Thermo-hydraulic investigation of nanofluid as a coolant in VVER-440 fuel rod bundle

The main purpose of this study is to perform numerical simulation of nanofluids as the coolant in VVER-440 fuel rod bundle. The fuel rod bundle contains 60 fuel rods with length of 960 mm and 4 spacer grids. In VVER-440 fuel rod bundle the coolant fluid (water) is in high pressure and temperature condition. In the present Thermo-hydraulic simulation, water-AL2O3 nanofluids containing various volume fractions of AL2O3 nanoparticles are investigated. Calculations performed for Reynolds number of 125000 to 203000, nanoparticles fraction of 0 to 0.05 and nanoparticles diameter of 20 to 100 nm. In this literature, the effects of diameter and volume fraction of nanoparticles on thermo-hydraulic parameters are studied. To perform correct calculation, different grid qualities of fuel rod bundle are studied and results are compared with reference results. Empirical studies show that as the temperature rises, the effect of nanoparticles on enhancing thermal conductivity intensifies. So it can be said that as the VVER-440 fuel rod bundle works in high temperature condition, using the nanofluids in this rod bundle can be effective. Results of our numerical study showed that by using nanofluids as coolant fluid the heat transfer coefficient increases significantly and heat transfer enhancement raises with increase in volume fraction of nanoparticle.