Heat Transfer Analysis of the High-Power LED Lamp With Liquid-Cooled Package

In this study, the technique of immersed LEDs in ambient fluids of air, silicone oil or FC-40, respectively, to cool the LEDs which will generate large amount of heat in operation is investigated by methodologies of experimental measurements and numerical simulations. In experiments, three powers are sequentially input to the LEDs and three fluids, air, silicone oil, and FC-40, respectively, are used to cool the LEDs immersed in these fluids. Temperatures are measured by TCs and IR thermal imager. Detailed temperature and flow fields inside the lamp enclosure are analyzed, and results are compared to experimental measurements. Inclinations of LED lamp in four orientations of 0, 90, 135, 180, respectively, are studied to explore the inclination effects to thermal design of LED lamp. Simulation results found that it is not significant to the LEDs temperature responses. Thermal resistances R_ja of the liquid-cooled package of LED lamp are calculated from simulation results, and it is around 13.7 °C/W in this design. In illuminance measurements, measured illuminances show tendency of reciprocal to distance square and proportional to the luminous intensity which is similar to the illuminance principle, and its values are in the sequence of 5W>4W>3W for three kinds of fluids. Basically, illuminances for air, FC-40, and silicone oil fluids are in the sequence of air>FC-40>silicone oil.