Paper 15: Volume 5 No.1 June 2006 Edition
Mixing Property and the Heat Exhaust Effect under Cross
Ventilation in a Full-Scale Experimental Model
S. Nishizawa1,
T. Sawachi2, K. Narita3, H. Seto1, Y.
Ishikawa1 and T. Goto3
1 Building
Research Institute, 1 Tachihara, Tsukuba 305-0802, Japan
2 National Institute for Land and Infrastructure Management, 1
Tachihara, Tsukuba 305-0802, Japan
3 Nippon Institute of Technology, 4-1 Gakuendai, Miyashiro,
Saitama 345-8501, Japan
Abstract
Cross ventilation is one
of the most important techniques for achieving energy conservation and for
maintaining a comfortable indoor environment in hot summer periods.
However it is difficult to evaluate the effect of cross ventilation
quantitatively and to undertake design based on a quantitative evaluation.
This is because the indoor environment is uneven and changes according to
the outside conditions. It is difficult to predict the ventilation rate
under cross ventilation due to the variation in wind. Hence it is still
difficult to estimate indoor comfort conditions given by cross
ventilation. In this paper
full-scale model cross ventilation experiments are described and the
properties of airflow in and around the full-scale model (velocity field,
pressure distribution on surface, visualized flow pattern, heat transfer
coefficient distribution, discharge coefficient of openings and so on)
have been examined. The mixing property and heat exhaust effect of cross
ventilation are discussed. Tracer gas concentration decay measurements
were made in the model to determine the spatial unevenness of mixing
property, the air change index and the velocity distribution. It is shown
that the different mixing properties are formed according to the airflow
pattern. The heat exhaust effect, was determined by using plasterboard
that was set on the floor for heat storage. The temperature of the air and
surface was measured, and exhaust heat by cross ventilation was
calculated. The relation between temperature reduction and the flow path
was examined, and the total exhaust heat by cross ventilation was compared
to the total convective heat transfer from the plasterboard. These
experiments showed that ventilation rate is the most important factor in
determining the amount of exhaust heat and the room mean age of air.
However the airflow path has an influence in the exhaust heat and mixing
property in the cross ventilated space.
Key
words: cross ventilation,
full-scale model experiment, mixing property, heat exhaust effect, tracer
gas, ventilation index, room mean age.
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