Heat transfer enhancement inside semi-insulated horizontal pipe by controlling the secondary flow of oil-based ferro-fluid in the presence of non-uniform magnetic field: A general correlation for the Nusselt number

摘要

In the present study, hydrodynamic and hydrothermal behavior of the laminar nano-fluid actuated by the non-uniform magnetic field in a horizontal semi-insulated tube was numerically investigated. Firstly, the impact of key parameters such as Reynolds number (Re), magnetic field intensity (Mn), wall heat flux (q) as well as the wire location (as a source of magnetic field producer) was examined on the flow and heat transfer characteristics and compared with the non-magnetic case. Numerical results showed that the heat transfer and pressure drop in the presence of the magnetic field were about 3.7 and 1.8 times higher than the non-magnetic case (Re = 500, Mn = 5.7e8), respectively. As a result, to gain a more general conclusion, the effectiveness parameter (epsilon) was evaluated in different vital situations, in which both heat transfer and pressure drop were involved. Accordingly, using the magnetic field is affordable to increase heat transfer in the practical works. Finally, a general correlation for the Nusselt as a function of non-dimensional length (x*), magnetic number (Mn) and non-dimensional heat flux (Q(mag)*) is presented with an average error of 3.43%.