Interview Questions on Heat Transfer Refrigeration and Air Conditioning

1. How many types of convection process are there?
  1. One
  2. Three
  3. Four
  4. Two

Answer:B

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2. According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)
  1. Pb = pa - pv
  2. Pb = pa + pv
  3. Pb = pa x pv
  4. Pb = pa/pv

Answer:B

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3. The literature of heat transfer generally recognizes distinct modes of heat transfer. How many modes are there?
  1. One
  2. Two
  3. Three
  4. Four

Answer:C

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4. Thermal conductivity is maximum for which substance
  1. Silver
  2. Ice
  3. Aluminium
  4. Diamond

Answer:D

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5. A radiator in a domestic heating system operates at a surface temperature of 60 degree Celsius. What will be the heat flux at the surface of the radiator if it acts as a black body
  1. 697.2 W/m2
  2. 786.9 W/m2
  3. 324.7 W/m2
  4. 592.1 W/m2

Answer:A

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6. The heat transfer by conduction through a thick sphere is same as through a thick cylinder.
  1. True
  2. False

Answer:B

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7. Which of the following is an example of forced convection?
  1. Heat exchange on cold and warm pipes
  2. Flow of water in condenser tubes
  3. Cooling of billets in the atmosphere
  4. None of the above

Answer:B

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8. In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively
  1. water and water
  2. water and lithium bromide
  3. ammonia and lithium bromide
  4. ammonia and water

Answer:D

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9. As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature.
  1. same as
  2. lower than
  3. higher man

Answer:B

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10. The relevant boundary conditions in case of heat dissipation from a fin insulated at the tip are
  1. t = t 0 at x = 0 and d t/d x = 0 at x = 0
  2. t = t 0 at x = 0 and d t/d x = 0 at x = 1
  3. t = t 0 at x = infinity and d t/d x = 0 at x = infinity
  4. None of the above

Answer:B

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11. 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.
  1. True
  2. False

Answer:A

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12. The optimum effective temperature for human comfort is
  1. higher in winter than in summer
  2. lower in winter than in summer
  3. same in winter and summer
  4. not dependent on season

Answer:B

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13. The wet bulb temperature lines, on the psychrometric chart, are curved lines.
  1. True
  2. False

Answer:B

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14. The temperature distribution in case of fin insulated at the tip is given by
  1. t – t 0/t0 – t a = cos h m (3 – x)/cos ml
  2. t – t 0/t0 – t a = cos h m (2 – x)/sin h ml
  3. t – t 0/t0 – t a = cos h m (l – x)/cos h ml
  4. t – t 0/t0 – t a = cos m (l – x)/sin ml

Answer:C

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15. Thermal diffusivity is a
  1. function of temperature
  2. physical property of a substance
  3. dimensionless parameter
  4. all of these

Answer:B

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16. The condition of refrigerant after leaving the compressor and before entering the condenser is superheated vapour
  1. Yes
  2. No

Answer:A

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17. 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.
  1. equal to
  2. directly proportional to
  3. inversely proportional to

Answer:B

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18. In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. Calculate the sensible heat factor for this psychometric process.
  1. 0.3
  2. 0.6
  3. 0.67
  4. 1.5

Answer:B

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19. The rate of heat transfer from the fin in case of fin insulated at the tip is
  1. (h P k A)1/2 (t 0 – t a) tan h ml
  2. (h k A)1/2 (t 0 – t a) tan h ml
  3. (h P A)1/2 (t 0 – t a) tan h ml
  4. (h P k)1/2 (t 0 – t a) tan h ml

Answer:A

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20. The amount of radiation mainly depends upon the
  1. nature of the body
  2. temperature of the body
  3. type of surface of the body
  4. all of these

Answer:D

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21. For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of
  1. Copper
  2. Aluminium
  3. Steel
  4. Brass

Answer:C

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22.The highest thermal diffusivity is of
  1. Iron
  2. Lead
  3. Concrete
  4. Wood

Answer:B

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23. While designing the refrigeration system of an aircraft, the prime consideration is that the
  1. system has high C.O.P.
  2. power per TR is low
  3. mass of the refrigeration equipment is low
  4. None of the above

Answer:C

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24. The heat transfer takes place according to
  1. Zeroth law of thermodynamics
  2. First law of thermodynamics
  3. Second law of thermodynamics
  4. Kirchhoff's law

Answer:C

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25. “Fin is insulated at the tip”. What does that mean?
  1. Less heat is transferred from the tip
  2. Heat will transferred from tip only
  3. More heat is transferred from the tip
  4. No heat is transferred from the tip

Answer:D

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26. An electrolux refrigerator is called a __________ absorption system.
  1. single fluid
  2. two fluids
  3. three fluids

Answer:C

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27. The heat transfer by radiation __________ a medium.
  1. Requires
  2. does not require

Answer:B

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28. Thermal conductivity of water __________ with rise in temperature.
  1. remains same
  2. Decreases
  3. Increases
  4. may increase or decrease depending upon temperature

Answer:D

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29. During adiabatic saturation process on unsaturated air __________ remains constant.
  1. relative humidity
  2. dew point temperature
  3. dry bulb temperature
  4. wet bulb temperature

Answer:D

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30. Find the heat transfer rate from a hot surface for 6 fins of 10 cm length? The base temperature of the fin is maintained at 200 degree Celsius and the film is exposed to a convection environment at 15 degree Celsius with convective coefficient 25W/square m K. Each fin has cross-sectional area 2.5 square centimeter and is made of a material having thermal conductivity 250W/m K
  1. 120.34W
  2. 130.18W
  3. 145.46W
  4. 165.43W

Answer:B

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31. The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is
  1. equal to one
  2. greater than one
  3. less than one
  4. equal to Nusselt number

Answer:A

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32. A perfect black body is one which
  1. is black in colour
  2. absorbs heat radiations of all wave lengths falling on it
  3. reflects all the heat radiations
  4. transmits the heat radiations

Answer:B

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33. The coefficient of performance of Heat Pump is always __________ one.
  1. equal to
  2. less than
  3. greater than

Answer:C

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34. During a refrigeration cycle, heat is rejected by the refrigerant in a
  1. compressor
  2. condenser
  3. evaporator
  4. expansion valve

Answer:B

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35. A refrigeration system
  1. takes away or absorbs heat from a low temperature body and delivers it to a high temperature body
  2. takes away or absorbs heat from a high temperature body and delivers it to a low temperature body
  3. rejects energy to a low temperature body
  4. none of the above

