[EnergyPlus_Support] Re: Precooling chilled water return

["zhaicq98" <chaoqin.zhai@xxxxxxxxxxxxxxx>]

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, 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
> 
> UCF - From Promise to Prominence: Celebrating 40 Years
>




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