3-D numerical simulation of forced convection heat transfer in microscale rectangular channels for low GWP refrigerants

Abstract

This study presents a numerical evaluation of the performance of low Global Warning Potential (GWP) refrigerants R600a, R290, R1270, and R134a in heat dissipation by forced convection in a microchannel heat sink. The heat sink comprises 50 parallel microchannels with a cross-sectional area equal to 123 × 494 [µm2]. The differential equations describing the physical behavior interaction between the refrigerant and the copper matrix are solved using the finite volume method and the SIMPLEC coupling algorithm. The numerical model is used to predict fluid mechanics and heat transfer for single-phase laminar conditions including the friction factor, the Nusselt number and the average wall temperatures, as well as the whole performance of the microchannel heat sink. The accuracy of the numerical model is validated by comparing the performance of R600a with experimental data, resulting in deviations within the range of the uncertainty of each parameter. The evaluation of the performance of different refrigerants reveals that the friction factor and Nusselt number are significantly influenced by the microchannel geometry and thermal conditions, exhibiting unique yet similar trends for different refrigerants. Furthermore, the analysis of the average wall temperature in the microchannels demonstrates that the hydrocarbon-based refrigerants effectively reduce the temperature of the copper matrix compared to R134a, suggesting a superior performance in the dissipation of heat flux under single-phase laminar conditions.