Changes In Temperature Distribution Research Articles

Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method

PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method.

Experimental Study on Combustion Characteristics of Solvent and Fire Behavior During a Solvent Fire at Nuclear Fuel Cycling Facility

A fire accident is one typical postulated accident in a nuclear fuel cycling facility. Safety-related data on a combustible fire are necessary to evaluate the safety of nuclear fuel cycling facilities under fire accident conditions quantitatively. Accurate and reliable data should be obtained by performing some demonstration tests. This study deals with the ignition and combustion characteristics of solvent involved at a nuclear fuel cycling facility and the fire behavior during a solvent fire. Small-scale and large-scale tests were conducted at the China Institute for Radiation Protection. The minimum ignition energy of the solvent under different temperatures was obtained. The test data were used to judge the possibility that the organic solvent ignited by a spark. Parameters such as combustion rate, smoke gas, aerosol release of solvent combustion, temperature distribution, and pressure change in the solvent fire cell were also obtained. The test results can be used as conservative estimates of the amount of aerosol release during a solvent fire. The experimental data also can be used to develop preventive and mitigation measures for solvent fire accidents. This paper puts forward information based on the experimental data and the recent international study.

Changes of Temperature and Moisture Distribution over Time by Thermo-Hydro-Chemical (T-H-C)-Coupled Analysis in Buffer Material Focusing on Montmorillonite Content

Bentonite is used as a buffer material in engineered barriers for the geological disposal of high-level radioactive waste. The buffer material will be made of bentonite, a natural clay, mixed with silica sand. The buffer material is affected by decay heat from high-level radioactive waste, infiltration of groundwater, and swelling of the buffer material. The analysis of these factors requires coupled analysis of heat transfer, moisture transfer, and groundwater chemistry. The purpose of this study is to develop a model to evaluate bentonite types and silica sand content in a unified manner for thermo-hydro-chemical (T-H-C)-coupled analysis in buffer materials. We focused on the content of the clay mineral montmorillonite, which is the main component of bentonite, and developed a model to derive the moisture diffusion coefficient of liquid water and water vapor based on Philip and de Vries, and Kozeny–Carman. The evolutions of the temperature and moisture distribution in the buffer material were analyzed, and the validity of each distribution was confirmed by comparison with the measured data obtained from an in situ experiment at 350 m in depth at the Horonobe Underground Research Center, Hokkaido, Japan.

Analysis of Thermal Management Strategies for 21700 Lithium-Ion Batteries Incorporating Phase Change Materials and Porous Copper Foam with Different Battery Orientations

The significant amount of heat generated during the discharge process of a lithium-ion battery can lead to battery overheat, potential damage, and even fire hazards. The optimal operating temperature of a battery ranges from 25 °C to 45 °C. Hence, battery thermal management cooling techniques are crucial for controlling battery temperature. In this work, the cooling of 21700 lithium-ion batteries during their discharging processes using phase-change materials (PCMs) and porous pure copper foams were simulated. The effects of discharge intensities, battery orientations, and battery arrangements were investigated by observing the changes in temperature distributions. Based on current simulations for a 2C discharge, air-cooled vertical batteries arranged in unidirectional configuration exhibit an increase in heat dissipation by 44% in comparison to the horizontal batteries. This leads to a decrease in the maximum battery temperature by about 10 °C. The use of either PCMs or copper foams can effectively cool the batteries. Regardless of the battery orientation, the maximum battery temperature during a 2C discharge drops dramatically from approximately 90 °C when air-cooled to roughly 40 °C when the air is replaced by PCM cooling or when inserted with a copper foam of 0.9 porosity. If the PCM/copper foam approach is implemented, this maximum temperature further decreases to slightly above 30 °C. Although not very significant, it has been discovered that crossover arrangement slightly reduces the maximum temperature by no more than 1 °C. When a pure copper foam with a porosity ranging from 0.90 to 0.97 is saturated with a PCM, the excellent thermal conductivity of pure copper, combined with the PCM latent heat absorption, can best help maintain the battery pack within its range of optimal operating temperatures. If the porosity of the copper foam decreases from 0.95 to 0.5, the volumetric average temperature of the batteries may increase from 30 °C to 31 °C.

