University Of Pune Question Paper,MECHANICAL OPERATIONS,2011 Question Paper,S.E. (Chemical) (Semester – II)

University Of Pune Question Paper
S.E. (Chemical) (Semester – II) Examination, 2011
MECHANICAL OPERATIONS
(2003 Course)
Time : 3 Hours Total Marks : 100
 Instructions : 1) Answer three questions from Section I and three
questions from Section II.
2) Answers to the two Sections should be written in
separate books.
3) Neat diagrams must be drawn wherever necessary.
4) Use of logarithmic tables, slide rule, Mollier charts,
electronic pocket calculator and steam tables is
allowed.
5) Assume suitable data, if necessary.
SECTION – I
1. a) Differentiate differential and cumulative analysis with proper examples. 6
b) The screen analysis shown applies to a sample crushed quartz. Estimate :
i) Average particle size of the product
ii) Specific surface area for the product using both differential and cumulative
analysis :
Data : Density of sample = 2.65 gm/CC, a = 2, b = 3.5. 10
Mesh No.               4/6      6/8        8/10  10/14  20/28   28/35
Aperture size
(CMS)                 0.4013 0.2844 0.206 0.1409 0.0711 0.0503
Mass Fraction
retained on screen 0.0251 0.125 0.3207 0.257 0.0538 0.021
c) Explain the need of size reduction in process industries. 2
OR
2. a) Why the gyratory crushers are more widely used than jaw crushers ? 4
b) Differentiate crushing efficiency and mechanical efficiency. 4
c) In a certain blake jaw crusher it is necessary to apply a maximum force of
1000 Kgs. at a toggle point. The toggle block is 80 cms from the pivot point.
The angle between pitman and toggle is 85°, what will be the force on pitman ?
What is the force on particle at distance 35 cm from the pivot ? Derive the
expression that you have used. 10
3. a) Describe the working of belt conveyor with suitable sketches. List advantages
and disadvantages of belt conveyors and typical applications. 8
b) Describe with a sketch the working of a screw conveyor. List advantages and
disadvantages. 8
OR
4. Write short notes on :
a) Closed loop pneumatic conveying system.
b) Chain and flight conveyor.
c) Bucket elevator.
d) Apron conveyor. 16
5. a) Describe the types of mixers for pastes and plastic mass. 8
b) With the help of neat sketches distinguish the axial flow and radial flow impeller. 8
OR
6. a) A silty soil containing 14% moisture was mixed in a large muller mixer with
10 weight percent of a tracer consisting of dextrose and picric acid. After
4 min. of mixing 10 random samples were taken from the mixture and analysed
for tracer material. The measured concentrations in the same were, in weight
percent tracer 10.28, 9.20, 7.8, 11.03, 10, 11.51, 9.25, 9.65, 10.65, 10.77. Calculate
the mixing index Ip of the operation. 8
b) What is degree of mixing and rate of mixing in case of mixing of dry solids
and derive the expressions. 8
-3- [3962] – 340
SECTION – II
7. a) A plate and frame press filtering a slurry, gave a total of 25 m3
 of filterate in
30 minutes and 35m3
 in 60 minutes when filtration was stopped. Estimate the
washing time in minutes if 10m3
 of wash water are used. The resistance of the
cloth can be neglected and a constant pressure is used through-out. 10
b) Explain construction, working and applications of Rotary Drum vacuum
filter. 8
OR
8. a) Explain leaf filter and filter press in detail. 8
b) A constant pressure filtration tests gave data that can fit an expression :
9.3V 8.5
dV
dt = +
where t in seconds, V in liters. If the resistance of the filter medium is assumed
unaffected with pressure drop and the compressibility cofficient of the filter
cake is 0.3, what will be the time taken for the collection of 3.5 liters of filtrate
at a filtration pressure twice that used in the test ? 10
9. a) Explain the sink and float method and differential settling method in sorting
classifiers. 8
b) Explain principle, construction and working of the electrofloation plant. 8
OR
10. a) Describe aggregative and particulate fluidization. If fine catalyst particles are
fluidized in water then which type of fluidization would be observed ? 8
b) A tube of 0.05m2
 cross-sectional area is packed with spherical particles up to
a height of 0.25 m. The porosity of the bed is 0.35. It is desired to fluidize the
particles with water (ρ =1000 kg/m3
, 3 10− μ = Pa-sec). Calculate minimum
velocity of fluidization by Ergun’s equation.
