Records with Subject: Process Design
Showing records 1 to 25 of 132. [First] Page: 1 2 3 4 5 Last
Multi-Objective Optimization of a Solar Chimney Power Plant with Inclined Collector Roof Using Genetic Algorithm
Ehsan Gholamalizadeh, Man-Hoe Kim
February 5, 2019 (v1)
Keywords: inclined collector roof, multi-objective genetic algorithm, Renewable and Sustainable Energy, solar chimney power plant
This paper presents an optimization of a solar chimney power plant with an inclined collector roof using genetic algorithms. Five design parameters that affect the system performance are the collector radius, collector inlet height, collector outlet height, chimney height and diameter. A multi-objective design to simultaneously optimize three conflicting objectives including system efficiency, power output and expenditure is used. Based on this approach, obtaining the best combination of the possible geometrical parameters, performance of two built pilot power plants in Kerman (Iran) and Manzanares (Spain) are optimized thermo-economically. The heights of the zero-slope collectors of the Kerman and Manzanares systems are 2 m and 1.85 m, respectively. The results show that in the Kerman pilot the optimal collector inlet and outlet heights are 1.5 m and 2.95 m, respectively, while those optimal heights in the Manzanares prototype are 1.5 m and 4.6 m, respectively. It is found that select... [more]
Simple Design Approach for Low Torque Ripple and High Output Torque Synchronous Reluctance Motors
Mohamed Nabil Fathy Ibrahim, Peter Sergeant, Essam Rashad
February 5, 2019 (v1)
Keywords: design, finite element method (FEM), flux-barriers, sensitivity analysis, synchronous reluctance motor, torque ripple
The rotor design of Synchronous Reluctance Motors (SynRMs) has a large effect on their efficiency, torque density and torque ripple. In order to achieve a good compromise between these three goals, an optimized rotor geometry is necessary. A finite element method (FEM) is a good tool for the optimization. However, the computation time is an obstacle as there are many geometrical parameters to be optimized. The flux-barrier widths and angles are the two most crucial parameters for the SynRM output torque and torque ripple. This paper proposes an easy-to-use set of parametrized equations to select appropriate values for these two rotor parameters. With these equations, the reader can design a SynRM of distributed windings with a low torque ripple and with a better average torque. The methodology is valid for a wide range of SynRMs. To check the validity of the proposed equations, the sensitivity analysis for the variation of these two parameters on the SynRM torque and torque ripple is c... [more]
Comparison of Cooling System Designs for an Exhaust Heat Recovery System Using an Organic Rankine Cycle on a Heavy Duty Truck
Nicolas Stanzel, Thomas Streule, Markus Preißinger, Dieter Brüggemann
February 5, 2019 (v1)
Keywords: 1-D simulation, cooling system, Ethanol, heat recovery, heavy-duty truck, Organic Rankine Cycle (ORC)
A complex simulation model of a heavy duty truck, including an Organic Rankine Cycle (ORC) based waste heat recovery system and a vehicle cooling system, was applied to determine the system fuel economy potential in a typical drive cycle. Measures to increase the system performance were investigated and a comparison between two different cooling system designs was derived. The base design, which was realized on a Mercedes-Benz Actros vehicle revealed a fuel efficiency benefit of 2.6%, while a more complicated design would generate 3.1%. Furthermore, fully transient simulation results were performed and are compared to steady state simulation results. It is shown that steady state simulation can produce comparable results if averaged road data are used as boundary conditions.