Mechanism underlying the tenderness evolution of stir-fried pork slices with heating rate revealed by infrared thermal imaging assistance

This study aimed to explore the mechanism of cooking intensity on the tenderness of stir-fried pork slices from the perspective of the changes in temperature distribution. Infrared thermal imaging was used to monitor the distribution of temperature. Results showed that the high-level heat (HH) treatment could improve tenderness. When the center temperature increased to 100 °C, the shear force of samples from the low-level heat (LH) group increased by around 3-fold, and HH reduced this upward trend. This result was mainly attributed to the shorter heating time undergone by the HH-treated samples compared to the LH treatment, which resulted in less structural shrinkage and faster passing through the protein denaturation interval of the samples. These changes alleviated temperature fluctuations caused by water loss. This explanation could be confirmed by the results of T2 relaxation time and Fourier transform-infrared spectroscopy (FT-IR). However, the LH treatment caused a slower rise in oil temperature due to more moisture migration, which required the samples to undergo longer thermal denaturation, leading to a deterioration in tenderness. Moreover, histological analysis revealed that the greater integrity of endomysium in the HH group inhibited water loss and oil absorption, which contributed to obtain low-fat meat products with higher tenderness. This study provides support for the industrialization of traditional pork cuisines using oil as the heating medium.

CFD–DEM Simulation of Heat Transfer and Reaction Characteristics of Pyrolysis Process of MSW Heated by High-Temperature Flue Gas

Pyrolysis is a promising disposal method for municipal solid waste (MSW) due to the high-value utilization of the organic components of MSW. Traditional indirect heating has low heat transfer efficiency and requires an increase in the heat exchange area. In this study, a refined numerical simulation model for the pyrolysis of four typical MSW components with high-temperature flue gas was established to study the influence of flue gas on the heat transfer and reaction characteristics of MSW. The temperature distribution and particle size change in different components were obtained, and the effects of flue gas temperature and velocity on the pyrolysis process were analyzed. It was found that the temperature difference of the four components along the bed height direction was about 1.36–1.81 K/mm, and the energy efficiency was about 55–61%. When the four components were uniformly mixed, the temperature increase rates of each component were similar during the pyrolysis process. As the flue gas temperature increased, the amount of gas consumption decreased and the energy efficiency increased. When the flue gas velocity increased, the flue gas consumption increased and the energy efficiency decreased. The research results are of great significance for the promotion and application of pyrolysis technology to MSW with high-temperature flue gas.

A method for estimating the effect of climate change on monthly mean temperatures: September 2023 and other recent record‐warm months in Helsinki, Finland

AbstractWe describe a method for quantifying the contribution of climate change to local monthly, seasonal, and annual mean temperatures for locations where long observational temperature records are available. The method is based on estimating the change in the monthly mean temperature distribution due to climate change using CMIP6 (Coupled Model Intercomparison Project Phase 6) model data. As a case study, we apply the method to the record‐warm September 2023 in Helsinki, and then briefly examine all record‐warm months of the 21st century. Our results suggest that climate change made the record‐warm September in Helsinki 9.4 times more likely and 1.4°C warmer. Thus, the new monthly mean record in September 2023 would probably not have been set without the observed global warming. The presented and provided tool allows operational meteorologists and climatologists to monitor and report the impact of climate change on local temperatures in near real time.

Simulation analysis on magnetic core loss characteristic of valve reactor in UHVDC system

Valve reactors (VR) with multiple magnetic cores are important electrical components in ultra-high voltage direct current systems. The impact current and high-order harmonics during their operation can lead to additional losses and temperature rise in the valve reactors, posing a threat to insulation aging, and even causing serious incidents such as combustion and explosions. Therefore, it is necessary to accurately quantify and analyze the loss characteristics of valve reactors under different magnetic materials. This article first theoretically analyzes the electromagnetic and temperature characteristics during the actual operation of VR; then, it analyzes and calculates the magnetic field distribution and electromagnetic losses of a single magnetic core. Finally, it establishes a three-dimensional equivalent model of VR and conducts transient electromagnetic-thermal coupled finite element simulation to reveal the magnitude and spatial distribution of VR temperature changes.

