How is capacity controlled on a screw-type rotary air conditioning compressor?

In a screw-type rotary air conditioning compressor, capacity control is primarily achieved using sliding valves. This mechanism allows for the adjustment of the flow of refrigerant within the compressor, which in turn regulates the capacity based on the cooling demand.

Sliding valves work by opening or closing paths within the compressor to either allow more or less refrigerant to flow through the system, thereby altering the effective compressor displacement without cycling the compressor on and off. This offers a more efficient and smooth adjustment of the cooling capacity, making the system more responsive to varying load conditions.

The other options do involve aspects of refrigeration and air conditioning systems, but they do not specifically pertain to the mechanism by which capacity is controlled in screw-type rotary compressors. Adjusting refrigerant volume, for example, is not as direct and efficient as sliding valves. Variable speed operation can also be a method for controlling capacity, particularly in different compressor technologies, but sliding valves remain the hallmark of capacity control in screw-type compressors. Changing the compressor oil does not influence capacity control in the manner that sliding valves do.