of adsorption makes the apparent heat capacity of an adsorption bed much larger than the heat capacity of the adsorbent material itself. The present results indicate that the heat diffusion and vapor penetration depths can be used to specify the desired working pair properties and the adsorbent layer thickness for producing the maximum cooling power. From the results of scaling analysis, it can be concluded that the inter-particle permeation resistance has a considerable effect on the performance of an adsorption silica gel bed when the particle diameter to adsorbent layer thickness ratio is less than 0.1. It can also be concluded that performance of a silica gel packed bed is controlled by the conductive thermal resistance when the Fourier number of the adsorbent-adsorbate layer (F o ) is less than 1.0. The convective resistance (i.e., external resistance) dominates the bed performance when the dimensionless temperature ratio ( Θ ) of adsorption silica gel packed bed is more than 0.2. [ABSTRACT FROM AUTHOR]

Highlights • A power dispatching model is developed for a heat recovery cogeneration system. • The model maximizes plant owner benefits considering power export to the grid. • The cogeneration system designed generates both electrical and cooling power. • Operation of furnaces is modeled to determine the waste heat available for recovery. • Energy and cost savings obtained are used to evaluate feasibility of the system. Abstract A Organic Rankine Cycle waste heat recovery cogeneration system for heat recovery and power generation to relieve grid pressure and save energy cost for a ferrochrome smelting plant is investigated. Through the recovery and utilization of previously wasted heat from the facility’s internal smelting process off-gases, the cogeneration system is introduced to generate electrical power to supply the on-site electricity demand and feed electricity back to the utility grid when it is necessary and beneficial to do so. In addition, the cogeneration system generates cooling power through a lithium bromide-water solution absorption refrigeration cycle to meet the cooling requirements of the plant. The heat recovery process for power generation is modeled and the optimal power dispatching between the on-site loads and the utility grid is formulated as an economic power dispatching (EPD) problem, which aims to maximize the plant’s economic benefits by means of minimizing the cost of purchasing electricity from the utility and maximizing revenue from selling the generated electricity to the grid. Application of the developed model to a ferrochrome smelting plant in South Africa is presented as a case study. It is found that, for the studied case, more than $1,290,000 annual savings can be obtained as a result of the proposed heat recovery power generation system and the associated EPD model. In addition to this, more than $920,000 annual savings is obtained as a result of the generated cooling power via the proposed absorption refrigeration system. The combined cogeneration system is able to generate up to 4.4 MW electrical power and 11.3 MW cooling power from the recovered thermal energy that was previously wasted. [ABSTRACT FROM AUTHOR]

Thermosphere Climate Indexes (TCI) represent the 60-day running average of the global infrared cooling power radiated from the thermosphere by nitric oxide and by carbon dioxide. The TCI are accurately expressed as linear combinations of the 60-day running averages of the F10.7, Ap, and Dst indexes, thus providing terrestrial context to the long record of solar and geomagnetic indexes. We examine the percentile distribution in quintiles of the TCI generated using solar and geomagnetic indexes covering five complete solar cycles. We further assign adjectival descriptors (Cold, Cool, Neutral, Warm, or Hot) to these quintiles as the TCI largely indicate the global thermal state of the thermosphere. We suggest that the TCI are valuable new solar-terrestrial indexes due to the information they contain about the global thermosphere and due to their ease of calculation from standard indexes. Specifically, given dynamic range of the TCI associated with NO cooling, and its significant dependence on both solar irradiance and geomagnetic processes, we recommend that it be included henceforth as a new, standard solar-terrestrial Index. The NO TCI data show that the thermosphere was “Warm” only for a brief period of time at the maximum of solar cycle 24 and thus experienced the coolest solar maximum of the past seven solar cycles. As of February, 2018, the thermosphere power is in the lowest quintile of values, to which we assign the level of ‘Cold.’ [ABSTRACT FROM AUTHOR]

Structure and magnetic properties of the GdAl2-GdCo2 system including magnetocaloric effect have been investigated for various compositions. The as-cast GdCoxAl2-x alloys prepared by arc-melting crystallize in the dual-phase structure of cubic MgCu2-type and hexagonal MgZn2-type phases. All the as-cast dual-phase alloys exhibit only one magnetic phase transition near 77K even though two ferrimagnetic phases coexist. The magnetic transition was broadened by the continuous transitions of the component phases, which resulted in enhancement of relative cooling power at the expense of the magnetic entropy changes. [ABSTRACT FROM AUTHOR]

