|The measurement of positive air pressure and air leakage in ventilation section of full-scale toilet drainage stack and its significance
|Wong, Ling-tim (BEEE)
|Plumbing -- Waste-pipes
Hong Kong Polytechnic University -- Dissertations
|Department of Building Environment and Energy Engineering
|v, 93 pages : color illustrations
|The emergence of COVID-19 makes it very important to study the way of virus transmission. The mode of fecal mouth transmission causing the vertical transmission of residential buildings has been confirmed by many studies. The transient change of air pressure in the stack connecting each floor is the reason for the vertical propagation of fecal aerosol in residential buildings. In previous studies, people have used three methods to explore the distribution of gas pressure in the pipe during drainage. In addition, people also explored the water seal failure caused by the average negative pressure in the pipe through simulation and experiment, and confirmed that the water seal failure will cause the leakage of gas in the pipe. Previous studies have also mentioned the formation of positive pressure in the pipe and the failure of water seal caused by positive pressure, and some studies have provided the technology to reduce the positive pressure in the pipe, but these studies only stay in the literature review and the establishment of mathematical model, and there is no clear experiment on whether the positive pressure will cause the leakage of gas in the pipe. This study measured the positive pressure at the upper part of the drainage stack ventilation section during drainage through three experiments: laboratory drainage set-up pressure measurement experiment, full-scale toilet pressure measurement experiment and full-scale toilet tracer gas experiment. In the set-up experiment, the ventilation conditions at the top of the drainage stack were changed, and the negative correlation between the peak value of positive air pressure and the size of orifice plate was obtained. In the full-scale experiment, by changing the opening and closing degree of the top of the stack, the opening and closing of the toilet cover, whether to flush at the same time and the drainage height, it is concluded that the full closing of the top of the stack, the closing of the toilet cover, high-rise drainage and flushing at the same time are the reasons for the increase of the peak positive air pressure. In the tracer gas experiment, through the change of tracer gas concentration, it is determined that the positive gas pressure will aggravate the gas leakage in the pipe in the case of water seal failure or pipe damage. Through the research results, some suggestions on preventing disease transmission and disinfection during the epidemic period are given.
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