Dear Zhe & David<div><br></div><div>I have discovered the same problem as Zhe. Did you find a solution to the problem he had? If yes, maybe it could be a solution to my problem too.</div><div><br></div><div>Kind Regards </div>
<div>Amdi<br><br><div class="gmail_quote">2012/12/4 David BRADLEY <span dir="ltr"><<a href="mailto:d.bradley@tess-inc.com" target="_blank">d.bradley@tess-inc.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Dear Zhe,<br>
Would you mind sending me project? From your explanation, it
certainly sounds as though everything is correct. I am curious as to
which component is generating an error saying that the buffer tank
is too small.<br>
Kind regards,<br>
David<div><div class="h5"><br>
<br>
<br>
<div>On 12/4/2012 05:03, Zhe Li wrote:<br>
</div>
<blockquote type="cite">
<div>
<p class="MsoNormal"><span style="color:#1f497d">Dear David,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Thank you very
much for your reply. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">I did a number
of calculations followed by your recommendation in designing
the correct size of buffer tank. However, The answer I am
getting is far from the size of buffer tank that I am
allowed to simulate my model. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">The rated flow
rate I am using is 1548kg/h and time step is 0.1h. For one
time step, the volume is 154.8kg. I would think the buffer
tank having a size of 0.2m<sup>3</sup> is sufficient to hold
one step volume liquid. However, I always get error when
performing the simulation. The minimum size of buffer tank
that I have to use is 0.37m<sup>3 </sup>in order to carry
out the simulation without error occurring.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">I have also
worked out the total amount liquid is in the loop. I am
using a pipe inside diameter is 0.022m, the total length of
pipe is 60m, this gives me a total volume water is 22.8kg, I
am not sure how this is related to the size of the buffer
tank. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Hope you don’t
mind to explain to me a little more.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Thank you very
much.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Zhe Li<u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d"><u></u> <u></u></span></p>
<div>
<div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext" lang="EN-US">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext" lang="EN-US"> David BRADLEY
[<a href="mailto:d.bradley@tess-inc.com" target="_blank">mailto:d.bradley@tess-inc.com</a>] <br>
<b>Sent:</b> 03 December 2012 17:56<br>
<b>To:</b> Zhe Li<br>
<b>Cc:</b> <a href="mailto:trnsys-users@cae.wisc.edu" target="_blank">trnsys-users@cae.wisc.edu</a><br>
<b>Subject:</b> Re: Capacity of buffer tank<u></u><u></u></span></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">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>
<u></u><u></u></p>
<div>
<p class="MsoNormal">On 11/28/2012 11:07, Zhe Li wrote:<u></u><u></u></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Dear David,<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Thanks for your time.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></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. <u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></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?<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Hope I have explained the problem
clearly.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Thank you very much.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Zhe Li<u></u><u></u></p>
<p class="MsoNormal"><span><br clear="all">
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</blockquote>
<p class="MsoNormal"><span><br>
<br>
<u></u><u></u></span></p>
<pre>-- <u></u><u></u></pre>
<pre>***************************<u></u><u></u></pre>
<pre>David BRADLEY<u></u><u></u></pre>
<pre>Principal<u></u><u></u></pre>
<pre>Thermal Energy Systems Specialists, LLC<u></u><u></u></pre>
<pre>22 North Carroll Street - suite 370<u></u><u></u></pre>
<pre>Madison, WI 53703 USA<u></u><u></u></pre>
<pre><u></u> <u></u></pre>
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<pre><u></u> <u></u></pre>
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<pre cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI 53703 USA
P:<a href="tel:%2B1.608.274.2577" value="+16082742577" target="_blank">+1.608.274.2577</a>
F:<a href="tel:%2B1.608.278.1475" value="+16082781475" target="_blank">+1.608.278.1475</a>
<a href="mailto:d.bradley@tess-inc.com" target="_blank">d.bradley@tess-inc.com</a>
<a href="http://www.tess-inc.com" target="_blank">http://www.tess-inc.com</a>
<a href="http://www.trnsys.com" target="_blank">http://www.trnsys.com</a></pre>
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