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Title:Modeling contaminant spread and mitigation in the indoor environment
Author(s):Meng, Lingjun
Director of Research:Jacobi, Anthony M.
Doctoral Committee Chair(s):Jacobi, Anthony M.
Doctoral Committee Member(s):Bullard, Clark W.; Hrnjak, Predrag S.; Wang, Xinlei
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Indoor Air Quality
Contaminant mitigation
Pressurization protection
Crack estimation
Protection factor
Abstract:Experimental and modeling efforts, using a pilot-scale testbed and multizone modeling, are undertaken to develop filtration and ventilation strategies aimed at improving indoor air quality (IAQ). As part of this effort, a model is developed to effectively estimate crack areas of the multizone testbed. The model is divided into two sub-approaches: one approach is to assume the same crack area for the same type of opening and determine them by minimizing the sum of the squares of relative error between the calculated and experimental ventilation rates for the whole facility; the other is to assume that the crack areas are independent of each other and a similar least-squares minimization is applied to determine these crack areas zone by zone. A comparison of the two approaches shows that both can provide satisfactory results, and the latter approach is preferred, because it provides more flexibility and detail. Ventilation systems are explored using multizone simulations. The model results suggest a distributed unbalanced ventilation system is preferred for maintaining IAQ, because 1) it can provide positive pressure difference across the building envelope to prevent exterior contaminant infiltration; and 2) some contaminated indoor zones can be “isolated” from adjacent ones by adjusting the relative pressure differences. Realistic particle distributions typical to a particular contamination threat of interest are considered, and an acoustically enhanced impaction (AEI) filtration device is investigated together with other filters. The protection factor (PF, a ratio of concentration integrated over time in the ambient to that indoors) is chosen as a performance metric. A PF-oriented evaluation framework has been established such that ventilation system/strategy (or filter) comparison in terms of IAQ enhancement is straightforward. For instance, 16 filtration schemes are compared to identify preferred ventilation and filtration strategies. For the indoor environment, a highly efficient outside air (OA) filter is recommended, but a recirculated air (RA) filter is relatively much less effective. For vestibule protection, a stand-alone balanced system with 100% RA filtration is recommended. The AEI device can be an alternative to a HEPA filter when the ambient contamination level is low to moderate. Extension of an existing analytical steady-state PF model is undertaken to demonstrate the advantages of pressurization protection of buildings over non-pressurization protection. The analytical PF model can be used to determine the ventilation flow rate and filter efficiency at a specific PF level and guide the vestibule door operation. It is found that the minimum closing period of the vestibule interior door typically should be 20 minutes to protect the room.
Issue Date:2014-05-30
Rights Information:Copyright 2014 Lingjun Meng
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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