A rotary vane compressor typically operates at what compression ratio?

• A. 20:1
• B. 4:1
• C. 8:1
• D. 12:1

Answer: (B)

A rotary vane compressor is designed to deliver a moderate pressure rise in one stage, because the vane seals and clearances limit how high the discharge pressure can efficiently go. This keeps heat of compression, leakage around the vanes, and wear in check, preserving efficiency and longevity. For ammonia refrigeration, this practical balance sits around a compression ratio of four to one, so the discharge pressure is about four times the suction pressure. Higher ratios push discharge temperatures up, increase mechanical stress, and reduce efficiency for a single-stage vane design, while a ratio near four to one provides the needed head with better overall performance. So the typical operating ratio is about four to one.