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Questions and Answers
A common application for centrifugal compressors is?
A common application for centrifugal compressors is?
- Commercial water chilling systems (correct)
- Residential air conditioning
- Refrigerators
- Heat pumps
What is a compressor that compresses gas between a fixed spiral and an orbiting spiral?
What is a compressor that compresses gas between a fixed spiral and an orbiting spiral?
Scroll compressor
What is a compressor that uses a large off-center rotating shaft and multiple blades that follow the cylinder walls as the shaft rotates?
What is a compressor that uses a large off-center rotating shaft and multiple blades that follow the cylinder walls as the shaft rotates?
Rotary blade rotary compressor
What compressor uses an impeller to throw refrigerant from the center outward?
What compressor uses an impeller to throw refrigerant from the center outward?
What compressor uses an offset rolling piston that seals against a blade that remains stationary?
What compressor uses an offset rolling piston that seals against a blade that remains stationary?
What do all refrigeration compressors pump?
What do all refrigeration compressors pump?
What is an advantage of open drive compressors?
What is an advantage of open drive compressors?
What lubrication method do reciprocating compressors use with an oil slinger?
What lubrication method do reciprocating compressors use with an oil slinger?
Which application requires more horsepower to produce a ton of cooling: a 0°F evaporator or a 40°F evaporator?
Which application requires more horsepower to produce a ton of cooling: a 0°F evaporator or a 40°F evaporator?
How does compressor cylinder unloading reduce the capacity of a reciprocating compressor?
How does compressor cylinder unloading reduce the capacity of a reciprocating compressor?
How can hermetic compressors be characterized?
How can hermetic compressors be characterized?
How can semihermetic compressors be characterized?
How can semihermetic compressors be characterized?
How does a reciprocating compressor operate?
How does a reciprocating compressor operate?
How does a two-step scroll compressor achieve capacity reduction?
How does a two-step scroll compressor achieve capacity reduction?
In which system does less refrigerant enter the cylinder for each compression cycle, requiring more horsepower for each BTU of cooling?
In which system does less refrigerant enter the cylinder for each compression cycle, requiring more horsepower for each BTU of cooling?
What is one technique for improving efficiency and comfort through compressor selection?
What is one technique for improving efficiency and comfort through compressor selection?
What type of compressors meet refrigeration needs on trucks, tractor trailers, and shipping containers?
What type of compressors meet refrigeration needs on trucks, tractor trailers, and shipping containers?
Where are rotary compressors commonly used?
Where are rotary compressors commonly used?
What is the advantage of compliance in a scroll compressor?
What is the advantage of compliance in a scroll compressor?
What is the function of the compressor in the refrigeration cycle?
What is the function of the compressor in the refrigeration cycle?
What are the major types of compressors listed by mechanical design?
What are the major types of compressors listed by mechanical design?
What is the match of the motor and compressor inside a hermetic compressor?
What is the match of the motor and compressor inside a hermetic compressor?
Why is the shaft seal on an open compressor more complicated than the gaskets and seals on other parts?
Why is the shaft seal on an open compressor more complicated than the gaskets and seals on other parts?
What seals the small gaps between the screws on a screw compressor?
What seals the small gaps between the screws on a screw compressor?
What is the space left between the piston and the valve plate of a reciprocating compressor when the piston is at the top of the cylinder called?
What is the space left between the piston and the valve plate of a reciprocating compressor when the piston is at the top of the cylinder called?
What are the three different design screw compressors?
What are the three different design screw compressors?
What is the lowest percentage of full capacity that a digital scroll can be safely operated for extended periods?
What is the lowest percentage of full capacity that a digital scroll can be safely operated for extended periods?
What opens and closes the valves in a reciprocating compressor?
What opens and closes the valves in a reciprocating compressor?
What type of compressors contain the compressor and motor together inside a welded steel housing?
What type of compressors contain the compressor and motor together inside a welded steel housing?
Which compressor has a piston that is driven up and down in the cylinder by a connecting rod and crankshaft?
Which compressor has a piston that is driven up and down in the cylinder by a connecting rod and crankshaft?
Which compressor type draws refrigerant gas in through the inlet port into voids created by turning rotors?
Which compressor type draws refrigerant gas in through the inlet port into voids created by turning rotors?
Which of the following compressors is NOT considered a positive-displacement compressor?
Which of the following compressors is NOT considered a positive-displacement compressor?
Which of the following has the capacity range for a centrifugal compressor?
Which of the following has the capacity range for a centrifugal compressor?
It is TRUE of a medium-temperature refrigeration unit that it requires 1 hp to produce 2/3 ton of cooling.
It is TRUE of a medium-temperature refrigeration unit that it requires 1 hp to produce 2/3 ton of cooling.
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Study Notes
Centrifugal Compressors
- Commonly used in commercial water chilling systems.
- Operate by throwing refrigerant outward using an impeller.
Scroll Compressors
- Function by compressing gas between a fixed spiral and an orbiting spiral.
- Capacity is adjustable through an internal rotating plate that manages drilled ports.
- Advantage includes the ability to handle small liquid slugs due to compliance in design.
Rotary Compressors
- Utilize a large off-center rotating shaft with blades that follow the cylinder walls.
- Commonly found in window units and can be classified as rotary blade rotary compressors or stationary blade rotary compressors.
Reciprocating Compressors
- Operate through a piston driven up and down by a connecting rod and crankshaft.
- Capacity can be decreased by making the valves in the head inoperative (cylinder unloading).
- The clearance volume is the space between the piston and the valve plate when the piston is at the top.
Hermetic and Semihermetic Compressors
- Hermetic compressors have a welded shell containing both the compressor and motor.
- Semihermetic compressors are enclosed in a bolted housing.
- Both types feature specific motor-compressor matching for optimal application.
Compression Efficiency
- Compressors designed to pump only vapor reduce risk of liquid damage.
- Low-evaporator-temperature systems may require more horsepower for cooling due to less refrigerant entering the cylinder.
- Digital scroll compressors can operate safely at a minimum capacity of 10% for proper lubrication.
Various Compressor Types
- Classifications include reciprocating, rotary, scroll, screw, and centrifugal.
- Screw compressors draw refrigerant through turning rotors and rely on oil flooding to seal small gaps.
- Centrifugal compressors are not classified as positive-displacement compressors.
Other Key Points
- Open-drive compressors allow for separate replacement of the motor and compressor.
- Oil slingers provide splash lubrication in reciprocating compressors.
- A medium-temperature refrigeration unit typically requires 1 hp to produce 2/3 ton of cooling.
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