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Records with Subject: Process Design
Showing records 132 to 156 of 2098. [First] Page: 1 3 4 5 6 7 8 9 10 11 Last
Effect of Connection Resistance between Cyclones and Backpass on Furnace Solids Suspension Density Profile and Circulation Rates in CFB
Guanwen Luo, Leming Cheng, Liyao Li, Junfeng Wang, Xiaoguo Jiang, Weiguo Zhang
April 25, 2023 (v1)
Keywords: CFB, connection between cyclones and backpass, resistance, solids circulation rate, solids suspension density, theoretical model
The connection section between cyclones and backpass is an important configuration in multi-cyclone circulating fluidized bed boilers (CFB). In this work, the resistance coefficient of different connection modes, and connection resistance distribution from each cyclone outlet to backpass (connection branch) in one mode are defined and calculated, in order to investigate their effects on furnace solids suspension density distribution and circulation rates. Three connection modes with different overall resistance coefficients were tested experimentally and analyzed by a 1.5-dimensional model in a four-cyclone scaling CFB apparatus. Both experimental and theoretical results show that, with larger overall resistance of a connection, there are more solids suspended in the furnace bottom and fewer in the top section. The investigation of the C-type connection has revealed that when the branch resistance of the connection decreases from branch No. 1−4, the solids suspension density and circul... [more]
The Analysis of Power Transformer Population Working in Different Operating Conditions with the Use of Health Index
Patryk Bohatyrewicz, Andrzej Mrozik
April 25, 2023 (v1)
Keywords: condition assessment, health index, population management, power transformer
The management of the power transformer population is a complex process, as the grid companies operate thousands of devices. For this issue, the health index method can be applied to facilitate asset management. The algorithm can be used not only in the technical assessment of the individual units, but also to determine the relationships within the whole population. In this paper, the presented health index method consists of periodic oil diagnostics, including the physicochemical properties, dissolved gas analysis, and furfural content, and further assessment in terms of the criticality of the device to determine the technical condition. The algorithm was specifically designed to reflect even the smallest changes of the input parameters in the final score. The performance of the health index was tested on 620 oil analyses from 220 transformers divided into four subpopulations based on the service conditions. The results have proven to be largely dependent on the criticality level and... [more]
Winding MMF and PM MMF Analysis of Axial-Flux Machine with Multi-Phase and Multi-Layer Winding
Qixu Chen, Guoli Li, Wenping Cao, Zhe Qian, Qunjing Wang
April 24, 2023 (v1)
Keywords: air permeance function method, axial-flux integrated starting/generator (ISG), multi-phase multi-layer winding, PM MMF, winding function method, winding MMF
According to star graph and winding distribution, winding MMFs of three kinds of 12-slot/10-pole multi-phase and multi-layer winding layout are analyzed by the improved winding function method. Analysis results show that multi-phase and multi-layer winding can suppress even order and (12n ± 1) order harmonics, thereby reducing the eddy-current loss in PMs. Based on the unfolded LPMSM model, rotor MMF, air gap flux density, and no-load back-EMF are analyzed by the analytical permeance function method, which is validated by Teslameter and no-load experiment. Winding MMF is validated by FEM. An axial-flux integrated starting/generator (ISG) with double-three-phase four-layer (DTP-FL) winding, segmented armature and PM, and centrifugal fan is designed and manufactured. The no-load and load test with two groups of resistance established has validated the reasonability of the mentioned method. Experiments show that the axial-flux ISG prototype can run at a relative temperature rise.
