Evaporator Excel

  • View
    230

  • Download
    3

Embed Size (px)

Text of Evaporator Excel

  • 8/11/2019 Evaporator Excel

    1/44

    Simulation of a multiple-effect evaporator

    Instructions1. a. On the Toolsmenu, click Options, then click the Calculationtab and tick on t

    2. For a forward feed 2-effect evaporator

    In the spreadsheet "2-Effect"

    a. Insert parameter values in the yellow cells

    b. Turn the "SWITCH" ON (set the value in the cell B9 (red cell) equal to 1)

    c. Iterate (by pressing F9) until "FINISH" or "ALARM" signal is shown in the contr

    d. If a signal to "REDUCE Tsor mwin" is shown in the control panel, turn the SWI

    in cells B28 or B29 respectively and start again from 2b

    e. If a signal to "INCREASE Tsor mwin" is shown in the control panel, turn the S

    in cells B28 or B29 respectively and start again from 2b f. When "FINISH" is shown in the control panel, read the results in the green cell

    g. If a solution can not be reached under any combination of Ts and mwinvalues,

    and repeat steps 2a to 2f

    h. To recalculate for different parameter values turn the "SWITCH" OFF (set the

    3. For a forward-feed 4-effect evaporator

    In the spreadsheet "4-Effect Forward"

    a. Insert parameter values in the yellow cells

    b. Turn the "SWITCH" ON (set the value in the cell B9 (red cell) equal to 1)

    c. Iterate (by pressing F9) until "FINISH" or "ALARM" signal is shown in the contr

    d. If a signal to "REDUCE Tsor mwin" is shown in the control panel, turn the SWI

    in the cells B28 or B29 respectively and start again from 2b

    e. If a signal to "INCREASE Tsor mwin" is shown in the control panel, turn the S

    in the cells B28 or B29 respectively and start again from 2b

    f. When "FINISH" is shown in the control panel, read the results in the green cell

    g. If a solution can not be reached under any combination of Tsand mwinvalues,

    and/or Q19 and repeat steps 2a to 2f

    h. To recalculate for different parameter values turn the "SWITCH" OFF (set the

    4. For a backward-feed 4-effect evaporator

    In the spreadsheet "4-Effect Backward"

    a. Insert parameter values in the yellow cells

    b. Turn the "SWITCH" ON (set the value in the cell B9 (red cell) equal to 1)

    c. Iterate (by pressing F9) until "FINISH" or "ALARM" signal is shown in the contr

    d. If a signal to "REDUCE Tsor mwin" is shown in the control panel, turn the SWI

  • 8/11/2019 Evaporator Excel

    2/44

    in the cells B28 or B29 respectively and start again from 2b

    e. If a signal to "INCREASE Tsor mwin" is shown in the control panel, turn the S

    in the cells B28 or B29 respectively and start again from 2b

    f. When "FINISH" is shown in the control panel, read the results in the green cell

    g. If a solution can not be reached under any combination of Tsand mwinvalues,

    and/or Q19 and repeat steps 2a to 2f

    h. To recalculate for different parameter values turn the "SWITCH" OFF (set the

  • 8/11/2019 Evaporator Excel

    3/44

  • 8/11/2019 Evaporator Excel

    4/44

    heIterationbox. On Maximum iterationsbox write 1000

    l panel

    CH OFF, reduce the value of either Tsor mwin

    ITCH OFF, increase the value of either Tsor mwin

    (B34-B38)

    change the heat transfer area in the cells H19 and/or J19 and/or M19

    alue in the cell B9 equal to 0) and repeat steps 2a to 2f

    l panel

    CH OFF, reduce the value of either Tsor mwin

    ITCH OFF, increase the value of either Tsor mwin

    (B33-B37)

    change the heat transfer area in the cells H19 and/or J19 and/or L19 and/or N19

    alue in the cell B9 equal to 0) and repeat steps 2a to 2f

    l panel

    CH OFF, reduce the value of either Tsor mwin

  • 8/11/2019 Evaporator Excel

    5/44

    ITCH OFF, increase the value of either Tsor mwin

    (B33-B37)

    change the heat transfer area in the cells H19 and/or J19 and/or L19 and/or N19

    alue in the cell B9 equal to 0) and repeat steps 2a to 2f

  • 8/11/2019 Evaporator Excel

    6/44

  • 8/11/2019 Evaporator Excel

    7/44

  • 8/11/2019 Evaporator Excel

    8/44

  • 8/11/2019 Evaporator Excel

    9/44

  • 8/11/2019 Evaporator Excel

    10/44

  • 8/11/2019 Evaporator Excel

    11/44

  • 8/11/2019 Evaporator Excel

    12/44

  • 8/11/2019 Evaporator Excel

    13/44

    The following assumptions are used

    1) The pressure drop in the vapour lines is neglected

    2) The effect of superheating on the vapour enthalpy due to the BPE is neglected

    3) The heat losses to the environment are taken into account. If cells B23 or B24 for4) The condensate from each effect exits at the condensation temperature

