The thickness of condensate layer in filmwise condensation depends on the__________________?

Liquid flow rate from the surface

The thermal boundary layer at NPr > 1 ?

And the hydrodynamic boundary layers are identical

Is thicker than hydrodynamic boundary layer

Is thinner than hydrodynamic boundary layer

And the hydrodynamic boundary layers are identical

The steam ejector is used to__________________?

Remove condensate from the steam pipelines

The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti – T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?

q = [2π k (Ti + T0)/2]/ln (ri/r0)

q = 2π ri k (Ti – T0)/(r0/ri)

q = 2π k (Ti – T0)/[(r0 + ri)/2]

The rate of emission of radiation by a body does not depend upon the__________________?

Surface temperature of the body

The purpose of providing expansion bellows in the shell of tubular exchanger is to _____________________?

Facilitate increase of shell length, if needed

Account for the uneven expansion of shell and tube bundles

Facilitate increase of shell length, if needed

The purpose of providing bleed points in the evaporator is to__________________?

Facilitate removal of non-condensable gases

The main purpose of providing fins on heat transfer surface is to increase the_________________?

Mechanical strength of the equipment

The main function of baffles provided in a shell and tube heat exchanger is to______________?

Facilitate the cleaning of outer tube surface

The interchange factor for radiation heat transfer from surface ‘x’ to surface ‘y’ in case of an infinite parallel planes with emissivities εx & εy is given by_______________?

(εx + εy)/( εx + εy – εx . εy)

The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________________?

Giving the surface a mirror finish

Painting the surface white (with aluminium paint)

Giving the surface a mirror finish

The Graetz number is concerned with the___________________

Mass transfer between a gas and a liquid

Absorption with chemical reaction

Heat transfer in turbulent flow

The film thickness for laminar film condensation on vertical surface _____________ from top to bottom?

And the surface conductance increase

The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?

Either more or less; depends on the nature of vapor

The film co-efficient between condensing vapour and metal wall increases with _____________________?

Decreasing temperature of the vapour

Increasing temperature of the vapour

Decreasing temperature of the vapour

Increasing viscosity of the film of condensate

425 + Mcqs in Chemical Heat Transfer in Chemical Engineering Page 2 McqOptions

51.	The unit of conductance in SI unit is_______________?
A.	W/m
B.	W/m2
C.	W/°K
D.	W/m°K
Answer» D. W/m°K

Discussion

52.	The type of liquor circulation system to be ‘ employed in evaporators (viz. natural or forced circulation) is determined mainly by the ______________ of the liquid?
A.	Viscosity
B.	Density
C.	Thermal conductivity
D.	Corrosive nature
Answer» B. Density

Discussion

53.	The thickness of condensate layer in filmwise condensation depends on the__________________?
A.	Condensation rate
B.	Surface configuration
C.	Liquid flow rate from the surface
D.	All A., B. and C.
Answer» E.

Discussion

54.	The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4) ?
A.	1000
B.	727
C.	800
D.	1200
Answer» B. 727

Discussion

55.	The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of ‘n’ is exactly 4 for__________________?
A.	Black painted bodies only
B.	All bodies
C.	Polished bodies only
D.	A black body
Answer» C. Polished bodies only

Discussion

56.	The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are _______________?
A.	(COP)R = (COP)HP = 0.6
B.	(COP)R = 2.5; (COP)HP = 1.5
C.	(COP)R = 1.5; (COP)HP = 2.5
D.	(COP)R = (COP)HP = 2.5
Answer» D. (COP)R = (COP)HP = 2.5

Discussion

57.	The thermal boundary layer at NPr > 1 ?
A.	Is thicker than hydrodynamic boundary layer
B.	Is thinner than hydrodynamic boundary layer
C.	And the hydrodynamic boundary layers are identical
D.	Disappears
Answer» C. And the hydrodynamic boundary layers are identical

Discussion

58.	The sum of reflectivity and absorptivity for an opaque body is equal to____________________?
A.	0.5
B.	1
C.	0
D.	2
Answer» C. 0

Discussion

59.	The Stefan-Boltzmann constant depends on the_________________?
A.	Medium
B.	Temperature
C.	Surface
D.	None of these
Answer» E.

