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

In summary, a diagram of an internal simultaneous up and down air circulation within a cylinder could help explain how heat is transferred.
  • #1
foal_11
4
2
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)
 
Engineering news on Phys.org
  • #2
Can you please provide a diagram?
 
  • #3
Would this help? Can ignore the material for the cylinder for now.
 

Attachments

  • Image.png
    Image.png
    19.3 KB · Views: 262
  • #4
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

:cool:
 
  • Like
Likes foal_11
  • #5
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.
 
  • #6
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).
 
  • Like
Likes foal_11
  • #7
Lnewqban said:
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.
 
  • #8
You are welcome. :smile:
 

1. What is the formula for determining airflow due to a change in temperature?

The formula for determining airflow due to a change in temperature is Q = m * Cp * ΔT, where Q is the airflow in cubic feet per minute (CFM), m is the mass flow rate in pounds per minute (lb/min), Cp is the specific heat of air at constant pressure (0.24 BTU/lb°F), and ΔT is the change in temperature in degrees Fahrenheit.

2. How does temperature affect airflow?

Temperature affects airflow by changing the density of air. As temperature increases, air becomes less dense and therefore takes up more space. This leads to an increase in airflow as the same mass of air occupies a larger volume.

3. What is the role of air velocity in determining airflow due to a change in temperature?

Air velocity plays a crucial role in determining airflow due to a change in temperature. It is directly proportional to the mass flow rate and therefore has a significant impact on the overall airflow. Higher air velocity results in a higher mass flow rate and thus, a higher airflow.

4. How can I measure the change in temperature to determine airflow?

The change in temperature can be measured using a thermometer or a temperature sensor. It is essential to ensure that the temperature is measured accurately and at the same location as the airflow to get an accurate calculation.

5. Are there any other factors that can affect airflow due to a change in temperature?

Yes, there are other factors that can affect airflow due to a change in temperature. These include humidity, altitude, and air pressure. These factors can impact the density of air and, in turn, affect the overall airflow calculation.

Similar threads

A few questions about airflow and filters...
    • Mechanical Engineering
Replies
5
Views
1K
Calculating the change of a Wind Turbine's RPM due to Airflow as f(t)
    • Mechanical Engineering
Replies
3
Views
1K
Underground pump vault airflow considerations
    • Mechanical Engineering
Replies
15
Views
843
How to determine mdot for choked airflow through a valve, given T,P
    • Mechanical Engineering
Replies
3
Views
997
Calculating force input to air cylinder by airflow rate
    • Mechanical Engineering
Replies
2
Views
1K
I Wondering how much thrust a drone propeller generates
    • Classical Physics
Replies
6
Views
2K
Total force from air spring model (double acting piston)
    • Mechanical Engineering
Replies
8
Views
1K
Airflow Across a Persistent Cold Air Pool in a Basin
    • Mechanical Engineering
Replies
1
Views
2K
I Airflow direction -- Improving the cooling of my computer
    • Other Physics Topics
Replies
5
Views
3K
Calculating energy requirements to sustain temperature
    • Mechanical Engineering
Replies
6
Views
934

Hot Threads

Recent Insights

Back
Top