A magnetic nanofluid device for excellent passive cooling of light emitting diodes. (November 2022) - Varma, Vijaykumar B.
Abstract: Efficient thermal management is an urgent unmet need for a plethora of energy-generating and consuming devices and systems. An improved cooling of high-power light-emitting diodes (LED) used in modern lighting will enhance energy savings, lifetime, and maintain high luminosity for a longer time. However, current passive techs are unable to address this challenge. We have performed detailed experimental and simulation investigations to address this challenge, resulting in the magnetic nanofluid cooling (MNFC) device providing the highest passive cooling of a high-power LED. For a versatile MNFC device suitable for cooling in a broad range of heat flux and temperatures of a heat load, the role of hydrodynamic and magnetic properties on the MNFC device performance was quantified. Several types of ferrofluid coolants with a range of viscosity and magnetic property values were studied. The MNFC device performance was compared with other passive devices by normalized cooling to applied heat flux and found that our device provided the highest reported temperature drop of 197 °C and the most efficient normalized cooling of 29 °C ⋅ kW −1 ⋅ m 2 . The simulation model was modified significantly and included practical device parameters of temperature-dependent viscosity and electrical heating of the heat load, obtaining an excellent quantitative agreement with experiments obtaining dominant parameters for superior MNFC and relevant nondimensional numbers. We developed a material selection map by combining experimental and simulation findings, which were utilized to develop an efficient MNFC device demonstrating an excellent passive cooling of a high-power LED by ≈ 100 °C. The developed device and green, passive cooling methodology are useful to enhance the efficiency and lifetime, ensuring continuous high performance of a target device by removing generated waste heat. Graphical abstract: