On the representation of thermodynamic processes

Anacleto denies that macroscopic thermodynamics is necessarily free of dissipative effects. This allows him to introduce friction into the quasistatic description of classical thermodynamics. Here, we show that such an approach is a contradiction; there is no quasistatic process P=P(V) that describes work done against friction. As a consequence, friction is not included in classical thermodynamics and his conclusions are incorrect.

“…In an earlier paper [2], Anacleto agreed. He states, 'to be reversible a process (1) should be a sequence of equilibrium states, i.e.…”

mentioning

confidence: 90%

Reply to Comment on ‘An ideal gas and the increasing (total) entropy principle: what is allowed in the PV plane and what is not’

Marcella¹

2023

“…Considering surroundings consisting of reservoirs, the heat dQ and the dissipative work dW D (which accounts for mechanical dissipative effects) are given by [2][3][4] The term / dW T D e of (5) is missing in [1], which is relevant in the subsequent analysis leading to the conclusion that the term…”

Section: ( )mentioning

confidence: 99%

Comment on ‘An ideal gas and the increasing (total) entropy principle: what is allowed in the PV plane and what is not’

Anacleto¹

2023

Self Cite

This comment deals with an issue in Marcella’s paper, 2022 Eur. J. Phys. 43 045104. We point out that the statement that quasistatic processes are necessarily free of dissipative effects is wrong, which led to an incorrect expression for entropy generation. We derive the correct expression, our aim being to remove persistent misconceptions in thermodynamics, in a constructive and pedagogical spirit.

“…Macroscopic thermodynamics is about equilibrium states and quasistatic processes [5,6]. A quasistatic process, represented by the curve P = P (V), passes through a succession of points in the PV plane from initial equilibrium state (P A V A ) to final equilibrium state (P B V B ).…”

Section: The Pv Diagram and Quasistatic Processesmentioning

confidence: 99%

An ideal gas and the increasing (total) entropy principle: what is allowed in the PV plane and what is not

Marcella¹

2022

In a recent article in this journal, Brown and Singh present the results of an extensive in-class survey of student difficulties with the second law of thermodynamics. Here, we discuss in detail some issues identified by them in an attempt to resolve some of the problems. We do this by making clear the distinction between the ‘system entropy’, ‘reservoir entropy’, ‘total entropy’, and the ‘entropy of the universe’. We identify, without ambiguity, which quasistatic processes are ‘internally reversible’, which are ‘totally reversible’, and which are ‘irreversible’. We discuss the meaning of quasistatic processes represented by curves in the PV plane. We show that the process P=P(V) that takes an ideal gas from initial state (P_A V_A) to final state (P_B V_B) always takes the gas away from the adiabat PV^γ=P_A V_A^γ. We establish the increasing (total) entropy principle as the quantitative expression of the second law of thermodynamics. This establishes the fundamental role of the total entropy in macroscopic thermodynamics. Expressing the increasing (total) entropy principle in the form 〖(T〗_res-T_gas)d(PV^γ)>0 reveals which processes are allowed, which are not, and which points in the PV plane are accessible from a given initial state. Students can now observe the limitations on individual processes mandated by the second law. Such second law analysis is suitable for the introductory physics course.