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The objective of this study that proposed new correlations to predict pressure drop during condensation
of R134a for the flattened tubes. The flattened tubes are made from 3.55 mm inner diameter of round tubes. The tested tube configurations are as follows: circular tube with 3.55 mm inner diameter; flattened tube with aspect 0.72 (FT1); 3.49 (FT2); and 7.06 (FT3) aspect ratio respectively. The experimental range covers mass flux of 200-800 kg/m2s, heat flux 10 - 40 kW/m2, saturation pressure 8, 10 and 12 bar, and vapor quality 0.1 - 0.8. The results showed that condensation pressure drop increased with the increase of mass flux, heat flux and vapor quality in the other hand; pressure drop decreased that have significantly affected by saturation pressure 8, 10, and 12 respectively. The existing correlations are not successful for the prediction condensation pressure drop of flattened tubes. A proposed correlation can be used to predict pressure drop as 80 % of the experimental data within ± 30 %.
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