Fluid In Organic Rankine Cycle Research Articles

Energy and parametric analysis of Organic Rankine Cycle combined with a vapor compression refrigeration cycle (ORC-VCR) system using natural refrigerants

The dependency on fossil fuels for power generation can be reduced by enhancing the energy efficiency of power generating systems. The refrigeration systems that typically use electricity consume a significant portion of the electricity supplied to cities. The STAND-ALONE refrigeration system which consists of a combined Organic Rankine Cycle and Vapor Compression (ORC-VCR) system is analyzed using the first law of thermodynamics. Dry natural hydrocarbons such as n-Dodecane is used as the working fluid in Organic Rankine Cycle (ORC) and natural Working fluid such as isobutane (R600a) is utilized in Vapor Compression Refrigeration (VCR) Cycle. The study shows that the system can be driven efficiently with Low-grade waste heat from industries or thermal energy from renewable energy sources typically in the range from 1000C to 3500C thus reducing reliance on fossil fuel sources. The results also show that the overall Coefficient of performance COP overall of the system and the energy efficiency of the ORC was greatly affected by the evaporation temperature of ORC, Teva_ORC followed by, the evaporation temperature of VCR, Teva_VCR. The maximum COP overall of the system was found to be 0.558 and the energy efficiency of ORC was found to be 20.69% for Teva_ORC of 3150C and Teva_VCR of -300C.

Multi-objective optimization and algorithm improvement on thermal coupling of SOFC-GT-ORC integrated system

Optimizing thermal coupling of an integrated system and improving its energy cascade utilization (ECU) level are important ways to improve system performance. An integrated power generation system consisting of an anode recirculation internal reforming solid oxide fuel cell (ARIR-SOFC), a gas turbine (GT), an organic Rankine cycle (ORC) waste heat recovery system and a liquefied natural gas (LNG) supply system is established. Additionally, heat exchange network (HEN) subsystem formed by heat exchange streams is specially considered to further improve ECU level. Optimization model is proposed where HEN scheme is optimized simultaneously with operating parameters and working fluids of ORC. Because of the complexity of model, it is key to focus on the solution strategy. An adaptive improved multi-objective particle swarm optimization (IMOPSO) algorithm is established to improve diversity and accuracy of solutions. Finally, a case is solved and results show that HEN scheme plays an important role in system performance.

Energy, exergy and economic benefits deriving from LNG-fired power plant: Cold energy power generation combined with carbon dioxide capture

According to The Paris Agreement, countries need to strictly control carbon emissions before global warming causes great damage to the environment. Therefore, how to reduce carbon emissions to restore carbon neutrality has become an inevitable life-and-death matter for all countries from a long-term perspective. In view of the ever-increasing LNG-fired power plants and the wasted LNG cold energy in vaporization process, a new environment-friendly cold energy utilization method is proposed to meet energy conservation and pollution reduction targets in this paper, integrating the organic Rankine cycle and the carbon dioxide capture cycle. Moreover, a full and deliberate comparison of pure and binary fluids is made to determine the optimal fluids of organic Rankine cycle (R600a) and carbon dioxide capture cycle (NH3+R125), respectively. After being optimized by genetic algorithm, the thermal efficiency is 33.7% and exergy efficiency reaches 47.2%. Meanwhile, the net specific work and total carbon dioxide capture generated by the system are 110.1 kWh/tLNG and 0.78 t/tLNG. In terms of economic benefit, this cold energy utilization system can recover the total investment cost in 1.85 years. Thus, the practical application of this proposed method is completely feasible and economical, and it can recover capital in a short time.

Solar driven micro-ORC system assessment for residential application

The purpose of this study is to estimate the electricity production obtainable by coupling an existing kW-size recuperated Organic Rankine Cycle (ORC) prototype with a commercial solar thermal collector to reduce the yearly electricity purchased by a single-family user. A detailed semi-empirical steady-state model, validated against experimental data, is employed for the power plant simulation. The optimal sizes of both the collector surface and the storage tanks were assessed considering that a solar collector surface larger than 32.25 m2 would lead the micro-ORC working in off-design conditions; while storage volumes higher than 6000 l become too large to be completely exploited.Then, different low global warming potential fluids and blends were simulated for comparison with HFC-134a, the reference fluid for low-temperature ORC. Results show that the integrated system working with R134a can cover approximately 39% of the yearly electricity demand, corresponding to more than 1150 kWh. The replacement of R134a with the alternative fluids results in a penalization in the output electric power, related to thermodynamic properties such as density, liquid viscosity, and latent heat. Indeed, with R1234yf barely 16% (466 kWh) of the yearly electricity demand is covered; whilst the blend R513A allows to reach only 17.5% (525 kWh).

