7-8
Engineering Guide CDA3000
7 System installation
The thermal resistance in heat conductance, the temperature lag R
thL
, is
produced from:
(2)
R
thL:
Temperature lag
d: Wall thickness m
λ: Thermal conductivity
A. Wall area m²
Thus equation (1) can be reformulated:
If a wall comprises more than one layer, the resultant temperature lag is
equal to the sum of the temperature lags of the individual layers.
The specific thermal contact resistance ( ) of metal on metal is
halved when heat transfer compound is used between two metal sur-
faces.
Good heat conductors
Material
λ
Aluminum, pure 230
Cast iron 58
V2A steel 15
Sheet-steel 59
Tabelle 7.2 Thermal conductivity of some materials at
ϑ
= 20°
K
W
----
W
mK⋅
-----------
∆ϑ ϑ
1
ϑ
2
PR
thL
⋅=–=
ϒin
Cm
2
K⋅
W
-----------------
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