Refrigeration Quiz & Flashcards on Secondary Refrigerants

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Questions and Answers

A solution used as a secondary refrigerant in chillers consisting of water and a chemical which lowers the water's freezing point is called?

Brine

Air-conditioning tube-and-fin coils are commonly available as?

Slant coils (correct)

Slab coils (correct)

"N" coils (correct)

"A" coils (correct)

An evaporator in which refrigerant enters as a saturated liquid vapor mix and leaves as a superheated vapor is a?

Direct expansion evaporator

An evaporator that covers the coils being cooled with liquid refrigerant is a?

Flooded evaporator Signup and view all the answers

As a mixture travels through an evaporator, the liquid percentage?

Decreases Signup and view all the answers

Chillers can be classified as?

Direct expansion Signup and view all the answers

Commercial refrigeration equipment for dry storage typically uses?

High-temperature evaporators Signup and view all the answers

Commercial refrigeration equipment for eggs, produce, and dairy uses?

Medium-temperature evaporators Signup and view all the answers

Commercial refrigeration equipment for ice cream storage typically uses?

Low-temperature evaporators Signup and view all the answers

Compared to air-conditioning evaporator coils, commercial refrigeration coils have?

Fewer fins per inch Signup and view all the answers

Direct-expansion coils operating below the dew point of the entering airstream will?

Cool the water vapor (humidity) in the air and condense it as droplets on the coil Signup and view all the answers

Flooded evaporators are used in?

Large chillers Signup and view all the answers

For which of the following actions is the last part of the evaporator used?

Superheating the refrigerant Signup and view all the answers

Heat flows from the product into the evaporator because?

The evaporator is at a lower temperature than the product Signup and view all the answers

How can a technician verify that a condenser and evaporator are an AHRI match?

Check them out on the AHRI website Signup and view all the answers

How deep should the condensate drain trap be?

4 inches deep Signup and view all the answers

How does a hot-gas defrost system work?

Hot compressor discharge gas is routed to the evaporator Signup and view all the answers

How does an air-defrost system work?

Air from inside the store is directed over the evaporator Signup and view all the answers

How is a brine solution created?

Salt and water are mixed Signup and view all the answers

If an evaporator does not have to superheat refrigerant vapor, which of the following can be produced?

Greater cooling capacity Signup and view all the answers

In a direct-expansion chiller?

The water is in the shell and the refrigerant is in the tubes Signup and view all the answers

In a flooded chiller?

The water is in the tubes and the refrigerant is in the shell Signup and view all the answers

In what circumstances would bare-pipe evaporators most likely be used?

Low-temperature refrigeration storage Signup and view all the answers

Increasing the airflow across a coil?

Increases the static pressure drop across the coil Signup and view all the answers

Increasing the airflow across a coil?

Increases the bypass factor Signup and view all the answers

Increasing the airflow across a coil?

Increases the sensible capacity Signup and view all the answers

It is possible for the same air conditioner to have a different capacity and efficiency with each coil it is matched to.

True Signup and view all the answers

Latent cooling:

Removes water from the air Signup and view all the answers

Medium-temperature applications are usually between?

28°F to 40°F Signup and view all the answers

On a commercial refrigeration system with electric defrost, what does the compressor do during the defrost cycle?

It shuts off Signup and view all the answers

On a commercial refrigeration system with hot-gas defrost, what does the compressor do during the defrost cycle?

It operates to provide the heat for defrost Signup and view all the answers

Refrigerant enters a direct expansion evaporator as a saturated mixture and leaves as a?

Superheated vapor Signup and view all the answers

Sensible cooling:

Reduces the air temperature Signup and view all the answers

Small domestic refrigerators and freezers use?

Plate evaporators Signup and view all the answers

The distance between fins is classified as the?

Fin spacing Signup and view all the answers

The most common types of defrost for commercial refrigeration evaporators are?

Electric and hot-gas defrost Signup and view all the answers

The percentage of air that travels through a tube-and-fin coil without touching any coil surface is called the?

Bypass factor Signup and view all the answers

The published SEER rating of a unit is accurate?

Only with an AHRI matched evaporator Signup and view all the answers

The purpose of the trap in a condensate drain is to?

Offset the negative pressure on the drain, which can prevent the water from draining Signup and view all the answers

The refrigeration system component that absorbs heat out of the product is the?

Evaporator Signup and view all the answers

The substance being cooled by a refrigeration system is called?

The product Signup and view all the answers

The tight bond between the refrigerant tube and the fins on tube-and-fin coils is made by?

Expanding the tubing into the fins Signup and view all the answers

The wet coil static pressure drop is?

