unit9 Basic Concepts of Compression and Absorption Refrigeration Flashcards
1
Q
Refrigerant compressors:
Select one:
a. Must have intercoolers
b. Could be the centrifugal type
c. Use automotive-style suction and discharge valves
d. Have more cooling fins than air compressors
A
b. Could be the centrifugal type
2
Q
The major building occupancy classes include all of the following, except:
Select one:
a. Institutional
b. Industrial
c. Educational
d. Commercial
A
c. Educational
3
Q
Heat that causes an increase in temperature, is called \_\_\_\_\_ heat: Select one: a. Radiant b. Sensible c. Latent d. Convective
A
b. Sensible
4
Q
One tonne of refrigeration is: Select one: a. 13958 kJ per day b. 1000 kg of mass c. 233 kJ per minute d. 13958 J per hour
A
c. 233 kJ per minute
5
Q
In a closed vessel, the boiling point of a liquid can be raised by:
Select one:
a. Raising the liquid level in the vessel
b. Lowering the pressure in the vessel
c. Raising the pressure in the vessel
d. Decreasing the temperature in the vessel
A
c. Raising the pressure in the vessel
6
Q
R-134a Select one: a. is non-toxic b. has a strong, pungent odour c. is explosive when mixed with air d. is an ozone-depleting substance
A
a. is non-toxic
7
Q
With regard to economizers installed on packaged air-conditioning chillers, which of the following statements is FALSE?
Select one:
a. Economizers control the flow of liquid refrigerant from the evaporator to the condenser
b. Liquid refrigerant levels in each chamber are controlled by float operated valves
c. The upper float chamber is connected to the bottom of the condenser
d. The economizer is made of two chambers
A
a. Economizers control the flow of liquid refrigerant from the evaporator to the condenser
8
Q
The CSA B52 code requires that \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ shall be provided on all systems operating above atmospheric pressure. Select one: a. pressure limiting devices b. temperature cutout devices c. flow switches d. purgers
A
a. pressure limiting devices
9
Q
All refrigeration evaporators:
Select one:
a. require regular defrosting
b. are part of the high side of the system
c. are located between the expansion valve and the king valve.
d. are flooded with refrigerant
e. boil liquid refrigerant at low pressure and low temperature
A
e. boil liquid refrigerant at low pressure and low temperature
10
Q
Refrigeration valves should be identified with a tag that has:
Select one:
a. the valve number in the system, the fluid temperature, and its state
b. the valve number in the system, the fluid, and its state
c. the temperature, pressure, and type of fluid
d. the fluid temperature, pressure, and state
A
b. the valve number in the system, the fluid, and its state
11
Q
Which of the following is not found on the low side of an ammonia absorption refrigeration system? Select one: a. Evaporator b. Generator c. Absorber d. Low pressure ammonia vapour
A
b. Generator
12
Q
What must be located outside a Class T machinery room?
Select one:
a. Light switches
b. Machinery shut off switch
c. Spare flashlights
d. Disposable coveralls
A
b. Machinery shut off switch
13
Q
A chemical dot placed under the lens of a sight glass that is exposed to liquid refrigerant monitors
Select one:
a. Liquid flow
b. Refrigerant levels
c. The presence of moisture in the refrigerant
d. Vapour flow
A
c. The presence of moisture in the refrigerant
14
Q
What type of evaporator contains only a small amount of liquid refrigerant at any time? Select one: a. Dry evaporator b. Flooded evaporator c. A liquid overfeed evaporator d. A bare-tube evaporator
A
a. Dry evaporator
15
Q
If the first column of a refrigeration table lists the saturation temperature of a refrigerant, which column will most likely list the saturation pressure? Select one: a. Column 1 b. Column 2 c. Column 3 d. Column 4
A
b. Column 2
16
Q
The refrigeration evaporator that increases heat exchange by crimping several thin metal plates to single-wall tubes is a Select one: a. Plate surface evaporator b. Bare tube evaporator c. Shell and tube evaporator d. Finned tube evaporator
A
d. Finned tube evaporator
17
Q
Positive pressure testing of a new refrigeration system may be done
Select one:
a. by pressurizing the system with the compressor
b. by filling the system with oxygen, and then checking for leaks
c. by filling the system with an inert gas, and then performing a soap bubble test.
d. by performing a hydrostatic test, using softened water
A
c. by filling the system with an inert gas, and then performing a soap bubble test.
