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Leen,<br>
Unless I am misunderstanding what you want to do, the solution is
quite easy as long as you are able and willing to write a new Type;
TRNSYS has a built-in kernel subroutine called InterpolateData
(formerly called DynamicData) that performs exactly the function
that you are looking for. The subroutine is called from a Type with
the values of as many as 6 independent variables. The subroutine
looks through an external file, finds and returns the values of as
many as 10 dependent variables that correspond to the input values.
The subroutine interpolates linearly between values but cannot
extrapolate beyond the range of values that is given in the data
file.<br>
<br>
Before you go too far down the path of writing a new heat pump
model, I would recommend that you look through the TESS HVAC Library
documentation on existing heat pump models and also take a look at
the code of some of those models. Most of them stay away from energy
rate control (in which a precalculated load is imposed on the heat
pump) and stick with temperature level control (in which case heat
pump capacity and fraction of full load power are computed based on
inlet and ambient conditions.) Those models may be what you are
looking for or could be modified with little effort to better suit
your needs.<br>
Best,<br>
David<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 1/8/2013 06:35, leen peeters wrote:<br>
</div>
<blockquote
cite="mid:CAB_-mWP-4Vp+Lf_j2ykXqOxMUHe0Xf8OB2D0by188Yj096W+jg@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>Hi all,</div>
<div> </div>
<div>We are trying to model more accurately a heat pump for
which the performance should ideally be read out from a text
or excel file.</div>
<div>The data depend on 3 parameters (outdoor and indoor air
temperature, requested output). </div>
<div>Part load ratios are hard to define, as the actual capacity
depends on the model type and the outdoor conditions. So it
seems logic to use excell. However, values are not a function,
but should be looked up in the excell table, potentially
interpolated, ... and to make it more challenging, the final
SPF does depend on PLR, outdoor and indoor temperature. So it
is not just using the external temperature and required
capacity to calculate PLR and consequently use that PLR plus
indoor temperature to calculate SPF.</div>
<div> </div>
<div>Calling 6 different excell files in a simulation of 8760*4
steps will take considerable time. The current standard TRNSYS
look up model allows two independent parameters defining the
output ... so insufficiently accurate.</div>
<div> </div>
<div>any suggestions on how to solve that? </div>
<div> </div>
<div>thanks,</div>
<div> </div>
<div>leen</div>
</div>
<br>
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<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>
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