Question 1. The ductility of a material with work hardening

(A) Increases

(B) Decreases

(C) Remains unaffected

(D) Unpredictable

GATE-ME-2002

Hint

Question 2. Hardness of steel greatly improves with

(A) Annealing

(B) Cyaniding

(C) Normalizing

(D) Tempering

GATE-ME-2003

Hint

Question 3. During heat treatment of steel, the hardness of various structures in increasing order is

(A) Martensite, fine pearlite, coarse pearlite,spherodite

(B) Fine pearlite, coarse pearlite, spherodite, martensite

(C) Martensite, , coarse pearlite, fine pearlite, spherodite

(D) Spherodite, coarse pearlite, fine pearlite, martensite

GATE-ME-2003

Hint

Question 4. From the list given below, choose the most appropriate set of heat treatment process and the corresponding process characteristics

(A) P-3, Q-1,  R-5

(B) P-4, Q-3,  R-2

(C) P-4, Q-1,  R-2

(D) P-1, Q-5,  R-4

GATE-ME-2004

Hint

Question 5. Grey cast iron blocks  are to be cast in sands moulds. Shrinkage allowance for pattern making is 1 %. The ratio of the volume of pattern to that of casting will be

(A) 0.97

(B) 0.99

(C) 1.01

(D) 1.03

GATE-ME-2004

Hint

Question 6. The percentage of carbon in grey cast iron is in the range  of

(A) 0.25 to 0.75 percent

(B) 1.25 to 1.75 percent

(C) 3 to 4 percent

(D) 8 to 10 percent

GATE-ME-2004

Hint

Question 7. When the temperature of a solid metal increases.

(A) Strength of the metal decreases but ductility increases.

(B) Both strength and the ductility of the metal decreases.

(C) Both strength and the ductility of the metal increases.

(D) Strength of the metal increases but ductility decreases.

GATE-ME-2005

Hint

Question 8. Match the items in column I and II.

(A) P-4, Q-5, R-3, S-2

(B) P-3, Q-5, R-1, S-4

(C) P-2, Q-4, R-3, S-5

(D) P-4, Q-2, R-1, S-3

GATE-ME-2006

Hint

Question 9. The ultimate tensile strength of a material is 400 MPa and the elongation up to maximum load is 35%. If the material obeys power law of hardening, then the rue stress –true strain relation (stress in MPa) in the plastic deformation range is :

(A) 

(B) 

(C)

(D)

GATE-ME-2006

Hint

Question 10. The main purpose of spheroidising treatment is to improve

(A) Hardenability of low carbon steels

(B) Machinability of low carbon steels

(C) Hardenability of high carbon steels

 (D) Machinability of high carbon steels

GATE-ME-2006

Hint

Question 11. If a particular Fe-C alloy contains less than 0.83 % carbon, it is called

(A) High speed steel

(B) Hypoeutectoid steel

(C) Hypereutectoid steel

(D) Cast iron

GATE-ME-2006

Hint

Question 12. The effective number of lattice points in the unit cell of simple cubic, body centered cubic, and face centered cubic  space lattices, respectively are

(A) 1,2,2

(B) 1,2,4

(C) 2,3,4

(D) 2,4,4

GATE-ME-2009

Hint

Question 13. The material property which depends only on the basic crystal structure is

(A) Fatigue strength

(B) Work hardening

(C) Fracture strength

(D) Elastic constant

GATE-ME-2010

Hint

Question 14. The operation in which oil is permeated into the pores of a powder metallurgy product is known as

(A) Mixing

(B) Sintering

(C) Impregnation

(D)Infiltration

GATE-ME-2011

Hint

Question 15. The crystal structure of austenite is

(A) Body centered Cubic

(B) Face centered Cubic

(C) Hexagonal closed packed

(D) Body centered tetragonal

GATE-ME-2011

Hint

Answer Keys

The post Previous Years GATE Questions on Engineering Materials 2002-2011 appeared first on Engineering Tutorials.

