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. 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 (saturation temperatures at ambient pressure: 56°C and 61°C, respectively). 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%).
Effects of Ionic Jets on Nucleate Boiling and CHF on a Horizontal Plate
TESTI, DANIELE
2009-01-01
Abstract
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. 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 (saturation temperatures at ambient pressure: 56°C and 61°C, respectively). 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%).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.