Thermal comfort prediction of an underfloor air distribution system in a large indoor environment

• The location of the UFAD plays a vital role in the maximum change in airflow.
• Controlling the velocities can be effective for thermal environment with UFAD.
• Applicability of UFAD has been verified for a huge space with high ceiling.

The use of air distribution in HVAC has grown in popularity in buildings, and, to this end, the method chosen to deliver the conditioned air is strongly associated with increasing concerns about indoor environmental quality and its effect on occupants’ well-being. In the underfloor air distribution (UFAD) system, air is directly supplied to the base of the occupied zone, which causes temperature stratification from the lower to the upper layer of the zone. This flow pattern gives UFAD the advantage of using less energy while providing better thermal comfort than overhead air distribution (OHAD) system. This paper investigates the effectiveness of UFAD in a large space with a higher ceiling for various velocities of supply air and locations of diffusers at an identical air supply temperature. In particular, the goals of providing satisfactory comfort conditions for the occupants and its practical application to buildings have been examined. Computational fluid dynamics (CFD) software was used to simulate the thermal environment, along with the control variables for a huge theater space equipped with a UFAD system. Results show that the UFAD is capable of creating smaller vertical variations of air temperature and a more comfortable environment than conventional OHAD systems

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