Radiant heat and respiratory droplet distribution with stratified air distribution system

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Radiant heat and respiratory droplet distribution with stratified air distribution system

 

Author: Cheng, Shan
Title: Radiant heat and respiratory droplet distribution with stratified air distribution system
Degree: M.Eng.
Year: 2011
Subject: Air conditioning.
Stratified flow.
Heat -- Radiation and absorption.
Indoor air pollution.
Air quality management.
Displacement ventilation.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: x, 67 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2449792
URI: http://theses.lib.polyu.edu.hk/handle/200/6409
Abstract: Stratified air distribution systems such as Displacement Ventilation (DV) and Under-Floor Air Distribution (UFAD) systems proved to provide better indoor air quality compared with Traditional Mixing Ventilation (MV) system. Furthermore, radiant heat and respiratory droplet in an enclosed space are regarded as critical factors respectively related to energy efficiency and indoor air quality. Different air distribution systems have their own characteristics of the distribution of respiratory droplet, and affects the spatial actual cooling load in UFAD systems. This study investigates the distribution of radiant heat which is generated from human body and the respiratory droplet with the size varied from 0.1um to 10um in the room installed with Displacement Ventilation system. In addition, the convective heat is also analyzed to compare with the radiant heat in this case. A stainless steel chamber installed with air-conditioning system was supplied to conduct the experiment for this research. Two thermal manikins and some basic office equipments were placed in the chamber to simulate the circumstance of a real office. The flow rate of supply air was controlled around 0.2m/s which was coincided with displacement ventilation system. That manikin produced heat by winding around heating wire according to the value of real person. The aerosols were produced by Ions generator to imitate the respiratory droplet. Multiple measuring points were set on vertical, horizontal and nostril area to obtain the concentration distribution of particles with different diameters under Displacement Ventilation system. Lots of previous researches have studied on the case that only one person seated in the room. This paper aims to find out the results of radiant heat distribution when two persons are working in the room simultaneously. From the experiment data, it can be observed that the radiant heat of the lower zone is slightly larger than that in the upper zone generally. The distribution radio of radiant heat and convective heat are related to the velocity and temperature of the air in the chamber. The conclusions also indicate the aerosols are easily trapped in the middle-height of the room which disobeys the general two-zone theory of the DV system. Due to the limitations of this study, the current results only provide a first attempt to perform basic analysis. The precision of the experiments can be enhanced in the future study to obtain a more powerful and representative results which can be applied to improve the indoor air quality.

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