_ Heat transfer takes place as per$?

Second law of the thermodynamics

_ Stefan Boltzmann law is applicable for heat transfer by$?

Conduction and radiation combined

_ Sensible heat is the heat required to$?

Convert water into steam and superheat it

Increase the temperature of a liquid of vapour

Convert water into steam and superheat it

_ Thermal diffusivity is a$?

Physical property of a substance

_ Fourier's law of heat conduction is valid for$?

Regular surfaces having non-uniform temperature gradients

_ In counter flow heat exchangers$?

Both the fluids at exit are in their hottest state

Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state

Both the fluids at inlet are in their hottest state

Both the fluids at exit are in their hottest state

One fluid is in hottest state and other in coldest state at inlet

__In a shell and tube heat exchanger, baffles are provided on the shell side to__

Prevent stagnation of shell side fluid

__Which of the following is the case of heat transfer by radiation?__

Heat received by a person from fireplace

_A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h‚Äö√á√Ö, h‚Äö√á√á and h‚Äö√á√â respectively. The average heat transfer coefficient for the cube is$?

h‚Äö√á√Ö + h‚Äö√á√á + h‚Äö√á√â

(h‚Äö√á√Ö.h‚Äö√á√á.h‚Äö√á√â)1/3

1/h‚Äö√á√Ö + 1/h‚Äö√á√á + 1/h‚Äö√á√â

_Which of the following statement is correct?$?

The energy absorbed by a body to the total energy falling on it, is called emissivity.

A grey body is one which absorbs all radiations incident on it.

At thermal equilibrium, the emissivity and absorptivity are same.

The energy absorbed by a body to the total energy falling on it, is called emissivity.

A perfect body is one which is black in colour.

_A composite slab has two layers of different materials with thermal conductivities k‚Äö√á√Ö and k‚Äö√á√á. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be$?

k‚Äö√á√Ö k‚Äö√á√á

(k‚Äö√á√Ö + k‚Äö√á√á)

(k‚Äö√á√Ö + k‚Äö√á√á)/ k‚Äö√á√Ö k‚Äö√á√á

2 k‚Äö√á√Ö k‚Äö√á√á/ (k‚Äö√á√Ö + k‚Äö√á√á)

_Total heat is the heat required to$?

Increase the temperature of a liquid or vapour

Convert water into steam and superheat it

_Film coefficient is defined as Inside diameter of tube$?

Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity

Thermal conductivity Equivalent thickness of film Specific heat ‚àö√≥ Viscosity

Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity

Film coefficient ‚àö√≥ Inside diameter Thermal conductivity

A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,$?

The better insulation must be put outside

The better insulation must be put inside

The better insulation must be put outside

One could place either insulation on either side

One should take into account the steam temperature before deciding as to which insulation is put where

Fourier's law of heat conduction gives the heat flow for$?

Nonuniform temperature surfaces

Reynolds number is the ratio of$?

Energy transferred by convection to that by conduction

Kinematic viscosity to thermal diffusivity

Thermal conductivity of water in general with rise in temperature$?

May increase or decrease depending on temperature

The value of the wave length for maximum emissive power is given by$?

Kirchhoff‚Äö√Ñ√¥s law

362 + Mcqs in Heat And Mass Transfer in Mechanical Engineering Page 6 McqOptions

251.	_ Heat transfer takes place as per$?
A.	Zeroth law of thermodynamics
B.	First law of thermodynamic
C.	Second law of the thermodynamics
D.	Kirchoff's law
Answer» D. Kirchoff's law

Discussion

252.	_ Depending on the radiating properties, body will be transparent when (Where a = absorptivity, p = reflectivity, x = transmissivity)$?
A.	P = 0, x = 0 and a = 1
B.	P=1, x = 0, and a = 0
C.	P = 0, T= 1, and a = 0
D.	X = 0, a + p = 1
Answer» D. X = 0, a + p = 1

Discussion

253.	_ Total emissivity of polished silver compared to black body is$?
A.	Same
B.	Higher
C.	More or less same
D.	Very much lower
Answer» E.

Discussion

254.	_ Which of the following has least value of conductivity?$?
A.	Glass
B.	Water
C.	Plastic
D.	Air
Answer» E.

