Numerical study on magnetic nanofluid (MNF) film boiling in non-uniform magnetic fields generated by current carrying wires

Film boiling of magnetic nanofluid (MNF) in non-uniform magnetic fields generated by current carrying wires is numerically studied in this paper. The calculation model for the flow and heat transfer of MNF film boiling is established by incorporating both Maxwell's equation for magnetic fields and transport equations for interfaces into the basic governing equations of two-phase flows. The interface of boiling vapor film is captured by the VOSET method. Influence of the non-uniform magnetic field generated by single and multiple current carrying wires on the MNF film boiling is studied by analyzing the coupling among the magnetic field, flow field and interface distribution based on the numerical results. It is shown that the locations of the current carrying wire have a great influence on the MNF film boiling. The non-uniform magnetic field generated by current carrying wires may promote or inhibit the growth and departure of the vapor bubbles, which is determined by the distance between the current carrying wire and the top of initial vapor film. Compared with the cases without magnetic field, when the current carrying wire is near the bottom of the initial vapor film (located at x = 0, lambda(0)/6, 5 lambda(0)/6 and lambda(0)), the average wall temperature of the heated wall decreases and the average Nu number increases, resulting in enhancing the heat transfer. While the wire is below the bottom of the initial vapor film and H-0 = 10 kA m(-1), the averaged Nu number increases to 2.98, which is 4.2% higher than that in the case without magnetic fields. However, when the wire is near the top of the initial vapor film (located at x = lambda(0)/3, lambda(0)/2 and 2 lambda(0)/3), the bubble departure time increases slightly, and the averaged Nu number decreases by 1.1%. Further, the influence of the coupled magnetic field of four current carrying wires on the MNF boiling heat transfer is explored. Compared with the single wire, the coexistence of multiple current carrying wires can further promote the heat transfer performance of MNF film boiling. When the H-0 = 20 kA m(-1) generated by four current carrying wires, compared with the condition without magnetic field, the average Nu number increases from 2.87 to 3.80, increasing by 32.4%.

Automated summary

In this paper, the film boiling of magnetic nanofluid in non-uniform magnetic fields generated by current carrying wires has been numerically studied. The influence of the non-uniform magnetic field on the film boiling process has been analyzed, and it is found that the magnetic field can promote or inhibit the growth and departure of vapor bubbles. Additionally, the effect of multiple current carrying wires on the heat transfer performance of the nanofluid film boiling has been explored, and it is found that the coexistence of multiple wires can further enhance the heat transfer.