Book Description
We have simulated two-dimensional heat transfer in ferrofluid channel flow under the influence of the magnetic field created by magnetic dipole using computational fluid dynamics code COMSOL based on finite element method. At the left end of rectangular channel there was assumed a parabolic laminar flow profile. The upper plate was kept at constant temperature Tu and the lower at Tl . The flow was relatively uninfluenced by the magnetic field until its strength was large enough for the Kelvin body force to overcome the viscous force. The magnetoconvection was induced by the presence of magnetic field gradient. We observed that the cooler ferrofluid flows in the direction of the magnetic field gradient and displaced hotter ferrofluid. Ferrofluids have promising potential for heat transfer applications because a ferrofluid flow can be controlled by using an external magnetic field. The Kelvin body force arises from the interaction between the local magnetic field within the ferrofluid and the molecular magnetic moments characterized by the magnetization. An imposed thermal gradient produces a spatial variation in the magnetization through the temperature-dependent magnetic susceptibility for ferrofluids and therefore renders the Kelvin body force non-uniform spatially. This thermal gradient induced inhomogeneous magnetic body force can promote or inhibit convection in a manner similar to the gravitational body force. A strong magnet placed near the device which produces heat will always attract colder ferrofluid towards it more than warmer ferrofluid thus forcing the heated ferrofluid away, towards the heat sink. This is an efficient cooling method which requires no additional energy input.
