RACT unit 23 Flashcards
Using two compressors can lower the ________ temperature and increases efficiency
discharge
______ refrigerant passes through the suction valve of the compressor to fill the cylinders
cool
Reciprocating compressors are used most frequently in _____ and _____ sized commercial refrigeration systems
small and medium
The screw compressor is used in ______ commercial and _______ systems
large commercial and industrial systems
The rotary, the scroll, along with the reciprocating compressors are used in ________ and light commercial air conditioning
residential
Centrifugal compressors are used extensively for ___________ in large buildings
air-conditioning
A hermetic reciprocating compressor has a __________ mechanism. The same shaft drives the compressor and motor
direct drive
Difference between hermetic and semi hermetic
hermetic is welded and semi-hermetic is serviceable
What is the only way to service a hermetic compressor?
cutting open the shell
hermetic compressors usually have a _____________ system but smaller hermetics are splash lubricated
pressure lubrication
semi hermetic compressors are ______ together so that it is easier to service and repair
bolted
smaller semi hermitic compressor use _______ lubrication
splash type
larger semi hermetic compressors use ________ lubrication
pressure
Motor and crankshaft are connected in a semi hermetic compressor although the ________ is usually horizontal
crankshaft
Open drive compressors are manufactured in two styles; ______ drive and ______ drive
belt driven and direct drive
Any compressor with the drive on the outside of the casting must have a ____ _____ to keep the refrigerant from escaping
shaft seal
rotary screw compressor has an open _____
motor
In a screw compressor, a ______ seal traps refrigerant in the compressor housing where the rotating shaft leaves the housing
shaft
Screw compressors are used in ______ systems
large
The ________ of a reciprocating compressor transmits the circular motion of the rods into a back-and-forth motion for the pistons
crankshaft
Crankshafts are normally manufactured or _____ iron or _____
cast iron or steel
The off-centre shafts normally have _____ main bearing surfaces. One is on the _____ end and the other on the other end
two
motor
some reciprocating compressor crankshafts are straight and have a cam-type arrangement called an ________
eccentric
All reciprocating compressor shafts must be ________
lubricated
Smaller reciprocating compressors using the splash system may have a ______ basin to catch oil and
catch
In a reciprocating compressor, when the compressor runs the oil is then slung to the outside of the __________ surface
crankshaft
(Recip) Connecting rods connect the ________ to the ______
crankshaft to the piston
(reciprocating) Two types of connecting rods; one fits the _______ with off centre throws and the other fits the ________ crankshaft
crankshaft
eccentric
(recip) rods with large holes in the shaft end are for ______ shafts
eccentric
The ______ is the part of the cylinder assembly exposed to the high pressure gas during compression
piston
Pistons have high pressure gas on _____ and suction or low pressure gas on the ______
top
bottom
Piston rings are used on the larger pistons and are of two types; _______ and ____
compression and oil
Smaller compressors use the oil on the cylinder walls as a _____
seal
The valves in the top of the compressor determine the _______ the gas entering the compressor will flow
direction
Reed valves and ring valves serve both the _____ and _______ ports of the compressor
suction and discharge ports
The _____ _____ holds the suction and discharge flapper valves
valve plate
Heads need to accomplish two things;
hold the pressure in and hold the valve plate on the cylinder
Mufflers are used in many fully _______ compressors to muffle compressor pulsation noise
hermetic
Compressor housing holds the compressor and sometimes the ______
motor
Internal ________ protection devices in hermetic motors protect the motor from overheating
overload
open drive compressors are manufactured with the motor external to the __________ shell
compressor
the shaft protrudes through the casing to the outside where either a _____ or _______ is attached
pulley or coupling
The pulley on the motor of a belt drive compressor is called the ______ pulley
drive
The pulley on the compressor of a belt-drive compressor is called the _______ pulley
driven
On a belt drive compressor, the drive pulley is sometimes adjustable, which allows the compressor ______ to be adjusted
speed
direct drive compressors at limited to the _____ speed that the drive motor is turning
motor
direct drive compressors can be ______ and serviced in place
rebuilt
The closer tolerance makes the compressor more efficient because it reduces the ______________
clearance volume
Scroll compressors conduct their ______, compression, and discharge phases simultaneously
intake
Scroll compressor is known as a ____________________ type because the scroll compressor compresses the discharge gas to a zero volume
fixed compression ratio
Scroll compressors have the ability to handle some ______
liquid
Scroll type compressors are gaining popularity due to the efficiency, _______, and quieter operations
reliability
The rotor shaft and impellers are the only moving parts in the _________ compressor
centrifugal
Soft starting reduces __________ currents at start up
high inrush
The centrifugal compressor is ___ free
oil
In a centrifugal compressor, the rotor shaft has ___________ levitated bearings for frictionless operation
magnetically
When small amounts of liquid enter the compressor it ______ the oil which means no lubrication and can cause the compressor to fail
dilute
A dirty evaporator will cause the suction pressure to _____
drop
Most manufacturers recommend that the compression ratio not be more than ___:1
10:1
Dirty condensers and dirty evaporators cause the ______________ to rise
compression ratio
Dirty condenser means high _____ pressure
head
dirty evaporator means ____ suction pressure
low
