Prospect Evaluation of Low-GWP Refrigerants R1233zd(E) and R1336mzz(Z) Used in Solar-Driven Ejector-Vapor Compression Hybrid Refrigeration System

In this paper, the entrainment ratio, pump work, heat loads of heat exchangers and COPthermal were theoretically evaluated for a solar-driven ejector-vapor compression hybrid refrigeration system with R1233 zd(E) and R1336 mzz(Z) as the working fluids. The evaluation of the utilization potentials of R1233 zd(E) and R1336 mzz(Z) was presented by comparing the system performance with that of R245 fa, a commonly used refrigerant in the ejector system. The results indicated that the systems with R1233 zd(E) and R1336 mzz(Z) had a higher entrainment ratio and lower pump work. The pump works when using R1233 zd(E) and R1336 mzz(Z) can be up to 14.59% and 38.05% lower than those of R245 fa, respectively. Meanwhile, the system showed the highest COP_(thermal) utilizing R1233 zd(E) followed by that of R245 fa, with the R1336 mzz(Z) system having the lowest value. The differences between R1233 zd(E) and R1336 mzz(Z) systems, R1233 zd(E) and R245 fa systems were 4.33% and 2.0%, respectively. This paper was expected to provide a good reference for the utilizing prospect of R1233 zd(E) and R1336 mzz(Z) in ejector refrigeration systems.     

Experimental comparison of R245fa and R245fa/R601a for organic Rankine cycle using scroll expander

An experimental test was conducted to compare R245fa with R245fa/R601a on the organic Rankine cycle performance. The major objective of this paper is to ascertain the highest thermal efficiency and the optimal dimensionless volume ratio using the two working fluids. The experimental system consists of an electrically heated boiler, a vapor generator, a scroll expander, a condenser, a working fluid pump, and so on. For the typical weather conditions of May in Tianjin, the experiment results show that the working fluid charge has an important influence on the organic Rankine cycle performances. The optimal isentropic efficiency of the scroll expander corresponds to the design expansion ratio. Underexpanded and overexpanded processes result in the decline of the isentropic efficiency of the scroll expander, with the former playing a major role. R245fa/R601a improves the heat transfer performance in the vapor generator because of the nonisothermal phase change. The highest thermal efficiency for R245fa and R245fa/R601a is 4.38% and 4.45%, thereby illustrating that R245fa/R601a precedes R245fa. The optimal dimensionless volume ratios for R245fa and R245fa/R601a are 0.38 and 0.41, respectively. The experimental test lays foundation of the 500‐kW geothermal plant for demonstration in the next step. Copyright © 2014 John Wiley & Sons, Ltd.     

Performance evaluation of a low-temperature solar Rankine cycle system utilizing R245fa

A low-temperature solar Rankine system utilizing R245fa as the working fluid is proposed and an experimental system is designed, constructed and tested. Both the evacuated solar collectors and the flat plate solar collectors are used in the experimental system, meanwhile, a rolling-piston R245fa expander is also mounted in the system. The new designed R245fa expander works stably in the experiment, with an average expansion power output of 1.73 kW and an average isentropic efficiency of 45.2%. The overall power generation efficiency estimated is 4.2%, when the evacuated solar collector is utilized in the system, and with the condition of flat plate solar collector, it is about 3.2%. The experimental results show that using R245fa as working fluid in the low-temperature solar power Rankine cycle system is feasible and the performance is acceptable.     

Experimental investigation of moderately high temperature water source heat pump with non-azeotropic refrigerant mixtures

Experimental investigations were carried out on non-azeotropic refrigerant mixtures, named M1A (mass fraction of 20%R152a and 80%R245fa), M1B (mass fraction of 37% R152a and 63%R245fa) and M1C (mass fraction of 50%R152a and 50%R245fa), based on a water-to-water heat pump system in the condensing temperature range of 70–90 °C with a cycle temperature lift of 45 °C. Performance of R245fa was tested for comparison. Unfair factors in experimental comparative evaluation research with the same apparatus were identified and corrected. Experimental cycle performance of the mixtures were tested and compared with improved experimental assessment methodology. The results show that all of the mixtures deliver higher discharge temperature, higher heating capacity, higher COP and higher ε_h,c than R245fa. M1B presents the most excellent cycle performance and is recommended as working fluid for moderate/high temperature heat pump.     

