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
Yeo
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@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@tess-inc.com
http://www.tess-inc.com
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