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

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 1

Contact: B&B−AGEMA GmbH is an independent engineering service company providing consultancy, expertise, B&B-AGEMA GmbH design and calculation for turbo machinery and power Juelicher Strasse 338 plants. Established in 1995 and located in Aachen 52070 Aachen, Germany (Germany), B&B-AGEMA GmbH operates worldwide Phone: +49 (0) 241 – 56878 – 0 Fax: +49 (0) 241 – 56878 – 79 and independently for the benefits of its customers. E-mail: info@bub-agema.de Web: www.bub-agema.de B&B-AGEMA GmbH 2

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion Contents 3

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion Contents 4

• 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 5

Contribution of increased plant efficiency for reduction of CO 2 emissions Specific CO2 emissions [g/kWh] Average World Average Germany State-of- 700°C the-art steam techn. Source: ALSTOM, press release 2008 on the „725°C high Plant Efficiency [%] temperature – test track at the GKM“ • 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. Background – CO 2 Reduction 6

Steam turbine 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 Chromium Nickel-base steel alloys • High pressure loads (e. g. >320 bar internal pressure) • High thermal gradients during start-up and shut-down (Thermal low cycle fatigue). Materials steam generator: • There are only few experiences and limited knowledge in operation and design calculations for such component application (e. g. steam generator, valves, Plant etc.) with Ni-base alloys in power plants . efficiency Source: ALSTOM, press release 2008 on the „725°C high temperature – test track at the GKM“ Background – Material Requirements 7

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion Contents 8

Research Project 725 HWT GKM: 725 °C high temperature – test track at the GKM*  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 9

725°C Test Track at the GKM 10

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 Infrared camera with housing Ni-base Alloy 617 mod camera view angle Numerical tasks: (B&B-AGEMA): • Transient thermal behavior (transient conjugate heat transfer calculation of steam valve flow during open/close-cycle) Measurements & thermography analysis: • Transient stress & strain (FEM) (IKDG, Aachen): • Life cycle analysis • Contribution of measurement data for the Source: Welland & Tuxhorn AG, , press release 2008 on the „725°C high validation of the numerical results temperature – test track at the GKM By-pass Valve Research Topics 11

The Task: Numerical simulation of cyclic thermal loading of by-pass valve based on the conjugate heat transfer and flow simulation approach. 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. Current Task 12

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion Contents 13

Conventional procedure: Transient „Conjugate Calculation“:  Transient calculation of the temperature  Conjugate heat transfer and flow simulation: distribution in valve body by FEM by Heat transfer is calculated directly and requirement of heat transfer coefficients locally by taking into account the fluid-solid interaction explicitly  Heat transfer coefficients based on experience or on correlations with limited  Heat transfer boundary conditions (e.g. heat validity transfer coefficients) are no longer needed at solid/fluid contact faces Heat transfer coefficients given for relatively  large areas not locally! The time-dependent, three-dimensional Such transient FEM calculations are possible on modern computers with relatively low temperature field in the solid body is a effort (Calculation time: Minutes to hours). direct result of the „Conjugate Calculation“  Large calculation effort for transient  Significant uncertainties related to the calculations transient thermal behavior of the valve body  Large uncertainties in the determination of  Not always applicable for transient flow thermal stresses and strains and thus phenomena e.g. transient mass flow inaccurate life cycles prediction changes due to different time scales within fluid and solid simulation Calculation Approach 14

• steady state conjugate calculation of closed valve condition to 1 get the initial temperature distribution in the solid domain • steady state conjugate calculation of open valve condition with start steam parameters to get the initial flow field in the fluid 2 domain • combine initial conditions of solid domain and fluid domain by 3 exchanging the region solution • transient conjugate calculation of start-up process till steady 4 operation Calculation Procedure 15

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion Contents 16

valve body steam inlet steam outlet as installed polyhedral mesh CAD Model By-pass Valve Geometry 17

approx. 400.000 polyhedral cells steam inlet solid domain steam outlet fluid domain Conjugate Calculation Model 18

 Background  Motivation & Task  Calculation Approach  Geometrical Model & Boundary Conditions  Results  Conclusion Contents 19

steam inlet temperature 480°C steam outlet boundary Start Solution in Solid Domain 20

porous region steam temperature 480°C valve closed valve body Initial Temperature in Solid Domain 21

T 2 T 3 T 1 T 4 Start Solution Measured Calculated Position [ - ] Values Values T1 [ °C ] 247 246 T2 [ °C ] 164 163 measurement positions T3 [ °C ] 159 160 T4 [ °C ] 159 158 T Inlet [ °C ] 480.00 480.00 Validation of Initial Solution 22

start solution solid domain start solution fluid domain valve open steam inlet temperature: 480°C Steam outlet boundary Initial Solution in Fluid Domain & Mapping 23

mass flow trend time dependent temperature simplified to constant defined at inlet boundary in calculation (due to large time steps) Inlet conditions Transient Calculation – Inlet Conditions 24

T 2 T 3 T 1 T 4 Transient Thermal Load at T1 25

T 2 T 3 T 1 T 4 Transient Thermal Load at T2 26

T 2 T 3 T 1 T 4 Transient Thermal Load at T3 27

T 2 T 3 T 1 T 4 Transient Thermal Load at T4 28