advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...

Test
number
Inlet
temperature
[°C]
Advanced Building Skins
Table 1: Comparison between prototype and numerical simulation
Fluid
velocity
[l/h]
Air
temperature
[C°]
- 5 -
Measured outlet
temperature at the
prototype [°C]
Calculated outlet
temperature by numerical
simulation [°C]
1 22,8 0,9 16,6 16,8 17,3
2 29,5 11,4 16,7 26,7 26,8
3 35,8 11,3 17,5 31,5 31,7
4 36,0 8,0 16,9 28,6 29,3
5 37,4 3,4 16,9 24,7 25,6
Figure 3: Distribution of heat during test number 4
In the next step the excessive computing times of the model get reduced by straightening the pipe. For
the realistic application possible curves of the pipes are negligible compared to length of the straight
sections. But nevertheless the influence of the curves toward straight pipes is investigated by using
different boundary conditions. Figure 3 shows the results of the comparison. There are no remarkable
descrepacnies.
Figure 4: Comparison of the numerical solutions between curved and straight pipes
For transferring heat from the fluid to the inner wall of the pipe, the heat transfer coefficient is the
most important parameter. It is dependent on the temperature and velocity of the fluid and the
diameter of the pipe. In this case of a sandwich panel with an integrated solar system, heat transfer
coefficients from 200 to 2000 W/(m 2 K) are theoretically possible. But to achieve an economic
performance the fluid flow is assumed to be laminar. This results from the investigations documented