Higher than the dry coil static pressure drop Signup and view all the answers

To increase latent cooling capacity:

Reduce the airflow over the evaporator Signup and view all the answers

To prevent liquid slugs from leaving the evaporator and entering the compressor, direct expansion evaporators?

Are typically fed at the bottom with suction gas leaving at the top Signup and view all the answers

Water that condenses on an evaporator coil and is blown off by the velocity of the air through the coil is called condensate?

Blowoff Signup and view all the answers

Water vapor in the air condenses on the evaporator coil?

Whenever the evaporator is below the dew point of the air Signup and view all the answers

Water-cooling evaporator constructions include?

Tube-in-tube, shell-and-coil, and shell-and-tube Signup and view all the answers

What controls the length of the defrost cycle on most commercial refrigeration systems?

The defrost termination thermostat Signup and view all the answers

What does it mean for a condenser and evaporator coil to be an "AHRI Match"?

AHRI has tested the components and certified that they work correctly together Signup and view all the answers

What happens to the evaporator fan motor when the defrost cycle is terminated?

The fan shuts off until the defrost termination thermostat senses that the evaporator is cold again Signup and view all the answers

What is the main purpose of the fins on tube-and-fin evaporators?

Fins increase the surface area of the coil Signup and view all the answers

What is the purpose of epoxy coating on evaporator coils?

To provide corrosion resistance Signup and view all the answers

When an evaporator coil gets dirty?

The temperature drop across the coil decreases Signup and view all the answers

When selecting an evaporator for an air-conditioning system, the best way to ensure that the evaporator will work with the condenser is?

An AHRI match for the condensing unit Signup and view all the answers

Where are plate evaporators typically used?

Small residential refrigerators Signup and view all the answers

Which of the following is NOT a high-temperature refrigeration application?

Fresh meat storage Signup and view all the answers

Which of the following is a type of sports arena that uses flooded evaporators?

Ice rink Signup and view all the answers

Which of the following is considered an advantage of a flooded evaporator?

Its ability to maintain a very accurate temperature across the entire evaporator surface Signup and view all the answers

Which of the following is the range of fin spacing on low-temperature coils?

1—4 fins per inch Signup and view all the answers

Why might there be a negative pressure on the condensate outlet in a coil operating at a positive static pressure?

The air velocity can create a negative pressure Signup and view all the answers

Study Notes

Refrigeration Concepts

Brine: A secondary refrigerant solution used in chillers that consists of water mixed with a chemical to lower the freezing point.
Types of Coils: Air-conditioning tube-and-fin coils are available as slab coils, slant coils, "A" coils, and "N" coils.
Direct Expansion Evaporator: An evaporator where the refrigerant enters as a saturated liquid vapor mix and exits as a superheated vapor.

Evaporator Types and Functions

Flooded Evaporator: An evaporator that cools coils by covering them with liquid refrigerant.
Mixture Behavior: The liquid percentage of a mixture decreases as it passes through an evaporator.
Chiller Classifications: Chillers can be categorized into flooded or direct expansion types.

Refrigeration Applications

High-Temperature Evaporators: Used in commercial refrigeration equipment for dry storage.
Medium-Temperature Evaporators: Designed for storing eggs, produce, and dairy.
Low-Temperature Evaporators: Specially used for ice cream storage.

Evaporator Efficiency

Coil Design: Commercial refrigeration coils have fewer fins per inch than air-conditioning evaporator coils.
Condensation Process: Direct-expansion coils below dew point cool water vapor, causing condensation as droplets on the coil.

Defrost Systems

Hot-Gas Defrost: Involves routing hot compressor discharge gas to the evaporator for defrosting purposes.
Air-Defrost Method: Utilizes air from inside the store directed over the evaporator for defrosting.

Performance Metrics

Cooling Capacity: Evaporators without the need to superheat refrigerant vapor can produce greater cooling capacity.
Sensible Cooling: This process reduces air temperature, while latent cooling specifically removes moisture from the air.
Evaporator Fan Operation: The fan shuts off during the defrost cycle and only resumes once the evaporator cools sufficiently.

System Specifications

AHR Matching: To ensure compatibility, condenser and evaporator coils should be AHRI matched, indicating they have been tested for proper function together.
Fin Spacing: The distance between fins affects the coil's efficiency, classified as fin spacing.

Maintenance and Performance

Condensate Drain Trap: Its purpose is to counteract negative pressure, allowing proper drainage of condensate.
Dirty Coils: If an evaporator coil becomes dirty, the temperature drop across the coil decreases, affecting performance.

