Air Conditioning / Refrigeration
Air conditioning and refrigeration systems move heat by circulating refrigerant through a controlled cycle of compression, condensation, expansion, and evaporation.
This course begins with the basic refrigeration cycle, develops the physical theory behind refrigerant behavior, examines the major components and piping systems that make the refrigeration cycle possible, and then shows how those components are arranged into complete air-conditioning systems encountered in the field.
Build the System One Section at a Time
The sections are arranged so that each group of lessons builds on the concepts that came before it. Begin with the refrigeration cycle, develop the supporting theory, study the individual components and refrigerant piping, and then apply that knowledge to complete air-conditioning systems.
Understand the Cycle
Learn where refrigerant travels and where heat is absorbed and rejected.
Understand the Theory
Connect heat, pressure, saturation, phase change, superheat, and subcooling.
Study the Equipment
Examine the major components, refrigerant piping, and how they are arranged into complete air-conditioning systems.
Air Conditioning / Refrigeration Lessons
The Basic Refrigeration Cycle
Begin with the basic principles of mechanical refrigeration and follow refrigerant through the compressor, condenser, metering device, and evaporator.
Refrigeration Cycle
Four Components
- Introduction to Mechanical Refrigeration
- The Refrigeration Cycle
Refrigeration Theory
Develop the physical theory needed to understand refrigerant behavior, saturation, pressure-temperature relationships, superheat, subcooling, and refrigeration capacity.
Pressure
Saturation
P-T Relationships
- Matter, energy, heat, and temperature
- Sensible and latent heat
- Conduction, convection, and radiation
- Gauge pressure, absolute pressure, and vacuum
- Pressure-temperature relationships
- Bubble point, dew point, and temperature glide
- Superheat and subcooling
- Refrigeration capacity
- Pressure-enthalpy diagrams
Compressors
Study the component that moves refrigerant and creates the pressure difference between the high and low sides of the refrigeration system.
Compressor Types
Lubrication
Protection
Learn compressor construction, operation, electrical components, lubrication requirements, failure modes, and troubleshooting principles.
Condensers
Follow high-pressure refrigerant through the heat-rejection side of the refrigeration cycle.
Condensation
Subcooling
Airflow
Study condenser construction, desuperheating, condensation, subcooling, airflow, condensing temperature, and common operating problems.
Evaporators
Study the heat-absorbing portion of the refrigeration system, where low-pressure refrigerant boils while removing heat from air, water, or a refrigerated product.
Evaporation
Superheat
Airflow
Learn evaporator construction, boiling refrigerant, sensible and latent cooling, superheat, airflow, frost formation, and common evaporator problems.
Metering Devices
Study the devices that control refrigerant flow into the evaporator and create the major pressure transition between the high and low sides of the system.
Refrigerant Flow
TXV
Fixed Orifice
EEV
Compare fixed metering devices, thermostatic expansion valves, electronic expansion valves, refrigerant distribution, superheat control, and common metering-device problems.
Refrigerant Line Sets in Split Systems
Connect the indoor and outdoor refrigeration components with properly sized, routed, supported, insulated, brazed, tested, and evacuated refrigerant piping.
Oil Return
Line Sizing
Brazing
Evacuation
- Line-set construction and ACR tubing
- Oil return and vertical risers
- R-410A and A2L piping requirements
- Bends and equivalent length
- Filter-driers and sight glasses
- Factory charge and line length
- Suction-line insulation
- Ductless and variable-capacity piping
- Nitrogen purging, testing, and evacuation
- Routing and installation review
Types of Air-Conditioning Systems
See how refrigeration components are assembled into complete air-conditioning systems and learn to recognize packaged units, conventional split systems, ductless mini-splits, and direct evaporative cooling equipment.
Split Systems
Ductless Mini-Splits
Evaporative Cooling
System Identification
- Understanding air-conditioning system configurations
- Gas/electric package units
- All-electric package units
- Split systems with air handlers
- Split systems with gas furnaces
- Ductless mini-split systems
- Comparing refrigeration-based air-conditioning systems
- Introduction to evaporative cooling
- Evaporative cooler construction
- Evaporative cooler operation and application
- System selection and final review
One Refrigeration System
Compressor
Raises refrigerant vapor pressure and moves refrigerant through the system.
Condenser
Rejects heat and changes high-pressure vapor into liquid.
Metering Device
Controls refrigerant flow and creates the pressure reduction into the evaporator.
Evaporator
Absorbs heat as low-pressure refrigerant boils and becomes vapor.
The refrigerant line set connects these components. Refrigeration theory explains why the pressure, temperature, phase, superheat, and subcooling change as refrigerant travels through them. The Types of Air-Conditioning Systems section then shows how these components are arranged into complete equipment configurations encountered in the field.
Why Refrigeration Theory Comes Before the Components
The refrigeration cycle tells us what the refrigerant does. Refrigeration Theory explains why it does it.
Why Does Refrigerant Boil at Low Temperature?
Because saturation temperature changes with pressure.
Why Does the Condenser Need High Pressure?
The higher pressure creates a saturation temperature above the cooling medium so heat can be rejected.
Why Measure Superheat?
It tells us how far refrigerant vapor has moved above its vapor-side saturation condition.
Why Measure Subcooling?
It tells us how far liquid refrigerant has been cooled below its liquid-side saturation condition.
How to Work Through This Material
Start With the Basic Refrigeration Cycle
Learn the four major components and establish the direction of refrigerant and heat flow.
Complete Refrigeration Theory
Learn the physics behind heat transfer, saturation, refrigerant pressure-temperature behavior, superheat, and subcooling.
Study Compressors, Condensers, Evaporators, and Metering Devices
With the theory established, study what each major component does to refrigerant pressure, temperature, state, and energy.
Study Refrigerant Line Sets
Learn how the components are connected in real split-system installations and how piping affects refrigerant flow and system operation.
Study Types of Air-Conditioning Systems
See how the refrigeration cycle, components, piping, heating equipment, blowers, and air-distribution systems are assembled into complete packaged, split, and ductless systems, then compare those systems with direct evaporative cooling.
This Course Will Continue to Grow
The Air Conditioning / Refrigeration material is being organized into section landing pages so individual lessons can be expanded without making the main course page difficult to navigate.
Additional sections can be added as the course develops while the existing refrigeration-cycle, theory, component, piping, and complete-system material remains organized in a consistent sequence.
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