What device is utilized for capacity control on a screw type compressor?

A slide valve is a crucial component used for capacity control on a screw type compressor. In these compressors, the slide valve adjusts the volume of refrigerant that is compressed, thereby controlling the cooling capacity of the system. As operating conditions change, such as varying loads, the slide valve can move to either increase or decrease the amount of refrigerant that the compressor processes.

This feature allows for efficient operation and energy savings, as the compressor can match its output to the specific cooling demand. By optimizing the flow of refrigerant, the slide valve helps maintain system stability and reduces the wear and tear on the compressor, which can lead to longer equipment life.

In contrast, other devices mentioned serve different functions: a throttle valve regulates the flow of refrigerant in response to pressure differences, an expansion valve controls the flow of refrigerant into the evaporator based on temperature and pressure conditions, while a piston valve is typically used in different types of compressors and does not provide the same functionality for capacity control as a slide valve on a screw compressor.