流动沸腾条件下微通道壁面温度的红外特征

Infrared characteristics of wall temperature for single microtube during in-tube flow boiling

设计并搭建了沸腾换热试验台,采用TH5104红外热像仪测量微通道壁面温度来研究混合制冷工质在微通道内的沸腾换热特性。测量试件是一外径为1.22mm,内径为0.86mm,长为200mm的不锈钢单圆管。实验利用红外热像仪测量并记录下质量流量为1 726～8 635kg/m2.s,热流密度为65～231kW/m2时壁面温度的变化情况。实验分析和讨论结果显示:微通道壁面的温度分布沿着轴向变化有明显的规律性;水平微尺度通道内流动沸腾过程中,试件前后段有较大的温差效应,温差的正负与热流密度的大小有关;壁面温度的变化与热流密度、管内工质的流型和换热形式关系密切,流型越复杂,壁面温度变化越剧烈。

Abstract： A boiling heat transfer test unit was designed and built. The TH5104 infrared thermogra phy was used to measure the wall temperature of a microtube to research the characteristics of boiling heat transfer of refrigerant in the microtube. The test piece was a single stainless circular tube with an external diameter of 1.22 mm, an internal diameter of 0.86 mm and a length of 200 mm. The infrared photography was used to test and record the wall temperature of the microtube with heat flux ranging from 65 kW/m2 to 231 kW/m2 at different mass fluxes from 1 726 kg/m2 ~ s to 8 635 kg/m2 ~ s. Ex perimental results indicate that the wall temperature distribution along the axial direction has a regular change obviously. For the flow boiling in the horizontal microtube, a large temperature difference a long the whole tube is shown during the evaporation of fluid in the microtube. Whether the differenee of wall temperature is positive or negative, it is relative to the heat flux. The variation of the wall tem perature is affected by the heat flux, flow patterns of working fluid and the heat transfer model,and the more complex the flow pattern is, the more severe the wall temperature varies.