problem with cfx expressions
 

personnel must enter the equation in the cfx expressions:

Q = stefan*0.7139*(((1114.15^4)[K^4] ) - (Ts^4)[K^4] ) The Stefan-Boltzmann Law

This term is used to heat the pipe, Ts is the surface temperature of geometry in my case is a pipe, the question is how should I call Ts in the expressions cfx??

If you are applying this to a surface then simply use T. That is the local surface temperature.

are you sure? I thought the variable T is the temperature at each node of the mesh, not only the surface ...

It might be in this case, good point. If the small difference is important to you then I would do a quick check case to test exactly how this is done.

I found this explication in manual cfx:

This is the hybrid temperature field at a wall boundary condition. For Fixed Temperature walls, the wall temperature is the specified value Tw. For all other heat transfer boundary conditions, the wall temperature is backed out from turbulent wall functions when running a turbulent flow model. For laminar flow modelling the wall temperature is just the local fluid temperature at the vertex adjacent to the wall.