微通道内R22制冷剂流动沸腾的压降特性

Pressure drop of flow boiling R22 in microchannels

为探讨热流密度对二相流动沸腾摩擦压降的影响,并结合可视化探究改变热流密度时产生压降不稳定现象的机理,文章以R22制冷剂为实验工质,在截面尺寸高×宽分别为2.0 mm×2.0 mm,2.0 mm×1.0 mm和2.0 mm×0.6 mm 3种不同矩形微通道中,进行二相沸腾传热实验。实验表明:此实验条件下,R22制冷剂在微通道内进行二相沸腾传热时,二相摩擦压降是产生压降的主要因素;二相摩擦压降随热流密度的增加而增大,而且低热流密度下增幅较快,当热流密度增加到一定程度后,二相摩擦压降增加趋势变缓;在质量通量为253.2 kg/(m2·s)的条件下,热流密度从4.5 k W/m2增加到18.1 k W/m2时,流体流型经历了局部干涸再润湿的周期性变化,这种变化过程中压降波动较大。

To investigate the influence of heat flux on pressure drop and study the fluctuations of pressure drop through visualization when heat flux was changed, with R22 refrigerant as the working fluids, the experiment through the aluminum-based rectangular micro-channel with different sizes of 2.0 mm×2.0 mm,2.0 mm×1.0 mm and 2.0 mm×0.6 mm, was investigated. The results show that the two-phase frictional pressure drop is the main part of the total pressure drop. With the increasing of heat flux, the two-phase frictional pressure drop increases, and when heat flux exceeds a certain value , the pressure drop increases slowly. When the mass flux is 253.2 kg/（ m2·s） and heat flux increases from 4.5 kW/m2 to 18.1 kW/m2, the flow pattern changes from local dry to rewetting periodicity, and pressure drop shows the fluctuations during the periodic change.