Summary of Ventilation Analysis
Qingyan Chen; Associate Professor
Building Technology Program
Phone: 617-253-7714, Fax: 617-253-6152, Email: qchen@mit.edu
This is a summary
Developer. The first
Vanke City Garden
results are based on
Carriho-da-Graca.
report on the ventilation analysis conducted at MIT for Vanke
part of this report is for the 12 m x 12 m demonstration building in
and the second is a site analysis for Vanke Duoshi Garden. The
the individual reports from Yi Jiang, Haiyun Xing, and Guilherme
The 12 m x 12 m Demonstration Building in Vanke City Garden
The aim of ventilation analysis is to answer the following questions:
1.
Can we use natural ventilation in Beijing?
2.
If we can use natural ventilation, is there sufficient wind around the 12 m x 12 m
building?
3.
If there is wind around the building, how should the building layout look like?
4.
If there is insufficient wind around the building but natural ventilation is a good
design strategy, how could we design the building with ventilation?
(1) Can we use natural ventilation in Beijing?
The following figure shows that there is a good potential to use natural ventilation in
Beijing (The light green color stands for natural ventilation benefits). The air
conditioning period in Beijing can be reduced in half in the summer with sufficient
natural ventilation alone. The air-conditioned period (the read color) can be further
reduced with night cooling. It may be possible to eliminate completely the air
conditioning system with natural ventilation.
Comfort Hours Beijing
0
0
0
0
10
21
15
33
110
121
0
0
0
554
107
111
677
308
1750
319
345
744
672
(B. Givoni)
235
744
720
Hot and/or Humid
Comfort 2m/s
Comfort
Below comfort
744
625
599
375
257
5623
331
333
331
152
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Ju
ly
Ju
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M
ay
pr
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A
M
ar
ch
83
Ja
nu
ar
y
Fe
br
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ry
hours per month (year)
131
Comfort Zones
for Developing
Countries
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(2) If we can use natural ventilation, is there sufficient wind around the 12 m x 12 m
building?
By using a computational fluid dynamics package, we have calculated the airflow in the
12 m x 12 m building with typical wind direction and speed. Unfortunately, the results
show that the 12 m x 12 m building cannot take advantage of the cross ventilation
because the wind speed around the building is too small (0.1 m/s ~ 0.4 m/s with north
wind and 0.3 m/s ~ 0.8 m/s with south wind). This is because the high rise building in the
north and relatively high buildings in the south block the wind approaching to the 12 m x
12 m building.
(3) If there is wind around the building, how should the building layout look like?
Since the wind around the 12 m x 12 m building is small, the architects hoped to
maximize natural ventilation by using a courtyard that may catch wind into the building.
Two different sizes of courtyard have been proposed. Unfortunately, the airflow
distributions are similar between the two designs. This implies that the courtyard does
not help to enhance the natural ventilation in the building.
The current design has a relatively open indoor layout. The results show good cross
ventilation in the 12 m x 12 m building.
(4) If there is in sufficient wind around the building but natural ventilation is a good
measure, how could we design the building with ventilation?
Due to the small wind around the 12 m x 12 m building, current investigation has
studied the possibility to use stack-effect and mechanical ventilation to cool the
building. The preliminary results show that the stack-effect is not very strong. With a
large 2 m2 aperture area, the corresponding ventilation rate is two air changes per hour for
the whole building. However, mechanical ventilation seems a good option. With a
maximum fan energy consumption of 700W it is possible to extract 1 m 3/s room air to
the outside (6 air changes per hour). Hence, mechanical ventilation is recommended
for the building ventilation design.
Wind Analysis on Vanke Duoshi Garden
The current study is to answer the following questions:
1. How about the outdoor thermal comfort in the existing design by the Singaporean
architect?
2. If there is a comfort problem, how could it be solved?
(1) How about the outdoor thermal comfort in the existing design by the Singaporean
architect?
The existing design by the Singaporean consists of 10 high-rise buildings. The computed
airflow pattern around the building by the CFD package shows that, with the north
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prevailing wind, the wind speed at some locations is around 8 ~ 9m/s (Grade 5) at the
ground level. The wind speed is above the thermal comfort limit even for a short stay
(5m/s). The reason is that the wind can pass freely through the linear arrangement of the
buildings. At the height of 70 meters, the wind speed is above 12 m/s (Grade 6). It is
difficult to shelter the wind in the winter and to use the wind for natural ventilation in the
summer.
(2) If there is a comfort problem, how could it be solved?
We have developed a new design of the buildings in the Vanke Duoshi garden site. The
new design has the same building density. The results show that the new design is much
better in terms of outdoor thermal comfort and has the opportunity to use natural
ventilation. However, some minor problems in the new design need to be solved, such as
to turn 90o those blocks in the south site. The design is being continued.
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