Shape and Stability of a Local Heat-Transfer Magnetofluid Coating on a Plate

Abstract

Purpose. Investigate the shape and stability of a magnetic fluid coating on a flat surface in a non-uniform magnetic field of a permanent magnet.Methods. Magnetic fluids based on transformer oil MMT-44 and MMT-21 with saturation magnetization of 43.8 and 21.2 kA/m, respectively, were used in the experiments. A magnetic-fluid coating was formed on the surface of horizontal and vertical non-magnetic plates in a locally inhomogeneous magnetic field of permanent magnets. The source of the inhomogeneous magnetic field is a system of two rectangular magnets. The size of the magnetic system is 40×12×10 mm. The maximum values of the magnetic field strength and gradient reach 180 kA/m and 8∙104 kA/m2, respectively. The shape and stability of a sessile and suspended magnetic fluid coating were studied for various plate orientations.Results. The shape and stability of the magnetic fluid coating on horizontal and vertical plates are studied. The experimental dependences of the height and length of the coating on the volume of the magnetic fluid are established. It is established that the coating can have a certain maximum volume. When this volume is exceeded, the liquid spreads over the surface of the plate or a part of the liquid volume is separated. The limiting volume of the coating is determined by the magnetic characteristics of the ferrofluid and the magnetic field.Conclusion. The possibility of forming a sessile and suspended local magnetic fluid coating on horizontal and vertical plates is established. The height and length of the magnetic fluid coating on the plate depend on the volume of the magnetic fluid, as well as on the characteristics of the magnetic system and the magnetization of the magnetic fluid. The results obtained can be used in the formation of magnetic fluid coatings of cooled sections of heated surfaces.