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In this paper a novel method to determine the specific heat capacity of lithium-ion cells is proposed. The specific heat capacity is an important parameter for the thermal modelling of lithium-ion batteries and is not generally stated on cell datasheets or available from cell manufacturers. To determine the specific heat capacity can require the use of an expensive (>£100 k) calorimeter or the deconstruction of the cell whereas the method proposed by the authors in this paper uses common equipment found in most battery laboratories. The method is shown to work for cylindrical, prismatic and pouch cells, with capacities between 2.5 Ah and 10 Ah. The results are validated by determining the specific heat capacity of the cells with use of a calorimeter and a maximum error of 3.9% found. Thermal modelling of batteries is important to ensure cell temperatures are kept within specified limits. This is especially true at rates over 1C, such as the fast charging of electric vehicles, where more heat is generated than lower rate applications. The paper ends by demonstrating how the thermal model that underpins the authors' methodology can be used to model the surface temperature of the cells at C-rates greater than 1C. [ABSTRACT FROM AUTHOR]

Numerical simulations of film boiling heat transfer on a horizontal surface are conducted in this paper using a modified pseudo-potential liquid-vapor phase change lattice Boltzmann model. A conjugate heat transfer problem, including heat conduction in the heater and its thermal responses during the film boiling process, is investigated. Unlike previous numerical studies which needed to initialize the shape of the liquid-vapor interface wave at the beginning of the computation, the computation domain for fluid region is occupied initially by saturated liquid in this paper. Taylor instability at the liquid-vapor interface is triggered by small temperature perturbations imposed at the bottom of the heater during a short initial period. Consequently, this paper represents a more direct and complete numerical simulation for film boiling heat transfer on a horizontal heater. The simulated time- and space-averaged Nusselt number is found in good agreement with a previous correlation equation. Temporal and spatial variations of the vapor film thickness are also investigated numerically and compared with existing correlation equations. It is demonstrated that the temperature at the top surface of the heart changes with position and time during the film boiling process. Although the transient film boiling patterns may depend on temperature perturbations imposed on he bottom of the heater during an initial period, the time- and space-averaged film boiling heat flux is independent of initial temperature perturbations. [ABSTRACT FROM AUTHOR]

The thermal performance of a novel solar air collector with metal corrugated packing in the buildings of cold regions is studied in this paper. Mathematical models are developed to investigate the thermal performance of the collector and the results are verified by experiments. The hydraulic analysis is conducted experimentally to study the pressure drops of the air flows in the corrugated packing. Effects of the structural and operating parameters, such as the collector width, height, specific surface area and solar radiation intensity, ambient air temperature, air inlet temperature and velocity are studied to optimize the thermal performance of the collector. Comparisons are conducted among the metal corrugated packing solar air collector, the unglazed transpired solar collector, the glazed transpired solar collector and the packed bed solar collector with iron chips. The results indicate that the metal corrugated packing solar air collector is more appropriate to be used in the rural buildings of cold regions for its advantages of large heat transfer area, high heat transfer coefficient and good economic performance. [ABSTRACT FROM AUTHOR]

Mathematical modelling and the dynamic simulation of battery storage systems can be challenging and demanding due to the nonlinear nature of the battery chemistry. This paper introduces a new dynamic battery model, with application to state of charge estimation, considering all possible aspects of environmental conditions and variables. The aim of this paper is to present a suitable convenient, generic dynamic representation of rechargeable battery dynamics that can be used to model any Lithium-ion rechargeable battery. The proposed representation is used to develop a dynamic model considering the thermal balance of heat generation mechanism of the battery cell and the ambient temperature effect including other variables such as storage effects, cyclic charging, battery internal resistance, state of charge etc. The results of the simulations have been used to study the characteristics of a Lithium-ion battery and the proposed battery model is shown to produce responses within 98% of known experimental measurements. [ABSTRACT FROM AUTHOR]

The strong coupling heat transfer between subassemblies and inter-wrapper gaps is closely related to the safety of the sodium-cooled fast reactor (SFR). Therefore, it is very important to carry out a detailed thermal hydraulic analysis of the core. In this paper, the inter-wrapper channel is modeled using the subchannel analysis method. A core thermal-hydraulic analysis code SACOS-Na (Subchannel Analysis Code Of Safety for SFR) is developed by using SIMPLE algorithm. For the subassembly module, a total of three experiments, including ORNL 19-pin experiment, TOSHIBA 37-pin experiment and KNS 37-pin experiment, are adopted to demonstrate the feasibility of the mathematical and physical models and numerical algorithms of the SACOS-Na as well as the rationality of the selected auxiliary models. For the inter-wrapper gap module, WEISS 2-subassembly experiment and CCTL-CFR 3-subassembly experiment are used to verify not only the simulation capability for backflow and strong inter-subassembly heat transfer, but also the heat structure model and the subchannel modeling approach on inter-wrapper gaps. In addition, the prediction accuracy of SACOS-Na has reached the advanced international level by comparing with the worldwide well-known core thermal hydraulic analysis codes. • The subchannel modeling method is adopted to build the mesh for inter-wrapper channels. • The SIMPLE algorithm is used to solve the problems of the reverse flow and inter-subassembly heat transfer occurred in SFRs. • The universal core thermal-hydraulic analysis code SACOS-Na for SFRs is developed. • The accuracy and reliability of the SACOS-Na are discussed from all aspects. [ABSTRACT FROM AUTHOR]

