Forced convective heat transfer characteristics of solar salt-based SiO₂ nanofluids in solar energy applications

Nowadays, molten salts are widely used in concentrated solar plants as working media to transfer and store solar energy. However, the relatively poor thermal properties of molten salts have restricted their further application. Nevertheless, the addition of nanoparticles to molten salts excellently improves these thermal properties. In present work, solar salt-based nanofluids were prepared using a lyophilizer. The specific heat of solar salt-based SiO₂ nanofluids was experimentally measured based on the sapphire method, and its heat transfer performance was numerically investigated using the lattice Boltzmann method. Results indicated that an optimum nanoparticle mass fraction that could enhance heat transfer performance existed. This optimum nanoparticle mass fraction, which was found to be 1.0 wt%, improved the heat transfer coefficient and Nu number by 8.58 and 7.29%, respectively. The parameter analysis indicated that the considerably large change in the specific heat dominated the change in heat transfer performance. Meanwhile, the simulation results of the average Nu numbers exhibited good agreement with the Shah-London correlation prediction to within ±3.0%, indicating the feasibility of using this correlation in designing heat exchangers that utilize solar salt-based SiO₂ nanofluids.