Unanswered questions in heat transfer research: technological limitations in the characterization of heat transfer at interfaces
An area that has received considerable attention is the time-dependent heat transfer between two surfaces placed suddenly in contact. Recently, an entirely new area is centered around the question of what happens when at least one of the surfaces is initially covered with a layer of highly viscous fluid. When the bodies are pressed into contact, the liquid is squeezed slowly out of the gap, while preventing the two parts from making direct contact. The applied force is supported by the excess pressure built in the liquid film. Further analyzation of the solid-fluid contact is presented. Several questions are brought out.