AccompanyingMaterial ABB INDIA

8/13/2019 AccompanyingMaterial ABB INDIA

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Dr.Hans-Peter Wolf Status: 15.02.2012 / Rev 1.02

Accompanying Material for the EBSILONProfessional

training course


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Accompanying Material for the EBSILONProfessional training course

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1 Introduction......................................................................................................3

2 EBSILONProfessional....................................................................................4

2.1 Principles................................................................................................................6

2.1.1 Philosophy and functionality of EBSILONProfessional.............................................. 6

2.1.2 Structure and solution of Equation system ................................................................. 7

2.1.3 Fluid Properties........................................................................................................ 12

2.1.4 Component Physics ................................................................................................. 14

2.1.4.1 Turbine ................................................................................................................................. 142.1.4.2 Heat exchanger .................................................................................................................... 172.1.4.3 Condenser ............................................................................................................................ 192.1.4.4 Feedwater preheater ............................................................................................................ 202.1.4.5 Feedwater container............................................................................................................. 222.1.4.6 Steam drum .......................................................................................................................... 232.1.4.7 Pump and Compressor ........................................................................................................ 242.1.4.8 Generator ............................................................................................................................. 252.1.4.9 Motor .................................................................................................................................... 262.1.4.10 Steam generator .............................................................................................................. 272.1.4.11 Furnace / combustion area .............................................................................................. 282.1.4.12 Piping ............................................................................................................................... 292.1.4.13 Throttle ............................................................................................................................. 302.1.4.14 Splitter .............................................................................................................................. 312.1.4.15 Drain................................................................................................................................. 322.1.4.16 Dryer................................................................................................................................. 332.1.4.17 Selective splitter ............................................................................................................... 342.1.4.18 Mixers............................................................................................................................... 352.1.4.19 NoX removal .................................................................................................................... 362.1.4.20 Controller.......................................................................................................................... 372.1.4.21 Measured value input....................................................................................................... 38

2.2 Application of EBSILONProfessional...............................................................39

2.2.1 Creation of Topology................................................................................................ 39

2.2.2 Component library.................................................................................................... 40

2.2.3 Simulation ................................................................................................................ 44

2.2.4 Design / Off-design .................................................................................................. 45

3 Literature ........................................................................................................49


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1 Introduction

The document Accompanying Material for the EBSILONProfessional training course is

meant as a supplement to the training course.

While during the training course the learning by doing-principle is prevalent, the

thermodynamic and mathematical principles are not covered in detail. Therefore this

document describes the main features of EBSILONProfessional, namely the

mathematical and physical principles underlying the software. The purpose is to get a

better understanding of the operations behind the screen.

An even deeper understanding of the mathematical and physical principles can be

obtained by studying the Online-help and some of the mentioned literature reference.


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2 EBSILONProfessional

EBSILONProfessionalis a tool for the stationary simulation of all kinds of thermodynamic

power (and even refrigeration) cycles.

Its main features are:

User-friendliness by intuitive handling and full-graphical user-interface with 100 %

Windows functionality (see Fig. 1)

Graphical objects for components and pipes

Component library with presently 110 different components

Excel-functionality, Import of measured data and export of simulation results Interface to external database possible

Validation of measurements as an option

Easy extendibility of existing simulation models regarding type and size

Complete observance of first principles of physics

Design calculation using key performance figures

Identification of components at design and off-design load possible

Complete and partial design-calculation possible No programming skills required

Supply of control- and specification properties possible

Calculation methods of components can be customized by user-defined

adaptation-polynomials

Creation of self-defined components (macros) from existing components possible

Programming of self-defined components in source-code possible

Many different fluids considered (water/steam, air/flue gas, refrigerants, fuels, salt-water, mixtures)

Extendable by user-defined fluids

Realistic design-calculation and off-design calculation of components

User-friendly diagnosis of topological and specification errors

User-interface and dialogs in many languages (German, English, French, Spanish,

Turkish, Chinese)

Different Unit-systems (SI and derived units, BTU)


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Topology and results can be exported to a variety of graphical formats and to

HTML.

