A theoretical study on a novel combined power and ejector refrigeration cycle

A new combined power and refrigeration cycle is proposed for the cogeneration, which combines the Rankine cycle and the ejector refrigeration cycle by adding an extraction turbine between heat recovery vapor generator (HRVG) and ejector. This combined cycle could produce both power output and refrigeration output simultaneously, and could be driven by the flue gas from gas turbine or engine, solar energy, geothermal energy and industrial waste heats. Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the performance and exergy destruction in each component for the combined cycle. The results show that the condenser temperature, the evaporator temperature, the turbine inlet pressure, the turbine extraction pressure and extraction ratio have significant effects on the turbine power output, refrigeration output, exergy efficiency and exergy destruction in each component in the combined cycle. It is also shown that the biggest exergy destruction occurs in the heat recovery vapor generator, followed by the ejector and turbine.     

一种新型跨临界CO2冷电联供系统热力分析

提出一种新型跨临界二氧化碳（trans-critical carbon dioxide,TCO₂）再压缩循环和喷射器制冷循环耦合的冷电联供系统。该系统在输出电能的同时,利用低品位热能驱动喷射器工作输出冷量。以输出电量1 MW为设计目标,对比冷电联供系统和再压缩发电系统的性能,研究联供系统各部件（火用）损和主要热力参数对其性能的影响。结果表明：联供系统利用CO₂余热驱动喷射器输出冷量,循环热效率高于单一再压缩系统;加热器（火用）损所占比例最大,回热器次之;透平进口温度、压力和背压对联供系统工质流量、循环效率、输出功率、加热器功率、压缩机耗功及喷射器制冷量等参数影响较大;而冷凝温度和蒸发温度仅对制冷循环制冷量影响较大。在设定条件下,联供系统的循环热效率和（火用）效率可分别达到46.99%和47.21%。     

Thermal and exergoeconomic analysis of a novel solar driven combined power and ejector refrigeration (CPER) system

In the present study, a novel solar driven combined power and ejector refrigeration system (CPER) of 50 kW power capacity composed of an ORC (organic Rankine cycle) and an ejector refrigeration system is investigated. Solar driven CPER system is composed of two main cycles: collector cycle and refrigeration cycle. The collector cycle is made of a U-tube ETC and circulation pump and the ejector refrigeration cycle consists of generator, turbine, ejector, heat exchanger, condenser, evaporator, expansion valve, and pump. Thermodynamic performance of the proposed CPER system is evaluated and a thermo-economic analysis is conducted using the SPECO (specific exergy costing) method. A parametric study showed the effects of condenser temperature, evaporator temperature, generator pressure, turbine back pressure and turbine extraction ratio. The genetic algorithm optimization analysis is conducted which shows 25.5% improvement in thermal energy, 21.27% in exergy efficiency, and 7.76% reduction in the total cost of the CPER system. The results reveal that the performance of the CPER system is considerably improved at higher temperatures of generator and evaporator.     

A theoretical study on a novel solar based integrated system for simultaneous production of cooling and heating

An integrated system for simultaneous production of triple-effect cooling and single stage heating is proposed in this paper to harness low grade solar energy. The proposed system combines the heliostat field with a central receiver and the ejector-absorption cycle with the shaft power driven transcritical CO₂ cycle. A parametric study based on first and second laws of thermodynamics is carried out to ascertain the effect of varying the exit temperature of duratherm oil, turbine inlet pressure, and evaporators temperature on the energy and exergy output as well as on the energy and exergy efficiencies of the system. The results obtained indicate that major source of exergy destruction is the central receiver where 52.5% of the inlet solar heat exergy is lost followed by the heliostat where 25% of the inlet exergy is destroyed. The energy and exergy efficiencies of the integrated system vary from 32% to 39% and 2.5%–4.0%, respectively, with a rise in the hot oil outlet temperature from 160 °C–180 °C. It is further shown that increase in evaporator temperature of transcritical CO₂ cycle from −20 °C to 0 °C increases the energy efficiency from 27.45% to 43.27% and exergy efficiency from 2.51% to 2.97%, respectively. The results clearly show how the variation in the values of hot oil outlet temperature, turbine inlet pressure, and the evaporator temperature of transcritical CO2 cycle strongly influences the attainable performance of the integrated system.     