Combination of Metal Oxide and Polytriarylamine: A Design Principle to Improve the Stability of Perovskite Solar Cells
Marina M. Tepliakova, Alexandra N. Mikheeva, Pavel A. Somov, Eugene S. Statnik, Alexander M. Korsunsky, Keith J. Stevenson
April 24, 2023 (v1)
Keywords: hole-transport layer, perovskite solar cells, secondary ion spectroscopy, stable photovoltaics
In the last decade, perovskite photovoltaics gained popularity as a potential rival for crystalline silicon solar cells, which provide comparable efficiency for lower fabrication costs. However, insufficient stability is still a bottleneck for technology commercialization. One of the key aspects for improving the stability of perovskite solar cells (PSCs) is encapsulating the photoactive material with the hole-transport layer (HTL) with low gas permeability. Recently, it was shown that the double HTL comprising organic and inorganic parts can perform the protective function. Herein, a systematic investigation and comparison of four double HTLs incorporating polytriarylamine and thermally evaporated transition metal oxides in the highest oxidation state are presented. In particular, it was shown that MoOx, WOx, and VOx-based double HTLs provided stable performance of PSCs for 1250 h, while devices with NbOx lost 30% of their initial efficiency after 1000 h. Additionally, the encapsulati... [more]
Techno-Economic Performance Assessment of a Trigeneration System Operating in a Hospital
Aikaterini Papadimitriou, Anastasios Tosios, Eugenia Giannini
April 24, 2023 (v1)
Keywords: capacity factor, CCHP, CHP, energy saving, hospital, key performance indicators, performance evaluation
The techno-economic performance evaluation of a combined cooling heating and power (CCHP) system installed in a hospital building in Greece is presented. The aim was to verify performance standards and evaluate real behavior, while highlighting the economic gains. In this research, system performance was evaluated using actual and year-round field measurements. The data were used to calculate the recovered heat and the generated electric energy. Furthermore, the performance was modeled and compared to the manufacturer specifications. Financial assessment was conducted through energy cost analysis to verify the operating viability of the system, both for its heating and cooling functions. The results showed that, overall, after eight years of operation, the energy efficiency was still within design standards. Electrical efficiency was constantly above 30%, while thermal efficiency was around 40−45%. Total efficiency was usually above the 75% threshold, characterizing the system as fully... [more]
Experimental Evaluation of Energy-Efficiency in a Holistically Designed Building
Raluca Buzatu, Viorel Ungureanu, Adrian Ciutina, Mihăiţă Gireadă, Daniel Vitan, Ioan Petran
April 24, 2023 (v1)
Keywords: building performance, energy management system, holistic, indoor comfort, sustainable, thermal performance
The building sector continues to register a significant rise in energy demand and environmental impact, notably in developing countries. A considerable proportion of this energy is required during the operational phase of buildings for interior heating and cooling, leading to a necessity of building performance improvement. A holistic approach in building design and construction represents a step to moderate construction costs in conjunction with reduced long-term operating costs and a low impact on the environment. The present paper presents an experimental evaluation of the energy efficiency of a building under real climate conditions; the building, which represents a holistically designed modular laboratory, is located in a moderate continental temperate climate, characteristic of the south-eastern part of the Pannonian Depression, with some sub-Mediterranean influences. Considerations for the holistic design of the building, including multi-object optimization and integrated design... [more]
Biofuels for Maritime Transportation: A Spatial, Techno-Economic, and Logistic Analysis in Brazil, Europe, South Africa, and the USA
Francielle Carvalho, Joana Portugal-Pereira, Martin Junginger, Alexandre Szklo
April 24, 2023 (v1)
Keywords: biomass residues, GIS, IMO, logistics, maritime biofuel, transport fuels