The research and design of liquid-cooled integrated circuits (IC) relies heavily on accurate simulation. Ideally, finite-element-method (FEM) based tools should be used for this purpose. However, in most cases a fully coupled thermo-fluidic simulation of complex ICs is very long, mostly due to the fact that the simulation of fluid dynamics is very time consuming. Therefore, in this paper we propose a novel model for thermal simulation of ICs cooled by integrated microchannels which significantly reduces the simulation time. The new approach is based on removing the fluid from the model and treating the solid-liquid boundary as a convective boundary, described by the convection equation. It is shown that the proposed model offers very good accuracy in steady-state, with errors below 3 °C in every chip point. In transient domain the results are equally good, with the maximum error around 3.3 °C (6% relative error). Moreover, the simulation times have been reduced by about two orders of magnitude with respect to fully coupled FEM simulation. However, the proposed model has also important limitations: currently ICs with only one layer of straight microchannels are supported and the model requires recalculation if some chip parameters are changed. [ABSTRACT FROM AUTHOR]

In this paper, a numerical model describing the heat transfer and air flow inside and outside the casing of the permanent magnet brushless direct current (PM BLDC) motor is presented. In the model, a conjugate heat transfer including the heat conduction with heat sources in windings, magnets, bearings, natural and forced convection and radiation phenomena within internal and external air domain were analysed. The complex geometrical model included windings, a magnet circuit, a rotor with neodymium magnets, a PCB electronic plate, plastic covers, internal air between solid parts as well as a portion of the external air. The validation process of the developed model was realised on the basis of the velocity and temperature fields. The experimental data were recorded by 7 constant temperature anemometers at 4 levels above the motor housing, Laser Doppler Anemometry sensors in two axes inside the rear portion of the motor and 25 thermocouples fixed inside and outside the motor. The experimental and numerical tests were performed for 4 motor loadings and 3 rotational speeds. The average temperature error for the internal point was of 9 K, while that of the external points was of 2 K. The velocity field was very well predicted close to the housing wall in terms of horizontal and vertical components. A slightly worse agreement was found for the vertical component, especially in the vicinity of the shaft. The results were consistent for all the considered motor loadings and rotational speeds. [ABSTRACT FROM AUTHOR]

The transient response of heat exchangers plays a significant role in the time-dependent performance of thermal management systems, particularly in resource-limited situations with high power density and fast-acting heat sources. A scaled thermal management testbed with a plate-frame heat exchanger was built to emulate a thermal subsystem. This paper describes a methodology for dynamically characterizing the behavior of a commercial, off-the-shelf plate-frame heat exchanger both experimentally and computationally. Statistical design of experiments principles was used to develop a test plan composed of 20 test cases for dynamic model validation. The dynamic performance of the heat exchanger was evaluated with a physics-based model, and statistical surrogate models were derived from the experimental results. Additionally, a lumped mass model was employed to determine the dynamic parameters of the heat exchanger using the experimental data. The model efficiently and accurately predicts the experimental results across the entire experimental exploration space. The lumped mass model predicts the transient response without using computationally expensive resources such as a full numerical, thermo-fluid dynamic solvers. This approach has significant implications for developing practical models of thermal components particularly for the field of thermal controls. [ABSTRACT FROM AUTHOR]

HyperVapotrons are highly robust and efficient heat exchangers able to transfer high heat fluxes of the order of 10–20 MW/m 2 . They employ the Vapotron effect, a complex two phase heat transfer mechanism, which is strongly linked to the hydrodynamic structures present in the coolant flow inside the devices. HyperVapotrons are currently tested in the Joined European Torus (JET) and the Mega Amp Spherical Tokamak (MAST) fusion experiments and are considered a strong candidate for the International Thermonuclear Experimental Reactor (ITER). The efficiency of heat transfer and the reliability of the components of a fusion power plant are important factors to ensure its longevity and economical sustainability. Optimisation of the heat transfer performance of these devices by the use of nanofluids is investigated in this paper. Nanofluids are advanced two phase coolants that exhibit heat transfer augmentation phenomena. A cold isothermal nanofluid flow is established inside two HyperVapotron models representing the geometries used at JET and MAST. A hybrid particle image velocimetry (PIV) method is employed to measure the flow and create a dense velocity vector map of a region of interest. The vector spatial resolution is 30 μm. The instantaneous and mean flow structures of a nanofluid are compared to those present during the use of a traditional coolant (water) in order to detect any departure from the hydrodynamic design operational regime of the device. It was discovered that the flow field of the JET model is considerably affected when using nanofluids, while the flow in the MAST geometry does not change significantly by the introduction of nanofluids. Evidence of a shear thinning mechanism is found inside the momentum boundary layer of the nanofluid flows and it might be important to calculating the pumping power losses of a functional nuclear fusion power plant cooling system ran with nanofluids instead of water. [ABSTRACT FROM AUTHOR]

