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Recovering Generation Losses due to Faulty Air Heater Operation

Challenge: 

Faulty systems operation is a major factor which results in significant generation losses. The air heater is one system that recovers waste heat and increases the performance of the power station, thus making it one of the mayor components that contribute to the amount of power generated. It requires the proper operation and maintenance of individual systems and the plant as a whole to ensure the ability and availability of plants to reliability and safely generate power at a maximum. This case study will focus on the draught group of a power plant and show the impact of a faulty air heater operation on the generated power. 

Benefits: 

Combining on-site measurements with expected results from a model such as Flownex assist with the early detection of faults and abnormal process behaviour in plants. Early detection offers the ability to act fast and recover power generation losses. This together with increased systems performance as a result of proper maintenance and operation offers the benefit of increased power generation which inherently leads to minimized operation expenditure and increased capital income for the power plant. 

Solution: 

A power plant Draught Group network was developed in Flownex. For comparison, plant data was obtained from flow measurements taken at the induced draught (ID) fan inlet. Abnormalities in the measurements triggered an investigation of the performance of upstream systems. On Flownex, the operations of upstream components were varied until the same results as the plant measurements we obtained. In doing this, Flownex provided a tool which enabled the identification of the component that caused the problem. In short, combining the measurements with the Flownex model results narrowed down the under-performing system which gave rise to the root cause. In this case, it was a failure in the operation of an air heater. 

 

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Maintenance Effectiveness comparison for a Half Station Shutdown Outage

Challenge: 

The main challenge is to determine the effectiveness of the work conducted during a half station shutdown. This is normally a difficult task, since most external factors influencing the process (fuel quality, ambient conditions and process configuration) are not the same before and after the shutdown. 

Benefits: 

One of the major advantages by using Flownex® is that the performance of a unit today, can be compared directly with the performance of the same unit at some point in the past even though external factors (ambient conditions, coal quality) and process configuration (e.g. number of feedwater heaters in service) may differ. This is accomplished by characterising the model according to the historic unit and then applying the current external factors and process configuration to that model. In simple terms, this equates to a previous “version” of the same unit that is placed next to the current plant and is provided with the same environmental conditions, fuel and process configuration. The differences that is then observed in the change of the fundamental loss coefficients (AH dP, condenser pressure, ID fan vane positions) between the pre- and post-characterised units, is the actual mechanical changes that occurred due to degradation or maintenance. 

This method is very useful in evaluating the effectiveness of maintenance that has been performed, or to identify where actual degradation has occurred, without having the data clouded by external factors or varying process configurations 

Solution: 

Flownex® can be used to investigate the effectiveness of the work conducted during a half station shutdown as all of the external factors can be taken into account and therefore a direct comparison is possible. 

 

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Economic Pipe Sizing Using the Generaux Equation

Challenge: 

The main challenge is to analyse pipeline sizing in terms of its total cost of ownership using the Generaux Equation. 

Benefits: 

Flownex® allows the user to model pipe networks with ease but does not implement tools to optimise the design in terms of cost. Flownex®’s excellent scripting capabilities do however allow easy implementation of any additional analysis theory and in this case the Generaux Equation. This case study offers a ready-made script that implements the Generaux Equation in SI units. 

Solution: 

The Generaux Equation has been implemented in a simple script and is demonstrated by connecting it via a data transfer link (DTL) to a single pipe flowing gas or water. 

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Simple Bare Tube Cross Flow Recuperator Flownex Model

Challenge: 

The main challenge is the application of Flownex® to model simple recuperator designs that are based on bare tubes in cross flow. 

Benefits: 

One of the main strengths of Flownex® is its ability to model heat transfer to and from piping systems. As a result, it is relatively straightforward to create a Flownex® model for a recuperator which performs the relevant heat transfer and fluid mechanics calculations. 

Solution: 

A Flownex® recuperator compound component was developed and is presented in this case study. The model is based on single pass bare tubes in cross flow to a rectangular shell. Components can be connected in series (or parallel) to model multi-pass recuperators. The model presented utilises Flownex®’s gas mixture capabilities to model the shell side fluid which is typically a flue gas. As such, the shell side fluid is only valid for low-pressure applications. 

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Fouling factors in Flownex Heat Transfer Models

Challenge: 

The main challenge is the incorporation of thermal fouling factors in heat transfer applications such as fired heaters and heat exchangers. 

Benefits: 

Flownex® allows the user to model heat transfer through piping walls in a simple manner. However the effect of fouling is not incorporated. This case study offers two simple methods to account for the overall heat transfer reduction that will result from fouling. The calculation of tube wall temperatures are also investigated and the two methods compared. 

