Component 63: Feedwater Tank (Extended)

In This Topic

Component 63: Feed Water Tank / Deaerator (Extended)

Specifications

Line connections
1	Condensate inlet
2	Feed water outlet
3	Extraction /Heating steam inlet
4	Secondary condensate inlet
5	Vent / Exhaust gas
6	Additional heating steam
7	Heating water
8	Bypass steam

General User Input Values Physics Used Displays Example

General

Component 63 is a component for simulating the different operation and control conditions of the feed water tank or the deaerator, respectively.

Component 63 simulates the operating conditions that are set as default by means of the variable FSPEC:

preheating with extraction steam OR additional heating steam, extraction steam (pressure given externally) (FSPEC=1)
preheating with extraction steam as well as pure sliding pressure operation (FSPEC=2)
preheating with heating water and additional heating steam as well as sliding pressure operation (FSPEC=3, can also be used in design mode.) When exceeding M7MAX is pulled support steam via port 6).
preheating with heating steam and additional heating steam, heating steam pressure calculated internally PN (FSPEC=4)
preheating with heating steam and/or additional heating steam as well as fixed-pressure operation (FSPEC=5)
preheating with heating steam and/or additional heating steam at specified sliding pressure of the bypass steam (FSPEC=6)
preheating with heating water and / or heating steam if heating water demand> heating water (max) at sliding pressure (FSPEC = 7

Condition on connection point 2 is always identified by state H'(P2). This also applies if the energy balance of feed water tank / deaerator can not be closed, because for example the enthalpy of the heating media is too small. An error message "Energy balance violated" then appears.

If no additional heating steam is used for operating condition 1 in off-design operation, PMIN (or analogue TMIN) is to be assigned to 0.01 (minimum pressure permitted).

Similar components:

Component 9 feed water tank/deaerator 1:

This component simulates the feed water tank/deaerator just like component 63 with the following differences:

component 9 only has connections 1-5:

M3 is ALWAYS calculated from the energy balance

Some options, available in component 63, for heating media and control methods can not be considered in component 9.

In this component, the output of the nominal values M3N, M5N, M6N, and M7N was supplemented. However, they are not used within Ebsilon but are only intended to be used by the user in expressions and scripts.

User Input Values

FMODE	Calculation mode Like in Parent Profile (Sub Profile option only) Expression =0: Global =1: Local off-design =-1: Local design
FSPEC	Flag for possible operating conditions Like in Parent Profile (Sub Profile option only) Expression =1: Set sliding pressure between PMIN and PN, M3 (if P3>= P2) or M6. = 2: always sliding pressure, always set M3 = 3: P2 given internally, M7 calculated and M6 if M7> M7MAX = 4: M3 given, P2 calculated; if> PMAX set M8, if <set PMIN M6 = 5: P2 = P2N (constant), M3 given from outside, set either M6 or M8 = 6: P2 = P8, M3 given externally, set either M6 or M8 = 7: P2 = P3 (sliding pressure), M7 calculated and M3 if M7> M7MAX (see below for more information)
FPT	Flag for using temperature or pressure values Like in Parent Profile (Sub Profile option only) Expression =0: use of PN, PMIN, PMAX; (TN, TMIN, TMAX values dummies) =1: use of TN, TMIN, TMAX; (PN, PMIN, PMAX values dummies)
PN	Pressure in the tank (nominal)
PMIN	Minimum pressure in the tank
PMAX	Maximum pressure in the tank
TN	Temperature in the tank (nominal)
TMIN	Minimum temperature in the tank
TMAX	Maximum temperature in the tank
M7MAX	Maximum heating water mass flow (upon reaching M7MAX, the additional heating steam line 6 is opened)
M5	Exhaust vapour loss
M3N	Heating steam mass flow (nominal)
M5N	Vent mass flow (nominal)
M6N	Supplementary heating steam flow (nominal)
M7N	Heating water mass flow (nominal)

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

FSPEC

The various options for FSPEC are described below in more detail.