Recently researchers have proposed innovative solutions aiming to improve the energy performance of building envelope components such as Trombe walls, ventilated storage walls. The principle of all the innovative systems can be simplified as heat/cold sources in walls. However, the thermal performance and energy savings potential of the innovative heating walls comparing to the traditional heating pattern with heat sources in room air are still lack of clarification. In this paper, the thermal response of an ideal building model under two ideal heating patterns, are analyzed by using a simple thermal and airflow macroscopic model. The analytical formulas for indoor air temperature and thermal mass temperature are also derived to identify the critical parameters that affect the levels and fluctuations of them. By numerical calculation, it can be observed that the indoor air temperature under HP1 quickly falls down as the heat source removed and has big variation, while the results of HP2 look favourable with less variation, and the mean air temperature during the non-heating period is higher than that of HP1. This implies that the heating pattern HP2 has the potentials to create a stable indoor thermal environment. [ABSTRACT FROM AUTHOR]

When designing ground source heat pump systems in northern regions, we usually face the problem of soil freezing/melting around ground heat exchanger. The impact of freezing on heat transfer should be evaluated. An improved thermal resistance and capacity model based on the effective heat capacity method is developed in the paper to evaluate the effect. Further comparisons have been carried out against measured data from an experimental set-up, and agreement of the results validates the proposed model when the parameters of the model are set properly. The heat transfer capacity could rise by 30% because of phase change. The quantity of heat transfer could stay at 75 W/m to 80 W/m during three-month operation, which is feasible for a GSHP system to operate normally in such extreme condition. [ABSTRACT FROM AUTHOR]

In this paper, two sets of design schemes of air source heat pump heating and gas boiler heating are given, and the economical performance of the two heating modes is compared. Through the simulation and calculation of the two kinds of heating system economy, it can be concluded that the operating cost of the gas-fired boiler is about 21.39 RMB•m -2 in the normal operation of the whole year. The operating cost of the air-source heat pump system in the regular operation is about 17.81 RMB•m -2 , and it is about 10.82 RMB•m -2 in the valley operation. [ABSTRACT FROM AUTHOR]

The focus of this paper is on an integrated approach for HVAC modeling (semantic and physical), optimization, and control. It utilizes the Building Control Virtual Test Bed (BCVTB) platform to integrate ontologies along with rule sets into Model Predictive Control (MPC) routines and Modelica-based simulations. The ontologies represent the data in the form of semantic models of the domain. They include concepts and the relationships between them, i.e., mechanical equipment, zones, and sensors. While the MPC ensures optimized physical control, the ontologies and rule sets are responsible for data-driven and inference-based semantic control. The Web Ontology Language (OWL) is used to describe the ontologies, and Jena API was used as the framework to create the ontologies and define the rule sets. [ABSTRACT FROM AUTHOR]

Semi-cylindrical diffusers are widely popular in displacement ventilation and lower air supply systems. The big point of the air flow characteristics of the curved surface jet is the “Cold Lake Effect”, arounding the ground. In this paper, we derive a theoretical model of this “Cold Lake Effect” to investigate semi-cylindrical diffusers. The temperature distribution of the air supply in the main section was calculated with different air flow rate and initial air supply temperature. The temperature distribution model was experimentally verified. It is a good agreement with the calculated results, whereby the maximum deviation is 0.812°C. The study of the temperature characteristics, is a reference for making indoor thermal environment comfort better, and it can provide technical measures for designing air distribution systems in displacement ventilation and lower air supply systems. [ABSTRACT FROM AUTHOR]

The coaxial parallel-type hybrid power gas engine-driven heat pump (HPGHP) system combines hybrid power technology with gas engine-driven heat pump, which can be divided into three parts: the power-driven system, the heat pump system and the heat reclaim system. In this paper, on the basis of HPGHP system experiments, the mode of the heat reclaim system is established, then the engine waste heat reclaim coefficient of flue gas waste heat, cylinder liner waste heat and total heat is researched. The results show that the waste heat reclaim coefficient of cylinder liner waste heat is significantly higher than the flue gas waste heat. In addition, to evaluate the thermal performance and fuel economy of flue gas heat exchanger, the annual net income of unit flue gas heat reclaim model is established. Finally, the heat transfer area of flue gas heat exchanger is optimized. The results show that when NTU is approximately 0.6, the annual net income of per unit flue gas heat reclaim reaches a maximum value, this moment, the economic optimum heat transfer area is 1.79 m 2 approximately. [ABSTRACT FROM AUTHOR]

In this paper, we propose a pulsed flow control of the radiant system with a fixed on-time to replace the storage water in pipes and a variable off-time to regulate the capacity. We developed a three-dimension numerical model to simulate the performance of the radiant heating and cooling system in the pulsed flow control method. Through numerical simulation on radiant systems with various thermal masses, the average supply and return water temperature difference and surface temperature non-uniformity were compared between the pulsed flow control and the variable flow rate control. The results demonstrate that the pulsed flow control achieves a comparable supply and return water temperature difference and pump energy consumption to the variable flow rate control. However, the pulsed flow control method saves the initial cost by substituting proportional valves by two-way position valves and has a higher controllability in part load. Furthermore, the pulsed flow control yields a smaller surface temperature non-uniformity than variable flow rate control, which is beneficial to reduce the condensation risk in cooling condition. [ABSTRACT FROM AUTHOR]

In this paper, The utility model relates to a heating system which is composed of a traditional solar air collector, a floor air supply and a phase change heat storage air duct, which is used for heating the room in winter. Using Fluent software to simulate the whole system in winter. The results show that this system conforms to the standard of winter heating. The system needs to add an electric heating auxiliary heat source, which is used to heat the room in the night or rainy day. [ABSTRACT FROM AUTHOR]

