A test rig for condensation heat transfer was developed and the cooling heat transfer characteristics of R22 and R410Ain small-diameter tubes were compared. The test conditions were as follows: the mass flow rate 200–800 kg/(m2?s)

saturation temperature 40 ℃

the range of quality 0–1

and the outer diameter of the horizontal smooth copper tube5 mm. The effects of the mass flow rate and quality on condensation heat transfer were analyzed and the correlation formula applied to the traditional pipeline was compared with experimental data. The analysis results showed that the condensation surface heat transfer coefficient was positively correlated with the mass flow rate and quality; in addition

the condensation surface heat transfer coefficient increased significantly in the high quality area. The Shah correlation was not ideal in predicting the test data and the maximum deviation from the actual values reached 60%. However

the Shah correlation was ideal for predicting data in a low mass flow rate and low quality area; when the mass flow rate (G=200 kg/(m2?s)) was small

the condensation surface heat transfer coefficient of R410A was lower than that of R22. Furthermore

with the increases in the mass flow rate (G=400 kg/(m2?s))

the disparity between the two condensation surface heat transfer coefficients decreased. The condensation surface heat transfer coefficient of R410A was similar to that of R22 when a medium to high mass flow rate (G=600 kg/(m2?s)) was reached. When the mass flow rate (G=800 kg/(m2?s)) continued to increase

the condensation surface heat transfer coefficient of R410A rose higher than that of R22 as the quality increased.