| Generally numerical simulation via Computational Fluid Dynamics (CFD) is being
utilized to estimate room air distribution of industrial and commercial buildings due to the easy
access of high-performance computing resources. For example, CFD can be used to predict
indoor airflow, thermal comfort, and carbon dioxide dispersion. Consequently, CFD has become
a significant design and analytical technique for analyzing ventilation inside any building to
optimize air diffusion because it is crucial for maintaining good indoor air quality, comfort, and
energy efficiency. For this study, the MCERC Room 113 with the original ceiling-based mixed
ventilation, was modified to underfloor air distribution and displacement ventilation air
distribution using CFD analysis. The CFD result for ceiling-based mixed ventilation was
evaluated with measured experimental temperature data to develop and identify the better
turbulence model between standard k-epsilon and k-omega shear stress transport (SST). The
standard k-epsilon model was selected as a better model with a lower Root Mean Square Error
(RMSE) of 0.97 than k-omega shear stress transport with RMSE of 1.93. The standard k-epsilon
turbulence model was used to compare the performances of different ventilation strategies
[mixed ventilation (MV), underfloor air diffusion (UFAD), and displacement ventilation (DV)]
using the air diffusion performance index (ADPI). With the ADPI performance index, UFAD
outperformed MV and DV ventilation strategies by 32 to 41%. At varying airflow rate in steps of
±100 CFM, UFAD continued to outperform the other ventilation strategies. Given that the ADPI
values for the three ventilation strategies exceeded 80%, the ADPI American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE) standard, at the various airflow rates
in the occupied zone, the three ventilation strategies allow for good occupant comfort. However,
the head region in the UFAD system satisfied the Effective Draft Temperature (EDT) criteria
(used for the evaluation of air distribution performance) compared to MV and DV. Even though
ventilation strategies are recommended based on air diffusion performance in occupied zones,
UFAD performed well in both occupied zones and the whole room. Our findings support the
superiority of the UFAD system's design strategy for this room and may be applicable in more
general building scenarios.
Keywords: mixed ventilation, displacement ventilation, underfloor air diffusion, effective draft
temperature, and occupied zone. |