Which compression ratio is characteristic of a screw compressor?

Which compression ratio is characteristic of a screw compressor?

• A. 20:1
• B. 8:1
• C. 4:1
• D. 6:1

Answer: (A)

A screw compressor handles gas in a continuous, trapping-and-compressing way as the two rotors mesh. This rotary positive-displacement action lets the gas be compressed to a relatively high pressure rise, giving a higher discharge-to-suction pressure ratio than many other compressor types. In practice, ammonia screw systems are commonly designed with a fairly large pressure ratio, around twenty to one, which is why twenty-to-one is seen as characteristic. The smaller ratios listed would be more typical of lighter-duty or different compressor configurations and don’t reflect the high, continuous compression capability of a screw unit.

A screw compressor handles gas in a continuous, trapping-and-compressing way as the two rotors mesh. This rotary positive-displacement action lets the gas be compressed to a relatively high pressure rise, giving a higher discharge-to-suction pressure ratio than many other compressor types. In practice, ammonia screw systems are commonly designed with a fairly large pressure ratio, around twenty to one, which is why twenty-to-one is seen as characteristic. The smaller ratios listed would be more typical of lighter-duty or different compressor configurations and don’t reflect the high, continuous compression capability of a screw unit.