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Dear Zhe,<br>
In order for the simulation to be numerically stable, the buffer
tank must be large enough to hold at least one time step of liquid.
So the answer to your question depends upon the rated flow rate of
the pump in the loop and on the time step that you have chosen. In
the actual system, there is liquid volume contained in the piping
network. I would recommend that you determine how much liquid volume
there is (knowing the inside diameter and length of each pipe
section), then create a buffer tank of equivalent size and reduce
your time step accordingly.<br>
Kind regards,<br>
David<br>
<br>
<br>
<div class="moz-cite-prefix">On 11/28/2012 11:07, Zhe Li wrote:<br>
</div>
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<p class="MsoNormal">Dear David,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks for your time.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">As we discussed before, due to the fact
that the current air-water heat pump (Type 941) is a single
stage heat pump, a buffer tank is used to prevent overheating
when a imposed thermal load is employed. Even though the
desired system is not working with a buffer tank, this does
solve the original problem I had. However, I have discovered a
new problem. What would be the right capacity of this buffer
tank to built into in order to simulate the actual system
(system without using buffer tank)? I have tried to simulate
using varies capacity tank ( from 0.3m<sup>3</sup> to 1m<sup>3</sup>)
as the buffer tank, the electricity consumption can be
different as much as 5% which it is significant as far as I am
concerned. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Also, I understand there is an auxiliary
heater built into the air-water heat pump component. Would you
recommend to use this auxiliary heater or use an external
heater built into the circuit where after the buffer tank
which makes it more realistic?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hope I have explained the problem clearly.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you very much.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Zhe Li<o:p></o:p></p>
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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>
<a class="moz-txt-link-freetext" href="http://www.trnsys.com">http://www.trnsys.com</a></pre>
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