R32制冷剂在小管径水平管内的沸腾换热与阻力特性实验研究

In this paper, the boiling heat transfer characteristics of the new R32 alternative refrigerant with low pollution, high energy efficiency, poor flammability and low toxicity are investigated under low-temperature conditions in horizontally orientated tubes. The flow boiling system is established and applied to study the R32 flow boiling heat transfer and pressure drop in small-diameter tubes with 3 mm and 4 mm diameters in horizontal orientation. The impact of mass flow rate, heat flux, saturated temperature and vapor quality on the R32 two-phase thermohydraulic performance is experimentally considered. The heat transfer jeopardization by the dry-out mechanism is also observed. The result shows that the heat transfer coefficient of the 3mm tube can be improved by 8%~12% compared to that of the 4mm tube while the critical heat flux is independcnt of tube diameter at a high flow rate. Meanwhile, compared with heat transfer characteristics, R32 saturation temperature is more sensitive to the two-phase flow resistance, the resistance loss increases by about 23% when the saturation temperature is reduced from 13 °C to 11 °C. Finally, the corrected Fang's correlation is applied to precisely predict the two-phase heat transfer coefficient of R32 in which over 88. 56% of data can be controlled within the error of ± 10%.