Which ratio correctly matches a rotary vane compressor?

Which ratio correctly matches a rotary vane compressor?

• A. 12:1
• B. 4:1
• C. 20:1
• D. 6:1

Answer: (B)

The key idea here is the typical compression ratio a rotary vane compressor is designed to achieve in a single stage. A rotary vane compressor traps and compresses gas in pockets between a rotor and sliding vanes, and its ability to raise pressure in one pass is limited by heat generation, lubrication, and mechanical design. In ammonia refrigeration, a single-stage rotary vane unit commonly delivers about a 4:1 pressure ratio (discharge to suction). This ratio reflects a balance where the compressor can efficiently compress and discharge vapor without excessive heat buildup or wear on the vanes. Ratios like 12:1 or 20:1 would push the discharge pressure far beyond what a single stage can handle efficiently, making overheating and lubrication problems likely; such high ratios typically require multiple stages with cooling between stages. A ratio around 6:1 is less common for a standard single-stage rotary vane unit, though some special designs might approach it. The 4:1 figure is the conventional match for a typical rotary vane compressor in this context. So, the ratio that best fits a rotary vane compressor in this setting is 4:1.

The key idea here is the typical compression ratio a rotary vane compressor is designed to achieve in a single stage. A rotary vane compressor traps and compresses gas in pockets between a rotor and sliding vanes, and its ability to raise pressure in one pass is limited by heat generation, lubrication, and mechanical design.

In ammonia refrigeration, a single-stage rotary vane unit commonly delivers about a 4:1 pressure ratio (discharge to suction). This ratio reflects a balance where the compressor can efficiently compress and discharge vapor without excessive heat buildup or wear on the vanes.

Ratios like 12:1 or 20:1 would push the discharge pressure far beyond what a single stage can handle efficiently, making overheating and lubrication problems likely; such high ratios typically require multiple stages with cooling between stages. A ratio around 6:1 is less common for a standard single-stage rotary vane unit, though some special designs might approach it. The 4:1 figure is the conventional match for a typical rotary vane compressor in this context.

So, the ratio that best fits a rotary vane compressor in this setting is 4:1.