Thermodynamic modelling and optimization of a dual pressure reheat combined power cycle

Heat recovery steam generator (HRSG) plays a key role on performance of combined cycle (CC). In this work, attention was focused on a dual pressure reheat (DPRH) HRSG to maximize the heat recovery and hence performance of CC. Deaerator, an essential open feed water heater in steam bottoming cycle was located to enhance the efficiency and remove the dissolved gasses in feedwater. Each of the heating section in HRSG is solved from the local flue gas condition with an aim of getting minimum possible temperature difference. For high performance, better conditions for compressor, HRSG sections, steam reheater and deaerator are developed. The CC system is optimized at a gas turbine inlet temperature of 1400°C due to the present available technology of modern gas turbine blade cooling systems. The exergetic losses in CC system are compared with each other. The present DPRH HRSG model has been compared and validated with the plant and published data.     

水产品低温贮藏库的节能分析

通过利用线性拟合的方法对氨的物性进行模拟,在变冷凝温度和变冷间温度,以及在蒸发器和冷凝器压力降变化的条件下,分别对冷库中的氨双级蒸汽压缩系统进行能量分析,对系统各部件的炯损失和系统的炯效率进行计算分析,得出随着冷凝温度和冷间温度的改变,系统各设备的炯损失的排序变化的结果,以及随着压力降的变化系统的性能发生了变化,提出改进系统的性能可从减少冷凝传热温差和减少冷间传热温差,提高冷却水有效利用,改善蒸发器的压力降方面考虑。     

两级双效溴化锂制冷-热泵复合循环

在热电冷联产系统中,溴化锂吸收式制冷机在制冷过程中排放了大量的废热,这些废热品味低,难以直接回收利用。在此提出了两级双效溴化锂制冷-热泵复合循环,该循环具有冷凝温度较高的特点,便于直接回收冷凝排放热。系统以背压汽轮机的背压蒸汽为热源,制冷的同时利用循环所排出的废热加热锅炉补充水至较高温度。以具有相同功效的双效溴冷机与单效溴化锂热泵联合运行作为对比循环,制冷-热泵复合循环系统省去了一台蒸发器与冷凝器,减少了两个换热温差,并且通过热力计算、能量分析和分析表明,该循环的能量利用率与效率均有很大的提高,效率比对比循环提高了45%。     

新Kalina循环系统（KCS）34的热力学分析

本文提出新Kalina循环即一次抽汽回热式KCS34和分级抽汽回热式KCS34,根据热力学第一定律和第二定律,利用EES软件仿真模拟对该循环进行热力性能分析,并与基本KCS34进行相同条件下的性能对比,研究了抽汽压力、透平进口压力和透平进口温度变化对一次抽汽回热式KCS34性能的影响。研究结果表明：额定工况下,一次抽汽回热式KCS34的热效率为12.33%,比基本KCS34高0.35%;效率为46.07%,比基本KCS34高1.35%。且与一次抽汽回热式KCS34相比,分级抽汽回热式KCS34热效率高0.13%,效率高0.49%。另外,抽汽压力增加,一次抽汽回热式KCS34发电量和效率逐渐降低,热效率在10bar时达到最大;随着透平进口压力增加,一次抽汽回热式KCS34热效率逐渐增加,发电量和效率在30.79 bar时达到最大;随着透平进口温度增加,一次抽汽回热式KCS34热效率逐渐、发电量和效率都增大。     

Working fluids comparison and thermodynamic analysis of a transcritical power and ejector refrigeration cycle (TPERC)

The combined power and cooling cycles driven by waste heat and renewable energy can provide different kinds of energy forms and achieve a higher thermodynamic efficiency. However, only a few researchers have focused on the improvement of temperature matching between the heat source and working fluid. This paper proposes a transcritical power and ejector refrigeration cycle (TPERC) to improve temperature matching between the heat source and working fluid. Based on the modelling of the TPERC system, a comparison of working fluids and the effects of system parameters on the cooling capacity, work output, thermal efficiency and exergy efficiency are discussed. The results show that of the seven working fluids selected, R1234ze has the largest thermal efficiency and exergy efficiency, principally due to having the highest critical temperature. At the identical turbine back pressure, condensing temperature and evaporation temperature, the turbine inlet temperature and its corresponding generation pressure have little impact on thermal efficiency.     

