Component 139: Steam generator with 2 reheats

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Component 139: Steam Generator with 2 reheats

Specifications

Line connections
1	Feed water inlet
2	HP live steam outlet
3	First reheat inlet
4	First reheat outlet
5	Thermal boiler duty (as H), (e.g. provided by component 21)
6	High pressure spray (without throttling)
7	First reheat spray (without throttling)
8	Drain / Blow down
9	Second reheat inlet
10	Second reheat outlet
11	Second reheat spray (without throttling)

General User Input Values Characteristic Lines Physics Used Displays Example

General

This component is an expansion of Component 5 (“Steam generator“) by an additional leg for a second reheat.

Like Component 5, also Component 139 represents an easy way to model a steam generator with specifiable steam parameters without the need to display the individual heating surfaces in detail. It only contains the water/steam side of the boiler. As, however, the required heat demand is determined and output on Logic Pin 5 in an overall balancing of all incoming and exiting energy flows, it can be used as set point value of a controller (Component 12) for modeling a combustion with Component 21. For this purpose, also Component 139 features a view (Form 2) to place the component on a Component 21 (with Form 2, 4, or 5) and optically represent the boiler as an entity.

The expansion for Component 5 consists in an inlet (Pin 9) and an outlet (Pin 10) for the fluid to be heated in the second reheat (by default: steam) as well as an inlet (Pin 11) for a possible injection. The steam outlet temperatures for all legs can optionally be set internally in the component as specification value T2, T4, and T10 respectively or they can be specified from outside. In the case of internal specification, the temperature is assumed to be constant in all load cases.

The inlet temperatures for the feed water and the steam for the two reheat legs are to result from the model from outside.

In the design case, the pressure on the high pressure leg can be set internally with the specification value P2N. The load dependence of the live steam pressure is then defined with the characteristic line CP2. The outlet pressures of the two reheat legs are to result from the model from outside.

In the design case, the pressure drops of the individual legs are set in the specification values DP12N, DP34N, and DP910N. In off-design, a characteristic line CDP12 is available for the high pressure leg. Usually (i.e. FVOL=1) the two reheat legs are scaled according to Bernoulli’s law:

DP34 =(M3/M3N)² * (V3/V3N) * DP34N and

DP910 =(M9/M9N)² * (V9/V9N) * DP910N

Here the flag FVOL allows to use the simplified formulae

DP34 =(M3/M3N)² * DP34N and

DP910 =(M9/M9N)² *DP910N

For using incompressible fluids with FVOL=0 or in order not to scale the pressure drop at all (FVOL=2):

DP34 = DP34N

DP910 = DP910N

The mass flows for all legs have to be specified from outside.

The mass flows of the three injections, however, can be specified in the component relative to the feed water mass flow.

For the high pressure leg, this is effected in the specification value M6M1. This value applies to all load cases.

For the injections into the reheat legs, the mass flows can be defined load-dependent via the characteristic lines CM7M1 and CM11M1. Here it has to be considered that for both characteristic lines the “load” refers to the feed water mass flow (M1/M1N) and not to the mass flow of the respective reheat. Also the result refers to the feed water mass flow in the case of both characteristic lines. This is because it is the respective injection mass flow, related to the feed water mass flow. In contrast to many other characteristic lines, these characteristic lines do not have the value 1 at the position M1/M1N=1, but the ratio of the injection mass flow to the feed water mass flow in the design point. Therefore these characteristic lines are also used in the design calculation.

Like in Component 5, also in Component 139 there is an outlet for a blow-down. Its mass flow can optionally be specified via the internal specification value M8M1 or from outside. The pressure of the blow-down is defined by the specification value DPECON. Here DPECON is the pressure drop between the feed water inlet and the blow-down. The enthalpy of the liquid boiling at this pressure is assumed as the enthalpy of the blow-down.

In Component 139, a separate flag has been implemented for each optionally specifiable quantity. Here “0“ stands for the specification in the component and “1“ for the specification from outside. The use of combined flags like in Component 5 (e.g. “T2, P4 given from outside, T4 internally“) would have been too confusing here.

CAUTION:

While modeling injections and drains care must be taken to use these with the remaining circulation, as otherwise a violation of the mass balance can occur.

