Air movement in an exhaust systems

Hello I'm trying to understand how exhaust systems work .In general I want to understand how air movement changes according to leight of vent tubes. Example I have made little vent system with in lane fan that sucks air out of room. As I understand air speed in tube that is pulling air from chamber to fan is constant depending of fan speed, but air movement in exhaust part of tube(after fan)? Will air apeed will change if I will change leight of exhaustion tube, and making some angles will level down noise but will it lower air speed in end or maybe air will gather in exhaust tube if it will be too
long?
Raivis

 

[russ_watters]

There volumetric flow rate has to be the same everywhere in the duct and adding more ductwork adds friction, reducing that flow rate.

 

There volumetric flow rate has to be the same everywhere in the duct and adding more ductwork adds friction, reducing that flow rate.

Thanks for response!
So it mens there must be some way to calculate optimal leight of duct. If there is can I get formula for thoes calculations. I tried to google Volumetric flow rate I got simple explanation and SI unit, but there's no other formulas that would explain efficiency.

 

[russ_watters]

Thanks for response!
So it mens there must be some way to calculate optimal leight of duct.

What does "optimal length of duct" mean?

 

What does "optimal length of duct" mean?

Leight of duct that will allow air travel trough it and not lose high amount of velocity.

 

[russ_watters]

Leight of duct that will allow air travel trough it and not lose high amount of velocity.

In that case, the optimal duct length is zero.

 

Leight of duct that will allow air travel trough it and not lose high amount of velocity.

In that case, the optimal duct length is zero.

After 3h scrooling and reading in google I found things I was looking for. But thanks for helping brighten my flat brain.