Exergy and Thermoeconomic Analyses of Central Receiver Concentrated Solar Plants Using Air as Heat Transfer Fluid
Claudia Toro, Matteo V. Rocco, Emanuela Colombo
January 31, 2019 (v1)
Keywords: concentrated solar plant, exergoeconomic cost analysis, exergy cost analysis
The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP) plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the heat transfer fluid for a Rankine thermal cycle as an alternative to more traditional working fluids thereby reducing maintenance operations and providing the power section with a higher degree of flexibility To supply thermal needs when the solar source is unavailable, an auxiliary burner is requested. This configuration is adopted in the Julich CSP (J-CSP) plant, operating in Germany and characterized by a nominal power of 1.5 MW, the heat transfer fluid (HTF) is air which is heated in the solar tower and used to produce steam for the bottoming Rankine cycle. In this paper, the J-CSP plant with thermal energy storage has been compared with a hybrid CSP plant (H-CSP) using air as the working fluid. Thermodynam... [more]
Comprehensive Exergy Analysis of Three IGCC Power Plant Configurations with CO₂ Capture
Nicholas S. Siefert, Sarah Narburgh, Yang Chen
January 31, 2019 (v1)
Keywords: coal gasification, exergy analysis, precombustion CO2 capture, process system modeling
We have conducted comprehensive exergy analyses of three integrated gasification combined cycle with carbon capture and storage (IGCC-CCS) power plant configurations: (1) a baseline model using Selexol™ for H₂S/CO₂ removal; (2) a modified version that adds a H₂-selective membrane before the Selexol™ acid gas removal system; and (3) a modified baseline version that uses a CO₂-selective membrane before the Selexol™ acid gas removal system. While holding the coal input flow rate and the CO₂ captured flow rates constant, it was determined that the H₂-selective membrane case had a higher net power output (584 MW) compared to the baseline (564 MW) and compared to the CO₂-selective membrane case (550 MW). Interestingly, the CO₂-selective membrane case destroyed the least amount of exergy within the power plant (967 MW), compared with the Baseline case (999 MW) and the H₂-membrane case (972 MW). The main problem with the CO₂-selective membrane case was the large amount of H₂ (48 MW worth of H₂... [more]
A New Switching Impulse Generator Based on Transformer Boosting and Insulated Gate Bipolar Transistor Trigger Control
Ming Ren, Chongxing Zhang, Ming Dong, Rixin Ye, Ricardo Albarracín
January 30, 2019 (v1)
Keywords: boosting transformer, impulse generator, impulse waveform parameters, insulated gate bipolar transistor (IGBT), switching impulse (SI)
To make the switching impulse (SI) generator more compact, portable and feasible in field tests, a new approach based on transformer boosting was developed. To address problems such as triggering synchronization and electromagnetic interference involved with the traditional spark gap, an insulated gate bipolar transistor (IGBT) module with drive circuit was employed as the impulse trigger. An optimization design for the component parameters of the primary winding side of the transformer was realized by numerical calculation and error correction. Experiment showed that the waveform parameters of SI and oscillating switching impulse (OSI) voltages generated by the new generator were consistent with the numerical calculation and the error correction. The generator was finally built on a removable high voltage transformer with small size. Thus the volume of the generator is significantly reduced. Experiments showed that the waveform parameters of SI and OSI voltages generated by the new ge... [more]
A Concentrator Photovoltaic System Based on a Combination of Prism-Compound Parabolic Concentrators
Ngoc Hai Vu, Seoyong Shin
January 30, 2019 (v1)
Keywords: compound parabolic concentrator, concentrator photovoltaic, solar cell
We present a cost-effective concentrating photovoltaic system composed of a prism and a compound parabolic concentrator (P-CPC). In this approach, the primary collector consists of a prism, a solid compound parabolic concentrator (CPC), and a slab waveguide. The prism, which is placed on the input aperture of CPC, directs the incoming sunlight beam to be parallel with the main axes of parabolic rims of CPC. Then, the sunlight is reflected at the parabolic rims and concentrated at the focal point of these parabolas. A slab waveguide is coupled at the output aperture of the CPC to collect focused sunlight beams and to guide them to the solar cell. The optical system was modeled and simulated with commercial ray tracing software (LightTools™). Simulation results show that the optical efficiency of a P-CPC can achieve up to 89%. when the concentration ratio of the P-CPC is fixed at 50. We also determine an optimal geometric structure of P-CPC based on simulation. Because of the simplicity... [more]
Effect of Photoanode Design on the Photoelectrochemical Performance of Dye-Sensitized Solar Cells Based on SnO₂ Nanocomposite
