Heat conduction in general

Heat conduction:

Heat conduction occurs in substances that do not have a uniform temperature. Similarly, if substances with different temperatures come into contact with each other.
All aggregate states allow this transfer mechanism.

Heat conduction is a process that occurs over distances in the respective substance. There is a temperature difference over a length. This indicates a flowing heat flux.

The following quantities affect the size of the heat flux:

Temperature difference

Lots of technical applications use the temperature difference to control the heat flux.

The image shows the section (A-A) through a heated saucepan. The hot stove (1) transfers the heat through the bottom of the saucepan (2) to the water (3). The heat flux is represented by red arrows.

A larger or smaller heat flux is dissipated depending on the temperature difference between the hot stove and the contents of the pan.

Substance

In many applications the choice of material is a significant indication of whether an object is meant to conduct heat or contribute to insulation.

Preferred substances for heat conduction are metals such as copper and aluminium. Foamed materials are usually used as insulation.

The material value that characterises this property is the thermal conductivity.
For any given heat flux, the temperature difference is smaller the higher the thermal conductivity.

Distance / Cross-sectional area

The length which the heat traverses by heat conduction has a decisive influence.
The greater the heat-conducting length, the lower the transferred heat flux.

The heat flux can also be affected by the heat-conducting cross-section.

On the left the image shows the stove (A). In this case the heat is meant to be conducted as well as possible. Therefore the area A is large and the heat-conducting length L relatively small.

In contrast is a candle snuffer (B). The long thin stem is designed to insulate heat so that the user does not burn their fingers.