The paper reports the results obtained during an experimental study on film boiling on wires in the presence of an externally imposed electric field. The arrangement allowed achieving various combinations of pressure and subcooling independently of the environmental conditions. The test section was an electrically heated platinum wire with diameters of 0.1 and 0.2 mm. The working fluid was FC-72. The results showed that two different film boiling regimes, separated by an additional boiling transition, can exist in the presence of an electric field. The first regime, at low wire superheat, was strongly influenced by the electric field, showing a remarkable heat transfer enhancement with increasing voltage. The second regime, at higher superheat, was weakly dependent on the field strength and almost coincident with the zero field one. These results are analogous to the ones previously obtained using R113 as working fluid. The reasons for the occurrence of the transition were investigated. A simple model of the effect of the electric field on the interface behavior was developed, taking into account the variation of the thickness of the vapor layer with the increase of the heat flux, thus providing a possible explanation for the occurrence of the transition.
Effect of Externally Applied Electric Field on Pool Film Boiling on FC-72
DI MARCO, PAOLO;GRASSI, WALTER
2004-01-01
Abstract
The paper reports the results obtained during an experimental study on film boiling on wires in the presence of an externally imposed electric field. The arrangement allowed achieving various combinations of pressure and subcooling independently of the environmental conditions. The test section was an electrically heated platinum wire with diameters of 0.1 and 0.2 mm. The working fluid was FC-72. The results showed that two different film boiling regimes, separated by an additional boiling transition, can exist in the presence of an electric field. The first regime, at low wire superheat, was strongly influenced by the electric field, showing a remarkable heat transfer enhancement with increasing voltage. The second regime, at higher superheat, was weakly dependent on the field strength and almost coincident with the zero field one. These results are analogous to the ones previously obtained using R113 as working fluid. The reasons for the occurrence of the transition were investigated. A simple model of the effect of the electric field on the interface behavior was developed, taking into account the variation of the thickness of the vapor layer with the increase of the heat flux, thus providing a possible explanation for the occurrence of the transition.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