Data : Diameter of particles = 0.01 m
Density of solid particles = 2600 kg/m3
. 8
11. a) Describe with neat sketches the operation of a patch centrifuge and continuous
centrifuge. 8
b) Describe with a neat sketch the sedimentation operation. Also sketch typical
commercial equipment. 8
OR
12. Write short notes :
a) Cyclone separator
b) Scrubbers
c) Fabric filter
d) Mineral Jig. 16
————

S.E. (Chemical) (Semester – II),University Of Pune Question Paper,2011 Question Paper,CHEMICAL ENGG. THERMODYNAMICS – I

University Of Pune Question Paper
S.E. (Chemical) (Semester – II) Examination, 2011
CHEMICAL ENGG. THERMODYNAMICS – I
(2003 Course)
Time : 3 Hours Max. Marks : 100
 Instructions : 1) Answer three questions from Section I and three questions
from Section II.
2) Answers to the two Sections should be written in separate
books.
3) Neat diagrams must be drawn wherever necessary.
4) Black figures to the right indicate full marks.
5) Use of logarithmic tables, slide rule, Mollier charts, electronic
pocket calculator and steam tables is allowed.
6) Assume suitable data, if necessary.
SECTION – I
1. a) State and explain first law of thermodynamics with its scope and limitations. 6
b) 1 kg of air is heated at constant pressure from an initial state of 300 K and 1 bar
untill its volume triples. Calculate W, Q, ΔH, ΔU for the process. Assume that
air obeys the relation PV/T = R = 83.14 cm3
/mol.k, Cp
 = 29 J/mol.k. 10
OR
2. a) Air at 1 bar and 298°C is compressed to 5 bar and 298 K by two mechanically
reversible processes.
a) Cooling at constant pressure followed by heating at constant volume.
b) Heating at constant volume followed by cooling at constant pressure
Calculate the heat and work requirements and ΔE and ΔH of the air for
each path. CV = 20.78 J/mol.k, CP = 29.10 J/mol.k for air PV/T = constant.
At 298 K and 1 bar the molar volume of air is 0.026 m3/mol. 16
3. a) Explain the P-T diagram for pure water showing clearly all the phase
regions. 8
b) State the importance of Van der Walls equation of state. Explain how this
equation was developed. 8
OR
[3962] – 339 -2-
4. a) Calculate the molar volume and compressibility factor for methanol vapor
at 500 k and 10 bar by using the following equations of state
i) Virial equation
ii) Redlich-Kwong equation
Virial coefficients are B = –2.19×104 m3/mol,
C = –1.73 × 10–8 m6/mol2,Tc = 512.6 k, Pc = 81 bar. Constants for
Radlich-Kwong equation
A = 21.7181 Nm4 k0.5/mol2, B = 4.5617 × 10–5 m3/mol. 10
b) Derive an equation for work done for the reversible adiabatic process. 6
5. Methanol is synthesized according to the following reaction.
CO(g) + 2H2
 (g) → CH3
OH (g)
