Magnetic field and magnetic fluids types effect on heat and mass transfer at the cooling of the magnetizable ball in magnetic fluids. Experiment and its explanation

V. V. Gogosov¹ - Kh. D. Iskanderov² - V. V. Kiryushin¹ - A. Ya. Simonovskii²

¹ Institute of Mechanics of the M.V.Lomonosov Moscow State University, 117192, Moscow, Russia
² Academy of Stavroplol, 355014 Stavroplol, Russia

Abstract
Experiments on cooling of the magnetizable heated ball in various magnetic fluids in the applied magnetic fields are described. It is found that the magnetic fluid boiling at the different points of the ball surface occurs in the different modes and depends significantly on the magnetic fluids properties, the temperature of the cooled ball, the magnetic field magnitude and position of the surface points relative to the direction of the applied magnetic field vector. It is shown that the magnetic fluid may stratify at the contact with the heated ball surface and deposit on the surface. The structure of the precipitate observed on the surface of the ball at the various temperatures of the ball cooling are described. Conclusions about the boiling modes of the magnetic fluids at the different cooling temperatures are made from the analysis of the precipitate structure. Stratified magnetic fluid deposition on the magnetizable ball surface is explained theoretically. The formula for the pressure distribution in the magnetic fluid near the ball surface are presented. The magnetic forces pressing the magnetic fluid against the ball surface depend on the fluid magnetization, the magnetic field magnitude and the direction of the magnetic field vector relative to the outward normal to the surface of the ball. It is shown that the pressure in the magnetic fluid is maximize in the neighbourhood of the poles of the ball and minimize in the neighbourhood of the equator. As a result, in the neighbourhood of the poles the magnetic fluid is held against the hot ball surface, stratifies and settles out on the surface in the form of flakes precipitate. In the neighbourhood of the equator the pressure force is insufficient to press the fluid against the surface. Here the vapour layer is situated between the magnetic fluid and the ball surface. Figs 5, refs 13.