Low or zero carbon fuels are crucial for maritime transportation decarbonization goals. This paper assesses potential localities for maritime biofuels (biobunkers) production in Brazil, Europe, South Africa, and United States considering geographical, logistic, and economic aspects. This assessment combines georeferenced and techno-economic analyses to identify suitable fuel production hotspots based on not only plant performance and costs but also on logistic integration and biomass seasonality. Five technology pathways were considered: Straight vegetable Oils (SVO), Hydrotreated Vegetable Oils (HVO), Fischer−Tropsch Biomass-to-liquids (FT-BTL), Alcohol oligomerization to middle distillates (ATD), and Hydrotreated Pyrolysis Oil (HDPO). Findings reveal that biomass concentration in Brazil makes it the region with highest biobunker potential, which are mostly close to coastal areas and surpasses regional demand. Although other regions registered more limited potentials, hotspots proximi... [more]
Capsule Vehicle Dynamics Based on Levitation Coil Design Using Equivalent Model of a Sidewall Electrodynamic Suspension System
Ranhee Yoon, Birhan Abebaw Negash, Wonhee You, Jungyoul Lim, Jinho Lee, Changyoung Lee, Kwansup Lee
April 24, 2023 (v1)
Keywords: capsule vehicle, electrodynamic suspension, guidance stiffness, levitation stiffness, vehicle dynamics
A levitation system based on sidewall electrodynamic suspension (EDS) is considered for a capsule vehicle, which is a next-generation high-speed transportation system currently being studied. This levitation system does not require controlling of the gap between the guideway and the vehicle on which the superconducting electromagnet is mounted. However, when the vehicle is operated in a levitated state, the ride comfort is worse than that of the levitation system based on electromagnetic suspension (EMS), making it necessary to develop methods that can ensure good riding comfort. In addition, because the EDS system is complex and nonlinear with a combination of electromagnetics and mechanical dynamics, it is complicated to analyze the dynamic characteristics of the capsule vehicle, and the corresponding numerical analysis is time-consuming. Therefore, to easily understand the running dynamics of a capsule vehicle in the sidewall EMS system, the magnetic suspension characteristics corre... [more]
The Influences of NP100 Surfactant and Pine-Oil Concentrations on Filtrate Volume and Filter-Cake Thickness of Microemulsion-Based Drilling Fluids (O/W)
Agostinho C. B. Junior, Raphael R. Silva, Giovanna L. R. Leal, Tarsila M. Tertuliano, Rafael P. Alves, Alfredo I. C. Garnica, Fabiola D. S. Curbelo
April 24, 2023 (v1)
Keywords: drilling fluid, experimental design, filter-cake thickness, filtrate volume, microemulsion
In this work, nonionic surfactant NP100 and pine oil influences on the filtrate volume (FV) and the filter-cake thickness (thkns) of microemulsified drilling fluids were studied. A ternary phase diagram was obtained to define the microemulsion region, where a 2k factorial design was used with the addition of four center points and axial points. Twelve microemulsion points were defined and used later in the formulation of the investigated drilling fluids. The results showed that the increase in the surfactant and pine oil’s concentration increased FV and thkns, withthe oil phase being the most influential component in the filtrate volume and the surfactant being the most influential in the filter-cake thickness. Statistically significant models were obtained. The optimal concentrations were determined for the lowest FV and thkns; 45% of surfactant and 5% of pine oil for the filtrate volume (1.3 mL), and 45% of surfactant and 15% of pine oil for the filter-cake thickness (0.64 mm).
A Review on Techno-Economic Assessment of Solar Water Heating Systems in the Middle East
Mehran Dehghan, Carlos F. Pfeiffer, Elyas Rakhshani, Reza Bakhshi-Jafarabadi
April 24, 2023 (v1)
Keywords: domestic hot water, Renewable and Sustainable Energy, solar thermal system, solar water heating system, space heating
