Experimental investigations on transport properties of magnetic fluids

Experimental investigations are carried out to measure the viscosity and the thermal conductivity of the aqueous magnetic fluids in either the absence or the presence of the external magnetic field. The effects of the volume fraction of the suspended magnetic particles, concentration of surfactants and the external magnetic field strength as well as its orientation on the transport properties of the magnetic fluid are analyzed. The experimental results show that the viscosity of the sample magnetic fluids increases with the percentages of the suspended magnetic particles and the surfactants. The viscosity first increases with the magnetic field and finally approaches a constant as the magnetization of the magnetic fluid arrives at a saturation state. For the same magnetic fluid, the viscosity in the magnetic field being perpendicular to the flow direction is bigger than that in the parallel field under the same magnetic field. The thermal conductivity of the sample magnetic fluids is larger than that of pure fluids in both the absence and presence of the external magnetic field. Almost no change in the thermal conductivity of the sample magnetic fluid is found in the magnetic field perpendicular to the temperature gradient. The thermal conductivity of the magnetic fluid increases with the strength of the applied magnetic field being parallel to the temperature gradient.