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Records with Keyword: Optimization
Showing records 1 to 25 of 89. [First] Page: 1 2 3 4 Last
A Review of Exergy Based Optimization and Control
Corey James, Tae Young Kim, Robert Jane
May 22, 2020 (v1)
Keywords: control, Energy, Exergy, Optimization
This work presents a critical review of the use of exergy based control and optimization for efficiency improvements in energy networks, with a background of exergy based analysis given for context. Over the past three decades, a number of studies using exergy were conducted to gain a performance advantage for high energy consumption systems and networks. Due to their complexity and the increased scale of the systems, the opportunity to misuse energy inevitability leads to inefficient operations. The studies accomplished in this area are grouped into either control or optimization to highlight each method’s ability to minimize system irreversibilities that lead to exergy destruction. The exergy based optimization and control studies featured demonstrate substantial improvements (as high as 40%) over traditional methods based on the first law of thermodynamics. This paper reviews the work completed in the area of exergy based optimization and control as of the end of September 2019, out... [more]
Multi-Objective Optimal Configuration of the CCHP System
Liukang Zheng, Xiaoli Wang, Baochen Jiang
May 22, 2020 (v1)
Keywords: combined cooling, environmental benefits, heating and power (CCHP) system, microgrid, Optimization, particle swarm optimization (PSO), reliability
The combined cooling, heating and power (CCHP) system not only has high energy efficiency but also has different load structures. Traditional separate production (SP) system and power supply system do not consider the land cost in terms of the environmental benefits, and in the aspect of the power supply reliability, the grid-connected inverter cost is also ignored. Considering the deficiency of the traditional energy supply system, this paper builds the CCHP system construction cost model. The particle swarm optimization (PSO) is adopted to find out the minimum value of the construction cost, and the optimal system construction scheme is constructed from three aspects which are system reliability, economic benefits and environmental benefits. In this paper, the typical daily data, as well as the meteorological data and the load data, in the last four years are taken as experimental dataset. The experimental results show that compared with the traditional SP system and power supply sys... [more]
Ultrasonic-Assisted Extraction (UAE) Process on Thymol Concentration from Plectranthus Amboinicus Leaves: Kinetic Modeling and Optimization
Nur Amirah Asifa Raisha Zahari, Gun Hean Chong, Luqman Chuah Abdullah, Bee Lin Chua
May 22, 2020 (v1)
Keywords: kinetic modeling, mechanism, Optimization, Plectranthus amboinicus, response surface methodology (RSM), Ultrasonic-assisted extraction (UAE)
Thymol shows potential medical values and it can be extracted from plants and herbs. In this study, ultrasonic-assisted extraction (UAE) was used to extract thymol from Plectranthus amboinicus leaves. From the extraction kinetics analysis of UAE on thymol, it was found that the highest concentration was collected at temperature of 25 °C with 5.51% of thymol concentration yield. An equilibrium-dependent solid−liquid extraction (EDSLE) model was found to be the best fitted model for thymol extraction using UAE. The parameters for optimization were the temperature of extraction (40 to 60 °C), extraction time (20 to 40 min), and the solid to solvent ratio (1:30 to 1:40 g/mL). The optimal UAE conditions were found at a temperature of 55 °C, 23 min of extraction, and a solid−solvent ratio of 1:35 g/mL. The changes in the structural surface of P. amboinicus after undergoing the UAE process were investigated using scanning electron microscopy (SEM). The possible mechanism of UAE was explained... [more]
Methodologies for the Design of Solar Receiver/Reactors for Thermochemical Hydrogen Production
M.A. Murmura, M.C. Annesini
May 18, 2020 (v1)
Keywords: design, Modelling, Optimization, solar reactor, solar receiver
Thermochemical hydrogen production is of great interest due to the potential for significantly reducing the dependence on fossil fuels as energy carriers. In a solar plant, the solar receiver is the unit in which solar energy is absorbed by a fluid and/or solid particles and converted into thermal energy. When the solar energy is used to drive a reaction, the receiver is also a reactor. The wide variety of thermochemical processes, and therefore of operating conditions, along with the technical requirements of coupling the receiver with the concentrating system have led to the development of numerous reactor configurations. The scope of this work is to identify general guidelines for the design of solar reactors/receivers. To do so, an overview is initially presented of solar receiver/reactor designs proposed in the literature for different applications. The main challenges of modeling these systems are then outlined. Finally, selected examples are discussed in greater detail to highli... [more]
