Q.1

During dehumidification process, __________ remains constant.

  • wet bulb temperature
  • relative humidity
  • dry bulb temperature
  • specific humidity
Q.2

In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced.

  • Correct
  • Incorrect
Q.3

The super-heating in a refrigeration cycle

  • does not alter C.O.P.
  • increases C.O.P.
  • decreases C.O.P.
  • none of these
Q.4

When the temperature of the surrounding is higher than the temperature of the body, then the heat loss by convection from the body to the surrounding will be

  • positive
  • negative
  • zero
  • none of these
Q.5

One tonne of refrigeration (1TR) means that the heat removing capacity is

  • 21 kJ/min
  • 210 kJ/min
  • 420 kJ/min
  • 620 kJ/min
Q.6

The freezing point of R-is

  • -86.6°C
  • -95.2°C
  • -107.7°C
  • -135.8°C
Q.7

The freezing point of carbon dioxide is equal to boiling point of R-12.

  • Correct
  • Incorrect
Q.8

Air refrigeration cycle is used in

  • commercial refrigerators
  • domestic refrigerators
  • air-conditioning
  • gas liquefaction
Q.9

The process of adding moisture to the air, without change in its dry bulb temperature, is known as humidification.

  • Agree
  • Disagree
Q.10

In a saturated air-water vapour mixture, the

  • dry bulb temperature is higher than wet bulb temperature
  • dew point temperature is lower than wet bulb temperature
  • dry bulb, wet bulb and dew point temperature are same
  • dry bulb temperature is higher than dew point temperature
Q.11

Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since

  • these react with water vapour and cause acid rain
  • these react with plants and cause green-house effect
  • these react with oxygen and cause its depletion
  • these react with ozone layer
Q.12

The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to

  • bright green
  • yellow
  • red
  • orange
Q.13

A good refrigerant should have

  • high latent heat of vaporisation and low freezing point
  • high operating pressures and low freezing point
  • high specific volume and high latent heat of vaporisation
  • low C.O.P. and low freezing point
Q.14

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

  • Stanton number
  • Biot number
  • Peclet number
  • Grashoff number
Q.15

In electrolux refrigerator

  • ammonia is absorbed in hydrogen
  • ammonia is absorbed in water
  • ammonia evaporates in hydrogen
  • hydrogen evaporates in ammonia
Q.16

A thermostatic expansion valve in a refrigeration system

  • ensures the evaporator completely filled with refrigerant of the load
  • is suitable only for constant load systems
  • maintains different temperatures in evaporator in proportion to load
  • none of the above
Q.17

The relative humidity lines on a psychrometric chart are

  • vertical and uniformly spaced
  • horizontal and uniformly spaced
  • horizontal and non-uniformly spaced
  • curved lines
Q.18

The cooling of air, without any change in its specific humidity, is known as sensible cooling.

  • Correct
  • Incorrect
Q.19

A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintainingK. If the temperature at the end of constant pressure cooling isK and rise in the temperature of air in the refrigerator isK, then the net work of compression will be (assume air as working substance with cp = 1 kJ/kg)

  • 25 kJ/kg
  • 50 kJ/kg
  • l00 kJ/kg
  • 125 kJ/kg
Q.20

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

  • increases
  • decreases
Q.21

The operating temperature of a cold storage is -C. The heat leakage from the surrounding iskW for the ambient temperature ofC. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is

  • 1.86 kW
  • 3.72 kW
  • 7.44 kW
  • 18.6 kW
Q.22

If a gas is to be liquified, its temperature must be

  • increased to a value above its critical temperature
  • reduced to a value below its critical temperature
  • equal to critical temperature
  • none of the above
Q.23

The operating pressure for refrigerating units using R-as a refrigerant is

  • 2 bar
  • 8 bar
  • 15 bar
  • 30 bar
Q.24

The refrigerant supplied to a compressor must be

  • superheated vapour refrigerant
  • dry saturated liquid refrigerant
  • a mixture of liquid and vapour refrigerant
  • none of these
Q.25

The condition of refrigerant as it leaves the compressor in a vapour compression system is

  • saturated liquid
  • wet vapour
  • dry saturated vapour
  • superheated vapour
Q.26

Reynolds number is the ratio of

  • energy transferred by convection to that by conduction
  • kinematic viscosity to thermal diffusivity
  • inertia force to viscous force
  • none of the above
Q.27

In case of liquids and gases, the heat transfer takes place according to

  • conduction
  • convection
  • radiation
  • none of these
Q.28

Dew point temperature corresponds to the saturation temperature of vapour at its partial pressure.

  • True
  • False
Q.29

When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by

  • operating the machine at higher speeds
  • operating the machine at lower speeds
  • raising the higher temperature
  • lowering the higher temperature
Q.30

The thermal diffusivity for gases is generally __________ those for liquids.

  • equal to
  • less than
  • greater than
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