Answer:A

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36. The subcooling in a refrigeration cycle
  1. does not alter C.O.P.
  2. increases C.O.P.
  3. decreases C.O.P.
  4. none of these

Answer:B

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37. During sensible cooling of air __________ decreases.
  1. wet bulb temperature
  2. relative humidity
  3. dry bulb temperature
  4. specific humidity

Answer:C

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38. The critical radius is the insulation radius at which the resistance to heat flow is
  1. Maximum
  2. Minimum
  3. Zero
  4. none of these

Answer:B

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39. In case of solids, the heat transfer takes place according to radiation.
  1. Correct
  2. Incorrect

Answer:B

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40. A water cooled condenser operates at a __________ condensing temperature than an air-cooled condenser.
  1. Higher
  2. Lower

Answer:B

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41. The relative humidity decreases as air gets wet.
  1. True
  2. False

Answer:A

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42. What is the temperature of ammonia after compression in a vapour compression system
  1. 20 to 50° C
  2. 50 to 70° C
  3. 70 to 110° C
  4. none of these

Answer:C

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43. The centrifugal compressors are generally used for refrigerants that require
  1. small displacements and low condensing pressures
  2. large displacements and high condensing pressures
  3. small displacements and high condensing pressures
  4. large displacements and low condensing pressures

Answer:D

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44. The water, alcohol and ammonia have same refrigerating effect at different altitudes.
  1. Yes
  2. No

Answer:B

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45. The automobile radiator is a heat exchanger of
  1. parallel flow type
  2. counter flow type
  3. cross flow type
  4. regenerator type

Answer:C

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46. In mechanical refrigeration system, the refrigerant occurs as liquid between condenser and expansion valve.
  1. True
  2. False

Answer:A

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47. If a heat pump operating on a reversed Carnot cycle having a C.O.P. of 5 and is working as a refrigerator taking 1 kW of work input, then the refrigerating effect will be
  1. 1 kW
  2. 2 kW
  3. 3 kW
  4. 4 kW

Answer:D

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48. What does the curved lines on a psychrometric chart denotes
  1. dry bulb temperature
  2. wet bulb temperature
  3. dew point temperature
  4. relative humidity

Answer:D

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49. During humidification process, __________ increases.
  1. wet bulb temperature
  2. relative humidity
  3. dry bulb temperature
  4. specific humidity

Answer:B

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50. A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be
  1. lack of cooling water
  2. water temperature being high
  3. dirty condenser surface
  4. all of these

Answer:D

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51. The counter-current flow heat exchanger can transfer __________ heat than parallel flow heat exchanger.
  1. Less
  2. More

Answer:B

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52. The freon group of refrigerants are
  1. halo-carbon refrigerants
  2. azeotrope refrigerants
  3. inorganic refrigerants
  4. hydro-carbon refrigerants

Answer:A

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53. For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is __________ that for counter flow.
  1. equal to
  2. less than
  3. greater than

Answer:A

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54. A vapour absorption refrigerator uses __________ as a refrigerant.
  1. Water
  2. Ammonia
  3. Freon
  4. aqua-ammonia

Answer:D

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55. Thermal conductivity of air increases with rise in temperature.
  1. Correct
  2. Incorrect

Answer:A

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56. The material of pipe lines for a system using ammonia as a refrigerant should be copper.
  1. Yes
  2. No

Answer:B

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57. The wave length corresponding to the maximum energy is inversely proportional to the absolute temperature. This statement is called Planck's law.
  1. Yes
  2. No

Answer:B

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58. Which of the following refrigerant has the highest freezing point.
  1. Ammonia
  2. Carbon dioxide
  3. Sulphur dioxide
  4. R-12

Answer:B

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59. Air conditioning means
  1. Cooling
  2. Heating
  3. Dehumidifying
  4. all of these

Answer:D

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60. The emissivity for a black body is
  1. 0
  2. 0.5
  3. 0.75
  4. 1

Answer:D

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61. Free convection flow depends on
  1. Density
  2. coefficient of viscosity
  3. gravitational force
  4. all of these

Answer:D

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62. The critical pressure of a liquid is the pressure
  1. above which a liquid will remain a liquid
  2. above which a liquid will explode
  3. below which a liquid will always be in vapour form
  4. None of the above

Answer:A

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63. Thermal diffusivity of a substance is
  1. directly proportional to the thermal conductivity
  2. inversely proportional to density of substance
  3. inversely proportional to specific heat
  4. all of the above

Answer:D

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64. Fouling factor is used
  1. in heat exchanger design as a safety factor
  2. in case of Newtonian fluids
  3. when a liquid exchanges heat with a gas
  4. none of the above

Answer:A

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65. The natural convection air cooled condensers are used in
  1. domestic refrigerators
  2. water coolers
  3. room air conditioners
  4. all of these

Answer:A

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66. The process, generally used in winter air-conditioning to warm and humidity the air, is called
  1. humidification
  2. dehumidification
  3. heating and humidification
  4. cooling and dehumidification

Answer:C

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67. At 100% relative humidity, wet bulb temperature, dry bulb temperature, dew point temperature and saturation temperature are equal.
  1. Correct
  2. Incorrect

Answer:A

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68. Bell-Coleman cycle is a
  1. reversed Carnot cycle
  2. reversed Otto cycle
  3. reversed Joule cycle
  4. reversed Rankine cycle

Answer:C

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69. Sulphur dioxide is extremely toxic and non-flammable.
  1. True
  2. False

Answer:A

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70. The transfer of heat from one body to another takes place only when there is a temperature difference between the bodies.
  1. Yes
  2. No

Answer:A

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71. Which of the following statement is correct for ammonia as a refrigerant?
  1. It is toxic to mucous membranes.
  2. it needs large displacement/TR compared to fluoro carbons.
  3. It reacts with copper and its alloys.
  4. all of these

Answer:D

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72. The wet bulb temperature at 100% relative humidity is __________ dew point temperature.
  1. same as
  2. lower than
  3. higher than

Answer:A

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73. The use of heat exchangers is made in
  1. radiators in automobile
  2. condensers and boilers in steam plants
  3. condensers and evaporators in refrigeration and air conditioning units
  4. None of the above

Answer:C

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74. In what type of flow would be the surface area required be minimum in a heat exchanger with one fluid evaporating or condensing
  1. parallel flow
  2. counter flow
  3. cross flow
  4. all of these

Answer:D

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75. The horizontal and uniformly spaced lines on a psychrometric chart indicates relative humidity.
  1. Correct
  2. Incorrect

Answer:B

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76. The sensible heat gain is due to the __________ difference between the fresh air and the air in space
  1. Temperature
  2. Humidity