Currently, the economy of Middle Eastern countries relies heavily on fossil fuel sources. The direct and indirect adverse consequences of fossil fuel utilization for power generation enforce the region’s countries to raise the share of renewable energy. In this context, various incentive policies have been developed to encourage the residential and industrial sectors to support a portion of energy needs through renewable energy resources. In this case, a solar water heating system (SWHS) as an application of solar thermal technology provides some of the heat energy requirements for domestic hot water (DHW) and space heating, supported conventionally by electricity or natural gas, or even other fossil fuels. This paper reviews the feasibility of the SWHS in the Middle East region from technical and economical standpoints and investigates some of the progress, challenges, and barriers toward this market. The pay-back times and CO2 emission reduction under different incentive frameworks a... [more]
Modified Model for Shallow Soil Strength Recovery Calculation during Set-Up Periods of Jetted Conductor—A Case Study of Equatorial Guinea Bay Deep-Water Drilling
Wei Yan, Said Juma Kambi, Xin Huang, Hai Lin, Hailong Liu, Jingen Deng
April 24, 2023 (v1)
Keywords: conductor setting depth, deep-water drilling, set-up time, shallow soil strength recovery
Jetted conductor setting depth is crucial for deep-water drilling. This paper presents an innovative method for determining the shallow soil resistance strength recovery factor based on the field data of Equatorial Guinea bay. It shows that the soil strength recovery factor of Equatorial Guinea bay is lower than that of the Gulf of Mexico. The conductor setting depth calculation referring to other place will have a high risk of wellhead sinking. According to the newly established designing charts, the conductor setting depth was recommended for the S1 well. Each preferred set-up period requires a specific setting depth. If the chosen set-up period is 2 days, the expected setting depth of a 36″ conductor should be 250 ft (76.2 m) and, similarly, 295 ft (89.9 m) for a 30″ conductor. The relationship between set-up period and surface conductor setting depth is established as well. Wellhead landed load appears to be the crucial factor for determining the conductor setting depth. The ration... [more]
Application of an Improved Mayr-Type Arc Model in Pyro-Breakers Utilized in Superconducting Fusion Facilities
Jun He, Ke Wang, Jiangang Li
April 24, 2023 (v1)
Keywords: black-box arc model, DC circuit breaker, PSCAD, pyro-breaker
Pyro-breaker, a fast-responding, highly reliable and explosive-driven circuit breaker, is utilized in several Quench Protection Systems (QPS). The commutation process and its parameters are the main technical considerations in the process of designing a new pyro-breaker. The commutation parameters, such as the commutation time and the current change rate, are not only determined by the electrical parameters of the commutation circuit but also the arc behavior during the operation. The arc behavior is greatly affected by the structure and the driving mechanism of the Commutation Section (CS) in the pyro-breaker. The arc model was developed decades ago and the black-box arc model is considered a valid method to study arc behavior. In this paper, the Schavemaker black-box arc model, an improved Mayr-type arc model, is applied to study the commutation process of a newly designed pyro-breaker. Unlike normal circuit breakers, the arc discussed in this paper is discharged in deionized water.... [more]
Optimal Selection of Asynchronous Motor-Gearhead Couple Fed by VFD for Electrified Vehicle Propulsion
Shailendra Rajput, Eliyahu Farber, Moshe Averbukh
April 24, 2023 (v1)
Keywords: AC motor, electrified vehicles, gearbox, optimal system design, variable frequency drive
Widespread applications of AC motors fed by variable frequency drives in electrified vehicles have become a conventional technical solution. The flexibility of control, low cost, and high energy efficiency attract developers and engineers to apply these appliances in cars, railway trains, trams, etc. The distinctive characteristic of vehicles is a wide range of required rotation speed and torque. This circumstance means that the problems of the AC motor (nominal power, synchronous speed) and gearbox (transmission ratio) become non-trivial and necessitate optimal selection to ensure the best functionality of the entire driving system. This study proposes an approach for the optimal choice of a specific AC motor (nominal rating, synchronous speed) and the transmission ratio of the gearbox by analyzing the entire system’s losses. The optimal selection of an AC motor ensures maximum energy efficiency for a specific transportation driving cycle.
