HVAC UNIT 3 REVIEW TEST
A refrigerant replacing R-502 in low- and medium-temperature refrigeration applications, which is a near-azeotropic refrigerant blend with a small temperature glide is a. R-404A. b. R-407C. c. R-134a. d. R-500.
A
According to the pressure/enthalpy chart, as refrigerant flows through the compressor a. the pressure, temperature, and heat content of the refrigerant all increase. b. the pressure and temperature of the refrigerant increase, while the heat content of the refrigerant decreases. c. the pressure and heat content of the refrigerant increase, while the temperature of the refrigerant decreases. d. the pressure, temperature, and heat content of the refrigerant all decrease.
A
It is important for technicians to recover refrigerants so that they a. will not be released into the atmosphere. b. may be used again. c. may be reclaimed for future use. d. All of the above.
A
Lines of constant temperature on a pressure/enthalpy diagram are referred to as a. Isotherms. b. isometrics. c. isobars. d. fractionation lines.
A
Near-azeotropic refrigerant blends all exhibit some a. temperature glide and fractionation. b. oil problems. c. high boiling points. d. low condensing pressures.
A
R-134a is a refrigerant most commonly used in ________ systems. a. medium-temperature b. residential air-conditioning c. primarily low-temperature d. All of the above.
A
R-22 is a refrigerant most commonly used in _________ systems. a. residential air-conditioning b. light commercial refrigeration c. industrial refrigeration d. household refrigeration
A
Reciprocating compressors have a. a piston and a cylinder. b. two scrolls that mesh together. c. a rotor to compress the refrigerant. d. a large fan-type compressor component.
A
Reciprocating compressors have ____. a. a piston and cylinder b. two scrolls that mesh together c. a rotor to compress the refrigerant d. a large fan compressor component
A
Rejects both sensible and latent heat from the refrigeration system. a. Condenser b. Compressor c. Evaporator d. Metering Device
A
The condenser a. rejects the heat from the refrigerant. b. meters the refrigerant throughout the system. c. causes super-heat in-the refrigerant. d. All of the above.
A
The condenser ____. a. rejects the heat from the refrigerant b. controls the refrigerant flow throughout the system c. adds superheat to the refrigerant d. All of the above.
A
The cylinder color code for R-410A is a. rose. b. white. c. yellow. d. green.
A
The law requires technicians to recover refrigerant from all refrigeration systems so that they ____. a. will not be released into the atmosphere b. may be used again c. may be reclaimed for future use d. All of the above.
A
When a refrigerant enters the compressor, it is a ____ and when it leaves the compressor, it is a ____. a. low pressure low temperature superheated vapor, high pressure high temperature superheated vapor b. low pressure low temperature superheated vapor, low pressure low temperature subcooled vapor c. high pressure superheated vapor, low pressure superheated vapor d. low pressure low temperature subcooled liquid, high pressure high temperature superheated vapor
A
The refrigerant vapor picks up additional heat as it flows from the evaporator to the compressor. The heat is picked up from the ___________________
AREA BEING CONDITIONED
A refrigerant that has properties very similar to R-12 and is used primarily in medium- and high-temperature refrigeration applications, refrigerators and freezers, and automotive air-conditioning is a. R-22. b. R-134a. c. R-404A. d. R-407C.
B
A ton of refrigeration is equal to a. 1 ton of Ice. b. 288,000 Btu/24 h. c. 144 Btu/h. d. a large refrigerator.
B
A ton of refrigeration is equal to ____. a. 1 ton of ice b. 288,000 Btu/24 h c. 144 Btu/h d. 12,000 Btu/min
B
High temperature refrigeration is that produced by ____. a. heat from a furnace b. an air-conditioning system c. the vegetable cooling system of a refrigerator d. the freezer section of a refrigerator
B
High-temperature refrigeration is that produced by a. heat from a furnace. b. an air-conditioning system, c. the vegetable cooling system of a refrigerator. d. the freezer section of a refrigerator.
B
Is the heart of the refrigeration system. a. Condenser b. Compressor c. Evaporator d. Metering Device
B
It is believed that certain refrigerants such as CFCs and HCFCs, when allowed to escape into the atmosphere, will a. destroy the hydrogen layer and allow more of the sun's rays to overheat the earth. b. deplete the stratospheric ozone layer and allow harmful ultraviolet rays from the sun to reach the earth. c. reduce the nitrogen content of the air surrounding the earth. d. reduce the carbon dioxide necessary for plant life.
B
The ____ relationship correlates the vapor pressure and the boiling point of water and is the basis for controlling the cooling system's temperatures. a. boiling/pressure b. temperature/pressure c. temperature/vapor d. boiling/vapor
B
The cylinder color code for R-404A is a. orchid. b. orange. c. purple. d. green.
B
A near-azeotropic refrigerant blend replacing R-22 in residential and commercial air-conditioning applications is a. R-404A. b. R-407C. c. R-410A. d. R-134a.
C
Absorbs heat from the system a. Condenser b. Compressor c. Evaporator d. Metering Device
C
Enthalpy describes a. the moisture content in air. b. the amount of refrigerant needed in a system. c. the amount of heat a substance contains from some starting point. d. the amount of harmful ultraviolet rays in the atmosphere.
C
Good ventilation is important when working around refrigeration equipment because modern refrigerants ____. a. are toxic and can poison you b. have an unpleasant odor c. are heavier than air and may displace the oxygen around you d. Both a and c.
