Critical evaluation by field studies on the performance of ventilation systems in enclosed car park in Hong Kong

This thesis critically reviews the design guidelines for ventilation systems installed in underground car parks. The design approaches, practical assumptions and final outcomes are reviewed and examined. Ventilation engineers in Hong Kong have long been following design codes from overseas, such as those of CIBSE and ASHRAE, and these approaches continue to be in use.; A comprehensive field survey was carried out in 103 underground car parks in Hong Kong. The scope of survey included the systematic measurement of carbon monoxide (CO) levels, thermal comfort and activity levels. It also gathered information on the physical configuration and capacity of car parks workers' conditions and details of ventilation systems. The health guidelines for both car park employees and car park users are discussed. The introduction of an exposure index is used for assessing protection for vulnerable groups within the general population of users.; A methodology for assessment of ventilation system performance was developed. This focuses on the degree of mixing, air quality index in occupied areas, time constant, pollutant load and turnover time of the key pollutant. The use of a 2-level ventilation strategy was shown to provide an effective approach to energy saving, whilst maintaining the appropriate indoor air quality. A sensitivity analysis was carried out to demonstrate different percentages of energy saved under various scenarios. Multi-cell numerical modelling is recommended for analysis of air flow. Future development of this modelling approach is suggested.; The thesis provides a procedure to aid the design of underground car parks used for different purposes. Nomographs are produced to provide probable emissions strength at different usage rate. Typical profiles of residential buildings, commercial buildings and shopping complex are given. Designers can derive the required ventilation rate through a standard procedure once they have determined the key design parameters. (Abstract shortened by UMI.)...