Chillers Unit 47 Quiz

Questions and Answers

The evaporator of a chiller can be used to absorb heat from ____.

A solution of water and polyethylene glycol

Both A and B are correct (correct)

Water

Two basic categories of chillers are the ____.

Compression cycle

Both A and B are correct (correct)

Absorption

A benefit of operating a compressor unloaded is ____.

Reduced compression ratios

Reduced energy costs

Both A and B are correct (correct)

A reciprocating compressor with six cylinders, three banks of two cylinders each, can have its capacity reduced by unloading to ____% of full capacity.

33-1/3 Signup and view all the answers

Speeds up to ____ rpm are used in centrifugal compressors.

30,000 Signup and view all the answers

A centrifugal compressor uses ____ for capacity control.

Guide vanes Signup and view all the answers

Direct expansion evaporators have ____.

An established superheat at the outlet of the evaporator Signup and view all the answers

The compressors used in low pressure chillers are the ____ type.

Centrifugal Signup and view all the answers

When a chiller using a low-pressure refrigerant is operating, the low pressure side of the system ____.

Is always in a vacuum Signup and view all the answers

A purge unit ____.

Relieves non-condensable gases from the system to the atmosphere Signup and view all the answers

To unload a reciprocating compressor, hot gas bypass across the cylinder is the best method.

False Signup and view all the answers

When referring to evaporators, the terms 'direct expansion' and 'dry type' can be used interchangeably.

True Signup and view all the answers

High pressure chillers use either air- or water-cooled condensers.

True Signup and view all the answers

Thermostatic expansion valves are the only metering devices used in high pressure chillers.

False Signup and view all the answers

Low pressure chillers use either air- or water-cooled condensers.

False Signup and view all the answers

Lithium bromide is ideal for use in absorption systems because it is non-corrosive.

False Signup and view all the answers

Electronic starters are much smaller than conventional starters.

True Signup and view all the answers

A chiller typically cools ____________________ (what liquid?) for the purpose of air conditioning.

Water Signup and view all the answers

In centrifugal compressors, capacity control is accomplished by the use of ___________________________________ at the impeller inlet.

Guide vanes Signup and view all the answers

The pressure difference in a low-pressure chiller is produced by a(n) ____________________ compressor.

Centrifugal Signup and view all the answers

The device that automatically helps to remove non-condensables from a chiller is called a(n) ____________________.

Purge unit Signup and view all the answers

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.

Lithium bromide Signup and view all the answers

The refrigerant in an absorption chiller whose source of energy is steam or hot water is ____________________.

Water Signup and view all the answers

Name two methods commonly used to unload a reciprocating compressor.

Two methods commonly used to unload a reciprocating compressor are cylinder unloading and fan cycling Signup and view all the answers

Why are multiple smaller compressors sometimes preferred over one large compressor?

Smaller compressors are sometimes preferred over large compressors because a large compressor is usually responsible for cooling down multiple cases of food and if it fails, more product will be spoiled and it would be a greater loss to the store than if a small compressor that was responsible for one case goes out. Signup and view all the answers

What is accomplished by having a compressor that is equipped with unloaders?

A compressor that is equipped with unloaders is able to operate at different capacities in order to save energy. Signup and view all the answers

What is the reason to use cylinder unloading in high pressure chillers?

To provide capacity control for longer runtimes and closer control of chilled water. Signup and view all the answers

Since there are no 'valves' in a scroll compressor, what must be done to prevent refrigerant from flowing backward when the compressor cycles off?

The heater is used to prevent off cycle refrigerant migration to the compressor crankcase. Signup and view all the answers

Why are open-drive compressors often started up for a short time in the off season?

The shaft seal on the compressor is kept lubricated by the circulation of refrigerant. Signup and view all the answers

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.

Chillers Unit 47 Quiz

Questions and Answers

The evaporator of a chiller can be used to absorb heat from ____.

Two basic categories of chillers are the ____.

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.

Speeds up to ____ rpm are used in centrifugal compressors.

A centrifugal compressor uses ____ for capacity control.

Direct expansion evaporators have ____.

The compressors used in low pressure chillers are the ____ type.

When a chiller using a low-pressure refrigerant is operating, the low pressure side of the system ____.

A purge unit ____.

To unload a reciprocating compressor, hot gas bypass across the cylinder is the best method.

When referring to evaporators, the terms 'direct expansion' and 'dry type' can be used interchangeably.

High pressure chillers use either air- or water-cooled condensers.

Thermostatic expansion valves are the only metering devices used in high pressure chillers.

Low pressure chillers use either air- or water-cooled condensers.

Lithium bromide is ideal for use in absorption systems because it is non-corrosive.

Electronic starters are much smaller than conventional starters.

A chiller typically cools ____________________ (what liquid?) for the purpose of air conditioning.

In centrifugal compressors, capacity control is accomplished by the use of ___________________________________ at the impeller inlet.

The pressure difference in a low-pressure chiller is produced by a(n) ____________________ compressor.

The device that automatically helps to remove non-condensables from a chiller is called a(n) ____________________.

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 refrigerant in an absorption chiller whose source of energy is steam or hot water is ____________________.

Name two methods commonly used to unload a reciprocating compressor.

Why are multiple smaller compressors sometimes preferred over one large compressor?

What is accomplished by having a compressor that is equipped with unloaders?

What is the reason to use cylinder unloading in high pressure chillers?

Since there are no 'valves' in a scroll compressor, what must be done to prevent refrigerant from flowing backward when the compressor cycles off?

Why are open-drive compressors often started up for a short time in the off season?

Study Notes

Chillers and Compressors

Compressor Specifications

Evaporators and Purge Units

Chiller Operation and Controls

Absorption Systems

Compressor Operation and Efficiency

Specifics on Compressor Types

Studying That Suits You

Description

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