ME6502– HEAT AND MASS TRANSFER
UNIT - I
PART –A
1.
2.
3.
4.
What is conduction? Dec 09, Dec 12)
State Fourier’s law of conduction(May 09, May 15)
Define Thermal conductivity
Write down the equation for conduction of heat through a slab or plane wall. (May 09,
May 15)
5. What are the factors affecting the thermal conductivity? Dec 09, Dec 12)
6. What is Fourier's Law of heat conduction? (May 05, May 06, Dec 09, May 10, May 11,)
7. Differentiate between heat transfer and thermodynamics. (May 10)
8. What is coefficient of Thermal conductivity? (Dec 09, Dec 12)
9. Write the three dimensional heat equations in Cartesian co-ordinate system. (May 06,
May 05)
10. What is Newtonian heating or cooling process? (May 09)
11. Define heat flux. (Dec 07)
12. Define thermal Diffusivity. (May 09, May 15)
13. Discuss the mechanism of heat conduction in solids. (May 09, May 13)
14. What is Poisson's equation for heat flow? (May 10)
15. What critical radius of insulation? (MAY 04, Nov 04, Nov 06, Dec 08, May 14)
16. What is a Fin? What are the different types of fin profiles?(Nov 04, May 07, Dec 08,
Nov 11, May 13, May 15)
17. Define efficiency of the fin. (Nov 04, Nov 05, May 07, Dec 08, May 13)
18. Define effectiveness of the fin. (Nov 04, Nov 05, May 07, Dec 08, May 13)
19. What is meant by Transient heat conduction? (May 09)
20. What is lumped analysis. When it is used? (Dec 08, May 10, May 11, May 13)
21. What is Biot number? (May 10)
22. What are the two mechanisms of heat conduction in solids? (Nov 11)
23. Write any two examples of heat conduction with heat generation. (Nov 13)
24. What is meant by transient heat Conduction? (May 15)
PART –B
First half
1. A hot steam pipe having an inside surface temp of 250°C has an inside diameter of 80 mm
and a wall thickness of 5.5mm. it is covered with a 90mm layer of insulation having thermal
conductivity of 0.5W/mK followed by a 40mm layer of insulating having thermal conductivity
of 0.25 W/mk. The outside surface temp of insulation is 20°C.calculate heat loss per meter
length. Assume thermal conductivity of the pipe as 47 W/mK. (May 98, May 02, Nov 14)
2. A furnace wall consists of three layers. The inner layer of 10 cm thickness is made of
fire brick (k =1.04 W/mK). The intermediate layer of 25 cm thickness is made of masonry brick
(k = 0.69 W/mK) followed by a 5 cm thick concrete wall (k = 1.37 W/mK). When the furnace is
in continuous operation the inner surface of the furnace is at 800°C while the outer concrete
surface is at 50°C. Calculate the rate of heat loss per unit area of the wall, the temperature at the
interface of the firebrick and masonry brick and the temperature at the interface of the masonry
brick and concrete. (June 06)
3. Derive the heat conduction equation in Cartesian co-ordinates using an elemental volume
for a stationary isotropic solid. (May 10, Nov 14)
4. A composite wall consists of 10 cm thick layer of building brick, k = 0.7 W/mK and 3 cm
thick plaster, k = 0.5 W/mK. An insulating material of k = 0.08 W/mK is to be added to reduce
the heat transfer through the wall by 40%. Find its thickness. (14) (May 10)
5.A composite slab is made of three layers 15cm, 10cm and 12cm thickness respectively. the first
layer is made of material with k = 1.45W/mK for 60% of the area and the rest of material with k
= 2.5 W/mK. the second layer is made of material with k = 12.5 W/mK for 50% of area and rest
of material with k = 18.5 W/mK. the third layer is made of single material of k = 0.76 W/mK.
