Density of fluid with respect to temperature and pressure

akash_max · November 3, 2011, 15:16

Hi All,

I not able to find how to input material property for the fluid(diesel) with respect to temperature and pressure. I have complete data that is pressure range 0 to 2000 bar and temperature range 0 to 200 degree Celcius.

Do i need to write a expression to it or any way i can just feed the excel data into the CFX where in it produces the graph and uses the same.

Similarly I need to give cavitation saturation pressure with respect to temperature.

If this is done then i can run my model with thermal conditions first and then the cavitation model to find the effect of thermal effects on cavitation.

I need to check out with raise in temperature how much the cavitation raises as the fluid passes through different orifice.

I need to also give specific heat capacity with respect to temperature and also the dynamic viscosity with respect to temperature.

I am using thermal energy with inlet as total pressure and temperature and outlet as static pressure. Wall being the adabatic.

Kindly help me out resolving this issue.

Best Regards
Akash A V

stumpy · November 3, 2011, 16:46

What you want is bi-linear interpolation since the density depends on two variables. There's no built-in bi-linear interpolation in CFX-Pre, so yes, you need to come up with an expression that describes the density as a function of (T,p). I don't think Excel can curve fit a bi-linear function, but it would be nice if it could (and please tell me how to do it!). Anybody know of any software that can do that curve fit?

akash_max · November 4, 2011, 09:12

Hi,

Thanks for your reply.

I would request to kindly send me formulae for density variation with respect to temperature and pressure separately. (Density with repect to temp)( Density with repect to temp)

So that I will assign them individually and check how much is the variation.

Please let me know the CEL function for above mentioned variations.

Thanks in Advance

Regard
Akash A V

ghorrocks · November 6, 2011, 05:54

You already have defined the density as a function of pressure. Just do the same for temperature and it is straightforward from there.

mauricio · November 6, 2011, 10:00

Try a software like Curveexpert to find a fit for your temperature and pressure data points. The just use that expression in the material properties. Do check how precise is the fit though.

November 3, 2011, 15:16	Density of fluid with respect to temperature and pressure	#1
akash_max New Member Akash Join Date: Sep 2011 Posts: 12 Rep Power: 16	Hi All, I not able to find how to input material property for the fluid(diesel) with respect to temperature and pressure. I have complete data that is pressure range 0 to 2000 bar and temperature range 0 to 200 degree Celcius. Do i need to write a expression to it or any way i can just feed the excel data into the CFX where in it produces the graph and uses the same. Similarly I need to give cavitation saturation pressure with respect to temperature. If this is done then i can run my model with thermal conditions first and then the cavitation model to find the effect of thermal effects on cavitation. I need to check out with raise in temperature how much the cavitation raises as the fluid passes through different orifice. I need to also give specific heat capacity with respect to temperature and also the dynamic viscosity with respect to temperature. I am using thermal energy with inlet as total pressure and temperature and outlet as static pressure. Wall being the adabatic. Kindly help me out resolving this issue. Best Regards Akash A V

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November 3, 2011, 16:46		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 22	What you want is bi-linear interpolation since the density depends on two variables. There's no built-in bi-linear interpolation in CFX-Pre, so yes, you need to come up with an expression that describes the density as a function of (T,p). I don't think Excel can curve fit a bi-linear function, but it would be nice if it could (and please tell me how to do it!). Anybody know of any software that can do that curve fit?

November 4, 2011, 09:12		#3
akash_max New Member Akash Join Date: Sep 2011 Posts: 12 Rep Power: 16	Hi, Thanks for your reply. I would request to kindly send me formulae for density variation with respect to temperature and pressure separately. (Density with repect to temp)( Density with repect to temp) So that I will assign them individually and check how much is the variation. Please let me know the CEL function for above mentioned variations. Thanks in Advance Regard Akash A V

November 6, 2011, 05:54		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,011 Rep Power: 146	You already have defined the density as a function of pressure. Just do the same for temperature and it is straightforward from there.

November 6, 2011, 10:00		#5
mauricio Member Mauricio Labarca Join Date: Aug 2009 Posts: 35 Rep Power: 18	Try a software like Curveexpert to find a fit for your temperature and pressure data points. The just use that expression in the material properties. Do check how precise is the fit though.