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“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 Wuhan China

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 Wuhan China

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

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 Wuhan China

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

Influence of Granularity and Content of Tungsten Carbide by Surfacing with Flux-cored Wire on Structure and Wear Resistance

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稀有金属材料与工程 2011年第S3期40卷 107-110页

作者： Li Lianjie, Gui Chibin, Dai Le Naval University of Engineering, Wuhan 430033, China Naval Univ Engn Coll Ship & Power Engn Wuhan 430033 Peoples R China

The wire was made with foundry tungsten carbide particles as core. Iron-based tungsten carbide wearable composite coatings of different granularity and content on mild steel were prepared by the method of MIG welding. Microstructure of the welded coating was investigated. Surface hardness and wear resistance to rubber wheel were tested. The results indicate that the small particles dissolved more, which separate out with net on crystal boundary. As a result the hardness and wear resistance of that matrix are relative higher. The big particles dissolved less and tree crystal separates out along particles. The gaps of particles are big and the particles tend to fall off when the coating is worn. So the hardness and wear resistance of the matrix are relative lower. The admixture with 80% big particles and 20% small particles has the best wear resistance and its wear resistance is quintupling of that of quenched 45 steel. With particles content up to 50wt%, the hardness and wear resistance increase.

关键词： tungsten carbide surfacing flux-cored wire wear

APPROXIMATE SOLUTIONS FOR TRANSIENT RESPONSE OF CONSTRAINED DAMPING LAMINATED CANTILEVER PLATE

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Acta Mechanica Solida Sinica 2010年第4期23卷 312-323页

作者： Liuwei Mao Anwen Wang Mingyong Hu (College of Science, Naval University of Engineering, Wuhan 430033, China) College of Science Naval University of Engineering Wuhan China

The series composed by beam mode function is used to approximate the displacement function of constrained damping of laminated cantilever plates, and the transverse deformation of the plate on which a concentrated force is acted is calculated using the principle of virtual *** solving Lagrange＇s equation, the frequencies and model loss factors of free vibration of the plate are obtained, then the transient response of constrained damping of laminated cantilever plate is obtained, when the concentrated force is withdrawn *** theoretical calculations are compared with the experimental data, the results show：both the frequencies and the response time of theoretical calculation and its variational law with the parameters of the damping layer are identical with experimental ***, the response time of steel cantilever plate, unconstrained damping cantilever plate and constrained damping cantilever plate are brought into comparison, which shows that the constrained damping structure can effectively suppress the vibration.

关键词： constrained damping cantilever plate damping laminated plate transient response beam mode function combination

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 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

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 Wuhan China

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

Thermodynamic characteristics of a Brownian heat pump in a spatially periodic temperature field

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Science China(Physics,Mechanics & Astronomy) 2010年第5期53卷 876-885页

作者： DING ZeMin,CHEN LinGen & SUN FengRui Postgraduate School,Naval University of Engineering,Wuhan 430033,China Postgraduate School Naval University of Engineering Wuhan China

This paper has studied the thermodynamic performance of a thermal Brownian heat pump,which consists of Brownian particles moving at a periodic sawtooth potential with external forces and contacting with the alternating hot and cold reservoirs along the space *** heat flows driven by both potential and kinetic energies are taken into *** analytical expressions for the heating load,coefficient of performance(COP) and power input of the Brownian heat pump are derived and the performance characteristics are obtained by numerical *** is shown that due to the heat flow via the change of kinetic energy of the particles,the Brownian heat pump is always irreversible and the COP can never attain the Carnot *** study has also investigated the influences of the operating parameters,*** external force,barrier height of the potential,asymmetry of the sawtooth potential and temperature ratio of the heat reservoirs,on the performance of the Brownian heat *** effective regions of external force and barrier height of the potential in which the Brownian motor can operates as a heat pump are *** results show that the performance of the Brownian heat pump greatly depends on the parameters;if the parameters are properly chosen,the Brownian heat pump may be controlled to operate in the optimal regimes.

关键词： Brownian heat pump COP heating load heat flow performance characteristics finite time thermodynamics