    5) The condenser is assumed to be a surface condenser

    The following empirical relationships are used in the calculations

    a) Heat capacity of liquid foods (equation of Dickerson), J/kgoC

    where xwis the mass fraction of water content

    b) Boiling Point Elevation,oC

    where xsis the mass fraction of solids content

    c) Heat capacity of liquid water, J/kgoC

    where T is temperature in

    o

    C

    d) Enthalpy of saturated steam and vapour, kJ/kg

    where T is temperature inoC

    e) Latent heat of vaporization of water, kJ/kg

    where T is temperature ino

    C

    f) Vapour pressure of liquid water, atm (Ref. 15)

    where with T in Kelvin

    wp x25081672c

    2

    p T015.0T34.14211c

    2

    v T0017.0T919.12501H

    16.273

    10110x50474.1log02808.5)1(79586.10plog

    29692.84

    w

    2T0018.0T265.22501

    3

    s

    2

    ss x2.21x8.8x7.2BPE

  • 8/11/2019 Evaporator Excel

    14/44

  • 8/11/2019 Evaporator Excel

    15/44

    los and AoLare set equal to 0, the heat losses are neglected

    2195983.211010x42873.0 176955.431

  • 8/11/2019 Evaporator Excel

    16/44

  • 8/11/2019 Evaporator Excel

    17/44

  • 8/11/2019 Evaporator Excel

    18/44

  • 8/11/2019 Evaporator Excel

    19/44

  • 8/11/2019 Evaporator Excel

    20/44

  • 8/11/2019 Evaporator Excel

    21/44

  • 8/11/2019 Evaporator Excel

    22/44

  • 8/11/2019 Evaporator Excel

    23/44

    Parameters 1st EFFECT 2nd EFFECT C

    Heat transfer area (m2), A 80 80 Heat transf. area

    Overall heat transfer coef. (W/m2o

    C), U 1800 1000 Overal heat transf. coef.

    Liquid flow rate at the inlet (kg/s), mi 2.778 1.878 Cooling water flow rate in

    Solids content at the inlet, xi 0.1 0.148 Cooling water temper. in

    Liquid temperature at the inlet (oC), Ti 70 105.3 Water vapour temper. in

    Boiling temperature (oC), Tb 105.3 79.8 Cooling water temp. out

    Saturation temperature (oC), Tv 105.0 79.2 Condensation temperat.

    Saturation pressure (atm), P 1.194 0.453 Water vapour pressure

    Temperature drop (oC), 16.7 25.2

    Boiling Point Elevation (oC), BPE 0.3 0.6

    Heat capacity of liquid at inlet (J/kgoC), cpi 3929 3809

    Heat capacity of liquid at outlet(J/kgoC), cpo 3809 3427

    Heat losses (W), qL 0 0

    Evaporation rate (kg/s), mv 0.899 0.953

    Liquid flow rate at the outlet (kg/s), mo 1.878 0.925

    Solids content at the outlet, xo 0.148 0.300

    Heating steam/vapour flow rate (kg /s), ms 1.094 0.899

    Heating steam/vapour temperature (oC), Ts 122 105.0

    steam/vapour/condensate cooling waliquid food

    mf , xf , Tf

    ms,Ts

    mv1,Tv1

    mc1,Tc1 mc2,Tc2

    mWin

    Twinm

    WoutTwout

    mc,Tc

    mi2, xi2, Ti2

    mp, xp,Tp

    mo1, xo1,To1

    Tb1 Tb2

    mv2,Tv2

  • 8/11/2019 Evaporator Excel

    24/44

  • 8/11/2019 Evaporator Excel

    25/44

    NDENSER

    50 m2

    2500 W/m2o

    C

    10.639 kg/s

    25oC

    79.2oC

    74.5oC

    79.1oC

    0.452 atm

    ter

  • 8/11/2019 Evaporator Excel

    26/44

  • 8/11/2019 Evaporator Excel

    27/44

  • 8/11/2019 Evaporator Excel

    28/44

  • 8/11/2019 Evaporator Excel

    29/44

    Forward-Feed 4-Effect Evaporator

    Control panel

    SWITCH= 1

    FINISHED

    0.0000

    Input data

    Feed flow rate, mf = 20000 kg/h

    Feed solids content, xf = 9%

    Desired product solids content, Xspec = 48%

    Feed temperature, Tf = 60oC

    Temperature of the environment, Te= 20oC

    Overall Heat transfer coeffic. for heat losses, Ulos= 0 W/moC

    Outside Area of each effect of the evaporator, AoL= 50 m

    Cooling water temper. at the inlet of the cond., Twin= 25oC

    Control variables

    Steam temperature, Ts = 75oC

    Mass flow rate of cooling water in the conden.,mWin = 530000 kg/h

    Results

    Concentrated product flow rate, mp= 3756 kg/h

    Solids content at the outlet, xp= 47.9%

    Steam consumption, ms= 4244 kg/h

    Steam economy 3.8 kg/kg

    Cooling water flow rate, mWin= 530000 kg/h

  • 8/11/2019 Evaporator Excel

    30/44

  • 8/11/2019 Evaporator Excel

    31/44

    1st EFFECT 2nd EFFECT 3rd EFFECT 4th EFFECT

    Heat transfer area (m2), A 270 270 270 270

    Overall heat transfer coef. (W/m2o

    C), U 2200 1800 1300 506

    Liquid flow rate at the inlet (kg/s), mi 5.556 4.481 3.372 2.230

    Solids content at the inlet, xi 0.09 0.112 0.148 0.224

    Liquid temperature at the inlet (oC), Ti 60 70.4 65.0 57.3

    Boiling temperature (oC), Tb 70.4 65.0 57.3 37.1

    Saturation temperature (oC), Tv 70.2 64.7 56.9 35.7

    Saturation pressure (atm), P 0.310 0.244 0.170 0.058Temperature drop (

    oC), 4.

Search related