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Re: [EnergyPlus_Support] problems about vav simulation
My apologies for the delay in diagnosing the problem with this simulation. The
short answer is that the system is undersized, this causes the supply air
temperature to be above setpoint and the airflow to the zone increases to the
maximum in a failed attempt to meet the zone load.
Why is the system undersized?
1) The system airflow has been sized to exactly meet the design day load
(sizing factor = 1.0), but some of the days in the weather file are more
extreme than the design day.
2) There is a bug in the chilled water coil sizing in version 1.2.0 which is
causing the coil water flow rate to be undersized by approximately 20%. The
easiest solution is to raise the zone sizing factor to approximately 1.2. The
system should then operate as expected. (This bug has been fixed for the next
release, CR6350.)
Mike
On 22 Jul 2004, at 9:05, Xu H.T wrote:
> Dear,
>
> I have check as the following two suggestion. However, the results seem still
> unreasonable. For VAVsystems, it appears constant flowrate at fixed supply
> temperature. Please help me to inspect this problem.
>
> The simulated system is very simple: mixed air flow through a cooling coil and
> then suppied into room, using Hong Kong weather data file. I have uploaded the
> folder: single room vav simulation
>
> Thanks very much.
>
> Rgs,
> Xu
> ----- Original Message -----
> From: Michael J. Witte
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Sent: Monday, June 28, 2004 2:17 AM
> Subject: Re: [EnergyPlus_Support] one about vav system
>
>
> This behavior indicates the coil is not large enough. Suggestions:
>
> 1. Make sure the OA flow rate and the supply air temperatures in teh ZONE
> SIZING and SYSTEM SIZING objects are consistent with the simulation OA flow
> and temperature setpoints.
>
> 2. Use COIL:Water:DetailedFlatCooling, do not use COIL:Water:SimpleCooling.
>
> If this does not fix the problem, please upload the input file to the files
> area in the Yahoo group or e-mail zipped idf to energyplus-support@xxxxxxxx.
>
> Mike
>
>
> On 24 Jun 2004, at 16:24, Xu H.T wrote:
>
> > Like the following email.
> >
> > I do a simulation for VAV system. The design day is used for sizing of
> zone, > system and plant. I set the supply air temperature to 19C. I find
> with the > design day simulation, the supply air temperature isn't 19
> (20.5 actually) and > the air flowrate is constant. However, for the run
> period simulation, the > supply air temperature is actually 19 and the
> supply air flowrate is also > constant. Why? Any suggestion for this
> problem. Thanks. > > Xu > > ----- Original Message ----- > From:
> zhaicq98 > To: EnergyPlus_Support@xxxxxxxxxxxxxxx > Sent: Thursday,
> June 24, 2004 8:51 AM > Subject: [EnergyPlus_Support] questions about dx
> vav system > > > I have two questions here. > > First, I am
> simulating a VAV system with no terminal reheat. I > specify the supply
> air temperature to be 12.8oC in cooling season and > 35oC in heating
> season. According to results I got, it works well in > cooling season,
> trying to keep the indoor temperature under 23oC by > varing the supply
> air flow rate. While in winter, it keeps heating > the space to a high
> temperature. In heating season, the supply air > flow rate is always at
> its maximum value. I can not understand why > the supply air flow rate
> in heating season does not vary. > > Second question is about the
> iteration. I am using a multispeed DX > coil. The program terminates
> when simulating the system in May. There > is a fatal error which says
> the iteration limit is exceeded when > calculating the speed of the
> compressor. I have no idea how to > resolve the problem. > > I have
> uploaded the file named BOX4_VAV.idf to the files area. > > Thanks.
>
> ----- Original Message -----
> From: Michael J. Witte
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Sent: Wednesday, July 21, 2004 11:09 PM
> Subject: Re: [EnergyPlus_Support] Glare index
>
>
> My guess is that the coordinates or facing angle of the daylighting
> reference point in these zones is incorrect. Remember that daylighting
> reference points are always relative to the zone origin, even when World
> Coordinates have been specified. In the dxf drawing file, the daylighting
> reference points are drawn as a small red circle to help you verify the
> location. You may need to comment out all of the daylighting objects and
> then add them back one by one to make sure each reference point is within
> the appropriate zone. If you are unable to resolve this, please submit your
> input file.
>
> Mike
>
>
>
>
> On 8 Jul 2004, at 4:26, leeslwong wrote:
>
> > Hi,
> >
> > I've simulated the daylight performance of a residential block which >
> includes a kitchen, a living room, 2 bedrooms and a master bedroom. I >
> called out the annual glare index with hourly basis of each rooms. > The
> results show that there is no glare (means '0') in the kitchen, a > bedroom
> and a living room. What situations would have these results? > But there are
> glare index in other two rooms. Those five room have a > window facing with
> the same direction (east). As I know glare index > never reaches '0'.
> Anybody can tell me what's happening and how to > solve it? > > Thanks > >
> lee > > > > > 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. > > Yahoo! Groups Links > > > > > >
>
>
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@xxxxxxxx
>
>
>
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>
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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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>
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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