壳管式相变蓄热换热器换热特性的模拟研究

Simulation study on heat transfer characteristics of a shell-and-tube phase change heat storage heat exchanger

设计了一种以石蜡为相变材料的圆柱型壳管式相变蓄热换热器,以三维单元相变储热模型为研究对象进行了换热数值模拟。分析了相变材料的液相比、温度场、平均温度及换热介质出口温度的变化规律,研究了该壳管式相变蓄热换热器在蓄、放热阶段的换热特性。结果表明:液相石蜡的自然对流会增强相变材料与换热介质之间的换热,并加快石蜡的熔化和凝固速率;蓄热阶段液相比达到18.6%后,自然对流换热的影响逐渐明显;放热阶段初期,液相比在80 s内下降了63%,固态石蜡层完全包裹传热管束前的自然对流换热最强,之后逐渐减弱。

This paper designs a cylindrical shell-and-tube phase change heat storage heat exchanger with paraffin as the phase change material.A numerical simulation of heat transfer is carried out based on the three-dimensional unit phase change heat storage model.The variation rules of the liquid phase ratio,temperature field,average temperature of the phase change material and the outlet temperature of the heat transfer medium are analysed,and the heat transfer characteristics of the shell-and-tube phase change heat storage heat exchanger during heat storage and release are studied.The results show that the natural convection of liquid paraffin can enhance the heat transfer between the phase change material and the heat transfer medium,and accelerate the melting and solidification rate of the paraffin.The effect of natural convective heat transfer is gradually evident after the liquid phase ratio reaches 18.6%in the heat storage phase.In the initial phase of heat release,the liquid phase ratio decreases by 63%within 80 s.The natural convective heat transfer is the strongest before the solid paraffin layer completely wrapped around the heat transfer tube bundle,and then gradually weakens.