Analyses of Thermal Comfort and Indoor Air Quality under Stratum, Displacement and Mixing Ventilation Systems

Abstract

The well-designed ventilation system ensures thermal comfort, indoor air quality and yield energy saving by avoiding excessive high values of Air Changes per Hour (ACH). Stratum ventilation has been a recently proposed air distribution system. The current CFD research investigates the performance of stratum ventilation in an office by using two values of the air change per hour, changing the exhaust location, and changing the supply location. In addition, the numerical model studied the displacement ventilation and mixing ventilation and their results were compared with that of stratum ventilation. The temperature, velocity distribution, CO2 concentration, ventilation effectiveness, effective draft temperature, and air diffusion performance index (ADPI) are discussed for all cases. The model was built and the mesh was generated using gambit ® 2.3.16 yielding 1.4 million cells. In addition, the model was simulated using Fluent ® 14. Model validation was done against experimental data using standard k-e model turbulence model with acceptable agreement to ensure the reliability of the Computational Fluid Dynamic (CFD). From the research, the air change per hour (ACH) has a large effect on the stratum ventilation performance, and it was found that using 5 ACH gives better conditions in terms of thermal comfort and indoor air quality. The supply location is recommended to be above the occupant height to ensure that, the air reaches the breathing zone well. From investigating the stratum, displacement and mixing ventilations, the stratum ventilation provides better velocity, temperature, CO2 concentration, ventilation effectiveness, and air diffusion performance index and ensures thermal comfort and indoor air quality.