water temperature rise and resulting psi.

Curtis Ridley

Thanks hope you can find it!

Curtis Ridley

Forrmula?

Is there a formula or rule of thumb on temperature rise in a closed system giving me a reulting psi? Ex. 50 degree F entering water temperature at 70 psi, rises to 140 degrees F water tempertature, what would be my resulting psi at 140?

Unknown

Curtis, I have been looking

around for some info to help you and I know I once had something on that just can't seem to find it. Maybe Brad White will chime in with something he may have or others.

Empire_2

Curtis, I to have been looking.

The specific weight of water is 1.0. The only way to measure your expansion of the water is to correctly know the total Volume in whatever system you are looking at. I to will Waite for Brad's response.

Mike T.

Brad White_191

Oh Jeez

You guys are going to make me find my old textbooks again, aren't you?

I do not have the formula in my head right now but the pressure gradient is very rapid (water being essentially incompressible; not absolutely correct but for our purposes it is).

A short answer: There is a chart which shows this and the pressure curve rises rapidly with relatively little, often very little, temperature increase. It starts slowly then rapidly climbs by some higher exponent.

Any air in the system (e.g. an expansion tank or similar captive volume) will have to be fully compressed before the system pressure really takes off. The presence of the expansion tank will slow the initial rise and after that, well, this is why we have ASME pressure relief valves...

I cannot promise, but you have my memory piqued and I may go looking for my old textbooks...

zeke

The worst case of no entrained air yields a pressure that is dependent on the largest storage volume such as the waterlogged expansion tank, its diameter and wall thickness and material. For example, if the water is heated from 65 deg to 180, the formula is

2tEa/D,

where

t is the wall thickness

E is modulus of elasticity for tank material

a is the difference in % linear expansion of water vs copper

D is diameter of storage vessel

For copper

E=12,000,000

expansion coefficient over 120 deg F

a=.0031

Assuming

t=1/16"

D= 12"
Then, I get

P=2*1/16*12,000,000*.0031/12= 387 psi(plus the nominal pressure)

However, I wouldn't bet the farm on this.