3D Helmholtz Coil System Design for Measuring the Thermal Conductivity of Magnetic Nanofluids

Abstract

Magnetic nanofluids are special colloids that have many potential application areas because their thermophysical properties can be tuned under an applied magnetic field. One of the thermophysical properties that can be tuned using an external magnetic field is the thermal conductivity of these fluids. The studies on the measurement of the thermal conductivity of the magnetic nanofluids put emphasis on the direction and the uniformity of the magnetic field applied to the fluid. The measurement results show that thermal conductivity results change when the external magnetic field is applied parallel or perpendicular to the temperature gradient of the thermal conductivity measurement probe. Permanent magnets and electromagnets are commonly employed in these studies. The proposed design of 3D Helmholtz coil system as the magnetic field generator enables to measure the thermal conductivity of the magnetic nanofluids under uniform and rotating magnetic field. By using the rotating magnetic field, the external magnetic field can be applied in any desired direction to the temperature gradient. The rotating of the magnetic field was demonstrated in this study by changing the current values of the coil pairs. The simulation results of the study show that the proposed 3D Helmholtz coil system can generate a uniform magnetic field in the measurement area and the field direction can be altered by only controlling the current values without any mechanical adjustments.