For large-tonnage central air-conditioning applications (greater than 200 TR), which compressor type is most commonly recommended and widely used in chillers?

Introduction / Context:
Selecting a compressor type for high-capacity chillers requires balancing efficiency, reliability, vibration, and maintainability. At very large capacities (200 TR and above), industry practice favors dynamic compressors that can deliver large flow rates smoothly.

Given Data / Assumptions:

• Tonnage > 200 TR for central plant chillers.
• Continuous-duty commercial/industrial HVAC context.
• Typical refrigerants compatible with large chillers.

Concept / Approach:
Centrifugal compressors are dynamic machines that impart kinetic energy to refrigerant, converting it into pressure in the diffuser/volute. They are particularly efficient at large flow rates, deliver low vibration, and integrate well with shell-and-tube heat exchangers. This makes them the dominant choice for very large tonnage applications. While screw compressors can also handle medium-to-large loads (commonly up to several hundred TR), centrifugal units have historically been preferred for the very largest plants due to scalability and efficiency at design points.

Step-by-Step Solution (Reasoning):

Verification / Alternative check:
Survey of chiller catalogs shows centrifugal machines occupying high-tonnage ranges (e.g., several hundred to thousands of TR), confirming the trend.

Why Other Options Are Wrong:

• (a) Reciprocating units have higher vibration and are rarely used at very large capacities.
• (b) Rotary vane is uncommon in central large-tonnage chillers.
• (d) Screw is viable but typically selected below the largest centrifugal ranges.
• (e) Scrolls are for small packaged systems.

Common Pitfalls:
Assuming screw always replaces centrifugal; application specifics matter, but centrifugal remains dominant above 200 TR in many central plants.

Final Answer:
Centrifugal compressor