The effect of the phase boundary of ferromagnetic metallic and ferromagnetic insulator state (FMM-FMI) on magnetotransport and magnetocaloric properties in the Pr 0.775 Sr 0.225 MnO 3 compound has been described in this study. An enhancement of magnetoresistance (MR) has been observed in the Pr 0.775 Sr 0.225 MnO 3 compound compared to the compounds, reside on both sides of the phase boundary (i.e. FMI and FMM phases for Sr doping 0.2 and 0.3 respectively in Pr 1 - x Sr x MnO 3 ). Moreover, a large relative cooling power (RCP), an important parameter for utilization of magnetocaloric materials, has also been achieved in this compound. The large value of RCP has been attributed to the formation of ferromagnetic clusters, formed above the ferromagnetic ordering temperature ( T > T C ) . On the other hand, enhancement of MR is achieved because of the suppression of enhanced phase fluctuations, arises due to the closeness of FMM-FMI phases. [ABSTRACT FROM AUTHOR]

This study includes a diagnostic and evolutive analysis of the bioclimate of Republic of Moldova, made by using the Wind Chill (WCI) and Cooling Power (CP) indices. The bioclimate of the cold season (October-March) had, in the time period 1960-2012), a warming trend, highlighted by the decrease of WCI values. During the warm season, the bioclimate of Republic of Moldova recorded a gradual warming, highlighted by the decrease in CP index values. The CP index values were analyzed in relation to those of the Tourism Climate Index (TCI), useful for planning the tourist activities of any kind. The actual values of TCI and the ones anticipated for the future indicate, for the Republic of Moldova, an increasing bioclimate favorability for all forms and types of tourism. [ABSTRACT FROM AUTHOR]

A control system describing the dynamic behavior of a car thermostat is considered. The cooling power of the car's radiator is allowed to depend on the ambient temperature. This physically natural assumption presents some challenges to mathematical investigation of the model. The existence and some properties of solutions of the control system are established. [ABSTRACT FROM AUTHOR]

Thermal energy storage materials for transient thermal management applications must exhibit large energy storage densities as well as large cooling/heating power densities. The latter property has proven difficult to quantify on a materials basis because it depends on extrinsic effects. Here, we apply a previously defined cooling power figure of merit, a measure of a material’s intrinsic capacity to absorb a transient heat pulse, to analyze composite phase change material heatsinks and insulants. The results demonstrate important limits on the effects of high- and low-conductivity component volume fractions, orientations, and the critical lengthscales of individual components. Champion composites are predicted to have up to 5 times greater figure of merit than pure high-conductivity materials and up to 30 times greater figure of merit than pure phase change materials. Furthermore, composites consisting of insulating materials containing dispersed phase change materials are predicted to exhibit an order of magnitude increase in their characteristic response time. These results demonstrate the utility of the cooling power figure of merit to design compact high power and energy density heatsink and insulant materials. [ABSTRACT FROM AUTHOR]

Based on the modified Arrott plots and the critical isotherm analysis, the critical exponents of both LaCaMnO and LaCaAgMnO systems have been comprehensively studied and investigated near the paramagnetic-ferromagnetic (PM-FM) phase transition. Critical exponents, β, γ, and δ, which are corresponding to the thermal variation of the spontaneous magnetization, initial susceptibility, and the isothermal magnetization, respectively, obeyed the Widom scaling law δ = 1 + γ/β. It indicates thus the validity the obtained results. We performed then another analysis of the critical behavior via the magnetocaloric effect presenting an accord with the analysis of magnetization measurements. Relative cooling power (RCP) follows the evolution of the magnetic field as RCP ∼ H . The acquired critical exponents were in conformity with those gotten from the modified Arrott plots and Widom scaling law. [ABSTRACT FROM AUTHOR]

