Boiling heat transfer and pressure drop in single rectangular microchannel

One of the goals of this paper is to investigate the two-phase flow characteristics of the refrigerant changing phase in a high aspect ratio (1:30) rectangular vertically placed microchannel. The hydraulic diameter of the channel is 0,39 mm. The experimental data were collected for the refrigerant R134a for mass fluxes varying from 200 to 970 kg/m2s and a heat flux range of 0,6-28 kW/m2. The results of the heat transfer investigation have shown that the heat transfer coefficient is not influenced by the mass flux or vapour quality but only by heat flux, thus indicating the dominance of nucleate boiling or a related mechanism. In comparison to several conventional correlations from the literature, it was shown that the correlations by Lazarek and Black, 1982 predict the heat transfer coefficient best, the data scattering up to 35%. Measurements have shown that the pressure drop increases approximately linearly with the mass flux.Qc 2012020