Condensation heat transfer and pressure drop inside tubes with propane (R290) refrigerant. A review of experimental data and correlations

Air-source heat pumps using propane as refrigerant represent a promising long-term solution in the shift towards sustainable thermal energy systems. Driven by tightening refrigerant regulations and rapid market growth, propane-based heat pumps represent one of the most impactful alternatives for cutting heating-sector emissions. The heat transfer coefficient (HTC) and the pressure drop are the two most important factors for designing heat exchangers in these devices. This review provides a comprehensive analysis of experimental studies and correlations focusing on condensation HTC and pressure drops in smooth and microfin tubes using propane. This review analyses a total of 3170 experimental data points of propane extracted from the literature. Specifically, 1740 data points correspond to condensation HTC measurements reported in 19 studies, while 1430 data points pertain to pressure drop measurements from 18 studies. The data covers a wide range of conditions, including inner diameters from 0.952 to 20.8 mm, mass velocities from 47 to 1000 kg/m2-s and saturation temperatures from -19 to 94°C. The effect of the key variables on condensation HTC and pressure drops are systematically analysed. In addition, 41 correlations are evaluated with the experimental datasets to assess their accuracy. The paper identifies the best HTC and pressure drop correlations for smooth conventional tubes, smooth mini tubes and microfin tubes; however, inconsistencies were found in the experimental data and correlations for condensation HTC in microfin tubes. There is a lack of experimental data involving microfin tubes and the presence of oil, emphasizing the need for further research in these areas.