[Felggv]

Hi everyone,

Recently I've developed a preliminar model to simulate air conditioning.

In my model, we calculate the absolute humidity on the insuflation nozzle of the air conditioner by giving the abs humidity on the entrance of the air conditioner, temperature at the entrance and by making some assumptions.

Using this on CFX is giving me some solver errors because I set the abs humidity at the entrance of the air conditioner as the Mass Fraction at the Outlet of the room (the one that returns to the AC) by defining an expression that is ave(Water Vapour at 25 C.Mass Fraction)@Outlet since my fluid is Air + Water Vapour. I've also tried the @Default Domain location so CFX could read an initial value from Initialization at my Default Domain.

Since the abs humidity on the insuflation nozzle depends on the one from the entrance and the temperature at it depends on the abs humidity of the insuflation nozzle seems like the software can't get the initial input at the entrance and crashes saying:

Error processing expression 'Static Temperature'.
The expression is invalid because:
Mass Fraction is not available for use in this term

Error processing expression: Static Temperature = Ts

Just for you to know, Ts is my expression for the Temperature at the insuflation nozzle set on Inlet Boundary condition and as I said, it depends on the abs humidity at the insufl nozzle. The expression is: Ts = (15.66*ln(1000*ws)-21.70) [C] and again, ws depends on the abs humidity at the entrance (we) that seems to be unavaliable or cannot be read.

I'm wondering how can I make CFX read the Water Vapour Mass Fraction on each iteration and do all the calculations because from what I understood, Ts cannot be calculated because the entrance properties cannot be obtained.

My settings are: Air Ideal Gas (Constraint) and Water Vapour 25 C (Transport Equation) with the Water Vapour mass fraction at t=0 set to 0.

Thanks in advance and sorry for the long text.

Felipe.