Chapter 5 - Compressors - RMO EXAM

5.06.) In a two-stage centrifugal compressor with an economizer, which stage holds the largest volume of vapor?

1st stage

5.07.) In a two-stage centrifugal compressor with an economizer, in which stage is the refrigerant pressure greatest?

2nd stage

5.08.) Which of the following compressors uses non-positive (variable) displacement to increase the pressure of a refrigerant?

Centrifugal

5.11.) What type of compressor is most likely to be used in a system which is operating in a vacuum?

Centrifugal

5.05.) Modern compressors use what type of material at their seal shafts?

Copper and packing

5.14.) Which of the following is closest to the crankcase pressure of an operating reciprocating compressor?

Evaporator pressure

5.19.) What advantage do semi-hermetic compressors have over hermetic compressors?

Field serviceable

5.13.) In which of the following compressor construction arrangements are the motor and compressor enclosed within a permanently sealed housing?

Hermetic

5.04.) Which of the following best describes the operational characteristics of a centrifugal refrigeration machine?

High volume, low pressure

5.20.) The pressure developed by a centrifugal compressor is determined by:

Impeller tip speed

5.01.) Which of the following best describes the state of the refrigerant at the inlet and outlet of the compressor?

Low pressure vapor in, High pressure vapor out

5.17.) Which compressor construction arrangement is characterized by one end of the compressor's shaft extending beyond the compressor housing?

Open-type

5.03.) What type of compressors valves need the most clearance space when used on vertical compressors?

Poppet

5.02.) A double acting compressor has which of the following operational characteristics?

Produces suction and discharge at both ends of the cylinder

5.15.) Which of the following states one of the functions of a compressor?

Provide the differential pressure needed to circulate the refrigerant through the cycle

5.09.) A two-cylinder single-acting vertical compressor has a suction pressure of 45 PSIG. The purpose of the shaft seal is to keep:

Refrigerant and oil from escaping

5.16.) In which compressor design is suction gas compressed between rotating gears (helical lobes), after having entered the compressor through a sliding vane type capacity control valve?

Screw compressor

5.18.) For a given operating condition and motor horsepower, which of the following compressors will have the smallest displacement?

Scroll

5.12.) If a refrigeration system is said to have 3 stages, this implies:

The pressure of the refrigerant is increased 3 times before it is discharged to the condenser

5.10.) Which of the following best describes how a "positive displacement" compressor increases the pressure of a refrigerant?

Volume reduction