Two-Phase Refrigerant Mixture (R-407C) Flow in Smooth Meso-Scale Heat Exchangers

Abstract

The paper presents results from an experimental study on refrigerant mixture flow (R-407C) in which the heat transfer coefficient was measured across a range of heat and mass fluxes. Flow characteristics in smooth horizontal mesochannels were measured for two different conditions, 1) subcooled and 2) saturated boiling with diameters of 1.59, 2.78, and 3.97 mm and a length of 50.8 mm in refrigerant mixture (R-407C). Experiments were performed at heat fluxes of 2 and 11 kW/m2 for the subcooled boiling and 15 and 29 kW/m2 for the saturated boiling. The mass flux was varied from 0.45 to 1.55 kg/min and the refrigerant was subcooled to 8°C. The saturated boiling experiments were conducted for ΔTsat = 0 to 27°C. The heat transfer coefficients were found to be dependent on channel size, heat flux, and mass flux variations. For smaller channel diameters, the heat transfer rate significantly increased as compared to larger channel diameters. The results showed an increase of 100% in heat transfer coefficient when compared to traditional and micro-channel boiling characteristics.