18
Q
The safety head of a refrigeration compressor is designed to:
Select one:
a. Unload cylinders if over-loaded
b. Relieve pressure due to liquid in the cylinder
c. Prevent damage due to freeze-up
d. Take the place of a safety relief valve
A
b. Relieve pressure due to liquid in the cylinder
19
Q
Which of the following is not a component of a closed cycle compression refrigeration system? Select one: a. Evaporator b. Compressor c. Absorber d. Condenser
A
c. Absorber
20
Q
Group “A” refrigerants: Select one: a. are non-flammable b. are moderately flammable c. have low toxicity d. are natural refrigerants
A
c. have low toxicity
21
Q
Ammonia piping (according to IIAR), should be labelled in:
Select one:
a. Orange background with black letters
b. Red background with white letters
c. Orange background with white letters
d. Yellow background with black letters
A
a. Orange background with black letters
22
Q
The absorber in the lithium bromide refrigeration system is equipped with a pump
Select one:
a. To force water into a finely divided state
b. To decrease the refrigerant evaporation point
c. To speed the absorption of water vapour
d. To keep the cycle pressure constant
A
c. To speed the absorption of water vapour
23
Q
Ammonia systems are seldom used for air conditioning purposes in large building mainly because ammonia:
Select one:
a. systems require more power than most building systems can provide.
b. is too toxic.
c. does not provide sufficient cooling capacity for large installations.
d. systems require too much maintenance.
A
b. is too toxic.
24
Q
The refrigerant R-134a belongs to the following safety group: Select one: a. A2 b. B1 c. A3 d. A1
A
d. A1
25
```
In a refrigeration system, the liquid refrigerant is changed to a gas in the:
Select one:
a. Condenser
b. Receiver
c. Compressor
d. Evaporator
```
d. Evaporator
26
Which of these statements about automatic expansion valves is FALSE?
Select one:
a. The automatic expansion valve maintains constant evaporator pressure, while the compressor is operating, regardless of the load.
b. The automatic expansion valve is usually used with multiple cooling coils connected to the same compressor.
c. A spring exerting a downward force on the diaphragm tends to open the automatic expansion valve.
d. When the compressor stops, the valve automatically closes.
b. The automatic expansion valve is usually used with multiple cooling coils connected to the same compressor.
27
```
In an Ammonia Absorption refrigeration system, what is used as the absorbent?
Select one:
a. Ammonia
b. Lithium Bromide
c. Water
d. R-717
```
c. Water
28
```
The rate at which a refrigeration system removes heat from the refrigerated medium is defined as:
Select one:
a. the Coefficient of Performance
b. the Net Cooling Effect
c. the refrigeration capacity.
d. the Compression Ratio
```
c. the refrigeration capacity.
29
Dry and flooded evaporators differ primarily in what respect?
Select one:
a. The dry evaporator is designed to cool gases only
b. The heat transfer surfaces of a flooded evaporator are kept covered with liquid refrigerant
c. Flooded systems primarily use Group B1 and B2 refrigerants
d. Dry evaporators use low-side floats, whereas flooded evaporators use high-side floats
b. The heat transfer surfaces of a flooded evaporator are kept covered with liquid refrigerant
30
```
When a liquid evaporates, it
Select one:
a. Gains sensible heat
b. Gains latent heat
c. Loses sensible heat
d. Loses latent heat
```
b. Gains latent heat
31
Absorption refrigeration systems may use waste in order to
Select one:
a. pressurize the system
b. evaporate water from the weak lithium bromide
c. decrease the evaporation point of the refrigerant
d. maintain a minimum load on the system, during periods of low cooling demand
e. To increase the lithium boiling point.
b. evaporate water from the weak lithium bromide
32
```
The most common Group B refrigerant is
Select one:
a. R-290
b. R-717
c. R-134a
d. R-22
```
b. R-717
33
An example of a high leak probability system is a:
Select one:
a. a double indirect system
b. a Class T system
c. a direct expansion system
d. an indirect closed system
c. a direct expansion system
34
```
In an ammonia absorption refrigeration system, the _____ ammonia is absorbed by the _____ aqua.
