Component 66: Feed Water Preheater - Outdated

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Component 66: Feed Water Preheater - outdated!

General

This component is available only for ensuring a backward compatibility with the earlier versions of Ebsilon and is not maintained any more. Instead of this component, component 10 should be used in new cycles.

The required mass flow of heating steam 3 is calculated on the assumption, that the condensate 4 is saturated.

The easiest method of deactivating a heat exchanger without removing it from the cycle is to set FFU = off. However, pressure losses continue to be considered.

Relative radiation losses can be defined by a loss factor.

Specifications

Line connections
1	Primary inlet
2	Primary outlet
3	Secondary inlet
4	Secondary outlet
5	Secondary inlet of auxiliary condensate flow

DTN	Temperature input (nominal) owing to FSPEC
FDP12RN	Primary pressure loss handling Like in Parent Profile (Sub Profile option only) Expression =1: calculated by DP12N= DP12RN (absolute) =2: calculated by DP12N=P1N*DP12RN (relative)
DP12RN	Pressure loss 12 (nominal) [absolute or relative to P1]
FDP34RN	Secondary pressure loss handling Like in Parent Profile (Sub Profile option only) Expression =1: calculated by DP34N= DP34RN (absolute) =2: calculated by DP34N=P1N*DP34RN (relative)
DP34RN	Pressure loss 34 (nominal) [absolute or relative to P3]
DQLR	Heat loss (QL relative to Q34)
FMODE	Flag for calculation mode Design/Off-design Like in Parent Profile (Sub Profile option only) Expression =0: Global =1: local off-design (i.e. always off-design mode (KAN and characteristic lines), even when a design calculation has been done globally) =2: special local off-design, calculation is analogous to off-design, but without considering the characteristic lines (Special case for compatibility with the earlier Ebsilon-versions, should not be used in new models, because the results of the real off-design calculations are not always consistent)
FFLOW	Direction of flow Like in Parent Profile (Sub Profile option only) Expression =0: counter current flow
FSPEC	Specifications Like in Parent Profile (Sub Profile option only) Expression =0: Input DTN=DT3S2N=T3S-T2 (upper terminal temperature difference) =5: T2 given from outside (design mode only)
FVOL	Volume dependency on pressure drop Like in Parent Profile (Sub Profile option only) Expression =0: without DP/DPN = (M/MN)*2 =1: with DP/DPN = V/VN(M/MN)**2
FADAPT	Flag for adaption polynomial ADAPT / adaptation function EADAPT Like in Parent Profile (Sub Profile option only) Expression =0: =0: Not used and not evaluated =1: Correction for kA [KA = KAN char lines factor * polynomial] =2: Calculation of kA [KA = KAN polynomial] =1000: Not used but ADAPT evaluated as RADAPT (Reduction of the computing time) =-1: Correction for kA [KA = KAN char lines factor * adaptation function] =-2: Calculation of kA [KA = KAN adaptation function] =-1000: Not used but EADAPT evaluated as RADAPT (Reduction of the computing time)
EADAPT	Adaptation function
FFU	On-/Off switch Like in Parent Profile (Sub Profile option only) Expression =0: Heat-exchanger inactive =1: Heat-exchanger active
KAN	K*A (nominal)
M1N	Primary mass flow (nominal)
M3N	Secondary mass flow (nominal)
QN	Heat-exchanger power (nominal)=Q34N
V1N	Specific volume for primary side inlet 1 (nominal)
V3N	Specific volume for secondary side inlet 3 (nominal)

The parameters marked in blue are reference quantities for the off-design mode. The actual off-design values refer to these quantities in the equations used.

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

The following table shows, whether KAN or DTN is to be used, or whether T2 or M2 are to be calculated or specified as defaults respectively:

	GLOBAL = Design		GLOBAL = Off-design
	FMODE = Design	FMODE = Off-design (local) =1,2	FMODE = Design	FMODE = Off-design (local) =1,2
KAN	Value optional	specified by the user	specified by the user	specified by the user
DTN	Value optional	Value optional	Value optional	Value optional

Characteristic lines

1. Characteristic line FK1 = f (M1/M1N)

2. Characteristic line FK2 = f (M3/M3N)

(k*A) / (k*A)N = FK1 * FK2

Characteristic line 1: (k*A)-characteristic line: (k*A)1/(k*A)N = f (M1/M1N)

     X-axis          1         M1/M1N                     1. point
                        2          M1/M1N                     2. point
                        .
                      N         M1/M1N                    last point

