Evaporative heat transfer of R134a and R407C inside a smooth tube with different inclinations

An experimental investigation on two phase flow evaporative heat transfer of refrigerants R134a and R407C in a smooth copper tube inclined at five different angles between 0° and 90° was conducted. The experimental data were obtained over a mass velocity range of 100-300 kg/m2 s, heat flux range of 3-10 kW/m2, inlet temperature range of 5-9 °C and vapor quality varied from 0.1 to 0.9. The test section was 1.2 m long, smooth copper tube with inner diameter of 7.0 mm and outside diameter of 9.52 mm. The effects of mass velocity, heat flux, and vapor quality and tube inclinations on evaporative heat transfer coefficient of both refrigerants are thoroughly compared. The experimental heat transfer coefficients were also compared with some existing correlations.