共查询到19条相似文献,搜索用时 156 毫秒
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为提高海洋温差能发电系统的综合性能,以单位换热面积发电量和单位海水流量发电量为基础建立综合目标函数,选取蒸发温度、冷凝温度、蒸发器和冷凝器的海水出口温度为优化变量,利用粒子群算法对海洋温差能朗肯循环系统进行多目标参数优化。研究结果表明,在28℃温海水和5℃冷海水条件下,循环工质为R717时,蒸发器内的最佳蒸发温度为23.10℃,温海水出口温度为23.42℃;冷凝器内的最佳冷凝温度为12.31℃,冷海水出口温度为10.80℃;在换热器的海水进出口温差超过4℃时,换热器的海水出口温度对系统性能的影响较小。综上,采用多目标优化可实现对各评价指标间的协调,相比单目标优化的传统模型,多目标优化改善了系统的综合性能。 相似文献
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基于稳态分布参数模型的光伏蒸发器的数值模拟 总被引:1,自引:0,他引:1
该文采用分布参数法,从制冷工质动力学原理出发,根据平衡均相流理论,建立了光伏太阳能热泵光伏蒸发器的稳态分布参数模型。通过数值模拟对光伏蒸发器在给定的太阳辐照强度、环境温度以及制冷工质不同的进口流速下,工质的平均比焓、空隙率、干度、温度、压力等参数沿制冷管道的分布、蒸发器的温度和光伏电池发电效率的二维分布等进行研究。了解这些参数的分布情况对研究光伏蒸发器的光电、光热性能具有十分重要的意义,可作为蒸发器结构以及系统设计的依据,为系统的优化奠定了一定的理论基础。 相似文献
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以地热发电有机朗肯循环系统中蒸发器为研究对象,利用R245fa与R601组成非共沸混合工质为研究背景,建立变蒸发温度变工质配比的有机朗肯循环系统模型。采用Pearson相关系数法研究蒸发器热力学性能与其影响因素之间的相关关系,相关程度以及相关方向,并与热力学计算分析结果进行对比。研究表明:温度滑移与热效率、蒸发器损分别存在显著性正相关和高度负相关;与对数平均温差的相关性随蒸发温度的升高由微弱负相关增强至显著性负相关;利用Pearson相关系数法能解决多目标优化过程中影响因素耦合的问题,优化热力学计算结果与分析过程。 相似文献
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海上油气平台存在大量的燃气轮机余热。通过建立海上平台余热朗肯循环发电系统仿真模型,开展平台余热发电热力学及热经济性分析。选取工质泵功率、发电机输出功率、系统热效率、换热面积和单位面积发电量等参数作为优化目标,研究不同冷凝温度下优化目标函数随蒸发器烟气进出口温差的变化规律。结果表明:随着蒸发器烟气进出口温差的增加,工质泵功率、发电机输出功率和系统APR先增大后减小。冷凝温度越高,工质泵功率越大,发电机输出功率和系统热效率越小。当冷凝温度为65℃时,系统APR最大。受透平出口蒸汽干度的限制,所研究工况下,系统发电机最大输出功率为7 496 kW,系统最大热效率和APR分别为14.16%和5 kW·m~(-2)。研究结果可为撬装化、集成化海上油气平台余热发电系统研制提供理论参考。 相似文献
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《Applied Thermal Engineering》2003,23(12):1567-1575
The sugar industry in India has a potential of 3500 MW to export to the grid. In this paper an energy balance has been carried out for an actual 5000 TCD plant and a Sankey diagram is drawn. A pinch analysis is done for the sugar factory and reveals that the minimum hot utility requirement is lower than the actual by 9%. Modified evaporator designs are proposed as it has been found that the existing plant is not optimum with regard to the surface area of the evaporators and the amount of steam being consumed. Exergy analysis is applied to the existing and the proposed evaporator effects and the results are compared. It is concluded that the amount of steam consumption will reduce by 9 T/h and exergy losses are reduced by 48% of its original value if the existing quadruple effect is modified to a quintuple effect. The turbine hardware model is used to predict the optimum amount of power that can be cogenerated from the system for different generation temperatures at a pressure of 45 bar. The optimum superheat temperature is found to be 600 °C for a backpressure turbine with single extraction. A cost analysis is performed to determine the variation of the average cost of generation of power with the generation temperature of the steam. 相似文献
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In a double-effect series flow vapour absorption refrigeration system (VARS), an optimum value of the low-pressure generator temperature exists at which all the vapour generated at the high-pressure generator is condensed. At these conditions, a comparative study of the performance of VARS using environment friendly refrigerants such as, R32, R134a, and R124 with N,N′-dimethyl acetamide (DMAC) as the absorbent is made. It is found that the system with R32-DMAC gives the best performance at high evaporator temperatures. R124-DMAC may be preferred at extreme operating conditions like low evaporator and high heat rejection temperatures. Influence of operating temperatures (high-pressure generator, evaporator, condenser and absorber) and the effectiveness of heat exchangers on the optimum low-pressure generator temperature, cut-off temperature, circulation ratio and coefficient of performance are studied. © 1998 John Wiley & Sons, Ltd. 相似文献
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In this study, superheating and sub‐cooling heat exchangers in vapor‐compressed refrigeration system are analyzed from thermodynamics and economical (refrigeration system operation cost, investment cost) viewpoints. Using four different refrigerants (R22, R502, R134a and R404a), the temperature of condenser at the interval of (35–55°C) and temperature of evaporator at the interval of (?10 to 10°C) have been obtained from the calculation process. The second law analysis (analysis of irreversibility) of a refrigeration system is carried out and then the whole system is optimized thermo‐economically. As a result of calculations, optimum superheating and sub‐cooling temperatures of heat exchanger (superheating, sub‐cooling) areas corresponding to these temperatures are obtained. