Analysis of a refrigeration cycle driven by refrigerant steam turbine

The objectives of this paper are to develop a novel cycle with refrigerant Rankine and refrigeration cycles, and to discuss the thermodynamic analysis of the cycle and the adequacy of the development. The combined cycle uses only one working fluid, has a simple mechanical system and does not have abrading parts. Three different refrigerants are evaluated to find the best candidate for the novel combined cycle—R123, R134a and R245ca. It is found that the R123 cycle gives the highest cycle efficiency among all cycles considered in the present study. The base cycle has a low efficiency because of the high temperature at the turbine outlet. By recovering the heat at the turbine outlet, the overall COP increases by 47% in case of the R245ca cycle. In the base cycle, COP depends mostly on the boiler pressure, while in the modified cycle with the recuperator, the cycle efficiency depends mostly on the boiler temperature. Considering the cycle efficiency and environmental issues, it is concluded that R245ca is the most promising refrigerant out of the cycles considered in the present paper.     

Investigation on gradient thermal cycle for power and refrigeration cogeneration

In order to improve energy utilization efficiency of low grade heat, a novel gradient thermal cycle for power and refrigeration cogeneration is proposed. The cycle is cascaded with two stages based on different thermal driven temperature. The first stage is pumpless Organic Rankine Cycle (PRC) while the second stage is two-stage sorption refrigerator. R245fa is selected as the working fluid of PRC, whereas CaCl₂-BaCl₂-NH₃ working pair is chosen for two-stage sorption refrigerator. Different heat source temperatures from 80°C to 95°C are adopted for analysis and comparison. Results indicate that the highest average power output and cooling effect are able to reach 204 W and 0.91 kW under the condition of 95°C heat source temperature and 10°C refrigeration temperature. For different heat source temperatures, total energy and exergy efficiency of the gradient thermal cycle for power and refrigeration cogeneration range from 9.49% to 9.9% and 10.9% to 11.8%, respectively. For gradient thermal cycle exergy efficiency of heat utilization ranges from 24% to 18.8% which is 126.5% and 70.9% higher than the PRC and two-stage sorption refrigerator, respectively, when the heat source temperature is 80°C.     

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.     

Thermodynamic Properties of Ammonia–Water Mixtures for Power Cycles

Power cycles with ammonia–water mixtures as working fluids have been shown to reach higher thermal efficiencies than the traditional steam turbine (Rankine) cycle with water as the working fluid. Different correlations for the thermo-dynamic properties of ammonia–water mixtures have been used in studies of ammonia–water mixture cycles described in the literature. Four of these correlations are compared in this paper. The differences in thermal efficiencies for a bottoming Kalina cycle when these four property correlations are used are in the range 0.5 to 3.3%. The properties for saturated liquid and vapor according to three of the correlations and available experimental data are also compared at high pressures and temperatures [up to 20 MPa and 337°C (610 K)]. The difference in saturation temperature for the different correlations is up to 20%, and the difference in saturation enthalpy is as high as 100% when the pressure is 20 MPa.     

An experimental study of an ejector cycle refrigeration machine operating on R113 Etude expérimentale d'une machine frigorifique à éjecteur au R113

This paper discusses an ejector cycle refrigeration machine that can use a wide range of refrigerants including halocarbons. The feature of such a system is the possibility of using a low grade heat source such as solar energy and waste heat to operate the system. A theoretical analysis was carried out to select a suitable refrigerant for the system. The influence of boiler, condenser and evaporator temperatures on system heat transfer is investigated experimentally under different operating conditions. The experimental machine uses R113 as a working refrigerant.     

Highly efficient high-power continuous extreme ultraviolet source for irradiating samples with a large total area

An original arc-discharge source of cw extreme ultraviolet (10–75 nm) radiation is described, which provides an output power level of ∼10 kW at an efficiency of ∼10% (at least, in the 30–70 nm range). The source is simple to manufacture, possesses a working life of ∼1000 h, and is capable of irradiating samples with a total exposed area of 0.1–1 m².     

