Condensation Heat Transfer and Pressure Drop of R-404A in 7.0 mm O.D. Smooth and Microfin Tube at Low Mass Fluxes

摘要

R-404A condensation heat transfer and pressure drop data are provided for 7.0 mm O.D. smooth and microfin tubes. Tests were conducted for a range of mass fluxes (from 80 to 200 kg/m~2s) and quality (from 0.2 to 0.8). The heat flux was 6kW/m~2 and saturation temperature was 45°C. It was found that both the heat transfer enhancement factor and the pressure drop penalty factor increase as mass flux increases. The range of pressure drop penalty factor (0.99-1.27) was smaller than that of heat transfer enhancement factor (1.21-1.96). Smooth tube heat transfer coefficients and pressure drops are reasonably predicted by Shah [An improved and extended general correlation for heat transfer during condensation in plain tubes, Int. J. HVAC&R Res. 15 (2009) 889-913] and Jung and Radermacher [Prediction of pressure drop during horizontal annular flow boiling of pure and mixed refrigerants, Int. J. Heat Mass Transfer 32 (1989) 2435-2446] correlation, respectively. For the microfin tube, however, all the existing correlations do not adequately predict the present data. Poor predictions may be attributed to the lack of R-404A and low mass flux data in their database.