Publication: HVAC & R Research
Publication Date: 01-JUL-07
Delivery: Immediate Online Access
Author: Nielsen, Peter V. ; Hyldgaard, Carl Erik ; Melikov, Arsen ; Andersen, Heine ; Soennichsen, Mads
Article Excerpt
Received January 13, 2006; accepted May 16, 2006
This paper describes an investigation made in a room ventilated by an air distribution system based on a textile terminal. The air distribution in the room is mainly controlled by buoyancy forces from the heat sources, although the flow from the textile terminal can be characterized as a displacement flow with a downward direction in areas of the room where no thermal load is present. The system was extended by a personalized ventilation system to study the improved protection of people in a room. The investigation involved full-scale experiments with two breathing thermal manikins. One manikin is the source and the other the target. In general it was found that when the air is supplied from the textile terminal alone, the flow in the room is fully mixed with limited protection of the occupants. Selected locations of supply, return, and heat sources can produce a displacement flow in the room with increased protection of the occupants. It is shown that personalized ventilation improves the protection of occupants by increasing the personal exposure index.
INTRODUCTION
More and more people are spending a considerable amount of time in an indoor environment. It is important to minimize the amount of pollutants that people are exposed to indoors, to give an experience of good air quality, and to minimize the danger of, e.g., passive smoking and cross-infection. The latter problem was clearly demonstrated in the worldwide SARS outbreak in 2003 (Li et al. 2004a, 2004b).
Different air distribution systems, such as mixing ventilation and displacement ventilation, offer different possibilities for the protection of people against pollutants. The pollutants are almost fully mixed in the occupied zone in a room ventilated by mixing ventilation, and they are removed by a diluting process (Jensen et al. 2001). If the pollutant source is also a heat source, displacement ventilation offers possibilities to work with two zones, a low zone with clean air and an upper zone with pollutants. It is possible to design a system with low exposure of people under certain conditions (Brohus and Nielsen 1996; Skistad et al. 2002), but high exposure can also exist in rooms with displacement flow in certain situations, as shown by Bjoern and Nielsen (2002) and Qian et al. (2006).
An investigation was made in a room ventilated by an air distribution system based on a textile terminal. The air distribution in the room is mainly controlled by buoyancy forces from the heat sources, although the flow from the textile terminal can be characterized as a displacement flow with a downward direction in areas of a room where no thermal load is present. The displacement flow, which exists in different areas of the room, may indicate the possibility of obtaining improved protection in those areas. The air distribution system is evaluated and compared with other systems by Nielsen et al. (2005). To study the possibility of improved protection, the textile terminal is extended by a personalized ventilation system in some of the experiments. Personalized ventilation systems are intensively studied...
NOTE: All illustrations and photos have been removed from this article.
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