Select one:
a. Vapourized, weak
b. Vapourized, strong
c. Liquid, weak
d. Liquid, warm
```
a. Vapourized, weak
35
Which of the following steps is NOT part of a start-up of a reciprocating or rotary compressor refrigerating system?
Select one:
a. Check for proper oil level in the compressor
b. Open shutoff valves in the cooling water supply and return lines of water-cooled condensers
c. Valves in pressure piping should be closed
d. Check the setting of high and low pressure cut-off switches
c. Valves in pressure piping should be closed
36
With regard to a refrigeration system pressurestat, which of the following statements is FALSE?
Select one:
a. The control is connected to the suction line of the compressor
b. The control consists of a switch actuated through a linkage arrangement connected to a bellows or diaphragm
c. A pressurestat should be used in conjunction with an automatic expansion valve
d. When the pressure drops to the minimum allowable the switch acts opposite to a thermostat and opens
c. A pressurestat should be used in conjunction with an automatic expansion valve
37
Which of the following is NOT a function of the refrigeration compressor?
Select one:
a. Raises the pressure of the refrigerant
b. Raises the temperature of the refrigerant
c. Maintains a low pressure in the evaporator
d. Removes energy from the vapour
d. Removes energy from the vapour
38
```
If the chilled water temperature drops approximately 2.5-3°C below the chilled water temperature set point, the chilled water low temperature cut out will:
Select one:
a. Start the compressor
b. Shut down the compressor
c. Stop the chilled water pumps
d. Start the condenser pump
```
b. Shut down the compressor
39
```
The accessory that maintains efficient heat transfer by collecting oil before it coats the tubes of the condenser is called:
Select one:
a. A filter-drier
b. An oil scrubber
c. An adsorber
d. An oil separator
```
d. An oil separator
40
```
Which of the following is NOT considered a rotary refrigeration compressor design?
Select one:
a. Screw
b. Sliding vane
c. Scroll
d. Centrifugal
```
d. Centrifugal
41
Moisture in a refrigeration system will NOT cause
Select one:
a. The formation of ice inside the refrigeration system.
b. Acid formation inside the refrigeration system.
c. The deterioration of the motor insulation of a hermetic compressor.
d. Excessive high-side pressures.
d. Excessive high-side pressures.
42
Which is NOT a factor in determining the degree of hazard of a refrigerant?
Select one:
a. Amount of refrigerant in the system
b. Leakage probability of the system
c. Type of compressor used
d. Toxicity or flammability
c. Type of compressor used
43
```
Which of the following characteristics is common to all of the group B refrigerants?
Select one:
a. High toxicity
b. High flammability
c. Low Ozone Depleting Potential
d. High Global Warming Potential
```
a. High toxicity
44
```
A liquid trap located in the suction line before a refrigeration compressor, which evaporates liquid refrigerant and returns it to the compressor as a gas, is called:
Select one:
a. An oil separator
b. A strainer-drier
c. A distributor
d. An accumulator
```
d. An accumulator
45
```
Ammonia, as well as being toxic, is also:
Select one:
a. Miscible with oil
b. Odourless
c. Flammable
d. A low pressure refrigerant
```
c. Flammable
46
To drain oil from an NH3 system, a special self-closing __________ valve may be installed as a safety feature.
