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[EnergyPlus_Support] Re: ZoneVentilation Volume Standard Density vary

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: ZoneVentilation Volume Standard Density vary
From: "rgen1202" <robin.genoud@xxxxxxxxx>
Date: Thu, 05 May 2011 12:53:26 -0000
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Thanks for the irony... This is only an example in order to understand how EnergyPlus calcul the Flow transfers!
       In my simulation I am studying a double flow ventilation system with a heat exchanger. I extract air at a constant rate (45 m3/h in total) from one zone and reinject the same amount of outside air in the second zone, after having warmed it with an heat exchanger and the extracted air. Of course, i assure the circulation of the same amount of air between mùy 2 zones.
In fact, i want to analyse the difference between this detailed model, and an approximation where I have no heat exchanger ad where I inject (1-heat exchanger efficiency)*45m3/h of 100% OUSIDE AIR!

So I don't think that my question is so stupid... The next step is the model of a 10 floor building, so I have to make sure of the differences between different models. And in fact, if there is a significative difference between the MassFlow from an AirLoop model and from the VentilationDesignFlow rate tool, this implies a difference in the heat loads! And the problem is the same regarding the infiltration rate!  

Regards.

Robin



--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
>
> 
> The  100% OA is usually only a small fraction of the building volume.  Why bother to calculate the heat balance  using the OA property.
> Unless you are modelling Tarzan's tree house (no walls) or a very small hut (small air volume)..
> 
>  Dr. Li   
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: robin.genoud@...
> Date: Thu, 5 May 2011 08:15:53 +0000
> Subject: [EnergyPlus_Support] Re: ZoneVentilation Volume Standard Density vary
> 
> 
> 
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>  
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>   
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>     
>       
>       
>       Lixing,
> 
> 
> 
> I think my last problrm comes from the Actuator Node of the OutdoorAir Mixer of my loop. In fact, I have an Outdoor Air Node for Actuator Node (called Outdoor Air Inlet Node). When I look at the features of this node (current density, temperature, pressure) they are the same as the oudoor air, which is what I want. But when I look at this Node MassFlowRate, I have a constant value and the flow seams to be calculated with a constant density of 1.1704 kg/m3. I don't understand why EE+ doesn't take the current outdoor air density to calcul the MassFlow. I have uploaded my file, called venti_ailloop_1zone.idf
> 
> 
> 
> Thanks in advance.
> 
> 
> 
> Robin 
> 
> 
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "rgen1202" <robin.genoud@> wrote:
> 
> >
> 
> > Lixing,
> 
> > 
> 
> > I am aware of this density calculation. But I am still surprized of the way EnergyPlus model the ventilation(and the infiltration too) because if I model the mechanical ventilation with an Air Loop containing one exhaust fan constant volume and a 100% OA mixer, I get a constant Mechanical Ventilation Volume Standard Density. Therefore, the MassFlowRate in this case isn't calculated with the outdoor air density but with the standard density and I don't understant why.
> 
> > 
> 
> > In fact, I am interested in the building energy consumption, and I don't know which model is the more accurate, since I have a significative difference in the cooling load due to outdoor air.
> 
> > 
> 
> > Robin 
> 
> > 
> 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@> wrote:
> 
> > >
> 
> > > Robin:
> 
> > > 
> 
> > > This is caused by air density calculations using different pressures,
> 
> > > temperature, and humidity ratio.
> 
> > > 
> 
> > > In the calculation subroutine, the mass flow rate is required in the
> 
> > > calculations and is equal to the volumetric flow rate from your input times
> 
> > > air density as a function of outdoor conditions (T, P, and W). In the report
> 
> > > subroutine, the volumetric flow is calculated using the mass flow rate
> 
> > > divided by the air density as a function of standard condition. The
> 
> > > different densities are used in calculation and reporting. That is why you
> 
> > > see minor differences shown in outputs.
> 
> > > 
> 
> > > Hope this helps.
> 
> > > 
> 
> > > Lixing
> 
> > > 
> 
> > > -----Original Message-----
> 
> > > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> > > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of rgen1202
> 
> > > Sent: Wednesday, May 04, 2011 3:17 PM
> 
> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> > > Subject: [EnergyPlus_Support] Re: ZoneVentilation Volume Standard Density
> 
> > > vary
> 
> > > 
> 
> > > Lixing,
> 
> > > 
> 
> > > Thanks for your answer. I uploaded the file in Files>Problem_Submittals 
> 
> > > http://tech.groups.yahoo.com/group/EnergyPlus_Support/files/_Problem_Submitt
> 
> > > als/. 
> 
> > > Its called ventilation_mech.idf . Its a single zone building with only
> 
> > > ZoneVentilationDesign Flow Rate. I used the FRA_LYON_IWEC.epw for the
> 
> > > weather (I uploaded it too). 
> 
> > > 
> 
> > > Thanks in advance.
> 
> > > 
> 
> > > Regards.
> 
> > > 
> 
> > > Robin
> 
> > > 
> 
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@> wrote:
> 
> > > >
> 
> > > > Robin:
> 
> > > > 
> 
> > > > If you report Zone Ventilation Volume Standard Density, it should give you
> 
> > > a
> 
> > > > constant value. Please upload the input file and tell us the weather file