In this paper, the comfort thermal environment of the migrants from distinct regions in a short term is studied. The changes of migrants’ adaptation intensity over time are also presented, especially concerning physiological adaptation. One-month tracking experiment in climate chamber has been conducted in Xi’an (the cold region in central north of China), including both physiological measurements and subjective questionnaires. The migrant groups from severe cold area (the further northern region) and hot summer and cold winter area (the south of China) were recruited, and the indigenes were selected as control group. The results show the migrants’ adaptive responses over time fluctuate with the trend to close to that of the locals. The proper temperature ranges of S-N and EN-N groups are 21.02-29.73°C and 20.8-30.59°C to develop the adaptation. The results could contribute to develop the theory of migrants. [ABSTRACT FROM AUTHOR]

Currently the indoor thermal environment control is mainly conducted based on the set points given by room occupants or based on PMV, which might cause problems of unreasonable temperature setting and unsatisfied individual thermal preferences of room occupants. The indoor thermal environment control method based on thermal sensation expression can solve these problems. However, control based on thermal sensation expression might frequently interrupt room occupants’ concentrations on work because this method needs occupants to input their thermal sensations, when their comfortable temperature range changes with the differences of the metabolic rate, clothing level etc. In an attempt to solve this problems, a new indoor thermal environment control method is proposed, which is to collect occupants’ skin temperature measured by infrared imaging to estimate the occupants’ current thermal sensation and predict their future thermal sensations. This paper introduces the control method of the system based on thermal sensation prediction. The control method was verified by building the test-beds and conducting a series of experiments. Experiment results show that 98% of the evaluations are neutral/satisfied/very satisfied with this control system, which means the proposed indoor thermal environment control method based on thermal sensation prediction is feasible for actual application. [ABSTRACT FROM AUTHOR]

The scale of urban construction has increased gradually, a large amount of energy consumption and human activities have affected the outdoor thermal environment and the quality of the urban air. Based on this situation, this paper uses PHOENICS to simulate and evaluate outdoor thermal environment, taking a university campus in Jinan as an example. Google Sketchup and AutoCAD software are used to build a three-dimensional model with 30m elevation difference. It is found that among the main outdoor area of the university campus, the thermal environment meets the requirements of the Green Campus Evaluation Criteria basically. Because of the variation of the terrain height, the distribution of average wind speed and temperature mostly exist the lamination at the pedestrian level. The simulation results provide the reference for the optimization of thermal environment. [ABSTRACT FROM AUTHOR]

Based on a public building in China, this paper built a benchmark model and analyzed the influence of main thermal performance of building envelopes on energy consumption in different climatic regions by EnergyPlus. The results showed that in the order of hot summer and warm winter region, hot summer and cold winter region, cold region, severe cold region, the energy-saving effect was getting better and better with the increase of roof insulation, exterior wall insulation and exterior window insulation. If SHGC of exterior window was reduced, building energy consumption decreased in hot summer and warm winter region, hot summer and cold winter region, but it increased in cold region and severe cold region. For hot summer and warm winter region, hot summer and cold winter region, the factors that affected energy consumption was as follows: SHGC > K win > K wal > K ro, for cold region and severe cold region, it was as follows: K win > K wal > SHGC > K ro . [ABSTRACT FROM AUTHOR]

Waste heat recovery of low-to-medium grade heat sources such as solar energy or biomass using Organic Rankine Cycle (ORC) technology has received growing attention recently. Few manufacturer of biomass (wood logs) stoves utilizes silicon-carbide as the material for manufacturing of their stoves to facilitate slow-heat-release for a long period of time for up to twelve hours. Despite good performance of these stoves, there is still significant amount of heat that is wasted through exhaust at the temperature of between 240 °C to 270 °C. This paper investigated various strategies to minimize heat losses to the environment by introducing an ORC system that can capture the waste heat and convert it into useful power. The stove’s temperature distribution as well as identification of potential location for the ORC evaporator were obtained using experimental testing. Such results were then employed for validation of a CFD model and it was shown that this CFD model can fairly accurately predict both temperature distribution and recovered heat on the ORC evaporator coils. Among investigated scenarios, “Modification 2” proved to be most effective as it not only preserved the heating functionality of the stove but also improved the stove’s efficiency by about 20% while generating 1.113 kW of electricity. [ABSTRACT FROM AUTHOR]

This paper proposes a mathematical model for a solar Dish/Stirling system. Firstly, it is presented a methodology to calculate the appropriate angles and characterize the solar tracking control system for the city of Itajubá-MG/Brazil, in order to maximize the heat flow on the cavity of the receiver. Secondly, it was developed an algorithm for sizing and to determine the effects of opto-geometric parameters on the overall efficiency of the Dish/Stirling system. The model allows defining different configurations and geometric distances between the concentrator and the receiver, in order to obtain the desired heat in the receiver cavity. Finally, it is carried out a thermal balance for the evaluation of the maximum efficiency and overall efficiency of the system. The results obtained for a concentrator with a diameter of 10.5 [m] and solar irradiation of 1000 W/m 2 are: theoretical maximum working temperature in the receiver surface of 1596 K and a maximum thermal efficiency of 68%. It is observed that for collectors between 10 and 20 m of diameter, the overall efficiency variation is not significant (23–25%), since the variation of the temperature of the receiver and the thermal losses in the cavity are minimal for the evaluated conditions. [ABSTRACT FROM AUTHOR]

