Can Heat Transfer Occur Unevenly in a System with Constant Temperature?

  • Context: Undergrad 
  • Thread starter Thread starter fluidistic
  • Start date Start date
  • Tags Tags
    Heat
Click For Summary

Discussion Overview

The discussion revolves around the concept of heat transfer in a system where a continuously heated metal (A) maintains a constant temperature, while two other identical materials (B and B') are subjected to different temperatures. Participants explore whether heating B by 1K results in a similar temperature increase in B', considering the effects of convection and temperature gradients.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions if heating B by 1K means B' also heats by 1K, given that they have the same specific heat.
  • Another participant argues that the question cannot be answered without specifying how the temperature change occurs and how B and B' are cooled, noting that energy is removed more rapidly from B' than from B.
  • A later reply clarifies that the temperature change occurs via convection due to the air between A and B, and A and B', and acknowledges that B' will likely heat by more than 1K when B is heated by 1K.
  • Participants discuss the relationship between temperature gradients and energy transfer rates, suggesting that energy moves faster down steeper gradients and that this is related to Newton's law of cooling.

Areas of Agreement / Disagreement

Participants express differing views on the specifics of heat transfer and the implications of temperature gradients. There is no consensus on the exact relationship between the heating of B and B' or the mechanisms involved.

Contextual Notes

Participants note the importance of defining the cooling mechanisms and the initial conditions of B and B' to fully understand the heat transfer dynamics. The discussion highlights the complexity of thermal interactions in non-uniform systems.

Who May Find This Useful

This discussion may be useful for those interested in thermodynamics, heat transfer principles, and the effects of temperature gradients in physical systems.

fluidistic
Gold Member
Messages
3,934
Reaction score
286
I just thought about the following case and I have a doubt.
Say I have a system like this : B-------A-------B' where A is a continuously heated metal so that it's temperature remains constant with time. Imagine there's a fluid like air between A, B and B' so that A transfers heat to B and B' via convection. Suppose that the temperature of B is almost the one of A and the temperature of B' is much lower than the one of A. Suppose also that B and B' don't transfer heat to each other (because they are too far from each other).
Last supposition : B and B' are the same material, say a metal (whose specific heat is a constant).
My question is : If B get heated by 1K, does B' also get heated by 1K? I was tempted to say yes because they have the same specific heat but now I have doubts. I think that maybe B' can be heated more than 1K while B got heated by 1K, because the temperature of B is closer to the one of A than the one of B' is.
Maybe I should write down some equations, but I'll soon learn about gradient in cases similar to this one.
Thanks in advance.
 
Science news on Phys.org
fluidistic said:
My question is : If B get heated by 1K, does B' also get heated by 1K?

This question can't be answered unless you specific how the change in temperature occurs and how B and B' are being cooled. So far you've described a steady-state system where B-------A-------B' is symmetric up to a point; however, energy is being removed more rapidly from B' than from B (that's the only way to explain the difference in temperature of two identical materials).
 
Mapes said:
This question can't be answered unless you specific how the change in temperature occurs and how B and B' are being cooled. So far you've described a steady-state system where B-------A-------B' is symmetric up to a point; however, energy is being removed more rapidly from B' than from B (that's the only way to explain the difference in temperature of two identical materials).

Ok I understand. I precise : the change in temperature occurs by convection due to air between A and B, and A and B'. And initially B and B' have different temperature. For example B and B' could have been cooled/heated in another systems and then put in the one I described.
I realize that if B is heated by 1K then B' will be heated by more than 1K. However I don't know why since they have the same specific heat.
Why does B receive less energy from A than B' does? Because of the slight difference of temperature?
My question is also equivalent to ask why a very hot body in air loses its heat quickly and then less and less quickly.
Is it because of the gradient of temperature? Newton's law of cooling? Are they (Newton law of cooling and the gradient) related?
I don't understand why the process of change of temperature works like it works.
By the way thanks for helping me.
 
OK, got it. The general principle is that energy moves down a steeper gradient faster. Well, actually energy is moving everywhere all the time, but it's unlikely for it to move from a colder to a hotter material (Second Law). The unlikeliness increases with increasing temperature difference. So as a gradient increases, energy transfer down the gradient becomes more and more favorable, which translates into an increasing transfer rate. Yes, this is the origin of Newton's cooling and Fourier's conduction laws.
 
Mapes said:
OK, got it. The general principle is that energy moves down a steeper gradient faster. Well, actually energy is moving everywhere all the time, but it's unlikely for it to move from a colder to a hotter material (Second Law). The unlikeliness increases with increasing temperature difference. So as a gradient increases, energy transfer down the gradient becomes more and more favorable, which translates into an increasing transfer rate. Yes, this is the origin of Newton's cooling and Fourier's conduction laws.

Thank you very much for the good explanation.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 15 ·
Replies
15
Views
2K
Replies
7
Views
2K
Replies
2
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 28 ·
Replies
28
Views
4K
  • · Replies 28 ·
Replies
28
Views
4K
  • · Replies 9 ·
Replies
9
Views
4K