Categories: 6th Semester

1

Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY

BE – SEMESTER ?VI (NEW) – EXAMINATION ? SUMMER 2018

Subject Code:2160405 Date:01/05/2018

Subject Name:Principles of Process Engineering-III

Time:10:30 AM to 01:00 PM Total Marks: 70

Instructions:

1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

MARKS

Q.1 (a) State assumptions of McCabe Thiele method to calculate number of stages. 03

(b) i. What is the effect of temperature and pressure on adsorption equillibria for gas-

solid adsorption?

ii. Mention Frieundlich- Adsorption isotherm.

04

(c) Define:

i. Bound Moisture

ii. Unbound Moisture

iii. Free Moisture

iv. Supersaturation

v. Nucleation

07

Q.2 (a) Explain Adsorption Hysteresis. 03

(b) Explain Clausius- Clapeyron Equation and state its usefulness. 04

(c) Explain the following terms for air- water system:

i. Absolute Humidty

ii. Dew point

iii. Dry bulb temperature

iv. Wet bulb

v. Humid volume

vi. Humid heat

vii. Saturated and unsaturated mixture.

07

OR

(c) Explain multi- stage cross current adsorption operation with neat sketch and

also determine the equation for intermediate concentration of liquid stream for

minimum total adsorbent in case of 2- stage cross- current operation.

07

Q.3 (a) Compare Azeotropic and Extractive distillation. 03

(b) Outline the McCabe-Thiele design method for obtaining number of theoretical

trays by graphical method.

04

(c) A feed solution contains 100 moles of Benzene- Toluene mixture having 70 mol %

benzene. One third of feed is vaporized. The total pressure is 1 atmosphere. Calculate

the distillate and bottom composition by using flash distillation. Average relative

volatility of solution mixture is 2.5.

07

OR

Q.3 (a) What is reflux ratio? Write a note on different types of reflux ratio used in

distillation?

03

(b) Define following: (1)Distillation (2) Adsorption (3) Ion Exchange (4) Drying 04 1

Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY

BE – SEMESTER ?VI (NEW) – EXAMINATION ? SUMMER 2018

Subject Code:2160405 Date:01/05/2018

Subject Name:Principles of Process Engineering-III

Time:10:30 AM to 01:00 PM Total Marks: 70

Instructions:

1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

MARKS

Q.1 (a) State assumptions of McCabe Thiele method to calculate number of stages. 03

(b) i. What is the effect of temperature and pressure on adsorption equillibria for gas-

solid adsorption?

ii. Mention Frieundlich- Adsorption isotherm.

04

(c) Define:

i. Bound Moisture

ii. Unbound Moisture

iii. Free Moisture

iv. Supersaturation

v. Nucleation

07

Q.2 (a) Explain Adsorption Hysteresis. 03

(b) Explain Clausius- Clapeyron Equation and state its usefulness. 04

(c) Explain the following terms for air- water system:

i. Absolute Humidty

ii. Dew point

iii. Dry bulb temperature

iv. Wet bulb

v. Humid volume

vi. Humid heat

vii. Saturated and unsaturated mixture.

07

OR

(c) Explain multi- stage cross current adsorption operation with neat sketch and

also determine the equation for intermediate concentration of liquid stream for

minimum total adsorbent in case of 2- stage cross- current operation.

07

Q.3 (a) Compare Azeotropic and Extractive distillation. 03

(b) Outline the McCabe-Thiele design method for obtaining number of theoretical

trays by graphical method.

04

(c) A feed solution contains 100 moles of Benzene- Toluene mixture having 70 mol %

benzene. One third of feed is vaporized. The total pressure is 1 atmosphere. Calculate

the distillate and bottom composition by using flash distillation. Average relative

volatility of solution mixture is 2.5.

07

OR

Q.3 (a) What is reflux ratio? Write a note on different types of reflux ratio used in

distillation?

03

(b) Define following: (1)Distillation (2) Adsorption (3) Ion Exchange (4) Drying 04

2

(c)The temperature of air in a room is 40.2

o

C and the total pressure is 101.325 kPa absolute.

The air contains water vapor with a partial pressure of 3.74 kPa. The vapor pressure of

water at this temperature is 7.415 kPa. Calculate the humidity, the saturation humidity,

percentage humidity and the percentage relative humidity.

07

Q.4 (a) Explain Tray Dryers in brief. 03

(b) Explain rate of drying curve with a diagram. 04

(c) A batch of solid is to be dried from initial moisture of 25% to final moisture of

6% under the conditions of constant and falling rate of drying. The initial weight

of wet solid is 160 kg, and the drying surface is 1 m

2

/40 kg dry weight. Determine

the time of drying. Note: The equilibrium moisture to be considered is: x*= 0.05

kg moisture/ kg dry solid. Table 1:

x (kg

moisture/

kg dry

solid.)0.333 0.20 0.18 0.16 0.14 0.12 0.10 0.09 0.08 0.07 0.064

N *10

3

0.300 0.300 0.266 0.239 0.208 0.180 0.150 0.097 0.070 0.043 0.025

1/N * 10

–

3

3.33 3.33 3.76 4.18 4.80 5.55 6.67 10.3 14.3 23.3 40.0

07

OR

Q.4 (a) Explain Freeze Drying in brief. 03

(b) Explain Rotary Dryers. 04

(c) Derive the relation to determine the time needed for constant & falling rate period of

the batch drying operations.

07

Q.5 (a) Compare adiabetic saturation theory and wet bulb temperature theory. 03

(b) State various types of cooling towers and their arrangements. 04

(c) Explain differential distillation and derive Rayleigh equation.

07

OR

Q.5 (a) Explain the stages of Crystallization in brief. 03

(b) Explain Swenson- Walker Crystallizer in brief. 04

(c) Derive Fenske?s equation for the minimum number of theoretical stages. 07

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