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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

EXPERIMENTAL INVESTIGATION OF CONDENSATION HEAT TRANSFER COEFFICIENTS IN AN INCLINED SMOOTH TUBE AT LOW MASS FLUXES

Get access (open in a dialog) DOI: 10.1615/IHTC16.mpf.023113
pages 6769-6776

要約

It was the purpose of this study to present the heat transfer coefficients and flow patterns during the condensation of R134a inside an inclined smooth tube at low mass fluxes and different temperature differences (the temperature differences were between the saturation temperature and wall temperature). Condensation experiments were carried out at various inclination angles ranging from -90° (vertical downwards) to +90°; (vertical upwards), at low mass fluxes of 50 kg/m2s, 75 kg/m2s, and 100 kg/m2s, and temperature differences from 1°C to 10°C. Measurements were taken at different mean vapour qualities between 0.1 to 0.9 in a smooth tube test section with an internal diameter of 8.38 mm and a length of 1.5 m. The average saturation temperature was kept constant at 40°C. It was found that inclination significantly influenced the flow patterns and the heat transfer coefficients. Downwards flows accounted for an increase in heat transfer coefficient with the maximum heat transfer coefficient found at inclinations of -15°; and -30° (downward flow) at the corresponding minimum temperature difference tested for in each case. The maximum inclination effect was about 60% and was obtained at the lowest mass flux of 50 kg/m2s. In general, it was concluded that the heat transfer coefficients were more sensitive to the temperature difference for downward flows than for upward flows. Furthermore, there was no significant effect of the temperature difference in the heat transfer coefficients for upward flows. It was also found that the downward and upward vertical orientation was almost independent of the temperature difference. Concerning the inclination effect, it was found that in general, it decreased with an increase in temperature difference, but decreased with an increase in mass flux and vapour quality.