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Thermodynamic Processes
Published in S. Bobby Rauf, Thermodynamics Made Simple for Energy Engineers, 2021
A thermodynamic reversible process is a process that changes the state of a system in such a way that the net change in the combined entropy of the system and its surroundings is zero. The system and the surroundings can be restored to their initial states at the conclusion of a reversible process. No heat is wasted in a reversible process, therefore, the machine or engine’s efficiency is maximized.
Energy Conservation
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
A reversible process is one where changes occur due to driving forces (e.g., temperature differences that are differentially small); the system may therefore be considered to be in a state of equilibrium during the change [3,4].
Second Law of Thermodynamics
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
A reversible process is defined as the one which can be reversed without leaving any trace on the surroundings and at the end of the process, both the system and surroundings are returned to their initial states. If the net heat and net work exchange between system and surroundings for the combined process is zero, then the process is reversible. In both reversible and irreversible processes, the system can be brought back to its initial state at the completion of a process. Whereas for a reversible process, the restoration can be possible without leaving any net change on surroundings, in the case of an irreversible process, the surroundings do some work on the system and consequently it does not return to the initial state. Some of the processes that tend to be reversible are explained with the following examples: a very slow frictionless adiabatic process anddeflection of a spring.
Thermodynamic sustainability assessment for residential building heating comparing different energy sources
Published in Science and Technology for the Built Environment, 2022
Sustainable development requires not only usage of sustainable energy resources, but also the efficient use of these resources (Rosen et al. 2008). Exergy analysis is directly linked to sustainability and environmental impact of energetic processes. Hepbasli (2016) emphasized the importance of exergy analyses in his study and suggested novel exergy management approach instead of energy. In thermodynamically ideal, reversible process there is no exergy loss, the exergy efficiency has value 1, or 100%, and negative impact on the environment does not exist, in other words the process would be completely sustainable. Actual processes are irreversible and exergy destruction and losses exist. As exergy efficiency approaches value 0, sustainability approaches zero and environmental impact approaches infinity. Increasing exergy efficiency in utilization contributes to development over a longer period of time, decreasing the impact on environment. As exergy efficiency approaches 100%, environmental impact approaches zero and sustainability approaches infinity, because exergy is converted from one form to another without losses, and process approaches reversibility.
On the practicality of Clausius’ maxim
Published in Canadian Metallurgical Quarterly, 2019
Since the entropy is a function of state, a change of the entropy of the system, , is the difference between the entropies of its final and initial states. Since the entropy is an additive function, the entropy of the universe can be written asLet us recall that , rewrite (3) as and realise that there are only three possibilities. If , then , which, according to Clausius, is impossible, which, in turn, means that a process whose is prohibited.If , then . A process with is irreversible, because the entropy of the world increases as a result of it; according to Clausius, it is permissible.If , then . It would be erroneous to name such a process reversible, because, strictly speaking, reversible processes do not exist [7]. In order to understand why, let us recall that any process resulting in detectable changes needs a non-zero driving force to befall. An axiom that the equilibrium state is attainable means that mobilities are greater than zero. Consequently, it can be stated that any process bringing about identifiable changes has a finite rate, and the finite rate means friction, which unavoidably results in a heat generation, which inevitably increases the entropy of the universe. If , then all possible driving forces are not merely infinitesimally small, they all must be precisely equal to zero, which is another way of saying that they do not exist. An absence of the driving forces reflected by the condition corresponds to the equilibrium state.