Commercial Refrigeration FINAL TEST questions and answers A+
Grade 2026\2027
How is the cooling effect in a mechanical refrigeration system produced?
- correct answer Evaporation of liquid refrigerant into vapor
What is the primary purpose of a compressor?
- correct answer It circulates and pressurizes the refrigerant vapor before the vapor Is condensed for re
use
Name another function that must be performed by the compressor
- correct answer Is raise the pressure and temperature of the refrigerant vapor. This allows the
refrigerant to condense into a liquid as it circulates through the condenser
What characteristic defines an "open" type compressor?
- correct answer Has a drive shaft protruding from the compressor
What are the two main disadvantages of a hermetic compressor?
- correct answer If either the motor or compressor malfunctions, the entire unit must be replaced. The
motor is actually a part of the refrigerant circulation system. This means that a burnout can contaminate
the entire system
In a reciprocating compressor, the piston is connected to the crankshaft by a _____
- correct answer Connecting rod
Name the three elements of performance that are the major factors in evaluating a compressor
- correct answer Efficiency, capacity, and economy of operation
If the suction gas superheat is too low, What could be the result?
- correct answer Liquid refrigerant might enter the compressor. This causes stress on the compressor
valves, wrist pins, rods, shaft, etc. It also causes excessive foaming of the oil in the crankcase and other
damaging effects. The compressor will not reach its rated capacity
, What will happen if the suction gas temperature is too high?
- correct answer Will cause the compressor to run hot
How is compressor efficiency often judged?
- correct answer Btu per cubic foot (Btu/ft^3) of displacement
When the same model of open type compressor is used with both air cooled and water cooled
condensing units, which is usually run at a slightly higher rpm?
- correct answer Water cooled
What is the equation for ratio of compression?
- correct answer The absolute discharge pressure (psig plus 14.7) divided by the absolute suction
pressure (psig plus 14.7)
What type of compressor is found in large applications up to 10000 tons?
- correct answer Centrifugal compressors
Which compressor utilizes two helical rotors to compress the refrigerant gas?
- correct answer Screw compressor
What is the most outstanding advantage of the hermetically sealed compressor over the open type?
- correct answer Has no protruding crankshaft or shaft seal
How are the disadvantages overcome in compressors that are employed in low temperature
applications?
- correct answer Use supplementary cooling
How are the disadvantages overcome in water cooled hermetic compressor systems?
- correct answer Have water jackets, or water coils around the compressor/motor shell or housing
Is the condenser load greater or less for compressors designed for low temperature applications than
for compressors designed for high temperature applications?
- correct answer The condenser load is less for the low temperature applications
Grade 2026\2027
How is the cooling effect in a mechanical refrigeration system produced?
- correct answer Evaporation of liquid refrigerant into vapor
What is the primary purpose of a compressor?
- correct answer It circulates and pressurizes the refrigerant vapor before the vapor Is condensed for re
use
Name another function that must be performed by the compressor
- correct answer Is raise the pressure and temperature of the refrigerant vapor. This allows the
refrigerant to condense into a liquid as it circulates through the condenser
What characteristic defines an "open" type compressor?
- correct answer Has a drive shaft protruding from the compressor
What are the two main disadvantages of a hermetic compressor?
- correct answer If either the motor or compressor malfunctions, the entire unit must be replaced. The
motor is actually a part of the refrigerant circulation system. This means that a burnout can contaminate
the entire system
In a reciprocating compressor, the piston is connected to the crankshaft by a _____
- correct answer Connecting rod
Name the three elements of performance that are the major factors in evaluating a compressor
- correct answer Efficiency, capacity, and economy of operation
If the suction gas superheat is too low, What could be the result?
- correct answer Liquid refrigerant might enter the compressor. This causes stress on the compressor
valves, wrist pins, rods, shaft, etc. It also causes excessive foaming of the oil in the crankcase and other
damaging effects. The compressor will not reach its rated capacity
, What will happen if the suction gas temperature is too high?
- correct answer Will cause the compressor to run hot
How is compressor efficiency often judged?
- correct answer Btu per cubic foot (Btu/ft^3) of displacement
When the same model of open type compressor is used with both air cooled and water cooled
condensing units, which is usually run at a slightly higher rpm?
- correct answer Water cooled
What is the equation for ratio of compression?
- correct answer The absolute discharge pressure (psig plus 14.7) divided by the absolute suction
pressure (psig plus 14.7)
What type of compressor is found in large applications up to 10000 tons?
- correct answer Centrifugal compressors
Which compressor utilizes two helical rotors to compress the refrigerant gas?
- correct answer Screw compressor
What is the most outstanding advantage of the hermetically sealed compressor over the open type?
- correct answer Has no protruding crankshaft or shaft seal
How are the disadvantages overcome in compressors that are employed in low temperature
applications?
- correct answer Use supplementary cooling
How are the disadvantages overcome in water cooled hermetic compressor systems?
- correct answer Have water jackets, or water coils around the compressor/motor shell or housing
Is the condenser load greater or less for compressors designed for low temperature applications than
for compressors designed for high temperature applications?
- correct answer The condenser load is less for the low temperature applications