A Numerical Study on the Effects of Trust in Supplier Development
Haniyeh Dastyar, Daniel Rippel, Jürgen Pannek, Klaus-Dieter Thoben, Michael Freitag
May 18, 2020 (v1)
Keywords: decision making support, Model Predictive Control, Optimization, supplier development, trust
Supplier development constitutes one of the current tools to enhance supply chain performance. While most literature in this context focuses on the relationship between manufacturers and suppliers, supplier development also provides an opportunity for distinct manufacturers to collaborate in enhancing a joint supplier. This article proposes a model for the optimization of such joint supplier development programs, which incorporates the effects of trust in the manufacturer-to-manufacturer relationship. This article uses a model-predictive formulation to obtain optimal supplier development investment decisions to consider the strong dynamics of the markets. Thereby, the model is designed to be highly customizable to the needs and requirements of different companies. We analyzed the price development related to Mercedes’ A-Class cars and the cost development in the automotive sector over the last ten years in Germany. According to the obtained result, the proposed model shows a sensible b... [more]
Cavitating Flow Suppression in the Draft Tube of a Cryogenic Turbine Expander through Runner Optimization
Ning Huang, Zhenlin Li, Baoshan Zhu
May 2, 2020 (v1)
Keywords: cryogenic cavitation, draft tube, expander runner, Optimization
The application of a cryogenic liquefied natural gas expander can reduce the production of flash steam and improve the efficiency of natural gas liquefaction. Like traditional hydraulic machinery, cavitation will occur during the operation of a liquefied natural gas expander, in particular, there is a strong vortex flow in the draft tube, and the cavitation phenomenon is serious. In this paper, the energy loss coefficient of the draft tube is used to describe the cavitation flow in the draft tube, and the goal of reducing the cavitation in the draft tube is achieved through the optimization design of the runner. Different runner models within the range of design parameters were obtained using the Latin hypercube test, and the relationship between design parameters and objective functions is constructed by a second-order response surface model. Finally, the optimized runners were obtained using a genetic algorithm. The effects of blade loading distribution and blade lean angles on the c... [more]
Systematic Boolean Satisfiability Programming in Radial Basis Function Neural Network
Mohd. Asyraf Mansor, Siti Zulaikha Mohd Jamaludin, Mohd Shareduwan Mohd Kasihmuddin, Shehab Abdulhabib Alzaeemi, Md Faisal Md Basir, Saratha Sathasivam
April 14, 2020 (v1)
Keywords: Hopfield Neural Network, logic programming, Optimization, Radial Basis Function Neural Network, satisfiability
Radial Basis Function Neural Network (RBFNN) is a class of Artificial Neural Network (ANN) that contains hidden layer processing units (neurons) with nonlinear, radially symmetric activation functions. Consequently, RBFNN has extensively suffered from significant computational error and difficulties in approximating the optimal hidden neuron, especially when dealing with Boolean Satisfiability logical rule. In this paper, we present a comprehensive investigation of the potential effect of systematic Satisfiability programming as a logical rule, namely 2 Satisfiability (2SAT) to optimize the output weights and parameters in RBFNN. The 2SAT logical rule has extensively applied in various disciplines, ranging from industrial automation to the complex management system. The core impetus of this study is to investigate the effectiveness of 2SAT logical rule in reducing the computational burden for RBFNN by obtaining the parameters in RBFNN. The comparison is made between RBFNN and the exist... [more]
Heat Exchanger Network Synthesis Integrated with Compression−Absorption Cascade Refrigeration System
Xiaojing Sun, Linlin Liu, Yu Zhuang, Lei Zhang, Jian Du
April 14, 2020 (v1)
Keywords: CACRS, HEN synthesis, MINLP, operating condition, Optimization