A comparative investigation on the flame inhibition characteristics and mechanism of 1,1,2,3,3,3-hexafluoro-1-propene (R1216)

R1216 (1,1,2,3,3,3-hexafluoro-1-propene), which has a low global warming potential, is regarded as the new generation of environmentally friendly working fluid in ORCs (organic Rankine cycle) and refrigeration systems. Besides, it also has the advantage of nonflammable property. Thus, R1216 can be mixed with some flammable working fluids to develop new mixed alternatives, which can possess a combination of chemical, environmental, thermodynamic, and safety properties. In this work, the flammability limits of R1216/R32 and R1216/R152a were measured in a 12L spherical glass vessel according to the method of ASTM E681. And the critical flammable volumetric ratios of R1216 on R32 and R152a were about 0.15 and 1.1, respectively. This study also found that the ratio of F atoms to H atoms for the two mixtures had a close relationship with the flammability limit ranges. Finally, the flame inhibition performances of R1216 were compared with other commonly used flame retardants, such as R134a, R13I1 (trifluoroiodomethane), and R1233zd(E) (trans-1-Chloro-3,3,3-trifluoro-propene). It can be concluded that the rank of the inhibition effects was R1216 > R13I1 > R134a > R1233zd(E). And a flame retardant, which contained a higher F/H ratio and much more Cl, I, and CF3 radicals, can possess a higher flammability inhibition efficiency.

A rigorous approach for characterising the limiting optimal efficiency of working fluids in organic Rankine cycles

Organic Rankine cycles (ORCs) are a standard and simple layout to convert thermal energy to mechanical energy and, subsequently, electrical energy. On the one hand, it is essential to select the proper working fluids. On the other hand, criteria to choose optimal operation conditions are also necessary. This contribution presents a rigorous and general approach based on the Helmholtz energy function to analyse the optimal performance of an organic Rankine cycle irrespective of the working fluid. The new approach is applied for the n-alkane series and a set of refrigerants using the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state as a calculation tool. The study reveals that a dry global optimum cannot be achieved without partial condensation, and guidelines to avoid this fact are shown. Also, it is parametrically demonstrated that the optimum behaviour of an organic Rankine cycle is not directly connected to the isentropic behaviour of the fluids. However, it is proved that a slightly dry fluid is more suitable for a good performance than a very dry fluid, because the optimum range of expansion lies in a feasible range of temperature, avoiding problems with the limit of the solid phase.

Measurement of kinematic viscosity and thermal conductivity of 3,3,4,4,5,5-HFCPE in liquid and vapor phases

1H, 2H-hexafluorocyclopentene (3,3,4,4,5,5-HFCPE) is being expected as a suitable alternative working fluid for organic Rankine cycles and high-temperature heat pumps due to the attractive environmentally friendly properties, particularly for the low GWP value. The key objectives are to measure the kinematic viscosity and thermal conductivity of 3,3,4,4,5,5-HFCPE in both liquid and vapor phases, as well as to establish simple correlations at saturation conditions. In this study, the kinematic viscosity measurements were performed by the tandem capillary tubes method over the pressures up to 4.0 MPa and temperatures from 332 to 494 K for the liquid phase and from 413 to 514 K for the vapor phase. The measurement uncertainties were calculated using the propagation law of uncertainties by the GUM guideline, where the expanded uncertainties were estimated at 2.2% for the liquid phase and 2.9% for the vapor phase with k = 2 and a 95% confidence level. On the other hand, the thermal conductivity measurements were performed by the transient hot-wire technique at pressures up to 4.0 MPa and temperatures from 333 to 473 K for the liquid phase, and from 393 to 473 K for the vapor phase. The expanded uncertainties were calculated as 3.0% and 3.5% for liquid and vapor phases with k = 2 and a 95% confidence level, respectively. Also, simple correlations were developed to predict the kinematic viscosity and thermal conductivity at saturated conditions.

