Optimized HVAC Air Distribution for Improved Air Quality Using CFD Analysis

Abstract

The energy consumption of Heating Ventilation and Air Conditioning (HVAC) systems accounts for a large proportion of global energy usage so even a small percentage of energy savings in these systems will account for important absolute value savings. One such saving can be realized by better designs as well as optimizing existing air distribution system. The indoor air quality (IAQ) is also greatly impacted by the air distribution system. In this work, the task of optimizing both the placement and the design of diffusers is investigated so acceptable Air Changes per Hour (ACH) numbers are attained with less energy consumption and good thermal comfort. The ANSYS Fluent software was used to optimize the design and placement of a newly developed diffuser. The proposed air distribution system is design to produce conditions like what one would experience while standing outside in a small breeze while experiencing perfect weather (room temperature, uniform air temperature distribution, air speed less than 2 m/s) [1]). This work is an extension of a previous study where a new diffuser design was proposed, which takes advantage of the Coanda effect [2]. The numerical analysis includes realistic models of a 9 × 9 × 3 m (width × length × height) classroom, which is occupied by students and a teacher. To be more realistic, it includes furniture, a door and windows. The simulated Heating Ventilation and Air Conditioning (HVAC) system complies with ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standards for acceptable air quality. This investigation proposes a template on how anyone can optimize the location and placement of the air diffusers while achieving both thermal comfort and good IAQ. While this work was inspired by the COVID-19 pandemic this is foreseen to be an important ongoing issue and could lead to future advances in HAVC system that improve IAQ and produce better thermal comfort with improved energy savings.