“The low thermal conductivity and high viscosity of FLiBe make it a high Prandtl number medium – meaning heat transport from a heated wall into the core of the coolant flow is dominated by turbulent motion rather than thermal diffusion. Near wall flow structures are especially important because thermal boundary layer is much thinner than the momentum boundary layer. In the case where the thermal boundary layer lies within the viscous sub-layer, the heat transfer through the wall decreases considerably. This makes the investigation of the fluid mechanics and heat transfer of high Prandtl number fluid compared to low Prandtl number fluid very important from the design point of view in order to assess the applicability of FLiBe to high heat flux removal system as well as the prospect for heat transfer enhancement mechanisms.” Takeuchi et al.