Refrigeration and Air Conditioning

71. The coefficient of performance is the ratio of the refrigerant effect to the

1. heat of compression
2. work done by compressor
3. enthalpy increase in compressor
4. all of the above
5. none of the above.

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72. The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for condensing temperatures without non-condensable gases,

1. will be higher
2. will be lower
3. will remain unaffected
4. may be higher or lower depending upon the nature of non-condensable gases
5. unpredictable.

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73. The COP of a domestic refrigerator

1. is less than 1
2. is more than 1
3. is equal to 1
4. depends upon the make
5. depends upon the weather conditions.

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74. The COP of a vapour compression plant in comparison to vapour absorption plant is

1. more
2. less
3. same
4. more/less depending on size of plant
5. unpredictable.

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75. The domestic refrigerator uses following type of compressor

1. centrifugal
2. axial
3. miniature sealed unit
4. piston type reciprocating
5. none of the above.

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76. The evolution of heat of solution takes place in ammonia absorption plant when

1. ammonia vapour goes into solution
2. ammonia vapour is driven out of solution
3. lithium bromide mixes with ammonia
4. weak solution mixes with strong solution
5. lithium bromide is driven out of solution.

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77. The general rule for rating refrigeration systems (excepting for C02 system) is to approximate following h.p. per ton of refrigeration

1. 0.1 to 0.5 h.p. per ton of refrigeration
2. 0.5 to 0.8 h.p. per ton of refrigeration
3. 1 to 2 h.p. per ton of refrigeration
4. 2 to 5 h.p. per ton of refrigeration
5. 5 to 10 h.p. per ton refrigeration.

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78. The higher temperature in vapour compression cycle occurs at

1. receiver
2. expansion valve
3. evaporator
4. condenser discharge
5. compressor discharge.

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79. The leaks in a refrigeration system using Freon are detected by

1. halide torch which on detection produces greenish flame lighting
2. sulphur sticks which on detection gives white smoke
3. using reagents
4. smelling
5. sensing reduction in pressure.

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80. The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy-diagram represents

1. condensation of the refrigerant vapour
2. evaporation of the refrigerant liquid
3. compression of the refrigerant vapour
4. metering of the refrigerant liquid
5. none of the above.

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