Performance Assessment of Solar Parabolic Trough Collector-Assisted Combined Organic Rankine Cycle and Triple Pressure Level Ejector-Absorption Refrigeration Cycle

Abstract A novel solar-assisted combined power and cooling system comprising a parabolic trough collector (PTC) assisted organic Rankine cycle (ORC) and ejector-absorption cooling cycle (EARC) is presented and analyzed in this paper. The use of Ammonia-Lithium Nitrate (NH3-LiNO3) as the working pair in EARC is investigated. First and second law thermodynamics analysis revealed that PTC accounted for 60–80% of the total exergy destruction. Using different ORC fluids revealed that Toluene showed the best performance. The energy utilization factor of Toluene is found to be 25.31% at turbine inlet temperature of 550 K and solar irradiation of 1 kW/m2, whereas for other ORC fluids like R134a (tetrafluoroethane, CH2FCF3), R245fa (pentafluoropropane, CF3CH2CHF2), n-pentane, R410a (near azeotropic mixture of difluoromethane, CH2F2 and pentafluoroethane, C2HF5), it was found to be 17–20%. The exergy efficiency of the combined system using Toluene has reached up to 17%, while the rest of the ORC fluids exhibited 8–12% exergy efficiency. The pump power consumption was significantly reduced due to the use of the ejector in the EARC. Generator temperature and solution heat exchanger (SHX) effectiveness were also found to highly influence the performance of the refrigeration system.

Performance evaluation of small scale solar organic Rankine cycle using MWCNT + R141b nanorefrigerant

The principal purpose of the current investigation is to analyze the thermal performance of a small scale solar organic Rankine cycle (ORC). Herein, a flat plate solar collector (FPSC) was utilized to feed heat to ORC. A mathematical model formulated in Engineering Equation solver (EES), uses FPSC’s experimental output to assess the thermal performance of ORC. To choose the most appropriate organic fluid for ORC, a preliminary study is conducted for the comparison of the performance of R141b with other organic fluids of previous research studies. In the preliminary analysis of this study, the MWCNT + WO3/water nanofluid is used in the solar collector for its performance enhancement and obtained a maximum thermal efficiency of 73.21% at 3 lpm and 1.5 vol%. Moreover, MWCNT/R141b nanorefrigerant is used as an organic fluid in ORC due to its enhanced thermophysical properties. The parametric analysis is also executed to compute the energetic and exergetic performance of ORC at different nanoparticle concentrations and volume flow rates. The parametric study demonstrated a significant increment from 16.30 to 24.82% and 9.03 to 15.33% in energy and exergy efficiency, respectively, for 0.5 vol% of nanorefrigerant and 3 lpm volume flow rate in collector when nanofluid volumetric concentration changes from 0.5 to 1.5 vol%.

A ReaxFF-based molecular dynamics study of the pyrolysis mechanism of hexamethyldisiloxane

Hexamethyldisiloxane (MM) is one of the commonly used working fluids of organic Rankine cycle at medium and high temperatures, but there is a risk of decomposition of organic working fluids in high temperature environment. In this study, the pyrolysis mechanism of MM is analyzed by using ReaxFF force field and density functional theory (DFT). During the simulation process, three initial reaction routes were observed. By calculating the reaction energy barriers, it is found that the fracture of C-Si bond is the main initial reaction of pyrolysis. In the MM pyrolysis process, small molecule gases such as CH4, C2H6 and H2, linear siloxane represented by C8H24O2Si3（MDM）are the main thermal decomposition products. Free radical attacking reaction and free radical binding reaction are the main formation mechanism of methane. The intermediate condensation reaction is the formation mechanism of MDM. Most of the chain reactions are exothermic reactions, which can provide the energy for the system and further promote the decomposition of MM.

