Sereda V. Heat Transfer during Film Condensation of Moving Vapor in Smooth Horizontal Tube

The dissertation is devoted to the experimental researches which are aimed at increasing the efficiency of horizontal tube condensers by strictly accurate evaluation of heat transfer and regime parameters in condensing various refrigerants in horizontal tubes of such devices. The unique measurements of heat fluxes and heat transfer coefficients local by circumference have been carried out during condensation of Freon R-22 and steam which varies over a wide range of the main regime parameters (G, х, q, Rel). The improved model of film condensation inside horizontal tubes for prediction of heat transfer with application of the results of numerical solutions of Bae et al. is proposed. In this model more precise definition of friction coefficient on interphase as the main parameter crucial for condensation is given. This more precise definition contains experimental substantiation of prediction for calculation of pressure losses by friction and correction that takes into account surface suction at the interphase. Heat exchange predicted by the proposed method was compared with the experimental data of various authors for 13 substances (steam, Freon's R-22, R-123, R-134a, R-245fa, carbon dioxide, propylene, propane, ether, isobutene, refrigerants FC-72, Novec®649, HFE-7000) in annular and intermediate modes. Good agreement of the experiments with calculations (divergence within 25%) proves correctness of the proposed method both for laminar flow of condensate film and turbulent flow.