Component 107: Condenser for binary mixtures

In This Topic

Component 107: Condenser for binary mixtures

Specifications

Line connections
1	Cooling medium inlet
2	Cooling medium outlet
3	Exhaust steam inlet
4	Condensate outlet
5	Secondary condensate inlet
6	for future use

General User Input Values Characteristic Lines Physics Used Displays Example

General

This component differs from component 7 by using a binary mixture at the inlet on the hot side. Because such a mixture does not have a fixed condensation temperature, but at first the solvent condenses and at lower temperatures eventually also the cooling agent, the outlet temperature of the cooling water can be above the condensation temperature range in the case of this component.

Flag FSPECPD:

In Release 13 it is possible specify the design pressure (and also the start value for the internal iteration in off-design) in the component as specification value P3N.
The specification is controlled via the flag FSPECPD (see "User Input Values").

Flag FDQLR

It is possible to use the FDQLR flag to define how DQLR (factor for modeling heat losses) should be interpreted.

External Specification of the Pressure of the Auxiliary Condensate

Since the auxiliary condensate is at the same pressure level as the condensate, it is necessary during modeling to install a control valve or a condensate valve on the auxiliary condensate line in to decrease the pressure to the Preheater / Heating condenser level.

To simplify the modeling, there is now a mode “P5 given externally“ that can be set by means of the flag FP5. This mode allows to connect a line with a higher pressure on
Pin 5. Within the component, the auxiliary condensate is then reduced to the preheater / heating condenser pressure. The result is the same as with an external control valve.

This mode is the default setting for newly inserted components. For existing models, FP5 is set to “P5=P3“.

Pressure drop limitations in off-design (Extras --> Model Options--> Calculation -->Relative pressure-drop maximum) :
As the pressure drop rises quadratically with the mass flow, pressure drops that are significantly too high can quickly arise in the event of a transgression of the nominal mass flow. These will then cause phase transitions and convergence problems. For this reason, pressure drop limitations have been installed.

Note about the result values:

Performance factor RPFHX

The quotient from the current value for k*A (result value KA) and the k*A expected in the respective load point due to the component physics and characteristic lines respectively (result value KACL) serves to assess the condition of a heat exchanger.

The quotient KA / KACL is displayed as a result value RPFHX.

Treatment of mixtures: Note about the result values:

In the process of the unification of this component with Component 7, an inconsistency when using water/lithium bromide as working fluid was noticed. As no lithium bromide exists in the gaseous phase, this component has to condense pure steam in this case and should therefore behave exactly like Component 7. The reference temperature for specification value DT3S2N should therefore also be the boiling temperature of water. That was not so, in this case the temperature at Inlet 3 was used. This has been corrected. The error message at too high values of DT3S2N now contains information on what the reference temperature is, so that the value can be adjusted accordingly.

The error message at too high values of DT3S2N contains information on what the reference temperature is, so that the value can be adjusted accordingly.

User Input Values

DT3S2N	Upper terminal temperature difference (nominal)
FSPECPD	Design specification for vapour pressure Like in Parent Profile (Sub Profile option only) Expression =0: Design vapour pressure given by specification value P3N (The specification value P3N is used as condenser pressure in the design case and as start value for the pressure calculation in off-design. If, additionally, a pressure specification is effected on the line, a double entry will be reported.) =1: Design vapour pressure given externally (In the design case, the pressure given on the line will be used as condenser pressure and saved in P3N when the reference values are subsequently taken over. In off-design, P3N is then used as start value for the pressure calculation. If, additionally, a pressure specification is effected on the line in off-design, a double entry will be reported.) =-1: Design vapour pressure given externally (in off-design as start value) (The pressure given on the line is used as condenser pressure in the design case and as start value for the pressure calculation in off-design. No double entry will be reported due to the specification on the line even if the pressure is defined by the condenser. (This case corresponds to the behaviour up to Release 12.)
P3N	Steam pressure (nominal)
DP12N	Cold side pressure drop, for line 1 to 2 (nominal)
DP34N	Hot side pressure drop, for line 3 to 4 (nominal)
TOL	Tolerance in energy balance
FDQLR	Heat loss handling Like in Parent Profile (Sub Profile option only) Expression =0: Constant (DQLRQN in all load cases) DQLR refers to the design value QN (which equals the heat quantity given off by the hot flow in the design case) in all load cases, i.e. it has a constant value in all load cases. If, however, this value exceeds 10 percent of the heat quantity given off by the hot flow, the heat loss will be limited to this value, and a warning will be output. =1: Relative to actual heat input (DQLRQ354) DQLR refers to the heat quantity given off by the hot flow. If the corresponding warning is ignored, losses of more than 10 percent can be modelled here too.
DQLR	Heat loss to the environment by radiation (relative to the radiating current)
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, even if global design mode was selected) =2: special local off-design (special case for compatibility with earlier EBSILON^®Professional versions, should not be used in newer models, because the results of the real off-design calculations are not consistent) = -1: local design
FSPEC	Flag for the setting, which parameters are specified and which have to be calculated (concerns only off-design) Like in Parent Profile (Sub Profile option only) Expression Normal calculation modes (characteristic line or adaptation polynomial is used): 0: M1=M1N, T2 and P3 calculated (using kA) 1: T2 given, M1 and P3 calculated (using kA) 2: M1 given, T2 and P3 calculated (using kA) Identification modes (characteristic line and adaptation polynomial are ignored, kA is calculated from measurement values): 3: T2 and P3 given, M1 calculated, identification of kA 4: P3 given, M1=M1N, identification of kA 5: M1 and P3 given, T2 calculated, identification of k*A This flag is ignored in the design mode.
FADAPT	Flag for using the adaptation polynomial ADAPT / adaption function EADAPT Like in Parent Profile (Sub Profile option only) Expression =0: Not used and not evaluated =1: Correction factor for kA [KA = KAN carline factor polynomial] =2: Calculation of kA [KA = KAN * polynomial] =1000:Not used but ADAPT evaluated as RADAPT (Reduction of the computing time) =-1: Correction factor for kA [KA = KAN carline factor adaption function] =-2: Calculation of kA [KA = KAN * adaption function] = -1000: Not used but EADAPT evaluated as RADAPT (Reduction of the computing time)
EADAPT	Adaption function
KAN	k*A (nominal) - Design Heat Transfer Capability
M1N	Cold side mass flow (nominal)
M3N	Hot side mass flow (nominal)
QN	Condenser duty (nominal)