Selection of working fluids for solar organic Rankine cycle—A review

The performance of renewable energy systems can be significantly improved if power is produced from low-temperature heat sources. The organic Rankine cycle (ORC) is suitable for producing power from low-temperature heat sources. ORC finds applications alongside solar power, geothermal power, waste heat and biomass. ORC-enabled systems can contribute significantly to raising the effectiveness of renewable power sources. Solar power, for example, can deliver affordable electricity to remote locations and small industries. By employing ORC, power generation is possible at lower temperatures on cloudy days. Its main difference from the steam Rankine cycle is its working fluid. The ORC makes use of an organic, high molecular mass fluid as the working fluid. Compared to steam Rankine cycles, ORC works at a lower temperature (<250°C) and pressure. The only working fluid in the steam Rankine cycle is water, but the ORC can operate on hundreds of different working fluids. The design and performance of ORC systems are entirely dependent upon the suitable working fluid and, hence identification of the working fluid for ORCs is of utmost importance for diverse applications. Properties of working fluid have a considerable impact on the efficiency of the system. The main objective of this study is to identify the most suitable organic fluids having characteristics necessary for use in solar ORCs. In addition, a detailed review of the various types of heat transfer fluids now available in the market that are often used in ORC systems was conducted. This research assists in selecting the most appropriate organic fluids for various solar ORC applications in terms of operating circumstances.

Thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid for organic Rankine cycle

Organic Rankine Cycle (ORC) is an effectively technology for the utilization of industrial waste heat and renewable energy. Zeotropic working fluids are more attractive than pure working fluids due to their lower exergy losses, higher cycle efficiencies and higher work outputs. The thermal stability is the major limitation factor for the selection of working fluid in the high temperature ORCs. This paper investigates the thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid by using ReaxFF reactive molecular dynamic simulations and density functional theory calculations. The thermal decomposition process, the effects of temperature and HFC-227ea to n-hexane ratio on the thermal decomposition of HFC-227ea/n-hexane zeotropic working fluid, and the interaction between HFC-227ea to n-hexane for the thermal stability of zeotropic working fluid were investigated. The results showed that the hydrogen bond formed between HFC-227ea and n-hexane in HFC-227ea/n-hexane zeotropic working fluid improved the thermal stability of n-hexane and weakened the thermal stability of HFC-227ea. Therefore, the thermal stability of the HFC-227ea/n-hexane zeotropic working fluid is better than that of pure n-hexane and weaker than that of pure HFC-227ea.

Selection of working fluid for organic Rankine cycle used in low temperature geothermal power plant

In this paper, for the low-temperature geothermal organic Rankine (ORC) power generation system, the subcritical saturated vapor cycle is selected as the key research object, the mathematical and physical model of the thermal process of the ORC system is established, and five organic working fluids are selected. With the net power produced per unit mass of geothermal water(PPH) as the optimization target, the optimal parameters of the ORC system are determined. Based on the selection of the best organic working fluid, various parameters that affect the performance and economic performance of the ORC system are analyzed. After simulation calculation, the results show that: when the system takes PPH as the optimization target, the working fluid R245fa can be selected as the best applicable working fluid.

Techno-economic performance of the 2-propanol/1-butanol zeotropic mixture and 2-propanol/water azeotropic mixture as a working fluid in Organic Rankine Cycles

The techno-economic performance of the novel 2-propanol/1-butanol zeotropic mixture and 2-propanol/water azeotropic mixture as a working fluid in Organic Rankine Cycles (ORC) for waste heat recovery applications is analyzed. The ORC with two different architectures is modeled in the Aspen Plus V.10 environment for heat recovery from hot gases at 250 and 350 °C with atmospheric and sub-atmospheric condensation scenarios. The effects of different heat source/sink conditions on the performance of zeotropic mixture are studied in detail to show under which condition the zeotropic mixtures may result in higher efficiencies. The propanol/butanol mixtures (P/B) rich in propanol and propanol/water mixtures (P/W) with composition near the azeotropic point can result in 15–75% higher overall efficiencies compared to toluene and MM. However, cyclopentane shows higher efficiencies than these mixtures when atmospheric condensation is considered. According to the economic assessment, the 55%P/45%W and 75%P/25%B mixtures lead to superior results for the atmospheric condensation scenario compared to other fluids. Also, it was found that only under a tailored boundary condition, the zeotropic mixture can perform superiorly compared to the most efficient component in the mixture.

