Thermomagnetic convection of a magnetic nanofluid influenced by a magnetic field

Abstract

We present a numerical study of thermomagnetic convection in a differentially heated cavity. The magnetic nanofluid (ferrofluid) is subjected to a uniform magnetic gradient oriented at an angle, ?, with respect to the thermal gradient. The motivation for this work stems largely from a desire to extent preexisting works focused on horizontal and vertical orientations ? = 0?, 90?, 180?, and 270?. Our main goal is to get data on the flow and heat transfer for any orientation in the entire range 0-360?. The generalized problem lends itself to the investigation of orientations that give maximum heat transfer. It is found that, (1) at a given magneto- gravitational coupling number, N, orientations 0?, 90?, and 270?, for which magnetization gradient is unstable, are not the optimum ones, (2) for 0 < N ? 1, heat transfer reaches a maximum between 270? and 360?, (3) for N > 1, a second maximum occur between 0? and 90? owing to reverse flow phenomenon, (4) at strong magnetic gradients, the two heat transfer peaks take the same value, and (5) optimization parameter, ?, reflecting the strongest magnetic effect, grows with N. Unlike the gravity, magnetic gradient may supply various strengths and spatial configurations, which makes thermomagnetic convection more controllable. Also, the magnetic mechanism is a viable alternative for the gravity one in microgravity, where thermo-gravitational convection ceases to be efficient..