PART-SG and PART-RKM Should Be Answered Separate Answerbooks
PART-SG and PART-RKM Should Be Answered Separate Answerbooks
PART-SG and PART-RKM Should Be Answered Separate Answerbooks
Note: This is a No Book - No Notes Examination. Answer all questions. All parts of a
question must be answered together. Please do not raise any queries with the invigilators.
In case of insufficient information, if any, make and mention suitable assumptions and
proceed further.
BEGIN PART-SG
Question-1 [10]
A double pipe heat exchanger made up of a 3" steel outer pipe and 2" steel core pipe is to
be designed for the following service:
Assumptions:
Thermal conductivity of steel: 60 W/(m.K)
Friction factor is 30% greater than that predicted by the Blasius formula
Entrance and exit pressure losses are ignored
All fluid properties can be calculated at mean temperatures
The liquid viscosities are not temperature sensitive in the operating range
Question-2 [10]
For the liquid flowing on the shell side as detailed below, using the Kem method,
determine,
Flow area at centre line
Equivalent diameter
Shell side Reynolds No.
Total shell side pressure drop
Question-3 [10]
No Question Marks
1. What is the function of sealing strips in a shell and tube heat exchanger? 1
2. In horizontal shell side boiling in a shell and tube exchanger, what is the 1
function of baffles?
3. What is the minimum spacing allowed for baffles in TEMA standards? 1
4. Why are 'U' tubes not preferred for cooling water service? 1
5. When would you use a 90° square pitch for tubes? 1
6. What is the default pitch for a triangular layout? 1
7. A heat exchanger is designed to operate with saturated steam at 10 bara 1
(Saturation temperature, 179.88°C). Accidentally 10 bara superheated
steam at a temperature of 300 ° C is piped to the exchanger. What can
you say about the performance of the exchanger?
2
8. A horizontal thermosyphon reboiler is designed for a setting depth of 1
3000 mm. If in operation the setting depth increases to 4000 mm, with
the other parameters being the same, what can you say about the
performance of the exchanger?
Note: Setting depth is the elevation difference between the bottom of the
shell and the level of liouid in the sump.
9. An exchanger is designed with a 30 ° triangular pitch. By mistake the 1
exchanger is fabricated with a 60 ° triangular layout. What can you say
of the performance of the exchanger?
10 On the shell side, as compared to the Kem method, does the Bell 1
Delaware method predict a higher or lower pressure drop? Give reasons.
END OF PART-SG
BEGINPART-RKM
Question-1 [10]
(b) It is desired to determine the most advantageous method for depreciation for income-
tax purposes of a chemical plant investment. The three methods that are being
considered are the Straignt Line Method (SLM), Double Declining Balance Method
(DDBM), and the Sum-of-the-year's-digits Method (SYDM). It may be assumed that
the economic life of the plant is 5 years, and that the company's earning rate is
constant at 10%. Make your recommendation on the most advantageous method if it
is assumed that the salvage value is negligible at the end of economic life. What
percentage of initial investment remains unrecovered in the case of DDBM?
Question-2 [10]
(a) For the process design of a distillation column, setting column pressure is one of the
most important steps in design. In this connection, state whether the following effects
are True or False. In each case, provide very precise supporting arguments to get
credit. No credit will be given for correct answers if proper supporting arguments
are missing.
3
Raising column pressure,
1. Lowers relative volatility and increases separation difficulty. This raises reflux
and stage requirements and reboiler and condenser duties.
2. Reduces column bottom temperature. This decreases chemical degradation,
increases
polymerization, and fouling.
3. For super-atmospheric separations, it increases leakage, and if process materials
are inflammable or toxic, also the hazard potential.
4. For a given heating medium in the reboiler, it increases the reboiler area
requirement.
5. For a given cooling medium in condenser, it reduces the condenser area
requirement.
reduce
6. Increases the size Jr vapor pipes and valves.
reduces
7. Below 1 atm, increases air leakage into the system.
8. Increases vapor density and therefore vapor handling capacity.
9. Increases the column diameter and capital costs of columns.
10. Below 1 atm, reduces the costs of creating and maintaining a vacuum.
(b) For design of a multi-component distillation column, state the heuristics that relate:
2. Actual stages with minimum stages optimum number of trays is near 2 the minimum value Nm (Found with Fenske Underwod eq.
3. Pressure drop with stages Pressure drop is 0.1 in per stage
4. Top temperature with cooling medium
(c) For process design of distillation columns, how does one decide whether a partial
condenser, or a total condenser, will be required? Give examples.
The composition of the distillate is same as the vapor leaving the top tray