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NUMERICAL COMPARISONS OF PASSIVE AND ACTIVE COOLING STRATEGIES ON LEDS WITH OPTICAL CONCERNS: NATURAL, FORCED and IMMERSION COOLING

DOI: 10.1615/ICHMT.2014.IntSympConvHeatMassTransf.290
pages 403-411

Enes Tamdogan
Ozyegin University Faculty of Engineering Cekmekoy, Istanbul, Turkey

Mehmet Arik
EVATEG Center, Ozyegin University, Istanbul, Turkey

Аннотация

Lighting consumes a significant position of energy used in residential and commercial buildings. Future seems bright with solid-state lighting (SSL) technologies, especially with LEDs, due to inherit advantages such as energy savings, long life, and exceptional color quality. Moreover with the recent advancements in wide band gap devices, high lumen outputs from very small chip surfaces have been demonstrated. This led to solid state lighting (SSL) a favorable choice for many lighting applications. However, they are currently cost higher than conventional lighting systems and strongly sensitive to temperature. This affects their penetration into general illumination applications. Especially, LED chips driven at high currents quickly get warm and may cause thermal degradation and undesirable failures. Thus, existing thermal issues have turned attention on more effective cooling strategies for extended lifetime and high optical efficiency. While, natural convection air cooling with the added effect of thermal radiation is effective at heat fluxes below approximately 0.1 W/cm2, it is unlikely to provide an efficient cooling capability over 0.1 W/cm2. In this study, CFD analyses for a set of LED systems in terms of current cooling technologies; passive natural and forced convection, have been performed with a computational comparison of same samples with immersion cooling. Thus, heat transfer enhancement by liquids is much more than air cooling. In addition to the CFD based thermal findings, an experimental study with dielectric fluids has been performed to investigate the optical impacts of those novel cooling method and about 10% of better optical performance has also been during liquid cooling.

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