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PSAEIV-ABE BRM > AREA III - Refrigeration and Air conditioning > Flashcards

AREA III - Refrigeration and Air conditioning Flashcards

1
Q

It is the process of cooling

A

Refrigeration

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2
Q

It is the process of treating air to control simultaneously its temperature, humidity, cleanliness, and distribution to meet the comfort requirements of the occupants of the conditioned space

A

Comfort air conditioning

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3
Q

Provides a heat transfer surface through which heat can pass from the refrigerated space or product into the vaporizing refrigerant

A

Evaporator

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4
Q

Conveys the low-pressure vapor from the evaporator to the suction inlet of the compressor

A

Suction line

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5
Q

Removes the vapor from the evaporator and raises the temperature and pressure of the vapor to a point such that the vapor can be condensed with normally available condensing media

A

Vapor compressor

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6
Q

Delivers the high pressure, high-temperature vapor from the discharge of the compressor to the condenser

A
  1. “Hot gas” or discharge line
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7
Q

Provides a heat transfer surface through which heat passes from the hot refrigerant vapor to the condensing medium

A

Condenser

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8
Q

Provides storage for the condensed liquid so that a constant supply of liquid is available to the evaporator as needed

A

Receiver tank

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9
Q

Carries the liquid refrigerant from the receiver tank to the refrigerant flow control

A

Liquid Line

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10
Q

Meters the proper amount of refrigerant to the evaporator and reduces the pressure of the liquid entering the evaporator so that the liquid will vaporize in the evaporator at the desired low temperature

A

Refrigerant flow control

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11
Q

The substance employed as the heat absorber or cooling agent

A

refrigerant

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12
Q

the absorbed heat causes an increase in the temperature of the refrigerant

A

Sensible

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13
Q

the absorbed heat causes a change in the physical state of the refrigerant
(either melting or vaporizing)

A

Latent

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14
Q

Medium of heat transfer which absorbs heat by evaporating at a low
temperature and gives up heat by condensing at a high temperature and pressure

A

Refrigerant

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15
Q

The principal use of this refrigerant is in the air-cycle refrigeration unit for aircraft

A

Air

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16
Q

A refrigerant used in large industrial and low-temperature
installations

A

Ammonia

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17
Q

A refrigerant with high horsepower requirements and high condensing pressures that has been used on low - temperature cycle in a cascade system.

A

Carbon dioxide

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18
Q

A refrigerant suitable for service in centrifugal compressors.

A

Refrigerant 11

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19
Q

Two most-used refrigerants in
centrifugal compressor system

A

R11 and R113

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20
Q

A refrigerant that is most widely used refrigerant. It is used primarily with
reciprocating compressors for service in household refrigeration appliances, commercial and industrial air conditioning, and in a multitude of other types of refrigeration systems

A

Refrigerant 12

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21
Q

A refrigerant similar to R12 that is also nontoxic and has a low power requirement per ton.

A

Refrigerant 22

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22
Q

A refrigerant that possesses desirable properties, having convenient operating pressures, low power requirement per ton, and is nontoxic and noncorrosive.

A

Refrigerant 12

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23
Q

A refrigerant that is competitive with ammonia in industrial low-temperature systems in cases where the toxicity of the refrigerant is of concern.

