153 + Mcqs in Heat Transfer (HT) Page 1 McqOptions

1.	Thermal conductivity of non-metallic amorphous solids with decrease in temperature
A.	increases
B.	decreases
C.	remains constant
D.	may increase or decrease depending on temperature
E.	unpredictable.
Answer» C. remains constant

Discussion

2.	When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by
A.	conduction
B.	convection
C.	radiation
D.	conduction and convection
E.	convection and radiation.
Answer» B. convection

Discussion

3.	When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by
A.	conduction
B.	convection
C.	radiation
D.	conduction and convection
E.	convection and radiation.
Answer» D. conduction and convection

Discussion

4.	When heat is Transferred by molecular collision, it is referred to as heat transfer by
A.	conduction
B.	convection
C.	radiation
D.	scattering
E.	convection and radiation.
Answer» C. radiation

Discussion

5.	Pick up the wrong case. Heat flowing from one side to other depends directly on
A.	face area
B.	time
C.	thickness
D.	temperature difference
E.	thermal conductivity.
Answer» D. temperature difference

Discussion

6.	Thermal conductivity of air at room temperature in kcal/m hr C is of the order of
A.	0.002
B.	0.02
C.	0.01
D.	0.1
E.	0.5.
Answer» C. 0.01

Discussion

7.	Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is
A.	IR
B.	I2R
C.	IR2
D.	I2R2
Answer» C. IR2

Discussion

8.	For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are
A.	Same
B.	Different
C.	Never different
D.	Linearly related
Answer» C. Never different

Discussion

9.	In case of surface condensers, a straight line is obtained on plotting 1/U vs. __________ on an ordinary graph paper.
A.	1/V -0.8
B.	V -0.8
C.	V -2
D.	1/ V -2
Answer» B. V -0.8

Discussion

10.	When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids?
A.	At high fluid velocity
B.	At low velocity
C.	When fluid flows past a smooth surface
D.	None of these
Answer» B. At low velocity

Discussion

11.	For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is
A.	Nu = 0.023 Re0.8. Pr0.4
B.	Nu = ( /2) Gz
C.	Nu = (2/ ) Gz
D.	Nu = 2Gz0.5
Answer» D. Nu = 2Gz0.5

Discussion

12.	For hot feed, forward feeding as compared to backward feeding results in __________ economy.
A.	Increased
B.	Decreased
C.	No effect on
D.	None of these
Answer» B. Decreased

Discussion

13.	Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling?
A.	Square pitch
B.	Triangular pitch
C.	Diagonal square pitch
D.	None of these
Answer» C. Diagonal square pitch

Discussion

14.	A multiple effect evaporator as compared to a single effect evaporator of the same capacity has
A.	Lower heat transfer area
B.	Lower steam economy
C.	Higher steam economy
D.	Higher solute concentration in the product
Answer» D. Higher solute concentration in the product

Discussion

15.	Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?
A.	Corrosiveness
B.	Fouling characteristic
C.	Viscosity
D.	None of these
Answer» E.

Discussion

16.	In a shell and tube heat exchanger, the shell side fluid velocity can t be changed by changing the
A.	Tube layout
B.	Tube diameter
C.	Tube pitch
D.	Number of baffles
Answer» C. Tube pitch

Discussion

17.	The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.
A.	Greater than
B.	Lower than
C.	Is same as
D.	Half
Answer» C. Is same as

Discussion

18.	Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?
A.	Corrosiveness & fouling characteristics
B.	Pressure
C.	Viscosity
D.	Density
Answer» E.

Discussion

19.	In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.
A.	Increases
B.	Decreases
C.	Remain constant
D.	May increase or decrease, depends on the vacuum
Answer» B. Decreases

Discussion

20.	A body cools down from 75 C to 70 C in 10 minutes. It will cool down from 70 C to 65 C in __________ minutes.
A.	10
B.	> 10
C.	< 10
D.	Either (B) or (C), depends on the mass of the body
Answer» C. < 10

Discussion

21.	Heat flux through several resistances in series in analogous to the current flowing through several
A.	Resistances in parallel
B.	Capacitors in series
C.	Resistances in series
D.	None of these
Answer» D. None of these

Discussion

22.	Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the
A.	Maximum resistance in the series
B.	Sum of all resistances
C.	Average of all resistances
D.	Minimum resistance presents in the series
Answer» C. Average of all resistances

Discussion

23.	Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.
A.	No
B.	The least
C.	The largest
D.	Lower
Answer» D. Lower

Discussion

24.	Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)
A.	x/KA
B.	KA/x
C.	K/Ax
D.	A/Kx
Answer» C. K/Ax

Discussion

25.	The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is
A.	2.36
B.	4.36
C.	120.36
D.	Dependent on NRe only
Answer» C. 120.36

Discussion

26.	The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.
A.	Average
B.	Geometric mean
C.	Product
D.	Sum
Answer» E.

Discussion

27.	The driving potential for the crystal growth during crystallisation is the __________ of the solution.
A.	Concentration
B.	Viscosity
C.	Super-saturation
D.	Density
Answer» D. Density

Discussion

28.	For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)
A.	NPr
B.	NPr 1/3
C.	NPr -1
D.	NPr -1/3
Answer» C. NPr -1

Discussion

29.	A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides
A.	Higher economy
B.	Lower capacity
C.	Both (A) & (B)
D.	Lower economy
Answer» B. Lower capacity

Discussion

30.	For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in
A.	Increased economy
B.	Decreased economy
C.	Lower capacity
D.	No effect on economy
Answer» B. Decreased economy

Discussion

31.	A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
A.	Condensation
B.	Grashoff
C.	Stanton
D.	Brinkman
Answer» E.

Discussion

32.	Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?
A.	Thickness of the wall
B.	Area of the wall perpendicular to heat flow
C.	Material of the wall
D.	Temperature difference between the two surfaces of the wall
Answer» E.