Study of spatial temperature features of road tunnel fires under multiple factors

AbstractAfter a highway tunnel fire, the rapid change of the internal ambient temperature directly affects the personal safety of pedestrians. Based mainly on the lateral possibility of fire location and considering the coupling effect of multiple factors in a two‐lane highway tunnel, this study systematically carried out 63 full‐size tunnel fire simulation studies relying on Fluent software. The smoke temperature distribution patterns in the transverse and longitudinal spaces of the tunnel after the fire were revealed. This study shows that the smoke temperature below the tunnel vault is susceptible to the effect of sidewall restraint, making the maximum temperature of the tunnel vault of the offset fire source large; considering the lateral location of the fire source, the maximum temperature prediction formula of the tunnel vault is modified to expose the change law of the longitudinal temperature decay of the vault. This paper reveals for the first time the law of temperature distribution changes at the characteristic height of the human eye on the evacuation platform in the tunnel; the systematic study of the fire source cross‐sectional temperature distribution changes at the key lining structure points, and it is found that a low‐temperature space conducive to personnel escape exists in the lower part of the tunnel away from the fire source side. The results of the study are beneficial to the design of safe evacuation paths in the tunnel and the active emergency evacuation of personnel in the near‐fire source area.

Effects of Current Collector on Internal Visualization of Solid Oxide Cells

Introduction Visualization of spatial distribution in solid oxide fuel cells (SOFCs) operating under high temperature is difficult to use various measurement equipment and sensors due to their recommended operating temperature. Therefore, it is difficult to reveal the distributions of gas species and reactions in the cell, as well as the loading current, using only electrochemical measurement methods. Simulation technology can be used to visualize various distributions in the cell and predict cell performance. While many simulation studies have revealed various spatial distributions in the SOFCs such as current density, they have also indicated that it is essential to accurately reflect the cell shape and multiphysics to simulate the cell performance1, 2.In our previous study, simulation and experimental thermal imaging combined temperature visualization method was developed. It was suggested that the temperature distribution under actual operating conditions is affected by Joule heating due to loading current distribution depending on the current collector geometry. Therefore, in order to evaluate the influence of the collector shape on the spatial temperature distribution, the influences of Joule heating and the collector geometry on the temperature distribution are evaluated. Then, we also analyze the influence of the current collector on the SOFC performance and propose a current collection method suitable for visualizing the reaction in an SOFC. Simulation Method In this study, the calculation was performed using a three-dimensional model that simulates the actual cell geometry used in the experiments. The simulated 3-D model was based on an electrolyte-supported plate cell with Scandia-stabilized Zirconia (ScSZ, 5 cm × 5 cm in size) as the support, LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ composite material for the air electrode, and Ni-ScSZ cermet for the fuel electrode, respectively. The electrode area was 4 cm × 4 cm (16 cm2), and a platinum mesh and wire were used as a current collector. A schematic diagram of one of these examples is shown in Fig. 1. COMSOL Multiphysics (Ver. 6.0) was used as the 3-D simulation software to calculate the I-V characteristics and cell temperature distribution.The cell operating conditions were set to 800 ℃ for the operating temperature, 100 ml min-1 of 3 % humidified hydrogen as the incoming fuel, and the air electrode side opened to the atmosphere. I-V characteristics and cell temperature distributions were calculated under current density loading conditions ranging from 0.01 A cm-2 to 0.15 A cm-2. Based on each result, the relationship between current density and cell temperature distribution was evaluated. Results and Discussion As a result of numerical analysis and experiments focusing on the effect of the current collector shape, it was confirmed that the influence of the current collector shape appeared significantly in the cell temperature distribution as shown in Fig. 2. In addition, it was found that the visualization of the spatial distribution may be difficult because the effect of the heat generated by the Pt wire used as the current collector appears in the results of the temperature distribution on the surface. Based on these findings, we improved the current collector shape. Although the effect of the improvement on the Joule heating at Pt wire appeared in the temperature distribution result, the temperature distribution change was confirmed due to the loading current flow pattern, which depends on the shape of the current collector. The simulation results of the further improved collector shape showed that the temperature distribution change depending on the collector shape became smaller, suggesting that this collector shape is promising as a current collecting method suitable for visualizing the cell inside. In this presentation, we report the simulation results and discussion on the changes in current density distribution, gas distribution, and I-V characteristics, in addition to the changes in temperature distribution. References (1) M. Andersson, H. Paradis, J. Yuan, and B. Sundén, Electrochimica Acta, 109, 881 (2013).(2) A. Li, C. Song, and Z. Lin, Applied Energy, 190, 1234 (2017). Figure 1