     Y-axis         1          (k*A)1/(k*A)N            1. point
                        2          (k*A)1/(k*A)N             2. point
                        .
                        N         (k*A)1/(k*A)N            last point

Characteristic line 2: (k*A)-characteristic line : (k*A)2/(k*A)N = f (M3/M3N)

     X-axis         1          M3/M3N                     1. point
                        2          M3/M3N                     2. point
                        .
                        N         M3/M3N                     last point

     Y-axis        1          (k*A)2/(k*A)N            1. point
                        2          (k*A)2/(k*A)N           2. point
                        .
                        N         (k*A)2/(k*A)N           last point

Physics used

Equations

All Cases

if FDP12RN=relative, then {DP12N=P1*DP12RN}

else {DP12N=DP12RN}

if FDP34RN=relative, then {DP34N=P3*DP34RN}

else {DP34N=DP34RN}

Design case

(Simulation flag:

GLOBAL = design case

AND

FMODE = design case)

T3S = f'(P3)

P2 = P1 - DP12N (1)

if upper terminal temperature difference is given by FSPEC, then {

T2 = T3S DTN

}

if T2 is given by FSPEC, then {

T2 = DTN

}

H2 = f(P2,T2)

M2 = M1 (7)

Q2 = M2 * H2

DQ = M2 * H2 - M1 * H1 (5)

P4 = P3 - DP34N (2)

P5 = P4 (3)

H4S=f(P4)

M3 = (DQ/(1-DQLR) - M5 * (H5 - H4S))/(H3 - H4S) (6)

Q4 = Q3 + Q5 - DQ/(1-DQLR)

M4 = M3 + M5 (8)

H4S = Q4/M4 (4)

T4 = f(P4)

DTLO = T4 - T1 (for FFLOW = counter current)

DTUP = T3 - T2 (for FFLOW = counter current)

LMTD = (DTUP - DTLO)/(ln(DTUP) - ln(DTLO))

KAN = DQ/LMTD

Off-design case

(Simulation flag:

GLOBAL = off-design

FMODE = off-design)

F1 = (M1/M1N) ** 2

for GLOBAL = design, F1= 1.0

P2 = P1 - DP12N * F1 (1)

F3 = (M3/M3N) ** 2

for GLOBAL = design, F3= 1.0

P4 = P3 - DP34N * F3 (2)

M2 = M1 (7)

if GLOBAL = design {

Fk1 = 1.0

Fk2 = 1.0

}

if GLOBAL = off-design {

Fk1 = f (M1/M1N) from characteristic line 1

Fk2 = f (M3/M3N) from characteristic line 2

}

KA = KAN * Fk1 * Fk2

P4 = P5 (3)

M4 = M3 + M5 (8)

Maximum/minimum values for the iteration {

T4=f(P4) (4)

H4S=f(P4)

H2max = f(P2,T3)

Q21max = M1 * (H2max - H1)

Q34max = Q3 + Q5 M4*H4S

Qmax = min(Q21max,Q34max)

Q21 = 0.5*Qmax

Iteration {

H2 = H1 + Q21/M2

T2 = f(P2,H2)

DTLO = T4 - T1 (for FFLOW = counter current)

DTUP = T3 - T2 (for FFLOW = counter current)

LMTD = (DTUP - DTLO)/(ln(DTUP) - ln(DTLO))

QQ = KA * LMTD

DQQ_1 = DQQ

DQQ = Q21 - QQ

regula - falsi method {

Size = (Q21 - Q21_1)/(DQQ - DQQ_1)

for iteration step 1: Size of the last global step

Q21X = Q21 - DQQ * Size

Q21_1 = Q21

Q21 = Q21X

}

DQ = |DQQ /((Q21+QQ)*.5)|

if DQ < TOL, then end the iteration

else continue the iteration

}

M3 = (Q21/(1-DQLR) - M5 * (H5 - H4S))/(H3 - H4S)

(6)

Q4 = M4 * H4S

Q21 = (Q3 + Q5 - Q4) * (1-DQLR)

Q2 = Q1 + Q21

H2 = Q2 / M2

T2 = f (P2,H2)

DQ = M2 * H2 - M1 * H1 (5)

Variable connection table

Eq. No.		Line
		1	2	3	4	5
1	P	X	X
2	P			X	X
3	P			X		X
4	H				(X)
5	H	X	X
5	M	X	X
6	H	X	X	X	X	X
6	M	X	X	(X)	X	X
7	M	X	X
8	M			X	X	X

Example

Click here >> Component 66 Demo << to load an example.

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