Efficiency of ferromagnetic nanoparticles suspended in ethylene glycol for applications in energy devices: Effects of particle size, temperature, and concentration

In this paper, the efficiency of Fe/ethylene glycol nanofluids as coolants is investigated in both laminar and turbulent flow regimes. The effects of particle size, temperature and concentration of nanofluids on the efficiency are examined. To determine the efficiency of nanofluids, the thermal conductivity and viscosity of the nanofluids with concentrations up to 3% in the temperature range of 26–55 °C are measured. Three different average particle sizes including 40 nm, 70 nm, and 100 nm are utilized. The results show that, in laminar flow, the nanofluids with low concentrations and containing particles with big size are not useful. For the turbulent flow, the efficiency analysis reveals that the efficiency of nanofluids increases with an increase in the temperature and solid volume fraction. The nanoparticles with the average size of 70 nm are found to be the best option in the turbulent flow and at the concentration of 3%, while in lower concentrations, the nanoparticles with the average size of 40 nm provide the maximum efficiency.