Effects of Ionic Jets on Nucleate Boiling and CHF on a Horizontal Plate
Walter Grassi and Daniele Testi
The application of a strong electric field within a dielectric medium can produce a jet-like motion of ionized liquid from a high-voltage electrode to a grounded heated plate. Ionic jet impingement on the upper surface of a horizontal plate where boiling is occurring significantly modifies the boiling curve. Heat transfer enhancement has been observed both at saturation temperature and in subcooled conditions, up to a regime of fully-developed nucleate boiling. In addition, the ionic jet is capable of preventing the formation of a vapor film on the boiling surface up to much higher heat fluxes. The working fluids are FC-72 and HFE-7100. Two different high voltage electrodes have been tested: a single pin and an array of 7 points. This novel electrohydrodynamic technique of ionic-jet impingement boiling can greatly increase, with negligible or very low power input, both the heat transfer coefficients on a heated plate and the critical heat flux for the transition to the film boiling regime (up to 160%).
Keywords: Nucleate Boiling, Critical Heat Flux, Subcooled Boiling, Jet Impingement Boiling, Electrohydrodynamics, Ionic Jets