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Rambod,<br>
I assume that by umin and umax, you mean inputs 4 and 5. If that
is the case then this inputs simply define the range of the
controller's output. If you want to control a pump between fully off
and fully on at its rated flow rate then you might choose 0 and 1
for your limits (as in the SDHW-Feedback example). If you wanted the
controller to set the flow rate directly then you would set umin to
0 and umax to the maximum allowable flow rate.<br>
<br>
As for the issue of the temperature being above 120C when flow
rate is zero, that seems quite possible since collectors can reach
very high "stagnation" temperatures when there is no flow through
them. It may be that under those circumstances, your controller
cannot meet 120C at any flow rate so hits its limit on the number of
times that it can change control decisions before it "sticks"
(oscillation limit parameter).<br>
Kind regards,<br>
David<br>
<br>
<br>
On 1/16/2011 16:49, Rambod Rayegan wrote:
<blockquote
cite="mid:AANLkTi=KcE3AYMhfHUEHuYRcvgE--0Y4O0yMf9A9CMw9@mail.gmail.com"
type="cite"><br clear="all">
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">Dear TRNSYS users,</font></font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font
face="Calibri" size="3"> </font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">I created a TRNSYS file to simulate the
performance of a flat plate collector. In this file I used a
feedback controller to set the collector’s output
temperature on 120 <span style="">°</span>C.<span style="">
</span>I checked the TRNSYS example “SDHW-Feedback
controller” and I chose umin and umax equal to 0 and 1
respectively. </font></font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">When I check the results I see that in some
time steps temperature is higher than 120 <span style="">°</span>C
while flow rate is zero. BY changing umax in feedback
controller the results are being modified slightly but I
don’t know how I can find the optimum umax. </font></font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">Actually I am not sure that changing umax
will solve the problem.</font></font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">Attached to this email you can find a copy of
my file.</font></font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">Thank you.</font></font></p>
<p style="margin: 0in 0in 10pt;" class="MsoNormal"><font size="3"><font
face="Calibri">Rambod</font></font></p>
<br>
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<pre class="moz-signature" cols="72">--
***************************
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
<a class="moz-txt-link-abbreviated" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>
<a class="moz-txt-link-freetext" href="http://www.tess-inc.com">http://www.tess-inc.com</a>
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