Fig. 1: Windows conform graphical user interface


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2.1 Principles

2.1.1 Philosophy and functionality of EBSILONProfessional

During the engineering of power-cycles for the design 2 different tasks have to be

distinguished:

Process simulation based on balance of mass and heat

Detailed designof individual components

For the balance of the process the task is, to design the complete process, to calculate

heat and mass balance of the main aspects of the power cycle operation and to optimize

by applying what-if studies. Therefore process simulation is characterised by thefollowing properties:

The context of a large number of process components (for example compressors,

pipes, pumps, turbines, heat-exchangers, etc.) has to be investigated.

The modeling of process-oriented components has to be confined to relatively

simple models

The full- and part load behavior must be modeled

Modeling must be possible without knowing about details of geometry and material

of a specific component.

During the detailed designof individual components the purpose is to find out about the

details (geometry, material etc.) required for the construction of a component. Properties

of this method are:

High detail of modeling (for example FEM or CFD-simulation)

Determine the principal thermodynamic data and

Finding out the constructive details

Therefore process-simulationis the main task of EBSILONProfessional!


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The simulation is based on two types of elements:

components

pipes

The components are connected with each other by pipes. The physical properties of a

fluid in a pipe are uniquely determined by specifying 3 properties: mass flow m& , pressure

pand specific enthalpyh.

In the components algorithms based on physical equations are used, which correlate the

properties on the outgoing lines with the properties on the ingoing lines.

In EBSILONProfessional a power-cycle can be modeled as detailed as required. The

components are connected through the pipes, in which mass- and energy transfer takes

place. Such pipes can transport fluid, gaseous or solid media (water/steam, air/flue gas,

fuels etc.) , but also mechanical or electrical power.

2.1.2 Structure and solution of Equation system

A power cycle consists of n connecting pipes between the individual components. The

simulation is complete, when based on the physical laws- to every pipe i values of the

following base variables can be associated

p: pressure

h: specific enthalpy

m& : mass flow

The dependant variables, like temperature Tor power Qcan be calculated from the base

variables through

A property state function ),( hpTT =

An algebraic correlation hmQ = &

Therefore it is necessary to solve a (non-linear) system of equations for

3= nN unknowns (npipes with 3 base variables each)

The mathematical relation between the N equations is formulated in the individual

components.


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The following balances are valid for the base variables:

pressure (the pressure drop DP12 can be configured inside the component)

12)2()1( DPipip = (1)

34)4()3( DPipip = (2)

enthalpy (from conservation of energy and heat-transfer)

mTAkihimihim = )1()1()2()2( && (3)

mTAkihimihim = )4()4()3()3( && (4)

Mass flow (from conversation of mass)

0)2()1( = imim && (5)

0)3()4( = imim &&

(6)

Through those balance equations the outlet variables are correlated with ingoing variables.

For a cycle, consisting of several components, a non-linear inhomogeneous system of

equations is created, which correlates the base variables ix (pressure, specific enthalpy

and mass-flow) of different pipes

0)...,,,(

......

......

0)...,,,(

0)...,,,(

321

3212

3211

=

=

=

NN

N

N

xxxxf

xxxxf

xxxxf

(7)

The system of equation is non-linear, because of

variable coefficients (for examplem& is present also in enthalpy equations) and

variable right hand sides (for example the mean logarithmic temperature difference

mT depends on pand hof all connecting pipes of a heat-exchanger)

Because of the non-linearity the system of equation can only be solved iteratively.


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In vector formulation the system of equation (7) can be written as

0F(x) = (8)

x is the vector containing the values of all base variables ),...,1( Nixi = and F denotes the

vector of all functions if.

