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Transient natural ventilation of a room with a distributed heat source

Published online by Cambridge University Press:  30 October 2007

SHAUN D. FITZGERALD  and
ANDREW W. WOODS
SHAUN D. FITZGERALD
Affiliation:
BP Institute for Multiphase flow, University of Cambridge, Cambridge, CB3 0EZ, UK
ANDREW W. WOODS
Affiliation:
BP Institute for Multiphase flow, University of Cambridge, Cambridge, CB3 0EZ, UK
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Abstract

We report on an experimental and theoretical study of the transient flows which develop as a naturally ventilated room adjusts from one temperature to another. We focus on a room heated from below by a uniform heat source, with both high- and low-level ventilation openings. Depending on the initial temperature of the room relative to (i) the final equilibrium temperature and (ii) the exterior temperature, three different modes of ventilation may develop. First, if the room temperature lies between the exterior and the equilibrium temperature, the interior remains well-mixed and gradually heats up to the equilibrium temperature. Secondly, if the room is initially warmer than the equilibrium temperature, then a thermal stratification develops in which the upper layer of originally hot air is displaced upwards by a lower layer of relatively cool inflowing air. At the interface, some mixing occurs owing to the effects of penetrative convection. Thirdly, if the room is initially cooler than the exterior, then on opening the vents, the original air is displaced downwards and a layer of ambient air deepens from above. As this lower layer drains, it is eventually heated to the ambient temperature, and is then able to mix into the overlying layer of external air, and the room becomes well-mixed. For each case, we present new laboratory experiments and compare these with some new quantitative models of the transient flows. We conclude by considering the implications of our work for natural ventilation of large auditoria.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 591 , 25 November 2007 , pp. 21 - 42
Copyright
Copyright © Cambridge University Press 2007

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References

REFERENCES

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
Cooper, P. & Linden, P. F. 1996 Natural ventilation of an enclosure containing two buoyancy sources. J. Fluid Mech. 311, 153–176.Google Scholar
Deardorff, J. W., Willis, G. E. & Lilly, D. K. 1969 Laboratory investigation of non-steady penetrative convection. J. Fluid Mech. 35, 7–31.Google Scholar
Denton, R. A. & Wood, I. R. 1981 Penetrative convection at low Péclet number. J Fluid Mech. 111, 1–21.CrossRefGoogle Scholar
Fitzgerald, S. D. & Woods, A. W. 2004 Natural ventilation of a room with vents at multiple levels. Building and Environ. 39, 505–521.CrossRefGoogle Scholar
Gladstone, C. & Woods, A. W. 2001 On buoyancy-driven natural ventilation of a room with a heated floor. J. Fluid Mech. 441, 293–314.CrossRefGoogle Scholar
Haywood, R. W. 1972 Thermodynamic Tables in SI (metric) Units. Cambridge University Press.Google Scholar
Kaye, N. B. & Hunt, G. R. 2004 Time-dependent flows in an emptying filling box. J. Fluid Mech. 520, 135–156.CrossRefGoogle Scholar
Linden, P. F. 1999 The fluid mechanics of natural ventilation. Annu. Rev. Fluid Mech. 31, 201–238.Google Scholar
Linden, P. F. & Cooper, P. 1996 Multiple sources of buoyancy in a naturally ventilated enclosure. J. Fluid Mech. 311, 177–192.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
Lister, J. A. 1995 On penetrative convection at low Péclet number. J. Fluid Mech. 292, 229–248.Google Scholar
Zilitinkevich, S. S. 1991 Turbulent Penetrative Convection. Avebury.Google Scholar