Answer:A

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77. During cooling and dehumidification, dry bulb temperature
  1. remains constant
  2. Increases
  3. Decreases

Answer:C

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78. The sulphur sticks, in case of leakage of ammonia refrigerant, gives white smoke.
  1. True
  2. False

Answer:A

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79. During gas charging in an ammonia vapour compression system, the connection is made at the compressor outlet.
  1. Agree
  2. Disagree

Answer:A

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80. The conditioned air supplied to the room must have the capacity to take up
  1. room sensible heat load only
  2. room latent heat load only
  3. both room sensible heat and latent heat loads
  4. none of the above

Answer:C

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81. The process of removing moisture from the air, without change in its dry bulb temperature, is called dehumidification.
  1. Correct
  2. Incorrect

Answer:A

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82. The specific humidity during dehumidification process
  1. remains constant
  2. Increases
  3. Decreases

Answer:C

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83. Which of the following refrigerant has the lowest freezing point?
  1. R-11
  2. R-12
  3. R-22
  4. Ammonia

Answer:C

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84. Which one is having highest value of overall heat transfer coefficient?
  1. Steam condensers
  2. Feed water heaters
  3. Alcohol condensers
  4. Steam

Answer:B

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85. In a white body, reflectivity(ρ) is 1, absorptivity(α ) is 0, and transmittivity(τ) is 0.
  1. Correct
  2. Incorrect

Answer:A

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86. Which of the following refrigerant has the maximum ozone depletion potential in the stratophere?
  1. Ammonia
  2. Carbon dioxide
  3. Sulphur dioxide
  4. Flourine

Answer:D

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87. In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
  1. Reynold's number
  2. Grashoff's number
  3. Reynold's number, Grashoff's number
  4. Prandtl number, Grashoff's number

Answer:D

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88. As perStefan's law: “the total radiation from a black body per second per unit area is directly proportional to the 4th power of the absolute temperature”
  1. Correct
  2. Incorrect

Answer:A

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89. The wet bulb temperature during sensible heating of air
  1. remains constant
  2. Increases
  3. Decreases

Answer:B

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90. In electrolux refrigerator
  1. ammonia is absorbed in hydrogen
  2. ammonia is absorbed in water
  3. ammonia evaporates in hydrogen
  4. hydrogen evaporates in ammonia

Answer:C

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91. A boot-strap air cooling system has
  1. one heat exchanger
  2. two heat exchangers
  3. three heat exchangers
  4. four heat exchangers

Answer:B

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92. The boiling point of __________ is -10.5°C.
  1. Ammonia
  2. R-12
  3. sulphur dioxide
  4. carbon dioxide

Answer:C

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93. One tonne of refrigeration (1TR) means that the heat removing capacity is
  1. 21 kJ/min
  2. 210 kJ/min
  3. 420 kJ/min
  4. 620 kJ/min

Answer:B

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94. The operating pressure for refrigerating units using R-12 as a refrigerant is
  1. 2 bar
  2. 8 bar
  3. 15 bar
  4. 30 bar

Answer:B

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95. The specific humidity during heating and humidification process.
  1. remains constant
  2. Increases
  3. Decreases

Answer:B

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96. What is the value of overall heat transfer coefficient for air to heavy tars and liquid?
  1. As low as 45 W/m2 K
  2. As low as 40 W/m2 K
  3. As low as 35 W/m2 K
  4. As low as 30 W/m2 K

Answer:A

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97. The superheated vapour region, in a pressure enthalpy chart, is represented by the space
  1. to the left of saturated liquid line
  2. to the right of saturated liquid line
  3. between the saturated liquid line and saturated vapour line
  4. none of the above

Answer:C

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98. What is the min temperature to which water can be cooled in a cooling tower
  1. dew point temperature of air
  2. wet bulb temperature of air
  3. dry bulb temperature of air
  4. ambient air temperature

Answer:B

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99. The index which corelates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as
  1. mean radiant temperature
  2. effective temperature
  3. dew point temperature
  4. none of these

Answer:B

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100. The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to
  1. Stanton number
  2. Biot number
  3. Peclet number
  4. Grashoff number

Answer:A

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101. If a gas is to be liquified, its temperature must be
  1. increased to a value above its critical temperature
  2. reduced to a value below its critical temperature
  3. equal to critical temperature
  4. none of the above

Answer:C

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102.Which one is having lowest value of overall heat transfer coefficient?
  1. Steam
  2. Air condensers
  3. Air to heavy tars
  4. Ammonia condensers

Answer:C

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103.The thermostatic expansion valve is used in __________ type of evaporators.
  1. Flooded
  2. DX coil
  3. Dry

Answer:C

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104. According to Prevost's theory of exchanges, every body irrespective of its temperature continuously emit heat radiations to the surrounding bodies and at the same time receives heat radiations from the surrounding bodies.
  1. True
  2. False

Answer:A

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105. According to Stefan-Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the
  1. absolute temperature
  2. square of the absolute temperature
  3. cube of the absolute temperature
  4. fourth power of the absolute temperature

Answer:D

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106. A good refrigerant should have
  1. high latent heat of vaporisation and low freezing point
  2. high operating pressures and low freezing point
  3. low C.O.P. and low freezing point
  4. None of the above

Answer:A

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107. The thermal diffusivity for gases is generally __________ those for liquids.
  1. equal to
  2. less than
  3. greater than

Answer:C

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108. The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is
  1. high pressure saturated liquid
  2. wet vapour
  3. very wet vapour
  4. dry vapour

Answer:C

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

Answer:A

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110. In case of liquids and gases, the heat transfer takes place according to
  1. Conduction
  2. Convection
  3. Radiation
  4. none of these

Answer:B

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111. What is the value of overall heat transfer coefficient for air to low viscosity liquid?
  1. As high as 900 W/m2 K
  2. As high as 800 W/m2 K
  3. As high as 700 W/m2 K
  4. As high as 600 W/m2 K

Answer:D

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112. The radiation emitted by a black body is known as
  1. black radiation
  2. full radiation
  3. total radiation
  4. all of these

Answer:D

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113. The sensible heat during humidification process decreases.
  1. True
  2. False

Answer:B

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114. According to Newton's law of cooling, the heat transfer from a hot body to a cold body is
  1. directly proportional to the surface area
  2. directly proportional to the difference of temperatures between the two bodies
  3. either (a) or (b)
  4. both (a) and (b)

Answer:D

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115. The freezing point of carbon dioxide is equal to boiling point of R-12.
  1. Correct
  2. Incorrect

