Re: [Fwd: [EnergyPlus_Support] Mass flow equation in AirflowNetwork]]

[Lixing Gu <gu@xxxxxxxxxxxx>]

Kyung-hun:

Sorry for the late response, because my E-mail folders were crashed two days 
ago.

There are two mistakes in object AirflowNetwork:Multizone:Surface Effective 
Leakage Area in the Input Output Reference on page 601. The first mistake 
occurs in the equation where the square root of air density is missed. The 
correction equation should be:

m = ELA*Cd*(2*Air Density)^0.5*(dPr)^(0.5-n)*(dP)^n.

The second mistake is the unit of effective leakage area (Field:Effective 
Leakage Area) on the next page. The correct unit should be m2, instead of 
m2/m2. The program uses m2.

You may find detailed description in the NIST publication on page 144:

Dols, W. S. and G. Walton, 2002, "CONTAMW 2.0 User Manual," NISTIR 6921

I am going to correct the mistakes in both Input Output Reference and 
Energy+.idd.

Please let me know if you have more questions.

Lixing Gu


>
> -------- Original Message --------
> Subject: [EnergyPlus_Support] Mass flow equation in AirflowNetwork
> Date: Tue, 16 May 2006 07:31:35 +0000
> From: kh_woo <kh_woo@xxxxxxxxxxx>
> Reply-To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
>
>
>
> Usually the units of Effective Leakage Area is cm2 in SI
> In EnergyPlus AirflowNetwork ELA means m2/m2, which is the ratio of the
> leakage area of the associated surface.
>
> Comparing with the equation in the ASHRAE HANDBOOK-Fundamentals 2005
> p27.13, there is no figure on the density of air.
> Is the equation correct?
> I could not find any explanations about this equation in the references.
>
> Please tell me how this equation made and why do EnergyPlus use the
> units of m2/m2.
>
> Thank you
>
>
> Kyung-hun
>
>
>
>
>
>
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