Mixed Convection in Horizontal Porous Layers Heated From Below

[+] Author and Article Information
V. Prasad

Department of Mechanical Engineering, Columbia University, New York, NY 10027

F.-C. Lai, F. A. Kulacki

Department of Mechanical and Aerospace Engineering, University of Delaware, Newark, DE 19716

J. Heat Transfer 110(2), 395-402 (May 01, 1988) (8 pages) doi:10.1115/1.3250498 History: Received March 07, 1987; Online October 20, 2009


Numerical studies are reported for steady, mixed convection in two-dimensional horizontal porous layers with localized heating from below. The interaction mechanism between the forced flow and the buoyant effects is examined for wide ranges of Rayleigh number Ra* and Peclet number Pe*. The external flow significantly perturbs the buoyancy-induced temperature and flow fields when Pe* is increased beyond unity. For a fixed Peclet number, an increase in Rayleigh number produces multicellular recirculating flows in a domain close to the heat source. This enhances heat transfer by free convection. However, for a fixed Ra*, an increase in forced flow or Peclet number does not necessarily increase the heat transfer rate. Hence, there exists a critical Peclet number as a function of Ra* for which the overall Nusselt number is minimum. The heat transfer is, generally, dominated by the buoyant flows for Pe* < 1 whereas the contribution of free convection is small for Pe* > 10 when Ra* ≤ 10.

Copyright © 1988 by ASME
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