Modeling and Numerical Investigation of Transient Two-Phase Flow with Liquid Phase Change in Porous Media

Abstract

Two-phase flow with phase change in microstructure or nanostructure is an important issue in many fronts and critical applications nowadays, but with a lack of comprehensive understanding of the mechanism. This paper numerically investigates the transient behavior of two-phase flow with liquid phase change in the porous media, which consists of a series of connected pores at micro and nanoscale with the transient form of the semi-mixed model and self-compiled programs. Transient variation and spatial distribution of structure temperature, thermal non-equilibrium characteristic, phase change location and fluid-driven pressure are obtained and analyzed, and effects of initial system temperature, structure parameter and material property on the transient behaviors of two-phase flow and fluid-structure coupling heat transfer are discussed. The numerical simulations indicate that the two-phase flow with phase change in porous media is complex and ever-changing before reaching a steady state and affected by the above-mentioned three kinds of parameters significantly. Particularly, distinct phenomena of transient heat transfer deterioration and vapor block are discovered, and it is revealed that the transient heat transfer deterioration and vapor block are more serious in a porous matrix with smaller porosity and made of materials with higher heat capacity and density.

Investigation of phase change characteristics for refrigerant R-134a flow in a double pipe heat exchanger with the use of thermal non-equilibrium model

“…Complete evaporation processes within metal foam could be theoretically designated by two models, the separate flow model (SFM) and the two-phase mixture model (TPMM). So, as to eliminate the difficulties related with SFM [1] many modifications and it could be solved on a fixed grid, without need to an intuition information of the phase boundaries, that might be unequal in dimension in addition to transmit in time.…”

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