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Material will expand or contract depending on the material's thermal expansion coefficient. As long as the material is free to move, the material can expand or contract freely without generating stresses. Once this material is attached to a rigid body at multiple locations, thermal stresses can be created in the geometrically constrained region.
In fact, one property function can be given as an expression of the two others, up to a reference state value. [1] The second principle of thermodynamics has implications on the sign of some thermodynamic properties such isothermal compressibility. [1] [2]
A temperature drop is observed at the interface between the two surfaces in contact. This phenomenon is said to be a result of a thermal contact resistance existing between the contacting surfaces. Thermal contact resistance is defined as the ratio between this temperature drop and the average heat flow across the interface. [1]
A number of materials contract on heating within certain temperature ranges; this is usually called negative thermal expansion, rather than "thermal contraction".For example, the coefficient of thermal expansion of water drops to zero as it is cooled to 3.983 °C (39.169 °F) and then becomes negative below this temperature; this means that water has a maximum density at this temperature, and ...
When two bodies with rough surfaces are pressed against each other, the true contact area formed between the two bodies, , is much smaller than the apparent or nominal contact area . The mechanics of contacting rough surfaces are discussed in terms of normal contact mechanics and static frictional interactions. [ 29 ]
Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. The higher temperature object has molecules with more kinetic energy ; collisions between molecules distributes this kinetic energy until an object has the same kinetic energy throughout.
Interfacial thermal resistance, also known as thermal boundary resistance, or Kapitza resistance, is a measure of resistance to thermal flow at the interface between two materials. While these terms may be used interchangeably, Kapitza resistance technically refers to an atomically perfect, flat interface whereas thermal boundary resistance is ...
= the thermal conductivity of the material (W/(m·K)) This represents the heat transfer by conduction in the pipe. The thermal conductivity is a characteristic of the particular material. Values of thermal conductivities for various materials are listed in the list of thermal conductivities.