What is the heat transfer that occurs through direct contact of molecules called?

The process of heat transfer through direct contact of molecules is referred to as conduction. This occurs when heat energy is transmitted from one molecule to another in a solid material. In conduction, when one part of a solid is heated, the molecules in that region vibrate more vigorously and collide with neighboring molecules, passing on their kinetic energy. This chain reaction continues throughout the material, allowing heat to spread through it.

Understanding conduction is critical in power engineering and other fields because many systems rely on efficient heat transfer through solid materials. It is especially important in contexts such as heat exchangers, boiler tubes, and various components where solid interfaces are present.

In contrast, convection involves the transfer of heat through the movement of fluids (liquids or gases) and does not occur through direct molecular contact as conduction does. Radiation refers to heat transfer through electromagnetic waves, and thermal expansion involves the physical expansion of materials as they are heated, rather than the process of heat transfer itself.