[TRNSYS-users] Type 666 Chiller Queries

Fri Feb 15 09:11:17 PST 2013

Dear Yeo,
   Jean's responses are all quite accurate. I wanted to add a little bit 
to the discussion in the hopes that it might make your life a little 
easier. Some years ago, we participated in a research project in which 
we were looking at whether the performance of certain pieces of HVAC 
equipment can effectively be normalized. In other words you look at the 
COP and capacity of a device at a particular combination of inlet 
conditions and then divide the COP and the capacity by the rated COP and 
capacity for the device. Then you plot the normalized performance over 
the entire operation range of the equipment and you do the same for the 
same piece of equipment from other manufacturers and of other rated 
capacities. It turns out that some kinds of equipment (particularly 
single stage heat pumps and both air and water cooled chillers) 
normalize very well meaning that their normalized performance curves all 
look about the same. Unloading (part load ratio) curves can look a bit 
different but they begin to look similar again if you first sort them by 
compressor type (screw, rotary, etc.). Other pieces of equipment do not 
look the same at all if you normalize them (absorption chillers are a 
good example).

   The lesson in all this is that if you have a specific chiller, it is 
best to get the manufacturer's data for that chiller and to create a 
data file from it. If, however, you just need a generic chiller, you can 
use the default performance curves in the \Trnsys17\Tess 
Models\SampleCatalogData\ directory and set the rated capacity and COP 
parameters in the Type; you will be quite close in your performance 
estimates.

   One other note; make sure that the rated capacity and COP that you 
enter for parameters are at the same conditions to which the external 
data file is normalized. In other words, if the data file is normalized 
to a 5C oulet chilled water temperature and a 16C inlet cooling water 
temperature then make sure that the capacity and COP that you enter as 
the rated values are at those same conditions.
Best,
  David

On 2/15/2013 07:10, Jean Marais wrote:
> Wow. You stated these questions so well that I can only think that you 
> did so already knowing the answeres.
> 1. You can't. You need a comprehensive data set from your chiller 
> supplier, specifying a matrix of COPs at different water temperatures 
> on supply and return side as well as condenser supply and return side.
> 2. This will be clear in the data set. It is very possible.
> 3. There is no mathematical thermal corrolation. It is chiller 
> dependant. It is a different data set.
> 4. Yes. You'll need data at all the points where your chiller may 
> operate at. For example if you don't have data for the chiller 
> performance at less than 20% of full rated capacity, then the 
> simulation will issue a warning when your chiller model is required to 
> output results at these conditions (most chillers will turn off below 
> 20% demand).
> 5. Correct.
> I stand corrected on any points.
>
> On 15 February 2013 10:36, #YEO KEAT KEE# <YEOK0031 at e.ntu.edu.sg 
> <mailto:YEOK0031 at e.ntu.edu.sg>> wrote:
>
>     Dear Fellow Trnsys Users
>
>     I am a new user to Trnsys and is modeling a water cooled chiller
>     system using type 666 as the chiller.
>
>     I understand that if I want to model a specific chiller model in
>     the system, I will have to make changes to the chiller performance
>     data file and the part load performance data file.
>
>     In the chiller performance data file, I see that there the
>     capacity ratio and the COP ratio being defined as 1 at 7C Outlet
>     CHWT 30C INLET CWT.
>
>     1.If I only have the performance data of the chiller at  6.7C
>     Outlet CHWT 29.4C INLET CWT, how can I make use of this data to
>     input it into the chiller performance data file?
>
>     2.Must the capacity ratio and the COP ratio being defined as 1 at
>     7C Outlet CHWT 30C INLET CWT, or can it be defined as 1 at other
>      Outlet CHWT and Inlet CWT ?
>
>     3.How does the part load ratio data of the chiller relate to the
>     different Capacity Ratio and COP ratio ?
>
>     4.In the parameter tab of the type 666 chiller, it is stated that
>     "The capacity of the machine at its rated condition (typically 30
>     C (85 F) inlet cooling water temperature and 7 C (44 F) chilled
>     water set point temperature)The data file associated with this
>     model should be consistent with this rating conditions." . Does it
>     mean that I have to include the chiller performance at 7C chilled
>     water set point and 30C inlet cooling water temperature in the
>     chiller performance data file ?
>
>     5.In the chiller performance data file, it is observed that the
>     chiller capacity ratio can be more than 1.  Does this means that
>     the chiller current capacity is higher than the rated capacity?
>
>     Can anyone kindly advice on the above mentioned queries ?
>
>     Thank You !
>
>     Best Regards
>
>     KK Yeo
>
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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