What type of heat transfer occurs with no physical contact?

The type of heat transfer that occurs without any physical contact is radiation. This process involves the transfer of heat through electromagnetic waves, such as infrared radiation, which can travel through empty space. Unlike conduction and convection, which require a medium (solid, liquid, or gas) for heat transfer, radiation can occur in a vacuum.

For example, the heat from the sun reaches the Earth through the vacuum of space via radiation; it does not require air or any other medium to be felt. This makes radiation distinct from conduction, where heat moves through direct contact between materials, and convection, which relies on the movement of fluids (liquids or gases) to transfer heat. Understanding radiation is crucial in HVAC applications for energy efficiency and effective heating and cooling strategies.