Liquid-liquid interfacial instability model for boiling refrigerant transition by pool boiling of immiscible mixtures

Abstract

Boiling heat transfer using immiscible liquid mixtures is an innovative cooling method for electronic devices operated at high heat flux density. Immiscible liquid mixtures discussed here are composed of more-volatile liquid with higher density and less-volatile liquid with lower density such as combination of FC-72 and water. In the case of pool boiling in a vessel using appropriate composed ratio of immiscible liquid mixtures, more-volatile liquid on the heating surface is boiled and as the heat flux increases, the more-volatile liquid reaches the critical heat flux. Subsequently, the less-volatile liquid is replaced with the more-volatile liquid and moves onto the heating surface, and this liquid is started boiling. This phenomenon is called a boiling refrigerant transition (BRT) and is an important feature of pool boiling by immiscible mixtures. To clear the phenomena of BRT in pool boiling by immiscible mixtures, the experiments under the conditions of various heights of more-volatile liquid layer and various mixture composed ratio by using several combinations of immiscible mixtures are carried out. And a new model derived by Kelvin-Helmholtz instability at the liquid-liquid interface is proposed for the occurrence of BRT. The unique heat transfer characteristics of the immiscible liquid mixtures were obtained from the experimental results; occurrence of BRT depends on the height of more-volatile liquid, and the characteristics after BRT is corresponding to the characteristics of pure less-volatile liquid. Experimental results including data from past literatures agreed well with newly proposed model.