Select one:
a. Check
b. Butterfly
c. Dead man
d. Safety shut-off
c. Dead man
47
The amount of water used in an evaporative condenser is only a small percentage of that used in a water-cooled condenser of the same capacity, because
Select one:
a. Evaporative condensers also use air to cool the refrigerant.
b. Evaporative condensers spray refrigerated water onto the condensing coil.
c. The cooling water evaporates, removing far more heat per kilogram of system coolant.
d. Water is scarce where evaporative condensers are used.
c. The cooling water evaporates, removing far more heat per kilogram of system coolant.
48
The three main classifications of refrigeration compressors are:
Select one:
a. Axial, centrifugal, and positive displacement
b. Centrifugal, dynamic, and positive displacement
c. Reciprocating, rotary, and centrifugal
d. Rotary, reciprocating, and lobe
c. Reciprocating, rotary, and centrifugal
49
Which of these is not a requirement in a Class T machinery room?
Select one:
a. Inward opening doors
b. Restrictions on open flames and hot surfaces
c. Ventilation
d. Restricted access
a. Inward opening doors
50
In the lithium bromide refrigeration system, what is the function of the concentrator (generator)?
Select one:
a. To exchange heat between the high temperature refrigerant vapour and the atmosphere
b. To increase the absorbency potential of used absorbent
c. To speed up the evaporation of the refrigerant
d. To cool the concentrated absorbent
b. To increase the absorbency potential of used absorbent
51
```
) A compression refrigeration system can be divided into two sections: a high pressure section containing the head pressure and a low pressure section carrying the _____ pressure:
Select one:
a. Discharge
b. Saturation
c. Absolute
d. Suction
```
d. Suction
52
What is the Permissible Exposure Limit for R-717?
Select one:
a. 2 ppm
b. 50 ppm
c. 300 ppm
d. 70 ppm
b. 50 ppm
53
Which of the following is NOT an advantage of a factory assembled, packaged refrigeration unit?
Select one:
a. Components are designed to match each other
b. The final installation does not need to meet CSA B52 code
c. The unit is equipped with all the required auxiliary equipment
d. The unit is factory tested in operation
b. The final installation does not need to meet CSA B52 code
54
The function of the condenser in a refrigeration system is to:
Select one:
a. Lower the temperature of the liquid refrigerant
b. Change high pressure refrigerant vapour to liquid
c. Lower the temperature of the refrigerant vapour
d. Lower the liquid refrigerant pressure
b. Change high pressure refrigerant vapour to liquid
55
```
A sulfur candle is used to test for
Select one:
a. R-744 leaks
b. R-717 leaks
c. R-290 leaks
d. CFC leaks
```
b. R-717 leaks
56
```
An evaporator that can easily be cleaned and defrosted manually without interrupting the cooling process is which type of evaporator?
Select one:
a. Liquid recirculating evaporator
b. Finned evaporator
c. Plate surface evaporator
d. Shell and tube evaporator
```
c. Plate surface evaporator
57
```
The refrigeration compressor's operating control that uses a bimetal element is a:
Select one:
a. Fluid expansion actuating control
b. Pressurestat
c. Humidistat
d. Temperature actuated control
```
d. Temperature actuated control
58
Refrigeration plant workers should never wear
Select one:
a. Contact lenses
b. Latex gloves
c. Cotton clothing
d. Long sleeve shirts
a. Contact lenses
59
```
Which of the following is NOT a common type of refrigeration condenser?
Select one:
a. Flooded
b. Air-cooled
c. Shell and tube
d. Shell and coil
```
a. Flooded
60
The net refrigerating effect of a refrigerant is the amount of heat:
Select one:
a. Discharged by the condenser
b. Absorbed by the refrigerant in the evaporator
c. Added to the refrigerant by the compressor
d. Discharged by the refrigerant in the evaporator
b. Absorbed by the refrigerant in the evaporator
61
```
R-744 is non-toxic and non-flammable. Which safety group does it belong to?
Select one:
a. Group A2
b. Group B4
c. Group A1
d. Group A3
```
c. Group A1
62
```
Which of the following characteristics is common to all of the group B refrigerants?
