JEC COMPOSITES MAGAZINE - Issue #98 - July/August 2015 - 27

Fig. 7: Circular heat sink - baseline case with
aluminium

Fig. 4: Comparison of an aluminium/plastic LED housing versus a BN-filled plastic housing

Current work

Fig. 5: Aluminium and plastic heat sinks

housing and the heat sink. A comparison
of the heat transfer between a metal and a
plastic heat sink is shown in Figure 3.
When comparing two different constructions for an LED bulb housing, Figure 4
shows that a housing made from BN-filled
plastic (on the right) is 13°C cooler and
45-60% lighter than an aluminium housing (on the left). By utilizing the design
freedom of plastics, adding just one extra
fin to a heat sink will result in a lower
temperature at the heat source, as shown
in Figures 5 and 6.

As weight is a challenge in many applications, choosing plastics has the added
benefit of enabling weight reductions
of 30-55%. The above examples used
finite element analysis to demonstrate
the possibility of substituting aluminium

Fig. 8: Circular heat sink case with 5 W/mK plastic

heat sinks with thermally-conductive
plastics for various heat sink geometries in
convection-limited environments. Further
analysis showed that BN-filled plastics
may also perform adequately in forced
convection conditions.

What does heat
management mean for new
composite applications?
The change in powertrain design for new
vehicles is leading to the integration of
more electrical and electronic parts in
cars. Hybrid technology or fully electric
cars require a larger number of devices
around the controls, batteries or powertrain.
In general, there are several areas in cars
where thermal management is critical, as
fully electric or hybrid cars. The housing protects the battery, which is often
underneath the car, from stones, water

Fig. 9: Circular heat sink case with 3 W/mK plastic

No98 July - August 2015 /

Feature Automotive

Fig. 6: Efficiency of a 6-fin aluminium heat sink
versus a 7-fin BN-plastic heat sink

Current work is further exploring this
concept for other relevant heat sink
geometries.
A load of 3W was applied to the top
surface of a circular heat sink in a static
convection environment. The steadystate temperature distributions for all
circular heat sink cases are shown below.
The dimensions of the three heat sinks
are identical - the only difference is the
number of fins between the aluminium
and plastic heat sinks. Figure 7 shows the
baseline case of the aluminium heat sink.
Figure 8 shows a plastic heat sink with
a thermal conductivity of 5 W/mK and
Figure 9 shows a plastic heat sink with a
thermal conductivity of 3 W/mK.
The maximum temperature for the aluminium heat sink and the 3W/mK plastic
heat sink was the same (69°C), whereas
the hottest spot on the 5 W/mK plastic
heat sink was 11°C cooler (58°C). This
demonstrates that a thermally-conductive
plastic made from Momentive's BN with a
small design change can achieve the same
performance or even result in a lower
maximum temperature versus a heat sink
made from aluminium.

jec composites magazine 27
Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #98 - July/August 2015
