At the Department of Mechanical Engineering at Purdue University, scientists have succeeded in developing a carbon nanotubes based device to provide enhanced cooling applicable to insulated gate bipolar transistors, and to high-power switching transistors in power electronics for military and hybrid vehicles applications. The device is based on the new wicking technology representing the heart of a new ultrathin hollow plate containing water. The heat exchange functionality is enhanced from 50W/cm2, typical of standard computer chips cooling devices, to 550W/cm2.
Inside the cooling system, water circulates as it is heated, boils and turns into a vapor in a component called the evaporator. The water then turns back to a liquid in another part of the heat pipe called the condenser. The wick eliminates the need for a pump because it draws away fluid from the condenser side and transports it to the evaporator side of the flat device. The greater heat dissipation is provided by devising thinner heat pipes (1/5 w.r.t. commercial ones) and covering a larger area with respect to conventional devices. The wicking part of the heat pipe is created by sintering, or fusing together tiny copper spheres with heat. Liquid is drawn sponge-like through spaces, or pores, between the copper particles by a phenomenon called capillary wicking. The researchers are creating smaller pores by "nanostructuring" the material with carbon nanotubes, which have a diameter of about 50 nanometers, or billionths of a meter. However, carbon nanotubes are naturally hydrophobic, hindering their wicking ability, so they were coated with copper using a device called an electron beam evaporator. Devices based on the research could be in commercial use within a few years
The Defense Advanced Research Projects Agency (DARPA) funded the research project carried out by a composite team from Purdue: Thermacore Inc., Georgia Tech Research Institute and Raytheon Co. (leader), creating the compact cooling technology in work. The technical details of these novel systems are provided in the International Journal of Heat and Mass Transfer (August 2010)
More information at http://www.purdue.edu/