内可逆空气制冷机性能的生态学优化

基于[火用]分析的观点，运用有限时间热力学方法对内可逆空气制冷机进行生态学优化，导出了换热器热导最优分配时的最佳制冷功率、熵产率以及生态学（E）目标函数的解析式，进一步求得最大E目标值时的工质等熵温比（压比）界限及相应的制冷系数、制冷功率和熵产率；采用数值计算分析了热源温比、换热器总热导以及高温热源温度和环境温度之比对该制冷机生态学最优性能的影响。结果表明：生态学目标函数不仅反映了[火用]输出率和熵产率之间的最佳折衷，而且也反映了制冷功率和制冷系数之间的最佳折衷。     

内可逆四热源吸收式制冷循环的热经济性能优化

应用内可逆四热源吸收式制冷循环模型，分析吸收式制冷机受传热不可逆性影响时的热经济性能。在牛顿传热定律下，导出了循环的最佳热经济性目标和制冷系数的基本优化关系和最大热经济性目标及相应的制冷系数与比制冷率；通过数值算例，得出循环参数对循环的热经济性目标、制冷系数和比制冷率的影响关系。     

不可逆半导体固态热离子制冷器性能分析和优化

建立了考虑外部有限速率传热过程和热源间热漏的不可逆半导体固态热离子制冷器模型,基于非平衡热力学和有限时间热力学理论导出了热离子制冷器的制冷率和制冷系数的表达式;对比分析了不可逆热离子制冷器与可逆热离子制冷器的发射电流密度特性、电极温度特性以及制冷系数特性;研究了不可逆系统的制冷率与制冷系数最优性能,得到了制冷率和制冷系数的最优运行区间;通过数值计算,详细讨论了外部传热以及内部导热、热源间热漏损失、热源温度、外加电压、半导体材料势垒等设计参数对热离子装置性能的影响。在总传热面积一定的条件下,进一步优化了高、低温侧换热器的面积分配以获得最佳的制冷率和制冷系数特性。结果表明,由于存在内部和外部的不可逆性,热离子装置的发射电流密度及制冷系数都会明显降低;不可逆半导体固态热离子制冷器的制冷率与制冷系数特性呈扭叶型;合理地选外加电压、势垒等参数,可以使制冷器设计于最大制冷率或最大制冷系数的状态。     

热漏对内可逆四热源制冷系统的影响

在恒温热源内可逆四热源吸收式制冷循环的基础上，建立不可逆吸收式制冷循环的模型，考虑环境热源到制冷空间的热漏以及工质与外部热源间的热阻损失，导出牛顿定律下循环的制冷率和制冷系数的基本优化关系、最大制冷系数及相应的制冷率和最大制冷率及相应的制冷系数；并通过数值计算分析了循环参数对循环的制冷率、制冷系数的影响。     

Performance analysis of an irreversible cogeneration heat pump cycle

An irreversible heat engine-driven vapour compression and absorption heat pump system is considered as a cogeneration cycle. The effects of thermal resistances and internal irreversibilities on the coefficient of performance (COP) of this cogeneration cycle were investigated using finite-time thermodynamic approach. An improved equation for the COP of the system under consideration was obtained. The results obtained here may serve as a good guide for the evaluation of existing real cogeneration heat pumps or provide some theoretical bases for the optimal design of future cogeneration heat pumps. © 1998 John Wiley & Sons, Ltd.     

回热式变温热源空气制冷循环容积制冷率优化

考虑热阻损失、压缩机与膨胀机的内损失及管路系统的压力损失，研究一个比较接近实际装置的回热式交温热源空气制冷循环，得出了循环容积制冷率制冷系数的解析关系式。由数值计算分析了压比、热导率分配以及工质与热源间的热容率匹配等参数对容积制冷率的影响。     

线性唯象传热规律下广义不可逆卡诺热机生态学性能系数优化

以反映热机循环输出功率和火用损失率之比的生态学性能系数(ECOP)为目标,用有限时间热力学理论和方法研究广义不可逆卡诺热机的循环性能。导出了线性唯象传热规律(Q∝Δ(T-1))下ECOP的解析式,通过数值计算分析了各种目标极值条件下ECOP与循环功率、效率、熵产率、生态学函数E之间的关系,主要研究了热源温比对最优性能的影响。     

