[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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