Nigel Wordsworth features NanoHex in the June Isse of Rail Engineer
Nanotechnology sounds like something from science fiction. After all, weren’t Seven of Nine and the Borg created by Nanites? (if you don’t understand, you aren’t a Star Trek fan!) So the thought of nanoengineering is perhaps a bit scary to some.
Nanites, microscopically small machines or robots that in size are close to a nanometre (10−9 metres), don’t exist although they are theoretically possible and work is continuing on them. However Nanotechnology, which deals with items smaller than 100 nanometres in size, does exist and is even being applied to railway engineering. Specifically in the field of electrical machines.
 NanoHex is a three-year pan-European project funded by the European Commission’s Framework 7 Programme to the tune of £5.5 million. The twelve members of the consortium are tasked with developing a cutting-edge liquid coolant that incorporates purpose-engineered nano-particles for more efficient cooling.
Traction Motors
One of the programme partners is Siemens, and their specific interest is the cooling of electric traction motors. As Dr. Gerhard Mitic of Siemens Research explained, when starting a train, the power consumed generates a high thermo-mechanical stress in the electrical devices, and this needs to be cooled. Modern motors make use of polytronics (polymer electronics, or conductive plastics) which have to have a 30-year life so they need to be cooled properly. Poor thermal management can too easily result in failures in the field.
The best coolant is water. However, this has the unfortunate property that it freezes in cold conditions making it impossible to use in its pure form in most countries. The most popular additive to prevent this happening is to add glycol, usually in a 50-50 mix with water. However glycol is a poor conductor so cooling efficiency suffers. What is needed is another additive that will improve the conductivity of the water/glycol mix. And as coolants are typically changed every five years the additives have to be stable.
Particle Physics
That’s where the nanotechnology comes in. NanoHex is studying the introduction of small particles, typically 20-50 nanometres in size, into the coolant. The particles themselves are conductive, metallic particles of copper, ceramics and also non-tubes of carbon fibre.
Larger particles would also improve conductivity, but they would also cause wear in pump impellor blades and other mechanical devices. However the nano-particles are so small they don’t interact with surfaces and so don’t cause wear. They also don’t sedimentate or accumulate (form clusters) so they are an attractive option.
However, nothing is ever quite that simple so a lot of work needs to be done to choose the correct mix of nano-particles that will make for a good coolant.
Future Programme
Previous work has been done with commercially-available nano-particles in laminar flow, but now NanoHex is extending that work to look at turbulent flow, as well as new types of nano-particles developed specifically for this application.
The three year programme started in September 2009. The first year will be taken up with developing a good coolant fluid, one which works well with polytronics systems and has both good shock-stability and good long-term stability. The next two years will be spent refining the design of the whole cooling system. ItN Nanovation AG of Saarbrücken, Germany , is working on the particle research, particularly ceramic particles, and also looking at stabilising chemicals. The University of Birmingham department of Chemical Engineering is also working on particle research. 
Meanwhile Thermacore Europe, based in Northumberland, is designing the cooling devices, heat exchangers and cold blades, and Siemens will combine all the elements into a practical application. 
At the end of the three year NanoHex programme the system should be ready to test. Six more years of field trials will be required before the first nanocoolants can go into commercial operation. Seven of Nine will be proud….