Engineering Guide CDA3000
7-7
7 System installation
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7
A
7.2
Heat transfer
by heat
conductance
When a constant flow of heat P flows through a flat wall, the temperatures
ϑ
1
and
ϑ
2
are produced on the two surfaces (Figure 7.3). The relati-
onship is described in the equation
(1)
P:
Heat flow
W
λ
:
Thermal conductivity
A:
Area of wall
m²
d:
Thickness of wall
m
ϑ
1
,
ϑ
2
: Surface temperatures
°C or K
Figure 7.3
Stationary heat conductance through a wall
The thermal conductivity
λ
is a temperature-dependent material property.
In electronic devices it can be considered as constant for most applica-
tions. Tabelle 7.2 summarizes
λ
values for a number of key materials.
Depending on the task at hand - provision of good heat conductance or
high insulation - materials with the corresponding thermal conductivity are
selected.
P
λ
A
d
---
ϑ
1
ϑ
2
–
(
)
=
W
m K
⋅
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