Experimental Study on Active Cooling Systems Used for Thermal Management of High-Power Multichip Light-Emitting Diodes

The objective of this study was to develop suitable cooling systems for high-power multichip LEDs. To this end, three different active cooling systems were investigated to control the heat generated by the powering of high-power multichip LEDs in two different configurations (30 and 2 × 15 W). The following cooling systems were used in the study: an integrated multi-fin heat sink design with a fan, a cooling system with a thermoelectric cooler (TEC), and a heat pipe cooling device. According to the results, all three systems were observed to be sufficient for cooling high-power LEDs. Furthermore, it was observed that the integrated multifin heat sink design with a fan was the most efficient cooling system for a 30 W high-power multichip LED. The cooling system with a TEC and 46 W input power was the most efficient cooling system for 2 × 15 W high-power multichip LEDs

Infrared thermographic analysis of LED lights on a ceramic layer

LED svetila intenzivno nadomeščajo žarnice z volframovo žarilno nitko, pri čemer je poleg doseganja dobrih optičnih lastnosti pomembno zagotavljati njihovo učinkovito hlajenje. V tej nalogi obravnavamo infrardečo termografsko analizo dveh različnih LED svetil na keramični plasti z debelinami od 0,25 mm do 5 mm. Razvita je bila eksperimentalna proga, ki omogoča napajanje LED svetila z omejevanjem električnega toka in napetosti ter sočasno spremljanje porabe električne moči in merjenja temperature s pomočjo hitrotekoče infrardeče kamere. V okviru meritev smo analizirali segrevanje keramičnih plasti različnih debelin, vpliv orientacije LED svetila, dinamični odziv segrevanja in čas, potreben za doseganje ustaljenega temperaturnega stanja pri različnih električnih močeh. Prikazani so tudi temperaturni profili in dvodimenzionalna temperaturna polja. Rezultati meritev kažejo, da razviti merilni postopek omogoča vrednotenje segrevanja LED svetil in določanja maksimalne dovoljene električne moči, da zadostimo temperaturnim omejitvam.LED lamps intensively replace incandescent lamps, and in addition to achieving good optical properties, it is important to ensure their efficient cooling. In this paper, the infrared thermographic analysis of two different LED lamps on a ceramic layer with thicknesses from 0.25 mm to 5 mm is considered. An experimental track has been developed that enables the power supply of LED lights by limiting current and voltage, while simultaneously monitoring electrical power consumption and temperature measurement using a high-speed infrared camera. As part of the measurements, the heating of ceramic layers of different thicknesses, the influence of LED light orientation, the dynamic heating response and the time required to achieve a steady-state temperature at different electrical powers were analyzed. Temperature profiles and two-dimensional temperature fields are also shown. The measurement results show that the developed measurement procedure enables the evaluation of the heating of LED lights and the determination of the maximum allowable electrical power in order to meet the temperature limits

Development of effective thermal management strategies for LED luminaires

The efficacy, reliability and versatility of the light emitting diode (LED) can outcompete most established light source technologies. However, they are particularly sensitive to high temperatures, which compromises their efficacy and reliability, undermining some of the technology s key benefits. Consequently, effective thermal management is essential to exploit the technology to its full potential. Thermal management is a well-established subject but its application in the relatively new LED lighting industry, with its specific constraints, is currently poorly defined. The question this thesis aims to answer is how can LED thermal management be achieved most effectively? This thesis starts with a review of the current state of the art, relevant thermal management technologies and market trends. This establishes current and future thermal management constraints in a commercial context. Methods to test and evaluate the thermal management performance of a luminaire system follow. The defined test methods, simulation benchmarks and operational constraints provide the foundation to develop effective thermal management strategies. Finally this work explores how the findings can be implemented in the development and comparison of multiple thermal management designs. These are optimised to assess the potential performance enhancement available when applied to a typical commercial system. The outcomes of this research showed that thermal management of LEDs can be expected to remain a key requirement but there are hints it is becoming less critical. The impacts of some common operating environments were studied, but appeared to have no significant effect on the thermal behaviour of a typical system. There are some active thermal management devices that warrant further attention, but passive systems are inherently well suited to LED luminaires and are readily adopted so were selected as the focus of this research. Using the techniques discussed in this thesis the performance of a commercially available component was evaluated. By optimising its geometry, a 5 % decrease in absolute thermal resistance or a 20 % increase in average heat transfer coefficient and 10 % reduction in heatsink mass can potentially be achieved . While greater lifecycle energy consumption savings were offered by minimising heatsink thermal resistance the most effective design was considered to be one optimised for maximum average heat transfer coefficient. Some more radical concepts were also considered. While these demonstrate the feasibility of passively manipulating fluid flow they had a detrimental impact on performance. Further analysis would be needed to conclusively dismiss these concepts but this work indicates there is very little potential in pursuing them further