Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Middterm Review > Mechanical Final Compressor Review > Flashcards

Mechanical Final Compressor Review Flashcards

1
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The scroll compressor is one type of reciprocating compressor.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

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

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

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

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

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

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Rotary compressors have pistons that rotate inside the cylinders.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

An overload relief valve must be built into an oil pump to protect the system against excessively high oil pressure.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In an open-drive compressor, the motor is often cooled by passing refrigerant and oil over the windings.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Adjustable baffles in a centrifugal compressor’s inlet regulate the amount of refrigerant vapor flowing into the impeller.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The purpose of the cylinder head is to support the valve plate and to seal the cylinder so compression can occur.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The reed valve type of reciprocating compressor has a long piston with an elliptical slot in the bottom of the piston skirt.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

A crankshaft and connecting rods convert the rotary motion of the motor shaft to rotary motion of the pistons.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The component that connects the crankshaft to the piston is the shaft seal.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

On open-drive and semi-hermetic compressors, the mating surfaces between bolted parts are usually sealed with gaskets.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

A crankcase heater prevents liquid refrigerant from being trapped with the oil in compressor crankcase.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

In a pressure lubrication system, the crank throw dips into the oil at each crankshaft revolution.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

A full-floating piston pin is free to turn in both the connecting rod bushing and the piston bushings.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

The volume between the top of the piston when it is at top dead center and cylinder plate is known as clearance space.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The types of unloader mechanisms and controls used on screw compressors can provide variable unloading.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

A compressor with a splash lubrication system must have greater clearances than a compressor with a pressure lubrication system.

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

The movement of blades in and out of their slots provides the pumping action for lubrication systems in some rotary compressors.

A

True

28
Q

A screw compressor produces the most vibration of all compressor types.

A

False

29
Q

The pistons of some small hermetic compressors do not have piston rings.

A

True

30
Q

In a water-cooled compressor, cool water is sprayed onto the motor windings inside the compressor dome.

A

False

31
Q

On external drive compressors, the crankshaft seal rubbing surfaces should be lubricated.

A

True

32
Q

All hermetic compressors require a crankshaft seal.

A

False

33
Q

Poppet valves are suitable only for low-speed compressors.

A

True

34
Q

The vanes on a rotating vane compressor may be brought into contact with the cylinder walls by spring pressure or centrifugal force.

A

True

35
Q

A typical shaft seal is a two-part seal with half of it rotating with the shaft and the other half remaining stationary in the case.

A

True

36
Q

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

damaged valves

damaged piston rings

damaged expansion valves

both a and b

A

both A and B

37
Q

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

it allows a compressor design with less clearance volume

it operates with less spring tension

the amount of expanded vapor in the cylinder is greater

it will not allow liquid refrigerant in the cylinder

A

it allows a compressor design with less clearance volume

38
Q

The clearance volume of a compressor cylinder is the ____.

amount of refrigerant vapor the compressor cylinder will hold during each stroke

volume by which the compressor is rated

volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke

the total volume of the cylinder when the piston is at the bottom dead-center

A

volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke

39
Q

Rotary compressors are used primarily in ____.

large industrial refrigeration and air conditioning systems

residential air conditioning

small commercial refrigeration units

high volume residential refrigeration

A

residential air conditoning

40
Q

The screw compressor is used primarily in ____.

large industrial refrigeration and air-conditioning systems

residential air conditioning

small commercial refrigeration units

domestic refrigerators

A

large industrial refrigeration and air-conditioning systems

41
Q

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

cold

cool

warm

very warm

A

very warm

42
Q

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

subcooled from the condenser

superheated from the condenser

superheated from the evaporator

subcooled from the evaporator

A

superheated from the evaporator

43
Q

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

will increase

will decrease

will remain the same

cannot be determined

A

will increase

44
Q

A ____ compressor compresses vapor between a matched set of helical rotors.

screw

scroll

centrifugal

rotary

A

screw

45
Q

A(n) ____ is used to temporarily reduce cylinder pressure during compressor start-up.

splash system

gasket

muffler

unloader

A

unloader

46
Q

An unloader on a reciprocating compressor reduces compressor load by _____.

holding the intake valve open

holding the exhaust valve open

decreasing piston stroke

diverting compressed vapor back to the compressor intake

A

holding the intake valve open

47
Q

Oil pumps are typically located _____.

on the cylinder head

at the bottom of the crankcase

at one end of the compressor shaft

remotely outside the compressor

A

at one end of the compressor shaft

48
Q

Which of the following statements regarding mufflers is false?

Mufflers may be installed on the compressor inlet, the compressor outlet, or both.

Mufflers reduce noise caused by gas pulsation.

Mufflers are used only on hermetic compressors.

All of the above.

