added media for dry air

[Mathadon]

this is for #4
@dhblum care to have a look at this?

[dhblum]

Yes I'll take a look.

[dhblum]

Thanks for this.

Why are both T0 and reference_T defined and not equal? In BuildingMpc.Media.PartialSimpleMedium there is the line constant Temperature T0=reference_T "Zero enthalpy temperature";.

Also, the cp and cv values seem a bit high if assuming gas as ideal and at 20 C (cp = 1005, cv = 718).

[Mathadon]

Good point. I'm not sure where I got the high cv from. Probably I miscalculated it from cp.

I don't think the two different temperatures make any difference, but I'll change it just to be sure.

[dhblum]

@Mathadon When I use this model with the most recent IBPSA master, I get the following error upon compilation in JModelica. I don't get this error with IBPSA v2.0.0.

Error at line 15, column 40, in file '/home/dhb-lx/git/ibpsa/modelica-ibpsa/IBPSA/Fluid/Interfaces/PartialTwoPort.mo':
  The attribute nominal for the variable h_outflow is set to Medium.h_default, evaluating to 0.0. A nominal value of zero is not meaningful. Please set the nominal value to the expected magnitude of the variable.

[Mathadon]

@dhblum that makes sense since the last changes in the IBPSA library. Medium.h_default is computed with respect to some reference reference_T. If T0 = reference_T then h_default=0 and such a nominal value is indeed not meaningful. A fix would be to set T0=reference_T+10 or something like that.

[dhblum]

Ok thanks this worked.