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Re: [EnergyPlus_Support] error in drawing file
Neslihan:
Discharge coefficient is defined as the ratio of the actual discharge of
water through an opening to its corresponding theoretical value
(http://www.answers.com/topic/discharge-coefficient?cat=technology) or the
ratio of actual flow rate to its ideal flow rate without flow resistance.
Therefore, the maximum value is 1.0 with ideal conditions. Please rethink
about physics.
Lixing
----- Original Message -----
From: "neslihan turkmenoglu" <neslihanturkmenoglu@xxxxxxxxx>
To: <EnergyPlus_Support@xxxxxxxxxxxxxxx>
Sent: Tuesday, February 05, 2008 3:45 PM
Subject: 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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