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| 1 | Entransy dissipation minimization for liquid-solid phase change processes显示文摘The liquid-solid phase change process of a simple one-dimensional slab is studied in this paper.By 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 time.The 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 parameters.The 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 examples.The obtained results can provide some theoretical guidelines for the choice of optimal cooling or heating strategy in practical liquid-solid phase change processes. | XIA ShaoJun,CHEN LinGen & SUN FengRui Postgraduate School,Naval University of Engineering,Wuhan 430033,China | 2010 | Science China(Technological Sciences)2010，53，4： | 41 |
| 2 | Principle of equipartition of entransy dissipation for heat exchanger design显示文摘In the present work,a principle of equipartition of entransy dissipation(EoED) for heat exchanger design is established,which says that for a heat exchanger design with given heat duty and heat transfer area,the total entransy dissipation rate reaches the minimum when the local entransy dissipation rate is uniformly distributed along the heat exchanger.When the heat transfer coefficient is unfixed,the total entransy dissipation obtained by the EoED principle is less than that obtained by the principle of equipartition of temperature difference(EoTD).Furthermore,the exchanger effectiveness obtained by the EoED principle is larger than that obtained by the EoTD principle.When the heat transfer coefficient is fixed,the EoED principle is equivalent to the EoTD principle.We show that the equipartition of entropy production(EoEP) and EoED principles give rise to difference in entropy generation and entransy dissipation for a heat exchanger optimization design.The discrepancies are caused by distinct features of entropy production minimization and entransy dissipation minimization principles,the former is to optimize the design of heat exchanger by making the lost available work minimum,while the latter is not involved with heat-work conversion.It is found that the entropy generation number is not suitable for evaluating heat exchanger performance,since it directly depends on the inlet and outlet temperatures of working fluids.On the contrary,the entransy dissipation number is not directly related to the inlet and outlet temperatures of working fluids.Therefore,the entransy dissipation number is more suitable for serving as a criterion to evaluate heat exchanger performance. | GUO JiangFeng,XU MingTian & CHENG Lin Institute of Thermal Science and Technology,Shandong University,Jinan 250061,China | 2010 | Science China(Technological Sciences)2010，53，5： | 46 |
| 3 | Progress in entransy theory and its applications显示文摘The entransy and entransy dissipation extremum principle proposed have opened up a new direction for the heat transfer optimi-zation. 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. | CHEN LinGen | 2012 | Chinese Science Bulletin2012，57，34： | 42 |
| 4 | Constructal entransy dissipation rate minimization for 'disc-to-point' heat conduction显示文摘Based on constructal theory,'disc-to-point' heat conduction is optimized by minimizing the entransy dissipation rate whereby a critical point is determined that distributes the high-conductivity material according to optimized radial or branch patterns.The results show that the critical point is determined by the product of the thermal conductivity ratio of the two materials and the volume fraction of the high-conductivity material allocated to the entire volume.The notion of optimal heat transfer performance can be attributed to the disc based on the entransy dissipation extremum principle.Comparing the results based on EDR minimization (entransy dissipation rate minimization) with those based on MTD minimization (maximum temperature difference minimization),one finds that the performance derived from the two optimization procedures are different.When the product of the thermal conductivity ratio and volume fraction is 30,the critical point of the former procedure is that for which the nondimensional radius of the disc equals 1.75,while that of the latter procedure is that for which this radius of the disc equals 2.18.Comparing heat transfer performances from the two procedures,the mean heat transfer temperature difference is decreased more for the former procedure thereby receiving an improved performance quota. | XIAO QingHua CHEN LinGen SUN FengRui | 2011 | Chinese Science Bulletin2011，56，1： | 31 |
| 5 | Progress in optimization of mass transfer processes based on mass entransy dissipation extremum principle显示文摘The mass entransy and its dissipation extremum principle have opened up a new direction for the mass transfer optimization. Firstly, the emergence and development process of both the mass entransy and its dissipation extremum principle are reviewed. Secondly, the combination of the mass entransy dissipation extremum principle and the finite-time thermodynamics for optimizing the mass transfer processes of one-way isothermal mass transfer, two-way isothermal equimolar mass transfer, and isothermal throttling and isothermal crystallization are summarized. Thirdly, the combination of the mass entransy dissipation extremum principle and the constructal theory for optimizing the mass transfer processes of disc-to-point and volume-to-point problems are summarized. The scientific features of the mass entransy dissipation extremum principle are emphasized. | CHEN Lin Gen | 2014 | Science China(Technological Sciences)2014，57，12： | 34 |
