Experimental and numerical investigation on the thermal performance of linear LED housings under forced convection

Abstract

This study aims to experimentally and numerically test the thermal performances of three different linear housings (Model 1-without fin, Model 2-with inner fin, and Model 3-with inner and outer fin) with medium power light-emitting diode (LED) arrays at 30 degrees C and 40 degrees C ambient temperatures under forced convection for 25 W and 35 W. Although the mass of Model-3 was reduced by 54.2% and 34.67% compared to Model-1 and Model-2, its surface area was increased by 46.3% and 9.11%, resulting in an improvement in junction temperature (T-j) up to 4.4 degrees C and 7.75 degrees C, respectively. Thermal resistance (Rth) for Model-3 is approximately 1.38-3.1% and 7.85-9.72% smaller than that of Model-1 for 25 W at ambient air temperature (T-aa = 30 degrees C and T-aa = 40 degrees C), respectively. The Rth for Model-3 is approximately 1.39-2.6% and 8.65-6.07% smaller than that of Model-1 for 35 W at the same T-aa, respectively. The Model-3 offers lower junction temperature, lower cost, and safe operating temperature range by inner and outer fins compared to the others. The results demonstrated that all of the temperatures reduced with the increase in air mass flow rate; however, it was found that as the LED power and ambient temperature increased, the junction temperature increased. Experiment and simulation results show that adding a fan to the luminaire significantly lowers the LED junction temperature, in which case it provides a safe operating range and protects the luminaire against thermal shocks. The forced application allows using of comparatively smaller housing as it provides a lower junction temperature.