相变蓄热水箱蓄热性能数值模拟研究

在封闭静止的蓄热水箱中添加相变材料可以增加水箱热容量、延长水箱升温时间。分别建立了有、无相变单元蓄热水箱的物理模型，利用有限体积分析法对蓄热水箱加热过程进行数值模拟，探讨了封闭水箱加热过程中相变单元的熔化规律和相变单元对水箱温升的影响规律。研究结果表明相对于纯水蓄热水箱，当蓄热水箱中加入占水箱容积9.05%(体积分数)的相变单元、其平均温升29 K时，蓄热水箱的整体热容量提高了25.58%,加热时间延长了1 100 s;蓄热水箱内只在垂直方向上存在热分层，导致含有相变单元的蓄热水箱较高位置处的相变单元先熔化，降低了较高位置处水的温升速率，使得相变蓄热水箱和纯水蓄热水箱的热分层剧烈程度存在差别；以最大温差值作为判断水箱热分层剧烈程度的依据，不同加热功率下相变蓄热水箱的热分层特征变化规律大致相同，但加热功率越大，热分层现象越剧烈。

Numerical simulation of the heat storage performance of heat storage tanks containing phase change materials

Adding a phase change material to a closed static heat storage tank can increase the heat capacity of the tank and prolong the heating time of the tank. In this paper, a two-dimensional physical model of heat storage tanks with and without a phase change element is established, the heating process of the heat storage tanks is simulated numerically by the finite volume analysis method, and the melting law of the phase change element and the influence of the phase change element on the temperature rise of the water tank are discussed. The results show that compared with a pure water heat storage tank, adding a phase change material with an effective volume of 9.1% increases the overall heat capacity of the heat storage tank by 25.6% and the heating time is prolonged by 1 100 s when the average temperature of the heat storage tank is increased by 29 K. Temperature stratification in the hot water storage tank only occurs in the vertical direction, which leads to the melting of the phase change element at higher positions in the heat storage tank, which reduces the rate of water temperature rise at higher positions, and leads to differences in the intensity of thermal stratification between the phase change heat storage tank and the pure water heat storage tank. Taking the maximum temperature difference as the criterion for judging the intensity of thermal stratification in the water tank, the variation in thermal stratification characteristics of the phase change heat storage tank are essentially independent of heating power, but thermal stratification in the phase change heat storage tank becomes more intense with increasing heating power.