FSPEC = 1:

with extraction steam or additional heating steam (given extraction pressure from the outside)

Design case

Tank pressure = PN, quantity of extraction steam from the energy balance

Off-design case

Tank pressure = PN, if PN < extraction steam pressure, quantity of extraction steam from the energy balance
Tank pressure = extraction steam pressure, if PMIN < extraction steam pressure < PN, quantity of extraction steam from the energy balance
Tank pressure = PMIN, if extraction steam pressure < PMIN, quantity of extraction steam = 0, quantity of additional heating steam from the energy balance

FSPEC = 2:

with extraction steam for pure sliding pressure operation

Design case

Tank pressure = Extraction steam, quantity of extraction steam from the energy balance

Off-design case

Tank pressure = Extraction steam pressure, quantity of extraction steam from the energy balance

FSPEC = 3:

with heating water and additional heating steam for sliding pressure

Design case

Tank pressure = PN, quantity of heating water from the energy balance

Off-design case

Calculation of H2MIN with heating water quantity = 0,
H2MAX with heating water quantity = M7MAX

if H2MAX < H'(PMIN)
Tank pressure = PMIN and quantity of heat water = M7MAX (maximum possible), quantity of additional heating steam from the energy balance

           if H2MIN < H'(PMIN)
           Tank pressure = PMIN and quantity of  additional heating steam = 0, quantity of heating water from the energy balance

           if H2MIN >= H'(PMIN)
           Calculation of the tank pressure, P(Balance) from the energy balance with the heating water quantity = 0 and  additional heating steam quantity = 0

FSPEC = 4:

with heating steam and additional heating steam, heating steam pressure determined by PN

Design case

Tank pressure = PN, extraction steam quantity from the energy balance

Off-design case

calculation of the balance pressure of the tank, P(balance) from the energy balance with the quantity of extraction steam according to the input

if PMIN <= P(Balance) <= PMAX
Tank pressure = P(Balance) and the quantity of additional heating steam = 0 and the quantity of bypass steam = 0

           if PMIN > P(Balance)
           Tank pressure = PMIN and the quantity of  additional heating steam from the energy balance as well as the quantity of bypass steam = 0

          if PMIN < P(Balance)
          Tank pressure = PMAX and the quantity of  additional heating steam = 0 as well as the quantity of bypass steam from the energy balance

FSPEC = 5:

with heating steam and/or additional heating steam operating at fixed pressure

design case:

Tank pressure = PN
Amount of extraction steam given from outside
Amount of pegging steam from the energy balance

off-design:

Calculation of a fictive outlet enthalpy H_TEST from the energy balance without pegging steam and without bypass steam

if HTEST < H'(PN)
Calculation of the amount of pegging steam from the energy balance, amount of bypass steam = 0

if HTEST = H'(PN)
Amount of pegging steam = 0, amount of bypass steam = 0

if HTEST > H'(PN)
Calculation of the amount of bypass steam from the energy balance, amount of pegging steam = 0

FSPEC = 6:

with heating steam and/or additional heating steam for sliding pressure (specified by bypass steam)

All cases:

Tank pressure = P8
Amount of extraction steam given from outside
Amount of bypass steam from the energy balance

Previously, both mode FSPEC=2 and FSPEC=3 were called “floating pressure“. However, the pressure is taken over from the extraction line (Pin 3) only at FSPEC=2, while at FSPEC=3 it is variable indeed but is calculated by the component itself. Therefore a new mode FSPEC=7 has now been implemented; it has the following properties:

The tank pressure (and thus also the pressure of the feed water outlet on Line 2) results from the extraction pressure of Pin 3 in all load cases.

The heating is effected – insofar as it is possible – by the heating water at Pin 7. If this is not possible (no line connected or temperature too low) or insufficient (after the heating water mass flow has reached its maximum value of M7MAX), heating steam from Pin 3 is used for the (remaining) heating.

FSPEC=7: Sliding pressure

All cases:

The tank pressure (and thus also the pressure of the feed water outlet on line 2) results in all load cases from the tap pressure from port 3
(Sliding pressure)
The heating takes place - as far as possible - by the heating water at connection 7. If this is not possible (no pipe connected or temperature too low) or not sufficient (after the heating water mass flow has reached its maximum value of M7MAX), the ( remaining) heating steam from port 3 is used.

