MIXED CONVECTION FROM MULTIPLE-LAYERED BOARDS WITH CROSS-STREAMWISE PERIODIC BOUNDARY-CONDITIONS

Abstract

A comprehensive analysis is made of the flow and heat transfer characteristics of mixed convection in a channel with rectangular blocks attached on one channel wall. The flow geometry models the cooling process of integrated chips of high-power densities mounted on a multi-layered printed circuit board system. Extensive numerical solutions are acquired to the governing Navier-Stokes equations under the Boussinesq-fluid assumption. The finite thickness of the board is fully accounted for; the conjugate nature of the heat transfer within a single module is described. In an effort to move closer to realism, the thermally-periodic boundary condition is imposed on the two successive plates. Details of the flow and thermal fields, for Reynolds numbers ranging from 100 to 1500 and Grashof numbers in the range of 0 to 2 x 10(6), are presented for two representative cases, i.e. a horizontally-oriented channel and a vertically-oriented channel. The behavior of the local Nusselt number along the block surfaces is portrayed. The distributions of the temperature and of the heat transfer rate on the surface of the base plate are illustrated. The trend of the maximum chip temperature vs Re is depicted. In light of the conjugate heat transfer analyses of the present study, it is asserted that such oversimplified assumptions as the isothermal or adiabatic surface wall conditions may not be entirely appropriate for simulating the cooling of modern electronic devices.