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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

EFFECT OF NUMBER OF BLOCKS ON THE PERIODIC NATURAL CONVECTION INSIDE AN ENCLOSURE HEATED FROM THE SIDE

S. Moussa Mirehei
Department of Mechanical and Aerospace Engineering, University of Florida

Jose Lage
Southern Methodist University

Abstract

Numerical simulation results are reported investigating the effects of placing discrete and disconnected solid blocks inside an enclosure filled with a fluid undergoing periodic natural convection. The blocks are square, conductive, distributed uniformly inside the enclosure in a regular "lattice" square pattern, with a fixed solidvolume fraction – i.e., as the number of blocks inside the enclosure increases, their sizes decrease as to maintain the same total volume of solid material. The natural convection inside the enclosure is achieved by imposing a time-periodic and spatially uniform high temperature condition at one of the walls of the enclosure, while the other wall is maintained at a constant, uniform and low temperature; the horizontal surfaces are set as adiabatic. The number of blocks varies from 4 to 36, while the solid-volume fraction is kept at 36%. With this small number of blocks, the natural convection process is modeled using the continuum-approach rather than the porous-continuum approach for more accurate predictions. Heat transfer results are reported on a parametric form with the Prandtl number fixed equal to 1, and the Rayleigh number inside the enclosure equal to 104 and 107. The boundary layer interference phenomenon, observed in constant horizontal heating, is also observed in the case of periodic heating, and is strongly affected by the number of blocks inside the enclosure. Isotherms and streamlines, together with the periodic (time-varying) Nusselt number, allows the identification of a singular dynamic behavior within the investigated parametric range, including the heating and cooling of the enclosure through the heated wall.

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