Compression−absorption cascade refrigeration system (CACRS) is the extension of absorption refrigeration system, which can be utilized to recover excess heat of heat exchanger networks (HENs) and compensate refrigeration demand. In this work, a stage-wise superstructure is presented to integrate the generation and evaporation processes of CACRS within HEN, where the generator is driven by hot process streams, and the evaporation processes provide cooling energy to HEN. Considering that the operating condition of CACRS has significant effect on the coefficient of performance (COP) of CACRS and so do the structure of HEN, CACRS and HEN are considered as a whole system in this study, where the operating condition and performance of CACRS and the structure of HEN are optimized simultaneously. The quantitative relationship between COP and operating variables of CACRS is determined by process simulation and data fitting. To accomplish the optimal design purpose, a mixed integer non-linear pr... [more]
Optimization of Microwave-Assisted Extraction Process of Callicarpa candicans (Burm. f.) Hochr Essential Oil and Its Inhibitory Properties against Some Bacteria and Cancer Cell Lines
Quoc Toan Tran, Thu Le Vu Thi, Tien Lam Do, Hong Minh Pham Thi, Bich Hoang Thi, Quang Truyen Chu, Phuong Thao Lai Phuong, Huu Nghi Do, Hoai Thu Hoang Than, Thu Thuy Ta Thi, Van Huyen Luu, Phuong Thi Mai Duong, Huong Thi Thu Phung
April 1, 2020 (v1)
Keywords: anti-proliferative activity, antimicrobial activities, Callicarpa candicans, essential oil, microwave-assisted extraction, Optimization, response surface methodology, the MAHD
Callicarpa candicans (Burm. f.) Hochr. (Callicarpa cana L.) is a medicinal plant that is distributed mainly in the tropics and subtropics of Asia and finds a wide range of uses in traditional medicine. In this study, we attempted and optimized the microwave-assisted hydro-distillation (MAHD) process to obtain essential oil from the leaves of C. candicans. In addition, the obtained oil was analyzed for volatile composition by gas chromatography−mass spectrometry (GC-MS) and assayed for bioactivity against several bacteria and cancer cell lines. To optimize the extraction process, response surface methodology (RSM) in combination with central composite design (CCD) was adopted. Experimental design and optimization were carried out with respect to three experimental factors including the ratio of water to raw material, extraction time, and microwave power. The optimal extraction conditions were obtained as follows: water to raw material ratio of 6/1 (v/w), extraction time 42 min, and micr... [more]
Layout Optimization Process to Minimize the Cost of Energy of an Offshore Floating Hybrid Wind−Wave Farm
Jorge Izquierdo-Pérez, Bruno M. Brentan, Joaquín Izquierdo, Niels-Erik Clausen, Antonio Pegalajar-Jurado, Nis Ebsen
March 12, 2020 (v1)
Keywords: farm layout, floating offshore energy generation, hybrid wind-wave platform, LCOE, Optimization, Particle Swarm Optimization, PSO, sustainable energy generation
Offshore floating hybrid wind and wave energy is a young technology yet to be scaled up. A way to reduce the total costs of the energy production process in order to ensure competitiveness in the sustainable energy market is to maximize the farm’s efficiency. To do so, an energy generation and costs calculation model was developed with the objective of minimizing the technology’s Levelized Cost of Energy (LCOE) of the P80 hybrid wind-wave concept, designed by the company Floating Power Plant A/S. A Particle Swarm Optimization (PSO) algorithm was then implemented on top of other technical and decision-making processes, taking as decision variables the layout, the offshore substation position, and the export cable choice. The process was applied off the west coast of Ireland in a site of interest for the company, and after a quantitative and qualitative optimization process, a minimized LCOE was obtained. It was then found that lower costs of ~73% can be reached in the short-term, and th... [more]
A Modular Framework for the Modelling and Optimization of Advanced Chromatographic Processes
Johannes Schmölder, Malte Kaspereit
February 3, 2020 (v1)
Keywords: CADET-Process, column configuration, Optimization, preparative chromatography, process design
A framework is introduced for the systematic development of preparative chromatographic processes. It is intended for the optimal design of conventional and advanced concepts that exploit strategies, such as recycling, side streams, bypasses, using single or multiple columns, and combinations thereof. The Python-based platform simplifies the implementation of new processes and design problems by decoupling design tasks into individual modules for modelling, simulation, assertion of cyclic stationarity, product fractionation, and optimization. Interfaces to external libraries provide flexibility regarding the choice of column model, solver, and optimizer. The current implementation, named CADET-Process, uses the software CADET for solving the model equations. The structure of the framework is discussed and its application for optimal design of existing and identification of new chromatographic operating concepts is demonstrated by case studies.