Question 1. Spot welding of two 1 mm thick sheets of steel (density=8000 kg/) is carried out successfully by passing a certain amount of current for 0.1 second through the electrodes. The resultant weld nugget formed is 5 mm in diameter and 1.5 mm thick. If the latent heat of fusion of steel is 1400 kJ/kg and the effective resistance in the welding operation in 200Ω, the current passing through the electrodes is approximately

(A) 1480 A

(B) 3300 A

(C) 4060 A

(D) 9400 A

GATE-ME-2005

Hint

Question 2. The strength of a brazed joint

(A) Decrease with increase in gap between the two joining surfaces

(B) Increase with increase in gap between the two joining surfaces

(C) Decrease up to certain gap between the two joining surfaces beyond which it increases

(D) Increases up to certain gap between the two joining surfaces beyond which it decreases

GATE-ME-2005

Hint

Question 3. In an arc welding process, the voltage and current are 25 V and 300 A respectively. The arc heat transfer efficiency is 0.85 and welding speed is 8 mm/sec. The net heat input (in J/mm) is :

(A) 64

(B) 797

(C) 1103

(D) 79700

GATE-ME-2006

Hint

Question 4. Two metallic sheets, each of 2.0 mm thickness, are welded in a lap joint configuration by resistance spot welding at a welding current of 10 kA and welding time of 10 milli second. A spherical fusion zone extending up to the full thickness of each sheet is formed. The properties of the metallic sheets are given as:

Ambient temperature = 293 K

Melting temperature = 1793 K

Density =7000 kg/

Latent heat of fusion=300 kJ/kg

Specific heat =800 J/kg K

Assume : (i) contact resistance along sheet—sheet interface is 500 micro-ohm and along electrode—sheet interface is zero; (ii) no conductive heat loss through the bulk sheet materials; and (iii) the complete weld fusion zone is at the melting temperature.

(A) 50.37

(B) 60.37

(C) 70.37

(D) 80.37

GATE-ME-2007

Hint

Question 5. A direct current welding machine with a linear power source characteristic provides open circuit voltage of 80 V and short circuit current of 800 A. During welding the machine, the measured arc current is 500 A corresponding to an arc length of 5.0 mm and the measured arc current is 460 A corresponding to an arc length of 7.0 mm. the linear voltage (E)-arc length (L) characteristic of the welding arc can be given as (where E is in volt and L is in mm)

(A) E=20+2L

(B) E=20+8L

(C) E=80+2L

(D) E=80+8L

GATE-ME-2007

Hint

Question 6. Which one of the following is a solid state joining process?

(A) Gas tungsten arc welding

(B) Resistance spot welding

(C) Friction welding

(D) Submerged arc welding

GATE-ME-2007

Hint

Question 7. In arc welding of a butt joint, the welding speed is to be selected such that highest cooling rate is achieved. Melting efficiency and heat transfer efficiency are 0.5 and 0.7 respectively.the artea of the weld cross-section is  and the unit energy required to melt the metal is . If the welding power is 2 kW, the welding speed in mm/s is closest to

(A) 4

(B) 14

(C) 24

(D) 34

GATE-ME-2008

Hint

Question 8. Two pipes of inner diameter 100 mm and outer diameter 110 mm each are joined by flash welding using 30 V power supply. At the interface, 1 mm of material melts from each pipe which has a resistance of 42.4 Ω. If the unit melt energy is , then time required for welding (in s) is

(A) 1

(B) 5

(C) 10

(D) 20

GATE-ME-2010

Hint

Question 9. Which one of the following welding processes used non–consumable electrode?

(A) Gas metal arc welding

(B) Submerged arc welding

(C) Gas tungsten arc welding

(D) Flux coated arc welding

GATE-ME-2011

Hint

Question 10. Match the correct pairs.

(A) P—4,  Q—3,   R—1,   S—2

(B) P—4,  Q—2,   R—3,   S—1

(C) P—2,  Q—3,   R—4,   S—1

(D) P—2,  Q—4,   R—1,   S—3

GATE-ME-2011

Hint

Answer Keys

The post Previous Years GATE Questions on Joining Process 2005-2011 appeared first on Engineering Tutorials.

