An electric vertical take-off and landing flying vehicle (eVTOL) is a potential technology for future urban air mobility. A major challenge for thermal management systems is the high cooling requirement and the variable application scenarios. To overcome this challenge, a multi-scene eVTOL-integrated thermal management system was developed. In this study, an eVTOL thermal management simulation platform based on Amesim simulation software was developed to investigate the effects of flight conditions on thermal management and range. The simulation results show that increasing the cruise altitude can reduce the thermal management energy consumption when the ground temperature is high. The maximum reduction of energy consumption for thermal management energy is 4 kW when the cruising temperature ranges from 10 ℃ to 26 ℃. When the hovering rescue duration is more than 150 s during the emergency rescue operation, the temperature difference inside the battery becomes too pronounced. A reduced payload improves the range, with the unloaded range being 1.33 times greater than the fully loaded range.

A transcritical CO₂ heat-pump air-conditioning system has effective heating performance at low temperatures, and the variation of dynamic parameters during operation significantly affects the thermal comfort inside the passenger cabin. To study the comfort of the passenger compartment and the coupling law of the dynamic changes in the parameters of the transcritical CO₂ heat-pump air-conditioning system, a joint simulation model was built based on the one-dimensional simulation software GT-Suite and the three-dimensional computational fluid dynamics (CFD) software STAR-CCM+. The three-dimensional cabin model can provide accurate real-time state parameters of the supply and return air for a one-dimensional simulation system of heat-pump air conditioners. The results show that the temperature distribution of the thermal environment of the passenger compartment is relatively non-uniform, necessitating the application of the weighted predicted mean vote (PMV) to evaluate this non-uniformity. In a multi-PID control transcritical CO₂ automobile heat pump air conditioning system, a control method based on the weighted PMV comfort model can maintain the regulation and stability of the system's target parameters. Under ambient temperature conditions of 43 ℃ in cooling mode, the control method can reduce the compressor's power consumption by 9.4%. At an ambient temperature of -10 ℃ in heating mode, this method can reduce compressor's the power consumption by 17.9%. This control method can reduce the power consumption of the system compressor while satisfying comfort requirements, constituting a highly efficient energy-saving strategy.

With the development of cold chain Internet of Things (IoT) technology, real-time temperature monitoring and data sharing have become important means to improve the efficiency of chilled meat supply chain management. In this paper, a strategy for optimizing time and temperature coordination based on the cold chain IoT was proposed to improve the operational efficiency of the chilled meat supply chain. Based on predictive microbiology and system reliability theory, this study investigated the effects of time and temperature on the quality of chilled meat. A quality-change model for chilled meat and an energy consumption model for the chilled meat supply chain were developed. To illustrate this approach, a case study of a chilled chicken supply chain was conducted. The findings revealed that there is an optimal level of freshness in the chilled meat supply chain that maximizes the benefits of the supply chain. If the freshness level in one stage deviates from this optimal value, subsequent stages can adjust the time and temperature to achieve maximum supply chain efficiency.

Nucleator nozzles play an important role in promoting the rapid nucleation, crystallization, and snow formation of artificial snow droplets. A visual experimental platform was designed to investigate the gas-liquid two-phase flow process inside the nucleator nozzle and its influence on atomization behavior. The results showed the presence of a two-phase annular flow within the nucleator nozzle and a continuous hollow-cone spray field outside the nucleator nozzle. As the gas-liquid pressure ratio (Φ_GL) increases, the interfacial disturbance waves at the gas-liquid interface of the internal flow gradually disappear. As the air core occupied more space, the liquid film thickness gradually decreased and became uniform and stable. This markedly improved the atomization efficiency and quality. When the Φ_GL was increased from 20% to 67%, the uniformity and stability of droplet distribution increased by 17% and 60%, respectively. This research offers important guidance for the structural design of high-performance atomized components.

Heat pump technology has become an essential solution in the field of medium- and low-temperature heating due to its superior efficiency in converting electrical energy into thermal energy. However, owing to the lack of stable heat sources during winter in northern China, it is necessary to store the heat sources within the urban area throughout the seasons to ensure the stability of the heat provided by the heat pump system. In this study, based on the project of seasonal/daily thermal storage of river water in Guantao, a simulation model was constructed using the Transient System Simulation Tool (TRNSYS). A sensitivity analysis of the thermal energy storage unit parameters was conducted under the constraint of the fixed site area. The configurations and strategies of the daily thermal energy storage were optimized. The results show that the temperature rise of the thermal energy storage unit reaches 3.2 ℃ after 10 years of operation, effectively preventing the soil heat imbalance. The distance between the buried pipes and the depth had the greatest influence on the performance of the system. The total length of the pipes could be reduced by approximately 23% with a spacing of 4 m and a depth of 150 m. The daily thermal energy storage system should be matched to the valley power storage heat and heat release load to avoid wasting the valley power. If the storage heat power is large, the volume of the storage tank can be increased, and the flat power heat release is considered. The optimized system improves the utilization rate of valley power and reduces annual operating costs by 11.2%.

