Flow condensation pressure drop characteristics of R410A–oil mixture inside small diameter horizontal microfin tubes

Flow condensation pressure drop characteristics of R410A–oil mixture inside small diameter (5.0 mm and 4.0 mm O.D.) horizontal microfin tubes were investigated experimentally covering nominal oil concentrations from 0% to 5%. The research results indicate that, comparing with the frictional pressure drop of pure R410A, the frictional pressure drop of R410A–oil mixture may decrease by maximum of 18% when the vapor quality is lower than 0.6, and increase by maximum of 13% when the vapor quality is higher than 0.6. A new frictional pressure drop correlation for R410A–oil mixture flow condensation inside microfin tubes is developed based on the refrigerant–oil mixture properties, and can agree with 94% of the experimental data within a deviation of −30% to +30%.