EHD-assisted external condensation of R-134a on smooth horizontal and vertical tubes

In this paper, results of an experimental study on the EHD-assisted externa l condensation of R-134 over a plain tube will be presented and discussed. The experiments performed can be divided into two groups: (1) EHD-assisted external condensation on a vertical smooth tube and (2) EHD-assisted extern al condensation experiments on a horizontal smooth tube. In each case, expe riments were conducted as a function of parametric values such as heat flux , electrode gaps and applied electric field potential. All of the experimen ts were conducted using a specially designed helical electrode and with R-1 34a as the working fluid. Experimental results demonstrate a remarkable potential in utilizing EHD to enhance external condensation heat transfer. It is concluded that the enha ncement is driven by the effective removal of the condensate through EHD-in duced liquid extraction and dispersion phenomena. (C) 1998 Elsevier Science Ltd. All rights reserved.