Answer:B

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116. The condition of refrigerant as it leaves the compressor in a vapour compression system is
  1. saturated liquid
  2. wet vapour
  3. dry saturated vapour
  4. superheated vapour

Answer:D

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117. The super-heating in a refrigeration cycle
  1. does not alter C.O.P.
  2. increases C.O.P.
  3. decreases C.O.P.
  4. none of these

Answer:C

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118. During sensible heating of air, specific humidity remains constant.
  1. Agree
  2. Disagree

Answer:A

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119. Air refrigeration cycle is used in
  1. commercial refrigerators
  2. domestic refrigerators
  3. air-conditioning
  4. gas liquefaction

Answer:D

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120. Reynolds number is the ratio of
  1. energy transferred by convection to that by conduction
  2. kinematic viscosity to thermal diffusivity
  3. inertia force to viscous force
  4. none of the above

Answer:C

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121. The wet bulb depression is zero when relative humidity is
  1. Zero
  2. 0.5
  3. 0.75
  4. 1.0

Answer:D

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122. In a shell and coil condenser, water flows in the shell and the refrigerant in the coil.
  1. True
  2. False

Answer:B

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123. What is the value of overall heat transfer coefficient for air condensers?
  1. 350-780 W/m 2 K
  2. 250 -900 W/m2 K
  3. 200-350 W/m2 K
  4. 200-1950 W/m2 K

Answer:A

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124. Dew point temperature corresponds to the saturation temperature of vapour at its partial pressure.
  1. True
  2. False

Answer:A

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125. The capillary tube is not used in large capacity refrigeration systems because
  1. cost is too high
  2. capacity control is not possible
  3. it is made of copper
  4. required pressure drop can not be achieved

Answer:B

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126. The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity.
  1. Agree
  2. Disagree

Answer:A

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127. The thermostatic expansion valve operates on the changes in the
  1. degree of superheat at exit from the evaporator
  2. temperature of the evaporator
  3. pressure in the evaporator
  4. none of the above

Answer:A

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128. In a vapour compression system, what is the condition of refrigerant before entering the expansion or throttle valve
  1. high pressure saturated liquid
  2. wet vapour
  3. very wet vapour
  4. dry vapour

Answer:A

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129. The freezing point of R-12 is
  1. -86.6°C
  2. -95.2°C
  3. -107.7°C
  4. -135.8°C

Answer:D

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130. The refrigerant supplied to a compressor must be
  1. superheated vapour refrigerant
  2. dry saturated liquid refrigerant
  3. a mixture of liquid and vapour refrigerant
  4. none of these

Answer:A

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131. The unit of thermal diffusivity is
  1. m/hK
  2. m/h
  3. m2/h
  4. m 2/hK

Answer:C

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132. Which out of the below represents the comfort conditions in air conditioning (DBT= Dry bulb temperature, RH= Relative humidity)
  1. 25°C DBT and 100% RH
  2. 20°C DBT and 80% RH
  3. 22°C DBT and 60% RH
  4. 25°C DBT and 40% RH

Answer:C

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133. The dry bulb temperature lines, on the psychometric chart are
  1. vertical and uniformly spaced
  2. horizontal and uniformly spaced
  3. horizontal and non-uniformly spaced
  4. curved lines

Answer:A

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134. The pressure at the outlet of a refrigerant compressor is called
  1. suction pressure
  2. discharge pressure
  3. critical pressure
  4. back pressure

Answer:B

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135. Which one is having highest value of overall heat transfer coefficient?
  1. Steam
  2. Alcohol condensers
  3. Air condensers
  4. Air to various gases

Answer:C

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136. A simple air cooling system is good for __________ flight speeds.
  1. Low
  2. High

Answer:A

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137. The highest temperature during the cycle in a vapour compression system occurs after evaporation.
  1. True
  2. False

Answer:B

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138. In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced.
  1. Correct
  2. Incorrect

Answer:A

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

Answer:B

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140. The evaporator used in house-hold refrigerators is
  1. frosting evaporator
  2. non-frosting evaporator
  3. defrosting evaporator
  4. none of these

Answer:A

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141. The drier in a refrigeration system removes moisture in the system.
  1. Correct
  2. Incorrect

Answer:A

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142. The __________ point of ammonia is -77.7°C.
  1. Freezing
  2. Boiling

Answer:A

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143. Sulphur dioxide has the lowest boiling point.
  1. Yes
  2. No

Answer:B

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144. For a given dry bulb temperature, as the relative humidity __________ the wet bulb temperature will increase.
  1. Increases
  2. Decreases

Answer:B

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145. The lowest thermal diffusivity is of
  1. Iron
  2. Lead
  3. Aluminium
  4. Rubber

Answer:D

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146. A low wet bulb temperature indicates very __________ humidity.
  1. Low
  2. High

Answer:A

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147. In chemical dehumidification process,
  1. dew point temperature decreases
  2. wet bulb temperature decreases
  3. dry bulb temperature increases
  4. all of these

Answer:D

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148. A one tonne refrigerating machine means that
  1. one tonne is the total mass of machine
  2. one tonne refrigerant is used
  3. one tonne of water can be converted into ice
  4. one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min

Answer:D

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149. The air cooling system mostly used in transport type aircrafts is
  1. simple air cooling system
  2. simple evaporative air cooling system
  3. boot-strap air cooling system
  4. all of these

Answer:C

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150. The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (h0).
  1. True
  2. False

Answer:A

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151. In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.
  1. same
  2. less
  3. greater

Answer:C

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152. Which one is having the lowest value of overall heat transfer coefficient?
  1. Air condensers
  2. Air to low viscosity liquids
  3. Steam condensers
  4. Feed water heaters

Answer:B

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153. Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since
  1. these react with ozone layer
  2. these react with plants and cause green-house effect
  3. these react with oxygen and cause its depletion
  4. None of the above

Answer:A

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154. What needs to be done to improve the coefficient of performance when the lower temperature of a refrigerating machine is fixed
  1. operating the machine at higher speeds
  2. operating the machine at lower speeds
  3. raising the higher temperature
  4. lowering the higher temperature

Answer:D

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

Answer:B

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156. Dehydration is the process of removing water vapour from the surrounding air.
  1. True
  2. False

Answer:A

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157. The cooling of air, without any change in its specific humidity, is known as sensible cooling
  1. Correct
  2. Incorrect

Answer:A

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158. The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.
  1. Increases
  2. Decreases

Answer:A

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159. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called
  1. dry air
  2. moist air
  3. saturated air
  4. specific humidity

