NATE Refrigeration

Question 1

What is the refrigeration effect and how is it calculated?

Accepted Answer

Heat absorbed in the evaporator; calculated as evaporator outlet enthalpy minus evaporator inlet enthalpy

Answer

Heat rejected at the condenser; calculated as condenser enthalpy minus compressor inlet enthalpy

Answer

Work input to the compressor

Answer

Heat gained by subcooling the liquid line

Question 2

What refrigerant is commonly used in medium-temperature commercial refrigeration cases in the US?

Accepted Answer

R-404A / R-448A

Answer

R-410A

Answer

R-134a only

Answer

R-22

Question 3

What does a suction line accumulator protect in a refrigeration system?

Accepted Answer

Compressor from liquid refrigerant slugging

Answer

Liquid line from high pressure

Answer

Condenser from excess load

Answer

Expansion device from debris

Question 4

At what temperature range does a medium-temperature refrigeration system typically maintain a reach-in display case?

Accepted Answer

28°F to 40°F

Answer

-10°F to 0°F

Answer

0°F to 10°F

Answer

45°F to 55°F

Question 5

What is the purpose of a filter-drier in a refrigeration system?

Accepted Answer

Remove moisture and contaminants from the refrigerant circuit

Answer

Reduce system sound levels

Answer

Increase subcooling of liquid refrigerant

Answer

Regulate refrigerant mass flow

Question 6

What does a high discharge temperature on a refrigeration compressor typically indicate?

Accepted Answer

High compression ratio due to high head pressure, low suction pressure, or high superheat

Answer

Low compression ratio

Answer

Properly operating system

Answer

Overcharged refrigerant