联箱-小孔型气液分离器的CFD数值模拟

Simulation of Vapor-liquid Separation in Header-baffle with Hole using Computational Fluid Dynamics

在冷凝过程中采用气液分离(分液冷凝)能同时实现强化传热和降低压降。高效的气液分离是提升分液冷凝器性能的关键。本文针对联箱-小孔型气液分离器,建立了三维数值模型,研究了其气液分离特性。基于实验结果对模型进行了验证,分析了分液孔径(0.5~2.0 mm)和分液孔位置(居中、不居中)对联箱内工质流动特性的影响。结果表明:在入口流量为3 g/s,入口干度为0.5时,分液效率和漏气率随着分液孔的增大而逐渐增大;在孔径为1.6 mm,分液孔居中时有最优的气液分离性能,此时分液效率为70.23%,漏气率为0.14%。分液孔位置主要影响分液孔处速度分布和压力分布,当孔径为2.0 mm且分液孔不居中时,其气液惯性力比值可达1.51×10^(-2),因此,不合理的分液孔大小和位置导致分液孔处存在“冲击现象”。

The implementation of vapor-liquid separation during condensation enhances heat transfer and reduces the pressure drop simultaneously.The vapor-liquid separator is vital for the performance improvement of such liquid-separation condensers.This study focuses on a header baffle with a small hole as the vapor-liquid separator.A 3D numerical model for the separator was established to investigate the vapor-liquid separation characteristics.The model was validated by experimental data first,and then it was used to analyze the effects of hole diameter(0.5-2.0 mm)and hole position(centered or not)on the flow features of the working fluid in the header.The results showed that when the inlet mass flow rate was 3 g/s and the inlet vapor quality was 0.5,the liquid-separation efficiency and vapor drainage ratio increased with increasing hole diameter.The best performance is achieved when the hole diameter is 1.6 mm and centered.In this case,the liquid-separation efficiency was up to 70.23%,and the vapor drainage ratio was 0.14%.The hole position mainly affects the velocity and pressure distributions.It was found that the vapor-liquid inertial force ratio can reach up to 1.51×10^(-2) as the hole diameter is 2.0 mm and its position is not centered.Hence,the unreasonable arrangement of hole diameter and position could lead to“fluid impact”at the liquid-separation hole.