Evaporation Heat Transfer Characteristics of Fourth-Generation Refrigerants in Nano/Microchannels

Fourth-generation refrigerants are characterized by their ultralow global warming potential (GWP), negligible ozone depletion potential (ODP), and superior thermophysical properties. These advantages have spurred growing interest in their adoption, with hydrocarbon-based alternatives such as R290 and R600a emerging as particularly promising options. However, the evaporation heat transfer performance of these next-generation refrigerants remains insufficiently explored, particularly in miniaturized thermal management systems. In this paper, we systematically investigate the evaporation heat transfer characteristics of fourth-generation refrigerants in nano- to microscale channels using the contact line heat transfer theory. We compare the heat transfer performances of R290 and R600a with those of R134a, a third-generation refrigerant. The results demonstrate that R290 and R600a are effective ecofriendly alternatives for nano/microchannel evaporation applications. On this as a basis, we designed a micro-nano composite wick evaporator, consisting of a nanochannel membrane for evaporation and an underlying microchannel liquid supply structure. The optimal channel dimensions for maximizing device-level heat flux are determined using R290 and R600a as the working fluids. This study elucidates the evaporation heat transfer mechanisms of fourth-generation refrigerants in nano/microchannels, providing fundamental insights for the design and optimization of nanochannel evaporators.