Thermal analysis of extruded aluminum fin heat sink for LED cooling application

Abstract

Light Emitting Diode or LED now is becoming a popular lighting used at many types of applications. LED becomes more favorable to use than other types of lighting such as fluorescent or even light bulb. This is because LED can provide high lumens with low power electricity and does not contain any toxic material, such as fluorescent lights having mercury inside which is not good towards the environment. Advantages of using LED are high luminosity, more energy saving, high lifetime hours, and applicable in many applications. However, LED operating temperature should be considered. LEDs with high power, such as 10 Watts or more, can generate bright lighting, but also will have high operating temperature. This high operating temperature of LED should be lowered, since high operating temperature will lead to reductions of the luminosity and the lifetime of LED. Many cooling systems can be used to reduce the operating temperature of LED; a simple one is to use the extruded-fin heat sink. Heat sink is easy to manufacture, relatively low in cost, light in weight, and can become an adequate cooling means with good reliability. The choice of an optimal heat sink dimension depends on the power of heat source. In this work, 10-Watt LED with the 58 °C operating temperature was used. The aim for this study was to add extruded-fin heat sink to dissipate heat generated by the LED, with target temperature of LED decreased down to 50°C. Initial experiment was done to check the LED operating temperature and then ANSYS ICEPAK was used for numerical simulation; ANSYS ICEPAK is computational software for the study of thermal management of electronic devices and systems. For the present study, the numerical simulation of LED using extruded-fin as heat sink was performed. Through numerical simulation accounting for the variations in fin heights, fin thicknesses, fin pitches, and base heights, the optimal dimension of the heat sink was determined to achieve the target temperature of 50°C. Subsequently, prototype of aluminum fin heat sink was build to carry out the experiments for the purpose of validating the results obtained from numerical simulations. In the experiment, two kinds of thermal conductive pastes — a heat transfer compound and silver paste — were used to assemble the heat sink and LED. The effect of thermal conductive pastes on the overall thermal management of LED was investigated. Through the experiments, silver paste was proven to enhance the thermal conductivity, measured by the heat sink thermal resistance, reducing 0.02 °C/W compared with those using heat transfer compound. Both experimental tests and numerical simulations were done. Results obtained from the experiments and those obtained from the simulations were in good agreement, having percentage of differences less than 12%. From this study, it was shown that heat sinks with a good thermal conductive paste have proven to be an effective solution for the LED heat dissipation. Using ANSYS ICEPAK also has proven to be able to save time and cost for design of thermal management in electronic cooling applications.