Carbon Nanotubes Improve Cold Plate Performance

Engineers at Mainstream demonstrated the benefits of carbon nanotube coated cold-plate fluid passages, carbon nanotube-coated boiling heat transfer surfaces, carbon nanotube-impregnated thermal joint compound, and carbon nanotube surface treatments (for reduced thermal resistance when attaching electronics).

Our experiments demonstrated that carbon nanotubes will improve the conductive heat transfer, the interface conduction, and both the single- and two-phase convective heat transfer. We also demonstrated that the cost of nanotubes can be dramatically reduced and mass production of nanotubes is practical.

During this project, our researchers also investigated the use of the 9-Tesla magnetic-field of a super-conducting magnet for fabricating aligned carbon nanotube composites. Contrary to some published data in the literature however, no substantial improvement in thermal conductivity of these aligned nanotube composites was achieved.

Nanotube-Enhanced Air-Cooled Heat Sinks

Mainstream researchers demonstrated a patent-pending method to grow nanotubes on metallic air-cooled heat sinks. We also demonstrated the performance benefits of these coatings on air-cooled natural-convection surfaces. We conducted side-by-side, natural-convection heat sink experiments to demonstrate the improved heat rejection capability of carbon nanotube-coated heat sinks. The nanotube coating of the natural convection heat sinks that were tested tested (operating at 70° C) was experimentally demonstrated to improve heat removal by 45%.

Fabrication of High Conductivity Heat Pipes using
Multi-Walled Carbon Nanotubes

Mainstream developed a new (patent-pending) nanotube surface treatment for heat pipes that dramatically improved the performance of copper-water heat pipes. Side-by-side experiments confirmed a 285% improvement in the heat flux capability of copper-water heat pipes (when experimentally compared to an uncoated, but otherwise identical, copper-water heat pipe). The performance improvement may actually be even greater than the measured 285% because the experiments reached the maximum heat flux capacity of the test fixture, not the heat pipe. In fact, the data show that the minimal thermal gradient in the CNC heat pipe was continuing to decrease when the limit of the test stand (not the heat pipe) was reached.

Our engineers also successfully demonstrated an innovative high thermal conductivity composite material fabricated from carbon nanotubes embedded in a polymeric resin. Experiments to date resulted in more than a 1,100% increase in the thermal conductivity of the composite with the addition of 40% carbon nanotubes.