Natural draft stack effect

I’m no CFD analyst by any stretch of the imagination, so would appreciate some help selecting the correct parameters for a ‘simple’ natural draft cooling tower using the stack effect. The tower is outside exposed to atmosphere at both the bottom/ inlet and top/outlet.

Is it as simple as running the convective heat transfer with air as the fluid and then setting the pressure at the respective elevation based on altitude or are there other conditions that need to be set as well?
Thanks in advance

Hello @mwightman , and thanks for posting your question in the Forum!

Did you already import your model to one of your projects? If possible, could you please share a link to your project so we can have a look at it?


Hi @kaany ,
Thanks for replying. I’ve created the model in CAD and then created the flow region and split it twice to reduce the size on the basis its a very basic tube. Hopefully this link works.

I want to be able to compare this to the hand calc for stack effect to make sure I have the correct settings before making exploring more complex geometries. If you are able to help, and there’s a relevant tutorial you can also share it would be nice to understand the CFD as well.
Many thanks

Hello @mwightman , thanks for the information and the link!

I don’t think there is a particular tutorial focusing on the subject, however I will do my best to assist you here.

  • Convective heat transfer analysis type is indeed the correct type, as you’re only dealing with the internal flow region rather than flow + solid volumes.

  • Please make sure that Gravity is correctly defined once analysis type is created by using the model tab. Gravity direction and magnitude is quite important as we’re going to investigate hot air rising.

  • You will need two different boundary condition types. Wall boundary condition to create constraints on the thermal properties of your boundaries. (a fixed temperature, heat gain, heat release, etc.). And a Natural convection inlet/outlet boundary condition to allow air to enter or exit the domain freely.

Other steps should be very similar to the workflows provided in other tutorial pages. Therefore, I recommend following one of them, incorporating a convective heat transfer analysis, to quickly familiarize yourself with the platform.

I hope these would be helpful!

Thanks, Kaan