RFRG 6010 - Refrigeration Compressors (Chp 18)

Question 1

Which of the following compressor types uses impellers to draw in vapour?

A) Reciprocating Compressors
B) Centrifugal compressors
C) Rotary compressors
D) All of the above
E) None of the above

Answer 1

B) Centrifugal compressors

Note: draw vapour

Question 2

In a rotating vane design rotary compressor, a good seal is maintained between the vanes and the cylinder by:

A) Low pressure suction
B) Centrifugal force
C) The oil
D) High pressure refrigerant vapour
E) The eccentric rotor size

Answer 2

B) Centrifugal force

Question 3

The safety head of a refrigeration compressor is designed to:

A) Prevent explosion damage
B) Relieve pressure due to liquid in the cylinder
C) Pop when the pressure is too high
D) Relieve high-pressure gas compression
E) Operate in place of a safety relief valve

Answer 3

B) Relieve pressure due to liquid in the cylinder

Question 4

Rotary compressors have several different designs, some of which are:

1. Sliding vane
2. Stationary single-rotor
3. Helical rotor
4. Rotating impeller
5. Reciprocating piston
   Incorrect Response
   A) 1, 3, 4
   B) 2, 3, 4
   C) 1, 2, 3
   D) 1, 3, 5
   E) 3, 4, 5

Answer 4

C) 1, 2, 3

Question 5

Pistons and connecting rods are found in which of the following types of compressors?

A) Centrifugal
B) Axial
C) Dynamic
D) Reciprocating
E) Rotary

Answer 5

D) Reciprocating

Question 6

Piston displacement is defined as the:

A) Piston stroke length of the compressor
B) Cylinder bore of the compressor
C) Revolutions per minute of the compressor motor
D) Volume of refrigerant that can be circulated through all the cylinders per unit time
E) Distance along which the compressor piston travels

Answer 6

D) Volume of refrigerant that can be circulated through all the cylinders per unit time

Question 7

Which of the following statements is true in regard to rotary screw refrigeration compressors?

A) All of the above
B) The compressor consists of three opposing grooved rotors
C) The cylinders around the rotor screws must be considerably larger in diameter than the screws
D) The vapour is drawn in via the closed space between the driving rotor and the casing
E) The driving rotor has helical lobes and the driven rotor has flutes

Answer 7

E) The driving rotor has helical lobes and the driven rotor has flutes

Question 8

A typical stationary crankshaft seal consisting of metallic bellows soldered at one end to a ring (seal nose) which bears either against a shoulder on the shaft or against a seal ring on the shaft is called a:

A) Bellows seal
B) Diaphragm seal
C) Rotating mechanical seal
D) Setscrew seal
E) Packing gland seal

Answer 8

A) Bellows seal

Question 9

Which of the following are functions of a refridgeration compressor?

i. Maintain a high pressure in the condenser
ii. Maintain a low pressure in the evaporator
iii. Raise the pressure of the refrigerant

A) Both i and iii
B) Both ii and iii
C) iii only
D) i, ii, and iii
E) i only

Answer 9

D) i, ii, and iii

Question 10

A disadvantage of hermetic type refrigeration compressors is:

A) Field servicing is not possible
B) The compressor is driven by an electric motor
C) The compressor and motor are mounted within the same housing
D) Shaft sealing is not required
E) The motor is cooled by the low-pressure, low-temperature vapour drawn into the housing

Answer 10

A) Field servicing is not possible

Question 11

An advantage of centrifugal refrigeration compressors is:

A) Small pistons
B) High outlet pressure
C) No valves or pistons
D) High velocity, high pressure
E) Positive displacement

Answer 11

C) No valves or pistons