Application of entransy theory in the heat transfer optimization of flat-plate solar collectors

“…New physical quantities, such as entransy, entransy dissipation and entransy dissipation-based thermal resistance are introduced by analogy between the heat conduction process and the electric conduction process. On this basis, the principle of least action in heat transfer and the principle of minimum entransy dissipation-based thermal resistance for the optimization of heat transfer process are proposed (Chen et al, 2013;Cheng et al, 2012;Wang et al, 2017;Guo et al, 2003;Meng et al, 2005;Chen and Guo, 2010;Li and Chen, 2012;Song and Guo, 2011;Chen et al, 2007;Ren, 2008, Yuan andJia et al, 2012;Liu et al, 2009). Finally, an energy method (similar to that in analytical mechanics) in heat transfer is established for energy efficiency optimization of thermal systems Xia et al, 2017).…”

Section: Frontiers In Heat and Mass Transfermentioning

confidence: 99%

Physical Heat Transfer

Wang¹,

Guo²

2019

Frontiers in Heat and Mass Transfer

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The classical heat transfer theory is established on the empirical models of Fourier's heat conduction law and Newton's cooling law. Although the classical theory has been successfully used in a wide range of industrial engineering applications, it lacks deep understanding of the physical mechanisms for energy transport and analytical methodology based on solid mathematical and mechanical principles. The rapid development of modern science and technology challenges the traditional heat transfer theory in two aspects: (1) Fourier's law of heat conduction is no longer valid under the ultra-fast laser heating or nanoscale conditions; (2) The optimization principle minimizing entropy generation is not suitable for heat transfer problems without heat to work conversion. In order to solve the first challenge, we reexamined the nature of heat and introduced new physical quantities, such as thermomass, thermomass velocity, thermomass energy. Then the heat transfer problems can be analyzed in the framework of vectorial fluid mechanics, and the thermomass momentum conservation equation has been established and known as a general law of heat transfer. For the second challenge, we introduced new physical quantities, entransy and entransy dissipation, by analogy between the heat conduction process and the electric conduction process. Unlike entropy as the core physical quantity in thermodynamics dealing with energy conversion, entransy is the quantity to represent the ability of heat transfer in an incompressible system. The entransy dissipation represents the irreversibility of heat transfer process. On this basis, the least action principle to minimize entransy dissipation can be used to optimize the heat transfer process and enhance energy efficiency. Because the physical essence of entransy is the thermomass potential energy, the entransy-based variational method is actually the energy method in heat transfer. All the new physical quantities, principles and methods form a new and independent knowledge system in heat transfer, which may be named "Physical heat transfer".

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“…The concepts of entransy and entransy dissipation were further applied into performance optimizations of transport network [82][83][84], spacecraft thermal control fluid parallel loop [85,86], lat-plate solar collectors [87], and district heating networks [88]. Cheng et al [89,90] analyzed the physical phenomena of electrical conduction, heat transfer and mass transfer, summed up these into a generalized flow.…”

Section: Other Applicationsmentioning

confidence: 99%

Progress in entransy theory and its applications

Chen

2012

Chin. Sci. Bull.

115

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The entransy and entransy dissipation extremum principle proposed have opened up a new direction for the heat transfer optimization. The emergence and development of entransy theory are reviewed. Entransy theory and its applications are summarized from several aspects, such as heat conduction, heat convective, heat radiation, heat exchanger design and mass transfer, etc. The emphases are focused on four aspects, i.e., the comparison between entropy generation rate and entransy dissipation rate, the combination of entransy dissipation extreme principle with finite time thermodynamics, the combination of entransy dissipation extreme principle with the heat conduction constructal theory, and the combination of entransy dissipation extreme principle with the heat convective constructal theory. The scientific features of entransy theory are emphasized. Influenced by oil crisis in the 1970's directly, the heat transfer enhancement was world-widely paid attention by the scientific community, and was quickly developed into one of very important branches in thermal science and technology fields. With the progress of social development ideas, such as sustainable development, low-carbon technology and low-carbon economy, the concept of heat transfer enhancement has developed into a broader scope concept of heat transfer optimization [1]. In the past 30 years, the basic theory of heat transfer optimization has been made considerable progresses, and finite-time thermodynamics, field synergy principle, constructal theory as well as entransy theory are the representative achievements. The emergences of these theories promoted the developments of thermodynamics and heat transfer. Finite-time thermodynamics, which combined thermodynamics, heat transfer and fluid mechanics, provided a theoretical fundament for performance optimizations of practical processes and devices with the constraints of a finite size and finite time. Field synergy principle unified the essential physical understandings of convective heat transfer and heat transfer enhancement phenomena, and provided a theoretical fundament for the development of heat transfer enhancement technology to achieve better energy saving effects. Constructal theory, which was called the thermodynamics of non-equilibrium system with configuration in the field of thermal science, provided a theoretical fundament for the unified descriptions of the generation of flow structures in natural organization and the designs of various flow structures. Fourier's law of heat conduction, Newton's law of cooling and Stephen-Boltzmann law of blackbody radiation only gave the concept of heat transfer rate, while the concepts of entransy and entransy dissipation lay the foundation of defining the concept of heat transfer efficiency which did not appear in the heat transfer theory before. Entransy theory provided a new theoretical fundament for heat transfer optimization, which is different from that of the entropy generation minimization.

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Application of entransy theory in the heat transfer optimization of flat-plate solar collectors

Cited by 21 publications

References 21 publications

Constructal design for flat plate collector in a solar ocean thermal energy conversion system

Constructal design for flat plate collector in a solar ocean thermal energy conversion system

Physical Heat Transfer

Progress in entransy theory and its applications

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