Flow and heat transfer features during propane (R290) and isobutane (R600a) boiling in a tube

Abstract

The purpose of this paper is to present a numerical study of the flow and heat transfer characteristics during boiling of two hydrocarbon-based natural refrigerants, namely propane (R290) and isobutane (R600a) in a smooth horizontal tube of 10.0 mm internal diameter. The cross-sectional average heat transfer coefficients are obtained using the temperatures at the top, bottom, left and right sides of the tube. Trends of the heat transfer coefficient are displayed for different operating conditions in terms of saturation temperature (5 — 65 °C) and heat flux (9 — 24 kW/m2), and mass flux (120 and 220 kg/m2.s). Results showed that the heat transfer coefficient depends strongly on the operating parameters. It is augmented as the wall heat flux and the saturation temperature are raised. A dryout region appears for all refrigerants at vapor quality ranging between 0.7564 and 0.8824. Furthermore, from a heat transfer point of view, R290 and R600a are better than R134a.