Integrating Feedback Control and Run-to-Run Control in Multi-Wafer Thermal Atomic Layer Deposition of Thin Films
Yichi Zhang, Yangyao Ding, Panagiotis D. Christofides
February 2, 2020 (v1)
Keywords: batch processes, control, data-driven modeling, design of batch processes, first principles modeling, monitoring, Optimization, quality control
There is currently a lack of understanding of the deposition profile in a batch atomic layer deposition (ALD) process. Also, no on-line control scheme has been proposed to resolve the prevalent disturbances. Motivated by this, we develop a computational fluid dynamics (CFD) model and an integrated online run-to-run and feedback control scheme. Specifically, we analyze a furnace reactor for a SiO2 thin-film ALD with BTBAS and ozone as precursors. Initially, a high-fidelity 2D axisymmetric multiscale CFD model is developed using ANSYS Fluent for the gas-phase characterization and the surface thin-film deposition, based on a kinetic Monte-Carlo (kMC) model database. To deal with the disturbance during reactor operation, a proportional integral (PI) control scheme is adopted, which manipulates the inlet precursor concentration to drive the precursor partial pressure to the set-point, ensuring the complete substrate coverage. Additionally, the CFD model is utilized to investigate a wide ran... [more]
Modeling and Economic Optimization of the Membrane Module for Ultrafiltration of Protein Solution Using a Genetic Algorithm
Tuan-Anh Nguyen, Shiro Yoshikawa
February 2, 2020 (v1)
Keywords: cross-flow, membrane module, Modelling, Optimization, protein solution, ultrafiltration
The performance of cross-flow ultrafiltration is greatly influenced by permeate flux behavior, which depends on many factors, including solution properties, membrane characteristics, and operating conditions. Currently, most research focuses on improving membrane performance, both in terms of permeability and selectivity. Only a few studies have paid attention to how the membrane module is configured and operated. In this study, the geometric design and operating conditions of a membrane module are considered as multivariable optimization variables. The objective function is the annual cost. The cost consists of a capital investment depending on the plant scale and an operating expense associated with energy consumption. In the optimization problem, the channel dimensions (width × length × height), and operating conditions (the inlet pressure and recirculation flow rate) were considered as decision variables. The operating configuration of the membrane plant is assumed to be feed and b... [more]
Splitting Triglycerides with a Counter-Current Liquid−Liquid Spray Column: Modeling, Global Sensitivity Analysis, Parameter Estimation and Optimization
Mark Nicholas Jones, Hector Forero-Hernandez, Alexandr Zubov, Bent Sarup, Gürkan Sin
January 2, 2020 (v1)
Keywords: hydrolysis, Modelling, Optimization, parameter estimation, sensitivity analysis, spray column, vegetable oil
In this work we present the model of a counter-current spray column in which a triglyceride (tripalmitic triglyceride) is hydrolyzed by water and leads to fatty acid (palmitic acid) and glycerol. A finite volume model (FVM) of the column was developed to describe the reactive extraction process with a two-phase system and validated with an analytical model from the literature with the given data set encompassing six experimental runs. Global, variance-based (Sobol) sensitivity analysis allowed assessment of the sensitivity of the sweet water glycerol content in respect to liquid density, overall mass-transfer coefficient, reaction rate coefficient and the equilibrium ratio to rank them accordingly. Furthermore, parameter estimation with a differential evolution (DE) algorithm was performed to obtain among others the mass transfer, backmixing and reaction rate coefficients. The model was used to formulate and solve a process design problem regarding economic and sustainable performance.... [more]
Salp Swarm Optimization Algorithm-Based Controller for Dynamic Response and Power Quality Enhancement of an Islanded Microgrid
Touqeer Ahmed Jumani, Mohd. Wazir Mustafa, Madihah Md. Rasid, Waqas Anjum, Sara Ayub
December 13, 2019 (v1)
Keywords: dynamic response enhancement, microgrid, Optimization, power quality, salp swarm optimization algorithm, voltage and frequency regulation
The islanded mode of the microgrid (MG) operation faces more power quality challenges as compared to grid-tied mode. Unlike the grid-tied MG operation, where the voltage magnitude and frequency of the power system are regulated by the utility grid, islanded mode does not share any connection with the utility grid. Hence, a proper control architecture of islanded MG is essential to control the voltage and frequency, including the power quality and optimal transient response during different operating conditions. Therefore, this study proposes an intelligent and robust controller for islanded MG, which can accomplish the above-mentioned tasks with the optimal transient response and power quality. The proposed controller utilizes the droop control in addition to the back to back proportional plus integral (PI) regulator-based voltage and current controllers in order to accomplish the mentioned control objectives efficiently. Furthermore, the intelligence of the one of the most modern soft... [more]
