90% argon in the cavity

alice110 · Posts: 15

Hi,
I would like to know if there is the possibility to put a mixed gas in the cavity of a double glass,like 90% argon and 10% air. I know that it is possible to put specific values, but I can't find all the values that EnegyPlus require to me, like all the coefficient B for viscosity, for specific heat and for conductivity. Do you know if there is a database where I can find these values?
Thank you very much,
best regards,
alice

bhandari · Posts: 86

Alice,

You can use WINDOW 5 program, a freely available software ( windows.lbl.gov), to calculate the gas mixtures. For 90% Argon and 10% air mixture the properties are as follows:

Name Arg 90% - air 10%
ConductivityA 0.002873
ConductivityB 0.0000776
ViscosityA 0.000003723
ViscosityB 4.94E-08
CpA 1002.737
CpB 0.012324
MolecularWeight 28.97

regards,
Mahabir

Florent · Posts: 2

I think you may have made a mistake.
It is the same properties of pure air.

regards,
Florent

alice110 · Posts: 15

Hi,
thank'you! I'm trying to find these values in window 5 but there is just 1 value of viscosity, conductivity e cp. Where are the coefficient B?
Thank you very much for your prompt answer.
Best regards
alice

bhandari · Posts: 86

You are right, Florent. My apologies for not cross checking it. It looks like there is a glitch in reporting the coefficients for the mixtures in WINDOW5. I will clarify with LBNL and get back to you.
thanks
Mahabir
PS: Alice - You would need to open the mdb file in Access to see the coefficients.

alice110 · Posts: 15

ok thank you.
Please let me know the values that you find.
Best regard
Alice

alice110 · Posts: 15

I found the values:
conductivity A: 0,013
conductivity B: 0
Viscosity A: 0,0007214
Viscosity B: 0,00004928
CpA: 0,4186
CpB: 0
Molecular weight: 146,1

I didn't know about the possibility to open window5 with access..thank you!
alice

alice110 · Posts: 15

this values seems strange..dont'you?

bhandari · Posts: 86

Alice,
I would recommend not to use the values you listed. You would be better off using just pure Argon. It looks like W5 does not store the coefficients correctly in gas table. It does calculate the properties required for glazing system U factor calculation; only the reported coefficients in Gas table are not correct. The development team is looking into it.

Mahabir

Andy Tindale · Posts: 1165 Location: Stroud

These coefficients A, B, C make sense for perfect gases but they are not calculated for mixes. That is the reason these coefficients A, B and C for the mixture do not exist in WINDOW5/WINDOW6, one can only get (overall) conductivity, viscosity etc. for the mix at given temperature.

In a future version DesignBuilder will allow window gas mixes to be defined but in the meantime the only workaround I can suggest is to use the EnergyPlus Material:WindowGasMixture data type instead of Material:WindowGas

Andy

alice110 · Posts: 15

Dear Andy,
I would like to simulate the model just with Desgin Builder. I didn't want export the model in E+. So..you suggest to me to use pure argon in Design Builder? I tried to find the values that E+ uses for a mixed gas but I can't find theme..I would like to copy that values in Desgin Builder.
Thank's a lot, best regards.
alice

bhandari · Posts: 86

Alice,
As Andy mentioned earlier coefficients cannot be used for defining the gas mixture. E+ uses separate object (NOT the COEFFICIENTS) to define the gas mixture. DesignBuilder will introduce the new objects in near future. In the meantime I would recommend using Argon. It will not make a significant difference in overall energy results.
regards,
Mahabir

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