| 6 | Entransy decrease principle of heat transfer in an isolated system显示文摘The entropy increase principle for an isolated system and the criteria of thermal equilibrium for an isolated system and systems with prescribed temperature and volume can be derived on the basis of the concept of entropy and the first and second laws of thermodynamics. In this paper, the entransy decrease principle for an isolated system is introduced on the basis of the concept of entransy. It is found that the entransy of an isolated system always decreases during heat transfer. This principle can be taken as an expression of the second law of thermodynamics for heat transfer. The thermal equilibrium criteria for an isolated system and a closed system are also introduced. It is found that when an isolated system reaches thermal equilibrium, its entransy is a minimum value. This criterion is referred to as the minimum entransy principle. When a closed system reaches thermal equilibrium, its free entransy is also a minimum value. This criterion is referred to as the minimum free entransy principle. Therefore, like entropy, entransy can be considered an arrow of time in heat transfer and used to describe the thermal equilibrium state. | CHENG XueTao LIANG XinGang GUO ZengYuan | 2011 | Chinese Science Bulletin2011，56，9： | 29 |
| 7 | Constructal optimization of discrete and continuous-variable cross-section conducting path based on entransy dissipation rate minimization显示文摘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 path.The 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 increases.The 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 proposed.With 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. | WEI ShuHuan,CHEN LinGen & SUN FengRui Postgraduate School,Naval University of Engineering,Wuhan 430033,China | 2010 | Science China(Technological Sciences)2010，53，6： | 27 |
| 8 | Constructal entransy dissipation rate and flow-resistance minimizations for cooling channels显示文摘Based on constructal theory,a construct of a volume that generates heat at every point and is cooled by the coolant in the constant or tapered channel is optimized by minimizing entransy dissipation rate and flow resistance.The optimal constructs of the rectangular elements with dimensionless mean thermal resistance minimization as well as the first-,secondand thirdorder assemblies with dimensionless global flow resistance minimizations are obtained respectively.The results show that both the mean temperature difference and the limiting temperature difference of rectangular elements based on EDR (entransy dissipation rate) and MTD (maximum temperature difference) minimizations respectively are almost equal.Comparing heat transfer performances from the two optimization procedures,the dimensionless global flow resistance is decreased more for the former procedure when the assembly’s order is high.It may create great superiority for constructal optimization to combine the entransy dissipation extreme principle with heat convection. | XIAO QingHua,CHEN LinGen & SUN FengRui Postgraduate School,Naval University of Engineering,Wuhan 430033,China | 2010 | Science China(Technological Sciences)2010，53，9： | 27 |
| 9 | Constructal optimization on T-shaped cavity based on entransy dissipation minimization显示文摘The entransy dissipation extremum principle provides new warranty and criterion for optimization of heat transfer. For a heat transfer model of a rectangular solid wall with an open T-shaped cavity, a dimensionless equivalent thermal resistance based on entransy dissipation is taken as optimization objective, and constructal optimization for the model is carried out when the system volume, the cavity volume and the volume of rectangle occupied by T-shaped cavity are fixed. Numerical results indicate that the optimal geometry construct of cavity can be schemed out based on entransy dissipation extremum principle. The formulation of dimensionless global (maximum) thermal resistance presented in a literature is modified; some new rules which are different from those reported in the literature are obtained based on the minimization of the modified objective. Comparisons of the numerical results show that the optimal system constructs deduced respectively from the two thermal resistance objectives are very different. The optimization by taking equivalent thermal resistance minimization as objective can more effectively reduce mean temperature difference of heat transfer than the optimization by taking maximum thermal resistance minimization as objective, so that the performance of heat transfer for the total system can be improved. The more freedom the cavity has, the better the total system performance is. The correlations of the equivalent thermal resistance and the maximum thermal resistance of the system and three geometric degrees of freedom are found by using function fitting. | XIE ZhiHui CHEN LinGen SUN FengRui | 2009 | Chinese Science Bulletin2009，54，23： | 28 |
