Computational investigation of backward facing step effect on heat transfer from flush mounted electronic chips in turbulent flow

Abstract

This study aims to investigate computationally the effect of the backward-facing step on the heat transfer from flush-mounted three electronic chips located downstream of the backward step. Heat transfer is compared for two different step heights and two distances of chips from backward facing step. Heat transfer is also compared with the case without backward facing steps. For this purpose, conservation, and Std. k-& omega; model equations considering two-dimensional, incompressible flow are solved by Computational Fluid Dynamics (CFD) method using ANSYS-Fluent software. Velocity, temperature and pressure distributions are obtained and compared for five different cases. Presence of backward-ward facing step decreases the heat transfer according to base case without backward-facing step, and high step height and short distance of chips from backward-facing step also increases this negative effect. When all chips' average Nusselt numbers are examined, the average Nusselt number decreases by 12,32%, 14,76%, 22,28%, and 22,69%, respectively in the 2nd, 3rd, 4th, and 5th geometries. So possible backward-facing step effect of other circuit elements during placement of electronic chips on circuit boards must be accounted in the thermal design of printed circuit boards.