In order to produce a better adsorption bed with ideal SCP (specific cooling power) and COP (coefficient of performance), in this paper, ammonia-Cacl2 which can be combined with expanded graphite to overcome many disadvantages is studied. Genetic algorithm can be used to realize the multi-objective optimization which may balance the SCP and COP to satisfy our different needs-a better COP or a better SCP in different systems. The beds with Cacl2/expanded graphite composite adsorbent made under different pressures have different porosities which may lead to different SCPs and COPs. In detail, using genetic algorithm to choose different coefficients, the final solutions can be obtained to meet the needs. By introducing the genetic algorithm to find out the appropriate porosity, making more efficient adsorption beds with Cacl2/expanded graphite composite adsorbents seems to be possible in the simulation. And the proportion of materials can be easily changed to obtain different porosities of the adsorption beds with better COP and SCP. [ABSTRACT FROM AUTHOR]

In the present work, the performance of an adsorption refrigerator driven by a solar collector was investigated. The adsorbent used in this study was 6.5 kg ordinary granular activated carbon of coconut shell produced in the Sumatera Utara province of Indonesia, 3 liters of methanol as adsorbate and 4.5 litres of water as the medium that was cooled. The experiments were carried out under varying weather conditions during seven cycles with total solar radiation about 2.681-3.918 kWh/m2/cycle. In this study, the values of the coefficient of performance (COP) obtained were about 0.0827-0.1271. The values of specific cooling power (SCP) obtained were in the range of 0.01839-0.01883 kW/kg. The experimental results show that the adsorption refrigerator system can deliver an evaporator temperature of about 2.81-13.61°C. [ABSTRACT FROM AUTHOR]

The scaling critical behaviors of Gd 12 Co 7 compound around T C were investigated based on the M-H curves in a magnetic field change of 0–2 T. The critical exponents β and γ determined by modified Arrott plot (MAP) and Kouvel–Fisher (KF) methods are [ β =0.479(5) and γ =1.004(2)] and [ β =0.473(2) and γ =0.983(3)], respectively. The exponents δ derived from Widom scaling relation ( M T = T C = 163 K = D H 1 δ ) and universal relation of the relative cooling power ( R C P ∝ H 1 + 1 δ ) are δ =3.032(8) and δ =2.903(1). The average values of critical exponent ( β =0.476(3) , γ =0.993(7), and δ =2.967(9)) are very close to mean-field model ( β =0.5 , γ =1, and δ =3), which indicates that the magnetic interactions in Gd 12 Co 7 compound are long–range interactions. The average value of critical exponent n for MAP (0.649(1)), KF (0.638(3)), and | Δ S M | ∝ H n (0.714(8)) at T C is 0.667(4) and well in agreement with mean field long–range interaction model ( n = 2 / 3 ). The plot M 1 β vs. ( H / M ) 1 γ constructed by above critical exponents fall into two distinct branches above and below T C and completely complies with the scaling hypothesis. At the same time, the normalized curve of magnetic entropy change shows that renormalized magnetic entropy change Δ S ′ of Gd 12 Co 7 is mainly determined by a =1.548(1) and b =1.549(3) in Lorentz function. [ABSTRACT FROM AUTHOR]

In the present work, an experimental study on a lab-scale adsorption refrigerator, based on activated carbon/ethanol working pair is reported. An extensive testing campaign has been carried out at the CNR ITAE laboratory, with multiple aims. First, the performance has been evaluated in terms of both COP and Specific Cooling Power (SCP), under different boundary conditions, including both air conditioning and refrigeration applications. Attractive SCPs, up to 180 W/kg and 70 W/kg for air conditioning and refrigeration, respectively, were measured. Under the same conditions, COP between 0.17 and 0.08 were obtained. In addition, different management strategies, namely, heat recovery between adsorbers and re-allocation of phase durations, were evaluated to identify their influence on the system. Both strategies confirmed the possibility of increasing COP and SCP up to 40% and 25%, respectively. Moreover, a design analysis based on the experimental results has been carried out, to suggest possible improvements of the system. The obtained results demonstrated the possibility of employing a non-toxic refrigerant like ethanol reaching performance comparable with other harmful refrigerants like ammonia and methanol. [ABSTRACT FROM AUTHOR]

