微通道内表面活性剂水溶液饱和流动沸腾换热特性的数值模拟

Numerical Simulation of the Saturated Flow Boiling Heat Exchange Characteristics of a Surfactant Water Solution in a Microchannel

针对微尺度下表面活性剂水溶液的饱和流动沸腾换热,应用VOF模型和用户自定义函数,分别对竖直矩形微通道内水溶液、纯水的饱和流动沸腾过程进行数值模拟。对比水溶液与纯水的饱和沸腾换热效果与换热可靠性的差异,分析浓度对水溶液换热的影响。结果表明:Tin=368K,v=0.5m/s,qw=200kW/m^2工况下,沿流动方向,饱和沸腾阶段表面活性剂水溶液加热壁面的Nu数均值高于纯水;t=60ms时,邻近通道出口的区域内,水溶液、纯水对应的加热壁面均出现局部过热现象,但水溶液对应的最高过热温度低于纯水,且过热面积较小;0.256~0.769mol/L浓度范围内,增大水溶液浓度,流动沸腾换热效果增强,0.513mol/L的水溶液换热可靠。

For the saturated flow and boiling heat exchange of a surfactant water solution in a microscale,a VOF( volume of fluid) model and a user-defined function were used to conduct a numerical simulation of the saturated flow and boiling process of a water solution and pure water inside a vertical rectangular microchannel. Through comparison of the difference between the saturated flow and boiling heat exchange effectiveness and reliability of the water solution and pure water,the influence of the concentration on the heat exchange of the water solution was analyzed. It has been found that under the operating condition when Tin= 368 K,v = 0. 5 m / s and qw= 200 k W / m2,the average value of the Nu number of the wall surface heated by the surfactant water solution along the flow direction in the saturated boiling stage will be higher than that of pure water. When t = 60 ms,in the zone closing to the outlet of the flow passage,both wall surfaces heated by the water solution and pure water will be locally overheated but the highest overheated temperature corresponding to the water solution will be higher than that corresponding to pure water and the overheated surface areas will be relatively small. In a range from 0. 256 mol / L to 0. 769 mol / L,to increase the concentration of the water solution will enhance the saturated flow and boiling heat exchange effectiveness and the heat exchange of water solution at a concentration of 0. 513 mol/L will be reliable.