Experimental study on flow condensation heat transfer and pressure drop characteristics of zeotropic mixtures propane/isopentane in a mini-channel

R290 and R601a are important components of mixed-refrigerant recuperative heat pump. Recuperation heat transfer is a key process for efficient operation of a heat pump system. In this paper, the condensation heat transfer and frictional pressure drop characteristics of R290 and R290/R601a (0.75/0.25, 0.5/0.5, 0.3/0.7 by mass) in a mini-channel with a diameter of 2 mm were studied. Experiments were carried out at mass flux from 100 to 500 kg/(m²·s), and saturation pressure from 1 to 1.5 MPa over the entire range of vapor quality. The effects of mass fraction, mass flux, saturation pressure, and vapor quality on heat transfer coefficient and frictional pressure drop were studied and discussed. When the mass fraction of R290 changes from 0.75 to 0.5, the heat transfer coefficient of R290/R601a decreases by 11.26%, and the frictional pressure drop decreases by 39.23%. When the mass flux decreases by 100 kg/(m²·s) and the saturation pressure increases by 0.25 MPa, the heat transfer coefficient of R290/R601a decreases by 14.69% and 10.28%, and the frictional pressure drop decreases by 34.42% and 54.28%. The experimental data are compared with the existing correlations. Finally, improved heat transfer correlation and frictional pressure drop correlation were proposed with the average absolute relative deviations of 13.47% and 21%, respectively. © 2025 Elsevier Ltd.