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[Butterfly]

Hello. I have an oil flooded screw compressor in a propane refrigeration cycle. Capacity control is made by mean of variable slide valve regulation (vendor datasheet states: "method: variable slide valve regulation; signal source: suction pressure".

I have a natural gas flow which is dew point adjusted thanks to this refrigeraton cycle. Propane flow in the system is controlled via a LCV in the Chiller

I want to adress the topic of energy efficiency in this compressor. My questions are:

• I need a fixed discharge pressure (because of the refrigeration cycle). What I understand is that depending on the flow entering the compressor, the slide valve moves so that I use the exact length of the rotor needed to get my discharge P with less flow. Am I correct? Or is it that I adjust the slide valve position so that I have the same inlet pressure?
• Now help me see if I understand the way the screw compressor works so that I can understand the control process: the screw compressor increases gas P by reducing the volume, thanks to the two screws rotatong against each other. So I have discharge P2, V2. If my propane flow is reduced and I wanto to maintain P2, first thing I see is that I need to reduce V2. Does the slide valve permit me to reduce this V2 so I can get the same P2?
• Now, let's focus on the inlet pressure. My propane enters at a Pa fixed. In the inlet of the compressor, I have P1. What happens if the flow is reduced? Do I have less P1 because the inlet space is the same, but flow is less? If I have less P1 and maintain P2, my compression ratio increases and efficiency decreases. Or does the slide valve also allow me to reduce V1 in the suction so that P1 is maintained when flow is reduced?
• Finally, how does this capacity control method affects my compressor efficiency? Why? I think there is some kind of recirculation but I don't know the role it plays in all this control process...

I hope I made myself clear. Thakns in advance