Select one:
a. High toxicity
b. High flammability
c. Low Ozone Depleting Potential
d. High Global Warming Potential
```
a. High toxicity
63
```
Which of the following is NOT a physical property of refrigerants?
Select one:
a. Saturation temperature
b. Leakage tendency
c. Corrosiveness
d. Miscibility
```
c. Corrosiveness
64
```
Of the following refrigeration system evaporators, the ___________ evaporators require the largest refrigerant charge.
Select one:
a. Direct expansion
b. Bare tube
c. Plate surface
d. Flooded
e. Finned tube
```
d. Flooded
65
```
The safety control of a centrifugal compressor, that ensures the compressor only starts under a no-load condition, is called the
Select one:
a. Condenser high pressure cut-off
b. Chilled water flow switch
c. Motor demand limiter
d. Vane closed switch
```
d. Vane closed switch
66
Which of the following statements about strainers is false?
Select one:
a. Strainers prevent foreign particles from damaging compressor valves.
b. Piping must be disconnected to clean the strainer.
c. Hermetic type compressors are equipped with a built-in suction strainer.
d. Strainers typically consist of a fine mesh screen basket.
b. Piping must be disconnected to clean the strainer.
67
Which of the following statements about refrigeration pressure gauges is TRUE?
Select one:
a. Refrigeration pressure gauges can indicate saturation temperatures in a system.
b. The CSA B52 Code requires permanently installed pressure gauges on all refrigeration systems.
c. Only one pressure gauge is normally installed on a system.
d. Permanently installed pressure gauges shall be constructed for at least 1.5 times the high side design pressure.
a. Refrigeration pressure gauges can indicate saturation temperatures in a system.
68
```
When a chiller has stopped due to low water temperature, and the chilled water temperature subsequently rises approximately 5 to 6°C above the chilled water temperature set point, the:
Select one:
a. Compressor will restart
b. Compressor will unload
c. Cooling tower fan will restart
d. Condenser pump will restart
```
a. Compressor will restart
69
The ideal refrigerant should:
Select one:
a. Have a high boiling point at atmospheric pressure.
b. Have high condensing pressure
c. Have a low ozone depleting potential and a low global warming potential
d. Have a low latent heat capacity
c. Have a low ozone depleting potential and a low global warming potential
70
Pressure limiting devices must shut down the pressure imposing element at ___________% of the high side design pressure.
Select one:
a. 80%
b. 90%
c. 110%
d. 100%
b. 90%
71
When removing oil from an NH3 system, place a hose in_________and drain slowly, until all oil is removed from the vessel.
Select one:
a. A sealed container
b. A bucket of a oil
c. A bucket of water
d. An empty bucket
c. A bucket of water
72
The low oil pressure cut-off switches of a mechanical refrigeration system
Select one:
a. keep the compressor oil pressure at a level where the oil will not freeze
b. prevent compressor start-up if the oil heater fails
c. shut down the compressor when the oil pressure drops below the minimum required value
d. keep the oil from gelling at low pressure
c. shut down the compressor when the oil pressure drops below the minimum required value
73
```
In order to lower the boiling point of the refrigerant in the lithium bromide refrigeration system, it is important that the system maintain
Select one:
a. An extremely high vacuum
b. Very high pressure
c. Very low temperatures
d. High absorbent circulation rates
```
a. An extremely high vacuum
74
```
Before operating a new refrigeration plant, or one in which piping alterations have been made, the system must be tested for:
Select one:
a. High pressure
b. Moisture content
c. Excessive oil consumption
d. Leaks
```
d. Leaks
75
```
Which of the following is an example of a loss of latent heat?
Select one:
a. Steam condenses
b. Water evaporates
c. Ice melts
d. Refrigerant evaporates
```
a. Steam condenses
76
```
Which of the following is NOT a form of refrigeration evaporator construction?
