RTHD螺杆机结构与工作原理介绍.ppt

* At full load, the slide valve is closed. The compressor pumps its maximum volume of refrigerant, discharging it through both the radial and axial ports. * At part load, the slide valve modulates toward the open position. The opening created by the valve movement allows refrigerant vapor to bypass from the rotor pockets back to the suction side of the compressor. This reduces the volume of vapor available for the compression process. It also reduces the amount of rotor length available for compression. In this manner, the volume of refrigerant that is pumped by the compressor is varied, unloading it to balance the existing chiller load. * As the slide valve continues to open, further unloading the compressor, its radial discharge port eventually travels past the opening in the compressor housing. Once this occurs, all of the refrigerant vapor being pumped by the compressor is discharged through the axial port in the compressor’s end-plate. The compressor discharge ports and slide valve are designed to allow the compressor to operate efficiently over a wide range of conditions. * The slide valve is operated by a piston and cylinder assembly. Extension and retraction of the operator shaft positions the slide valve along the compressor rotors. High-pressure refrigerant vapor, controlled by 2 solenoid valves, is fed to or bled from this assembly in order to position the valve. To close the slide valve and load the compressor, the load valve is opened and the unload valve is closed. This allows high-pressure refrigerant vapor to enter the cylinder from the discharge of the compressor, extending the operator shaft and moving the slide valve so that it covers more of the rotor length. Conversely, to open the slide valve and unload the compressor, the load valve is closed and the unload valve is opened. This allows the high-pressure refrigerant vapor to bleed out of the cylinder into the low-pressure area within the compressor housing. A spring helps return the piston, r