Adiabatic cooling to decentralized air handling units

There are currently no compact decentralized ventilation systems combined with indirect adiabatic cooling, ideal for renovation tasks and new buildings. 

The project is to develop and long-term demonstrate/test a smal ler decentralized ventilation system with capacity up to 1600 m3/h, where a coated aluminum counter flow heat exchanger is combined with indirect adiabatic cooling. The size of the air handling-/cooling unit will be able to ventilate/cool a classroom or equivalent office environment. 

Combining the counter flow exchanger with indirect adiabatic cooling provides cooling without increasing indoor humidity, eliminating the operation and installation costs of traditional compressor cooling with refrigerants and high-power consumption. This makes the unit ideal for comfort cooling and legal use in public buildings, where traditional compressor cooling is banned. 
The entire unit is designed for low energy operation. The average dry basis temperature recovery reaches 82-85% efficiency during the heating period, thereby meeting the requirements of future building regulations. During the cooling period, a cooling of 6 - 8 ° C relative to ambient conditions is achieved by moisturizing filtered water on the return air. By using a compact water filter befare humidifying the return air, ordinary tap water can be used, even combined with rainwater. 

An important result of the project is water droplet size, orientation of heat exchanger in relation to gravity and adiabatic efficiency. lf the water drops receive positive "help" by gravity, the water drop size plays a mi nor role. This is the case if the heat exchanger has a marked tilt in relation to the horizontal. The entire surface area of the heat exchanger is wetted. 

On the ether hand, if the heat exchanger is more horizontal, the water drop size must be small, 20 mikrometers or lower. In this way, the transport of water droplets is main ly dominated by the vector motion of the air.