Refrigeration And Air Conditioning MCQ Questions & Answers

61

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

A) Operating the machine at higher speeds B) Operating the machine at lower speeds C) Raising the higher temperature D) Lowering the higher temperature

Discuss

Answer & Solution

Answer: Option D

Solution:

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

62

The evaporator changes the low pressure liquid refrigerant from the expansion valve into

A) High pressure liquid refrigerant B) Low pressure liquid and vapour refrigerant C) Low pressure vapour refrigerant D) None of these

Discuss

Answer & Solution

Answer: Option C

Solution:

The evaporator changes the low pressure liquid refrigerant from the expansion valve into Low pressure vapour refrigerant

63

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

A) Heat of compression B) Work done by compressor C) Enthalpy increase in compressor D) All of the above

Discuss

Answer & Solution

Answer: Option D

Solution:

The coefficient of performance is the ratio of the refrigerant effect to the
- Heat of compression
- Work done by compressor
- Enthalpy increase in compressor

64

In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is

A) Less than 2 kg B) More than or equal to 3.65 kg C) More than 10 kg D) There is no such consideration

Discuss

Answer & Solution

Answer: Option B

Solution:

In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is More than or equal to 3.65 kg

65

Pressure of water vapour is given by

A) $$\frac{{0.622{{\text{P}}_{\text{v}}}}}{{{{\text{P}}_{\text{b}}} - {{\text{P}}_{\text{v}}}}}$$ B) $$\frac{\mu }{{1 - \left( {1 - \mu } \right)\frac{{{{\text{P}}_{\text{s}}}}}{{{{\text{P}}_{\text{b}}}}}}}$$ C) $$\frac{{{{\text{P}}_{\text{v}}}\left( {{{\text{P}}_{\text{b}}} - {{\text{P}}_{\text{d}}}} \right)}}{{{{\text{P}}_{\text{d}}}\left( {{{\text{P}}_{\text{b}}} - {{\text{P}}_{\text{v}}}} \right)}}$$ D) None of these

Discuss

Answer & Solution

Answer: Option D

Solution:

Pressure of water vapour is given by, $$ln\left( {\frac{{{{\text{P}}_1}}}{{{{\text{P}}_2}}}} \right) = \left( {\frac{{\Delta {\text{Hvap}}}}{{\text{R}}}} \right)\left( {\frac{1}{{{{\text{T}}_2}}} - \frac{1}{{{{\text{T}}_1}}}} \right)$$

66

In vapour compression cycle using NH₃ as refrigerant, initial charge is filled at

A) Suction of compressor B) Delivery of compressor C) High pressure side close to receiver D) Low pressure side near receiver

Discuss

Answer & Solution

Answer: Option C

Solution:

In vapour compression cycle using NH₃ as refrigerant, initial charge is filled at high pressure side close to receiver.

67

If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be

A) 0.2 B) 1.2 C) 5 D) 6

Discuss

Answer & Solution

Answer: Option D

Solution:

If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be 6

68

Vertical lines on pressure-enthalpy chart show constant

A) Pressure lines B) Temperature lines C) Total heat lines D) Entropy lines

Discuss

Answer & Solution

Answer: Option C

Solution:

Vertical lines on pressure-enthalpy chart show constant Total heat lines

69

A vapour absorption refrigerator uses _________ as a refrigerant.

A) Water B) Ammonia C) Freon D) Aqua-ammonia

Discuss

Answer & Solution

Answer: Option D

Solution:

A vapour absorption refrigerator uses Aqua-ammonia as a refrigerant.
In the vapor absorption system the refrigerant used is ammonia, water or lithium bromide. The refrigerant gets condensed in the condenser and it gets evaporated in the evaporator. The refrigerant produces cooling effect in the evaporator and releases the heat to the atmosphere via the condenser.

70

Which of the following statement is correct for ammonia as a refrigerant?

A) It is toxic to mucous membranes. B) It requires large displacement per TR compared to fluoro carbons. C) It reacts with copper and its alloys. D) All of these

Discuss

Answer & Solution

Answer: Option D

Solution:

Advantages of ammonia as a refrigerant:
- It is toxic to mucous membranes.
- It requires large displacement per TR compared to fluoro carbons.
- It reacts with copper and its alloys.

Refrigeration And Air Conditioning MCQ Questions & Answers | Mechanical Engineering