The Use of Electric Force as a Replacement of Buoy

Authors: Paolo Di Marco

Publish Date: 2012/06/29

Volume: 24, Issue: 3, Pages: 215-228

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Abstract

When an electrostatic field is applied to a medium an electric force arises originated by polarization and by the possible presence of free charge If the medium is a twophase fluid this force drives the vapor of lower dielectric permittivity towards the zone of weaker electric field giving the opportunity of separating phases and enhancing boiling heat transfer in microgravity conditions where buoyancy is lacking Electric force is also responsible for bubble deformation In this paper after a comprehensive description of electrohydrodynamics EHD mechanisms in a twophase fluid some relevant literature data about EHDinduced phase separation are reported confirming the effectiveness of the technique The electric force on a growing and rising bubble is then evaluated numerically in some simple cases with a fem technique Finally original experiments on gas bubble detachment are analyzed in the attempt to enucleate the role of different mechanisms contributing to EHD enhancement In particular it is stressed that the role of electric forces in altering bubble shape and increasing bubble internal pressure seems to be the most significant in promoting bubble detachment

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