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The influence of viscous heating on the entransy in two-fluid heat exchangers

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Science China(Technological Sciences) 2011年第5期54卷 1267-1274页

作者： GUO JiangFeng xu mingtian CHENG Lin Institute of Thermal Science and Technology Shandong University Jinan 250061 China Insititute of Engineering Thermophysics Chinese Academy of Science Beijing 100190 China

In the present work, water and olive oil are taken as working fluids to study the influence of viscous heating on the entransy dissipation caused by heat transfer in two-fluid heat exchangers. The results show that the influence of viscous heating on the entransy loss associated with heat transfer can not be neglected for the liquids having large dynamic viscosity. The viscous heating effect maintains the heat transfer ability of the working fluids, relatively reduces the entransy loss in heat exchangers; the viscous heating effect relatively augments the entropy generation due to heat transfer and the available energy destruction in heat exchangers. For the working fluid having large dynamic viscosity, the increasing rates of the entransy and entropy generation contributed by the viscous heating are even larger than those contributed by heat transfer, when the mass flow rate of working fluid reaches a certain value under the fixed heat transfer area condition. Thus, the entransy loss rate decreases and the growth rate of entropy generation increases as the mass flow rate of the working fluid increases. Under the same other conditions, the heat transfer entransy loss rate and entropy generation rate per unit heat transfer rate obtained when the fluid having a smaller heat capacity rate is cold fluid are less than those obtained when the fluid having a smaller heat capacity rate is hot fluid.

关键词： entransy entransy dissipation viscous heating heat exchanger entropy generation

The entransy dissipation minimization principle under given heat duty and heat transfer area conditions

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Chinese Science Bulletin 2011年第19期56卷 2071-2076页

作者： GUO JiangFeng xu mingtian CHENG Lin Institute of Thermal Science and Technology Shandong University Jinan 250061 China

Under given heat duty and heat transfer area conditions, the equipartition of the entransy dissipation (EoED) principle, the equipartition of the temperature difference (EoTD) principle, and the equipartition of the heat flux (EoHF) principle are applied to the optimization design of a heat exchanger with a variable heat transfer coefficient. The results show that the difference between the results obtained using the EoED and EoTD principles is very small, far smaller than that between the results obtained using the EoED and EoHF principles. The correct entransy dissipation minimization principle is chosen to optimize the parameters in the hot and cold fluids in a two-fluid heat exchanger, under given heat duty and heat transfer area conditions. The results indicate that the proper choice of the two alternative fluids has an important role in the successful application of the entransy dissipation minimization principle. The fluid that could improve the total heat transfer coefficient should be chosen, or the fluid that makes the temperature profiles of the hot and cold fluids parallel and decreases the temperature difference between the hot and cold fluids after optimization simultaneously, could be the proper one.

关键词：换热面积最小化热负荷耗散总传热系数优化设计热流体温度分布

Thermal vibration phenomenon of single phase lagging heat conduction and its thermodynamic basis

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Chinese Science Bulletin 2008年第22期53卷 3597-3602页

作者： CHENG Lin xu mingtian WANG LiQiu Institute of Thermal Science and Technology Shandong University Ji'nan 250061 China Department of Mechanical Engineering the University of Hong Kong Hong Kong China

In the present work it is shown that the single phase lagging heat conduction not only avoids the infinite heat propagation speed assumed by the conventional Fourier law, but also complies with Galilean principle of relativity. Therefore it is more advantageous than the Cattaneo-Vernotte model. Based on the single-phase-lagging heat conduction model, the condition for the occurrence of thermal vibration of heat conduction is established. In order to resolve the contradiction that the thermal vibration violates the second law of thermodynamics, the extended irreversible thermodynamics is improved and a generalized entropy definition is introduced. In the framework of the newly-developed extended irreversible thermodynamics the thermal vibration phenomena are consistent with the second law of thermodynamics.

关键词：傅里叶定律热传输热力学物理研究

Theoretical analysis of a method for segmented heat exchanger design

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Chinese Science Bulletin 2011年第20期56卷 2179-2184页

作者： SONG JiWei xu mingtian CHENG Lin Institute of Thermal Science and Technology Shandong UniversityJinan 250061China

In the process of the design of heat exchangers,it is difficult to establish the factors governing the optimal points of the design objective functions due to the contradictions and uncertainties of the design *** variation of fluid properties is one of the main factors causing this type of *** design methods have not completely solved these *** the present work,based on the logarithmic mean temperature difference,a new heat exchanger design method(called the segmented design method) is proposed which takes into account the variation of fluid properties with respect to the *** this method,the whole heat exchanger is first divided into several *** by applying the principle of the conservation of energy and taking into account the initial conditions as well as the connecting conditions of the adjacent segments,the inlet and outlet temperatures of each segment are ***,the application of the logarithmic mean temperature difference method on each segment defines the heat transfer area.