In the neighbourhood of the sought solution vector x any function if can be developed

into a Taylor series

)()()( 2

1

xxxx Ox

x

fff

N

j

j

j

iii +

+=+

=

(9)

The matrix of the partial derivatives, which occur in the summation, is the Jacobian matrix

J of the partial derivatives of F with the matrix elements ijJ given by

j

iij

x

fJ

= (10)

In vector formulation therefore the Taylor series expansion (9) can be written as

)()()( 2xOxJxFxxF ++=+ (11)

Neglecting the terms with quadratic deviations 2x and taking into account only the linear

deviations and assuming

0xxF =+ )( (12)

For 0x the following linear system of equation is obtained

0xJ = (13)

The partial derivatives of the Jacobian matrix (10) are substituted by numerical derivatives

(finite differences). Therefore the system of equations (13) is linear.

The system of equations (13) is only sparsely populated. Direct methods (like Gaussian

elimination) cannot take advantage of the sparse population because computing time

depends on the square of the rank of the matrix. Therefore an iterative method (Gauss-


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Seidel) is used, because the computing time depends only linearly on the rank of the

matrix:

With the found values for x a new approximation for x is generated.

xxx +=+ kk 1 (14)

The values 1+kx together with kx are again substituted into (13) and the method is

continued in an outer iterative loop ( max,....0 kk= ) until a certain precision is reached.

A relaxation factor can accelerate the rate of convergence

xxx +=+ kk 1 (15)

The method converges faster if the starting values 0x (i.e. of the 0-th iteration step) are

close to the sought solution vector x .


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2.1.3 Fluid Properties

The computation of thermophysical fluid properties is a central task of program systems

for thermodynamic simulations and optimizations. Therefore EBSILONProfessional

contains several libraries for the calculation of state properties of a variety of fluids and

other substances.

The following substances are taken into consideration :

Air / Flue gas, mixtures of up to 22 components

Water / Steam (either IAPWS-IF97 formulation for the actual standard or IFC-1967

for calculations based on the older standard).

Seawater

Solid (Coal, lignite) and liquid fuels (Oil)

Gaseous fuels

Raw gases

Predefined 2-Phase fluids (NH3, CO2, )

Externally in DLL definable fluids, extendable

Refprop Database (approx. 80 fluids) of the National Institute of Standards and

Technology integrated

Self-definable cp-Polynomials

Binary mixtures (NH3/H2O, LiBr/H2O)

The libraries integrated into EBSILONProfessional for water/steam and the 2-Phase

fluids take into account the phases liquid, gaseous and wet-steam and allow almost

all conceivable combinations of variable dependencies.

The libraries mentioned are not only used by the solution algorithm, but can also be

accessed from the programming language EbsScriptand from the User-Interface through

pre-defined dialogs (Fig. 3). Fluid for a specific component or pipe can be calculated, but

also for several components of a model (for example h-s diagram of turbine expansion,

Fig. 4).


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Fig. 3: Dialog for water/steam table call using IAPWS-IF97 steam table

Fig. 4: HS-Diagram of turbine expansion


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2.1.4 Component Physics

In the following chapters the physics underlying the most important components is

described in more detail (Literature /1/,/2/,/3/,/8/,/9/).

2.1.4.1 Turbine

2.1.4.1.1 Steam turbine

A steam turbine converts the enthalpy difference of the steam between inlet and outlet of

a turbine into mechanical work. Every steam turbine can be separated into different

sections, according to the number of extractions. The balances for mass, energy and

pressure are then valid for each single section.

111 ,, phm&

222 ,, phm&

Fig. 5: Section of a steam turbine and fluid properties used in the balance equations

Mass balance: 021 =mm && (16)

Energy balance: turbPhmhm = 2211 && (17)

Pressure: 1221 ppp = (18)

For the calculation of the outlet enthalpy h2the following relation is used:

)( 2112 shhhh = (19)


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denotes the isentropic efficiency. The off-design performance of the isentropic

efficiency is stored as a characteristic line and depends on other variables, for example

),,( pm&= . Enthalpy losses due to exhaust losses or due to wet steam can be taken

into account.

Fig. 6: Effect of isentropic efficiency on outlet enthalpy of a turbine

The relation between inlet and outlet pressure in off-design is described by the law of

ellipses of Stodola.

