相变材料对家用水箱性能的影响及相变层厚度优化

基于相变蓄热水箱的发展现状,结合家用生活热水系统相关设计规范及标准,对相变水箱的结构进行了设计,并采用有限元软件对相变水箱的性能进行了模拟研究.首先建立了相变水箱的数值计算模型并利用实验数据验证模型的准确性;在此基础上,通过蓄放热阶段水温响应特性、相变材料温度及液相比等参数,对相变水箱的蓄放热特性进行了研究;另外,比较分析了不同相变层厚度参数对相变水箱蓄放热过程的影响,并对相变材料的用量进行了优化.结果表明,对于家用水箱,增设相变材料层可以延长水箱蓄热过程;在水箱放热过程中,放热时间随着相变层厚度的增加呈现先延长后缩短的变化趋势;与其他相变厚度的模拟工况相比,相变层厚度为30 mm时,水箱的释热性能最佳,放热时间较普通水箱增加10％左右,且维持水温处于较高温度的时间有所延长.可见相变材料的蓄放热特性直接影响着家用水箱的性能,寻求相变材料的最优用量可为相变水箱的设计及实际应用提供参考.

Effect of Phase Change Material on Performance of Domestic Water Tank and Optimization of Phase Change Layer Thickness

Based on the analysis of current development of the heat storage water tank comprising phase change material (PCM), the structure of phase change water tank was designed in combination with the relevant design codes and standards of domestic hot water system, and the performance of it was simulated by a finite element software based on multi physical field coupling. The numerical calculation model of the phase change water tank was established firstly and then the accuracy of the model was verified by the experimental data. On this basis, through the parameters of water temperature, PCM temperature and liquid ratio in the heat storage and release stage, the heat storage and release characteristics of the phase change water tank were studied, in addition, the influence of different thickness of phase change layer on the heat storage and release performance of the water tank was compared and analyzed, and the amount of phase change material was optimized as well. The results demonstrate that for the domestic water tank, adding a PCM layer can prolong the heat storage process. In the heat release process, the heat release time show a trend of prolonging firstly and then shortening with the increase of the thickness of PCM layer. Compared with other simulation conditions, when the thickness of the PCM layer is 30mm, the heat release performance of water tank is the best. The heat release time of the proposed tank is about 10% longer than that of the common water tank, and the time to keep the water at a higher temperature increases. It is concluded that the heat storage and release characteristics of PCM directly affect the performance of domestic water tanks. Seeking the optimal amount of PCM can provide a reference for the design and practical application of phase change heat storage tanks.