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Improvement of tree-like network constructal method for heat conduction optimization

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Science China(Technological Sciences) 2006年第3期49卷 332-341页

作者： WU Wenjun CHEN Lingen sun fengrui Postgraduate School Naval University of Engineering Wuhan 430033 China Postgraduate School Naval University of Engineering Wuhan 430033 China Postgraduate School Naval University of Engineering Wuhan 430033 China

The analysis of the “tree-like network” construct method has been repeated. The high effective conduction channel distribution has been optimized again, without the premise that the new order assembly construct must be assembled by the optimized last order construct. It is proved that the “tree-like network” construct method is faultiness. A more optimal construct is obtained,; when the thermal conductivity; the proportion of the two heat conduction materials are constant, the limit of the minimum heat resistance is derived. All these conclusions can be used to guide the engineering application.

关键词： constructal theory, 'tree-like network' construct method, high effective conduction channel distribution, generalized thermodynamic optimization.

Optimal performance of a generalized irreversible four-reservoir isothermal chemical potential transformer

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Science China Chemistry 2008年第10期51卷 958-970页

作者： XIA Dan CHEN LinGen sun fengrui Postgraduate School Naval University of EngineeringWuhan 430033China

A new cyclic model of a four-reservoir isothermal chemical potential transformer with irreversible mass transfer, mass leakage and internal dissipation is put forward in this paper. The optimal relation be-tween the coefficient of performance (COP) and the rate of energy pumping of the generalized irre-versible four-reservoir isothermal chemical potential transformer has been derived by using finite-time thermodynamics or thermodynamic optimization. The maximum COP and the corresponding rate of energy pumping, as well as the maximum rate of energy pumping and the corresponding COP, have been obtained. Moreover, the influences of the irreversibility on the optimal performance of the iso-thermal chemical potential transformer have been revealed. It was found that the mass leakage affects the optimal performance both qualitatively and quantitatively, while the internal dissipation affects the optimal performance quantitatively. The results obtained herein can provide some new theoretical guidelines for the optimal design and development of a class of isothermal chemical potential trans-formers, such as mass exchangers, electrochemical, photochemical and solid state devices, fuel pumps, etc.

关键词： is othermal four-reservoir chemical potential transformer coefficient of performance rate of energy pumping finite time thermody-namics

“Volume-point” heat conduction constructal optimization based on entransy dissipation rate minimization with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale

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Science China(Technological Sciences) 2012年第3期55卷 779-794页

作者： FENG HuiJun CHEN LinGen sun fengrui College of Naval Architecture and Power Naval University of EngineeringWuhan 430033China

Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are optimized by taking minimum entransy dissipation rate as optimization *** optimal constructs of the three "volume-point" heat conduction models with minimum dimensionless equivalent thermal resistance are *** results show that the optimal constructs of the three-dimensional cylindrical assembly based on the minimizations of dimensionless equivalent thermal resistance and dimensionless maximum thermal resistance are different,which is obviously different from the comparison between those of the corresponding two-dimensional rectangular assembly based on the minimizations of these two *** optimal constructs based on rectangular and triangular elements on microscale and nanoscale when the size effect takes effect are obviously different from those when the size effect does not take *** the thermal current density in the high conductivity channel of the rectangular and triangular second order assemblies are not linear with the length,the optimal constructs of these assemblies based on the minimization of entransy dissipation rate are different from those based on the minimization of maximum temperature *** dimensionless equivalent thermal resistance defined based on entransy dissipation rate reflects the average heat transfer performance of the *** studies on "volume-point" heat conduction constructal problems at three-dimensional conditions and microscale and nanoscale by taking minimum entransy dissipation rate as optimization objective extend the application range of the entransy dissipation extremum principle.