Question 1. Resistance spot welding is performed on two plates of 1.5 mm thickness with 6 mm diameter electrode, using 15000 A current for a time duration of 0.25 seconds. Assuming the interface resistance to be 0.0001Ω, the heat generated to form the weld is

(A) 5625 W-sec

(B) 8437 W-sec

(C) 22500 W-sec

(D) 33750 W-sec

GATE-ME-2001

Hint

Question 2. Two plates of the same metal having equal thickness are to be butt welded with the electric arc. When the plate thickness changes, welding is achieved by

(A) Adjusting the current

(B) Adjusting the duration of current

(C) Changing the electrode size

(D) Changing the electrode coating

GATE-ME-2001

Hint

Question 3. The temperature of a carburizing flame in gas welding is ……….. that of a neutral or an oxidizing flame.

(A) lower than

(B) higher than

(C) equal to

(D) unrelated to

GATE-ME-2002

Hint

Question 4. Which of the following arc welding processes does not use consumable electrodes?

(A) GMAW

(B) GTAW

(C) Submerged Arc Welding

(D) None of these

GATE-ME-2002

Hint

Question 5. Match the following

(A) P-2   Q-5   R-1   S-3

(B) P-6   Q-3   R-4   S-4

(C) P-4   Q-1   R-6   S-2

(D) P-5   Q-4   R-2   S-6

 GATE-ME-2003

Hint

Question 6. In oxyacetylene gas welding, temperature at the inner core of the flame is around

(A) 3500

(B) 3200 

(C) 2900 

(D) 2550 

GATE-ME-2003

Hint

Question 7. A soldering operation was work-sampled over two days (16 hours) during which an employee soldered 108 joints. Actual working time was 90 % of the total time and he performance rating was estimated to be 120 percent. If the contract provides allowance of 20 percent of the total time available, the standard time for the operation would be

(A) 8 min

(B) 8.9 min

(C) 10 min

(D) 12 min

GATE-ME-2004

Hint

Question 8. Two 1 mm thick steel sheets are to be spot welded with a current of 5000 A. Assuming effective resistance to be 200 micro-ohms and current flow time of 0.2 second, heat generated during the process will be

(A) 0.2 joule

(B) 1 joule

(C) 5 joule

(D) 1000 joules

GATE-ME-2004

Hint

Hint

The post Previous Years GATE Questions on Joining Process 2001-2004 appeared first on Engineering Tutorials.

Question 1. The force requirement in a blanking operation of low carbon steel sheet is 5.0 kN. The thickness of the sheet is ‘t’ and diameter of the blanked part is ‘d’. For the same work material, if the diameter of the blanked part is increased to 1.5 d and thickness is reduced to 0.4 t, the new blanking force in kN is

(A) 3.0

(B) 4.5

(C) 5.0

(D) 8.0

GATE-ME-2007

Hint

Question 2. Match the correct combination for following metal working processes.

(A) P-2,  Q-1,  R-3,  S-4

(B) P-3, Q-4,  R-1,  S-5

(C) P-5, Q-4, R-3, S-1

(D) P-3, Q-1, R-2, S-4

GATE-ME-2007

Hint

Question 3. The thickness of a metallic sheet is reduced from an initial value of 16 mm to a final value 10 mm in one single pass rolling with a pair of cylindrical rollers each of diameter 400 mm. The true strain is

(A) 5.936

(B) 7.936

(C) 8.936

(D) 9.936

GATE-ME-2007

Hint

Question 4. In open-die forging, a disc of diameter 200 mm and height 60 mm is compressed without any barreling effect. The final diameter of the disc is 400 mm. The true strain is

(A) 1.986

(B) 1.686

(C) 1.386

(D) 0.602

GATE-ME-2007

Hint

Question 5. In the deep drawing of cups, blanks show a tendency to wrinkle up around the periphery (flange).

