Analysis of particle-laden fluid flows, tortuosity and particle-fluid behaviour in metal foam heat exchangers

Abstract

Tortuosity and porosity are critical parameters for characterizing fluid flow in porous media. These parameters are of paramount importance in the design of porous compact heat exchangers, packed bed reactors, and catalysis supports; however, in the context of heat exchangers, these parameters are generally formulated for single-phase fluid flow under steady-state conditions. However, most industrial flows in a porous medium such as metal foams comprise of transient particle-laden fluid flow. A coupled finite volume and discrete element method (FVM-DEM) is developed to examine transient particle-laden Stokesian flow, particulate fouling (deposition), and fluid flow patterns in an idealized porous metal foam. This work presents a comparative analysis of the analytical and numerical pressure drop profiles. The solid-gas suspension in a porous media is discussed. Secondly, a new time-dependent pore-level fluid tortuosity relation is established which is linked with a modified porosity-based Darcy-Forchheimer equation. Fluid disturbance attributable to the inception of particle deposition is quantified by the tortuosity and instantaneous shift in streamline angle ratio. It is shown that the streamline angle ratio and the meandering of fluid flow paths vary with changing porosity and tortuosity. Moreover, the Reynolds number and particle density play a critical role in the alteration of the resistance to fluid flow and permeability which is related to the tortuosity and variation in fluid flow behaviour. The results and numerical method serves as a steppingstone to better optimize various heat exchangers while taking into account complex multiphase flow behaviour and the tortuous flow paths of porous structures.