On Decentralized Air-conditioning for Hot and Humid Climates: Performance Characterization of a Small Capacity Dedicated Outdoor Air System with Built-in Sensible and Latent Energy Recovery Wheels

Abstract

In large commercial buildings facing high cooling loads, conventional heating, ventilation, and air-conditioning (HVAC) systems are typically based on the use of one, or few, large-capacity air handling units (AHUs) to supply conditioned air throughout a centrally-managed air distribution network. The alternative concept of ‘decentralized’ HVAC typically entails the deployment of multiple, small capacity fan coil units (FCUs) operating as dedicated outdoor air systems (DOAS) and located closest to the individual thermal zones they must condition. For this study, the authors commissioned the development of a small capacity, packaged cooling coil with built-in enthalpy recovery devices. This customised unit, intended for use in a cooling-only, decentralized DOAS configuration, includes: two rotary wheels for sensible and latent energy recovery, a single cooling coil, and both supply and exhaust fans. The unit has been intended for building air conditioning use in the Singaporean climate. This paper provides energy performance data based on laboratory testing of the unit with independent control of the following variables: outdoor air conditions, return air conditions, and chilled water flow rate. It is intended that empirical data offered by this study can be adapted for use in future building energy models of decentralized HVAC systems.