吸附式制冷循环的分析

以吸附式制冷循环的热力过程为依据，使用火用分析的方法对连续回热循环做了分析，对循环中各部分火用损进行了比较。指出了连续回热循环中火用损的主要部位，并探讨了回热率及吸附床的传热性能对循环火用效率的影响。     

露点蒸发冷却装置性能评价指标的研究

本文通过搭建逆流式露点蒸发冷却装置,实验研究了空气入口温度、湿度和风速对露点效率、湿球效率、?效比等各性能评价指标的影响,提出了能够反映湿通道潜热交换的强弱和装置性能的适用于露点蒸发冷却的评价指标——换热放大系数.研究结果表明:进口温度为33、相对湿度为22％时,当风速从1 m/s增至3 m/s,制冷量从29.5 kW...     

冷前回热式Kalina循环系统(KCS)34g的热力学分析

提出冷前回热式KCS34g,根据热力学第一定律和第二定律,利用EES软件对该循环进行热力性能分析,并与基本KCS34g进行相同条件下的性能对比,研究透平进口压力、氨质量分数和透平出口压力变化对冷前回热式KCS34g性能的影响。研究结果表明:在额定工况下,冷前回热式KCS34g的热效率为11.93%,比基本KCS34g高0.99%;效率为52.26%,比基本KCS34g高4.34%;随着氨质量分数增大和透平出口压力降低,冷前回热式KCS34g热效率、发电量和效率均增大;随着透平进口压力增加,冷前回热式KCS34g热效率逐渐增加,发电量和效率在29 bar时达到最大。     

理论[火用]分析在冷冻厂高温库中的应用

通过对一定环境温度条件下的高温冷库中的氨蒸汽压缩系统进行[火用]分析,利用线性拟合的方法对氨的物性进行模拟,并对定冷凝温度和变冷凝温度时,制冷系统的各部件的炯损失和系统的[火用]效率进行计算分析,得出在冷库氨蒸汽压缩系统中的蒸发器中的[火用]损失最大,压缩机和冷凝器次之的结果。提出要对冷库氨蒸汽压缩系统的性能进行改进,必须首先考虑提高其蒸发器、压缩机和冷凝器的[火用]效率着手;认为在一定环境温度条件下,降低冷凝温度是提高[火用]效率的较好的改进措施之一．     

Exergy analysis of multistage cascade low temperature refrigeration systems used in olefin plants

This paper provides an exergy analysis for multistage cascade low temperature refrigeration systems used in olefin plants. The equations of exergy destruction and exergetic efficiency for the main system components such as heat exchangers, compressors and expansion valves are developed. The relations for total exergy destruction in the system and the system overall exergetic efficiency are obtained. Also, an expression for minimum work requirement for the refrigeration systems of olefin plants is developed. It shows that the minimum work depends only on the properties of incoming and outgoing process streams cooled or heated with refrigeration system and the ambient temperature. Using actual work input values, the exergetic efficiency of the low temperature cascade refrigeration system of a typical olefin plant is determined to be 30.88% indicating a great potential for improvements. The novelty of this paper includes the suggestions for increasing efficiencies, along with discussion about the reasons for deviation from reversible processes.     

Numerical optimisation of a two-stage ejector refrigeration plant

Jet-refrigeration cycles seem to provide an interesting solution to the increasing interest in environment protection and the need for energy saving due to their low plant costs, reliability and possibility to use water as operating fluid. A steam/steam ejector cycle refrigerator is investigated introducing a two-stage ejector with annular primary at the second stage. The steady_state refrigerator, exchanging heat with the water streams at inlet fixed temperatures at the three shell and tube heat exchangers, evaporator, condenser and generator, is considered as an open system. Heat transfer irreversibilities in the heat exchangers and external friction losses in the water streams are considered, ignoring the internal pressure drop of the vapor. A simulation program numerically searches the maximum COP at given external inlet fluid temperatures as a function of mass flows, dimensions and temperature differences in the heat exchangers. The code gives the ejector and heat exchangers design parameters.     