Refrigeration cycle for cryogenic separation of hydrogen from coke oven gas

Ten billion cubic meters of hydrogen are dissipated to the environment along with the emission of coke-oven gas every year in China. A novel cryogenic separation of hydrogen from coke oven gas is proposed to separate the hydrogen and liquefy it simultaneously, and the cooling capacity is supplied by two refrigeration cycles. The performance of the ideal vapor refrigeration cycle is analyzed with methane and nitrogen as refrigerant respectively. The results show that the coefficient of performance (COP) of methane refrigeration cycle is 2.7 times that of nitrogen refrigeration cycle, and the figure of merit (FOM) of methane refrigeration cycle is 1.6 times that of nitrogen refrigeration cycle. The performance of ideal gas refrigeration cycle is also analyzed with neon, hydrogen and helium as refrigerant respectively. The results show that both the coefficient of performance and figure of merit of neon refrigeration cycle is the highest. It is thermodynamically possible to arrange the refrigeration cycle with methane and neon as refrigerant, respectively. __________ Translated from Cryogenics and Superconductivity, 2007, 35(5): 387–390, 394 [译自: 低温与超导]     

A dimensionless numerical analysis for the optimization of an active magnetic regenerative refrigerant cycle

Refrigeration by an active magnetic regenerative system (AMR) is potentially more attractive, as compared to conventional techniques. Indeed, devices based upon an AMR cycle are more efficient, compact, environment‐friendly and can operate over a broad range of temperatures. In this paper, attention is focused to the near room‐temperature range. On the other hand, however, the AMR cycle poses a variety of complex problems, in terms of fluid dynamics, heat transfer and magnetic field. In order to identify the optimal operational parameters, the design and optimization of a magnetic refrigeration system can be supported by modelling. In this paper, a dimensionless approach was adopted to simulate an AMR cycle following a Brayton regenerative cycle. In the simulation, the temperature range that has been explored is 260 – 280 K and 275 – 295 K. The heat transfer mediums are, respectively, water–glycol mixture (50% by weight) and pure water. The Gd_0.8Dy_0.2 alloy and pure Gd have been chosen as constituent material for the regenerator of the AMR cycle. With this model, the influence of the different parameters on cycle efficiency has been analysed. In particular, the study has been focused on the influence of the secondary fluid properties, magnetic material particle diameter, fluid blow time, secondary fluid mass flow rate, regenerator geometry and effect of axial thermal conduction. The model enables to find optimal dimensionless numbers in order to maximize the cycle performances. The results can be extended to widely different situations and therefore can be easily employed for the design and the optimization of new experimental prototypes. Copyright © 2012 John Wiley & Sons, Ltd.     

Exergetic sustainability evaluation and optimization of an irreversible Brayton cycle performance

Owing to the energy demands and global warming issue, employing more effective power cycles has become a responsibility. This paper presents a thermodynamical study of an irreversible Brayton cycle with the aim of optimizing the performance of the Brayton cycle. Moreover, four different schemes in the process of multi-objective optimization were suggested, and the outcomes of each scheme are assessed separately. The power output, the concepts of entropy generation, the energy, the exergy output, and the exergy efficiencies for the irreversible Brayton cycle are considered in the analysis. In the first scheme, in order to maximize the exergy output, the ecological function and the ecological coefficient of performance, a multi-objective optimization algorithm (MOEA) is used. In the second scheme, three objective functions including the exergetic performance criteria, the ecological coefficient of performance, and the ecological function are maximized at the same time by employing MOEA. In the third scenario, in order to maximize the exergy output, the exergetic performance criteria and the ecological coefficient of performance, a MOEA is performed. In the last scheme, three objective functions containing the exergetic performance criteria, the ecological coefficient of performance, and the exergy-based ecological function are maximized at the same time by employing multi-objective optimization algorithms. All the strategies are implemented via multi-objective evolutionary algorithms based on the NSGAII method. Finally, to govern the final outcome in each scheme, three well-known decision makers were employed.     

