Large Eddy Simulations are performed in a T-junction to analyze the feasibility of wall-functions in accurately predicting the thermal fluctuations acting on the pipe walls. The WALE sub-grid-scale model employed in the LES solver is validated by performing OECD/NEA T-Junction benchmark test-case. In order to reduce the computational costs, Reynolds number scaling is performed while preserving the essential flow features. While the wall-function based simulation showed good agreement with the wall-resolved approach for the bulk velocity and temperature field, the corresponding RMS components were consistently under-estimated close to the wall boundaries. The same was true for the RMS fluctuations of the wall heat-flux. As a consequence, it is concluded that any similarity in the bulk profiles does not guarantee any kind of similarity in the wall heat flux behavior.