Increased Availability From Improved Condenser Design

2002 ◽  
Author(s):  
Joseph W. Harpster
Keyword(s):  
Flow Characteristics ◽  
Life Cycle Management ◽  
Theoretical Description ◽  
Fuel Savings ◽  
The Past ◽  
Noncondensable Gases ◽  
Plant Life Cycle ◽  
Air Ingress ◽  
Air Removal ◽  
Removal Equipment

Performance parameters and flow characteristics on the shell side of surface condensers are becoming better understood. Contributing to this knowledge base is the recent ability to measure the physical properties as well as the quantity of gases being removed from the condenser by air removal equipment. Reviewed here are the commonality of these data from many operating condensers obtained over the past six years and other known condenser measurements, theory and laboratory experiments. These are combined to formulate global theoretical description of condenser dynamics describing the mechanism responsible for aeration and de-aeration, excess back pressure buildup due to air ingress or generation of other noncondensable gases, and the dissolubility of corrosive gases in condensate. The theoretical description supports a dynamic model useful for deciding condenser configuration design and design improvements. Features of design found in many operating condensers that promote aeration and resulting corrosion are presented. The benefits of the model and engineering design modifications to plant life cycle management, improved condenser performance, outage reduction and reliability improvements, lost load recovery and fuel savings are discussed.

scholarly journals Environmental assessment of the Tung cultivation through life cycle analysis

2014 ◽  
Vol 3 (1) ◽  
pp. 70 ◽  
Author(s):  
Marcelo Bern�l ◽  
Rosana Schneider ◽  
�nio Machado
Keyword(s):  
Life Cycle ◽  
Production Systems ◽  
Life Cycle Management ◽  
Assessment Method ◽  
Agroforestry Systems ◽  
Family Farms ◽  
Conventional Agriculture ◽  
The Past ◽  
Ecosystem Changes ◽  
Poor Soil

Over the past few decades, conventional agriculture has been facing serious crises caused by numerous factors, including poor soil management and the excessive application of pesticides. Thus, alternative production systems have been developed, including agroforestry systems, especially those that produce both energy and food. The objective of this study was to environmentally evaluate the culture of Aleurites fordii Hemls. (Tung) using the Life Cycle Assessment method with the SimaPro 7.3.2 software. The results revealed that in family farms that use less mechanization to harvest crops, the primary category of environmental impact was land use, which included the removal of animal and vegetable species and ecosystem changes. The full impact of this category was 1741.21 m2yr PDF (potentially disappeared fraction). Subsequently, prognostics were established for the reduction of such impacts, and we conclude that Tung has a high potential for agricultural installation with high responsibility to the environment. Keywords: Environmental factors, Aleurites fordii Hemls, Life Cycle Management, Tung.

Experimental and Numerical Analysis of Mixing Process of Two Component Gases in a Vertical Fluid Layer in a VHTR

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Tetsuaki Takeda
Keyword(s):  
High Temperature ◽  
Natural Convection ◽  
Numerical Analysis ◽  
Pressure Vessel ◽  
Storage Tank ◽  
Molecular Diffusion ◽  
Flow Characteristics ◽  
Mixing Process ◽  
Two Component ◽  
Air Ingress

When a depressurization accident of a very-high-temperature reactor (VHTR) occurs, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. Therefore, in order to predict or analyze the air ingress phenomena during a depressurization accident, it is important to develop a method for the prevention of air ingress during an accident. In particular, it is also important to examine the influence of localized natural convection and molecular diffusion on the mixing process from a safety viewpoint. Experiment and numerical analysis using a three-dimensional (3D) computational fluid dynamics code have been carried out to obtain the mixing process of two-component gases and the flow characteristics of localized natural convection. The numerical model consists of a storage tank and a reverse U-shaped vertical rectangular passage. One sidewall of the high-temperature side vertical passage is heated, and the other sidewall is cooled. The low-temperature vertical passage is cooled by ambient air. The storage tank is filled with heavy gas and the reverse U-shaped vertical passage is filled with a light gas. The result obtained from the 3D numerical analysis was in agreement with the experimental result quantitatively. The two component gases were mixed via molecular diffusion and natural convection. After some time elapsed, natural circulation occurred through the reverse U-shaped vertical passage. These flow characteristics are the same as those of phenomena generated in the passage between a permanent reflector and a pressure vessel wall of the VHTR.

