The technique of the twin screw compressor has a long history.
The compressor was run on a fixed drive speed and the capacity was corrected by creating an internal leak by slide valve in the compressor.
One of the changes of today is :The capacity of the compressor is controlled by changing the drive speed. (Variable drive speed – VSD)
The introduction of the VSD compressors units leads to changes in design of compressors.
Today we find Rotor profiles of 5/7 instead the well known 4/6 profiles.
Also SRMtec used the 5/7 rotor profile in the model ranges SRM and SRS .
One of the reasons to use this profile is to reduce the stress on the rotors by VSD operation.
The amount of the force on the rotors is related on the amount and mixture of the refrigerant captured between the rotor lobs. The rotors are flexible and will bend under this pressure. The tolerance between the rotors and the housing terminate losses and effectivity.
In short :
The captured amount of refrigerant between the lobs by the 5/7 profiles is less, however the captured amount of the refrigerant in total of the compressor is the same.
Less captured refrigerant gas between lobs makes the 5/7 profile more suitable for speed drive.
The speed up process goes in more little bites of the refrigerant gas in the suction. In the decrease process the little bites reduce the speed which is even more important. Compressors with little but more bites are running more smoothly and create less stress on the rotors.
More benefits:
By the 5/7 profiles the cutting of the rotors is less deep. Therefore we can install bigger bearings for more stableness.
That’s why drive speed can be much higher. New development will lead to new material, less maintenance and even more stableness.
If you are an user, a service contractor or a builder of compressors and you are interested in our vision and co-operation, if you are ready to turn into the new time in refrigeration industry where compressors are smaller, more effective and powerful against less maintenance, -than do not hesitate and contact us!
