Hasan Najafi Khaboshan - Department of Mechanical Engineering, Imam Khomeini International University, Qazvin, Iran .Young Researchers and Elites Club, Science and Research Branch, Tehran, Iran
Elnaz Yousefi - Department of Mechanical Engineering, Imam Khomeini International University, Qazvin, Iran
Hamid Reza Nazif - Department of Mechanical Engineering, Imam Khomeini International University, Qazvin, Iran

In this research, the effect of tube flattening on thermal-hydraulic performance of ferrofluids flow has been investigated numerically under the non-uniform magnetic field. The non-uniform magnetic field is applied by the current-carrying wire, and the effect of various positions of the current-carrying wires on the convection coefficient and pressure loss of ferrofluids flow are also investigated. The positions of wires are one wire near the flat part of the flattened tube (Case 1), and two parallel wires near the flat part (Case 2) or circular part (Case 3) of the flattened tubes. The laminar flow of ferrofluids is simulated using the two-phase mixture model under the constant heat flux boundary conditions. Numerical results demonstrate that when the two parallel wires are located in the flat part of the flattened tubes (Case 2), the heat transfer is reached to its maximum in comparison to the other cases. Moreover, by applying the current- carrying wires with 5 Ampere, the average heat transfer coefficient is increased about 32.27%, 239.72% and 172.03% for Case 1, 2 and 3, respectively. However, in contrast to this enhancement, the pressure drop also increases. In addition, the heat transfer is improved gradually in Case 2 while flattening the tube. So, the position of the wires in Case 2 is proper to enhance the heat transfer for all flattened tubes in this research.

Heat transfer enhancement, Non-uniform magnetic field, Two-phase mixture model, Flattened tubes.