Estimating cooling and heating energy requirements is an integral part of designing and managing buildings. Further, as buildings are among the largest energy consumers in cities, the estimates are important for formulating effective energy conservation strategies. Where complex hourly simulation models are not favored, such estimates may be derived by simplified methods that are less computationally intensive but still provide results that are reasonably close to those obtained from the more complicated approach. The equivalent full load hours (EFLH) method is a simplified energy estimation method that has recently gained popularity. It offers a straightforward means of evaluating energy efficiency programs. However, to date, easily accessible EFLH data exist only for a very limited number of countries in North America and Europe, but not Asia. This current work provides previously unavailable monthly EFLH data for building cooling and heating in three large Asian cities, viz. Hong Kong, Seoul and Tokyo. To assess the effects of changing temperature over the course of decades on building cooling and heating energy consumption, EFLH data are calculated for three time periods: past (1983–2005), present (2006–2014) and future (2015–2044). The projections for the future time period are based on the climate scenarios Representative Concentration Pathways (RCPs) 4.5 and 8.5 of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report. RCP-4.5 assumes a stabilization of future greenhouse gas (GHG) emissions followed by a reduction, while RCP-8.5 assumes their further increase. From the EFLH data, considering just the effects of ambient temperature changes, it is projected the total energy required to heat and/or cool residential dwellings in Hong Kong, Seoul and Tokyo to increase by 18.3%, 4% and 10.4%, respectively over 62 years from 1983 to 2044 in the case of RCP-4.5, and by 23.3%, 9.3% and 15.8%, respectively in the case of RCP-8.5. This shows that even with future stabilization and reduction of GHG emissions, as per scenario RCP-4.5, the energy needs of the three cities for building heating and cooling combined can be expected to increase over the next few decades. This has significant implications, namely increased demands for additional primary energy, which will result in further GHG emissions. These effects, however, can be controlled with adjustments to the electricity fuel mix of each location, and also by use of more efficient heating, ventilation and air-conditioning (HVAC) devices. [ABSTRACT FROM AUTHOR]

In an adsorption chiller, the refrigerant (water) operating pressure is low (0.5–5 kPa) and the cooling power generation of a flooded evaporator is affected by the height of water column. To resolve this issue, we experimentally investigate the performance of a flooded evaporator as a function of water height. The results show an optimum water height equal to 80% of the tube diameter leading to achieve the highest cooling power. Under this condition, the internal and external thermal resistances on the inside and outside of the evaporator tubes account for up to 73% of the overall thermal resistance. To reduce the internal thermal resistance, twisted and Z-type turbulent flow generators are incorporated into the evaporator tubes. The evaporator cooling power shows an increase by 12% and 58% when twisted tape and Z-type turbulators are used at a cost of an increase in the internal pressure drop by 2.5 and 14.5 times, respectively. The twisted tape and Z-type turbulators improve the average specific cooling power of the adsorption chiller by 9% and 47%, respectively. To reduce the external thermal resistance, the outside surface of the evaporator tubes is coated with porous copper. The coated evaporator increases the overall heat transfer coefficient by 1.4 times and improves the specific cooling power of the adsorption chiller by 48% compared to the uncoated tubes. [ABSTRACT FROM AUTHOR]

This paper presents experimental results and numerical evaluation of a Vuilleumier (VM) type pulse tube cryocooler. The cryocooler consists of three main subsystems: a thermal compressor, a low temperature pulse tube cryocooler, and a Stirling type precooler. The thermal compressor, similar to that in a Vuilleumier cryocooler, is used to drive the low temperature stage pulse tube cryocooler. The Stirling type precooler is used to establish a temperature difference for the thermal compressor to generate pressure wave. A lowest no-load temperature of 15.1 K is obtained with a pressure ratio of 1.18, a working frequency of 3 Hz and an average pressure of 2.45 MPa. Numerical simulations have been performed to help the understanding of the system performance. With given experimental conditions, the simulation predicts a lowest temperature in reasonable agreement with the experimental result. Analyses show that there is a large discrepancy in the pre-cooling power between experiments and calculation, which requires further investigation. [ABSTRACT FROM AUTHOR]

