hot water expansion pressure calculation
hot water expansion pressure calculation
(OP)
I'm trying to reverse-engineer a hot water expansion situation and can't find the formulas. All I have is expansion tank sizing software, but that's not getting me a direct answer. Here is my situation:
I have a 50 gallon radiant PEX tubing system that has a 4.5 gallon diaphram tank with 2.5 gal acceptance. The system was cold filled with 50 deg water to a fill pressure at the tank of 0 psig. I don't know why it wasn't filled to the typical 12 psig, but it wasn't. The tank is at the top of the system.
The water is heated with a plate exchanger by steam. A situation occured where 220 deg water entered the PEX. I'm trying to determine based on the 50 gallon volume, the expansion tank size, and the two temps, what my elevated pressure will be. I'm thinking it's under 20 psig as I play around with the expasion tank selection software, but I have no confidence.
Any thoughts on how to calculate the pressure at 220 deg?
I have a 50 gallon radiant PEX tubing system that has a 4.5 gallon diaphram tank with 2.5 gal acceptance. The system was cold filled with 50 deg water to a fill pressure at the tank of 0 psig. I don't know why it wasn't filled to the typical 12 psig, but it wasn't. The tank is at the top of the system.
The water is heated with a plate exchanger by steam. A situation occured where 220 deg water entered the PEX. I'm trying to determine based on the 50 gallon volume, the expansion tank size, and the two temps, what my elevated pressure will be. I'm thinking it's under 20 psig as I play around with the expasion tank selection software, but I have no confidence.
Any thoughts on how to calculate the pressure at 220 deg?





RE: hot water expansion pressure calculation
Calculate the volumetric expansion of the water in the system.
Subtract that change in volume from the initial gas volume in the expansion tank.
P1V1 = P2V2 gets you the gas pressure in the expansion tank which will equal the water pressure.
RE: hot water expansion pressure calculation
RE: hot water expansion pressure calculation
You have to achieve pressure balance in cold/static condition to have your vessel working normally. I think you will have constant interference with regular air bleeding - when vessel is on the bottom and you specify ca. 0,5 of water gage pressure higher than actual hydrostaic height, you are protected from vacuum. But in your situation every air bleeding can lead to zeroing pressure on the top of the system?!
It looks that you will allways have air in the water side. And that is the air which can travel along the lines and cause constant problems.
RE: hot water expansion pressure calculation
CB
RE: hot water expansion pressure calculation
That is above the temperature limit for some PEX.