Development of Boiling Type Cooling System Using Electrohydrodynamics Effect

Abstract

This paper describes results from an experimental study of the effect of an electric field on nucleate boiling and the critical heat flux (CHF) in pool boiling at atmospheric pressure. A dielectric liquid ofHFE-7100 (3 M Co.) was used as working fluid. A heating surface was polished with the surface roughness (Ra) of 0.05 ßm. A microsized electrode, in which the slits were provided, was designed in order to generate non uniform high electric fields and to produce electrohydrodynamic (EHD) effects with the application of high voltages. The obtained results confirmed the enhancement of CHF since the EHD effects increased the CHF to 4TWIcn? at the voltage of -1500V, which was three times as much as CHF for the free convection boiling. From the observations of the behavior of bubbles over the electrode and of the boiling surface condition, the instability between the liquid and the vapor increased the heat flux, the heat transfer coefficient (HTC), and the CHF. The usual traveling wave on the bubble interface induced by the KelvinHelmholtz instability was modified by adding the EHD effects. The ratio of critical heat flux increase with and without the electric field was sufficiently predicted by the frequency ratio of liquid-vapor surface at the gap between the boiling surface and the electrode.

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

“…The CHF with the disk surface at the height of 500 p m was 5% of the CF1F without the disk. We also studied the confinement effect using the present slit electrode at previous experiment [10]. The CFIF at the electrode height of 100-300 p m was about 60% of the CHF with out the electrode.…”

“…Using this electrode, the input voltage was successfully decreased to -1500 V at a CHF of 47 W/cm2. A fluorinated dielectric liquid is chosen because the liquid demonstrated a strong enhancement of boiling heat transfer in the experiments of Hristov et al [9] and Kano et al [10]. In addition, this study is a theoretical study describing the effect of an electric field on CHF.…”

“…The micro-electrode was previously designed to create nonuniform electric fields over the boiling surface and produce EHD effects with the application of a dc voltage [10]. Using this electrode, the input voltage was successfully decreased to -1500 V at a CHF of 47 W/cm2.…”

Pool Boiling Enhancement by Electrohydrodynamic Force and Diamond Coated Surfaces

“…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 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].…”