the composite slab is exposed on one side to warm at 26°C and cold air at -20°C. the inside heat
transfer co-efficient is 15 W/m2K. the outside heat transfer co-efficient is 20 W/m2K.determine
heat flow rate and interface temperature. (June 96)
6. A current of 200A is passed through a stainless steel wire( k = 19 W/mK), 3mm in diameter.
the resistivity of the steel may be taken as 70μΩ cm and the length of the wire is submerged in a
liquid at 110°C. calculate the centre temperature of the wire. (May2000)
7. An aluminum cube 6cm on a side is originally at a temperature of 500°C. it is suddenly
immersed in a liquid at 10°C for which h is 120 W/m2K. estimate the time required for the cube
to reach a temperature of 250°C. for aluminum ρ=2700kg/m3.Cp=900J/kgK, k=204 W/mK (June
02)
Second half
1. Explain the different modes of heat transfer with appropriate expressions. (14) (May 07)
2. An aluminum rod (k =204 W/mK) 2 cm in diameter and 20 cm long protrudes from a wall
Which is maintained at 300°C.The end of the rod is insulated and the surface of the rod is
exposed to air at 30°C. The heat transfer coefficient between the rod's surface and air is 10
W/m2K. Calculate the heat lost by the rod and the temperature of the rod at a distance of 10 cm
from the wall. (Nov 14)
3. Explain the mechanism of heat conduction in solids and gases. (May 2013)
4. Derive the heat conduction equation in cylindrical co-ordinates using an elemental Volume for
a stationary isotropic solid. (May 07, May 10, Nov 14)
5. An electrical wire of 10m length and 1mm diameter dissipates 200W in air at 25°C. The
convection heat transfer co-efficient is 15W/m2K. the thermal conductivity of wire is 0.582
W/mK. calculate the critical radius of insulation and also determine the temperature of the wire.
if it is insulated to the critical thickness of insulation. (Nov 14)
6. A concrete wall of 1m thick is poured with concrete. the hydration of concrete generates
150W/m3 heat. if both the surfaces of the wall are maintained at 35°C. find the maximum
temperature in the wall (May 99)
7. A large block of steel is initially at 35°C. the surface temperature is suddenly raised and
maintained at 250°C. calculate the temperature at a depth of 2.5 cm after a time of 30s. The
thermal diffusivity and thermal conductivity of steel are 1.4X 10-5 m2/s and 45 W/mK
respectively. (Nov 97)
8.A long steel cylinder 12cm diameter and initially at 20°C is placed into furnace at 820°C with
h=140 W/m2K. Calculate the time required for the axis temperature to reach 800°C. also
calculate the corresponding temperature at a radius of 5.4cm at that time. physical properties of
steel are k =21 W/mK,α=6.11X 10-6 m2/s(Nov 99)
UNIT 2
PART -A
1. What is Convective heat transfer? (A.U., apr/may 2003 : apr/may 2005)
2. Sketch formation of boundary layer and show laminar, transition & turbulent flow. (A.U.,
nov/dec 2006(2) : nov/dec 2007
3. Write down differential equation for Continuity of fluid flow. (A.U., apr/may 2003 : apr/may
2005)
4. State Newton's law of cooling. (A.U., apr/may 2003 : apr/may 2005)
5. Differentiate between Natural & Forced convection. (A.U., apr/may 2003 : apr/may 2005)
6. State Buckingham's π theorem. (A.U., apr/may 2003 : apr/may 2005)
7. What is meant by Dimensional analysis? (A.U., apr/may 2003 : apr/may 2005)
8. Sketch boundary layer development in a circular pipe. (A.U., nov/dec 2006(2) : nov/dec
2007(2))
9. What is Reynolds analogy? (A.U., nov/dec 2006(2) : nov/dec 2007(2))
10. Define the Bulk temperature. (A.U., nov/dec 2006(2) : nov/dec 2007(2))
11. Define velocity boundary layer thickness. (A.U., nov/dec 2006(2) : nov/dec 2007(2))
12. Define thermal boundary layer thickness. (A.U., nov/dec 2006(2) : nov/dec 2007(2))
