Thermal Management of LEDs Packages Within Inclined Enclosures for Lighting Applications

Abstract

LED lighting still suffers from its thermal problem linked mainly to the increase in junction temperature. The situation becomes more and more aggravated when it comes to decorative lighting. Indeed, this type of lighting application sometimes requires that the heat sink of the LED lamp be integrated into a narrow space, such as false or sloped ceilings, which limits the transfer of heat to the outside. In this article, the current study reports a numerical analysis of natural convection heat transfer around rectangular heat sink for LEDs lighting applications. The radiator is put in an inclined cavity with an orientation angle varying from 0° to 60°. The effects of the enclosure inclination and its length on thermal behavior, flow structure in the cavity as well as on optical properties of the light source were highlighted. The CFD simulation showed a significant effect on the heat transfer rate when varying the cavity length (presented as an aspect ratio <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> ) and its orientation. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> = 4 was determined as an optimal cavity aspect ratio, and it was found that higher orientations are more sensitive to the increase of the length of the cavity. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> = 60°, the luminous efficiency is ameliorated by about 10% when increasing the cavity length from one to four. Accordingly, we proposed correlations in simple form to predict the heat transfer rate for different configurations studied.