212

212

1

1

1

1

2

1

1

)(1

)(1

NN

N

NN pp

pp

v

v

p

p

m

m

=

&

&

(20)

With a given outlet pressure p2 (for example condenser pressure), given mass flow m& ,

specific volume at inlet v1 and the nominal values (denoted by subscript N) the inlet

pressure p1 can be calculated for any load condition (off-design).

Actual expansion


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Fig. 7: Relation between inlet pressure 1p , outlet pressure 2p and mass flow m&

(law of ellipses of Stodola)

2.1.4.1.2 Gas turbine

For the gas turbine the same physical laws like for the steam turbine are valid. Compared

to the steam turbine no wet-steam conditions have to be taken into account and therefore

the equation of state for ideal gases can be used.


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2.1.4.2 Heat exchanger

Heat is transferred form the secondary side (pipe with index 3) to the primary side (pipe

with index 1) The balances for mass, energy and pressure for an ideal heat-exchanger

without losses are given according to the diagram

111 ,, hpm&222 ,, hpm&

333 ,, hpm&

444 ,, hpm&

Q&

Fig. 8: Fluid properties used in the balance equations

Mass: 021

=mm

&&

(21)043 =mm && (22)

Enthalpy: Qhmhm &&& = 1122 (23)

Qhmhm &&& = 4433 (24)

Pressure: 1221 ppp =

3443 ppp =

For the heat transferred the following relation is used

mTAkQ =& , (25)

which is valid for parallel flow as well as for counter-flow heat-exchangers. In this formula

k denotes the heat-transfer coefficient, A the heat-transfer area and mT the mean

logarithmic temperature difference.


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The mean logarithmic temperature difference is calculated as:

)ln( kw

kwm

TT

TTT

= (26)

Parallel flow heat-exchangers: 2413 , TTTTTT kw == (27)

Counter flow heat-exchangers: 1423 , TTTTTT kw == (28)

The off-design performance for the heat-transfer is described by a characteristic line for

the heat-transfer coefficient kand the nominal value NAk )( :

NNN kAmmmmfAk )(),( 3311 = &&&& (29)

The off-design behavior of the pressure drop is calculated as :

N

N

pm

mp

=

2

&

& (30)

where Np denotes the nominal pressure drop.

The relations given are in principal valid for all types of heat-exchangers, also for

condensing heat-exchangers and desuperheaters..


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2.1.4.4 Feedwater preheater

For a feedwater preheater the same physical laws like for a condenser a valid.

For calculating the off-design performance of the heat-transfer a characteristic line

NkAmmfAk )(),( 31 = && can be used.

Similarly like for the turbine condenser it is possible to use a formula relation instead of a

characteristic line for the off-design performance. This relation is known as the Method of

Rabek.

2.1.4.4.1 Method of Rabek

This method works even without knowing the constructive or material data of the

preheater. The relative change of the heat-transfer coefficient calculated by this method

together with the nominal value of the heat-transfer coefficient allows calculating the off-

design-performance.

This method (Literature /6/) assumes that the following data are available in an off-design

state

Inlet parameters 111 ,, hpm& of the primary flow (feedwater)

Inlet parameters 33 ,hp of the secondary flow (extraction steam)

The Rabek-method also takes into the account that the secondary flow may be

superheated. Then it separates the heat-transfer area into a desuperheating zone and a

condensing zone.

For the Ak - value in off-design the following approximate relation is given by Rabek

(Index 1 denotes primary side, index 3 secondary side):

( )N

V

V AkAk )(1

1

3

3

+

+=

(32)

with2

330

3

3

3

80

1

1

1 =

=

=

V

.

N

.

N andm

m

andm

m

&

&

&

&

(33)


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For the ratio of the Ak - values of the desuperheating zone (Index II) and condensing

zone (Index I) the following relation is used by Rabek :

( )( )

( )

+

+=

3

11

1

V

E

II

I

Ak

Ak (34)

with 15=E

Because the given relations include approximation and do not consider constructive and

material data an exact quantitative calculation of the off-design performance is not

possible. Nevertheless the results for Ak are close to the actual values, with a deviation

of normally less than 10 %. An advantage of the Rabek method is, that it allows to handle

negative upper terminal temperature differences more accurate than is possible with

characteristic lines.


