Organic Fluids Research Articles

Use of Organic and Copper-Based Nanoparticles on the Turbulator Installment in a Shell Tube Heat Exchanger: A CFD-Based Simulation Approach by Using Nanofluids

Heat exchangers with unique specifications are administered in the food industry, which has expanded its sphere of influence even to the automotive industry due to this feature. It has been used for convenient maintenance and much easier cleaning. In this study, two different nanomaterials, such as Cu-based nanoparticles and an organic nanoparticle of Chloro-difluoromethane (R22), were used as nanofluids to enhance the efficiency of heat transfer in a turbulator. It is simulated by computational fluid dynamics software (Ansys-Fluent) to evaluate the Nusselt number versus Reynolds number for different variables. These variables are diameter ratio, torsion pitch ratio, and two different nanofluids through the shell tube heat exchanger. It is evident that for higher diameter ratios, the Nusselt number has been increased significantly in higher Reynolds numbers as the heat transfer has been increased in turbulators. For organic fluids (R22), the Nusselt number has been increased significantly in higher Reynolds numbers as the heat transfer has been increased in turbulators due to the proximity of heat transfer charges. At higher torsion pitch ratios, the Nusselt number has been increased significantly in the higher Reynolds number as the heat transfer has been increased in turbulators, especially in higher velocities and pipe turbulence torsions.

The Optimal Design on the Molecular Structure of a Fluid Transport Inhibitor Applied to Reinforced Concrete Structures.

Inhibiting the penetration of water molecules and aggressive ions is of considerable significance in improving the durability of reinforced concrete structures. In this work, molecular dynamics(MD) is employed to design a high-efficiency organic fluid transport inhibitor. MD results indicate that there is mutual complementation between the hydrophilic and hydrophobic functional groups in the chemical structure of this polymer. One end with the carboxyl groups can stably adsorb on the surface of the cementitious matrix due to the strong attraction from calcium ions. Simultaneously, the rest of the hydrophobic part of the polymer can stand up to maximize the repelling effect on the penetration of fluids. Furthermore, for high cost-effectiveness performance, the minimum number and the optimum position of the carboxyl groups of one polymer inhibitor have been determined. As the molecular structure contains two hydrophilic groups, only if located at the same end, the polymer chain can display the most preferable adsorption morphology.

Design and performance analysis of compressed CO2 energy storage of a solar power tower generation system based on the S-CO2 Brayton cycle

Two kinds of S-CO2 Brayton cycle tower solar thermal power generation systems using compressed CO2 energy storage are designed in this paper. The energy storage system uses excess solar energy to compress CO2 near the critical point to a high-pressure state for energy storage during the day, and the high-pressure CO2 is heated by a gas-fired boiler or the heat of stored high-temperature molten salt at night, so that it enters the turbine for work and drives the generator to generate electricity. The traditional molten salt heat storage scheme and the proposed compressed CO2 energy storage system model are established with Ebsilon software, and then the equipment selection, structure layout, and parameter design processes are carried out for the energy storage and heating systems. The thermoeconomic and technoeconomic indexes of the three energy storage schemes are calculated under the operating conditions of a typical day. The results show that the efficiency of the combined cycle is higher than that of other organic working fluids when T-CO2 is used as the bottom cycle working fluid. The integrated scheme of compressed CO2 energy storage and auxiliary combustion has the highest average daily efficiency (26.62% on summer solstice and 23.04% on winter solstice) and the lowest initial equipment investment. However, due to the additional cost of natural gas, the scheme has the highest levelized cost of energy (LCOE) at $0.1168/kWh. The LCOE of the integrated scheme of compressed CO2 energy storage and molten salt heat storage was the lowest at $0.1046/kWh.

Performance analysis and optimisation of a reheat organic Rankine cycle

ABSTRACT A reheat Organic Rankine Cycle (ORC) is investigated to recuperate a low-grade heat source using six different organic working fluids (WFs). The results indicate that wet fluids produce more power output compared to dry and isentropic fluids. The reheat pressures of the selected WFs were optimised to maximise the exergy efficiency and minimise the total UA. Reheat pressure ranges of 27–48% and 45–54% of the evaporation pressure were obtained, for ORCs with and without IHE, respectively. A maximum of 49.1% exergetic efficiency is achieved by the addition of IHE: a 13.6% improvement compared to the ORC without IHE. Finally, the results indicate that R236ea and propyne are the best WFs for the ORC with and without IHE, respectively.