> 
> > > > name if this weather file is downloaded from the energyplus web site. We
> 
> > > > will take a look.
> 
> > > > 
> 
> > > > Lixing
> 
> > > > 
> 
> > > > -----Original Message-----
> 
> > > > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> > > > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Lixing Gu
> 
> > > > Sent: Wednesday, May 04, 2011 1:29 PM
> 
> > > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> > > > Subject: RE: [EnergyPlus_Support] ZoneVentilation Volume Standard Density
> 
> > > > vary
> 
> > > > 
> 
> > > > Robin:
> 
> > > > 
> 
> > > > I think you may use one of two output variables to report volume flow
> 
> > > rates:
> 
> > > > 
> 
> > > > HVAC,Sum,Zone Ventilation Volume Flow Rate Current Density [m3/s]
> 
> > > > HVAC,Sum,Zone Ventilation Volume Flow Rate Standard Density [m3/s]
> 
> > > > 
> 
> > > > It was found as a bug to report volume flow rates and was fixed for the
> 
> > > next
> 
> > > > release. It is a report error and has no impact of simulation results.
> 
> > > > 
> 
> > > > Lixing  
> 
> > > > 
> 
> > > > -----Original Message-----
> 
> > > > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> > > > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of rgen1202
> 
> > > > Sent: Wednesday, May 04, 2011 11:56 AM
> 
> > > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> 
> > > > Subject: [EnergyPlus_Support] ZoneVentilation Volume Standard Density vary
> 
> > > > 
> 
> > > > Hello,
> 
> > > > 
> 
> > > > I have a question about the ZoneVentilation DesignFlowRate.When I set the
> 
> > > > Design Flow Rate to a constant value (assuming 0.086162 m3/s, for a single
> 
> > > > zone), I don't understand why the output variable Zone Ventilation Volume
> 
> > > > Standard Density (hourly) is varying. Can someone explain it? I have
> 
> > > checked
> 
> > > > the settings and I have all minimum and maximum temperature setted to
> 
> > > > default value (this mean no shutoff of ventilation) , the maximum wind
> 
> > > speed
> 
> > > > is 40 m/s (no shutoff) and only the constant term coeeficient is set to 1,
> 
> > > > the other are to 0. Of course, I have tested this setting for a single
> 
> > > zone,
> 
> > > > without any infiltration or other air system.
> 
> > > > 
> 
> > > > Thanks in advance.
> 
> > > > 
> 
> > > > Robin GENOUD
> 
> > > > 
> 
> > > > 
> 
> > > > 
> 
> > > > ------------------------------------
> 
> > > > 
> 
> > > > Primary EnergyPlus support is found at:
> 
> > > > http://energyplus.helpserve.com or send a message to
> 
> > > > energyplus-support@
> 
> > > > 
> 
> > > > The primary EnergyPlus web site is found at:
> 
> > > > http://www.energyplus.gov
> 
> > > > 
> 
> > > > The group web site is:
> 
> > > > http://groups.yahoo.com/group/EnergyPlus_Support/
> 
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> > > > 
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> > > > 
> 
> > > > 
> 
> > > > ------------------------------------
> 
> > > > 
> 
> > > > Primary EnergyPlus support is found at:
> 
> > > > http://energyplus.helpserve.com or send a message to
> 
> > > > energyplus-support@
> 
> > > > 
> 
> > > > The primary EnergyPlus web site is found at:
> 
> > > > http://www.energyplus.gov
> 
> > > > 
> 
> > > > The group web site is:
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> > > > http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> > > > 
> 
> > > > Attachments are currently allowed but be mindful that not everyone has a
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> > > > high speed connection.  Limit attachments to small files.
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> > > > 
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> > > > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
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> > > > Documentation link and press the "search" button.
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> > > > Yahoo! Groups Links
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> > > >
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> > > 
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> > > 
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> > > 
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> > > 
> 
> > > ------------------------------------
> 
> > > 
> 
> > > Primary EnergyPlus support is found at:
> 
> > > http://energyplus.helpserve.com or send a message to
> 
> > > energyplus-support@
> 
> > > 
> 
> > > The primary EnergyPlus web site is found at:
> 
> > > http://www.energyplus.gov
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> > > 
> 
> > > The group web site is:
> 
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
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> > > 
> 
> > > Attachments are currently allowed but be mindful that not everyone has a
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> > > high speed connection.  Limit attachments to small files.
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> > > 
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> > > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
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> > > Documentation link and press the "search" button.
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> > > Yahoo! Groups Links
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> > >
> 
> >
>




------------------------------------

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- RE: [EnergyPlus_Support] Re: ZoneVentilation Volume Standard Density vary
  - From: YuanLu Li

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