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Austin's Sheet Metal 4th Year > Refrigeration/AC > Flashcards

Refrigeration/AC Flashcards

1
Q

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

A

On the low side

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2
Q

Where is the sensing bulb on a TXV located?

A

The piping leaving the evaporator

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3
Q

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

A

144 BTU’s

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4
Q

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

A

970 BTU’s

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5
Q

Which refrigerants are considered the most harmful?

A

CFC’s

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6
Q

How is pressure defined?

A

As force per unit area

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7
Q

How is a refrigerant defined?

A

As a substance used for heat transfer

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8
Q

What happens to refrigerants when they absorb heat?

A

They evaporate

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9
Q

What do refrigerants contain that can produce dangerous poisonous gases?

A

Fluorocarbons

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10
Q

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

A
  • Compressor
  • Liquid metering device
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11
Q

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

A
  • Evaporator
  • Liquid to gas
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12
Q

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

A

On the high side

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13
Q

Give 3 examples of an ideal refrigerant?

A
  1. Refrigerant A - a refrigerant with lower toxicity
  2. Refrigerant B - a refrigerant with higher toxicity
  3. Refrigerant C - a refrigerant with higher flamability

Refrigerants are also classified by a numeral that indicates their flammability. Other refrigerant safety classes include:
Class 2: Lower flammability
Class 2L: Lower burning velocity
Class 1: No flame propagation

Specific refrigerants can vary based on application, but ideal refrigerants typically have low environmental impact and high efficiency.

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14
Q

What should the latent heat of vaporization be for an ideal refrigerant?

A

High

A high latent heat of vaporization allows for efficient heat absorption during the refrigeration cycle.

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15
Q

Why is a TXV the most commonly used valve?

A

It is the most efficient

A Thermal Expansion Valve (TXV) allows for precise control of refrigerant flow, optimizing system efficiency.

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16
Q

What is the greatest method of heat transfer?

A

Conduction

Conduction is the transfer of heat through direct contact between materials.

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17
Q

Where should a filter drier be installed?

A

In the liquid line leaving the condenser

This placement helps to remove moisture and contaminants from the refrigerant before it enters the evaporator.

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18
Q

What is the sequence for refrigerant entering the evaporator?

A

Refrigerant enters as a high pressure liquid at the expansion valve

The refrigerant then expands and absorbs heat as it vaporizes in the evaporator.

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19
Q

When must the filter drier be replaced?

A

Whenever the refrigeration system needs to be opened for service

This ensures that any moisture or contaminants introduced during service are removed.

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20
Q

What PPE is recommended when dealing with refrigerant?

A

Gloves, glasses and face shield

Personal protective equipment (PPE) is crucial for safety when handling refrigerants.

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21
Q

What is the temperature on the low pressure side?

A

40-45 degrees F

This range is typical for the low pressure side in refrigeration systems.

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22
Q

What is the temperature on the high pressure side?

A

110-115 degrees F

These temperatures are common for the high pressure side in refrigeration systems.

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23
Q

The amount of heat a substance holds is?

A

Enthalpy

Enthalpy is a thermodynamic quantity that represents the total heat content.

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24
Q

The speed at which heat is released is?

A

Entropy

Entropy is a measure of the disorder or randomness in a system and relates to the energy dispersion.

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25
Q

What is the temperature of supply air?

A

55 degrees F

This temperature is typically used for conditioned air in HVAC systems.

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26
Q

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

A

It drops instantly

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27
Q

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

A

Dehumidifier

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28
Q

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

A

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

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29
Q

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

A

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

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30
Q

What is found in a compressor to help cool it?

A

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

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31
Q

What type of metering device is distributed evenly across the coil?

A

Orifice

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32
Q

What is the line from the evaporator to the compressor known as?

A

Suction or vapour line

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33
Q

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

A

5 tons or 60000 btu’s

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34
Q

What does CFC stand for?

A

Chlorofluorocarbon

35
Q

What capacity should a recovery cylinder be filled to?

A

80% maximum

36
Q

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

A

Liquid

37
Q

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

A

Two - liquid to vapour

38
Q

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

A

Sub cooling

Sub cooling refers to the process where a liquid is cooled below its saturation point without changing into a solid.

39
Q

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

A

Super heat

Super heating is the process where a liquid is heated beyond its boiling point without turning into vapor.

40
Q

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

A

Temperature increases

This relationship is explained by the principles of thermodynamics, particularly for gases.

41
Q

What happens to pressure in refrigerant if the temperature decreases?

A

Pressure decreases

This is a fundamental principle of gas behavior, where a decrease in temperature typically leads to a decrease in pressure.

42
Q

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

A

Between the compressor and condenser

The discharge line carries refrigerant from the compressor to the condenser in a split system.