I-Ming Hung, Ripon Bhattacharjee
January 30, 2019 (v1)
Keywords: dye-sensitized solar cells (DSSCs), nanocomposite, nanoflower, nanoparticle, photoanode
Li-doped ZnO (LZO) aggregated nanoparticles are used as an insulating layer in SnO₂ nanocomposite (SNC) photoanodes to suppress the recombination process in dye-sensitized solar cells (DSSCs). Various weight percentages of SnO₂ nanoparticles (SNPs) and SnO₂ nanoflowers (SNFs) were used to prepare SNC photoanodes. The photocurrent-voltage characteristics showed that the incorporation of an LZO insulating layer in an SNC photoanode increased the conversion efficiency of DSSCs. This was due to an increase in the surface area, charge injection, and charge collection, and the minimization of the recombination rate of photoanodes. Electrochemical impedance spectroscopy (EIS) results showed lower series resistance, charge injection resistance, and shorter lifetimes for DSSCs based on an SNC photoanode with an LZO insulating layer. The open circuit voltage and fill factor of the DSSCs based on SNC photoanodes with an LZO insulating layer significantly increased. The DSSC based on a SNC photoan... [more]
Comparison of Organic Rankine Cycle Systems under Varying Conditions Using Turbine and Twin-Screw Expanders
Matthew Read, Ian Smith, Nikola Stosic, Ahmed Kovacevic
January 7, 2019 (v1)
Keywords: expander, geothermal, Organic Rankine Cycle, turbine, twin screw, waste heat
A multi-variable optimization program has been developed to investigate the performance of Organic Rankine Cycles (ORCs) for low temperature heat recovery applications using both turbine and twin-screw expanders when account is taken of performance variation due to changes in ambient conditions. The cycle simulation contains thermodynamic models of both types of expander. In the case of the twin-screw machine, the methods used to match the operation of the expander to the requirements of the cycle are described. The performance of turbine expanders in a superheated ORC has been modelled using correlations derived from operational data for single stage reaction turbines to predict the turbine efficiency at “off-design” conditions. Several turbine configurations have been considered including variable nozzle area and variable speed. The capability of the cycle model has been demonstrated for the case of heat recovery from a steady source of pressurized hot water at 120 °C. The system par... [more]
Unshrouded Plate Fin Heat Sinks for Electronics Cooling: Validation of a Comprehensive Thermal Model and Cost Optimization in Semi-Active Configuration
Luigi Ventola, Gabriele Curcuruto, Matteo Fasano, Saverio Fotia, Vincenzo Pugliese, Eliodoro Chiavazzo, Pietro Asinari
January 7, 2019 (v1)
Keywords: cost optimization, electronics cooling, genetic algorithms, heat transfer enhancement, plate fin heat sinks
Plate Fin Heat Sinks (PFHS) are among the simplest and most widespread devices for electronics cooling. Because of the many design parameters to be considered, developing both cost and thermal effective PFHS is a critical issue. Here, a novel thermal model of PFHS is presented. The model has a broad field of applicability, being comprehensive of the effects of flow bypass, developing boundary layers, fin efficiency and spreading resistance. Experiments are then carried out to validate the proposed thermal model, and its good accuracy is demonstrated. Finally, an optimization methodology based on genetic algorithms is proposed for a cost-effective selection of the design parameters of PFHS, which is particularly effective with semi-active configurations. Such an optimization methodology is then tested on a commercial heat sink, resulting in a possible 53% volume reduction at fixed thermal performances.
Thermal Hydraulic Performance in a Solar Air Heater Channel with Multi V-Type Perforated Baffles
Anil Kumar, Man-Hoe Kim
January 7, 2019 (v1)
Keywords: friction factor, heat transfer enhancement, perforated baffle, solar air heater (SAH) channel, solar energy
This article presents heat transfer and fluid flow characteristics in a solar air heater (SAH) channel with multi V-type perforated baffles. The flow passage has an aspect ratio of 10. The relative baffle height, relative pitch, relative baffle hole position, flow attack angle, and baffle open area ratio are 0.6, 8.0, 0.42, 60°, and 12%, respectively. The Reynolds numbers considered in the study was in the range of 3000⁻10,000. The re-normalization group (RNG) k-ε turbulence model has been used for numerical analysis, and the optimum relative baffle width has been investigated considering relative baffle widths of 1.0⁻7.0.The numerical results are in good agreement with the experimental data for the range considered in the study. Multi V-type perforated baffles are shown to have better thermal performance as compared to other baffle shapes in a rectangular passage. The overall thermal hydraulic performance shows the maximum value at the relative baffle width of 5.0.
