Podcast
Questions and Answers
Which of the following best describes the action of a dual-capacity reciprocating compressor? (Select all that apply)
Which of the following best describes the action of a dual-capacity reciprocating compressor? (Select all that apply)
- One piston is attached to a quick-release connecting rod. When the crankshaft reverses direction, the connecting rod disconnects from the crankshaft, disabling the piston.
- One piston is on a movable eccentric. When the crankshaft reverses direction, the eccentric centers on the crankshaft, disabling the piston. (correct)
- One piston has a release valve built into the piston head. When the crankshaft reverses direction, the valve opens to prevent compression.
The vanes on a rotating vane compressor may be brought into contact with the cylinder walls by ___?
The vanes on a rotating vane compressor may be brought into contact with the cylinder walls by ___?
- Centrifugal force
- Spring pressure (correct)
- Hydraulic pressure
- All of the above
If a belt-driven compressor with a 6" pulley is being turned by a motor operating at 3600 RPM and equipped with a 3" pulley, the compressor's shaft will be turning at ____.
If a belt-driven compressor with a 6" pulley is being turned by a motor operating at 3600 RPM and equipped with a 3" pulley, the compressor's shaft will be turning at ____.
- 1800 RPM (correct)
- 3600 RPM
- 1200 RPM
- 7200 RPM
Which of the following best explains why the electrical connections and starting relays on hermetic compressors are typically installed outside the compressor housing?
Which of the following best explains why the electrical connections and starting relays on hermetic compressors are typically installed outside the compressor housing?
Reciprocating compressors can be classified by ____.
Reciprocating compressors can be classified by ____.
In reciprocating compressors, the intake and exhaust valves are located on the ___.
In reciprocating compressors, the intake and exhaust valves are located on the ___.
Which of the following types of valves have a valve stem that moves up and down in a valve guide?
Which of the following types of valves have a valve stem that moves up and down in a valve guide?
One end of a connecting rod is attached to the piston and the other end is attached to the __.
One end of a connecting rod is attached to the piston and the other end is attached to the __.
Which of the following explains why exhaust valves present more problems than intake valves?
Which of the following explains why exhaust valves present more problems than intake valves?
A unique feature of screw compressors is the ability to control capacity through __ unloading.
A unique feature of screw compressors is the ability to control capacity through __ unloading.
Which type of screw compressor is typically used in ammonia or other high-pressure systems?
Which type of screw compressor is typically used in ammonia or other high-pressure systems?
Which of the following statements regarding mufflers is false?
Which of the following statements regarding mufflers is false?
Oil pumps are typically located __.
Oil pumps are typically located __.
Systems that have a capillary tube metering device do not require an unloader because ____.
Systems that have a capillary tube metering device do not require an unloader because ____.
The volume between the top of the piston when it is at top dead center and the cylinder plate is known as __________ space.
The volume between the top of the piston when it is at top dead center and the cylinder plate is known as __________ space.
A full-floating piston pin is free to turn in both the connecting rod bushing and the ________ bushings.
A full-floating piston pin is free to turn in both the connecting rod bushing and the ________ bushings.
In a(n) __________ lubrication system, the crank throw dips into the oil at each crankshaft revolution.
In a(n) __________ lubrication system, the crank throw dips into the oil at each crankshaft revolution.
A(n) _________ lubrication system uses a pump to distribute the oil.
A(n) _________ lubrication system uses a pump to distribute the oil.
On open-drive and semi-hermetic compressors, the mating surfaces between bolted parts are usually sealed with _________.
On open-drive and semi-hermetic compressors, the mating surfaces between bolted parts are usually sealed with _________.
A crankshaft and connecting rods convert the rotary motion of the motor shaft to _____ motion of the pistons.
A crankshaft and connecting rods convert the rotary motion of the motor shaft to _____ motion of the pistons.
The _______ type of reciprocating compressor has a long piston with an elliptical slot in the bottom of the piston skirt.
