In the illustrated R-134a high pressure centrifugal chiller refrigerant flow circuit, by what means is the heat removal capacity of the system regulated? See illustration GS-RA-26.
• How centrifugal chillers control capacity compared to reciprocating or screw compressors • The role of refrigerant mass flow rate through the compressor in determining cooling (tons of refrigeration) • Which component in the diagram is shown with an actuator or control linkage tied into the capacity control system
• Look at the compressor section in the illustration: what adjustable device is located at or near the suction/inlet of the impeller? • Ask yourself: if I wanted to reduce the load on a centrifugal compressor without changing its speed, what flow path would I throttle or direct? • For each choice, consider whether that method would be a primary capacity control for this type of high‑pressure centrifugal R‑134a chiller, or more of a secondary/trim control.
• Identify on the drawing which part actually has a mechanical control element (linkage, actuator, or control motor). • Confirm which option directly changes the amount of refrigerant vapor entering the compressor, not just water temperatures or bypass protection. • Verify whether hot gas bypass in this system is drawn to the cooler or used only for special conditions, rather than normal capacity modulation.
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