Hi,
For one of the Chilled water network project, it is required to estimate the temperature drop at the end user.
Following are the process parameter
1. Chilled Water Pipe Size: 30" (OD)
2. Pipe Insulation (Polyurethane Foam 60 kg/m3 density + HDPE Jacket) = 60 mm thk & 0.0212 W/mk conductivity
3. Buried Pipe Depth: 2 m
4. Water inside temperature: 4.4 Deg C
5. Pipe Length : 14000 m
Currently I do not have soil properties or data and hence I assumed the thermal conductivity as 0.52 W/mk
I used the following formulas
Q = (T1-T2) / Rtot
Rtot = Rins + Rsoil
Rins= Ln (D2/D1) / (2*Pi*L*Kins)
Rsoil = 1/(SKsoil)
S = 2*Pi*L/(ln(4z/D2))
Plugging in the values I get Q = 12.46 W/m
And using the same Q and using Q= m*Cp*Delta T, I arrive at very high Delta T of 43 deg C which is highly unrealistic.
T1 = Soil Temperature assumed as 30 Deg C
T2 = Fluid inside temperature = 4.4 C
D2 = Pipe Outside dia + insulation thickness = 0.882 m
D1 = Pipe Outside dia = 0.762 m
z = pipe depth = 2 m from ground till the outer surface of the pipe
Kins = Insulation Thermal conductivity = 0.0212 W/mk
Ksoil = Thermal conductivity of soil = 0.52 W/mk
Q = Heat Loss
L = pipe Length = 14000 m
Cp = Specific heat of water at 4.4 C = 4.2 kJ/kg C
Delta T = Temp at end user - 4.4
m = water flowrate of 15000 gpm
Guys can you point out the mistake or right direction or correct equations to be used with reference.
Thanks