The most likely cause and remedy  of the phenomenon are, respectively,

(A) Buckling due to circumferential compression; Increase blank holder pressure

(B) High blank holder pressure and high friction; Reduce blank holder pressure and apply lubricant

(C) High temperature causing increase in circumferential length; Applt coolant to blank

(D) Buckling due to circumferential compression; decrease blank holder pressure

GATE-ME-2008

Hint

Question 6. In a single pass rolling operation, a 20 mm thick plate width of 100 mm, is reduced to 18 mm. the roller radius is 250 mm and rotational speed is 10 rpm. The average flow stress for the plate material is 300 MPa. The power required for the rolling operation in kW is closest to

(A)15.2

(B) 18.2

(C) 30.4

(D) 45.6

GATE-ME-2008

Hint

Statement for linked Answer Questions 7 and 8:

In shear cutting operation, a sheet of 5mm thickness is cut along a length of 200 mm. the cutting blade is 400 mm (see figure) and zero –shear (S=0) is provided on the edge. The ultimate shear strength of the sheet is 100MPa and penetration to thickness ratio is 0.2. Neglect friction.

Question 7. Assume force vs displacement curve to be rectangular, work done (in J) is

(A) 100

(B) 200

(C) 250

(D) 300

GATE-ME-2010

Hint

Question 8. A shear of 20 mm (S=20 mm) is now provided on the blade. Assume force vs displacement curve to be trapezoidal, the maximum force (kN) exerted is

(A) 5

(B) 10

(C) 20

(D) 40

GATE-ME-2010

Hint

Question 9. The shear strength of a sheet metal is 300 MPa. The blanking force required to produce a blank of 100 mm diameter from a 1.5 mm thick sheet is close to

(A) 45 kN

(B) 70 kN

(C) 141 kN

(D) 3500 kN

GATE-ME-2011

Hint

Question 10. The maximum possible draft in cold rolling of sheet increases with the

(A) Increase in coefficient of friction

(B) Decrease in coefficient of friction

(C) Decrease in roll radius

(D) increase in roll velocity

GATE-ME-2011

Hint

Question 11. In a rolling process, the state of stress of the material undergoing deformation is

(A) Pure compression

(B) Pure shear

(C) Compression and shear

(D) Tension and shear

GATE-ME-2013

Hint

Answer Keys

The post Previous Years GATE Questions on Forming Process 2007-2013 appeared first on Engineering Tutorials.

Question 1. Match the following

 
(A) P—1  Q—4  R—6  S—3

(B) P—4  Q—5  R—2  S—3

(C) P—1  Q—5  R—3  S—2

(D) P—5  Q—1  R—2  S—2

GATE-ME-2004

Hint

Question 2. In a rolling process, sheet of 25 mm thickness is rolled to 20 mm thickness. Roll is of diameter 600 mm and it rotates at 100 rpm. The roll strip contact length will be

(A) 5 mm

(B) 39 mm

(C) 78 mm

(D) 120 mm

GATE-ME-2004

Hint

Question 3. Ten millimeter holes are to be punched in a steel sheet of 3mm thickness. Shear strength of the material is 400  and penetration is 40%. Shear provided on the punch is 2mm. The blanking force during the operation will be

(A) 22.6 kN

(B) 37.7 kN

(C) 61.6 kN

(D) 94.3 Kn

GATE-ME-2004

Hint

Question 4. A 2 mm thick metal sheet is to be bent at an angle of one radian with a bend of 100 mm. If the stretch factor is 0.5, the bend allowance is

(A) 99 mm

(B) 100 mm

(C) 101 mm

(D) 102 mm

GATE-ME-2005

Hint

Question 5. Match the items in columns I and II.

(A)  P-6  Q-3  R-1  S-2

(B) P-4  Q-5  R-6  S-1

(C) P-2  Q-5  R-3  S-4

(D) P-4  Q-3  R-1  S-2

GATE-ME-2006

Hint

Question 6. In a wire drawing operation, diameter of a steel wire is reduced from 10 mm to 8 mm. The mean flow stress of the material is 400 MPa. The ideal force required for drawing (ignoring friction and redundant work) is :

(A) 4.48 kN

(B) 8.97 kN

(C) 20.11 kN

(D) 31.41 kN

GATE-ME-2006

Hint

Question 7. A 4 mm thick sheet is rolled with 300 mm diameter rolls to reduce thickness without ant change in its width. The friction coefficient at the work-roll interface is 0.1. The minimum possible thickness of the sheet that can be produced that can be produced in a single pass is :

(A) 1.0 mm

(B) 1.5 mm

(C) 2.5 mm

(D) 3.7 mm

GATE-ME-2006

Hint

Answer Keys

The post Previous Years GATE Questions on Forming Process 2004-2006 appeared first on Engineering Tutorials.

