Title

Experimental evaluation of indoor air cleaning technologies and modeling of UV-PCO (photocatalytic oxidation) air cleaners under multiple VOCs conditions

Date of Award

2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical and Aerospace Engineering

Advisor(s)

Jianshun Zhang

Keywords

Indoor air, Photocatalytic oxidation, Air cleaners, VOCs

Subject Categories

Engineering | Mechanical Engineering

Abstract

The objectives of this study were to: (1) develop much needed test methods and datasets for determining the performance of various air cleaning technologies, and (2) improve the understanding and develop a simulation model for the performance prediction of ultraviolet photocatalytic oxidation (UV-PCO) devices under multiple volatile organic compounds (VOCs) conditions.

A ''pull-down'' test method and a ''constant-source'' test method were developed. Fifteen air cleaners, representing different technologies and types of devices, were tested with a mixture of representative VOCs in a full-scale chamber by using the ''pull-down'' method. Their initial performances were evaluated in terms of single-pass efficiency (η) and clean air delivery rate (CADR). Ozone generation (if any) was also monitored during the tests. Technologies evaluated include sorption filtration, UV-PCO, ozone oxidation, air ionization, and botanical air cleaning. Based on test results, the relative effectiveness of the available technologies tested, and the effect of product configuration and VOC properties on the VOC removal efficiencies were analyzed.

Individual compound vs. multi-VOC mixture tests on selected groups of compounds (aromatics, alkanes, aldehydes and a complex mixture of 15 or 16 VOCs) were conducted for a honeycomb UV-PCO reactor in a full-scale chamber and for an annular tube reactor in small-scale and mid-scale chambers. Results indicate that the multi-VOC interference effects became more pronounced as the number of VOC species or the total concentration of VOCs increased (e.g., in 16-VOC mixture test) and the UV-intensity decreased (i.e., from 14.35 mW/cm 2 to 1 mW/cm 2 for annular tube reactor). A computer simulation model and a "model-based" design procedure were developed for UV-PCO devices. The model consists of a one-dimensional fluid and concentration field model, a VOC reaction kinetics sub-model and a UV-irradiation sub-model. The intrinsic rate models and coefficients obtained from literatures or from independent kinetic experiments are needed as model inputs. The parametric and trend analysis was conducted to investigate the interference effects of other VOCs on toluene removal observed in full-scale experiments. The model developed is useful for investigating the multi-VOC interference effects (surface competition, byproduct generation, etc.) on the effectiveness of UV-PCO devices under various design and operating conditions.

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