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Heat Loss Through Buried & Insulated Pipe


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#1 sangp4

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Posted 16 May 2017 - 09:32 AM

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

 

 

 

 

 



#2 sangp4

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Posted 16 May 2017 - 10:37 PM

Hey!!

 

Silly me !!

 

Did not consider the density factor in the heat equation to calculate the temp drop.

Hence the temp drop is 43/1000 = 0.043 deg C.

 

Your comments are still welcomed.



#3 breizh

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Posted 17 May 2017 - 06:38 AM

hi ,

let you consider the document and link  attached to support your work .

 

https://www.osti.gov...ets/purl/629429

 

 

hope this helps

 

Breizh

Attached Files


Edited by breizh, 17 May 2017 - 06:09 PM.


#4 ankur2061

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Posted 17 May 2017 - 12:01 PM

sangp4,

 

Refer the link below:

 

https://www.cheresou...quid-pipelines/

 

Soil temperature at a depth of 2 m is unlikely to be 30 deg C. It is more likely to vary from 15 to 25 deg C as a maximum depending on winter and summer. You may consider an average value of 21-22 deg C. If you want to do precise calculations refer the link below:

 

http://www.ewp.rpi.e...Measurement.pdf

 

Regards,

Ankur.



#5 breizh

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Posted 22 May 2017 - 07:23 AM

Hi ,

I have attached a spreadsheet to support your work .... take a look and review if necessary .

Hope this helps

Good luck

Breizh

Attached Files



#6 sangp4

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Posted 27 May 2017 - 10:57 PM

Thanks Ankur & Breizh !!






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