The standard heats of formation at 298 K are – 110.125 KJ/mol for CO and –
200.660 KJ/mol for methanol. The specific heats (J/mol.k) are
CP
 (CH3
OH) = 19.382 + 101.564 × 10–3 T – 28.683 × 10–6 T2
CP (CO) = 28.068 + 4.631 × 10–3 T – 2.5773 × 10+4 T–2
CP
 (H2
) = 27.012 + 3.509 × 10–3 T + 6.9006 × 104
 T–2
a) Calculate the standard heat of reaction at 1073 K
b) Express the heat of reaction as a function of temperature. 18
OR
6. It is desired to carry out the following reaction at 600°C.
CO(g) + H2
O(g) → CO2
(g) + H2(g)
Estimate the standard enthalpy change of the reaction at 600°C if the standard
heat of reaction at 298 K is – 41.116 kJ. Use the following data :

CP= a + bT + cT2 + dT3
 + eT–2 J/mol.k
Compound a b × 103 e × 10–5
CO 28.068 4.631 – 0.258
H2
O 28.850 12.055 1.006
CO2 45.369 8.688 – 9.619
H2 27.012 3.509 0.690 18
-3- [3962] – 339
SECTION – II
7. a) Derive the following relation for the efficiency of carnot heat engine.
TH η = TH − TL 8
b) A nuclear power plant generates 750 MW, the reactor temp. is 588.15 k, and a
river with water temperature of 293.15 is available.
a) What is the maximum possible thermal efficiency of the plant, and what is
the minimum rate at which heat must be discarded to the river ?
b) If the actual thermal efficiency of the plant is 60% of the maximum, at what
rate heat must be discarded to the river, and what is the temperature
rise of the river if it has a flow rate of 165 m3/sec. 10
OR
8. a) Explain the concept of entropy. For irreversible thermodynamic process,
show that the total entropy change is positive. 8
b) Two compartments each of 1m3
 capacity are connected by a valve and
insulated from the surrounding and from each other. One compartment
contains saturated steam at 683.6 KPa and the other contains steam at the
same but at a pressure of 101.3 KPa. The valve is opened and the pressure
is allowed to equalize. Determine the change in entropy of the system
consisting of the two vessels. Comment on irreversibility of the process.
The thermodynamic properties of steam are as follows : 10
Pressure (KPa) H(KJ/kg) S(KJ/kgK)V(m3/kg) V(KJ/kg)
683.6 (T = 437.2 k) 2761 6.7133 278.9×10–3 2570.4
101.3 (T = 437.6 k) 2804 7.6712 1976.2 2603.3
9. a) Explain residual properties. Derive the fundamental residual property relation
for 1 mol of substance for closed thermodynamic system 8
( ) dT
RT
H dp RT
V
RT d G
2
R R R
= −
b) Derive the Clausius – Clapeyron equation for a two phase system. 8
OR
10. a) Show that
i) T P dV K dE CVdT ⎟
⎠
⎞ ⎜
⎝
⎛ − β = +
ii) dV
K
dT
T
CV dS β = + 10
b) Explain thermodynamic diagrams. 6
11. a) Explain absorption refrigeration cycle with neat sketch. 8
b) A vapor compression cycle using ammonia as refrigerant is employed in an
ice manufacturing plant. Cooling water at 288 k enters the condenser at a
rate of 0.25 kg/sec and leaves at 300 k. Ammonia at 294 k condenses at a rate
of 0.50 kg/min. Enthalpy of liquid ammonia at 294 k is 281.5 KJ/kg. The
compressor efficiency is 90%. Saturated ammonia vapor at 258 k and the
enthalpy of 1426 kJ/kg enters the compressor. What is the power
requirement of the compressor and refrigeration capacity in tons ? 8
OR
12 a) Explain Linde process for gas liquefaction. 6
b) A carnot engine is coupled to carnot refrigerator so that all the work produced
by the engine is produced by the engine is used by the refrigerator in extraction
of heat from a heat reservior at 0°C at the rate of 35 KW. The source of
energy for the carnot engine is a heat reservior at 250°C. If both devices
discard heat to the surrounding at 25°C how much heat does the engine
absorb from its heat source reservior ? If the actual coefficient of performance
of the refrigerator, COPactual = 0.60 COP carnot and if thermal efficiency of the
engine is ηactual = 0.60 ηcarnot, how much heat does the engine absorb from
its heat source reservoir ? 10
————————

2011 Question Paper,S.E. (Chemical) (Semester – II),University Of Pune Question Paper,PRINCIPLES OF DESIGN

University Of Pune Question Paper
S.E. (Chemical) (Semester – II) Examination, 2011
PRINCIPLES OF DESIGN
(2003 Course)
Time : 3 Hours Max. Marks : 100
 Instructions : 1) Answer 3 questions from Section I and 3 questions
from Section II.
