A mechanistic approach to developing two phase flow pattern transition maps for two-phase dielectric fluids subject to high voltage polarization

High voltage electric fields can be used as an active heat transfer enhancement technique for convective boiling or condensing dielectric fluids, with the major component of this enhancement being attributed to phase redistribution and mixing in the system due to electric body forces. Many performance prediction tools for convective boiling and condensation rely on flow pattern maps to identify the flow regime for use with flow pattern specific heat transfer and pressure drop correlations [1,2]. In this paper, a mechanistic approach to developing two phase flow pattern maps for two-phase dielectric fluids subject to high voltage fields using a fully contained, equation-based electric Froude number approach is presented and compared against the experimental flow pattern data for EHD convective boiling & condensation available in the literature and from the current experimental study. Despite the development of newer diabatic, semi-mechanistic flow pattern models for free-field heat exchanger performance analysis, it is recommended that the Steiner equations for flow pattern transition be used as a basis for the mapping when additional physics such as EHD is coupled, as the empirical fits in newer semi-mechanistic maps are unreliable when additional physics is present.