Mixed Convection from an Elliptic Tube at Different Angles of Attack Placed in a Fluctuating Free Stream

Abstract

The problem of mixed-convection heat transfer from a straight isothermal elliptic tube at different angles of attack ( u ), placed in a convective environment with fluctuations in the free-stream velocity, is investigated numerically, including the effect of buoyancy forces. The free-stream direction is horizontal and normal to the tube axis, and the flow field is essentially two-dimensional. The investigation is based on a numerical solution of the conservation equations of mass, momentum, and energy. The parameters involved are fluctuations amplitude g , Strouhal number S, Reynold number Re, Grashof number Gr, Prandtl number Pr, the tube geometry, and its orientation presented by its angle of attack u . The study focuses on the effect of S, Re, Gr, and u on the heat transfer process. The time average of the Nusselt number is found to increase with increasing amplitude of fluctuations and with decreasing Strouhal number. The response of the total rate of heat transfer to changes in inclination angle is found to depend, also, on Reynolds number and fluctuation parameters. The details of the velocity and thermal fields are presented in the form of isotherms and streamline patterns.