13. Distinguish between laminar and turbulent flow. (A.U., nov/dec 2006(2) : nov/dec 2007(2))
14. What is meant by critical Reynolds number? (A.U., nov/dec 2006(2) : nov/dec 2007(2))
15. Define skin friction coefficient. (A.U., apr/may 2003 : apr/may 2005)
16. Give examples for free convection. (A.U., apr/may 2003 : apr/may 2005)
17. Define Grashoff number. (A.U., apr/may 2003 : apr/may 2005)
18. Define momentum thickness (A.U., apr/may 2003 : apr/may 2005)
19. Define Displacement thickness. (A.U., nov/dec 2006(2) : nov/dec 2007(2))
20. List the dimensionless numbers. (A.U., nov/dec 2006(2) : nov/dec 2007(2))
21. What are the uses of dimensional analysis? (A.U., apr/may 2003 : apr/may 2005)
PART – B
First half
1. Air at atmospheric pressure and 200°C flows over a plate with a velocity of 5m/s. the plate is
15mm wide and is maintained at temp of 120°C. Calculate the thickness of hydrodynamic and
thermal boundary layers and the local heat transfer coefficient at a distance of 0.5m from the
leading edge assume that the flow is on one side of the plate. ρ= 0.815kg/m 3,μ =24.5x10-6
Ns/m2, Pr =0.7, K=0.0364 w/mk (16) (A.U., apr/may 2003 : apr/may 2005)
2. (i) What is Reynolds analogy? Describe the relation between fluid friction and heat transfer?
(4)
(ii) Air at 25°C flows over 1 m x 3 m (3 m long) horizontal plate maintained at 200°C at 10 m/s.
Calculate the average heat transfer coefficients for both laminar and turbulent regions. Take Re
(critical) = 3.5 x 105 (12) (A.U., nov/dec 2006(2),nov/dec 2007(2))
3. (i) Distinguish between free and forced convection giving examples. (4)
(ii) A steam pipe 10 cm OD runs horizontally in a room at 23° C. Take outside temperature of
pipe as 180 ° C. Determine the heat loss per unit length of the pipe. (12) (A.U., apr/may 2003:
apr/may 2005)
4. (i) Define Reynold’s, Nusselt and Prandtl numbers. (6) (A.U., nov/dec 2006(2) : nov/dec
2007(2))
(ii) A steam pipe 10 cm outside diameter runs horizontally in a room at 23°C. Take the outside
surface temperature of pipe as 165°C. Determine the heat loss per unit length of the pipe. If pipe
surface temp reduces to 80°C with 1.5cm insulation what is the reduction in heat loss.? (10)
(A.U., apr/may 2003: apr/may 2005)
5. (i) Explain for fluid flow along a flat plate: (a) Velocity distribution in hydrodynamic
boundary layer (b) Temperature distribution in thermal boundary layer (c) Variation of local heat
transfer co-efficient along the flow. (8) (A.U., nov/dec 2006(2) : nov/dec 2007(2))
Second half
1. A flat plate 1m wide and 1.5m long is to be maintained at 90°c in air with free stream
temperature of 10°C. determine the velocity with which air must flow over flat plate along 1.5m
side ,so the rate of energy dissipation from the plate is 3.75kw .take the following properties of
air at 50°c ρ=1.09kg/m3,k=0.028w/m°c,Cp=1.007kj/kg°c,,μ=2.03x10- 5kg/ms, pr=0.7 (A.U.,
nov/dec 2006(2) : nov/dec 2007(2))
2. Air at a pressure of 8KN/m2and the temperature of 250°C flows over a flat plate 0.3m wide
and 1m long and a velocity of 8m/s .if the plate is to be maintained at the temperature of 78°C,
estimate the rate of heat to be removed continuously from the plate. (A.U., apr/may 2003 :
apr/may 2005)
3.A thin 80cm long and 8cm wide horizontal plate is maintained at a temperature of 130°C in
large full of water at 70°C. Estimate the rate of heat input in to the plate necessary to maintain
the temperature of 130°C(A.U., nov/dec 2006(2) : nov/dec 2007(2))
4. A hot plate 20cm in height and 6cm wide is exposed to the ambient air at 30°c assuming the
temperature of the plate is maintained at 110°C. find the heat loss from both surface of plate
assume horizontal plate (A.U., apr/may 2003 : apr/may 2005)
