Minimum entropy production rate in plug flow reactors: An optimal control problem solved for SO2 oxidation

Nonlinear Thermodynamic Analysis and Optimization of a Carnot Engine Cycle

“…Thereby, one can conclude that for the endoreversible engine the equipartition of heat transfer conductances corresponds to the maximum mechanical power of the engine, and also to the maximum entropy production rate. This confirms other works' results [7,22,[28][29][30][31] and shows that the entropy generation minimization (EGM) recommended in quite an important number of works [32][33][34] does not have the character of generality we would like to give it. It was widely used in the 1990's as a powerful optimization tool.…”

“…The equipartition of the transfer entropies in the general case involves equality of Equations (33) and (34) under the condition (9a), leading to a system of two equations with two unknowns to be solved:…”

Numerical evidence for a “highway in state space” for reactors with minimum entropy production

“…In order to make the model complete, we also need flux-force relations (reaction rate expressions, heat transfer law and friction parameters). Further details can be found in Johannessen and Kjelstrup (2004). These flux-force relations are often nonlinear for conditions relevant for engineering purposes.…”

“…The entropy production in a cross-section in the reactor has contributions from the reactions, the heat exchange across the reactor wall and the frictional flow inside the reactor. This was expressed by Johannessen and Kjelstrup (2004) …”

“…As control variable, we used the temperature of the coolant, T a . The optimisation problem was formulated for these conditions using optimal control theory, see Johannessen and Kjelstrup (2004). In a full paper to come, we shall see that the formulation is invariant for a change of the space coordinate with time as a variable, making us able to generalise the findings to systems which are not in a stationary state, for instance to batch reactors.…”