Need help on calculating change in pressure of trapped water in a pipe due to temperature

[MechEng92]

Hi, I'm looking for help on finding the change in pressure of water trapped in a section of pipe due to changes in temperature.

The scenario is, water is trapped in length of pipe which is full of water and no air, the ambient temperature rises causing the temperature of the water to also rise, and I want to know the pressure of the water in the pipe after the temperature has risen.

I'd also like to know to begin with how the initial pressure of the trapped water in the pipe is known. I've tried to look through many forums online, some suggest steam tables should be used but it's been many years since I last looked at those so I'm not sure exactly what I should be doing with them.

I've also tried the following formulas to find the change in volume due to temperature change but not sure where to go from there:

https://www.engineeringtoolbox.com/volumetric-temperature-expansion-d_315.html

Any help would be appreciated, thanks!

 

[LittleInch]

Try this FAQ - top of the page.

https://www.eng-tips.com/faqs.cfm?fid=1339

It's usually about 3 bar per degree C for a truly locked in section of pipe.

The strength of the pipe has a lot to do with it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

Initial pressure is just whatever pressure you could have from a locked in no flow situation.

So e.g. if you have a pump it would be the differential pressure the pump could produce at no flow plus it's inlet pressure when you close the outlet valve and then lock it in with an isolating valve.

This is why Thermal Relief Valves exist....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

If you don't know the closed in pressure, then you must assume it is at the pipe's design pressure.

 

[bimr]

Has been discussed on here before:

https://www.eng-tips.com/viewthread.cfm?qid=393399

The attachment has a method to calculate the pressure.