Politecnico di Torino - Corso Duca degli Abruzzi, 24 - 10129 Torino, ITALY

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AdsorbementAir humidifierHeat recovery


A system for carrying out air humidification and heat recovery in air conditioning units. It uses adsorbent substances, such as silica gel or zeolites, to transfer energy and water vapour between the extracted air and the air that flows into a building. The device works both as a conventional enthalpy heat recovery unit and as an active humidifier of the fresh air flow rate, replacing conventional adiabatic or water vapour humidifiers

Technical features

Adiabatic (sources of possible bacterial contamination) and isothermal (which require high-temperature heat sources) systems currently used require a connection to a water supply and a drain for excess water that is not fed into the air stream (or used for periodic flushing of the system). In the absence of the water treatment systems, maintenance work is more frequent and the life of the system is thereby reduced. The proposed air humidification system exploits the properties of adsorbents for the air conditioning of buildings. The system uses two fixed beds (or alternatively a desiccant wheel), made up of adsorbing substances, which are periodically switched in order to remove water vapour from the air stream that is extracted from the air-conditioned environment, and subsequently to humidify the fresh air stream. The invention also includes a heat exchanger and an air heating coil. The device, through suitable variation, can operate both through passive operation as a simple heat and steam recuperator between the two air flows, as well as a true humidifier by active operation.

Possible Applications

  • Mechanical ventilation units in the residential sector;
  • Air treatment units in the tertiary sector;
  • Humidification and air treatment systems for industrial plants;


  • Lack of liquid water leads to lower risk of contamination;
  • Lack of connection to a water supply (and possible water treatment system) and drainage;
  • Low energy consumption;
  • Integration of steam recovery and humidification into a single component;