NEWS - HEAT EXCHANGE / HEATSINK :
27/08/2013

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Directionality test of metal foam in natural convection conditions

info:

Unlike traditional heat sinks with cooling fins, performances of heat sinks made in metal foam, for natural convection, are independents from radiator’s direction. Temisth Company and Alvéotec have realized a test which demonstrated these results.

Case of heat sinks with cooling fins in natural convection conditions

In natural convection conditions, a cooling fin has to be absolutely parallel to direction of the flow, which is vertical. However, when the cooling pin is oriented (not parallel to the flow), heat exchange process is seriously disturbed; therefore total power dissipated is lower.

The following figure illustrates this test: On the left, the cooling fin is parallel to the direction of the flow; consequently the whole surface is used. On the right, the cooling fin is oriented and its performance is therefore reduced.

Benefits of metal foam structures

Main benefits of metal foam in this situation are:

  • Less pressure loss
  • Good thermal conductivity of the material
  • Important developed exchange surface

The last benefit that we will develop in this test is substantial. Compare to a surface extension by adding cooling fins, opened honeycombed materials won’t block the flow. And we can observe this result whatever the component’s orientation (the component that we want to cool). The experimentation has been realized to demonstrate and quantify it.

Experimental device

This is the schema of the device.

We use a containment system to protect the test section from external disturbance such as air flows and temperature changes. However, the containment system is still opened on its lower part to ensure the aeration process. We are able to control experimental tests with a system which controls test’s setting and recording of the data.

The imputed data are:

  • Heat power supply (potential heat flow that we have to dissipate)
  • The angle formed by the test section and the vertical holder

The recorded data are:

  • Thermal power dissipated by the heat sink
  • Temperature of the containment system and the heat sink

 

Results

We tried several directions from 0° to 90° and results were unexpectedly goods. Therefore the heat exchange rate is invariant whatever the direction of the heat sink made in metal foam (metal foam structure is “multi symmetrical”).

These results have substantial consequences because they demonstrate the fact that orientation of metal foam does not influence heat dissipation performances in natural convection environment.

Conclusions

The metal foam technology is now a breakthrough innovation compare to previous technologies.

  • Performances of heat dissipation is higher than results of heat sink with cooling fin or “pin block” (see Piseo Test)
  • Thanks to metal foam structure, performances do not depend on orientation of the heat sink; thus it creates new solutions and opportunities for our customers
  • Unlike cooling fins which are necessary place on a base and cannot be dissociated from it, metal foam structure does not need a base; therefore it creates a flow of natural convection.

You can also consult the full study (only in French): “Evaluation des performances d’un dissipateur thermique par convection naturelle”.