Study on the Temperature Field Change Characteristics of Coal Gangue Dumps under the Influence of Ambient Temperature in Heat Pipe Treatment

In order to investigate the influence of ambient temperature on the temperature field of coal gangue dumps governed by heat pipes (HPs), using self-developed heat pipe and intelligent cloud monitoring software, a 1-year field test was conducted in the spontaneous combustion coal gangue dump of Danao liang. This study analyzed the temperature distribution changes of a spontaneous combustion coal gangue dump under different ambient temperatures, as well as the temperature changes of the coal gangue at different time scales. Correlation analysis between ambient temperature and coal gangue temperature was conducted, and a quadratic regression model was established for goodness of fit and significance testing. The results show that ambient temperature affects the distribution of the temperature field of the spontaneous combustion coal gangue dump under the action of the HPs, and the cooling effect on the high-temperature zone is stronger in autumn and winter. The daily change in coal gangue temperature at each measurement point is similar, showing a peak-shaped curve of low at night and high during the day. The inter-day changes of each measuring point have seasonal characteristics: the cooling rate of the high-temperature zone measuring point is affected by the ambient temperature; the seasonal characteristics of the low-temperature zone measuring point are more obvious than the high-temperature zone, and its daily average temperature is affected by the ambient temperature. The ambient temperature and the internal temperature of the coal gangue dump are correlated, and the quadratic regression equation has a high degree of goodness of fit and meets the F-test, indicating that the quadratic regression model can be used for the empirical regression formula of the ambient temperature and the internal temperature of the coal gangue dump. The results of this study provide some references for the sustainable development of mining environments.

In-Bulk Temperature Profile Mapping Using Fiber Bragg Grating in Fluids.

The capabilities of Fiber Bragg Grating (FBG) sensors to measure temperature variations in the bulk of liquid flows were considered. In the first step of our research project, reported in this paper, we investigated to what extent the use of thin glass fibers without encapsulation, which only minimally disturb a flow, can fulfill the requirements for robustness and measurement accuracy. Experimental tests were performed in a benchmark setup containing 24 FBG measuring positions, which were instrumented in parallel with thermocouples for validation. We suggest a special assembly procedure in which the fiber is placed under a defined tension to improve its stiffness and immobility for certain flow conditions. This approach uses a single FBG sensor as a reference that measures the strain effect in real time, allowing accurate relative temperature measurements to be made at the other FBG sensor points, taking into account an appropriate correction term. Absolute temperature readings can be obtained by installing another well-calibrated, strain-independent thermometer on the reference FBG. We demonstrated this method in two test cases: (i) a temperature gradient with stable density stratification in the liquid metal GaInSn and (ii) the heating of a water column using a local heat source. In these measurements, we succeeded in recording both spatial and temporal changes in the linear temperature distribution along the fiber. We present the corresponding results from the tests and, against this background, we discuss the capabilities and limitations of this measurement technique with respect to the detection of temperature fields in liquid flows.

