Reciprocating compressor terminology: what do we call the geometric volume swept by the piston (i.e., the volume of air drawn in during the suction stroke)?

Introduction / Context:
Multiple volumetric terms are used in compressor practice: swept volume, free air delivery, and capacity. Distinguishing these avoids confusion when reading datasheets and selecting equipment.

Given Data / Assumptions:

• Piston-cylinder compressor with defined bore and stroke.
• Negligible leakage for the basic geometric definition.
• No correction to standard conditions unless explicitly stated.

Concept / Approach:
The swept volume (also called displacement) is purely geometric: area of piston * stroke (per cycle) multiplied by the number of cylinders and cycles per unit time when expressing as a rate. It is the volume traversed by the piston, i.e., the nominal volume of air a cylinder would draw during suction absent re-expansion and losses. By contrast, Free Air Delivery (FAD) is the delivered volume converted to standard conditions, and “capacity” is often used synonymously with FAD on a standardized basis.

Step-by-Step Solution:
Compute swept volume V_s = (pi/4) * D^2 * L for one stroke.Recognize this is the volume the piston sweeps, unrelated to standard condition corrections.Therefore, the correct term for “volume of air sucked during suction stroke” is swept volume (displacement).

Verification / Alternative check:
Manufacturer literature lists both displacement (geometric) and FAD (corrected to standard conditions) to distinguish ideal from delivered performance.

Why Other Options Are Wrong:

• Free air delivery: standardized delivered volume, not geometric sweep.
• Compressor capacity: commonly synonymous with FAD or standardized delivered volume.
• Standard flow rate: general term; lacks the geometric meaning.
• Receiver volume: storage tank volume, unrelated to piston sweep.

Common Pitfalls:
Using displacement to size downstream equipment; always use standardized delivered flow for piping and tool sizing.

Final Answer:
Swept volume (displacement)