Mixed convection from a horizontal cylinder rotating in a cooling cross-stream

Abstract

The problem of mixed convection from a rotating horizontal isothermal cylinder placed in a cooling cross stream is considered. Heat transfer by convection is known to depend on Grashof number, Gr, Reynolds number, Re and the speed ratio, a. The study focuses on the effect of the ratio, Gr/Re², on the local and average heat transfer coefficients for selected values of Re and a while keeping Prandtl unchanged. The study is based on the solution of the unsteady Navier-Stokes and energy equations. The study covered the ranges of Re from 20 to 500, Gr from 0.0 to 10⁶ and from 0.0 to 8.0. Comparison with the previous theoretical results showed a good agreement where the differences did not exceed 1.0% while comparison with experimental correlations showed maximum percentage difference of 3.4%. The two terms Gr and were found to have a great influence on the local and average Nusselt numbers. Increasing Grashof number for constant speed ratio tended to increase the average Nusselt number, Nu, whereas increasing a for constant Gr and Re caused significant decrease in the average Nusselt number. On the other hand, high rotational speeds resulted in almost flat distributions of the local Nusselt number and consequently heat transfer rates. Isotherms, streamlines and equi-vorticity lines are plotted and different aspects of the phenomenon are discussed.