Numerical, theoretical and experimental investigation on THERMO-MAGNETIC convection

Abstract

A magnetic fluid is a colloidal liquid-solid suspension, formed by a carrier Newtonian liquidand nanometric particles of ferromagnetic material. The stability of the suspension againstthe formation of particle clustering and consequently sedimentation is achieved through the addition of large molecules of polymeric material. These molecules, adhere to the surfaceof the particles and act as nano-springs that prevent particle clustering. Since the discoveryof these fluids in the 60s, this new class of materials has been used in many interesting applications. These applications go from the development of new tumor treatment techniques(magneto-hyperthermia) to the possibility of cooling electronic devices through a phenomenonknown as thermo-magnetic convection. Different from the classical phenomenon of natural convection, which has been extensively studied since the XIX century, the thermo-magnetic convection occurs when a stratification of magnetic susceptibility induced by a temperaturegradient is combined with the application of an external magnetic field. We estimate that it is possible to increase up to 20% the heat transfer rates inside a thin cavity with only 0.5% of particles (in volume) and an applied field of 300 G. Although this technique may sound very promising, its use to solve practical problems involving heat transfer enhancement still requires a better comprehension on some operational details as well as of the phenomenonological equations that describe this new kind of flow. This work aims to investigate the thermo-magnetic phenomenon from an experimental/operational perspective as well as from a numerical/theoretical point of view, so this knowledge can be used in the development of new technologies applied to the cooling of electronic devices. (AU)