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Chen,<br>
Type60 allows you to specify three of the four flows, in which
case it will internally compute what the required fourth flow must
be. The two inlet flows are defined as a positive value meaning flow
into the tank. The two outlet flows are defined as a positive
indicating a flow out of the tank. Flows may be zero but they cannot
be negative (in other words you can't have fluid coming in through
an outlet port nor out through an inlet port).<br>
<br>
In your simulation, inlet flow 1 comes from the load side of the
heat exchanger, inlet flow 2 is set to the value zkmassflow, and
outlet flow 2 is set to the value of zkmassflow+zkflow. If there is
no flow from the heat exchanger into the tank and zkflow is positive
then the mass balance can't work. In order for it to work, flow
would have to enter the tank through outlet port 2.<br>
<br>
One other thing that I noticed: check the answer to the question
about how many nodes there are in the tank on the Type60 "output"
tab. The question is "besides the top and bottom nodes, how many
nodes are there?" so the answer needs to be 8 whereas the other two
tabs ask simply "how many nodes are there?" <br>
Best,<br>
David<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 2/11/2013 11:34, Chen Luo wrote:<br>
</div>
<blockquote cite="mid:DUB002-W154111CBC3DE68AF52D1920880A0@phx.gbl"
type="cite">
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<div dir="ltr">Hello,
<div><br>
</div>
<div>I am using this model to simulate a water heating system.</div>
<div>But there is always this problem "a negative flow was
encountered". I have tried to change the flow of cold water
income, and change "-2" to each of the 4 in/outlets of
Type60f. However, it doesn't work.</div>
<div><br>
</div>
<div>Chen</div>
</div>
<br>
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<br>
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