Unit 21 Test and Quiz Review
C
A finned-tube evaporator equipped with fans is called a (n) _________________ evaporator A. bare-tube B. stamped C. induced-or forced-draft D. liquid cooling
C
A low evaporator superheat may indicate a (n) ______________. A. undercharge B. system restriction C. overcharge D. high heat load
B
A medium-temperature evaporator uses a (n) ____________ defrost method. A. hot gas B. random or off-cycle C. electric resistance heat D. liquid-injection
A
A medium-temperature refrigeration box typically operates within what temperature range? A. 28 degrees F to 40 degrees F B. 40 degrees F to 60 degrees F C. 0 degrees F to 220 degrees F D. 0 degrees F to 50 degrees F
C
A refrigeration system's evaporator typically runs at about _________________ of superheat A. 15 degrees F to 20 degrees F B. 12 degrees F to 15 degrees F C. 8 degrees F to 12 degrees F D. 3 degrees F to 8 degrees F
A
An evaporator that does not operate flooded is thought of as what type of evaporator? A. A dry-type evaporator B. A starved evaporator C. A float-type evaporator D. A low-pressure evaporator
B
Flooded evaporators typically use a (n) _____________ type of expansion device A. automatic B. float C. TXV D. fixed-bore
A
Flooding the compressor crankcase with liquid refrigerant can cause _______________________ A. oil foaming B. moisture to accumulate in the compressor oil C. excessive superheat D. starved evaporator
A
Low temperature food storage applications typically have a temperature range of ____________________ A. 0 to -20 degrees F B. 0 to -32 degrees F C. 0 to 32 degrees F D. -20 to -32 degrees F
C
Low-temperature evaporator coils ______________________ A. require more oil circulation that medium temperature coils B. operate the same as medium temperature evaporator coils C. have fewer fins per inch than medium temperature evaporator coils D. have more fins per inch than medium temperature evaporator coils
A
Low-temperature refrigeration systems typically operate at what temperature range? A. -20 degrees F to 0 degrees F B. -50 degrees F to -20 degrees F C. 0 degrees F to 35 degrees F D. 28 degrees F to 40 degrees F
False
Natural-convection evaporators use a blower to force or induce air over the coil to improve the efficiency of the heat exchange True or False
B
Refrigerant in the evaporator ___________________________ A. changes from vapor to liquid B. changes from liquid to vapor C. stays in the vapor state D. stays in the liquid state
B
The best heat exchange occurs between _________________ A. a vapor and a liquid B. two liquids C. two solids D. a liquid and a solid
D
The difference in temperature between the boiling refrigerant temperature and the evaporator outlet temperature is known as ____________________ A. delta T B. suction line superheat C. temperature difference D. evaporator superheat
C
The difference in the amount of heat (in Btu/lb) that the refrigerant contains at the point where it enters the evaporator and the point at which it leaves the evaporator is known as _______________________ A. mass flow rate B. total heat of rejection C. the net refrigeration effect D. the heat of compression
D
The greater the difference in temperature between the evaporator and the air being cooled, ______________ A. the less moisture will be removed from the air B. the less moisture will be added to the air C. the more moisture will be added to the air D. the more moisture will be removed from the air
A
The sensible heat that is added to a saturated vapor after all of the liquid has boiled away is referred to as ______________________ A. superheat B. latent heat C. subcooling D. specific heat
A
Two common methods for defrosting a low temperature evaporator are _________________ A. hot gas and electric heat B. reserve cycle and hot gas C. off-cycle and hot gas D. off-cycle and electric heat
C
What determines the pressure on the low-pressure side of the system? A. The condensing temperature of the refrigerant in the condenser B. The length of the liquid line feeding the TXV C. The boiling temperature of the refrigerant in the evaporator D. The relative humidity percentage in the conditioned space
D
What does a high evaporator superheat indicate? A. A flooded evaporator B. Proper system operation C. Low evaporator heat load D. A starved evaporator
B
What is commonly used to defrost the ice from a low temperature evaporator? A. Random or off-cycle defrost B. Hot gas or electric resistance heat defrost C. Off-cycle or manual defrost D. Low-temperature evaporators do not require a defrost
D
What is the function of the evaporator in the refrigeration system? A. To add heat to the space or product being cooled B. To add humidity to the space being refrigerated C. It condenses superheated refrigerant vapor to a liquid D. It absorbs heat into the refrigeration system
B
When a refrigerant space has been allowed to warm up considerably, the system must _______________. A. turned off and the product being cooled moved to another cooler B. go through a hot pulldown C. be overcharged to remove the excess heat D. be defrosted at regular intervals
D
When an evaporator experiences a heat-load increase, the suction pressure __________________ A. remains constant B. decreases C. varies up and down D. increases
A
When liquid refrigerant floods the compressor crankcase, the oil level in the crankcase can drop causing ____________________ A. bearing washout B. condenser flooding C. valve damage D. excessive superheat
True
When moisture is removed from the air, latent heat is removed True or False
D
When the evaporator removes heat from the air and lowers the temperature of the air, _____________________ A. refrigerant vapor condenses to liquid B. latent heat is added to the air C. moisture is added to the air D. sensible heat is removed from the air
D
Which of the following is not a function of an evaporator efficiency control? A. Monitors evaporator efficiency and performance B. Initiates a defrost when coil efficiency drops below 90% C. Contains an Ethernet network device that supports industry standard protocols D. Regulates condensate removal by activating a condensate pump
A
Why is a multicircuit evaporator used? A. To reduce pressure drop through larger evaporators B. To ensure proper compressor operation C. To prevent ice buildup on the fins D. They are easily defrosted in low-temperature applications