Incentive-Based Demand Response Framework for Residential Applications: Design and Real-Life Demonstration
Angelina D. Bintoudi, Napoleon Bezas, Lampros Zyglakis, Georgios Isaioglou, Christos Timplalexis, Paschalis Gkaidatzis, Athanasios Tryferidis, Dimosthenis Ioannidis, Dimitrios Tzovaras
April 24, 2023 (v1)
Keywords: demand-response, incentive-based, load management, optimisation
In 2020, residential sector loads reached 25% of the overall electrical consumption in Europe and it is foreseen to stabilise at 29% by 2050. However, this relatively small increase demands, among others, changes in the energy consuming behaviour of households. To achieve this, Demand Response (DR) has been identified as a promising tool for unlocking the hidden flexibility potential of residential consumption. In this work, a holistic incentive-based DR framework aiming towards load shifting is proposed for residential applications. The proposed framework is characterised by several innovative features, mainly the formulation of the optimisation problem, which models user satisfaction and the economic operation of a distributed household portfolio, the customised load forecasting algorithm, which employs an adjusted Gradient Boosting Tree methodology with enhanced feature extraction and, finally, a disaggregation tool, which considers electrical features and time of use information. T... [more]
Structural Response of a Single-Stage Centrifugal Compressor to Fluid-Induced Excitations at Low-Flow Operating Condition: Experimental and Numerical Study
Kirill Kabalyk, Andrzej Jaeschke, Grzegorz Liśkiewicz, Michał Kulak, Tomasz Szydłowski, Robert Pietruszewski
April 24, 2023 (v1)
Keywords: centrifugal compressor, fluid-structure interaction, off-design operation
The article describes an assessment of possible changes in constant fatigue life of a medium flow-coefficient centrifugal compressor impeller subject to operation at close-to-surge point. Some aspects of duct acoustics are additionally analyzed. The experimental measurements at partial load are presented and are primarily used for validation of unidirectionally coupled fluid-structural numerical model. The model is based on unsteady finite-volume fluid-flow simulations and on finite-element transient structural analysis. The validation is followed by the model implementation to replicate the industry-scale loads with reasonably higher rotational speed and suction pressure. The approach demonstrates satisfactory accuracy in prediction of stage performance and unsteady flow field in vaneless diffuser. The latter is deduced from signal analysis relying on continuous wavelet transformations. On the other hand, it is found that the aerodynamic incidence losses at close-to-surge point are un... [more]
Impedance Matching Method for 6.78 MHz Class-E2-Based WPT System
Yi Zhang, Yue Feng, Sheng Liu, Jiande Wu, Xiangning He
April 24, 2023 (v1)
Keywords: class-E2-based WPT system, double-L-type IMN, impedance matching method
The performance of a conventional Class-E2-based WPT system is sensitive to system parameters such as the coil coupling coefficient and load variation. System efficiency decreases rapidly when the coil coupling coefficient and load deviate from their optimum values. In this paper, an impedance matching method and a design procedure are proposed to maintain high system efficiency over a wider range of coupling coefficient and load variations. The load-pull technique is adopted to identify the high-efficiency load region of a Class-E power amplifier (PA), and a double-L-type impedance matching network (IMN) is proposed to transform the load impedance of a Class-E PA into a high-efficiency working region. Compared to a single L-type IMN, a double-L-type IMN is more flexible and has better tuning performance. A 6.78 MHz Class-E2-based WPT system was built to validate the proposed design method. The experimental results show that the proposed double-L-type IMN can significantly attenuate th... [more]
Transition to Zero Energy and Low Carbon Emission in Residential Buildings Located in Tropical and Temperate Climates
Modeste Kameni Nematchoua, José A. Orosa, Paola Ricciardi, Esther Obonyo, Eric Jean Roy Sambatra, Sigrid Reiter
April 21, 2023 (v1)
Keywords: low carbon, residential buildings, temperate climate, tropical, zero-energy
Different methods to achieve zero-energy and low carbon on the scale of a building are shown by most of the research works. Despite this, the recommendations generally offered by researchers do not always correspond to the realities found during the construction of new buildings in a determined region. Therefore, a standard may not be valid in all climate regions of the world. Being aware of this fact, a study was carried out to analyse the design of new buildings respecting the “zero-energy and low carbon emission” concept in tropical climatic regions when they are compared with a base case of temperate regions. To reach this objective, the comparison between real and simulated data from the different buildings studied was developed. The results showed that the renovation of existing residential buildings allows for reducing up to 35% of energy demand and a great quantity of CO2 emissions in both climate types. Despite this, the investment rate linked to the construction of zero-energ... [more]
Performance Analysis of a Printed Circuit Heat Exchanger with a Novel Mirror-Symmetric Channel Design
Cheng-Yen Chang, Wei-Hsin Chen, Lip Huat Saw, Arjay Avilla Arpia, Manuel Carrera Uribe
April 21, 2023 (v1)
Keywords: efficiency, heat transfer coefficient, NTU value, nusselt number, PCHE, print circuit heat exchanger, thermal performance
The printed circuit heat exchanger (PCHE) is a promising waste heat recovery technology to improve energy efficiency. The current investigation presents the experimental results on the thermal performance of a novel PCHE for low-temperature waste heat recovery. The novel PCHE was manufactured using precision machining and diffusion bonding. The thermal performances, such as effectiveness and NTU values at different temperatures, are evaluated, and water is used as a working fluid. The experimental results indicate that the PCHE’s effectiveness is around 0.979 for an inlet flow temperature of 95 °C. The predominant factors affecting the thermal performance of the PCHE are the inlet flow temperature and the flow rate of the working fluid. In addition, a comparison of the experimental results and the literature shows that the effectiveness of the PCHE is better than the others, which have fewer layers of PCHE fins.
