Heatpipes as a thermal solution

 
  
Thermacore design, prototype and manufacture heat pipes and heat pipe assemblies
 
A heat pipe is a two-phase heat transfer device with an extremely high "effective" thermal conductivity. It can be cylindrical or planar, and the inner surface is lined with a capillary wicking material. Heat transfer occurs through the evaporation and condensation of a "working fluid".  
                       
                   
Sintered wick pipes (above) have a wick made from minute copper spheres which have been sintered at high temperatures creating a structure with very high capilary power which will even work against gravity.
A pipe which uses a mesh wick (above) can transmit very high power for a given diameter pipe, however these pipes need gravity to get the working fluid back to the heat source.
The heat pipes shown above are "grooved" heat pipes. These are light weight, aluminium pipes used in space applications.