The parameters marked in blue are reference parameters for off-design, which are calculated by EBSILON^®Professional in the design mode. The actual off-design values refer to these parameters 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

Characteristic Lines

There are two characteristic lines, which describe the effect of the primary mass flow or of the secondary mass flow respectively on k*A. The complete correction factor for k*A results from the multiplication of both the influencing factors.

1. Characteristic line CKAM1 FK1 = f (M1/M1N)
2. Characteristic line CKAM2 FK2 = f (M3/M3N)

Total: (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^st Point
                    2        M1/M1N                 2^nd Point
                    .
                    N        M1/M1N                 last Point
     Y-axis      1        (k*A)1/(k*A)N          1^st Point
                    2        (k*A)1/(k*A)N          2^nd 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^st Point
                    2        M3/M3N                 2^nd Point
                    .
                    N        M3/M3N                 lastPoint
   Y-axis      1        (k*A)2/(k*A)N          1^st Point
                    2        (k*A)2/(k*A)N          2^nd Point
                    .
                    N        (k*A)2/(k*A)N          last Point

Physics Used

Equations

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

P2 = P1 - DP12N
P4 = P3 - DP3N
P5 = P3

M2 = M1
M4 = M3 + M5

T3S = fsat (P3)
T2 = T3S - DT3S2N
H2 = H(P3, T3S)

T4S = fsat(P4)
T4 = T4S
H4 = fsat(P4)
Q3 = M3*H3
Q4 = M4*H4
Q5 = M5*H5
DQ = (Q3 + Q5 - Q4)*(1-DQLR)
M1*(H2 - H1) = DQ

DTL = T4 - T1
DTU = T3 - T2
LMTD = (DTU - DTL)/(ln(DTU) - ln(DTL))

KAN = DQ/LMTD

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

F1 = (M1/M1N) ** 2
P2 = P1 - DP12N * F1

F3 = (M3/M3N) ** 2
P3 = P4 + DP34N * F3
P5 = P3

M2 = M1
M4 = M3 + M5

     Fk1   = f (M1/M1N) from Characteristic Line 1
     Fk2   = f (M3/M3N) from Characteristic Line 2
     KA = KAN * Fk1 * Fk2

Start of the iteration

T4 = fsat(P4)
H4 = fsat(P4)
Q12 = (Q3 + Q5 - M4*H4) * (1-DQLR)

If FSPEC = 0,2, then{

H2 = H1 + Q12/M2
T2 = f(P2,H2) }

If FSPEC = 1, then{ T2 from user input }

DTL = T4 - T1
DTU = T3 - T2
LMTD = (DTU - DTL)/(ln(DTU) - ln(DTL))

QQ = KA * LMTD
DQQ = Q12 - QQ

Start of the Regula Falsi Method
grad = (P4- P4old)/(DQQ - DQQold)
P4 = P4 - DQQ * grad
End of the Regula Falsi Method

DQ = | DQQ/((Q12+QQ)*.5) |

If DQ < TOL, then end the iteration

else continue the iteration

If FSPEC = 0, then{

M2 = M1 = M1N }

If FSPEC = 1, then{

M2 = Q12/(H2 - H1) }

If FSPEC = 2, then{

M2 = M1 from the start value setter }

Result values

Note:

Like in the simple steam turbine condenser (Component 7), there were the result values DT3S2 and DT4S1 in this component. As for binary mixtures, however, the boiling temperature is not constant, specifying temperature differences for the boiling temperature does not make much sense here.

Therefore

DTLO (lower terminal temperature difference) and
DTUP (upper terminal temperature difference)

is output for Component 107.

Attention: If DT3S2 or DT4S1 has been used for Component 107 in an EbsScript, there will now be a compiler error, which can be remedied by renaming to DTUP and DTLO respectively.

Component Displays

	Display Option 1		Display Option 2
	Display Option 3

Example

Click here >> Component 107 Demo << to load an example.

Impressum Disclaimer