Answer:C

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160. The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called
  1. Kinetic theory of gases
  2. Newton's law of gases
  3. Dalton's law of partial pressures
  4. Avogadro's hypothesis

Answer:C

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161. The expansion valve in a refrigerator controls the flow of refrigerant.
  1. Correct
  2. Incorrect

Answer:A

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162. Upto the critical radius of insulation,
  1. added insulation will increase heat loss
  2. added insulation will decrease heat loss
  3. heat flux will decrease
  4. None of the above

Answer:A

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163. The relative humidity lines on a psychrometric chart are
  1. vertical and uniformly spaced
  2. horizontal and uniformly spaced
  3. horizontal and non-uniformly spaced
  4. curved lines

Answer:D

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164. Most unsteady heat flow occurs
  1. Through the walls of the refrigerator
  2. During annealing of castings
  3. Through the walls of the furnace
  4. Through lagged pipe carrying steam

Answer:B

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165. A vapour absorption refrigeration system
  1. gives noisy operation
  2. gives quiet operation
  3. requires little power consumption
  4. cools below 0° C

Answer:B

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166. The rato of energy transferred by convection to that by conduction is called
  1. Stanton number
  2. Nusselt number
  3. Biot number
  4. Peclet number

Answer:B

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167. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K. Assuming air as working substance with cp = 1 kJ/kg then calculate the net work of compression
  1. 25 kJ/kg
  2. 50 kJ/kg
  3. l00 kJ/kg
  4. 125 kJ/kg

Answer:B

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168. Wet bulb temperature indicates the moisture content in air.
  1. Agree
  2. Disagree

Answer:A

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169. The inclined and non-uniformly spaced straight lines on a psychrometric chart indicates wet bulb temperature.
  1. Agree
  2. Disagree

Answer:A

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170. The heat is transferred by conduction, convection and radiation in
  1. melting of ice
  2. boiler furnaces
  3. condensation of steam in condenser
  4. none of these

Answer:B

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171. The temperature rise, between the condenser outlet and expansion valve in ammonia vapour compression system, should be as low as possible.
  1. Yes
  2. No

Answer:A

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172. 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
  1. humidity ratio
  2. relative humidity
  3. absolute humidity
  4. degree of saturation

Answer:D

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173. For unsaturated air, the dew point temperature is __________ wet bulb temperature.
  1. equal to
  2. less than
  3. more than

Answer:B

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174. During dehumidification process, __________ remains constant.
  1. wet bulb temperature
  2. relative humidity
  3. dry bulb temperature
  4. specific humidity

Answer:C

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175. The value of the wave length for maximum emissive power is given by
  1. Kirchhoff's law
  2. Stefan's law
  3. Wein's law
  4. Planck's law

Answer:C

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176. Emissivity of a body will be equal to its absorptivity at all temperatures.
  1. Yes
  2. No

Answer:B

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177. R-12 is generally preferred over R-22 in deep freezers since
  1. it has low operating pressures
  2. it gives higher coefficient of performance
  3. it is miscible with oil over large range of temperatures
  4. all of the above

Answer:C

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178. The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is known as
  1. wet bulb temperature
  2. dry bulb temperature
  3. dew point temperature
  4. none of these

Answer:A

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179. During sub-cooling, sensible heat from a liquid refrigerant is removed.
  1. Yes
  2. No

Answer:A

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180. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
  1. heated and dehumidified
  2. heated and humidified
  3. cooled and humidified
  4. cooled and dehumidified

Answer:B

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181. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
  1. automatic expansion valve
  2. high side float valve
  3. thermostatic expansion valve
  4. low side float valve

Answer:D

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182. During a cold winter season, a person prefers to sit near a fire. The maximum heat reaching the person would be due to
  1. conduction from the fire
  2. convection from the fire
  3. convection and radiation together
  4. Radiation from the fire

Answer:D

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183. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The by-pass factor of the heating coil is
  1. 0.376
  2. 0.4
  3. 0.6
  4. 0.67

Answer:C

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184. The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air.
  1. Lower
  2. Higher

Answer:B

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185. The emissivity of a polished silver body is __________ as compared to black body.
  1. Same
  2. Low
  3. very low
  4. High

Answer:C

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186. In a pressure enthalpy chart, the space between the saturated liquid line and saturated vapour line, represents sub-cooled liquid region.
  1. True
  2. False

Answer:B

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187. R-11 has the highest critical point temperature.
  1. Correct
  2. Incorrect

Answer:A

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188. The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called
  1. coefficient of performance of refrigeration
  2. coefficient of performance of heat pump
  3. relative coefficient of performance
  4. refrigerating efficiency

Answer:A

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189. Air refrigerator works on
  1. reversed Carnot cycle
  2. Bell Coleman cycle
  3. both (a) and (b)
  4. none of these

Answer:C

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190. The reciprocating refrigerant compressors are very suitable for
  1. small displacements and low condensing pressures
  2. large displacements and high condensing pressures
  3. small displacements and high condensing pressures
  4. large displacements and low condensing pressures

Answer:C

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191. The boiling point of carbon dioxide is
  1. -20.5°C
  2. -50°C
  3. -63.3°C
  4. -78.3°C

Answer:D

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192. The mass of water vapour present in __________ is called absolute humidity
  1. 1 m3 of wetair
  2. 1 m3 of dry air
  3. 1 kg of wet air
  4. 1 kg of dry air

Answer:B

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193. The cooling system used for supersonic aircrafts and rockets is
  1. simple air cooling system
  2. boot-strap air cooling system
  3. reduced ambient air cooling system
  4. regenerative air cooling system

Answer:D

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194. The desirable property of a refrigerant is
  1. low boiling point
  2. high critical temperature
  3. high latent heat of vaporisation
  4. all of these

Answer:D

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195. The humidification process, on the psychrometric chart is shown by
  1. horizontal line
  2. vertical line
  3. inclined line
  4. curved line

Answer:B

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196. The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to
  1. bright green
  2. Yellow
  3. Red
  4. Orange

Answer:A

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197. The wet bulb depression indicates __________ humidity of the air.
  1. Absolute
  2. Relative
  3. Specific

Answer:B

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198. Prandtl number (PN) is given by PN = μ.cp/k.
  1. Yes
  2. No

Answer:A

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199. In a vapour compression system, the condition of refrigerant before passing through the condenser is
  1. saturated liquid
  2. wet vapour
  3. dry saturated vapour
  4. superheated vapour

Answer:D

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200.The appropriate rate equation for convective heat transfer between a surface and adjacent fluid is prescribed by
  1. Newton’s first law
  2. Wein’s displacement law
  3. Kirchhoff’s law
  4. Newton’s law of cooling