Nonlinear wave propagation in dense vapor of Bethe–Zel'dovich–Thompson fluids subjected to temperature gradients

Flows of fluids made of complex organic molecules exhibit unconventional fluid dynamic behavior in the vapor phase if their thermodynamic state is close to that of the vapor–liquid critical point. If the molecule is sufficiently complex, this thermodynamic domain is characterized by negative values of the fundamental derivative of gasdynamics Γ, the fluid is called Bethe–Zel'dovich–Thompson (BZT) fluid, and atypical phenomena, such as rarefaction shockwaves, are theoretically admissible. The nature of the steepening of nonlinear waves in dense vapor flows of organic fluids evolving in this thermodynamic region can be significantly affected by the presence of temperature gradients in the flow. This study investigates the evolution of finite-amplitude acoustic waves in these conditions. The steepening of the wavefront is analyzed using the wavefront expansion technique, and the deformation of the wavefront is simulated numerically by solving the Westervelt equation. The results of simulations of wave propagation in dense vapors indicate that, though Γ governs the nature of steepening waves, local gradients in sound speed and density can alter the rate of steepening and can enhance or delay shock formation in the medium, a result relevant also to the envisaged experiments aimed at proving the existence of nonclassical gasdynamics phenomena in BZT vapors.

The Effect of Using Different Refrigerants on System Performance in Two-Stage Organic Rankine Cycle

In this study, energy analysis of a double-stage Organic Rankine Cycle (ORC) was performed using the Engineering Equation Solver program (EES). In the first and second stages, eight different organic working fluids (R134a, R410a, RC318, R407c, R22, R23, R116, and R218) were used in pairs for certain temperature limits. Choosing a suitable refrigerant or refrigerant pair is crucial for the ORC’s high thermal efficiency and net work output value. This study aims to determine the effect of working fluid on system efficiency and find out the most suitable working fluid pair. The results showed that the highest net power output and the highest thermal efficiency were obtained from the R23+R23 pair. It was also observed that the lowest net power output from the RC318+RC318 pair and the lowest thermal efficiency was obtained from the R218+R218 pair.

Study on the Concept of Organic-Cooled Microreactor

In order to study the concept of organic-cooled reactor, this paper firstly analyzes the important characteristics and key technical problems of the organic fluid used as the reactor coolant and moderator, as well as the main technical schemes for organic-cooled reactors. On this basis, this paper studies the neutronic characteristics of the 5 MW microreactor core. As shown in the study, under the same core layout conditions, the absolute value of the moderator temperature coefficient of the organic-cooled reactor is below that of the pressurized water reactor (PWR), and the power distribution is more flat. The study results from this paper can provide an important reference for the determination of the technology roadmap for multi-purpose microreactor power supplies and heating systems, which are rapidly developed in China.

Fuel Burn Reduction of Hybrid Aircraft Employing an Exhaust Heat Harvesting System

This study investigates the application of an exhaust gas energy harvesting hybrid powertrain to three general aviation aircraft with reciprocating spark-ignition piston engines. The hybridization process involves downsizing the internal combustion engine to save weight and installation of an exhaust heat harvesting system composed of a harvester, a generator, lithium-ion traction battery, an electrical conversion system, and an electric motor. Novel calculations for a hybrid powertrain performance envelope are presented that estimate the upper limits to the degree of downsizing and mass of the harvester. An organic Rankine cycle (ORC) has been proposed as a potential compact, high-efficiency harvester. Five hydrofluroolefins (which have no ozone depletion potential and very low global warming potential) are considered as organic fluids for the ORC. It is found that R-1336mzz(Z) performs best in this application. Each ORC design parameter is investigated, and an optimized design with 14.3% thermal efficiency is found. At this efficiency, the internal combustion engine may be downsized up to 34.5%. The fuel burn reduction at this degree of downsizing may be as high as 12.7–14.5%.

Near-Infrared Femtosecond Laser Ablation of Au-Coated Ni: Effect of Organic Fluids and Water on Crater Morphology, Ablation Efficiency and Hydrodynamic Properties of NiAu Nanoparticles.

