Akademik Veri Yönetim Sistemi
ISI BILIMI VE TEKNIGI DERGISI-JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, cilt.34, sa.1, ss.93-99, 2014 (SCI-Expanded)
In that study, condensation of R134a refrigerant vapor inside a smooth and vertical tube is investigated experimentally. Results presented in this paper is a part of experimental and theoretical studies about condensation of R134a vapor inside smooth and helical micro-fin tubes under different operating conditions such as inclination angle, saturation pressure and mass flux. Condensation of refrigerants inside smooth and helical micro-fin tubes is dependent on so many different parameters. For that reason, experimental studies are very important to determine heat transfer characteristics and to check the validity of correlations. Outside diameter of the test section that used in this study is 9.52 nun and its length is 1m. To condense more amount of matter and to provide laminar liquid film flow, experimental tests were carried out for the mass flux range of 30-40 kg/m(2)s with saturation pressure of 5.8-5.9 bar. In that way, effects of temperature difference between saturated vapor and tube wall, vapor quality change on condensation heat transfer can be exposed clearly. Obtained results showed that average Nusselt number decreases as temperature difference between saturated vapor and tube wall or vapor quality change increase. It is found that local Nusselt number decreases throughout the test tube. In addition to this, most widely used condensation heat transfer coefficient correlations for condensation in smooth tubes were analyzed through the experimental data. Best fit was obtained with Akers et. al. (1959) correlation with an absolute mean deviation of %14.8. Besides that, obtained experimental data was compared with classical Nusselt condensation model. This model predicted average Nusselt number with % 35 absolute mean deviation.