Numerical Analysis of Magnetic Field Influence on Heat Transfer in Helical Tubes Using Magnetic Fluids Under Laminar Flow Conditions

This study investigates the thermal and hydraulic behavior of a 4% volume-concentration Fe3O4 magnetic nanofluid flowing through a helical tube under constant wall temperature conditions of 373.15 K. The main objective is to improve heat transfer while reducing hydraulic losses, thereby enhancing the overall thermal–hydraulic performance of the system. The simulations were performed under laminar-flow conditions for Reynolds numbers ranging from 600 to 1100. A uniform magnetic field with an intensity between 0 and 1 Tesla was applied. The effects of tube pitch length and inclination angle were also examined. Two pitch lengths, 2.5 cm and 5 cm, and three inclination angles, 0°, 45°, and 90° relative to the horizontal, were considered. The helical tube geometry was created in SolidWorks, and the computational mesh was generated using ANSYS Meshing. A mesh-independence study was carried out before applying the boundary conditions. The magnetic field effect was introduced into the numerical model through a user-defined function. The model was validated by comparing its results for a straight channel with published data, and good agreement was obtained. The results showed that applying a magnetic field can improve both heat-transfer and hydraulic performance. The maximum thermal enhancement, equal to 33.78%, was obtained at Re = 600, with a pitch length of 2.5 cm, a tube inclination angle of 45°, and a magnetic-field intensity of 1 Tesla. The hydraulic performance improved most significantly for a tube with a 5 cm pitch length and a 90° inclination angle. Under these conditions, the friction coefficient decreased by 4.26% at Re = 600 and by 14.29% at Re = 1100, both at a magnetic-field intensity of 1 Tesla. The optimum magnetic-field intensity for overall thermal and hydraulic performance was not affected by the pitch length but depended on the tube inclination angle. The optimum value was 0.1 Tesla for horizontal tubes and 0.3 Tesla for both vertical and 45° inclined tubes. Overall, the best thermal hydraulic performance coefficient improved by 3.25% at Re = 600, with a pitch length of 2.5 cm, a 45° inclination angle, and the corresponding optimum magnetic-field intensity.

کلیدواژه ها:

Magnetic Field ، Magnetic Fluids ، Helical Tubes ، nanofluid ، ANSYS Meshing