The effect of inclined angle on flow, heat transfer and refrigerant charge of R290 condensation in a minichannel

Abstract

As an ideal pollution-free refrigerant, R290 has been acceleratingly widely used. It is important to enhance the heat transfer performance and decrease the refrigerant charge of R290 in heat exchangers for its flammable and explosive properties. For this purpose, the research on condensation flow and refrigerant charge of R290 in a minichannel with different inclined angles is numerically carried out to obtain the optimal inclined angle. In the simulation, the VOF multiphase flow model and SST k−ω turbulence model are used for transient calculation, and the effect of surface tension is analyzed. The results show that as the inclined angle increases, heat transfer coefficient and frictional pressure drop increase. For heat transfer coefficient and refrigerant charge, the optimal inclined angle is 90° (downward flow), which is different from the existing results of R134a in a large channel. When G = 100, 200 kg/(m2s), at high vapor quality (x>0.8), heat transfer coefficient and frictional pressure drop almost do not increase with the increase of vapor quality. With the increase of inclined angle and mass flux, the refrigerant charge of R290 in a minichannel shows a downward trend. The maximum reduction is about 8% under the same heat transfer rate and heat transfer temperature difference. Therefore, changing the inclined angle is an effective approach to reduce the refrigerant charge of R290 in minichannel heat exchangers.