Indirect evaporative cooling systems leverage a highly efficient heat exchanger to deliver 100% fresh air cooling without increasing humidity levels. The cool air generated by indirect evaporative coolers can rival the output of traditional refrigerated air conditioning, achieving temperatures below the outdoor wet bulb point, while consuming up to 80% less energy. Regardless of the scorching temperatures outside, indirect evaporative coolers maintain consistent energy consumption and continue to supply fresh &s cool air inside. This starkly contrasts with conventional refrigerated air conditioning units, which demand more energy as external temperatures gets higher.

The efficiency and cost-effectiveness of indirect evaporative cooling systems become even more evident during peak heat, showcasing an enhancement in performance with rising temperatures a direct opposite of how refrigerated systems operate. These systems are perfectly suited for applications such as Dedicated Outdoor Air Systems (DOAS), cooling for data centers, or providing comfort in various settings. Indirect evaporative coolers are versatile, supporting a broad spectrum of configurations across numerous industries, making them a flexible and sustainable cooling solution.


  • Cooling performance increases when air temperature rises.
  • Vastly reduce running costs (retrofit or new install)
  • No moisture added (dry air cooling)
  • 100% fresh air
  • Wide product range to meet application requirements.
  • Flexible design & engineering configurations
  • Can be retrofitted to existing air conditioning systems.

What Is Indirect Evaporative Technology?

a. Hot air enters the cooler

The process begins when hot ambient air is drawn into the cooler through the inlet. This is facilitated by a high-efficiency, electric fan that propels the air toward the cooler’s core.

The system lies in an air-to-air heat exchanger, which is structured with alternating dry and wet channels. The air flows exclusively through the dry channels, ensuring that it does not pick up any additional moisture during this phase.

Finally, the air that has traveled through the dry channels, now cooled and devoid of added moisture, is circulated into the building. This system ensures a continuous supply of fresh, cool air, making it an efficient solution for maintaining comfortable indoor conditions.

Upon exiting the dry channels, a portion of the conditioned air is redirected through the wet channels. Here, it undergoes evaporation and conduction, absorbing moisture and heat as the channels are constantly drenched in water. This process results in the expulsion of warm, moist air from the premises. It’s important to note that the membranes separating the dry and wet channels only allow for the transfer of heat, not moisture. Heat is transferred from the air in the dry channels to the air in the wet channels, effectively cooling the air in the dry channels without increasing its moisture content.

Indirect Evaporative Air Cooling

The concept of indirect evaporative air cooling is to cool using the principles of evaporation in a heat exchanger. The exchanger prevents moisture from being added to the product air stream (the air that is going into the building).

Cross section sketch shows an indirect evaporative cooler


This is a typical cross flow indirect evaporative cooler. The physical limitations of construction means that about 10 percent of the working air and 10 percent of the surface area perform about 70 percent of the cooling. In theory, the product air stream should be able to almost reach the wet bulb temperature without adding any water to the final product output. In practice, however, the effectiveness of these types of coolers is reported to approach 54 percent of the incoming air wet bulb temperature. This is largely due to limitations of geometry and manufacturing.

The Maisotsenko Cycle

The Maisotsenko Cycle uses the same wet and dry channels as described in the above indirect evaporative cooler but with a much different geometry and airflow creating a new thermodynamic cycle. It works by incrementally cooling and saturating working air, and benefiting from that cooling on the next increment.


This two-dimensional, simplified diagram of the Maisotsenko Cycle, shows how air is incrementally cooled by the continuous exhaust of heat followed by additional cooling.

The Maisotsenko Cycle uses the same wet side and dry side of a plate as described in the above indirect evaporative cooler but with a much different geometry and airflow, creating a new thermodynamic cycle. This cycle allows any liquid or vapor to be cooled below the wet bulb and toward the dew point temperature of the incoming working air. The Maisotsenko Cycle utilizes the psychrometric energy (or the potential energy) available from the latent heat in an evaporating gas. The Maisotsenko Cycle has been realized in a uniquely designed plate wetting and channel system which achieves optimum cooling temperatures within a few degrees of dew point for the product air. In addition, the working air is saturated with high enthalpy, accounting for the sensible heat loss in the product air.