微细通道纳米制冷剂流动沸腾阻力特性

分别以质量分数为0.2%、0.5%和0.8%的Al₂O₃-R141b纳米制冷剂和纯制冷剂R141b为工质，在水力直径为1333μm的矩形微细通道内进行了流动沸腾实验，分析了纳米颗粒浓度对工质两相摩擦压降的影响，对比了实验前后换热壁面的表面能。研究结果表明：实验工况相同时，质量分数为0.2%、0.5%和0.8%的纳米制冷剂的两相摩擦压降均比纯制冷剂低，降低的最大幅度分别约为11.6%、14.8%和19.2%；实验后纳米颗粒在换热壁面附着，使壁面表面能增大，质量分数为0.2%、0.5%和0.8%的纳米制冷剂实验后换热壁面表面能比实验前分别增大了1.26倍、1.44倍和1.91倍，减小了换热表面的粗糙度和提高其润湿性，使得工质两相摩擦压降减小；根据实验值与模型预测值的对比情况，对Qu-Mudawar模型进行修正，拟合得到的关联式能很好预测实验值，平均绝对误差为9.78%。

A study on flow boiling resistance of nanorefrigerant in rectangular microchannels

The flow boiling characteristics were experimentally investigated through the aluminum-based rectangular microchannels with a hydraulic diameter of 1333μm,using Al₂O₃-R141b nanorefrigerants with a different partical of 0.2%,0.5% and 0.8%(mass fraction) and pure refrigerant as the working fluids. The effect of concentration on the two-phase frictional pressure drop were investigated by comparing the surface energy of heat transfer surface before and after experiment. Results showed that when nanorefrigerants with a different particles of 0.2%,0.5% and 0.8% were working fluids,the two-phase frictional pressure drop was lower than pure refrigerant under the same experimental conditions,and the biggist drop were 11.6%,14.8% and 19.2%. Nanoparticles adhered to the surface after experiment and increased the surface energy of heat transfer surface by 1.26 times,1.44 times and 1.91 times,respectively. It reduced the roughness and improved the surface wettability of heat transfer surface,made two-phase frictional pressure drop decrease. Based on the comparison of experimental data with predicted value of models,modified Qu-Mudawar,the new correlation had a better predict ability. The mean absolute error decreased to 9.78%.