EHD enhancement of shell-side boiling heat transfer coefficients of R-123/oil mixture

Results of an experimental study on electrohydrodynamic (EHD) enhancement of nucleate pool boiling heat transfer of R-123 on a tube are reported in this paper. Effects of surface heat flux, electric field voltage, and lubricant oil concentration on heat transfer enhancements are presented. For comparison purposes, experiments were also performed for R-11 over the same range of parameters as those for R-123. It is demonstrated that R-123 has a much better response to the EHD enhancement mechanism. For the range of parameters investigated here, up to 450% enhancement was obtained for R-123, which compared with a corresponding 170% enhancement for R-11. The lubricating oil has only a modest degrading effect on the EHD-enhanced heat transfer coefficients. The oil effect is more pronounced at the lower surface heat fluxes and it is reduced with increase in the heat flux. Flow visualization experiments facilitated interpretation of the EHD boiling mechanism and the results obtained in this study.