Trond
Petroleum
- Jul 31, 2002
- 33
Hi,
I am trying to calculate heat loss from a pipeline in a forced convection (sea current) scenario. I have been going through several heat transfer textbooks, but all I can find are formulas for pipe bundles (for heat exchangers).
A bit of background info: In this particular case, we have several existing interfield multiphase pipelines that have seen internal corrosion at locations where the pipelines are exposed to seawater, e.g. at external sacrificial anodes, subsea flanges, etc, as this is where water condenses out, especially at the top of the line, where conventional corrosion inhibitors can not reach (as these remain dissolved in the liquids at the bottom of the pipe - stratified flow). A suggestion has been made to cover these sections with sandbags or some other type of cover, thus effectively reducing the external seawater velocity to zero (or close to). The pipes will still be exposed to seawater, but hopefully the new convection will now be natural rather than forced.
Considering the amount interfield pipelines we have (in excess of 120), and the cost of covering these cold spots, we would like to make a comparison of the heat transfer coefficients for the two cases. Calculating the natural convection is easy enough, but I have not been able to find a suitable equation for forced convection for single large diameter (10-16 inches) pipes.
Would be very grateful for any leads you guys can give me.
Cheers,
Trond
I am trying to calculate heat loss from a pipeline in a forced convection (sea current) scenario. I have been going through several heat transfer textbooks, but all I can find are formulas for pipe bundles (for heat exchangers).
A bit of background info: In this particular case, we have several existing interfield multiphase pipelines that have seen internal corrosion at locations where the pipelines are exposed to seawater, e.g. at external sacrificial anodes, subsea flanges, etc, as this is where water condenses out, especially at the top of the line, where conventional corrosion inhibitors can not reach (as these remain dissolved in the liquids at the bottom of the pipe - stratified flow). A suggestion has been made to cover these sections with sandbags or some other type of cover, thus effectively reducing the external seawater velocity to zero (or close to). The pipes will still be exposed to seawater, but hopefully the new convection will now be natural rather than forced.
Considering the amount interfield pipelines we have (in excess of 120), and the cost of covering these cold spots, we would like to make a comparison of the heat transfer coefficients for the two cases. Calculating the natural convection is easy enough, but I have not been able to find a suitable equation for forced convection for single large diameter (10-16 inches) pipes.
Would be very grateful for any leads you guys can give me.
Cheers,
Trond
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) gives various relationships for the flow of liquids normal to single cylinders and recommends the following one:
