387 + Mcqs in Heat Transfer Refrigeration and Air Conditioning Page 8 McqOptions

351.	The rate of heat flow through a body is . The term x/kA is known as
A.	thermal coefficient
B.	thermal resistance
C.	thermal conductivity
D.	none of these
Answer» C. thermal conductivity

Discussion

352.	During a refrigeration cycle, heat is rejected by the refrigerant in a
A.	compressor
B.	condenser
C.	evaporator
D.	expansion valve
Answer» C. evaporator

Discussion

353.	Nusselt number (NN) is given by
A.	NN = hl/k
B.	NN = μ cp/k
C.	NN = ρ V l /μ
D.	NN = V²/t.cp
Answer» B. NN = μ cp/k

Discussion

354.	In case of solids, the heat transfer takes place according to radiation.
A.	Correct
B.	Incorrect
C.	-
D.	-
Answer» C. -

Discussion

355.	The relative humidity decreases as air gets wet.
A.	True
B.	False
C.	-
D.	-
Answer» B. False

Discussion

356.	A water cooled condenser operates at a __________ condensing temperature than an air-cooled condenser.
A.	higher
B.	lower
C.	-
D.	-
Answer» C. -

Discussion

357.	The critical radius is the insulation radius at which the resistance to heat flow is
A.	maximum
B.	minimum
C.	zero
D.	none of these
Answer» C. zero

Discussion

358.	During sensible cooling of air __________ decreases.
A.	wet bulb temperature
B.	relative humidity
C.	dry bulb temperature
D.	specific humidity
Answer» D. specific humidity

Discussion

359.	The subcooling in a refrigeration cycle
A.	does not alter C.O.P.
B.	increases C.O.P.
C.	decreases C.O.P.
D.	none of these
Answer» C. decreases C.O.P.

Discussion

360.	A refrigeration system
A.	removes heat from a low temperature body and delivers it to a high temperature body
B.	removes heat from a high temperature body and delivers it to a low temperature body
C.	rejects energy to a low temperature body
D.	none of the above
Answer» B. removes heat from a high temperature body and delivers it to a low temperature body

Discussion

361.	The coefficient of performance of Heat Pump is always __________ one.
A.	equal to
B.	less than
C.	greater than
D.	-
Answer» D. -

Discussion

362.	Degree of saturation or percentage humidity is
A.	the mass of water vapour present in 1 m 3 of dry air
B.	the mass of water vapour present in 1 kg of dry air
C.	the ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure.
D.	the ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure
Answer» D. the ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure

Discussion

363.	The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is
A.	equal to one
B.	greater than one
C.	less than one
D.	equal to Nusselt number
Answer» B. greater than one

Discussion

364.	During adiabatic saturation process on unsaturated air __________ remains constant.
A.	relative humidity
B.	dew point temperature
C.	dry bulb temperature
D.	wet bulb temperature
Answer» E.

Discussion

365.	Thermal conductivity of water __________ with rise in temperature.
A.	remains same
B.	decreases
C.	increases
D.	may increase or decrease depending upon temperature
Answer» E.

Discussion

366.	The heat transfer by radiation __________ a medium.
A.	requires
B.	does not require
C.	-
D.	-
Answer» C. -

Discussion

367.	An electrolux refrigerator is called a __________ absorption system.
A.	single fluid
B.	two fluids
C.	three fluids
D.	-
Answer» D. -

Discussion

368.	The heat transfer takes place according to
A.	Zeroth law of thermodynamics
B.	First law of thermodynamics
C.	Second law of thermodynamics
D.	Kirchhoff's law
Answer» D. Kirchhoff's law

Discussion

369.	For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of
A.	copper
B.	aluminium
C.	steel
D.	brass
Answer» D. brass

Discussion

370.	In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be
A.	0.3
B.	0.6
C.	0.67
D.	1.5
Answer» C. 0.67

Discussion

371.	The condition of refrigerant after leaving the compressor and before entering the condenser is superheated vapour.
A.	Yes
B.	No
C.	-
D.	-
Answer» B. No

Discussion

372.	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.	-
Answer» C. inversely proportional to

Discussion

373.	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

374.	The wet bulb temperature lines, on the psychrometric chart, are curved lines.
A.	True
B.	False
C.	-
D.	-
Answer» C. -

Discussion

375.	The process of heat transfer from a hot body to a cold body, in a straight line, without affecting the intervening medium, is called radiation.
A.	True
B.	False
C.	-
D.	-
Answer» B. False

Discussion

376.	The optimum effective temperature for human comfort is
A.	higher in winter than in summer
B.	lower in winter than in summer
C.	same in winter and summer
D.	not dependent on season
Answer» C. same in winter and summer

Discussion

377.	As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature.
A.	same as
B.	lower than
C.	higher man
D.	-
Answer» C. higher man

Discussion

378.	In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively
A.	water and water
B.	water and lithium bromide
C.	ammonia and lithium bromide
D.	ammonia and water
Answer» E.

