Numerical study on the effects of supercritical CO2-based nanofluid on heat transfer deterioration

The drastic variation of thermoproperties of supercritical CO2 may induce heat transfer deterioration (HTD). To solve the HTD problem, the effects of nanoparticles on supercritical CO2 heat transfer performance was numerically studied. Results show that with the increase of nanoparticle concentration, the local temperature peak is further suppressed. The wall temperature has a maximum decrease of 168.9 K, and the optimal heat transfer enhancement of the supercritical CO2 nanofluid has a maximum increase of 51.4%. Detailed flow field analysis indicates that the decrease of density gradient in the buffer layer significantly suppresses the coupling effect of buoyancy and flow acceleration, which leads to better heat transfer performance. Also, the convective heat transfer benefits from the reduced specific heat and improved thermal conductivity of nanofluid. Eventually, it is the high-density-nanoparticle rather than the high thermal-conductivity-nanoparticle that plays a more effective role in the mitigation of the HTD phenomenon.