Power Plants STAR GLOBAL CONFERENCE 2012 21 March 2012 Amsterdam, - - PowerPoint PPT Presentation

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Conjugate Heat Transfer Simulations of a Bypass Valve for the Next Generation of Highest-efficient Power Plants

STAR GLOBAL CONFERENCE 2012 21 March 2012 Amsterdam, The Netherlands

Anis Haj Ayed, Martin Kemper, Karsten Kusterer B&B-AGEMA GmbH, Aachen, Germany Olaf Tebbenhoff Welland & Tuxhorn AG, Bielefeld, Germany

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B&B−AGEMA GmbH is an independent engineering service company providing consultancy, expertise, design and calculation for turbo machinery and power

• plants. Established in 1995 and located in Aachen

(Germany), B&B-AGEMA GmbH operates worldwide and independently for the benefits of its customers.

Contact:

B&B-AGEMA GmbH Juelicher Strasse 338 52070 Aachen, Germany Phone: +49 (0) 241 – 56878 – 0 Fax: +49 (0) 241 – 56878 – 79 E-mail: info@bub-agema.de Web: www.bub-agema.de

B&B-AGEMA GmbH

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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• Power generation for Renewables will increase significantly in the next two decades (from

600 TWh to 5200 TWh.

• In the same time the world wide total power generation will also increase significantly.
• Despite the increase in renewables the power generation from coal will further increase in

absolute values.

• Reduction of CO2 can only be reached if new technologies as CCS and highest efficient

technologies are applied for the steam power plants operated with coal.

Background – Future Power Generation

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Plant Efficiency [%] Average World Average Germany State-of- the-art 700°C steam techn. Specific CO2 emissions [g/kWh]

• Increased plant efficiency can contribute significantly to the CO2 reduction.
• The difference in specific CO2 emissions between the World average and the investigated

700°C technology is 42%.

• The theoretical potential of the specific CO2 reduction is therefore also 42%.
• The Carbon Capture and Storage (CCS) technologies are only meaningful for high-efficient

power plants so that the additional efforts for the CCS are reduced.

Contribution of increased plant efficiency for reduction of CO2 emissions

Source: ALSTOM, press release 2008 on the „725°C high temperature – test track at the GKM“

Background – CO2 Reduction

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Steam turbine

Nickel-base alloys Chromium steel Plant efficiency

Materials steam generator:

Materials in the future high-efficient steam power plants are exposed to extreme conditions:

• High steam temperatures (>700 °C)
• Damage due to enhanced chemical

reactions

• High pressure loads (e. g. >320 bar

internal pressure)

• High thermal gradients during start-up

and shut-down (Thermal low cycle fatigue).

• There are only few experiences and

limited knowledge in operation and design calculations for such component application (e. g. steam generator, valves, etc.) with Ni-base alloys in power plants.

Source: ALSTOM, press release 2008 on the „725°C high temperature – test track at the GKM“

Background – Material Requirements

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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 Vision: „700°C power plant“ with increased efficiency to realize the coal fired Zero Emission Plant  Idea: Erection of a test rig for innovative boiler materials in a fossil fired power plant with an adequate load profile  Participants: Utility, boiler manufacturer, manufacturer of power plant components, inspection authority, scientific research and testing institutes  Duration: 2008 – 2015  Funding: Total project costs 5.4 million EUR, 50% sponsored by German Government, 50% industry contribution  Work packages: Several work packages on planning and construction, material technology investigations, test rig operation (e. g. cyclic bypass valve operation), concepts for damage development, etc...

*GKM: Grosskraftwerk Mannheim (Utility company for Mannheim area)

(Source: VGB Workshop „Material and Quality Assurance“, May 13-15, 2009, Copenhagen, K. Metzger, Grosskraftwerk Mannheim AG)

Research Project

Research Project 725 HWT GKM: 725 °C high temperature – test track at the GKM*

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725°C Test Track at the GKM

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Research topics for the Welland&Tuxhorn bypass valve

• Valve functions check:

combined stop&control with hydraulic drive

• Mechanical integrity:

materials and coatings at 725°C

• Measurement data:

pressures (in/out), temperatures, leackages

• Transient thermal behaviour:

automatic infrared camera measurements

• Numerical analyses:

Simulation of thermal transient cycles (FEM/CFD)

Welland&Tuxhorn bypass valve made of Ni-base Alloy 617mod Infrared camera with housing

camera view angle Numerical tasks: (B&B-AGEMA):

• Transient thermal behavior (transient conjugate

heat transfer calculation of steam valve flow during open/close-cycle)

• Transient stress & strain (FEM)
• Life cycle analysis

Source: Welland & Tuxhorn AG,, press release 2008 on the „725°C high temperature – test track at the GKM

Measurements & thermography analysis: (IKDG, Aachen):

• Contribution of measurement data for the

validation of the numerical results

By-pass Valve Research Topics

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The Task: Numerical simulation of cyclic thermal loading of by-pass valve based on the conjugate heat transfer and flow simulation approach.

