Vibrational effect on heat transfer and entropy generation in an elliptic porous cavity

Abstract

Purpose

Free convection inside a square, circular, or elliptic cavity with gravity oscillation is a special class of problems. In a microgravity environment, the reduction or elimination of natural convection can enhance the properties and performances of materials such as crystals. However, aboard orbiting spacecrafts, all objects undergo low‐amplitude broadband perturbed accelerations, or g‐jitter, caused by crew's activities, orbiter maneuvers, equipment vibrations, solar drag, and other sources. Therefore, there is a growing interest in understanding the effects of these perturbations on the systems' behavior. There is no information of flow, heat transfer, and irreversibility analyses in the current literature that considers such a situation in a porous medium. This motivates this paper to conduct the current research.

Design/methodology/approach

As a special case, an elliptic enclosure is considered here. The enclosure is filled with a porous medium whose flow is modeled by the Darcy momentum equation. The full governing differential equations are simplified by the Boussinesq approximation and solved by a finite volume method. Prandtl number (Pr) is fixed at 1.

Findings

The average Nusselt number (Nu), Bejan number (Be), and entropy generation number (Ns) are adopted to characterize the heat transfer and irreversibilities. Gravity oscillation introduces periodic behavior to the Nu, Be, and Ns rate. Depending on the frequency and the Rayleigh number (Ra), three distinguishable regimes of ψ behavior are identified: periodic and synchronous, periodic and asynchronous, and non‐periodic and asynchronous.

Research limitations/implications

Current research is valid only for laminar Darcy type flow situation in the porous media.

Originality/value

This paper will extend the existing theory of thermovibrational convection to porous media.

Citation

Mahmud, S. and Fraser, R.A. (2006), "Vibrational effect on heat transfer and entropy generation in an elliptic porous cavity", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 16 No. 2, pp. 151-171. https://doi.org/10.1108/09615530610644244