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Particle Filtration in a Ventilated Room
KTH, Superseded Departments, KTH Syd.
KTH, Superseded Departments, KTH Syd.ORCID iD: 0000-0003-1882-3833
2002 (English)In: Indoor Air 2002: 9th International Conference on Indoor Air Quality and Climate / [ed] Levin, H., 2002, 1070-1075 p.Conference paper, Published paper (Refereed)
Abstract [en]

Several studies based on analytical models and numerical simulations have shown that it is difficult to control airborne particle movements in a ventilated room. However, more knowledge and information on particle characteristics and particle movements, in combination with new numerical simulation tools, have recently made it easier to estimate particle patterns. In the present paper new information is used to evaluate the role of filtration and ventilation in the particle elimination process. Key parameters found include the particle aerodynamic diameter and the particle settling velocity governed by Stokes formula. Particle dispersion and settling are highly dependent on the ventilation airflow structure. Calculations with CFD (Computational Fluid Dynamics) show characteristic patterns of particle movements in rooms with displacement ventilation.

Place, publisher, year, edition, pages
2002. 1070-1075 p.
Keyword [en]
Filtration, CFD, Simulations, Displacement ventilation, Breathing zone
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-5311OAI: oai:DiVA.org:kth-5311DiVA: diva2:8394
Note
QC 20101007Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-10-07Bibliographically approved
In thesis
1. Air diffusion and solid contaminant behaviour in room ventilation: a CFD based integrated approach
Open this publication in new window or tab >>Air diffusion and solid contaminant behaviour in room ventilation: a CFD based integrated approach
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

One of the most fundamental human needs is fresh air. It has been estimated that people spend comparatively much time in indoor premises. That creates an elevated need for high-quality ventilation systems in buildings. The ventilation airflow rate is recognised as the main parameter for measuring the indoor air quality. It has been shown that the ventilation airflow rates have effects on respiratory diseases, on “sick building syndrome” symptoms, on productivity and perceived air quality. Ventilation is necessary to remove indoor-generated pollutants by diluting these to an acceptable level. The choice of ventilation airflow rate is often based on norms or standards in which the airflow rate is determined based on epidemiological research and field or laboratory measurements. However, the determination of ventilation flow rate is far more complex. Indoor air quality in the occupied zone can be dependent of many factors such as outdoor air quality, airflow rate, indoor generation of pollutants, moisture content, thermal environment and how the air is supplied into the human occupied zone. One needs to acknowledge the importance of air distribution which clearly affects the comfort of occupants. To design a ventilation system which considers all aspects of room ventilation can only be achieved by computer modelling. The objective of this thesis is to investigate air diffusion, indoor air quality and comfort issues by CFD (computational fluid dynamics) modelling. The crucial part of the CFD modelling is to adopt BCs (boundary conditions) for a successful and accurate modelling procedure. Assessing the CFD simulations by validated BCs enabled constructing the ventilation system virtually and various system layouts were tested to meet given design criteria. In parallel, full-scale measurements were conducted to validate the diffuser models and the implemented simplified particle-settling model. Both the simulations and the measurements reveal the full complexity of air diffusion coupled with solid contaminants. The air supply method is an important factor for distribution of heat, air velocity and solid contaminants. The influence of air supply diffuser location, contaminant source location and air supply method was tested both numerically and by measurements to investigate the influence of different parameters on the efficiency of room ventilation. As example of this, the well-known displacement ventilation is not fully able to evacuate large 10 μm airborne particles from a room. Ventilation should control the conditions in the human breathing zone and therefore the ventilation efficiency is an important parameter. A properly designed ventilation system could use less fresh air to maintain an acceptable level of contaminant concentration in the human breathing zone. That is why complete mixing of air is not recommended as the ventilation efficiency is low and the necessary airflow rate is relatively high compared to other ventilation strategies. Especially buoyancy-driven airflows from heat sources are an important part of ventilation and should not be hampered by supply airflow from the diffusers. All the results revealed that CFD presently is the only reliable method for optimising a ventilation system considering the air diffusion and contaminant level in all locations of any kind of room. The last part of the thesis addresses the possibility to integrate the CFD modelling into a building design process where architectural space geometry, thermal simulations and diffuser BCs could be embedded into a normal building design project.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 95 p.
Series
Trita-KRV, ISSN 1100-7990 ; 2005:03
Keyword
Technology, CFD modelling, airflow rate, ventilation efficiency, diffusers, solid contaminants, IAQ, TEKNIKVETENSKAP
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-270 (URN)91-7178-037-8 (ISBN)
Public defence
2005-06-16, sal 2105, KTH Syd, Campus Haninge, Haninge, 14:00
Opponent
Supervisors
Note
QC 20101007Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-10-07Bibliographically approved

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