R245fa作为有机朗肯循环工质的材料相容性研究

对于可再生能源和工业余热资源,有机朗肯循环技术(organic Rankine cycle,ORC)被认为是一种高效的能源回收利用技术。其中R245fa因为其自身良好的环保性以及热力性能,被认为是一种具有良好应用前景的ORC工质。对于ORC系统来说,工质的材料相容性是保证系统稳定运行的基础。针对ORC系统实际工况,确定部件、温度、材料等因素的对应关系,提出一套适用于ORC工质材料相容性研究的实验方法,并以R245fa为例开展了实验研究。实验结果表明,在高温条件下,304不锈钢与R245fa的相容性要优于铜材料;同时在橡胶密封材料的选择上,不建议使用氟橡胶,且三元乙丙橡胶的相容性要优于聚四氟乙烯。     

中温地热能驱动的跨临界有机朗肯-蒸气压缩制冷系统的性能分析

跨临界有机朗肯?蒸气压缩制冷系统可以使工质与地热流体更好地匹配,减小系统的不可逆性。本文建立该系统的热力学模型,利用EES软件编程,分别对以R143a、R218及R125为工质的系统进行性能分析。计算结果表明,相比R218及R125,以R143a为工质的系统的性能是最佳的。为了避免膨胀机内产生湿蒸气,对于一定的膨胀机进口温度,膨胀机入口存在一个极限压力,并且存在一个最优压力使得系统的性能最佳。地热流体温度的升高可以提高系统的制冷能力,但系统的性能系数则随之先增大后减小;随着地热流体干度的增加,地热流体释放的潜热会大大增加系统的制冷量,而系统的性能系数保持不变。冷凝温度及蒸发温度对系统性能有着重要影响,其中冷凝温度的影响更为明显。以R143a为工质的跨临界有机朗肯?蒸气压缩制冷系统的最佳性能优于以R245fa为工质的亚临界有机朗肯-蒸气压缩制冷系统的最佳性能。     

Optimum composition ratios of multicomponent mixtures of organic Rankine cycle for engine waste heat recovery

With the temperature glide in saturation states, the mixture working fluids have the advantages in thermal energy conversion. In this study, through the investigation in optimum mass fractions of multicomponent mixture working fluids, the economic performance enhancement of the organic Rankine cycle system is obtained for recovering waste heat from engine. The zero ozone-depletion-potential and dry working fluids of R236fa, R245fa, and R1336mzz(Z) are selected as the components of multicomponent mixtures in the system. The net power output, heat transfer calculation, and apparatus cost evaluation are employed to evaluate the power cost of the organic Rankine cycle system. Parameters of temperatures of waste heat sources and efficiencies of expanders are taken into account. The comparisons of economic performances for single-component working fluid and multicomponent mixtures with optimum mass fractions are proposed. The results show that R245fa, having a levelized cost of energy, LCOE, of 8.75 × 10⁻² $/kW-h, performs the best for single-component working fluids, better than R236fa by 1.6% and R1336mzz(Z) by 8.3%. All the two-component mixtures are superior to their single-component working fluids in economic performance. Among the three two-component mixture working fluids, R1336mzz(Z)/R236fa has the lowest LCOE_min, 8.57 × 10⁻² $/kW-h, followed by R236fa/R245fa and R245fa/R1336mzz(Z). In addition, R236fa/R245fa/R1336mzz(Z) mixture, which has a LCOE_min of 8.47 × 10⁻² $/kW-h, economically outperforms all other working fluids and has a lower LCOE_min than R236fa/R245fa by 1.7% and R245fa/R1336mzz(Z) by 2%.     

