Transition duct, rectangular section to circular section

[abrewmaster]

So I was trying to understand how fluid flow is affected through a transition duct when I found this study that was done. In the study it was noticed that there was a dramatic drop in velocity near the end of the transition near the edges and was also dependent on the length in the transition (Which makes sense). I was curious if anyone knew anything about the math behind this relationship to basically calculate the pressure drop and or velocity change based on the initial cross section, final cross section,and length of the transition (possibly even angle of transition and other things like that).

 

[MikeHalloran]

I don't know if the basis is experimental or theoretical, but the 'ASHRAE Handbook' has tabular tools that cover an exhausting range of possibilities.

Bring your wallet.


Mike Halloran
Pembroke Pines, FL, USA

 

[racookpe1978]

I have not used the for design (only for interference analysis within a 3D model), but do the ASHREA tables work for typical liquid flow and losses, or only at the gas-air-vapor densities and speeds and coefficients?

Nominally, the same equations hold if the analysis is dimensionless, but practically? Do they work for design of real world parts with real world speeds and wall properties?

 

[MikeHalloran]

I've used the ASHRAE tables to analyze custom exhaust gas systems for Diesel engines, with temperatures up to 1000F and velocities up to 100mph. Our measured backpressures on systems as installed usually correlated pretty well to our calculations from the tables, for exhaust gas with no added water. We guaranteed that our complete systems would meet backpressure specs at sea trial. ... and I don't recall having to cough up money on that account.

For 'wet' systems, where engine cooling water is injected to cool the piping, backpressure is much more difficult to calculate, but that's another discussion.



Mike Halloran
Pembroke Pines, FL, USA