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Constructal optimization of a vertical insulating wall based on a complex objective combining heat flow and strength

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Science china(Technological Sciences) 2010年第8期53卷 2278-2290页

作者： XIE ZhiHui,chen lingen &sun fengrui postgraduate school,naval university of engineering,wuhan 430033,china postgraduate school Naval University of Engineering Wuhan China

For a vertical insulating wall,a product function of heat flow and strength with power weight is introduced as the complex optimization objective to compromise between insulating performance and mechanical *** the global constraints of fixed external dimensions and safety requirements,the constructal optimization of the wall is carried out by taking the complex function maximization as the *** is shown that the maximum of the complex-objective function and its corresponding optimal internal structure design under a certain environmental condition can be obtained by allowing the internal structure of the wall to vary(evolve)*** validity,effectivity and applicability of the complex function are proved by the results and the power weight parameter in the range from 0.4 to 4 can compromise between the requirements of insulating and strength simultaneously and *** constructal optimization with coequal attention to heat flow and strength and the corresponding results are discussed in *** optimal structure design and the corresponding performance analyses under various environmental conditions of application are *** the change of environment is greater and the total Rayleigh number is bigger,the insulating wall with large number of cavities should be *** the total Rayleigh number is small,the better performance can be obtained by reasonably employing the insulating wall with small number of *** complex function has better selfadaptability,and the results in the recent literature are special cases of this paper.

关键词： constructal theory insulating wall multidiscipline generalized thermodynamic optimization

Optimal paths for a light-driven engine with a linear phenomenological heat transfer law

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Science china Chemistry 2010年第4期53卷 917-926页

作者： MA Kang, chen lingen & sun fengrui postgraduate school, naval university of engineering, wuhan 430033, china postgraduate school Naval University of Engineering Wuhan China

An irreversible light-driven engine is described in this paper, in which the heat transfer between the working fluid and the environment obeys a linear phenomenological heat transfer law [ q ∝Δ(T -1)], with a working fluid composed of the bimolecular reacting system 2SO 3 F■S 2 O 6 F2. Piston trajectories maximizing work output and minimizing entropy generation are determined for such an engine with rate-dependent loss mechanisms of friction and heat leakage. The optimal control theory is applied to determine the optimal configurations of the piston motion trajectory and the fluid temperature. Numerical examples for the optimal configuration are provided, and the obtained results are compared with those derived with Newtonian heat transfer law [ q ∝Δ(T )].

关键词： linear phenomenological heat transfer law maximum work output minimum entropy generation irreversible lightdriven engine optimal control finite time thermodynamics

Constructal optimization of twice Y-shaped assemblies of fins by taking maximum thermal resistance minimization as objective

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Science china(Technological Sciences) 2010年第10期53卷 2756-2764页

作者： XIE ZhiHui, chen lingen & sun fengrui postgraduate school, naval university of engineering, wuhan 430033, china postgraduate school Naval University of Engineering

In this paper,constructal optimization of the twice Y-shaped assemblies of fins with six freedom degrees (characteristic parameters of geometry) is performed by employing finite element method and taking dimensionless maximum thermal resistance as a performance index,and the heat transfer performance of the twice Y-shaped assemblies of fins under various conditions with different freedom degrees are analyzed. The results show that the twice assemblies can improve the heat transfer performance of Y-shaped fin remarkably,and the minimum maximum thermal resistance of the twice Y-shaped assemblies of fins decreases by 36.37% compared with that of once Y-shaped assembly of fins. It is also proved again that the larger the number of freedom degrees for evolving is,the more perfect the system performance is. The effects of different characteristic parameters of geometry on the performance of the twice Y-shaped assemblies of fins are different,one should pay different attention to these parameters in practical engineering designs. The effects of two angles on the maximum thermal resistance are larger,but the optima of the two angles are robust. The effects of two height ratios on the maximum thermal resistance are more remarkable than those of two thickness ratios.

关键词： constructal theory fin multi-scale enhanced heat transfer generalized thermodynamic optimization

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

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Science china(Technological Sciences) 2010年第6期53卷 1666-1677页

作者： WEI ShuHuan,chen lingen & sun fengrui postgraduate school,naval university of engineering,wuhan 430033,china postgraduate school Naval University of Engineering

Using constructal entransy dissipation rate minimization method based on discrete variable cross-section conducting path,constructal optimizations of elemental area with variable cross-section conducting path are performed,and the results are compared with the optimization results of elemental area with the constant cross-section conducting *** comparison shows that the minimum mean temperature difference based on elemental area with variable cross-section conducting path increases and approaches a constant as the assembly's order increases,but the minimum mean temperature difference based on elemental area with constant cross-section conducting path decreases and approaches a constant as the assembly's order *** difference between them is caused by the different dimensionless mean temperature difference of the first order assembly.A universal constructal optimization method by self similar organization to improve heat transfer ability and its corresponding rule are *** the constructal optimization method by self similar organization based on entransy dissipation rate minimization objective,the mean temperature difference approaches a constant as the assembly's order increases.

