Air movement in an exhaust systems

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Discussion Overview

The discussion revolves around understanding the dynamics of air movement in exhaust systems, specifically focusing on how the length and configuration of vent tubes affect air speed and volumetric flow rate. Participants explore the implications of duct length and angles on airflow efficiency and noise levels.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how air speed changes in the exhaust part of the tube after the fan, particularly with varying lengths and angles of the exhaust tube.
  • Another participant asserts that the volumetric flow rate must remain constant throughout the duct, noting that additional ductwork introduces friction which can reduce flow rate.
  • A participant seeks a formula for calculating the optimal length of duct to maintain efficiency, indicating a desire for more technical details on volumetric flow rate.
  • There is a discussion about what constitutes "optimal length of duct," with one participant suggesting it refers to a length that minimizes velocity loss.
  • A later reply humorously suggests that the optimal duct length could be zero, indicating a playful disagreement about the concept.

Areas of Agreement / Disagreement

Participants express differing views on the concept of optimal duct length and its implications for airflow efficiency. There is no consensus on what the optimal length should be or how to calculate it effectively.

Contextual Notes

Limitations include a lack of specific formulas for calculating duct efficiency and the dependence on various assumptions regarding airflow dynamics and duct configurations.

Who May Find This Useful

Individuals interested in HVAC systems, mechanical engineering, or anyone looking to understand airflow dynamics in exhaust systems may find this discussion relevant.

RaavensLv
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
 
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There volumetric flow rate has to be the same everywhere in the duct and adding more ductwork adds friction, reducing that flow rate.
 
russ_watters said:
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.
 
RaavensLv said:
Thanks for response!
So it mens there must be some way to calculate optimal leight of duct.
What does "optimal length of duct" mean?
 
russ_watters said:
What does "optimal length of duct" mean?
Leight of duct that will allow air travel trough it and not lose high amount of velocity.
 
RaavensLv said:
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.
 
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RaavensLv said:
Leight of duct that will allow air travel trough it and not lose high amount of velocity.
russ_watters said:
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.
 
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