In the face of rising global temperatures and the challenges posed by global warming, traditional cooling methods – often energy-hungry and unsustainable – are no longer sufficient to meet the growing needs of business and industry. In this context, indirect adiabatic cooling is positioned as an innovative, energy-efficient solution, capable of reconciling employee comfort, energy savings and respect for the environment. By exploiting the principles of water evaporation and heat exchange, these indirect adiabatic coolers provide effective temperature control without adding humidity to the air. This article looks at the operating principles, benefits and applications of indirect adiabatic cooling, illustrating its essential role in modern building climate management.
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Understanding adiabatic cooling: direct and indirect
Direct adiabatic cooling
Direct adiabatic cooling is a process that exploits the evaporation of water to reduce air temperature. In this system, warm air is drawn through a wet adiabatic exchanger, where the water evaporates, absorbing the air’s sensible heat and reducing its temperature. This type of cooling is particularly efficient and energy-saving, and is often used to cool air in large open spaces and in the tertiary sector.
However, cooled air leaving a direct adiabatic cooler has a higher humidity level, as sensible heat is converted to latent heat through evaporation, increasing the humidity level. This can lead to discomfort, particularly in enclosed spaces, and can also pose specific challenges, especially in buildings where hygrometric control is essential for optimal equipment operation.
Indirect adiabatic cooling
Indirect adiabatic cooling is a technology that enables outdoor air to be cooled while maintaining an appropriate level of humidity. This system relies on heat exchange between incoming warm air and exhaust air, without direct contact with water. In this process, the warm air is directed to a heat exchanger. This heat exchanger is made up of two types of channels: dry channels and wet channels. The air flows through the dry channels, which are insulated from water, while the wet channels are soaked in water. When air extracted from the building passes through the wet ducts, evaporation of the water cools the air.
This cooling creates a temperature differential, allowing the outside air circulating in the dry channels to cool by heat exchange, without coming into direct contact with the water. The resulting cool, dry air is then blown into the building, while the warm air is exhausted to the outside. This system provides cooling that distributes cooled fresh air without adding excessive humidity; particularly suitable for cooling sensitive environments such as data centers, some factories, laboratories and hospitals.
Advantages of adiabatic cooling
Substantial savings on energy costs
The indirect adiabatic cooling system stands out for its economic efficiency. Consumption is based exclusively on ventilation and water requirements, resulting in significant energy savings compared with other cooling systems. What’s more, operating and maintenance costs are significantly lower than those of traditional air-conditioning systems, such as heat pumps or air conditioning. Initial installation costs are lower overall, and the need for maintenance is minimized, making this solution a wise and advantageous choice over the long term.
Improved air quality
In addition to its economic benefits, the indirect adiabatic system plays an important role in improving indoor air quality. By creating a temperature differential between the air blown into the building and the outside air, it ensures pleasant thermal conditions for occupants. This process also ensures constant renewal of the air, which is filtered and cooled. This is essential in environments where clean, renewed air is essential, such as hospitals and laboratories.
An energy-efficient solution for industry
Global warming is leading to an increase in the number of heatwaves, with heat waves becoming more intense, more prolonged and more frequent throughout France. These conditions lead to overheating in buildings, which can worsen health conditions and cause significant productivity losses.
What’s more, rising energy costs and the increasing scarcity of energy are prompting companies to look for alternatives to traditional air conditioning, which is often synonymous with exponential power consumption. Professionals need to equip themselves with cooling methods that are not only more efficient, but also consume less energy and are less harmful to the environment. Indirect adiabatic systems offer energy-efficient, natural and simple solutions for business air cooling.
Selection and applications
When to use an indirect adiabatic cooler?
While direct adiabatic cooling is particularly suited to large, open industrial and service premises, the adiabaticindirect chilleris ideal for applications requiring more precise control of humidity and temperature. It is suitable for self-contained cooling of buildings that require fresh air, but have a high heat input.
It can also be used in conjunction with air handling units (AHUs), as a pre-cooler for fresh air, ensuring that the treated air is not humidified. The chiller can also be used as a supplementary cooling solution, supporting an existing air-conditioning system to compensate for additional heat input.
Industries requiring indirect adiabatic cooling
- Commercial buildings: shopping centers, offices, schools, hospitals – improving air quality and reducing energy costs.
- Industries: factories, workshops, data centers – maintain a constant temperature without increasing humidity.
- Public spaces: sports halls, places of worship, leisure areas – thermal comfort essential for large crowds.
- Offices and open spaces: improving air quality and comfort.
Application examples
- Data centers and telecommunications: computer rooms, server rooms, technical premises.
- Offices: workspaces, open spaces.
- Public authorities: schools, universities, crèches, retirement homes.
- Industries: factories, workshops, pharmaceutical sector.
- Hotels and restaurants
- Sports and leisure centers: multi-purpose halls, fitness centres
Mistaken ideas
Indirect adiabatic cooling is not effective in hot, humid environments. Wrong.
In hot, humid regions, it’s true that the efficiency of an indirect adiabatic cooler can be reduced, as the air is closer to its water saturation point. This means that the delta T (temperature difference between incoming and outgoing air) is lower, resulting in a higher discharge temperature. However, this does not mean that the system is inefficient. To compensate for this limitation, the air exchange rate can be increased, i.e. a greater volume of air can be circulated through the system. This ensuresoptimum working conditions.
Indirect adiabatic cooling is effective in very hot, dry environments…. but it does have certain limitations.
Under these conditions, dry air promotes efficient evaporation, enabling significant cooling without adding humidity. However, when temperatures become extremely high, an indirect adiabatic cooling system may not be sufficient. Although the air is cooled, it may still remain relatively warm. This is why a two-stage cooling system (indirect followed by direct) is often more appropriate in these cases. This method optimizes cooling: the first, indirect stage reduces the air temperature without humidity, while the second, direct stage further reduces the temperature by adding a small amount of humidity, thus ensuring a comfortable indoor climate.
There is only one type of indirect adiabatic cooler. False
In fact, there are several types of indirect adiabatic cooler, each offering different humidification and cooling methods. For example, evaporation can be external, upstream, or even simultaneous with the heat exchanger. The typology and sizing of an indirect adiabatic cooler in a building is based on the expertise of the suppliers of these technologies.
