LAUSR

Abstract This work presents a numerical analysis of heat transfer and flow characteristics of a ferrofluid inside an annulus. The ferrofluid flow is subjected to multiple magnetic fields emanating from current-carrying wires. The inner tube of the annulus is heated uniformly while the outer tube is insulated. Two-phase modeling is conducted by incorporating Brownian, thermophoretic, and magnetophoretic effects. The dependence of ferrofluid viscosity and thermal conductivity on the magnetic field intensity and temperature is considered. The finite volume approach is applied to solve the governing equations. The influences of magnetic number, relative angular position, the number of magnetic sources, and also radius ratio of the annulus on the augmentation of heat transfer and pressure losses are examined. Numerical findings show that the applied magnetic fields induce a strong secondary flow whose magnitude may be several times higher than that of the inlet velocity. In the case of two current-carrying wires, the rate of heat transfer is enhanced by increasing the relative angular distance between the two magnetic sources and shows a maximum at Δ θ = 180 °. It is found that there exists an optimum number of magnetic fields that maximize the rate of heat transfer. Additionally, the average Nusselt number declines as the radius ratio rises.