Thermodynamic optimization of combined power and refrigeration cycle using binary organic working fluid

A combined cycle has been proposed for the production of power and refrigeration simultaneously. The cycle can be driven by low grade heat sources such as solar, geothermal and waste heat sources. In the first part of this paper, a model has been developed to perform a parametric analysis to evaluate the effects of important parameters on the performance of the cycle, which is a combination of Rankine and absorption refrigeration cycle. Propane–decane has been used as an organic dual working fluid. In the second part, multi objective genetic algorithm is applied for Pareto approach optimization of the cycle. There are three important conflicting objectives namely, turbine work (W_t), cooling capacity (Q_c) and thermal efficiency (η_th) which have been selected to find the best possible combination of these performance parameters. Optimization has been carried out by varying turbine inlet pressure, superheated temperature and condenser temperature as design variables. Among optimum design parameters, a trade-off point is selected. Turbine inlet pressure, superheated temperature and condenser temperature are assumed to be 29.5 bar, 410 K and 386.6 K respectively as the values assigned to this point. Furthermore, it has been shown that some interesting and important relationships can be discovered among optimal objective functions and decision variables involved, consequently.     

Methodology for thermal design of novel combined refrigeration/power binary fluid systems

Refrigeration cogeneration systems which generate power alongside with cooling improve energy utilization significantly, because such systems offer a more reasonable arrangement of energy and exergy “flows” within the system, which results in lower fuel consumption as compared to the separate generation of power and cooling or heating. This paper proposes several novel systems of that type, based on ammonia–water working fluid. Importantly, general principles for integration of refrigeration and power systems to produce better energy and exergy efficiencies are summarized, based primarily on the reduction of exergy destruction. The proposed plants analyzed here operate in a fully-integrated combined cycle mode with ammonia–water Rankine cycle(s) and an ammonia refrigeration cycle, interconnected by absorption, separation and heat transfer processes. It was found that the cogeneration systems have good performance, with energy and exergy efficiencies of 28% and 55–60%, respectively, for the base-case studied (at maximum heat input temperature of 450 °C). That efficiency is, by itself, excellent for cogeneration cycles using heat sources at these temperatures, with the exergy efficiency comparable to that of nuclear power plants. When using exhaust heat from topping gas turbine power plants, the total plant energy efficiency can rise to the remarkable value of about 57%. The hardware proposed for use is conventional and commercially available; no hardware additional to that needed in conventional power and absorption cycles is needed.     

The CNPM thermal heat pump. Part 1 — general description and thermodynamic analysis

A research programme, funded by CNR (National Research Council), has been undertaken by CNPM since 1973. The aim of the programme is the construction and testing of a prototype thermal heat pump. The most significant component is an organic Rankine cycle engine, driving the compressor of a heat pump. Since the heat rejected by the engine is supplied to the user — water for domestic heating — the whole system performs as a ‘heat multiplier’, converting the high temperature heat given to the engine into a larger amount of low temperature heat, to be used for domestic heating.In this paper, the selection criteria for the working fluid — a completely fluoro-substituted hydrocarbon — and the main thermodynamic data of both power and heat pump cycles, are discussed; the finally adopted plant configuration is described, with particular emphasis on the influence exterted by the working fluid nature on the heat exchangers and turbo-machinery dimensions and performance. A discussion on the merits of the single fluid solution (ie the same working fluid in the power and the heat pump cycle) and dual fluid solution is also carried out. The feasibility of a low-temperature heat distribution, based on compact-surface, natural-draft convectors, with the relevant advantages on the Rankine and heat-pump cycles, is also investigated.Finally, the expected overal; system performance is given, both at design and part-load conditions. As a premium for the rather complex but efficient thermodynamicscv of the system, significant energy savings are obtained in all situations.     

有机朗肯循环的发电系统的实验研究

以低温热蒸汽来模拟废热作为有机朗肯循环(ORC)的热源,建立了以R134a为制冷剂的有机朗肯循环发电系统。通过EES(engineering equation solver)软件对ORC系统进行了数学建模,并将实验与模拟结果进行了比较。结果表明:系统以R134a为工质运行,可以达到8%的发电效率;当膨胀机进口的状态为饱和或者过热时,系统的热效率与发电量都会随着进口压力的增加而增加;系统压力较低的时候,系统的不可逆程度较大,系统效率会有较大损失。     

利用燃气轮机烟气余热的复合有机朗肯循环系统优化分析

本文针对燃气轮机烟气余热设计了一种复合有机朗肯循环系统,对其进行了详细的热力学分析,以某燃驱压气站烟气条件(400℃,26 kg/s)为例,以系统净输出功为目标,利用Matlab和Refprop 9. 0选择了13种工质,并确定了系统最优工况。结果表明,甲苯、R141b、丙酮分别作为3个子系统的工质时,系统可实现最大净输出功为1 587 k W,热效率和火用效率分别可达20. 26%和42. 68%,比单级循环可实现的最大净输出功高23. 33%。对系统各部件进行火用损失分析,发现蒸发器火用损失最大,并提出了改进方案。     

Statistical dynamics of turbomachine rotor wheels with a technological mistuning

Random harmonic vibrations of the steam turbine working stage have been studied with allowance for mistuning. An approach to the determination of the mathematical expectation and spectral density of the displacements of the system under study is proposed, which is based on the model of a single sector. __________ Translated from Problemy Prochnosti, No. 5, pp. 105–113, September–October, 2008.     

