Experimental investigations of respiratory droplet dispersion under stratified ventilation

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Experimental investigations of respiratory droplet dispersion under stratified ventilation


Author: Tong, Kwan Po
Title: Experimental investigations of respiratory droplet dispersion under stratified ventilation
Degree: M.Eng.
Year: 2012
Subject: Communicable diseases -- Transmission.
Airborne infection.
Air conditioning -- Health aspects.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: xii, 106, vi leaves : ill. (chiefly col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2525568
URI: http://theses.lib.polyu.edu.hk/handle/200/6647
Abstract: After the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003, air borne disease transmission in ventilated space has been studied intensively with computational fluid dynamics (CFD) approach. Respiratory droplets are suspected to be the major sources to distribute bacteria and viruses. In order to provide some reliable data of droplet residual dispersions and the factors influencing the dispersions, a full scale chamber was established to collect the experimental data for the analyses. Two manikins were placed in the chamber oppositely to simulate the situation during chatting. At the first stage, the typical conditions of offices were simulated in the ventilated chamber. After that, different parameters including droplet temperature, the flow direction of droplet, the existence of heat sources and the air change rate (ACH) of the air conditioning system were adjusted to investigate their impacts on the aerosol profiles. In the measurements simulating typical offices, droplet residual tend to stay at the upper levels of the chamber and the exact heights of the aerosol trapping levels are mainly related to the aerosol sizes, the balance between different forces and also the distance from the polluting manikin. Also, the comparisons between normal case and the cases with modified parameters indicated that higher aerosol temperature, existence of the thermal plume provided by polluting manikin, shorter distance from the aerosol source and lower air change rate(ACH) of ventilation system are helpful to raise the aerosols to the upper levels of the ventilated room. The current study provides substantial information to enhance our understanding of the factors affecting the aerosol dispersion which is helpful to optimize the air-conditioning system design in typical offices. Further investigation with a variety of seating plans and positions of exhaust air outlets should be conducted to widen the applications of the study. Moreover, detailed analysis of the impacts of air change rate on vertical aerosol dispersion is recommended.

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