In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated compartments. We show that steady state burning rates are accurately predicted using a detailed model for the liquid phase heat transfer. The effect of lowered oxygen vitiation on the burning rate of pool fires is correctly captured. Simulations were done using the Fire Dynamics Simulator and the experiments considered were conducted in the OECD PRISME project. The main difference between the present study and previous simulation studies is the use of a detailed liquid evaporation model and the direct calculation of the vitiation and thermal environment interactions through the CFD solver. [ABSTRACT FROM AUTHOR]

This paper introduces a new optimization model for the single and multiple-effect evaporation (SEE/MEE) systems design, including vapor recompression cycle and thermal integration. The SEE/MEE model is specially developed for shale gas flowback water desalination. A superstructure is proposed to solve the problem, comprising several evaporation effects coupled with intermediate flashing tanks that are used to enhance thermal integration by recovering condensate vapor. Multistage equipment with intercooling is used to compress the vapor formed by flashing and evaporation. The compression cycle is driven by electricity to operate on the vapor originating from the SEE/MEE system, providing all the energy needed in the process. The mathematical model is formulated as a nonlinear programming (NLP) problem optimized under GAMS software by minimizing the total annualized cost. The SEE/MEE system application for zero liquid discharge (ZLD) is investigated by allowing brine salinity discharge near to salt saturation conditions. Additionally, sensitivity analysis is carried out to evaluate the optimal process configuration and performance under distinct feed water salinity conditions. The results highlight the potential of the proposed model to cost-effectively optimize SEE/MEE systems by producing fresh water and reducing brine discharges and associated environmental impacts. [ABSTRACT FROM AUTHOR]

Welding can highly modify the mechanical properties of materials due to the extreme thermal solicitations applied. For precipitation hardened materials, such as aluminium alloy 6xxx, a welding operation implies a modification of the microstructural state and, consequently, of the mechanical properties, both phenomena being highly nonlinear. The purpose of this paper is to propose a methodology to predict the post-welding mechanical properties of a welded joint. For this, three models are coupled: (i) a thermal finite element model of the welded structure that allows the prediction of the material’s thermal history at every point; (ii) a precipitation model to predict the microstructural state in the joint using the thermal history; and (iii) a mechanical model to link the microstructural state to the mechanical properties, i.e. hardness, yield limit and hardening. A coupling between these models and a finite element commercial code is then performed to predict the precipitation state and mechanical properties of a 6xxx-T6 aluminium alloy after welding. To validate this methodology a tensile test is performed on a specimen extracted from a 6061-T6 welded plate. Using Digital Image Correlation, the in-plane strain fields across the weld are measured and compared with the finite element simulation of the tensile test, thereby providing good prediction. [ABSTRACT FROM AUTHOR]

This paper deals with the thermal modeling of temperature rise in a pouch lithium-ion battery with LiFePO 4 (also known as LFP) cathode material. The developed model represents the main thermal phenomena in the cell in terms of temperature change. The proposed model is validated with the collected experimental data from a module composed of 11 cells. In the conducted experiments, the different charge and discharge rates of 1/2C, 1C, 2C and 2.5C are applied. It is seen that, the increased discharge rates result in increased temperature on the surface of the battery. When the discharge rate is doubled, from 1C to 2C, cell temperatures have risen by 3.5 times. A simplified model for determining the heat generation is developed and validated with the test results. [ABSTRACT FROM AUTHOR]

Genetic algorithms have been used for matching temperature values generated using thermal mathematical models against actual temperatures measured in thermal testing of spacecrafts and space instruments. Up to now, results for small models have been very encouraging. This work will examine the correlation of a small-medium size model, whose thermal test results were available, by means of genetic algorithms. The thermal mathematical model reviewed herein corresponds to Tribolab, a materials experiment deployed on board the International Space Station and subjected to preflight thermal testing. This paper will also discuss in great detail the influence of both the number of reference temperatures available and the number of thermal parameters included in the correlation, taking into account the presence of heat sources and the maximum range of temperature mismatch. Conclusions and recommendations for the thermal test design will be provided, as well as some indications for future improvements. [ABSTRACT FROM AUTHOR]

Short duration wind tunnels offer an economical approach to study the aero-thermal operation of propulsion components, while reproducing temperature ratios, Reynolds and Mach numbers of the actual engine conditions. The present paper aims at modeling with high fidelity the von Karman Institute compression tube facility. This wind tunnel was simulated using the EcosimPro suite to characterize the behavior of each subcomponent during the whole test envelope, including the turbine map at off-design. The numerical predictions were then assessed through the comparison with experimental data. The model was proven to be an effective tool to accurately evaluate all the operating regimes that a research turbine experienced during the experimental sequence. Consequently, the present model allows exploiting the complete test run duration to obtain unique experimental data from the turbomachinery operating at far off-design conditions. The capability to experimentally test components at off-design is fundamental to understand the flow physics of any gas turbine engine operating at extreme conditions and to characterize the transient performances of fluid-machinery in high-speed propulsion concepts. However, technical dissemination on these aspects is scarce. [ABSTRACT FROM AUTHOR]

