CARD-LOKS AND THERMAL RESISTANCE
Testing
performed by numerous users of Calmark's Series 225 and similar size Card-Loks
(approx .25 high) has shown that the thermal resistance across the interface of
a card which is clamped to a cold plate will usually fall within the range of
2° to 4°C inch/watt. Three piece Card-Loks of shorter lengths
will usually provide results close to the 2, while longer Card-Loks (over 6
inches) may fall closed to the 4. These thermal resistance numbers apply
when testing is performed at or near sea level. When the same testing is
performed at high altitude or near vacuum conditions the results can be
significantly affected. Increases of from 10 to 40 percent would not be
unusual, especially with longer three piece Card-Loks Five piece Card-Loks,
such as Series 260 or 265, with their greater and more evenly distributed
clamping forces, will greatly reduce these potential gradients.
The following chart provides an easy method of estimating the temperature rise
across the interface (junction) of the card and cold plate when thermal
conductivity is the only means of heat transfer considered (heat loss due to
radiation and convection minimized).
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