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Re: [EnergyPlus_Support] error in drawing file
I calculated them with the expressions below;
(Karava,P.,Stathopoulos,T.,Athienitis,A,K.,Wind-induced
natural ventilation analysis, Solar Energy 81
(2007)p-22)
Cd-inlet=Q/(A*V*(Cpw-Cpin)0.5=u/V*(Cpw-Cpin)0.5
Q=Airflow rate through the opening
A=Opening area
V=Reference wind speed at reference height
Cpw=Pressure Coefficient on windward facade
u=local velocity in the opening
Cpin=internal pressure coefficient, determined for a
building with two openings by;
Cpin=Cp2+(á2*Cp1)/1+ á2
large openings(windows,doors-turbulant flow)
Cp1=External pressure in front opening
Cp2=External pressure coefficient in back opening
á=A1/A2
A1=Inlet area
A2=Outlet area
For example one of my result is 1.512 for window with
no shading device in front of it;
Cp2 -0.716 Cp1 0.840 A1 0.048
A2 0.013 á 3.625 á2 13.141 á2*cp1 11.038 á2+1 14.141
Cpin=(Cp2+á2*Cp1)/(1+á2)(for large opening) 0.730
TOPLAM Q 0.056 A1 0.048
V 2.5 m/s cpw 0.827 Cpw-Cpin 0.097
(Cpw-Cpin)0.5 0.312 CDin=Q/A*V*(Cpw-Cpin)0.5 1.512
and on page 26 it says that for large opening
areas discharge coefficient values might be outside
the standard range of 0.6-1
Thank you very much for your help.
--- Lixing Gu <gu@xxxxxxxxxxxx> wrote:
> Neslihan:
>
> 2) Discharge coefficient
>
> The discharge coefficient is between 0 and 1. Could
> you let me know how you
> obtain the value above one? Do you have math and
> physics to support?
>
> 3- What is 'mass flow exponent when the opening is
> closed'?
> Here is definition extracted on page 633 from Input
> Output Reference:
>
> Field: Air Mass Flow Exponent When Opening Is Closed
> Crack flow is assumed when the window or door is
> closed. In this case, the
> value of this field is the exponent, n, in the crack
> air flow equation. The
> valid range for this exponent is 0.5 to 1.0, with
> the default value being
> 0.65.
>
> When the opening is closed, the model treats the
> opening equivalent to a
> crack. Air mass flow coefficient and flow exponent
> are used to calculate
> airflow across an opening: Mass flow rate = Air Mass
> Flow Coefficient *
> (dP)^Air Mass Flow Exponent.
>
> Thanks.
>
> Lixing
>
>
> ----- Original Message -----
> From: "neslihanturkmenoglu"
> <neslihanturkmenoglu@xxxxxxxxx>
> To: <EnergyPlus_Support@xxxxxxxxxxxxxxx>
> Sent: Tuesday, February 05, 2008 7:55 AM
> Subject: [EnergyPlus_Support] error in drawing file
>
>
> > Hi Lixing
> > I had uploaded my file on Feb 3,2008 for which I
> had questions, hoping
> > to be answered by you:)But I forgot to ask others.
> > My first other question is; why does ofis zone2
> floor and roof seem
> > larger in the drawing? My coordinates are true.
> >
> > 2- input /output reference book tells discharge
> coefficient values
> > must be between 0-1. In my example for front large
> opening I calculated
> > discharge coefficient values greater than 1. So
> how am I supposed to
> > enter my own values.
> > 3- What is 'mass flow exponent when the opening is
> closed'?
> >
> >
> > Thank you very very much.
> >
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are not allowed -- please post any
> files to the appropriate
> > folder in the Files area of the Support Web Site.
> >
> > EnergyPlus Documentation is searchable. Open
> EPlusMainMenu.pdf under the
> > Documentation link and press the "search" button.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
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