The main aim of this work was the analysis of the transient thermal behavior of several typologies of power MOSFET devices. The commonly used thermal model has been applied to different device families with different breakdown voltages. The large difference between the experimental results and the simulation runs, performed with the classic approach for some kinds of devices, leads to correct the traditional mathematical thermal model and to build up a new one in which the real size of the epitaxial layer is taken into account. A new model will be shown performing a better fitting with the experimental evidence and confirming its suitability for all the proofed families of devices. The mathematical process developed to build up the model is shown, and a comparison is carried out between the measured temperatures on the device and estimation by the model. The results discussed in the paper show how the developed model allows a better fitting of the achieved model with the experimental measurements and demonstrate the suitability of the proposed approach. [ABSTRACT FROM AUTHOR]

Due to computational costs, radiation is usually neglected or solved in plane parallel 1D approximation in today's numerical weather forecast and cloud resolving models. We present a fast and accurate method to calculate 3D heating and cooling rates in the thermal spectral range that can be used in cloud resolving models. The parameterization considers net fluxes across horizontal box boundaries in addition to the top and bottom boundaries. Since the largest heating and cooling rates occur inside the cloud, close to the cloud edge, the method needs in first approximation only the information if a grid box is at the edge of a cloud or not. Therefore, in order to calculate the heating or cooling rates of a specific grid box, only the directly neighboring columns are used. Our so-called Neighboring Column Approximation (NCA) is an analytical consideration of cloud side effects which can be considered a convolution of a 1D radiative transfer result with a kernel or radius of 1 grid-box (5 pt stencil) and which does usually not break the parallelization of a cloud resolving model. The NCA can be easily applied to any cloud resolving model that includes a 1D radiation scheme. Due to the neglect of horizontal transport of radiation further away than one model column, the NCA works best for model resolutions of about 100 m or lager. In this paper we describe the method and show a set of applications of LES cloud field snap shots. Correction terms, gains and restrictions of the NCA are described. Comprehensive comparisons to the 3D Monte Carlo Model MYSTIC and a 1D solution are shown. In realistic cloud fields, the full 3D simulation with MYSTIC shows cooling rates up to −150 K/d (100 m resolution) while the 1D solution shows maximum coolings of only −100 K/d. The NCA is capable of reproducing the larger 3D cooling rates. The spatial distribution of the heating and cooling is improved considerably. Computational costs are only a factor of 1.5–2 higher compared to a 1D solution. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation of the air-based building integrated photovoltaic/thermal (BIPV/T) system with multiple inlets for a cold climate for a solar house with a typical roof having 4-5 inlets. The experimental investigation of the BIPV/T prototypes with one and two air inlets in a full-scale solar simulator was conducted to develop the correlation for the convective heat transfer coefficient of the PV air channel with multiple inlets. The mathe-matical model for air-based BIPV/T systems with multiple inlets is proposed, based on which a computer program is developed. The computer program is verified with experi-mental results. With the computer program, the performance of an air-based BIPV/T system with multiple inlets for a cold climate for a solar house is evaluated. The results show that the thermal efficiency of the system can be increased by 7% with four air inlets compared to one inlet, given that the total air flow rates are the same. It is shown that the novel design of introducing multiple inlets in the BIPV/T air system enhances its energy performance. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive review of various theories for the modeling and analysis of functionally graded plates and shells is presented. The review is devoted to theoretical models which were developed to predict the global responses of functionally graded plates and shells under mechanical and thermal loadings. This review mainly focuses on the equivalent single layer theories including the classical plate theory, first-order shear deformation theory, higher-order shear deformation theories, simplified theories and mixed theories since they were widely used in the modeling of functionally graded plates and shells. In addition, a thorough review of the literature related to the development of three-dimensional elasticity solutions and a unified formulation is also presented. [ABSTRACT FROM AUTHOR]

Motivated by the need for small scale distributed hydrogen generation and lack of detailed modeling tools to aid in reformation system design, two fully coupled models were developed to extend the current understanding of reformation processes as it relates to temperature and fuel conversion, two critical design criteria. This paper, describes the construction and validation of a steam and autothermal reformation model which was then experimentally validated. Experiments were carried out to obtain the necessary parameters to construct and validate the model. Two reactor geometries were used to verify the model using methanol as a feedstock on a copper-based catalyst. The model captured the important characteristics of the reformer with fuel flow rate, geometry, and Oxygen to carbon ratio. The model has several advantages including the ability to estimate the required reformer length for 100% fuel conversion as well as the effect that flow rate and geometry have on conversion efficiency. [ABSTRACT FROM AUTHOR]

The interest in stratospheric airships has increased and great progress has been achieved since the late 1990s due to the advancement of modern techniques and the wide range of application demands in military, commercial, and scientific fields. Thermal issues are challenging for stratospheric airships, while there is no systematic review on this aspect found yet. This paper presents a comprehensive literature review on thermal issues of stratospheric airships. The main challenges of thermal issues on stratospheric airships are analyzed. The research activities and results on the main thermal issues are surveyed, including solar radiation models, environmental longwave radiation models, external convective heat transfer, and internal convective heat transfer. Based on the systematic review, guides for thermal model selections are provided, and topics worthy of attention for future research are suggested. [ABSTRACT FROM AUTHOR]

