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[EnergyPlus_Support] Re: Precooling chilled water return



Thanks. I will try and keep you posted on that. 

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad 
<RRaustad@...> wrote:
>
> 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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