A PSO-Based Recurrent Closed-Loop Optimization Method for Multiple Controller Single-Output Thermal Engineering Systems
Xingjian Liu, Lei Pan
December 13, 2019 (v1)
Keywords: identification, Optimization, PID, PSO, thermal engineering process
For solving the problems of closed-loop optimization on controller parameters of multiple-controller single-output thermal engineering system, this paper proposes a recurrent optimization method that is based on the particle swarm computing and closed-loop simulation (PSO-RCO). It consists of a set of closed-loop identification, simulation, and optimization functions that are organized in a recurrent working flow. The working flow makes one controller tuned at a time whilst others keep their values. It ends after several rounds of overall optimizations. Such a recurrently alternative tuning can greatly speed up the convergence of controller parameters to reasonable values. Verifications on practical data from a superheated steam temperature control system show that the optimized control system performance is greatly improved by reasonable controller parameters and practicable control action. With the advantage of not interfering system operation and the potential supporting on big data... [more]
Optimal Design of Permanent Magnet Arrangement in Synchronous Motors
Xiaoyu Liu, Qifang Lin, Weinong Fu
December 10, 2019 (v1)
Keywords: finite element method, Optimization, parallel, permanent magnet, synchronous motor
A general pattern, which can include different types of permanent magnet (PM) arrangement in PM synchronous motors (PMSMs) is presented. By varying the geometric parameters of the general pattern, the template can automatically produce different types of PM arrangement in the rotor. By choosing the best arrangement of PMs using optimization method, one can obtain a better performance and lower manufacturing cost. Six of the most widely used conventional types of rotor structures can be obtained through the parameter variation of the general pattern. These types include five embedded PM types and a traditional surface-mounted PM type. The proposed approach combines optimization method embedded with finite element method (FEM) for solving the multi-objective optimization for the PM structures. To save computing load, this paper employs a strategy of sub-group optimization, which is on account of the impact levels of the design parameters on the objective functions, and a parallel computa... [more]
Biogas Engine Waste Heat Recovery Using Organic Rankine Cycle
Alberto Benato, Alarico Macor
December 10, 2019 (v1)
Keywords: biogas engine, fluid selection, Optimization, organic Rankine cycle, Technoeconomic Analysis, waste heat recovery
Italy is a leading country in the biogas sector. Energy crops and manure are converted into biogas using anaerobic digestion and, then, into electricity using internal combustion engines (ICEs). Therefore, there is an urgent need for improving the efficiency of these engines taking the real operation into account. To this purpose, in the present work, the organic Rankine cycle (ORC) technology is used to recover the waste heat contained in the exhaust gases of a 1 MWel biogas engine. The ICE behavior being affected by the biogas characteristics, the ORC unit is designed, firstly, using the ICE nameplate data and, then, with data measured during a one-year monitoring activity. The optimum fluid and the plant configuration are selected in both cases using an “in-house” optimization tool. The optimization goal is the maximization of the net electric power while the working fluid is selected among 115 pure fluids and their mixtures. Results show that a recuperative ORC designed using real... [more]
Surrogate Modeling for Liquid−Liquid Equilibria Using a Parameterization of the Binodal Curve
Christian Kunde, Tobias Keßler, Steffen Linke, Kevin McBride, Kai Sundmacher, Achim Kienle
December 10, 2019 (v1)
Keywords: liquid–liquid equilibrium, multistage extraction, numerical continuation, Optimization, parameterization, surrogate modeling
Computational effort and convergence problems can pose serious challenges when employing advanced thermodynamic models in process simulation and optimization. Data-based surrogate modeling helps to overcome these problems at the cost of additional modeling effort. The present work extends the range of methods for efficient data-based surrogate modeling of liquid−liquid equilibria. A new model formulation is presented that enables smaller surrogates with box-constrained input domains and reduced input dimensions. Sample data are generated efficiently by using numerical continuation. The new methods are demonstrated for the surrogate modeling and optimization of a process for the hydroformylation of 1-decene in a thermomorphic multiphase system.