| 10 | Comparative study on constructal optimizations of T-shaped fin based on entransy dissipation rate minimization and maximum thermal resistance minimization显示文摘The constructal optimizations of T-shaped fin with two-dimensional heat transfer model are carried out by finite element method and taking the minimization of equivalent thermal resistance based on entransy dissipation and the minimization of maximum thermal resistance as optimization objectives, respectively. The effects of the global parameter a (integrating the coefficient of convective heat transfer, the overall area occupied by fin and its thermal conductivity) and the volume fraction ? of fin on the minimums of equivalent thermal resistance and maximum thermal resistance as well as their corresponding optimal configurations are analyzed. The comparison of the results based on the above two optimization objectives is conducted. The results show that the optimal structures based on the two optimization objectives are obviously different from each other. Compared with the optimization result by taking the minimization of maximum thermal resistance as the objective, the optimization result by taking the equivalent thermal resistance minimization as the objective can reduce the average temperature difference in the fin obviously. The increases of a and ? can all improve the working status of local hot spot and the global heat transfer performance of the system. But the improvement effects of the increases of a and ? on the minimization of equivalent thermal resistance are different from those on the minimization of maximum thermal resistance. For either objective, the effect of a is different from that of ?. The T-shaped fin with minimum equivalent thermal resistance is much taller than that with minimum maximum thermal resistance; for either optimization objective, the stem of fin is thicker than the branches of fin, and the stem thickness is relatively close to branch thickness when the minimization of equivalent thermal resistance is taken as the optimization objective. The T-shaped fin with flat stem and slender branches can benefit the reduction of the maximum thermal resistance. | XIE ZhiHui CHEN LinGen SUN FengRui | 2011 | Science China(Technological Sciences)2011，54，5： | 25 |
| 11 | Constructal entransy dissipation rate minimization for umbrella-shaped assembly of cylindrical fins显示文摘Umbrella-shaped assembly of cylindrical fins is optimized by adopting analytical method and taking dimensionless mean thermal resistance (MTR) as performance index. The optimal construct of umbrella-shaped assembly is obtained. The results show that the heat conductance performance of the assembly becomes ever worse with ever greater number of elemental cylindrical fins,the umbrella-shaped assembly reduces to cylindrical fin in some values of design parameters,and the diameters’ dependence on design parameters is weak for the optimized assembly. An equivalent thermal resistance defined based on entransy dissipation rate (EDR) reflects an average heat transfer effect of the assembly. The constructal design corresponding to the minimum EDR (or MTR) should be adopted for designing an assembly of fins in engineering at the limit safe condition. | XIAO QingHua CHEN LinGen SUN FengRui | 2011 | Science China(Technological Sciences)2011，54，1： | 24 |
| 12 | Constructal optimization of a vertical insulating wall based on a complex objective combining heat flow and strength显示文摘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 performance.Under 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 objective.It 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)freely.The 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 preferably.The constructal optimization with coequal attention to heat flow and strength and the corresponding results are discussed in detail.The optimal structure design and the corresponding performance analyses under various environmental conditions of application are presented.When the change of environment is greater and the total Rayleigh number is bigger,the insulating wall with large number of cavities should be employed.When the total Rayleigh number is small,the better performance can be obtained by reasonably employing the insulating wall with small number of cavities.The complex function has better selfadaptability,and the results in the recent literature are special cases of this paper. | XIE ZhiHui,CHEN LinGen &SUN FengRui Postgraduate School,Naval University of Engineering,Wuhan 430033,China | 2010 | Science China(Technological Sciences)2010，53，8： | 21 |
| 13 | Constructal optimization of twice Y-shaped assemblies of fins by taking maximum thermal resistance minimization as objective显示文摘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. | XIE ZhiHui, CHEN LinGen & SUN FengRui Postgraduate School, Naval University of Engineering, Wuhan 430033, China | 2010 | Science China(Technological Sciences)2010，53，10： | 21 |
| 14 | A comparison of optimization theories for energy conservation in heat exchanger groups显示文摘In general,thermal processes can be classified into two categories: heat-work conversion processes and heat transfer processes. Correspondingly,the optimization of thermal processes has to have two different criteria:the well known entropy generation minimization method and the recently proposed entransy dissipation maximization method. This study analyzes the thermal issues in a heat exchanger group,and optimizes the unit arrangements under different constraints based on a suitable optimization crite-rion. The result indicates that the principle of minimum entropy generation rate is valid for optimizing heat exchangers in a ther-modynamic cycle with given boundary temperatures. In contrast,the entransy dissipation maximization is more suitable in heat exchanger optimizations involving only heat transfer processes. Furthermore,the entropy generation rate induced by dumping used streams into ambient surroundings has to be taken into account,except for that originating from the hot and cold-ends of heat exchangers,when using the entropy generation minimization to optimize heat exchangers undergoing a thermodynamic cycle. | CHEN Qun WU Jing WANG MoRan PAN Ning GUO ZengYuan | 2011 | Chinese Science Bulletin2011，56，4： | 20 |
