Heat transfer between the working fluid and the cylinder wall in an engine can significantly affect engine performance, efficiency and emissions. The heat flux through the chamber walls is mainly due to gas-phase convection, fuel-film conduction and radiation. Under typical engine operating conditions, gas-phase convective heat transfer is the dominant factor [32]. At rigid walls, boundary conditions must be specified or assumed for each of the gas-phase governing equations. Typically, the boundary layer of an engine in-cylinder flow is thin relative to the practical computational grid size. For this reason, velocity and temperature wall functions are often employed to solve for the near-wall shear stress and heat transfer.