Computational Modelling of Entropy Generation and Heat Transfer Coefficient for Condensation of Climate-Friendly Refrigerants in Microchannels

This study numerically investigates the condensation heat transfer coefficient and entropy generation characteristics of hydrocarbon refrigerants R290 and R600a in single circular microchannels with hydraulic diameters ranging from 0.2 to 0.6 mm. A computational model employing the volume of fluid method was presented to simulate microchannel condensation flow. The proposed computational model was verified against experimental data that exists in the literature. Simulations were conducted under varying mass fluxes (200–600 kg/m2s), vapor qualities (0.3–0.9). A comparison between analytical and simulated entropy generation was provided. It is found that heat transfer coefficients rise significantly with increasing vapor quality and mass flux, driven by liquid film thinning and interfacial shear stress. To evaluate the tradeoff between thermal performance and thermodynamic losses, a modified entropy generation number was investigated. The findings reveal that the enhancement in heat transfer coefficient outweighs the penalty of increased frictional entropy generation at higher mass fluxes. It concluded that the system achieves optimal thermodynamic efficiency, which is maximizing heat transfer per unit of irreversibility, within microchannel with 0.2 mm diameter operating at high mass flux.