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Re: [EnergyPlus_Support] Re: Condenser Water Plant - 4 Two-Speed Cooling Towers Parallel+Headered Pumps
The plant loops and condenser loop are treated differently in 2
different modules in EnergyPlus. So you may be correct that the headered
pumps do not work for a condenser loop ( I thought those pump objects
were interchangable). The plant loop developers are currently combining
the condenser and plant loop code which should take care of this issue.
I have cc'd one of the plant loop developers to see if there is any
other information you should know about.
berlinclownfish wrote:
>
>
> Dear Richard,
>
> Thank you very much for your immediate response.
>
> I have tried once more to model a headered pump object in lieu of a
> variable speed pump in my condenser loop. I have also verified that it
> is the very first object in the condenser loop ("Supply Inlet Branch")
> and received the proper node declaration. Unfortunately and once more
> the simulation terminated with a fatal error:
> ** Fatal ** SimCondEquip: Invalid Equipment type
> requested=HEADEREDPUMPS:CONSTANTSPEED
> ...Summary of Errors that led to program termination:
> ..... Reference severe error count=0
> ..... Last severe error=
>
> I don't think headered pumps can be currently modeled in a condenser
> loop, opposed to a chilled water loop (which works really well).
>
> I have studied the example file "HeaderedPumpsConSpeed.idf" that
> specifically describes how to model a headered pump object in a
> chilled water loop but unfortunately does not advise on modeling a
> headered pump in a condenser loop. Are there any other files in this
> specific regard I should pay attention to and what are their dedicated
> filenames?
>
> The engineering reference still states, that a pump object can only be
> modeled on the supply side of a condenser loop (opposed to plant loop).
>
> In regards to the issue of evenly diverting flow into all of the four
> parallel arranged cooling towers. My first attempt considered all of
> the four cooling towers with a description of their nominal capacity,
> hence it is not possible to enter a design water flow rate. I would
> very much like to retry once more and follow your suggestion and
> describe the cooling tower's capacity with
> "UFactorTimeAreaAndDesignWaterFlowrate" and have to rely on my best
> judgement when entering the remaining fields (U Factor...etc).
>
> Thank you Richard,
>
> Sandro
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> <RRaustad@...> wrote:
> >
> > Well actually the pump can now be on the demand or supply side of the
> > loop. Just make sure it's the first object. It is usually listed on the
> > inlet branch (either Plantloop or Condenserloop). Looking at some of
> the
> > water cooled example files may help. You can also read the description
> > for "Pumps" in the Engineering Reference.
> >
> > Richard Raustad wrote:
> > >
> > >
> > > Sorry, the pump must be on the plant supply side. Check the first
> > > "supply" branch (see Plantloop object) and make sure the pump is
> listed
> > > on that branch.
> > >
> > > Richard Raustad wrote:
> > > >
> > > >
> > > > Your first attempt delivers a warning that tells you that the
> pump must
> > > > be the first object at the inlet of the plant loop. Check the demand
> > > > side branchlist and make sure the pump is defined on that branch.
> > > >
> > > > Your alternative of modeling 4 cooling towers in parallel may be
> running
> > > > into the fact that the cooling towers are passive devices and
> can handle
> > > > up to 2.5 times the nominal or design flow rate. You might try
> reducing
> > > > the water flow rate through each tower (by a factor of 2.5) and
> see if
> > > > that gets you the performance you are looking for.
> > > >
> > > > berlinclownfish wrote:
> > > > >
> > > > >
> > > > > Dear EnergyPlus-Support,
> > > > >
> > > > > I'd like to model a typical Condenser Water Plant consisting
> of four
> > > > > Two-Speed Cooling towers in a parallel arrangement and fed by a
> > > > > headered constant speed pump.
> > > > >
> > > > > First attempts to incorporate a headered pump object instead of a
> > > > > common single and constant speed condenser water pump (reflecting
> > > > > total volume flow rate) ended in a fatal error with the following
> > > > > message:"The following pump is not the first component on its
> > > > > loop/branch: TOWERWATERSYS1 PUMP". Did I overlook anything,
> possibly a
> > > > > mistake in node connections and declarations?
> > > > >
> > > > > As an alternative, I have modeled a single variable speed pump
> in an
> > > > > attempt to reflect a variable volume flow condenser loop
> depending on
> > > > > the demand by a set of 4 parallel Two-Speed Cooling towers.
> > > > > However, I was unable to divert any flow into 3 of the 4 cooling
> > > > > towers, irregardless of the amount of trial combinations in
> creating
> > > > > various operation schemes and branch control types. Did I possibly
> > > > > miss a "smart" combination.
> > > > >
> > > > > It turned out, that the very first cooling tower in the
> arrangement
> > > > > requested/received the entire amount of flow available from the
> > > > > variable speed pump. Replacing the condenser pump in this
> arrangement
> > > > > with a headered pump or constant speed pump was unsuccessful.
> By the
> > > > > way, a headered pump works extremely well for the staged
> arrangement
> > > > > of 4 parallel centrifugal chillers, supplying appropriate
> amounts of
> > > > > chilled water in a staged fashion.
> > > > >
> > > > > As another alternative, I attempted to model branch pumps for each
> > > > > cooling tower, which also did not end very well.
> > > > >
> > > > > I am well aware of simplification methods when modeling, but would
> > > > > like to reflect upon the free convection regime on all of the four
> > > > > cooling towers as realistic as possible and furthermore
> evaluate the
> > > > > option of replacing a single or two out of the four cooling
> towers by
> > > > > upgrading it to a variable speed tower, hence the effort.
> > > > >
> > > > > EnergyPlus-Users, did anyone come across this challenge and
> succeeded?
> > > > > Submitting a working reference example file would be outmost
> generous
> > > > > and I would be very thankful!
> > > > >
> > > > > Thank you,
> > > > >
> > > > > Sandro
> > > > >
> > > > >
> > > >
> > > > --
> > > > Richard A. Raustad
> > > > Senior Research Engineer
> > > > Florida Solar Energy Center
> > > > University of Central Florida
> > > > 1679 Clearlake Road
> > > > Cocoa, FL 32922-5703
> > > > Phone: (321) 638-1454
> > > > Fax: (321) 638-1439 or 1010
> > > > Visit our web site at: http://www.fsec.ucf.edu
> <http://www.fsec.ucf.edu>
> > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>
> <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>
> > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>>
> > > >
> > > > UCF - From Promise to Prominence: Celebrating 40 Years
> > > >
> > > >
> > >
> > > --
> > > Richard A. Raustad
> > > Senior Research Engineer
> > > Florida Solar Energy Center
> > > University of Central Florida
> > > 1679 Clearlake Road
> > > Cocoa, FL 32922-5703
> > > Phone: (321) 638-1454
> > > Fax: (321) 638-1439 or 1010
> > > Visit our web site at: http://www.fsec.ucf.edu
> <http://www.fsec.ucf.edu> <http://www.fsec.ucf.edu
> <http://www.fsec.ucf.edu>>
> > >
> > > UCF - From Promise to Prominence: Celebrating 40 Years
> > >
> > >
> >
> > --
> > Richard A. Raustad
> > Senior Research Engineer
> > Florida Solar Energy Center
> > University of Central Florida
> > 1679 Clearlake Road
> > Cocoa, FL 32922-5703
> > Phone: (321) 638-1454
> > Fax: (321) 638-1439 or 1010
> > Visit our web site at: http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>
> >
> > UCF - From Promise to Prominence: Celebrating 40 Years
> >
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
UCF - From Promise to Prominence: Celebrating 40 Years
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