Natural convection experiments have been carried out with and without electric field under variable gravity field during parabolic flights. The heater was a 0.2-mm Pt wire immersed in a pool of slightly subcooled FC-72 at nearly atmospheric pressure. A non-uniform electric field distribution was obtained by applying high voltage between the wire and a co-axial cylindrical squirrel cage. Experimental refer to the single-phase convective regime, taking place before the onset of boiling. The set of data in the absence of electric field shows the expected trend of thermal convection, increasing with the acceleration of gravity. The introduction of an electric field caused a very large improvement of convective heat transfer. Besides, the convection coefficient revealed to be independent of gravity above a threshold of the applied electric field: the effect of electric forces prevailed on buoyancy ones and allowed rather high heat transfer coefficients in any gravity condition, with negligible energy consumption.
Natural Convection in the Presence of an Electric Field Under Variable Gravity Conditions
DI MARCO, PAOLO;GRASSI, WALTER
1998-01-01
Abstract
Natural convection experiments have been carried out with and without electric field under variable gravity field during parabolic flights. The heater was a 0.2-mm Pt wire immersed in a pool of slightly subcooled FC-72 at nearly atmospheric pressure. A non-uniform electric field distribution was obtained by applying high voltage between the wire and a co-axial cylindrical squirrel cage. Experimental refer to the single-phase convective regime, taking place before the onset of boiling. The set of data in the absence of electric field shows the expected trend of thermal convection, increasing with the acceleration of gravity. The introduction of an electric field caused a very large improvement of convective heat transfer. Besides, the convection coefficient revealed to be independent of gravity above a threshold of the applied electric field: the effect of electric forces prevailed on buoyancy ones and allowed rather high heat transfer coefficients in any gravity condition, with negligible energy consumption.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
