Selecting
the Heat Sink
Once the necessary Heat Sink performance has
been established a suitable Heat Sink can be
selected. The choice will be influenced by a
number of factors of which performance, available
space, mounting arrangements and cost will be
the most important.
Performance
The performance figures shown in this brochure
indicate the performance which can be expected
from each Marston Heat Sink operating under
natural convection conditions in the optimum
mounting attitude of vertical plate and fins
and in typical lengths. Unless otherwise atated,
the data presented is applicable only to the
condition of a 6O°C rise above ambient of
the Heat Sink surface in contact with the device.
Data relating to other temperature rises is
available on request, but the approximate effect
of such a change can be established by using
the formula:
Thermal resistance at T1 =
where T1 = actual temperature rise above ambient.
This will give a rough guide within the range
40 - 80°C.
Performance of all Heat Sinks can be affected
by several factors including mounting attitude,
interferance from other equipment, position
and number of devices mounted on the sink, and
a temperature rise of the sink above ambient
which substantially differs from that used to
establish the published data. For this reason
the performance figures quoted should be regarded
as indicative only and if there is any significant
doubt about the suit ability of a sink, we strongly
recommend that its effectiveness is confirmed
in the particular operating conditions to which
it is subjected. In addition Marston is willing
to offer advice concerning the performance to
be expected in such conditions.
Size and Mounting Arrangements
This information is self-evident from the illustrations
and dimensional information included in the
brochure.
Cost
Prices depend on Heat Sink type, the provision
of holes and notches, finish and quality. Generally
the lighter the section the less expensive;
and a plain finish is less expensive than an
anodised. A specially designed sink may well
be a little more expensive than a standard.
