含油制冷剂在小管径换热管内流动沸腾换热关联式

The Correlations of Heat Transfer of Refrigerant-Oil Mixture Flow Boiling inside Small Smooth Tubes

通过对现有关联式预测值与6.34 mm和2.50 mm小管径换热管内实验数据的对比分析,发现其对6.34 mm换热管的适用性明显高于2.50 mm的换热管.相对而言,Zurcher修正的Kat-tan-Thome-Favrat模型对于6.34 mm换热管适用性最好,该关联式80%的预测值与实验数据点的偏差在±30%内.但对于2.50 mm的换热管只有40%数据点偏差在±30%内.根据实验结果,开发了适用于小管径换热管的基于局部油浓度和制冷剂-润滑油混合物性的两相换热增强因子模型,该模型能较好地反映润滑油在制冷剂中的实际存在状态及对制冷剂换热的影响规律,且物理意义明确,对于6.34 mm和2.50 mm的两种换热管,其预测值与90%以上的实验数据的偏差均在±20%以内.

The state-of-the-art correlations were analyzed and the predicted values of correlations for refrigerant-oil mixture were compared with the present experimental data of small tubes with inside diameter of 6.34 mm and 2.50 mm. The conclusions can be drawn that all the current correlations have more satisfactory prediction for 6.34 mm tube than for 2.50 mm tube. Relatively, Zurcher＇s modified Kattan-Thome -Favrat correlation is the best for the present data because almost 80% data points for 6. 34mm tube lie within the deviation of ±30%, while it fails to predict the heat transfer coefficient of 2.50 mm because only 40% data points lie within the deviation of ±30%. A new correlation of the two phase heat transfer multiplier based on local properties of refrigerant-oil mixture was developed, which approaches the actual physical mechanism of refrigerant-oil flow boiling heat transfer and can reflect the co-existing conditions of refrigerant and oil mixture. The new correlation shows good predictability to experiment data. It can accurately represent more than 90% of the experimental data within ±20% for the both tubes.