| 15 | Radiative entransy flux in enclosures with non-isothermal or non-grey,opaque,diffuse surfaces and its application显示文摘The spectral radiative entransy flux and the total radiative entransy flux are defined for the steady radiative heat transfer processes in enclosures composed of non-isothermal or non-grey,opaque,diffuse surfaces.Based on the definitions,the radiative entransy flux balance equation and the radiative entransy dissipation functions are introduced under spectral and total wavelength condition.Furthermore,the minimum principle of radiative entransy loss,the extreme principle of radiative entransy dissipation and the minimum principle of radiative thermal resistance are developed.The minimum principle of radiative entransy loss shows that the potential and the net radiative heat flux distribution which meet the control equations and the boundary conditions would make the radiative entransy loss minimum if the net radiative heat flux or the potential distribution of the radiative heat transfer system is given.The extreme principle of radiative entransy dissipation indicates that the minimum radiative entransy dissipation leads to the minimum average potential difference for the prescribed total radiative heat exchange and the maximum radiative entransy dissipation leads to the maximum radiative heat exchange for the prescribed average potential difference.Moreover,the minimum principle of radiative thermal resistance tells us that the aforementioned extreme values of radiative entransy dissipation both correspond to the minimum value of radiative thermal resistance.Application examples are given for the extreme principle of spectral radiative entransy dissipation and the minimum principle of spectral radiative thermal resistance,and the principles are proved to be applicable. | CHENG XueTao XU XiangHua LIANG XinGang | 2011 | Science China(Technological Sciences)2011，54，9： | 20 |
| 16 | Application of entransy to optimization design of parallel thermal network of thermal control system in spacecraft显示文摘For distribution optimization of the flow rate of cold fluid and heat transfer area in the parallel thermal network of the thermal control system in spacecraft,a physical and mathematical model is set up,analyzed and discussed with the entransy theory.It is found that the optimization objective of this problem and the optimization direction of the extremum entransy dissipation principle are consistent in theory.For a two-branch thermal network system,the distributions of the flow rate of the cold fluid and the heat transfer area are optimized by calculating the extremum entransy dissipation with the Newton method.The influential factors of the optimized distributions are also analyzed and discussed.The results show that the main influence factors are the heat transfer rate of the branches and the total heat transfer area.The total flow rate of the cold fluid has a threshold,beyond which further increasing its value brings very little influence on the optimization results.Moreover,the difference between the extremum entransy dissipation principle and the minimum entropy generation principle is also discussed when they are used to analyze the problem in this paper,and the extremum entransy dissipation principle is found to be more suitable.In addition,the Newton method is mathematically efficient to solve the problem,which could accomplish the optimized distribution in a very short time for a ten-branch thermal network system. | CHENG XueTao XU XiangHua LIANG XinGang | 2011 | Science China(Technological Sciences)2011，54，4： | 19 |
| 17 | Constructal entransy optimizations for insulation layer of steel rolling reheating furnace wall with convective and radiative boundary conditions显示文摘Based on the entransy dissipation extremum principle for thermal insulation process,the constructal optimizations for a plane insulation layer of the steel rolling reheating furnace wall with convective and radiative boundary conditions are carried out by taking the minimization of entransy dissipation rate as optimization objective.The optimal construct of the plane insulation layer is obtained.The results show that for the convective heat transfer boundary condition,the optimal constructs of the insulation layer obtained based on the minimizations of the entransy dissipation rate and heat loss rate are obviously different.Comparing the optimal construct obtained based on the minimization of the entransy dissipation rate with that based on the minimization of the heat loss rate,the entransy dissipation rate is reduced by 5.98%,which makes the global thermal insulation performance of the insulation layer improve.For the combined convective and radiative heat transfer boundary condition,compared the insulation layer having an increasing thickness with that having constant thickness and a decreasing thickness,the entransy dissipation rates are reduced by 16.59%and39.72%,respectively,and the global thermal insulation performance of the insulation layer is greatly improved.There exits an optimal constant coefficient a2;optwhich leads to the minimum dimensionless entransy dissipation rate of the insulation layer.The difference between the optimal constant coefficients a2;optobtained based on the minimizations of the entransy dissipation rate and the maximum temperature gradient of the insulation layer is small.This makes the corresponding thermal stress obtained based on the minimum dimensionless entransy dissipation rate also be small,and the global thermal insulation performance and thermal safety of the insulation layer are improved simultaneously.The results obtained can provide some guidelines for the optimal designs of the insulation layers. | Huijun Feng Lingen Chen Zhihui Xie Fengrui Sun | 2014 | Chinese Science Bulletin2014，59，20： | 19 |
