age of air calculations

October 19, 2007, 08:38

Hello,

I am modelling natural ventilation of an office with star-ccm. I want to get the the age of air in the office so I defined a new region at the window to release the scalar.In this region I have the scalar source set to 1/density. In the air properties I have set the Schmidt number to a high value to reduce molecular diffusivity.

This should be correct, shouldn't it? I am asking this because I seem to be getting extremely small values, e.g circa 0.01-0.1 s, for 60 m^3 room with 20m^3/s ventilation rate. I assume values should be circa 3 s? Am I doing something wrong?

October 20, 2007, 08:38

Fixed it; I just hadn't the source term included in all other regions

October 28, 2007, 07:26

Dude, why have you increased the schmidt number to high value, what is the reasoning behind this? what is the rationale?

October 19, 2007, 08:38	age of air calculations	#1
tom Guest Posts: n/a	Hello, I am modelling natural ventilation of an office with star-ccm. I want to get the the age of air in the office so I defined a new region at the window to release the scalar.In this region I have the scalar source set to 1/density. In the air properties I have set the Schmidt number to a high value to reduce molecular diffusivity. This should be correct, shouldn't it? I am asking this because I seem to be getting extremely small values, e.g circa 0.01-0.1 s, for 60 m^3 room with 20m^3/s ventilation rate. I assume values should be circa 3 s? Am I doing something wrong?

October 20, 2007, 08:38	Re: age of air calculations	#2
tom Guest Posts: n/a	Fixed it; I just hadn't the source term included in all other regions

October 28, 2007, 07:26	Re: age of air calculations	#3
bruce mceldrick Guest Posts: n/a	Dude, why have you increased the schmidt number to high value, what is the reasoning behind this? what is the rationale?

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