Thermal characteristics of a compact LED luminaire with a cooling system based on heat pipes

Abstract

To increase the compactness of a LED luminaire, in this work it has been suggested to use 8 radial thermal pipes as a heat sink from a COB (Chip-on-Board) matrix to the heat-transfer surface, while the latter should be rings of heat exchanger located concentrically around the light source. These rings are cooled utilizing natural convection of ambient air. The used computer modelling enabled us to evaluate the possibility of the suggested cooling system to provide the normal thermal regime for a power COB matrix. It has been shown that for the power 500 W, as the LED light source, provided that all electric power is converted into thermal power, the temperature of the luminaire base frame in the place of contact with the light source does not exceed 85.5 °C. When using the heat-conducting paste of Arctic Silver 5 type with the thermal conductivity of 8.7 W/(m·°C) in the contact zone and the paste layer thickness 0.1·10-3 m, it corresponds to the temperature of the LED light source case 89.5 °C. With account of the thermal resistance inherent to the COB matrix, the temperature of its semiconductor crystals reaches 139.5 °C, which does not exceed the acceptable value of operation temperature for these crystals 140 °C. At lower values (from 50 to 80%) of the consumed electric power, which is converted into thermal energy, depending on the type of COB, the value of the working temperature of the semiconductor crystal is from 112.5 to 128.7 °C.