重型卡车朗肯−朗肯制冷系统热力学研究

本文针对重型卡车发动机冷却液余热工况,采用R245fa作为循环工质建立了朗肯−朗肯制冷系统,剖析了此系统的基本原理和结构特点,根据系统分析建立了数学模型,模拟分析了发生温度、冷凝温度、蒸发温度对系统性能的影响。结果表明：在发生温度85℃、冷凝温度50℃、蒸发温度5℃时,系统COP（coefficient of performance）达到0.254,虽然此系统的效率要低于相同工况下的吸收制冷循环,但是朗肯−朗肯制冷系统相对于吸收制冷系统具有尺寸小、易于控制和快速响应等优点,利用朗肯−朗肯循环回收重型卡车发动机冷却液余热进行制冷是可行的。     

A comparative study of pure and zeotropic mixtures in low-temperature solar Rankine cycle

The paper presents an on site experimental study of a low-temperature solar Rankine cycle system for power generation. The cycle performances of pure fluid M₁ (R245fa) and zeotropic mixtures M₂ (R245fa/R152a, 0.9/0.1) and M₃ (R245fa/R152a, 0.7/0.3) are compared, respectively, based on the experimental prototype. The experiments have been conducted under constant volume flow rate of different fluids. The results show that, with the component of R152a increasing, the system pressure level increases and the power output varies accordingly, which provides an additional means of capacity adjustment. The collector efficiency and thermal efficiency of zeotropic mixtures are comparatively higher than pure fluid of R245fa in the experimental condition, which indicates that zeotropic mixtures have the potential for overall efficiency improvement. Due to the non-isothermal condensation of zeotropic mixture, the condensing heat could be partially recovered by adding an external heat exchanger. Thus, compared with pure fluid R245fa the system overall efficiency of zeotropic mixtures could be improved.     

A combined power and ejector refrigeration cycle for low temperature heat sources

A combined power and ejector refrigeration cycle for low temperature heat sources is under investigation in this paper. The proposed cycle combines the organic Rankine cycle and the ejector refrigeration cycle. The ejector is driven by the exhausts from the turbine to produce power and refrigeration simultaneously. A simulation was carried out to analyze the cycle performance using R245fa as the working fluid. A thermal efficiency of 34.1%, an effective efficiency of 18.7% and an exergy efficiency of 56.8% can be obtained at a generating temperature of 395 K, a condensing temperature of 298 K and an evaporating temperature of 280 K. Simulation results show that the proposed cycle has a big potential to produce refrigeration and most exergy losses take place in the ejector.     

采用不同工质的高温复合热泵开水器特性研究

热泵开水器具有较高的能源利用效率,是公共场所电加热开水装置的理想替代品。从提高能源效率和一机两用的角度,构建了一种高温复合热泵开水器系统。建立了系统热力学模型,选R236fa、R245fa、R365mfc、R245ca、RC318和R236ea等6种较高临界温度的制冷工质,通过能量分析和[火用]分析的方法,探讨了不同制冷工质对高温复合热泵开水器系统性能的影响。研究结果表明:R245fa作为工质的高温复合热泵开水器系统具有最佳的性能,而以RC318作为工质的系统性能最差。在给定工况下,R245fa作为工质系统制热性能系数(COP_h)为2.47,而其制冷性能系数(COP_c)为3.37,[火用]损失和[火用]效率分别为9.47 kW和49.07%;与R245fa相比,RC318作为工质系统的总能耗增加了39.53%。     

太阳能驱动的有机朗肯-喷气增焓（带二次吸气的增效）蒸汽压缩制冷系统性能分析

为有效利用太阳能,以有机朗肯−喷气增焓（带二次吸气的增效）蒸汽压缩式制冷系统为研究对象,建立了系统的热力学模型,分别选取R236fa、R245fa、RC318和R141b作为系统工质,研究了发生温度、凝结温度、冷凝温度、蒸发温度、膨胀机等熵膨胀效率及压缩机等熵压缩效率对系统性能的影响,并以系统性能最佳为目标对工质进行了优选。计算结果表明：对整个系统而言,R141b是最合适的工质,凝结温度和冷凝温度对系统性能有重要影响。以R141b为例,当发生温度在85℃、凝结温度为40℃、冷凝温度为40℃、蒸发温度为 −15℃时,系统COP_s达到0.2528,采用喷气增焓技术对于环境温度很低、太阳能资源丰富的北方地区具有很大的优势。     