| 18 | Constructal entransy dissipation rate minimization for heat conduction based on a tapered element显示文摘Based on constructal theory,the structure of a tapered element and high-conductivity link is optimized by taking the minimization of the entransy dissipation rate as the optimization objective.The results show that the mean temperature difference of the heat transfer cannot always decrease when the internal complexity of the control-volume increases.There exists an optimal constructal order leading to the minimum mean temperature difference for heat transfer.The thermal current density in high-conductivity links with variable shapes does not linearly depend on the length.Therefore,the optimized constructs based on the minimization of the entransy dissipation rate are different from those based on the minimization of the maximum temperature difference.Compared with the construct based on the minimization of the maximum temperature difference,the construct based on the minimization of the entransy dissipation rate can reduce the mean temperature difference,and improve the heat transfer performance significantly.Because entransy describes the heat transfer ability more suitably,various constructal problems in heat conduction may be addressed more effectively using this basis. | XIAO QingHua CHEN LinGen SUN FengRui | 2011 | Chinese Science Bulletin2011，56，22： | 17 |
| 19 | Constructal optimization for H-shaped multi-scale heat exchanger based on entransy theory显示文摘Analogizing with the definition of thermal efficiency of a heat exchanger,the entransy dissipation efficiency of a heat exchanger is defined as the ratio of dimensionless entransy dissipation rate to dimensionless pumping power of the heat exchanger.For the constraints of the total tube volume and total tube surface area of the heat exchanger,the constructal optimization of an H-shaped multi-scale heat exchanger is carried out by taking entransy dissipation efficiency maximization as optimization objective,and the optimal construct of the H-shaped multi-scale heat exchanger with maximum entransy dissipation efficiency is obtained.The results show that for the specified total tube volume of the heat exchanger,the optimal constructs of the first order T-shaped heat exchanger based on the maximizations of the thermal efficiency and entransy dissipation efficiency are obviously different with the lower mass flow rates of the cold and hot fluids.For the H-shaped multi-scale heat exchanger,the entransy dissipation efficiency decreases with the increase in mass flow rate when the heat exchanger order is fixed;for the specified dimensionless mass flow rate M(M<32.9),the entransy dissipation efficiency decreases with the increase in the heat exchanger order.The performance of the multi-scale heat exchanger is obviously improved compared with that of the single-scale heat exchanger.Moreover,the heat exchanger subjected to the total tube surface area constraint is also discussed in the paper.The optimization results obtained in this paper can provide a great compromise between the heat transfer and flow performances of the heat exchanger,provide some guidelines for the optimal designs of heat exchangers,and also enrich the connotation of entransy theory. | FENG HuiJun CHEN LinGen XIE ZhiHui SUN FengRui | 2013 | Science China(Technological Sciences)2013，56，2： | 16 |
| 20 | Optimization of flue gas convective heat transfer with condensation in a rectangular channel显示文摘Conservation equations of sensible entarnsy and latent entransy are established for flue gas convective heat transfer with condensation in a rectangular channel and the entransy dissipation expression is deduced.The field synergy equation is obtained on the basis of the extremum entransy dissipation principle for flue gas convective heat transfer with condensation.The optimal velocity field is numerically obtained by solving the field synergy equation.The results show that the optimal velocity field has multiple longitudinal vortices,which improve the synergy not only between the veloctiy and temperature fields but also between the velocity and vapor concentration fields.Therefore,the convective heat and mass transfers are significantly enhanced.Flow with multiple longitudinal vortices close to the optimal velocity field can be generated by discrete double-inclined ribs set in the rectangular channel.The numerical results show that the total heat transfer rate in the discrete double-inclined rib channel increases by 29.02% and the condensing heat transfer rate increases by 27.46% for Re = 600 compared with the plain channel. | SONG WeiMing MENG JiAn LI ZhiXin | 2011 | Chinese Science Bulletin2011，56，3： | 14 |
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