Industrial refrigeration system and its thermodynamic operation

Industrial refrigeration systems are important in sectors such as food, pharmaceuticals, chemicals, and petrochemicals. Their main function is to remove heat from a process or space to maintain specific temperatures required by the operation. These systems are based on thermodynamic principles to extract thermal energy from one place and transfer it to another, using various types of refrigerant as the working medium.

In this article, we will discuss how these systems work, what types of refrigerant gases are currently used and how to effectively detect refrigerant leaks, a key aspect for the safety and efficiency of the process.

What is an industrial refrigeration system?

An industrial refrigeration system is a set of equipment designed to maintain controlled thermal conditions in production processes. The most commonly used thermodynamic cycle is the vapor compression cycle, which consists of four fundamental stages:

• Compression: Process by which the temperature and pressure of the refrigerant is increased.
• Condensation: Cooling and condensation of gas into liquid.
• Expansion: Decrease of the liquid pressure through an expansion valve.
• Evaporation: The refrigerant absorbs heat from the medium or process as it evaporates, and the cycle repeats.

The following is a detailed description of each of the stages that make up this refrigeration cycle:

Industrial compression refrigeration cycle

The industrial refrigeration cycle by compression is performed by circulating refrigerant through the four main components that make up the refrigeration system. That is, refrigerant is circulated through the compressor, condenser, expansion valve and evaporator, as shown in the following image¹.

Through these components of the industrial refrigeration system, the refrigerant gas performs a continuous thermodynamic cycle. This thermodynamic cycle allows heat to be extracted and dissipated to the outside.

Main components of the compression refrigeration system

1.Compressor: It is the equipment where the pressure of the refrigerant in gaseous state (such as NH₃, CO₂, HFC, among others) is increased, simultaneously raising its temperature. This compression allows the refrigerant to circulate continuously through the thermodynamic cycle. Depending on the system configuration and demand, different types of compressors are used: reciprocating piston, screw (rotary) and scroll, each with specific operating characteristics in terms of capacity, efficiency, and maintenance.

2. Condenser: The condenser is a heat exchanger responsible for dissipating to the external environment the thermal energy contained in the compressed refrigerant, which reaches this component at high pressure and temperature. During this heat transfer process, the refrigerant undergoes a phase change from a gaseous to a liquid state. This condensation phenomenon is essential to ensure the continuity of the refrigeration cycle and the energy efficiency of the system.

3. Expansion valve: The flow of liquid refrigerant from the condenser expands by decreasing the pressure through a physical restriction orifice), producing a significant reduction in temperature.

4. Evaporator: In this component, the refrigerant at low pressure and temperature absorbs thermal energy from the environment, promoting evaporation. During this process, the refrigerant changes phase from liquid to gas, returning again and thus closing the thermodynamic cycle.

Cooling system design configurations

These systems are designed according to the specific industrial application, can be open, closed or hybrid, each adapted to different operating, climatic and energy efficiency conditions.

Open cooling systems

The open system is characterized by exposing the cooling fluid (usually water) to the environment. Heat is transferred by direct contact with the air, as in cooling towers. It is efficient in hot climates, but is subject to evaporation losses, fouling and external contamination.

Evaporative cooling towers represent an example of these forced evaporative cooling systems; they are used in civil and industrial applications. The following video shows an animated illustration that explains in detail how these systems work. Source: Torraval Cooling S.L

Closed cooling systems

In contrast, the closed system circulates a fluid within a sealed circuit, without direct contact with air. It uses heat exchangers to dissipate thermal energy. This design minimizes fluid losses, reduces system contamination and offers greater thermal control, making it ideal for clean environments or where water is scarce or expensive.

Continuing with the classification, here is a video courtesy of Torraval Cooling SL, where we explain how it operates a closed cooling system.

Hybrid systems

The hybrid system combines the best of both approaches. It integrates a closed primary circuit that protects the process, with an open secondary system to maximize heat transfer to the environment. This configuration optimizes energy efficiency and allows for flexible operation in the face of seasonal or thermal load variations.

The selection of the appropriate system must consider variables such as the thermal profile of the process, water availability, environmental regulations and operating costs. A well-dimensioned and maintained design ensures reliable heat dissipation, prolonging equipment life and improving the overall efficiency of the production system.

