Thermal contact

In heat transfer and thermodynamics, a thermodynamic system is said to be in thermal contact with another system if it can exchange energy through the process of heat. Perfect thermal isolation is an idealization as real systems are always in thermal contact with their environment to some extent.
When two solid bodies are in contact, a resistance to heat transfer exists between the bodies. The study of heat conduction between such bodies is called thermal contact conductance (or thermal contact resistance).