Select one:
a. Bare tube
b. Plate surface
c. Shell and tube
d. Finned tube
e. Double-tube
```
e. Double-tube
77
The amount of water used in an evaporative condenser is only a small percentage of that used in a water-cooled condenser of the same capacity, because
Select one:
a. Evaporative condensers also use air to cool the refrigerant.
b. Evaporative condensers spray refrigerated water onto the condensing coil.
c. The cooling water evaporates, removing far more heat per kilogram of system coolant.
d. Water is scarce where evaporative condensers are used.
c. The cooling water evaporates, removing far more heat per kilogram of system coolant.
78
```
A pressure relief device on a refrigeration system shall have sufficient capacity to prevent the pressure in the pressure vessel from rising more than _____ above the setting of the pressure relief device.
Select one:
a. 10%
b. 150%
c. 103 kPa
d. 25%
```
a. 10%
79
Refrigerants will evaporate when the:
Select one:
a. Pressure is increased
b. Temperature is increased to saturation temperature
c. Temperature is reduced below saturation temperature
d. Heat is removed from them
b. Temperature is increased to saturation temperature
80
```
The two major types of compression refrigeration systems are:
Select one:
a. Frosting and non-frosting
b. commercial and residential
c. Indirect and Direct
d. High pressure and low pressure
```
c. Indirect and Direct
81
One function of vibration absorbers is to:
Select one:
a. Lower noise levels
b. Allow the load on the system to increase dramatically without straining the components in the system
c. Insulate piping and make the system more efficient
d. Align piping
a. Lower noise levels
82
The expansion valve in a refrigeration system
Select one:
a. Expands the liquid to the receiver
b. Regulates the liquid refrigerant flow to the evaporator
c. Is used to charge the refrigeration system
d. Isolates the compressor from the condenser
b. Regulates the liquid refrigerant flow to the evaporator
83
Which of the following statements about the shell and tube evaporator is FALSE?
Select one:
a. A shell and tube evaporator is also called a chiller.
b. In a direct expansion chiller, the brine circulates through the tubes.
c. In the flooded chiller, the refrigerant is contained in the shell, and surrounds the tubes.
d. Refrigerant vapour is drawn from the evaporator by the compressor.
b. In a direct expansion chiller, the brine circulates through the tubes.
84
```
The saturation temperature of a refrigerant is the same as its:
Select one:
a. Boiling point
b. Freezing point
c. Saturation pressure
d. Fire point
```
a. Boiling point
85
```
The refrigeration condenser design that requires chemical cleaning, because it cannot be mechanically cleaned, is the:
Select one:
a. Shell and tube condenser
b. Shell and coil condenser
c. Air-cooled condenser
d. Evaporative condenser
```
b. Shell and coil condenser
86
Which of the following is not a component of the low pressure side of a compression refrigeration system?
Select one:
a. Compressor discharge piping
b. The evaporator
c. The downstream side of the expansion valve
d. The suction line
a. Compressor discharge piping
87
```
The most widely used refrigerant metering device, which consists of a pressure-sensitive bellows or diaphragm connected to a temperature sensing bulb, is the
Select one:
a. thermostatic expansion valve
b. automatic expansion valve
c. capillary tube
d. manual expansion valve
```
a. thermostatic expansion valve
88
```
A safety control designed to protect the chiller from freezing is the:
Select one:
a. Vane closed switch
b. Low oil pressure shut down switch
c. Motor demand limiter
d. Chilled water flow switch
```
d. Chilled water flow switch
89
Pressure limiting devices must shut down the pressure imposing element at ___________% of the high side design pressure.
Select one:
a. 100%
b. 90%
c. 110%
d. 80%
b. 90%
90
The low oil pressure cut-off switches of a mechanical refrigeration system
Select one:
a. keep the compressor oil pressure at a level where the oil will not freeze
b. prevent compressor start-up if the oil heater fails
c. shut down the compressor when the oil pressure drops below the minimum required value
d. keep the oil from gelling at low pressure
c. shut down the compressor when the oil pressure drops below the minimum required value
