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Re: [EnergyPlus_Support] Can someone advice me the trick in simulating stack effect.


The appropriate solution depends on what you are trying to model.

If you are trying to model a multifloor atrium, you will need to create an AirflowNetwork as Pedro has mentioned, however, this type of analysis will most likely be better suited to a CFD model.

If you are trying to model a more typical occupied zone that employs thermal stratification via displacement ventilation, or underfloor air distribution, EnergyPlus has a "RoomAirModelType" object which will allow you to create subzones within each EnergyPlus zone that model thermal stratification effects.  There are corresponding RoomAirSettings objects specifically tailored to model UFAD and displacement ventilation, and allow you to control the thermal gradients as well as the vertical heights of the subzones.

When employing the RoomAirModelType objects and using temperature gradients, be sure to change the SurfaceConvectionAlgorithm:Inside setting to "Detailed" for the thermally stratified zones.

If you are indeed modeling the UFAD system, check out this link to the Center for the Built Environment.


They have created an excel based tool that gives a good example of how to model UFAD in EnergyPlus.

Hope this helps,


On Mon, Jan 10, 2011 at 3:17 AM, Pedro Peixeiro <ppeixeiro@xxxxxxx> wrote:

Hello Wonjun

By what i could tell so far from my own experience, the approach you're considering is correct but you also need to have a way to specify airflow between those zones. AirflowNetwork objects can do the trick to some extent (it considers both stack effect and wind induced pressure difference). This approach looses reliability if the horizontal openings are too large (i'm not sure what is considered a "large" opening though). Read both the I/O and the enginnering reference for more details. hope it helps.


On 08-01-2011 15:32, Wonjun wrote:

Hello fellows.

When it comes to simulate buoyancy flow where the well-mixed assumption can be errorneous, how can I overcome ths problem in EnergyPlus?

When I wanna know just a vertical temperature gradient of a certain zone, I can apply IRT material of EnergyPlus.
But as far as I know it can't be applied to know the airflow by the temperature stratification. right?

How about this trick?
Divide vertical zone by a number of horizontal holes.
Discharge coefficient of each hole should be 1, I think.
By doing so, can I overcome it to some degree?

Thanks in advance.
Best regards.


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