Hostname: page-component-76fb5796d-2lccl Total loading time: 0 Render date: 2024-04-26T16:58:07.675Z Has data issue: false hasContentIssue false
  • English
  • Français

Emptying non-adiabatic filling boxes: the effects of heat transfers on the fluid dynamics of natural ventilation

Published online by Cambridge University Press:  23 May 2012

G. F. Lane-Serff  and
S. D. Sandbach
G. F. Lane-Serff*
Affiliation:
School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Pariser Building, Sackville Street, Manchester M13 9PL, UK
S. D. Sandbach
Affiliation:
College of Life and Environmental Sciences, University of Exeter, Amory Building, Rennes Drive, Exeter EX4 4RJ, UK
*
†Email address for correspondence: gregory.f.lane-serff@manchester.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

A model for steady flow in a ventilated space containing a heat source is developed, taking account of the main heat transfers at the upper and lower boundaries. The space has an opening at low level, allowing cool ambient air to enter the space, and an opening near the ceiling, allowing warm air to leave the space. The flow is driven by the temperature contrast between the air inside and outside the space (natural ventilation). Conductive heat transfer through the ceiling and radiant heat transfer from the ceiling to the floor are incorporated into the model, to investigate how these heat transports affect the flow and temperature distribution within the space. In the steady state, a layer of warm air occupies the upper part of the space, with the lower part of the space filled with cooler air (although this is warmer than the ambient air when the radiant transfer from ceiling to floor is included). Suitable scales are derived for the heat transfers, so that their relative importance can be characterized. Explicit relationships are found between the height of the interface, the opening area and the relative size of the heat transfers. Increasing heat conduction leads to a lowering of the interface height, while the inclusion of the radiant transfer tends to increase the interface height. Both of these effects are relatively small, but the effect on the temperatures of the layers is significant. Conductive heat transfer through the upper boundary leads to a significant lowering of the temperature in the space as a proportion of the injected heat flux is taken out of the space by conduction rather than advection. Radiative transfer from the ceiling to floor results in the lower layer becoming warmer than the ambient air. The results of the model are compared with full-scale laboratory results and a more complex unsteady model, and are shown to give results that are much more accurate than models which ignore the heat transfers.

JFM classification

Convection: Convection Convection: Plumes/thermals Turbulent Flows: Turbulent convection
Type
Papers
Information
Journal of Fluid Mechanics , Volume 701 , 25 June 2012 , pp. 386 - 406
Copyright
Copyright © Cambridge University Press 2012

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Chenviyadakarn, T. & Woods, A. W. 2008 On underfloor air-conditioning of a room containing a distributed heat source and a localized heat source. Energy Build. 40, 1220–1227.Google Scholar
2. Coffey, C. J. & Hunt, G. R. 2010 The unidirectional emptying box. J. Fluid Mech. 660, 456–474.Google Scholar
3. Coomaraswamy, I. A. & Caulfield, C. P. 2011 Time-dependent ventilation flows driven by opposing wind and buoyancy. J. Fluid Mech. 672, 33–59.CrossRefGoogle Scholar
4. Cooper, P. & Linden, P. F. 1996 Natural ventilation of an enclosure containing two buoyancy sources. J. Fluid Mech. 311, 153–176.Google Scholar
5. Fitzgerald, S. D. & Woods, A. W. 2010 Transient natural ventilation of a space with localized heating. Build. Environ. 45 (12), 2778–2789.CrossRefGoogle Scholar
6. Gao, J., Zhao, J. N. & Gao, F. S. 2006 Displacement of natural ventilation in an enclosure with a convective/radiative heat source and non-adiabatic envelopes. J. Solar Energy Engng – Trans. ASME 128, 83–89.Google Scholar
7. 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
8. Hunt, G. R. & Coffey, C. J. 2010 Emptying boxes – classifying transient natural ventilation flows. J. Fluid Mech. 646, 137–168.CrossRefGoogle Scholar
9. Hunt, G. R. & Linden, P. F. 2001 Steady-state flows in an enclosure ventilated by buoyancy forces assisted by wind. J. Fluid Mech. 426, 355–386.Google Scholar
10. Kaye, N. B. & Hunt, G. R. 2004 Time-dependent flows in an emptying filling box. J. Fluid Mech. 520, 135–156.Google Scholar
11. Lau, J. & Chen, Q. 2007 Floor-supply displacement ventilation for workshops. Build. Environ. 42, 1718–1730.CrossRefGoogle Scholar
12. Li, Y. 2000 Buoyancy-driven natural ventilation in a thermally stratified one-zone building. Build. Environ. 35, 207–214.Google Scholar
13. Li, Y., Sandberg, M. & Fuchs, L. 1992 Vertical temperature profiles in rooms ventilated by displacement: full-scale measurement and nodal modelling. Indoor Air 2, 225–243.Google Scholar
14. Linden, P. F. 1999 The fluid mechanics of natural ventilation. Annu. Rev. Fluid Mech. 31, 201–238.CrossRefGoogle Scholar
15. Linden, P. F. & Cooper, P. 1996 Multiple sources of buoyancy in a naturally ventilated enclosure. J. Fluid Mech. 311, 177–192.Google Scholar
16. 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
17. Livermore, S. R & Woods, A. W. 2008 On the effect of distributed cooling in natural ventilation. J. Fluid Mech. 600, 1–17.Google Scholar
18. Morton, B. R., Taylor, G. I. & Turner, J. S. 1956 Turbulent gravitational convection from maintained and instantaneous sources. Proc. R. Soc. A234, 1–23.Google Scholar
19. Phillips, J. C. & Woods, A. W. 2004 On ventilation of a heated room through a single doorway. Build. Environ. 39, 241–253.Google Scholar
20. Sandbach, S. D. & Lane-Serff, G. F. 2011 Transient buoyancy-driven ventilation. Part 2. Modelling heat transfer. Build. Environ. 46 (8), 1589–1599.CrossRefGoogle Scholar