关键词： constructal theory entransy entransy dissipation area-point conduction generalized thermodynamic optimization

“Volume-Point” heat conduction constructal optimization with entransy dissipation minimization objective based on rectangular element

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Science china(Technological Sciences) 2008年第8期51卷 1283-1295页

作者： WEI ShuHuan, chen lingen & sun fengrui postgraduate school, naval university of engineering, wuhan 430033, china postgraduate school Naval University of Engineering

By taking equivalent thermal resistance, which reflects the average heat conduc- tion effect and is defined based on entransy dissipation, as optimization objective, the "volume to point" constructal problem of how to discharge the heat generated in a fixed volume to a heat sink on the border through relatively high conductive link is re-analyzed and re-optimized in this paper. The constructal shape of the control volume with the best average heat conduction effect is deduced. For the elemental area and the first order construct assembly, when the thermal current density in the high conductive link is linear with the length, the optimized shapes of assemble based on the minimization of entransy dissipation are the same as those based on minimization of maximum temperature difference, and the mean tem- perature difference is 2/3 of the maximum temperature difference. For the second and higher order construct assemblies, the thermal current densities in the high conductive link are not linear with the length, and the optimized shapes of assem- ble based on the minimization of entransy dissipation are different from those based on minimization of maximum temperature difference. For the same parame- ters, the constructs based on minimization of entransy dissipation and the con- structs based on minimization of maximum temperature difference are compared, and the results show that the constructs based on entransy dissipation can de- crease the mean temperature difference better than the constructs based on mini- mization of maximum temperature difference. But with the increase of the number of the order, the mean temperature difference does not always decrease, and there exist some fluctuations. Because the idea of entransy describes the heat transfer ability more suitably, all of the heat conduction constructal problems may be re-optimized based on it.

关键词： constructal theory entransy dissipation volume-point heat conduction generalized thermodynamic optimi- zation

Entransy dissipation minimization for liquid-solid phase change processes

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Science china(Technological Sciences) 2010年第4期53卷 960-968页

作者： XIA ShaoJun,chen lingen & sun fengrui postgraduate school,naval university of engineering,wuhan 430033,china postgraduate school Naval University of Engineering

The liquid-solid phase change process of a simple one-dimensional slab is studied in this *** taking entransy dissipation minimization as optimization objective,the optimal external reservoir temperature profiles are derived by using optimal control theory under the condition of a fixed freezing or melting *** entransy dissipation corresponding to the optimal heat exchange strategies of minimum entransy dissipation is 8/9 of that corresponding to constant reservoir temperature operations,which is independent of all system *** obtained results for entransy dissipation minimization are also compared with those obtained for the optimal heat exchange strategies of minimum entropy generation and constant reservoir temperature operations by numerical *** obtained results can provide some theoretical guidelines for the choice of optimal cooling or heating strategy in practical liquid-solid phase change processes.

关键词： liquid-solid phase change process entransy dissipation minimization optimal control finite time thermodynamics generalized thermodynamic optimization

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

Modeling and performance analysis of energy selective electron (ESE) engine with heat leakage and transmission probability

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Science china(Physics,Mechanics & Astronomy) 2011年第11期54卷 1925-1936页

作者： ding zemin chen lingen sun fengrui College of naval Architecture and Power Naval University of EngineeringWuhan 430033China

A model of an energy selective electron (ESE) engine with linear heat leakage and Lorentzian transmission probability is established in this *** expressions for the main performance parameters of the ESE engine operating as a heat engine or a refrigerator are derived by using the theory of finite time *** optimum performances of the ESE engine are explored and the influences of the heat leakage,the central energy level of the resonance,and the width of the resonance on the performance of the ESE engine are analyzed by using detailed numerical *** optimal operation regions of power output and efficiency (or cooling load and coefficient of performance (COP)) are also ***,the performances of the ESE engine with Lorentzian transmission probability are compared with those with rectangular transmission *** is shown that the power output versus efficiency (or cooling load versus COP) characteristic curves with and without heat leakage are all closed loop-shaped *** efficiency (or COP) of the ESE engine decreases as the heat leakage *** is found that as the resonance width increases,the power output and efficiency (or cooling load and COP) increase to a maximum and then decrease due to the finite range of energies which contribute positively to the power generation or refrigeration in the electron ***,when heat leakage is taken into account,the characteristic curves of maximum efficiency (or maximum COP) versus half resonance width are parabolic-like ones,which are quite different from the monotonic decreasing characteristic curves obtained in previous analyses without considering heat *** results obtained in this paper can provide some theoretical guidelines for the design and operation of practical electron energy conversion devices such as solid-state thermionic refrigerators.

关键词： energy selective electron (ESE) engine heat leakage Lorentzian transmission probability performance analysis finite time thermodynamics

Generalized constructal optimization for the secondary cooling process of slab continuous casting based on entransy theory

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Science china(Technological Sciences) 2014年第4期57卷 784-795页

作者： FENG HuiJun chen lingen XIE ZhiHui ding zemin 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 constructal theory and entransy theory,a generalized constructal optimization of a solidification heat transfer process of slab continuous casting for a specified total water flow rate in the secondary cooling zone was carried out.A complex function was taken as the optimization objective to perform the *** complex function was composed of the functions of the entransy dissipation and surface temperature gradient of the *** optimal water distribution at the sections of the secondary cooling zone were *** effects of the total water flow rate in the secondary cooling zone,casting speed,superheat and water distribution on the generalized constructal optimizations of the secondary cooling process were *** results show that on comparing the optimization results obtained based on the optimal water distributions of the 8 sections in the secondary cooling zone with those based on the initial ones,the complex function and the functions of the entransy dissipation and surface temperature gradient after optimization decreased by 43.25%,5.90%and 80.60%,*** quality and energy storage of the slab had obviously improved in this *** complex function,composed of the functions of the entransy dissipation and surface temperature gradient of the slab,was a compromise between the internal and surface temperature gradients of the ***,it is also the compromise between energy storage and quality of the ***"generalized constructal optimization"based on the minimum complex function can provide an optimal alternative scheme from the point of view of improving energy storage and quality for the parameter design and dynamic operation of the solidification heat transfer process of slab continuous casting.

关键词： slab continuous casting solidification heat transfer entransy dissipation complex function generalized constructal op- timization generalized thermodynamic optimization