Q.1

The difference between dry bulb temperature and dew point temperature, is called

  • dry bulb depression
  • wet bulb depression
  • dew point depression
  • degree of saturation
Q.2

The reduced ambient air cooling system has

  • one cooling turbine and one heat exchanger
  • one cooling turbine and two heat exchangers
  • two cooling turbines and one heat exchanger
  • two cooling turbines and two heat exchangers
Q.3

An ordinary passenger aircraft requires a cooling system of capacity.

  • 2 TR
  • 4 TR
  • 8 TR
  • 10 TR
Q.4

Kirchhoff's law states that

  • the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
  • the wave length corresponding to the maximum energy is proportional to the absolute temperature
  • the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
  • none of the above
Q.5

Kirchhoff's law states that

  • the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
  • the wave length corresponding to the maximum energy is proportional to the absolute temperature
  • the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
  • none of the above
Q.6

The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by

  • (C.O.P.)P = (C.O.P.)R + 2
  • (C.O.P.)P = (C.O.P.)R + 1
  • (C.O.P)P = (C.O.P)R - 1
  • (C.O.P)P = (C.O.P)R
Q.7

The leakage in a refrigeration system using freon is detected by

  • halide torch
  • sulphur sticks
  • soap and water
  • all of these
Q.8

Logarithmic mean temperature difference is the same as the arithmetic mean temperature difference.

  • Agree
  • Disagree
Q.9

The heat of sun reaches to us according to

  • conduction
  • convection
  • radiation
  • none of these
Q.10

In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is

  • reversed Carnot cycle
  • reversed Joule cycle
  • reversed Brayton cycle
  • reversed Otto cycle
Q.11

Dew point temperature is the temperature of air recorded by a thermometer, when the moisture present in it begins to condense.

  • Correct
  • Incorrect
Q.12

The temperature below which a gas is always liquified, is known as critical temperature.

  • Correct
  • Incorrect
Q.13

Film coefficient is defined as the ratio of

  • thermal conductivity to the equivalent thickness of the film of fluid
  • temperature drop through the films of fluids to the thickness of film of fluids
  • thickness of film of fluid to the thermal conductivity
  • thickness of film of fluid to the temperature drop through the films of fluids
Q.14

The specific humidity during humidification process

  • remains constant
  • increases
  • decreases
Q.15

The thermal diffusivity for solids is generally less than those for liquids and gases.

  • True
  • False
Q.16

If the condenser temperature is kept constant, the coefficient of performance of a refrigeration cycle increases with the increase in evaporator temperature.

  • Yes
  • No
Q.17

Conduction is the process of heat transfer from one particle of the body to another by the actual motion of the heated particles.

  • True
  • False
Q.18

The boiling point of ammonia is

  • -10.5°C
  • -30°C
  • -33.3°C
  • -77.7°C
Q.19

A condenser of refrigeration system rejects heat at the rate ofkW, while its compressor consumes a power ofkW. The coefficient of performance of the system will be

  • 1/4
  • 1/3
  • 3
  • 4
Q.20

In a vapour compression system, the condition of refrigerant is dry saturated vapour

  • before entering the compressor
  • after leaving the compressor
  • before entering the condenser
  • after leaving the condenser
Q.21

A furnace is made of a red brick wall of thickness 0.5 m and conductivity 0.7 W/mK. For the same heat loss and temperature drop, this can be replaced by a layer of diatomite earth of conductivity 0.W/mK and thickness

  • 0.5 m
  • 0.1 m
  • 0.2 m
  • 0.5 m
Q.22

The emissive power of a body depends upon its

  • temperature
  • physical nature
  • wave length
  • all of these
Q.23

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as

  • conduction
  • free convection
  • forced convection
  • radiation
Q.24

Moisture should be removed from refrigerants to avoid

  • freezing at the expansion valve
  • restriction to refrigerant flow
  • corrosion of steel plates
  • all of these
Q.25

A refrigerant with the highest critical pressure is

  • R-11
  • R-12
  • R-22
  • Ammonia
Q.26

In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature

  • which lies between the dry bulb and wet bulb temperatures of the incoming stream
  • which lies between the wet bulb and dew point temperatures of the incoming stream
  • which is lower than the dew point temperature of the incoming stream
  • of adiabatic saturation of incoming stream
Q.27

An evaporator is also known as

  • freezing coil
  • cooling coil
  • chilling coil
  • all of these
Q.28

In actual air-conditioning applications for R-and R-and operating at a condenser temperature ofC and an evaporator temperature ofC, the heat rejection factor is about

  • 1
  • 1.25
  • 2.15
  • 5.12
Q.29

In a refrigeration system, the expansion device is connected between the

  • compressor and condenser
  • condenser and receiver
  • receiver and evaporator
  • evaporator and compressor
Q.30

An electric cable of aluminium conductor (k =W/mK) is to be insulated with rubber (k = 0.W/mK). The cable is to be located in air (h = 6 W/m2). The critical thickness of insulation will be

  • 25 mm
  • 40 mm
  • 160 mm
  • 800 mm
0 h : 0 m : 1 s