5. 205 kg/hr of air are cooled from 1000C to 300C by flowing through a 3.5 cm inner dia pipe coil
bent in to a helix of 0.6m dia calculate the value of air side heat transfer coefficient if the
properties of air at 650C are ρ= 1.044/m3,μ =0.003 kg/hr-m, Pr =0.7, K=0.0298 w/mk (A.U.,
apr/may 2003 : apr/may 2005)
Unit -3
Part-A
1. Discuss the advantage of NTU method over the LMTD method. (Dec 12, May 13)
2. What is nucleate pool boiling? (May 04, Dec 08, Dec 12, May 13, May 14)
3. What is flow boiling? (Dec 08, Dec 12)
4. How does boiling differ from evaporation? (Dec 11)
5. What are the different types of fouling in heat exchangers? (Dec 11)
6. What are the types of heat exchangers? (Dec 05, May 12, May 15)
7. How does boiling differ from evaporation? (Dec 11)
8. What are the different types of fouling in heat exchangers? (Dec 06, Dec 11)
9. Define Drop wise condensation. (Dec 04, Dec 05, May 06)
10. Define Film wise condensation. (Dec 04, Dec 05, May 06)
11. What are parallel and counter flow heat exchangers (Dec 04, May 05 )
12. How the heat exchangers are classified based on flow arrangement? (Dec 05)
13. What is LMTD? (May 11, May 13)
14. What is effectiveness of a heat exchanger? (May 10)
15. Give the expression for NTU? (May 09, May 10)
16. What is fouling factor? (May 07)
17. What is meant by condensation? (May 07)
18. What is burnout point in boiling heat transfer? Why is it called so? (May 13)
19. What are the different regimes involved in pool boning? (May 14)
20. Write down the relation for overall heat transfer coefficient in heat exchanger with
fouling factor. (May 14)
Part-B
First half
1. Water is boiled at a rate of 24 kg/h in copper pan, 300 in diameter, at atmospheric pressure.
assuming nucleate boiling conditions, calculate the temperature of the bottom surface of the
pan (May 12)
2. An aluminium pan of 15cm diameter is used to boil water and the water depth at the time of
boiling is 2.5cm. The pan is placed on an electric stove and the heating element raises the
temperature of the pan to 1100C. Calculate the power input for boiling and the rate of
evaporation. Take Csf = 0.0132. (Dec 05)
3. Explain the various regimes of pool boiling. what is nucleate boiling? (May 07,May 09,
May 15) (May 13)
4. Dry saturated steam at a pressure of 2.45 bar condenses on the surface of a vertical tube of
height 1m. the tube surface temperature is kept at 1170C. estimate the thickness of the
condensate film. (May 05)
5. A tube of 2m length and 25mm outer diameter is to be condense saturated steam at 1000C
while the tube surface is maintained 920C estimate the average heat transfer co-efficient and
the rate of condensation of steam if the tube is kept horizontal. The steam condenses on the
outside of the tube. (May 12)
Second half
1. Classify the heat exchangers; draw temperature distribution in a condenser and evaporator
and derive the expression for effectiveness of parallel flow heat exchanger by NTU
method. (May 16)
2. A counter flow concentric tube heat exchanger is used to cool engine oil [C = 2130J/kg K]
from 1600C to 600C with water available at 250C as the cooling medium. The flow rate of
cooling water through the inner tube of 0.5m is 2kg/s while the flow rate of oil through the
outer annulus, Outer diameter = 0.7m is also 2kg/s. If U is 250W/m2K , how long must
the heat exchanger be to meet its cooling requirement? (May 05)
3. A parallel flow heat exchanger has hot and cold water stream running through it, the flow
rates are 10 and 25kg/min respectively. Inlet temperatures are 750C and 250C on hot and
cold sides. The exit temperature on the hot side should not exceed 500C. Assume hi = h0 =
600W/m2K. Calculate the area of heat exchangers using ε = NTU approach. (May 16)
4. In a counter flow double pipe heat exchanger, water is heated from 250C to 650C by oil with
a specific heat of 1.45 KJ/kg K and mass flow rate is 0.9 Kg/s. The oil is cooled from
2300C to 1600C. If the overall heat transfers co-efficient is 420 W/m2 0C, calculate the
following by using NTU method
a. Effectiveness of heat exchanger
b. The mass flow rate of water
c. The surface area of the heat exchanger. (May 04)
5. (i) Define LMTD for a parallel flow heat exchanger stating the assumptions. (May 10)
(ii) What are the different types of fouling in heat exchangers? (May 15)
UNIT -4 RADIATION
Part-A
1.What is Stefan's Boltz Mann law? (May 12)
2. Distinguish between black and grey body? (Dec.04, Dec.05 May 06,May 07,May 09,)
3. What is meant by Kirchhoff's law? (May 10,Dec 12, May 15)
4. Define Radiation heat transfer (Dec 12)
5. What are radiation shields? (May 08,Dec 11)
6. What is total hemispherical emissivity? (Dec 11)
7. What is meant by thermal radiation? (May 08,May 11)
8. Define intensity of Radiation
9. Define Irradiation and Radiosity. (May 05, Dec 08, May 13, May 15)
10. Explain electrical analogy? (May 07, May 13)
11. Define emissive power.[Eb]. (Oct 97, Oct 2000,Dec.05)
12. What is meant by absorptivity? (Dec.04)
13. What is meant by reflectivity? (Dec.04)
14.State Wiens Displacement law
15.What is Emissivity
16. What is the purpose of radiation shield? (May 04)
17. What is meant by shape factor and mention its physical significance? (May 05, Nov 14)
18. Discuss the radiation characteristics of carbon dioxide and water vapour ( Dec 05)
19. What is thermal radiation? What is its wavelength band? (May 13)
20. State Planck's law. (May 13)
21 How radiation from gases differs from solids? (May 13)
22. Define irradiation and emissive power. (May 14)
Part-B
First half
1. The inner sphere of liquid oxygen container is 40cm diameter and outer sphere is 50 cm
diameter. Both have emissivities of 0.03. determine the rate at which the liquid oxygen would
evaporate at -183°C when the outer sphere at 20°C Latent of heat of oxygen is 220kJ/kg.(May
12)
2. Calculate the net radiant heat exchange per m2 area for two large parallel plates at temperature
of 4270C and 270C respectively. ε[hot plate] = 0.9 and ε [cold plate] = 0.6. If a polished
aluminium shield is placed between them, find the percentage of reduction in the heat transfer.
ε[shiedl] = 0.4. (May 04)
3. Two large parallel planes at 800 K and 600 K have emissivities of 0.5 and 0.8 respectively. A
radiation shield having an emissivity of 0.1 on one side and an emissivity of 0.05 on the other
side is placed between the plates. Calculate the heat transfer rate by radiation per square meter
with and without radiation shield. Common on the results. (May 04,Dec 05)
4. Emissivities of two large parallel plate maintained at 800° C and 300° C and 0.3 and 0.5
respectively Find the net heat exchange per square meter of these plates. (Dec 12) (8 mark)
5.Emissivities of two large parallel plates maintained at 800°C and 300°C are 0.3 and 0.5
respectively. Find the net radiant heat exchange per square meter for these plate. Find the
percentage reduction in heat transfer when a polished aluminium radiation shield (€ = 0.05) is
placed between them. Also find the temperature of shield. (May 15)
6. Using the definition of radiosity and irradiation prove that the radiation heat exchange
between two grey bodies is given by the relation: (May 07)
σ (T1 4 –T24)
Q net = ------------------------------------------------------1-ε1
1
1-ε 2
----------- + ------------- + ------------A1ε1
A1 F12
A2 ε2
7. A two black discs of diameter 0.5m are placed directly opposite at a distance of 1m . The disc
are maintained at 1000K and 500K respectively. Calculate the heat flow between the discs.
