Evaporator Excel
Transcript of 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
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
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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), 4.6 5.2 7.4 19.8
Boiling Point Elevation (oC), BPE 0.2 0.3 0.4 1.6
Heat capacity of liquid at inlet (J/kgoC), cpi 3954 3900 3808 3618
Heat capacity of liquid at outlet(J/kgoC), cpo 3900 3808 3618 2979
Heat losses (W), qL 0 0 0 0
Evaporation rate (kg/s), mv 1.075 1.109 1.142 1.188
Liquid flow rate at the outlet (kg/s), mo 4.481 3.372 2.230 1.042
Solids content at the outlet, xo 0.112 0.148 0.224 0.479
Heating steam/vapour flow rate (kg /s), ms 1.179 1.075 1.109 1.142
Heating steam/vapour temperature (oC), Ts 75 70.2 64.7 56.9
mi2, xi2, Ti2
mc2,Tc2
mf , xf , Tf
ms,Ts
mv1,Tv1
mc1,Tc1 mc4,Tc4
mv3,Tv3
mc3,Tc3 Tb4
mo2, xo2,To2
mi3, xi3, Ti3 mi4, xi4, Ti4
mp, xp,T
mo3, xo3,To3mo1, xo1,To1
mv2,Tv2
Tb3Tb1 Tb2
steam/vapour/condensateliquid food
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CONDENSER
Heat transf. area 150 m2
Overal heat transf. coef. 2500 W/m2o
C
Cooling water flow rate in 147.2 kg/s
Cooling water temper. in 25oC
Water vapour temper. in 35.7oC
Cooling water temp. out 29.7oC
Condensation temperat. 35.7oC
Water vapour pressure 0.058 atm
mWinTwin
mWout
Twout
mc,Tc
p
cooling water
mv4,Tv4
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Backward-Feed 4-Effect Evaporator
Control panel
SWITCH= 1
FINISHED
0.000
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 = 220000 kg/h
Results
Concentrated product flow rate, mp= 3745 kg/h
Solids content at the outlet, xp= 48.1%
Steam consumption, ms= 4327 kg/h
Steam economy 3.8 kg/kg
Cooling water flow rate, mWin= 220000 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 1214 1400 1270 1044
Liquid flow rate at the inlet (kg/s), mi 2.202 3.312 4.350 5.556
Solids content at the inlet, xi 0.227 0.151 0.115 0.090
Liquid temperature at the inlet (oC), Ti 57.7 49.6 40.5 60.0
Boiling temperature (oC), Tb 66.5 57.7 49.6 40.5
Saturation temperature (oC), Tv 64.9 57.2 49.3 40.3
Saturation pressure (atm), P 0.246 0.173 0.118 0.074Temperature drop (
oC), 8.5 7.2 7.7 8.8
Boiling Point Elevation (oC), BPE 1.6 0.4 0.3 0.2
Heat capacity of liquid at inlet (J/kgoC), cpi 3611 3801 3892 3954
Heat capacity of liquid at outlet(J/kgoC), cpo 2974 3611 3801 3892
Heat losses (W), qL 0 0 0 0
Evaporation rate (kg/s), mv 1.162 1.110 1.037 1.206
Liquid flow rate at the outlet (kg/s), mo 1.040 2.202 3.312 4.350
Solids content at the outlet, xo 0.481 0.227 0.151 0.115
Heating steam/vapour flow rate (kg /s), ms 1.202 1.162 1.110 1.037
Heating steam/vapour temperature (oC), Ts 75 64.9 57.2 49.3
mi2, xi2, Ti2
mc2,Tc2
mf , xf , T
ms,Ts
mc1,Tc1
mv1,Tv1
mc4,Tc4mc3,Tc3
mv3,Tv3
Tb4
mo2, xo2,To2
mi3, xi3, Ti3
mo4, xo4, Tmp, xp,Tp
mo3, xo3,To3
mi1, xi1,Ti1
Tb3Tb1 Tb2
steam/vapour/condensateliquid food
mv2,Tv2
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CONDENSER
Heat transf. area 150 m2
Overal heat transf. coef. 2500 W/m2o
C
Cooling water flow rate in 61.1 kg/s
Cooling water temper. in 25oC
Water vapour temper. in 40.3oC
Cooling water temp. out 36.4oC
Condensation temperat. 40.2oC
Water vapour pressure 0.074 atm
f
mWinTwin
mWout
Twout
mc,Tc
o4
cooling water
mv4,Tv4
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