水平多管式换热器内部相变石蜡储热特性实验研究

Study on thermal storage characteristics of phase change paraffin inside horizontal multi-tube heat exchangers

设计并搭建了水平多管式相变储热系统,以水为传热流体(HTF)、石蜡为相变材料(PCM),通过实验对储热系统的具体蓄热特性和不同操作条件下HTF与PCM之间的传热特性进行定量分析,评估了HTF体积流量和进口温度对紧凑型低温相变储热系统功率输入、吸热完成时间以及储存能量的影响。该系统主要由一个聚碳酸酯壳和水平定向的多管换热器以及石蜡组成,其中石蜡相变温度约为41℃。结果表明:随着HTF进口温度或体积流量的增加,吸热完成时间减少,平均吸热功率增大,且增加速率都随着进口温度的增大而变小;HTF体积流量分别为4.5,6.0和7.5 L/min时,吸热过程耗时300.7,252.9和226.7 min;在58,64和70℃的进口温度下,吸热完成时间分别为270.1,226.7和204.9 min;提高HTF进口温度,会导致换热结束时石蜡温度与HTF出口温度出现越来越靠近的趋势,而在提高HTF体积流量时,却呈现相反的趋势。

We designed and built a horizontal multitube phase change heat storage system with water as the heat transfer fluid(HTF)and paraffin wax as the phase change material(PCM),quantitatively analyzed the specific heat storage characteristics of the heat storage system and the heat transfer characteristics between HTF and PCM under different operating conditions through experiments,and evaluated the effects of HTF volume flow rate and inlet temperature on the power input,heat absorption completion time and stored energy of the compact low-temperature phase change heat storage system.The system mainly consisted of a polycarbonate shell and a horizontally oriented multi-tube heat exchanger and paraffin,where the paraffin phase change temperature was about 41℃.The results show that the heat absorption completion time decreases and the average heat absorption power increases as the HTF inlet temperature or volume flow rate increases,and the increase rate becomes smaller with the increase of the inlet temperature;the heat absorption process spends 300.7,252.9 and 226.7 min at HTF volume flow rates of 4.5,6.0 and 7.5 L/min,respectively;at inlet temperatures of 58,64 and 70℃,the heat absorption completion time are 270.1,226.7 and 204.9 min,respectively;and increasing the HTF inlet temperature resultes in a trend that the paraffin temperature at the end of heat transfer is increasingly close to the HTF outlet temperature,while the opposite trend is observed when the HTF volume flow rate is increased.