Compressor Pre-test quiz 1

Question 1

The function of a compressor is to take refrigerant vapour at a ______ temperature and pressure and change it to a _____ pressure and temperature

Answer 1

low

high

Question 2

At a constant RPM, a compressor is a _____ displacement device and its capacity is variable depending on the _______ of the refrigerant at the intake of the pump

Answer 2

constant

pressure

Question 3

the reciprocating compressor has a built - in problem with efficiency, that is a portion of the discharge gas does not escape the cylinder and must re-expand before the suction gas can enter. The problem is caused by the ______ _______ which is designed in to the compressor to prevent _______

Answer 3

clearance pocket

contact between piston and valve plate

Question 4

A mechanical shaft seal is required in a _________ compressor

Answer 4

open type compressor

Question 5

All refrigeration compressor valves are opened and closed by ___________

Answer 5

pressure differential

Question 6

How does a compressor initiate flow in a system?

a) by raising pressure in the evaporator
b) lowering pressure in the evaporator
c) by discharging liquid
d) raising pressure in the condenser

Answer 6

by lowering pressure in the evaporator

by raising pressure in condenser

Question 7

In this compressor, a piston travels back and forth within a cylinder?

Answer 7

reciprocating

Question 8

In this compressor two offset spiral disks compress refrigerant vapour

Answer 8

Scroll

Question 9

This compressor has high speed impeller with many blades. The impeller rotates within a housing

Answer 9

centrifugal

Question 10

This compressor has a pair of helical rotors. They trap and compresses gases as they revolve in a cylinder.

Answer 10

Screw

Question 11

What is the fundamental difference between and hermetic and semi-hermetic compressor with regards to mechanical field service?

Answer 11

hermetic is much harder to service due to its metal housing

Question 12

Most of the heat energy in the suction vapour entering the compressor is:

a) heat of compression
b) sensible heat
c) latent heat
d) defrost heat

Answer 12

latent heat

Question 13

List four types of compressors

Answer 13

hermetic

semi hermetic

open drive

belt drive

Question 14

As suction pressure increases the amount of refrigerant pumped ________ because the specific volume of the refrigerant ________

Answer 14

increases

decreases

Question 15

List the types of compressor body styles?

Answer 15

hermetic

semi hermetic

open drive

Question 16

Explain what is meant by saying the compressor rides with the load?

Answer 16

suction pressure goes up, density goes up, capacity goes up, specific volume goes down and volumetric flow rate is constant

Question 17

List thee ways mechanical cylinder unloading is accomplished?

Answer 17

discharge bypass, suction cutoff, hydraulic

Question 18

The cylinder unloader method of capacity control is used mainly with?

centrifugal

screw

rotary

none of the above

Answer 18

none of the above

Question 19

In a scroll compressor;

a) both scrolls move
b) only the upper scroll moves
c) only the lower scroll moves
d) neither scroll moves

Answer 19

only the lower scroll moves

Question 20

the capacity of a compressor is related to;

a) the speed of the driving motor
b) the compressor displacement
c) number of cylinders
d) all of the above

Answer 20

all of the above

Question 21

The on/off method of capacity control is normally used with?

a) reciprocating, rotary, and scroll multi-compressor systems
b) rotary compressors
c) scroll compressors

Answer 21

a) reciprocating , rotary, and scroll multi-compressor systems

Question 22

Excessive foaming in the oil sight glass shows the oil is

a) mixed with refrigerant
b) air
c) acid
d) all of the above

Answer 22

mixed with refrigerant

Question 23

The contaminants present in a clean system are

a) moisture
b) air
c) acid
d) none of the above

Answer 23

none of the above

Question 24

Match the type or Capacity control used with the appropriate compressor type;

1. Motor speed control
2. Cylinder unloading
3. on off cycling
4. sliding vanes
5. inlet vanes

Reciprocating?

Answer 24

1,2,3

Question 25

Match the type or Capacity control used with the appropriate compressor type;

1. Motor speed control
2. Cylinder unloading
3. on off cycling
4. sliding vanes
5. inlet vanes

Rotary?

Answer 25

1,3

Question 26

Match the type or Capacity control used with the appropriate compressor type;

1. Motor speed control
2. Cylinder unloading
3. on off cycling
4. sliding vanes
5. inlet vanes

Scroll?

Answer 26

1,3

Question 27

Match the type or Capacity control used with the appropriate compressor type;

1. Motor speed control
2. Cylinder unloading
3. on off cycling
4. sliding vanes
5. inlet vanes

Screw?

Answer 27

1,4

Question 28

Match the type or Capacity control used with the appropriate compressor type;

1. Motor speed control
2. Cylinder unloading
3. on off cycling
4. sliding vanes
5. inlet vanes

Centrifugal?

Answer 28

1,5