Thermal and rheological properties of water-based ferrofluids and their applicability as quenching media

Water-based ferrofluids present a new energy transfer fluid with tunable properties. Previous research has shown the increase in thermal conductivity of water-based nanofluids with the addition of iron oxide. Such increased thermal properties show great potential for use in heat transfer. In this paper, several nanofluids were prepared with two step method. Iron (II, III) oxide nanoparticles with average paerticle size less than 50 nm were added to deionized water in following concentration: 0.01, 0.1, 0.5 and 1 g/L. Their thermal and rheological properties were measured at 20, 40 and 60 degrees C. Results showed increase in thermal conductivity and viscosity with increase in the addition of nanoparticles at all three temperature levels. The biggest increase was observed at 20 degrees C. For this research, all of the prepared nanofluids were tested as immersion quenching liquid according to ISO 9950 standard. Besides still conditions, quenching experiments were conducted under the magnetic field at two levels, 500 and 1000 Gauss. The magnetic field effect was least present at 60 degrees C with almost no influence on the cooling curve and cooling rates. At lower temperature levels quenching under the magnetic field shortened the full film boiling phase and increased the maximum cooling rate.