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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?
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?
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?
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?
An evaporator that covers the coils being cooled with liquid refrigerant is a?
As a mixture travels through an evaporator, the liquid percentage?
As a mixture travels through an evaporator, the liquid percentage?
Chillers can be classified as?
Chillers can be classified as?
Commercial refrigeration equipment for dry storage typically uses?
Commercial refrigeration equipment for dry storage typically uses?
Commercial refrigeration equipment for eggs, produce, and dairy uses?
Commercial refrigeration equipment for eggs, produce, and dairy uses?
Commercial refrigeration equipment for ice cream storage typically uses?
Commercial refrigeration equipment for ice cream storage typically uses?
Compared to air-conditioning evaporator coils, commercial refrigeration coils have?
Compared to air-conditioning evaporator coils, commercial refrigeration coils have?
Direct-expansion coils operating below the dew point of the entering airstream will?
Direct-expansion coils operating below the dew point of the entering airstream will?
Flooded evaporators are used in?
Flooded evaporators are used in?
For which of the following actions is the last part of the evaporator used?
For which of the following actions is the last part of the evaporator used?
Heat flows from the product into the evaporator because?
Heat flows from the product into the evaporator because?
How can a technician verify that a condenser and evaporator are an AHRI match?
How can a technician verify that a condenser and evaporator are an AHRI match?
How deep should the condensate drain trap be?
How deep should the condensate drain trap be?
How does a hot-gas defrost system work?
How does a hot-gas defrost system work?
How does an air-defrost system work?
How does an air-defrost system work?
How is a brine solution created?
How is a brine solution created?
If an evaporator does not have to superheat refrigerant vapor, which of the following can be produced?
If an evaporator does not have to superheat refrigerant vapor, which of the following can be produced?
In a direct-expansion chiller?
In a direct-expansion chiller?
In a flooded chiller?
In a flooded chiller?
In what circumstances would bare-pipe evaporators most likely be used?
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?
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.
It is possible for the same air conditioner to have a different capacity and efficiency with each coil it is matched to.
Latent cooling:
Latent cooling:
Medium-temperature applications are usually between?
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 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?
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?
Refrigerant enters a direct expansion evaporator as a saturated mixture and leaves as a?
Sensible cooling:
Sensible cooling:
Small domestic refrigerators and freezers use?
Small domestic refrigerators and freezers use?
The distance between fins is classified as the?
The distance between fins is classified as the?
The most common types of defrost for commercial refrigeration evaporators are?
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 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 published SEER rating of a unit is accurate?
The purpose of the trap in a condensate drain is to?
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 refrigeration system component that absorbs heat out of the product is the?
The substance being cooled by a refrigeration system is called?
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 tight bond between the refrigerant tube and the fins on tube-and-fin coils is made by?
The wet coil static pressure drop is?
The wet coil static pressure drop is?
To increase latent cooling capacity:
To increase latent cooling capacity:
To prevent liquid slugs from leaving the evaporator and entering the compressor, direct expansion evaporators?
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 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 vapor in the air condenses on the evaporator coil?
Water-cooling evaporator constructions include?
Water-cooling evaporator constructions include?
What controls the length of the defrost cycle on most commercial refrigeration systems?
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 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 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 main purpose of the fins on tube-and-fin evaporators?
What is the purpose of epoxy coating on evaporator coils?
What is the purpose of epoxy coating on evaporator coils?
When an evaporator coil gets dirty?
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?
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?
Where are plate evaporators typically used?
Which of the following is NOT a high-temperature refrigeration application?
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 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 considered an advantage of a flooded evaporator?
Which of the following is the range of fin spacing on low-temperature coils?
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?
Why might there be a negative pressure on the condensate outlet in a coil operating at a positive static pressure?
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.
