Hi Heiko,
I would like to use the “air exchange with ambient air for a given air change rate” for the simulation of a ventilated air gap and do have the following questions:
1.) I would still discretize the whole gap and assign the source [Airchange] to all grid elements?
2.) I would adapt the material “air” with a higher lambda value (to model the “convection” and not reflecting indirectly the surface resistances) the and assign the surface resistances as contact condition [Air MaterialBoundary] - or just as additional resistance (but the latter would not influence the vapour transport …)?
3.) The this way modelled air exchange would now be able to “discharge” moisture coming from one of the adjacent sides? And on the other hand side, moisture coming in with the air flow could be transferred to the material, if the conditions are such (to model the “condensation” if the surface has respectively low temperature)?
4.) Is there a way to keep track of the moisture change of the ventilation air? Are the MoistureLoadAirChange and MoistureEnthalpyAirChange referred to incoming or outgoing air?
Thanks a lot for clarification!
Alexandra
source AirChange for ventilated gap
Moderatoren: ghorwin, fechner, ruisinger
Re: source AirChange for ventilated gap
Hello Alexandra,
To your questions.
1) Yes, a discretisation is necessary
2) Yes, you can use the air from the database with the higher lambda value corrsponding to the thickness of the gap. The surface coefficients can be modelled by using the ai-material-boundary contact conditions. This doesn't add a resistance. It exchange the normal transport behaviour by a model like a boundary.
3) The air is a material. It will behave similar to other materials. That means vapor transport, and in case of condensation liquid transport to the adjacent materials is possible. The air exchangecan transport heat and moisture in and out depending on the conditions in the air gap and the state of the inflowing air.
4) The Moisture loadAirChange is the amount of moisture what is exchanged by the source. If positive its a source to the gap otherwise a sink. The enthalpy is only the latent heat exchanged by the flow.
Ciao
Heiko
To your questions.
1) Yes, a discretisation is necessary
2) Yes, you can use the air from the database with the higher lambda value corrsponding to the thickness of the gap. The surface coefficients can be modelled by using the ai-material-boundary contact conditions. This doesn't add a resistance. It exchange the normal transport behaviour by a model like a boundary.
3) The air is a material. It will behave similar to other materials. That means vapor transport, and in case of condensation liquid transport to the adjacent materials is possible. The air exchangecan transport heat and moisture in and out depending on the conditions in the air gap and the state of the inflowing air.
4) The Moisture loadAirChange is the amount of moisture what is exchanged by the source. If positive its a source to the gap otherwise a sink. The enthalpy is only the latent heat exchanged by the flow.
Ciao
Heiko