ARTICLE:

• HEAT TRANSFER ENHANCEMENT VIA LIQUID-LIQUID PHASE SEPARATION  download article

S. Gat
Tel-Aviv University, Tel-Aviv, Israel

Neima Brauner
School of Engineering, Tel-Aviv University, Tel-Aviv, Israel

Amos Ullmann
Department of Fluid Mechanics, School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv 6997, Israel

ABSTRACT

In this study the heat transfer and flow phenomenon during heterogeneous phase separation was investigated experimentally. These phenomena of heterogeneous phase separation and the associated heat transfer mechanism have not been yet investigated in the literature. The preliminary results support the premise that heat transfer coefficient can be augmented by inducing liquid-liquid phase separation. The experiments were conducted with a partially miscible solvent system (water, ethyl acetate and ethanol) with an upper critical solution temperature. Via a small temperature difference this system can alter from a state of a single liquid phase, to a state of two separated liquid phases.
The heat transfer rates were studied for convective heat transfer in a small diameter tube and free convection from a cylindrical surface. The heat transfer rates obtained with phase separation were compared with those obtained under the same flow conditions of single-phase liquid of the solvent system. It was found that with phase separation the convective heat transfer coefficient increases up to 400%, and more than 100% increase in the free convection heat transfer coefficient. Flow visualization from cylindrical and sphere surfaces revealed interesting phenomena during the phase separation. The associated mechanisms leading to the augmented heat transfer coefficients are discussed.

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