Ammonia refrigeration is a widely used and effective technology for cooling and preservation across various industries. This system employs ammonia as a refrigerant to absorb heat from specific spaces or products and then dissipate it into the environment.

The concept of ammonia refrigeration dates back to the 19th century, with its widespread adoption occurring in the early 20th century. Over the years, the technology has advanced considerably, making ammonia refrigeration systems more efficient, safer, and environmentally friendly.

Today, ammonia refrigeration is extensively utilised in sectors such as food processing, cold storage, and chemical manufacturing due to its high efficiency, cost-effectiveness, and eco-friendliness. With the growing demand for sustainable and energy-efficient cooling solutions, ammonia refrigeration is increasingly becoming the preferred choice for many businesses.

How Does Ammonia Refrigeration Work?

Ammonia refrigeration leverages the thermodynamic properties of ammonia to transfer heat from a designated area or product to the environment. This process involves several key components that work together to complete the refrigeration cycle.

Ammonia, a natural refrigerant, has excellent thermodynamic characteristics, such as a high latent heat of vaporisation and a low boiling point. The refrigeration process begins with the evaporation of liquid ammonia, which absorbs heat from the target space or product. The resulting gaseous ammonia is then compressed, raising its temperature and pressure, and moved to the condenser, where it cools and condenses back into a liquid. The liquid ammonia is subsequently expanded through an expansion valve, lowering its temperature and pressure, and the cycle restarts.

Components of an Ammonia Refrigeration System

An ammonia refrigeration system has several components that work in unison to provide efficient cooling. The continuous refrigeration cycle involves the movement of ammonia through four primary components: the evaporator, compressor, condenser, and expansion valve.

The 4 Main Components

Evaporator: Absorbs heat from the space or product by evaporating liquid ammonia.

Compressor: Increases the pressure and temperature of gaseous ammonia, then transfers it to the condenser.

Condenser: Cools and condenses gaseous ammonia into liquid form, releasing absorbed heat.

Expansion Valve: Reduces the pressure and temperature of liquid ammonia before it returns to the evaporator.

Types of Systems and Their Configurations

There are three main types of ammonia refrigeration systems:

Single-Stage Systems: Utilise one compressor to maintain a single refrigeration temperature.

Multi-Stage Systems: Employ multiple compressors and evaporators to maintain different refrigeration temperatures.

Cascade Systems: Combine two separate refrigeration systems, one using ammonia and the other a different refrigerant, to achieve extremely low temperatures.

Control and Monitoring Systems

Ammonia refrigeration systems incorporate various sensors and valves for process control and monitoring. The primary control and monitoring components include:

• Temperature Sensors: Monitor and control the temperature of the refrigerated space and the refrigerant.
• Pressure Sensors: Monitor and control the refrigerant pressure throughout the system.
• Control Valves: Regulate refrigerant flow, managing the temperature and pressure within the system.

Ammonia poses significant hazards to human health, as it is corrosive to the skin, eyes, and respiratory system. Exposure to concentrations of 300 parts per million (ppm) is immediately dangerous to life and health. Ammonia is flammable when present in air at concentrations ranging from approximately 15% to 28% by volume. Accidental releases of ammonia can have severe consequences for both workers and the general public.

When ammonia is stored under pressure, the risk of exposure increases dramatically, as larger quantities can be released rapidly into the atmosphere. Due to its high toxicity, stringent safety measures are essential during the handling, filling, and maintenance of ammonia systems, necessitating the involvement of trained engineers.

Inhalation of ammonia at concentrations of 300 ppm (0.03%) is life-threatening and poses an extreme health hazard, with lethality occurring at levels above 500 ppm. Even at much lower concentrations, an average healthy individual can detect the distinct odor of ammonia, typically at levels of 17 to 20 ppm.