User Input Values

FMODE	Flag for calculation mode =0: GLOBAL =1: Local off-design = -1: Local design
FP2	Live steam pressure specification Like in Parent Profile (Sub profile option only) Expression =0: P2 determined by P2N and CP2 =1: P2 given from outside
P2N	Live steam pressure (nominal)
DP12N	HP-pressure loss (between ports 1 and 2) (nominal)
FT2	Live steam temperature specification Like in Parent Profile (Sub profile option only) Expression =0: T2 given by specification value T2 =1: T2 given from outside
T2	Live steam temperature
FM6	High pressure spray specification Like in Parent Profile (Sub profile option only) Expression =0: M6 calculated from specification value M6M1 =1: M6 given from outside
M6M1	HP-injection mass flow, (relative to feed water M1)
DP34N	First reheat pressure drop (nominal)
FT4	First reheat hot temperature specification Like in Parent Profile (Sub profile option only) Expression =0: T4 given by specification value T4 =1: T4 given from outside
T4	First reheat hot temperature
FM7	First reheat spray specification Like in Parent Profile (Sub profile option only) Expression =0: M7 calculated from characteristic CM7M1 =1: M7 given from outside
DP910N	Second reheat pressure drop (between ports 9 and 10) (nominal)
FT10	Second reheat hot temperature specification Like in Parent Profile (Sub profile option only) Expression =0: T10 given by specification value T10 =1: T10 given from outside
T10	Second reheat hot temperature
FM11	Second reheat spray specification Like in Parent Profile (Sub profile option only) Expression =0: M11 calculated from specification value CM11M1 =1: M11 given from outside
FM8	Drainy specification Like in Parent Profile (Sub profile option only) Expression =0: M8 calculated from specification value M8M1 =1: M11 given from outside
M8M1	Draining mass flow (relative to nominal feed water flow)
DPECON	Economizer pressure drop (for determination of drain pressure), (nominal)
FVOL	Part-load pressure drop (reheat only) Like in Parent Profile (Sub profile option only) Expression =0: only depending on mass flow =1: depending on mass and volume flow =2: Constant (equal nominal value)
M1N	Feed water mass flow (nominal)
M3N	First reheat mass flow (nominal)
V3N	Specific volume of first reheat (cold side) (nominal)
M9N	Second reheat mass flow (nominal)
V9N	Specific volume of second reheat (cold side) (nominal)

The identification values marked in blue are reference values for off-design mode. These values are referred to for the actual off-design values used in the equations respectively. If these identification values are stream data, then these values are often taken from attached pipes or calculated values.

Generally, all inputs that are visible are required. But, often default values are provided.

For more information on colour of the input fields and their descriptions see Edit Component\Specification values

For more information on design vs. off-design and nominal values see General\Accept Nominal values

Characteristic Lines

Characteristic lines CPD12, CPD34, CPD910: The default characteristic lines have a constant value of 1.0. A calculation based on physical laws should be more accurate than a default characteristic curve in most cases. In particular, a dependence on the volume flow cannot be taken into account at all in the characteristic line. And to regard steam as an incompressible fluid is probably a rather rough approximation.

Characteristic 1 (CP2) : HP-sliding pressure-characteristic P2/P2N = f(M1/M1N)

     X-Axis     1        M1/M1N                 1^st point
                  2        M1/M1N                 2^nd point
                    .
                  N        M1/M1N                 last point

     Y-Axis     1        P2/P2N                     1^st point
                    2        P2/P2N                    2^nd point
                    .
                    N        P2/P2N                    last point

Characteristic 2 (CDP12) : HP-pressure loss DP12/DP12N = f(M1/M1N)

     X-Axis   1        M1/M1N                  1^st point
                    2        M1/M1N                 2^nd point
                    .
                    N        M1/M1N                 last point

     Y-Axis     1         DP12/DP12N          1^st point
                    2         DP12/DP12N         2^nd point
                    .
                    N        DP12/DP12N          last point

Characteristic 3 (CDP34) : RH-pressure loss DP34/DP34N = f(M3/M3N)

     X-Axis   1        M3/M3N                  1^st point
                    2        M3/M3N                 2^nd point
                    .
                    N        M3/M3N                 last point

     Y-Axis     1         DP34/DP34N          1^st point
                    2         DP34/DP34N         2^nd point
                    .
                    N        DP34/DP34N          last point

Characteristic 4(CDP910): RH-pressure loss , 2. RH DP910/DP910N = f(M9/M9N)

X-Axis        1        M9/M9N                 1^st point
                    2        M9/M9N                 2^nd point
                    .
                    N        M9/M9N                last point

Y-Axis        1         DP910/DP910N           1^st point
                    2         DP910/DP910N           2^nd point
                    .
                    N        DP910/DP910N           last point