Integrated Plant Life Cycle Management: The IAEA Contribution

2003 ◽  
Author(s):  
Ki-Sig Kang ◽  
Claude Russell Clark ◽  
Poong Eil Juhn
Keyword(s):  
Life Cycle ◽  
Service Life ◽  
Nuclear Power ◽  
Management Practices ◽  
Life Cycle Management ◽  
Member States ◽  
Life Management ◽  
Plant Life ◽  
Operational Life ◽  
Plant Life Cycle

For the past couple of decades there has been a change of emphasis in the world nuclear power from that of building new Nuclear Power Plants (NPP) to that of taking measures to optimize the life cycle of operational plants. National approaches in many countries showed an increase of interest in Plant Life Management (PLIM), both in terms of plant service life assurance and in optimizing the service or operational life of NPP. A strong convergence of views is emerging from different National approaches, particularly in the area of the economic aspects of NPP operation and in the evolution in the scope of NPP PLIM. The latter can directly affect the cost of electricity from NPP in an increasingly competitive environment. The safety considerations of a NPP are paramount and those requirements have to be met to obtain and to extend/renew the operating license. To achieve the goal of the long term safe, economic and reliable operation of the plant an Integrated Life Cycle Management Programme (ILCMP) is necessary. Some countries already have advanced PLIM Programmes while others still have none. The ILCMP objective is to identify all that factors and requirements for the overall plant life cycle. The optimization of these requirements would allow for the minimum period of the investment return and maximum of the revenue from the sell of the produced electricity. Recognizing the importance of this issue and in response to the requests of the Member States the IAEA Division of Nuclear Power implements the Sub-programme on “Engineering and Management Support for Competitive Nuclear Power”. Four projects within this sub-programme deal with different aspects of the NPP life cycle management with the aim to increase the capabilities of interested Member States in implementing and maintenance of the competitive and sustainable nuclear power. Although all four projects contain certain issues of PLIM there is one specific project on guidance on engineering and management practices for optimization of NPP service life including decommissioning. This particular project deals with different specific issues of NPP life management including aspects of ageing phenomena and their monitoring, issues of control and instrumentation, maintenance and operation issues, economic evaluation of NPP life cycle management including guidance on its earlier shut down and decommissioning. The paper describes in detail the full scope IAEA activities on different issues of NPP life management and some of its achievements in this field during the nearest past as well as plans for the future.

Reducing Dissolved Oxygen Under Conditions of High Air Ingress

2002 ◽  
Author(s):  
Joseph W. Harpster
Keyword(s):  
Dissolved Oxygen ◽  
Measurement Data ◽  
Theoretical Description ◽  
Back Pressure ◽  
Design Features ◽  
High Demand ◽  
Free Air ◽  
Mixture Dynamics ◽  
Air Ingress ◽  
Very High

Recent considerations of steam and air mixture dynamics in operating condensers has led to a more thorough understanding of how condenser performance is affected by air in-leakage. Results of this model-based theoretical description, which are in agreement with measurement data from operating condensers, are reviewed and used to propose beneficial design features for new and re-tubed condenser assemblies. It is anticipated from this work, that condensers can be designed which significantly reduce the amount of dissolved oxygen in condensate from locations of free air ingress above the hotwell level. This reduction also applies to other undesirable noncondensables that enter condensate driven by the same mechanism contributing to dissolved oxygen. When air in-leakage becomes sufficiently high, it contributes to excess back pressure on the turbine. In this region of high air in-leakage, the amount of dissolved oxygen can become very high. The design therefore, minimizes or eliminates the corrosive effects of air inleakage, both high and low, which is particularly important during periods of high demand when load must be maintained.

