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On the thermal buffering of naturally ventilated buildings through internal thermal mass

Published online by Cambridge University Press:  21 May 2007

J. M. HOLFORD  and
A. W. WOODS
J. M. HOLFORD
Affiliation:
BP Institute, University of Cambridge, Cambridge CB3 0EZ, UK
A. W. WOODS
Affiliation:
BP Institute, University of Cambridge, Cambridge CB3 0EZ, UK
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Abstract

In this paper we examine the role of thermal mass in buffering the interior temperature of a naturally ventilated building from the diurnal fluctuations in the environment. First, we show that the effective thermal mass which is in good thermal contact with the air is limited by the diffusion distance into the thermal mass over one diurnal temperature cycle. We also show that this effective thermal mass may be modelled as an isothermal mass. Temperature fluctuations in the effective thermal mass are attenuated and phase-shifted from those of the interior air, and therefore heat is exchanged with the interior air. The evolution of the interior air temperature is then controlled by the relative magnitudes of (i) the time for the heat exchange between the effective thermal mass and the air; (ii) the time for the natural ventilation to replace the air in the space with air from the environment; and (iii) the period of the diurnal oscillations of the environment. Through analysis and numerical solution of the governing equations, we characterize a number of different limiting cases. If the ventilation rate is very small, then the thermal mass buffers the interior air temperature from fluctuations in the environment, creating a near-isothermal interior. If the ventilation rate increases, so that there are many air changes over the course of a day, but if there is little heat exchange between the thermal mass and interior air, then the interior air temperature locks on to the environment temperature. If there is rapid thermal equilibration of the thermal mass and interior air, and a high ventilation rate, then both the thermal mass and the interior air temperatures lock on to the environment temperature. However, in many buildings, the more usual case is that in which the time for thermal equilibration is comparable to the period of diurnal fluctuations, and in which ventilation rates are moderate. In this case, the fluctuations of the temperature of the thermal mass lag those of the interior air, which in turn lag those of the environment. We consider the implications of these results for the use of thermal mass in naturally ventilated buildings.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 580 , 10 June 2007 , pp. 3 - 29
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
Bansal, N. K. & Bhandari, M. S. 1996 Comparison of the periodic solution method with TRNSYS and SUNCODE for thermal building simulation. Solar Energy 57, 9–18.CrossRefGoogle Scholar
Chartered Institution of Building Services Engineers 1999 Environmental Design: CIBSE Guide A. CIBSE, London.Google Scholar
Collatz, L. 1966 The Numerical Treatment of Differential Equations. Springer.Google Scholar
Cook, M. J., Lomas, K. J. & Eppel, H. 1999 Design and operating concept for an innovative naturally ventilated library. In Engineering in the 21st Century: The Changing World. In Proc. CIBSE Nat. Conf., pp. 500–507. CIBSE, London.Google Scholar
Crisp, V. H. C., Fisk, D. J. & Salvidge, A. C. 1984 The BRE Low-Energy Office. Department of the Environment, Building Research Establishment.Google Scholar
Department of Trade and Industry 2005 Energy Consumption in the UK. http://www.dti.gov.uk/energy/inform/energy_consumption.Google Scholar
Fisk, D. J. 1981 Thermal Control of Buildings. Applied Science.Google Scholar
Gebhart, B., Jaluria, Y., Mahajan, R. L. & Sammakia, B. 1988 Buoyancy-Induced Flows and Transport. Hemisphere.Google 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
Holford, J. M. 2004 Simple modelling of thermal mass. In Proc. of RoomVent '04, 9th Intl Conf. on Air Distribution in Rooms (ed. Silva, M. C. Gameiro da). ADAI Universidade de Coimbra.Google Scholar
Holford, J. M. & Hunt, G. R. 2000 Multiple steady states in natural ventilation. In Proc. 5th Intl Symp. on Stratified Flows (ed. Lawrence, G. A., Pieters, R. & Yonemitsu, N.), pp. 661–666. University of British Columbia.Google Scholar
International Energy Agency 2005 Key World Energy Statistics. http://Www.iea.org/dbtw-wpd/Textbase/nppdf/free/2005/key2005.pdf.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
Li, Y. & Yam, J. C. W. 2004 Designing thermal mass in naturally ventilated buildings. Intl J. Vent. 2, 313–324.Google 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, 300–335.CrossRefGoogle Scholar
Lombard, C. & Mathews, E. H. 1999 A two-port envelope model for building heat transfer. Build. Environ. 34, 19–30.CrossRefGoogle Scholar
Long, K. 2001 Underneath the arches. Building Design 12 April 2001 15–17.Google Scholar
Mitalas, G. P. 1968 Calculation of transient heat flow through walls and roofs. ASHRAE Trans. 74, 182–188.Google Scholar
Pratt, A. W. 1981 Heat Transmission in Buildings. Wiley.Google Scholar
Press, W. H., Flannery, B. P., Teukolsky, S. A. & Vetterling, W. T. 1989 Numerical Recipes. Cambridge University Press.Google Scholar
Rajapaksha, I., Nagai, H. & Okumiya, M. 2003 A ventilated courtyard as a passive cooling strategy in the warm humid tropics. Renewable Energy 28, 1755–1778.CrossRefGoogle Scholar
Stephenson, D. G. & Mitalas, G. P. 1967 Cooling load calculations by thermal response factors. ASHRAE Trans. 73, III1.1–III1.7.Google Scholar
Yam, J., Li, Y. & Zheng, Z. 2003 Nonlinear coupling between thermal mass and natural ventilation in buildings. Intl J. Heat Mass Trans. 46, 1251–1264.CrossRefGoogle Scholar
Zwillinger, D. 1992 Handbook of Differential Equations. Academic.CrossRefGoogle Scholar