Flow Boiling Heat Transfer and Pressure Gradient of R410A in Micro-Channel Flat Tubes at 25^○ C and 30^○ C

This study investigates the flow boiling heat transfer coefficient and pressure gradient of refrigerant R410A in micro-channel flat tubes. Experiments were conducted at saturation temperatures ranging from 25^○ C to 30^○ C, mass fluxes between 198 and 305 kg/m² s, and heat fluxes from 9.77 to 20.18 kW/m², yielding 99 sets of local heat transfer coefficient data. The results show that increasing heat flux and mass flux enhances the heat transfer coefficient, although the rate of enhancement decreases with increasing vapor quality. Conversely, higher saturation temperatures slightly reduce the heat transfer coefficient. Additionally, the experimental findings reveal discrepancies in the accuracy of existing pressure drop and heat transfer coefficient prediction models under the studied conditions. This study recommends using the Kim and Mudawar correlation to predict pressure gradients within the tested range, with a Mean Error (ME) of −5.24% observed in this study. For heat transfer coefficients, the Cooper and Kandlikar correlations are recommended, achieving a Mean Absolute Error (MAE) of approximately 22%. This research provides value for performance prediction and parameter selection of micro-channel technology in broader application scenarios within heating, ventilation and air-conditioning fields.