2) Answers to the two Sections should be written in
separate books.
3) Neat diagrams must be drawn wherever necessary.
4) Black figures to the right indicate full marks.
5) Use of logarithmic tables, slide rule, Mollier charts,
electronic pocket calculator and steam tables is
allowed.
6) Assume suitable data, if necessary.
SECTION – I
1. a) Explain the nature of machine design problem. Also explain the process of
machine design. 6
b) An equilateral triangular bar of 15 mm side and 2.5 m long is found to contract
in length by 2 mm. Calculate the push on the bar if E = 2 × 105 MPa. 6
c) A mild steel flat 150 mm wide, 20 mm thick and 6 m long carries an axial
push of 200 KN. Find compressive stress and strain with E = 2 × 105 MPa. 6
OR
2. a) Classify machine designs based on :
i) Nature of new idea, and
ii) The method used. 6
b) A metal rod having 16 mm diameter fractured at a tensile force of 90 KN.
Another hollow circular rod of 25 mm id made of same metal has to withstand
a tensile force of 40 KN. Adopting a F.O.S. of 3, determine the required wall
thickness. 6
c) A tie bar 25 mm in diameter carries an axial force which causes stress of
120 MPa in it. It is attached to a rigid bracket by means of 4 bolts, each of which
can be stressed to 90 MPa. Find the suitable diameter for bolts. 6
3. a) A singly overhang beam ‘ABC’ is simply supported at ‘A’ and ‘B’ with
AB = 9 m and BC = 3 m. (‘C’ is free end). The beam carries u.v.l. on portion
‘AB’ with zero intensity at ‘A’ and
m
KN 6 load at ‘B’. The end ‘C’ carries
C.W. moment of 18 KN-m :
i) Draw SFD and BMD for the beam
ii) Find maximum sagging and hogging BM alongwith their positions
iii) Find the point of contraflexure if any. 8
b) At a point in a bracket, the stresses on two mutually perpendicular planes are
600 MPa (t) and 400 MPa (c) along with complementary shear stress of
100 MPa. Find using Mohr’s circle method :
i) The position of principal planes with respect to the plane carrying 600 MPa
stress.
ii) Magnitudes and nature of principal stresses.
iii) The position of plane carrying maximum shear stress and value of
maximum shear stress.
iv) The normal, tangential and resultant stress on the plane at 30° with plane
carrying 600 MPa stress. Also find angle of obliquity. 8
OR
4. a) A cantilever of 2 m span has central downward load of 4 KN, an upward
force of 1.5 KN at free end and U.D.L. of 1.5 KN / m between two point
loads.
i) Construct SFD and BMD for the beam.
ii) Find maximum sagging and hogging BM values along with their positions.
iii) Find point of contraflexure if any. 8
b) At a point in strained material, there are two planes at right angles to each
other on which normal stress intensities are 75 MPa (t) and 45 MPa (c)
accoMPanied by complimentary shear stress. ( τ ). The major principal stress
is 105 MPa (t). Find using Mohr’s circle method or otherwise :
i) Shearing stress ( τ ) and minor principal stress.
ii) Maximum shearing stress and the plane on which it acts.