Answer:D

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201. The critical temperature is the temperature
  1. above which a gas will never liquefied
  2. above which a gas may explode
  3. below which a gas is always liquefied
  4. None of the above

Answer:A

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202. The evaporator changes the low pressure liquid refrigerant from the expansion valve into
  1. high pressure liquid refrigerant
  2. low pressure liquid and vapour refrigerant
  3. low pressure vapour refrigerant
  4. none of these

Answer:C

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203. For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is
  1. Zero
  2. 20
  3. 50
  4. 100

Answer:D

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204. The mass of water vapour present in 1 kg of dry air, is called humidity ratio.
  1. True
  2. False

Answer:A

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205. The unit of overall coefficient of heat transfer is
  1. W/m2 K
  2. W/m2
  3. W/mK
  4. W/m

Answer:A

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206. Most thermostatic expansion valves are set for a superheat of
  1. 5°C
  2. 10°C
  3. 15°C
  4. 20°C

Answer:A

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207. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is
  1. Reciprocating
  2. Rotating
  3. Centrifugal
  4. Screw

Answer:C

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208. The transfer of heat by molecular collision is smallest in
  1. Solids
  2. Liquids
  3. Gases
  4. none of these

Answer:C

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209. During dehumidification process, the relative humidity
  1. remains constant
  2. Increases
  3. Decreases

Answer:C

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210. The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.
  1. Good
  2. Bad

Answer:B

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211. The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness.
  1. Agree
  2. Disagree

Answer:A

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212. When the discharge pressure is too high in a refrigeration system, high pressure control is installed to stop the compressor
  1. Correct
  2. Incorrect

Answer:A

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213. The wet bulb temperature during sensible cooling of air
  1. remains constant
  2. Increases
  3. Decreases

Answer:C

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214. In absorption vapour systems, the refrigerant widely used is R-12.
  1. Correct
  2. Incorrect

Answer:B

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215. Heat transfer in a long, hollow cylinder which is maintained at uniform but different temperatures on its inner and outer surfaces may be assumed to be taking place in which direction?
  1. Axial only
  2. Unpredictable
  3. Radial only
  4. No heat transfer takes place

Answer:C

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216. Hydrogen is used in electrolux refrigeration system so as to __________ the rate of evaporation of the liquid ammonia passing through the evaporator.
  1. Equalise
  2. Reduce
  3. Increase

Answer:C

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217. A refrigerant with the highest critical pressure is
  1. R-11
  2. R-12
  3. R-22
  4. Ammonia

Answer:D

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218. In a shell and tube heat exchanger, baffles are provided on the shell side to
  1. improve heat transfer
  2. provide support for tubes
  3. prevent stagnation of shell side fluid
  4. all of these

Answer:D

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219. The average value of thermal conductivity for water at 20° C saturate is about 0.51.
  1. True
  2. False

Answer:A

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220. In aqua-ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in
  1. Condenser
  2. Evaporator
  3. Absorber
  4. none of these

Answer:A

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221. The boiling point of ammonia is
  1. -10.5°C
  2. -30°C
  3. -33.3°C
  4. -77.7°C

Answer:C

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222. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and
  1. carbon dioxide
  2. sulphur dioxide
  3. lithium bromide
  4. R-12

Answer:C

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223. In a black body, all radiations are rejected.
  1. True
  2. False

Answer:B

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224. Most air cooled condensers are designed to operate with a temperature difference of
  1. 5°C
  2. 8°C
  3. 14°C
  4. 22°C

Answer:C

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225. In a reversed Brayton cycle, the heat is absorbed by the air during
  1. isentropic compression process
  2. constant pressure cooling process
  3. isentropic expansion process
  4. constant pressure expansion process

Answer:D

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226. A device used for transfering heat from one fluid to another is called heat exchanger.
  1. True
  2. False

Answer:A

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227. The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by
  1. (C.O.P.)P = (C.O.P.)R + 2
  2. (C.O.P.)P = (C.O.P.)R + 1
  3. (C.O.P)P = (C.O.P)R - 1
  4. (C.O.P)P = (C.O.P)R

Answer:B

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228. The temperature below which a gas is always liquified, is known as critical temperature.
  1. Correct
  2. Incorrect

Answer:B

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229. A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in higher coefficient of performance.
  1. Agree
  2. Disagree

Answer:A

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230. The ratio of surface convection resistance to the internal conduction resistance is known as
  1. Grashoff number
  2. Biot number
  3. Stanton number
  4. Prandtl number

Answer:B

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

Answer:A

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232. The critical thickness of insulation for a sphere is
  1. k/h0
  2. 2k/h0
  3. h0/k
  4. h0/2k

Answer:B

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233. The difference between dry bulb temperature and dew point temperature, is called
  1. dry bulb depression
  2. wet bulb depression
  3. dew point depression
  4. degree of saturation

Answer:C

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234. Planck's law holds good for all coloured bodies.
  1. True
  2. False

Answer:A

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235. The formation of frost on cooling coils in a refrigerator
  1. increases heat transfer
  2. improves C.O.P. of the system
  3. increases power consumption
  4. reduces power consumption

Answer:C

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236. In mechanical refrigeration system, the refrigerant has the maximum temperature
  1. in evaporator
  2. before expansion valve
  3. between compressor and condenser
  4. between condenser and evaporator

Answer:C

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237. The condition of refrigerant after passing through the condenser in a vapour compression system is
  1. saturated liquid
  2. wet vapour
  3. dry saturated vapour
  4. superheated vapour

Answer:A

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238. The leakage in a refrigeration system using freon is detected by
  1. halide torch
  2. sulphur sticks
  3. soap and water
  4. all of these

Answer:A

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239. 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
  1. Conduction
  2. free convection
  3. forced convection
  4. Radiation

Answer:C

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240. When there is an addition of water vapour to the air of enclosed space, a gain in __________ is said to occur.
  1. sensible heat
  2. latent heat

Answer:B

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241. The relative humidity __________ as air gets drier.
  1. Increases
  2. Decreases

Answer:A

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242. Which statement is true regarding steady state condition?
  1. Internal energy of the system changes
  2. Heat exchange is constant
  3. It is a function of space and time coordinates
  4. None of the above

Answer:B

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243. The central air conditioning system has __________ overall efficiency as compared to individual systems.
  1. Same
  2. Lower
  3. Higher

Answer:C

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244. An ordinary passenger aircraft requires a cooling system of capacity.
  1. 2 TR
  2. 4 TR
  3. 8 TR
  4. 10 TR