The _______ type of reciprocating compressor has a long piston with an elliptical slot in the bottom of the piston skirt.
The purpose of the _______ is to support the valve plate and to seal the cylinder so compression can occur.
The purpose of the _______ is to support the valve plate and to seal the cylinder so compression can occur.
In a scroll compressor, gas pockets are formed between the fixed scroll and the _____ scroll.
In a scroll compressor, gas pockets are formed between the fixed scroll and the _____ scroll.
Adjustable ______ in a centrifugal compressor's inlet regulate the amount of refrigerant vapor flowing into the impeller.
Adjustable ______ in a centrifugal compressor's inlet regulate the amount of refrigerant vapor flowing into the impeller.
A(n) overload _________ must be built into an oil pump to protect the system against excessively high oil pressure.
A(n) overload _________ must be built into an oil pump to protect the system against excessively high oil pressure.
A(n)______ is used to temporarily reduce cylinder pressure during compressor start-up.
A(n)______ is used to temporarily reduce cylinder pressure during compressor start-up.
List two advantages of a multi-cylinder reciprocating compressor over a single-cylinder compressor of same capacity.
List two advantages of a multi-cylinder reciprocating compressor over a single-cylinder compressor of same capacity.
List the five basic types of compressors.
List the five basic types of compressors.
Why are check valves used in the suction line on some rotary compressors?
Why are check valves used in the suction line on some rotary compressors?
What is the purpose of a shaft seal?
What is the purpose of a shaft seal?
Why must the clearance space be kept as small as possible?
Why must the clearance space be kept as small as possible?
What is the purpose of the stationary blade in a stationary blade rotary compressor?
What is the purpose of the stationary blade in a stationary blade rotary compressor?
What two locations are mufflers sometimes used on a compression system?
What two locations are mufflers sometimes used on a compression system?
List three basic parts of a reed valve assembly.
List three basic parts of a reed valve assembly.
What is used to minimize the amount of compressed refrigerant that can leak past the piston into the crankcase?
What is used to minimize the amount of compressed refrigerant that can leak past the piston into the crankcase?
What are the lubrication methods in reciprocating?
What are the lubrication methods in reciprocating?
Define oil pressure.
Define oil pressure.
Define capacity control.
Define capacity control.
What could operating at lower evaporator temperatures result in?
What could operating at lower evaporator temperatures result in?
What are the mechanical unloaders?
What are the mechanical unloaders?
What are the capacity control methods for each compressor?
What are the capacity control methods for each compressor?
What are factors that affect compressor efficiency?
What are factors that affect compressor efficiency?
Flashcards
Dual-Capacity Compressor
Dual-Capacity Compressor
Disables one piston when the crankshaft reverses in a reciprocating compressor.
Rotating Vane Compressor
Rotating Vane Compressor
Vanes are brought in contact with the cylinder wall via spring pressure.
Reciprocating Compressor Classification
Reciprocating Compressor Classification
Classified by cylinder arrangement, number of cylinders, and crankshaft type.
Connecting Rod
Connecting Rod
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Exhaust Valves
Exhaust Valves
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Screw Compressor Advantage
Screw Compressor Advantage
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Open-Drive Screw Compressors
Open-Drive Screw Compressors
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Compressor Mufflers
Compressor Mufflers
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Oil Pump Location
Oil Pump Location
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Capillary Tube Systems
Capillary Tube Systems
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Clearance Space
Clearance Space
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Scotch Yoke Compressor
Scotch Yoke Compressor
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Scroll Compressor Operation
Scroll Compressor Operation
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Adjustable Vanes
Adjustable Vanes
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Overload Relief Valves
Overload Relief Valves
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Unloaders
Unloaders
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Reed Valve Assembly components
Reed Valve Assembly components
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Piston Rings
Piston Rings
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Reciprocating Compressor Lubrication
Reciprocating Compressor Lubrication
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Oil Pressure Definition
Oil Pressure Definition
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Capacity Control
Capacity Control
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Low Evaporator Temperature Effects
Low Evaporator Temperature Effects
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Mechanical Unloader Types
Mechanical Unloader Types
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Compressor Efficiency Factors
Compressor Efficiency Factors
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Hermetic Compressor Electrical Connections
Hermetic Compressor Electrical Connections
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Reciprocating Compressor Valve Location
Reciprocating Compressor Valve Location
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Poppet Valves
Poppet Valves
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Oil Pumps
Oil Pumps
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Clearance Space Purpose
Clearance Space Purpose
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Scroll Compressor
Scroll Compressor
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Study Notes
Compressor Functionality and Components
- Dual-capacity reciprocating compressors use a movable eccentric to disable one piston when the crankshaft reverses.
