The Significance of Fourier Number: Understanding Heat Conduction in Solids

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SUMMARY

The Fourier number (Fo) is a dimensionless quantity used in heat conduction analysis, defined as the ratio of thermal diffusivity multiplied by time to the square of a characteristic length (radius). It is crucial for determining the lumped heat capacity in solids, indicating when a conduction process has reached a steady state. Specifically, when the Fourier number exceeds one, the heat conduction process is considered to be in a steady state, allowing for simplified thermal analysis. The equation for Fourier number is expressed as Fo = αt/L², where α represents thermal diffusivity, t is time, and L is the characteristic length.

PREREQUISITES
  • Understanding of thermal diffusivity and its calculation
  • Familiarity with heat conduction principles
  • Knowledge of dimensional analysis in thermal systems
  • Basic grasp of solid mechanics and material properties
NEXT STEPS
  • Study the derivation and applications of the Fourier number in heat transfer analysis
  • Explore the concept of thermal diffusivity and its impact on material behavior
  • Learn about lumped system analysis in thermal engineering
  • Investigate the relationship between Fourier number and transient heat conduction
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Engineers, physicists, and students in thermal engineering or materials science who are looking to deepen their understanding of heat conduction principles and their practical applications in solid materials.

New2thermodyn
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What is Fourier number??

What exactly is Fourier number? I kno its Thermal diffusivity*time/square of radius. But what exactly is the meaning of Fourier number?

For eg: Why do we calculate Fourier number for finding out the lumped heat in solids?
 
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mathman said:

Thanks Mathman, and yes,Of course iv checked wikipedia b4 posting that question! In wiki it is just the explanation of the terms involved, ie"the ratio of the heat conduction rate to the rate of thermal energy storage", is not that pretty obvious just looking at the equation? but what i want to know is the significance of the equation
 


Sorry - I can't help you any more.
 


When the Fourier number is much larger than one, the conduction process is predicted to have reached steady state. Does this answer your question?
 


New2thermodyn said:
Thanks Mathman, and yes,Of course iv checked wikipedia b4 posting that question! In wiki it is just the explanation of the terms involved, ie"the ratio of the heat conduction rate to the rate of thermal energy storage", is not that pretty obvious just looking at the equation? but what i want to know is the significance of the equation

Fo = (Heat conduction rate)/(thermal energy storage rate)
Fo = [k A [STRIKE]dT[/STRIKE]/dx]/[(dm/dt)*Cp*[STRIKE]dT[/STRIKE]] -------------> dx = L
Fo = [kA/L]/[ρ*Cp*Q] -----------------------> A/Q = t/L
Fo = [kt]/[ρ*Cp*(L2)]---------------------->k/ρ*Cp = α
Fo = αt/L2
 

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