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A 1.5m diam chimney locally has been fitted with a 45degree cone in order to increase the exit velocity and thus project the pollution higher.

It seems visually to have failed, can you direct me to any standards that advise on the design such exit terminals for flues or ductwork ?

Thanks Tom.

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  • $\begingroup$ I would be surprised if tapering the top of a chimney with an exit cone increases the upward velocity enough to significantly project pollution much higher than it would go without the exit cone. The exhaust gases won't have that much momentum, and as soon as they hit the air above the chimney any enhancement of the gases' upward velocity due to an exit cone should be damped pretty quickly. Best solution to project exhaust pollution higher seems to be to simply build tall chimneys, which is what manufacturing industries actually do. $\endgroup$ – Samuel Weir Feb 17 at 22:51
  • $\begingroup$ Thanks Samuel, it has been recommended as a solution to planning permission height restrictions, but it seems the air does not come out as a vertical jet at the average angle of the 45degree "bend" of the air. It just seems to cause a lot of turbulence at the exit of the stack and would imagine the stack industry would have a design guide for stack problems such as this. I have seen straightening vanes in some fans, but never seen design details of a chimney. $\endgroup$ – TomTom Feb 18 at 10:26

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