Discussion

255.	_ Stefan Boltzmann law is applicable for heat transfer by$?
A.	Conduction
B.	Convection
C.	Radiation
D.	Conduction and radiation combined
Answer» D. Conduction and radiation combined

Discussion

256.	_ Sensible heat is the heat required to$?
A.	Change vapour into liquid
B.	Change liquid into vapour
C.	Increase the temperature of a liquid of vapour
D.	Convert water into steam and superheat it
Answer» D. Convert water into steam and superheat it

Discussion

257.	_ Thermal diffusivity is a$?
A.	Function of temperature
B.	Physical property of a substance
C.	Dimensionless parameter
D.	All of these
Answer» C. Dimensionless parameter

Discussion

258.	_ The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to$?
A.	Stanton number
B.	Biot number
C.	Peclet number
D.	Grashoff number
Answer» B. Biot number

Discussion

259.	_ Fourier's law of heat conduction is valid for$?
A.	One dimensional cases only
B.	Two dimensional cases only
C.	Three dimensional cases only
D.	Regular surfaces having non-uniform temperature gradients
Answer» B. Two dimensional cases only

Discussion

260.	_ In counter flow heat exchangers$?
A.	Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state
B.	Both the fluids at inlet are in their hottest state
C.	Both the fluids at exit are in their hottest state
D.	One fluid is in hottest state and other in coldest state at inlet
Answer» C. Both the fluids at exit are in their hottest state

Discussion

261.	__In a shell and tube heat exchanger, baffles are provided on the shell side to__
A.	Improve heat transfer
B.	Provide support for tubes
C.	Prevent stagnation of shell side fluid
D.	All of these
Answer» E.

Discussion

262.	__Which of the following is the case of heat transfer by radiation?__
A.	Blast furnace
B.	Heating of building
C.	Cooling of parts in furnace
D.	Heat received by a person from fireplace
Answer» E.

Discussion

263.	__The radiation emitted by a black body is known as__
A.	Black radiation
B.	Full radiation
C.	Total radiation
D.	All of these
Answer» E.

Discussion

264.	_Heat transfer by radiation mainly depends upon$?
A.	Its temperature
B.	Nature of the body
C.	Kind and extent of its surface
D.	All of the above
Answer» E.

Discussion

265.	_In case of liquids and gases, the heat transfer takes place according to$?
A.	Conduction
B.	Convection
C.	Radiation
D.	None of these
Answer» C. Radiation

Discussion

266.	_The automobile radiator is a heat exchanger of$?
A.	Parallel flow type
B.	Counter flow type
C.	Cross flow type
D.	Regenerator type
Answer» D. Regenerator type

Discussion

267.	_A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h‚Äö√á√Ö, h‚Äö√á√á and h‚Äö√á√â respectively. The average heat transfer coefficient for the cube is$?
A.	h‚Äö√á√Ö + h‚Äö√á√á + h‚Äö√á√â
B.	(h‚Äö√á√Ö.h‚Äö√á√á.h‚Äö√á√â)1/3
C.	1/h‚Äö√á√Ö + 1/h‚Äö√á√á + 1/h‚Äö√á√â
D.	None of these
Answer» E.

Discussion

268.	_According to Stefan's law, the total radiation from a black body per second per unit area is proportional to$?
A.	Absolute temperature
B.	T¬¨‚â§
C.	T‚Äö√Ö¬µ
D.	T
Answer» E.

Discussion

269.	_Heat is closely related with$?
A.	Liquids
B.	Energy
C.	Temperature
D.	Entropy
Answer» D. Entropy

Discussion

270.	_The value of the wavelength for maximum emissive power is given by$?
A.	Wien‚Äö√Ñ√¥s law
B.	Planck's law
C.	Stefan's law
D.	Fourier's law
Answer» B. Planck's law

Discussion

271.	_If the temperature of a solid surface changes form 27¬¨‚àûC to 627¬¨‚àûC, then its emissive power changes in the ratio of$?
A.	3
B.	9
C.	270
D.	81
Answer» E.

Discussion

272.	_The natural convection air cooled condensers are used in$?
A.	Domestic refrigerators
B.	Water coolers
C.	Room air conditioners
D.	All of these
Answer» B. Water coolers

Discussion

273.	_The heat of sun reaches to us according to$?
A.	Conduction
B.	Convection
C.	Radiation
D.	None of these
Answer» D. None of these

Discussion

274.	_The amount of radiation mainly depends on$?
A.	Nature of body
B.	Temperature of body
C.	Type of surface of body
D.	All of the above
Answer» E.

Discussion

275.	_Free convection flow depends on$?
A.	Density
B.	Coefficient of viscosity
C.	Gravitational force
D.	All of these
Answer» E.

Discussion

276.	_Cork is a good insulator because it has$?
A.	Free electrons
B.	Atoms colliding frequency
C.	Low density
D.	Porous body
Answer» E.