Scanning electron microscopy (SEM) and profilometry of the crater morphology and ablation efficiency upon femtosecond laser ablation of Au-coated Ni targets in various fluids revealed a pronounced dependence on the ablation medium. For ethanol, a sufficient ablation efficiency was obtained, whereas for 2-butanol a higher efficiency indicated stronger laser–target interaction. Hierarchical features in the crater periphery pointed to asymmetrical energy deposition or a residual effect of the Coulomb-explosion-initiating ablation. Significant beam deviation in 2-butanol caused maximum multiple scattering at the crater bottom. The highest values of microstrain and increased grain size, obtained from Williamson–Hall plots, indicated the superposition of mechanical stress, defect formation and propagation of fatigue cracks in the crater circumference. For n-hexane, deposition of frozen droplets in the outer crater region suggested a femtosecond-laser-induced phase explosion. A maximum ablation depth occurred in water, likely due to its high cooling efficiency. Grazing incidence micro X-ray diffraction (GIXRD) of the used target showed residual carbon and partial surface oxidation. The produced nanoparticle colloids were examined by multiangle dynamic light scattering (DLS), employing larger scattering angles for higher sensitivity toward smaller nanoparticles. The smallest nanoparticles were obtained in 2-butanol and ethanol. In n-hexane, floating carbon flakes originated from femtosecond-laser-induced solvent decomposition.

Origin of authigenic albite in a lacustrine mixed-deposition sequence (Lucaogou Formation, Junggar Basin) and its diagenesis implications

Authigenic albites occur widely in clastic reservoirs with important implications for diagenesis and reservoir formation. The middle Permian Lucaogou Formation in the Jimusaer Sag (Junggar Basin, NW China), where major exploration breakthroughs in shale oil have been achieved, reveals a new phenomenon that authigenic albites are abundant in unique mixed carbonate–volcanic–clastic sequences. This has not been reported in the literatures. To fill the knowledge gap, the origin of these authigenic albites and their relationship with dissolution pores (i.e. diagenesis implications) were investigated. Results show that two types (I and II) of authigenic albite were identified within the shale oil reservoirs. Euhedral Type I authigenic albites with 3–10 μm only occur in dolarenite intraclasts and are symbiotic with amorphous dolomite minerals with a pure chemical composition of >99% albite-end-member content. Larger Type II authigenic albites with 10–50 μm are widely distributed in reservoirs, primarily in dissolution pores, and coexist with authigenic dolomite minerals or dolomite overgrowths. Their chemical composition is less pure with anorthite-end-member contents that range from undetectable to 9.77%, with an average of 1.34%. A symbiotic relationship, pure chemical composition, size, and euhedral morphology indicate that Type I authigenic albites precipitated during syngenetic hydrothermal action. However, the morphology of dissolution pores, residual symbiotic “orthoclase”, impure chemical composition and carbon–oxygen isotope indicate that Type II were the products of the dissolution and reprecipitation of “perthite” crystal pyroclasts influenced by acid organic fluids in latter diagenesis. The differential dissolution of “orthoclase” and “albite” components in “perthite” crystal pyroclasts formed enormous intergranular secondary pores in the presence of dolomite minerals in the shale oil reservoirs.

Annual transient analysis of energetic, exergetic, and economic performances of solar cascade organic Rankine cycles integrated with PCM-based thermal energy storage systems

In this study, the annual transient analysis of the solar cascade organic Rankine cycle integrated with the phase change material (PCM) storage and parabolic trough collectors (PTC) has been conducted. The proposed system has been evaluated from energy, exergy, and economic points of view. Several PCMs, namely Isomalt, Adipic acid, Salicylic acid, Dimethylol propionic acid, A164, and KNO3–NaNO2–NaNO3 composition, have been compared to each other. Moreover, the effects of three different pairs of organic fluids, R245fa/R134a, R245fa/R500, and R245fa/R1234yf, have been examined on the system's performance. The annual investigation indicated that the closer the PCM melting temperature to the auxiliary heater setpoint temperature, the higher the solar fraction, exergy and energy efficiencies. Furthermore, the pair of R245fa/R500 had the best energy and exergy performances, which were 12.76% and 13.87%, respectively. The economic evaluation revealed that the case of R245fa/R500 combined with Dimethylol as the PCM thermal storage has the best economic performance with the NPV, LCOE, and PP of 186,622 $, 0.29 $/kWh, and 18 years, respectively. Also, the results of a sensitivity analysis showed that the NPV is extremely sensitive to the energy carriers prices and least sensitive to the PTC cost.

