Zhenlei Liu

Date of Award

9-20-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical and Aerospace Engineering

Advisor(s)

Jianshun Zhang

Second Advisor

Dacheng Ren

Subject Categories

Engineering | Mechanical Engineering

Abstract

This study presents a comprehensive investigation into volatile organic compounds (VOCs) in indoor environments, with a particular focus on their primary and secondary emission rates. Despite many previous experimental and modeling studies on VOCs, a significant gap remains in applying laboratory findings to actual building environments. This study bridges this gap by quantifying primary and secondary pollutant loads in an indoor environment, utilizing both existing models and novel approaches to estimate model parameters. In terms of primary emissions, the existing models are well-developed, but there is a need for determining essential model parameters for practical application in real buildings. This study proposed a novel method for estimating the material-to-air partition coefficient of VOCs based on the similarity between moisture and VOC adsorption. This approach employs the Brunauer–Emmett–Teller (BET) models to extract pertinent physical properties of building materials from moisture sorption isotherms, including specific surface area, porosity, and adsorption energy of water. These properties are then used to estimate monolayer adsorption capacity and adsorption energy accounting for the similarity and difference between VOCs and water vapor in sorption and transport in porous medium. Regarding secondary emissions, experiments were conducted in a test room to characterize emissions, particularly from hydrogen peroxide-based surface disinfection solutions (potential sources of hydroxyl radicals), and electronic air purifiers (sources of both hydroxyl radicals and ozone). An indoor VOC mixture was simulated in the test room, and emission rates of hydrogen peroxide, hydroxyl radicals, and ozone were obtained. These data were used in the IAQ model developed in this study that accounts for the effect of both the secondary and primary emissions. A model focused on indoor air quality concerns for secondary emissions as well as primary emissions was developed. This model, a simplification of existing models, concentrates on stable and detectable VOCs originating from indoor ozone and hydroxyl radical-initiated chemical reactions. Despite its simplification, the model capably represents primary and secondary emissions in the test room. Its reduced computational load makes it suitable for scaling up to the building level or integrating with building control systems. In conclusion, this study advances the understanding of VOCs, especially regarding their emissions, adsorption processes, and secondary emissions. The results contribute the development of a VOC-building material database and provide practical tools to predict VOC pollution load from primary and secondary emissions, which are essential IAQ design and control in buildings.

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Open Access

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