Effect on the Performance of Underfloor Air Distribution(UFAD) system under different supply air parameters

Underfloor Air Distribution (UFAD) systems have received increasing attention during the past decades due to thermal stratification and energy saving potential over conventional mixed air conditioning system. Different supply air parameters have significant impacts on the UFAD system performance. In this study, experimental study and energy simulation software EnergyPlus were used to investigate the UFAD performance in a full size experimental room. The distance between diffusers and human, supply air temperature and velocity were discussed. The orthogonal experiments were employed to discuss the effect of supply air parameters on the temperature distribution, thermal comfort and indoor air quality (IAQ). By the analysis, the most important factor is the distance between diffusers and human. Furthermore, the preferable supply air parameters are suggested by means of controlling parameters. The results show that better thermal stratification and thermal comfort can be achieved when the distance between the swirl diffusers and human is 0.7m, the Supply Air Temperature (SAT) is 18-20°C and the Supply Air Velocity (SAV) is 1.2-1.5m/s. Another contribution of this paper is that the energy consumption of UFAD system is calculated by EnergyPlus. The calculation shows that the satisfied thermal stratification and prominent energy saving can be achieved simultaneously by using reasonable supply air parameters, such as the SAT is 18°C and the SAV is 1.2m/s.