Heat transfer in a low aspect ratio horizontal enclosure for laptop computer application

Experiments were performed to characterize the combined conduction, convection, and radiation heat transfer from a horizontal component board in a shallow horizontal enclosure. Measurements were made in both a simulated enclosure with well controlled thermal boundary conditions and an actual electronic enclosure. Comparison was made with simulated results using a commercial three dimensional conduction code with heat transfer coefficient boundary conditions and two simple one-dimensional models which ignore z-direction conduction in the board. The one-dimensional models compared well with the three-dimensional simulations. Agreement between experimental and simulation results was excellent. The results point out the importance of thermal radiation in the enclosure. The results show that the magnitude of the heat transfer coefficient used in the predictive model does not have to be known extremely accurately to predict maximum board temperatures with good accuracy