Current Task

The Goal: Accurate estimation of cyclic thermal loading behaviour, which is the basis for cyclic thermal stress calculation and service life estimation for modern applications.

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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Conventional procedure: Transient „Conjugate Calculation“:

Calculation Approach

 Transient calculation of the temperature distribution in valve body by FEM by requirement of heat transfer coefficients  Heat transfer coefficients based on experience or on correlations with limited validity  Heat transfer coefficients given for relatively large areas not locally!  Conjugate heat transfer and flow simulation: Heat transfer is calculated directly and locally by taking into account the fluid-solid interaction explicitly  Heat transfer boundary conditions (e.g. heat transfer coefficients) are no longer needed at solid/fluid contact faces Such transient FEM calculations are possible

• n modern computers with relatively low

effort (Calculation time: Minutes to hours).  Significant uncertainties related to the transient thermal behavior of the valve body  Large uncertainties in the determination of thermal stresses and strains and thus inaccurate life cycles prediction The time-dependent, three-dimensional temperature field in the solid body is a direct result of the „Conjugate Calculation“  Large calculation effort for transient calculations  Not always applicable for transient flow phenomena e.g. transient mass flow changes due to different time scales within fluid and solid simulation

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Calculation Procedure

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• steady state conjugate calculation of closed valve condition to

get the initial temperature distribution in the solid domain

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• steady state conjugate calculation of open valve condition with

start steam parameters to get the initial flow field in the fluid domain

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• combine initial conditions of solid domain and fluid domain by

exchanging the region solution

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• transient conjugate calculation of start-up process till steady
• peration

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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By-pass Valve Geometry

steam inlet steam outlet valve body CAD Model polyhedral mesh as installed

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• approx. 400.000 polyhedral cells

steam outlet steam inlet

Conjugate Calculation Model

fluid domain solid domain

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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steam inlet temperature 480°C steam outlet boundary

Start Solution in Solid Domain

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valve body steam temperature 480°C porous region

Initial Temperature in Solid Domain

valve closed

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T 1 T 2 T 3 T 4

Validation of Initial Solution

Start Solution Position [ - ] Measured Values Calculated Values T1 [ °C ] 247 246 T2 [ °C ] 164 163 T3 [ °C ] 159 160 T4 [ °C ] 159 158 TInlet [ °C ] 480.00 480.00

measurement positions

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steam inlet temperature: 480°C Steam outlet boundary

start solution solid domain start solution fluid domain

Initial Solution in Fluid Domain & Mapping

valve open

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Transient Calculation – Inlet Conditions

mass flow trend simplified to constant in calculation (due to large time steps) time dependent temperature defined at inlet boundary Inlet conditions

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Transient Thermal Load at T1

T 1 T 2 T 3 T 4

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Transient Thermal Load at T2

T 1 T 2 T 3 T 4

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Transient Thermal Load at T3

T 1 T 2 T 3 T 4

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Transient Thermal Load at T4

T 1 T 2 T 3 T 4

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steam inlet temperature: 700°C Steam outlet boundary porous region valve body

Stationary Operation – Steam Flow Field

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Steam inlet: 700°C steam outlet boundary

Stationary Operation – Solid temperatures

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valve body steam outlet boundary steam inlet temperature 700°C

Stationary Operation – Solid Temperatures

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Validation of Stationary Operation Solution

T 1 T 2 T 3 T 4

Stationary operation Position [ - ] Measured Values Calculated Values T1 [ °C ] 682 678 T2 [ °C ] 637 629 T3 [ °C ] 518 510 T4 [ °C ] 633 625 TInlet [ °C ] 700 700

measurement positions

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Contents

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion

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 A new calculation approach has been applied to calculate transient temperature distribution in a valve body.  Results of steady state conjugate calculation at start condition (closed valve) show good agreement with measurement values (temperature measurement on different reference positions on valve body).  Results of transient conjugate calculation of start-up process could be compared with time dependent temperature measurements at reference positions and show qualitatively good agreement.  Design process of high temperature valves in modern power plants is improved by applying the advanced conjugate calculation approach within STAR-CCM+.

Summary & Conclusion