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<p class=MsoPlainText>Hello,<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>I have a couple more questions to add to the chiller
curve conversations going on. I posted the question to eSimForums so the
spreadsheet would stay with the topic and am forwarding the question along.
Below are the questions, and here is a link to the post:<o:p></o:p></p>
<p class=MsoPlainText><a href="http://www.esimforums.com/equest/viewtopic.php?f=13&t=105&view=unread%23unread">http://www.esimforums.com/equest/viewtopic.php?f=13&t=105&view=unread#unread</a><o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Thanks for any advice,<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Jeremy<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>-----Original Message-----<br>
From: admin@esimforums.com [mailto:admin@esimforums.com] <br>
Sent: Friday, November 05, 2010 2:18 PM<br>
Subject: [eSimForums] Custom Chiller Curves<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>New post:<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Hello all,<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Attached is a spreadsheet I used to gather information
from a manufacturer<o:p></o:p></p>
<p class=MsoPlainText>and create custom chiller curves using the EDR guidelines
for modeling<o:p></o:p></p>
<p class=MsoPlainText>energy efficient chillers (link to the document at the
bottom of the post).<o:p></o:p></p>
<p class=MsoPlainText> I have been testing the curves in two models. In a test
wizard model (also<o:p></o:p></p>
<p class=MsoPlainText>attached), both curves work. In another real model
(which I can't upload)<o:p></o:p></p>
<p class=MsoPlainText>the curves that I expected to be correct cause the
chiller to create<o:p></o:p></p>
<p class=MsoPlainText>energy. The difference between the curves is the PLR
equation. So, I have<o:p></o:p></p>
<p class=MsoPlainText>a few questions regarding gathering information from
manufacturers and the<o:p></o:p></p>
<p class=MsoPlainText>PLR equation.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>1) <o:p></o:p></p>
<p class=MsoPlainText>When I specify a %load for a part-load data point, does
this automatically<o:p></o:p></p>
<p class=MsoPlainText>dictate an operating capacity that a manufacturer must
input into their<o:p></o:p></p>
<p class=MsoPlainText>program? For example, in the attached spreadsheet, I
chose to ask for 90%<o:p></o:p></p>
<p class=MsoPlainText>load with a CHWS & ECT of 42 & 78. I take this
to mean that I am asking<o:p></o:p></p>
<p class=MsoPlainText>the manufacturer to input an operating capacity of 90% of
the full load<o:p></o:p></p>
<p class=MsoPlainText>capacity at the same CHWS & ECT’s (0.9*343=308.7 tons
in the attached<o:p></o:p></p>
<p class=MsoPlainText>spreadsheet) into their software and give me the
corresponding power drawn<o:p></o:p></p>
<p class=MsoPlainText>by the chiller. However, in the EDR guidelines for
modeling energy<o:p></o:p></p>
<p class=MsoPlainText>efficient chillers, there is an example Manufacturer Data
Request Form<o:p></o:p></p>
<p class=MsoPlainText>which has a note in both the capacity and power columns
that says “Note to<o:p></o:p></p>
<p class=MsoPlainText>Chiller Manufacturer Rep., Please allow your program to
size (don’t input<o:p></o:p></p>
<p class=MsoPlainText>capacity and kW into your program)”. This makes sense
for the full load<o:p></o:p></p>
<p class=MsoPlainText>capacity, but does it apply to the part load? If so, what
is the<o:p></o:p></p>
<p class=MsoPlainText>difference between %load and part load capacity?<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>2) <o:p></o:p></p>
<p class=MsoPlainText>Does there need to be a part load data point for every
full load data<o:p></o:p></p>
<p class=MsoPlainText>point?<o:p></o:p></p>
<p class=MsoPlainText>a. <o:p></o:p></p>
<p class=MsoPlainText>I would say yes based on page 26 of the EDR guidelines,
which says “each<o:p></o:p></p>
<p class=MsoPlainText>part-load point must have a corresponding full-load data
point with<o:p></o:p></p>
<p class=MsoPlainText>matching evaporator and temperatures.” This seems to
answer my question. <o:p></o:p></p>
<p class=MsoPlainText>But, on page 28 of the same document in the example
Manufacturer’s Data<o:p></o:p></p>
<p class=MsoPlainText>Request Form, they do not ask for part-load points that
correspond to<o:p></o:p></p>
<p class=MsoPlainText>full-load points. This is a bit confusing, so I would
just like to<o:p></o:p></p>
<p class=MsoPlainText>confirm.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>3) <o:p></o:p></p>
<p class=MsoPlainText>When asking for part load data from a manufacturer, does
it matter which<o:p></o:p></p>
<p class=MsoPlainText>%load I ask for at each data point corresponding to a
CHWS & ECT?<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>4) <o:p></o:p></p>
<p class=MsoPlainText>In the attached spreadsheet, the difference between
curves on the sheet<o:p></o:p></p>
<p class=MsoPlainText>named Curve 1 and the ones on sheet Curve 2 is the
divisor in the PLR<o:p></o:p></p>
<p class=MsoPlainText>equation (starting in cell W15). The given PLR equation
is PLR =<o:p></o:p></p>
<p class=MsoPlainText>Qi/(Qref*CAPFT). Curve 2 represents my interpretation of
this equation<o:p></o:p></p>
<p class=MsoPlainText>where Qref is a constant representing the capacity at the
point of unity. <o:p></o:p></p>
<p class=MsoPlainText>However, when I used this curve in a model, the chiller
energy came out<o:p></o:p></p>
<p class=MsoPlainText>negative (magically created energy instead of consuming
it). A colleague<o:p></o:p></p>
<p class=MsoPlainText>of mine read a document that suggested that Qref in the
PLR equation is a<o:p></o:p></p>
<p class=MsoPlainText>different Qref than in the other equations and it could
be interpreted as a<o:p></o:p></p>
<p class=MsoPlainText>variable reference (which I would call Qi, not Qref).
So, we tried it and<o:p></o:p></p>
<p class=MsoPlainText>it worked, or at least it caused the chiller to consume
energy instead of<o:p></o:p></p>
<p class=MsoPlainText>creating it. I have a difficult time believing that Qref
is a variable and<o:p></o:p></p>
<p class=MsoPlainText>not a constant, but the fact that the curve worked with
Qref as a variable<o:p></o:p></p>
<p class=MsoPlainText>and didn’t work as a constant forces me question it.
Since then, I tried<o:p></o:p></p>
<p class=MsoPlainText>the same curves in another model and they both work,
which confused the<o:p></o:p></p>
<p class=MsoPlainText>situation more. Is my interpretation that Qref is a
constant representing<o:p></o:p></p>
<p class=MsoPlainText>the capacity at the point of unity correct?<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>For ref, the EDR guidelines I am referring to can be
found at the following<o:p></o:p></p>
<p class=MsoPlainText>link:<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><a href="http://www.energydesignresources.com/Resources/Publications/DesignGuidelines/tabid/73/articleType/ArticleView/articleId/138/Design-Guidelines-HVAC-Simulation-Guidelines.aspx">http://www.energydesignresources.com/Resources/Publications/DesignGuidelines/tabid/73/articleType/ArticleView/articleId/138/Design-Guidelines-HVAC-Simulation-Guidelines.aspx</a><o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Reply to this post at:<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><a href="http://www.esimforums.com/equest/viewtopic.php?f=13&t=105&view=unread%23unread">http://www.esimforums.com/equest/viewtopic.php?f=13&t=105&view=unread#unread</a><o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
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