Impact of oscillating magnetic field on the thermal-conductivity of water-Fe3O4 and water-Fe3O4/CNT ferro-fluids: Experimental study

The aim of this experimental assessment is to examine the influence of an oscillating magnetic field on the thermal-conductivity of a water-Fe3O4 and water-Fe3O4/CNT ferro-fluids. Magnetic field is created by an electromagnet composed of a core made of ferrite and two copper windings. The impacts of magnetic field strength and frequency are also examined and the findings are compared with those of the constant magnetic field. The outcomes revealed that the pattern of thermal-conductivity in the attendance of a constant magnetic field is initially ascending and then descending. In addition, it was found that the descending trend of the thermal-conductivity can be prevented by using an oscillating magnetic field. Moreover, the results depicted that the most effective oscillating magnetic field has a frequency equal to the inverse of one minute less than time to reach the highest thermal-conductivity in the attendance of constant magnetic field. According to the results, the highest increase in the average thermal-conductivity of the water-Fe3O4 and water-Fe3O4/CNT ferro-fluids in the attendance of an oscillating magnetic field of 700 Gauss in comparison to the case of a constant magnetic field of 700 Gauss, is respectively 22.62 and 24.25%.