The surging that occurs in a centrifugal air conditioning compressor is a result of what conditions?

Correct Answer: Option D — low pressure in the evaporator at low load

Surging in centrifugal compressors occurs when the refrigerant mass flow rate drops below the critical limit for the compressor's pressure ratio. At low loads, the evaporator pressure drops, causing the compressor to operate near the surge line, leading to flow reversal and unstable, damaging mechanical vibrations.