43
Q

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

A

Liquid line

The liquid line transports the high-pressure liquid refrigerant from the condenser to the metering device.

44
Q

What type of metering device allows the system to equalize pressure?

A

Orifice

45
Q

What type of piping is used in air conditioning?

A

Copper, type K-thick wall

46
Q

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

A

A filter dryer

47
Q

How is a filter dryer installed?

A

With arrows pointing toward the direction of refrigerant flow

48
Q

How many BTUs per hour are needed to melt one ton of ice at 32 degrees?

A

12,000 BTUs

49
Q

What is the atmospheric pressure at sea level?

A

14.7 psi

50
Q

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

A

It enters as a liquid and leaves as a gas

51
Q

Name 3 types of condensers

A
  • Air cooled
  • Water cooled
  • Evaporative
52
Q

Name 3 types of metering devices

A
  • Thermostatic expansion valve (TXV)
  • Capillary tube
  • Electronic expansion valve
53
Q

How is a TXV controlled?

A

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

54
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

55
Q

Can a capillary tube be modified or adjusted?

A

No

56
Q

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

A

Compressor, Evaporator, Condenser, Liquid metering device

57
Q

Which component absorbs heat?

A

Evaporator

58
Q

Define a cooling system?

A

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

59
Q

What percentage is relative humidity?

A

50%

60
Q

What percentage of liquid and vapour leave the metering device?

A

75% liquid

61
Q

What is the compressor’s job in a refrigeration cycle?

A

It pumps the refrigerant through the system by establishing the two pressures

62
Q

What does the acronym CFC stand for?

A

chlorofluorocarbon

CFCs are compounds used in refrigeration and air conditioning.

63
Q

List the 3 types of condensers.

A
  • Air-Cooled
  • Water-Cooled
  • Evaporative

These condensers are used in various refrigeration systems.

64
Q

Define temperature.

A

Is a measure of the INTENSITY of heat of a substance and the measure of its …

Temperature is a fundamental physical quantity that indicates the thermal state of a system.

65
Q

What is a sub-cooled liquid?

A

A liquid that has been cooled below the boiling (condensing) temperature, at a …

Sub-cooling improves the efficiency of refrigeration systems.

66
Q

What is a superheated vapor?

A

A vapor heated to a temperature above its saturation point.

Superheating is used to ensure that the vapor does not condense in certain parts of the system.

67
Q

One ton of cooling is equivalent to how many Btu/hr?

A

12000 Btu/hr

This unit is commonly used to measure the cooling capacity of refrigeration systems.

68
Q

Explain why dehumidifying ventilators do not work in hot humid climates

A

Dehumidifying ventilators bring more outside air into the house which has more moisture in it

69
Q

The heat pump humidifier works under the same basic principles as an air conditioning heat pump

TRUE or FALSE

A

TRUE

70
Q

List 3 basic types of dehumidifiers

A
  1. Heat pump
  2. Chemical absorbant
  3. Ventilating humidifer
71
Q

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

A

Two

72
Q

Which side of the system is the evaporator considered to be in?

A

Low pressure side

73
Q

List 6 components of a basic cooling system

A
  1. Compressor
  2. Evaporator
  3. Condenser
  4. Metering device
  5. Piping
  6. Filter drier
74
Q

One type of filter can be used on all refrigerant.

TRUE or FALSE

A

FALSE

75
Q

List the 3 types of metering systems

A
  1. Thermostatic expansion
  2. Capillary tube
  3. Orifice
76
Q

Is it necessary to obtain a permit before installing a cooling system?

A

Yes, a permit must be taken out for every installation

77
Q

What type of PPE must be worn to prevent injury from frostbite

A
  1. Hand protection
  2. Eye protection
  3. Proper clothing
78
Q

A recovery cylinder should be filled to a maximum of ___% under capacity

A

80%

79
Q

One ton of cooling is equivalent to how many btu’s/hr

A

12000 btu/hr

80
Q

What is super heated vapor

A

A capour heated to a temperature above its saturation point.

After a liquid has vaporized, the heat that it continues to absorb raises its temperature so that it becomes superheated

81
Q

What is sub-cooled liquid

A

A liquid that has been cooled below the boiling (condensing) temperature, at a specified pressure.

82
Q

Define Temperature

A

Is the measure of INTENSITY of heat of a substance and the measure of its molecular speed expressed in degrees.

Fahrenheit is used in the refrigeration industry.

83
Q

List 3 types of condensers

A
  1. Air cooled
  2. Water cooled
  3. Evaporative
84
Q

What does the acronym CFC stand for?

A

Chlorofluorocarbon

Austin's Sheet Metal 4th Year (9 decks)

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