Experimental study of heat transfer coefficient, pressure drop and flow pattern of R1234yf condensing flow in inclined plain tubes

摘要

The purpose of the present study is to investigate the condensation heat transfer coefficient, pressure drop and flow pattern characteristics of R1234yf refrigerant in an inclined plain tube with an internal diameter of 8.3 mm. Experiments are conducted at four mass fluxes of 80, 160, 240 and 320 kg/m~2s, mean vapor qualities in the range of 0.12 to 0.75, saturation temperature of 25 °C, and for tubes with inclination angles in the range of -90° (vertically downwards) to +90° (vertically upwards). The effects of different parameters such as mass flux, mean vapor quality, and the inclination angle of the tube on flow pattern, condensation heat transfer coefficient, and pressure drop are investigated. According to the results, it is found that inclination angle significantly influenced the flow pattern. Furthermore, it is observed that generally, increasing vapor quality and mass flux, enhances the heat transfer coefficient for all the inclination angles. At low mass fluxes or low vapor qualities, the highest heat transfer coefficient occurs in the tube with the inclination angle of -30°, while at higher mass fluxes or higher vapor qualities, the effect of inclination angle on heat transfer is negligible. With increasing the vapor quality, total pressure drop increases for tubes with the negative or zero angles, while it generally decreases, for the tubes with positive angles. In addition, total pressure drop increases with increasing mass flux at constant vapor quality for all the inclination angles. Experimental results of this study are also compared with the existing correlations in literature that predict the amount of heat transfer coefficient and fric-tional pressure drop. Finally, based on the present data, a new correlation is developed and suggested to predict the flow condensation heat transfer coefficient in inclined plain tubes.