Classification of current refrigerants

Freon CFC and HCFC refrigerants: For decades, chlorofluorocarbons (CFCs), such as R-12, and hydrochlorofluorocarbons (HCFCs), such as R-22, dominated the market. Although effective and safe in terms of toxicity and flammability, their use has been restricted or banned due to their high ozone depletion potential. Due to their environmental footprint and atmospheric persistence, they are considered unsustainable in the long term².

Synthetic FFC refrigerants: Hydrofluorocarbons (HFCs), such as R-134a, R-410a and R-32, have gradually replaced CFCs and HCFCs, do not affect the ozone layer, but do have a high global warming potential (GWP), which has led to stricter regulations and the search for more environmentally friendly alternatives. They offer good efficiency, low flammability and easy availability.

Natural hydrocarbons: Environmentally friendly alternative: Natural hydrocarbons, such as propane (R-290) and isobutane (R-600a), are widely used by the refrigeration industry due to their low environmental impact. They do not damage the ozone layer and their GWP is minimal. In addition to their energy efficiency, they are economically viable. However, they present flammability risks, so their implementation requires careful design and robust safety systems.

Other sustainable refrigerants: NH₃ and CO₂: Two highly efficient and sustainable options in industrial refrigeration systems are ammonia (NH₃) and carbon dioxide (CO₂). NH₃ is highly energy efficient and does not contribute to climate change or ozone depletion, but it is toxic. CO₂, on the other hand, is safe, cheap and environmentally friendly, although its high operating pressure requires specific materials and designs.

Economic impact of refrigerant leakage

Refrigerants, particularly modern synthetics, can be quite expensive. Added to this is the cost associated with locating and repairing the leak. Depending on the severity and location of the leak, this process could involve a large number of man-hours and potentially expensive parts or equipment.

The economic consequences of refrigerant gas leaks are considerable and multifaceted. One of the most immediate costs is the cost of replacing the leaking gas. In addition, there is the expense associated with locating and repairing the leak, which involves specialized labor hours and expensive components.

In addition, a leaky system loses efficiency, resulting in higher energy consumption and higher operating costs. Downtime can also occur, severely affecting sensitive sectors such as food and data centers. Hence the importance of monitoring cooling system performance on a continuous basis.

Methods to detect refrigerant leaks

Refrigerant leaks are one of the biggest challenges in the operation and maintenance of these systems. Not only do they reduce efficiency, but they can pose a risk to personnel and the environment. Modern detection methods include:

• Electronic sensors: detect the presence of specific gases by means of conductivity variation or infrared response.
• Ultrasonic equipment: locate the sound of the leak under high pressure conditions.
• Reactive foam or bubbling: simple but effective method in small installations.
• Continuous monitoring systems: integrated into SCADA or IoT systems for immediate notifications and traceability.

Early leak detection helps maintain system efficiency, avoid unplanned shutdowns and comply with environmental regulations.

Function of refrigerant gas detectors

Refrigerant gas detectors are indispensable devices nowadays, especially considering the growing importance of industrial safety, environmental protection and operational efficiency.

Their function is to identify the presence of refrigerant gases in the environment, allowing the early detection of leaks that, if left unattended, can have serious consequences for people, the environment and the company’s economy.

Refrigerant selection and maintenance

The choice of coolant type should not be taken lightly. Factors such as thermal efficiency, environmental impact, cost, material compatibility and process conditions are decisive.

Detecting and preventing refrigerant gas leaks is an essential task for any industry using these systems. Investment in suitable detectors and knowledge of their operation represents a strategic measure to protect people, assets and the environment, as well as to ensure the sustainability and profitability of operations.

Conclusions

Industrial refrigeration systems are important components in refrigeration processes, and their efficiency depends largely on the type of refrigerant used, leakage control and maintenance.

As environmental regulations become more stringent, the transition to greener refrigerants and smarter systems will be not only desirable, but imperative.

Industrial thermodynamics provides the theoretical basis and fundamental principles to analyze, control and optimize energy and material processes in industry for innovation and sustainability in the productive sector.

References

1. Sonntag, R. E., Borgnakke, C., & Van Wylen, G. J. (2003). Fundamentals of thermodynamics (6th ed.). Wiley.
2. Hamdy, M., Askalany, A. A., Harby, K., & Kora, N. (2015). An overview on adsorption cooling systems powered by waste heat from internal combustion engine. Renewable and Sustainable Energy Reviews, 51, 1223–1234. https://doi.org/10.1016/j.rser.2015.07.034