conjugate heat transfer simulations of a bypass valve for...

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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: [email protected] 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



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.

Spec

ific

CO

2 em

issi

ons

[g/k

Wh]

• 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



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



Results

Conclusion

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Conventional procedure: Transient „Conjugate Calculation“:


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 on 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

1 • steady state conjugate calculation of closed valve condition to

get the initial temperature distribution in the solid domain

2 • steady state conjugate calculation of open valve condition with

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

3 • combine initial conditions of solid domain and fluid domain by

exchanging the region solution

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

operation

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Contents

Background

Motivation & Task



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



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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T 1

T 2 T 3

T 4

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T 1

T 2 T 3

T 4

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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


Stationary Operation – Solid temperatures

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valve body


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



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

conjugate heat transfer simulations of a bypass valve for...

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