A

Refrigerant 22

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24
Q

Examples of secondary refrigerants

A

brines and antifreezes

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25
Two of the most popular brines
calcium chloride and sodium chloride solutions
26
It is defined as the uncontrolled entry of unconditioned outside air directly into the building, resulting from natural forces, e.g., wind and buoyancy due to the temperature difference between inside and outside.
Infiltration
27
Heat gain due to the release of energy within a space
Internal load
28
It is defined as air intentionally brought into the building by mechanical means.
Ventilation
29
It is a mechanical mixture of gases and water vapor
Air
30
It is the temperature at which the water vapor in the air is saturated
Dew Point Temperature
31
It is the water vapor in the air
Humidity
32
It is the mass of water vapor per unit volume of air
Absolute humidity or vapor density
33
Ratio of the actual partial pressure exerted by the water vapor in any volume of air to the partial pressure that would be exerted by the water vapor if the water vapor in the air is saturated at the temperature of the air
Relative humidity
34
It is also called as specific humidity, is an expression of the mass of water vapor per unit mass of dry air
Humidity ratio
35
It is also called as percentage humidity, is the ratio of the mass of water vapor in the air per unit mass of dry air to the mass of water vapor required for saturation of the same air sample.
Saturation ratio
36
Temperature as measured by an ordinary dry bulb thermometer
Dry bulb temperature of the air
37
Temperature as measured by a wet bulb thermometer
Wet bulb temperature of the air
38
An ordinary thermometer whose bulb is enclosed in a wetted cloth sac or wick.
wet bulb thermometer
39
It is the sum of the enthalpy of the dry air and the enthalpy of the water vapor
Enthalpy
40
The difference between the dew point and dry bulb temperature of air
Degrees of superheat
41
The study of the properties of the mixtures of air and water vapor
Psychrometry
42
When the condition of the mixture lies on this line the air is said to be saturated
Saturation line
43
Refers to a rate of heat transfer attributable only to a change in dry-bulb temperature of the air.
Sensible heating or cooling
44
It may be adiabatic or with addition of heat
Humidification
45
Results in a reduction of both the dry-bulb temperature and the humidity ratio
Cooling and dehumidification
46
the water vapor from the air is absorbed or adsorbed by a hygroscopic material
Chemical dehumidification process
47
4 most commonly used valves
shutoff, backpressure, solenoid and backseating.
48
A valve installed in the line to block flow completely when it is closed
shutoff valve
49
A valve installed in the suction line to maintain a sufficiently high pressure in an evaporator to prevent freezing or excessive dehumidification of air in an air cooling coil.
back-pressure valve or evaporator-pressure regulator
50
A valve that is electrically powered magnetic valves which serve as automatic shutoff valves
Solenoid valves
51
It recovers as much of this oil as possible before it goes through the condenser and collects in the evaporator
Oil separator
52
These are installed in the suction and discharge lines to reduce the transmission of vibration from the compressor
Vibration eliminators
53
It causes irritating noise and weaken the solder connections in the piping
Vibrations
54
It contains desiccants such as silica gel or activated alumina which adsorb moisture.
Driers
55
It prevents foreign particles from flowing through the refrigerating system
Filters
56
A short transparent fitting that allows the flow of refrigerant to be viewed
Liquid indicators
57
Its purpose is to heat the vapor coming from the evaporator while it subcools liquid flowing between the condenser and the expansion valve
Heat exchanger
58
A vessel that stores liquid refrigerant
Liquid receiver
59
It prevents suction vapor from carrying slugs of liquid to the compressor from the evaporator.
Liquid accumulator
60
It removes air from the system
Purger
61
Three common methods of defrosting coils
use warm air, water and hot gas
62
A type of fan that consists of a wheel or rotor within a scroll spiral type housing
Radial flow or centrifugal fan
63
it has a large number of blades, i.e. up to 60, narrow in the radial dimension but wide parallel to the shaft and facing forward in the direction of rotation like a scoop.
Forward-curved-blade
64
It has about 12 blades, essentially flat and tilted backward from the direction of wheel rotation. It is a high-speed type of fan with a self-limiting horsepower characteristic. It is the most efficient and more expensive.
Backward-curved-blade
65
it has a smaller number of blades – from 6 to 20 – and the blades are essentially in a plane radiating from the shaft. The blades are normally about 2 to 3 times as long radially as they are wide.
