A general analytical model to predict the condensation heat transfer coefficient of pure refrigerants in horizontal microfin tubes is developed in this paper. The model basically follows the smooth tube correlation proposed by Haraguchi et al. (1994), in which the total condensation coefficient is composed of the contributions of film condensation and forced convective condensation. For the microfin tube, the film condensation term is estimated from the product of total unflooded area and local enhancement factor, while the heat transfer coefficient of forced convective condensation is set equal to that of the smooth tube. The predicted results show good agreement with experimental results, and it is shown that effects of the parameters that characterize the microfin tube, i.e., pipe diameter, fin height, fin pitch, and fin-tip angle, are well predicted for the first-order approximation. Also, high heat transfer coefficient is reproduced at high quality range with the present model, which assumes that the liquid phase is distributed only in the valley of the grooves for this quality region.

Units: SI