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Conversion potential energy and its application to thermodynamic optimization

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Science China(Technological Sciences) 2012年第8期55卷 2169-2175页

作者： WU Jing guo zengyuan College of Energy&Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

In general,heat transfers can be classified into two categories according to the purposes of object heating or cooling and the heat to work ***,a new physical quantity,entransy(or potential energy),was proposed to describe the ability of heat transfer with the former *** paper addresses the concept of potential energy in terms of the heat transfer processes for the latter purpose,named the conversion potential *** physical meaning of this newly introduced concept is the potential energy for the heat to work conversion stored in the equivalent mass of heat(thermomass) derived on the basis of the Einstein's special theory of *** dissipation of conversion potential energy occurs during the real irreversible heat to work conversion processes as a measure of the conversion ***,a heat to work conversion problem of a heat exchanger group is provided to show that the minimum conversion potential energy dissipation rate can be used as an optimization criterion for the heat transfer performance with the purpose of the heat to work conversion.

关键词： conversion potential energy entransy optimization exergy thermomass

The duality of internal energy of ideal gas

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Science Bulletin 2015年第15期60卷 1355-1358页

作者： Tian Zhao zengyuan guo Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua University

This contribution starts with the discussion on the classification of energy, and then the behaviors of various thermodynamic processes are analyzed, accompanying with the comparison of the adiabatic compression process of an ideal gas and an elastic rod. All these analyses show that the internal energy of ideal gases exhibits the duality of thermal energy–mechanical energy, that is,the internal energy acts as the thermal energy during the isochoric process, while the internal energy acts as the mechanical energy during the isentropic process. Such behavior of the internal energy is quite different from other types of energy during the energy conversion process because the internal energy of ideal gases exhibits the duality of thermal energy–mechanical energy. Because of this duality, the internal energy of ideal gas is proposed to be refered to as thermodynamic energy rather than thermal energy as indicated in some literature, although it consists of kinetics of the microscopic random motion of particles and can be expressed as the function of temperature only.

关键词： Internal energy Mechanical energy Ideal gas Duality

Thermon gas as the thermal energy carrier in gas and metals

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Chinese Science Bulletin 2010年第29期55卷 3350-3355页

作者： WANG HaiDong guo zengyuan Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering Mechanics Tsinghua Univer-sity Beijing 100084 China

The thermon gas may be seen as the main thermal-energy carrier in heat *** phonons,which are defined as the energy quanta for quantized lattice vibrationss,and the phonon gas,which consists of a large number of randomly moving *** the same way,a thermon in gas and metal is defined as the equivalent mass of thermal energy of a gas molecule or an electron,respectively,and the thermon gas consists of a large number of randomly moving *** the phonon and the photon,the rest mass of a thermon is *** the mass of a moving thermon changes continuously,the thermon may be regarded as a nonquantized ***,heat flux can be seen as the directional flow of the thermon gas due to a given temperature *** thermon mass is mh=E/c2,where E is the thermal energy and c is the speed of light,and the thermon gas is actually a compressible gas flow with real *** to the principle of aerodynamics,the state equations of a thermon gas in either gas or metal are obtained by different statistical ***,Newtonian mechanics may be applied to obtain the momentum-conservation equation of a thermon gas,which is actually the general heat-conduction law,and which reduces to Fourier's law when thermal inertia is *** general heat-conduction law is a damped wave equation that can be used to quantitatively investigate thermal wave phenomena caused by heating of thin metal films by ultrafast laser *** numerical solution of the general heat-conduction law is obtained using a finite-difference method with double precision,and the results show that the thermal wave increases as the spatial inertia of the thermon gas increases.