关键词：设计方法换热器分段式对数平均温差不确定性流体性质出口温度应用程序

Influence of size effect and boundary conditions on temperature overshooting in nanoscale thermal conduction

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Chinese Science Bulletin 2014年第12期59卷 1334-1339页

作者： xuefang Li mingtian xu David M.Christopher Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Tsinghua University Institute of Thermal Science and Technology Shandong University

The temperature overshooting phenomenon in one-dimensional nanoscale heat conduction in thin films is studied for various boundary *** results show that when ballistic heat transport strongly affects the heat transport process,temperature overshooting is more likely to occur.A sudden increase of temperature on only one surface of a thin film cannot trigger temperature overshooting,while symmetric boundary temperature perturbations lead to the largest temperature *** heat conduction is also studied in a nanoscale *** analytic results show that Fourier’s law may severely underestimate the temperatures in nanofilms as well as in nanoareas when temperature overshooting occurs.

关键词：边界温度过冲现象边界条件纳米级热传导尺寸效应纳米薄膜热传递过程

Entransy dissipation minimization for optimization of heat exchanger design

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Chinese Science Bulletin 2011年第20期56卷 2174-2178页

作者： LI xueFang GUO JiangFeng xu mingtian CHENG Lin Institute of Thermal Science and Technology Shandong UniversityJinan 250061China

In this paper,by taking the water-water balanced counterflow heat exchanger as an example,the entransy dissipation theory is applied to optimizing the design of heat *** certain conditions,the optimal duct aspect ratio is determined *** the heat transfer area or the duct volume is fixed,analytical expressions of the optimal mass velocity and the minimal entransy dissipation rate are *** results show that to reduce the irreversible dissipation in heat exchangers,the heat exchange area should be enlarged as much as possible,while the mass velocity should be reduced as low as possible.

关键词：耗散理论换热器设计优化最小化低质量流速传热面积热交换器

Principle of equipartition of entransy dissipation for heat exchanger design

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Science China(Technological Sciences) 2010年第5期53卷 1309-1314页

作者： GUO JiangFeng,xu mingtian & CHENG Lin Institute of Thermal Science and Technology,Shandong University,Jinan 250061,China 1. Institute of Thermal Science and Technology Shandong University Jinan 250061 China

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 *** 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 *** the heat transfer coefficient is fixed,the EoED principle is equivalent to the EoTD *** 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 *** 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 *** 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 *** the contrary,the entransy dissipation number is not directly related to the inlet and outlet temperatures of working ***,the entransy dissipation number is more suitable for serving as a criterion to evaluate heat exchanger performance.

关键词： heat exchanger entropy production entropy generation number entransy dissipation entransy dissipation number

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求解对流扩散问题的积分方程法

化工学报 2015年第10期66卷 3888-3894页

作者：魏涛许明田汪引山东大学土建与水利学院工程力学系山东济南250061

提出了一种求解对流扩散问题的积分方程法。在这一方法中,首先利用Laplace方程的级数形式的格林函数将对流扩散方程转化为积分方程,然后利用级数的正交性质,把积分方程进一步简化为代数方程组,求解该方程组即可得到对流扩散方程的级数... 详细信息

提出了一种求解对流扩散问题的积分方程法。在这一方法中,首先利用Laplace方程的级数形式的格林函数将对流扩散方程转化为积分方程,然后利用级数的正交性质,把积分方程进一步简化为代数方程组,求解该方程组即可得到对流扩散方程的级数形式的近似解。最后,分别利用Chebyshev多项式和Fourier级数求解了3个典型的一维和二维对流扩散问题。该方法和有限体积法、有限元法和迎风差分法相比,展现出非常高的精度并且避免了由解的不连续性造成的虚假振荡。

关键词：计算流体力学积分方程法对流扩散方程有限体积法传热

任意位置含振子圆板非轴对称振动的积分方程方法研究

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机械强度 2009年第3期31卷 481-486页

作者：王卫东程泉许明田山东大学土建与水利学院济南250061 山东大学能源与动力工程学院济南250061

运用特殊函数论和富里叶级数理论,采用由贝塞尔函数组成的平方可积空间上的一类完备正交函数系构造圆板的格林函数;应用积分方程和广义函数论,给出在圆板的任意位置带有弹性振子的耦合系统动态特性的积分方程方法。计算实践表明该方法... 详细信息

运用特殊函数论和富里叶级数理论,采用由贝塞尔函数组成的平方可积空间上的一类完备正交函数系构造圆板的格林函数;应用积分方程和广义函数论,给出在圆板的任意位置带有弹性振子的耦合系统动态特性的积分方程方法。计算实践表明该方法不仅算法简捷、收敛速度快、计算精度高,而且能从整体上对系统的动态特性加以研究,从而为这类结构的优化设计和安全性评估提供有效的途径。

关键词：振动固有频率积分方程正交函数系格林函数圆形板