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Produzione di entropia e Lavoro perduto in un semplice processo irreversibile
No full text[ITALIANO] Nei processi irreversibili c’è produzione di entropia, π , ed energia dissipata (o Lavoro perduto)
Lost W. In questo articolo, si analizza la relazione tra queste quantità relativamente al passaggio spontaneo di calore tra una sorgente calda 1 T ed una fredda 2 T. Viene mostrato che si possono definire diversi Lost W. Il più grande dei quali è per noi il giusto Lost W. Viene anche mostrato che lo stesso accade per le macchine termiche irreversibili e per trasformazioni meno semplici come
l’espansione adiabatica irreversibile di un gas ideale. / [ENGLISH] In the irreversible processes there is entropy production, π and dissipated energy (or lost Work), Lost W. In this paper we analyse the relation between such quantities for the irreversible process in which some heat flows spontaneously from an hot heat source 1 T to a colder one 2 T. We show that one can define different lost works. The biggest is for us the true Lost Work. It is also shown that the same happens for the irreversible heat engines and for some complex process like the irreversible adiabatic expansion of an ideal gas
Complexity in the stepwise ideal gas Carnot cycle
No full textA stepwise Carnot cycle is performed by means of N small weights (here called dw's), which are first added and then removed from the piston of the vessel containing the gas. The size of the dw's affects the entropy production. The work performed by the gas can be found as increase of the potential energy of the dw's. We identify each single dw and thus evaluate its raising, i.e., its increase in potential energy. In such a way we find how the energy output of the cycle is distributed among the dw's. The distribution depends on the removing process we choose. Since these processes are N!, there are N! distributions of the raisings of the dw's; it is therefore worthwhile to investigate how to find ni= n(ei) the number of the dw's whose energy increase is ei
On the uniqueness of the Equilibrium State for Antiferromagnetic Ising spin system in the phase transition region
No full textOn the uniqueness of the Equilibrium State for Antiferromagnetic Ising spin system in the phase transition region
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Lost work, extra work and entropy production for a system with complexity: The stepwise ideal-gas Carnot cycle
Full text linkThis paper is an extension of a previous paper [Phil. Mag. 87 (2007) p.569] devoted to lost work and entropy production. Here, we also introduce extra work (i.e. WExtra=Win-WRev) in an irreversible process and apply both concepts to the analysis of a system with complexity: the stepwise ideal-gas Carnot cycle. A stepwise Carnot cycle is performed by means of N small weights (here called dws), which are first added and then removed from the piston of the vessel containing the gas. The work performed by the gas can be found as an increase in the potential energy of the dws. We identify each single dw and evaluate the rise; i.e. its increase in potential energy. Thus, we find how the energy output of the cycle is distributed among the dws. The size of the dws affects entropy production and, therefore, the lost and extra work. The raising distribution depends on the removal process chosen. Since these processes are N!, there are N! distributions for the raisings of the dw
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