Session: 08-07-01: Energy Systems Components

Paper Number: 95730

95730 - Optimized HVAC Air Distribution for Improved Air Quality Using CFD Analysis 

Engineers and architects, school administrators, and equipment manufacturers understand that the quality of student educations and the quality of student environment are related to one another. The Heating Ventilation and Air Conditioning (HVAC) systems plays a crucial role in the quality of such environments. While a lot of effort was put into better HEPA filtration, changes in the air distribution system was mostly not considered, which is understandable, since it is a somewhat challenging problem and would require more resources. Even with better filtration and increased air velocity many of the spaces still contain dead zones or have noisy air diffusers. Thermal comfort also decreases. Microclimate metrics include air temperature, velocity, humidity, mean radiant temperature, etc. All of these have a significant impact on the indoor environmental quality which is expressed by thermal comfort.

Buildings accounts for over 40% of global energy consumption, with HVAC systems accounting for nearly half of that in developing nations. Air conditioning accounts for around 12% of all household energy expenditures in the United States. In 2018, primary energy consumption in the United States hit 101.3 quadrillion BTU, up 4% from 2017. Therefore, even perceived small energy savings at local level would have an important impact at the global level. One such savings can be realized by optimizing the HVAC air distribution system.

Air diffusers are an essential component of any HVAC system, and the level of comfort of the occupants of any ventilated space is influenced by their placement and design. Nevertheless, air diffusers did not receive a lot of attention lately mostly because of the perceived small savings that are obtained by optimizing their placement and design. One of the recommendations to improve the indoor air quality (IAQ) during the pandemic was to increase the air circulation, which translates in an increase in the Air Changes per Hour (ACH) parameter. This implies increase air speed with existing diffuser designs which requires more energy consumption and can potentially decreases the thermal comfort with unacceptable air speeds, noise and vibration. In this work we propose optimizing both the placement and the design of diffuser so better ACH numbers are attained with less energy consumption and good thermal comfort.

The optimization of diffuser placement and design was done using ANSYS Fluent. This work is an extension of a previous study where we proposed a new diffuser design that takes advantage of the Coanda effect. The model includes realistic building inhabitants, dimensions, and HVAC parameters. The simulated classroom is 9 × 9 m with 3 m height. The distance between students is 6 ft as per the COVID-19 recommendations. To be more realistic, it includes furniture, a door and windows. Each human is represented by a (0.5 × 0.25 × 1) m cubic body and a (0.15 × 0.15 × 0.2) m cubic head and a mouth opening. The simulated HVAC system complies with ASHRAE standards for acceptable air quality. The HVAC system consists of multiple supply and outlet diffusers distributed within the room. The CFM (Cubic Feet per Minute) that ensures suitable thermal comfort and better ACH numbers was taken into consideration, and the impact of opened/closed windows while the HVAC system is running is investigated as well.

Thus, the main goal of our work is to improve both the indoor air quality in a classroom as well as the thermal comfort of its occupants. Our investigations makes several important contributions, namely, demonstrates how one can optimize the location and placement of the air diffusers as well as the design of the diffuser themselves. We are also looking into how a portable air purifier, or placing a box fan in a window would improve the IAQ and optimizing their size, number, and placement in the classroom. While this work was inspired by the COVID-19 pandemic this is important while considering future improvements in the IAQ and better thermal comfort with improved energy savings.

Presenting Author: Hussein Kokash Wayne State University

Presenting Author Biography: Hussein Kokash worked as a Research Assistant and he has been a PhD student candidate in the<br/>Mechanical Engineering Department at Wayne State University since 2020. He is part of the Fluid<br/>Dynamics Research Laboratory (FDRLab) at Wayne State University, a research lab that focuses<br/>on a comprehensive understanding of phenomena and problems encountered in fluid dynamics.<br/>Hussein research interest lies in the field of flow analysis in general, with emphasis on<br/>computational fluid analysis. He earned a M.S. in Mechanical Engineering from the University of<br/>Michigan in 2020 and B.S. in Mechanical Engineering from Hashemite University, Jordan in 2011.<br/>Hussein acquired a solid background in the field of mechanical engineering through working in the<br/>industry field for close to 10 years which empowered him with experience and knowledge and<br/>further raised his interest in research and development in this field.

Authors:

Hussein Kokash Wayne State University
Mihai Burzo University of Michigan-Flint
Gbemeho Agbaglah Wayne State University
Fardeen Mazumder University of Michigan - Flint