微通道光管换热器的运行特性及影响因素

Research on the Operation Performance and Influencing Factors of Micro-channel Smooth-tube Heat Exchanger

为了研究微通道光管换热器的运行特性,在R22制冷系统中将其作为冷凝器、在R134a制冷系统中将其同时作为冷凝器和蒸发器分别进行试验研究,并进行单根微通道光管外空气绕流数值模拟。试验研究表明,微通道光管换热器具有较高的换热系数和单位面积换热量,且毛细管长度、制冷剂充注量对于其运行性能具有不同程度的影响。外径为0.7 mm的单根微通道光管外部流场数值模拟结果与试验结果吻合良好,而且与大管径光管相比,小管径光管边界层较薄,对流换热过程更强烈,换热效果更明显。

In order to study the operation characteristics of a micro-channel smooth-tube heat exchanger,it was used as condenser in R22 refrigeration system,and both as condenser and evaporator simultaneously in R134 a refrigeration system,so as to carry out experimental research. Furthermore,numerical simulation was conducted for air flow around a single micro-channel smooth tube. The experimental research shows that such micro-channel smooth-tube heat exchanger has high heat exchange coefficient and specific-area heat exchange amount. Moreover,capillary length and filling amount of refrigerant have different effect on the operation characteristics. Numerical simulation result for the single micro-channel smooth tube with external diameter of 0. 7mm agrees well with the experimental data,and compared to the tube with larger diameter,the tube with smaller diameter has thinner boundary layer,which corresponds to stronger convective heat transfer process and more apparent heat transfer effect.