| Author: | Kwok, Hiu-kwan |
| Title: | Development of personalized air supply systems |
| Degree: | M.Eng. |
| Year: | 2007 |
| Subject: | Hong Kong Polytechnic University -- Dissertations. Air filters. Air -- Purification -- Equipment and supplies. Demand controlled ventilation systems. |
| Department: | Department of Building Services Engineering |
| Pages: | xiii, 119 leaves : ill. (some col.) ; 30 cm. |
| Language: | English |
| Abstract: | Personalized Air Supply (PAS) system is designed to achieve good inhaled air quality, improve thermal comfort and provide individual thermal preferences for occupants. In this study, Chair-based Personalized Air Supply system with Air Terminal Device (AID) located at chin position of occupant was developed. Flexible "Neck goose" support has been designed to provide adjustment of position of the AID in the PAS system. The Chair-based Personalized Air Supply system is expected to be applicable to many other built environments. The objective of this study is to investigate the performance of air quality, thermal comfort and human acceptability of the improved Chair-based PAS system by experimental measurements and subjective surveys. In experimental measurements, a thermal manikin was used to simulate a human being. Tracer gas was used to evaluate the amount of personalized air inhaled by the manikin. Six experimental conditions at ambient temperature of 24oC and PAS supply temperature of 22oC and 24oC were designed to perform in the experiments. Flow rate of PAS was changed from 0.8L/S to 1.61/s. Two indices, Pollution Exposure Reduction effectiveness and Fresh Air Utilization Efficiency, were applied to analyze quality of inhaled air and system effectiveness. The Pollution Exposure Reduction effectiveness increased with the increase of the PAS flow rate. 53.6% of Pollution Exposure Reduction effectiveness was achieved at PAS flow rate of 1.6L/S under isothermal condition. In contrast, the Fresh Air Utilization Efficiency decreased with increase of the flow rate. The maximum Fresh Air Utilization Efficiency of 6.8% was obtained at PAS flow rate at 0.81/s also under isothermal condition. In addition to physical experiments, subjective surveys were conducted to assess human responses on different thermal conditions created by the PAS system. 30 human subjects participated in the survey. During the survey, perceived air quality, feelings of irritation, thermal sensation, thermal acceptability, as well as temperature and flow rate preferences were studied under nine experimental conditions as in the physical experiments. Significant improvement in the perceived air quality was obtained when PAS system was operated, compared to the case with mixing ventilation alone. High PAS flow rate can ensure larger amount of personalized air in the inhalation as proved in the experimental measurements; 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 0.8L/s under PAS temperature 22oC and 24oC, in which the air quality and thermal environment perceived are the most acceptable. The thermal sensations were reported at the ranged of the "Neutral" and "Less Irritation" feelings from the subjects. Most of the subjects preferred no change to the environment. Compared with the Mixing ventilation system alone, it can be found that the additional installation of the PAS system can improve the perceived air quality and the thermal sensation to the user at particular thermal condition. Recommendations for investigating the free convection flow and the personalized air flow interaction and identifying the minimum flow rate that obtains steady maximum effectiveness are given. Obtaining an extensive response to thermal acceptability of the PAS system from different age groups and genders is also suggested in the further studies. Future research needed on the development of the PAS system is outlined in the dissertation. |
| Rights: | All rights reserved |
| Access: | restricted access |
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| File | Description | Size | Format | |
|---|---|---|---|---|
| b21175755.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 12.99 MB | Adobe PDF | View/Open |
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