Conversion Technologies: Evaluation of Economic Performance and Environmental Impact Analysis for Municipal Solid Waste in Malaysia
Rabiatul Adawiyah Ali, Nik Nor Liyana Nik Ibrahim, Hon Loong Lam
December 10, 2019 (v1)
Subject: Energy Policy
Keywords: municipal solid waste conversion technology, Optimization, P-graph
The generation of municipal solid waste (MSW) is increasing globally every year, including in Malaysia. Approaching the year 2020, Malaysia still has MSW disposal issues since most waste goes to landfills rather than being utilized as energy. Process network synthesis (PNS) is a tool to optimize the conversion technologies of MSW. This study optimizes MSW conversion technologies using a PNS tool, the “process graph” (P-graph). The four highest compositions (i.e., food waste, agriculture waste, paper, and plastics) of MSW generated in Malaysia were optimized using a P-graph. Two types of conversion technologies were considered, biological conversion (anaerobic digestion) and thermal conversion (pyrolysis and incinerator), since limited data were available for use as optimization input. All these conversion technologies were compared with the standard method used: landfilling. One hundred feasible structure were generated using a P-graph. Two feasible structures were selected from nine,... [more]
Design and Verification of a Single-Channel Pump Model based on a Hybrid Optimization Technique
Jin-Hyuk Kim, Sang-Bum Ma, Sung Kim, Young-Seok Choi, Kwang-Yong Kim
December 10, 2019 (v1)
Keywords: computational fluid dynamics (CFD), hybrid PSO-GA, Optimization, radial force, single-channel impeller, unsteady RANS
This paper handles a hybrid multiple optimization technique to concurrently enhance hydraulic efficiency and decrease unsteady radial forces resulting from fluid-induced vibration of a single-channel pump for wastewater treatment. A single-channel impeller and volute was optimized systematically by using a hybrid particle swarm optimization and genetic algorithm coupled with surrogate modeling. Steady and unsteady Reynolds-averaged Navier−Stokes analyses were conducted to optimize the internal flow path in the single-channel pump. Design variables for controlling the internal flow cross-sectional area of the single-channel impeller and volute in the single-channel pump were chosen to concurrently optimize objective functions with hydraulic efficiency and the unsteady radial forces resulting from impeller−volute interaction. The optimization results clearly showed that the arbitrary cluster optimum design considerably enhanced hydraulic efficiency and decreased the unsteady radial force... [more]
Sustainable Personnel Scheduling Problem Optimization in a Natural Gas Combined-Cycle Power Plant
Emir Hüseyin Özder, Evrencan Özcan, Tamer Eren
December 9, 2019 (v1)
Keywords: analytic network process (ANP), electricity generation sector, goal programming (GP), natural gas combined-cycle power plant, Optimization, skill-based personnel scheduling
This paper deals with a sustainable personnel scheduling problem of personnel working in a large-scale natural gas combined-cycle power plant in Turkey. The proposed model focuses on employee complaints due to unfair work schedules and the results of balanced assignments based on power plant interruptions. Eighty personnel work in three shifts at this natural gas combined-cycle power plant. The model is solved with respect to some of the workers’ skills, and there are 20 criteria regarding skills. The analytic network process method is used to get the weights of workers’ skills, which are calculated and included in the model. Goal programming is used in this paper. Our proposed model gives cost minimization and fair work schedules for the power plant. Compared with the literature, the number and set of criteria are unique in terms of personnel competency in the energy sector. Minimizing cost and imbalanced assignments was achieved by the proposed model for the first time without consid... [more]
Application of CFD to Analyze the Hydrodynamic Behaviour of a Bioreactor with a Double Impeller
