Podcast
Questions and Answers
The evaporator of a chiller can be used to absorb heat from ____.
The evaporator of a chiller can be used to absorb heat from ____.
Two basic categories of chillers are the ____.
Two basic categories of chillers are the ____.
A benefit of operating a compressor unloaded is ____.
A benefit of operating a compressor unloaded is ____.
A reciprocating compressor with six cylinders, three banks of two cylinders each, can have its capacity reduced by unloading to ____% of full capacity.
A reciprocating compressor with six cylinders, three banks of two cylinders each, can have its capacity reduced by unloading to ____% of full capacity.
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Speeds up to ____ rpm are used in centrifugal compressors.
Speeds up to ____ rpm are used in centrifugal compressors.
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A centrifugal compressor uses ____ for capacity control.
A centrifugal compressor uses ____ for capacity control.
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Direct expansion evaporators have ____.
Direct expansion evaporators have ____.
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The compressors used in low pressure chillers are the ____ type.
The compressors used in low pressure chillers are the ____ type.
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When a chiller using a low-pressure refrigerant is operating, the low pressure side of the system ____.
When a chiller using a low-pressure refrigerant is operating, the low pressure side of the system ____.
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A purge unit ____.
A purge unit ____.
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To unload a reciprocating compressor, hot gas bypass across the cylinder is the best method.
To unload a reciprocating compressor, hot gas bypass across the cylinder is the best method.
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When referring to evaporators, the terms 'direct expansion' and 'dry type' can be used interchangeably.
When referring to evaporators, the terms 'direct expansion' and 'dry type' can be used interchangeably.
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High pressure chillers use either air- or water-cooled condensers.
High pressure chillers use either air- or water-cooled condensers.
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Thermostatic expansion valves are the only metering devices used in high pressure chillers.
Thermostatic expansion valves are the only metering devices used in high pressure chillers.
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Low pressure chillers use either air- or water-cooled condensers.
Low pressure chillers use either air- or water-cooled condensers.
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Lithium bromide is ideal for use in absorption systems because it is non-corrosive.
Lithium bromide is ideal for use in absorption systems because it is non-corrosive.
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Electronic starters are much smaller than conventional starters.
Electronic starters are much smaller than conventional starters.
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A chiller typically cools ____________________ (what liquid?) for the purpose of air conditioning.
A chiller typically cools ____________________ (what liquid?) for the purpose of air conditioning.
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In centrifugal compressors, capacity control is accomplished by the use of ___________________________________ at the impeller inlet.
In centrifugal compressors, capacity control is accomplished by the use of ___________________________________ at the impeller inlet.
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The pressure difference in a low-pressure chiller is produced by a(n) ____________________ compressor.
The pressure difference in a low-pressure chiller is produced by a(n) ____________________ compressor.
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The device that automatically helps to remove non-condensables from a chiller is called a(n) ____________________.
The device that automatically helps to remove non-condensables from a chiller is called a(n) ____________________.
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The pressure difference in an absorption chiller where the source of energy is steam or hot water is produced with the use of a(n) ____________________ solution.
The pressure difference in an absorption chiller where the source of energy is steam or hot water is produced with the use of a(n) ____________________ solution.
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The refrigerant in an absorption chiller whose source of energy is steam or hot water is ____________________.
The refrigerant in an absorption chiller whose source of energy is steam or hot water is ____________________.
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Name two methods commonly used to unload a reciprocating compressor.
Name two methods commonly used to unload a reciprocating compressor.
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Why are multiple smaller compressors sometimes preferred over one large compressor?
Why are multiple smaller compressors sometimes preferred over one large compressor?
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What is accomplished by having a compressor that is equipped with unloaders?
What is accomplished by having a compressor that is equipped with unloaders?
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What is the reason to use cylinder unloading in high pressure chillers?
What is the reason to use cylinder unloading in high pressure chillers?
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Since there are no 'valves' in a scroll compressor, what must be done to prevent refrigerant from flowing backward when the compressor cycles off?
Since there are no 'valves' in a scroll compressor, what must be done to prevent refrigerant from flowing backward when the compressor cycles off?
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Why are open-drive compressors often started up for a short time in the off season?
Why are open-drive compressors often started up for a short time in the off season?
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Study Notes
Chillers and Compressors
- Evaporators in chillers absorb heat from water or a water-polyethylene glycol solution.
- Two primary categories of chillers are compression cycle and absorption.
- Operating a compressor unloaded leads to reduced energy costs and compression ratios.
- A reciprocating compressor with six cylinders can unload to 33-1/3% of its full capacity.
Compressor Specifications
- Centrifugal compressors can operate at speeds up to 30,000 rpm.
- Capacity control in centrifugal compressors is achieved through guide vanes.
- Low pressure chillers primarily use centrifugal compressors, and the low pressure side of the system remains in a vacuum during operation.
Evaporators and Purge Units
- Direct expansion evaporators are characterized by an established superheat at the outlet.
- A purge unit helps remove non-condensable gases from the chiller system.
Chiller Operation and Controls
- Statements regarding unloading methods and system configurations are sometimes true or false; hot gas bypass is not the best method to unload reciprocating compressors, while "direct expansion" and "dry type" evaporators are interchangeable terms.
- High pressure chillers can utilize air- or water-cooled condensers, while low pressure chillers do not.
Absorption Systems
- Lithium bromide is used in absorption chillers due to its properties but is not entirely non-corrosive.
- Absorption chillers use water as the refrigerant, and steam or hot water solutions create pressure differences.
Compressor Operation and Efficiency
- A compressor equipped with unloaders can operate at variable capacities for energy efficiency.
- Cylinder unloading and fan cycling are methods for unloading reciprocating compressors.
- Multiple smaller compressors can be advantageous because their failure leads to less overall product loss compared to a single large compressor.
Specifics on Compressor Types
- The heater in a scroll compressor prevents refrigerant from migrating backward when the compressor is off.
- Open-drive compressors are sometimes operated briefly during the off-season to keep the shaft seal lubricated.
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Description
Test your knowledge on chillers with this Unit 47 quiz. This quiz covers key concepts such as evaporators, chiller categories, and compressor benefits. Perfect for students studying HVAC systems or related fields.
