Refrigeration Theory 2 - Unit 23 Compressors Exam Questions with Certified Answers
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Refrigeration Theory 2 - Unit 23 Compressors
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Refrigeration Theory 2 - Unit 23 Compressors
Refrigeration Theory 2 - Unit 23 Compressors Exam Questions with Certified Answers
What 4 processes take place during the reciprocating compression process? - Answer-1. Expansion (re-expansion)
2. Suction (intake)
3. Compression
4. Discharge
When installing a reciprocating compressor, which...
Refrigeration Theory 2 - Unit 23
Compressors Exam Questions
with Certified Answers
What 4 processes take place during the reciprocating compression process? - Answer-
1. Expansion (re-expansion)
2. Suction (intake)
3. Compression
4. Discharge
When installing a reciprocating compressor, which direction should the motor rotate? -
Answer-Doesn't matter
When servicing a reciprocating compressor, which direction should it rotate when put
back? - Answer-The same direction it was already rotating for best oil distribution
How does a Copeland reciprocating compressor unload? - Answer-A coil de-energizes
based on pressure and blocks suction valve to stop flow
How can reciprocating compressors control capacity? - Answer--Unloaders (stops
various cylinders from pumping)
How does a scroll compressor operate? - Answer-Vapor enters a pocket between two
spiral pieces. One spiral orbits to reduce pocket volume, increasing vapor pressure
What causes one spiral to oscillate/orbit in a scroll compressor? - Answer-The offset
operation of the centres of the journal bearing & motor
What are the advantages of a scroll compressor compared to reciprocating? - Answer--
No re-expansion volumetric losses
-Less moving parts
-Quieter
-Less vibration
-Continuous compression
-Leak-free contact
How can a scroll compressor control capacity? - Answer--Two-step modulation
(blocking bypass ports)
-Digital control separating orbiting scroll from fixed scroll
-Variable Frequency Drive (VFD)
, When installing a scroll compressor, which direction should it rotate? - Answer-Same
direction as condenser fan
How does a rotary compressor operate? - Answer-A rotor orbits in a cylinder, traps
suction air and reduces pocket volume before discharge
In which applications are rotary compressors typically used? - Answer-Residential and
light commercial applications
How do screw compressors operate? - Answer-Two tapered, screw-like gears transfer
& compress vapor into a smaller space
Which of the 3 classifications might a screw compressor be described as? - Answer-
Semi-hermetic or open-drive
In which applications are screw compressors typically used? - Answer-Large
commercial and industrial applications
How does a screw compressor control capacity? - Answer--Sliding valve
How do centrifugal compressors operate? - Answer-A spinning impeller sends vapor
outwards to diffuser to convert it's velocity into pressure
In which applications are centrifugal compressors used? - Answer-Air conditioning in
large structures
What causes a compressor's suction & discharge valves to open/close? - Answer-
Pressure differential
How do centrifugal compressors control capacity? - Answer--Inlet guide vanes
What's the formula for compression ratio? - Answer-CR = Discharge PSIA / Suction
PSIA
What is volumetric efficiency? - Answer-The amount of gas a compressor is pumping
vs. the max capacity it's designed to pump
If compression ratio increases, what does Volumetric Efficiency do? - Answer-Decrease
How is the direction of a 3-phase motor changed? - Answer-Reversing any 2 of the 3
legs of power (L1, L2, L3)
How are most motors cooled? - Answer-Air-cooled
How does refrigerant density change with pressure conditions? - Answer-Refrigerant
density increases in high pressure conditions
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