Recent research on an indirect evaporative cooler (IEC) Part 1: optimization of the COP

The paper presents an analysis for optimizing the coefficient of performance of an tube type indirect evaporative cooler (IEC) in terms of process stream air velocity and wet stream air velocity. Theoretical predictions of the optimum COP value have been compared with the experimental results obtained for an IEC at Indore in the summer months of May and June; the agreement is satisfactory. © 1997 John Wiley & Sons, Ltd.     

Study of performance characteristics of a small Stirling refrigerator

A prototype Stirling cycle refrigerator employing helium as a working fluid was investigated to determine whether a freon‐free machine was a viable alternative for the current household refrigerator. A displacer‐type or β‐type Stirling cycle machine of 100‐W capacity was designed and tested using varying design parameters such as dead volume ratio, working fluids, the ratio of the compression volume to the expansion volume, and the phase difference between a power piston and displacer. The detrimental effect of the dead space on the refrigeration capacity was confirmed. The refrigeration produced by nitrogen in an expansion space was 28% less than that produced by helium. The optimum volume ratio and the phase difference for maximum refrigeration was determined under the design operation conditions. Moreover, the refrigeration correlation formula as a function of these parameters was obtained. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(5): 344–361, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10033     

普适内可逆热机循环模型及其生态学优化

用有限时间热力学的方法分析了空气标准内可逆热机循环,导出了存在传热损失时,由两个加热过程、一个放热过程和两个绝热过程组成的普适的空气标准内可逆热机循环的功率、效率和生态学性能,并由数值计算分析了循环过程对循环性能的影响特点。所得结果包含了内可逆D iese l循环、O tto循环、B rayton循环、A tk inson循环和Dua l循环的特性。     

Ecological performance analysis of an endoreversible modified Brayton cycle

An endoreversible closed modified simple Brayton cycle model with isothermal heat addition coupled to variable-temperature heat reservoirs is established using finite-time thermodynamics. Analytical expressions of dimensionless power output, thermal efficiency, dimensionless entropy generation rate and dimensionless ecological function are derived. Influences of cycle thermodynamic parameters on ecological performance and optimal compressor pressure ratio, optimal power output, optimal cycle thermal efficiency and optimal entropy generation rate corresponding to maximum ecological function are obtained and compared with those corresponding to maximum power output. The results show that cycle thermal efficiency improvement and entropy generation rate reduction are obtained at the expense of higher compressor pressure ratio and a little sacrifice of power output at maximum ecological function. The compromises between power output and entropy generation rate and between power output and cycle thermal efficiency, respectively, are achieved.     

Ecological coefficient of performance analysis and optimization of an irreversible regenerative-Brayton heat engine

In this paper, a performance optimization based on the ecological coefficient of performance (ECOP) criterion has been carried out for an irreversible regenerative Brayton heat-engine. The results obtained were compared with those using the power-output criterion and alternative ecological performance objective-function defined in the literature. The design parameters, under the optimal conditions, have been derived analytically and their effects on the engine’s performance have been discussed. It is shown that, for the regenerative Brayton-engine, a design based on the maximum ECOP conditions is more advantageous from the point-of-view of entropy generation rate, thermal efficiency and investment cost.     

Cooling load density characteristics of an endoreversible variable‐temperature heat reservoir air refrigerator

The performance optimization of an endoreversible air refrigerator with variable‐temperature heat reservoirs is carried out by taking the cooling load density, i.e. the ratio of cooling load density to the maximum specific volume in the cycle, as the optimization objective in this paper. The analytical relations of cooling load, cooling load density and coefficient of performance are derived with the heat resistance losses in the hot‐ and cold‐side heat exchangers. The maximum cooling load density optimization is performed by searching the optimum pressure ratio of the compressor, the optimum distribution of heat conductance of the hot‐ and cold‐side heat exchangers for the fixed total heat exchanger inventory, and the heat capacity rate matching between the working fluid and the heat reservoirs. The influences of some design parameters, including the heat capacitance rate of the working fluid, the inlet temperature ratio of heat reservoirs and the total heat exchanger inventory on the maximum cooling load density, the optimum heat conductance distribution, the optimum pressure ratio and the heat capacity rate matching between the working fluid and the heat reservoirs are provided by numerical examples. The refrigeration plant design with optimization leads to a smaller size including the compressor, expander and the hot‐ and cold‐side heat exchangers. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance analysis and parametric optimal design of an irreversible multi-couple thermoelectric refrigerator under various operating conditions

