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Re: [EnergyPlus_Support] Chiller:Electric:EIR problem
wing sun lee <samwslee@xxxxxxxxxxxx> wrote: Hi,
1a. I have already double checked the chilled water supply temperature exactly the same between these two runs.
1b. The chilled flow rates are identical in these two runs.
However, the values of plant loop cooling demand of these two runs is still not identical.
3. I don't know which part of input idf file resulted in low COP in Chiller:Electric:EIR.
Encl. MWGO 050303e`.idf and MWGO 050303 6`(whole year).idf are attached in yahoo EnergyPlus Group/File/Input Problem/....
Regards,
SAMLEE
"Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
1. It is important to understand the meaning of "Plant Loop Cooling Demand".
It represents the energy required to bring the current return water temperature
to the plant loop setpoint. If the chiller(s) fail to meet the load and the
supply water temperature is warmer than the set point, the unmet demand will
carry over to the next time step and be included in the next value of "Plant
Loop Cooling Demand". So, if the two chillers maintain the same chilled water
supply temperatures, then, yes, the demand should be identical. So, my guess
is that the chilled water supply temperature is different between these two
runs.
2. It is difficult to answer your question, because the files have differences
other than the chillers. Please make two files which are completely identical
except for the chillers. Then compare the chiller performance. Check the
following:
2a. If the chilled water loop supply temperatures and flow rates are not
identical in the two runs, then the chillers are not providing the same
capacity. Check the capacity-related performance inputs.
2b. If the COP is too low, then there is something wrong with the performance
inputs.
2c. Also, one type of chiller is set to VariableFlow and the other is
ConstantFlow. These should both be the same for a valid comparison.
Mike
On 9 Mar 2005, at 21:40, wing sun lee wrote:
> There are two idf files. The different between these files is one using
> Chiller:electric while the other using
> Chiller:electric:eir .
>
> After simulation, as compare with the results of these idf files I found that
> the values of Plant Loop Cooling Demand have greatly different. I don't know
> why? Moreover, it is impossible that the result shown the COP in
> Chiller:electric:eir file are less than 1 (unrealistic!!).
>
> As I learned from university, the cooling capacity demand of chiller plant
> system is determined by the sensible load and latent load not the type of the
> chiller being used.
========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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