Condensation heat transfer characteristics of R410A–oil mixture in 5 mm and 4 mm outside diameter horizontal microfin tubes

Condensation heat transfer characteristics of R410A–oil mixture in 5 mm and 4 mm outside diameter horizontal microfin tubes were investigated experimentally. The experimental condensing temperature is 40 °C, and nominal oil concentration range is from 0% to 5%. The test results indicate that the presence of oil deteriorates the heat transfer. The deterioration effect is negligible at nominal oil concentration of 1%, and becomes obvious with the increase of nominal oil concentration. At 5% nominal oil concentration, the heat transfer coefficient of R410A–oil mixture is found to have a maximum reduction of 25.1% and 23.8% for 5 mm and 4 mm tubes, respectively. The predictabilities of the existing condensation heat transfer correlations were verified with the experimental data, and Yu and Koyama correlation [29] shows the best predictability. By replacing the pure refrigerant properties with the mixture’s properties, Yu and Koyama correlation has a deviation of −15% to  + 20% in predicting the local condensation heat transfer coefficient of R410A–oil mixture.