Condition at the start of compression (reciprocating air compressor): At the beginning of the compression stroke, the air temperature is typically __________ the local atmospheric temperature.

Introduction / Context:
Before compression begins in a reciprocating air compressor, the cylinder has just completed the suction process. Clarifying the expected air temperature at this instant helps separate suction effects from compression effects.

Given Data / Assumptions:

• Suction occurs from the ambient with small pressure losses.
• Cylinder walls near ambient; no significant preheating assumed.
• Clearance effects are neglected for this basic concept question.

Concept / Approach:

During suction, the intake valve opens and the cylinder fills with air drawn from the surroundings. Aside from minor heating due to throttling or frictional effects in the intake passage, the bulk air temperature is essentially the ambient (local atmospheric) temperature at the start of compression.

Step-by-Step Solution:

Verification / Alternative check:

Indicator diagrams and basic compressor models assume T1 equals ambient for isentropic-work calculations unless specific intake heating/cooling is provided.

Why Other Options Are Wrong:

“Less than” or “more than” would need pre-cooling or preheating hardware; “indeterminate” ignores the standard assumption; “much higher” contradicts the lack of compression before the stroke begins.

Common Pitfalls:

Confusing end-of-suction with mid-compression; overestimating throttling temperature rises in normal intakes.

Final Answer:

equal to