There is a air duct with know velocity inlet and pressure outlet, I want to add a source of water vapor in the middle of the duct with known flow rate and temperature. How can I use the source term menu in Boundary Condition of the water vapor zone? Actually the main problem is that fluent does not get the composition of mass source.

[sunilpatil]

Hello sir,
How can we include relative humidity while defining material in fluent and also which multiphase model we have to use for humidity related calculation

Thank you sir
sunil M P

[A CFD free user]

Hi, sunilpatil
You can include relative humidity in your problem by setting the calculated value for water mass fraction in B.C. Relative humidity is defined as:
RH=Ph2o/P*
From here, by having the value for RH, let say 0.5 for instance, you can now calculate Ph20 and therefore, obtain the mole fraction using:
Ph2O=x. P in which, P is total pressure and x is mole fraction. Having the values for mole fraction, you can readily convert them into mass fraction:

wi=xi.Mi/Mavg
Mavg=sum (xi.Mi)

where, wi is mass fraction of the species i and Mavg is average molecular weight of the involved species.
I don't know what exactly is your problem, but you can even access the values for RH by getting a contour of it from: Graphic and animation\contours\species and from drop-down option, select "relative humidity".
Hope it helps
Good luck

[sunilpatil]

Hello sir,
Thank you for your reply
i want define mass fraction in fluent how to do this and also which multiphase model i have to use for these kind of problems.
Thank you sir
Sunil