Low and High Pressure Experimental Analysis of
Ventilators for Natural Ventilation in Buildings
N Chilengwe
and S Sharples
Centre for
the Built Environment, Unit 9 Science Park, School of Environment and
Development, Sheffield Hallam University, Sheffield S1 1WB, UK
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Abstract
The wind and buoyancy pressure driving forces for
natural ventilation of buildings are very low, typically less than 10 Pa.
Depending upon the prevailing climatic and thermal conditions, or
even the location of a building on a site in relation to other surrounding
buildings and landscape, the predominant pressure force incident on a
purpose-provided natural ventilation opening can either be closer to the
lower range of pressure differentials (< 2 Pa) or vary over a wider
range of higher pressures (2 - 10 Pa). This study investigated, via a
series of experiments, variations in power law characteristic equations of
ventilators derived from low pressure measurements, relatively higher
(typical) pressures and those derived by considering the whole pressure
range. The results obtained indicate that the characteristic equation is
not only influenced by the constituent components of the ventilator but
also by the pressure range from which it was generated. As such, design
and operation of natural ventilation needs to incorporate some methods to
adapt resulting air flow rates to account for variations in pressure
differentials, thus ensuring that a given ventilator maintains a
consistent air flow pattern over the whole range of pressure differentials
encountered.
Key words: Air flow performance, building ventilation, power law,
pressure driving forces, ventilator.
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