Physics Used

All cases
	if FPT=1, then { TN = f'(PN) TMIN = f'(PMIN) TMAX = f'(PMAX) } IPA= 0

Operating condition 1

Preheating with extraction steam (Line 3)

OR additional heating steam (line 6)

P2=PN; (1)

if GLOBAL = Off-design, then
{
    if P2 < PMIN, then
            {
            P2     = PMIN                              (1)
            IPAD = 0
            }

    if H3 < H2, then
            {
            P2     = PMIN                              (1)
            IPAD = 1
            }
}

P1 = P2                                                 ( 3)
P4 = P2                                                 (4)
P5 = P2                                                 (5)
P7 = P2                                                (16)
P8 = P3                                                 (6)

T2 = f'(P2)
T5 = T2
H2 = f' (P2)                                             (7)
H5 = f''(P2)                                             (8)
H8 = H3                                                  (9)
M5 = M5                                                 (13)
M8 = 0                                                    (15)

M7 = 0                                                  (14)

if IPAD = 0 , then
   {
   M3 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7)/(H3-H2)                         (12)
   M6   = 0                                                                                                                       (11)
   }
   else
  {
M6 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7)/(H7-H2)                         (12)
M3 = 0                                                                                                                         (11)
}
  M1 + M3 + M4 + M6 + M7 = M2 + M5 + M8                                                               (10)

Operating condition 2

Preheating with extraction steam (line 3)

at pure sliding pressure operation

P2 = P3                                                 (1)
P1 = P2                                                 (3)
P4 = P2                                                 (4)
P5 = P2                                                 (5)
P7 = P2                                                 (16)
P8 = P3                                                 (6)

T2 = f'(P2)
T5 = T2
H2 = f'(P2)                                               (7)
H5 = f''(P2)                                              (8)
H8 = H3                                                  (9)
M5 = M5                                                (13)

M6 = 0                                                   (11)
M7 = 0                                                   (14)
M8 = 0                                                   (15)

M3 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7)/(H3-H2)         (12)

M1 + M3 + M4 + M6 + M7 = M2 + M5 + M8 (10)

Operating condition 3

Preheating with heating water (line 7)

AND additional heating steam (line 6) and sliding pressure

if GLOBAL = design, then
         {
         P2   = PN                                       (1)
         KFall = 2
         }
else
         {
         HMIN = f'(PMIN)
         DH2MIN = (M1*H1+M4*H4-M5*H5)/(M1+M4-M5)
         DH2MAX=(M1*H1+M4*H4-M5*H5+M7MAX*H7) /(M1+M4M5+M7MAX)

         if DH2MAX < H'(PMIN) then
         {
            P2 = PMIN                                         (1)
            KFall = 1
         }

         if DH2MIN < H'(PMIN) then
         {
            P2 = PMAX                                      (1)
            KFall = 2
         }

         if DH2MIN >= H'(PMIN) then
         {
            HX2 = (M1*H1+M4*H4-M5*H5)/(M1+M4-M5)
            P2 = f' (HX2)                                    (1)
            KFall = 3
        }

}
P1 = P2                                                 (3)
P4 = P2                                                 (4)
P5 = P2                                                 (5)
P7 = P2                                                (16)
P8 = P3                                                 (6)

T2 = f'(P2)
T5 = T2
H2 = f' (P2)                                              (7)
H5 = f''(P2)                                              (8)
H8 = H3                                                  (9)
M3 = 0                                                   (11)
M5 = M5                                                (13)

M8 = 0                                                   (15)

if H7>H2, then
    {
    M7MAX=0
    }

if Kcase = 1, then
    {
    M7   = M7MAX                                    (14)
    M6 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7)/(H6-H2)   (12)
     }

if Kcase = 2, then
    {
    M7 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4))/(H7-H2)                                  (14)
    if M7>M7MAX, then {M7=M7MAX}
    M6   = 0                                                                                                              (11)
    }

if Kcase = 3 then
    {
    M7 = 0                                                (14)
    M6 = 0                                                (11)
    }

M1 + M3 + M4 + M6 + M7 = M2 + M5 + M8 (10

Operating condition 4

Preheating with heating steam (line 3)

and additional heating steam (line 6)

if GLOBAL = design, then
{
P2 = PN (1)
Kcase = 0
}

else
{

HMIN = f' (PMIN)
HMAX = f' (PMAX)
M2 = M1+M3+M4-M5
HX2 = (M1*H1+M3*H3+M4*H4-M5*H5)/M2

if HX2 < HMIN then
      {
      P2 = PMIN                                                    (1)
      Kcase = 1
      }

   if HX2 > HMAX then
       {
       P2 = PMAX                                                  (1)
       Kcase = 2
       }
    if HMIN<=HX2 <= HMAX, then
        {
        P2 = f' (HX2)                                               (1)
        Kcase = 3
        }