i.
ii.
When no other surfaces are present
When the discs are connected by non conducting surface.
Second half
1. Two parallel plates of size 1 m x 1 m are spaced 0.5 m apart are located in a very large room,
the walls of which are maintained at a temperature of 27C. One plate is maintained at a
temperature of 900C and the other at 400C. Their emissivities are 0.2 and 0.5 respectively. If the
plates exchange heat between themselves and surroundings, find the net heat transfer to each
plate and to the room. Consider only the plate surfaces facing each other. (May 04)
2. A furnace of 25 m2 area and 12 m3 volume is maintained temperature of 9250C over its entire
volume. The total pressure of the combustion gaseous is 3 atm, the partial pressure of water
vapour is 0.1 atm and that of CO2 is 0.25 atm. Calculate the emissivities of the gaseous mixture.
(Dec 11)
3. A truncated cone has top and bottom diameters of 10 and 20 cm and a height of 10 cm.
Calculate the shape factor between the top surface and the side and also the shape factor between
the side and itself. (Nov 13)
4. a) i) Define emissivity, absorptivity and reflectivities (6)
ii) Describe the phenomenon of radiation from real surface (7)
5. i) Distinguish between black bodies and gray bodies and specular and diffuse surface (4)
ii) Discuss briefly the variation of black body emissive power with wave length for different
temperatures.(7)
6. i)State and Prove Kirchhoff s law of thermal radiation. (8)
ii) explain briefly the following i) thermal radiation ii) reciprocity rule (5) (May 13)
7. Determine the view factor F 1-2 and F 2-1 for the figure shown below. (Dec 08)
5m
A2
2m
A3
A1
1m
1m
Unit- 5 MASS TRANSFER
Part-A
1. What is Convective mass transfer? (May 12)
2. Describe the various mechanism of mass transfer? (May 12)
3. What is the physical meaning of Lewis number? (Dec 11)
4. State Fick’s law of diffusion. (May 09,Dec 12, May 13, Nov 14, May 15)
5. What is free convective mass transfer. (Dec 12)
6. Define forced convective mass transfer. (Dec 12)
7. Define the following: Ii) Mass concentration b) Molar concentration (May 10, May 15)
8. What is the Molar Diffusion velocity (May 10)
9. What is Diffusion mass transfer? (May 08, May 13)
10. What is Convective mass transfer? (May 08)
11. What is equmolar counter diffusion? (May 08, May 13)
12. Explain the physical meaning of Schmidt number. (May 08)
13. Define Fourier number & Biot number for mass transfer. (May 07)
14. What is meant by mass transfer co-efficient? (May 07)
15. What are the modes of mass transfer? (May 06)
16. What is molecular diffusion? (May 06)
17. What is convective mass transfer? (May 06)
18. Define Sherwood Number. (May 04)
19. Give two examples of convective mass transfer. (May 04)
20. Define the Mass Concentration. (Dec 04,Dec 05)
21. Write down the analogous terms in heat and mass transfer. (May 14)
21. Define the Molar Concentration. (Dec 04,Dec 05)
22. Define the following. (Dec 04 , Dec 05)
[i] Mass fraction. [ii] Mole fraction (May 13)
