BA-92-05-1 -- EHD Enhancement of Shell-Side Boiling Heat Transfer Coefficients of R123/Oil Mixture PDF

Results of an experimental study on electrohydrodynamic (EHD) enhancement of nucleate pool boiling heat transfer of R123 on a tube are reported. 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 R11 over the same range of parameters as those for R123. It is demonstrated that R123 has a much better response to the EHD enhancement mechanism. For the range of parameters investigated here, up to 450% enhancement was obtained for R123, which compared with a corresponding 170% enhancement for R11. The lubricating oil has a modest degrading effect on the EHD-enhancement 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 visualisation experiments facilitated interpretation of the EHD boiling mechanism and the results obtained in this study.

KEYWORDS: experiment, boiling, heat transfer coefficient, heat flow, refrigerants, R123, tubes, surfaces, voltage, lubricants, content, comparing, R11, refrigerants