Compressor Systems Flashcards
7 cards from real RSES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Compressor Systems flashcards as text
What is the effect of increasing suction gas superheat on compressor volumetric efficiency?
Answer: Decreases volumetric efficiency due to lower vapor density
Higher suction superheat reduces refrigerant vapor density, so the compressor moves less mass of refrigerant per stroke, decreasing volumetric efficiency.
A centrifugal compressor experiencing 'surge' will exhibit which symptom?
Answer: Rhythmic pressure oscillations and possible reverse flow
Surge occurs when the compressor cannot maintain sufficient flow to overcome discharge pressure, causing cyclical flow reversal and pressure oscillations.
Which lubrication system type is most commonly used in hermetic compressors?
Answer: Splash or slinger disc system
Hermetic compressors typically use a splash or slinger disc that picks up oil from the sump and distributes it to bearings and moving parts.
What does a high pressure differential across the compressor oil filter indicate?
Answer: Clogged or restricted oil filter requiring service
A high differential pressure across the oil filter indicates it is clogged with contaminants, restricting oil flow and risking bearing damage.
In a variable-speed compressor system, what is the primary benefit of reducing compressor speed at part load?
Answer: Reduces power consumption and improves part-load efficiency
Reducing compressor speed at part load lowers power draw proportionally and improves system efficiency by better matching capacity to actual cooling demand.
What condition can cause a compressor motor to draw high amperage while producing insufficient cooling capacity?
Answer: Leaking discharge valves allowing hot gas to recirculate
Leaking discharge valves allow compressed hot gas to flow back into the cylinder, forcing the motor to work harder while reducing net refrigerant pumping capacity.
Which refrigerant property most directly determines the required compressor displacement for a given cooling capacity?
Answer: Latent heat of vaporization and specific volume of suction vapor
Compressor displacement is determined by the required mass flow rate, which depends on cooling capacity divided by latent heat, multiplied by the specific volume of suction vapor.