Adiabatic cooling

Wellbeing and productivity

The quality of the air in rooms depends on various factors. The optimal humidity level for humans is between 40 and 60% rH and the temperature between 20 and 22 °C. The optimal humidity is crucial for preserving the health. It lowers the electrostatic voltage, prevents growth of bacteria and the spread of infections and microorganisms. Adiabatic high pressure cooling is not only economic in use itself, but also helps to reduce the monthly exploatation expenses. Along with Nessie® system, Danfoss company introduced a new product to the heating, air conditioning and ventilation market: air duct humidification and adiabatic cooling system.

The following facts are worth considering when choosing a humidification system:

  • reliable technology, used since over 20 years in direct air humidification systems
  • the system is based on adiabatic transformation- the heat of evaporation is drawn directly from humidified air
  • the system is safe in terms of hygiene- it does not require the use of any chemicals
  • it is designed to be used with tap water, softened or completely demineralised.


  • the total usage costs are much lower in comparasion to any other humidification systems on the market
  • very low power usage- around 4 watts per a liter of water
  • all of the elements have a high durability at minimal maintenance requirements.

The working principle of high pressure adiabatic cooling system

A pump of special construction compresses the water to a pressure of 75 bat. High pressure nozzles atomize the water, converting it to a mist that evaporates rapidly without the need of any additional energy. The transition is adiabatic in its principle and therefore the system is perfect to work with a crossover heat exchanger to cool the returning air and heat recuperation rotors. To achieve the most efficient water particle absorption, the system requires a path of minimum 1,5 m.

New installations

In case of new installations, the cost of a usage cycle of our systems are lowest in the market without any doubt. The section of the high pressure humidification air ducts allows a seamless integration with any kind of ventilation system. The humidifier is installed typically after the heater, to ensure the fastest water particle absorption. The drop of temperature due to adiabatic cooling effect may then be compensated by a secondary heater if needed. To acheive a desired humidity level we install a required number of high pressure nozzles, that we locate in an uniform way across the whole cross-section of the duct. The control of humidity output is acheived by turning single nozzles on and off. Using high pressure Danfoss valves even six increment regulation can be implemented, to acheive a desired cooling/ humidification level.

Modernisation of older systems

The traditional AHU control centers can be modified for use with high pressure humidification. In this case the existing air ducts, condensate tray as well as drainage can be used. The existing automated control unit can also be used in many cases. In case of the replacement of steam humidifiers to the ones working on adiabatic principles, the absorption path may be insufficient, what may require adding an additional section to the air duct. According to our experience, the adaptation to high pressure humidification from the one working on electric steam generating principle can lower the exploatation cost drastically.

Adiabatic cooling using high pressure humidification

In an analogical way to the high pressure humidifying, we use the adiabatic effect to cool the primary air. The temperature drop that is possible to acheive, which is around 10 °C is transfered through a certain type of rotor of heat recuperation or crossover heat exchangers into the inlet of ventillation device. Adiabatic cooling ststem can support the existing cooling system or even replace the air conditioning in certain, favorable conditions. Alternatively, it may allow to turn off the air conditioning in spring and autumn.

The possible temperature drop is a derivative of the air condition and can be red from the Molier chart. Every kilo of water that evaporates during an hour, has a cooling power of 640 watts. This means, that the system that has a 100 liters per hour output, corresponds to 64 kW cooling power, while consuming only 400 W of electrical energy.

For adiabatic cooling, treated water is not required. High pressure method is much more effective than the low pressure one.

General application

The margin conditions:

  • air capacity up to 5000 m3/h
  • humidifier capacity up to 50 l/h
  • the system can be fet by tap water, softened or entirely treated (VE, also at conductivity smaller than 1μS)
  • the optimal adaptation of the humidifier performance can be acheived through turning on and off groups of nozzles and the adjustment of the pressure through the Danfoss frequency converter
  • the number of nozzles that are installed is an outcome of humidifier efficiency and air duct geometry.

The delivery content

  • the set of high pressure pumps, along with control and regulation units, ready for plug-in
  • high pressure nozzles, with the diameter fitted for specific application
  • valves for the effective humidifier output regulation
  • installation fittings, pipes etc.

Planning, placement and installation

We support design offices as well as installation crews with our knowledge with regard to the location of specific elements of the humidifying systems as well as the measurement methods and the choice of ventillation components. To ensure the optimal exploatation conditions, we pay an especially close attention to possibly best location of high pressure nozzles. We are also competent to estimate the amortization parameters of new systems as well as additional equippment.