内壁填充环状金属泡沫的管内流动凝结换热

通过采用在圆管内壁填充环状金属泡沫的方法强化管内对流凝结换热，实验研究了制冷剂R134a在内壁填充环状金属泡沫管内的流动凝结的压降和换热，克服了完全填充金属泡沫管流动阻力大的缺点。用于计算传热系数的管壁温度通过热电偶测量得到。综合分析了质量流速和两相流体干度对流动凝结压降及传热系数的影响。研究结果表明内壁填充环状金属泡沫管压降远大于光管，压降随质量流速和干度的增加而迅速增大且呈非线性。通过壁面温度分布和温度波动对内壁填充环状金属泡沫管内的两相流型进行判别，发现影响该类强化管凝结换热的两种主要流型：分层流和环状流。内壁填充环状金属泡沫管的凝结传热系数大于光管，且随着质量流速和干度的增加传热系数增大，该类强化管流动凝结传热系数是光管的2倍左右。

Flow condensation in tube filled with annular metal foam

The tube with internally sintered annular metal foam layer is used to enhance the flow condensation heat transfer.The pressure drop and heat transfer of flow condensation for refrigerant R134a in the tube partially filled with annular metal foam are experimentally investigated to overcome the disadvantage of large pressure drop for tubes fully filled with metal foam.The tube wall temperatures are measured with thermal couples to determine the heat transfer coefficient.The effects of mass flux and vapor quality of two-phase fluid on the pressure drop and heat transfer coefficient are analyzed accordingly.It is found that the pressure drop of tubes partially filled with metal-foam is much higher than that of smooth tubes and the pressure drop increases non-linearly and greatly as the mass flux and vapor quality increase.The flow regime is predicted by monitoring the distribution and fluctuation of cross-section temperatures, from which the stratified wavy flow and annular flow are detected.It is also revealed that the flow condensation heat transfer coefficient for tubes partially filled with annular metal foam is about 2 times that of smooth tube and can be improved as mass flux or vapor quality increases.