Physiological models provide useful summaries of complex interrelated regulatory functions. These can often be reduced to simple input requirements and simple predictions for pragmatic applications. This paper demonstrates this modeling efficiency by tracing the development of one such simple model, the Heat Strain Decision Aid (HSDA), originally developed to address Army needs. The HSDA, which derives from the Givoni-Goldman equilibrium body core temperature prediction model, uses 16 inputs from four elements: individual characteristics, physical activity, clothing biophysics, and environmental conditions. These inputs are used to mathematically predict core temperature (T c ) rise over time and can estimate water turnover from sweat loss. Based on a history of military applications such as derivation of training and mission planning tools, we conclude that the HSDA model is a robust integration of physiological rules that can guide a variety of useful predictions. The HSDA model is limited to generalized predictions of thermal strain and does not provide individualized predictions that could be obtained from physiological sensor data-driven predictive models. This fully transparent physiological model should be improved and extended with new findings and new challenging scenarios. [ABSTRACT FROM AUTHOR]

A type of composite surface was manufactured for trial to achieve integrated solar heating and radiative cooling functions. The spectral properties of the composite surface present a relatively clear selectivity in the spectra of solar heating and radiation cooling wavelengths. A combined system for both solar heating and radiative cooling (named SH-RC system) based on the composite surface was mounted together with a traditional flat-plate solar heating system. Comparative experiments were carried out to investigate their thermal performances both at daytime and nighttime. Results showed that the composite surface has a relatively evident spectral selectivity. In diurnal collector testing mode, the thermal efficiency of the SH-RC collector was 62.7% at zero-reduced temperature, which was about 86.4% of that of the traditional flat-plate solar heating collector. In nocturnal collector testing mode, the SH-RC collector had net radiative cooling powers of 50.3 W/m 2 on a clear night and 23.4 W/m 2 on an overcast night; by contrast, the traditional flat-plate solar heating collector exhibited very little radiative cooling capacity. In diurnal system testing mode, the daily average thermal efficiency of the SH-RC system and the traditional flat-plate solar heating system at zero-reduced temperature was 38.6% and 48.4%, respectively. Based on experimental results, the SH-RC system showed a considerable performance for both diurnal solar heating and nocturnal radiative cooling. [ABSTRACT FROM AUTHOR]

Thermoelectric self-cooling was firstly conceived to increase, without electricity consumption, the cooling power of passive cooling systems. This paper studies the combination of heat pipe exchangers and thermoelectric self-cooling, and demonstrates its applicability to the cooling of power electronics. Experimental tests indicate that source-to-ambient thermal resistance reduces by around 30% when thermoelectric self-cooling system is installed, compared to that of the heat pipe exchanger under natural convection. Neither additional electric power nor cooling fluids are required. This thermal resistance reaches 0.346 K/W for a heat flux of 24.1 kW/m 2 , being one order of magnitude lower than that obtained in previous designs. In addition, the system adapts to the cooling demand, reducing this thermal resistance for increasing heat. Simulation tests have indicated that simple system modifications allow relevant improvements in the cooling power. Replacement of a thermoelectric module with a thermal bridge leads to 33.54 kW/m 2 of top cooling power. Likewise, thermoelectric modules with shorter legs and higher number of pairs lead to a top cooling power of 44.17 kW/m 2 . These results demonstrate the applicability of thermoelectric self-cooling to power electronics. [ABSTRACT FROM AUTHOR]

This work presents the development and validation of computational fluid dynamics (CFD) model of 500 W gamma-type Stirling engine prototype to highlight the effects posed by phase angle and dead volume variations on engine performance. The model is based on a realistic Local Thermal Non-Equilibrium (LTNE) approach for porous domains in the engine (cooler and regenerator). The simulation results showed an acceptable degree of accuracy of 9% and 5%, respectively when comparing with experimental results in predicting the indicated and cooling powers at different heating temperatures. It is found that the maximum indicated power is achieved at a phase angle of 105° rather than at the common phase angle of 90°. The dead volume (connecting pipe) is observed to pose negative effects on engine indicated power and therefore, an optimum value of pipe diameter exists. [ABSTRACT FROM AUTHOR]

