Use of CFD Tools in Internal Deflector Design for Cross Flow Turbine Efficiency Improvement

2012 ◽  
Author(s):  
Sergio D. Croquer ◽  
Jesus de Andrade ◽  
Jorge Clarembaux ◽  
Freddy Jeanty ◽  
Miguel Asuaje
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Small Scale ◽  
Efficiency Improvement ◽  
Hydropower Generation ◽  
Turbine Efficiency ◽  
Starting Point

Cross Flow Turbines (CFT), also known as Banki or Ossberger turbines are broadly used in small scale hydropower generation. Easy construction and operation, low CAPEX and OPEX and fairly independent efficiency from flow rate are the main characteristics of the CFT. However, they also tend to have a modest efficiency (80%), hence they are not considered for large scale power plants. Previous work have focused on use of Internal Deflectors (ID) for CFT efficiency improvement. However experimental flow observation and characterization inside CFT is hard to achieve. This work proposes use of Computational Fluid Dynamic (CFD) tools as an aid in ID design. A transient regime, two-dimensional, numerical model of a CFT without any internal deflectors was carried out. Deviation from experimental results at BEP was close to 5%. CFT w/o ID results were used as ID design starting point. Parameters: Upper Blade Position and ID Length were defined and varied obtaining six different ID versions. Numerical models were carried out for evaluation of ID effect on CFT. CFT hydraulic efficiency improvement was achieved for all ID versions studied (range 0.5%–3%, average:1.9%). Output power was also augmented (range 0.3%–4%, average:2.5%)for all cases.

scholarly journals Vanadium Redox Flow Batteries: A Review Oriented to Fluid-Dynamic Optimization

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 176
Author(s):  
Iñigo Aramendia ◽  
Unai Fernandez-Gamiz ◽  
Adrian Martinez-San-Vicente ◽  
Ekaitz Zulueta ◽  
Jose Manuel Lopez-Guede
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Vanadium Redox Flow Battery ◽  
Redox Flow Batteries ◽  
Design Flexibility ◽  
Flow Batteries ◽  
Exchange Membrane ◽  
Vanadium Redox

Large-scale energy storage systems (ESS) are nowadays growing in popularity due to the increase in the energy production by renewable energy sources, which in general have a random intermittent nature. Currently, several redox flow batteries have been presented as an alternative of the classical ESS; the scalability, design flexibility and long life cycle of the vanadium redox flow battery (VRFB) have made it to stand out. In a VRFB cell, which consists of two electrodes and an ion exchange membrane, the electrolyte flows through the electrodes where the electrochemical reactions take place. Computational Fluid Dynamics (CFD) simulations are a very powerful tool to develop feasible numerical models to enhance the performance and lifetime of VRFBs. This review aims to present and discuss the numerical models developed in this field and, particularly, to analyze different types of flow fields and patterns that can be found in the literature. The numerical studies presented in this review are a helpful tool to evaluate several key parameters important to optimize the energy systems based on redox flow technologies.

Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

2000 ◽  
Vol 663 ◽  
Author(s):  
J. Samper ◽  
R. Juncosa ◽  
V. Navarro ◽  
J. Delgado ◽  
L. Montenegro ◽  
...  
Keyword(s):  
Large Scale ◽  
Reference Model ◽  
Numerical Models ◽  
Full Scale ◽  
Small Scale ◽  
Model Parameters ◽  
In Situ Test ◽  
Wide Range ◽  
Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

On turbulent separation in the flow past a bluff body

1992 ◽  
Vol 241 ◽  
pp. 443-467 ◽  
Author(s):  
A. Neish ◽  
F. T. Smith
Keyword(s):  
Large Scale ◽  
Bluff Body ◽  
Separated Flow ◽  
Small Scale ◽  
Supporting Evidence ◽  
Turbulent Regime ◽  
Trailing Edge ◽  
Flow Past ◽  
Starting Point ◽  
Turbulence Factor

