Direct-contact condensation heat transfer model in RELAP5/MOD3.2 with/without noncondensable gases for horizontally stratified flow

Direct-contact condensation experiments on atmospheric steam and steam/air mixture on subcooled water flowing co-currently in nearly-horizontal channels are carried out and the local heat transfer coefficients are obtained. Inlet air mass fraction in the mixture is varied by up to 50%. Based on previous and present experimental data, a direct-contact condensation database is constructed. The horizontally stratified condensation model of RELAP5/ MOD3.2 overpredicts both co-current and counter-current experimental data. The correlation proposed by Kim predicts the database relatively well compared with that of RELAP5/MOD3.2. In the presence of noncondensable gases. RELAP5/MOD3.2 overpredicts the database with percentage errors of 55.1 and 61.1% for pipe inclination angles of theta = 2.1degrees and theta = 5.0degrees, respectively. The UCB correction factor is modified to consider the effects of noncondensable gases on heat transfer coefficients, When Kim's correlation is substituted with the Dittus-Boelter type correlation in RELAP5/MOD3.2 and a modified correction factor is used. the prediction errors are greatly reduced to 20.7 and 28.8% for inclination angles of theta = 2.1degrees and theta = 5.0degrees, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.