Abstract:

The heat storage rate of phase change components for a building envelope is low, because the thermal conductivity is low and the surface heat transfer is not sufficient for the phase change materials. In order to increase the rate of heat storage, the phase change component is placed under mechanical ventilation to test the regenerative rate of phase change component under different supply air temperature and air velocity conditions in the experimental platform for researching thermal performance of phase change component. Finite difference method is also used to calculate the thermal storage process of phase change component by Matlab software to expand the experimental air supply temperature conditions. It also calculates the energy consumption of the system considering the energy consumption of the fan, and an effective ventilation method is proposed. The results show that changing the supply air temperature or air velocity greater impacts on the heat storage rate of liquefaction process, but fewer impacts on the heat storage rate of regenerative process. Improving the supply air temperature or air velocity can shorten the phase change completion time, it also can improve heat flux of the component's surface. When the air velocity was 1.0 m·s^-1, and the supply air temperature increased from 34℃ to 80℃, the average heat flux of liquefaction process increased from 23 W to 322 W. The percentage of heat storage in liquefaction process decreases with the increase of air temperature, and can be constant with the increase of air velocity. In case of the phase change component is combined with mechanical air supply, it should be considered in heat storage of the system and power consumption of the fan. In the same air velocity conditions, the time of achieving maximum energy savings ultimate steady. When the supply air temperature is 80℃, the air velocity is 2.0 m·s^-1, the time is 1.6 h, the system can achieve maximum energy savings for 891.8 kJ.

Key words: phase change, mechanical air supply, heat transfer, thermal properties, numerical simulation

摘要：

现阶段用于建筑围护结构的相变构件在蓄热阶段存在蓄热速率较低的问题。为了提高相变构件在蓄热过程中的蓄热速率，将相变构件与机械通风相结合，搭建了相变构件热性能研究实验台，测试了不同送风温度和送风风速工况下相变构件的蓄热性能，采用了有限差分法通过Matlab软件对相变构件蓄热过程进行数值计算以拓展实验送风温度工况，将风机能耗考虑在内，对系统整体的节能效果进行了分析，提出了有效的送风方法。结果表明：提高送风温度或风速可缩短构件相变完成时间，同时可以提高构件表面蓄热热流，当送风风速为1.0 m·s^-1，送风温度由34℃提高到80℃时，液化过程的平均热流由23 W提高到322 W；同一送风风速工况下，最佳送风时间最终稳定在固定值；在送风温度80℃，送风风速2.0 m·s^-1条件下，送风1.6 h时，系统能达到最大节能量，为891.8 kJ。

关键词: 相变, 机械送风, 传热, 热性能, 数值模拟