NUMERICAL SIMULATION OF LAMINAR FILM CONDENSATION OF VAPOR IN A HORIZONTAL MINICHANNEL WITH AND WITHOUT A NONCONDENSABLE GAS

摘要

A steady two-dimensional volume of fl uid (VOF) simulation of laminar fi lm condensation of vapor with and without a noncondensable gas inside a 1-mm horizontal minichannel is presented. The uniform interface temperature and wall temperature are fi xed as boundary conditions, and the fl ow patt ern is expected to be annular. The numerical simulation results display the evolution of the liquid-gas interface, Nu, and heat fl ux. It is found that the global eff ect of gravity is negligible. Moving downstream the minichannel, the liquid fi lm grows rapidly near the entrance and then remains unchanged in the rest of the minichannel till the end. Higher inlet velocity and wall temperature of the minichannel lead to the augmentation of the average Nu value of condensation. The existence of a noncondensable gas makes the heat fl ux to decrease sharply compared to that vapor condensation, while a higher inlet velocity will aggravate this eff ect. Meanwhile, the noncondensable gas with smaller thermal conductivity would give rise to greater reduction of heat fl ux as a result of the higher thermal resistance in the noncondensable gas layer.