RSES Compressor Systems 2

Question 1

What condition is indicated when a reciprocating compressor's suction pressure is significantly lower than expected during operation?

Accepted Answer

Worn or leaking suction valves

Answer

Worn or leaking suction valves allow refrigerant vapor to flow back into the suction side, reducing pumping efficiency and lowering suction pressure.

Question 2

Which type of compressor uses a fixed-volume ratio and cannot adjust to varying system pressure ratios?

Accepted Answer

Screw compressor

Answer

Screw compressors have a fixed built-in volume ratio determined by the rotor geometry, making them less efficient when operating far from their design pressure ratio.

Question 3

What is the primary purpose of an unloader on a reciprocating compressor?

Accepted Answer

To reduce compressor capacity by disabling cylinders

Answer

Unloaders disable individual cylinders or hold suction valves open to reduce compressor capacity and match system cooling load.

Question 4

A compressor operates with high discharge temperature and low compression ratio. What is the most likely cause?

Accepted Answer

High suction superheat entering the compressor

Answer

High suction superheat means the refrigerant vapor enters the compressor at an elevated temperature, resulting in high discharge temperatures even with a normal compression ratio.

Question 5

In a two-stage compression system, what is the function of the intercooler?

Accepted Answer

To cool discharge gas between the first and second stage

Answer

The intercooler removes heat from the first-stage discharge gas before it enters the second-stage compressor, improving overall efficiency.

(RSES) Refrigeration Service Engineers Society Certification Practice Test

(RSES) Refrigeration Service Engineers Society Certification Practice Test

RSES Compressor Systems 2