CONDENSATION OF R417A ON HORIZONTAL SMOOTH TUBES. THEORETICAL MODEL AND EXPERIMENTAL VALIDATION

The paper reports on the numerical modelling and the experimental validation conducted to study the condensation of the ternary refrigerant mixture R417A on horizontal smooth tubes. The tested tubes are made of copper and have internal/external diameters of 16.75/18.95 mm. Experiments were carried out at saturation temperatures of 30, 40 and 50 degrees C and wall subcoolings from 2.5 to 25 degrees C. Experimental results of the overall condensation heat transfer coefficients (HTCs) are reported and discussed. A theoretical model based on the film theory proposed by Colbum and Drew and on the Maxwell-Stefan equations to describe the multicomponent mass transfer diffusion was developed and implemented in a computer application. The model was able to predict the trends of the experimental HTCs for the wide ranges of condensation temperatures and wall subcoolings considered in the experiments. The heat flow per unit length and the overall condensation HTCs were slightly overestimated with mean errors of 4.6% and 6.6%, respectively.