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# Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

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## Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

(OP)
I am trying to calculate the pressure change due to temperature fluctuations of an incompressible fluid (Transmission Fluid) inside a closed reservoir tank.

According to an equation I have found, h2 - h1 = c(T2-T1) + v(P2-P1), provides property changes of incompressible fluids where:

h = enthalpy
c = specific heat
T = Temperature
v = specific volume
P = Pressure

First, is this this the correct equation? Second, is there a good place to find these values for Transmission Fluid?

THANKS!!

### RE: Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

Is there any vapor space in the tank? The air/vapor will expand much more than the liquid will, so start there.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

Have you looked at this FAQ?

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

Liquids are not incompressible and you need to include the bulk modulus to get a sensible answer.

However even the smallest amount of compressible gas will nullify any liquid expansion case.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

I think you'll get into an iterative solution. The tank itself expands, due to temperature and due to increased pressure. The liquid expands due to temperature and compresses due to pressure. With known temperatures, assume a pressure, compare the resulting volumes of both and recalculate until you hit a solution. It MAY turn out that some of those effects are negligible, but you won't really know that without calculating them.

The first equation listed gives the change in enthalpy, but I don't see that it immediately relates to the problem at hand.

### RE: Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

(OP)
Thanks Everyone!!! Do you know of a good source for Bulk Modulus / Compressibility Factors and also Volumetric Coefficients of Expansions for fluids??

### RE: Pressure Change Due to Varying Temperature of a Closed Cell Oil Tank with No Expansion Chamber

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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