Experimental study on thermophysical properties of TiO, ZnO and Ag water base nanofluids

In this paper, heat transfer performance was experimentally tested in a helically coiled pipe using three types of nanofluids, TiO2, ZnO and Ag water-based nanofluids. TiO2, ZnO and Ag nanoparticles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The XRD results showed that the purity of ZnO and TiO2 were obtained. TEM and SEM results showed that the mean particles size of TiO2, ZnO and Ag are 14, 20 and 16 nm respectively. The three types of nanofluids, TiO2/water, ZnO/water and Ag/water were prepared with a volume concentration of 0.25%. To ensure a good mixture and measure particles distribution in each nanofluid, Zetsizer test was performed and showed a good distribution of nanoparticles in all tested nanofluids. The three different nanofluids have been thermally tested in helical coil with a flow rate from 1 to 3.5 L/s with different inlet temperatures in the range of 30 °C and 60 °C. The experimental results showed an enhancement in Nusselt number up to 27.31%, 16.03%, and 10.38% with augmentation in the heat transfer coefficient up to 32%, 21% and 16% utilizing TiO2, ZnO and Ag nanoparticles respectively.