Comparative Life Cycle Cost Analysis of Hardening Options for Critical Loads
Sungmin Park, Sung-Yeul Park, Peng Zhang, Peter Luh, Michel T. J. Rakotomavo, Camilo Serna
January 7, 2019 (v1)
Keywords: cost benefit analysis, emergency power supplies, microgrids, Monte Carlo method
In order to determine the most cost effective alternative among hardening options of power systems, the direct monetary benefits should be evaluated above all other things. Therefore, this paper presents a life-cycle cost model which describes total monetary costs experienced in annual time increments during the project with consideration for the time value of money. In addition, to minimize the risks associated with estimated cost errors due to uncertainties of input data, the stochastic input data are considered. Using the Monte Carlo method, the probabilities and cost ranges in the case studies can be predicted, in turn resulting in better decisions in the selection of hardening options which are cost effective.
Investigation of a Novel Mechanical to Thermal Energy Converter Based on the Inverse Problem of Electric Machines
Lei Chen, Yulong Pei, Feng Chai, Shukang Cheng
January 7, 2019 (v1)
Keywords: converter, eddy current, electric machine, permanent magnet, temperature, thermal energy
A novel converter that can directly transform electrical, wind, hydraulic and other types of mechanical energy into thermal energy is presented in this study. First, the thermal energy of the converter is classified and then calculated by a finite element method. The eddy current distribution in the stator of the converter is also discussed. Second, the temperature field of the converter is calculated using a boundary element method. Subsequently, a thermal power⁻temperature coupled calculation method is presented to calculate the actual thermal power and temperature of the converter. The characteristic curves of the actual thermal power and the increase in water flow temperature are then presented based on the calculation results. Lastly, an experimental system is built, the thermal power and temperature of the converter are measured and the experimental results and the analytical calculations are compared.
Performance Analysis of a Reciprocating Piston Expander and a Plate Type Exhaust Gas Recirculation Boiler in a Water-Based Rankine Cycle for Heat Recovery from a Heavy Duty Diesel Engine
Gunnar Latz, Olof Erlandsson, Thomas Skåre, Arnaud Contet, Sven Andersson, Karin Munch
January 7, 2019 (v1)
Keywords: piston expander, Rankine cycle, waste-heat recovery (WHR)
The exhaust gas in an internal combustion engine provides favorable conditions for a waste-heat recovery (WHR) system. The highest potential is achieved by the Rankine cycle as a heat recovery technology. There are only few experimental studies that investigate full-scale systems using water-based working fluids and their effects on the performance and operation of a Rankine cycle heat recovery system. This paper discusses experimental results and practical challenges with a WHR system when utilizing heat from the exhaust gas recirculation system of a truck engine. The results showed that the boiler’s pinch point necessitated trade-offs between maintaining adequate boiling pressure while achieving acceptable cooling of the EGR and superheating of the water. The expander used in the system had a geometric compression ratio of 21 together with a steam outlet timing that caused high re-compression. Inlet pressures of up to 30 bar were therefore required for a stable expander power output.... [more]
Design, Simulation and Experimental Investigation of a Solar System Based on PV Panels and PVT Collectors
Annamaria Buonomano, Francesco Calise, Maria Vicidomini
January 7, 2019 (v1)
Keywords: dynamic simulation, experimental, PV panes, PVT collectors
This paper presents numerical and experimental analyses aimed at evaluating the technical and economic feasibility of photovoltaic/thermal (PVT) collectors. An experimental setup was purposely designed and constructed in order to compare the electrical performance of a PVT solar field with the one achieved by an identical solar field consisting of conventional photovoltaic (PV) panels. The experimental analysis also aims at evaluating the potential advantages of PVT vs. PV in terms of enhancement of electrical efficiency and thermal energy production. The installed experimental set-up includes four flat polycrystalline silicon PV panels and four flat unglazed polycrystalline silicon PVT collectors. The total electrical power and area of the solar field are 2 kWe and 13 m², respectively. The experimental set-up is currently installed at the company AV Project Ltd., located in Avellino (Italy). This study also analyzes the system from a numerical point of view, including a thermo-economi... [more]