Discussion

277.	_The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to$?
A.	-1/3
B.	-2/3
C.	1
D.	-1
Answer» B. -2/3

Discussion

278.	_Which of the following statement is correct?$?
A.	A grey body is one which absorbs all radiations incident on it.
B.	At thermal equilibrium, the emissivity and absorptivity are same.
C.	The energy absorbed by a body to the total energy falling on it, is called emissivity.
D.	A perfect body is one which is black in colour.
Answer» C. The energy absorbed by a body to the total energy falling on it, is called emissivity.

Discussion

279.	_Two plates spaced 150 mm apart are maintained at 1000¬¨‚àûC and 70¬¨‚àûC. The heat transfer will take place mainly by$?
A.	Convection
B.	Radiation
C.	Forced convection
D.	Free convection
Answer» C. Forced convection

Discussion

280.	_The rate of energy transferred by convection to that by conduction is called$?
A.	Stanton number
B.	Nusselt number
C.	Biot number
D.	Peclet number
Answer» C. Biot number

Discussion

281.	_Planck‚Äö√Ñ√¥s law holds good for$?
A.	black bodies
B.	polished bodies
C.	all coloured bodies
D.	all of the above
Answer» B. polished bodies

Discussion

282.	_The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.$?
A.	Equal to
B.	Directly proportional to
C.	Inversely proportional to
D.	None of these
Answer» C. Inversely proportional to

Discussion

283.	_The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit$?
A.	Temperature
B.	Thickness
C.	Area
D.	Time
Answer» E.

Discussion

284.	_Depending on the radiating properties, a body will be white when (Where a = absorptivity, p = reflectivity, x = transmissivity)$?
A.	P = 0, x = 0 and a = 1
B.	P=1, T = 0 and a = 0
C.	P = 0, x = 1 and a = 0
D.	X = 0, a + p = 1
Answer» C. P = 0, x = 1 and a = 0

Discussion

285.	_A composite slab has two layers of different materials with thermal conductivities k‚Äö√á√Ö and k‚Äö√á√á. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be$?
A.	k‚Äö√á√Ö k‚Äö√á√á
B.	(k‚Äö√á√Ö + k‚Äö√á√á)
C.	(k‚Äö√á√Ö + k‚Äö√á√á)/ k‚Äö√á√Ö k‚Äö√á√á
D.	2 k‚Äö√á√Ö k‚Äö√á√á/ (k‚Äö√á√Ö + k‚Äö√á√á)
Answer» E.

Discussion

286.	_According to Wien's law, the wavelength corresponding to maximum energy is proportion to$?
A.	Absolute temperature (T)
B.	I¬¨‚â§
C.	F
D.	T
Answer» B. I¬¨‚â§

Discussion

287.	_When heat is transferred by molecular collision, it is referred to as heat transfer by$?
A.	Conduction
B.	Convection
C.	Radiation
D.	Scattering
Answer» C. Radiation

Discussion

288.	_Total heat is the heat required to$?
A.	Change vapour into liquid
B.	Change liquid into vapour
C.	Increase the temperature of a liquid or vapour
D.	Convert water into steam and superheat it
Answer» E.

Discussion

289.	_Film coefficient is defined as Inside diameter of tube$?
A.	Equivalent thickness of film
B.	Thermal conductivity Equivalent thickness of film Specific heat ‚àö√≥ Viscosity
C.	Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
D.	Film coefficient ‚àö√≥ Inside diameter Thermal conductivity
Answer» C. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity

Discussion

290.	A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,$?
A.	The better insulation must be put inside
B.	The better insulation must be put outside
C.	One could place either insulation on either side
D.	One should take into account the steam temperature before deciding as to which insulation is put where
Answer» B. The better insulation must be put outside

Discussion

291.	The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called$?
A.	Conduction
B.	Convection
C.	Radiation
D.	None of these
Answer» C. Radiation

Discussion

292.	In counter current flow heat exchanger, the logarithmic temperature difference between the fluids is ________ as compared to parallel flow heat exchanger.$?
A.	Same
B.	Less
C.	Greater
D.	None of these
Answer» D. None of these

Discussion

293.	Fourier's law of heat conduction gives the heat flow for$?
A.	Irregular surfaces
B.	Nonuniform temperature surfaces
C.	One dimensional cases only
D.	Two dimensional cases only
Answer» D. Two dimensional cases only

Discussion

294.	The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as$?
A.	Emissivity
B.	Transmissivity
C.	Reflectivity
D.	Intensity of radiation
Answer» E.

