考虑扁管换热的平行流蒸发器制冷剂两相分配特性

Two-phase Flow Distribution Characteristics of Parallel-flow Evaporator Considering Heat Transfer in Flat Tubes

摘要:

考虑换热扁管中制冷剂的相变过程，采用SST（shear stress transm ission）k-ω湍流模型和Eulerian-Eulerian两相流模型对平行流蒸发器内的制冷剂两相分配特性进行研究。发现制冷剂质量流量和入口干度的增加均会导致制冷剂分配均匀性下降：当制冷剂质量流量从15g·s^-1增加到25 g·s^-1，入口干度从0增加到0.3时，总流量分配不均匀指标分别升高39.4%和50.8%。适当增加出口集管内径和蒸发器长宽比有利于改善制冷剂分配的均匀性：出口集管内径增加一倍，总流量分配不均匀指标降低41.8%；长宽比从1.005增大到1.455，制冷剂分配不均匀指标降低21.6%。

关键词:平行流蒸发器;相变过程;两相流分配;不均匀指标;计算流体力学

Abstract:

Considering the phase change process of refrigerant in flat tubes， the SST（shear stress transm ission） k-ω model and the Eulerian-Eulerian two-phase flow model are used to simulate the two-phase distribution characteristics of refrigerant in parallel-flow evaporators. It is found that increasing the refrigerant mass flow rate and inlet quality will lead to a decrease in the uniformity of refrigerant distribution. When the refrigerant mass flow rate increases from 15g·s^-1 to 25 g·s^-1， the distribution inhomogeneity increases by 39.4%； When the inlet quality increased from 0 to 0.3， the corresponding increase in inhomogeneity is 50.8%. Appropriately increasing the inner diameter of the outlet header as well as the aspect ratio of the evaporator is beneficial to improve the uniformity of refrigerant distribution. Doubling the inner diameter of the outlet header results in a decrease of 41.8% in the inhomogeneity； compared with the basic structure， the evaporator with an aspect ratio of 1.455 achieves a decrease of 21.6% in the refrigerant inhomogeneity.

Key words:parallel flow evaporator;phase change process;two-phase flow distribution;inhomogeneity;computational fluid dynamics