Micromachined Joule–Thomson (JT) coolers are attractive for cooling small electronic devices. However, microcoolers operated with pure gases, such as nitrogen gas require high pressures of about 9 MPa to achieve reasonable cooling powers. Such high pressures severely add complexity to the development of compressors. To overcome this disadvantage, we combined a JT microcooler with a thermoelectric (TE) pre-cooler to deliver an equivalent cooling power with a lower pressure or, alternatively, a higher cooling power when operating with the same pressure. This hybrid microcooler was operated with nitrogen gas as the working fluid at a low pressure of 0.6 MPa. The cooling power of the microcooler at 101 K operating with a fixed high pressure of 8.8 MPa increased from 21 to 60 mW when the precooling temperature was reduced by the thermoelectric cooler from 295 to 250 K. These tests were simulated using a dynamic numerical model and the accuracy of the model was verified through the comparison between experimental and simulation results. Based on the model, we found the high pressure of the microcooler can be reduced from 8.8 to 5.5 MPa by lowering the precooling temperature from 295 to 250 K. Moreover, the effect of TE cooler position on the performance of the hybrid microcooler was evaluated through simulation analysis. [ABSTRACT FROM AUTHOR]

The performance of two adsorbent bed silica gel-water adsorption chiller and the influences of its adsorbent bed dimensions, the velocity of heat exchange fluid and the adsorbent particle diameter on the transient distributions of the solid phase temperature, adsorbate concentration and the pressure are numerically examined in this study. A transient two-dimensional local thermal non-equilibrium model that takes into account both internal and external mass transfer resistances is developed to simulate the adsorption chiller considered herein. The internal and external mass transfers are predicted by the linear driving force (LDF) model and Darcy's equation, respectively. It is found that an increase in the adsorbent particle diameter results in the decrease in both the coefficient of performance (COP) and specific cooling power (SCP) of the adsorption chiller. On the other hand, the system performance is nearly independent from the variation of velocity of heat exchange fluid. An increase in the bed thickness leads to an increase in COP and a decrease in the SCP. The influence of adsorbent bed length on the performances of system can be neglected. The results of our simulations provide useful guidelines for the design of this type of adsorption chillers. [ABSTRACT FROM AUTHOR]

Most electronic cooling devices consist of two reservoirs linked by an energy filter, which only allows high-energy electrons to transport from the cold reservoir to the hot reservoir. Here we propose a new type of cooling device, in which a cold reservoir is connected with two hot reservoirs by two energy filters and cooling is achieved by simultaneously removing high energy electrons from and injecting low energy electrons into the cold reservoir. The effects of key parameters such as the chemical potential difference of two hot reservoirs, the center interval and half width of two energy filters, etc. on the performances of the cooling device are discussed in detail. The optimal operating regions of the device are determined. Compared with the traditional electronic cooling device with a single energy filter between the cold and hot reservoirs, the optimal cooling power is doubly enhanced without reducing the COP (coefficient of performance) of the system. [ABSTRACT FROM AUTHOR]

Compact evaporators like plate heat exchangers can play a significant role in reducing the investment cost of low cooling power sorption systems. If water is used as refrigerant, their design remains mainly empirical. The objective of this paper is thus to investigate the specific characteristics of water pool boiling in narrow channel at subatmospheric pressure in order to acquire the fundamental knowledge needed to improve the design of compact evaporators in these sorption systems. An experimental test setup was thus designed and built to study water pool boiling in narrow channel at subatmospheric pressure (from 5 to 1.2 kPa) on a vertical heated copper disk. The influence of the thickness of the narrow channel and of the pressure on the heat transfer is discussed. As the pressure and the channel thickness decrease the occurrence of a specific subatmospheric pool boiling regime is observed, degrading heat transfer coefficient. Nevertheless, the general trends of evolution are in agreement with those generally observed in the literature: heat transfer is enhanced as the thickness of the narrow channel decreases but, depending on the pressure, decreasing too much the channel thickness could lead to a deterioration of the heat transfer coefficient. A particle image velocity (PIV) device was implemented to the experimental setup in order to highlight the effect of the wake-induced flow on the heat transfer. [ABSTRACT FROM AUTHOR]

We propose that chondrules are formed by radiative heating of pre-existing dust clumps during close fly-bys of planetesimals with incandescent lava at their surfaces. We show that the required temperatures and cooling rates are easily achieved in this scenario and discuss how it is consistent with bulk aspects of chondritic meteorites, including complementarity and the co-mingling of FeO-poor and FeO-rich chondrules. [ABSTRACT FROM AUTHOR]