Techno-Economic Modelling of Micro-Hydropower Mini-Grids in Nepal to Improve Financial Sustainability and Enable Electric Cooking
William Clements, Surendra Pandit, Prashanna Bajracharya, Joe Butchers, Sam Williamson, Biraj Gautam, Paul Harper
April 21, 2023 (v1)
Keywords: demand-side management, electric cooking, micro-hydropower, mini-grid, Nepal, techno-economic model
In rural Nepal, micro-hydropower plant mini-grids provide renewable electricity to thousands of communities but the plants often have poor financial sustainability. Widespread uptake of electric cooking in such communities is currently not feasible due to high peak loads and limited capacity. In this paper, we develop a Remote-Areas Multi-Energy Systems Load Profiles (RAMP)-based stochastic techno-economic model for evaluating the economic viability of off-grid communities and improving their financial sustainability by introducing new appliances, productive end uses, and demand-side management measures. The model can be used to understand community electricity demand, assess economic status, determine equitable and profitable tariff structures, and plan new connections including electric cooking promotion or new industrial machines. Detailed electric cooking load modelling functionality was developed to represent Nepali cooking practices, scalable to approximate widespread uptake of e... [more]
Biomethane Potential of Selected Organic Waste and Sewage Sludge at Different Temperature Regimes
German Smetana, Ewa Neczaj, Anna Grosser
April 21, 2023 (v1)
Keywords: algae biomass, anaerobic digestion, biochemical methane potential assay, co-digestion, grease trap sludge, organic fraction of municipal sewage waste, sewage sludge, specific cumulative methane production
Sewage sludge (SS) generation and its management still pose a problem in many countries. Anaerobic co-digestion (AcD) of SS with grease trap sludge (GTS) and organic fraction of municipal sewage waste (OFMSW), which are two easily biodegradable substrates, may improve biogas production and AcD kinetics. Algae biomass (AB) of the species Undaria pinnatifida can be the third co-digestion component that may also affect the AcD performance. The aim of the study was therefore to evaluate the performance of mesophilic and thermophilic SS batch AcD with OFMSW, GTS as well as AB through biochemical methane potential (BMP) assay in relation to cumulative specific biogas (YB) and methane yields (Ym). Three kinetic models were applied within the scope of the kinetic study. Results of the study showed that the mixture containing SS, GTS and AB brought the most noticeable improvements in Ym compared to other studied mixtures and in respect to standalone SS digestion, the improvement amounted to 88.... [more]
Determination of Nitrogen and Sulphur Mineralization in Batch and Semi-Continuous Anaerobic Digestion Using an Artificial Fiber Bag Technique
Jacob Rosholm Mortensen, Alastair James Ward, Martin Riis Weisbjerg, Sasha Daniel Hafner, Henrik Bjarne Møller
April 21, 2023 (v1)
Keywords: anaerobic digestion, artificial fiber bag technique, method validation, mineralization, nitrogen, sulphur
In the biogas industry, feedstock plans are used to estimate methane production and nutrient content in the digestate, however, these predictions do not consider the mineralized nitrogen fraction of the feedstock, which is useful when determining the quality of the digestate. In this study, the artificial fiber bag technique, which is commonly used to study feedstock degradation in ruminants, was implemented in anaerobic digestion to quantify mineralization of N and S. The artificial fiber bags were used to enclose substrates but with access to inoculum because of small pores in the bags, thereby enabling digestion. The content of the bags was analyzed before and after digestion to quantify residual mass as well as N and S concentration in the substrate. The method was validated through batch anaerobic digestion of a single substrate with and without bags, where the bags showed little influence on methane production and degradation. Semi-continuous anaerobic digestion experiments showe... [more]
