Refrigeration And Air Conditioning MCQ Questions & Answers | Mechanical Engineering

In the vapor compression refrigeration cycle, the refrigerant undergoes phase changes and pressure variations as it moves through different components of the system.

Explanation for each option:

After passing through the condenser: The refrigerant is in a high-pressure saturated liquid state after it has released heat and condensed in the condenser.
Before passing through the condenser: This is not the correct condition. Before the condenser, the refrigerant is typically in a high-pressure, high-temperature, and superheated vapor state.
After passing through the expansion or throttle valve: After passing through the expansion valve, the refrigerant undergoes a pressure drop and enters the evaporator as a low-pressure, low-temperature mixture of liquid and vapor.
Before entering the expansion valve: This is not the correct condition. Before the expansion valve, the refrigerant is typically in a high-pressure, high-temperature, and superheated vapor state.

Therefore, in the context of the question, the condition of the refrigerant as a high-pressure saturated liquid occurs after passing through the condenser

In a vapour compression system, the condition of refrigerant is dry saturated vapour Before entering the compressor

In vapour compression cycle the condition off refrigerant is dry saturated vapour Before entering the compressor

R-12 (Dichlorodifluoromethane) has been traditionally used in small tonnage commercial machines and hermetically sealed refrigeration units such as domestic refrigerators and small air-conditioning systems.

It is preferred because it is non-toxic, non-flammable, chemically stable, and has good thermodynamic properties, making it highly suitable for sealed systems where maintenance is minimal.

Other options like Ammonia are toxic, Carbon dioxide operates at very high pressures, and Sulphur dioxide is corrosive and toxic, which makes them unsuitable for small hermetically sealed units.

Although R-12 is now phased out due to its ozone depletion potential, it remains the correct theoretical answer for traditional refrigeration systems in examination contexts.

The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is Less

Highest pressure encountered in a refrigeration system should be Much below critical pressure

In a vapour compression system, the condition of refrigerant before passing through the condenser is Superheated vapour

The Bell Coleman Cycle also called as the Joule or "reverse" Brayton cycle.
it is a refrigeration cycle where the working fluid is a gas that is compressed and expanded, but does not change phase.

The heat rejection factor (HRF) is given by $$1 + \frac{1}{{{\text{C}}{\text{.O}}{\text{.P}}{\text{.}}}}$$

In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is Heated and humidified