低GWP工质闪蒸补气式高温热泵性能对比

高温热泵作为一种有效的节能技术可以满足大多数的工业用热需求,遴选安全、环保、高效的制冷剂是当前高温热泵技术研究的重要工作之一。针对闪蒸补气式高温热泵,基于EES（Engineering Equation Solver）软件建立系统数学模型,以性能系数（COP）、制热量、单位容积制热量、冷凝压力、压缩比以及压缩机排气温度为性能指标,在冷凝温度 ≥ 100℃,温升分别为40℃、50℃和60℃工况下,对R1224yd(Z)、R1233zd(E)、R1336mzz(Z)和R1234ze(Z) 四种氢氟烯烃制冷剂在闪蒸补气式热泵系统中的应用潜力进行分析,并与R245fa比较。结果表明,R1336mzz(Z) 的COP最大、冷凝压力最低,但单位容积制热量最小,相对适用于小容量供热系统;R1234ze(Z)的单位容积制热量最大,且COP与R245fa相当,是R245fa的良好替代工质,尤其适用于大容量高温升供热系统;R1233zd(E) 虽然单位容积制热量偏低,但其COP、制热量和冷凝压力相对R245fa具有显著优势,亦可作为R245fa的替代工质;与R245fa相比,R1224yd(Z) 的热力性能无明显优势。     

Critical Heat Flux of R134a and R245fa Inside Small-Diameter Tubes

This article presents new experimental critical heat flux results under saturated flow boiling conditions for a macro-/microscale tube. The data were obtained in a horizontal 2.20-mm inside diameter stainless-steel tube with heating lengths of 361 and 154 mm, R134a and R245fa as working fluids, mass velocities ranging from 100 to 1500 kg/m²-s, critical heat flux from 25 to 300 kW/m², exit saturation temperatures of 25, 31, and 35°C, and critical vapor qualities ranging from 0.55 to 1. The experimental results show that critical heat flux (CHF) increases with increasing mass velocity and inlet subcooling but decreases with increasing saturation temperature and heated length. The data also indicated a higher CHF for R245fa when compared with R134a at similar conditions. The experimental data were compared against four CHF predictive methods and the results of the comparisons are reported.     

不同工质对太阳能有机朗肯循环系统性能的影响

循环工质的特性是影响有机朗肯循环系统性能的重要因素之一,在不同的蒸发温度条件下,选取R600、R600a、R245fa、R236fa、R236ea、R601、R601a、RC318及R227ea共9种有机工质,基于热力学第一定律和第二定律对其热力循环特性进行了计算分析,并对各有机工质的蒸发压力、热效率、功比和不可逆损失等进行了比较.结果表明：R245fa作为太阳能低温热发电朗肯循环系统的循环工质具有较高的热效率和效率,并且产生的系统总不可逆损失较小,是一种较理想的有机工质;其次,R236fa和R236ea作为系统循环工质也具有较为良好的性能.     

R245fa阻燃特性理论与试验研究

分析了R245fa的阻燃,试验研究了R245fa在电打火(点火能约为100 J)和普通打火机点火两种条件下对R290、R152a、DME、R600a的阻燃特性,提出了新的评判阻燃组分阻燃特性强弱的指标(阻燃系数K),并对R245fa作用于各可燃工质的阻燃效果进行分类．试验结果表明,点火能大小、点火源形式对可燃工质燃爆极限影响很大；R245fa对碳氢类可燃工质阻燃效果差；对HFC类的阻燃效果相对较好；R245fa的阻燃效果比R134a的差．     

