Olivier, Stefan P.Meyer, Josua P.De Paepe, MichelDe Kerpel, Kathleen2015-10-152016-04Olivier, SP, Meyer, JP, De Paepe, M & De Kerpel, K 2015, 'The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube', International Journal of Multiphase Flow, vol. 80, pp. 1-14.0301-9322 (print)1879-3533 (online)http://hdl.handle.net/2263/50238Most work in literature on condensation in tubes has been done for smooth tubes in the horizontal and vertical configurations. Recent experimental works with condensation at different inclination angles showed that the heat transfer characteristics were a function of inclination angle. These works were limited to heat transfer and pressure drop measurements with visual observations. However, no work has been done on measuring the void fractions during condensation at different inclination angles. The purpose of this study was to measure void fractions and heat transfer coefficients during condensation for tube inclinations ranging from vertical downwards (-90ᵒ) to vertical upwards (90ᵒ) at a saturation temperature of 40 ᵒC. Measurements were taken in an experimental set-up in which condensation occurred on the inside of a test section. The test section was a circular tube with an inner diameter of 8.38 mm and a heat transfer length of 1.488. The refrigerant used was R134a, and the void fractions were measured using two capacitive void fraction sensors. Mass fluxes ranging from 100 – 400 kg/m2.s and vapour qualities ranging from 10 – 90% were considered. Heat transfer coefficients were also compared with void fractions. It was found that at combinations of low mass fluxes and vapour qualities, void fraction and heat transfer were significantly affected by changes in inclination angle. Generally, void fractions and heat transfer coefficients increased with downward inclination angles with an optimum angle between -10ᵒ and - 30ᵒ (downward flow). At some intermediate mass flux and vapour quality conditions, the void fraction and heat transfer coefficients were observed to be independent of the inclination angle despite changes in the prevailing flow patterns.en© 2015 Elsevier Ltd. All rights reserved . Notice : this is the author’s version of a work that was accepted for publication in International Journal of Multiphase Flow. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in International Journal of Multiphase Flow, vol. 80, pp. 1-14, 2016. doi : 10.1016/j.ijmultiphaseflow.2015.10.015.Void fractionTwo-phase flowCapacitanceFlow patternCondensationInclination angleHeat transfer coefficientEngineering, built environment and information technology articles SDG-07SDG-07: Affordable and clean energyEngineering, built environment and information technology articles SDG-09SDG-09: Industry, innovation and infrastructureEngineering, built environment and information technology articles SDG-13SDG-13: Climate actionPostprint Article