Analysis of the laminar flow and enhanced heat transfer rate through a triangular array of cylinders embedded in a fluid-saturated porous media with mixed convection

Abstract

An investigation of the laminar flow and enhanced heat transfer rate through a triangular array of cylinders embedded in a fluid-saturated porous media is considered. Mixed convection covering forced convection cases has been studied using a finite-volume approach considering the local thermal equilibrium model. Darcy–Brinkman–Forchheimer momentum equations are used to characterize the porous media in question. The study is constrained to the low and intermediate Peclet number (Re = 5 to 40, Pr = 50) and high range of Darcy number (Da = 10−3 to 10−1) for different cylinder spacings (0.7 ≤ φ ≤ 0.99). It is anticipated that porous media would enhance heat transfer, but it derives a multiple order in pressure drop indubitably not desirable in many heat applications. Investigation reveals that both mean drag coefficient (CD ) and Nusselt number (Nu) are strong functions of Da and φ; however, the influence of the buoyancy parameter is mainly witnessed in higher permeability levels and high Peclet numbers. The study also details the effect of governing parameters on mean gap velocities and pressure coefficients. Surprisingly, recirculation wakes exist for the lowest cylinder spacing (φ = 0.7) in high fluid momentum. Low φ and high permeability are desirable in a forced convection regime, whereas both φ and Da should be high in the case of mixed convection. This article also quantifies the combined effect of the Darcy number and buoyancy parameter on the heat-transfer enhancement ratio. A maximum of 112% increase in Nu for φ = 0.7 and 452% for φ = 0.99 are reported at Da = 10−1, but at the cost of higher pressure drop in the latter case.