Multi-objective optimisation of supercritical CO&lt;SUB align=right&gt;2 combined cycles based on energy-exergy-economy balanced analysis

In this paper, the supercritical CO2 (sCO2) recompression cycle combined cycles are analysed, where the bottom cycles include transcritical CO2 (tCO2), organic Rankine cycle (ORC) or trilateral flash cycle (TFC). The working fluid for the ORC and the TFC can be R123, R245fa, or n-Pentane. We implemented four sub-models in our calculation: 1) thermodynamic model; 2) heat transfer model; 3) economic model; 4) exergoeconomic model. The specific exergy costing (SPECO) method is utilised in the exergoeconomic model, and the multi-objective genetic algorithm is adopted to give the Pareto front of total unit exergy cost of the product (cPtot) and the thermal efficiency. Our model has been validated with the existing literature. The results show that the thermal efficiency standalone CO2 achieved 41.66% while attaching the tCO2, ORC, or TFC bottom cycle could improve the thermal efficiency by 1.1%, 1.68%, or 0.05%, respectively. In the meantime, the (cPtot, which is the representation of the cost, decreased by 0.2$/GJ for ORC and increased by 0.06$/GJ and 1.05$/GJ for tCO2 and TFC respectively. The influence of different working fluids for ORC and TFC is not obvious. Therefore, attaching the ORC as the bottom cycle will bring about the best performance and lowest cost.

Configuration Selection of the Multi-Loop Organic Rankine Cycle for Recovering Energy from a Single Source.

The Organic Rankine Cycle (ORC) is a well-established way to recover energy from a single waste heat source. This paper aims to select the suitable configuration, number of loops, and working fluids for the Multi-Loop ORC (MLORC) by using multi-objective optimization. The thermodynamic and economic performance of MLORC in three various configurations was analyzed. Multi-objective optimizations of the series and parallel MLORC using different working fluid groups were conducted to find the optimal configuration, number of loops, and working fluid combination. The analysis results show that the series–parallel MLORC performed the worst among the three configurations. The optimization results reveal that series MLORC has a higher exergy efficiency than the parallel MLORC. The exergy efficiency of the optimal solution in series dual-loop, triple-loop, and quadruple-loop ORC is 9.3%, 7.98%, and 6.23% higher than that of parallel ORC, respectively. Furthermore, dual-loop is the optimal number of cycles for recovering energy from a single heat source, according to the grey relational grade. Finally, the series dual-loop ORC using cyclohexane\\cyclohexane was the suitable configuration for utilizing a single waste heat source. The exergy efficiency and levelized cost of electricity of the series dual-loop ORC with the optimal parameters are 62.18% and 0.1509 $/kWh, respectively.

Thermodynamic design and parametric performance assessment of a novel cogeneration solar organic Rankine cycle system with stable output

In areas rich in solar energy, meeting the energy requirement using renewable energy sources can address environmental issues by reducing the use of fossil fuels. In this study, thermodynamic design, simulation, daily and monthly evaluation of a novel cogeneration solar organic Rankine cycle (ORC) system with the capability of electricity and domestic hot water (DHW) production with stable output are performed under transient environmental conditions. The main components of the integrated system are a solar field based on parabolic dish concentrators (PDCs), a direct thermal energy storage (TES) system using two separate tanks, and an ORC power field which was modeled using TRNSYS software. In this system, intending to generate 200 KW of electricity, Benzene fluid in a recuperative ORC indicated a better performance than Cyclohexane, Toluene, and n-Hexane fluids with an energy efficiency of 21.89% and the lowest required inlet temperature for the turbine as 266.1 °C. The highest working hours of the system were obtained in the middle months of the year with an average DHW production of 12.8 h/day (more than 200 m3/day) and 9.1 h of electricity generation. While during the coldest month of the year (December), the system could provide 4.1 h of DHW with 74.5 m3/day of storage. Also, with the annual average of energy efficiency for the solar field as 78.9%, thermal and electric efficiency of the integrated system was calculated as 69.4% and 15.08%, respectively. From the economic analysis of the proposed system, the net annual benefit of the system and return of capital’s period were calculated as 150,815.3 US$ and 7.3 years, respectively.

