内可逆四热源吸收式热变换器的基本优化关系及其性能分析

应用内可逆四热源吸收式热变化器循环模型，分析热变换器受传热不可逆性影响时的基本性能。导出了牛顿传热定律下循环的比泵热率和泵热系数的基本优化关系以及工质的最佳工作温度和传热面积的最佳分配关系。由此讨论了循环的各种优化性能，并通过数值算例，得出循环参数对循环特性的影响规律。所得结果对实际四热源吸收式热变换器的优化设计具有一定指导意义。     

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。     

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。     

内可逆四热源吸收式热泵生态学最优性能

基于能量分析的观点,建立了反映四热源吸收式热泵泵热率与熵产率之间最佳折衷的生态学准则,分析了线性(牛顿)传热定律下内可逆四热源吸收式热泵的生态学最优性能,导出了生态学目标与泵热系数的优化关系和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,确定了循环主要参数的生态学优化选择范围。数值算例分析了泵热率目标和生态学目标的相互关系,计算表明生态学准则对吸收式热泵优化设计是一种具有长期效应的可选优化目标。     

四温位吸收式热泵的热经济性能优化

基于一类不可逆四温住吸收式热泵模型,以单位成本的泵热率作为热经济学目标函数,导出了热经济学目标函数与泵热系数的优化关系.利用数值方法讨论内不可逆性、经济参数、外部热源温度对热泵热经济性能的影响.结论可为实际吸收式热泵的优化设计提供理论依据.     

回收工业废热的吸收式热变换器技术

介绍了提升工业废热温位的吸收式热变换器的工作原理 ,工质的热力循环过程。应用热力学第二定律和工质的热力学性能数据 ,分别对工质的理论循环过程与实际循环过程的性能系数进行了理论分析和计算 ,研究了操作参数对性能系数和温升的影响规律     

内可逆四热源吸收式制冷机生态学最优性能

基于能量分析的观点,建立了反映四热源吸收式制冷机制冷率与熵产率之间最佳折中的生态学准则,分析了线性(牛顿)传热定律下内可逆四热源吸收式制冷机的生态学最优性能.导出了生态学目标与制冷系数的优化关系和最大生态学目标值及其相对应的制冷系数、制冷率和熵产率,确定了循环主要参数的生态学优化选择范围.数值算例分析了制冷率目标和生态学目标的相互关系,计算表明生态学准则对吸收式制冷机优化设计是一种具有长期效应的可选优化目标.     

结合制冷的新型吸收式热变换器热力分析

提出了一种能同时制冷的溴化锂喷射-吸收式热变换器系统。根据热质平衡理论和喷射器理论,对该新型系统进行了热力学模拟,分析了各参数对系统性能的影响。并将该系统用于回收55℃的废热,解决同时需要制热、制冷场所的冷、热源问题。结果表明:废热先流经蒸发器的串联流程的性能优于其它流程;低压蒸发器内冷冻水出口温度越高、冷凝器中冷却水出口温度越低,系统性能越好;而吸收器中用户供水温度越高,系统制热火用效率ηr越大,系统能效比COP却越低。     

H_2O/LiBr双吸收式热变换器系统多目标参数优化

以双吸收式热变换器作为研究对象,综合考虑系统总传热面积Atot、热效率COP、总损失I和热源输入Exin,通过线性加权法建立了以Atot/COP和I/Exin为目标函数的多目标评价模型。利用多目标模型对系统进行参数优化的结果表明,多目标评价模型能同时考虑多个优化目标,相比单一目标更为合理;在给定的工况范围内,存在最优的发生温度、蒸发温度、吸收温度、吸收/蒸发温度以及第一溶液热交换器效能,使多目标函数最小;尽可能降低冷凝温度和提高第一溶液热交换器效能有利于提高系统的整体性能。     

回收合成橡胶凝聚余热的吸收式热变换器

针对工业化吸收式热变换器装置，分析了各单元组件的传热特性系统的性能系数和技术经济指标。在设计给定的操作状态下运行时，装置的性能系数(COP)平均值为0．47，投资回收期大约2a。利用工业吸收式热变换器装置回收胶厂凝聚废热，不但节省了能源，而且还可减少燃烧废气的排放及对周围的热污染，值得进一步开发和推广。     

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 improvement of absorption heat transformer

In this study, a mathematical model of absorption heat transformer (AHT) operating with the aqua/ammonia was developed to simulate the performance of these systems coupled to a solar pond in order to increase the temperature of the useful heat produced by solar ponds and used a special ejector located at the absorber inlet. By the use of the ejector, the obtained absorber pressure becomes higher than the evaporator pressure and thus the system works with triple-pressure-level. The ejector has two functions: (i) aids pressure recovery from the evaporator and (ii) upgrades the mixing process and the pre-absorption by the weak solution of the ammonia coming from the evaporator. The other advantage of the system with ejector is increased absorber temperature. Therefore, pressure recovery and pre-absorption in the ejector improves the efficiency of the AHT. Under the same circumstances, when compared to an AHT with and without an ejector, the system's COP and exergetic coefficient of performance (ECOP) were improved by 14% and 30%, respectively and the circulation ratio (f) was reduced by 57% at the maximum efficiency condition. Due to the reduced circulation ratio, the system dimensions can be reduced; consequently, this decreases overall cost. The maximum upgrading of the solar pond's temperature by the AHT was obtained at 57.5 °C and gross temperature lift at 97.5 °C with coefficients of performance of about 0.5. The maximum temperature of the useful heat produced by the AHT was 150 °C. In addition, exergy losses for each component in the system were calculated at different working temperatures and the results of both systems with and without an ejector were compared. Exergy analysis emphasised that both the losses and irreversibilities have an impact on the system performance and exergy analysis can be used to identify the less efficient components of the system. Exergy analyses also showed that the exergy loss of the absorber of AHT with ejector was higher than those of other components.     