The basic model problem of separation as predicted by the time-mean boundary-layer equations is studied, with the Cebeci-Smith model for turbulent stresses. The changes between laminar and turbulent flow are investigated by means of a turbulence ‘factor’ which increases from zero for laminar flow to unity for the fully turbulent regime. With an attached-flow starting point, a small increase in the turbulence factor above zero is found to drive the separation singularity towards the trailing edge or rear stagnation point for flow past a circular cylinder, according to both computations and analysis. A separated-flow starting point is found to produce analogous behaviour for the separation point. These findings lead to the suggestion that large-scale separation need not occur at all in the fully turbulent regime at sufficiently high Reynolds number; instead, separation is of small scale, confined near the trailing edge. Comments on the generality of this suggestion are presented, along with some supporting evidence from other computations. Further, the small scale involved theoretically has values which seem reasonable in practical terms.

Measurement of Flow-Induced Forces: A Single Flexible Tube in a Rigid Triangular-Pitch Bundle Subjected to Two-Phase Cross-Flow

2015 ◽  
Author(s):  
Enrico Deri ◽  
Joël Nibas ◽  
Olivier Ries ◽  
André Adobes
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Tube Bundle ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Maintenance Policy ◽  
Excitation Spectra ◽  
Two Phase ◽  
Force Coefficients ◽  
Out Of Plane

Flow-induced vibrations of Steam Generator tube bundles are a major concern for the operators of nuclear power plants. In order to predict damages due to such vibrations, EDF has developed the numerical tool GeViBus, which allows one to asses risk and thereafter to optimize the SG maintenance policy. The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be assessed by experiment. The database of dimensionless coefficients is updated in order to cover all existing tube bundle configurations. Within this framework, a new test rig was presented in a previous conference with the aim of assessing parallel triangular tube arrangement submitted to a two-phase cross-flow. This paper presents the result of the first phase of the associated experiments in terms of force coefficients and two-phase flow excitation spectra for both in-plane and out-of-plane vibration.

scholarly journals Social Preferences for Small-Scale Solar Photovoltaic Power Plants in South Korea: A Choice Experiment Study

2018 ◽  
Vol 10 (10) ◽  
pp. 3589 ◽  
Author(s):  
Hye-Jeong Lee ◽  
Sung-Yoon Huh ◽  
Seung-Hoon Yoo
Keyword(s):  
Choice Experiment ◽  
Power Plants ◽  
Large Scale ◽  
Preference Heterogeneity ◽  
Small Scale ◽  
Solar Photovoltaic ◽  
The South ◽  
Korean People ◽  
South Korean ◽  
Electricity Bill

To reduce greenhouse gas emissions, the South Korean government plans to expand the installation of small-scale solar photovoltaic (SPV) power plants, which do not occupy large spaces and have a smaller environmental impact than large-scale SPV power plants. This article applies a choice experiment to evaluate quantitatively the value given by people to the attributes of the installation of small-scale SPV power plants. To reflect the preference heterogeneity of South Korean people, a Bayesian estimation of a mixed-logit model is successfully performed. According to the results, South Korean people consider the electricity bill, the operating body, and the installation location as being more important than other attributes. The respondents prefer small-scale SPV power plants that are located in residential areas, have a large scale of installation, are operated by a private corporation and produce electricity for self-consumption. For these attributes, the South Korean people are willing to pay an additional electricity bill of South Korean won (KRW) 4286/month, KRW 3712/kW, KRW 2885/month and KRW 3731/month, respectively. The results provide meaningful implications regarding the aspects of installation on which the government should focus. In addition, the results can be utilized in policy making and decision making related to the installation of small-scale SPV power plants.

scholarly journals Narratives of everyday resilience: lessons from an urban kampung community in Surabaya, Indonesia

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shirleyana ◽  
Scott Hawken ◽  
Riza Yosia Sunindijo ◽  
David Sanderson
Keyword(s):  
Inner City ◽  
Design Methodology ◽  
Large Scale ◽  
Small Scale ◽  
Content Type ◽  
Disadvantaged Communities ◽  
Political Network ◽  
Starting Point ◽  
Resilience Factors ◽  
Depth Interviews

