Venturi Design?

[bnmorgan]

I'm trying to design a venturi tube to increase the velocity of warm rising air so that it can turn a small fan placed in the air stream.
Could someone give me some advice on proper design of a venturi, such as ratios of minimum diameter to intake, exhaust to intake, lengths, such things as this.

Thank you much

SW2006 & NX4

 

[Jalink]

bnmorgan,
It appears you do not get a reply on your request by people experienced on this subject. You are speaking about a small fan placed in warm rising air accellerated by a venturi boundary. The driving forces involved are small, which will lead to large geometries to achieve some real power on the fan.

I doubt whether there are ready available design data on this type of fluid system. You could start with an indicative study on the subject.

Take a height with corresponding difference in air density. Start with a normal venturi design and determine the air velocity following from the driving force (density difference). Use for the axial fan an actuator disc approach and assume streamlines in the venturi. Modify the air velocity and pressure distribution along the streamlines for the differential pressure over the axial fan. Using this approach diameter ratios for inlet, minimum diameter and outlet diameter in ideal conditions can be determined.

There after the influence of the boundary layer (prevention of boundary layer separation and minimalisation of the boundary layer thickness) can be investigated leading to length (height) requirements for the venturi.

I have heard of a study on power generation on the North Sea with such a venturi system, but have never heard anything more on it since.

Good luck with your design

 

[Jalink]

bnmorgan,

If you are just looking for a guide on the design of the venturi, you could try the geometry of a natural draft cooling tower as a starting point.