Comparison of a Novel Organic-Fluid Thermofluidic Heat Converter and an Organic Rankine Cycle Heat Engine
Christoph J.W. Kirmse, Oyeniyi A. Oyewunmi, Andrew J. Haslam, Christos N. Markides
December 3, 2018 (v1)
Keywords: combined heat and power (CHP), economic comparison, low-grade heat, non-linear, off-grid power generation, organic Rankine cycle (ORC), performance analysis, thermofluidic oscillator, two-phase, unsteady
The Up-THERM heat converter is an unsteady, two-phase thermofluidic oscillator that employs an organic working fluid, which is currently being considered as a prime-mover in small- to medium-scale combined heat and power (CHP) applications. In this paper, the Up-THERM heat converter is compared to a basic (sub-critical, non-regenerative) organic Rankine cycle (ORC) heat engine with respect to their power outputs, thermal efficiencies and exergy efficiencies, as well as their capital and specific costs. The study focuses on a pre-specified Up-THERM design in a selected application, a heat-source temperature range from 210 °C to 500 °C and five different working fluids (three n-alkanes and two refrigerants). A modeling methodology is developed that allows the above thermo-economic performance indicators to be estimated for the two power-generation systems. For the chosen applications, the power output of the ORC engine is generally higher than that of the Up-THERM heat converter. However... [more]
Cost Engineering Techniques and Their Applicability for Cost Estimation of Organic Rankine Cycle Systems
Sanne Lemmens
December 3, 2018 (v1)
Keywords: case study, cost estimate, heat recovery, investment costs, organic Rankine cycle (ORC)
The potential of organic Rankine cycle (ORC) systems is acknowledged by both considerable research and development efforts and an increasing number of applications. Most research aims at improving ORC systems through technical performance optimization of various cycle architectures and working fluids. The assessment and optimization of technical feasibility is at the core of ORC development. Nonetheless, economic feasibility is often decisive when it comes down to considering practical instalments, and therefore an increasing number of publications include an estimate of the costs of the designed ORC system. Various methods are used to estimate ORC costs but the resulting values are rarely discussed with respect to accuracy and validity. The aim of this paper is to provide insight into the methods used to estimate these costs and open the discussion about the interpretation of these results. A review of cost engineering practices shows there has been a long tradition of industrial cost... [more]
Energy Converter with Inside Two, Three, and Five Connected H₂/Air Swirling Combustor Chambers: Solar and Combustion Mode Investigations
Angelo Minotti
November 28, 2018 (v1)
Keywords: Computational Fluid Dynamics, detailed chemistry, fluid-structure interaction, hydrogen-air combustion, meso-combustor, whirl flow
This work reports the performance of an energy converter characterized by an emitting parallelepiped element with inside two, three, or five swirling connected combustion chambers. In particular, the idea is to adopt the heat released by H₂/air combustion, occurring in the connected swirling chambers, to heat up the emitting surfaces of the thermally-conductive emitting parallelepiped brick. The final goal consists in obtaining the highest emitting surface temperature and the highest power delivered to the ambient environment, with the simultaneous fulfillment of four design constraints: dimension of the emitting surface fixed to 30 × 30 mm², solar mode thermal efficiency greater than 20%, emitting surface peak temperature T > 1000 K, and its relative ∆T < 100 K in the combustion mode operation. The connected swirling meso-combustion chambers, inside the converter, differ only in their diameters. Combustion simulations are carried out adopting 500 W of injected chemical power, stoichio... [more]
NMOS-Based Integrated Modular Bypass for Use in Solar Systems (NIMBUS): Intelligent Bypass for Reducing Partial Shading Power Loss in Solar Panel Applications
Pieter Bauwens, Jan Doutreloigne
November 28, 2018 (v1)
Keywords: diode bypass, partial shading, photovoltaic power, power loss, smart bypass