Development of Prevention Method for Air Ingress During a Depressurization Accident of the VHTR

2016 ◽  
Author(s):  
Tetsuaki Takeda ◽  
Shumpei Funatani
Keyword(s):  
Natural Convection ◽  
Numerical Analysis ◽  
Storage Tank ◽  
Molecular Diffusion ◽  
Fluid Layer ◽  
Natural Circulation ◽  
Flow Characteristics ◽  
Mixing Process ◽  
Vertical Slot ◽  
Air Ingress

A depressurization accident is a design-basis accidents of a very high temperature reactor. When a depressurization accident occurs, air is expected to enter the reactor pressure vessel from the breach and oxidize in-core graphite structures. Therefore, it is important to know a mixing process of different kind of gases in the stable and unstable stratified fluid layer. Especially, it is also important to examine an influence of localized natural convection and molecular diffusion on mixing process from a viewpoint of safety. In order to predict and analyze the phenomena of air ingress during a depressurization accident, therefore, it is important to develop the method for prevention of air ingress during the accident. We have carried out an experiment and a numerical analysis using three-dimensional computational fluid dynamics (3D CFD) to obtain the mixing process of two component gases and flow characteristics of the localized natural convection. This study is also to investigate a control method of natural circulation of air by injection of helium gas. The numerical model consists of a storage tank and a reverse U-shaped vertical slot. They are separated by a partition plate. One side of the left wall of the left side vertical slot is heated and the other side was cooled. The right side vertical slot is cooled. The procedure of the experiment and the numerical analysis is as follows. Firstly, the storage tank was filled with heavy gas and the reverse U-shaped vertical slot was filled with light gas. In the left side vertical slot, the localized natural convection was generated by the temperature difference between the vertical walls. The flow characteristics were obtained by the experiment and steady state analysis. The unsteady state experiment and analysis were started after the partition plate was opened. The result obtained in the experiment was simulated by the numerical analysis quantitatively. The gases were mixed by molecular diffusion and natural convection. After the time elapsed, natural circulation occurred. When the temperature difference of the left vertical fluid layer was set to 100K and the combination of the mixed gas was helium and nitrogen, natural circulation produced after 110 minutes elapsed.

scholarly journals Block ramps for stream power attenuation in gravel-bed streams: a review

2020 ◽  
Author(s):  
Rakesh Kumar Chaudhary ◽  
Nayan Sharma ◽  
Zulfequar Ahmad
Keyword(s):  
Energy Dissipation ◽  
Flow Resistance ◽  
Simple Technique ◽  
State Of The Art ◽  
Flow Characteristics ◽  
Stream Power ◽  
Gravel Bed ◽  
The Past ◽  
Gravel Bed Streams ◽  
Block Ramp

Abstract Application of block ramp technique in steep gradient streams for energy dissipation as well as to maintain river stability finds increasing favor amongst researchers and practitioners in river engineering. This paper dwells on a comprehensive state-of-the-art review of flow resistance, energy dissipation,flow characteristics, stability, and drag force on block ramp by various investigators in the past. The forms and equations for each type are thoroughly discussed with the objective of finding the grey areas and gaps. While, more research is warranted further to improve the equations, essential for design analysis. Block ramps can be a promising simple technique to achieve reasonable attenuation of devastating fluvial forces unleashed in gravel-bed streams during cloud bursts.

Characterization of Visually Detected Coherent Motions in the Turbulent Boundary Layer

2001 ◽  
Author(s):  
Christopher Robin Hirschi
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Flow Characteristics ◽  
Viscous Sublayer ◽  
Vertical Transport ◽  
Momentum Transport ◽  
Coherent Motion ◽  
The Past

Abstract Research over the past 40 years indicates that coherent motions within the turbulent boundary layer account for disproportionate contributions to momentum transport (Robinson, 1991). To better understand these motions, low-Reynolds number turbulent boundary layer experiments were conducted to investigate the instantaneous velocity and vorticity fields associated with near-wall coherent motion interactions. The present study identifies and explores the most prevalent flow characteristics associated with the vertical transport of injected passive marker from the viscous sublayer.

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