Solution: 

Two simple scripts have been developed and are used in conjunction with the materials library to account for the effects of fouling in Flownex® heat transfer models. 

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Two Phase Flow Regimes

THEME: Root Cause Analysis of System Performance Anomalies 

This case study ‘Two-Phase Flow Regimes’, aims to demonstrate the capability of Flownex SE to carry out root cause analysis of a system to determine the cause of a system performance and safety issue. In addition to identifying the underlying cause, using Flownex SE it is possible to deliver an optimized design solution in the simulation model, in order to remove the root cause issue and generate an improved design configuration.

The case study presents how Flownex SE was successfully employed in a Power Plant commissioning project where it quickly identified the cause of a system performance anomaly, optimized the system design to remove the anomaly and efficiently returned the system performance back within desired performance parameters.

One of the considerable benefits aside from identifying and rectifying the design issue was that by using Flownex SE the analysis and optimization study was executed quickly and cost effectively keeping the commissioning schedule on track and mitigating the commercial impact on the project.

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Generator Seal Oil System

THEME: Failure Mode Analysis of Thermo Hydraulic Machine Components 

This case study ‘Generator Seal Oil System’, aims to demonstrate the capability of Flownex SE to simulate thermo hydraulic machine system components such as seals and simulate operational scenarios to test limits of the machine component to determine the failure modes and effects analysis of the component, to gain better understanding of how the system behaves and works. 

This case study presents how Flownex SE was successfully employed to model a power generation unit hydrogen seal ring and determine causes of seal failure leading to system trips. The Flownex simulation model clearly demonstrated the relationships between system pressure, seal clearances and turbine speeds.

One of the main benefits of modelling the system to determine failure modes and causes was the saving realised by being about to perform this investigative study in the simulation environment. In order to conduct an inspection and investigation in the plant after a trip the machine is shut down and the time required for cool down, stripping, inspection and restarting is considerably costly. This simulation study quickly highlighted the out of specification issue causing the system trips allowing the client to confidently take remedial action to eliminate the issue causing the system trips. 

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Dynamic Mid-Air Refueling

Perform critical analysis of failure cases during dynamic mid-air refueling of a Mirage F1 Fighter. Flownex allowed engineers to simulate flow rates and the refueling sequences of the system. Track fuel distribution and investigate valve failure cases. The simulations ensured that, for any single failure case, the system would remain safe and ensure the center-of-gravity (cg) position of the aircraft remained centered. Aerosud confirmed results predicted by Flownex with ground test results.  The simulation provided Aerosud with the confidence of delivering a final system design that is safe, reliable and conforms to customer requirements.

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Flow measurement orifice plate sizing and uncertainty analysis

This case study demonstrates the use of some of Flownex’s power features – the Designer and the Sensitivity Analysis capability – during the design and uncertainty evaluation of flow measurement using an orifice plate connected to a pressure transducer and transmitter. 

Challenge: The main challenge for this case study is the application of Flownex to: 

  • Size an orifice plate to be used in conjunction with a flow transmitter to serve as an accurate flow meter for natural gas. 
  • Evaluate the measurement uncertainty of the flow meter with variations in operating conditions and manufacturing tolerances. 

Benefits: Flownex is an ideal tool to design gas flow systems, including piping, valving and most other components that are typically found in the oil and gas industry. Not only is Flownex also the ideal tool to design accurate flow measurement orifice plates, but it also has the capability to evaluate the uncertainty of the flow meter in general and the orifice plate in particular with the inevitable variations in conditions and manufacturing tolerances. 

Solution: Using the Designer and the Sensitivity Analysis features built into Flownex, the orifice plate can be designed and its operational uncertainty evaluated when functioning in combination with the pressure transducer/flow transmitter. 

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Coalescing filter sizing and life cycle analysis using rated and specified pressure loss components

This case study discusses the sizing of a coalescer filter and demonstrates its fouling life cycle analysis using a Flownex® model which implements two new pressure loss components: 

  • A rated pressure loss component. 
  • A specified pressure loss component. 

Challenge: The main challenge is the sizing and life cycle analysis of a typical coalescing filter. To simplify the Flownex model and assist with the analysis of the system performance, two new pressure loss components have been developed and are also presented in this case study. 

Benefits: Although not overly complicated, the design and lifecycle analysis of a filter system has a few interesting aspects that need to be highlighted. The two new components specifically developed to assist with this analysis should prove useful to other Flownex users by simplifying the specification of typical pressure losses in complex networks. 

Solution: A complete filter life cycle analysis is presented which may be applied to other similar filtration systems in Flownex networks. Two simple compound components have been developed and are discussed and demonstrated in this case study. 

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