Fire fighting is a hazardous occupation and the use of good quality thermal protective clothing is vital in the prevention of heat related injuries. Protective fire fighting clothing is generally chosen for its thermal and fire resistant properties, while also considering the weight, bulk and ease of movement of the suit. This research proposes incorporating a phase change material (PCM) into the fabric of the fire fighting suit in conjunction with air gaps to increase the thermal protection. A mathematical model of heat transport through a suit that contains PCMs and air gaps is presented. We investigate the distribution of temperature within the fabric during exposure to different fire situations. To assess the protective nature of the clothing, we model the skin as three layers with differing thermal properties (the epidermis, dermis and the subcutaneous layer) and examine the temperatures within the skin. The model can then be used to determine if the inclusion of a PCM layer would provide increased thermal protection to the fire fighter. Our earlier research has indicated that the most effective position for a PCM layer is near the outside of the suit. This paper will focus on the effect of the PCM layer in combination with air layers in the suit. Our results clearly show that an additional air layer increases the protection provided by the suit. This benefit comes without significantly increasing the overall weight of the suit. [ABSTRACT FROM AUTHOR]

Energy conversion devices undergo thermal loading during their operation as a result of inefficiencies in the energy conversion process. This will eventually lead to degradation and possible failure of the device if the heat generated is not properly managed. The ability to accurately predict the thermal behavior of such a device during the initial developmental stage is an important requirement. However, accurate predictions of critical temperature is challenging due to the variation of heat transfer parameters from one device to another. The ability to determine the model parameters is key to accurately representing the heat transfer in such a device. This paper presents the use of an inverse identification technique to estimate the model parameters of an energy conversion device designed for vehicular applications. To simulate the imperfect contact and the presence of insulating materials in the permanent magnet electric machine, thin material are introduced at the component interface of the numerical model. The proposed inverse identification method is used to estimate the equivalent thermal conductance of the thin material. In addition, the electromagnetic losses generated in the permanent magnet is also derived indirectly from the temperature measurement using the same method. With the thermal properties and input parameters of the numerical model obtained from the inverse identification method, the critical temperature of the device can be predicted more accurately. The deviation between the maximum measured and predicted winding temperature is less than 2.4%. [ABSTRACT FROM AUTHOR]

This paper presents a detailed flexible mathematical model for planar solid oxide fuel cells (SOFCs), which allows the simulation of transient performance characteristics. This mathematical model includes the incorporation of a thermal modelling into an electrochemical model with physico-chemical governing equations and a detailed multi-component gas diffusion mechanism, Dusty Gas Model (DGM). Spatial discretization can be applied up to quasi 3-D geometries and is resolved with the FDM (Finite Difference Method). The model is built and implemented in the commercially available modelling and simulations platform gPROMS™. The model was compared against existing models, the differences in results are identified and attributed to assumptions. Several transient operation case studies are examined such as load change and start-up: the results illustrate how important such a tool is for analyzing SOFC operation. [ABSTRACT FROM AUTHOR]

The design of the thermal control system of space vehicles, needed to maintain the equipment components into their admissible range of temperatures, is usually developed by means of thermal mathematical models. These thermal mathematical models need to be correlated with the equipment real behavior registered during the thermal test campaign, in order to adapt them to the real state of the vehicle “as built”. The correlation of this type of mathematical models is a very complex task, usually based on manual procedures, which requires a big effort in time and cost. For this reason, the development of methodologies able to perform this correlation automatically, would be a key aspect in the improvement of the space vehicles thermal control design and validation. The implementation, study and validation of a genetic algorithm able to perform this type of correlation in an automatized way are presented in this paper. The study and validation of the algorithm have been performed based on a simplified model of a real space instrument. The algorithm is able to correlate thermal mathematical models in steady state and transient analyses, and it is also able to perform the simultaneous correlation of several cases, as for example hot and cold cases. [ABSTRACT FROM AUTHOR]

This study deals with the modelling of a tubular flow microreactor and an annular flow microreactor that are used for kinetic studies of thermal reactions (873-1273 K) at very short residence times (10-100 ms). The construction of a kinetic model on the basis of experimental reaction data requires the precise characterization of the thermal behaviour and the hydrodynamics of the reactor. In kinetic studies, the reactor is usually considered as an isothermal Plug Flow Reactor. In this paper, we demonstrate that an annular flow microreactor used at very short residence time not only leads to a temperature profile which is better controlled than in a tubular flow microreactor, but also to less axial dispersion for laminar flow. The comparison between both reactors is performed on the basis of temperature measurements, RTD measurements at room temperature, dimensionless numbers calculations and Computational Fluid Dynamics in typical reaction conditions. [ABSTRACT FROM AUTHOR]

The paper concerns modelling an influence of self-heating and mutual thermal coupling on power LEDs characteristics. The electrothermal model of a power LED for SPICE software taking into account electric, thermal and optical properties of the considered devices, and particularly mutual thermal coupling between the devices situated on the common heat-sink, is presented. The method of estimating model parameters values is proposed and the method of measuring their own and mutual thermal resistance between power LEDs is described. Using the elaborated model the characteristics of selected diodes are calculated at different cooling conditions of the investigated LED. The obtained results of calculations are compared with the measurements results for a single diode, two diodes situated on the common heat-sink and a LED module. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid energy supply system, which is composed of two subsystems (gas engine-driven heat pump system (GEHP) and organic Rankine cycle system (ORC)) and three major thermodynamic cycles (the vapor compression refrigeration cycle, the internal combustion gas engine cycle and ORC). In order to convert the low-grade gas engine waste heat into high-grade electricity, the ORC system is built up using R245fa, R152a and R123 as working fluids, and the ORC thermal model is also developed. Meanwhile, experiments of GHEPs in cooling mode are conducted, and several factors which influence the cooling performance are also discussed. The results indicate that the cooling capacity, gas engine energy consumption, gas engine waste heat increase with increasing of gas engine speed and decrease with decreasing of evaporator water inlet temperature. The waste heat recovered from gas engine is more than 55% of gas engine energy consumption. F6urthermore, R123 in ORC system yields the highest thermal and exergy efficiency of 11.84% and 54.24%, respectively. Although, thermal and exergy efficiency of R245fa is 11.42% and 52.25% lower than that of R123, its environmental performance exhibits favorable utilization for ORC using gas engine waste heat as low-grade heat source. [ABSTRACT FROM AUTHOR]

