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Contaminants in ventilated filling boxes

Published online by Cambridge University Press:  30 October 2007

D. T. BOLSTER  and
P. F. LINDEN
D. T. BOLSTER
Affiliation:
Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92037, USAdbolster@uscd.edu
P. F. LINDEN
Affiliation:
Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92037, USAdbolster@uscd.edu
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Abstract

While energy efficiency is important, the adoption of energy-efficient ventilation systems still requires the provision of acceptable indoor air quality. Many low-energy systems, such as displacement or natural ventilation, rely on temperature stratification within the interior environment, always extracting the warmest air from the top of the room. Understanding buoyancy-driven convection in a confined ventilated space is key to understanding the flow that develops with many of these modern low-energy ventilation schemes. In this work we study the transport of an initially uniformly distributed passive contaminant in a displacement-ventilated space. Representing a heat source as an ideal sourced of buoyancy, analytical and numerical models are developed that allow us to compare the average efficiency of contaminant removal between traditional mixing and modern low-energy systems. A set of small-scale analogue laboratory experiments was also conducted to further validate our analytical and numerical solutions.

We find that on average traditional and low-energy ventilation methods are similar with regard to pollutant flushing efficiency. This is because the concentration being extracted from the system at any given time is approximately the same for both systems. However, very different vertical concentration gradients exist. For the low-energy system, a peak in contaminant concentration occurs at the temperature interface that is established within the space. This interface is typically designed to sit at some intermediate height in the space. Since this peak does not coincide with the extraction point, displacement ventilation does not offer the same benefits for pollutant flushing as it does for buoyancy removal.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 591 , 25 November 2007 , pp. 97 - 116
Copyright
Copyright © Cambridge University Press 2007

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References

REFERENCES

Baines, W. D. & Turner, J. S. 1969 Turbulent buoyant convection from a source in a confined region. J. Fluid Mech. 37, 51–80.CrossRefGoogle Scholar
Brohus, H. & Nielsen, P. V. 1996 Personal exposure in displacement ventilated rooms. Indoor Air 6, 157.CrossRefGoogle Scholar
Caulfield, C. P. & Woods, A. W. 2002 The mixing in a room by a localized finite-mass-flux source of buoyancy. J. Fluid Mech. 471, 33–50.CrossRefGoogle Scholar
Coffey, C. J. & Hunt, G. R. 2007 Ventilation efficiency measures based on heat removal. Part 1. Definitions. Building Environ. 42, 2241–2248.CrossRefGoogle Scholar
Cook, M. J., Ji, Y. & Hunt, G. R. 2003 CFD modelling of natural ventilation: Combined wind and buoyancy forces. Intl J. Ventilation 1, 169–180.CrossRefGoogle Scholar
Germeles, A. E. 1975 Forced plumes and mixing of liquids in tanks. J. Fluid Mech. 71, 601–623.CrossRefGoogle Scholar
He, G., Yang, X. & Srebric, J. 2005 Removal of contaminants released from room surfaces by displacement and mixing ventilation: Modeling and validation. Indoor Air 15, 367–380.CrossRefGoogle ScholarPubMed
Hunt, G. R., Cooper, P. & Linden, P. F. 2000 Thermal stratification produced by jets and plumes in enclosed spaces. In Proc. Roomvent 2000: 7th Intl Conf. on Air Distribution in Rooms (ed. Awbi, H. B.), pp. 191–198. Elsevier.Google Scholar
Hunt, G. R. & Kaye, N. B. 2006 Pollutant flushing with natural displacement ventilation. Building Environ. 41, 1190–1197.CrossRefGoogle Scholar
Jenkins, P. L., Phillips, T. J., Mulberg, E. J. & Hui, S. P. 1992 Activity patterns of Californians: Use and proximity to indoor pollutant sources. Atmos. Environ. A 26, 2141–2148.CrossRefGoogle Scholar
Ji, Y., Cook, M. J. & Hanby, V. 2007 CFD modelling of natural displacement ventilation in an enclosure connected to an atrium. Building Environ. 42, 1158–1172.CrossRefGoogle Scholar
Kaye, N. B. & Hunt, G. R. 2007 Heat source modelling and natural ventilation efficiency. Building Environ. 72, 1624–1631.CrossRefGoogle Scholar
Kaye, N. B. & Hunt, G. R. 2004 Time-dependent flows in an emptying filling box. J. Fluid Mech. 520, 135–156.CrossRefGoogle Scholar
Lin, Y. J. P. & Linden, P. F. 2002 Buoyancy-driven ventilation between two chambers. J. Fluid Mech. 463, 293–312.CrossRefGoogle Scholar
Lin, Z., Chow, T. T., Fong, K. F., Tsang, C. F. & Wang, Q. 2005 Comparison of performances of displacement and mixing ventilations. Part II. Indoor air quality. Intl J. Refrigeration 28, 288–305.CrossRefGoogle Scholar
Linden, P. F. 1999 The fluid mechanics of natural ventilation. Annu. Rev. Fluid Mech. 31, 201–238.CrossRefGoogle Scholar
Linden, P. F., Lane-Serff, G. F. & Smeed, D. A. 1990 Emptying filling boxes: The fluid mechanics of natural ventilation. J. Fluid Mech. 212, 309–335.CrossRefGoogle Scholar
Liu, Q & Linden, P. F. 2006 The fluid dynamics of an underfloor air distribution system. J. Fluid Mech. 554, 323–341.CrossRefGoogle Scholar
Morton, B. R., Taylor, G. I. & Turner, J. S. 1956 Turbulent gravitational convection from maintained and instantaneous sources. Proc. R. Soc. Lond. A 234, 1–23.Google Scholar
Mundt, E. 2001 Non-buoyant pollutant sources and particles in displacement ventilation. Building Environ. 36, 829–836.CrossRefGoogle Scholar
Murakami, S., Ohira, N. & Kato, S. 2000 CFD analysis of a thermal plume and the indoor air flow using k models with buoyancy effects. Appl. Sci. Res. 63, 113–134.CrossRefGoogle Scholar
Qiu-Wang, W. & Zhen, Z. 2006 Performance comparison between mixing ventilation and displacement ventilation with and without cooled ceiling. Engng Comput. 23, 218–237.CrossRefGoogle Scholar
Sandberg, M. & Etheridge, D. 1996 Building Ventilation: Theory and Measurement, 1st edn. Wiley.Google Scholar
Woods, A. W., Caulfield, C. P. & Phillips, J. C. 2003 Blocked natural ventilation: The effect of a source mass flux. J. Fluid Mech. 495, 119–133.CrossRefGoogle Scholar
Xing, H., Hatton, A. & Awbi, H. B. 2001 A study of the air quality in the breathing zone in a room with displacement ventilation. Building Environ. 36, 809–820.CrossRefGoogle Scholar
Yan, Z. 2007 Large eddy simulations of a turbulent thermal plume. Heat Mass Transfer 43, 503–514.CrossRefGoogle Scholar
Zhang, Z. & Chen, Q. 2006 Experimental measurements and numerical simulations of particle transport and distribution in ventilated rooms. Atmos. Environ. 40, 3396–3408.CrossRefGoogle Scholar