Conceptual Design of an Energy System for High Altitude Airships Considering Thermal Effect
Qiumin Dai, Daoming Xing, Xiande Fang, Yingjie Zhao
April 21, 2023 (v1)
Keywords: energy system, high altitude airships, solar array, thermal-electric model
High altitude airships possess tremendous potential for long-endurance spot hovering platforms for both commercial and strategic applications. The energy system, which is mainly made up of solar array and regenerative fuel cell, is the key component of a high altitude airship. The thermal effect is a major factor that affects the performance of the energy system of long endurance stratospheric vehicles. In this paper, a conceptual design method focusing on the thermal and power characteristics of an energy system for stratospheric airships is proposed. The effect of thermal behavior of solar array on the energy system is analyzed. An optimized case is obtained on the consideration of power supply, thermal behaviors of helium and solar array. Results show that the maximum temperature difference of the solar array may be reduced by about 20 K and the mass of payload can be improved by up to 5%.
Design of a Low-Cost Multiplexer for the Study of the Impact of Soiling on PV Panel Performance
Gabriel López, Diego Ramírez, Joaquín Alonso-Montesinos, Juan Sarmiento, Jesús Polo, Nuria Martín-Chivelet, Aitor Marzo, Francisco Javier Batlles, Pablo Ferrada
April 21, 2023 (v1)
Keywords: I–V curves, multiplexer, PV plants monitoring, soiling
Atmospheric factors, such as clouds, wind, dust, or aerosols, play an important role in the power generation of photovoltaic (PV) plants. Among these factors, soiling has been revealed as one of the most relevant causes diminishing the PV yield, mainly in arid zones or deserts. The effect of soiling on the PV performance can be analyzed by means of I−V curves measured simultaneously on two PV panels: one soiled and the other clean. To this end, two I−V tracers, or one I−V tracer along with a multiplexer, are needed. Unfortunately, these options are usually expensive, and only one I−V tracer is typically available at the site of interest. In this work, the design of a low-cost multiplexer is described. The multiplexer is controlled by a low-cost single-board microcontroller manufactured by ArduinoTM, and is capable of managing several pairs of PV panels almost simultaneously. The multiplexer can be installed outdoors, in contrast to many commercial I−V tracers or multiplexers. This adva... [more]
Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage
Botao Zhang, Xiaochen Mao, Xiaoxiong Wu, Bo Liu
April 21, 2023 (v1)
Keywords: shock wave, stall margin, tip clearance size, tip leakage flow, transonic compressor
To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the inve... [more]
The Equivalent Thermal Conductivity of the Micro/Nano Scaled Periodic Cubic Frame Silver and Its Thermal Radiation Mechanism Analysis
Haiyan Yu, Haochun Zhang, Heming Wang, Dong Zhang
April 21, 2023 (v1)
Keywords: equivalent thermal conductivity, micro scale, thermal radiation, thermal radiation mechanism
Currently, there are few studies on the influence of microscale thermal radiation on the equivalent thermal conductivity of microscale porous metal. Therefore, this paper calculated the equivalent thermal conductivity of high-porosity periodic cubic silver frame structures with cell size from 100 nm to 100 µm by using the microscale radiation method. Then, the media radiation characteristics, absorptivity, reflectivity and transmissivity were discussed to explain the phenomenon of the radiative thermal conductivity changes. Furthermore, combined with spectral radiation properties at the different cross-sections and wavelength, the radiative transmission mechanism inside high-porosity periodic cubic frame silver structures was obtained. The results showed that the smaller the cell size, the greater radiative contribution in total equivalent thermal conductivity. Periodic cubic silver frames fluctuate more in the visible band and have better thermal radiation modulation properties in the... [more]
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