Constructal optimization of discrete and continuous-variable cross-section conducting path based on entransy dissipation rate minimization

Self Cite

114

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.

“…[154]. (6) The process of constructal optimization based on variable cross-section shape and variable high conducting path element is shown in Figure 17 [155].…”

Section: Figure 16mentioning

confidence: 99%

Progress in entransy theory and its applications

Chen

2012

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114

“…Based on the concept of entransy dissipation, Guo et al [4] developed the extremum entransy dissipation principle, defined the entransy-dissipation-based thermal resistance, and proposed the minimum thermal resistance principle. It was found that the principles of the entransy theory are appropriate to the optimization of heat conduction [5][6][7][8][9][10][11][12][13], heat convection [14][15][16][17], thermal radiation, design of heat exchangers [21][22][23][24][25][26][27] and phase change heat transfer processes [28]. Eqs.…”

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confidence: 99%

Relationship between microstate number and available entransy

Cheng

Liang

2012

Based on the relationship between entransy and microstate number, we discuss the variations of the available transport entransy, the unavailable transport entransy, the available conversion entransy and the unavailable conversion entransy with the microstate number. We focus on physical processes in which heat is used for heating/cooling or doing work. When heat is transported for heating or cooling, the available transport entransy increases if the increase in microstate number is due to the increase in internal energy of the system, and decreases if the increase in microstate number is due to spontaneous heat transfer. When heat is used to do work, both the available conversion entransy and the unavailable conversion entransy increase if the increase in microstate number relates to the growth in internal energy of the system. The available conversion entransy decreases and the unavailable conversion entransy increases if the increase in microstate number results from spontaneous heat transfer. microstate number, entransy, available entransy, unavailable entransy

“…With the concept of entransy dissipation or thermal resistance based on entransy dissipation, researchers have conducted many optimization studies of heat conduction, heat convection and mass convection [17][18][19][20][21][22][23]. Chen and co-authors [21][22][23] combined the extremum entransy dissipation principle with the constructal theory and optimized many heat transfer systems based on entransy dissipation rate minimization. In researches of heat exchangers and HENs, Song et al [24] demonstrated the uniformity principle of temperature difference field for one-dimensional heat exchanger based on the extremum entransy dissipation principle.…”

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confidence: 99%

Entransy-dissipation-based thermal resistance analysis of heat exchanger networks

Qian

2011

Heat exchanger network optimization has an important role in high-efficiency energy utilization and energy conservation. The thermal resistance of a heat exchanger network is defined based on its entransy dissipation. In two-stream heat exchanger networks, only heat exchanges between hot and cold fluids are considered. Thermal resistance analysis indicates that the maximum heat transfer rate between two fluids corresponds to the minimum entransy-dissipation-based thermal resistance; i.e. the minimum thermal resistance principle can be exploited in optimizing heat exchanger networks.heat exchanger network, entransy-dissipation-based thermal resistance, optimization, minimum thermal resistance principle Citation:Qian X D, Li Z, Li Z X. Entransy-dissipation-based thermal resistance analysis of heat exchanger networks. Chinese Sci Bull, 2011Bull, , 56: 3289-3295, doi: 10.1007 Heat exchanger networks (HENs) are widely used in energy transport and utilization. Two-stream HENs are a type of HENs in which hot and cold fluids do not exchange thermal energy directly through one heat exchanger due to environmental constraints or practical demands. Trivedi et al. [9] improved on this approach and introduced the dual temperature and pseudo-pinch method in HEN optimization. Analyzing by a mathematical programming method, a HEN is described by an objective function and constraint conditions. Cerda et al. [10] and Floudas et al.[11] solved this HEN optimization problem using linear programming (LP) and mixed-integer nonlinear programming (MINLP) methods respectively.In optimization designs of two-stream HENs, the heat transfer rate is mainly of concern to designers. To maximize the heat recovery or heat transfer rate, much research has been performed. In the research of run-around heat recovery system, Fan et al. [12] found that the system had the highest efficiency when the heat capacity ratio of air and the medial fluid was in the range 0.8-1.2. Zhou et al. [13] found that a ground-coupled liquid loop heat recovery ventilation system had an optimal allocation ratio between heat exchangers and an optimal brine flow rate that provided maximum heat recovery efficiency. These authors found the optimum working condition for the networks but did not explain the phys-