Purpose This paper aims to discuss what people perceive as risks and resilience factors, and how they build everyday resilience. Design/methodology/approach The study focuses on Kampung (literally “village”) Plampitan, a neighbourhood in the inner-city part of Surabaya. The research used field observation, in-depth interviews and workshops during community meetings to collect data. Findings The results show how people respond to daily risks and find the support necessary to survive. The problems and risks revealed in the study include crime and economic difficulties, such as unemployment and insufficient income. Coping strategies identified are classified into place-based adaption, people-based network and political network. These strategies can serve as a starting point for local communities to assess their resilience and assist them in enhancing “everyday” resilience. Originality/value The paper argues that the concept of resilience must go beyond top-down approaches to disaster risk management and integrate bottom-up understanding from the perspective of local people, especially among marginal and disadvantaged communities. The paper develops the emerging and overlooked concept of “everyday resilience” and suggests that it is essential in surviving both “everyday” or small-scale chronic risks and large-scale disasters.

scholarly journals A highly flexible laboratory setup to demonstrate granular flow characteristics

2020 ◽  
Vol 104 (2) ◽  
pp. 1581-1596
Author(s):  
Thomas Heinze
Keyword(s):  
Granular Flow ◽  
Large Scale ◽  
Numerical Models ◽  
Low Cost ◽  
Experimental Investigations ◽  
Small Scale ◽  
Local Pressure ◽  
Slope Length ◽  
Runout Distance ◽  
Laboratory Setup

Abstract Dynamics of snow avalanches or landslides can be described by rapid granular flow. Experimental investigations of granular flow at laboratory scale are often required to analyze flow behaviour and to develop adequate mathematical and numerical models. Most investigations use image-based analysis, and additional sensors such as pressure gauges are not always possible. Testing various scenarios and parameter variations such as different obstacle shapes and positions as well as basal topography and friction usually requires either the construction of a new laboratory setups for each test or a cumbersome reconstruction. In this work, a highly flexible and modular laboratory setup is presented based on LEGO bricks. The flexibility of the model is demonstrated, and possible extensions for future laboratory tests are outlined. The setup is able to reproduce published laboratory experiments addressing current scientific research topics, such as overflow of a rigid reflector, flow on a bumpy surface and against a rigid wall using standard image-based analysis. This makes the setup applicable for quick scenario testing, e.g. for hypothesis testing or for low-cost testing prior to large-scale experiments, and it can contribute to the validation of external results and to benchmarks of numerical models. Small-scale laboratory setups are also very useful for demonstration purposes such as education and public outreach, both crucial in the context of natural hazards. The presented setup enables variation of parameters such as of slope length, channel width, height and shape, inclination, bed friction, obstacle position and shape, as well as density, composition, amount and grain size of flowing mass. Observable quantities are flow type, flow height, flow path and flow velocity, as well as runout distance, size and shape of the deposited material. Additional sensors allow further quantitative assessments, such as local pressure values.

A Perspective on Energy Storage and Other Means to Integrate Increasing Shares of Renewable Electricity Generation

Green ◽  
2014 ◽  
Vol 4 (1-6) ◽  
Author(s):  
Arndt Neuhaus ◽  
Frank-Detlef Drake ◽  
Gunnar Hoffmann ◽  
Friedrich Schulte
Keyword(s):  
Energy Storage ◽  
Power Plants ◽  
Large Scale ◽  
Distributed Storage ◽  
Renewable Energy Sources ◽  
Energy Transition ◽  
System Stability ◽  
Small Scale ◽  
Specific Class ◽  
High Level

AbstractThe transition to a sustainable electricity supply from renewable energy sources (RES) imposes major technical and economic challenges upon market players and the legislator. In particular the rapid growth of volatile wind power and photovoltaic generation requires a high level of flexibility of the entire electricity system, therefore major investments in infrastructures are needed to maintain system stability. This raises the important question about the role that central large-scale energy storage and/or small-scale distributed storage (“energy storage at home”) are going to play in the energy transition. Economic analyses show that the importance of energy storage is going to be rather limited in the medium term. Especially competing options like intelligent grid extension and flexible operation of power plants are expected to remain favourable. Nonetheless additional storage capacities are required if the share of RES substantially exceeds 50% in the long term. Due to the fundamental significance of energy storages, R&D considers a broad variety of types each suitable for a specific class of application.

