Throttling operation in a refrigeration cycle is carried out in the Expansion Valve.

Explanation:
The expansion valve is a key component in a refrigeration cycle that controls the flow of refrigerant from the high-pressure side to the low-pressure side of the system. It is responsible for creating a pressure drop in the refrigerant, which allows it to expand and cool down.

The throttling operation in the expansion valve can be explained in the following steps:

1. Pressure reduction: The high-pressure refrigerant from the condenser enters the expansion valve. The valve restricts the flow of refrigerant, causing a significant pressure drop. This pressure reduction is necessary for the refrigerant to change from a high-pressure liquid to a low-pressure mixture of liquid and vapor.

2. Temperature drop: As the refrigerant passes through the expansion valve, it undergoes a rapid expansion due to the pressure drop. This expansion results in a decrease in the refrigerant's temperature. The refrigerant absorbs heat from its surroundings, which leads to a cooling effect.

3. Phase change: The refrigerant undergoes a phase change from a saturated liquid to a saturated vapor during the throttling process. This phase change occurs as a result of the reduced pressure and temperature drop in the expansion valve.

4. Quality control: The expansion valve also helps to regulate the quality of the refrigerant leaving the valve. It ensures that the refrigerant leaving the expansion valve is in the desired state, with the correct ratio of liquid to vapor. This is important for the proper functioning of the evaporator and the overall refrigeration cycle.

The expansion valve plays a crucial role in the refrigeration cycle by controlling the flow and pressure of the refrigerant. It allows for the efficient transfer of heat from the conditioned space to the evaporator, where the refrigerant absorbs heat and cools down the space. Without the expansion valve, the refrigeration cycle would not be able to operate effectively, and the desired cooling effect would not be achieved.