A New Computational Procedure for Heat Transfer and Pressure Drop During Refrigerant Condensation Inside Enhanced Tubes

Abstract

A new computational procedure for heat transfer coefficient and pressure drop during condensation of pure refrigerants and refrigerant mixtures inside enhanced tubes is presented. A modified form of the Cavallini and Zecchin equation (Cavallini and Zecchin, 1971, 1974) for smooth tube has been implemented for condensation inside low-fin, micro-fin and cross-grooved tubes: the comparison with a set of around 300 experimental data points, including both pure refrigerants, azeotropic and zeotropic refrigerant mixtures, shows an absolute mean deviation of around 15%. Two traditional models for adiabatic pressure losses inside smooth tubes, Sardesai et al. (1982) and Friedel (1979), have been modified for condensation inside micro-fin tubes. The comparison with available experimental data, a set of around 120 data points, shows an absolute mean deviation between 21 and 24%. A further extension of the same models has been used to predict pressure drop during vaporization inside micro-fin tubes: calculated values compare very well with experimental ones.