Computational analysis of laminar forced convection in rectangular enclosures of different aspect ratios

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

Computer development has followed trends of increasing power and smaller size. Having more power increases the amount of heat the computer produces, while the more compact form makes effective air cooling a more challenging task. These two factors have led to component failures and a need for new ideas to keep the component temperatures down. Air-cooling is one of the preferred methods for cooling computer systems and other electronic equipment, due to its simplicity and low cost. It is very important that such cooling systems are designed in the most efficient and effective way. At the same time the power requirement has to be minimized. The electronic components are treated as heat sources embedded on flat surfaces in the electronic circuit board. A small fan blows air over the heat sources which give rise to combined (mixed) forced and natural convection. In this study it has been proposed that the air flow area used to cool computers can be approximated as a two dimensional narrow enclosure with laminar forced convection. Commercially available software ANSYS-FLUENT was used to solve the laminar flow field. The hot wall temperature, cold wall temperature, Reynolds number, and aspect ratio (AR) of the enclosure are the variables for this computational simulation work. The effect on air velocity, isotherms, surface heat flux, and average surface Nusselt number in the system are the outcomes for this study. With the increase of aspect ratio of the enclosure the average heat flux from both hot and cold walls decreases. Also with the increase of aspect ratio the surface Nusselt number decreases for both hot and cold walls. From these findings more effective cooling strategies can be developed. It has also been found that with the increase of the hot wall temperature the magnitude of the average heat flux and the Nusselt number fromboth hot and cold walls increased for all six aspect ratio cases.