NMOS-based Integrated Modular Bypass for Use in Solar systems (NIMBUS) is designed as a replacement for the traditional bypass diode, used in common solar panels. Because of the series connection between the individual solar cells, the power output of a photovoltaic (PV) panel will drop disproportionally under partial shading. Currently, this is solved by dividing the PV panel into substrings, each with a diode bypass placed in parallel. This allows an alternative current path. However, the diodes still have a significant voltage drop (about 350 mV), and due to the fairly large currents in a panel, the diodes are dissipating power that we would rather see at the output of the panel. The NIMBUS chip, being a low-voltage-drop switch, aims to replace these diodes and, thus, reduce that power loss. NIMBUS is a smart bypass: a completely stand-alone system that detects the failing of one or more cells and activates when necessary. It is designed for a 100-mV voltage drop under a 5-A load cu... [more]
Thermo-Economic and Heat Transfer Optimization of Working-Fluid Mixtures in a Low-Temperature Organic Rankine Cycle System
Oyeniyi A. Oyewunmi, Christos N. Markides
November 28, 2018 (v1)
Keywords: heat transfer coefficients, low-grade heat, low-pressure expanders, multi-objective optimization, ORC capital costs, organic Rankine cycles (ORC), thermo-economic analysis, working-fluid mixtures
In the present paper, we consider the employment of working-fluid mixtures in organic Rankine cycle (ORC) systems with respect to thermodynamic and heat-transfer performance, component sizing and capital costs. The selected working-fluid mixtures promise reduced exergy losses due to their non-isothermal phase-change behaviour, and thus improved cycle efficiencies and power outputs over their respective pure-fluid components. A multi-objective cost-power optimization of a specific low-temperature ORC system (operating with geothermal water at 98 °C) reveals that the use of working-fluid-mixtures does indeed show a thermodynamic improvement over the pure-fluids. At the same time, heat transfer and cost analyses, however, suggest that it also requires larger evaporators, condensers and expanders; thus, the resulting ORC systems are also associated with higher costs. In particular, 50% n-pentane + 50% n-hexane and 60% R-245fa + 40% R-227ea mixtures lead to the thermodynamically optimal cyc... [more]
Optimization of Internal Cooling Fins for Metal Hydride Reactors
Vamsi Krishna Kukkapalli, Sunwoo Kim
November 28, 2018 (v1)
Keywords: exothermic hydriding reaction, finned surface, hydrogen storage, metal hydride reactor
Metal hydride alloys are considered as a promising alternative to conventional hydrogen storage cylinders and mechanical hydrogen compressors. Compared to storing in a classic gas tank, metal hydride alloys can store hydrogen at nearly room pressure and use less volume to store the same amount of hydrogen. However, this hydrogen storage method necessitates an effective way to reject the heat released from the exothermic hydriding reaction. In this paper, a finned conductive insert is adopted to improve the heat transfer in the cylindrical reactor. The fins collect the heat that is volumetrically generated in LaNi₅ metal hydride alloys and deliver it to the channel located in the center, through which a refrigerant flows. A multiple-physics modeling is performed to analyze the transient heat and mass transfer during the hydrogen absorption process. Fin design is made to identify the optimum shape of the finned insert for the best heat rejection. For the shape optimization, use of a pred... [more]
Design and Optimization of the Slide Guide System of Hydraulic Press Based on Energy Loss Analysis
Mengdi Gao, Haihong Huang, Zhifeng Liu, Xinyu Li, John W. Sutherland
November 28, 2018 (v1)
Keywords: design optimization, eccentric loads, energy loss, hydraulic press, stiffness
The clearances in the slide guide system of a hydraulic press are one of the significant factors affecting its accuracy. These clearances also affect the energy consumption of the press. An energy loss model that considers the oil leaks and friction associated with these clearances was proposed, and the size of clearances was optimized based on the model. The maximum allowable eccentric load and the energy loss on the wedge clearance condition were calculated to ensure the slide and guide pillars function properly. The stiffness of pillars and wear of guide rails were checked under an eccentric load condition. A case for rapid sheet metal forming with a 20 MN hydraulic press was examined. For this case, the optimum fit clearances were found to be approximately 0.4 mm. The energy loss under an eccentric load condition was increased by approximately 83% compared to a non-eccentric load condition. The pillars were optimized by reducing excessive stiffness, which served to decrease the pi... [more]
