Compressor pressure ratio check: For any practical compressor, the compression ratio is always __________ unity.

Introduction / Context:
Pressure ratio is the cornerstone metric for compressors, defined as discharge pressure divided by inlet (usually atmospheric) pressure. Its magnitude indicates the machine’s ability to raise pressure and drive downstream processes.

Given Data / Assumptions:

• Pressure ratio r_p = p_out / p_in.
• Normal compressor operation (not a throttling valve).
• Positive-displacement or turbocompressors considered.

Concept / Approach:

By definition, a compressor increases pressure; therefore p_out > p_in and r_p > 1. An r_p of 1 would imply no compression, and less than 1 is a pressure reducer (throttle/expander), not a compressor. This simple inequality holds across single-stage and multi-stage machines when referenced at the same stations.

Step-by-Step Solution:

Verification / Alternative check:

Datasheets list r_p values (e.g., 1.5–3 for blowers, 3–10+ for multistage air compressors), all exceeding unity, confirming the definition.

Why Other Options Are Wrong:

“Equal to” contradicts compression; “less than” corresponds to throttling/expansion devices, not compressors.

Common Pitfalls:

Mixing up absolute and gauge pressures; comparing pressures at different elevations or temperatures without proper station definition.

Final Answer:

more than