Discussion

60.	The steam ejector is used to__________________?
A.	Remove condensate from the steam pipelines
B.	Create vacuum
C.	Superheat the steam
D.	None of these
Answer» C. Superheat the steam

Discussion

61.	The statement that “maximum wavelength of radiation is inversely proportional to the temperature” is ______________ law?
A.	Stefan-Boltzmann’s
B.	Planck’s
C.	Wien’s displacement
D.	None of these
Answer» D. None of these

Discussion

62.	The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?
A.	D-1.8
B.	D-0.2
C.	D0.2
D.	D1.8
Answer» C. D0.2

Discussion

63.	The separation of liquid droplets from the vapor is done by a/an _____________ in the evaporators?
A.	Steam ejector
B.	Entrainment separator
C.	Compressor
D.	Vacuum pump
Answer» C. Compressor

Discussion

64.	The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is ________________?
A.	2
B.	1/2
C.	4
D.	1/4
Answer» E.

Discussion

65.	The ratio of total radiating power to the absorptivity of the body depends upon the _____________ as per Kirchoff‟s law?
A.	Wavelength of radiation
B.	Nature of the body
C.	Temperature of the body
D.	None of these
Answer» D. None of these

Discussion

66.	“The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is ______________ law?
A.	Kirchoff’s
B.	Planck’s
C.	Wien’s displacement
D.	Stefan-Boltzmann
Answer» B. Planck’s

Discussion

67.	The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?
A.	Prandtl
B.	Nusselt
C.	Stanton
D.	Grashoff
Answer» B. Nusselt

Discussion

68.	The ratio of kinematic viscosity to thermal diffusivity is called the _______________ number?
A.	Peclet
B.	Prandtl
C.	Stanton
D.	Nusselt
Answer» C. Stanton

Discussion

69.	The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the___________________?
A.	Heating volume
B.	Heat transfer area
C.	Nusselt number
D.	None of these
Answer» C. Nusselt number

Discussion

70.	The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti – T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?
A.	q = [2π k (Ti + T0)/2]/ln (ri/r0)
B.	q = 2π ri k (Ti – T0)/(r0/ri)
C.	q = 2π k (Ti – T0)/(r0/ri)
D.	q = 2π k (Ti – T0)/[(r0 + ri)/2]
Answer» E.

Discussion

71.	The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as______________?
A.	(ΔT)1/4
B.	(ΔT)1/2
C.	(ΔT)5/4
D.	(ΔT)3/4
Answer» E.

Discussion

72.	The rate of emission of radiation by a body does not depend upon the__________________?
A.	Wavelength of radiation
B.	Surface temperature of the body
C.	Nature of the surface
D.	Shape and porosity of the body
Answer» E.

Discussion

73.	The range of electromagnetic spectrum important in heat transfer by radiation is ______________ microns?
A.	0.38-0.78
B.	0.5-50
C.	100-1000
D.	5-50
Answer» C. 100-1000

Discussion

74.	The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?
A.	11.2 kW/m2
B.	12.0 kW/m2
C.	14.6 kW/m2
D.	16.5 kW/m2
Answer» E.

Discussion

75.	The purpose of providing expansion bellows in the shell of tubular exchanger is to _____________________?
A.	Increase the heating load
B.	Impart structural strength
C.	Account for the uneven expansion of shell and tube bundles
D.	Facilitate increase of shell length, if needed
Answer» D. Facilitate increase of shell length, if needed

Discussion

76.	The purpose of providing bleed points in the evaporator is to__________________?
A.	Admit the feed
B.	Remove the product
C.	Facilitate removal of non-condensable gases
D.	Create vacuum
Answer» D. Create vacuum

Discussion

77.	The purpose of providing a ‘catchall’ in the vapor line of an evaporator is to__________________?
A.	Create vacuum
B.	Regulate the vapor flow
C.	Vent the non-condensable gases
D.	Arrest the entrained liquid
Answer» E.

Discussion

78.	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

79.	The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is _____________________?
A.	1200 W/m2.K
B.	894 W/m2.K
C.	333 W/m2.K
D.	287 W/m2.K
Answer» D. 287 W/m2.K

Discussion

80.	The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is______________?
A.	1.66
B.	88.66
C.	3.66
D.	Dependent on NRe only
Answer» D. Dependent on NRe only

Discussion

81.	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

82.	The number of kg vaporised per kg of steam fed to the evaporator is defined as____________?
A.	Capacity
B.	Rate of evaporation
C.	Economy
D.	Rate of vaporisation
Answer» D. Rate of vaporisation

Discussion

83.	The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?
A.	Heat flux
B.	Nusselt number
C.	Prandtl number
D.	Schmidt number
Answer» B. Nusselt number

Discussion

84.	The most conducive surface for dropwise condensation to occur is the _____________ surface?
A.	Coated
B.	Oily
C.	Glazed & polished
D.	Smooth
Answer» C. Glazed & polished

Discussion

85.	The maximum heat transfer co-efficient from steam heating will be attained when the steam is_________________?
A.	Supersaturated
B.	Saturated
C.	Wet
D.	None of these
Answer» C. Wet

Discussion

86.	The main purpose of providing fins on heat transfer surface is to increase the_________________?
A.	Temperature gradient
B.	Mechanical strength of the equipment
C.	Heat transfer area
D.	Heat transfer co-efficient
Answer» D. Heat transfer co-efficient

Discussion

87.	The main function of baffles provided in a shell and tube heat exchanger is to______________?
A.	Facilitate the cleaning of outer tube surface
B.	Enhance turbulence
C.	Hold the tubes in position
D.	All A , B & C
Answer» C. Hold the tubes in position

Discussion

88.	The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in °C is____________________?
A.	77.2
B.	71.2
C.	63.8
D.	48.7
Answer» E.

