Turbulent Forced Convection Air Cooling of Electronics

Abstract

Air cooling is still the dominant method for dissipating the heat produced by electronic components. In a typical electronic device, the components are situated on a Printed Circuit Board (PCB). For most applications natural convection is sufficient to cool the components. However in some cases forced convection air cooling, which provides more effective cooling, has to be used. The size of the components is often considerably smaller than the PCB. Since the air flow is seeking the path of least resistance, the geometry of the electronic components is of major importance. This air flow pattern has a major impact on the performance of the heat dissipation, why knowledge of the flow pattern is of vital importance. The aim of this work has been to investigate the influence of flow pattern on the performance of heat exchange used for electronics cooling. The focus has been set on determining the parameters that influence the geometry, and to quantify their relative importance using experimental and numerical techniques. Experimental and numerical parametric studies are presented. The influence of the array arrangement over the plate as well as the dimensions and air velocity, on the thermal and hydraulic performance have been investigated. The flow was turbulent, and the measurements have been performed in a wind tunnel. Numerical predictions have been performed by using two different numerical schemes: a parabolic differential scheme and a k-ε model used for integrating Reynolds-Average Navier-Stokes (RANS) equations and the continuity equation. For turbulence modeling wall functions that take into account turbulent wall shear stress and turbulent heat fluxes are used to specify the boundary conditions. The experimental data can be used to validate the numerical model, which in turn can be used for parametric studies. The parameterization uses the displacement in origin concept for the velocity and the temperature fields.