How does heat loss through conduction occur?

In summary, heat loss through a material due to conduction is directly proportional to the difference in temperature and inversely proportional to the thickness of the material. This can be represented by the equation ΔQ = K*S*ΔT/D, where ΔQ is the energy flow, K is a constant specific to the material, S is the area of energy flow, ΔT is the temperature difference, and D is the thickness of the material. However, during the stabilization process, the thickness of the material can actually decrease the flow of energy. This is due to the fact that the material also stores heat, so it takes time for each layer to heat up and transfer the heat to the next layer. At steady state, the temperature distribution
  • #1
burashka5719
5
0
Usually it is said that loss of heat through a chunk of material because of conduction is proportional to difference in temperature and inversely proportional to thickness of material.
E.g. if I got a wall to ΔQ = K*S*ΔT/D.
where ΔQ - is energy flow through material. K - constant characteristic to material , S - area through which energy flow happens, ΔT difference in temperature on both sides of material ( in direction of flow) and D - material thickness in direction of the flow.

What I don't understand, is why in case when the process has stabilised ( temperatures are constant on both side of material for a long time) D works to diminish the flow. I know that it is common sense, but I don't understand physics of this process. Can someone explain what happens it terms of atomic or molecular model?
Also, let's say we got a bar of homogenise material which is heated on one side. how looks distribution of temperature through a bar of material as function of time and distance from the point where heat is applied.
 
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  • #2
burashka5719 said:
Also, let's say we got a bar of homogenise material which is heated on one side. how looks distribution of temperature through a bar of material as function of time and distance from the point where heat is applied.
At steady state, the graph of temperature from T1 to T2 through distance D is a straight line of constant slope.
 
  • #3
256bits said:
At steady state, the graph of temperature from T1 to T2 through distance D is a straight line of constant slope.
Yes, but before the system stabilised? During this period distribution of temperature as function of time and distance from 0 can be different.
 
  • #4
Think of the block as a series of layers stacked together . First layer has to heat up before it can heat next layer etc sequentially through the total thickness .

The layers don't just conduct heat they store it as well so it takes time for their temperatures to rise .

May be better to put this in mathematical form rather than descriptive . The mathematics for one dimensional heat conduction is relatively easy to understand .
 
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  • #5
burashka5719 said:
Yes, but before the system stabilised? During this period distribution of temperature as function of time and distance from 0 can be different.
Have a look at this Excel Animation. It shows the way the temperature varies in time over a 2D area when a hot object appears in it. It's a diffusion model.
 
  • #6
Hello,
There are two questions in my original e-mail:
The second one - about temperature distribution as function of time and distance from heat source is more or less clear, but if someone can recommend where I can read about relevant math it would be great.
The first question actually is more of a problem: on one hand common sense tells that thicker insulation diminishes heat flow from high temperature area to cool area,
on the other hand, once the system reaches equilibrium ( constant temperature difference on both sides of insulator) it seams to me that insulator thickness shouldn't have any effect on amount of energy loss.
I try a very simplified model - a long bar of homogeneous material with constant cross section ( 1 dimensional problem) with constant temperature difference on both sides . Once equilibrium is reached insulator doesn't store heat anymore. So taking as example the above model - series of layers stacked together, why 10 or 1000 of layers will conduct less heat then a single one.
My feeling is that there is something that plays a role of resistance in electrical current transfer of flued transfer through a pipe, but in those cases there is energy loss through heat, which doesn't haven here,
 

Related to How does heat loss through conduction occur?

1. What is conduction?

Conduction is the transfer of heat through direct contact between two objects. The heat energy is transferred from the object with higher temperature to the object with lower temperature.

2. How does heat loss through conduction occur?

Heat loss through conduction occurs when there is a temperature difference between two objects in contact. The heat energy flows from the warmer object to the cooler object until they reach a thermal equilibrium.

3. What factors affect heat loss through conduction?

The rate of heat loss through conduction depends on the thermal conductivity of the materials in contact, the temperature difference, the surface area of contact, and the distance between the two objects.

4. How can we reduce heat loss through conduction?

To reduce heat loss through conduction, we can use materials with low thermal conductivity, increase the distance between the two objects, or use insulating materials to reduce the surface area of contact.

5. What are some real-life examples of heat loss through conduction?

Some common examples of heat loss through conduction include feeling the coldness of a metal object when it is left outside on a cold day, using a metal spoon to stir hot soup and feeling the heat in the handle, or feeling the warmth of a heated car seat.

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