Experimental investigation on heat transfer characteristics of various nanofluids in an indoor electric heater

Heat transfer characteristics of an electric heater were experimentally investigated by using various fluids in this paper, including Cu-EGW (a mixture of ethylene glycol and DI-water), Al2O3-EGW, Fe3O4-EGW nanofluids. A 4:6 mixture of ethylene glycol and deionized water was used as the base liquid. All these nanofluids were prepared by ultrasonic treatment, and nanoparticle mass concentration of samples varies from 0.5% to 2%. In addition, natural convective heat transfer of Fe3O4-EGW nanofluid in an electric heater was carried out by considering an effect of different magnetic fields. The results indicated that heat transfer performance of Cu-EGW nanofluid was significantly higher than the Al2O3-EGW and Fe3O4-EGW nanofluids, and the heating efficiency of the Cu-EGW nanofluid increased with the mass concentration of Cu particles. Compared with that of the base fluid, equilibrium temperature values of electric heaters filled with 2.0% Cu-EGW, 1.0% Al2O3-EGW and 1.0% Fe3O4-EGW nanofluids increase by 13.18%, 3.77% and 4.52%, respectively. It was also found that the magnetic field had a positive effect on the heat transfer enhancement of the Fe3O4-EGW nanofluid. In addition, for the 0.5% Fe3O4 nanofluid under a magnetic intensity of 100 mT, the equilibrium temperature on the middle fin increases by 14.68%