水平微细圆管内R290流动沸腾流态可视化研究

Visualization Research on Flow Pattern of R290 Flow Boiling in Horizontal Micro-tubes

本文对水平微细圆管内R290流动沸腾的流态进行了可视化研究,分析不同管径下流动沸腾换热主要流态形式及影响因素,基于理论流态图对比分析流态转变规律。实验工况:热流密度1~70 kW/m^(2),质量流率50~1020 kg/(m^(2)·s),饱和温度-10~25℃,管径1~3 mm,干度0~1。实验中共观察到8种R290微细通道内流动沸腾换热流态,其中间歇流和波状流为3 mm管的主要换热流态,弹状流和环状为1 mm管的主要换热流态;实测流态图中3 mm管的泡状流、混状流,2 mm管的泡状流,1 mm管的弹状流与D&W流态转变准则较为吻合,而2 mm管和1 mm管的离散流区域匹配性较差;管径的变化对流态有重要影响,随着管径的减小,气泡形状、流态形式、流态分布及流态转变曲线均发生变化,管径微尺度效应出现。

This study conducts visualization research on the flow pattern of R290 flow boiling in horizontal micro-tubes.The main flow patterns and influence factors of flow boiling heat transfer under different pipe diameters were analyzed,in addition to the summary of the flow pattern transformation law by comparing to the theoretical flow pattern diagrams.The experimental conditions were as follows:heat flux(1-70 kW/m^(2)),mass flow rate(50-1020 kg/m^(2)·s),saturation temperature(-10-25℃),pipe diameter(1-3 mm),and vapor quality(0-1).Eight types of flow patterns of R290 flow boiling heat transfer in micro-channels were observed,among which intermittent flow and wave flow were the main flow patterns in 3 mm-tubes,while slug flow and annular flow were the main heat transfer patterns in 1 mm-tubes.Bubble flow and mixed flow in 3 mm-tubes,bubble flow in 2 mm-tubes,and slug flow in 1 mm-tubes were consistent with the Damianides and Westwater flow pattern transition criterion.However,the discrete flow regions in 2 mm-tubes and 1 mm-tubes were poorly matched;the change in pipe diameter had an important influence on the flow pattern.A decrease in pipe diameter caused changes in the bubble shape,flow pattern,flow pattern distribution,and flow pattern transition curve,and the micro-scale effect of the pipe diameter can be observed.