Water Volume in an Closed Loop System 2

[elirezz]

Hi all,

I was wondering how to calculate the required volume in a hot-water closed loop.

Interested to know how much volume of water will be necessary to fill the system and also to calculate volumetric expansions.


Thanks

 

[LittleInch]

Errr, add up all the volume in the pipe and any vessels?

For expansion, search this site for water expansion or perhaps, hydrostatic test pressure change as the same calculations often apply. I think there's an FAQ on the pipelines page which gives expansion formulae or just google it for charts which give you change in volume per degree.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[LittleInch]

See

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

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[JohnGP]

Once you add up all the bits, typically I would think that an expansion tank would be included in the loop sized to take any increase in liquid volume when heated, and return liquid to the loop when cooled. The link gives some insight into the sizing process-

http://sunearthinc.com/design-resources/sizing-expansion/

As to how big a system you need, that will depend on what you are trying to heat and what you have as a heating source.
Cheers,
John

 

[elirezz]

Thanks for info,

For calculating the expansion vessel volume I would need to know how much volume of water is actually is in my loop. Is it only a factor of pipe capacity?? So pipes total lenght and thereby total volume capacity?

I know the volumetric flow rate (per hour) but since its a loop, I cannot figure out actually how much volume I would require (for initial filling of the system and also for other calculations eg. expansion volume)

The Table you sent " Pipe Capacity (US Gal/100 ft)" is upto 3" pipe, I guess I will keep googling more then...

Thanks again

 

[JohnGP]

Hi elirezz,
It is essential to know the length of pipe in the system, then multiplying by cross sectional area gives volume in the piping. Then just add a bit for the expansion tank (once you work out the size of that, but not full), and it's done!
Cheers,
John

 

[elirezz]

Hey Jhon,

Yup got it now.

Thanks

 

[racookpe1978]

So pipes total lenght and thereby total volume capacity?

Usually you do not include elbow length (or bend length) in pipe weight calc's for pipe supports and hangers. Straight-line (work-point-to-work-point) distance approximations are adequate for weight purposes.

HOWEVER, here you need to accurately use the weld-to-weld distances for INTERNAL diameter of the pipe in the design, AND then add in the INTERNAL volume of every elbow or bend AND add in the INTERNAL volume of your heat exchangers, tanks, and valves and pumps.

And, uh, internal volume of pipe can be calculated (not just from Google)
volume = length x 3.14 x [(internal dia)/2][sup]2[/sup]

Do you know the internal volume of one-quarter of a torus? 8<)

 

[dcasto]

same hint as for the question on a tower going on a vacuum mass is conserved

 

[elirezz]

Hey,

Yeah I did actually calculated all my pipes volume... but wanted to check it with google values as well.

I dont think I can do straight line lenght calculations for the coils (its have over 100 bends). So I added everything as you said.

Thanks