Additional Insights

Plate Evaporators: Commonly used in small domestic refrigerators and freezers.
Flooded Evaporators Advantage: Known for maintaining consistent temperatures across the evaporator surface.
Negative Pressure Insights: Negative pressure may occur on the condensate outlet due to air velocity creating suction effects.

General Knowledge

Refrigerant Functions: The evaporator's role is to absorb heat from the product, with the substance being cooled referred to as the product.
Epoxy Coating Advantage: Provides corrosion resistance on evaporator coils and enhances longevity.
Sports Arena Applications: Flooded evaporators are notably used in ice rinks for efficient temperature control.

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Description

Test your knowledge on refrigeration concepts including types of coils, evaporators, and their various applications. Understand the behavior of refrigerants in different systems, and how they are utilized in commercial settings. This quiz covers essential principles and classifications of chillers and evaporators.

Refrigeration Concepts and Applications

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Questions and Answers

A solution used as a secondary refrigerant in chillers consisting of water and a chemical which lowers the water's freezing point is called?

Air-conditioning tube-and-fin coils are commonly available as?

An evaporator in which refrigerant enters as a saturated liquid vapor mix and leaves as a superheated vapor is a?

An evaporator that covers the coils being cooled with liquid refrigerant is a?

As a mixture travels through an evaporator, the liquid percentage?

Chillers can be classified as?

Commercial refrigeration equipment for dry storage typically uses?

Commercial refrigeration equipment for eggs, produce, and dairy uses?

Commercial refrigeration equipment for ice cream storage typically uses?

Compared to air-conditioning evaporator coils, commercial refrigeration coils have?

Direct-expansion coils operating below the dew point of the entering airstream will?

Flooded evaporators are used in?

For which of the following actions is the last part of the evaporator used?

Heat flows from the product into the evaporator because?

How can a technician verify that a condenser and evaporator are an AHRI match?

How deep should the condensate drain trap be?

How does a hot-gas defrost system work?

How does an air-defrost system work?

How is a brine solution created?

If an evaporator does not have to superheat refrigerant vapor, which of the following can be produced?

In a direct-expansion chiller?

In a flooded chiller?

In what circumstances would bare-pipe evaporators most likely be used?

Increasing the airflow across a coil?

Increasing the airflow across a coil?

Increasing the airflow across a coil?

It is possible for the same air conditioner to have a different capacity and efficiency with each coil it is matched to.

Latent cooling:

Medium-temperature applications are usually between?

On a commercial refrigeration system with electric defrost, what does the compressor do during the defrost cycle?

On a commercial refrigeration system with hot-gas defrost, what does the compressor do during the defrost cycle?

Refrigerant enters a direct expansion evaporator as a saturated mixture and leaves as a?

Sensible cooling:

Small domestic refrigerators and freezers use?

The distance between fins is classified as the?

The most common types of defrost for commercial refrigeration evaporators are?

The percentage of air that travels through a tube-and-fin coil without touching any coil surface is called the?

The published SEER rating of a unit is accurate?

The purpose of the trap in a condensate drain is to?

The refrigeration system component that absorbs heat out of the product is the?

The substance being cooled by a refrigeration system is called?

The tight bond between the refrigerant tube and the fins on tube-and-fin coils is made by?

The wet coil static pressure drop is?

To increase latent cooling capacity:

To prevent liquid slugs from leaving the evaporator and entering the compressor, direct expansion evaporators?

Water that condenses on an evaporator coil and is blown off by the velocity of the air through the coil is called condensate?

Water vapor in the air condenses on the evaporator coil?

Water-cooling evaporator constructions include?

What controls the length of the defrost cycle on most commercial refrigeration systems?

What does it mean for a condenser and evaporator coil to be an "AHRI Match"?

What happens to the evaporator fan motor when the defrost cycle is terminated?

What is the main purpose of the fins on tube-and-fin evaporators?

What is the purpose of epoxy coating on evaporator coils?

When an evaporator coil gets dirty?

When selecting an evaporator for an air-conditioning system, the best way to ensure that the evaporator will work with the condenser is?

Where are plate evaporators typically used?

Which of the following is NOT a high-temperature refrigeration application?

Which of the following is a type of sports arena that uses flooded evaporators?

Which of the following is considered an advantage of a flooded evaporator?

Which of the following is the range of fin spacing on low-temperature coils?

Why might there be a negative pressure on the condensate outlet in a coil operating at a positive static pressure?

Study Notes

Refrigeration Concepts

Evaporator Types and Functions

Refrigeration Applications

Evaporator Efficiency

Defrost Systems

Performance Metrics

System Specifications

Maintenance and Performance

Additional Insights

General Knowledge

Studying That Suits You

Description

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