Isothermal compressibility & volume expansitivity 2

[adesline]

I am on a research project concerning refrigerants and I need to find relations in terms of pressure and temperature for Isothermal compressibility & volume expansitivity. Do u know where I can get those or do u have any?

 

[25362]

Tabulated values of thermophysical properties for the common liquid refrigerants such as ethane, ethylene, propane, propylene, butane, i-butane, ammonia and R-22 can be found in the free NIST webbook tables. Values for their isothermal compressibility and cubic thermal expansion, can be inferred from the tabulated data.
For tetrachloromethane and others I think the CRC Handbook of Chemistry and Physics can be of help.

 

[adesline]

Thanks a lot. Pls can you give me info on how to get them because I have not been able to access free tables before now (NIST).

Also would the information there be in form of values or a correlation or an equation. The last two would be most helpful for me.

Thanks again

 

[25362]

From the data on densities and speed of sound at various P,T conditions you can estimate isothermal compressibility and thermal expansion.
The source I mentioned can be raised by asking

http://webbook.nist.gov/chemistry/

Press name => write name => condensed phase => search => fluid properties => choose units => select range => delete v in small square, and press for data.

If you need an example of how to estimate those properties just ask. Good luck.

 

[adesline]

Thanks a billion!!! You are great. Please I would love to have an example.

 

[25362]

Take, for example, liquid ammonia under 14 atm pressure and 30^oC.

temp., ^oC Vol., m³/kg

29 0.0016751
30 0.0016795
31 0.0016839

Cubic thermal expansion, (1/V)(dV/dT)_p:

(16795-16751)/16751=0.0026267
(16839-16795)/16795=0.0026198

Average:0.0026232/^oC​

Isothermal compressibility at 30^oC, (1/V)(dV/dp)_T

Press. bar Volume, m³/kg

13.5 0.0016797
14.5 0.0016794

The change:

(3/16797)=1.786*10^-4/bar​

The exercise could have been made also estimating the bulk volume modulus of elasticity via the sound speed and the density, but with larger deviations. The isothermal compressibility being its reciprocal.

 

[Montemayor]

Kudos to 25362 for an excellent example of practical and profitable use of authoritative, available, & free engineering information!

Art Montemayor
Spring, TX

 

[adesline]

God bless you real good!!!!!!!!
Thanks!!!!!!
Ade

 

[msmedesign]

I am trying to calculate the pressure increase due to temperature increase of a fluid which is trapped in the pipiline under temerature increase. I know the P1 and T1, T2 and thermal expansion ratio of the fluid. Please let me know how to calculate the P2

Thanks

 

[25362]

To msmedesign, assuming the pipe is rigid, divide the cubic thermal expansion (1/V)(dV/dT)_p by the isothermal compressibility
(1/V)(dV/dp)_T at the starting conditions.

Here is an example for ethanol at 70^oC with data taken from the CRC Handbook of Chemistry and Physics:

(1/V)(dV/dT)_p = 0.00167/^oC

(1/V)(dV/dp)_T = 0.001593/Mpa

(1/V)(dV/dT)_p / (1/V)(dV/dp)_T = dp/dT =​

0.00167/0.001593=1.05 Mpa/^oC= 10.5 bar/^oC​

This is an approximate result since the compressibility is assumed at relatively low pressures, but it may serve as an indication of what is to be expected.