- Rotating vane compressors bring vanes into contact with cylinder walls primarily through spring pressure.
- A 6” pulley driven by a 3” pulley motor operates at a compressor shaft speed of 1800 RPM.
- Electrical connections on hermetic compressors are outside the housing to prevent refrigerant contamination from electrical arcing.
Classification and Valve Mechanics
- Reciprocating compressors can be classified by cylinder arrangement, number of cylinders, and type of crankshaft.
- Intake and exhaust valves in reciprocating compressors are located externally from the cylinder head and valve block.
- Poppet valves have a valve stem that moves vertically within a guide, unlike reed and check valves.
Connecting Rod and Compressor Systems
- Connecting rods attach the piston to the crankshaft journal, linking reciprocating and rotary motion.
- Exhaust valves face issues due to higher operating temperatures and carbon accumulation compared to intake valves.
- Screw compressors have the advantage of infinitely variable capacity control through unloading.
Compressor Types and Features
- Open-drive screw compressors are typically used in high-pressure ammonia systems.
- Mufflers can be installed on both the inlet and outlet of compressors to reduce noise from gas pulsation.
- Oil pumps are typically situated at one end of the compressor shaft, ensuring effective lubrication.
Specialized Components and Operational Insights
- Capillary tube systems balance high and low side pressures during off cycles, eliminating the need for unloaders.
- Clearance space is defined as the volume between the piston at top dead center and cylinder plate, kept minimal to enhance vapor force into the high side.
- The Skotch yoke reciprocating compressor features a long piston with an elliptical slot for efficiency.
Scroll and Centrifugal Compressor Mechanics
- In scroll compressors, gas pockets are formed between fixed and orbiting scrolls, creating continuous compression.
- Adjustable vanes in centrifugal compressors modulate refrigerant vapor flow into the impeller.
- Overload relief valves are crucial in oil pumps, protecting against excessive pressure.
Start-Up and Maintenance Considerations
- Unloaders temporarily reduce cylinder pressure during compressor start-up, enhancing efficiency.
- Key components in a reed valve assembly include the valve retainer, discharge valve, suction valve, and valve plate.
- Piston rings minimize refrigerant leakage into the crankcase, ensuring system integrity.
Lubrication and Efficiency Factors
- Reciprocating compressors commonly utilize splash and force lubrication methods.
- Oil pressure is defined as the difference between crankcase pressure and oil pump pressure.
- Capacity control defines the design cooling load based on anticipated maximum conditions.
Effects of Operating Conditions
- Lower evaporator temperatures may lead to frost on coils, poor oil return, humidity control issues, and short cycling.
- Mechanical unloaders include suction bypass, suction cutoff, and hydraulic types, enhancing operational flexibility.
Compressor Efficiency Considerations
- Factors affecting compressor efficiency include piston displacement, valve performance, clearance pockets, and cylinder counts.
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Description
Test your knowledge about dual-capacity reciprocating compressors with this quiz. Through flashcards, explore the mechanics and functionalities of these crucial machines. Perfect for students and professionals in the HVAC field.
