Thermal Performance Testing of a Solar Water Heating System Using Core-Shell Structured Nanofluids

ABSTRACT This study investigates the impact of core-shell based nanofluids on the thermal performance of a solar water heating system by studying the changes in the useful heat gain and collector efficiency. This work would be the first to report the use of core-shell nanoparticles in solar water heating systems. The core-shell structure allows for dual improvements in thermal conductivity and better nanofluid stability, even without a surfactant. Therefore, three novel nanofluids were prepared by adding 2 wt% TiO2@SiO2, Fe3O4@SiO2, and ZnO@SiO2 core-shell nanoparticles to pure water to be used in the experiments. The experimental thermal performances of the nanofluids were individually compared with pure water by the simultaneous operation of two identical systems. The results showed that the nanofluids with Fe3O4@SiO2 and ZnO@SiO2 particles had better performance than the base fluid. In particular, 16.65% and 5.40% increase in the useful energy gain and a 17.12% and 7.39% increase in the collector efficiency were observed with Fe3O4@SiO2 and ZnO@SiO2 core-shell based nanofluids, respectively. It is possible to conclude that, with their improved performance, the Fe3O4@SiO2-based nanofluids have great potential to be used in solar hot water systems instead of water.