Discussion

33.	Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?
A.	Dittus-Boelter equation
B.	Sieder-Tate equation
C.	Nusselt equation
D.	None of these
Answer» C. Nusselt equation

Discussion

34.	Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?
A.	Long vertical evaporator
B.	Horizontal tube evaporator
C.	Agitated film evaporator
D.	Calandria vertical tube evaporator
Answer» D. Calandria vertical tube evaporator

Discussion

35.	Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.
A.	Boiling point
B.	Dynamic viscosity
C.	Kinematic viscosity
D.	Density
Answer» B. Dynamic viscosity

Discussion

36.	Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively).
A.	C/E
B.	E/C
C.	CE
D.	1/CE
Answer» B. E/C

Discussion

37.	Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger?
A.	Tube side pressure drop and the heat transfer rate
B.	Convective heat transfer co-efficient
C.	Effective tube surface area for convective heat transfer
D.	All (A) (B) and (C)
Answer» E.

Discussion

38.	For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area
A.	Increases
B.	Decreases
C.	Remain constant
D.	Passes through a maxima
Answer» E.

Discussion

39.	A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95 C is available for heating purpose, also at a rate of 10 Kg.s-1 . A 1 - 1 shell and tube heat exchanger is available. The best arrangement is
A.	Counter flow with process stream on shell side
B.	Counter flow with process stream on tube side
C.	Parallel flow with process stream on shell side
D.	Parallel flow with process stream on tube side
Answer» B. Counter flow with process stream on tube side

Discussion

40.	For turbulent flow in a tube, the heat transfer co-efficient is obtained from the DittusBoelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of
A.	1
B.	1.74
C.	6.1
D.	37
Answer» D. 37

Discussion

41.	In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is
A.	Infinity
B.	Zero
C.	Same as average heat transfer co-efficient for tube side
D.	None of these
Answer» B. Zero

Discussion

42.	In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always
A.	< 1
B.	> 1
C.	1
D.
Answer» B. > 1

Discussion

43.	To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is
A.	1-2 heat exchanger
B.	1-1 heat exchanger
C.	3-2 heat exchanger
D.	2-4 heat exchanger
Answer» C. 3-2 heat exchanger

Discussion

44.	Log mean temperature difference in case of counter flow compared to parallel flow will be
A.	same
B.	more
C.	less
D.	depends on other factors
E.	none of the above.
Answer» C. less

Discussion

45.	If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will
A.	Increase by 1.8 times
B.	Decrease by 22
C.	Increase by 216
D.	Remain unchanged
Answer» D. Remain unchanged

Discussion

46.	The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
A.	t
B.	1/t
C.	t
D.	Independent of 't'
Answer» C. t

Discussion

47.	The film thickness for laminar film condensation on vertical surface __________ from top to bottom.
A.	Cumulatively increases
B.	Cumulatively decreases
C.	Remain constant
D.	And the surface conductance increase
Answer» B. Cumulatively decreases

Discussion

48.	The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are
A.	Re.Gz
B.	Nu, Pr
C.	Nu, Pr, Re
D.	Nu, Gz
Answer» E.

Discussion

49.	In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is
A.
B.	0
C.	Equal to the difference between hot and cold fluids inlet temperature
D.	Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature
Answer» C. Equal to the difference between hot and cold fluids inlet temperature

Discussion

50.	Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be
A.	0.35
B.	0.45
C.	0.55
D.	0.85
Answer» C. 0.55

Discussion

Explore topic-wise MCQs in Mechanical Engineering.

Thermal conductivity of non-metallic amorphous solids with decrease in temperature

When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by

When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

When heat is Transferred by molecular collision, it is referred to as heat transfer by

Pick up the wrong case. Heat flowing from one side to other depends directly on

Thermal conductivity of air at room temperature in kcal/m hr C is of the order of

Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is

For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are

In case of surface condensers, a straight line is obtained on plotting 1/U vs. __________ on an ordinary graph paper.

When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids?

For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is

For hot feed, forward feeding as compared to backward feeding results in __________ economy.

Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling?

A multiple effect evaporator as compared to a single effect evaporator of the same capacity has

Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?

In a shell and tube heat exchanger, the shell side fluid velocity can t be changed by changing the

The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.

Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?

In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator.

A body cools down from 75 C to 70 C in 10 minutes. It will cool down from 70 C to 65 C in __________ minutes.

Heat flux through several resistances in series in analogous to the current flowing through several

Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the

Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.

Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)

The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is

The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.

The driving potential for the crystal growth during crystallisation is the __________ of the solution.

For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides

For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in

A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.

Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?

Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?

Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?

Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.

Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively).

Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger?

For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area

A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95 C is available for heating purpose, also at a rate of 10 Kg.s-1 . A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

For turbulent flow in a tube, the heat transfer co-efficient is obtained from the DittusBoelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of

In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is

In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always

To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is

Log mean temperature difference in case of counter flow compared to parallel flow will be

If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will

The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)

The film thickness for laminar film condensation on vertical surface __________ from top to bottom.

The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are

In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is

Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be