Photothermal characteristic and evaporation efficiency of core-shell Ag@Fe3O4 nanofluids

In order to improve the solar photothermal conversion efficiency, core-shell Ag@Fe3O4 nanoparticles with strong absorbance were prepared, and the prepared nanofluids have good stability, photothermal and recovery performance. Effects of nanoparticle concentration (omega = 0, 50, 100, 150, 200 ppm), light intensity (I = 2, 3, 4, 5 sun), and nanofluids depth (h = 20, 30, 40, 50 mm) on the photothermal performance and evaporation efficiency were investigated in an evaporation device incorporating Ag@Fe3O4 nanofluids. It was shown that the SPR effect of Ag@Fe3O4 nanoparticles can well induce the conversion of solar energy from photons to heat, and the temperature and evaporation are increased by 21.52% and 117.42% at a concentration of 200 ppm, respectively, compared with deionized water. The increase of nanofluids depth increases the temperature gradient inside the fluid and heat loss. Also, the increasing light intensity increases the evaporation volume, but it is unfavorable for the improvement of sensible heat efficiency.