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Re: [EnergyPlus_Support] Re: Precooling chilled water return



I thought you wanted them in series, I see now you were asking about a 
bypass around the smaller chiller. I can't say for sure if that will 
work correctly. You will just have to try it and see. I think you need 
the same number of splitters and mixers, so put a splitter at the inlet 
(return) of the small chiller and a mixer at the outlet (supply) of the 
small chiller and connect with a bypass pipe. Let us know if this works 
correctly.

zhaicq98 wrote:
>
> Thanks Richard. I donot quite understand when you said both chillers
> will operate at the same evaporator volumeric flowrate. Can I bypass
> some of the chilled water flow around the small chiller? In this
> way, the big chiller can have a higher flow and the small chiller
> has a lower flow.
>
> Thanks again,
> Chaoqin
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> <RRaustad@...> wrote:
> >
> > This should work in E+. You would need to use constant flow
> chillers and
> > the chillers should not be auto-sized (or at least the smaller
> one). The
> > only problem I see is that you can not have a significant
> difference in
> > the capacities of the series chillers. The reason is that both
> chillers
> > will operate at the same evaporator volumetric flow rate (and the
> > performance curves should account for off-design flow rates).
> There is
> > an upper (and lower) limit to the water velocities through a
> chiller's
> > heat exchanger. Above the upper limit, erosion of heat exchanger
> will be
> > excessive (and so will the pressure drop). Below the lower limit
> there
> > is a chance of freezing the heat exchanger or reducing oil
> transport
> > through the refrigeration system. Of course this will not hurt the
> > simulation, but you want to be as close to reality as possible.
> And if
> > you actually built a chiller with an over-sized heat exchanger,
> you
> > would not have this problem. Check with manufacturers for
> appropriate
> > ranges of water flow rates through the evaporators for your type
> of
> > chiller. The same holds true for the condenser heat exchangers,
> but you
> > could pipe the condensers in parallel.
> >
> > zhaicq98 wrote:
> > >
> > > I have a big and a small water cooled vapor compression chiller
> in the
> > > system. They are configured in series, but the chilled water
> flowrate
> > > of the
> > > big chiller is much greater than the small one. The small
> chiller is
> > > used to
> > > pre-cool a portion of the chilled water return to the big
> chiller.
> > >
> > > I wonder if EnergyPlus is able to handle this system. Thanks for
> your
> > > help.
> > >
> > > -Chaoqin
> > >
> > >
> >
> > --
> > 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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