Liquid cooling systems are either active or passive 7. Hence, there is an urgent need to improve the coolant fluid medium. One of the technique to improve the heat transfer is by increasing the surface area of heat transfer between the heat load and the cooling device, however it results in a much bulkier cooling device 6. Several important industrial sectors, e.g., electrical, electronics, mechanical, and transportation, demand better heat transfer solutions 4, 5. Removal of waste heat can increase reliability, efficiency, and service life. According to the energy consumption data from Lawrence Livermore National Laboratory, a significant fraction of overall energy is wasted due to inefficient processes 2, 3. A significant percentage of the energy supplied to devices and systems is lost to the surroundings as waste heat 1. Inefficient use of energy is a major challenge that aggravates the global energy crisis. These results can be used to select the optimum magnetic nanoparticle-based ferrofluid for a specific magnetic cooling device application. The saturation magnetization of the magnetic nanoparticles is found to be a significant parameter to enhance heat transfer and heat load cooling. FeCo nanoparticles had the best cooling performance for the case of metallic ferrofluids. γ-Fe 2O 3, Fe 3O 4, and CoFe 2O 4 nanoparticles exhibited superior cooling performance among ferrite-based ferrofluids. We also investigated the significance of the magnetic properties of the nanoparticles used in the ferrofluid on cooling performance. The magnetic pressure, friction factor, power transfer, and exergy loss were determined to predict the performance of such cooling devices. Hence, we studied the performance metrics, non-dimensional parameters, and thermomagnetic cooling performance of various ferrite and metal-based ferrofluids. Magnetic cooling, governed by the thermomagnetic convection of a ferrofluid, is a promising emerging passive heat transfer technology to meet these challenges. Superior passive cooling technologies are urgently required to tackle device overheating, consequent performance degradation, and service life reduction.

Ferrofluid