In thermodynamics, a boundary or thermodynamic boundary is the division, which may be material or not, between a system and its surroundings. [1] The original thermodynamic boundary was edge or region of demarcation of the volumetric body of water or water vapor in a steam engine. Through the actions of the opening and closing of valves, the body of water was able to move around to different parts of the engine, specifically the region of the boiler (burning coal) and the region of the condenser (an external stream of cooling water); hence the boundary was moving one.

In 1824, French physicist Sadi Carnot generalized this by defining a "working substance" to be any generalized body, such as a metallic bar, an aeriform fluid, etc., that may configured to do work when put in alternating contact with hot and cold bodies able to supply or absorb heat. [2]

Human thermodynamics
In human thermodynamics the definition is the same, however, the assignment of a "boundary" to human systems, e.g. social, territorial, work, family, community, "relationship boundaries", etc., is difficult area of research. In general, a thermodynamic boundary in human terms can be defined as an "energetic boundary" that partitions off a set of thermodynamically-coupled human molecules in evolving interaction. [2] This boundary can be considered as a quantitative spatial demarcation, such as a town boarder, a social barrier, state lines, corporate boundaries, occupational orbitals, social circles, family boundaries, etc., comprise a closed thermodynamic system of working molecules, i.e. a working body in the words of Clausius, according to which first and second law energy balances apply in the production of system external work W due to the action of cyclical solar heat input Qin. When human molecules pass into the system, across the boundary, inside of which energy interactions occur, chemical potential calculations must be introduced. [3]

See also
Boundary problem
Chimpanzee war

References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics, Oxford: Oxford University Press.
2. Carnot, Sadi. (1824). “Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power.” Paris: Chez Bachelier, Libraire, Quai Des Augustins, No. 55.
3. Thims, Libb. (2007). Human Chemistry (Volume One), (preview), (Index: "boundary", pgs. 61-80). Morrisville, NC: LuLu.

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