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Samuele,<br>
I am not quite sure what you are trying to model. The loop that
contains Type654-2, Type700, Type650, and Type60 is not converging. The
pump is ON from 06h00 to 18h00. The liquid gets hot going through the
boiler then goes into a heat exchanger whose hot side flow rate is
modulated in order for the cold side <i>outlet </i>temperature not to
come out any hotter than the temperature profile set by Type14e. Water
comes into the heat exchanger at 0C with a flow rate of 8000 kg/h. The
set point temperature function becomes 0 at 15h00 but the pump is still
running on the hot side so the heat exchanger is trying to maintain a 0C
temperature rise across the cold side between 15h00 and 18h00.<br><br>
The other pump is ON if it is between 18h30 and 0h00 and the
temperature of the tank is greater than 44C. Using equations as control
signals can be a little dangerous because you lose the ability to model
hysteresis in the controller. The pump would turn on at a tank
temperature of 44.0000000000000001 and off again at a temperature of
44.0000000000000000. I would recommend using a controller model such as
Type2 or Type503 (cooling aquastat in the TESS controllers library)
because those models have deadbands that can avoid the convergence
problems of equations.<br>
Cheers,<br>
David<br><br>
<br><br>
At 04:51 6/6/2007, Samuele wrote:<br>
<blockquote type=cite class=cite cite=""><font size=2>
Dear all,<br>
</font> <br>
<font size=2> I have done a simple project (enclosed)
in which there are a pump, a boiler, an heat exchanger, a thermal storage
and another pump controlled by an equation.<br>
</font> <br>
<font size=2> I think there are no errors but, if I
changed some values ( for example the temperature's value in type 14e-2
or the value for the gt equation which controlls the function of the
pump)<br>
It doesn't run.<br>
</font> <br>
<font size=2> Could anybody tell me if the problem is
the equation which calculates the control function of the pump?<br>
</font> <br>
<font size=2> Best regards,<br>
Samuele.<br>
<br>
</font><br>
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