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%.