Visualization and thermal resistance measurements for a magnetic nanofluid pulsating heat pipe

Abstract The use of a nanofluid as the working fluid in pulsating heat pipes (PHPs) is currently an attractive technique for heat transfer enhancement. Applying a magnetic field on a magnetic nanofluid-charged PHP enhances thermal performance. To study the mechanism of a magnetic field with magnetic nanofluid can help to reach startup faster in low heat input. A glass PHP with five turns as well as an internal diameter of 3 mm and external diameter of 6 mm was used in the study experiment. Heat input was applied at 20, 55, 90, 125, and 160 W. Deionized (DI) water and iron oxide nanofluid at concentrations of 90, 270, and 450 ppm were used as working fluids. The cooling water temperature was set at 25 °C. The experiment was conducted with and without a magnetic field. A video camera was set up to record the motion of the working fluid in the PHP, and temperatures were measured. The results revealed that the addition of a magnetic nanofluid could improve the performance of the PHP, and in the magnetic field, thermal resistance decreased with an increase in heat input for all experimental parameters. When the heat input was increased from 20 to 55 W, a marked drop in thermal resistance was observed. In addition, the nanofluid particles were securely deposited on the wall under the influence of the magnetic field. Moreover, the nanofluid enhanced boiling by depositing a layer of nanoparticles on the boiling surface.