The performance of a thermoelectric refrigeration device, consisting of multi-couple thermoelectric elements and operating between two heat-reservoirs at constant temperatures, is investigated. The influence of the external and internal irreversibilities of the thermoelectric refrigeration device on the performance of the system is analyzed. The general expressions of the coefficient of performance and power input are derived by introducing some dimensionless parameters and variables. The coefficient of performance of the refrigeration device is maximized for a given cooling-load and total heat-transfer area of the system, and consequently, the structure parameters of the device and the area ratio of the heat exchangers of the system are determined optimally. The effects of the various parameters on the optimal performance of the device are discussed further. The results obtained here will be useful for a more detailed investigation and for the optimal design and manufacture of real thermoelectric refrigeration devices.     

线性唯象传热定律下不可逆四热源制冷循环最优性能

在恒温热源内可逆四热源吸收式制冷循环的基础上，考虑环境热源到制冷空间的热漏、工质的内部耗散以及工质与外部热源问的热阻损失，建立传热服从线性唯象定律的不可逆吸收式制冷循环的模型，导出循环的制冷率和制冷系数的基本优化关系、最大制冷系数及相应的制冷率和最大制冷率及相应的制冷系数，给出了最佳换热面积，并通过数值计算分析了设计参数对循环的制冷率、制冷系数的影响。所得结果对实际吸收式制冷机的设计和运行有一定的指导意义。     

Performance optimization of transcritical CO2 refrigeration cycle with thermoelectric subcooler

Use of thermoelectric subcooler is one of the techniques to improve the performance of transcritical CO₂ cycle. Thermodynamic analyses and optimizations of transcritical CO₂ refrigeration cycle with thermoelectric subcooler are presented in this paper. Further, the effects of various operating parameters on cycle performances are studied. It is possible to optimize current supply, discharge pressure, and CO₂ subcooling simultaneously based on maximum cooling COP for thermoelectrically enhanced transcritical CO₂ refrigeration cycle to get best performance. Results show that thermoelectric current supply, COP improvement, and discharge pressure reduction increase with increase in cycle temperature lift, with maximum values of 11 A, 25.6%, and 15.4%, respectively, for studied ranges. Use of thermoelectric subcooler in CO₂ refrigeration system not only improves the cooling COP, also reduces the system high‐side pressure, compressor pressure ratio, and compressor discharge temperature, and enhances the volumetric cooling capacity. Component‐wise irreversibility distribution shows similar trend with basic CO₂ cycle, although values are lower leading to higher second law efficiency. Cooling capacity may be enhanced by increasing the current supply for the same thermoelectric configuration with penalty of COP. Study reveals that thermoelectrically enhanced CO₂ refrigeration cycle yields significant performance improvement especially for higher‐cycle temperature lift. Copyright © 2011 John Wiley & Sons, Ltd.     

内可逆四热源吸收式热变换器生态学最优性能

基于能量分析的观点，建立了反映四热源吸收式热变换器泵热率与熵产率之间最佳折衷的生态学准则。导出了线性(牛顿)传热定律下生态学目标与泵热系数的优化关系、最大生态学目标值及其相对应的泵热系数、泵热率和熵产率以及最大泵热率时的生态学目标和熵产率。通过数值算例分析得到了吸收式热变换器的生态学优化准则。计算发现，与最大泵热率目标相比，最大生态学目标牺牲了27．3％的泵热率。使循环熵产率降低了77．0％。泵热系数增加了55．4％，表明生态学准则对吸收式热变换器优化设计是一种具有长期效应的可选优化目标。