Answer:C

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245. The thermal diffusivity for solids is generally less than those for liquids and gases.
  1. True
  2. False

Answer:B

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246. Conduction is the process of heat transfer from one particle of the body to another by the actual motion of the heated particles.
  1. True
  2. False

Answer:B

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247. Moisture should be removed from refrigerants to avoid
  1. freezing at the expansion valve
  2. restriction to refrigerant flow
  3. corrosion of steel plates
  4. all of these

Answer:D

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248. During humidification process, dry bulb temperature
  1. remains constant
  2. Increases
  3. Decreases

Answer:A

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249. Fourier's law of heat conduction gives the heat flow for
  1. irregular surfaces
  2. non-uniform temperature surfaces
  3. one dimensional cases only
  4. two dimensional cases only

Answer:C

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250. The product of Reynolds number and Prandtl number is known as
  1. Stanton number
  2. Biot number
  3. Peclet number
  4. Grashoff number

Answer:C

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251. Carbon dioxide is
  1. Colourless
  2. Odourless
  3. non-flammable
  4. all of these

Answer:D

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252. The reduced ambient air cooling system has
  1. one cooling turbine and one heat exchanger
  2. one cooling turbine and two heat exchangers
  3. two cooling turbines and one heat exchanger
  4. two cooling turbines and two heat exchangers

Answer:C

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253. Regarding one dimensional heat transfer, choose the correct statement
  1. Steady- f (x), Unsteady- f (x, t)
  2. Steady- f (x, t), Unsteady- f (x)
  3. Steady- f (y, z), Unsteady- f (y)
  4. None of the above

Answer:C

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254. The heat of sun reaches to us according to
  1. Conduction
  2. Convection
  3. Radiation
  4. none of these

Answer:C

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255. The specific humidity during humidification process
  1. remains constant
  2. Increases
  3. Decreases

Answer:B

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256. Stefan-Boltzmann law is applicable for heat transfer by convection
  1. Agree
  2. Disagree

Answer:B

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257. The most commonly used method for the design of duct size is the
  1. velocity reduction method
  2. equal friction method
  3. static regain method
  4. dual or double method

Answer:C

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258. In a vapour compression system, the condition of refrigerant is dry saturated vapour
  1. before entering the compressor
  2. after leaving the compressor
  3. before entering the condenser
  4. after leaving the condenser

Answer:A

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259. An evaporator is also known as
  1. freezing coil
  2. cooling coil
  3. chilling coil
  4. all of these

Answer:D

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260. Oil separator in a refrigeration cycle is installed
  1. before compressor
  2. between compressor and condenser
  3. between condenser and evaporator
  4. between condenser and expansion valve

Answer:B

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261. In larger industrial and commercial reciprocating compression systems, refrigerent widely used is
  1. Ammonia
  2. carbon dioxide
  3. sulphur dioxide
  4. R-12

Answer:A

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262. During sensible cooling of air, specific humidity
  1. remains constant
  2. Increases
  3. Decreases

Answer:A

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263. Convective heat transfer coefficient doesn’t depend on
  1. Surface area
  2. Space
  3. Time
  4. Orientation of solid surface

Answer:A

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264. The transfer of heat by molecular collision is known as
  1. Conduction
  2. Convection
  3. Radiation
  4. none of these

Answer:A

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265. In a psychrometric chart, specific humidity (moisture content) lines are
  1. vertical and uniformly spaced
  2. horizontal and uniformly spaced
  3. horizontal and non-uniformly spaced
  4. curved lines

Answer:B

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266. The expression Q = ρ AT4 is called
  1. Fourier equation
  2. Stefan-Boltzmann equation
  3. Newton-Rikhmann equation
  4. Joseph-Stefan equation

Answer:B

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267. Thermal conductivity of solid metals __________ with rise in temperature.
  1. remains same
  2. Decreases
  3. Increases

Answer:B

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268. The horizontal and non-uniformly spaced lines on a psychrometric chart indicates
  1. dry bulb temperature
  2. wet bulb temperature
  3. dew point temperature
  4. specific humidity

Answer:C

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269. Which of the following refrigerant is highly toxic and flammable?
  1. Ammonia
  2. Carbon dioxide
  3. Sulphur dioxide
  4. R-12

Answer:A

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270. The unit of Stefan-Boltzmann constant is
  1. Watt/Mk
  2. Watt/m2 K2
  3. Watt/m2K4
  4. Watt/mK2

Answer:C

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271. The emissive power of a body depends upon its
  1. Temperature
  2. physical nature
  3. wave length
  4. all of these

Answer:D

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272. Unit of the rate of heat transfer is
  1. Joule
  2. Newton
  3. Pascal
  4. Watt

Answer:D

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273. In a refrigerating machine, heat rejected is __________ heat absorbed.
  1. equal to
  2. less than
  3. greater than

Answer:C

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274. The coefficient of performance (C.O.P.) is the reciprocal of the efficiency of a heat engine.
  1. True
  2. False

Answer:A

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275. The wet bulb temperature at 100% relative humidity is __________ dry bulb temperature.
  1. same as
  2. lower than
  3. higher than

Answer:A

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276. The freezing point of sulphur dioxide is
  1. -56.6°C
  2. -75.2°C
  3. -77.7°C
  4. -135.8°C

Answer:B

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277. The ratio of the energy absorbed by the body to the total energy falling on it, is called
  1. absorptive power
  2. emissive power
  3. Emissivity
  4. none of these

Answer:A

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278. The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner.
  1. Same
  2. Less
  3. More

Answer:B

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279. The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body
  1. move actually
  2. do not move actually
  3. affect the intervening medium
  4. does not affect the intervening medium

Answer:B

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280. Defrosting of a refrigerator may be done by stopping the compressor for a short period.
  1. Correct
  2. Incorrect

Answer:A

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281. In a refrigeration system, the expansion device is connected between the
  1. compressor and condenser
  2. condenser and receiver
  3. receiver and evaporator
  4. evaporator and compressor

Answer:C

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282. Wein's law states that the wave length corresponding to __________ is proportional to the absolute temperature.
  1. minimum energy
  2. maximum energy

Answer:B

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283. In a domestic vapour compression refrigerator, the refrigerant commonly used is
  1. CO2
  2. Ammonia
  3. R-12
  4. all of these

Answer:C

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284. The coefficient of performance of vapour compression refrigeration system is quite __________ as compared to air refrigeration system.
  1. low
  2. High

Answer:B

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285. Which of the following refrigerant has the lowest boiling point?
  1. Ammonia
  2. Carbon dioxide
  3. Sulphur dioxide
  4. R-12

