Cooling of high-power LEDs by liquid sprays: Challenges and prospects

Highlights: • Next generation high power LEDs require specialized thermal management. • Spray cooling is potentially an excellent solution for LED packages. • A comprehensive review of spray cooling in the context of LEDs is presented. • Thermal and hydrodynamic design strategies of liquid sprays are delineated. • Intrinsic connection between local droplet level physics and global spray is outlined. Light Emitting Diodes (LEDs) are getting popular due to their wide applicability in various domestic and industrial applications. However, the advent of high-power LEDs is accompanied with the critical issue of higher heat power management, coupled with enhanced flux levels. Natural and forced convection techniques with air as the working fluid are unable to provide thermal management at required operating safe temperatures in several upcoming compact LED array designs. Hence, there is substantial advancement in the development of thermal management solutions for the packaging of high-power LEDs. Liquid jets and sprays are potential candidates which need further exploration, especially from a point of view of packaging with LED modules. Both configurations can operate in single-phase and two-phase boiling regimes. While considerable literature is available on single-phase liquid jets, liquid sprays pose several challenges in terms of flow parameter management and associated transport physics. In this paper, we review nuances of the latter technology, i.e., spray cooling technique, crucial for thermal management of LEDs. A comprehensive overview of flow distribution and heat transfer during impingement of liquid sprays on heated surfaces is presented from the viewpoint of temperature control of high power LED sources. Additionally, the data presented will help in developing a configuration design of a liquid spray-based thermal management system integrated with high heat flux devices.