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[EnergyPlus_Support] Windows & Convection
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:
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