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Re: [EnergyPlus_Support] Windows & Convection

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Windows & Convection
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Wed, 30 Nov 2005 19:14:47 -0600
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1.  Yes and Yes.
2.  Yes there is sky radiation heat loss, but I am not sure if it accounts for 
cloud cover.  
I am surprised that you are seeing little impact.  To narrow down what is 
happening, I would suggest running some design days with all internal gains off 
and no sun to emphasize window conduction.  Also, check the reported nominal 
conductivity for the window constructions in the eio output file 
(report,construction;)

Mike


On 28 Nov 2005, at 23:52, Troy Harvey wrote:

> I?ve modeling different windows in a building (double, low-e,
> low-e/multipane/gas-fill), and have been surprised by how little the choice of
> window makes in the simulation. This has led me to wonder how these surfaces are
> modeled, here are my questions.
> 
> 
> 
> 1.	I believe that EnergyPlus calculates a air-surface convection
> heat-transfer as a faction of temperature, I?m wondering if this is true,
> and if it is factored in the window losses? Does it fully account for the
> outside-inside temp diff at the window? (as either lack could explain the
> problem)
> 2.	Does the sky model account for heat radiation to the night time sky?
> Does it account for cloud cover?
> 
> 
> 
> Troy Harvey
> 
> 
> 
> -----Original Message-----
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Michael J. Witte
> Sent: Monday, November 28, 2005 3:44 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] Set point not met
> 
> 
> 
> The sizing routines will size the reheat coils to be large enough to raise
> the 
> full flow rate from the cooling supply temperature to the heating supply 
> temperature.  For a system like this, the reheat coils will tend to be 
> significantly oversized and the entire hot water plant will also be
> oversized.  
> I would suggest lowering the design heating supply temperature in the zone
> sizing objects for zones that will not require heating.  
> 
> Mike
> 
> 
> On 24 Nov 2005, at 0:10, Emanuel Sá wrote:
> 
> > Hi
> > 
> > Thanks, that worked just fine!!
> > 
> > I have one other problem.
> > In this building that i'm simulating, there are high internal gains, so it
> > requires cooling all year. It also requires humidity control so I instaled
> a
> > terminal reheat coil and a boiler. In the design file (eio) says that the
> design
> > hot water flow is " Design Boiler Water Flow Rate [m3/s],  0.31956E-02"
> which is
> > 3.1956 kg/s aprox. however, in the spreadsheet I see that the demand
> bypass flow
> > is never less than 3.17 kg/s !!! so, I dont understand how this design
> flow rate
> > is possible! the gas consuming is almost equal to the chiller electric
> > consuming!! Am'I doing anything wrong?
> > 
> > Thank you very much!
> > 
> > 
> > ----- Original Message ----- 
> > From: "Michael J. Witte" <mjwitte@xxxxxxxx>
> > To: <EnergyPlus_Support@xxxxxxxxxxxxxxx>
> > Sent: Wednesday, November 23, 2005 9:26 PM
> > Subject: Re: [EnergyPlus_Support] Set point not met
> > 
> > 
> > > Yes, a properly autosized system should be able to meet the zone
> setpoints on
> > > the design days.  Things to check:
> > >
> > > 1.  If using coil:water:cooling, we have recently learned that it may
> not size
> > > properly if the design delta humidity ratio is less than 0.01.  Check
> the
> > > component sizing report for the cooling coil(s) in the eio output file.
> If the
> > > design entering minus leaving humidity ratio is smaller than 0.01,
> change to
> > > using the COIL:Water:DetailedFlatCooling
> > >
> > > 2.  Is the supply air temperature setpoint being met?  The design supply
> air
> > > temperatures in the sizing objects must match the setpoint controls in
> the
> > > simulation.
> > >
> > > 3.  Are the chillled water/hot water supply setpoints being met?  Again,
> the
> > > setpoint controls must match the specifications in the plant sizing
> objects.
> > >
> > > 4.  Also check availability schedules.
> > >
> > > Mike
> > >
> > >
> > > On 23 Nov 2005, at 5:07, dust_broom wrote:
> > >
> > >> Dear all.
> > >>
> > >> I've simulated a cooling system for a 4 zone bilding using a chiller a
> > >> boiler(for reheat), coils and a single duct . Every component was suposed
> > >> to be autosized. So I did the autosize. But than, in the results I saw that
> > >> only one of the four zones had its temperature correct. the others were
> > >> floating arround 6 degrees. Even in the design day simulation some zones
> > >> were too hot. shouldn't the design day be sizing those equipments in order
> > >> to maintain the zone temperatura as specified? Am I doing anything wrong?
> > >>
> > >> Thank you, Emanuel
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >> 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.idf and
> press the
> > >> "search" button.
> > >>
> > >> Yahoo! Groups Links
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
> > >
> > >
> > > ========================================================
> > > Michael J. Witte, GARD Analytics, Inc.
> > > EnergyPlus Testing and Support
> > > EnergyPlus-Support@xxxxxxxx
> > >
> > >
> > >
> > >
> > >
> > > 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.idf and
> press the
> > > "search" button.
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > 
> > 
> > 
> > 
> > 
> > 
> > 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.idf and press
> the
> > "search" button.
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@xxxxxxxx
> 
> 
> 
> 
> 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.idf and press
> the "search" button.
> 
> 
> 
> 
> 
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> 
> 
> 
> The primary EnergyPlus web site is found at:
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> 
> The group web site is:
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> 
> Attachments are not allowed -- please post any files to the appropriate folder
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> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press the
> "search" button.
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> 
> 



========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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References:
- Re: [EnergyPlus_Support] Set point not met
  - From: Michael J. Witte
- [EnergyPlus_Support] Windows & Convection
  - From: Troy Harvey

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