Stationary Thermomagnetic Convection of Ferrofluid in an Enclosed Loop

This paper presents an experimental study of thermal convection of ferrofluid inside a closed hydrodynamic loop heated from the side in the presence of a magnetic field applied to the loop section nearby the heater. The pipes of the circuit are blown with a stream of thermostatic air, which ensures a constant heat transfer coefficient on the outer surface of the pipes and an exponential temperature distribution along the circuit. The value of the exponent measured provide information on the integral axial heat flux (Nusselt number). The experiments were conducted with undecane under natural gravitational convection and with a colloidal solution of magnetite in kerosene of moderate concentration under mixed (gravitational and thermomagnetic) convection at the Rayleigh numbers varied in the range 10³ – 10⁴. It is shown that thermomagnetic convection causes a 4 – 6 – fold increase in heat transfer. (paper)