Flow boiling heat transfer of Freon R11 and HCFC123 in narrow passages

Flow boiling heat transfer coefficients for Freon R11 and HCFC123 in a smoo th copper tube with an inner diameter of 1.95 mm have been experimentally i nvestigated. The parameter ranges examined are: heat fluxes from 5 to 200 k W m(-2); mass fluxes from 50 to 1800 kg m(-2) s(-1); vapour quality from 0 to 0.9; system pressures from 200 to 500 kPa; and experimental heat transfe r coefficients from 1 to 18 kW m(-2) K-1. It was found that the heat transf er coefficients are a strong function of the heat flux and the system press ure, while the effects of mass flux and vapour quality are very small in th e range examined. This suggests that the heat transfer is mainly via nuclea te boiling. The present experimental data were compared with some existing correlations and recommendations on their use is made. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.