Question 1. For rigid perfectly-plastic work material, negligible interface friction and no redundant work, the theoretically maximum possible reduction in the wire drawing operation is

(A) 0.36

(B) 0.63

(C) 1.00

(D) 2.72

GATE-ME-2001

Hint

Question 2. The cutting force in punching and blanking operations mainly depends on

(A) the modulus of elasticity of metal

(B) the shear strength of metal

(C) the bulk modulus of metal

(D) the yield strength of metal

GATE-ME-2001

Hint

Question 3. In blanking operation, the clearance is provided on

(A) the die

(B) both the die and punch equally

(C) the punch

(D) neither the punch nor the die

GATE-ME-2002

Hint

Question 4. Hot rolling of mild steel is carried out

(A) at recrystallization temperature

(B) between 100 to 150

(C) below recrystallization temperature

(D) above recrystallization temperature

GATE-ME-2002

Hint

Question 5. A metal disc of 20 mm diameter is to be punched from a sheet of 2mm thickness. The punch and the die clearance is 3%. The required punch diameter is

(A) 19.88 mm

(B) 19.44 mm

(C) 20.06 mm

(D) 20.12 mm

GATE-ME-2003

Hint

Question 6. A brass billet is to be extruded from its initial diameter of 100 mm to a final diameter of 50 mm. The working temperature of 700 and the extrusion constant is 250 MPa. The force required for extrusion is

(A) 5.44 MN

(B) 2.72 MN

(C) 1.36 MN

(D) 0.36 MN

GATE-ME-2003

Hint

Question 7. A shell of 100 mm diameter and 100 mm height with the corner radius of 0.4 mm is to be produced by cup drawing. The required blank diameter is

(A) 118 mm

(B) 161 mm

(C) 224 mm

(D) 312 mm

GATE-ME-2003

Hint

Question 8. Cold working of steel is defined as working

(A) At its recrystallization temperature

(B) Above its recrystallization temperature

(C) Below its recrystallization temperature

(D) At two third of the melting temperature of the metal

GATE-ME-2003

Hint

Answer Keys

The post Previous Years GATE Questions on Forming Process 2001-2003 appeared first on Engineering Tutorials.

Question 1. A 200 mm long down sprue has an area of cross—section of 650  where the pouring basin meets the down sprue (i.e. at the beginning of the down sprue). A constant head of molten metal is maintained by the pouring basin. The molten metal flow rate is 6.5 . Considering the end of the down sprue to be open to atmosphere and an acceleration due to gravity of , the area of the down sprue in  at its end (avoiding aspiration effect) should be

(A) 650.0

(B) 350.0

(C) 290.7

(D) 190.0

GATE-ME-2007

Hint

Question 2. Volume of a cube of side ‘l’ and volume of a sphere of radius ‘r’ are equal. Both the cube and the sphere are solid and of same material. They are big cast. The ratio of the solidification time of the cube to the same of the sphere is

(A) 

(B) 

(C) 

(D)  

GATE-ME-2007

Hint

Question 3. Which of the following engineering materials is the most suitable material for the chamber die casting?

(A) Low carbon steel

(B) Titanium

(C) Copper

(D) Tin

GATE-ME-2007

Hint

Question 4. While cooling, a cubical casting of side 40 mm undergoes 3%, 4% and 5% volume shrinkage during the liquid state, phase transition and solid state, respectively. The volume of the metal compensated from the riser is

(A) 2 %

(B) 7 %

(C) 8 %

(D) 9%

GATE-ME-2008

Hint

Question 5. Match the items in Column I and Column II.

