Effect of Electric Field Distribution Generated in a Microspace on Pool Boiling Heat Transfer

Abstract

This study describes the effect of an electric field on nucleate boiling and critical heat flux (CHF) in pool boiling. A dielectric liquid of AE-3000 was used as the working fluid. A heating surface was polished to a surface roughness of 0.05 pm. A microsized elec trode, in which slits were provided, was designed to generate a nonuniform electric field and produce electrohydrodynamic (EHD) effects with the application of high dc voltages. The obtained results confirmed CHF enhancement as the EHD effects increased CHF to 86.2 W/cm2 with a voltage o f -3000 V, which was four times greater than pool boiling in the absence of the electrode. The usual traveling wave on the bubble interface, induced by the Kelvin-Helmholtz instability, was modified by adding the EHD effects. The travel ing wave model exhibits the essential features of the phenomenon and shows good agree ment with the experimental data.

Pool Boiling Enhancement by Electrohydrodynamic Force and Diamond Coated Surfaces

“…Kano [19] confirmed that the electrostriction pressure (the first term of Eq. (5)) and the normal component of the electric field on the liquid-gas interface in the dielectric liquid of AE-3000, used for the present boiling performance test, were small, and Eq.…”

“…On the basis of the many advantages of electric field application, Kano et al [19,23] proposed a boiling heat transfer enhancement model as shown in Fig. 3.…”

“…The electrostatic pressure and capillary force are generated at the interface and continually supply the liquid to the boiling surface. The interface [19] oscillation at the bottom rim of the boiling bubble creates the periodic thin liquid film which continuously evaporates and strongly increases the heat flux. The EHD convection and dielectrophoretic force are no longer generated because vapor is continuously occupied in the slits space.…”

“…They measured the boiling heat flux in the saturated dielectric liquid (Asahi Glass Co., Ltd., AE-3000), and successfully increased the CHF from 22 W/cm 2 of pool boiling without the electrode to 86 W/cm 2 at H ¼ 600 lm with the application of À3000 V [19]. In addition to the EHD effect enhancing boiling heat transfer, a number of investigations have focused on reducing the incipient boiling temperature using a microstructured boiling surface.…”

“…The microelectrode was previously designed to create a nonuniform electric field over the boiling surface and to produce the EHD effect upon application of dc voltages [19,23]. A fluorinated dielectric liquid, AE-3000 (Asahi Glass Co., Ltd.), was selected because the liquid demonstrated a strong enhancement of boiling heat transfer in experiments done by Kano [19]. The experimental conditions are similar to those of Kano [19] except for the microstructured surfaces.…”