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%. (C) 2019 Elsevier Ltd. All rights reserved.