Urban Design Impact on Local Climate and its Consequences on Building Energy Demand in Morocco

Urban design has a profound impact on the local climate, which can result in changes in temperature distribution and energy demand. The Urban Heat Island (UHI), a well-documented issue where cities typically experience higher temperatures than the cooler rural surroundings that envelop them, is closely tied to urban design and its geometrical features. This increase in temperature can lead to increased energy consumption, particularly for air conditioning, as populations strive to maintain thermal comfort. Within this framework, this paper seeks to advance our comprehension of the influence of urban design on the Urban Heat Island (UHI) effect and building energy requirements. It makes a valuable contribution to the expanding body of research in this field, offering insightful guidance on optimal urban design strategies tailored to diverse climate zones in Morocco. To achieve these goals, we explore multiple urban design scenarios incorporating variations in building heights, street aspect ratios, building layout configurations, and street orientations. We employ the Urban Weather Generator and EnergyPlus for our analysis, with the former enabling the generation of synthetic weather data that accounts for the UHI effect in urban contexts, and the latter facilitating building energy simulations. The simulation results reveal a wide-ranging hourly variation in Urban Heat Island (UHI) intensity, spanning from 11°C to -5°C across the cities under study. Among these cities, Ifrane, Marrakesh, and Fes exhibit the highest average annual UHI intensity. Incorporating UHI considerations into energy simulations has yielded notable outcomes. Low-rise buildings experience a reduction in total energy requirements, while mid-rise and high-rise buildings exhibit an increase. For instance, adopting an urban design scenario featuring 20-story buildings and a street aspect ratio of 0.33 led to a rise in total energy demands between 8% and 19%. Furthermore, the street aspect ratio (H/W) emerges as the primary driver of UHI, whereas street orientation and building layout exert the most substantial influence on building energy requirements. Inefficient building layouts result in a significant increase in building energy needs, ranging from 106% to 121%, while less energy-efficient street orientations lead to total energy needs escalating by 28% to 76%.

Detecting Extreme Temperature Events Using Gaussian Mixture Models

AbstractExtreme temperature events have traditionally been detected assuming a unimodal distribution of temperature data. We found that surface temperature data can be described more accurately with a multimodal rather than a unimodal distribution. Here, we applied Gaussian Mixture Models (GMM) to daily near‐surface maximum air temperature data from the historical and future Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations for 46 land regions defined by the Intergovernmental Panel on Climate Change. Using the multimodal distribution, we found that temperature extremes, defined based on daily data in the warmest mode of the GMM distributions, are getting more frequent in all regions. Globally, a 10‐year extreme temperature event relative to 1985–2014 conditions will occur 13.6 times more frequently in the future under 3.0°C of global warming levels (GWL). The frequency increase can be even higher in tropical regions, such that 10‐year extreme temperature events will occur almost twice a week. Additionally, we analyzed the change in future temperature distributions under different GWL and found that the hot temperatures are increasing faster than cold temperatures in low latitudes, while the cold temperatures are increasing faster than the hot temperatures in high latitudes. The smallest changes in temperature distribution can be found in tropical regions, where the annual temperature range is small. Our method captures the differences in geographical regions and shows that the frequency of extreme events will be even higher than reported in previous studies.

A REVIEW ON THE INFLUENCE OF COOLING APPLICATIONS IN FRICTION STIR WELDING PROCESS

Welding, despite being the most efficient joining process, has significant negative impact on the environment and worker health. This paper presents the environmental impact of various conventional welding processes and sustainability of Friction Stir Welding–a Green technology which requires no filler material, no shielding gas, no flux and involves no gas emissions. It is an energy-efficient process that saves significant amount of power and energy when compared to conventional welding processes. The defect-free welds produced have better mechanical and metallurgical properties than other processes. The higher temperature distributed due to the friction heat is established as the source of weld failure. Cooling the weld joint controls the heat conduction thus further enhancing the weld properties. This review paper explores the different cooling techniques employed for cooling the joint during Friction Stir Welding process. The changes in temperature distribution and microstructure caused by the cooling applied and the consequential transformation in material flow, tensile strength, hardness, corrosion, wear, residual stress are discussed. The changes in weld properties obtained by using different cooling media on different materials are reviewed.

