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Re: [EnergyPlus_Support] ideal cooling + constVolSystem
I think I see the problem now. At the zone level EnergyPlus tries to balance
airflows. The airflow on the return air node is equal to the sum of inlet
flows less exhaust node flows. Because Purchased Air only places flow on an
inlet node, the zone air balance does not see a corresponding flow at an
exhaust node. This is causing a flow at the return node that does not balance
with the rest of the air loop. So, it appears that you cannot combine
Purchased Air with an air loop serving the same zone.
I will ask the air loop expert if there is a way to make this work, but I
suspect you will need to use a piece of zone equipment (fan coil, window ac,
ptac) to provide cooling.
Mike
On 22 Jun 2007 at 17:31, Sebastian Dietz wrote:
> Dear Mike,
>
> the max iteration errors occur only if I run the simulation with air
> loop system in combination with the purchased air object. When I turn
> off the purchased air the System runs fine. So it seems, that the
> problem is the use of both. I chanced your suggestions, but the max
> iteration errors are sitll the same.
>
> best regards
> sebastian
>
> Michael J. Witte schrieb:
> > I tried turning off the air loop system and the max iteration errors went
> > away.
> > So the problem is in that part of the simulation.
> >
> > I see that most (or all) of the air loop components are autosized, and all but
> > one of the DIRECT AIR units has a hard number for flow rate (not autosized).
> > The autosizing algorithm will not see the flow rates in the DIRECT AIR
> > objects.
> > If you want to force a certain flow rate for a terminal unit, you must enter
> > this in the ZONE SIZING object. In the ZONE SIZING objects, add these fields:
> >
> > ZONE SIZING,
> >
> > flow/zone, !- cooling design air flow method
> > 0.7, !- cooling design air flow rate {m3/s}
> >
> > For each zone, specify the desired flow rate here. This should result in an
> > air loop where all the flow rates are consistent and it should get rid of the
> > max iteration errors.
> >
> > Mike
> >
> >
> > On 20 Jun 2007 at 10:28, Sebastian Dietz wrote:
> >
> >
> >> Hello Mike,
> >> please disregard my last mail.
> >> The iteration warnings still appear. I changed the priorities in the
> >> ZONE EQUIPMENT LIST Objects, but it didn´t solve the Problem.
> >> Furthermore I increased the number of maximum iterations with no result. It
> >> would be nice, if you have another suggestion. I spent a lot of time on that
> >> problem and I`m stuck.
> >>
> >> thanks in advance
> >> sebastian
> >>
> >> Michael J. Witte schrieb:
> >>
> >>> In the ZONE EQUIPMENT LIST objects the "priority" is the order in which the
> >>> equipment is simulated. Because the impact of the outside air can change
> >>> the net heating or cooling load required, it should always be simualted
> >>> first. So, change the heating and cooling priority for the DIRECT AIR units
> >>> to be 1, and adjust the other equipment prioirities accordingly. This
> >>> should solve the problem.
> >>>
> >>> Mike
> >>>
> >>>
> >>> On 19 Jun 2007 at 10:08, Sebastian Dietz wrote:
> >>>
> >>>
> >>>
> >>>> Hello everybody
> >>>>
> >>>> currently I'm modelling a building with 10 zones. Each zone gets heated by
> >>>> a basebord and is served with outside air by a constant volume System. Up
> >>>> to here the system runs quite good. Now I want to model a ideal cooling
> >>>> System to limit the maximal indoor temperature. Thus I used the Object
> >>>> "PurchasedAir", in order to provide cool air for each Zone. But I get
> >>>> miximum iterations Warnings for each timestep. I changed the values for
> >>>> tolerances with no effect. Does anybody know, how to solve the problem, or
> >>>> is there another easy way to model an ideal cooling system. For more
> >>>> information I uploaded my "Typgebaeude.idf" file
> >>>>
> >>>> Thanks in advance
> >>>> Sebastian
> >>>>
> >>>> --
> >>>> Sebastian Dietz
> >>>> Fraunhofer-Institut for Solare Energiesysteme ISE
> >>>> Heidenhofstrasse 2, 79110 Freiburg, Germany
> >>>> Phone: +49 (0) 7 61/ 45 88-51 36
> >>>> Sebastian.Dietz@xxxxxxxxxxxxxxxxx
> >>>> http://www.ise.fraunhofer.de
> >>>> -------------------------------------------
> >>>>
> >>>>
> >>>>
> >>>> 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
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>> ========================================================
> >>> Michael J. Witte, GARD Analytics, Inc.
> >>> EnergyPlus Testing and Support
> >>> EnergyPlus-Support@xxxxxxxx
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >> --
> >> Sebastian Dietz
> >> Fraunhofer-Institut for Solare Energiesysteme ISE
> >> Heidenhofstrasse 2, 79110 Freiburg, Germany
> >> Phone: +49 (0) 7 61/ 45 88-51 36
> >> Sebastian.Dietz@xxxxxxxxxxxxxxxxx
> >> http://www.ise.fraunhofer.de
> >> -------------------------------------------
> >>
> >>
> >>
> >> 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
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support
> > EnergyPlus-Support@xxxxxxxx
> >
> >
> >
> >
> >
>
>
> --
> Sebastian Dietz
> Fraunhofer-Institut for Solare Energiesysteme ISE
> Heidenhofstrasse 2, 79110 Freiburg, Germany
> Phone: +49 (0) 7 61/ 45 88-51 36
> Sebastian.Dietz@xxxxxxxxxxxxxxxxx
> http://www.ise.fraunhofer.de
> -------------------------------------------
>
>
>
> 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
>
>
>
>
>
========================================================
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.pdf under the Documentation link and press the "search" button.
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