Entropy and entransy analyses and optimizations of the Rankine cycle

Wang, Wenhua; Cheng, Xi; Liang, Xin-Gang

doi:10.1016/j.enconman.2012.12.020

Cited by 45 publications

(20 citation statements)

References 32 publications

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“…In the recent investigations of thermodynamic cycles, Cheng et al [15,44,47] defined a new concept, entransy loss rate, that is the difference between the entransy flow rate into the system and that out of the system. It is shown that the maximum entransy loss rate leads to the maximum output work for the discussed systems [15,44,[47][48][49][50].…”

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confidence: 97%

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Entransy and entropy analyses of heat pump systems

Cheng

Liang

2013

Chin. Sci. Bull.

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In this paper, heat pump systems are analyzed with entransy increase and entropy generation. The extremum entransy increase principle is developed. When the equivalent temperatures of the high and low temperature heat sources are fixed, the theoretical analyses and numerical results both show that the maximum COP leads to the maximum entransy increase rate for fixed input power, while it leads to the minimum entransy increase rate for fixed heat flow absorbed from the low temperature heat source.The minimum entropy generation principle shows that the minimum entropy generation rate always leads to the maximum COP for fixed input power or fixed heat flow absorbed from the low temperature heat source when the equivalent thermodynamic forces of the high and low temperature heat sources are given. Further discussions show that only the entransy increase rate always increases with increasing heat flow rate into the high temperature heat source for the discussed cases. entransy loss, entransy increase,entropy generation, heat pump, optimizationHeat pump systems are common industrial equipments and have many applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. For instance, in the heating and air conditioning system, the heat pump is applied to driving the heat from the environment into the room [15]. The optimization design of heat pump systems has received more and more attention because it can improve the system performance and increase the energy utilization efficiency [6][7][8][9][10][11][12].There are different optimization objectives for heat pump systems, such as the thermo-economic performance [6] and the thermodynamic performance optimization [4,5,[7][8][9][10][11][12]. For instance, Quoilin et al. [6] analyzed the thermo-economic performance of heat pump systems. Chen et al. [4] optimized the piston speed ratios to get the maximum COP for the irreversible Carnot refrigerator and heat pump using the finite time thermodynamics. In this paper, we focus on the thermodynamic performance optimization. As the thermodynamic processes in heat pump systems are mainly composed of heat transfer processes and thermodynamic cycles, the analyses of the heat transfer processes and thermodynamic cycles are very important for the optimization designs. In the past decades, some optimization theories have already been developed and applied to heat transfer and thermodynamic cycles [15][16][17][18].Practical heat transfer processes are irreversible from the thermodynamic viewpoint, and entropy generation will be produced. Many researchers applied the entropy generation minimization method to analyzing and optimizing heat transfer processes [18][19][20]. However, the entropy generation paradox tells us that the effectiveness of heat exchangers ε does not always decrease when the entropy generation number increases [18]. When Bejan [18] analyzed a balanced counter flow heat exchanger, he explained the entropy generation paradox as following: when ε→0, the heat exchanger would disappear as an engineering component, a...

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“…The entransy theory is also used to analyze thermodynamic cycles [15,[44][45][46][47][48][49][50]. Wu [45] defined the conversion entransy by which the thermodynamic processes with work were analyzed.…”

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Entransy and entropy analyses of heat pump systems

Cheng

Liang

2013

Chin. Sci. Bull.

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“…In the analyses of thermodynamic cycles, Cheng and Liang [22] proposed the concept of entransy loss, which is the entransy consumed during the thermodynamic processes. Under some conditions, it was found that larger entransy loss leads to larger output power for the discussed systems [9,12,[22][23][24][25][26]. In heat pump systems, it was found that the system entransy does not decrease but increase, so the concept of entransy increase was proposed [26].…”

Section: Introductionmentioning

confidence: 97%

Entransy variation associated with work

Cheng

Liang

2015

International Journal of Heat and Mass Transfer

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“…Similar to the process of entropy generation, the more entransy dissipates, the higher its degree of irreversibility is. Thus the entransy dissipation becomes a quantitative index for evaluating the performance of heat exchangers, and there is no entropy generation paradox in applications of heat exchanger design [11,12]. In general, there are two types of irreversible energy loss in the heat exchanger-heat transfer and fluid friction irreversibility degrees, which are competing functions.…”

Section: Introductionmentioning

confidence: 99%

Irreversibility analysis for optimization design of plate fin heat exchangers using a multi-objective cuckoo search algorithm

Wang

2015

Energy Conversion and Management

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Entropy and entransy analyses and optimizations of the Rankine cycle

Cited by 45 publications

References 32 publications

Entransy and entropy analyses of heat pump systems

Entransy and entropy analyses of heat pump systems

Entransy variation associated with work

Irreversibility analysis for optimization design of plate fin heat exchangers using a multi-objective cuckoo search algorithm

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