综述180°回转型弯头对U型管内的气液两相流流型压降与传热的影响

从流型,压降和传热三个方面综述了以前研究者在U型管中所做的研究。指出了180°弯头对整个U型管的流型及其流型转变,压降损失及其预测方法和增强换热的影响。同时提出了今后关于U型管可能的研究方向:(1)细化曲率比等几何因素对流型压降传热的影响;(2)关注低温介质的U型管中的流动与传热;(3)以180°弯头加上距其一定距离的上下游为一个单元考虑其整体的压降损失;(4)量化气液两相流在U型管中的传热。

A review of the influence of 180 degree return bend on the gas-liquid two-phase flow pattern and pressure drop and heat transfer

A review was conducted to elaborate the influence of 180 degree return bend on U-tubes from three aspects: flow pattern,pressure drop and heat transfer.The secondary flow induced in the 180 degree return bend changed the incoming flow pattern,increased the pressure loss and enhanced the heat transfer in U-tubes.It is advised that there four possible research directions of the U-tubes.(1)Refining the influence of geometric factors such as the curvature ratio on the flow pattern transition and pressure drop and heat transfer.(2)Focus on the low temperature fluid medium flowing in U-tubes.(3)Reconsider the pressure loss of U-tube taking the 180 degree return bend and its up-and downstream section as a unit.(4)Qualify the heat transfer of gas-liquid two-phase flow in U-tubes.