Condensation heat transfer and pressure drop in flat tubes having different aspect ratio

In this study, condensation heat transfer coefficients of R-410A were obtained in flattened stainless tubes made from 5.0 mm inner diameter round tubes. The test range covered saturation temperature 45 , heat flux 10 °C kW/m, mass flux 100~400 kg/ms and quality 0.2~0.8. Results showed the effect of aspect ratio on condensation heat transfer coefficient was dependent on the flow pattern. For annular flow, the heat transfer coefficient increased as the aspect ratio increased. For stratified flow, however, the reverse was true. The pressure drop increased as aspect ratio increased. Existing correlations adequately predicted the heat transfer coefficients and pressure drops of the flattened tubes.