Discussion

379.	The heat transfer by conduction through a thick sphere is same as through a thick cylinder.
A.	True
B.	False
C.	-
D.	-
Answer» C. -

Discussion

380.	The relative humidity is defined as
A.	the mass of water vapour present in 1 m 3 of dry air
B.	the mass of water vapour present in 1 kg of dry air
C.	the ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure.
D.	the ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure
Answer» E.

Discussion

381.	According to Dalton's law of partial pressures, (where p b = Barometric pressure, p a = Partial pressure of dry air, and p v = Partial pressure of water vapour)
A.	P b = p a - p v
B.	P b = p a + p v
C.	P b = p a x p v
D.	P b = p a / p v
Answer» C. P b = p a x p v

Discussion

382.	The difference between dry bulb temperature and wet bulb temperature, is called
A.	dry bulb depression
B.	wet bulb depression
C.	dew point depression
D.	degree of saturation
Answer» C. dew point depression

Discussion

383.	Defrosting of a refrigerator may be done by stopping the compressor for a short period.
A.	Correct
B.	Incorrect
C.	-
D.	-
Answer» B. Incorrect

Discussion

384.	The by-pass factor for a cooling coil
A.	increases with increase in velocity of air passing through it
B.	decreases with increase in velocity of air passing through it
C.	remains unchanged with increase in velocity of air passing through it
D.	may increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering
Answer» B. decreases with increase in velocity of air passing through it

Discussion

385.	In a refrigerating machine, heat rejected is __________ heat absorbed.
A.	equal to
B.	less than
C.	greater than
D.	-
Answer» D. -

Discussion

386.	The humidity ratio or specific humidity is the mass of water vapour present in
A.	1 m 3 of wet air
B.	1 m 3 of dry air
C.	1 kg of wet air
D.	1 kg of dry air
Answer» E.

Discussion

387.	In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
A.	Reynold's number
B.	Grashoff's number
C.	Reynold's number, Grashoff's number
D.	Prandtl number, Grashoff's number
Answer» E.

Discussion

Explore topic-wise MCQs in Automobile Engineering.

The rate of heat flow through a body is . The term x/kA is known as

During a refrigeration cycle, heat is rejected by the refrigerant in a

Nusselt number (NN) is given by

In case of solids, the heat transfer takes place according to radiation.

The relative humidity decreases as air gets wet.

A water cooled condenser operates at a __________ condensing temperature than an air-cooled condenser.

The critical radius is the insulation radius at which the resistance to heat flow is

During sensible cooling of air __________ decreases.

The subcooling in a refrigeration cycle

A refrigeration system

The coefficient of performance of Heat Pump is always __________ one.

Degree of saturation or percentage humidity is

The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

During adiabatic saturation process on unsaturated air __________ remains constant.

Thermal conductivity of water __________ with rise in temperature.

The heat transfer by radiation __________ a medium.

An electrolux refrigerator is called a __________ absorption system.

The heat transfer takes place according to

For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of

In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be

The condition of refrigerant after leaving the compressor and before entering the condenser is superheated vapour.

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.

Thermal diffusivity is a

The wet bulb temperature lines, on the psychrometric chart, are curved lines.

The process of heat transfer from a hot body to a cold body, in a straight line, without affecting the intervening medium, is called radiation.

The optimum effective temperature for human comfort is

As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature.

In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively

The heat transfer by conduction through a thick sphere is same as through a thick cylinder.

The relative humidity is defined as

According to Dalton's law of partial pressures, (where p b = Barometric pressure, p a = Partial pressure of dry air, and p v = Partial pressure of water vapour)

The difference between dry bulb temperature and wet bulb temperature, is called

Defrosting of a refrigerator may be done by stopping the compressor for a short period.

The by-pass factor for a cooling coil

In a refrigerating machine, heat rejected is __________ heat absorbed.

The humidity ratio or specific humidity is the mass of water vapour present in

In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the