An experimental platform was built to evaluate the thermal switching performance of a parallel pulsating multi-channel heat pipe using fluoroether HFE-7100 as the working fluid with a liquid filling ratio of 80%. The heating and cooling temperatures of the pulsating heat pipe were controlled using water baths for heating and cooling. The thermal switching characteristics of the pulsating heat pipe at different cooling temperatures were investigated experimentally. The results showed that after the complete start-up of the multi-channel parallel pulsating heat pipe, the average temperature of the evaporation section decreased, the average temperature of the condensation section increased, the thermal resistance decreased, and the heat transfer performance improved rapidly. The temperature and thermal resistance transient processes exhibited a sudden step change, which can be used as a thermal switch. As the cooling temperature increased, the closing time of the thermal switch and the switch temperature increased. At a cooling temperature of 10 ℃, the closing time of the thermal switch was 12 s, and the switch temperature was 59.3 ℃. At higher cooling temperatures, the thermal switch performed better, characterized by a greater increase in the switch ratio and heat transfer rate. When the cooling temperature was 30 ℃, the heat transfer rate increased by 26.8 W following the closure of the thermal switch, with a switch ratio of 5.05.

As the power density of lithium-ion batteries continues to increase and high-power fast-charging technologies emerge, the development of battery thermal management systems has become an important and challenging area of research. In this study, a direct-cooling thermal management system for multi-box battery packs using roll-bond cold plates was presented, and the performance of the system was experimentally investigated under different operating conditions. The experimental results show that at a charging rate of 0.5 C and a compressor speed of 2 400 r/min, the average coefficient of performance (COP) of the system can reach 5.83, the maximum dimensionless loss coefficient of the cold plate is 6.27%, and the maximum temperature difference between the cold plates is 1.90 ℃. Notably, the temperature difference between the plates escalates with increasing compressor speed and the thermal load on the cold plate, reaching a maximum value of 3.99 ℃ during the tests. Concurrently, the COP of the system showed a decreasing trend with the compressor speed, reaching a maximum value of 7.41 throughout the duration of the experiments.

To investigate the effect of different drying conditions on the efficacy of a closed heat pump clothing-drying system, parametric studies with control variables were carried out on the circulating air volumetric flow rate, expansion valve opening, and air inlet temperature within the drying chamber and their impact on system heat production, heat pump system coefficient of performance (S_COP), cooling capacity utilization ratio (E_R), and exergy loss. The findings indicated that when the expansion valve was set to 70% opening, the circulating air volumetric flow rate was increased from 500 m³/h to 1 000 m³/h, and the heat generation of the system increased by 59.73%. In contrast, the S_COP, E_R, and exergy loss decreased by 31.29%, 56.65%, and 31.31%, respectively. Furthermore, when the circulating air volumetric flow rate of 1 000 m³/h was maintained while adjusting the expansion valve opening from 20% to 70%, the heat generation, S_COP, and E_R of the system increased by 32.58%, 6.51%, and 29.51%, respectively. At the same time, the exergy loss decreased by 12.44%. Finally, under the conditions of a 70% open expansion valve, a circulating air volumetric flow rate of 1 000 m³/h, and an increase in the desiccator′s air intake temperature from 40 ℃ to 70 ℃, the heat generation of the system increased by 43.71%, while the S_COP, E_R, and exergy loss decreased by 11.22%, 60.84%, and 14.17%, respectively. These results emphasize the advantages of reducing the circulating air volumetric flow rate and inlet air temperature within the drying chamber while increasing the expansion valve opening, as these adjustments help to improve the overall performance of the system and promote energy efficiency.

In this study, the critical snow formation height of a mixed single-aperture nucleator in an artificial snow machine was examined. The threshold values of critical snow formation height were experimentally measured at different air-water pressure ratios and ambient temperatures, and the effects of air-water pressure ratios and ambient temperatures on the threshold values of critical snow formation heights were analyzed. The results showed that the threshold value for the critical height of critical snow formation did not exist at temperatures of -5 ℃ and -10 ℃ under the working conditions with a gas-water pressure ratio of 0.40 MPa∶0.40 MPa, but snow formation could be realized at -15 ℃, and the threshold value for the critical height of critical snow formation was 50-55 cm. When the gas-water pressure ratio is 0.50 MPa∶0.45 MPa or 0.50 MPa∶0.40 MPa, snow can be formed at ambient temperatures of -5 ℃, -10 ℃, and -15 ℃. The gas-water pressure ratio and ambient temperatures have a certain influence on the height of critical snow formation. Under the same ambient temperature, the greater the gas-water pressure ratio, the lower the critical snow height. Provided that the gas-water pressure ratio remains constant, the critical snow height decreases when the ambient temperature lowers from -5 ℃ to -15 ℃, and the trend of the change is more obvious in the temperature interval from -5 ℃ to -10 ℃.

This study utilizes machine learning techniques to conduct an in-depth analysis of time-series historical data on energy consumption in buildings. A generalized model identification method was developed using an optimization algorithm based on black-box models. The final identification model was determined after optimizing three machine learning methods, including polynomial regression, artificial neural networks, and extreme gradient boosting. A near-zero energy office building in Beijing is the primary focus of this study. Using historical building data and simulation data of the heating system in TRNSYS, load prediction and equipment energy consumption models were established using the developed model identification method. During deployment, the predicted R² value and total energy consumption deviation were 0.87 and 5.18%, respectively. The results demonstrate that the prediction models established through this method possess high accuracy, providing a reliable basis for subsequent system energy consumption optimization.