关键词： constructal theory entransy dissipation rate three-dimensional cylindrical element microscale and nanoscale vol-ume-point heat conduction generalized thermodynamic optimization

Constructal entransy dissipation rate minimization of a rectangular body with nonuniform heat generation

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Science China(Technological Sciences) 2016年第9期59卷 1352-1359页

作者： FENG HuiJun[[ CHEN LinGen[[ XIE ZhiHui[[ sun fengrui[[ Institute of Thermal Science and Power Engineering Naval University of Engineering Military Key Laboratory for Naval Ship Power Engineering Naval University of Engineering College of Power Engineering Naval University of Engineering

Based on construtal theory, a nonuniform heat generation problem in a rectangular body is investigated in this paper. Entransy dissipation rate(EDR) is taken as the optimization objective. The optimal body shapes with constant and variable widths of the high conductivity channel(HCC) are derived. For the rectangular first order assembly(RFOA) with constant cross-section HCC, the shape of the RFOA and width ratio of the HCCs are optimized, and the double minimum EDR is obtained. The heat transfer performance of the RFOA becomes worse when the nonuniform coefficient increases. For the RFOA with variable cross-section HCC, the EDR of the RFOA can be minimized for four times. Compared the optimal construct based on minimum EDR of the RFOA with that based on minimum maximum temperature difference, the shape of the former optimal construct is tubbier, and the average temperature difference is lower. In the practical design of electronic devices, when the thermal safety is ensured, the constructal design scheme of the former optimal construct can be adopted to improve the global heat transfer performance of an electronic device.

关键词： constructal theory entransy theory nonuniform heat generation rectangular body generalized thermodynamic optimization

The minimum heat consumption for heat-driven binary separation processes with linear phenomenological heat transfer law

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Science China Chemistry 2009年第8期52卷 1154-1163页

作者： SHU LiWei CHEN LinGen sun fengrui Graduate School Naval University of EngineeringWuhan 430033China

The optimal performance of heat-driven binary separation processes with linear phenomenological heat transfer law(q∝△(T-1)) is analyzed by taking the processes as heat engines which work between high-and low-temperature reservoirs and produce enthalpy and energy flows out of the system,and the temperatures of the heat reservoirs are assumed to be time-and space-variables.A numerical method is employed to solve convex optimization problem and Lagrangian function is employed to solve the average optimal control *** dimensionless entropy production rate coefficient and dimensionless enthalpy flow rate coefficient are adopted to indicate the major influence factors on the performance of the separation process,such as the properties of different materials and various separation requirements for the separation *** dimensionless minimum average entropy production rate and dimensionless minimum average heat consumption of the heat-driven binary separation processes are *** obtained results are compared with those obtained with the Newtonian heat transfer law(q∝△(T)).

关键词： linear phenomenological heat transfer law heat-driven separation binary separation process heat consumption entropy production rate finite time thermodynamics

Constructal optimization for a solid-gas reactor based on triangular element

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Science China(Technological Sciences) 2008年第9期51卷 1554-1562页

作者： ZHOU ShengBing CHEN LinGen sun fengrui Postgraduate School Naval University of EngineeringWuhan 430033China

Entropy generation minimization for heat and mass transfer process in a solid-gas reactor is carried out based on constructal theory by using triangular elemental area. The aspect ratio of the triangular elemental area is optimized under constraint conditions. A number of optimal triangular elements are assembled to a new large rectangular area, which is optimised again. The procedure is repeated until the control-volume is covered, and the complete analytical results are obtained. The effects of some parameters on minimum entropy generation are analysed by nu-merical examples. The results show that smaller entropy generation can be ob-tained when the optimization for a given volume is carried out on the basis of tri-angular elements than those obtained on the basis of rectangular elements.

关键词： constructal theory porous medium solid-gas reactor heat and mass transfer entropy generation minimization

Constructal entransy dissipation rate minimization for helm-shaped fin with inner heat sources

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Science China(Technological Sciences) 2015年第6期58卷 1084-1090页

作者： FENG HuiJun CHEN LinGen XIE ZhiHui sun fengrui Institute of Thermal Science and Power Engineering Naval University of Engineering Military Key Laboratory for Naval Ship Power Engineering Naval University of Engineering College of Power Engineering Naval University of Engineering

A model of three-dimensional helm-shaped body composed of a helm-shaped fin and inner heat sources is built in this paper. For the specified volumes of the body, fin and heat source, the constructal optimizations of the body with single and multiple inner heat sources are implemented. The entransy-dissipation-rate-based equivalent thermal resistance(ETR) is minimized in the optimizations. It shows that for the helm-shaped body with multiple inner heat sources, there exist an optimal ratio of the heat source distance to the radius of the extended fin and a twice optimal radius ratio of the centre fin to the extended fin which lead to the double minimum dimensionless ETR. Comparing the optimal result of the body with helm-shaped fin with that with annular fin, the radius of the centre fin and the distance between the heat source and the center of the body are decreased, and the ETR is decreased by 9.57%. Essentially, the temperature gradient field of the helm-shaped body is more homogenous, and its global heat transfer performance is improved.