关键词：金属材料能源载体天然气热传导规律气体分子空气动力学原理傅里叶定律等效质量

Monte Carlo simulation of thermodynamic properties for two-dimensional Lennard-Jones fluids

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Chinese Science Bulletin 2000年第21期45卷 2004-2009页

作者： Xiaoli Feng Zhixin Li zengyuan guo Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

Canonical ensemble Monte Carlo simulations have been carried out to investigate thethermodynamic properties of two-dimensional fluids subjected to truncated Lennard-Jones 12-6 potential. The simulations of thermodynamic states sweep across liquid-vapor regime over a wide range of thermodynamic conditions. Simulated isotherms behave van der Waals loop-like characteristics in the liquid-vapor phase-transition region. It suggests a continuous isothermal phase transition in the case of micro system, in which the system size prohibits phase separation. Two-dimensional dimensionless van der Waals equation of states has been obtained from theoretical analysis. By fitting simulated data to this equation, temperature-dependent parameters in the equation have been determined.

关键词： Monte Carlo simulation thermodynamic properties isotherm liquid-vapor transition.

Entransy decrease principle of heat transfer in an isolated system

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Chinese Science Bulletin 2011年第9期56卷 847-854页

作者： CHENG XueTao LIANG XinGang guo zengyuan Key Laboratory for Thermal Science and Power Engineering of Ministry of Education School of Aerospace Tsinghua University Beijing 100084China

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.

关键词：孤立系统传热原理热力学第二定律熵增加原理封闭系统平衡系统平衡条件时间箭头

Physical quantity synergy in laminar flow field of convective heat transfer and analysis of heat transfer enhancement

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Chinese Science Bulletin 2009年第19期54卷 3579-3586页

作者： LIU Wei LIU ZhiChun guo zengyuan School of Energy and Power Engineering Huazhong University of Science and Technology Wuhan 430074 China School of Aerospace Tsinghua University Beijing 100084 China

Based on the principle of field synergy for heat transfer enhancement, the concept of physical quantity synergy in the laminar flow field is proposed in the present study according to the physical mechanism of convective heat transfer between fluid and tube wall. The synergy regulation among physical quantities of fluid particle is revealed by establishing formulas reflecting the relation between synergy angles and heat transfer enhancement. The physical nature of enhancing heat transfer and reducing flow resistance, which is directly associated with synergy angles α, β, γ, φ, θ and ψ, is also explained. Besides, the principle of synergy among physical quantities is numerically verified by the calculation of heat transfer and flow in a thin cylinder-interpolated tube, which may guide the optimum design for better heat transfer unit and high-efficiency heat exchanger.

关键词：对流换热过程广义热阻耗散进展

Thermal management of space stations

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Chinese Science Bulletin 2001年第23期46卷 2019-2024页

作者： zengyuan guo Xingang Liang Xinrong Zhang Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

Thermal management aims at making full use of energy resources available in the space station to reduce energy consumption, waste heat rejection and the weight of the station. It is an extension of the thermal control. This discussion introduces the concept and development of thermal management, presents the aspects of thermal management and further extends its application to subsystems of the space station.

关键词： space station thermal management thermal control environmental control and life support system.

Molecular dynamics simulations on specific heat capacity and glass transition temperature of liquid silver

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Chinese Science Bulletin 2001年第12期46卷 1051-1053页

作者： Chun Yang Min Chen zengyuan guo Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The embedded-atom method is adopted to simulate the specific heat capacity of liquid silver. The relationship between the specific heat capacity and the temperature above and below melting point is derived. The results show that there exists an anormaly of the specific heat capacity of liquid silver near 950 K. Simulated pair distribution functions show that the liquid-to-glass transition takes place at this temperature.

关键词： molecular dynamics simulation glass transition specific heat capacity silver.

Entropy generation extremum and entransy dissipation extremum for heat exchanger optimization

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Chinese Science Bulletin 2009年第6期54卷 943-947页

作者： LIU XiongBin MENG JiAn guo zengyuan Key Laboratory of Thermal Science and Power Engineering of Ministry of Education School of Aerospace Tsinghua University Beijing 100084 China

The applicability of the extremum principles of entropy generation and entransy dissipation is studied for heat exchanger optimization. The extremum principle of entransy dissipation gives better optimiza-tion results when heat exchanger is only for the purpose of heating and cooling, while the extremum principle of entropy generation is better for the heat exchanger optimization when it works in the Brayton cycle. The two optimization principles are approximately equivalent when the temperature drops of the streams in a heat exchanger are small.

关键词：优化原则换热器熵产生极值耗散布雷顿循环产生原理适用性