Experimental investigation of frictional pressure drop in inclined tubes

Abstract

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.The present paper reports on the two-phase frictional pressure drop calculated during the condensation of R134a in a tube of inner diameter of 8.38 mm at different inclination angles. The pressure drops were calculated using the most recent void fraction model of Bhagwat and Ghajar. The condensation tests were carried out in an experimental test facility with a 1.704 m distance between the differential pressure taps. The operating conditions were for mass fluxes of 200 kg/m2s and 300 kg/m2s, mean vapour qualities between 0.25 and 0.75, a saturation temperature of 40°C and for inclination angles ranging between -90° (downward flow) and +90° (upward flow). The highest values of the void fractions and frictional pressure drops were obtained during the vertical downward flow while the lowest were obtained during the vertical upward flow.