两种三维双侧强化管管外R245fa凝结换热的实验对比

为研究环保制冷剂R245fa在水平强化管外凝结换热特性及表面结构对管内外换热性能的影响,分别对三维齿结构低肋管(A管)和斜翅管(B管)进行管外凝结换热实验。在数据处理方法上,采用Wilson-Gnielinski图解法获得管内水侧对流换热系数及其计算关联式,再利用热阻分离法获得管外凝结换热系数。实验结果分析得出A管和B管的管内换热系数强化倍率分别为2.04和2.98,管外强化倍率分别为1.77～1.94,1.87～2.14,B管管内外换热性能都优于A管,造成两种强化管内外换热性能差异的主要因素是强化管内的螺纹高度和管外翅化比。     

余热驱动的有机朗肯循环-复叠式制冷系统?分析

针对余热的有效利用,建立了有机朗肯循环-复叠式制冷系统的热力学模型,其中:有机朗肯循环系统分别采用R123、R1234ze、R245fa、R600a、RC318、R141b等六种工质;复叠式制冷系统分别采用R22/R23、R404/R23、R290/R744、R717/R744等四种工质对。选择系统?效率作为性能评价指标,运用热力学第二定律研究系统运行参数对系统?效率的影响,分析了系统各部件的?损失,并指出了能量利用的薄弱环节,提出了有效提高系统性能的建议,为系统的优化提供参考。结果表明,对系统?效率而言,R141b和R717/R744是最佳工质。系统主要部件按?损失大小依次为凝汽器、膨胀机、高温级冷凝器、发生器、高温级压缩机、低温级蒸发器、蒸发冷凝器。尽可能提高压缩机的等熵效率,优化设计换热器的结构,减小传热温差,才能减少不可逆损失,提高换热器的?效率。     

Comparison of a Basic Organic Rankine Cycle and a Parallel Double-Evaporator Organic Rankine Cycle

ABSTRACT

The applications of zeotropic mixtures and multi-evaporator systems are two viable options to improve the performance of the organic Rankine cycle (ORC). This paper conducts the thermo-economic comparison of a basic ORC with R245fa/R600a and a parallel double-evaporator organic Rankine cycle (PDORC) with R245fa. Four indicators are used to evaluate the system performance: net power, cycle efficiency, area of heat exchangers, and area of heat exchangers per net power output. Submodels of condensers and evaporators are established specially for pure organic fluids and zeotropic mixtures. The performance optimization using genetic algorithm is conducted to compare the two systems quantitatively. The optimization indicates a zeotropic mixture is more profitable than a pure work fluid in a basic ORC with a worthy additional investment of heat exchanger. Though PDORC can increase net power obviously, it would decrease the thermo-economic performance of ORC.     

Preliminary analysis of compound systems based on high temperature fuel cell, gas turbine and Organic Rankine Cycle

This article presents a novel proposal for complex hybrid systems comprising high temperature fuel cells and thermal engines. In this case, the system is composed by a molten carbonate fuel cell with cascaded hot air turbine and Organic Rankine Cycle (ORC), a layout that is based on subsequent waste heat recovery for additional power production. The work will credit that it is possible to achieve 60% efficiency even if the fuel cell operates at atmospheric pressure.The first part of the analysis focuses on selecting the working fluid of the Organic Rankine Cycle. After a thermodynamic optimisation, toluene turns out to be the most efficient fluid in terms of cycle performance. However, it is also detected that the performance of the heat recovery vapour generator is equally important, what makes R245fa be the most interesting fluid due to its balanced thermal and HRVG efficiencies that yield the highest global bottoming cycle efficiency. When this fluid is employed in the compound system, conservative operating conditions permit achieving 60% global system efficiency, therefore accomplishing the initial objective set up in the work.A simultaneous optimisation of gas turbine (pressure ratio) and ORC (live vapour pressure) is then presented, to check if the previous results are improved or if the fluid of choice must be replaced. Eventually, even if system performance improves for some fluids, it is concluded that (i) R245fa is the most efficient fluid and (ii) the operating conditions considered in the previous analysis are still valid.The work concludes with an assessment about safety-related aspects of using hydrocarbons in the system. Flammability is studied, showing that R245fa is the most interesting fluid also in this regard due to its inert behaviour, as opposed to the other fluids under consideration all of which are highly flammable.