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2.1.4.5 Feedwater container

A feedwater container (a.k.a. deaerator) is a mixing preheater where hot steam from an

extraction of the turbine is mixed with the main and auxiliary condensate.

111 ,, phm&444 ,, phm&

222 ,, phm&

333 ,, phm&

555 ,, phm&

Fig. 9: Fluid properties of the feedwater container

Mass balance: 054321 =++ mmmmm &&&&& (35)

Energy balance: 05544332211 =++ hmhmhmhmhm &&&&& (36)


The off-design behavior of the pressure drop is calculated as :

N

N

pm

mp 32

2

3

332

=

&

&

(38)

The condition )( 2.2 hpp sat= is used to calculate the extraction steam flow 3m& .


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2.1.4.6 Steam drum

A steam drum is used for the separation of saturated steam from saturated water.

111 ,, phm&

222 ,, phm&

333 ,, phm&

444 ,, phm&

555 ,, phm&

Fig. 10: fluid properties of the steam drum

Mass balance: 054321 =+ mmmmm &&&&& (39)

Energy balance: 05544332211 =+ hmhmhmhmhm &&&&& (40)

Pressure: 54321 ppppp ==== (41)

The enthalpies532hand,hh of the outlet streams are calculated from the energy balance

using the conditions

)( 153 phhh ==

)( 12 phh =


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2.1.4.7 Pump and Compressor

Pumps and compressors are described by the same physics. The medium (liquid or

gaseous) is brought from a low pressure level to a higher pressure level.

111 ,, hpm& 222 ,, hpm&

motorP

Fig. 11: Fluid properties of pump and compressor


Energy balance: motorPhmhm = 1122 &&

(43)


For the calculation of the outlet enthalpy h2, especially in off-design the following relation

is used:

)(1

1212 hhhh s+=

(45)

The off-design performance of the isentropic efficiency can be supplied in a characteristicline )(m& .

The outlet pressure can either be provided by other neighbouring components or it can be

calculated from the delivery head )(2121 Vpp &= .

In these cases the required motor power is calculated.


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2.1.4.8 Generator

The generator converts mechanical power to electrical power.

mechP electrP

Fig. 12: conversion of mechanical power to electrical power

For the calculation of the electrical power the generator efficiency is taken into account.

For the calculation of the generator efficiency the following effects are considered:

Dependency of efficiency on power factor : ))(cos(1cos f=

Dependency of efficiency on H2-Pressure 2Hp : )( 222 HH pf=

Dependency of efficiency on grid frequency : )(3 f=

NGenHGen = 2cos (46)

NGen denotes the nominal value (i.e. in design condition) of the generator efficiency.

The electrical power then is calculated as:

mechGenelectr PP = (47)


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2.1.4.9 Motor

The motor converts electrical power to mechanical power.

mechPelectrP

Fig. 13: conversion of electrical power to mechanical power

For the calculation of the mechanical power the motor efficiency is taken into account. For

the calculation of the motor efficiency the following effects are considered:

Dependency of electrical efficiency on power: )( electrelectr Pf1=

Dependency of mechanical efficiency on power: )( electrmech Pf2=

NMotormechelectrMotor = (48)

NMotor is the nominal value (i.e. at design conditions) of the motor efficiency.

The mechanical power then is calculated as:

electrMotormech PP = (49)


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2.1.4.10 Steam generator

In the steam generator the feedwater is converted from a sub-cooled state to a

superheated state (main steam). Additionally the reheat of the steam for the intermediate

pressure turbine is considered.

