[TRNSYS-users] TYPE 666 Chiller Queries

[Jeff Thornton]

I would run a simulation with just the chiller in it and vary one
factor at a time to make sure the chiller is behaving as expected. If I
was a betting man, I would say that the part load impacts are what are
driving your COP swings. As the ECWT decreases, the capacity of the
machine increases and for a given load, the part-load ratio decreases.
If you have a rather part-load curve on the chiller it would explain
what you are seeing. 

Jeff 

---

Jeff Thornton 

_President - TESS
LLC_ 

_22 N. Carroll Street, Madison WI USA 53703_ 

_Office: (608)
274-2577 Fax: (608) 278-1475_ 

_www.tess-inc.com_ 

_E-Mail:
thornton at tess-inc.com_ 

On 03/27/2013 2:29 am, #YEO KEAT KEE# wrote:


> Hi Jeff, 
> 
> You are definitely right that there are spikes in the
power plot that complements the spike in the COP. 
> 
> Using the same
performance map, and running at known conditions, the model is actually
predicting the expected results. 
> 
> The problem arises when I try to
run the chiller at part load, in this case, the chiller is actually
running at half of its capacity. 
> 
> The spikes observed were not
present when the chiller was made to run at its full capacity. 
> 
> I
would like to expand the discussion by bringing in the Entering
Condenser Water Temperature (ECWT) VS the COP. 
> 
> According to the
default chiller performance map, as the ECWT is lowered, the COP ratio
of the Chiller will increase, all other parameters kept constant. 
> 
>
In the attached file, the first picture COP VS ECWT ,shows the reverse
instead, when the ECWT Is lowered, the COP of the Chiller decreases. 
>

> In the second picture, when I ramp down the fan speed of the cooling
tower further, and hence increasing the ECWT, the COP of the chiller
stabilized. 
> 
> Does anyone knows why is such relationship being
observed ? Or is there be a fundamental mistake in my understanding of
the program ? 
> 
> Best Regards, 
> 
> Yeo 
> 
> FROM:
trnsys-users-bounces at cae.wisc.edu
[mailto:trnsys-users-bounces at cae.wisc.edu] ON BEHALF OF Jeff Thornton
>
SENT: Wednesday, 27 March, 2013 11:58 AM
> TO: TRNSYS users mailing list
at the Solar Energy Lab, UW-Madison
> SUBJECT: Re: [TRNSYS-users] TYPE
666 Chiller Queries 
> 
> Well if you look carefully at your plots,
power is not "almost constant". Change the scale of the power plot and
you'll see the spikes that you are observing in your COP. Have you
spot-checked your performance map by running the chiller at "known
conditions" and seeing that you're getting out of your model what you
are expecting? 
> 
> Jeff 
> 
> ---
> 
> Jeff Thornton 
> 
> _President
- TESS LLC_ 
> 
> _22 N. Carroll Street, Madison WI USA 53703_ 
> 
>
_Office: (608) 274-2577 Fax: (608) 278-1475_ 
> 
> _www.tess-inc.com
[1]_ 
> 
> _E-Mail: thornton at tess-inc.com [2]_ 
> 
> On 03/26/2013 10:44
pm, #YEO KEAT KEE# wrote: 
> 
>> Dear Fellow Trnsys Users, 
>> 
>> I am
running a parametric study using the TYPE 666 Chiller and I have some
unexplainable observations with regards to the Chiller COP. 
>> 
>> It
seems that the chiller COP has a lot of unexplainable spikes and
fluctuations throughout the simulated year. 
>> 
>> This is observed
despite 
>> 
>> 1. An almost constant part load ratio (load) handled by
the chiller. 
>> 
>> 2. Entering Condenser Water Temperature to the
chiller remains almost constant, with little fluctuations. 
>> 
>> 3.
Power consumed by the chiller remaining almost constant. 
>> 
>> I
understand that in TRNSYS, COP=Qmet/P, if both the Qmet and P are
relatively constant, what could be causing the spike observed in the COP
? 
>> 
>> I have attached some screen shots from the results of my
simulation. 
>> 
>> Has anyone encountered the same situation before ?
Or any advice on why this is happening ? 
>> 
>> Best Regards, 
>> 
>>
Yeo
 

Links:
------
[1] http://www.tess-inc.com
[2]
mailto:thornton at tess-inc.com
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