Solar Energy, Vol.206, 900-906, 2020
Experimental study on forced convection heat transfer of KNO3-Ca (NO3)(2) + SiO2 molten salt nanofluid in circular tube
Molten salt is a major heat storage medium for medium-high temperature solar thermal power applications. The heat storage density and heat transfer efficiency of molten salt are important factors of solar thermal power efficiency. Recently, many studies have reported that molten salt nanofluid, which is formed by adding nanoparticles in molten salt, can remarkably enhance the specific heat capacity of molten salt. However, research on the forced convection heat transfer of molten salt nanofluid is inadequate. In this study, the forced convection heat transfer experiments were carried out in a circular tube of a previously reported promising molten salt nanofluid composed of KNO3-Ca(NO3)(2) + 1 wt% of 20 nm SiO2 nanoparticles (K-C-S-nm). Results showed that compared with its base pure molten salt, the K-C-S-nm molten salt nanofluid exhibited substantially better forced convection heat transfer performance under the same working condition. The Nusselt number and the convective heat transfer coefficient of K-C-S-nm molten salt nanofluid were 16.3% and 39.9% higher than its base pure molten salt, respectively. The experimental data of K-C-S-nm molten salt nanofluid largely differed from the classical correlation equations. Hence, a new empirical heat transfer correlation equation was set for K-C-S-nm molten salt nanofluid, and the deviation between the experiment data and new correlation was within +/- 7%.