Feedwater

Cold

reheat

Main

steam

Hot

reheat

111 ,, phm&

222 ,, phm&

333 ,, phm&

444 ,, phm&

666 ,, phm& 777 ,, phm&

888 ,, phm&

Q&

Fig. 14: Fluid properties of the steam generator

Mass balance: 08612

=+ mmmm

&&&&

und 0734 =

mmm &&&

(50)

Energy balance:)(

)(

337744

88116622

hmhmhm

hmhmhmhmQ

+

+=

&&&

&&&&&

(51)

Pressure: 1221 ppp = und 3443 ppp = (52)

For the pressure drops the following relation for off-design is used:

NN pm

m

p

=

2

&

&

(53)


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2.1.4.11 Furnace / combustion area

For the furnace a stoichiometric combustion calculation is done. For the energy balance

the lower heating value HWh of the fuel and its composition must be known.

air

Ashand

Slag

Flue

gas

111 ,, phm&

222 ,, phm&

Q&

fuel

HWhphm ,,, 444& 555 ,, phm&

RadQ&

Fig. 15: Fluid properties of the combustion area

Mass balance: 05142 =+ mmmm &&&& (54)

Energy balance: .552244411 StrahlHW QhmhmhmhmhmQ &&&&&&& ++= (55)


For den pressure drop in off-design the following relation is used:

N

N

pm

mp 12

2

12

=

&

& (57)

The composition of the flue gas is calculated from the composition of the fuel and the air.

If more air is added than is necessary for a complete combustion of the fuel, the excess

air is calculated.


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2.1.4.12 Piping

In a piping pressure drops and heat losses of a pipe can be considered.

111 ,, hpm& 222 ,, hpm&

Q&

Fig. 16: Fluid properties of piping


Energy balance: Qhmhm &&& = 2211 (59)


The pressure drop in off-design is calculated according to the following relation from the

nominal values and the actual mass flow:

v

ygp

m

m

v

vp

NNN

12

2

1

112

=

&

& (61)

The dependency of the pressure drop on specific volume vfor compressible fluids and a

geodetic height y (g: gravitational acceleration, v : mean specific volume in piping,

y : geodetic height) is considered in the calculation of the pressure drop.

The heat loss in off-design conditions is taken into account as:

( )NN

NN

hhm

m

T

TQ 12

1

1

2

2

=

&

&&


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2.1.4.13 Throttle

A throttle is used to reduce the pressure.

111 ,, phm& 222 ,, phm&

Fig. 17: Fluid properties of a throttle


Energy balance: 02211 = hmhm && (63)


The dependency of the pressure drop on specific volume v for compressible fluids is

considered in the calculation of the pressure drop:

NNN

pm

m

v

vp 12

2

1

112

=

&

& (65)


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2.1.4.14 Splitter

A splitter is used to split one mass flow into two mass flows.

111 ,, phm& 222 ,, phm&

333 ,, phm&

Fig. 18: Fluid properties of a splitter

Mass balance: 0321 = mmm &&& (66)

Energy balance: 0332211 = hmhmhm &&& (67)

Pressure: 321 ppp == (68)

2m& and

3m& are determined from the splitting ratio.


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2.1.4.15 Drain

A drain is used to reduce the water content in a wet steam flow with 10

03 =X

Fig. 19: Fluid properties of a drain




If f denotes the ratio of the water drained from the inlet, then the mass flows and the

dryness fractions are calculated as follows:

113 )1( mXfm && = (72)

112 ))1(1( mXfm && = (73)

))1(1( 1

12

Xf

XX

= (74)

The mass flow 3m& is saturated liquid with 03 =X


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2.1.4.16 Dryer

A dryer is used to reduce the humidity of a gas flow

111 ,, phm& 222 ,, phm&

333 ,, phm&

OLHX

21 OLHX

22

Fig. 20: Fluid properties of a dryer




The mass flow 3m& of the separated water is calculated from the degree of drying gand

the mass fractionH2OL1

X of liquid water (H2OL) on inlet 1.

1H2OL13X mgm && = (78)

1H2OL12 )X1( mgm && = (79)

)1(21

21

22 gX

XX

OH

OHOLH

= (80)


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2.1.4.17 Selective splitter

The selective splitter is used for the selective separation of mass flows. Examples are gas

cleaning, cyclones or venturi scrubbers.