Compression heat pump with solution circuit Part 1: design and experimental results

This Paper presents the design and experimental results of a compression heat pump with solution circuit (CHSC) that has been constructed at the Swiss Federal Institute of Technology. The CHSC offers two major advantages over a single fluid Rankine cycle: 1, the heating capacity is easily varied by a large factor by adjusting the composition of the mixture; and 2, the approximation of the Lorenz process allows for substantially high COP values in cases with gliding temperatures. The test plant heats water from 40 to 70°C and cools water from 40 to 15°C. The heating capacity can be varied from 5 to 15 kW. A COP of 4.3 was measured, representing an energy saving of 23%, compared with a good single fluid Rankine cycle. Measured heat and mass transfer coefficients are presented and discussed.     

Thermodynamic optimization of ejector actuated refrigerating cycles

A cold generation system featuring a Rankine cycle powered refrigeration cycle actuated by a supersonic ejector was theoretically investigated in view of the thermo-fluid-dynamic optimization of the working fluid characteristics.

The ejector model was validated against well established performance charts relating to water. A reference system was considered in which a Rankine cycle at moderate top temperature delivers its expansion power by means of an ideal turbine to an ideal compressor of a refrigeration cycle. Two main optimizing variables were ascertained: the fluid critical temperature and the complexity of the fluid molecule. The best performance of such reference cycle is around 80% of that of an ideal fully reversible, Carnot cycle based, system (COP of 2.0 for t_E,PC = 150 °C, t_E,RC = 5 °C, and t_C = 35 °C). As easily predictable the ejector compression introduces severe losses mainly due to the normal shock and the mixing of the motive and of the driven fluid. Overall COP for the above quoted temperatures decreases from 2.0 (reference cycle) to 0.4–0.7. The optimization of the working fluid showed that comparatively low critical temperatures are favoured and that a fluid complexity similar to that of CH₅N or CH₂Cl₂ gives the best performance. A detailed losses analysis explains this behaviour. In particular at low reduced temperatures the theoretical gain related to the better shape in the T–S plane of both the power and the refrigeration cycle is more than offset by the higher ejector losses due to the stronger normal shock needed to cope with an increased pressure ratio.

Notwithstanding an extensive fluid screening we did not succeed in finding a fluid that could be considered optimum from all points of view including ambient and safety issues. However, a number of traditional (non-zero ODP) chloro-fluoro-carbons and of new (zero ODP) refrigerants were found that yield, on the whole, a satisfactory performance.

Provided calculated COP will be confirmed by experimental testing, ejector powered refrigerators could compete with absorption systems in many applications.     

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.     

Development and test of solar Rankine cycle heating and cooling systems

This paper describes the design, fabrication and test of a prototype 63.3 kW (18 ton) solar-powered Rankine cycle heat pump, as well as the assembly and field test of a 63.3 kW (18 ton) solar powered chiller.     

氨蒸气压缩高温热泵系统研究现状

高温热泵是解决冷热双利用、实现节能减排的重要方法.由于工质使用的限制,自然工质成为研究的重点,氨作为自然工质,具有优良的热力性能.本文通过热力计算对氨和其它常用热泵工质进行了性能对比分析,并对氨蒸气压缩式高温热泵进行了综述,发现氨在80～95℃范围内综合性能最佳,适合用于60～110℃高温工况.同时本文基于单级压缩热泵...     

COMPROMISE: AN EFFECTIVE APPROACH FOR SOLVING MULTIOBJECTIVE THERMAL DESIGN PROBLEMS

In this paper, the application of the compromise Decision Support Problem Technique to the design of a Rankine power cycle to be used in a solar powered irrigation system is described. The system consists of a solar collector cycle coupled with a simple Rankine cycle. The uniqueness or the present approach lies in the interfacing of the thermal system simulation routines with a multi-objective optimization algorithm^1.2, as opposed to the traditional iterative design procedure. The problem, though simple in a mathematical sense, is complete in that it is representative of the complexities associated with the design or thermal systems dealing with thermodynamic property changes.