CRST Refrigeration Systems & Components 2 — Questions and Answers
Question 1: What is the primary function of a receiver in a refrigeration system?
- Store liquid refrigerant after the condenser (Correct answer)
- Separate oil from refrigerant vapor
- Superheat refrigerant before the compressor
- Subcool refrigerant before the evaporator
Correct answer: Store liquid refrigerant after the condenser
A receiver stores liquid refrigerant downstream of the condenser to ensure a steady supply to the metering device.
Question 2: Which type of compressor uses a rotating eccentric to compress refrigerant without inlet/outlet valves?
- Reciprocating compressor
- Scroll compressor (Correct answer)
- Screw compressor
- Centrifugal compressor
Correct answer: Scroll compressor
Scroll compressors use two interleaved spiral scrolls to compress refrigerant continuously without the need for suction or discharge valves.
Question 3: What happens to refrigerant subcooling when liquid line length increases significantly?
- Subcooling increases
- Subcooling decreases due to heat gain (Correct answer)
- Subcooling is unaffected by line length
- Subcooling doubles with each 10 ft of line
Correct answer: Subcooling decreases due to heat gain
Longer liquid lines expose refrigerant to more ambient heat, reducing subcooling and risking flash gas formation before the metering device.
Question 4: A refrigeration system uses a flooded evaporator. What distinguishes it from a dry-expansion evaporator?
- Refrigerant exits as superheated vapor
- Refrigerant fills the entire evaporator with liquid (Correct answer)
- The metering device is located at the outlet
- Oil return is not required
Correct answer: Refrigerant fills the entire evaporator with liquid
In a flooded evaporator, the entire heat exchanger is filled with liquid refrigerant, maximizing heat transfer surface contact.
Question 5: What is the purpose of a suction accumulator in a refrigeration system?
- Increase suction pressure
- Prevent liquid refrigerant from entering the compressor (Correct answer)
- Store refrigerant on the low side
- Filter debris from the suction line
Correct answer: Prevent liquid refrigerant from entering the compressor
A suction accumulator catches liquid slugs before the compressor, protecting it from hydraulic damage.
Question 6: In a two-stage refrigeration system, what is the purpose of the intercooler?
- Cool suction gas before the first stage
- Cool discharge gas between compression stages (Correct answer)
- Superheat refrigerant before the evaporator
- Separate refrigerant from oil between stages
Correct answer: Cool discharge gas between compression stages
The intercooler removes heat from the refrigerant between the first and second compression stages, improving efficiency and reducing discharge temperature.
Question 7: Which refrigerant circuit component is most responsible for controlling system capacity in a variable-speed system?
- Thermostatic expansion valve
- Variable-frequency drive on the compressor motor (Correct answer)
- Suction line filter-drier
- Head pressure control valve
Correct answer: Variable-frequency drive on the compressor motor
A variable-frequency drive (VFD) modulates compressor speed, directly controlling refrigerant mass flow and system capacity.
CRST Refrigeration Systems & Components 2
What is the primary function of a receiver in a refrigeration system?