111 ,, phm& 222 ,, phm&

333 ,, phm&

Fig. 21: Fluid properties of a selective splitter




The mass flow 3m& of the separated stream is calculated from the separation efficiencies

iJ of the individual components iX1 as follows :

113 mXJm ii

i && = (84)

The individual components at outlet 2 are given by

3

113

m

mJXX iii &

&

= (85)


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2.1.4.18 Mixers

Mixers are used to mix two fluid flows.

111 ,, phm& 222 ,, phm&

333 ,, phm&

Fig. 22: Fluid properties of a mixer

Mass balance: 0321 =+ mmm &&& (86)

Energy balance: 0332211 =+ hmhmhm &&& (87)

Pressure: for example ),min( 312 ppp = (88)

While for a splitter the outlet pressures are same like the inlet pressure, for the mixer

there are several options how to specify the pressures in the connecting pipes.


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2.1.4.19 NoX removal

In the NoX removal ammonia (NH3) is used to reduce the fractions of nitrogen oxides in

the flue gas (NO, NO2).

111 ,, phm& 222 ,, phm&

333 ,, phm&

Fig. 23: Fluid properties of NoX removal

Mass balance: 0321 =+ mmm &&& (89)

Energy balance: 0332211 =++ )()( evapreact hhmhmhhm &&& (90)


reacth is the reaction heat of the chemical reactions and evaph the evaporation heat of

NH3.

The pressure drop in off-design is calculated asN

NN

pm

m

v

vp 12

2

1

112

=

&

& (92)

The reduction of the nitrogen oxides in the flue gas is described by 3 characteristic lines:

Characteristic line 1 describes the dependency on the flue gas mass flow:

)( 1112 NmmfNOXNOX &&=

Characteristic line 2 describes the dependency on the NH3 mass flow:

)( 3312 NmmfNOXNOX &&=

Characteristic line 2 describes the dependency on the flue gas temperature:

)( 112 TfNOXNOX =


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2.1.4.20 Controller

During an iteration solving the system of equations the task of a controller is, by means of

a correction value to modify an actual value until a given reference value is achieved.

Fig. 24: Iterative controller

The controller works as follows:

The correction value in the i+1-th iteration step is calculated from the correction value of

the i-th iteration step

)1(1 csgfff iiiii +=+ (93)

With the relative difference from the reference value:S

ASs ii

= (94)

With the relative change of the correction value

from the last iteration step:1

1)(

=

i

iii

fffK (95)

with the gradient:i

ii

s

Kg = (96)

and the controller characteristic:sticcharacterinegativeafor

sticcharacteripositiveafor

1

1

=

=

c

c


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2.1.4.21 Measured value input

A measured value input is used to specify a physical property (i.e. pressure p ,

temperature Tor mass flow m& ) on a pipe.

pm,& h,,pm&

),( Tphh=

Fig. 25: measured value input

A measured value input does not have its own component physics. Nevertheless if a

physical property which is not one of the 3 base variables hpm or,&

an underlying

function library (for example water/steam table) can be accessed and the base variable

can be calculated, for example to calculate specific enthalpy from pressure and

temperature ),( Tphh= (Fig. 25).

Furthermore it is possible to access a pipe variable and to calculate a property derived

from the pipe variables. For example, to calculate the saturation pressure )(Tpsat from the

temperature given in the pipe.


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2.2.2 Component library

An integral part of EBSILONProfessional is a library of presently 118 (Release 9.0 of

EBSILONProfessional) components. These components can be selected in the toolbar

and inserted into the workspace.

Fig. 27: Symbols for the components available in the component library


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The specification of component and process variables is done interactively through

dialogs (Fig. 28).

Fig. 28: specification values

In the dialog Specification-Values specification data for a component can be provided.

For every specification value a pre-defined default value is supplied. The specification

values are displayed in black color. Blue color is used for reference values which are only

created in Design-calculations. These reference values define the operation of

components in off-design calculations and should not be modified after the Design-

calculation.


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Process values can be specified by placing a General value input component on a pipe

(Fig. 29). With this component it is possible to specify the physical state of a fluid (mass

flow, pressure, specific enthalpy resp. temperature).

