An improved analysis model is presented for predicting the local heat transfer coefficient of forced condensation in the annular flow region inside smooth horizontal tubes. Heat transfer experiments for R-12 and R-134a are conducted inside a condensing tube with an loiter diameter of 11mm and a length of 13 m. The mass flux ranged from 200 to 510 kg/m{sup}2 s, and the vapor qualities varied from 1.0 to 0.0. Compared with the experimental data, the numerical results have a deviation afoot more than 20% and 25% for 80% of the total 47 points of R-12 and 88% of the total 226 points of R-134a, respectively.
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