Experimental parametric study on the temperature distribution of an underfloor air distribution (UFAD) system with grille diffusers

The underfloor air distribution (UFAD) system has attracted great attention from many researchers and designers due to its advantages of energy conservation and air quality enhancement. In a UFAD system, the conditioned air is directly delivered to the occupied zone, causing thermal stratification from the lower zone to the upper zone. This flow pattern provides better distribution of temperature and airflow than the overhead air conditioning system for its improved ventilation and indoor air quality at the breathing level. This paper focuses on a new and unconventional way of conditioning the interior zones in UFAD buildings by employing large-area grille diffusers in a full-scale experimental room. The influences of swirl diffusers and grille diffusers on the temperature distribution in the UFAD system are compared. The effects of supply air temperature, airflow rates, and number of diffusers on the performance of the UFAD system with grille diffusers are discussed in details. The results show that the large-area grille diffusers can create stratification comparable to the more traditional swirl diffusers and thus provide an alternative way of configuring a UFAD system.