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Refrigeration Concepts and Applications
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Refrigeration Concepts and Applications

Created by
@WellRunHydrogen

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?

    <p>Flooded evaporator</p> Signup and view all the answers

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

    <p>Decreases</p> Signup and view all the answers

    Chillers can be classified as?

    <p>Direct expansion</p> Signup and view all the answers

    Commercial refrigeration equipment for dry storage typically uses?

    <p>High-temperature evaporators</p> Signup and view all the answers

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

    <p>Medium-temperature evaporators</p> Signup and view all the answers

    Commercial refrigeration equipment for ice cream storage typically uses?

    <p>Low-temperature evaporators</p> Signup and view all the answers

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

    <p>Fewer fins per inch</p> Signup and view all the answers

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

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

    Flooded evaporators are used in?

    <p>Large chillers</p> Signup and view all the answers

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

    <p>Superheating the refrigerant</p> Signup and view all the answers

    Heat flows from the product into the evaporator because?

    <p>The evaporator is at a lower temperature than the product</p> Signup and view all the answers

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

    <p>Check them out on the AHRI website</p> Signup and view all the answers

    How deep should the condensate drain trap be?

    <p>4 inches deep</p> Signup and view all the answers

    How does a hot-gas defrost system work?

    <p>Hot compressor discharge gas is routed to the evaporator</p> Signup and view all the answers

    How does an air-defrost system work?

    <p>Air from inside the store is directed over the evaporator</p> Signup and view all the answers

    How is a brine solution created?

    <p>Salt and water are mixed</p> Signup and view all the answers

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

    <p>Greater cooling capacity</p> Signup and view all the answers

    In a direct-expansion chiller?

    <p>The water is in the shell and the refrigerant is in the tubes</p> Signup and view all the answers

    In a flooded chiller?

    <p>The water is in the tubes and the refrigerant is in the shell</p> Signup and view all the answers

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

    <p>Low-temperature refrigeration storage</p> Signup and view all the answers

    Increasing the airflow across a coil?

    <p>Increases the static pressure drop across the coil</p> Signup and view all the answers

    Increasing the airflow across a coil?

    <p>Increases the bypass factor</p> Signup and view all the answers

    Increasing the airflow across a coil?

    <p>Increases the sensible capacity</p> 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.

    <p>True</p> Signup and view all the answers

    Latent cooling:

    <p>Removes water from the air</p> Signup and view all the answers

    Medium-temperature applications are usually between?

    <p>28°F to 40°F</p> Signup and view all the answers

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

    <p>It shuts off</p> Signup and view all the answers

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

    <p>It operates to provide the heat for defrost</p> Signup and view all the answers

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

    <p>Superheated vapor</p> Signup and view all the answers

    Sensible cooling:

    <p>Reduces the air temperature</p> Signup and view all the answers

    Small domestic refrigerators and freezers use?

    <p>Plate evaporators</p> Signup and view all the answers

    The distance between fins is classified as the?

    <p>Fin spacing</p> Signup and view all the answers

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

    <p>Electric and hot-gas defrost</p> 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?

    <p>Bypass factor</p> Signup and view all the answers

    The published SEER rating of a unit is accurate?

    <p>Only with an AHRI matched evaporator</p> Signup and view all the answers

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

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

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

    <p>Evaporator</p> Signup and view all the answers

    The substance being cooled by a refrigeration system is called?

    <p>The product</p> Signup and view all the answers

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

    <p>Expanding the tubing into the fins</p> Signup and view all the answers

    The wet coil static pressure drop is?

    <p>Higher than the dry coil static pressure drop</p> Signup and view all the answers

    To increase latent cooling capacity:

    <p>Reduce the airflow over the evaporator</p> Signup and view all the answers

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

    <p>Are typically fed at the bottom with suction gas leaving at the top</p> 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?

    <p>Blowoff</p> Signup and view all the answers

    Water vapor in the air condenses on the evaporator coil?

    <p>Whenever the evaporator is below the dew point of the air</p> Signup and view all the answers

    Water-cooling evaporator constructions include?

    <p>Tube-in-tube, shell-and-coil, and shell-and-tube</p> Signup and view all the answers

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

    <p>The defrost termination thermostat</p> Signup and view all the answers

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

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

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

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

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

    <p>Fins increase the surface area of the coil</p> Signup and view all the answers

    What is the purpose of epoxy coating on evaporator coils?

    <p>To provide corrosion resistance</p> Signup and view all the answers

    When an evaporator coil gets dirty?

    <p>The temperature drop across the coil decreases</p> 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?

    <p>An AHRI match for the condensing unit</p> Signup and view all the answers

    Where are plate evaporators typically used?

    <p>Small residential refrigerators</p> Signup and view all the answers

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

    <p>Fresh meat storage</p> Signup and view all the answers

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

    <p>Ice rink</p> Signup and view all the answers

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

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

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

    <p>1—4 fins per inch</p> 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?

    <p>The air velocity can create a negative pressure</p> 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.

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