Solar absorption heat transformer applications to absorption refrigerating machines

This paper concerns the study of a two-stage vapour absorption system (heat transformer and refrigerating machine) employing the refrigerant absorbent combinations of LiBr-H₂O and NH₃-H₂O successively. The system consists of coupling the previous absorption cycles so that the first-stage absorber produces heating water to circulate in the generator of the second stage. The performances of a solar installation (two stage system plus solar collector) had been tested in Rabat (Morocco). It is found that the system can be operated at lower hot source temperatures and, thus, it can be supplied either from flat plate collectors or from thermal effluents.     

Optimization of a finned heat sink array based on thermoeconomic analysis

The design and specification of heat sinks for electronic systems is not easily accomplished through the use of standard thermal design and analysis tools since geometric and boundary conditions are not typically known in advance. A second-law based thermoeconomic optimization procedure is presented for a finned heat sink array. This involves including costs associated with material, and irreversible losses due to heat transfer and pressure drop. The influence of important physical, geometrical and unit cost parameters on the overall finned array are optimized for some typical operating conditions that are representative of electronic cooling applications. The optimized cost results are presented in terms of Re_D, Re_L, λ_P / λ_H, and q for a finned system in a graphical form. In addition the methodology of obtaining optimum parameters for a finned heat sink system which will result in minimum operating cost is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.     

Performance analysis on a new multi-effect distillation combined with an open absorption heat transformer driven by waste heat

In this paper, a new water distillation system, which consists of either a single- or multi-effect distiller combined with an open absorption heat transformer (OAHT), has been proposed.The new integrated system can be used for distilling waste water with high amounts of SiO₂ from heavy oil production, and the resultant distilled water can be supplied to steam boilers to produce high quality steam which in turn is injected into oil reservoirs to assist with heavy oil recovery. The thermodynamic cycle performances for these new integrated distillation systems were simulated based on the thermodynamic properties of the aqueous solution of LiBr as well as the mass and energy balance of the system. The results indicate that combined with OAHT, the waste heat at 70 °C can be elevated to 125 °C and thereby produce steam at 120 °C in the absorber, which is able to drive a four-effect distiller to produce distilled water. For a single-effect and four-effect distiller, the coefficients of performance (COP) are approximately 1.02 while the performance ratios are 2.19 and 5.72, respectively. Therefore, the four-effect distillation system combined with an OAHT is more thermally effective and is an ideal option to process the waste water in oilfields.     

第二类吸收式热泵的研究及应用

介绍了第二类吸收式热泵的工作原理,阐述了第二类吸收式热泵在工质对、吸收器、表面添加剂和缓蚀剂四个方向的研究现状,例举了第二类吸收式热泵在冶金、酒精以及橡胶工业中的应用.指出以节能为目的的第二类吸收式热泵在工业中具有广阔的应用前景.     

太阳能双吸收式热变换器系统的热力性能研究

建立了一种太阳能双吸收式热变换器的数学模型,研究了设计工况以及不同环境因素影响下的系统热力性能,分析了太阳辐射强度、环境温度、集热温度、吸收/蒸发温度和温升对系统热效率和制热功率的影响。研究结果表明:系统存在最佳的吸收/蒸发温度;辐射强度增加时系统性能明显提高,辐射强度从0.3 k W/m2变化到1.0k W/m2时,系统热效率提高了10.9%,制热功率增加了10.6倍;随环境温度或集热温度的升高,系统性能呈现了先升后降的趋势,在环境温度为26℃或集热温度为82℃时,系统性能分别达到最佳;最佳集热温度随着辐射强度的增大和环境温度的升高呈升高趋势。     

具有热阻和热漏的再热布雷顿循环性能分析

用有限时间热力学方法建立了一个工作在恒温热源TH、TL之间,存在热阻、热漏和再热的定常流空气标准闭式布雷顿循环模型。导出了其功率、效率的一般关系并对其进行优化,得到循环的基本优化关系;分析了在傅立叶导热定律下再热对循环最优性能的影响。     

Performance analysis and optimization of heat exchangers: a new thermoeconomic approach

A thermoeconomic performance optimization has been carried out for a single pass counter-flow heat exchanger model. In the considered model, the irreversibilities due to heat transfer between the hot and cold stream are taken into account and other irreversibilities such as pressure drops and flow imbalance are ignored. The objective function is defined as the actual heat transfer rate per unit total cost considering lost exergy and investment costs. The optimal performance and design parameters which maximize the objective function have been investigated. The effects of the technical and economical parameters on the general and optimal thermoeconomical performances have been also discussed.     

The efficiency of endoreversible heat engines with heat leak

Finite-time thermodynamics are used for studying the performance of endoreversible heat engines with heat leak. A comprehensive formulation and a general solution methodology, valid for any mode of heat supply or release, are presented. Detailed analyses are conducted for several heat transfer modes and universal analytical and numerical results for the efficiency at maximum power are generated. Many established laws and major conclusions derived in several references are shown to represent very special cases of the new formulation. Furthermore, the nature of the leakage power law is found to deeply affect the efficiency at maximum power. Finally, for no leakage situations, if the heat to the engine is supplied and released via similar heat transfer modes, then the lowest efficiency at maximum power, when the only thermal resistance is between the working fluid and the hot reservoir, is found to be given by 1/n, n being the power of the heat transfer law.