Abstract
In this paper we analyse how the presence of the thermal capacity of a vertical flat plate of finite thickness, which is embedded in a porous medium affects the transient free convection boundary-layer flow. At the time t = 0, the plate is suddenly loaded internally with a constant heat flux rate q″, so that a transient boundary-layer flow is initiated adjacent to the plate. Initially, the transient effects due to the imposition of the uniform heat flux rate at the plate are confined to a thin fluid region near to the surface and are described by a small time solution. These effects continue to penetrate outwards and eventually evolve into a new steady state flow. Analytical solutions have been derived for these transient (small time) and steady state (large time) flow regimes, which are then matched by a numerical solution of the full boundary-layer equations. It has been found that the non-dimensional fluid temperature (or fluid velocity) profiles are reduced when the thermal capacity effects, described by a parameter Q *, are reduced. For small values of Q *, the approach of these profiles to their steady state values is monotonic. However, for large values of Q *, the temperature profiles are observed to locally exceed (pass through a maximum value) the final steady state values at certain distances from the plate. In general, the maxima in the temperature profiles increase in size as Q * increases and the time taken to approach the steady state solutions increases significantly.
Similar content being viewed by others
References
Bradean, R., Ingham, D. B., Heggs, P. J. and Pop, I.: 1998, Convective heat flow from suddenly heated surfaces embedded in porous media, in: D. B. Ingham and I. Pop (eds), Transport Phenomena in Porous Media. Oxford: Pergamon, pp. 411-438.
Carnahan, B., Luther, H. A. and Wilkes, J. O.: 1969, Applied Numerical Methods, Wiley, New York.
Cheng, P. and Pop, I.: 1984, Transient free convection about a vertical flat plate embedded in a porous medium, Int. J. Engng Sci. 22, 253-264.
Gebhart, B.: 1961, Transient natural convection from vertical elements, J. Heat Transfer 83, 61-70.
Gebhart, B. and Adams, D. E.: 1962, Measurements of transient natural convection on flat vertical surfaces, J. Heat Transfer 83, 1-4.
Gebhart, B. and Dring, R. P.: 1967, The leading edge effect in transient natural convection from a vertical plate, J. Heat Transfer 89, 274-275.
Harris, S. D., Ingham, D. B. and Pop, I.: 1996, Transient free convection on a vertical plate subjected to a change in surface heat flux in porous media, Fluid Dynamics Res. 18, 313-324.
Harris, S. D., Ingham, D. B. and Pop, I.: 1997, Free convection from a vertical plate in a porous medium subjected to a sudden change in surface heat flux, Transport in Porous Media 26, 207-226.
Ingham, D. B. and Pop, I. (eds): 1998, Transport Phenomena in Porous Media, Pergamon, Oxford.
Joshi, Y.: 1987, On the termination of one-dimensional transport in transient buoyancy induced flow adjacent to a vertical surface, Int. J. Heat Mass Transfer 30, 1766-1769.
Joshi, Y.: 1990, Transient natural convection flows, in: N. P. Cheremisinoff (ed.): Encyclopedia of Fluid Mechanic; Aerodynamics and Compressible Flows. Texas: Gulf Publ. Comp. Vol. 8, pp. 389-440.
Joshi, Y. and Gebhart, B.: 1987, Transition of transient vertical natural convection flows in water, J. Fluid Mech. 179, 407-438.
Nield, D. A. and Bejan, A.: 1999, Convection in Porous Media, 2nd edition, Springer, New York.
Pop, I. and Cheng P.: 1983, The growth of a thermal layer in a porous medium adjacent to a suddenly heated semi-infinite horizontal surface, Int. J. Heat Mass Transfer 26, 1574-1576.
Pop, I., Ingham, D. B. and Merkin, J. H.: 1998, Transient convection heat transfer in a porous medium: external flows, in: D. B. Ingham and I. Pop (eds): Transport Phenomena in Porous Media. Oxford: Pergamon, pp. 205-231.
Sammakia, B. and Gebhart, B.: 1978, Transient and steady-state numerical solutions in natural convection, Numer. Heat Transfer 1, 529-542.
Sammakia, B. and Gebhart, B.: 1981, Transient natural convection adjacent to a vertical flat surface: the thermal capacity effect, Numer. Heat Transfer 4, 331-344.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Harris, S., Ingham, D. & Pop, I. Thermal Capacity Effect on Transient Free Convection Adjacent to a Vertical Surface in a Porous Medium. Transport in Porous Media 46, 1–18 (2002). https://doi.org/10.1023/A:1013839132372
Issue Date:
DOI: https://doi.org/10.1023/A:1013839132372