Refrigeration Systems Quiz
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Questions and Answers

What is the result of moisture present in the refrigeration system?

  • Increased efficiency of the electric motor
  • Improved thermal transfer properties
  • Formation of ice crystals in the compressor
  • Corrosion and sludge formation (correct)

    • What corrosive compound is formed when ammonia combines with water?

  • Ammonium chloride
  • Ammonium sulfate
  • Ammonium nitrate
  • Ammonium hydroxide (correct)

    • Which material should NEVER be used in ammonia refrigeration systems due to corrosion risk?

  • Cast iron
  • Copper alloys (correct)
  • Aluminium
  • Stainless steel

    • In the context of the refrigeration system, what does the term 'sludge' refer to?

    <p>Moisture combining with oil in the crankcase</p> Signup and view all the answers

    What does the compressor in a refrigeration system primarily do?

    <p>Compresses refrigerant vapour from low pressure to high pressure</p> Signup and view all the answers

    How does compression affect the refrigerant vapour in a refrigeration system?

    <p>It raises the temperature and pressure of the vapour</p> Signup and view all the answers

    Which component in the refrigeration system is responsible for heat transfer from the refrigerant to the coolant?

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

    What is the role of the evaporator in a vapour compression refrigeration system?

    <p>To absorb heat from the surrounding environment</p> Signup and view all the answers

    What determines the operating pressures and temperatures in a vapour compression refrigeration system?

    <p>The desired temperature of air leaving the cooling coil</p> Signup and view all the answers

    Which of the following is a mandatory component of a refrigeration system?

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

    What is the purpose of the refrigerant metering device in a refrigeration system?

    <p>To maintain consistent evaporator temperatures</p> Signup and view all the answers

    In a refrigeration cycle, the refrigerant returns to which component after condensing in the condenser?

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

    What does the ASHRAE designation for refrigerants include?

    <p>A capital letter 'R' followed by a dash and a number</p> Signup and view all the answers

    Which of the following properties does NOT directly affect the movement of heat in refrigerants?

    <p>Chemical name</p> Signup and view all the answers

    Why is no single refrigerant considered ideal for all applications?

    <p>The thermodynamic properties vary significantly between refrigerants</p> Signup and view all the answers

    At what standard operating conditions is the thermodynamic comparison of refrigerants made?

    <p>-15°C evaporator temperature and +30°C condenser temperature</p> Signup and view all the answers

    Which of the following refrigerants is mentioned as an example in the context of thermodynamic properties?

    <p>R-134a</p> Signup and view all the answers

    What is the average temperature of the chilled water in a cooling coil designed for a 10°C temperature difference?

    <p>5°C</p> Signup and view all the answers

    At what temperature does the water leave the cooling coil?

    <p>10°C</p> Signup and view all the answers

    What is the lowest operating temperature for the evaporator to remain practical?

    <p>0°C</p> Signup and view all the answers

    What condenser pressure is required to maintain the condensing temperature of 30°C?

    <p>770 kPa absolute</p> Signup and view all the answers

    How are thermodynamic properties of refrigerants primarily obtained?

    <p>By careful experiments</p> Signup and view all the answers

    What average cooling water temperature is utilized in the condenser design?

    <p>22°C</p> Signup and view all the answers

    What is the primary purpose of refrigerant tables in a refrigeration system?

    <p>To calculate system performance and capacity</p> Signup and view all the answers

    What is the significance of the temperature drop in the condenser design?

    <p>It affects the overall efficiency of the system</p> Signup and view all the answers

    What is the primary definition of a tonne of refrigeration?

    <p>The heat required to produce 1 tonne of ice at 0°C from water at 0°C over 24 hours.</p> Signup and view all the answers

    How much energy does 1 tonne of refrigeration equate to in kJ/day?

    <p>335,000 kJ/day</p> Signup and view all the answers

    What is the energy output of 1 tonne of refrigeration in kJ/hour?

    <p>13,958 kJ/hour</p> Signup and view all the answers

    In terms of kW, how is one tonne of refrigeration expressed?

    <p>1 TR = 3.877 kW</p> Signup and view all the answers

    What criteria are used for classifying refrigerants?

    <p>Flammability, toxicity, and environmental impact.</p> Signup and view all the answers

    Why is it important to consistently refer to refrigerants?

    <p>To allow for the proper identification and selection for applications.</p> Signup and view all the answers

    What is the equivalent energy of 1 tonne of refrigeration expressed in kJ/s?

