Chapter - 116,117 Flashcards
What are the three classes of compressors?
Reciprocating
Rotary
Centrifugal
EXAM QUESTION
The operating cycle of a reciprocating compressor has two strokes, what are they?
Suction and discharge
What are the three types of reciprocating compressors?
Hermetic
Open
Semi-hermetic
What is the difference between a hermetic compressor and a semi-hermetic compressor?
Hermetic is un-serviceable and semi-hermetic can be serviced in the field
Reciprocating compressors are also identified by?
The number of cylinders
What are the two types of crankshafts?
Eccentric and conventional
What are the two types of compressor valves?
Flexible reed and disc and non-flexible valves
What is the role of a safety head?
It lifts when excessive pressure occurs in the cylinder
What are the types of compressor bearings?
Sleeve and shell
How are the bearings lubricated?
By the splash system or the pressure system
What are the three designs of Rotary compressors?
Single blade
Rotating sliding vane
Helical rotor
The screw compressor is a…?
Positive displacement unit
What is the advantage of a centrifugal compressor?
It’s simplicity of operation
What are the four types of compressor seals?
Packing gland seal
Bellows seal
Diaphragm seal
Rotating mechanical seal
What is piston displacement?
It is the volume of refrigerant that can be circulated through all the cylinders in a reciprocating compressor
What is pressure ratio?
It’s the clearance volume plus the piston displacement divided by the clearance volume
Which compressor type requires the use of a shaft seal?
Open type
What are the two main heat exchangers use in a refrigeration system?
Evaporator and condenser
What are the two classes of evaporators?
Dry and flooded
What is the difference between a dry evaporator and a flooded evaporator?
A dry evaporator contains only a small amount of liquid refrigerant at any time whereas the flooded evaporator is almost always completely filled with liquid
What are the four types of evaporators?
Bare tube
Plate surface
Finned tube
Shell and tube
What is a shell and tube evaporator also known as?
A Chiller
What are the three types of condensers?
Air cooled
Water cooled
Evaporative
Explain how an air cooled condenser works
It uses air to remove heat from the refrigerant vapour, vapour flows through tubes while the cooling air is circulated by fans around the outside of the tubes
