Deck 23: Compressors

Question 1

Rotary compressors are used primarily in ____.

A) large industrial refrigeration and air conditioning systems
B) residential and light commercial air-conditioning
C) small commercial refrigeration units
D) high volume residential refrigeration

Answer 1

B

Question 2

The higher the rpm of a compressor, the higher the pumping efficiency.

Answer 2

False

Question 3

The clearance volume of a compressor cylinder is the ____.

A) amount of refrigerant vapor the compressor cylinder will hold during each stroke
B) volume by which the compressor is rated
C) volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke
D) total volume of the cylinder when the piston is at the bottom dead-center

Answer 3

C

Question 4

The discus valve design is more efficient than a flapper valve design because ____.

A) it allows a compressor design with less clearance volume
B) it operates with less spring tension
C) the amount of expanded vapor in the cylinder is greater
D) it will not allow liquid refrigerant in the cylinder

Question 5

The sight glass on a semihermetic compressor is used to allow light to enter the crankcase to keep the oil warm .

Question 6

Most of the heat energy in the suction vapor entering the compressor is ____.

A) subcooled from the condenser
B) superheated from the condenser
C) superheated from the evaporator
D) subcooled from the evaporator

Question 7

Liquid entering the compression chamber of a reciprocating compressor can lead to ____.

A) damaged valves
B) damaged piston rings
C) damaged expansion valves
D) Both a and b.

Question 8

The scroll compressor is one type of reciprocating compressor.

Question 9

Scroll compressors are becoming popular because they can handle liquid floodback without compressor damage.

Question 10

Rotary compressors have pistons that rotate inside the cylinders.

Question 11

Because a scroll compressor's has fewer moving parts, it operates much quieter than other compressor designs and technologies.

Question 12

The hermetic reciprocating compressor motor is essentially made of the same materials as an open type compressor motor.

Question 13

A bolted together motor-compressor assembly is sometimes referred to as a semihermetic type .

Question 14

The screw compressor is used primarily in ____.

A) large commercial and industrial systems
B) residential air conditioning
C) small commercial refrigeration units
D) domestic refrigerators

Question 15

The shell of a hermetic type reciprocating compressor is generally considered to be on the low pressure side of the system.

Question 16

If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____.

A) will increase
B) will decrease
C) will remain the same
D) cannot be determined

Question 17

SEER is calculated based on the total amount of cooling (in BTU) the system will provide over the entire season, divided by the total number Watt-Hours it will consume .

Question 18

Mufflers are used in many fully hermetic compressors to muffle compressor pulsation noise.

Question 19

The temperature of the compressed gas leaving the compressor can best be described as ____.

A) cold
B) cool
C) warm
D) very warm

Question 20

The rotary screw compressor uses an open motor instead of the hermetic design.

Question 21

What causes may lead to liquid slugging a compressor with liquid refrigerant ?

Question 22

Explain what happens to refrigerant that does not exit when the piston reaches top dead-center.

Question 23

The type of compressor that is driven by a belt is the ____________________ compressor.

Question 24

The space at the top of the cylinder when the piston reaches the top of its stroke is called ____________________.

Question 25

The compression ratio for an R-22 compressor operating with 68.5 psig suction pressure and 260 psig heat pressure is ____________________.

Question 26

A decrease in suction pressure will have what effect on a reciprocating compressor?

Question 27

A compressor that has the motor and compressor in one housing that is welded together is called a(n) ____________________ type.

Question 28

Explain when the compressor's lubrication system is fully effective.

Question 29

Pistons are connected to the crankshaft using connecting rods and ____________________.

Question 30

When the piston reaches the bottom of its stroke, it is called ____________________.

Question 31

Why can't reciprocating compressors pump liquid?

Question 32

Excessive heat and pressure on the oil in a compressor can cause oil to break down and cause the formation of ____________________ and acid.

Question 33

____________________ opens at approximately 400 ± 50 psi differential between high- and low-side pressures for R-22, and at a 500 to 625 psi differential for R-410A.

Question 34

A compressor that has the motor and compressor in a housing that is bolted together is called a(n) ____________________ type.

Question 35

____________________ is a bimetallic disc that senses compressor discharge temperature and opens at 270ºF.