RSES Compressor Systems 3

Question 1

What is the effect of increasing suction gas superheat on compressor volumetric efficiency?

Accepted Answer

Decreases volumetric efficiency due to lower vapor density

Answer

Higher suction superheat reduces refrigerant vapor density, so the compressor moves less mass of refrigerant per stroke, decreasing volumetric efficiency.

Question 2

A centrifugal compressor experiencing 'surge' will exhibit which symptom?

Accepted Answer

Rhythmic pressure oscillations and possible reverse flow

Answer

Surge occurs when the compressor cannot maintain sufficient flow to overcome discharge pressure, causing cyclical flow reversal and pressure oscillations.

Question 3

Which lubrication system type is most commonly used in hermetic compressors?

Accepted Answer

Splash or slinger disc system

Answer

Hermetic compressors typically use a splash or slinger disc that picks up oil from the sump and distributes it to bearings and moving parts.

Question 4

What does a high pressure differential across the compressor oil filter indicate?

Accepted Answer

Clogged or restricted oil filter requiring service

Answer

A high differential pressure across the oil filter indicates it is clogged with contaminants, restricting oil flow and risking bearing damage.

Question 5

In a variable-speed compressor system, what is the primary benefit of reducing compressor speed at part load?

Accepted Answer

Reduces power consumption and improves part-load efficiency

Answer

Reducing compressor speed at part load lowers power draw proportionally and improves system efficiency by better matching capacity to actual cooling demand.

(RSES) Refrigeration Service Engineers Society Certification Practice Test

(RSES) Refrigeration Service Engineers Society Certification Practice Test

RSES Compressor Systems 3