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[TRNSYS-users] Type 31; Parameter 3; loss coefficient

Hello,
Here is my first question in the Mailing list

I have a question about the Type 31: “Pipe Or Duct”. What is the Parameter
3? I will calculate a buried pipe with an air mass flow v=140m³/h = 168
kg/hr. Pipe material is Polyethylene with heat conductivity  λ=1.44 [kJ/hr
K m] = 0.4 [W/K m]. Pipe length is l=30m, inner diameter D=0.2m, thickness
d=5mm=0.005m. The inner pipe area is A=18.85m².
What is now my parameter 3 “loss coefficient”?
Parameter3=U=λ/d=1.44/0.005=288 [kJ/hr K m²]?
Or
Parameter3= U=1/(Rsi+d/λ+Rse)
With: Rse=0 for buried and Rsi must be calculate separate for a turbulence
flow.

Thank you very much