A Waste Energy Recovery Management for Electricity Generation from Two Temperature Grades of Energy Sources in Subcritical Organic Rankine Systems

Waste energy represents one of the most critical issues for the economic utilization and management of energy in modern industrial fields. This article outlines a scheme to utilize two different source temperature levels within the envelope of higher than 200 °C zones. Two regenerative organic Rankine cycles (RORC) were implemented to construct a compound regenerative organic Rankine cycle (CRORC) to improve the energy management of the sources. These two mini-cycles were integrated throughout an intermediate economizer circuit to extract a certain amount of energy from the high-temperature level mini-cycle. R-123 was circulated in the high-temperature cycle due to its high critical temperature at evaporation and condensation temperatures of 160 °C and 50 °C, respectively. R-123, R-21, and hydrocarbon R-600 were used as working fluids for the low-temperature cycle at evaporation and condensation temperatures of 130 °C and 35 °C, respectively. The R-123 fluid in the high-temperature mini-cycle was superheated to 170-240 °C, whereas the fluid in the low-temperature level was superheated to 180 °C. The results showed that the independent system (IRORC) requires more energy recovery than the compound system by a maximum of 2% to achieve the same net power output. This corresponds to the enhancement of 2% for the system net thermal efficiency of the compound (CRORC) system compared to the independent (IRORC) one. The compound (CRORC) system revealed a net thermal efficiency in the range of 14% and 15.6% for the test conditions. The mini-cycle net thermal efficiency of the low-temperature in the compound system was enhanced by a range of 2.5-5% compared to that of the independent arrangement. R-123/R-123 and R-123/R-21 systems exhibited higher net thermal efficiencies than the R-123/R-600 one by 3% and 2%, respectively. Increasing the superheat degree of the high-temperature mini-cycle from 10 °C to 80 °C for the compound system has improved the thermal efficiency by 7.6-7.9% for the examined fluid pairs and operating conditions. Keywords: compound cycle, regenerative, energy management, energy recovery, organic fluids

Design Parameter Influence on Losses and Downstream Flow Field Uniformity in Supersonic ORC Radial-Inflow Turbine Stators

The design of organic Rankine cycle (ORC) turbines often requires dealing with transonic flows due to the cycle efficiency requirements and the matching of the temperature profiles with heat sources and sinks, as well as the nature of organic fluids, often featuring high molecular weight. Consequently, the use of convergent–divergent turbine stators has been widely established as a solution in the published literature for use in both axial- and radial-inflow machines. With respect to the latter layout in particular, the available design guidelines are still limited. The present work shows the results of an investigation into a series of ORC radial-inflow convergent–divergent nozzles that differ with respect to the vane count and the designed metal angle of the outlet. These stators were designed by fitting the divergent portion of a sharp-edged minimum-length nozzle, designed by means of the method of characteristics (MoC) adapted to dense gases, into a radial-inflow turbine stator. The geometries were analysed by means of steady-state RANS CFD calculations, and the results were used to assess the influence of the design parameters on the nozzle losses and downstream flow field uniformity, showing that conflicting trends exist between optimum stator efficiency and optimum downstream flow field uniformity.

Energy, exergy, and environmental assessment of a small-scale solar organic Rankine cycle using different organic fluids