Performance Evaluation of a Helical Coil Heat Exchanger Working under Supercritical Conditions in a Solar Organic Rankine Cycle Installation
Marija Lazova, Henk Huisseune, Alihan Kaya, Steven Lecompte, George Kosmadakis, Michel De Paepe
November 28, 2018 (v1)
Keywords: concentrated PV collectors, heat exchanger design, helical coil heat exchanger, organic Rankine cycle (ORC), supercritical heat transfer
Worldwide interest in low grade heat valorization using organic Rankine cycle (ORC) technologies has increased significantly. A new small-scale ORC with a net capacity of 3 kW was efficiently integrated with a concentrated solar power technology for electricity generation. The excess heat source from Photovoltaic (PV) collectors with a maximum temperature of 100 °C was utilized through a supercritical heat exchanger that uses R-404A as working medium. By ensuring supercritical heat transfer leads to a better thermal match in the heat exchanger and improved overall cycle efficiency. A helical coil heat exchanger was designed by using heat transfer correlations from the literature. These heat transfer correlations were derived for different conditions than ORCs and their estimated uncertainty is ~20%. In order to account for the heat transfer correlation uncertainties this component was oversized by 20%. Next, a prototype was built and installed in an integrated concentrated photovoltaic... [more]
Combined Turbine and Cycle Optimization for Organic Rankine Cycle Power Systems—Part B: Application on a Case Study
Angelo La Seta, Andrea Meroni, Jesper Graa Andreasen, Leonardo Pierobon, Giacomo Persico, Fredrik Haglind
November 28, 2018 (v1)
Keywords: axial turbine, cycle optimization, mean line model, organic Rankine cycle (ORC), Surrogate Model, turbine design, turbine performance
Organic Rankine cycle (ORC) power systems have recently emerged as promising solutions for waste heat recovery in low- and medium-size power plants. Their performance and economic feasibility strongly depend on the expander. The design process and efficiency estimation are particularly challenging due to the peculiar physical properties of the working fluid and the gas-dynamic phenomena occurring in the machine. Unlike steam Rankine and Brayton engines, organic Rankine cycle expanders combine small enthalpy drops with large expansion ratios. These features yield turbine designs with few highly-loaded stages in supersonic flow regimes. Part A of this two-part paper has presented the implementation and validation of the simulation tool TURAX, which provides the optimal preliminary design of single-stage axial-flow turbines. The authors have also presented a sensitivity analysis on the decision variables affecting the turbine design. Part B of this two-part paper presents the first applic... [more]
Development and a Validation of a Charge Sensitive Organic Rankine Cycle (ORC) Simulation Tool
Davide Ziviani, Brandon J. Woodland, Emeline Georges, Eckhard A. Groll, James E. Braun, W. Travis Horton, Martijn van den Broek, Michel De Paepe
November 28, 2018 (v1)
Keywords: charge-based solver, cycle modeling, organic Rankine cycle, scroll expander, single-screw expander
Despite the increasing interest in organic Rankine cycle (ORC) systems and the large number of cycle models proposed in the literature, charge-based ORC models are still almost absent. In this paper, a detailed overall ORC simulation model is presented based on two solution strategies: condenser subcooling and total working fluid charge of the system. The latter allows the subcooling level to be predicted rather than specified as an input. The overall cycle model is composed of independent models for pump, expander, line sets, liquid receiver and heat exchangers. Empirical and semi-empirical models are adopted for the pump and expander, respectively. A generalized steady-state moving boundary method is used to model the heat exchangers. The line sets and liquid receiver are used to better estimate the total charge of the system and pressure drops. Finally, the individual components are connected to form a cycle model in an object-oriented fashion. The solution algorithm includes a prec... [more]
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