Application of a CFD tool for system level thermal simulation

A Computational Fluid Dynamics (CFD) tool is used to evaluate the velocity and the temperature fields of air flow in a computer system enclosure. Simulations focused on the six printed circuit board regions where approximately 37 W of power was generated on the component side of the board. Three-dimensional, steady-state, turbulent air flow is assumed. Solutions include pressure, velocities, and temperature. Both straight and swirl flow cases at fans were considered. The actual air flow rate at fans was determined by matching the predicted pressure rise across the fan to the given fan characteristics. Experiments were performed under real life conditions. The actual computer chassis was tested inside a temperature-controlled chamber. Air temperatures between two printed circuit boards were measured in various positions and compared with the simulations. Results demonstrate a reasonable agreement between the temperatures obtained by simulations and measurements. In all comparisons, average errors were less than 10%. The introduction of swirl at fans made no significant effect on temperatures. A hot spot appeared in the inner side of the air passage between boards; this hot spot was created due to the recirculation of low velocity air. Some recommendations on improvements of the simulation are also presented