Measurement of Condensation Heat Transfer Coefficients at Near-Critical Pressures in Refrigerant Blends

摘要

This paper presents the results of an experimental study on condensation heat transfer of refrigerant blends R404A and R410A flowing through horizontal tubes of 9.4 and 6.2 mm inner diameter at nominal pressures of 80% and 90% of the critical pressure. Local heat transfer coefficients were measured for the mass flux range 200 < G < 800 kg/m~2-s in small quality increments over the entire vapor-liquid region. Heat transfer coefficients increased with quality and mass flux, while the effect of reduced pressure was not very significant within this range of pressures. The heat transfer coefficients increased with a decrease in diameter.