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Dear Ahmadu,<br>
It looks as if your simulation is going in the right direction but
as though there are a lot of small errors. I don't have the *.bui
file for your building so I cannot run the simulation. However, in
taking a look at some components, here is what I noticed:<br>
<br>
- the equation for the return temperature from the building is
incorrect. It is Tout = Tin+(Qload/4190*mdot) and should be Tout =
Tin+(Qload/(4.190*mdot)). The cooling load output of Type56 is in
kJ/h.<br>
- the pump in that same loop has a rated flow rate of 100 kg/h,
which is unrealistically small. This pump sets the maximum rate of
flow to the load to 100 kg/h and will result in a VERY large
temperature increase. In fact, the same is true of all the pumps in
the system. If you aren't sure about pump sizes, try to get an idea
of what kind of temperature rise you want across a given branch of
the system and determine the flow rate that would obtain such a
temperature rise.<br>
- there is no thermal capacitance on your absorption chiller's
cooling water loop. I think you need to put a tank in that loop.<br>
- as in a previous email that I sent to the list today, make sure
that your tanks are large enough to hold more than one timestep of
fluid in them. <br>
- your time step should be on the order of 1 to 5 minutes, not an
hour. TRNSYS can only make one control decision per timestep and
systems that can only change their behavior once per hour rarely
converge.<br>
- on both of your Type4 tanks, go to the output tab and enter "4" in
the field that asks how many nodes there are in the tank besides the
top and bottom nodes. There is an inconsistency in your tanks as to
how many nodes they are modeling.<br>
<br>
I am afraid that this is not an exhaustive list. I would recommend
that you back up to the point where you have just the building
giving loads to the equation labeled "Equa." Give a constant flow of
water to that equation and make sure that you are seeing somewhere
between a 5 and 10C temperature rise in the water at the peak load.
Next, add pump "Type3b-5" and control the flow through "Equa." Add
one component at a time and each time you add a new now, attach a
type65 to it and plot some output or other to make sure that you
fully understand the results that you are seeing.<br>
Kind regards,<br>
David<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 10/29/2012 08:09, Talib Ahmadu
wrote:<br>
</div>
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cite="mid:1351516141.12270.YahooMailClassic@web133203.mail.ir2.yahoo.com"
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<td style="font: inherit;" valign="top">Dear all, I am
working on an absorption cooling system using trnsys 16.
each time I simulate it gives an error. "the utility
psychrometrics which calculates the thermodynamic
properties of moist air has been called with a wet bulb
temperature above the maximum wet bulb temperature for the
given pressure". All efforts to address the problem have
not worked out. Can anyone help me out on this. Pls I've
attached the tpf file. Thanks. <br>
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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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