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<DIV><FONT face=Arial size=2>Dear all,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I am using the borefield storage model
<STRONG>Trnsys Type557b</STRONG> to learn more about the borefield dynamics. I
have 2 problems: The first concerning the model accuracy for short time periods
(at start-up), the second concerning very long simulation times. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>1. Simulation of short time periods -->
determination of borehole resistance</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2>First, I would like to simulate the Thermal
Response Test, which is the evolution of the mean fluid temperature as response
to a step heat input. There exists an analytical solution to this problem
in case of a single borehole. This analytical solution shows that the
temperature rise versus the logarithmic (ln) of time, should be a straight line.
The slope of that line is the borehole resistance (see eg.PhD thesis of Gehlin
2002). </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>For short time periods, eg. 3 days, there is no
interference between the boreholes and therefore I suppose that the
response should correspond to the analytical solution of a single borehole
(after scaling the power by the number of boreholes, in this case 100). However,
if I apply a step heat input to the borefield, the temperature rise versus the
natural logarithm of time yields not a straight line, but looks
quadratic.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Is there a physical reason for this? </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>2. Simulation of long time periods -->
determination of borefield time constant</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2>Second, I would like to determine the largest time
constant of a borefield, by applying a step input during 20 years. The
simulation however stops somewhere in the middle. The program
returns:</FONT></DIV>
<DIV><FONT face="Arial Narrow"
size=2>
</FONT></DIV>
<DIV><FONT face="Arial Narrow"
size=2> TRNSYS
message 103: The TRNSYS TYPE checking routine has found an inconsistency in the
specified input file and the information expected by the Type</FONT></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV><FONT face="Arial Narrow" size=2>Reported information: The component
model has reported an unspecified error. Please check the input file for
possible sources of error. </FONT></DIV>
<DIV><FONT face=Arial size=2><FONT face="Arial Narrow">an unspecified error
from Type557b.</FONT> </FONT></DIV></BLOCKQUOTE>
<DIV><FONT face=Arial size=2>This error seems to depend on the simulation length
only. There is no error if I apply the step input for only a couple of
years. I don't expect that the error has a physical reason neither, because the
temperature at which it 'crashes' depends on the heat power applied. The lower
the heat power level, the longer the simulation continuous, but it eventually
chrashes too. So It is not possible to determine the time after which the
borefield is in 'steady state'. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I would be very grateful if someone could give
an answer to this physical/numerical (?) problems!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thank you very much in advance, </FONT></DIV>
<DIV><FONT face=Arial size=2>Clara Verhelst</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>University of Leuven, Belgium</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV><BR>
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