Hydrogen energy, as a carbon-free energy source and a pivotal technology for attaining the goals of "carbon peaking and carbon neutrality", has attracted considerable global interest in recent years. The storage of liquid hydrogen offers several advantages owing to its high hydrogen storage density, low storage pressure, and high energy density. However, the industrial development of hydrogen energy still faces many problems. Technologies for large-scale, long-term storage and long-distance transportation are crucial problems in the utilization of liquid hydrogen. Therefore, it is necessary to develop efficient technologies for storing and transporting liquid hydrogen and to build large liquid hydrogen storage tanks with good thermal insulation performance. In this paper, the development status of large liquid hydrogen storage tank storage technology at home and abroad is reviewed, and key problems such as cryogenic insulation and material thermal stress in liquid hydrogen storage are analyzed. The difficulties associated with hydrogen storage and transportation are highlighted, and the development direction of liquid hydrogen storage technology is examined.

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.

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.

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.

Dimethyl sulfoxide (Me₂SO) in cell banking exhibits significant side effects on both the cells and the human body. Therefore, an approach that mitigates the side effects of Me₂SO with comparable efficacy is urgently needed. The human umbilical cord mesenchymal was used as the research material. First, the thermal physical properties of trehalose, glucose, and L-proline and their regulation of ice crystal growth were measured using a differential scanning calorimeter and a cryomicroscope. Cryopreservation experiments were performed to determine the optimal concentration of each component in the cryopreservation solution, and the viability and functionality of the cells after cryopreservation were validated. The results show that there is no significant difference in cell viability (92.42%±0.28%) and recovery rate (87.80%±4.22%) between the use of the novel stem cell cryopreservation solution (1.25 mol/L ethylene glycol+10 g/L whey protein+0.1 mol/L trehalose+Normosol-R) and the conventional cryopreservation solution (a volume fraction of 10% Me₂SO). Moreover, after 3 days of culture, the cell number was (12.42±0.60) × 10⁶ (proliferation fold of 4.97), and the cell phenotype was not significantly different from that of fresh cells. The proposed novel solution for stem cell cryopreservation solves the problem of "Me₂SO-free" cryopreservation of cells and offers promising potential for clinical applications.

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 ℃.

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.

Ovarian tissue cryopreservation is an important method for female fertility preservation. Slow freezing of ovarian tissue results in poor follicular survival and low retransplantation efficiency. This study optimized the ovarian tissue cooling procedure by ice seeding, and the effects of ice seeding temperature and cooling rate after seeding on ovarian tissue cryopreservation were analyzed. The programmed cooling apparatus was combined with an ultrasonic device to achieve the ultrasonic seeding of ice crystals, and the ultrasonic intensity was screened. The ovarian survival and histology were assessed after rewarming. The results revealed that the optimized cooling procedure with ice seeding reduced the damage to ovarian tissues. When ice seeding was triggered at -11 ℃ with a cooling rate of 1 ℃/min after nucleation, follicle survival was 88.02%. Ultrasonic nucleation equipment enabled contactless ice seeding of the samples, reducing the risk of contamination and improving the success rate of ice seeding. Furthermore, the follicle survival rate of frozen ovarian tissue increased to 88.38%. The optimization of the procedure and the improvement of the equipment improved the effect of ovarian tissue cryopreservation, reduced the risk of introducing contamination during the cryopreservation process, and provided a new method for the slow cryopreservation of ovarian tissues in clinics.

Improving the energy efficiency of data centers by conserving energy in cooling systems is a priority strategy. In this study, thermal analysis of the prevailing air-water-air cooling system revealed inefficiencies caused by a significant discrepancy in the flow rate between the air and water sides of the server room air conditioning system. To mitigate such discrepancy, a new system architecture with a high-temperature differential on the waterside was proposed. Compared with a conventional system with a small temperature differential, the proposed high-temperature differential cooling system substantially augmented the proportion of natural cooling throughout the year, reduced the energy consumption of pumping fluids, and reduced the total energy consumption of the cooling system by approximately 20%-30%. Although the introduction of a high-temperature differential cooling system requires an increase in the heat exchange area and an increase in the cost of air conditioning for the server room, it concurrently reduces the investment in cooling towers, chillers, circulating pumps, chilled water storage tanks, pipelines, and valves, ultimately reducing the total investment in the cooling system by 15%-25%. Furthermore, the high-temperature differential cooling system facilitates operational adjustments, decouples control from external temperature variations and IT load changes, and minimizes maintenance requirements.

A household photovoltaic intelligent power supply system was proposed to increase the on-site consumption capacity of household photovoltaics and fulfill the requirements for a comfortable and convenient living environment. The system can fulfill the requirements of household electricity, space heating, space cooling, and hot water supply throughout the year. Heating and cooling were realized using air source heat pumps (ASHP), underfloor heating, fan coil units, and energy storage water tanks, which store hot water in winter and cold water in summer. A TRNSYS simulation model of the system was created based on residential buildings in Shandong, China. Based on the simulation results and local electricity prices, the energy storage operation plan was optimized, and the economic efficiency of the system was analyzed. The results indicate that the system can meet the building's year-round electricity consumption, maintain indoor temperatures in winter and summer, and generate revenue from photovoltaic power, yielding the maximum return on investment throughout the entire life cycle. The optimal operating schedule for the ASHP is from 09:00 to 16:00 and 22:00 to 05:00 in winter and from 07:00 to 18:00 and 22:00 to 05:00 in summer. Controllable electrical appliances were used from 10:00 to 16:00. In contrast, appliances with energy storage were used from 11:00 to 14:00 to consume and store the photovoltaic electricity. The energy-storage water tank reduces standard coal consumption by 46% compared to the case without a water tank, demonstrating a substantial energy-saving effect.