Health Monitoring of Power Semiconductor Module Using Temperature Sensitive Electrical Parameter

Power semiconductor modules (PSMs) are critical components in power electronics applications such as motor drives, renewable energy systems, and electric vehicles. The reliable operation of these modules is crucial for the safe and efficient operation of these systems. One of the most common failure mechanisms in PSMs is due to overheating or repeated heating and cooling, which can result in thermal stress and component degradation. Therefore, monitoring the temperature of PSMs is essential for ensuring their health and preventing catastrophic failures. By monitoring temperature-sensitive electrical parameters (TSEPs), such as the on-state voltage drop, it is possible to detect changes in the temperature of the PSM in real-time. The change in voltage drop can be used as an early warning sign of a potential failure or degradation of the PSM. The advantage of this method is that it provides a non-invasive and real-time monitoring solution that can detect changes in the PSM's temperature distribution.

NUMERICAL INVESTIGATION OF FORCED CONVECTION HEAT TRANSFER ON INLINE CYLINDERS IMMERSED IN A POROUS MEDIA

In the present study, forced convection heat transfer on eight inline cylinders immersed in a 10 × 10 × 30 cm packed bed of porous medium is numerically explored with a range of Reynolds numbers from 1100 to 2250. The airflow passes through eight cylinders with an inline arrangement, each having a diameter of 15 mm and a length of 10 cm, immersed in a horizontal porous channel at a constant heat flux of 2000W/m2. The commercial program ANSYS Fluent R.19 simulates the changes in pressure drop and temperature distribution by changing the Reynolds number and porosity. The dimensions of each porous pack are 10x10 cm in cross-section, 5 cm in length, and 5 cm in spacing from the next porous pack. The porosity values are (0.4001, 0.39112, and 0.3822). The general shape of all temperature contours shows that the high porosity near the cylinder wall enhances heat transfer from the heated cylinder surface. After that, the air temperature gradually decreases when going away from the cylinder surface. It can also be seen that the pressure drop decreases as particle diameter increases.

Decadal Modulation of the Atlantic Meridional Mode on the West Antarctic Climate during Austral Winter

Abstract Based on observations and simplified, comprehensive atmospheric models, we investigate the impact of the tropical Atlantic sea surface temperature (SST) on the West Antarctic temperature and sea ice concentration in austral winter (June–August) on decadal time scales. The tropical gradient SST anomaly (SSTA) associated with the positive phase of the Atlantic meridional mode (AMM) usually leads to cool anomalies over the Antarctic Peninsula (AP) and a dipole-like sea ice distribution, with ice growth in the Amundsen–Bellingshausen Sea and loss in the Ross Sea. When the AMM is in a positive phase, upward motion over the warm region in the North Atlantic and downward motion over the cold region in the South Atlantic strengthen the Southern Hemisphere Hadley cell, resulting in upper-level convergence over the southwestern Atlantic. This convergence induces a Rossby wave, leading to an anticyclone anomaly over the Amundsen–Bellingshausen Sea. Meridional component winds of this anticyclone anomaly are associated with wind-driven sea ice drift, temperature advection, and anomalous turbulence heat fluxes, leading to a dipole-like sea ice distribution and AP cooling. These findings are verified using two types of atmospheric models. Therefore, the AMM plays a vital role in modulating the decadal change in temperature and sea ice distribution in the West Antarctic.

In-Situ Observation of Temperature Distribution on a Planar Type SOEC During Start-Stop Cycle Operation

