I'm running a case of bouyancy driven flow in a box-test geometry; I've got an upper "pressure outlet" surface and a lower "pressure inlet" surface. Lateral surface are "symmetry" type but in the middle, on one hand, there's a "wall" type surface at 293.15 K. I'm running with only air as compressible ideal gas. The bulk temperature, as the inlet and outlet temperature, is fixed at 373.15K. Operating pressure is 2 bar. Viscosity model is RNG K-e. Is it necessary to use an Enanched Wall Treatment option to take into account correctly the effect of buoyancy near the cooled wall or it's possible to use Standard Wall Function?

You can use standard wall functions provided you check your y+ values.