Advanced Building Simulation

104 Hensen
Air flow (kg/s)
25.0
20.0
15.0
10.0
5.0
0.0
–5.0
–10.0
Upward air flow through atrium
Onion 1/h
Onion 10/h
Ping-pong 1/h
Ping-pong 10/h
240.0
241.0
242.0
243.0
244.0
Day of the year
245.0
246.0
10.0
244.5 245.0 245.5
–10.0
245.0 245.5
Day of the year
246.0
Figure 4.11 Simulation results for vertical airflow through atrium starting with day 241 and ending
with day 246 of a reference year. Frames on the right show selected results in more detail.
Flow rate in kg/s.
It is interesting to compare Figure 4.12 with Figure 4.11, because it shows that the
flow increases with the difference between zonal and ambient temperatures and not
with zonal temperature itself.
Obviously, the temperature difference depends on the amount of airflow, while the
amount of airflow depends on temperature difference. As is clearly shown in the
graphs, it takes an integrated approach to predict the net result.
Table 4.3 shows a statistical summary of the results. Included are the numbers of
hours above certain temperature levels, since such parameters are used in certain
countries to assess summer overheating. For the ground floor air temperatures there
are relative big differences in hours �27�C between the once per hour and the 10 per
hour time step cases. This is because the maximum air temperature for that zone is
close to 27�C and so the number of hours above 27�C is very sensitive.
This case study focuses on the relative comparison of methodologies to model
coupled heat and airflow in a building. Although no mathematical proof is presented,
16.0
15.0
14.0
13.0
12.0
11.0
10.0
5.0
0.0
–5.0