23. Define Schmidt and Lewis numbers. What is the physical significance of each? (May 13)
Part-B
First half
1. Dry air at 27oC and 1 atm flows over a wet flat plate 50 cm long at a velocity of 50 m/s.
Calculate the mass transfer co-efficient of water vapour in air at the end of the plate. Take the
diffusion coefficient of water vapour in air is Dab = 0.26 X I0-4 m2/s.(Dec 07, May 10,May 12)
2. Dry air at 200C [ρ = 1.2 kg/m3, υ = 15 x 10-6 m2/s. D = 4.2 x 10-5 m2/s] flows over a flat plate
of length 50cm which is covered with a thin layer of water at a velocity of 1m/s. Estimate the
local mass transfer co-efficient at a distance of 10cm from the leading edge and the average mass
transfer co-efficient. (May 06)
3. Air at 1 atm and 250C containing small quantities of iodine flow with a velocity of 6.2 m/s
inside a 35 mm diameter tube. Calculate mass transfer co-efficient for iodine. The thermo
physical properties of air are υ = 15.5 x 10-6 m2/s, D = 0.82 x 10-5 m2/s. (May 06)
4. An open pan 20cm in diameter and 8cm deep contains water at 250C and is exposed to dry
atmospheric air. If the rate of diffusion of water vapour is 8.54 x 10- 4 kg/h, estimate the
diffusion co-efficient of water in air. (May 05)
5. Air at 20° C with D = 4.166 x10-5 m²/s flows over a tray (length 320 mm, width 420mm) full
of water with a velocity of 2.8 m/s. The total pressure of moving air 1 atm and the partial
pressure of water present in the air is 0.0068 bar. If the temperature on the water surface is 15°C,
Calculate the evaporation rate of water. (May 08)
6. A vessel contains a binary mixture of oxygen and nitrogen with partial pressures in the ratio
0.21 and 0.79 at 20°C. The total pressure of the mixture is 1.1 bar. Calculate the following
(i) Molar concentrations
(ii) Mass densities
(hi) Mass Fractions
(iv) Molar fractions of each species. (Dec 08, May 04)
Second half
1. (i) Explain equimolal counter diffusion in gases.
(ii) Discuss briefly the Analogy between heat and mass transfer (May 13)
2. (i)Explain briefly the similarities between heat and mass transfer
(ii) Explain briefly the mode of mass transfer.
(iii) State Fick’s law of diffusion
3. Explain different modes of mass transfer and derive the general mass diffusion equation in
stationary media.(May 14)
4. Explain Reynold's number, Sherwood number and Schmidt number 6)
iii.
Derive Mass transfer equation in Cartesian Coordinates. (Dec 08, May 04)
7. The diffusivity of CCl4 in air is determined by observing the steady state evaporation of CCl4
in a tube of 1 cm diameter exposed to air. The CCl4 liquid is 10 cm below the top level of the
tube . the system is held at 25°C and 1 bar pressure. The saturation pressure of CCl4 at 25°C is
14.76 kPa. If it is observed that the rate of evaporation of CCl4 is 0.1 g/hr determine the
diffusivity of CCl4 into air. (Dec 09, May 04)
8. Two large tanks, maintained at the same temperature and pressure are connected by a circular
0.15m diameter direct, which is 3m length. One tank contains a uniform mixture of 60 mole %
ammonia and 40 mole % air and the other tank contains a uniform mixture of 20 mole %
ammonia and 80 mole % air. The system is at 273K and 1.013X105 pa. Determine the rate of
ammonia transfer between the two marks. Assuming a steady state mass transfer. (Dec 09, May
04)
9. Oxygen at 250C and pressure of 2 bar is flowing through a rubber pipe of inside diameter 25
mm and wall thickness 2.5mm. The diffusivity of O2 through rubber is 0.21X 10-9 m2/s and
solubility of O2 in rubber is 3.12 X 10-3 kg-mole/m3-bar. Find the loss of O2 by diffusion per
metre length of pipe. (May 09)