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Dear all,
I am using the borefield storage model
Trnsys Type557b 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.
1. Simulation of short time periods -->
determination of borehole resistance
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).
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.
Is there a physical reason for this?
2. Simulation of long time periods -->
determination of borefield time constant
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:
TRNSYS
message 103: The TRNSYS TYPE checking routine has found an inconsistency in the
specified input file and the information expected by the Type
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'.
I would be very grateful if someone could give
an answer to this physical/numerical (?) problems!
Thank you very much in advance,
Clara Verhelst
University of Leuven, Belgium
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