OSRAM PrevaLED Core Z2 User Manual
Page 16
16
THERMAL CONSIDERATIONS
4.2. Heat sink
Basically, the heat sink has to fulfi ll two tasks:
a) Heat spreading through heat conduction
The task here is to spread the heat as uniformly as possi-
ble from the contact surface of the LED module through
the heat sink material and into the cooling fi ns. In this
respect, the thermal conductivity and the material cross
sections of the heat sink play a decisive role (cf. the thermal
conductivities table below).
b) Heat dissipation to the surrounding medium
(usually ambient air)
For this task, the heat sink design in terms of fi n and sur-
face confi guration is decisive. By adequate geometrical
forming, heat conduction through convection and IR radia-
tion can be signifi cantly infl uenced and improved (cf. the
table with the IR emission coeffi cients on the next page).
Thermal conduction
resistance (R
th
) formula:
R
th
=
L
A
·
A
L
Thermal conductivities of selected materials
Material
Specifi c heat
conductance value
[W/(m · K)]
Copper
380–401
Aluminium
200–220
Brass
120
Steel
42–58
Stainless steel
15
Glass
1
Wood
0.13–0.18
Air (dry at 1013 mbar,
no dissipation)
0.0256 at 20 °C
Very good heat
conduction
Bad/no
cooling
L: Length through the material in
fl ow direction
[m]
A: Material cross section/surface
of the heat sink
[m
2
]