che lab evaporator

7/31/2019 Che Lab Evaporator

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EVAPORATOR

Titilayo Adeyemi BeckomPatner: Group 3

Abstract:

The objectives of this experiment include observation of the boiling action in the evaporator and

the determination of capacity and economy as they are affected by operating pressure.

Introduction:

The experiment is the large glass evaporator. Water is evaporated in a long tube surrounded by asteam jacket. The boiling mixture of liquid and water vapor enters a spherical separator. The

vapor flows on to a condenser whilst the water portion drops into the center section of the

evaporator and is recirculated. A water-driven aspirator is used to evacuate the apparatus for

reduced pressure runs. Steam used for heating has its pressure controlled with a pressure

regulator (please do not change the set pressure). Water level in the evaporator is manuallycontrolled by monitoring its level in the central glass column. Open the ball valve for not more

than 5 seconds at a time to admit city water into the equipment and close it again

Experimental:

To set the operating pressure, first turn on the aspirator drive water valve. Adjust the position ofthree-way vacuum valve located on the evaporator top product accumulator section, and set the

desired vacuum with the vacuum regulator. Starting with the highest vacuum, at least 3 data

points including one for the atmospheric pressure is required to plot the graphs of efficiency,economy, and capacity versus pressure. Use a graduated cylinder and a stop watch to determine

the volumetric flow rate of vapor product and the heating steam. The collection time is decided

by the rate of the vapor condensed in the condenser, the lower the operating pressure, the higher

is the rate of the vapor condensed.At the completion of the experiment notify the instructor to shut off the system. Do not leave the

equipment before the shut off completed. Open and leave the evaporator drain valves on.

Sample Calculations:

Heating Steam Pressure vs. Feed Temperature Plot

Fahrenheit-Celsius Conversion

T=212 deg. FT(deg C)=(5/9)*(212-32)=100 deg C

Pressure Conversion from inHg gauge to KPa absolute

PG = -7.2 inHg


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PABS = PATM+PG = (29.9-7.2) inHg = 22.7inHg

Feed WaterTemp (F)

Feed WaterTemp (C)

Feed WaterTemp (K)

HeatingSteam

Pressure

(inHggauge)

Heating

Steam

Pressure(inHg abs)

Heating

Steam

Pressure(KPa abs)

212 100 373.15 0 29.9 101.253

199 92.77778 365.9278 -7.2 22.7 76.87101

192 88.88889 362.0389 -9.8 20.1 68.0664

184 84.44444 357.5944 -13.2 16.7 56.55268

Steam Capacity

0

20

40

60

80

100

120

355 360 365 370 375

P(KPa)

T (K)

Pressure vs. Temperature

Pressure vs.

Temperature

Poly. (Pressure vs.

Temperature)


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Steam Economy**For given steam condensate flow rate, conversion to kg/h is done in the same manner as for

vapor condensate results are in table above**

P= 76.8 KPa; T=92.8 C; capacity=0.187113927 kg/h; kg/h steam used =2.688183432 kg/h

m condensed vaporproduct/capacity (kg/h)

m heating steam (kg/h) Economy

0.187113927 2.681399467 0.06978219

1.079047125 2.688183432 0.40140383

1.226491742 4.826197076 0.25413213

1.371840491 2.978140449 0.4606366

**Highlighted Data was removed from plot**

Efficiency

0

0.05

0.1

0.15

0.2

0.25

0.30.35

0.4

0.45

0.5

0 10 20 30 40 50

Economy

Vacuum (KPa)

Economy

Economy

Poly. (Economy)


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=Enthalpy of vapor= 2663KJ/kg =Enthalpy of saturated vapor = 2676KJ/kg = Temperature of saturated liquid =373.15 K=Temperature of liquid=365.9K

= Enthalpy steam = 2703 KJ/kg

=Enthalpy condensed steam = 495.2 KJ/kg =

Heat Absorbed by Process Fluid

Values in the numerator obtained from steam table

Heat Supplied by Steam (@12 psig)12 psig

620.6 mmHg gauge29.9 inHg 759.5 mmHg atmosphere

PABS= (620.6+759.5) mmHg gauge

= 1380.1 mmHg abs

Steam Table Interpolation yields Hs = 2702.666 KJ/kg; Hcs=493.8 KJ/kg

HV(KJ/

kg)

HVSat

(KJ/

kg)

TF (K) TFsat(K)

Cp(KJ/

kg*

K)

Hs(KJ/kg

)

Hcs(KJ/k

g)

Numerator(KJ)

Denominator(KJ)

Efficienc

y

2676 2676 373.15 373.15 4.18 2702.6

66

493.8 0 5922.852115

0.000000


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2663 2676 365.92777

78

373.15 4.18 2702.6

66

493.8 18.54762113 5937.836985

0.312363

2658 2676 362.0388889

373.15 4.18 2702.666

493.8 34.88687621 10660.42263

0.327256

2650 2676 357.59444

44

373.15 4.18 2702.6

66

493.8 53.53226449 6578.313181

0.813769

Highlighted Data was removed from plot

Efficiency plotted is in fraction form

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0 20 40 60

Efficiency

Vacuum (KPa)

Efficiency

Efficiency

Poly. (Efficiency)

che lab evaporator

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