[RageofaMonkey]

Hey guys,

Iam a CFD newbie and trying to simulate a sun collector with thermotropic glazing (changes optical properties when certain temperature is reached) and I can't figure out how to code it properly in the User Code without getting an error during the simulation.

So far I coded two User functions that should change the surface emissivity and surface transmissivity when a temperature of 55 °C is reached on the glazing. There for the cell temperature is passed to the function as an argument and the emissivity/transmissivity is returned as a result.

The surface reflectivity isn't changed and has a constant value of 0.1.

The code for the surface transmissivity is
.

and for the surface emissivity is
.

I registered both functions as
.

When I start the simulation an error pops up after 20 Iterations: Check that optical properties sum up to one at boundary [the names of the glazing boundarys] and the simulations stops. On paper the values of the transmissivity, emissivity and reflections sum up to one, but I still get this error and can't figure out why and how to solve it.

I hope someone can help me

Thank advanced!