Xin Xiao

Research on heat and mass transfer in microchannels represents the cutting-edge frontier in modern high-density electronic cooling, advanced energy systems, and precision microfluidic manipulation

To improve the heat dissipation efficiency of electric vehicle battery thermal management system (BTMS), a bionic shark-scale structure was proposed to optimize the thermal performance of flexible composite phase change material (PCM), with axial air cooling integrated to regulate the battery temperature. Experiments were conducted under four conditions, i.e., natural convection, air cooling, air cooling coupled with PCM, and air cooling coupled with bionic shark-scale PCM, to evaluate the thermal behaviour performance. In addition, pressure drop tests were conducted to assess the drag-reduction effects of the bionic structures. A numerical simulation model was also built with the verification of experimental data, which was subsequently applied to investigate the heat dissipation mechanisms and influences of the bionic structure together with optimizations. The results show that, under a 2C discharge, the temperature rise of the battery pack of air cooling coupled with bionic shark-scale PCM is only 49.30% of that under natural convection, while the maximum surface temperature is controlled at 50.90 °C, ensuring the safe operation. At an airflow velocity of 1.30 m/s, the duct pressure drop of the bionic shark-scale PCM is slight lower than that of the smooth PCM. Subsequently, the bionic shark-scale structure is further optimized in terms of axial aspect ratio, lateral structure, rib row number, and rib arrangement. The optimal configuration achieves an average battery pack temperature of 46.11 °C, with a aspect ratio of 0.5, a side structure of CR400AF, and 13 rows arranged in a cross pattern. The present research provides insights into the effective design of heat sink of BTMS.

In recent years, the fixed bed dehumidification system has received extensive attention. Research shows that the fixed bed can be combined with the vapor compression refrigeration system to replace the traditional air conditioning (A/C) system, improve the dehumidification efficiency of the system and reduce energy consumption of A/C. In this study, the optimization and improvement methods of the fixed bed dehumidifier in recent years are introduced in detail firstly. It points out that adding heating/cooling devices to the fixed bed can greatly improve the dehumidification capacity and efficiency of the system, which is the main method to improve the fixed bed currently; Optimizing the structure of fixed bed is also an effective method, but the current research results have limited improvement on dehumidification performance; Optimizing the regeneration mode of fixed bed can improve the utilization rate of renewable energy and improving the overall dehumidification efficiency of the system, but the research in the direction is still insufficient; The parallel double packed bed structure can ensure the continuous operation of the fixed bed to improve the dehumidification efficiency of the system, but such systems are large in scale and high in cost. Then the dehumidification performances of various systems are summarized and comprehensively compared. Finally, the future optimization and improvement direction of the fixed bed is pointed out.

The energy consumption in buildings is high currently, leading to the development of the building envelope with phase change material (PCM), while the application of PCMs to the building envelope has the potential to effectively regulate the temperature variations in the inner surfaces of walls. Eutectic PCM consists of lauric acid, myristic acid, and stearic acid (LA-MA-SA) and was synthesized first, while expanded graphite (EG) and diamote (DE) were used as additives. LA-MA-SA/10 wt.% EG/10 wt.% DE composite PCM was synthesized via the impregnation method; then, the phase change layer was compressed and formed under a pressure of 10 MPa. The sandwich phase change gypsum board was built with three layers, considering the phase change layer on the outside, middle and indoor sides of the board, respectively. The thermal responses of sandwich phase change gypsum boards were considered under various radiation conditions at controlled temperatures of 37 °C, 40 °C, 45 °C and 50 °C. The results indicated that the gypsum board with the addition of 16.7 wt.% composite PCMs showed a better relative time duration of thermal comfort in comparison with pure gypsum board. The indoor heating rate slowed down, and the environmental temperature fluctuation was within a smaller range, because of the latent heat of the phase change gypsum board. Comparing the phase change gypsum boards at different interlayer positions, we found that the phase change gypsum board with an interlayer on the indoor side shows better thermal performance and a relatively longer time duration of thermal comfort, e.g., when the setting temperatures were 37 °C, 40 °C, 45 °C and 50 °C, respectively, the relative time durations of the thermal comfort of the sandwich phase change gypsum board were 4825 s, 3160 s, 1980 s and 1710 s. This study provides insights into the thermoregulation performance of phase change walls, where the utilization of a PCM in a wall can increase thermal capacity and enhance the inner-zone thermal comfort. The findings can provide guidelines for phase change walls to ensure sustainable practices in the energy savings of buildings.