In thermodynamics, entropy flow, symbol deS, is flow of entropy across the boundary of a system due the exchanges of matter and or energy with the exterior. [1] The term, as developed by Belgian chemist Ilya Prigogine in 1947, is commonly used in open chemical systems that exchange matter and energy with the exterior of the system, such that "energy flows" and "entropy flows" can be identified with the exchanges of matter and energy with the surroudings, external to the boundary. [2]
Etymology
The concept and phraseology of an “entropy flow”, in large part, is peculiar to the work of Belgian chemist Ilya Prigogine who divides entropy into two parts:
dS | = | deS | + | diS |
|
"entropy" |
| "entropy flow" |
| |
|
where, in other contexts, he also refers to diS as internal entropy. Historically, although Prigogine seems to be the dominate promoter of the phrase entropy flow, he attributes the origination of the notions of entropy flow and entropy production to the Viennese school led by G. Jaumann and Polish researcher L. Natanson. [2] In other situations, to note, Prigogine implicitly refers to entropy flow as the derivative of deS with respect to time:

Prigogine also uses the logic of entropy flow in his explanation of evolution. [3]
References
1. Prigogine, Ilya. (1955). Introduction to Thermodynamics of Irreversible Processes (pgs. 16). Charles C. Thomas.
2. Kondepudi, Dilip and Prigogine, Ilya. (1998). Modern Thermodynamics – from Heat Engines to Dissipative Structures (pg. 87, 387-89). New York: John Wiley & Sons.
3. Prigogine, Ilya, Nicolis, Gregoire, and Babloyants, Agnes. (1972). "Thermodynamics of Evolution," (part I & II). Physics Today, Vol. 25, November, pgs. 23-28.