Heat Transfer Enhancement in Swirl Annulus Flows

Abstract: The characteristics of decaying swirling flows and forced convective heat transfer on the condition of turbulent flow in a narrow concentric annulus were simulated. The governing equations are solved numerically via a finite volume method. Uniform wall temperature at the inner wall and adiabatic wall at the outer wall are considered as thermal boundary conditions. Solutions for the axial and swirl velocity distributions and the Nusselt number are obtained for different values of the inlet swirl number and the Reynolds number. Simulations show that the inlet swirl number have great influences on the heat transfer characteristics. Under developed turbulent flow conditions, the increases of inlet swirl number will enhance the heat transfer. When the inlet swirl number increases it increases the axial velocity near the wall and reduces it at the mid-gap to achieve the conservation of mass due to the existence of secondary flows in the annulus due to centrifugal forces. The increase of the near-wall velocity, in turn, produces larger temperature gradients and higher heat transfer rate. The swirl velocity profiles decay gradually downstream as a result of friction which leads to damp the tangential velocity. The comparison between predicted and experimental data of average Nusselt numbers was found to be in good agreement