How to determine the airflow due to a change in temperature?

[foal_11]

TL;DR Summary

If I have a large hollow pipe and heat one end of it (by, say, 10 degrees Celsius), how do I calculate the air flow from the cold to the hot end?

(Sorry for the really basic question. Been 20 years since high school physics and I've been working in a different industry)

 

[Chestermiller]

Can you please provide a diagram?

 

[foal_11]

Would this help? Can ignore the material for the cylinder for now.

 

[Lnewqban]

An internal simultaneous up and down air circulation may be established within the cylinder, as long as the temperature differential is kept (that circulation itself tends to make the internal temperature homogeneous).

This is only a reference, as it is applicable for open ends shafts or chimneys, but it can give you an idea:
https://www.engineeringtoolbox.com/natural-draught-ventilation-d_122.html

 

[foal_11]

Thank you. I had a follow-up question on this.

When you say simultaneous internal up and down circulation, could it end up being unidirectional ?From the hot end (base) to the cold end, as the higher density of air at the base pushes air up as I maintain the temperature differential.

 

[Lnewqban]

In that situation, stratification happens, where static layers of air at different temperatures form.
Heat will then will be transferred from layers of higher temperature to ones of lower temperature until a thermal balance within the whole mass of air is reached, while inducing some internal flow of mass.

In most practical cases, some up-down movement of air will always happen as density becomes homogeneous and some heat is absorbed by or released from the cylinder to the surroundings (think of a lava lamp).

 

[foal_11]

In that situation, stratification happens, where static layers of air at different temperatures form.
Heat will then will be transferred from layers of higher temperature to ones of lower temperature until a thermal balance within the whole mass of air is reached, while inducing some internal flow of mass.

In most practical cases, some up-down movement of air will always happen as density becomes homogeneous and some heat is absorbed by or released from the cylinder to the surroundings (think of a lava lamp).

Great, thank you. This definitely helps.

 

[Lnewqban]

You are welcome.