Effect of Screening Solar Chimneys on Induced Air Flow
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Jongjit
Hirunlabh*, Puttirat Piamwongjit*,
Sombat Teekasap** and Joseph Khedari*
**
Engineering Management Program, South-East Asia University,
19/1 Petkasem Road, Nongkaem, Bangkok 10160
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Abstract
This paper reports on a
field investigation of the effect of screening on the induced flow rate in
solar chimneys. The solar chimney considered here was a roof solar
collector (RSC). It is composed of CPAC monier concrete tiles, an air gap
and gypsum board. Two RSC units were integrated into the south-facing roof
of a centre single room house of 25 m3 volume. Different types
of screening were considered, namely: mosquito net, square net, metal
grille and nylon filter. Different arrangements of one or more screens
were installed at the top of one RSC unit while the other unit was not
screened and served as a reference.
It can be concluded that the addition of screens
decreased the induced air ventilation depending on the remaining free
surface area of the opening. The smaller the remaining free surface area
of the opening, the higher the percentage decrease of air flow rate.
However, the induced air flow rate is still relatively important to ensure
sufficient space ventilation and indoor air motion. Based on experimental
data, a simple linear relationship between the percentage of remaining
opening area and the percentage decrease or drop of air flow rate was
derived. The use of a nylon filter yields the highest rate of decrease
(about 8%). When mosquito net, grille and nylon filter were used together,
the decrease of air flow rate was about 18 %. However, when the wind speed
is important, the drop of air flow rate is less significant.
Finally, since screening
(particularly the nylon filter) decreases the rate of dust admitted into
the house with the incoming ambient air, it will play an important role in
promoting the concept of the solar chimney ventilated house (SCVH)
Key words: Roof solar collector, screening, natural air
ventilation, indoor air quality, dust.
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