This paper examines a mathematical model of the thermal evolution in a specific room of “The City of Refuge”, built in Paris (1933) by Le Corbusier. Although the architect proposed an environmental conditioning system by combining two technological advances: the mur neutralisant – a double-glazed wall with an air cavity that can be heated or cooled – and the respiration exacte – a purified circulating air maintained at constant temperature –, this was never incorporated. This article aims to acquire knowledge of indoor air distribution in the room under study by considering the combination of the mur neutralisant and the respiration exacte . The problem is resolved through a “coupled code”. The first is a two-dimensional model simulating the temperature evolution in the room, while the second is a one-dimensional model used to represent the problem of the mur neutralisant . The numerical model develops the technical issues associated with the implementation of computational fluid dynamics (CFD). The numerical simulations carried out validate the solution of the system proposed. Control of the façade temperature using the active chamber ensures that the operative temperatures obtained for summer and winter fall within the comfort range. The City of Refuge is the clearest precursor of modern active façade systems. [ABSTRACT FROM AUTHOR]

This paper proposed a mathematical model and numerical model to investigate the output characteristics of photovoltaic (PV) array of stratospheric airship. In addition, considering with the influence of flight time, flight status,flight location, flight height, environmentaltemperature and other factors on the output power of the PV array, the model ofsolar radiation, and PV array on the surface ofStratospheric Airship are established. Then, the thermal effects of the PV array on the airship is investigated using CFD/Fluent, based on which the three-dimensional temperature profile of PV array and airship are presented. [ABSTRACT FROM AUTHOR]

Ball bearings of turbopumps of rocket engines work in very singular conditions; they are flooded into liquid oxygen or liquid hydrogen. Therefore, the use of any conventional lubricants (oil or grease) is prescribed. Although cryogenic fluids can cool this kind of ball bearing, they cannot separate the surfaces in contact. As a result, there is a significant increase in frictional power losses. This paper presents tests performed on a cryotechnic ball bearing flooded in liquid oxygen. The test results showed that beyond a critical loading of the bearing, a sudden increase in temperature occurred. A thermal model is also put forward, in order to understand and anticipate especially the thermal instability described above. [ABSTRACT FROM AUTHOR]

This paper describes a methodology for the modeling and simulation of a pulsed thermography inspection of carbon fiber-reinforced composites. A thermal–numerical model based on the 3D transient heat conduction equation for heterogeneous media is proposed to model the thermal response of the composite medium when a thermal pulse is applied to its surface. The solution of the model is developed using the finite volume method, in which the approximated equations are obtained by performing energy balances for each elementary volume. The experimental validation of the thermal–numerical model consisted of a comparison of the thermal decay curves for defective areas obtained through numerical simulation and with a pulsed thermography inspection of a laminated composite specimen with simulated defects (Teflon inserts). A parametric study was carried out in order to analyze the influence of the irradiation power density, non-uniform heating and characteristics associated with the defects on quantitative variables such as the onset time and thermal contrast. Numerical results showed that the variable thermal contrast is highly sensitivity to changes in the defect thickness, aspect ratio and parameters related to the external stimulation. Furthermore, an increase in the detectability of defects – especially those with lower aspect ratios – can be achieved by increasing the irradiation power. [ABSTRACT FROM AUTHOR]

Antioxidants are typically added to polyethylene to extend its durability, and recently clay nanoparticles have been blended into polyethylene to improve mechanical properties. However, the clay nanoparticles also accelerate the rate of antioxidant depletion in polyethylene. This paper uses a mathematical model to describe the underlying mechanisms of antioxidant (hindered-phenol) depletion and to predict experimentally-measured antioxidant profiles in polyethylene–clay nanocomposites. The mathematical model uses a reaction kinetic scheme that includes free radical initiation and propagation reactions, antioxidant stabilization reactions and free radical termination reactions. In the model, alkyl free radicals oxidize rapidly. The role of antioxidants is to stabilize the oxidized free radicals to hydroperoxides, and interrupt propagation reactions. However, in nanocomposites, continuous depletion of antioxidant is caused by the clay acting as a catalyst to decompose hydroperoxides and regenerate alkyl free radicals. This cyclic hydroperoxide generation and decomposition leads to much faster antioxidant depletion in polyethylene nanocomposites. Phenoxyl radicals of antioxidants generated by stabilization reactions contribute to terminate polymeric free radicals and limit their accumulation. Predictions of antioxidant depletion are compared to experimental results for accelerated aging of polyethylene and nanocomposite samples. [ABSTRACT FROM AUTHOR]