Answer:B

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286. During sensible cooling of air, the relative humidity increases.
  1. Yes
  2. No

Answer:A

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287. In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about
  1. 1
  2. 1.25
  3. 2.15
  4. 5.12

Answer:B

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288. The undesireable property of a refrigerant is
  1. non-toxic
  2. non-flammable
  3. non-explosive
  4. high boiling point

Answer:D

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289. The dry bulb temperature during sensible heating of air
  1. remains constant
  2. Increases
  3. Decreases

Answer:B

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290. Radiation is the process of heat transfer in which heat flows from a __________ , in a straight line, without affecting the intervening medium.
  1. cold body to hot body
  2. hot body to cold body
  3. smaller body to larger body
  4. larger body to smaller body

Answer:B

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291. The heating of air, without any change in its specific humidity, is known as sensible heating.
  1. True
  2. False

Answer:A

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292. The pressure at the inlet of a refrigerant compressor is called
  1. suction pressure
  2. discharge pressure
  3. critical pressure
  4. back pressure

Answer:A

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293. The process, generally used in summer air conditioning to cool and dehumidify the air, is called
  1. humidification
  2. dehumidification
  3. heating and humidification
  4. cooling and dehumidification

Answer:D

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294. The leakage in a refrigeration system using ammonia is detected by
  1. halide torch
  2. sulphur sticks
  3. soap and water
  4. all of these

Answer:B

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295. The lowest temperature during the cycle in a vapour compression system occurs after
  1. Compression
  2. Expansion
  3. condensation
  4. Evaporation

Answer:D

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296. The temperature of air recorded by a thermometer, when it is not effected by the moisture present in the air, is called
  1. wet bulb temperature
  2. dry bulb temperature
  3. dew point temperature
  4. none of these

Answer:B

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297. A human body feels comfortable when the heat produced by the metabolism of human body is equal to the
  1. heat dissipated to the surroundings
  2. heat stored in the human body
  3. sum of (a) and (b)
  4. difference of (a) and (b)

Answer:C

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298. During sensible cooling
  1. relative humidity remains constant
  2. wet bulb temperature increases
  3. specific humidity increases
  4. partial pressure of vapour remains constant

Answer:D

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299. The wave length of the radiation emitted depends only on the temperature and is independent of the material of the body.
  1. True
  2. False

Answer:A

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300. The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called
  1. Conduction
  2. Convection
  3. Radiation

Answer:B

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301. In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the
  1. expansion valve to the evaporator
  2. evaporator to the thermostat
  3. condenser to the expansion valve
  4. condenser to the evaporator

Answer:D

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302. The absolute humidity is the mass of water vapour present in 1 m3 of dry air.
  1. Agree
  2. Disagree

Answer:A

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303. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by
  1. liquid pump
  2. Generator
  3. absorber and generator
  4. absorber, generator and liquid pump

Answer:D

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304. A condenser is used in the __________ pressure side of a refrigerating system.
  1. Low
  2. High

Answer:B

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305. A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,
  1. the better insulation must be put inside
  2. the better insulation must be put outside
  3. one could place either insulation on either side
  4. None of the above

Answer:A

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306. In a parallel flow heat exchanger, the rate of flow of heat and the rate of decrease of temperature are maximum.
  1. Yes
  2. No

Answer:A

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307. During heating and dehumidification process, dry bulb temperature
  1. remains constant
  2. Increases
  3. Decreases

Answer:B

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308. A refrigerant compressor is used to
  1. raise the pressure of the refrigerant
  2. raise the temperature of the refrigerant
  3. circulate the refrigerant through the refrigerating system
  4. all of the above

Answer:D

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309. In which of the following refrigeration system, waste heat can be effectively used?
  1. Vapour compression cycle
  2. Vapour absorption cycle
  3. Air refrigeration cycle
  4. none of these

Answer:B

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310. The fluids used in electrolux refrigerator are
  1. water and hydrogen
  2. ammonia and hydrogen
  3. ammonia, water and hydrogen
  4. none of these

Answer:C

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311. The process in which the refrigerant after condensation process is cooled below the saturation temperature is known as
  1. sub-cooling or under-cooling
  2. super-cooling
  3. normal cooling
  4. none of these

Answer:A

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312. R-12 has the __________ freezing point.
  1. Lowest
  2. Highest

Answer:A

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313. The power per tonne of refrigeration is
  1. 3.5/C.O.P.
  2. C.O.P/3.5
  3. 3.5 x C.O.P.
  4. none of these

Answer:A

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314. Two rods A and B of the same length and diameter protrude from a surface at 120 degree Celsius and are exposed at air at 25 degree Celsius. The temperatures measured at the end of the rods are 50 degree Celsius and 75 degree Celsius. If thermal conductivity of material A is 20W/ m K, calculate it for B
  1. 31.13W/m K
  2. 41.13W/m K
  3. 51.13W/m K
  4. 61.13W/m K

Answer:C

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315. The thermostatic expansion valve is also called
  1. constant pressure valve
  2. constant temperature valve
  3. constant superheat valve
  4. none of these

Answer:C

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316. The specific humidity during cooling and dehumidification
  1. remains constant
  2. Increases
  3. Decreases

Answer:C

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317. The capillary tube, as an expansion device, is used in
  1. domestic refrigerators
  2. water coolers
  3. room air conditioners
  4. all of these

Answer:A

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318. In aircraft, air refrigeration Cycle is used because of
  1. low weight per tonne of refrigeration
  2. high heat transfer rate
  3. low temperature at high altitudes
  4. higher coefficient of performance

Answer:A

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319. The material of pipe lines for a system using freon as a refrigerant should be
  1. Brass
  2. Copper
  3. Steel
  4. Aluminium

Answer:B

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320. In a pressure enthalpy chart, the space to the left of the saturated liquid line represents
  1. wet vapour region
  2. superheated vapour region
  3. sub-cooled liquid region
  4. none of these

Answer:C

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321. During sensible heating of air __________ decreases.
  1. wet bulb temperature
  2. relative humidity
  3. dry bulb temperature
  4. specific humidity

Answer:B

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322. The overall coefficient of heat transfer is used in problems of
  1. conduction
  2. Convection
  3. radiation
  4. conduction and convection

Answer:D

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323. The boiling point of R-12 is about - 30°C.
  1. True
  2. False

Answer:A

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324. The difference between dry bulb temperature and wet bulb temperature, is called
  1. dry bulb depression
  2. wet bulb depression
  3. dew point depression
  4. degree of saturation

Answer:B

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