Four advanced types of adsorbent beds were designed, investigated and compared to each other in a double-adsorber adsorption refrigerator. The four types of adsorbent beds were assembled by several vehicle radiators with two different sizes. A prototype of the adsorption refrigerator built up in our laboratory was used to test the performances of the adsorbent beds. Silica gel-water was used as the working pair. The length, width and thickness of the radiators were measured. The amount of adsorbent filled into these four types of adsorbent beds was recorded. The dead area volume was estimated. The coefficient of performance (COP) and specific cooling power (SCP) of the system were tested after utilizing the four types of adsorbent beds. The COP and SCP of the four types of adsorbent beds were estimated under the standard operating condition and optimized operating condition. A SCP and a COP of the small-radiator adsorbent beds with 198.4 W/kg and 0.30 were achieved under the optimized operating condition with 480 s adsorption/desorption time, 90 s heat and mass recovery time, 9 L/min hot water and cooling water flow rate, 2 L/min chilled water flow rate, 16 °C chilled water inlet temperature, 90 °C hot water and 25 °C cooling water. Under the standard operating condition, the result showed that smaller dead volume leads to a slightly higher SCP. The adsorbent bed with smaller size radiator had a better heat and mass transfer ability and a higher SCP and COP could be achieved. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of cubic Laves phase rare earth intermetallic HoCo 0.25 Ni 1.75 compound have been investigated. Magnetization measurements show that HoCo 0.25 Ni 1.75 orders ferromagnetically at 22 K ( T C ). The magnetization vs field ( M – μ 0 H ) isotherm at 2 K shows negligible hysteresis. The isothermal magnetic entropy change (Δ S m ) is calculated from the measured M – µ 0 H data near T C . The maximum value of Δ S m , Δ S m max , is about −18.9 J/kg-K at T C for a field change of 5 T with a refrigerant capacity of 572 J/kg. The material exhibits large Δ S m max of −9.4 J/kg-K even for a low field change of 2 T. Universal master curve is constructed by rescaling Δ S m vs T curves for various fields to confirm the second order nature of the magnetic transition at T C . Large Δ S m max value, wide temperature span of cooling and high relative cooling power make HoCo 0.25 Ni 1.75 a potential magnetic refrigerant for low temperature applications such as hydrogen liquefaction. [ABSTRACT FROM AUTHOR]

Based on CAES (compressed air energy storage) and PM (pneumatic motor), a novel tri-generation system (heat energy, mechanical energy and cooling power) is proposed in this paper. Both the cheap electricity generated at night and the excess power from undelivered renewable energy due to instability, can be stored as compressed air and hot water by the proposed system. When energy is in great demand, the compressed air stored in this system is released to drive PM to generate mechanical power. The discharged air from PM can be further utilized as valuable cooling power. Compared to conventional CAES systems, the biggest characteristic of the proposed system is that the discharged air usually abandoned is used as cooling power. In order to study the performances of this system, a thermodynamic analysis and an experimental investigation are carried out. The thermodynamic model is validated by the experimental data. Using the validated thermodynamic model, the mechanical energy output, cooling capacity and temperature of discharged air, as well as the efficiency of the system are analyzed. The theoretical analysis indicates that the additional application of discharged air can improve total energy efficiency by 20–30%. Therefore, this system is very worthy of consideration and being popularized. [ABSTRACT FROM AUTHOR]

This paper is concerned with the design, development and performance testing of a cryogenic system for use in high cooling power instruments for ground-based environmental testing. The system provides a powerful tool for a combined environmental test that consists of high pressure and cryogenic temperatures. Typical cryogenic conditions are liquid hydrogen (LH2) and liquid oxygen (LO2), which are used in many fields. The cooling energy of liquid nitrogen (LN2) and liquid helium (LHe) is transferred to the specimen by a closed loop of helium cycle. In order to minimize the consumption of the LHe, the optimal design of heat recovery exchangers has been used in the system. The behavior of the system is discussed based on experimental data of temperature and pressure. The results show that the temperature range from room temperature to LN2 temperature can be achieved by using LN2, the pressurization process is stable and the high test pressure is maintained. Lower temperatures, below 77 K, can also be obtained with LHe cooling, the typical cooling time is 40 min from 90 K to 22 K. Stable temperatures of 22 K at the inlet of the specimen have been observed, and the system in this work can deliver to the load a cooling power of several hundred watts at a pressure of 0.58 MPa. [ABSTRACT FROM AUTHOR]