Pool Boiling Enhancement by Electrohydrodynamic Force and Diamond Coated Surfaces

Abstract

Boiling heat transfer enhancement via compound effect of the electrohydrodynamic (EHD) effect and microstructured surfaces has been experimentally and analytically investigated. A fluorinated dielectric liquid (Asahi Glass Co., Ltd., AE-3000) was selected as the working fluid. Pool boiling heat transfer in the saturated liquid was measured at atmospheric pressure. Microstructured surfaces, which are mainly used for cutting tools, were developed with diamond particles using electrodeposition technique. Four different particle diameters were prepared: 5, 10, 15, and a mixture of 5 and 1.5 lm. The critical heat flux (CHF) for diamond particle surfaces showed 27-30 W/cm 2 which was 26-40% increase for comparing with a noncoated surface (21.5 W/cm 2 ). Upon application of a À5 kV/mm electric field to the microstructured surface (a mixture of 5 and 1.5 lm particles), a CHF of 70.2 W/cm 2 at a superheat of 21.7 K was obtained. The previous theoretical equation of pool boiling predicted the CHF with electric field and without the electrode within 10%. Also, the CHF enhanced by the diamond coated surfaces was correlated well with the contact angle.

Experimental study on heat transfer enhancement in subcooled flow boiling under pressurized conditions

“…The boiling surface was electrically deposited with fine diamond particles (particle diameters of 20 and 1.5 m) to enhance the boiling heat transfer. Kano (2015) revealed that diamond electrodeposited boiling surface enhances boiling heat transfer and increases CHF by 40 % and HTC by 90 %, comparing with a smooth copper surface without electric filed since the diamond particles served as nucleation sites. In addition, the increased density of the nucleation sites resulted in reduction of superheat when CHF occurred.…”

“…Extended surfaces in MCs are categorized as passive methods, while fluid vibration, vapor suction, and application of AC or DC electrostatic fields are categorized as active methods. Electrohydrodynamic (EHD) force generated by the application of an electric field has been mainly studied as an active enhancement method (Johnson, 1968;Darabi and Ekula, 2003;Moghaddam and Ohadi, 2005;Pearson and Sayed-Yagoobi, 2013;Kano and Takahashi, 2013;Kano, 2014;Kano, 2015;Patel and Sayed-Yagoobi, 2017;Kano and Okamoto, 2017;Kano, 2019). Kano (2019) developed a micro-slit channel (MSC) as a cooling system providing active flow boiling heat transfer by applying a high electric field, as shown in Fig.…”

“…Figure 3 shows a two-dimensional experimental setup for measuring the electrostatic pressure (ESP), which is one of the main body force components of the EHD force (Panofsky, 2004). Kano (2015) prepared two transparent indium tin oxide (ITO) electrodes separated by a distance of 100 m to measure the ESP. The height of the liquid-gas interface was increased due to surface tension when the electrode was immersed in a dielectric liquid vertically in a laboratory dish.…”