# Evaporator Excel

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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

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

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

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

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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

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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

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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

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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

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

2195983.211010x42873.0 176955.431

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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

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NDENSER

50 m2

2500 W/m2o

C

10.639 kg/s

25oC

79.2oC

74.5oC

79.1oC

0.452 atm

ter

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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

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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.

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