How does a tank apply pressure without water movement in a closed system?

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Offline thedoc

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Mike Malone asked the Naked Scientists:
   
Please read the following forum Q&A on a PONPC (point of no pressure change) I have on a heating system with a circulator and the expansion tank connected to it, assuming the temp is a steady 100F.

Can you explain how the tank can apply pressure without any movement on a closed system?

http://www.heatinghelp.com/forum-thread/147640/pumping-away-PONPC

Sincerely, Mike Malone

What do you think?
« Last Edit: 22/12/2013 18:30:02 by _system »

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Offline CliffordK

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Most well tanks, and expansion tanks have a rubber bladder, and an air filled area around the bladder.  The air can be pressurized to assist with providing dynamic pressure to the system. 

Fill the system with water using a pump up to a certain pressure, and the pressure tank allows a portion of the pressure to drop as the tank is emptied.  With a solid steel tank, the pressure would drop too quickly, and any air in the tank would eventually be lost.

A one-way valve can aid with forward circulation of the water.

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Offline Pmb

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Quote from: CliffordK
Most well tanks, and expansion tanks have a rubber bladder, and an air filled area around the bladder.  The air can be pressurized to assist with providing dynamic pressure to the system. 
What is an expansion tank?

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Offline Bored chemist

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Please disregard all previous signatures.

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Offline JP

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http://en.wikipedia.org/wiki/Expansion_tank
Was that so difficult?


Between Wikipedia and lmgtfy.com, I don't think we need a TNS forum anymore.  :)
« Last Edit: 24/12/2013 15:51:26 by JP »