Numerical Investigation of a Banki Turbine in Transient State: Reaction Ratio Determination

2012 ◽  
Author(s):  
Sergio D. Croquer ◽  
Jesus de Andrade ◽  
Jorge Clarembaux ◽  
Freddy Jeanty ◽  
Miguel Asuaje
Keyword(s):  
Numerical Models ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Turbulence Models ◽  
Transient State ◽  
Major Influence ◽  
Small Scale ◽  
Complex Flow ◽  
Impulse Turbine ◽  
Reaction Ratio

Cross-Flow Turbines (CFT) also known as Banki Turbines, are often considered for small scale hydroelectric generation. They are known for their simple construction, maintenance and operation, which means they incur in lower CAPEX and OPEX when compared to other types of turbines. However, they also tend to have a modest efficiency (82% [1–3]), hence they are not considered for big scale operations. Little is known about the flow characteristics inside the runner of the CFT. The objective of this investigation is to better understand the flow inside CFTs using Computational Fluid Dynamics (CFD) tools. Steady and Transient State simulations were performed for a CFT at an specific speed NS = 45. SST and κ–ε turbulence models were compared in terms of simulation requirements and obtained results. A proposed runner-nozzle interface, considering real CFT existent gap between these two components (free space) was evaluated as well. Results were compared to available experimental data. Maximum, numerically calculated efficiency deviation from reported experimental global efficiency was 15%. Pressure and velocity profiles along nozzle outlet, energy transfer stages location and CFT reaction ratio values were addressed. Results were compared in terms of runner-nozzle interface (gap vs no-gap), turbulence model (SST vs κ–ε) and calculation regime (steady vs transient regime). Only calculation state (steady vs transient) was found to have major influence over results. Transient state calculations better representing complex flow inside the CFT. Obtained degrees of reaction (no runner-nozzle gap, SST, transient state) were 0.12 and 0.08, for 1st and 2nd stages respectively. Hence the CFT is defined, according to this numerical models, as an impulse turbine.

scholarly journals Overview of hydropower resources and development in Uganda

AIMS Energy ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1299-1320
Author(s):  
Vincent Katutsi ◽  
◽  
Milly Kaddu ◽  
Adella Grace Migisha ◽  
Muhumuza Ezra Rubanda ◽  
...  
Keyword(s):  
Power Generation ◽  
Social Factors ◽  
Power Plants ◽  
Future Prospect ◽  
Small Scale ◽  
Hydropower Generation ◽  
Hydropower Development ◽  
Hydro Power ◽  
Hydropower Plants ◽  
Total Capacity

<abstract> <p>Even though hydropower plants are currently the most dominant source of electricity in Uganda, the rate of development of these resources for power generation remains low. Using a semi-systematic review approach, this paper seeks to understand why there is a slow rate of hydropower development in Uganda (challenges) and thereby provide potential solutions to these challenges. With current total capacity of about 1011 MW, findings indicate that there is a higher future prospect for hydropower generation in Uganda, with an estimated potential of over 4500 MW. In terms of number of projects, small-scale hydropower plants dominate power plants in Uganda, currently accounting for 19 out of 35 grid-connected power plants. However, with 855 MW installation capacity, large hydropower plants dominate the power generation plants landscape in Uganda. This study found that the challenges to hydropower development in this country are multi-dimensional including technical, economic, environmental, and social factors, and shows that the cross-cutting challenge is lack of human capacity that possess adequate skills to handle hydropower projects in the country. Furthermore, this study discussed practical solutions to address the identified problems facing hydro power in Uganda.</p> </abstract>

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