Refrigerants, also known as refrigeration working fluids and sometimes colloquially referred to as "snow" in southern regions, are the essential substances in refrigeration systems. They enable cooling through continuous circulation and phase changes.

How Refrigerants Work: Heat Absorption and Release

Refrigerants operate by absorbing heat at low temperatures and releasing it at higher temperatures. This process is vital for the cooling cycle in refrigeration systems:

1. Evaporation: In the evaporator, refrigerants absorb heat from the cooling medium (like water or air) and vaporize.
2. Condensation: In the condenser, they release heat to the surrounding air or water and condense back into liquid form.

Types of Refrigerants

Refrigerants are categorized based on their application and phase behavior:

1. Vapor Compression Refrigerants

These are substances that can liquefy at room temperature or lower, including:

• Freon: Derivatives of saturated hydrocarbons containing fluorine, chlorine, and bromine.
• Azeotropic Mixtures: Solutions made by combining two types of Freon in specific ratios.
• Hydrocarbons: Examples include propane and ethylene.
• Ammonia

2. Gas Compression Refrigerants

Gaseous refrigerants like air, hydrogen, and helium remain in a gaseous state throughout the refrigeration cycle.

3. Absorption Refrigeration Refrigerants

Binary solutions combine an absorbent and refrigerant, such as:

• Ammonia and water
• Lithium bromide (LiBr, a highly water-soluble white crystalline substance) and water

4. Steam Jet Refrigerants

Water is used as the refrigerant in these systems.

Key Technical Indicators of Refrigerants

The properties of refrigerants significantly impact the performance, safety, and efficiency of refrigeration systems. The main technical indicators include:

• Saturated Vapor Pressure
• Specific Heat
• Viscosity
• Thermal Conductivity
• Surface Tension

Since the 1960s, non-azeotropic mixtures have become prominent, particularly for the liquefaction and separation of natural gas. These mixtures enhance efficiency by achieving lower evaporation temperatures, increasing cooling capacity, and reducing energy consumption in single-stage compression systems.

Importance of Understanding Refrigerants

The choice of refrigerant directly affects the:

• Cooling Efficiency: Determines how effectively heat is transferred.
• Economy: Influences energy consumption and operational costs.
• Safety: Considers the toxicity, flammability, and environmental impact.
• Operational Management: Ensures reliability and ease of maintenance.

Understanding refrigerant properties is crucial for optimizing the performance and sustainability of refrigeration equipment.