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