| Author: | Ma, Lai-yung |
| Title: | Development and evaluation of a prototype personal air supply system |
| Degree: | M.Eng. |
| Year: | 2005 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Air -- Purification Ventilation Air conditioning Indoor air pollution Air quality management |
| Department: | Department of Building Services Engineering |
| Pages: | xiii, 143 leaves : ill. (some col.) ; 30 cm |
| Language: | English |
| Abstract: | Personal Air Supply (PAS) system aims to provide clean air to the breathing zone of the occupants. Its performance depends to a large extent on the supply air temperature and flow rate. In this study, a prototype PAS system was developed with the Air Terminal Device (ATD) located at the occupant's chin position. A thermal manikin was used to simulate a human being. A total of eighteen experimental conditions at room air temperature of 22 C and PAS temperature of 15 C, 18 C and 22 C were performed. The flow rate of PAS was changed from 0.4 L/s to 2.5 L/s. Tracer gas was used to identify the amount of personalized air inhaled by the manikin. Two indices, pollutant exposure reduction effectiveness and fresh air utilization efficiency were used to assess the performance of the system in regard to quality of the air inhaled by the manikin and system efficiency respectively. The pollutant exposure reduction effectiveness increased with the increase of the PAS flow rate. A further increase of the flow rate appeared to have slightly effect on the effectiveness. 77 % effectiveness was achieved at PAS flow rate of 2.5 L/s under isothermal condition. In contrast, the fresh air utilization efficiency decreased with the increase of the PAS flow rate. The maximum efficiency of 14.6 % was obtained at PAS flow rate at 0.4 L/s also under isothermal condition. In additional to the physical measurement, subjective survey was conducted to assess the human responses on the conditions created by this PAS system. 12 human subjects participated in the survey. Perceived air quality, irritation feelings, thermal sensation, thermal acceptability, and air temperature as well as air flow rate preferences were studied under the eighteen experimental conditions. Significant improvement in the perceived air quality was obtained when PAS system was operated, compared to the case with mixing ventilation alone. Both the experiment and survey results suggested that the PAS system had a better performance under isothermal condition. High PAS flow rate can ensure larger amount of personalized air in the inhalation as proved in the experiment, however, the survey results indicate that at such a high flow rate, draught discomfort was experienced by the subjects. The optimum condition would be at 0.8 L/s and 1.2 L/s under isothermal condition, in which the air quality and thermal environment perceived are the most acceptable. Subjects' thermal sensation is much closer to neutral and nearly no irritation feeling is reported. The percentages preferring to change the environment, including air movement, ambient and PAS temperatures are significantly lower. Compared with the mixing ventilation alone, it was found that the additional installation of the PAS system improved the perceived air quality and thermal sensation to a large extent at a particular condition. |
| Rights: | All rights reserved |
| Access: | restricted access |
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|---|---|---|---|---|
| b18100247.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 10.14 MB | Adobe PDF | View/Open |
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