Investigations on Replacement of Fins with Flat Heat Pipes for High Power LEDs

Light Emitting Diodes have got wide acceptance in the twenty first century. The domestic and commercial systems use LEDs of various illumination and input power. It is found that up to 80% of the input power in the LEDs are converted to heat energy. The accumulation of heat energy at the base of the LED will lead to the failure of the system. In conventional passive method, fins made of high conductivity materials are used to improve heat transfer in the base plate.In the present work, the feasibility of straight heat pipes are analysed to improve the heat transfer in the base plate. The experiment has been carried out with copper-water heat pipes in place of the fins of 3 mm diameter and 75 mm length.The experimental result shows that significant reduction in base temperature using heat pipes. The start-up and shutdown tests are carried out to check the performance of heat pipes. The experimental results show that the effective thermal conductivity is very high in heat pipes compared to fins. The temperature distribution along the heat pipe is found to be constant along axial direction. The heat pipe is tested for orientations ranging from 0o to 180o and it is found that the maximum performance is found between 0o to 15o angles where the gravity aids the flow of water in the wick structure.