(A) P—1  Q—3  R—2  S—4

(B)  P—1  Q—4  R—2  S—3

(C) P—3  Q—4  R—2  S—1

(D) P—4  Q—1  R—2  S—3

GATE-ME-2009

Hint

Question 6. Two streams of liquid metal which are not hot enough to fuse properly result into a casting defect known as

(A) Cold shut

(B) Swell

(C)Sand wash

(D) Scab

GATE-ME-2009

Hint

Question 7. In gating system, the ratio 1:2:4 reprsents

(A) Sprue base area : runner area : ingate area

(B) Pouring basin area : ingate area : runner area

(C) Pouring basin area : ingate area : Casting area

(D) Runner area : ingate area : Casting area

GATE-ME-2010

Hint

Question 8. A cubic casting of 50 mm side undergoes volumetric solidification shrinkage and volumetric solid contraction of 4% and 6% respectively. No riser is used. Assumed uniform cooling in all directions. The side of the cube after solidification and contraction is

(A) 48.32 mm

(B) 49.90 mm

(C) 49.94 mm

(D) 49.96 mm

GATE-ME-2011

Hint

Question 9. Green sand mould indicates that

(A) Polymeric mould has been cured

(B) Mould has been totally dried

(C) Mould is green in colour

(D) Mould contains moisture

GATE-ME-2011

Hint

Question 10. A cube shaped casting solidifies in 5 min. The solidification time in min for a cube of the same material, which is 8 times heavier than the original casting, will be

(A) 10

(B) 20

(C) 24

(D) 40

GATE-ME-2013

Hint

Answer Keys

The post Previous Years Gate Questions on Casting 2007-2013 appeared first on Engineering Tutorials.

Solved Gate Questions on Casting

Question 1. The height of the down-sprue is 175 mm and its cross-sectional area at the base is . The cross sectional area of the horizontal runner is . Assuming no losses, indicate the correct choice for the time (in seconds) required to fill a mould cavity of volume .

(A) 2.67

(B) 8.45

(C) 26.72

(D) 84.50

GATE-ME-2001

Hint

Question 2. Shrinkage allowance on pattern is provided to compensate for shrinkage when

(A) The temperature of liquid metal drops from pouring to freezing temperature

(B) The metal changes from liquid to solid state at freezing temperature

(C) The temperature of the solid phase drops from freezing to room temperature

(D) The temperature of the metal drops from pouring to room temperature

GATE-ME-2001

Hint

Question 3. In centrifugal casting, the impurities are

(A) Uniformly distributed

(B) Forced towards the outer surface

(C) Trapped near the mean radius of the casting

(D) Collected at the centre of the casting.

GATE-ME-2002

Hint

Question 4. The primary of a sprue in a casting mould is to

(A) Feed the casting at a rate consistent with the rate of solidification

(B) Act as a reservoir for molten metal

(C) Feed molten metal from the pouring basin to the gate

(D) Help feed the casting until all solidification takes place

GATE-ME-2002

Hint

Question 5. With a solidification factor of , the solidification time (in seconds) for a spherical casting of 200 mm diameter is

(A) 539

(B) 1078

(C) 4311

(D) 3233

GATE-ME-2003

Hint

Question 6. Hardness of green sand mould increases with

(A) Increase in moisture content beyond 6 percent

(B) Increase in permeability

(C) Decrease in permeability

(D) Increase in both moisture content and permeability

GATE-ME-2003

Hint

Question 7. Misrun is a casting defect which occurs due to

(A) Very high pouring temperature of the metal

(B) Insufficient fluidity of the molten metal

(C) Absorption of the gases by the liquid metal

(D) Improper alignment of the mould flasks

GATE-ME-2004

Hint

Question 8. A mould has a down sprue whose length is 20 cm and the cross sectional area at the base of the down sprue is 1 . The down sprue feeds a horizontal runner leading into the mould cavity of volume 1000 . The time required to fill the mould cavity will be

GATE-ME-2005

(A) 4.05 s

(B) 5.05 s

(C) 6.05 s

(D) 7.25 s


Hint

Question 9.  Match  the items of List I (Equipment) with the items of List II (Process)and select the correct answer using the given codes.