iii) The normal, tangential and resultant stress on the plane at 35° with the plane
carrying 75 MPa. 8
5. a) A plate 75 mm wide and 12.5 mm thick is joined with another plate by a
single transverse weld and a double parallel fillet weld. Find the length of
weld if maximum tensile and shear stresses are 70 MPa and 56 MPa respectively. 6
b) i) Draw neat sketch of socket and spigot cotter joint showing all parts and
their dimensions. 2
ii) Design a cottered joint to resist safely a load of 40 KN that acts along the
coincident axes of the rods connected by the cotter. The material of the
cottert and rods will permit the stresses of 50 MPa in tension, 105 MPa in
compression and 40 MPa in shear. 8
OR
6. a) A plate 100 mm wide and 10 mm thick is to be welded with another plate by
means of transverse welds at the ends. If the plates are subjected to load of
70 KN, find the length of the weld for static as well as fatigue loading. Take
permissible shearing stress of 70 MPa and stress
concentration factor of 2.7. 6
b) i) Draw neat sketch of knuckle joint showing various parts along with their
dimensions. 2
ii) Design a knuckle joint for a tie rod of circular section to sustain a maximum
pull of 70 KN. The ultimate strength of rod in shear is 420 MPa, while that
for pin material is 510 MPa in tension and 396 MPa in shear. Taking
F.O.S. of 6, determine tie rod section and pin section. Also determine
other dimensions of the joint and check shear resistance of pin, tensile
resistance of rod end and forked end of the joint for safety. 8
SECTION – II
7. a) The shaft running at 120 rpm transmits 430 KW. The working conditions to
be satisfied by the shafts are :
i) The shear stress must not exceed 56 MPa
ii) The angle of twist must not be more than 1° in a length of 16 diameters.
Calculate the safe diameter of the shaft.
Take G = 0.85 × 105 MPa. 4
b) The shaft of uniform diameter is supported in bearings at ‘C’ and ‘D’ which
are 800 mm apart. The shaft carries pulleys ‘A’ and ‘B’ at the ends at distances
150 mm and 250 mm from ‘C’ and ‘D’ respectively. Pulley ‘A’ weighs 200 N,
which carries belt with tight side tension 2 KN while pulley ‘B’ weighs 400 N
with tight side tension 900 N. The shaft transmits 7.5 KW at 400 rpm. Estimate
a suitable shaft diameter for the shaft, adopting a working shear stress of
40 MPa (Use maximum shear stress theory of elastic failure). 6
c) A muff coupling is used to connect two steel shafts of 55 mm diameter,
transmitting 40 KW at 350 rpm. The allowable shear and crushing stresses
for shaft and key material are 40 MPa and 80 MPa respectively, while the
sleeve material has shear stress of 15 MPa. Design suitable key and sleeve
based on safety in crushing and shearing. 6
OR
8. a) Three pulleys ‘A’, ‘B’ and ‘C’ are mounted on a shaft and are at distances of
1200 mm, 2100 mm and 2700 mm respectively from the left hand bearing.
The bearings are 3600 mm apart. Pulley ‘A’ is 500 mm, ‘B’ 750 mm and ‘C’
375 mm in diameter. A power unit supplies 15 KW to ‘A’ and machinery
takes 9 KW from ‘B’ and 6 KW from ‘C’. A horizontal drive is arranged to
‘A’, while the drive ‘B’ has to be vertically downwards. The drive from ‘C’
is taken off at 45° to drive ‘A’ and in a downward direction. The speed of the
shaft is 200 rpm and the allowable shear stress in the shaft is 32 MPa. The
angle of lap of belt on pulley is 180° in each case, and the coefficient of
friction between belt and pulley is 0.32. Obtain the shaft diameter. 12
b) Draw neat sketch of bushed pin type flexible coupling. 4
9. a) A leather belt 9 mm × 250 mm is used to drive a cast iron pulley 900 mm in
diameter at 336 rpm. If the active arc on the smaller pulley is 120° and the
stress in tight side is 2 N / mm2, find the power capacity of the belt. The
density of leather is 980 kg / m3 and coefficient of friction of leather on cast
iron is 0.35. 8
b) The load on journal bearing is 150 KN due to turbine shaft of 300 mm
diameter running at 1800 rpm. Determine :
i) Length of the bearing if the allowable bearing pressure is 1.6 N / mm2 and
ii) Amount of heat to be removed by the lubricant per minute if the bearing
temperature is 60° C and viscosity of oil at 60° C is 0.02 kg / m-s and the
bearing clearance is 0.25 mm. Take K = 0.002. 8
OR
10. a) A compressor, requiring 90 KW, is to run at about 250 rpm. The drive is by
V-belts from an electric motor running at 750 rpm. The diameter of the
pulley on the compressor shaft must not be greater than 1 m while the centre
distance between the pulleys is limited to 1.75 m. The belt speed should not
exceed 1600 m / min. Determine the number of V belts required to transmit
the power if each belt has a cross-sectional area of 375 mm2 and the angle of
pulley is 35°. The coefficient of friction between the belt and the pulley is
0.25. Calculate the length required for each belt. 10
b) A journal bearing 60 mm in diameter and 90 mm long runs at 450 rpm. The
oil used for hydrodynamic lubrication has absolute viscosity of 0.06 kg / ms.
