Physics Help Forum Pressure inside a bladder when subjected to an outside liquid pressure

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Aug 3rd 2012, 04:51 PM #1 Junior Member   Join Date: Aug 2012 Posts: 1 Pressure inside a bladder when subjected to an outside liquid pressure I have an elastic bladder that is charged with 300 psi gage pressure of a nitrogen gas inside the bladder, at atmospheric pressure outside the bladder. This is being used as a pulsation dampner for a liquid dye pulsing pump. If I subject that bladder to a liquid dye pressure of 25 psi gage pressure on it's outside surface area, assuming a constant temperature, does the inside pressure increase, or does it take more than 300 psi of liquid pressure on it's outside surface area to compress the bladder and get the nitrogen gas pressure inside the bladder to increase?
 Aug 6th 2012, 06:47 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,352 If the bladder is elastic then increasing the outside pressure increases the inside pressure as well. Reason is that the increased outside pressure causes the bladder to shrink in volume. Think of it this way - the sum of the elastic force of the stretched bladder plus the outside pressure times surface area must equal the inside pressure times surface area. If you increase the outside pressure then that plus the elastic force will exceed the inside pressure, so the bladder shrinks, which raises the inside pressuer until you reach equilibrium.

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