As one of the most promising new energy sources, hydrogen energy is expected to usher in a full-fledged “hydrogen economy” in the 21st century. Compared with traditional high-pressure gaseous and cryogenic liquid hydrogen storage methods, solid-state chemical hydrogen storage shows significant advantages in safety, high efficiency, and cost-effectiveness. Magnesium-based lightweight hydrogen storage materials have attracted widespread attention due to their high gravimetric hydrogen storage density (7.6%) and favorable reversibility. However, their sluggish reaction kinetics and stringent operating conditions (with H2 release temperatures exceeding 350 °C and H2 absorption pressures above 4 MPa) pose major challenges for practical applications. Domestic and international researchers have conducted in-depth studies to address these issues, achieving substantial progress in the modification of magnesium-based hydrogen storage alloys. This paper systematically elaborates on major modification techniques such as alloying, nanostructuring, and catalytic material doping, providing a comprehensive analysis of the strengths and limitations of each approach. Furthermore, it offers prospects for the future development of magnesium-based hydrogen storage materials by integrating current theoretical and experimental research findings.
The frequency and the suction refrigerant state are complex in the actual operation of variable compressors, which leads to the variability of compressor performance under different operating conditions. The characterization and the modeling of the compressor have become hot research topics. For modeling, the electrical efficiency model of the compressor, which could be applied to the suction refrigerant state at both the superheated and the two-phase stages, the compressor frequency, the pressure ratio, and the evaporation temperature, is analyzed through experiments in this paper. The results show that the linear electrical efficiency decreases with the declining superheated temperature and the increasing suction vapor quality when the system is at the fixed and evaporating temperature. Moreover, the slope of the two-phase suction is above that of the superheated suction. In addition, the system’s electrical efficiency at the fixed pressure ratio is inversely proportional to the evaporation temperature, and the electrical efficiency of the system at the fixed evaporating temperature is also inversely proportional to the pressure ratio. The higher the variation of the pressure ratio, the smaller the evaporation temperature influences. To demonstrate the precision of the model, the theoretical value is compared with a confirmatory experiment in this paper. The maximum relative error is 1.81%, and the minimum is 0.035%.
立足化学化工类课程视角分析,课程思政的基本范式是将思政价值嵌入知识技能之中.但基于现实维度考虑,无论是充当媒介的化学化工类课程,还是思政元素、理念、观点等,均具有多元性特色,这就需要考虑化学化工内容与思政育人导向的统一性,即建立起化学化工教学内容与思政元素价值的对应关系.例如,化学实验与工匠精神的对应关系,化工生产中现象与本质的关系,古代化学领域成就与文化自信的对应关系等.
热泵与储能结合是缓解电网负荷压力的有效手段,文中基于TRNSYS软件,搭建空气源热泵耦合相变蓄热供暖系统仿真平台,编写新的相变储罐模块并通过实验数据对模型进行验证,并采用单因素试验法探究系统容量配置参数(空气源热泵性能系数)变化对系统经济与能耗的影响情况.研究结果表明:耦合系统机组空气源热泵性能系数COP比传统系统提高了 13.8％,根据需求响应制定的运行策略使耦合系统节能率达到15.68％.以系统全生命周期成本CLC与碳排放量EC为目标建立多目标优化函数,对配置参数进行优化.优化结果表明:当相变材料质量为195 kg,相变温度为49.5℃,水箱体积为1 m3时,可均衡满足经济性与节能性的优化需求.研究结果为满足不同空气源热泵耦合储能系统设计需求提供了指导方向.
It was found that the injection of bubbles into liquid can effectively improve heat transfer efficiency, so it is important for industrial applications to investigate the effect of bubble injection on heat transfer. The effect of bubble injection on natural convective heat transfer in steady laminar flows in a vertical channel is investigated using the volume of fluid (VOF) method, and the effects of bubble diameter, Eötvös number ( Eo ), bubble arrangement, and bubble distance from a hot wall on the heat transfer between the hot wall and liquid are studied, respectively. The results show that bubble injection can effectively improve the heat transfer between the hot wall and liquid; an increase in bubble diameter and Eo can improve the enhancement effect of heat transfer and can expand the enhancement area of heat transfer; the closer to the hot wall a bubble is, the better the enhancement of heat transfer is; and the spacing and arrangement of bubbles also have important effects on the heat transfer between the hot wall and liquid. The comparison shows that the enhancement of heat transfer is the best for the vertical arrangement of double bubbles, which increases the local heat transfer coefficient by 3.2 times. The enhancement of heat transfer generated by bubble injection is related to the degree of disturbance of the local liquid phase caused by bubble injection. The more strongly the local liquid is disturbed, the thinner the local temperature boundary layer becomes, and the better the enhancement of heat transfer is.
