Development of a prototype of self-contained personalized air supply system

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Development of a prototype of self-contained personalized air supply system


Author: Lin, Lin
Title: Development of a prototype of self-contained personalized air supply system
Degree: M.Eng.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
User-centered system design
Air -- Purification -- Equipment and supplies
Demand controlled ventilation systems
Department: Dept. of Building Services Engineering
Pages: xv, 122 leaves : ill. ; 31 cm.
InnoPac Record:
Abstract: In this study, a prototype of Self-contained Personalized Air Supply (SPAS) system, with Air Terminal Device (ATD) located at chin poSition of occupant and the Returned Air Devices (RADs) mounted at the back of the chair, was developed based on the Chair-based Personalized Air Supply (PAS) system by Kwok (2006). The Self-contained Personalized Air Supply (SPAS) system is designed to utilize the room air as personalized air supplied to occupants in a more convenient way, which is principally different from Chair-based PAS system. The SPAS system was used in conjunction with a background total volume ventilation system, which can achieve good inhaled air quality, improve thermal comfort and provide thermal preference for individual. The objective of this study is to assess the performance of SPAS system with analysis of inhaled air quality, thermal comfort and human acceptability by experimental measurement and subjective survey. In experimental measurement, nine experiment conditions with combination of different personalized flow rate and Return Air Devices (RADs) location at isothermal temperature of 22°C was conducted in the measurements. Flow rate of SPAS system was ranged from 0.8L/s to 1.8L/s and RADs was respectively located at Over head position, Both Side of Face position and Over Shoulders position. On the other hand, a thermal manikin was used to simulate a human being. Tracer gas was mixed with synthetic air to act as personalized air supplied to manikin. Then the concentration of tracer gas was measured at different condition in order to evaluate the amount of personalized air inhaled by the manikin. Finally, the performance of SPAS system, effectiveness as well as inhaled air quality was analyzed by two indices, Pollutant Exposure Reduction Effectiveness and Fresh Air Utilization Efficiency. In subjective survey, subjective, opinions on perceived air quality and thermal comfort as well as irritation were also obtained based on the performance of SPAS system. 20 human subjects, half are female and half are male, participated in the survey in the form of questionnaire. During the survey, thermal sensation, thennal acceptability, individual preference, perceived air quality as well as irritation were investigated with personalized flow rate ranged from 0.8L/s to 1.6L/s and RADs located at Over head position.
Generally, the Pollutant Exposure Reduction Effectiveness continued to increase with the elevated personalized flow rate with different location of RADs. The best Pollutant Exposure Reduction Effectiveness could be obtained at Overhead position when supplied air at 0.8L/s. However, the better Pollutant Exposure Reduction Effectiveness could be obtained especially at Over Shoulders position with elevated personalized air flow rate. The maximum Pollutant Exposure Reduction Effectiveness 0.326 was achieved at 1.8L/s at Over Shoulder position. It could be explained that the induced extraction action of the RADs at different position as well as flow rate have a significant impact on the Pollutant Exposure Reduction Effectiveness. Similarly, the best Fresh Air Utilization Efficiency was achieved at Overhead position at 0.8L/s. When the flow rate increased, the steady state of Fresh Air Utilization Efficiency was achieved and the maximum at 1.8L/s was obtained at Over Shoulders position. Therefore, both the personalized air flow rate and the positions of Air Inlets had a great impact on Fresh Air Utilization Efficiency when personalized air was supplied at low flow rate. In the subjective surveys, the difference of perceived air quality between "Without SPAS" and "With SPAS" was significant. The perceived air quality was improved with relative high flow rate. Nevertheless, stuffy air may be caused at high flow rate with large amount of personalize air probably due to insufficient air-filtrating capacity of the double-lay filter. Besides, the irritation feeling as well as draught discomfort increased with elevated flow rate resulting to dissatisfaction of the subjects with the thermal environment. Additionally, the operation of the SPAS system along with mixing ventilation can provide a cooler sensation for occupants. It is found that high SPAS flow rate and low room air temperature may be unfavorable to the subjects owing to the cool sensation and irritation as well as draught feeling created. Therefore, the low personalized air flow rate at low room air temperature was adopted to satisfy their thermal comfort whereas high flow rate would be expected for achieving better inhaled air quality for subjects. The most acceptable condition of thermal environment and irritation feeling would be at O.8L/s when the majority of the subjects preferred to unchange the personalized air temperature, room air temperature as well as the air movement and had a "Neutral" description of subjective feeling. At the end of the research, some recommendations, including the locations of Return Air Devices, acoustic treatment, efficiency of air filtration, survey group and so on, were given for further study as well as improvement for SPAS system.

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