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Middterm Review > Review Quiz > Flashcards

Review Quiz Flashcards

1
Q

An automatic expansion valve uses a thermal sensing bulb to help control the amount of refrigerant being fed to the evaporator

TRUE OR FALSE

A

False

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2
Q

The pin or valve port piston of the electronic step-motor expansion valve can move a linear motion of 300 steps per second

TRUE OR FALSE

A

False

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3
Q

A refrigeration system that continuously runs under high-load conditions (hot pull downs) would most likely use a thermostatic expansion valve with a vapour charged thermal bulb assembly

TRUE OR FALSE

A

True

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4
Q

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

TRUE OR FALSE

A

False

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5
Q

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

TRUE OR FALSE

A

True

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6
Q

Hard starting may also occur in a low ambient condition causing low head pressures

TRUE OR FALSE

A

True

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7
Q

When the evaporative condenser is used in colder climates, freeze protection must be provided in winter

TRUE OR FALSE

A

True

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8
Q

The film factor is a relationship between the medium giving up heat and the heat exchange surface

TRUE OR FALSE

A

True

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9
Q

A limited amount of flash gas created in the liquid line increases a systems efficiency

TRUE OR FALSE

A

False

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10
Q

Some thermostatic expansion valves are equipped with built-in check valves to prevent refrigerant from flowing backward through the TXV

TRUE OR FALSE

A

True

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11
Q

The higher the temperature in a low-side float system, the higher the low-side pressure

TRUE OR FALSE

A

True

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12
Q

If the orifice of a valve assembly is oversized, the valve will hunt or surge

TRUE OR FALSE

A

True

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13
Q

A liquid cross charged sensing bulb may use a mixture of different refrigerants to achieve the desired operating characteristics

TRUE OR FALSE

A

True

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14
Q

A liquid cross-charged sensing bulb uses a refrigerant that is the same as the one in the system

TRUE OR FALSE

A

False

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15
Q

TXV’s may be used on multiple-evaporator systems

TRUE OR FALSE

A

True

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16
Q

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

TRUE OR FALSE

A

False

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17
Q

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

TRUE OR FALSE

A

False

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18
Q

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

TRUE OR FALSE

A

True

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19
Q

All hermetic compressors require a crankshaft seal.

TRUE OR FALSE

A

False

20
Q

Poppet valves are suitable only for low-speed compressors.

TRUE OR FALSE

A

True

21
Q

The pressure limiting TXV ____.

a) allows the compressor to operate at low condenser entering air temperatures
b) shuts off the condenser fan during hot pull down
c) maintains the full refrigerant flow rate during a hot pull down
d) limits the refrigerant flow rate to the compressor capacity

A

d) limits the refrigerant flow rate to the compressor capacity

22
Q

When the load on the evaporator increases, the TXV ____.

a) increases the flow of refrigerant
b) decreases the flow of refrigerant
c) maintains constant head pressure
d) decreases the pressure drop across the evaporator

A

a) increases the flow of refrigerant

23
Q

Rotary compressors are used primarily in ____.

a) large industrial refrigeration and air conditioning systems
b) residential air conditioning
c) small commercial refrigeration units
d) high volume residential refrigeration

A

b) residential air-conditioning

24
Q

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

A

a) will increase

25
Q

If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much subcooling is the condenser operating?

a) 30°F
b) 15°F
c) 100°F
d) 130°F

A

b) 15F

26
Q

In a water-cooled condenser, a regulating valve is used to control the ____.

refrigerant flow through the pressure reducing device

refrigerant condensing temperature

suction pressure

water temperature

A

b) refrigerant condensing temperature

27
Q

If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator?

5 psig

10 psig

15 psig

25 psig

A

d) 25psig

28
Q

The ____ of the liquid refrigerant determines the coil operating temperature.

freezing point

melting point

transition temperature

boiling temperature

A

d) boiling temperature

29
Q

The superheating done by a suction line-liquid line heat exchanger helps prevent ____.

liquid slugging in the compressor

frozen drain pans

frosted evaporators

tripped thermal overloads

A

a) liquid slugging in the compressor

30
Q

A hot-water reclaim tank is a cylinder filled with water that absorbs heat from refrigerant flowing through a refrigeration system’s ____.

discharge line

suction line

accumulator

sight glass

A

a) discharge line

31
Q

A condenser that consists of an inner tube through which water flows in one direction and a surrounding outer tube through which refrigerant flows in the opposite direction of the water flow is a ____.

shell-and-tube

shell-and-coil

tube-within-a-tube

All of the above.

A

c) tube-within-a-tube

32
Q

Since a compressor continues to operate after a pump-down solenoid closes, ____.

refrigerant from the evaporator and low side is pumped down

refrigerant collects in the evaporator and accumulator

high-side pressure drops

a high-pressure control is used to turn off the compressor

A

a) refrigerant from the evaporator and low side is pump down

33
Q

Heat exchangers featuring metal fins of various styles and types connected to evaporator tubing are ____ evaporators.

baffle-tube

fin-and-tube

plate

shell-and-sheet

A

b) fin-and-tube

34
Q

Heat exchangers made from two metal sheets that are welded together to form a series of passages are ____ evaporators.

baffle-tube

fin-and-tube

plate

shell-and-sheet

A

c) plate

35
Q

The function of EEVs is to maintain ____ at a desired setting.

superheat

subcooling

ambient temperature

head pressure

A

a) superheat

36
Q

To maintain a constant pressure in the evaporator when the system is running, an AXV ____ refrigerant flow when the evaporator pressure drops.

decreases

stabilizes

increases

None of the above.

A

c) increases

37
Q

When used with thermostatic expansion valves, the term superheat refers to the difference in temperature between the evaporator inlet and the ____.

liquid line

sensing bulb

discharge line

ambient air

A

b) sensing bulb

38
Q

Metering devices that can change their orifice size to account for changes in cooling loads are referred to as ____ metering devices.

modulating

flow

fixed

limited

A

a) modulating

39
Q

An oil control device that regulates the level of oil within a compressor using a float mechanism is an ____.

oil changer

oil level regulator

oil level separator

oil collector tank

A

b) oil level regulator

40
Q

The compressor protection device that is specifically intended to protect a compressor from overcurrent is a(n) ____.

fuse and circuit breaker

thermal overload device

crankcase pressure regulator (CPR)

accumulator

A

a) fuse and circuit breaker

41
Q

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

screw

scroll

centrifugal

rotary

A

a) screw

42
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

d) poppet valves operate more quickly than reed valves

43
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

b) the inner diameter of a piston ring is slightly larger than the piston diameter

44
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

c) crank throw-type

45
Q

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

Rotary.

Reciprocating.

Centrifugal.

Screw.

A

b) reciprocating

Middterm Review (4 decks)

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