THERMAL DISSIPATION SYSTEM APPLIED TO LED DEVICES

Abstract

A thermal dissipation system, based on an aluminum case LED lamp system encapsulated in a PCM device, has been used to reduce LED device temperature, improving thermal performance of the LED unit. Three heating rates have been tested, low (0.6ºC/s), medium (1.3ºC/s) and high (1.8ºC/s). The system has been tested in an experimental prototype at reduced scale, showing a maximum reduction of temperature from 177.5º C to 56º C for the high heating rate, and a minimum from 133º C to 35.7º C. for the low rate. Theoretical predictions for the temperature reduction have been compared to experimental results showing a very good agreement within 98% accuracy. The performance of the proposed system is compared to a conventional dissipation unit based on metal comb-shaped heat sink obtaining similar results for low ambient temperature and much better efficiency for ambient temperature above 35º C. A simulation process, based on experimental results, has been made to predict the performance of the combined LED unit-PCM device at different ambient temperatures; the results shows that above 25º C, PCM device allows the LED unit to operate at higher performance than a heat sink. On the other hand, the PCM system allows the LED unit to operate at constant temperature, which increases the LED efficiency related to conventional dissipation systems that operate at sensible heat. The reduction of temperature also reduces thermal stress of the LED unit, thus increasing its lifespan, what redounds in lower maintenance and replacing costs. Simulated tests have proved that lifespan can be extended between 38.5% and 94.2% depending on the ambient temperature and on the heating rate.