[TRNSYS-users] Input of pipe parameters in TYPE 997: MULTILEVEL HORIZONTAL GROUND HEAT EXCHANGER

[dg.buck at t-online.de]

Dear TRNSYS-users,  I use the TYPE 997, which models pipes buried in
the ground with an optional insulating layer on the surface and
optional thermal insulations down the edges of the pipe area.  I am
not sure about the correct way for the input of the pipe parameters. I
want to model one or several pipe layers with 7 pipes /loops in each
layer,  100 m long each. The pipe spacing is 15 cm. These pipes are
arranged in the pipe layer in serpentines. All pipes are connected in
parallel.   My first attempt was to simply specify 7 pipes with the
appropriate length, each with the same input temperature equal to the
input temperature of the ground heat storage. Also I specified the
distances from the field of pipes to the downward insulation (10 cm)
and the properties of the downward insulation. But I wonder if this is
the right way for the specification of the pipes. Now, if the model
assumes the field of pipes to be 100m+2*0.1m = 100.2 m long and
6*0.15m+2*0.1m = 1.10 m wide, this leads to a much longer perimeter
and much higher heat losses than the configuration I want to model
with a roughly square area and about 40 m of perimeter. I want to
model the arrangement of the pipes in serpentines, meaning that a pipe
goes 10 m in one way, then back 10 m etc.  Should I specify 70 pipes,
10 m long each, spacing between pipes again 0.15 m, arranged in 7
groups, with the following temperature inputs for the pipes in each
group:  pipe No 1 has input temperture = input temperature to the
ground heat exchanger.  pipe No. 2 gets as input temperature the
output temperature of pipe 1 pipe No. 3 gets as input temperature the
output temperature of pipe2  etc. for the first 10 pipes  and the same
again for the next 10 pipes etc.  Will the code for this model then
calculate the area as being of  10m + 2*0.1 m = 10.2 m length and a
width of 69*0.15 m + 2*0.1 m = 10.55 m. This makes about hte same
area, but with a perimeter length that is about a forth as in the case
described above. For the heat losses along the perimeter of the ground
heat storage I guess that makes quite a big difference. I have'n tried
that yet. But still: For doing my calculations in the correct way I
need to know which is the correct way to input the parameters for the
pipes.  There is no description besides the short description and the
information about the inputs in the proforma. And these do not answer
my question. My description is a bit lenghty. But I tried to describe
my problem clear enough.  Thank you for your answer and help in
advance. With many kind regards.  Doris Buck
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