Convective Heat Transfer of Internal Electronic Components in a Headlight Geometry

Authors: Jan Langebach, Peter Fischer, Christian Karcher

Abstract:

A numerical study is presented on convective heat transfer in enclosures. The results are addressed to automotive headlights containing new-age light sources like Light Emitting Diodes (LED). The heat transfer from the heat source (LED) to the enclosure walls is investigated for mixed convection as interaction of the forced convection flow from an inlet and an outlet port and the natural convection at the heat source. Unlike existing studies, inlet and outlet port are thermally coupled and do not serve to remove hot fluid. The input power of the heat source is expressed by the Rayleigh number. The internal position of the heat source, the aspect ratio of the enclosure, and the inclination angle of one wall are varied. The results are given in terms of the global Nusselt number and the enclosure Nusselt number that characterize the heat transfer from the source and from the interior fluid to the enclosure walls, respectively. It is found that the heat transfer from the source to the fluid can be maximized if the source is placed in the main stream from the inlet to the outlet port. In this case, the Reynolds number and heat source position have the major impact on the heat transfer. A disadvantageous position has been found where natural and forced convection compete each other. The overall heat transfer from the source to the wall increases with increasing Reynolds number as well as with increasing aspect ratio and decreasing inclination angle. The heat transfer from the interior fluid to the enclosure wall increases upon decreasing the aspect ratio and increasing the inclination angle. This counteracting behaviour is caused by the variation of the area of the enclosure wall. All mixed convection results are compared to the natural convection limit.

Keywords: Enclosure, heat source, heat transfer, mixed convection.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1059637

References:

[1] S. Ostrach, "Natural convection in enclosures", in Advances in heat transfer, vol. 8, Academic Press, 1972, pp. 161-227.
[2] I. Catton, "Natural convection in enclosures", Proc. 6th Int. Heat Transfer Conference, vol. 6, pp. 13-31, 1972.
[3] G. S. Barozzi, M. A. Corticelli, "Natural convection in cavities containing internal sources", Heat Mass Transfer, vol. 36, no. 6, pp. 473-480, 2000.
[4] S. F. Dong, Y. T. Li, "Conjugate of natural convection and conduction in a complicated enclosure", Heat Mass Transfer, vol. 47, pp. 2233- 2239, 2004.
[5] Y. S. Sun, A. F. Emery, "Effects of wall conduction, internal heat sources and an internal baffle on natural convection heat transfer in a rectangular enclosure", Int. J. Heat Mass Transfer, vol. 40, no. 4, pp. 915-929, 1997.
[6] E. Papanicolaou, Y. Jaluria "Mixed convection from a localized heat source in a cavity with conducting walls: a numerical study", Num. Heat Transfer A, vol. 23, pp. 463-484, 1993.
[7] E. Papanicolaou, Y. Jaluria, "Mixed convection from simulated electronic components at varying relative positions in a cavity", J. Heat Transfer, vol. 116, pp. 960-970, 1994.
[8] E. Papanicolaou, Y. Jaluria, "computation of turbulent flow in mixed convection in a cavity with a localized heat source", J. Heat Transfer, vol. 117, pp. 649-658, 1995.
[9] H. Schlichting, K. Gersten, Boundary-Layer Theory, Berlin: Springer, 2000.
[10] B. E. Launder, D. B. Spalding, Lectures in mathematical models of turbulence, London: Academic Press, 1972.