Hvac vs supply/extract vents

[ShehabGamrah]

Hi all. I am interested in modelling a room with a supply and extract grilles at top and bottom to check the temp profile within room from supply to extract and velocity for cold draughts at the grilles. For these values would it matter If I model the HVAC duct and grille properties. Or can I just use supply and exhaust vent surfaces at floor and ceiling rather than using HVAC vents and ducts. The grilles would be supplying air with cold temperatures than environment.

[drjfloyd]

If you don't have recirculation (i.e. some of the exhaust is recirculated to the supply) and you don't care what happens to the gas that is exhaust, then you don't need to use HVAC. However, if you have a sealed room you will need to take care to maintain the room pressure. If you are exhausting hot gas and supply cold gas then equal volume flows at supply and exhaust will not mean equal mass flows.

[ShehabGamrah]

Thanks, supply is and exhaust are far away so wouldn’t need to care about recirculation. So what should be done with regards to pressure.