Two-phase Heat Transfer Measurements of R254fa At High Saturation Temperatures in Horizontal Mini-channels

Heat transfer measurements for R254fa were conducted. The heat transfer coefficient was determined for a smooth stainless steel tube with an inner tube diameter of 3 mm. The experiments were conducted for five mass fluxes (100, 300, 500, 700 and 1000 kg/(m².s)), three heat fluxes (10, 30 and 50W/m²) and at three saturation temperatures (40°C, 70°C and 125°C). The experiments were used to determine the influence of the saturation temperature, mass flux, heat flux and vapour quality on the heat transfer coefficient. At a low saturation temperature, the heat transfer coefficient increases with an increasing mass flux. However, at a high saturation temperature the heat transfer coefficient decreases with an increasing mass flux. Furthermore, the heat transfer coefficient increases with increasing vapour quality at a low saturation temperature. On the contrary, the heat transfer coefficient decreases at higher saturation temperatures.