Multi-objective teaching-learning-based optimization of combined commercial fuel cells for electricity production

In this research, an organic Rankine cycle (ORC) is run by the recovered heat from different commercial fuel cells and optimized to find the best configuration from the thermos-economic point of view for different refrigerants. We considered a multi-objective optimization approach based on teaching learning based optimization, referred to as the MOTLBO, which allows efficient and accurate determination of the optimum solutions, As a result, both the total cycle efficiency and price of electricity that are in conflict with each other have been selected as the objective functions, and six design variables have been selected. It has been tried to find the best working fluid as well as the best fuel cells from an economic and thermal efficiency point of view. The paper incorporates equipment selection for the different fuel cells, and cost corrections to estimate the investment cost, with the overall goal of the designing an optimal ORC system by considering different working fluids. Based on multi-objective optimization, the paper finds that R123 is the optimal fluid for ORC based the thermo-economic performance in the cases of all fuel cells except the MCFC (300 kW). We also conducted a parametric study for determination of the effect of varying selected design parameters on the overall efficiency and electricity cost to make comparisons. In all fuel cells except the PEMFC, the highest and lowest pressure ratios are needed when applying R123 and R134a, respectively. In addition, the effect of ORC mass flow rate has been investigated for different configurations using different working fluids. Finally, the results achieved for the design parameters in the case of different fuel cells have been discussed and compared.

A high-efficiency scheme for waste heat harvesting of solid oxide fuel cell integrated homogeneous charge compression ignition engine

Facing the energy shortage and environmental pollution problems in the world, a high-efficiency fuel cell scheme combined with waste heat recovery is regarded as an optimal selection of auxiliary power generation equipment for ships. In this study, a novel system, comprising solid-oxide-fuel-cell-preheating subsystem, homogeneous charge compression ignition engine and organic Rankine cycle, is designed and analysed. First, the mathematical model is established and verified to ensure the reliability of simulation results. Then, the effect of relevant parameters on homogeneous charge compression ignition engine performance is observed, and the optimal zeotropic working fluid of organic Rankine cycle is determined according to the exhaust temperature. Finally, the thermodynamic and economic analysis are carried out. The results indicate that the performance of the new system is better than that of the traditional combined system using gas turbine. Thermal efficiency and exergy efficiency of the system are more than 63.6% and 61.3%, which is about 18.76% and 17.95% higher than that of simple cell. In addition, the payback time is about 2.98 years, which is about half of the traditional combined system and can fully meet the economic requirements. This novel system can be a new selection of marine auxiliary power generation equipment.

Process Systems Engineering Evaluation of Prospective Working Fluids for Organic Rankine Cycles Facilitated by Biogas Combustion Flue Gases

The organic Rankine cycle (ORC) has recently emerged as a practical approach for generating electricity from low-to-high-temperature waste industrial streams. Several ORC-based waste heat utilization plants are already operational; however, improving plant cost-effectiveness and competitiveness is challenging. The use of thermally efficient and cost-competitive working fluids (WFs) improves the overall efficiency and economics of ORC systems. This study evaluates ORC systems, facilitated by biogas combustion flue gases, using n-butanol, i-butanol, and methylcyclohexane, as WFs technically and economically, from a process system engineering perspective. Furthermore, the performance of the aforementioned WFs is compared with that of toluene, a well-known WF, and it is concluded that i-butanol and n-butanol are the most competitive alternatives in terms of work output, exergy efficiency, thermal efficiency, total annual cost, and annual profit. Moreover, the i-butanol and n-butanol-based ORC systems yielded 24.4 and 23.4% more power, respectively, than the toluene-based ORC system; in addition, they exhibited competitive thermal (18.4 and 18.3%, respectively) and exergy efficiencies (38 and 37.7%, respectively). Moreover, economically, i-butanol and n-butanol showed the potential of generating 48.7 and 46% more profit than that of toluene. Therefore, this study concludes that i-butanol and n-butanol are promising WFs for high-temperature ORC systems, and their technical and economic performance compares with that of toluene. The findings of this study will lead to energy efficient ORC systems for generating power.