(A) P–2  Q–1  R–4  S–5

(B) P–4  Q–2  R–3  S–5

(C) P–4  Q–5  R–1  S–2

(D) P–3  Q–5  R–2  S–1

GATE-ME-2005

Hint

Question 10. In a sand casting operation, the total liquid head is maintained constant such that it is equal to the mould height. The time taken to fill the mould with a top gate is . If the same mould is filled with a bottom gate, then the time taken is . Ignore the time required to fill the runner and frictional effects. Assume atmospheric pressure at the top molten metal surfaces. The relation between  is :

(A) 

(B) 

(C) 

(D) 

GATE-ME-2006

Hint

Question 11. An expandable pattern is used in

(A) Slush casting

(B) Squeeze casting

(C) Centrifugal casting

(D) Investment Casting

GATE-ME-2006

Hint

Answer Keys

The post Previous Years Gate Questions on Casting 2001-2006 appeared first on Engineering Tutorials.

Question 1. For the circular tube of equal length and diameter shown below, the view factor  is 0.17. The view factor  in this case will be

(A) 0.17

(B) 0.21

(C) 0.79

(D) 0.83

GATE-ME-2001

Hint

Question 2. What is the value of the view factor for two inclined flat plates having common edge of equal width, and with an angle of 20 degrees?

(A) 0.83

(B) 1.17

(C) 0.66

(D) 1.34

GATE-ME-2002

Hint

Question 3. A plate having 10  area each side is hanging in the middle of a room of 100  total surface area. The plate temperature and emissivity are respectively 800 K and 0.6. The temperature and emissivity values for the surfaces of the room are 300 K and 0.3 respectively. Boltzmann’s constant . The total heat loss from the two surfaces of the plate is

(A) 13.66 W

(B) 27.32 W

(C) 27.87 W

(D) 13.66 MW

GATE-ME-2003

Hint

Question 4. A solar collector receiving solar radiation at the rate of 0.6 transforms it to the internal energy of a fluid at an overall efficiency of 50 %. The fluid heated to 350 K is used to run a heat engine which rejects heat at 313 K. if the heat engine is to deliver 2.5 kW power, then minimum area of the solar collector required would be

(A) 8.33 

(B) 16.66

(C) 39.68 

(D) 79.36 

GATE-ME-2004

Hint

Question 5. A solid cylinder (surface 2) is located at the centre of a hollow sphere (surface 1). The diameter of the sphere is 1 m, while the cylinder has a diameter and length of 0.5 m each.

The radiation configuration factor  is

(A) 0.375

(B) 0.625

(C) 0.75

(D) 1

GATE-ME-2005

Hint

Question 6. The following figure was generated from experimental data relating spectral black body emissive power to wave length at three temperatures .

The conclusion is that the measurements are

(A) Correct because the maxima in  show the correct trend.

(B) Correct because Planck’s law is satisfied.

(C) Wrong because the Stefan Boltzman law is not satisfied.

(D) Wrong because Wien’s displacement law is not satisfied

GATE-ME-2005

Hint

Question 7. A hollow enclosure is formed between two infinitely long concentric cylinders of radii 1m and 2m, respectively. Radiative heat exchange takes place between the inner surface of the larger cylinder (surface-2) and the outer surface of the smaller cylinder (surface-1). The radiating surfaces are diffuse and the medium in the enclosure is non-participating. The fraction of the thermal radiation leaving the larger surface and striking itself is

(A) 0.25

(B) 0.5

(C) 0.75

(D) 1

GATE-ME-2008

Hint

Common data  Question 8 and 9

Radiative  heat transfer is intended between the inner surfaces of two very small isothermal parallel metal plates. While the upper plate (designated as plate 1) is a black surface and the warmer on being maintained at 727, the lower plate (plate 2) is a diffuse and gray surface with an emissivity of 0.7 and is kept at 227 . Assume that the surface are sufficiently large to form surface enclosure and steady state conditions to exist. Stefan Boltzmann constant is given as 5.67.