关键词： constructal theory entransy theory helm-shaped fin inner heat source generalized thermodynamic optimization

Optimization of the power, efficiency and ecological function for an air-standard irreversible Dual-Miller cycle

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Frontiers in Energy 2019年第3期13卷 579-589页

作者： Zhixiang WU Lingen CHEN Yanlin GE fengrui sun Institute of Thermal Science and Power Engineering Naval University of EngineeringWuhan 430033China Military Key Laboratory for Naval Ship Power Engineering Naval University of EngineeringWuhan 430033China College of Power Engineering Naval University of EngineeringWuhan 430033China

This paper establishes an irreversible DualMiller cycle (DMC) model with the heat transfer (HT) loss, friction loss (FL) and other internal irreversible losses. To analyze the effects of the cut-off ratio (ρ) and Miller cycle ratio (rM) on the power output (P), thermal efficiency (η) and ecological function (E), obtain the optimal popt and optimal rMopt, and compare the performance characteristics of DMC with its simplified cycles and with different optimization objective functions, the P,η and E of irreversible DMC are analyzed and optimized by applying the finite time thermodynamic (FTT) theory. Expressions of P,η and E are derived. The relationships among P,η, E and compression ratio (ε) are obtained by numerical examples. The effects of ρ and rM on P,η, E, maximum power output (MP), maximum efficiency (MEF) and maximum ecological function (ME) are analyzed. Performance differences among the DMC, the Otto cycle (OC), the Dual cycle (DDC), and the Otto-Miller cycle (OMC) are compared for fixed design parameters. Performance characteristics of irreversible DMC with the choice of P,η and E as optimization objective functions are analyzed and compared. The results show that the irreversible DMC engine can reach a twice-maximum power, a twicemaximum efficiency, and a twice-maximum ecological fiinction, respectively. Moreover, when choosing E as the optimization objective, there is a 5.2% of improvement in η while there is a drop of only 2.7% in P compared to choosing P as the optimization objective. However, there is a 5.6% of improvement in P while there is a drop of only 1.3% in rj compared to choosing as the optimization objective.

关键词： finite-time thermodynamics Dual-Miller cycle power output thermal efficiency ecological function

Performance Optimization of Irreversible Air Heat Pumps Considering Size Effect

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Journal of Thermal Science 2018年第3期27卷 223-229页

作者： BI Yuehong CHEN Lingen DING Zemin sun fengrui Institute of Civil & Architectural Engineering Beijing University of Technology Beijing 100124 China Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology Beijing 100124 China Institute of Thermal Science and Power Engineering Naval University of Engineering Wuhan 430033 China

Considering the size of an irreversible air heat pump （AHP）, heating load density （HLD） is taken as thermodynamic opt/mization objective by using finite-time thermodynamics. Based on an irreversible AHP with infinite reservoir thermal-capacitance rate model, the expression of HLD of AHP is put forward. The HLD opti-mization processes are studied analytically and numerically, which consist of two aspects：（1） to choose pressure ratio; （2） to distribute heat-exchanger inventory. Heat reservoir temperatures, heat transfer performance of heat exchangers as well as irreversibility during compression and expansion processes are important factors influenc-ing on the performance of an irreversible AHP, which are characterized with temperature ratio, heat exchanger inventory as well as isentropic efficiencies, respectively. Those impacts of parameters on the maximum HLD are thoroughly studied. The research results show that HLD optimization can make the size of the AHP system smaller and improve the compactness of system.

关键词： Irreversible Air Heat Pump Thermodynamic Optimization Heating Load Density Size Effect Finite Time Thermodynamics