Heat transfer and pressure drop performance during in-tube condensation are presented for R-502 and R-507 in a 3/8 in.(9.52 mm)uter diameter smooth tube and microfin tube. Condensation tests were performed at saturation temperatures of 104 °F (40 °C) and 122 °F (50 °C) and over a mass flux range of 88,400 lb/h·ft² (120 kg/m^2. s)to 442,400 lb/h . ft² (600 kg/m^2.s). This study reports the local and average heat transfer coefficients and the pressure drops that were measured in a specially designed test section. The experimental results indicate that R-507 has a slightly better condensation performance than R-502. Specifically, the measured heat transfer coefficients for R-507 were slightly higher than those for R-502, while the pressure drops for R-507 were significantly lower. The microfin tube increased the heat transfer coefficients from 50% to 120% compared to the smooth tube, while also increasing pressure drop by 60% to 100%. A number of existing correlations were found to give reasonable predictions for the heat transfer coefficients.

Units: Dual