Discussion

295.	Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in$?
A.	Electric heater
B.	Steam condenser
C.	Boiler
D.	Refrigerator condenser coils
Answer» D. Refrigerator condenser coils

Discussion

296.	Reynolds number is the ratio of$?
A.	Energy transferred by convection to that by conduction
B.	Kinematic viscosity to thermal diffusivity
C.	Inertia force to viscous force
D.	None of the above
Answer» D. None of the above

Discussion

297.	Thermal conductivity of air at room temperature in kcal/m hr ¬¨‚àûC is of the order of$?
A.	0.002
B.	0.02
C.	0.01
D.	0.1
Answer» C. 0.01

Discussion

298.	Thermal conductivity of water in general with rise in temperature$?
A.	Increases
B.	Decreases
C.	Remain constant
D.	May increase or decrease depending on temperature
Answer» E.

Discussion

299.	An ordinary passenger aircraft requires a cooling system of capacity.$?
A.	2 TR
B.	4 TR
C.	8 TR
D.	10 TR
Answer» D. 10 TR

Discussion

300.	The value of the wave length for maximum emissive power is given by$?
A.	Kirchhoff‚Äö√Ñ√¥s law
B.	Stefan‚Äö√Ñ√¥s law
C.	Wine‚Äö√Ñ√¥s law
D.	Planck‚Äö√Ñ√¥s law
Answer» D. Planck‚Äö√Ñ√¥s law

Discussion

Explore topic-wise MCQs in Mechanical Engineering.

_ Heat transfer takes place as per$?

_ Depending on the radiating properties, body will be transparent when (Where a = absorptivity, p = reflectivity, x = transmissivity)$?

_ Total emissivity of polished silver compared to black body is$?

_ Which of the following has least value of conductivity?$?

_ Stefan Boltzmann law is applicable for heat transfer by$?

_ Sensible heat is the heat required to$?

_ Thermal diffusivity is a$?

_ The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to$?

_ Fourier's law of heat conduction is valid for$?

_ In counter flow heat exchangers$?

__In a shell and tube heat exchanger, baffles are provided on the shell side to__

__Which of the following is the case of heat transfer by radiation?__

__The radiation emitted by a black body is known as__

_Heat transfer by radiation mainly depends upon$?

_In case of liquids and gases, the heat transfer takes place according to$?

_The automobile radiator is a heat exchanger of$?

_A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h‚Äö√á√Ö, h‚Äö√á√á and h‚Äö√á√â respectively. The average heat transfer coefficient for the cube is$?

_According to Stefan's law, the total radiation from a black body per second per unit area is proportional to$?

_Heat is closely related with$?

_The value of the wavelength for maximum emissive power is given by$?

_If the temperature of a solid surface changes form 27¬¨‚àûC to 627¬¨‚àûC, then its emissive power changes in the ratio of$?

_The natural convection air cooled condensers are used in$?

_The heat of sun reaches to us according to$?

_The amount of radiation mainly depends on$?

_Free convection flow depends on$?

_Cork is a good insulator because it has$?

_The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to$?

_Which of the following statement is correct?$?

_Two plates spaced 150 mm apart are maintained at 1000¬¨‚àûC and 70¬¨‚àûC. The heat transfer will take place mainly by$?

_The rate of energy transferred by convection to that by conduction is called$?

_Planck‚Äö√Ñ√¥s law holds good for$?

_The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.$?

_The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit$?

_Depending on the radiating properties, a body will be white when (Where a = absorptivity, p = reflectivity, x = transmissivity)$?

_A composite slab has two layers of different materials with thermal conductivities k‚Äö√á√Ö and k‚Äö√á√á. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be$?

_According to Wien's law, the wavelength corresponding to maximum energy is proportion to$?

_When heat is transferred by molecular collision, it is referred to as heat transfer by$?

_Total heat is the heat required to$?

_Film coefficient is defined as Inside diameter of tube$?

A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,$?

The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called$?

In counter current flow heat exchanger, the logarithmic temperature difference between the fluids is ________ as compared to parallel flow heat exchanger.$?

Fourier's law of heat conduction gives the heat flow for$?

The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as$?

Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in$?

Reynolds number is the ratio of$?

Thermal conductivity of air at room temperature in kcal/m hr ¬¨‚àûC is of the order of$?

Thermal conductivity of water in general with rise in temperature$?

An ordinary passenger aircraft requires a cooling system of capacity.$?

The value of the wave length for maximum emissive power is given by$?

In a shell and tube heat exchanger, baffles are provided on the shell side to

Which of the following is the case of heat transfer by radiation?

The radiation emitted by a black body is known as