What Does Thermal Constriction Resistance Mean?
Thermal constriction resistance occurs when heat flow is hindered by surfaces that are not completely in contact with each other.
Unintended resistance can reduce the efficiency of equipment or processes that are intended to benefit from thermal conductivity.
Corrosionpedia Explains Thermal Constriction Resistance
Incomplete surface contact is a cause of thermal constriction resistance.
In virtually every instance where surfaces contact each other there will be some degree of constriction resistance because at a microscopic level every surface has peaks and valleys. Surfaces will contact at their microscopic peaks, but where microscopic recesses occur on a surface it is likely that a gap will be created between it and the other surface. This gap increases the thermal constriction resistance of the contacting surfaces because the medium in the gap (typically air) is a poorer conductor of heat than the materials themselves.
When electricity is ran through two or more contacting surfaces, the amount of constriction resistance (both electrically and thermally) can be reduced over time because the electricity eventually causes the materials to weld together. This welding creates a greater amount of contact among the materials, resulting in less air in between them. This reduces the constriction resistance both in terms of electrical conductivity and in terms of thermal conductivity.