If the diametral clearance is 0.1 mm, find the safe load on the bearing.
Take Sommerfield number = 14.3 × 106. 6
11. Write short notes on : 18
a) Globe valve
b) Steam trap
c) Centrifugal pump.
OR
12. Write short notes on : 18
a) 3-way valve
b) Diaphragm valve
c) Fans and blowers.
————————

University Of Pune Question Paper,HEAT TRANSFER,S.E. (Chemical) (Semester – II),2011 Question Paper

University Of Pune Question Paper
S.E. (Chemical) (Semester – II) Examination, 2011
HEAT TRANSFER
(Common to Bio-Tech.)
(2003 Course)
Time : 3 Hours Max. Marks : 100
 Instructions: 1) Solve Q.1 or Q.2, Q.3 or Q.4, Q.5 or Q.6, Q.7 or Q.8,
Q.9 or Q.10 and Q.11 or Q.12.
2) Answers to the two Sections should be written in separate
books.
3) Neat diagrams must be drawn wherever necessary.
4) Black figures to the right indicate full marks.
5) Use of logarithmic tables, slide rule, Mollier charts, electronic
pocket calculator and steam tables is allowed.
6) Assume suitable data, if necessary.
SECTION – I
1. a) State and explain : 9
i) Fourier’s law ii) Newton’s law of Cooling iii) Stefan-Boltzmann’s law.
b) Give the physical significance of the following dimensionless groups : 9
i) Reynolds number ii) Prandtl number iii) Nusselt number.
OR
2. a) Explain in detail “Modes of Heat Transfer”. 6
b) Calculate temperature at an interior point of the wall at a distance 15 cm from
inner surface of wall. The temperatures of the inner and outer surface are
200°C and 80°C respectively. The thickness of the wall is 0.5 m. 6
c) Explain any one method of Dimensional Analysis. 6
3. a) Derive the heat flow equation for steady state heat conduction through
composite cylinder. 8
b) A hollow sphere of 24 mm inner diameter and 36 mm outer diameter is subjected
to constant heat flow of 2.12 kW. In inner surface temperature is 390°K, find the
temperature of outer surface and temperature at a distance of 16 mm from the
centre of the sphere. Thermal conductivity of the material is 85 W/m°K. 8
OR
4. a) Derive the heat flow equation for steady state heat conduction through
composite wall. 8
b) A hollow cylinder of 20 mm inner diameter and 30 mm outer diameter is
maintained at 350°k (outer surface temperature) and 420°k (inner surface
temperature). Determine the heat loss per unit length and also determine the
temperature at a distance of 3 mm from outer surface towards the center.
(Thermal conductivity of material is 50 W/m°K). 8
5. a) Distinguish between : 8
i) Individual and overall heat transfer coefficient
ii) Natural convection and Forced convection.
b) Air at 300°C and atmospheric pressure is heated as it flows through a tube
with a diameter of 25 mm at a velocity of 12 m/sec. Calculate the heat transfer
rate per unit length of tube if a constant heat flux condition is maintained at the
wall which is at 32°C above the air temperature, over entire length of the tube.
Calculate the rise in bulk temperature over a 3.3 m length of the tube. 8
Properties of air are
i) Dynamic viscosity = 29.7×10–6 Kg/m.sec.
ii) Thermal conductivity = 0.0461 W/m°K.
iii) Prandtl Number = 0.674
iv) Cp = 1.047 KJ/Kg°K
v) Density = 0.615 Kg/m3.
