R417A在水平光滑管和内螺纹管中的流动沸腾换热

对非共沸混合制冷剂R417A在外径为9.52 mm的水平光滑管和2种不同几何参数的内螺纹管中的流动沸腾换热进行实验研究,分析讨论了制冷剂质量流速、热流密度、干度、强化管参数对换热系数的影响规律和影响机理.实验结果表明:换热系数随着质量流速的增大而增大.在以对流蒸发占优势的换热区,热流密度对换热系数的影响较小;换热系数随着干度的增大先呈现出增大趋势,增至高峰值后又迅速下降,高峰值随热流密度的增大和质量流速的减小向干度较大的方向移动;内螺纹管能有效强化制冷剂的流动沸腾换热,R417A在2种内螺纹管中的换热系数分别比在光滑管中高出130%~210%和150%~270%.

Evaporation Heat Transfer of R417A Flowing Inside Horizontal Smooth and Internally Grooved Tubes

The experimental study was carried out on the evaporation heat transfer of non-azeotropic refrigerant mixtures R417A flowing inside horizontal smooth and two internally grooved tubes of 9.52mm OD with different geometrical parameters.The influence and mechanism of mass flow rate,heat flux,vapor quality and geometrical parameters of enhanced tubes on heat transfer coefficients were analyzed and discussed.Experimental results indicate that heat transfer coefficients increase with increasing mass flow rate.There is no significant effect of heat flux on evaporation heat transfer in convective evaporation dominant region.The heat transfer coefficients increase with vapor quality firstly and begin to decrease after the peaks.Peaks move towards higher qualities with increasing heat flux and decreasing mass flow rate.The heat transfer coefficients of R417A inside two internally grooved tubes are 130%~210% and 150%~270% higher than those inside smooth tube,respectively.