C
Lines of constant pressure on a pressure/enthalpy diagram are referred to as a. isotherms. b. isometrics. c. isobars. d. glide lines.
C
Refrigeration can be described as ____. a. the process of making products cold b. the process of introducing heat to a location where it is not wanted c. the process of removing heat from a place where it is not wanted to a place where it makes little or no difference d. None of the above.
C
The boiling point of a refrigerant should be low enough at atmospheric pressure so that low temperatures can be reached and the refrigeration system will a. not overheat. b. not explode. c. not go into a vacuum. d. notice up.
C
The compressor in a refrigeration system a. compresses the refrigerant. b. pumps the refrigerant throughout the system. c. Both A and B. d. None of the above.
C
The compressor in a refrigeration system ____. a. raises the boiling point of the refrigerant b. pumps the refrigerant throughout the system c. Both a and b. d. None of the above.
C
The cylinder color code for R-134a is a. red. b. yellow. c. light blue. d. green.
C
The evaporator in a refrigeration system a. meters the refrigerant. b. condenses the refrigerant. c. is the component where refrigerant boils and absorbs heat. d. compresses the vaporized refrigerant.
C
The evaporator in a refrigeration system ____. a. reduces the boiling point of the refrigerant b. condenses the refrigerant c. absorbs heat from the product to be cooled d. compresses the refrigerant vapor
C
The quantity of heat expressed in Btu/lb that the refrigerant absorbs from the refrigerated space to produce useful cooling is a. a calorie. b. enthalpy. c. the net refrigeration effect. d. a degree.
C
The temperature inside the refrigerator fresh food section should be about ____. a. 25ºF b. 30ºF c. 35ºF d. 40ºF
C
What happens when room temperature soda is poured into a glass of ice? a. The ice gets colder. b. The ice melts because it is giving up the "cold" to the soda. c. The ice melts because it is absorbing heat from the soda. d. The ice melts because the soda is colder than the ice.
C
When the portion of a pressure/enthalpy diagram is beneath the saturation curve, then a. the refrigerant is at a constant temperature. b. the refrigerant is at a constant pressure. c. the refrigerant follows a temperature/pressure relationship. d. the refrigerant is 100% vapor.
C
The _________________________ is referred to as a kinetic displacement compressor.
CENTRIFUGAL COMPRESSOR
A valve or small fixed-size tubing or orifice that meters liquid refrigerant into the evaporator. a. Condenser b. Compressor c. Evaporator d. Metering Device
D
Good ventilation is important when working around refrigeration equipment because modern refrigerants a. are toxic and can poison you. b. have a very unpleasant odor. c. may get on your skin and cause a rash. d. are heavier than air and may displace the oxygen around you.
D
Ice melts in ice boxes because a. heat flows through the insulated walls. b. heat flows through the doorway when it is opened. c. heat is moved into the box when warm food is placed in it. d. All of the above.
D
Ice melts in iceboxes because ____. a. heat flows through the insulated walls b. heat enters when the door is opened c. heat enters when warm food is placed in the icebox d. All of the above.
D
The ____ are used to change the vapor to a liquid and the liquid form back into a vapor, the refrigeration cycle. a. condenser and compressor b. compressor and expansion device c. expansion device and evaporator d. condenser and evaporator
D
The amount of heat, in Btu/lb, that is given off by the system in the discharge line and the condenser is referred to as the a. net refrigeration effect. b. heat of work. c. heat of compression. d. total heat of rejection.
D
The cylinder color code for R-22 is a. orchid. b. white. c. purple. d. green.
D
The cylinder color code for R-404A is a. bright green. b. rose. c. aqua. d. orange.
D
Which of the following refrigerants has the lowest boiling temperatures at atmospheric pressure? a. R-12. b. R-22. c. R-134a. d. R-502.
D
The amount of heat a refrigerant contains with -40 degree F as the 0 heat content reference point is called ______________________
ENTHALPY
(T/F) The only location where the refrigerant vapor is superheated is in the evaporator.
F
(T/F) Vapor is more dense than liquid and, as the liquid refrigerant boils, it has a tendency to sink.
F
(T/F) If a cylinder of R-22 is moved from a 100°F truck body into an 80°F shop, the quantity of liquid refrigerant in the cylinder will remain the same.
F While the amount of refrigerant remains the same, the amount of liquid refrigerant increases as the refrigerant vapor condenses due to temperature drop.
The four (4) major components of a vapor compression refrigeration system are the compressor, condenser, evaporator, and ___________________
METERING DEVICE
From a performance standpoint, a substitute for R-12 is ____________
R-410A
The _______________________ is another positive displacement compressor and is used for larger air conditioning and refrigeration applications
SCREW COMPRESSOR
(T/F) An expansion valve is the pressure reducing device that controls the flow of liquid refrigerant into the evaporator.
T
(T/F) Modern refrigerators have become state-of-the-art appliances and some models even include automatic beverage and ice dispensers, built in television screens and connections to the World Wide Web.
T
(T/F) Only liquid refrigerant should enter the metering device.
T
(T/F) The boiling point of a refrigerant should be low enough at atmospheric pressure to keep the system pressure above 0 psig when operating at low temperatures.
T
(T/F) The discharge gas from the compressor is a high pressure, high temperature, superheated vapor.
T
(T/F) The evaporator can be thought of as a "heat sponge."
T
(T/F) The evaporator in a refrigeration system must be colder than the refrigerated space in order to absorb heat.
T
(T/F) The halide leak detector should be used in well ventilated areas as the resulting blue or green flame indicates that phosgene gas is being produced.
T