Refrigeration And Air Conditioning MCQ Questions & Answers

11

Choose the wrong statement

A) Temperature of medium being cooled must be below that of the evaporator B) Refrigerant leaves the condenser as liquid C) All solar thermally operated absorption systems are capable only of intermittent operation D) Frost on evaporator reduces heat transfer

Discuss

Answer & Solution

Answer: Option A

Solution:

As the temperature of the available water or air is always higher than that of the boiling refrigerant in the evaporator, the refrigerant cannot be condensed as it leaves the evaporator.

12

In a refrigeration system, the expansion device is connected between the

A) Compressor and condenser B) Condenser and receiver C) Receiver and evaporator D) Evaporator and compressor

Discuss

Answer & Solution

Answer: Option C

Solution:

In a refrigeration system, the expansion device is connected between the Receiver and evaporator

13

The human body feels comfortable when the heat stored in the body is

A) Positive B) Negative C) Zero D) None of these

Discuss

Answer & Solution

Answer: Option C

Solution:

The human body feels comfortable when the heat stored in the body is zero

14

The emissivity of a polished silver body is _________ as compared to black body.

A) Same B) Low C) Very low D) High

Discuss

Answer & Solution

Answer: Option C

Solution:

The emissivity of a polished silver body is very low as compared to black body.

15

Relative humidity is given by (where p_v = Partial pressure of water vapour, p_b = Barometric pressure, p_s = Pressure of saturated air, p_d = Pressure at dry bulb temperature, p_w = Saturation pressure corresponding to wet bulb temperature and $$\mu $$ = Degree of saturation)

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 B

Solution:

Relative humidity is given by $$\frac{\mu }{{1 - \left( {1 - \mu } \right)\frac{{{{\text{p}}_{\text{s}}}}}{{{{\text{p}}_{\text{b}}}}}}}$$
Where
p_v = Partial pressure of water vapour,
p_b = Barometric pressure,
p_s = Pressure of saturated air,
p_d = Pressure at dry bulb temperature,
p_w = Saturation pressure corresponding to wet bulb temperature,
$$\mu $$ = Degree of saturation

16

In which of the following refrigeration system, waste heat can be effectively used?

A) Vapour compression cycle B) Vapour absorption cycle C) Air refrigeration cycle D) None of these

Discuss

Answer & Solution

Answer: Option B

Solution:

It is generally recognized that considerable energy savings could result from installing a waste heat recovery system in the exhaust of a Gas Turbine power plant

17

Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since

A) These react with water vapour and cause acid rain B) These react with plants and cause greenhouse effect C) These react with oxygen and cause its depletion D) These react with ozone layer

Discuss

Answer & Solution

Answer: Option D

Solution:

Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since These react with ozone layer

18

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

A) 25°C DBT and 100% RH B) 20°C DBT and 80% RH C) 22°C DBT and 60% RH D) 25°C DBT and 40% RH

Discuss

Answer & Solution

Answer: Option C

Solution:

The comfort conditions in air conditioning are at 22°C DBT and 60% RH

19

In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by

A) Liquid pump B) Generator C) Absorber and generator D) Absorber, generator and liquid pump

Discuss

Answer & Solution

Answer: Option D

Solution:

In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by Absorber, generator and liquid pump

20

Which of the following statement is correct?

A) The constant enthalpy lines are also constant wet bulb temperature lines B) The wet bulb and dry bulb temperature are equal at saturation condition C) The wet bulb temperature is a measure of enthalpy of moist air D) All of the above

Discuss

Answer & Solution

Answer: Option D

Solution:

- The constant enthalpy lines are also constant wet bulb temperature lines
- The wet bulb and dry bulb temperature are equal at saturation condition
- The wet bulb temperature is a measure of enthalpy of moist air

Refrigeration And Air Conditioning MCQ Questions & Answers | Mechanical Engineering