AbstractThis work presents a numerical analysis of conjugate heat transfer in an annular channel with turbulence models for supercritical CO2 (tube side) and Pb‐Bi (annular side) as working fluids to understand the impact of flow constraints and heat transfer. By using the Navier‐Stokes formulation and the energy equation clarifying concurrent flow buildup and conjugate heat transmittance in tubes, several turbulent Prandtl models were solved numerically. The turbulent Prandtl number Prt of Pb‐Bi was used to refine the consistency of the arithmetical simulation. By comparing Prt, temperature fluctuation, and heat flux density, it was concluded that the existing Prt model should be used with caution in the numerical calculation of liquid metals having low Pr. The heat transfer and flow phenomena at different Prt values are significantly different.