Water Saturation properties 1

[visit]

In 1997 the International Association for Properties of water and steam (IAPWS) adopted the new industrial standard of (IAPWS-IF97) for thermodynamic properties of water and steam.
I need heat capacity Cp and speed of sound w for these point at saturation line or region 4
T,Kelvin , 622,623, 624 and 646,646.5 ,647

Thanks all

 

[prodeng]

I'm sure there are charts somewhere to give you this data. The only way I know to do it is the long way - calculate it. The Cp value at that point is dependent on the enthalpy and temperature (by definition). Not knowing your background at all, this could be a long, detailed process to come up with a good value. There are formulas, but each value (like enthalpy) usually leads to another unknown (like internal energy) to end up with the value you need. A good thermodynamics book has all of these formulas and values. If you know of an industry where the type of information you need is commonly used, there may be some charts you can find within that realm. Hope you can find what you need. As far as the speed of sound, it too can be calculated depending on pressure, temperature, etc. but there may be a chart somewhere giving you the information you need.

 

[gunsmith]

This link may help You (it is in German but a table):

http://hydra.nat.uni-magdeburg.de/phys/PT5.html

Speed of sound can calculated with the gas laws.

Andreas

 

[gunsmith]

Formula for the speed of sound is:

a=sqrt(kappa*R*T)

a= velocity of sound (m/s)
kappa=cp/cv ratio of specific heats (1)
R= gas constant (J/kg/°K)
T= temparatue (°K)

For example air 20°C (=293 °K):

kappa=1.4
T=293 °K
R=287 J/kg/°K

a=sqrt(1.4*293*287)

a=343.11 m/s

Good luck

Andreas

 

[poetix99]

I know that many of the "ideal gas" assumptions are significantly in error for steam at or near saturation conditions. It seems to me that this could very well be the case for speed of sound (can't imagine why not) but I don't know for sure.

I advise some caution to you regarging the previous posts.

 

[25362]

Sorry for the delayin answering: the NIST chemistry webbook should give the pertinent values.

 

[sailoday28]

To calculate sound speed on the saturation line

c^2=-v^2 (dp/dv) isentropic equation (1)
v is known from the sat temp or press.

To calculate dv/dp along an isentrope

v=vf+(So-Sf)*vfg/sfg equation (2)
But from Claus-Claper relation
dp/dT=sfg/vfg (3)
So that v=vf+(So-Sf)*dT/dp (4)
Take derivative of this last expression (with So know from the specified sat press or temp) with respect ot pressure
and equation (1) may be solved for sound speed.