Add total mass using sources to multi component fluids
 

I am trying to add water vapor to a air-water vapor mixture as it travels along a channel. I have the water vapor component using the transport equations and the air component using the constraint equation.

When I add a source term for water vapor to a wall, I notice the CFX help files note that "Sources for a particular component in a multicomponent fluid do not introduce any additional mass and so the sum of all component sources (including the constraint) must be zero."

I do not want this to be the case; I want the air massflow to be constant and the total massflow to increase.

Is there a way to do this?

Can you do a mass source as well to keep the air mass conservation?