Condensation of HFC-134a in an 18?? Helix Angle Micro-Finned Tube

An experimental study of local condensation heat transfer and pressure drop characteristics of HFC-134a in an 18?? helix angle, 0.375" o.d. micro-finned tube was , conducted. The main goal of the study was to compare the heat transfer and pressure drop characteristics during condensation in the micro-finned tube to those in a smooth tube. In general, the heat transfer enhancement factors decreased as the refrigerant mass flux increased. The average enhancement factors ranged from 2.0 at a mass flux of 110 klbm/ft2-hr, to 1.4 at a mass flux of 330 klbm/ft2-hr. The enhancement factors also depended on the flow regime. In the wavy flow regime, high enhancement factors were usually observed, while in the annular flow regime, low enhancement factors were observed except "at very high vapor qualities. The pressure drop penalty factors showed just a slight dependence on mass flux and vapor quality. In general, the penalty factors increased slightly as the mass flux increased and the vapor quality decreased The average penalty factors ranged from 1.19 to 1.26. A simple condenser model that combined the results of this study with pressure drop and heat transfer correlations from earlier studies was developed. The model was used to calculate the total length and refrigerant side pressure drop in a condenser for different operating conditions.Air Conditioning and Refrigeration Center Project 3