Characteristic 5 (CM7M1) : 1st RH spray water M7/M1 = f(M1/M1N)

     X-Axis    1        M1/M1N                  1^st point
                    2        M1/M1N                 2^nd point
                    .
                    N        M1/M1N                 last point

     Y-Axis    1         M7/M1                   1^st point
                    2         M7/M1                   2^nd point
                    .
                    N        M7/M1                    last point

Characteristic 6 (CM11M1) : 2nd RH spray water M11/M1 = f(M1/M1N)

     X-Axis    1        M1/M1N                  1^st point
                    2        M1/M1N                 2^nd point
                    .
                    N        M1/M1N                 last point

     Y-Axis    1         M11/M1                   1^st point
                    2         M11/M1                  2^nd point
                    .
                    N        M11/M1                    last point

Physics Used

Equations

Design case
(Simulation flag:
GLOBAL = Design case
and
FMODE = GLOBAL)

M2 - M1 - M6 + M8 = 0 (1)

if FM6=0:

M6 – M6M1 * M1 = 0 (2)

if FP2=0:

P2 = P2N (3)

P2 – P1 =DP12N (4)

if FT2=0:

H2 = f(P2,T2) (5)

M4 – M3 – M7 = 0 (6)

if FM7=0:

M7 – CM7M1(1)* M1 = 0 (7)
(CM7M1(1): Value of the characteristic curve for the 1st RH spray water at M1 / M1N = 1 )

P3 – P4 = DP34N (8)

if FT4=0:

H4 = f(P4,T4) (9)

M10 – M9 – M11 = 0 (10)

if FM11=0:

M11 – CM11M1(1)* M1 = 0 (11)
(CM11M1(1): Value of the characteristic curve for the 2nd RH spray water at M1 / M1N = 1 )

P9 – P10 = DP910N (12)

if FT10=0:

H10 = f(P10,T10) (13)

if FM8=0:

M8 – M8M1 * M1 = 0 (14)

P8 – P1 = DPECON (15)

H8 = H’(P8) (16)

H5+M1*H1+M3*H3+M9*H9+M6*H6+M7*H7+M11*H11-M2*H2-M4*H4-M10*H10-M8*H8=0 (17)

Off-design
(Simulation flag:
GLOBAL = Off-design
or
FMODE = Local off-design)

M2 - M1 - M6 + M8 = 0 (1)

if FM6=0:

M6 – M6M1 * M1 = 0 (2)

if FP2=0:

P2 = CP2(M1/M1N) * P2N (3)
(CP2: HP-sliding pressure-characteristic )

P2 – P1 = CDP12(M1/M1N) * DP12N (4)
(CDP12:HP-pressure loss -characteristic)

if FT2=0:

H2 = f(P2,T2) (5)

M4 – M3 – M7 = 0 (6)

if FM7=0:

M7 – CM7M1(M1/M1N)* M1 = 0 (7)
(CM7M1: 1st RH spray water-characteristic)

if FVOL =

0: DP34 =(M3/M3N)² * DP34N

1: DP34 = (M3/M3N)² * (V3/V3N)*DP34N

2: DP34 = DP34N

P3 – P4 = DP34 (8)

if FT4=0:

H4 = f(P4,T4) (9)

M10 – M9 – M11 = 0 (10)

if FM11=0:

M11 – CM11M1(M1/M1N)* M1 = 0 (11)
(CM11M1: 2nd RH spray water-characteristic)

if FVOL =

0: DP910 =(M9/M9N)² * DP910N

1: DP910 = (M9/M9N)² * (V9/V9N)* DP910N

2: DP910 = DP910N

P9 – P10 = DP910 (12)

if FT10=0:

H10 = f(P10,T10) (13)

if FM8=0:

M8 = M8M1 * M1N (14)

P8 – P1 = DPECON (15)

H8 = H’(P8) (16)

H5+M1*H1+M3*H3+M9*H9+M6*H6+M7*H7+M11*H11-M2*H2-M4*H4-M10*H10-M8*H8=0 (17)

Results

Relative mass flow feed water	M1/M1N
Relative mass flow reheat	M3/M3N
Relative live steam pressure	P2/P2N
Relative live steam pressure drop	DP12/DP12N
Relative reheat steam pressure drop	DP34/DP34N
2. RH :Relative mass flow reheat	M9/M9N
2. RH: Relative reheat steam pressure drop	DP910/DP910N

Component Display

Form 1

Form 2

Example

Click here >> Component 139 Demo << to load an example.

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