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[Butterfly]

I`m working to get the energetic efficiency of a gas plant. There are 3 trains of two-stage reciprocating compressors (one is spare). The compressors are moved by electrical asyncronous motors with adjustable speed driver (ASD condition). My question is: if the plant is not working at its operating point (and there is less gas flow entering it) does the compressor efficiency go down? And the motor efficiency? To calculate it, I suppose that I would need to ask for compressor curves to supplier. What about the motor?

Thanks in advance

[adammusthafa]

Correct me if i am wrong. yes, the manufacturer's performance prediction curve should always be used if possible. Pd compressor works on isentropic path, thus it is difficult to estimates the performance based on temerature rise like on centrifugal comp. Moreover, for pd comp, the efficiency is more related to the pressure ratio, not flowrates like centrifugal.

You could still compare the power consumption per compressed flowrate though. There is also simple equation relating the ghp, bhp. And isentropic efficiency to make a rough approximation. Still, manufacturer's performane prediction is the best way to get the most accurate results.