Doubt in Fourier's Law of Heat conduction

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Discussion Overview

The discussion revolves around the understanding of Fourier's Law of Heat Conduction, specifically addressing how the normal area (A) affects the rate of heat flow (Q) in relation to the temperature gradient (Dt/Dx). Participants explore the implications of this relationship and provide analogies to clarify their reasoning.

Discussion Character

  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant questions how the normal area (A) influences the rate of heat flow, seeking clarification on its role in Fourier's Law.
  • Another participant draws an analogy between heat flow and fluid dynamics, suggesting that just as a larger diameter pipe allows more water to flow under a constant pressure gradient, a larger area allows more heat to flow.
  • A third participant reiterates the initial question about the impact of the cross-sectional area on heat conduction, emphasizing the comparison between a wire and a larger rod of the same material.
  • A later reply indicates that the participant has come to understand that a larger cross-sectional area provides more medium for heat flow, thus increasing the total heat transfer.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the relationship between area and heat flow, with some clarifying their thoughts while others remain uncertain. The discussion does not reach a consensus on the underlying principles but explores different perspectives.

Contextual Notes

The discussion does not address specific assumptions about the materials involved or the conditions under which Fourier's Law applies, leaving open questions about the generalizability of the analogies used.

R Power
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Hello friends
Fourier law of heat conduction states that:

Q ~ A.(Dt/Dx) where A= area normal to direction of heat flow.
Dt/Dx= temp gradient in same direction.

Now, obviously rate of heat flow will depend upon temp gradient but my doubt is how/why rate of heat flow is affected by this NORMAL area A ?

Thnx
 
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Back in the 1800s they used to think heat was a fluid... called a caloric fluid. The reason they thought this was because it's behaviour was similar to that of a fluid.

Using the ideas of a fluid, in particular let's use water, if we maintain a *constant* pressure gradient on a pipe from one end to another and change its diameter, would you say more water now flows? It's the same idea for heat.
 
R Power said:
Hello friends
Fourier law of heat conduction states that:

Q ~ A.(Dt/Dx) where A= area normal to direction of heat flow.
Dt/Dx= temp gradient in same direction.

Now, obviously rate of heat flow will depend upon temp gradient but my doubt is how/why rate of heat flow is affected by this NORMAL area A ?

Thnx

Because the total heat flow depends on the size of the cross section. Think about it - will a wire conduct as much heat from one point to another as a large rod of the same material?
 
yeah, I get it now after a bit of thinking. If source of heat is placed at one end then more the area of cross section more the medium is available for flow so more heat will flow. It was simple.
Thnx coto and cj.
 

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