Introduction It is important to establish various analytical methods for solid oxide electrolysis cells (SOECs) under practical operating conditions in order to improve their performance and to analyze their degradation phenomena. In-situ observation of temperature distribution on a planar type SOEC enables to reveal the distributions of electrochemical reactions and the cell degradation. While there have been several reports on the internal visualization of solid oxide fuel cells (SOFCs)1, 2, there have been only a few reports on that of SOECs. Since the endothermic electrolysis reaction occurs in SOECs, comparing with SOFCs, a different temperature distribution will appear. Therefore, it should be necessary to evaluate the phenomena on the planar SOECs for analyzing the temperature distribution taking gas flow and current distribution into consideration.The purpose of this study is to evaluate the effect of cell degradation caused by the start-stop cycle operation on the temperature distribution using a 5 cm × 5 cm planar cell observed by infrared camera. Experimental In this study, a planar cell was fabricated using a scandia-stabilized zirconia electrolyte (ScSZ, 200 µm thick, 5 cm × 5 cm in area) as a substrate. LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ composite materials were used for the air electrode, and nickel and ScSZ cermet were used for the fuel electrode. The electrode area was 4 cm × 4 cm (16 cm2). Each electrode material was screen-printed and sintered. A platinum mesh was used as the current collector.In this test, the cell was operated at 800 °C and 50%-humidified hydrogen (200 ml min-1) was supplied to the fuel electrode. The durability test was conducted under the accelerated degradation conditions of a start-stop cycle repeated in every 1 hour with 0.2 A cm-2 for 500 cycles (1000 hours). Electrochemical characteristics were measured by connecting Pt wires, spot-welded every 1 mm on one side of both electrode surfaces, to the voltage terminals of the electrochemical measurement setup and to the current terminals of the external power supply unit.Figure 1 shows a schematic view of the experimental setup and temperature change compared with the initial condition. The temperature distribution was observed by infrared camera (FLIR SC2500 - NIR, uncertainty ±0.02 oC) from the air electrode side open to the electric furnace. The difference between the temperatures before and during current loading was derived as the distribution of temperature changes. Results and discussion First, the electrochemical characteristics of the planar type SOECs during the start-stop cycle test were obtained. The cell voltage at 0.2 A cm-2 increased from 1.19 V to 1.29 V during the test up to 500 cycles. The cell voltage was 1.27 V even after the initial 50 cycles. This suggests that SOEC electrode degradation3,4 occurred in the early stage of the start-stop cycling.The temperature changes after 50 cycles showed that each temperature change was relatively small because the cell was operated near the thermoneutral potential (around 1.29 V at 800 °C). It was confirmed that the endothermic electrolysis reaction was predominant near the fuel inlet. In addition, heat generation due to Joule heating was also appeared near the current collecting Pt wire connected to the power supply. Therefore, in SOEC operation, it is suggested that the temperature distribution is affected by the shape of current collector, gas supply condition, and electrochemical reaction distribution. The detailed analysis on the SOEC electrochemical properties and temperature distribution observed by in-situ measurements during cycling tests is also presented. Acknowledgements A part of this research was supported by New Energy and Industrial Technology Development Organization (NEDO), project No. JPNP14026. References (1) S. Shinichi and H. Iwai, J. Power Sources, 482, 229070 (2021).(2) Y. Shiratori, T. Ogura, H. Nakajima, M. Sakamoto, Y. Takahashi, Y. Wakita, T. Kitaoka, and K. Sasaki, Int. J. Hydrogen Energy, 38 (25), 10542 (2013).(3) M. Keane, M. K. Mahapatra, A. Verma, and P. Singh, Int. J. Hydrogen Energy, 37 (22), 16776 (2012).(4) M. Hubert, J. Laurencin, P. Cloetens, B. Morel, D. Montinaro, and F. Lefebvre, J. Power Sources, 397, 240 (2018). Figure 1

Parametric dependence and elementary modelling for compressor disc cavity heat transfer

A wall-modelled large-eddy simulation (WMLES) method previously validated against laboratory experiments is applied to a real engine disc cavity geometry with surface and air temperatures representative of maximum power conditions. An appropriate set of independent nondimensional parameters describing the problem is defined and the sensitivities to these parameters are investigated by independently varying each parameter in the WMLES. Effects of a change in disc temperature distribution and a reduction in radius of the downstream disc are also investigated. The flow and heat transfer mechanisms predicted are very similar to those found for the research rig configuration although rotating cavity flow structures with two or more lobes are found for the engine geometry rather than the single-lobed structures shown in previous work. The simulations are compared with an elementary model giving further insight into scaling of the flow and heat transfer with operating conditions. The model assumes a well-mixed core flow in the cavity with constant rothalpy, relates shroud heat transfer to that of natural convection under gravity for high Rayleigh number, and relates disc heat transfer to conduction across unsteady Ekman layers. An energy balance for the cavity is used to obtain an effective mass flow exchange rate between the axial throughflow and the disc cavity to the disc and shroud heat transfer and core temperature. The model is considered to give a useful basis for engineering calculations involving correlation and extrapolation of WMLES and experimental results.