3. PANEL DESIGN
Installation type according DIN-VDE 0660/500 standard Formula for A calculation (m
2
)
Panel free on all sides A = 1.8 * H * (L + P) + 1.4 * L * P
Panel with the back surface obstructed A = 1.4 * L * (H + P) + 1.8 * P * H
Panel with one side surface obstructed A = 1.4 * L * (H + L) + 1.8 * L * H
Panel with one side surface and the back surface obstructed A = 1.4 * H * (L + P) + 1.4 * L * P
Panel with both side surfaces obstructed A = 1.8 * L * H + 1.4 * L * P + P * H
Panel with both side surfaces and the back surface obstructed A = 1.4 * L * (H + P) + P * H
Panel with both side surfaces, the back surface and the front surface obstructed A = 1.4 * L * H + 0.7 * L * P + P * H
Table 6: Effective Dissipation Surface Calculation
L = Width (m), H = Height (m), P = Depth (m)
In built panels application with painted steel plate, for a null air flow surrounding it, the heat dissipation constant can be
considered 5.5 W/m
2 ◦
C.
The power dissipated by a panel can then be calculated through the equation Qs = k * A * (internal temperature – external
temperature), or obtained from figure below.
Figure 32: Dissipated Power x Surface x Temperature difference
However, this value may be triple if forced ventilation is applied in the panel interior.
The air flow inside a panel is obstructed by the equipment installed, generating concentrated heating points. In this case,
fans may be installed to increase the air flow within the panel.
The forced air circulation through fans in the panel interior brings an improvement in the natural convection and tendency
to keep the temperature degree equal throughout the panel. Without it, there’s a tendency to form a concentration of heat in the
upper part of the panel due to natural convection.
Examples:
For a panel free on all sides, with an effective area of 3.96 m
2
, installed power of 350 W and room temperature of 30
◦
C,
calculate the internal average temperature.
Qs = k * A * (Ti – Te)
37
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