HVAC dehumidification systems for thermal comfort: a critical review

This paper, on the basis of the main literature indications, deals with moisture control in buildings during the summer season; so, the dehumidification of the air is analysed. Dehumidification is considered as a key feature of HVAC systems for thermal comfort. Initially, the principles of mechanical and chemical dehumidification are shown. The first one utilises mechanical means—compression refrigeration systems—to cool the air and so to dehumidify it; the latter removes the water vapour from the air by transferring it towards a desiccant material (adsorption or absorption). In the mechanical dehumidification field, a proper control of ambient temperature and humidity can be obtained by means of an air handling unit (AHU) which treats outside air alone, while recirculating air is treated by a simple cooling coil. Various possible AHU configurations are examined. Afterwards, HVAC systems for a theatre and for a supermarket are analysed. The use of hybrid systems with desiccant wheel for these applications has provided the following main results: remarkable savings in operating costs and higher plant costs (a simple payback time of 2–3 years for supermarket); a notable reduction of the power electric demand; a better control of ambient humidity.