Q.1

The alignment circle is marked on the psychrometric chart at

  • 20°C DBT and 50% RH
  • 26°C DBT and 50% RH
  • 20°C DBT and 60% RH
  • 26°C DBT and 60% RH
Q.2

Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduceof the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be

  • one
  • two
  • three
  • four
Q.3

The temperature rise, between the condenser outlet and expansion valve in ammonia vapour compression system, should be as low as possible.

  • Yes
  • No
Q.4

A vapour absorption refrigeration system

  • gives noisy operation
  • gives quiet operation
  • requires little power consumption
  • cools below 0° C
Q.5

The __________ point of ammonia is -77.7°C.

  • freezing
  • boiling
Q.6

The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity)

  • 25°C DBT and 100% RH
  • 20°C DBT and 80% RH
  • 22°C DBT and 60% RH
  • 25°C DBT and 40% RH
Q.7

The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.

  • increases
  • decreases
Q.8

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

  • Kirchhoff's law
  • Stefan's law
  • Wein's law
  • Planck's law
Q.9

Wet bulb temperature indicates the moisture content in air.

  • Agree
  • Disagree
Q.10

In chemical dehumidification process,

  • dew point temperature decreases
  • wet bulb temperature decreases
  • dry bulb temperature increases
  • all of these
Q.11

The thermostatic expansion valve is used in __________ type of evaporators.

  • flooded
  • DX coil
  • dry
Q.12

The wet bulb depression is zero when relative humidity is

  • zero
  • 0.5
  • 0.75
  • 1.0
Q.13

The capillary tube is not used in large capacity refrigeration systems because

  • cost is too high
  • capacity control is not possible
  • it is made of copper
  • required pressure drop can not be achieved
Q.14

The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.

  • low
  • high
Q.15

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, is called

  • humidity ratio
  • relative humidity
  • absolute humidity
  • degree of saturation
Q.16

The rato of energy transferred by convection to that by conduction is called

  • Stanton number
  • Nusselt number
  • Biot number
  • Peclet number
Q.17

Sulphur dioxide has the lowest boiling point.

  • Yes
  • No
Q.18

The dry bulb temperature lines, on the psychrometric chart are

  • vertical and uniformly spaced
  • horizontal and uniformly spaced
  • horizontal and non-uniformly spaced
  • curved lines
Q.19

A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called

  • dry air
  • moist air
  • saturated air
  • specific humidity
Q.20

The rato of energy transferred by convection to that by conduction is called

  • Stanton number
  • Nusselt number
  • Biot number
  • Peclet number
Q.21

Emissivity of a body will be equal to its absorptivity at all temperatures.

  • Yes
  • No
Q.22

A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger atC and leaves atC. A cold fluid enters the heat exchanger atC. The mean temperature difference between the two fluids is

  • 20°C
  • 40°C
  • 60°C
  • 66.7°C
Q.23

The evaporator used in house-hold refrigerators is

  • frosting evaporator
  • non-frosting evaporator
  • defrosting evaporator
  • none of these
Q.24

A one tonne refrigerating machine means that

  • one tonne is the total mass of machine
  • one tonne refrigerant is used
  • one tonne of water can be converted into ice
  • one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
Q.25

The evaporator used in house-hold refrigerators is

  • frosting evaporator
  • non-frosting evaporator
  • defrosting evaporator
  • none of these
Q.26

The radiation emitted by a black body is known as

  • black radiation
  • full radiation
  • total radiation
  • all of these
Q.27

The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity.

  • Agree
  • Disagree
Q.28

The by-pass factor of a cooling coil decreases with

  • decrease in fin spacing and increase in number of rows
  • increase in fin spacing and increase in number of rows
  • increase in fin spacing and decrease in number of rows
  • decrease in fin spacing and decrease in number of rows
Q.29

The radiation emitted by a black body is known as

  • black radiation
  • full radiation
  • total radiation
  • all of these
Q.30

For unsaturated air, the dew point temperature is __________ wet bulb temperature.

  • equal to
  • less than
  • more than
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