CONTROL OF TEMPERATURE DISTRIBUTION AT CYLINDER SURFACE BY MAGNETIC FLUID

The present study deals with the influence of a magnetic fluid coating , held onto a circular cylinder surface by a magnetic field, on the te mperature distribution at the surface of a cylinder heated by a consta nt heat flux. The temperature distribution over the cylinder surface i n the fluid is determined by the heating power of the cylinder and the incoming flow structure. The flow structure near the cylinder can be changed by applying a magnetic fluid coating over its surface and by h olding it with a magnetic field. In this case, heat from its surface t o the external flow is removed by two modes. First, the heat is transf erred to the external flow due to heat conduction of the magnetic flui d. Second, the heated layers of the magnetic fluid are entrained due t o circulation and give up their heat to the external flow at the inter face. Thus, there are two mechanisms of removing the heat inside the m agnetic-fluid coating: conductive and convective. The balance of these two mechanisms is determined by the circulation intensity inside the coating and by the value of magnetic fluid thermal conductivity. A ste ady laminar flow of viscous fluid past a circular cylinder with magnet ic fluid kept on its surface under a magnetic field is investigated nu merically by finite-element method. A grid of 5751 nodes is used. The cases of Reynolds number Re = 10, 30, 100 are considered. The role of heat conduction ratio is determined for the meanings Lambda = 0.1, 1, 10. The great influence of magnetic fluid coating on surface temperatu re distribution is discovered in the paper. The distribution can be pr ofitably varied by the magnetic fluid properties and flow velocity: it can be nonmonotonic, and the temperature of a solid can increase in t he direction opposite to the direction of fluid flow.