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 bill September 13, 2004 09:16

natural ventilation on buildings

Hello. I am trying to simulate natural ventilation flow into a building. (Just a simple room 10 m x 10 m x 6 m with a velocity inlet and a pressure outlet). Some of the adjustments that I make in order to set up the model are: „« Boundary conditions on the walls (thermal+ heat flux). What is the difference between heat flux and heat generation rate. Does heat generation rate means the total thermal transfer in Watts that comes into the building from all the walls?

„« Is velocity inlet and pressure outlet the appropriate boundary conditions for inlet and outlet of the air. If I want to simulate negative pressure on pressure outlet should I adjust (gauge pressure) to a value less than 101325? „« On materialsˇXdensity I use the boussinesq model and on solution control I use for the discretization of pressure body force weighted. Please tell me if you think that I have to make extra adjustments or changes.

 carlos ortiz September 20, 2004 21:09

Re: natural ventilation on buildings

Hi Bill,

To start with you may have the right input/output boundary conditions for the flow. That combination may work as suggeted in the User's Guide. But do you have any idea of the values you are going to associate to those boundary conditions. Even if your air inlet and outlet are exposed to atmospheric pressure, you may have a pressure gradient between the two. Otherwise your flow will never take place.

In regards with the heat flux and the heat rate, try not to consider heat flux unless you are very familair with convection and radiation problems and you have means to measure heat fluxes.

What is the heat source inside your room?. If it's a volume you may consider the total heat dissipation in the volume. There is an easy way to measure it or compute it.