An Equivalent Mechanical Model for Representing the Entropy Generation in Heat Exchangers. Application to Power Cycles

Abstract

One of the most common difficulties students face in learning Thermodynamics lies in grasping the physical meaning of concepts such as lost availability and entropy generation. This explains the quest for new approaches for explaining and comprehending these quantities, as suggested by diagrams from different authors. The difficulties worsen in the case of irreversibilities associated with heat transfer processes driven by a finite temperature difference, where no work transfer takes place. An equivalent mechanical model is proposed in this paper. Heat exchangers are modelled by means of Carnot heat engines, heat pumps and mechanical transmissions; the use of mechanical models allows a thorough visualization of exergy quantities involved in heat transfer processes. The proposed model is further applied to a power cycle, thus obtaining an "equivalent arrangement" where irreversibilities become understood by means of a mechanical analogy.

Non-equilibrium Thermodynamic Extension of the Phenomenological Theories of First-order Phase Transitions

“…In addition, the theories and methods of nonequilibrium thermodynamics have been applied to many problems successfully [4,5]. But it is a pity that the Landau theory for continuous phase transitions was generalized unrealistically to process the first-order phase transitions (especially the first-order ferroelectric phase transitions) instead of applying the non-equilibrium thermodynamics to the first-order phase transitions directly [6,7].…”

Non-equilibrium Thermodynamic Extension of the Phenomenological Theories of First-order Phase Transitions

“…So, we should apply the non-equilibrium thermodynamics to processing the first-order phase transitions. In addition, the theories and methods of nonequilibrium thermodynamics have been applied to many problems successfully [4,5]. But it is a pity that the Landau theory for continuous phase transitions was generalized unrealistically to process the first-order phase transitions (especially the first-order ferroelectric phase transitions) instead of applying the non-equilibrium thermodynamics to the first-order phase transitions directly [6,7].…”