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Abstract: A new physical quantity, , has been identified as a basis for optimizing heat transfer processes in terms of the analogy between heat and electrical conduction. This quantity, which will be referred to as entransy, corresponds to the electric energy stored in a capacitor. Heat transfer analyses show that the entransy of an object describes its heat transfer ability, as the electrical energy in a capacitor describes its charge transfer ability. Entransy dissipation occurs during heat transfer processes as a measure of the heat transfer irreversibility. The concepts of entransy and entransy dissipation were used to develop the extremum principle of entransy dissipation for heat transfer optimization. For a fixed boundary heat flux, the conduction process is optimized when the entransy dissipation is minimized, while for a fixed boundary temperature the conduction is optimized when the entransy dissipation is maximized. An equivalent thermal resistance for multi-dimensional conduction problems is defined based on the entransy dissipation, so that the extremum principle of entransy dissipation can be related to the minimum thermal resistance principle to optimize conduction. For examples, the optimum thermal conductivity distribution was obtained based on the extremum principle of entransy dissipation for the volume-to-point conduction problem. The domain temperature is substantially reduced relative to the uniform conductivity case. Finally, a brief introduction on the application of the extremum principle of entransy dissipation to heat convection is also provided. [Copyright &y& Elsevier]

This note is our comments to the paper entitled, “Equivalence between the application of entransy and entropy generation” (Oliveira and Milanez, 2015). In this paper, the authors showed the equivalence between the application of the concepts of entransy and entropy by using several application examples including three physical models of solar energy collectors and a physical model of a sensible heat storage system. The main expressions regarding entransy in this paper come from our conference paper entitled, “Entransy transfer analysis and its application to optimizing irreversible thermodynamic cycles” (Wu and Guo, 2007). However, the authors did not distinguish between the entransy, the entransy transfer, and the thermodynamic entransy transfer. The application of which was shown to be equivalent to that of entropy generation by the authors using four examples, is the thermodynamic entransy transfer rather than the entransy transfer. Hence, the conclusion that the applications of entransy and entropy are equivalent is not appropriate. [ABSTRACT FROM AUTHOR]

Abstract: Heat transfer optimization methods to effectively improve heat transfer performance is of great importance for energy conservation and pollution reduction. A recently developed heat transfer optimization method based on entransy theory and related peer-reviewed papers published between 2003 and 2010 are reviewed and updated in this paper to describe entransy, entransy dissipation, optimization criteria and optimization principles and their applications to different heat transfer modes (thermal conduction, convection and radiation) and to different levels (heat transfer element, heat exchanger, and heat exchanger network). Entransy theory is then compared with entropy theory in several aspects, including the heat transfer purpose, irreversibility and optimization principle for energy savings or weight reductions of thermal facilities. Finally, entransy theory is also compared with constructal theory in terms of optimization objective, optimization method and optimized results. [Copyright &y& Elsevier]