Heat loss through conduction.

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, lets 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.

256bits
Gold Member
Also, lets 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.

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.

Nidum
Gold Member
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 .

Last edited:
sophiecentaur