The Refrigeration Cycle

Table of Contents

Chapter 1: Refrigeration and Air Conditioning Basics

Topics: Definition of refrigeration and air conditioning; Composition of matter; States of matter

Learning Objectives:

• Define refrigeration and air conditioning and explain how they differ.
• Describe the two methods of lowering the temperature of a material.
• Name the three physical states of matter.
• Identify what causes matter to change its state.

Chapter 2: Heat, Pressure, and Change of State

Topics: Heat; Temperature; Heat transfer; Sensible and latent heat; Heat quantity; Pressure; Importance of pressure in refrigeration

Learning Objectives:

• Explain the difference between sensible and latent heat.
• Compare the Fahrenheit and Celsius temperature scales and convert temperatures from one to another.
• Name and describe the three methods of heat transfer.
• Define latent heat of fusion and latent heat of vaporization.
• Explain the difference between absolute pressure and gauge pressure.
• Describe the effect of pressure changes on boiling point.

Chapter 3: The Basic Refrigeration Cycle

Topics: Vapor-compression refrigeration cycle; Refrigerant in action; Types of evaporators, compressors, condensers, and metering devices

Learning Objectives:

• Explain the function of each of the major refrigeration system components: evaporator, compressor, condenser, and metering device.
• Define the terms subcooling and superheating.
• Explain the function of the refrigerant in a refrigeration system and trace its path.
• Contrast dry-expansion and flooded evaporators.
• Name the five main types of compressors.
• Define cooling medium and name the two most commonly used.
• Explain the operation of the six most common metering devices.

Chapter 4: Air Properties and Simple Psychrometrics

Topics: Temperature; Humidity; Specific volume; Enthalpy; Psychrometric chart; Dewpoint temperature; Relative humidity

Learning Objectives:

• State the definition of psychrometrics.
• List the four air properties important in psychrometrics.
• Differentiate between dry- and wet-bulb temperature and tell how each is measured.
• Define the term saturated air.
• Define specific humidity and relative humidity.
• Define enthalpy and explain how it is calculated.
• Demonstrate how to use the psychrometric chart to determine dewpoint temperature, specific humidity, relative humidity, and enthalpy.

Chapter 5: Tools, Test Instruments, and Safe Work Practices

Topics: Pressure gauges; Vacuum-measuring instruments; Leak detection; Thermometers; Hygrometers; Electric test equipment; Recording instruments; Safety

Learning Objectives:

• Describe a gauge manifold and tell how it is used.
• Tell what it means to evacuate a refrigeration system and tell how it is done.
• List and describe at least three methods of leak detection.
• Explain the construction of a sling psychrometer and tell how and why it is used.
• Name the instrument used to measure relative humidity.
• Name the instrument used to measure each of the following electrical values: potential difference, current, resistance, and electric power.
• List the four classes of work area hazards, and give an example of each.

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