Nucleate Pool Boiling in the Presence of an Electric Field: Effect of Subcooling and Heat-up Rate

Paolo Di Marco Walter Grassi Dipartimento di Energetica, Universit?~ di Pisa, Pisa, Italy • The purpose of the paper is to experimentally assess the effect exerted by subcooling degree and heat-up rate (i.e., the rate of increase of thermal flux) on the phenomenon of nucleate boiling in the presence of an electric field. To this aim, an experimental facility was set up to investigate pool boiling on a heated platinum wire of 0.2-ram diameter. The working fluid was R-113 (C2C13F3). A cylindrical electric field (up to 21 M V / m at the heater surface) was imposed. The power was increased along a linear ramp, at a rate ranging from 2.5 m W / s to 6 W/s. Subcooling degrees up to 22 K (Ja = 0.146) were investigated. The results of zero-field measurements are in agreement with previous ones in the literature. The effect exerted by the electric field consists mainly of a strong increase in critical heat flux, whereas, for a given heat flux, the nucleate boiling performance can be either weakly degraded or slightly enhanced. The critical heat flux was found to remain nearly constant with increasing transient velocity up to a given heat-up rate and then to increase with it. The effect of subcooling on nucleate boiling is quite complex but, in any case, quite weak in the entire investigated range. © Elsevier Science Inc., 1997