Discussion

89.	The interchange factor for radiation heat transfer from surface ‘x’ to surface ‘y’ in case of an infinite parallel planes with emissivities εx & εy is given by_______________?
A.	εx + εy
B.	εx . εy
C.	1/εx + 1/εy
D.	(εx + εy)/( εx + εy – εx . εy)
Answer» E.

Discussion

90.	The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by ______________ times, when the number of tube passes is increased to 8?
A.	20.8
B.	40.8
C.	40.4
D.	20.4
Answer» C. 40.4

Discussion

91.	The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C- 1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is__________________?
A.	165.4
B.	167.5
C.	172.5
D.	175
Answer» B. 167.5

Discussion

92.	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

93.	The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________________?
A.	Painting the surface black
B.	Painting the surface white (with aluminium paint)
C.	Giving the surface a mirror finish
D.	Roughening the surface
Answer» C. Giving the surface a mirror finish

Discussion

94.	The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?
A.	(ΔT)2
B.	(ΔT)4
C.	(ΔT)3
D.	√(ΔT)
Answer» D. √(ΔT)

Discussion

95.	The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is___________________?
A.	25°C
B.	30°C
C.	35°C
D.	40°C
Answer» D. 40°C

Discussion

96.	The Graetz number is concerned with the___________________
A.	Mass transfer between a gas and a liquid
B.	Absorption with chemical reaction
C.	Heat transfer in turbulent flow
D.	Heat transfer in laminar flow
Answer» E.

Discussion

97.	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

98.	The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?
A.	More
B.	Less
C.	Some
D.	Either more or less; depends on the nature of vapor
Answer» D. Either more or less; depends on the nature of vapor

Discussion

99.	The film co-efficient between condensing vapour and metal wall increases with _____________________?
A.	Increasing temperature of the vapour
B.	Decreasing temperature of the vapour
C.	Increasing viscosity of the film of condensate
D.	Increasing temperature drop
Answer» B. Decreasing temperature of the vapour

Discussion

100.	The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?
A.	More
B.	Less
C.	Same
D.	Unpredictable
Answer» C. Same

Discussion

Explore topic-wise MCQs in Chemical Engineering.

The unit of conductance in SI unit is_______________?

The type of liquor circulation system to be ‘ employed in evaporators (viz. natural or forced circulation) is determined mainly by the ______________ of the liquid?

The thickness of condensate layer in filmwise condensation depends on the__________________?

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4) ?

The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of ‘n’ is exactly 4 for__________________?

The thermal boundary layer at NPr > 1 ?

The sum of reflectivity and absorptivity for an opaque body is equal to____________________?

The Stefan-Boltzmann constant depends on the_________________?

The steam ejector is used to__________________?

The statement that “maximum wavelength of radiation is inversely proportional to the temperature” is ______________ law?

The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?

The separation of liquid droplets from the vapor is done by a/an _____________ in the evaporators?

The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is ________________?

The ratio of total radiating power to the absorptivity of the body depends upon the _____________ as per Kirchoff‟s law?

“The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is ______________ law?

The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?

The ratio of kinematic viscosity to thermal diffusivity is called the _______________ number?

The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the___________________?

The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti – T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?

The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as______________?

The rate of emission of radiation by a body does not depend upon the__________________?

The range of electromagnetic spectrum important in heat transfer by radiation is ______________ microns?

The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?

The purpose of providing expansion bellows in the shell of tubular exchanger is to _____________________?

The purpose of providing bleed points in the evaporator is to__________________?

The purpose of providing a ‘catchall’ in the vapor line of an evaporator is to__________________?

The overall resistance for heat transfer through a series of flat resistance, is the _____________ of the resistances?

The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is _____________________?

The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is______________?

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 number of kg vaporised per kg of steam fed to the evaporator is defined as____________?

The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?

The most conducive surface for dropwise condensation to occur is the _____________ surface?

The maximum heat transfer co-efficient from steam heating will be attained when the steam is_________________?

The main purpose of providing fins on heat transfer surface is to increase the_________________?

The main function of baffles provided in a shell and tube heat exchanger is to______________?

The interchange factor for radiation heat transfer from surface ‘x’ to surface ‘y’ in case of an infinite parallel planes with emissivities εx & εy is given by_______________?

The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by ______________ times, when the number of tube passes is increased to 8?

The heat transfer co-efficient in film type condensation is _______________ that for dropwise condensation?

The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________________?

The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is___________________?

The Graetz number is concerned with the___________________

The film thickness for laminar film condensation on vertical surface _____________ from top to bottom?

The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?

The film co-efficient between condensing vapour and metal wall increases with _____________________?

The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?