This article presents an energetic, exergetic, and environmental (3E) analysis of a solar powered simple Rankine Organic Cycle (ORC). The ORC is simulated using three organic working fluids, such as Toluene, Cyclohexane, and Acetone, meanwhile the solar system uses thermal oil Therminol 75. The present study shows the performance of this coupled system using historical solar annual radiation data from four of the highest solar potential locations in Colombia. Data used correspond to data for the cities Rancho Grande, Puerto Bolivar, Manaure, and Nazareth. Simulations were performed using commercial programs as MATLAB® and REFPROP 9.0. Energy production, the energy and exergetic efficiencies of the system, the exergy destruction was calculated based on the input of the global solar radiation. Effects generated by each working fluid in the solar powered ORC system was determined. It was stablished that the heat obtained in the solar collector in combination with a storage tank is incorporated during non-radiation hours guarantees the thermal stability of the working fluid in the ORC. The best performance corresponds to the Rancho Grande city, being the Toluene the corresponding working fluid with the highest energy (14.6%) and exergetic (7.37%) efficiencies, as well as the maximum power generation (5.50 kW) for October month, meanwhile, the highest exergy destruction values correspond in April. A sensitivity analysis of the individual elements of the system was performed. This study revealed the preference of a lower evaporator pinch point temperature, higher turbine thermal efficiency, pump thermal efficiency, and pressure ratio to obtain better energy and exergy efficiency of the solar powered ORC system. Additionally, the potential environmental impact of the system was evaluated through a Life Cycle Analysis, obtaining for the solar system solar collector has the highest environmental impact with 78557850 mPts. Meanwhile for the ORC, the turbine registers the most significant environmental impact with 295516 mPts (7.34%), when Toluene is used as a working fluid and copper as a construction material in the location of Rancho Grande. In conclusion, the potentiality of planning the operation of solar powered ORC was successfully evaluated for four specific locations in Colombia.

Design optimization and test of the novel FeTu ‘compander’, utilising organic fluids within a closed cycle for HVACR applications

HVACR performance is influenced by the efficiency of the compression and expansion process. The ability to operate oil-free; with non-toxic, inert, natural working fluids such as air or CO2 holds high environmental value.This paper presents data of the FeTu™ compander operating in a closed cycle, for means of heating and cooling. A novel system, where compression and expansion is a continuous and simultaneous process; inherently regenerating energy to assist the compression process by expanding within a positive displacement chamber. This study documents the oil-free performance with organic working fluids pertaining to HVACR applications.Commercial 1D modelling software; GTSuite (GTS) is used to optimise cooling capacity (Q) and Coefficient of Performance (CoP). Different volume ratios (VR), pre-charge pressures, temperature inputs (ΔT) and running speeds are analysed. A multi-faceted test rig is built to compare and validate all performance data against the GTS fluid model which, once calibrated, can then be used with a high degree of certainty in predicting the performance of other applications and ΔTs. Increasing the system pre-charge pressure has a proportional impact on capacity, so this phenomenon is tested to consider the conflicting impacts of higher pressure against increased viscosity, with respect to volumetric efficiency.The CoP of the system ranges from 1 to 5 across typical HVACR ΔTs. Low VR offers highest CoP but lowest Q, so the optimal trade-off is explored. The strengths & weaknesses are then comparatively documented against incumbent vapour cycle systems.

Case studies on performance prediction of radial inflow turbine under multiple rotor structures and organic fluids

Due to the lack of selection criteria for the ORC radial inflow turbine's loss models, and information about the models' limitations. This paper presents a comprehensive analysis for performance prediction of the ORC radial inflow turbine, and a novel turbine performance prediction program is proposed. This study can be divided into two parts, during the analysis part, 125 cases of CFD simulation were conducted under 5 rotor structures and R245fa as the working fluid. The performance of 6 loss models and their 18 combinations were compared. And in the examination part, another three organic fluids from different categories were chosen to exam the reliability of the proposed prediction program. The results show that loss model combinations E, O, and Q have a good performance in rotor loss prediction. Besides, Δβ4 has an important influence on prediction reliability and turbine performance, it should be lower than a certain value (about 40° in this paper) during the analysis process to get relatively reliable results under different rotor structures. The proposed program can realize an acceptable accuracy for turbine performance prediction under multiple organic fluids and rotor structures, with an efficiency deviation within ±5% and an output power relative error within ±10%.

Thermo-economic analysis, working fluids selection, and cost projection of a precooler-integrated dual-stage combined cycle (PIDSCC) system utilizing cold exergy of liquefied natural gas

The technically efficient and cost-competitive design of an energy system is a key factor for its implementation. Precooler-integrated dual-stage combined cycle (PIDSCC) is a technically sound technology for recovering wasted cold exergy of Liquefied Natural Gas (LNG) during its regasification process, but its economic aspect remains unclear. In this paper, the thermo-economic model is built and the optimization procedure is applied, enabling to investigate the impacts of three key parameters. 10 common organic fluids are compared by using Capital Cost Per Power (CPP) as the optimization objective under different NG distribution pressures. Additionally, the mathematization of economic metrics (CPP and LCOE) at scaled-up capacities are realized and cost projection correlations are derived as a rule of thumb. Simulation results suggest that the occurrences of thermodynamically- and economically-optimal design points mismatch, and the economical optimum occurs at a lower pumped pressure. Within the selected fluids, high critical-temperature ones (70–150 °C, e.g., R290, R32, and R600) for the dual-stage ORC system lead to a lower CPP. The economic attractiveness of the PIDSCC system is more distinct at the low NG distribution pressure (6 bar) and medium to large scale applications (>1 MTPA). These insights enable engineers and project developers to design and implement this novel technology.

