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For an open thermodynamic system in which heat and work are transferred by paths separate from the paths for transfer of matter, using this generic balance equation, with respect to the rate of change with time of the extensive quantity entropy , the entropy balance equation is: [53] [54] [note 1] = = ˙ ^ + ˙ + ˙ where = ˙ ^ is the net rate ...
An entropy balance for an open system, or the change in entropy over time for a system at steady state, can be written as: = ...
[9] [15] The conditioner of this statement suffices that living systems are open systems in which both heat, mass, and or work may transfer into or out of the system. Unlike temperature, the putative entropy of a living system would drastically change if the organism were thermodynamically isolated.
An open system is also known as a flow system. The concept of an open system was formalized within a framework that enabled one to interrelate the theory of the organism, thermodynamics, and evolutionary theory. [1] This concept was expanded upon with the advent of information theory and subsequently systems theory. Today the concept has its ...
For open systems (also allowing exchange of matter): = ˙ + ˙ + ˙ with ˙ Here, ˙ is the flow of entropy into the system associated with the flow of matter entering the system. It should not be confused with the time derivative of the entropy.
Overall, in an isolated system, the internal energy is constant and the entropy can never decrease. A closed system's entropy can decrease e.g. when heat is extracted from the system. Isolated systems are not equivalent to closed systems. Closed systems cannot exchange matter with the surroundings, but can exchange energy.
The concept of thermodynamic entropy arises from the second law of thermodynamics.This law of entropy increase quantifies the reduction in the capacity of an isolated compound thermodynamic system to do thermodynamic work on its surroundings, or indicates whether a thermodynamic process may occur.
Here S is the entropy of the system; T k is the temperature at which the heat enters the system at heat flow rate ˙; ˙ = ˙ = ˙ represents the entropy flow into the system at position k, due to matter flowing into the system (˙, ˙ are the molar flow rate and mass flow rate and S mk and s k are the molar entropy (i.e. entropy per unit ...