Recent developments in the application of ferrofluids with an emphasis on thermal performance and energy harvesting

The term Ferrofluids is used to refer to the coherent colloidal suspension of nanometer size ferromagnetic particles or their oxides in base fluids such as oil, water etc. Due to decrease in size to nanometric level, the property of ferromagnetism shifts towards super-magnetism. It creates an opportunity to modify the thermophysical parameters of magnetic nanofluid when exposed to exterior magnetization field. A plethora of research on Ferrofluids has made way for varied applications ranging from dynamic loudspeakers, computer hard drives to room cleaning robots which exploit their exceptional operating characteristics. The field of thermal engineering in relation to the applications of ferrofluids have been explored extensively in the recent past. Innovative outlooks relating to thermal control of miniaturized systems have opened. Major properties which are under study by researchers are related to area of enhanced thermal conductivity along with improvement in thermal performance of the magnetic nanofluid. These studies involve analysis pertaining ferrofluid's heat transfer along with the controlling of parameters when external magnetic field is present. The alternative solutions to heat transfer can be provided with ferrofluids having improved thermal conductivity and the ability to externally control and change heat transfer coefficient. At present, the power supplied to miniaturized systems is being provided through batteries which have several limitations such as big size, shorter lifetime, holding hazardous and unsafe materials and troubles in replacement. Due to these limitations, an energy harvester based upon ferrofluid could provide an alternative source of energy. Recent studies also focus on the development of energy based harvester based upon vibrations. In this context, this paper will try to provide a wide-ranging review of present and developing applications of ferrofluids with special focus on the study of heat transfer and energy harvesters.