Dear my colleagues,

I'm looking for the method to calculate "Age of Air" for a small residence model in CFX 11.0.

Do you have any experience about air change efficiency?

How do I set up CFX-solve to calculate the age of air?

Thanks for your concerns and I always appreciate your ideas.

Hi,

you have to create a new variable e.g. age_of_air. Then the inlet condition for this variable is age_of_air = 0 and you have to create a subdomain for the whole domain and set a constant source term for age_of_air. Then you can calculate the air change efficiency and the local air change index as well.

If your simulation is already finished you can calculate the air change efficiency by freezing all variables. You just have to solve the new variable age_of_air.

Regards.

Thanks Martin,

I try to run a simulation with your comments.

You mean,

First, I have to make a new variable with CCL? or where I can creat a new variable?

How do I set the age_of_air = 0 at inlet condition?

Thank you for your kind response.

Hi,

you can create an additional variable in pre. The unit is seconds. Then you have to activate the variable in your domain -> fluid models and you can set that an additional transport equation should be solved. Then you can set the inlet boundary condition for this additional variable.

Regards Martin

Dear Martin,

Thank you for your kind response.

You said that I need to set an additional transport equation.

but I can find an transport equation for age of air.

Would you explain the equation more detail?

I appreciate your comment and idea

Regard,

Young

Hi, when you created the new variable, go to domain and there to fluid models and you can see that this new variable has appeared and you can choose that an transport equation should be solved for this variable. Then you can set inlet boundary condition and source term for this variable as mentioned before. You can also look in cfx help for additional variables and you will find more informations.

Regards Martin

Dear Martin,

Thank you for your helf!!

Best Regards,

Young