OR
6. a) Derive Nusselt’s equation of condensation. 8
b) Air at 27°C and 1 atm. Flow over a flat plate at a velocity of 2 m/sec. The
viscosity of air at 27°C is 1.85×10–5 Pa.s. Assume unit depth. If the plate is
maintained at 60°C. Calculate the heat transferred per unit time in the first
0.4 m of the plate. Properties of air are 8
i) Kinematic Viscosity = 17.36×10–6 m2/sec.
ii) Thermal conductivity = 0.0275 W/m°K.
iii) Prandtl Number = 0.7
iv) Cp = 1.006 KJ/Kg°K.
SECTION – II
7. a) A 50 mm internal diameter iron pipe at 423°K passes through a room in which
the surroundings are at temperature of 300°K. If the emissivity of the pipe
metal is 0.8, what is the net interchange of radiation energy per meter length of
pipe ? The outside diameter of pipe is 60 mm. 9
b) Explain the following : 9
i) Specular and Diffuse Reflection
ii) Radiation shields
iii) Wien’s displacement law.
OR
8. a) It is observed that the value of the radiation emitted by the sun is maximum
wavelength of 0.58 microns. Estimate the temperature of surface of sun and
emissive power. Consider sun to be a black body. 8
b) Discuss the following : 10
i) Electromagnetic spectrum
ii) Black body
iii) Emissive power
iv) Opaque body
v) Emissivity.
9. a) What is LMTD ? Derive LMTD for counter current flow heat exchanger. 8
b) 20 kg/s of water at 360°K entering a heat exchanger is to be cooled to 340°K
by using cold water at 300°K flowing at rate of 25 kg/sec. If the overall heat
transfer coefficient is 1500 w/m2
°k and c
p
 for water is 4187 J/Kg°K. Calculate
heat transfer area required in 8
i) Co current flow concentric pipe heat exchanger
ii) Countercurrent flow concentric pipe heat exchanger.
OR
10. a) What is Heat exchanger ? Give the detail classification of heat exchangers. 8
b) In oil cooler 60 gm/sec of hot oil enters a thin metal pipe of diameter 25 mm,
an equal mass of cooling water flows through the annular space between the
pipe and a large concentric pipe, the oil and water moving in opposite directions.
The oil enters at 420°K and is to be cooled to 320°K. If water enters at
290°K, what length of pipe is required ? Take heat transfer coefficient of
1.6 kW/m2
K on the oil side and 3.6 kW/m2K on water side. Specific heat
capacity of oil is 2 kJ/kg°K and that of water is 4.18 kJ/kg°K. 8
11. a) A solution of organic colloids in water is to be concentrated from 8% to 45%
in a single effect evaporator. Steam is available at a gauge pressure of
1.03 atm. A pressure of 102 mm Hg absolute is to be maintained in the vapor
space. The feed rate to the evaporator is 12,000 kg/hr. The overall heat transfer
coefficient can be taken as 2800 W/m2
.°C. The solution has a negligible
elevation in boiling point and a negligible heat of dilution. Calculate (a) steam
consumption (b) the economy and (c) the heating area required. 8
b) What is Evaporation ? Draw a neat sketch and explain any one evaporator. 8
OR
12. a) 1000 kg/hr of a dilute solution is to be concentrated from 10% to 40% by
weight in a single effect evaporator. The feed is available at 25°C. Boiling
point of the solution may be considered as 100°C. Specific heat capacity of
dilute solution is 4180 J/kg°K; Latent heat of vaporization of water is 2239 kJ/Kg,
saturated steam corresponding to 1.8 bar pressure and 117°C is available for
heating purpose. Latent heat of condensation of steam is 2212 kJ/kg. If the
overall heat transfer coefficient for the system is 850 W/m2
°K. 12
Calculate :
i) The quantity of water evaporated
ii) Steam consumed and steam economy
iii) Surface area of the evaporator.
b) Explain multiple effect evaporator with different feed arrangements. 4
————––––––———