}

P3   = P2                                                (3)
P1   = P2                                                (2)
P4   = P2                                                (4)
P5   = P2                                                (5)
P7   = P2                                                (16)
P8   = P3                                                (6)

T2 = f'(P2)
T5 = T2
H2 = f' (P2)                                             (7)
H5 = f''(P2)                                             (8)
H8 = H3                                                  (9)
M5 = M5                                                 (13)
M7 = 0                                                    (14)

if Kcase = 0, then
         {
         if H3>H2, then
            {
            M3 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7)/(H3-H2)
           }
        else
        {
         M3 = 0                                              (12)
        }
         M6 = 0                                              (11)
         }

if Kcase = 1, then
         {
         if H6>H2, then
            {
            M6 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7) +M3*(H2-H3)/(H6-H2)
            }
         else
           {
          M6 = 0
           }
          M8 = 0

}

if Kcase = 2, then
{

if H3>H2, then
{

M33 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4+M7*(H2-H7)/(H3-H2)
}

         else
         {
           M33 = 0
         }
         M6 = 0
         M8 = M3-M33                                        (15)
         }

if Kcase = 3, then

        {
         M6 = 0                                                   (11)
         M8 = 0                                                   (15)

}

M1 + M3 + M4 + M6 + M7 = M2 + M5 + M8 (10)

Operating condition 5

Preheating with heating steam (line 3)

and/or additional heating steam (line 6) at fixed pressure

if GLOBAL = Design, then
{
P2   = PN                                          (1)
Kcase = 1
}
else
  {
M2 = M1+M3+M4-M5
HX2 = (M1*H1+M3*H3+M4*H4-M5*H5) / M2
  if HX2 < H'(PN) then { Kcase = 1 }
  if HX2 > H'(PN) then { Kcase = 2 }
  if HX2 = H'(PN) then { Kcase = 3 }
}

P3   = P2                                               (3)
P1   = P2                                               (2)
P4   = P2                                               (4)
P5   = P2                                               (5)
P7   = P2                                               (16)
P8   = P3                                               (6)
T2 = f'(P2)
T5 = T2
H2 = f' (P2)                                             (7)
H5 = f''(P2)                                             (8)
H8 = H3                                                  (9)
M5 = M5                                                 (13)
M7 = 0                                                    (14)

if Kcase = 1, then
     {
     if H6>H2, then
     {
     M6 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7*(H2-H7)+M3*(H2-H3)/(H6-H2)   }    (11)
     else
     {
     M6 = 0 }                                     (11)
     M8 = 0                                       (15)
     }

if Kcase = 2, then
     {
     if H3>H2, then
     {
     M33 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4+M7*(H2-H7)/(H3-H2) }
     else
     {
     M33 = 0
      }
     M6 = 0                                        (11)
     M8 = M3-M33                            (15)
     }

if Kcase = 3, then
    {
    M6 = 0                                        (11)
    M8 = 0                                        (15)
     }

M1 + M3 + M4 + M6 + M7 = M2 + M5 + M8      (10)

Operating condition 6

preheating with heating (line 3) steam and/or additional heating at specified sliding pressure of the bypass steam (line 8)

P2   = P8                                                (1)
P3   = P2                                               (3)
P1   = P2                                               (2)
P4   = P2                                               (4)
P5   = P2                                               (5)
P7   = P2                                               (16)

T2 = f'(P2)
T5 = T2
H2 = f' (P2)                                             (7)
H5 = f''(P2)                                              (8)
H8 = H3                                                  (9)
M5 = M5                                                (13)
M7 = 0                                                   (14)

if H3>H2, then
     {
     M33 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4+M7*(H2-H7)/(H3-H2) }
else
    {
    M33 = 0
    }
M6 = 0                                                 (11)
M8 = M3-M33                                       (15)

M1 + M3 + M4 + M6 + M7 = M2 + M5 + M8 (10)

Operating condition 7
Preheating with heating water (line 4) / heating steam (line 3) - sliding pressure

M6 = 0                                                   (11)
M7 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4))/(H7-H2)                  (14)
    if M7>M7MAX, then
    {
    M7=M7MAX
    }

M6 = 0 (11)

M8 = 0 (15)

M3 = (M5*(H5-H2)+M1*(H2-H1)+M4*(H2-H4)+M7 *(H2-H7)/(H3-H2) (12)

M1+M3+M4+M6+M7 = M2+ M5+M8 (10)

Component Displays

Display Option 1

Example

Click here >> Component 63 Demo << to load an example.

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