    <p>3.877 kJ/s</p> Signup and view all the answers

    What is the relationship between the latent heat of fusion and the concept of tonnes of refrigeration?

    <p>The latent heat of fusion defines the heat extraction needed to freeze water at 0°C.</p> Signup and view all the answers

    What is the primary issue with using oil-miscible refrigerants in a refrigeration system?

    <p>They dilute compressor crankcase oil, lowering viscosity.</p> Signup and view all the answers

    Which refrigerant is known for being non-miscible with lube oil?

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

    What effect does oil build-up in the evaporator and condenser have on a refrigeration system?

    <p>It reduces system capacity and can block tubing.</p> Signup and view all the answers

    What is the purpose of oil separators in ammonia refrigeration systems?

    <p>To return oil to the compressor from low points.</p> Signup and view all the answers

    What characteristic of halocarbon refrigerants can make leak detection easier?

    <p>They have a slight odour resembling ether.</p> Signup and view all the answers

    What challenge can arise from the strong, pungent odour of ammonia in public spaces?

    <p>It can induce panic-like behaviour.</p> Signup and view all the answers

    Why is sizing of piping important in a refrigeration system utilizing oil-miscible refrigerants?

    <p>To prevent oil from settling in evaporator tubing.</p> Signup and view all the answers

    Which refrigerant does CSA B52 code restrict to industrial sites due to its flammability?

    <p>R-290 (propane)</p> Signup and view all the answers

    Study Notes

    Learning Outcomes and Objectives

    • Students will be able to explain the basic concept of refrigeration and refrigerants.
    • Objectives include explaining fundamental refrigeration, describing vapour compression refrigeration system operation cycles, and explaining operating temperatures and pressures.
    • Refrigerant classification and thermodynamic properties will also be covered, along with refrigerant properties related to miscibility, leak tendency, odour, moisture reaction, toxicity, and flammability.

    Chapter Introduction

    • Refrigeration is defined as the process of moving heat from one location to another to reduce and maintain the temperature of a material below its surroundings.
    • Refrigeration relies on the circulation of refrigerant in a closed cycle.

    Objective 1: Fundamentals of Refrigeration

    • The first principle of refrigeration is the concept of latent heat removal.
    • Evaporation of a liquid absorbs heat, leading to a cooling effect.
    • Pressure affects the boiling point of a liquid. Higher pressure leads to a higher boiling temperature.

    Objective 2: Vapour Compression Refrigeration System Cycle

    • Actual refrigeration systems use additional components for continuous operation.
    • A liquid receiver provides continuous refrigerant supply to the evaporator.
    • A metering device controls refrigerant flow rate to the evaporator.
    • Refrigerant vapour leaves the evaporator and is compressed.
    • The vapour is cooled in a condenser, changing it back to a liquid.
    • The liquefied refrigerant returns to the receiver, completing the cycle.
    • A compressor is needed to raise the vapour temperature and pressure.

    Objective 3: Operating Temperatures and Pressures

    • Operating temperatures and pressures are determined by the desired cooling effect.
    • System components are designed for the specific temperature/pressure ranges.
    • Proper equipment selection is based on refrigerant properties and operating conditions.

    Objective 4: Refrigeration System Capacity

    • Capacity is measured in tonnes of refrigeration (TR).
    • One TR is the amount of heat required to produce one tonne of ice at 0°C from water at 0°C in one day.
    • Conversion between SI and USCS units of refrigeration capacity is readily available.

    Objective 5: Refrigerant Classification

    • Refrigerants are categorized by their flammability, toxicity, and environmental impact.
    • Common refrigerants are identified by ASHRAE designations.

    Objective 6: Thermodynamic Properties of Refrigerants

    • Refrigerant properties include pressure, temperature, volume, density, enthalpy, and entropy.
    • These properties are tabulated in refrigerant tables and charts for various refrigerants.
    • These properties are used for calculations related to refrigeration cycles and performance.

    Physical Properties of Refrigerants - (OBJECTIVE 7)

    • Properties include miscibility (solubility with lubricants), leakage tendency, odour, moisture reaction, toxicity, and flammability.
    • Refrigerant choice often involves tradeoffs and compromises.

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    Description

    Test your knowledge on refrigeration systems and their components. This quiz covers key concepts including the function of compressors, the role of evaporators, and the effects of moisture and corrosion in refrigeration systems. Perfect for those studying HVAC or related fields.

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