Question 8. The irradiation () for the upper plate (plate 1) is

(A) 2.5

(B) 3.6

(C) 17.0

(D) 19.5

GATE-ME-2009

Hint

Question 9. If plate 1 is also a diffuse and gray surface with an emissivity value of 0.8, the net radiation heat exchange () between plate 1 and plate 2 is

(A) 17.0

(B) 19.5

(C) 23.0

(D) 31.7

GATE-ME-2009

Hint

Question 10. For an opaque surface, the absorptivity () transmissivity () and reflectivity () are related by the equation:

(A) 

(B) 

(C) 

(D) 

GATE-ME-2012

Hint

Question 11. Two large diffuse gray parallel plates separated by a small distance, have surface temperature of 400 K and 300 K. If the emissivities of the surfaces are 0.8 and the Stefan-Boltzmann constant is 5.67, the net radiation heat exchange rate in  between the two plates is

(A) 0.66

(B) 0.79

(C) 0.99

(D) 3.96

GATE-ME-2013

Hint

Answer Keys

The post Previous Years GATE Questions on Radiation appeared first on Engineering Tutorials.

Question 1. For the same inlet and outlet temperatures of hot and cold fluids, the Log Mean Temperature Difference (LMTD) is

(A) Greater for parallel flow heat exchanger than for counter flow heat exchanger.

(B) Greater for counter flow heat exchanger than for parallel flow heat exchanger.

(C) Same for both parallel and counter flow heat exchangers.

(D) Depends on the properties of fluid.

GATE-ME-2002

Hint

Question 2. In a counter flow heat exchanger, for the hot fluid the heat capacity , mass flow rate , inlet temperature , outlet temperature is 100. For the cold fluid, heat capacity , mass flow rate , inlet temperature . Neglecting heat transfer to the surroundings, the outlet temperature of the cold fluid in 0. is

(A) 7.5

(B) 32.5

(C) 45.5

(D) 70.0

GATE-ME-2003

Hint

Question 3. Hot oil is cooled from 80 to 50.in an oil cooler which uses air as the coolant. The air temperature rises from 30. To 40. The designer uses a LMTD value of 26. The type of heat exchanger is

(A) Parallel flow

(B) Double pipe

(C) Counter flow

(D) Cross flow

GATE-ME-2005

Hint

Question 4. In a counter flow heat exchanger, hot fluid enters at 60. And cold fluid leaves at 30. Mass flow rate of the fluid is 1 kg/s and that of the cold fluid is 5 kJ/kg K. The Log Mean Temperature Difference (LMTD) for the heat exchanger in  is

(A) 15

(B) 30

(C) 35

(D) 45

GATE-ME-2007

Hint

Question 5. The logarithmic mean temperature difference (LMTD) of a counter flow heat exchanger is 20. The cold fluid enters at 20 and the hot fluid enters at 100. Mass flow rate of the cold fluid is twice that of hot fluid. Specific heat at constant pressure of the hot fluid is twice that of hot fluid. Specific heat at constant pressure of the hot fluid is twice that of cold fluid. The exit temperature of the cold fluid

(A) is 40

(B) is 60

(C) is 80

(D) cannot be determined

GATE-ME-2008

Hint

Question 6. In a parallel flow heat exchanger operating under steady state, the heat capacity rates (product of specific heat at constant pressure and mass flow rate) of the hot and cold fluid are equal. The hot fluid, flowing at 1 kg/s with , enters the heat exchanger at 102, while the cold fluid has an inlet temperature of 15. The overall heat transfer coefficient for the heat exchanger is estimated to be and the corresponding heat transfer surface area is 5 .Neglect heat transfer between the heat exchanger and the ambient. The heat exchanger is characterized by the following relation:

The exit temperature (in ) for the cold fluid is

(A) 45

(B) 55

(C) 65

(D) 75

GATE-ME-2009

Hint

Question 7. In a condenser of a power plant, the steam condenser is at a temperature of 60. The cooling water enters at 30 and leaves at 45. The logarithmic mean temperature difference (LMTD) of the condenser is

(A) 16.2

(B) 21.6

(C) 30

(D) 37.5

GATE-ME-2011

Hint

Answer Keys

The post Previous Years GATE Questions on Heat Exchanger appeared first on Engineering Tutorials.