Straight or double-curved fan
66
Airflow is parallel to the shaft or axis
Axial-flow or Propeller fan
67
This is suited for ventilation of rooms and air ducts of low resistance. This is characterized by excessive noises at high speeds.
Propeller
68
It is distinguished by large hubs and short blades, in addition to stationary straight vanes on the discharge sides of the fan to prevent rotation or swirling of the air.
Vane-axial
69
This is similar to a vane-axial fan except that it does not contain guide vanes. It is simpler and somewhat less efficient than the vane-axial.
Tube-axial
70
A heat-operated unit, which uses a refrigerant that, is alternately absorbed and liberated by the absorbent
Absorption Refrigeration
71
A cylindrical vessel designed to trap any refrigerant liquid, which may not have changed to gas in the evaporator, from entering the suction line to the compressor
Accumulator
72
Which transfers energy from a low-level temperature to a high level temperature, requiring an additional external work for its operation
Carnot Refrigeration Cycle
73
Its operation is that the incoming gas enters the eye of the spinning impeller and is thrown by centrifugal force to the periphery of the impeller importing a high velocity to the gas, thus builds up the pressure.
Centrifugal Compressor
74
The ratio of useful refrigeration (or refrigerating effect) to the net work (or work of compression).
Coefficient of Performance
75
This unit condenses the high-pressure vapor (refrigerant) back into a liquid state so that it can be reused in the refrigeration cycle.
Condenser
76
It is a cooling equipment for refrigeration or an air conditioning system where water is cooled by contacting it with air and evaporating some of the water
Cooling Tower
77
Temperature at which the moisture (water vapor) in the air will begin to condense out of the air when the air is cooled
Dewpoint Temperature
78
Temperature of air measured with a standard thermometer with a minimum relative motion between the dry thermometer bulb and the surrounding air.
Dry-bulb Temperature
79
A type of evaporator when a portion of its area is used for superheating the refrigerant.
Dry Evaporator
80
A solid carbon dioxide which when heated at atmospheric pressure, the solid transforms directly into vapor
Dry Ice
81
A companion device for conserving water with the cooling tower.
Evaporative Condenser
82
It is a heat exchanger, which transfers heat from the substance being cooled to a boiling refrigerant
Evaporator
83
It is a primary refrigerant such as Freon 12 or Freon 22, under the trademark of Freon Products.
Freon
84
Quantity of heat that will pass
Heat of Respiration
85
Measure of the proportion of vapor present
Humidity
86
The weight of vapor interspersed per pound of dry air
Humidity Ratio
87
Volume of 1 kg dry gas plus its contained vapor
Humid Volume
88
Load added to the cooling equipment when cooled air is displaced by outdoor air entering through the cracks around doors and windows when door opens.
Infiltration Load
89
Heat loads principally coming from people, infiltration air, ventilation air and moisture-releasing appliances
Latent Load
90
Occurs when the temperature drops below the dew-point temperature of the air
Moisture Condensation
91
Amount of heat that must be removed from the product to lower its temperature to the room in which it is to be stored
Product Load
92
Measurement of physical properties of gas mixture
Psychrometrics
93
Chart of gas mixture properties
Psychrometric Chart
94
The study of properties of mixtures of air and water vapor
Psychrometry
95
Removing of air from the refrigeration system
Purging
96
A type of compressor consisting of a piston moving back and forth in a cylinder with suction and discharge valves arranged to allow pumping to take place
Reciprocating Compressor
97
The ratio of the partial pressure of the water vapor in saturated air at the same temperature
Relative Humidity
98
It is a positive-displacement machine with shaft, blade, and roller as its moving parts in the compression.
Rotary Compressor
99
It is a refrigerating system using steam as a refrigerant, which expands through a converging-diverging nozzle and rushes out a supersonic speed
Steam Jet Refrigeration
100
It is vapor pressure at a temperature above the boiling point when the volume is confined under pressure.
Steam Pressure
101
It is a change of phase from solid into a vapor, which may provide refrigeration
Sublimation
102
The insulating ability of a material or the resistance of the material to the flow of heat through it.
Thermal Resistance
103
It is the unit of refrigeration capacity requiring to freeze one (1) ton of water at 32°F into ice at 32°F in one (1) day equivalent to 200 Btu/min or 12,000 Btu/hr.
Ton of Refrigeration
104
The total heat energy in the air
Total Heat Content
105
When the water molecules in the air exert a particular pressure
Vapor Pressure

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