Convection heat transfer enhancement of air in a rectangular duct by application of a magnetic quadrupole field

Air is subjected to a magnetic body force in a magnetic gradient field and can be driven to flow by magnetic buoyancy force. The laminar flow and heat transfer characteristics of air in a rectangular duct confined to a magnetic quadrupole field were numerically investigated. Calculations were performed for both hydraulically and thermally developing and fully developed laminar flows at Reynolds numbers between 200 and 2000. The centrifugal-form magnetic body force can induce air flows in the spanwise direction, and form eight longitudinal vortices. The velocity and temperature fields were presented and the friction coefficients and Nusselt numbers were compared for different Reynolds numbers and duct wall temperatures. The results show that the convection heat transfer is remarkably enhanced at the cost of a relatively slight power loss by application of the magnetic quadrupole field. For hydraulically and thermally fully developed flows, the enhancement of convection heat transfer due to the longitudinal vortices resulting from the magnetic quadrupole field is more effective. (C) 2003 Elsevier Ltd. All rights reserved.