[TRNSYS-users] Type 666 Chiller Queries

#YEO KEAT KEE# YEOK0031 at e.ntu.edu.sg
Tue Mar 12 19:58:31 PDT 2013

Dear All,

I am just wondering , when David mentioned that the normalized performance curves of the water cooled chillers look about the same, does it refer to a specific type of water cooled chiller, i.e. Centrifugals, Screws or does it  refer to the normalized performance curves of all water cooled chillers in general, regardless of the type.

I am using TRNSYS 16, and attached is the performance file that are default with the program, does the relationship described in this file applies to all types of water cooled chiller ? If not, is it possible to find out what kind of chiller does it describe ?

Best Regards
From: David BRADLEY [mailto:d.bradley at tess-inc.com]
Sent: Saturday, 16 February, 2013 1:11 AM
To: Jean Marais
Cc: #YEO KEAT KEE#; trnsys-users at cae.wisc.edu<mailto:trnsys-users at cae.wisc.edu>
Subject: Re: [TRNSYS-users] Type 666 Chiller Queries

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.

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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