Modelling of aqueous foam flow for developing energy-efficient heat exchanger applications

Abstract

Two-phase aqueous foam flow was modelled for developing energy-efficient heat exchangers. Such heat exchangers can provide low consumption of energy resources due to enhanced heat transfer rates. In this study enhancement of heat transfer rates is achieved by applying aqueous foam, which is distinguished by an especially large inter–phase contact surface and reduced surface tension (when compared to pure liquids). However, the foam flow has complicated structure: gas bubbles separated by a thin liquid film. This structure is constantly rearranged in a channel flow when passing heated surfaces of a heat exchanger. It invokes changes in a foam structure and redistribution in local foam velocity and volumetric void fraction. Therefore this phenomenon was studied numerically by applying the finite volume method implemented in FLUENT software. The geometry of investigations includes a vertical heat exchanger channel with a heated cylindrical pipe. For description of two-phase flow, Eulerian Mixture model was employed. The distribution of velocity and volumetric void fraction was examined for the different inlet conditions, i.e., inlet velocity of 0.1 m/s – 0.3 m/s and volumetric void fraction ranging from 0.993 to 0.998.