Unit 23 Test and Quiz Review
hermetic
A _______________ compressor is usually considered to be a low-side device because the suction gas is vented to the inside of the shell, including the crankcase. screw hermetic open-drive belt-drive
D. crankshaft
A _________________ in a reciprocating compressor transmits the circular motion of the rods into a back-and-forth motion for the pistons A. muffler B. reed valves C. valve plate D. crankshaft
A. scroll
A compressor that has few moving parts, operates quieter than other models and at a higher efficiency is a __________________________ compressor A. scroll B. rotary C. screw D. reciprocating
1750 or 3450
A direct-drive compressor typically runs at _________________ rpm. 1750 or 3450 3450 or 4500 17,500 or 34,500 1800 or 4800
5.44 to 1
A medium-temperature R-134a system that has a suction pressure of 22 psig and a discharge pressure of 185 psig would have a compression ratio of _________________. 8.40 to 1 5.44 to 1 10.1 to 1 13.89 to 1
reciprocating
A piston, connecting rod, crankshaft, valves, valve plate, head, shaft seal, internal motor overload device, pilot-duty motor overload device, and coupling are parts that may be found in a _________________ compressor. scroll reciprocating variable capacity screw
False
Connecting rods connect the crankshaft to the valve plate. True or False
reciprocating, rotary, scroll, screw, and centrifugal
Five types of compressors are ______________. rotating, analog, scroll, screw, and binary reciprocating, rotary, scroll, screw, and centrifugal bolted, screw, scroll, binary, and centrifugal belt-drive, direct-drive, rotating, binary, and scroll
True
In a scroll compressor, there are no volumetric losses through gas re-expansion as with piston-type compressors True or False
D. belt drive and direct drive
Open-drive compressors are manufactured in two styles, _______________________ A. direct drive and rigid drive B. pneumatic and electronic C. belt drive and automatic drive D. belt drive and direct drive
True
Scroll compressors can use radial movement, which allow the compressor to handle small amounts of liquid. True or False
C. valve plate
The __________________, located between the head of the compressor and the top of the cylinder wall, holds the suction and discharge flapper valves. A. crankshaft B. muffler C. valve plate D. piston
B. piston
The part of the cylinder assembly that is exposed to high-pressure gas during compression is the ______________________ A. connecting rods B. piston C. valve plate D. crankshaft
B. hermetic and open
The two housings used for reciprocating compressors are _________________. A. rotary and open B. hermetic and open C. centrifugal and screw D. rotary and semi-hermetic
Clean the evaporator and condenser coils to keep pressures within design parameters.
What can the service technician do to keep the refrigeration system operating at peak efficiency? Recover the refrigerant charge and replace it annually. Replace the compressor oil every 3 years or 3000 hours of operation. Replace the compressor crankshaft and connecting rods regularly. Clean the evaporator and condenser coils to keep pressures within design parameters.
It dilutes the oil and causes wear on any moving parts.
What effect does a slight amount of liquid refrigerant have on a compressor over a long period of time? It causes excessive compressor cooling which may freeze the crankshaft. It adds to the compressor lubrication. It dilutes the oil and causes wear on any moving parts. It causes a rise in pressure which may open the internal pressure relief valve.
Oil
What lubricates the refrigeration compressor? Refrigerant Moisture Desiccants Oil
250F°
What would be considered a higher-than-normal temperature for a discharge gas line on a reciprocating compressor? 190F° 200F° 250F° 175F°
Increase drive pulley size
What would be done to increase the compressor speed on a belt-driven compressor? Decrease drive pulley size Increase drive pulley size Increase driven pulley size Both A and C
Reciprocating
Which compressor type uses pistons to compress the gas? Scroll Reciprocating Rotary Screw
Screw
Which compressor type uses tapered, machined gear components to trap the gas for compression? Scroll Reciprocating Rotary Screw
The compressor increases the pressure in the system from the low-side pressure to the high-side pressure.
Which of the following best describes the function of a compressor? The compressor restricts the flow of refrigerant that enters the evaporator. The compressor pumps liquid refrigerant into the condenser to transfer heat. The compressor is used to throttle a thermostatic expansion valve (TXV) open or closed. The compressor increases the pressure in the system from the low-side pressure to the high-side pressure.
The valve plate design and clearance volume.
Which of the following design factors can affect the efficiency of a reciprocating compressor? The two tapered, machined, screw-type gears. The connecting rod and the muffler. The piston and the internal springs. The valve plate design and clearance volume.
A compressor cannot compress a liquid.
Which of the following is true of HVACR compressors? A compressor cannot compress a liquid. A compressor can compress a liquid. A compressor requires liquid refrigerant for lubrication. A compressor takes in vapor and discharges liquid.
Open drive
Which style of compressor uses belts to turn the compressor? Open drive Closed drive Chassis drive Hermetic drive
B. Discus
___________________ compressors are refrigeration compressors that are available with capacity modulation from 10% to 100% A. Rotary B. Discus C. Reciprocating D. Open-drive