Bedding-parallel calcite veins indicate hydrocarbon–water–rock interactions in the over-mature Longmaxi shales, Sichuan Basin

Bedding-parallel calcite veins in shales archive hydrocarbon–water–rock interactions, but such processes in highly–over mature shales are poorly understood in terms of their geological and geochemical significance. To fill the knowledge gap, we conducted a combined petrographic, geochemical, isotopic, and fluid inclusion study of the Silurian Longmaxi Formation in the Sichuan Basin, China, to investigate these processes. Our results show that bedding-parallel calcite veins grow nearly vertically along the median plane, and exhibit antitaxial and two stages of growth. The early calcite veins have high δ13C values (0.08‰–4.75‰) and the diagenetic fluids were relatively low-temperature (120–150 °C) and high-salinity (11.2%), and formed during primary migration of hydrocarbon-bearing fluids in the oil window. The late calcite veins have relatively low δ13C values (−7.01‰ to −0.08‰) and the diagenetic fluids were high-temperature (180–210 °C) and low-salinity (8.9%), and formed in the gas window. The similar 87Sr/86Sr and δ13C values of the calcite veins and surrounding host rocks, combined with the relatively uniform fluid δ18OV-SMOW values, indicate that the calcite-precipitating fluids were derived mainly from the surrounding host-rocks and organic fluids. The formation of bedding-parallel calcite veins records the two-stage, fluid-overpressured evolution of organic matter in the oil and gas generation stages.

Multi-Objective Optimization and Fluid Selection of Different Cogeneration of Heat and Power Systems Based on Organic Rankine Cycle

Cogeneration of heat and power systems based on the organic Rankine cycle (ORC-CHP) has been proven to be an effective way to utilize waste heat at medium and low temperatures. In this work, three ORC-CHP (combined heat and power based on organic Rankine cycle) systems are simulated and compared, including the SS (serial system), the CS (the condensation system), and the SS/CS. The multi-objective genetic algorithm (MOGA) is used to optimize the three systems respectively to achieve higher exergy efficiency and profit ratio of investment (PRI). The optimal thermal-economic performance is obtained. Twelve organic fluids are adopted to evaluate their performance as working fluids. The calculation results show that SS has the highest exergy efficiency, while SS/CS has the best economic performance. Compared with the highest exergy efficiency of SS and the best economic performance of SS/CS, CS will be the optimal solution considering these two objective functions. Under the optimal working conditions, SS has the highest thermal efficiency because it has the highest net power output. The components with the largest proportion of exergy destruction are the heat exchangers, which also has the highest cost.

Thermodynamic analysis on the feasibility of a liquid energy storage system using CO2-based mixture as the working fluid

Pioneering investigation is conducted on the feasibility of designing novel liquid energy storage system by using working fluid blending CO2 with organic fluids to address the condensation problem of subcritical CO2. Organic substances are cautiously screened according to the criteria of environment effect, temperature glide, critical temperature and flammability of working fluid as well as the system performance. Mathematical model of the system is built for thermodynamic examination. An in-house code is developed to complete the system simulations combing with REFPROP subroutine. Results demonstrate that compared to the system with pure CO2, the system with mixture produces an improvement of net power output and energy density and a reduction of charge pressure at an expense of slightly decreasing round trip efficiency. The payment of 6.45 % for round trip efficiency can reduce 55.59 % of charge pressure by taking CO2/R32 as an instance. The system round trip efficiency, energy density and charge pressure decrease with the increase in organic fluid composition. An optimal compression ratio can be identified to reach a maximal round trip efficiency for all mixtures. The cooler outlet temperature is suggested being at the critical temperature of working fluid to reach better system performance.