Mohammadreza Ebrahimi, Melih Tamer, Ricardo Martinez Villegas, Andrew Chiappetta, Farhad Ein-Mozaffari
December 9, 2019 (v1)
Keywords: Computational Fluid Dynamics, dual-impeller, Optimization, Segment impeller, Stirred fermenter
Stirred bioreactors are commonly used unit operations in the pharmaceutical industry. In this study, computational fluid dynamics (CFD) was used in order to analyze the influence of the impeller configuration (Segment−Segment and Segment−Rushton impeller configurations) and the impeller rotational speed (an operational parameter) on the hydrodynamic behaviour and mixing performance of a bioreactor equipped with a double impeller. A relatively close agreement between the power values obtained from the CFD model and those measured experimentally was observed. Various parameters such as velocity profiles, stress generated by impellers due to the turbulence and velocity gradient, flow number, and mixing time were used to compare the CFD simulations. It was observed that the impeller’s RPM could change the intensity of the interaction between the impellers when a Segment−Rushton impeller was used. In general, increasing the RPM led to an increase in total power and the stress acting on the... [more]
Effective Use of Carbon Pricing on Climate Change Mitigation Projects: Analysis of the Biogas Supply Chain to Substitute Liquefied-Petroleum Gas in Mexico
Luis Alberto Díaz-Trujillo, Javier Tovar-Facio, Fabricio Nápoles-Rivera, José María Ponce-Ortega
December 3, 2019 (v1)
Subject: Energy Policy
Keywords: biogas, carbon emission trading, carbon tax, fossil fuel substitution, Optimization
There is presently an urgent demand for efficient and/or renewable energy technologies to correct global warming. However, these energy technologies are limited mainly by political and economic constraints of high costs and the lack of subsidy. Carbon-pricing strategies, such as carbon-emission taxes and carbon-emission trading schemes, may reduce this gap between sustainable and unsustainable energy technologies. Therefore, this paper seeks to analyze both of these carbon-pricing instruments in the Mexican energy sector to promote upgrading biogas investment and to substitute liquified petroleum gas consumption using an optimization approach. Furthermore, we propose a multi-objective optimization approach to encourage investment in the biogas supply chain supported by an effective use of carbon-pricing schemes. A case study of the central western region of Mexico was made to analyze the performance of the proposed methodologies. The results show that carbon-emission taxes and carbon-e... [more]
Numerical Investigation of a High-Pressure Submerged Jet Using a Cavitation Model Considering Effects of Shear Stress
Yongfei Yang, Wei Li, Weidong Shi, Wenquan Zhang, Mahmoud A. El-Emam
November 5, 2019 (v1)
Keywords: cavitation model, Computational Fluid Dynamics, nozzle, Optimization, shear stress, submerged jet
In the current research, a high-pressure submerged cavitation jet is investigated numerically. A cavitation model is created considering the effect of shear stress on cavitation formation. As such, this model is developed to predict the cavitation jet, and then the numerical results are validated by high-speed photography experiment. The turbulence viscosity of the renormalization group (RNG) k-ε turbulence model is used to provide a flow field for the cavitation model. Furthermore, this model is modified using a filter-based density correction model (FBDCM). The characteristics of the convergent-divergent cavitation nozzle are investigated in detail using the current CFD simulation method. It is found that shear stress plays an important role in the cavitation formation in the high-pressure submerged jet. In the result predicted by the Zwart-Gerber-Belamri (ZGB) cavitation model, where critical static pressure is used for the threshold of cavitation inception, the cavitation bubble on... [more]
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