Fig. 29: specification of process values

Depending on the type of the fluid the fluids composition can be specified in the dialog

Material Fractions. It is possible to use pre-defined compositions (for example for

particular coal qualities) which are supplied in an underlying database. But it is also

possible to supply a self-defined composition.


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In order to display the results of a simulation in the GUI, value crosses can be inserted

into the model (Fig. 30).

Fig. 30: Display of process values using value crosses

The properties to be displayed can be configured. Also the layout of the value cross can

be modified.


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2.2.3 Simulation

Having created the topology and having supplied the specification data for components

and certain process data, it is possible to start a simulation. At the end of the simulation a

message (Fig. 31) displays the simulation status and the number of iterations steps

Fig. 31: Status message at the end of the simulation (here with errors)

If an error or only a warning was recognized, or if the model is overdetermined, detailed

hints about type and location of error or warning are given. (Fig. 32).

Fig. 32: Information about type and location of errors

Warnings and errors can be caused by an overdetermination of the system of equations.

It is the aim to parameterize the model in such a way that the simulation is successful

without warnings. Only then it can be expected that the simulation is successful and

without contradictions for off-design conditions.


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There are various model-options (Fig. 33) to configure the iteration process regarding

convergence and precision. Also it is possible to configure the libraries (steam tables etc.)

for the calculation of fluid properties.

Fig. 33: model options of the Simulation

2.2.4 Design / Off-design

In EBSILONProfessionalthere exist two principally different calculation modes (Fig. 34):

The full load mode (design mode) is used for the balancing of processes at the

design point. i.e. the load for which the power-plant and its components are

optimized. The partial load mode (off-design mode) is used to investigate the performance of

the power-plant at conditions which are different from the design conditions

(different load, or different ambient conditions etc.). In this mode it is possible to

obtain information about the plant performance under different scenarios (for

example effect of cooling water temperature on heat-rate).


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Fig. 35: default characteristic line of a turbine

For some components it is possible to use standardized calculation methods for the off-

design performance and to ignore the characteristic lines. Examples are the turbine

condenser using the method of the Heat Exchange Institute for the calculation of the

heat-transfer coefficient (Fig. ) or the preheater using the method of Rabek also for the

heat-transfer coefficient (Fig. 37). As a consequence the tuning of the model for off-

design conditions is simplified. Nevertheless it has to be mentioned that the off-design

performance then can slightly differ from the off-design performance of the real power-

plant.


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Fig. 36: Specification of the off-design behavior of the turbine condenser using the method of the

Heat Exchange Institute

Fig. 37: Specification of the off-design behavior of the feedwater preheater using the

method of Rabek


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3 Literature

/1/ Thermische Kraftanlagen, Grundlagen, Technik, Probleme.

Hans-Joachim Thomas, Springer Verlag, 1985

/2/ Power Plant Technology

M.M.El-Wakil, McGraw-Hill International Editions, 1984

/3/ Kraftwerkstechnik

K.Strau, 4.Auflage, 1998, Springer Verlag,

/4/ Messunsicherheiten bei Abnahmemessungen an energie- und kraftwerkstechnischen Anlagen

VDI-Gesellschaft, VDI-Richtlinien, VDI 2048

/5/ Erfahrungen bei der Erstellung und dem Einsatz eines Datenvalidierungsmodells zur

Prozessberwachung und optimierung im Kernkraftwerk Isar 2

Von J.Tenner, P.Klaus und E.Schulze, VGB Kraftwerkstechnik 4/98

/6/ Die Ermittlung der Betriebsverhltnisse von Speisewasservorwrmern bei verschiedenen

Belastungen

G.Rabek, Energie und Technik, 1963

/7/ Wirksame Khlrohrlnge bei Kondensatoren

VDI-Gesellschaft, Energietechnische Arbeitsmappe,

/8/ Wrmebertragung

Walter Wagner, 1981, Vogelverlag,

/9/ Thermodynamik

Hans-Dieter Baehr, Springer Verlag, 2005, 12.Auflage

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