By combining a desiccant rotor, a heat-recovery rotor and an evaporative cooling unit the temperature and humidity in an air-stream can be controlled. Such a system offers an alternative to conventional air-conditioning based on compressor, evaporator and condenser. Desiccant cooling does not use refrigerants and the primary energy source needed to run it is anything that can accomplish a moderate increase of the temperature of an air-stream for reactivation of the desiccant rotor.
Air to be treated is first passing the desiccant rotor where moisture is picked up. This causes a temperature increase of the air so next step is to cool the dry air down in a sensible heat-
recovery rotor. In a final step the temperature is brought down in an evaporative cooling unit. In such a unit the air is put in close contact with water. Some water will evaporate, taking the energy for evaporation from the dry air. Depending on the condition of the air entering the desiccant cooler the three steps will bring the temperature down by 10-14°C.
A desiccant cooling system needs a second airstream, usually the exhaust air from the building it serves with cool supply air, to take care of the heat created by the dehumidification and to carry the energy needed to reactivate the desiccant rotor. The exhaust air can first be brought through an evaporative cooling unit before passing the sensible heat-recovery rotor to pick up the heat from the supply air having passed through the other half of the heat-recovery rotor. It will then pass through a heater bringing it up to typically 55-70°C before entering the desiccant rotor. Moisture will be given off from the desiccant rotor to the hot air and the rotor is now reactivated and able to dehumidify the supply air.
The desiccant cooling technology is above all competitive when a low cost energy source is available. Areas with district heating often offer cheap energy in the warm season when the demand for heating is low. Also in industry there can be waste-heat or steam available at a low cost.
The fact that the system also does heat-recovery in the cold season makes it in particular interesting where the climate demand both functions to keep comfortable conditions in the buildings.
Products from ProFlute for desiccant cooling