外压内吸薄壁弹性矩形阵列管相变蓄热装置放热研究

Study on the heat release of phase change thermal storage device formed by elastic rectangular thin wall tubes under external pressure and internal suction

针对由于相变材料导热系数较低且易与受热面相剥离而造成相变蓄热装置放热功率不能满足工程实际需要的现象,设计了外压内吸薄壁弹性矩形阵列管相变蓄热装置。在外部正压和内部负压的共同作用下,采用薄壁弹性矩形阵列管可以解决相变材料与受热面相剥离的问题,同时提高了蓄热装置受热面的紧凑性。搭建相变蓄热实验台并测试蓄热装置在不同流体温度、不同流体流量和不同相变材料工作温度下的放热性能。研究结果表明:矩形管外侧流体流量越大,其传热系数和热功率越大,并且随着放热过程的持续进行,这两个参数的下降速率越小;相变蓄热装置的传热系数随着剩余热功率的下降而迅速降低,当剩余热功率占最大热功率的70%~80%时,传热系数下降速率出现转折,此后下降速率有所减小,当剩余热功率占最大热功率低于20%时,相变蓄热装置的放热过程基本结束;相变材料起始温度和相变蓄热装置进口流体温度的差值以及矩形管外侧流体流量变化时,蓄热装置的传热系数相差不大。

In view of low thermal conductivity of phase change materials and its easiness to peel off the heating surface in phase change thermal storage device, these questions caused the heat release power of the heat storage device could not meet the actual project needs well. In this paper, a phase change thermal storage device was designed, using thin wall elastic rectangular tubes under external pressure and internal suction. It can solve the heating surface peeling problem caused by thermal expansion and contraction and at the same time it also can enhance the heating surface compactness of the heat storage device. The test bench to phase change heat storage was built and its exothermic performance was tested under different fluid temperature, different fluid flow rate and different temperature of phase change material. The experimental results were shown as follows： The greater the fluid flow rate outside the rectangular tubes, the greater the heat transfer coefficient and the heat power were and the lower releasing process was carried out to 1 h, both of the decline rate of both were. When the heat- them appeared to fluctuate and then decreased smoothly. Heat transfer coefficient decreased fastly with the decrease of the remainder heat power; When the percentage of remainder heat power was 70%-80%, there was a turning point for heat transfer coefficient decreasing rate and then it became slower. When the percentage of remainder heat power was 20%, the heat release process was basically over. The difference of heat transfer coefficient under different fluid flow rate and temperature difference, which is the initial temperature of the phase change material and the inlet fluid temperature of the phase change heat storage device, was not different very much.