Numerical modelling of thermal characteristics in a microstructure filled porous cavity with mixed convection

Abstract

In the present study, a two-dimensional, steady mixed convection flow in a porous square vented enclosure has been investigated. The interaction between the buoyancy and imposed forced flow effects are considered in this investigation. Two different thermal boundary conditions are considered such as all walls of the enclosure being isothermal and only the left wall isothermal and other three walls adiabatic. The mathematical model is developed using modified Darcy flow model and energy equation. Through the adaptation of the well-known finite element method, solution to this numerical problem is obtained. Validation of the modelling is achieved by comparing the numerical result with the available experimental data and a reasonable agreement is found. A number of parameters are considered such as Peclet number (Pe) (0.1, 1, 5, 10, 20, 50 and 100), Rayleigh number (Ra) (1, 50, 100, 500 and 1000), aspect ratio (H/W) and the width of the inlet as a fraction of the width (I/W) of the enclosure. Effect of inlet to cavity width ratio is examined within the range 0.1⩽I/W⩽0.5 for a particular aspect ratio. The performance of the enclosure in both cases; are determined by flow visualization and by analysing different parameters such as Bejan number, Nusselt number and entropy generation number. Isotherms, streamlines show considerable deviation in their pattern or magnitude. Average Nusselt number and average Entropy generation number rises whereas average Bejan number falls with increasing I/W. These variations also differ for different Rayleigh or Peclet numbers. The results for both the boundary conditions are also compared to find the most operative value of I/W.