ABSTRACT
This chapter examines the mechanisms of heat transfer, that is, conduction, convection and radiation. Conduction describes the heat transfer through a material due to collisions of the particles. For this reason, the heat transferred through this mechanism is exclusively confined inside the body. Convection is a heat transfer mechanism, typical of fluids, which transfers heat through its bulk motion. Radiation heat transfer can play a significant role in cryogenics. In order to minimize the effect of radiation, cryogenic systems use radiation shields. The thermal impedance occurring at the interface between two different mediums is called Kapitza resistance. Kapitza resistance plays an important role in all the situations where liquid helium is in contact with a metal and we require good thermal contact. A gas-gap heat switch is a sealed device that can modulate the thermal conductivity by controlling the gas pressure between two conducting surfaces.
