Document Type

Dissertation

Date of Award

Fall 2017

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical and Industrial Engineering

First Advisor

Chao Zhu

Second Advisor

Zhiming Ji

Third Advisor

Chao-Hsin Lin

Fourth Advisor

I. Joga Rao

Fifth Advisor

Eon Soo Lee

Abstract

Expiratory droplets from human coughing in an air-conditioned environment have always been considered to be potential carriers of pathogens, responsible for respiratory disease transmission. The air movement/circulation and ambient conditions such as pressure and temperature are all key factors of aerosol transport. To study the transmission of disease by human coughing in a depressurized air-conditioned chamber, there are many technical challenges, including the following: 1) the study of simulating human coughing; 2) the collection of aerosol generated by coughing; 3) the CFD simulation of coughing-induced aerosol transport in an air-conditioned chamber; 4) the validation of such a CFD simulation by experiment; 5) the depressurization of the air-conditioned chamber and 6) the mechanistic study of droplet evaporation. Accordingly, this work provides the following to study the aerosol transmission in a depressurized chamber: a transient repeatable bimodal cough simulator is designed and built; a chamber with air-conditioning and circulation is built; a breathing simulator is designed and built as well as measurement validation is done; a full field three dimensional CFD simulation of the aerosol transport in the air-conditioned chamber is established; a droplet evaporation model is built as well as the technology of depressurization for an open flow system.

The cough and breath simulators are designed for purposes of aerosol generation and collection. The CFD simulation is used to calculate various conditions of the aerosol transport and deposition, especially the effect of the air movement/circulation and ambient conditions. The experiment chamber is for validation of CFD simulation. The droplet evaporation is built to better simulate one of the most important factors for the droplets, the evaporation effect, and can be implemented into the CFD model by User-Defined Functions. The depressurization technology is to provide the vacuum environment for the experiment air-conditioned chamber. This study also seeks a breakthrough of a heat transfer model of latent heat partition, which would be a critical factor for the droplet evaporation. The whole project lays down the foundation of the study of aerosol transport in a depressurized air-conditioned chamber, for its inhalation by human, contamination into AC system and deposition on the environment surfaces. It also initiates the coupling with medical model by providing critical input conditions for coughing-induced disease transmission to study the disease transmission as well as decontamination. Future studies would include the calibration and measurement of the breath simulator, the aerosol transport measurement in the air-conditioned chamber, more parametric study of CFD simulation, a more sophisticated multi-component evaporation model and the implementation of this evaporation model in the CFD simulation through User-Defined Functions. If possible, one could couple the more realistic latent heat partition model with the droplet evaporation model and also include the depressurization effect for at least the CFD simulation if not for the experiment.

Share

COinS