Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
Few studies are available in the literature on diabatic liquid-vapour flows in inclined tubes. The present paper is dedicated to an experimental study of convective condensation of R134a in an 8.38 mm inner diameter smooth tube in inclined orientations. Flow patterns, heat transfer coefficients and pressure drops are presented as function of the inclination angle for different mass fluxes and vapour qualities. Tilting influences the flow patterns and thus the heat transfer coefficients for low mass fluxes and low vapour qualities. An optimum inclination angle that leads to the highest heat transfer coefficient can be found for downward flow. The study of the pressure drops in inclined orientations requires the distinction between the frictional and the gravitational pressure drops. However, a void fraction sensor is necessary to measure the gravitational pressure drops.