The present work focus on the study of the wall functions as a tool to capture the heat transfer rate in the near wall region. Various wall functions were tested such as: equilibrium wall function, enhanced wall function, scalable wall function and standard wall function. A vertical pipe case was tested and investigated thoroughly to ascertain the applicability of each wall function, the governing equations were solved with boundary conditions, finite volume method was used to solve the continuity equation, momentum equation and the energy equation. It was found that enhanced wall function showed a better behavior for capturing the heat performance in the vicinity of the wall.