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Sheet Metal 4th Year > Refrigeration > Flashcards

Refrigeration Flashcards

1
Q

What are the 4 components in a basic air conditioning system?

A

Compressor
Evaporator
Condenser
Liquid metering device

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2
Q

Which component absorbs heat?

A

Evaporator

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3
Q

Define a cooling system?

A

It is a system that takes heat from where it is not wanted and relocates it to where it does not matter

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4
Q

What percentage is relative humidity?

A

50%

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5
Q

What percentage of liquid and vapour leave the metering device?

A

75% liquid

25% vapour

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6
Q

What is the compressors job in a refrigeration cycle?

A

It pumps the refrigerant through the system by establishing the two pressure levels necessary for efficient operation of the system

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7
Q

What happens to the refrigerant as it travels through the evaporator?

A

It enters as a liquid and leaves as a gas

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8
Q

Name 3 types of condensers?

A

Air cooled
Water cooled
Evaporative

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9
Q

Name 3 types of metering devices?

A

Thermostatic expansion valve (TXV)
Capillary tube
Orifices

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10
Q

How is a TXV controlled?

A

By a sensing bulb attached to the piping on the discharge side of the evaporator

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11
Q

How is a capillary tube used as a metering device?

A

It reduces pressure from the high side of the system to the low side because of its length and proper bore size

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12
Q

Can a capillary tube be modified or adjusted?

A

No

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13
Q

What type of metering device allows the system to equalize pressure when the compressor is off?

A

Orifice

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14
Q

What type of piping is used in air conditioning?

A

Copper, type K-thick wall
Copper, type L-thin wall

Both are available in drawn temper which is hard or rigid and annealed temper which is soft or flexible

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15
Q

What removes contaminants that may be present in the refrigerant stream?

A

A filter dryer

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16
Q

How is a filter dryer installed?

A

With arrows pointing toward the direction of refrigerant flow

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17
Q

How many btu’s per hour is needed to melt one ton of ice at 32 degrees?

A

12000 btu’s

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18
Q

What is the atmospheric pressure at sea level?

A

14.7 psi

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19
Q

What happens when a liquid is cooled below 0 degrees but does not change state to ice?

A

Sub cooling

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20
Q

What happens to a liquid above 212 degrees F but does not change state to steam?

A

Super heat

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21
Q

What happens to the temperature in refrigerant if you increase the pressure?

A

Temperature increases

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22
Q

What happens to pressure in refrigerant if the temperature decreases?

A

Pressure decreases

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23
Q

Where do you find the discharge line on a split system?

A

Between the compressor and condenser

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24
Q

What is the line between the condenser and metering device called?

A

Liquid line

25
Q

The line from the evaporator to the compressor is known as what?

A

Suction or vapour line

26
Q

What size of system can licensed sheet metal workers install and service?

A

5 tons or 60000 btu’s

27
Q

What does CFC stand for?

A

Chlorofluorocarbon

28
Q

What capacity should a recovery cylinder be filled to?

A

80% maximum

29
Q

When the refrigerant leaves the condenser it is a hot, high pressure?

A

Liquid

30
Q

How many pressure changes will a refrigerant undergo in a complete cycle?

A

Two-liquid to vapour

31
Q

What happens to the temperature of refrigerant if it is released into the atmosphere?

A

It drops instantly

32
Q

What removes moisture from the air by condensing the moisture onto a cold surface?

A

Dehumidifier

33
Q

What components are found on the high side of the system?

A

Discharge side of compressor, condenser and piping to the metering device

34
Q

What components are found on the low side of the system?

A

Discharge side of metering device, evaporator, piping to the compressor and the inlet side of the compressor

35
Q

What is found in a compressor to help cool it?

A

Oil- either mineral in older systems or synthetic in newer systems

36
Q

What type of metering device distributed evenly across the coil?

A

Orifice

37
Q

What PPE is recommended when dealing with refrigerant?

A

Gloves, glasses and face shield

38
Q

What is the temperature on the low pressure side?

A

40-45 degrees F

39
Q

What is the temperature on the high pressure side?

A

110-115 degrees F

40
Q

The amount of heat a substance holds is?

A

Enthalpy

41
Q

The speed at which heat is released is?

A

Entropy

42
Q

What is the temperature of supply air?

A

55 degrees F

43
Q

Give 3 examples of an ideal refrigerant?

A

Latent heat of vaporization should be high
It should not burn or be explosive
It should evaporate at a low temperature and pressure
It should condense at a medium temperature and pressure
Must not be harmful to machinery
Should not be toxic

44
Q

Why is a TXV the most commonly used valve?

A

It is the most efficient

45
Q

What is the greatest method of heat transfer?

A

Conduction

46
Q

Where should a filter drier be installed?

A

In the liquid line leaving the condenser

47
Q

What is the sequence for refrigerant entering the evaporator?

A

Refrigerant enters as a high pressure liquid at the expansion valve, moves in one direction through the coil, reaches the sensor for super heat and leaves as a low pressure vapour

48
Q

When must the filter drier be replaced?

A

Whenever the refrigeration system needs to be opened for service

49
Q

How is pressure defined?

A

As force per unit area
P=F/A
Measured in psi

50
Q

How is a refrigerant defined?

A

As a substance used for heat transfer. It absorbs heat by evaporating at a low temperature and pressure and releases the heat by condensing at a high temperature and pressure

51
Q

When exposed to an open flame, what do refrigerants contain and what can they produce?

A

They contain fluorocarbons that break down to produce dangerous poisonous vapours

52
Q

In what 2 components is there a change in temperature of the refrigerant?

A

Compressor and liquid metering device

53
Q

In what two components is there a change in state of the refrigerant?

A

Evaporator-liquid to gas

Condenser-gas to liquid

54
Q

Where is pressure at or above condensing pressure in the cycle?

A

On the high side

55
Q

Where is pressure at or below vaporizing pressure in the cycle?

A

On the low side

56
Q

Where is the sensing bulb on a TXV located?

A

The piping leaving the evaporator

57
Q

How many BTU’s are required to change the state of water from a solid to a liquid (latent heat of fusion)?

A

144 BTU’s

58
Q

How many BTU’s are required to change the state of water from liquid to a gas?

A

970 BTU’s

59
Q

Which refrigerants are considered the most harmful?

A

CFC’s

Sheet Metal 4th Year (5 decks)

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