Refrigeration and Environmental Control Systems

Fundamentals of Thermodynamics and Heat Transfer

Overview of the principles governing the operation of cooling systems, including the laws of thermodynamics, sensible and latent heat, and the mechanisms of heat transfer: conduction, convection, and radiation.

Vapor-Compression Refrigeration Cycle

Detailed explanation of the four key components and processes within the most common cooling method: compressor, condenser, expansion valve (or metering device), and evaporator. Includes discussions of refrigerant properties, enthalpy, pressure-temperature relationships, and the concept of superheat and subcooling.

Refrigerants

Classification and properties of various substances utilized as cooling agents, including historical options (e.g., CFCs, HCFCs) and modern alternatives (e.g., HFCs, HFOs, natural refrigerants like ammonia and carbon dioxide). Addresses environmental impact, ozone depletion potential (ODP), global warming potential (GWP), safety considerations (flammability, toxicity), and specific applications for each refrigerant type.

System Components

• Compressors: Types (reciprocating, rotary, scroll, centrifugal), operating principles, efficiency considerations, and maintenance requirements.
• Condensers: Air-cooled, water-cooled, and evaporative types; design considerations for heat rejection.
• Expansion Devices: Thermostatic expansion valves (TXVs), electronic expansion valves (EEVs), capillary tubes; their role in controlling refrigerant flow and pressure.
• Evaporators: Direct-expansion (DX) and flooded types; design considerations for heat absorption.

Psychrometrics and Air Handling

Principles of psychrometry, including properties of moist air (dry-bulb temperature, wet-bulb temperature, humidity ratio, enthalpy, specific volume). Discusses the psychrometric chart and its use in analyzing and designing air handling systems for cooling, dehumidification, and humidification. Covers air distribution methods, ductwork design, and the selection of appropriate air handling units (AHUs).

System Design and Control

Considerations for selecting appropriate system capacity, layout, and control strategies to meet specific cooling requirements. Includes discussions of zoning, thermostats, sensors, and programmable logic controllers (PLCs) used to automate and optimize system performance.

Energy Efficiency and Sustainability

Strategies for improving the energy efficiency and environmental sustainability of cooling systems, including the use of high-efficiency components, proper maintenance practices, demand-controlled ventilation, and alternative cooling technologies (e.g., absorption chillers, geothermal heat pumps).

Maintenance and Troubleshooting

Common maintenance tasks, diagnostic procedures for identifying system malfunctions, and troubleshooting techniques for resolving problems related to refrigerant leaks, compressor failures, control system issues, and other common faults.