variable composition mixture properties
 

I created a variable composition mixture from water and salt particle solid (an aqueous solution), Any way to define its physical and thermodynamic properties as a function of its temperature and salt/water mass fractions.

If not, even by a FORTRAN subroutine, so any way to export the default CFX value of this properties

Re: variable composition mixture properties
 

Dear Neser25,

By default, the ANSYS CFX solver computes the properties of a mixture as the weigthed sum of the property components i.e.

Mixture prop = sum (Mass Fraction_i * property_i)

Of course, density is computed differently. The formula above is just a crude approximation.. If you do have a different mixture rule, you can do so under the MIXTURE PROPERTIES section for the mixture material.. You can basically override the ANSYS CFX calculation for each property using your own formulas..

Opaque.

Re: variable composition mixture properties
 

Dear Opaque,

Thank you for your reply

Under the MIXTURE PROPERTIES section for the mixture material, the program does not let me use the temperature and water mass fraction as a variables in the formula. I am modelling a spray evaporation process. Therefore, the mass fraction of water in the aqueous solution droplet is variable.

Any way to add the mass fraction to the formula?. If it is not possible, I can set it with its initial conditions before the spraying process. So, any way to define the properties during CFX calculation through a FORTRAN subroutine for example

Regards

Re: variable composition mixture properties
 

Your only option is to set the properties of the pure substances (in this case water & sand right?).

Other than mixture density the solver assumes the formula printed by Opaque.

Homogeneous binary mixture VERSUS Variable composition mixture.
 

Please, I want to know the difference between homogeneous binary mixture and variable composition mixture in Ansys cfx, and when can I use which.

Homogeneous Binary Mixture is a mixture of the same substance in two different states: solid+liquid (melting/solidification model), liquid+vapor (wet steam)

Variable Composition Mixture is a mixture of different substances where the composition can change as the solution progresses, say reacting components.

Hope the above helps,

Thank you very much for your reply @Opaque, I have a liquid material of saltwater and I also have a gaseous material for water vapour, I want to mix both materials together, should I use homogeneous binary mixture or variable composition mixture. Thank you.