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Dear Zhe,<br>
I have seen air(source)-to-water heat pumps used in two kinds of
applications. In one, the air side is outside the conditioned space
and you are correct that in this circumstance, the RH of the outlet
air is probably not going to be used for anything. In the other type
of application, however, the air side is in a conditioned space (for
example there are devices called heat pump water heaters that sit on
top of a water tank; they keep the water tank hot but in the process
they cool (and dehumidify) the air near the tank. In this case it is
important to know what happens on the air side. <br>
<br>
You are correct that the data cannot be extrapolated beyond the
range given in the file. If you give the heat pump entering
conditions that are below the range, the model will get the capacity
and power of the closest point (ie the bottom of the range). The
case is similar for the top of the range; the interpolation routine
will find the closest available point. If you want to be more
rigorous about your calculations, you can put additional data points
into the file that show a 0 capacity and 0 power draw for the device
if it gets very cold or very hot inlet conditions.<br>
Kind regards,<br>
David<br>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 4/22/2013 09:19, Zhe Li wrote:<br>
</div>
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<p class="MsoNormal"><span style="color:#1F497D">Dear David,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thank you very
much for your previous reply. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I am hoping you
can clarify some of my confusions with this source
code(Type941). I have studied this Type941 source code
carefully. From my understanding is the outlet fluid
temperature is not calculated from the amount of heat
contained in the air. The Capacity and Power is worked out
completely depending on the Rated Catalog Performance using
the hourly ambient temperature and temperature of the fluid.
So why does the relative humidity require at all? Is it only
used to calculate the inlet and the outlet air properties
which is not going to affect the fluid temperature in any
way? <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">As I understand
from previous questions, the interpolation Rated Catalog
Performance data could not be extrapolated from beyond the
range provided? However, what would be the calculation
(selection) if the inlet ambient temperature is 5oC and
inlet water temperature is 27.5oC, how would the fraction
capacity and power calculated out (decided)? <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thank you very
much for your kind answer.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Zhe Li<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
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<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 class="moz-txt-link-freetext" href="mailto:d.bradley@tess-inc.com">mailto:d.bradley@tess-inc.com</a>] <br>
<b>Sent:</b> 19 April 2013 18:04<br>
<b>To:</b> TRNSYS users mailing list at the Solar Energy
Lab, UW-Madison<br>
<b>Cc:</b> Zhe Li<br>
<b>Subject:</b> Re: [TRNSYS-users] Question about a line
in Type941 source code<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Zhe,<br>
lps_air is the volumetric flow rate of the air (in liters
per second) and rho_air_dry_in is the density (in kg/m3) of
the dry air at the heat pump inlet temperature.<br>
Best,<br>
David<br>
<br>
<o:p></o:p></p>
<div>
<p class="MsoNormal">On 4/19/2013 11:11, Zhe Li wrote:<o:p></o:p></p>
</div>
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<p class="MsoNormal">Dear All,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thank you for your time.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I am trying to understand how TRNSYS
calculates power output from this air-water heat pumps
(Type941).<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I am stuck in a line which I don’t know
what the two terms are standing for? <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">! Determine the dry air mass flow rate<o:p></o:p></p>
<p class="MsoNormal">Flow_air = lps_air*3.6*rho_air_dry_in <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Could somebody let me know what are the <b>lps_air</b>
and <b>rho_air_dry_in </b>standing for?<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I hope I did not break TRNSYS source code
rule by asking this question. <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thank you for your help in advance.<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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<o:p></o:p></span></p>
<pre>-- <o:p></o:p></pre>
<pre>***************************<o:p></o:p></pre>
<pre>David BRADLEY<o:p></o:p></pre>
<pre>Principal<o:p></o:p></pre>
<pre>Thermal Energy Systems Specialists, LLC<o:p></o:p></pre>
<pre>22 North Carroll Street - suite 370<o:p></o:p></pre>
<pre>Madison, WI 53703 USA<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>P:+1.608.274.2577<o:p></o:p></pre>
<pre>F:+1.608.278.1475<o:p></o:p></pre>
<pre><a moz-do-not-send="true" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a><o:p></o:p></pre>
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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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