废热驱动热管溴化锂制冷机的比较

利用热力学第一定律的热力平衡方法和热力学第二定律的火用分析方法,分别对单级单效、单级双效和两级热管废热回收双效溴化锂制冷系统的热力系数和火用效率进行比较。结果表明：不管从热经济性角度,还是从能源利用的完善性（[火用]效率）与合理性（能级匹配）角度,两级热管废热回收双效溴化锂制冷系统都更具合理性和实用性。     

Exergy analysis of R1234yf and R1234ze as R134a replacements in a two evaporator vapour compression refrigeration system

Exergy analysis is a useful way for determining the real thermodynamic losses and optimising environmental and economic performance in the systems such as vapour compression refrigeration systems. The present study deals with the exergy analysis on a two evaporator vapour compression refrigeration system using R1234yf, R1234ze and R134a as refrigerants. In the calculation of losses occurring in different system components, besides the exergy efficiency of the refrigeration cycle, a computer code was developed by using Engineering Equation Solver (EES-V9.172-3D) software package program. The effects of the evaporator and condenser temperatures on the exergy destruction and exergy efficiency of the system were investigated. R1234yf and R1234ze, which are good alternatives to R134a concerning their environmentally friendly properties and this is the most significant finding emerging from this study.     

Performance parameters for the design of a combined refrigeration and electrical power cogeneration system

This paper discusses the conservation of energy in a cogeneration system. A steam power cycle (Rankine) produces electrical power 2 MW and steam is bleeded off from the turbine at 7 bar to warm a factory or units of buildings during the winter or to supply a steam ejector refrigeration cycle to air-conditioning the same area during the summer. In the summer this system can be as alternative solution instead of absorption. Certainly the ejector refrigeration unit is more economical than absorption unit. The ratio of electrical power/heat is varied into the region (0.1–0.4) and the evaporator temperature of the ejector cycle is varied into the region (10–16 °C). A computer program has been developed for the study of performance parameters of the cogeneration system.     

回热器在高温气冷堆氦气透平循环中的应用

高温气冷堆相匹配的能量转换系统——氦气透平循环(布雷登循环)发电具有发电效率高、系统简单、安全可靠、经济性好等优点,是目前高温气冷堆领域的发展方向。影响布雷登循环效率的关键参数包括堆芯的进出口温度、压气机和透平的绝热效率、回热度、压比及循环系统的压力损失率。本文详细验证了回热器在高温气冷堆氦气轮机循环中的作用,并通过计算10MW高温气冷堆布雷登循环,分析这些参数对循环效率的影响。某于目前反应堆参数．给出了一组影响布雷登循环效率的参数值。     

Thermodynamic analyses on an ejector enhanced CO2 transcritical heat pump cycle with vapor-injection

In this paper, an ejector enhanced vapor injection CO₂ transcritical heat pump cycle with sub-cooler (ESCVI) for heating application in cold regions is proposed. The thermodynamic analysis using energetic and exegetic methods is carried out to predict the performance characteristics of the ejector enhanced cycle, and then compared with those of the conventional vapor injection heat pump cycle with sub-cooler (SCVI). The simulation results demonstrate that the ejector enhanced cycle exhibits better performance than the conventional vapor injection cycle under the specified operating conditions. The improvements of the maximum system COP and volumetric heating capacity could reach up to 7.7% and 9.5%, respectively. Exergetic analysis indicates that the largest exergy destruction ratio is generated at the compressor followed by the evaporator and gas cooler. Additionally, the exergy efficiency of the ejector is introduced to quantify the effectiveness of the exergy recovery process, which may be a new criterion to evaluate the performance of the ejector enhanced vapor compression cycle.