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Water as a refrigerant (R718) is compared with some current natural (R717 and R290) and synthetic refrigerants (R134a, R12, R22, and R152a) regarding environmental issues including ozone depletion potential (ODP) and global warming potential (GWP), safety (toxicity and flammability), operating cost, refrigeration capacity and coefficient of performance (COP). A computer code simulating a simple vapour compression cycle was developed to calculate COPs, pressure ratios, outlet temperatures of the refrigerants from the compressor, and evaporator temperatures above which water theoretically yields better COPs than the other refrigerants investigated. The main difference of this study from other similar studies is that both evaporator temperature and condenser temperature are changed as changing parameters, but the temperature lift, which is the temperature difference between condenser and evaporator, are held constant and the irreversibility during the compression process is also taken into consideration by taking the isentropic efficiency different from 100%. It is found that for evaporator temperatures above 20°C and small temperature lift (5 K), R718 gives the highest COP assuming exactly the same cycle parameters. For medium temperature lifts (20–25 K), this evaporator temperature is above 35°C, whereas for even greater temperature lifts it decreases again. Furthermore, with increased values of polytropic efficiency, R718 can maintain higher COPs over other refrigerants, at lower evaporator temperatures. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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《Energy Conversion and Management》1986,26(1):83-89
An economic analysis of biogas as a source of energy to the pumpless LiBrH2O absorption system has been carried out. The generator temperature and pressure, evaporator temperature, precooler and preheater effectivenesses were used as system variables. The optimum generator temperature has been presented graphically for a wide range of operating conditions. Multipliers have also been obtained for evaporator temperatures other than 5°C. 相似文献
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The ratios of gas flow to steam flow are huge in heat recovery steam generators (HRSGs) compared to other steam generators. So the volume which is occupied by components of the HRSG such as economizer, evaporator and superheater is important factor when the HRSG is applied in structures including buildings and ships. The optimum volume of a HRSG is deduced through optimization of entropy generation and cost evaluation. By increasing volume, second law of thermodynamics is improved, but this improvement may not be economical. In this work, the best dimensions and arrangements of flows in HRSG are obtained by constructal design and the optimization method is algorithm genetic. In this case, super heater temperature, pinch point, water/steam flow rate and gas pressure drop are derived from configuration which designed by constructal theory for HRSG. The effects of gas flow rate and inlet gas temperature are examined on the values of optimum volume. 相似文献
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An exergy-based thermoeconomic optimization application is applied to a subcooled and superheated vapor compression refrigeration system. The advantage of using the exergy method of thermoeconomic optimization is that various elements of the system—i.e., condenser, evaporator, subcooling and superheating heat exchangers—can be optimized on their own. The application consists of determining the optimum heat exchanger areas with the corresponding optimum subcooling and superheating temperatures. A cost function is specified for the optimum conditions. All calculations are made for three refrigerants: R22, R134a, and R407c. Thermodynamic properties of refrigerants are formulated using the Artificial Neural Network methodology. 相似文献
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A computational model is developed for the parametric investigation of single‐effect and series flow double‐effect LiBr/H2O absorption refrigeration systems. The effects of generator, absorber, condenser, evaporator and dead state temperatures are examined on the performance of these systems. The parameters computed are coefficient of performance (COP), exergy destruction rates, thermal exergy loss rates, irreversibility and exergetic efficiency. The results indicate that COP and exergetic efficiency of both the systems increase with increase in the generator temperature. There exist different optimum values of generator temperature for maximum COP and maximum exergetic efficiency. The optimum generator temperature is lower corresponding to maximum exergetic efficiency as compared to optimum generator temperature corresponding to maximum COP. The effect of increase in absorber, condenser and evaporator temperatures is to decrease the exergetic efficiency of both the systems. The irreversibility is highest in absorber in both systems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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《Energy Conversion and Management》2005,46(18-19):3117-3135
A theoretical analysis of the ejector refrigeration system based on the constant area ejector flow model is performed. Optimised results for R-123 are presented. It is determined that the variations in condenser and evaporator temperature have a greater effect on the optimum coefficient of performance (COP) than the variation in generator temperature. At the same operating temperatures of the ejector refrigeration system, the optimum COP and area ratio determined in this study using the constant area flow model are greater than the values given in the literature for the constant pressure flow model. For the same area ratio, the COP for the system with the constant pressure ejector is relatively higher than that with the constant area ejector. In this case, however, the condenser temperature should be lowered. In addition, the refrigeration systems have almost the same COP values at lower evaporator or higher condenser temperatures. 相似文献