age of air

January 30, 2007, 07:23

Hi all star-cd and ccm+ users,

I'm using star-ccm to calculate the ventilation efficiency in a HVAC application.

My building is naturally ventilated and I'm simulating the wind interaction with it.

When I calculate the mean age of air (using the scalar equation) I need to set the initial age,0, at the inlet boundary, i.e. with the wind profile. this obviously results in air being a certain age before reaching the building.

Therefore, my question is whether there is any way the initial time condition can be set to zero at the inlet openings of the building. Any help would be super.

January 30, 2007, 09:11

Im not so experienced with ccm+, but I think you can release the scalar directly at the window openings, instead of the inlet, through the use of source terms. You only need to define the regions (at the window openings) where you want to apply the source term.

February 1, 2007, 06:42

Thanks very much,

Your help is good, but I think my problem is related to ccm+,

I have the windows specified as porous baffles, as all my other geometry are impermeable baffles. My intention was to give the window 100% porosity and release the scalar.

Yet, I cannot release the scalar here as the interface boundary condition in ccm+ has no source term for passive scalar associated with it.

Can anyone else advise me?

February 9, 2007, 09:41

Cant you use a source term in the porous region? I have done that in CMM+ to track air from a radiator. The source term is not applied at boundaries but in regions.

January 30, 2007, 07:23	age of air	#1
teddy Guest Posts: n/a	Hi all star-cd and ccm+ users, I'm using star-ccm to calculate the ventilation efficiency in a HVAC application. My building is naturally ventilated and I'm simulating the wind interaction with it. When I calculate the mean age of air (using the scalar equation) I need to set the initial age,0, at the inlet boundary, i.e. with the wind profile. this obviously results in air being a certain age before reaching the building. Therefore, my question is whether there is any way the initial time condition can be set to zero at the inlet openings of the building. Any help would be super.

January 30, 2007, 09:11	Re: age of air	#2
tobbe Guest Posts: n/a	Im not so experienced with ccm+, but I think you can release the scalar directly at the window openings, instead of the inlet, through the use of source terms. You only need to define the regions (at the window openings) where you want to apply the source term.

February 1, 2007, 06:42	Re: age of air	#3
teddy Guest Posts: n/a	Thanks very much, Your help is good, but I think my problem is related to ccm+, I have the windows specified as porous baffles, as all my other geometry are impermeable baffles. My intention was to give the window 100% porosity and release the scalar. Yet, I cannot release the scalar here as the interface boundary condition in ccm+ has no source term for passive scalar associated with it. Can anyone else advise me?

February 9, 2007, 09:41	Re: age of air	#4
tobbe Guest Posts: n/a	Cant you use a source term in the porous region? I have done that in CMM+ to track air from a radiator. The source term is not applied at boundaries but in regions.