Investigation of heat transfer characteristics of nanofluid ice slurry flowing in spiral bellows

This paper employs a computational fluid dynamics numerical framework integrating the Euler-Euler two-fluid model with the particle dynamics method to analyze the heat and mass transfer characteristics of water-based graphene nanofluid slurries in helical corrugated tubes. The results indicate that, with ice crystal content ranging from 10% to 30% at the inlet, the heat transfer performance is positively correlated with the slurry concentration, and the increase in nanofluid concentration has minimal impact on the pressure drop inside the tube. The helical structure results in the maximum flow velocity occurring in the groove area. Compared to straight tubes, the increase in heat transfer area does not only promote the generation of vortices but also enhances turbulent intensity, reduces the thickness of the thermal boundary layer, and improves heat transfer efficiency. Graphene nanofluid slurries exhibit superior heat transfer capability compared to pure water slurries, with surface heat transfer coefficient increasing with graphene concentration. The maximum HTC of helical corrugated tubes is 1.4 times that of straight tubes, with an average Nusselt number (Nu) 1.44 times higher than that of straight tubes. Lastly, an empirical correlation for Nu is established to predict the thermal performance of water-based graphene nanofluid slurries flowing through helical corrugated tubes.