A

mufflers are used only on hermetic compressors

49
Q

Which type of screw compressor is typically used in ammonia or other high-pressure systems?

Open-drive.

Hermetic.

Both A and B.

Neither A nor B.

A

open-drive

50
Q

Which of the following methods is not used to modulate the capacity of a scroll compressor?

A port partway between the outer edges and centers of the scrolls is opened to allow partially compressed gas to return to compressor inlet.

A variable speed motor moves the orbiting scroll at different speeds, depending on load.

An unloader is used to hold the intake valve open so compression cannot take place.

The fixed and orbiting scrolls are briefly moved apart, opening gaps between the vapor pockets.

A

An unloader is used to hold the intake valve open so compression cannot take place.

51
Q

The volume of space between the top of the piston and the valve plate when the piston is at top dead center is referred to as the _____.

compression gap

clearance space

effective volume

dead space

A

clearance space

52
Q

Which of the following explains why exhaust valves present more problems than intake valves?

Intake valves are continuously lubricated by cool refrigerant oil.

Exhaust valves operate at a higher temperature than intake valves.

Exhaust valve seats are more likely to collect carbon than intake valve seats.

All of the above.

A

all of the above

53
Q

Which of the following statements regarding poppet valves is false?

Poppet valves are very sturdy.

Poppet valves are typically found in large compressors.

Poppet valves are closed by spring pressure.

Poppet valves operate more quickly than reed valves.

A

poppet valves operate more quickly than reed valves

54
Q

One end of a connecting rod is attached to the piston, and the other end is attached to the _____.

compressor dome

crankshaft journal

crankcase

None of the above.

A

crankshaft journal

55
Q

Which of the following types of valves has a valve stem that moves up and down in a valve guide?

Poppet valves

Reed valves

Check valves

All of the above.

A

poppet valves

56
Q

In reciprocating compressors, the intake and exhaust valves are located on the _____.

cylinder head

dome

crankcase

valve plate

A

valve plate

57
Q

Which of the following statements regarding piston rings is false?

A compression ring prevents pressurized refrigerant from blowing past the piston into the crankcase.

The inner diameter of a piston ring is slightly larger than the piston diameter.

The ends of piston rings are beveled to allow overlap.

An oil ring prevents excess oil from entering the cylinder.

A

The inner diameter of a piston ring is slightly larger than the piston diameter.

58
Q

A crankshaft that is cast with offset journals is called a(n) _____ crankshaft.

integrated

reciprocal-type

crank throw–type

None of the above.

A

crank throw-type

59
Q

Reciprocating compressors can be classified by _____.

cylinder arrangement

number of cylinders

type of crankshaft

All of the above.

A

all of the above

60
Q

Which of the following best explains why the electrical connections and starting relays on hermetic compressors are typically installed outside the compressor housing?

Electrical arcing could break down and contaminate the refrigerant, leading to a compressor burnout.

Most refrigerants are highly flammable and electrical arcing could result in a compressor explosion.

Refrigerant is highly corrosive and would damage the electrical components in a matter of days.

All of the above.

A

Electrical arcing could break down and contaminate the refrigerant, leading to a compressor burnout.

61
Q

If a belt-driven compressor with a 6″ pulley is being turned by a motor operating at 3600 RPM and equipped with a 3″ pulley, the compressor’s shaft will be turning at _____.

1200 RPM

1800 RPM

3600 RPM

7200 RPM

A

1800RPM

62
Q

Which of the following statements regarding open-drive compressors is false?

All open-drive compressors have a shaft seal.

Open-drive compressors are available in hermetic and semi-hermetic models.

Open-drive compressors may be belt-driven or direct-driven.

All of the above.

A

Open-drive compressors are available in hermetic and semi-hermetic models.

63
Q

Which of the following is a thin strip of spring steel that bends to open a valve passage and returns to a flat shape to close the passage?

Poppet valve.

Spring valve.

Reed valve.

Valve plate.

A

Reed valve

64
Q

Which of the following best describes the action of a dual-capacity reciprocating compressor?

One piston is attached to a quick-release connecting rod. When the crankshaft reverses direction, the connecting rod disconnects from the crankshaft, disabling the piston.

One piston has a release valve built into the piston head. When the crankshaft reverses direction, the valve opens to prevent compression.

One piston is on a movable eccentric. When the crankshaft reverses direction, the eccentric centers on the crankshaft, disabling the piston.

None of the above.

A

One piston is on a movable eccentric. When the crankshaft reverses direction, the eccentric centers on the crankshaft, disabling the piston.

65
Q

Which type of compressor is most similar in construction to an automobile engine?

Rotary.

Reciprocating.

Centrifugal.

Screw.

A

Reciprocating

Middterm Review (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions