Natural convection air-cooling of a substrate-mounted protruding heat source in a stack of parallel boards

The problem numerically investigated is that of steady, two-dimensional laminar natural convection in a system of parallel vertical channels with a single protruding heat module mounted mid-height on a substrate of finite-thickness. The input heat flux at the base of the module is removed through the module to the flow by convection and through the substrate by conduction. The system simulates cooling passages in a stack of printed circuit boards (PCB) with heat modules attached on the surface of one board. Heat transfer from both sides of the boards is taken into account. The solution is computed simultaneously in the solid (module and substrate) and in the fluid regions taking into account the continuity of the temperature and heat flux at the solid–fluid interfaces. The objective of this work is to determine heat transfer and fluid flow characteristics. A parametric study was conducted by varying the thermal conductivity and the thickness of the substrate and the width of the module. A variation in the substrate conductivity considerably affects the module tem- perature while the flow structure is only slightly altered. It is demonstrated that streamwise conduction through the substrate is an impor- tant cooling mechanism and must be accounted for.