On the everyday level, liquid coolant technology seems to have remained stable for a while. You’ve learned which colored liquids go with which engines and terms such as OAT and HOAT, G-05 and ELC, are commonplace. All that may change in the next few years as some serious research starts yielding saleable products.
Would it surprise you to learn that both water and the various glycols commonly found in coolant mixtures are actually rather poor at absorbing heat? While today’s mixtures do have other benefits, including higher boiling and lower freezing points, they’re still not the best at actually removing heat from the engine or other sources.
Over the last decade, scientists, chemists and engineers have been spending a lot of lab time to develop more efficient liquids, and some may be close to production within the coming years. Naturally, any improvement in vehicle cooling could also be applied to many other industries as diverse as pharmaceuticals and spaceflight as well so the work is seen as well worthwhile.
Enter the nanofluids, a recently emerged field of study. It looks at the behavior of a fluid under many conditions when extremely tiny “nanoparticles” are mixed into it. Research in this field involves several scientific disciplines and has attracted the interest of NASA, Argonne National Laboratory and several large corporations well known in our industry.
A nanometer (nm) is one one-billionth of a meter. A nanoparticle is generally accepted to have at least one dimension less than 100 nm but many are in the 10-50nm range. The particles can be made from many materials including aluminum, silicon carbide, molybdenum disulfide, copper and other metals, either individually or in combinations, and also from man-made carbon nanotubes. The carbon nanotubes can be made to a specific size and thus allow a very precise amount of mass to be added to the fluid, but they are currently very expensive to manufacture.
The nanoparticles, and often small amounts of other chemicals, are extensively mixed into the liquid coolant or lubricant base; they have to be perfectly distributed to prevent settling and clumping. Additional concerns involve caking or build-up that could plug small passages or reduce large ones.
But once properly distributed, the improved heat transfer properties of the fluid have provided dramatic results. Tests by various companies show that such mixtures can absorb as much as 45 percent more heat than the base coolant alone, with many tests averaging increases in the 20 to 30 percent range depending on the nature of the materials used. It’s obvious that such increases in heat removal could provide better cooling in any system, and particularly in high heat applications such as EV and hybrid batteries and motors.
Comparable improvements were also noted during tests of nano-lubricants: lower friction and reduced metal to metal wear. Interestingly, researchers also found that in most cases, small amounts of the nanoparticles – often only one to eight percent by volume – provided the most benefits for heat absorption and lubrication.
A 2007 study at the National Institute of Standards and Technology (NIST) showed that very small amounts of nanoparticles added to R-134a refrigerant oil substantially increases the mixture’s ability to absorb heat.
But obstacles do remain, and these products are nowhere close to mass production. Cost is of course a factor, as is packaging, product stability over time, possible implications of disposal, and developing new components to handle with the nanoliquids.
As well, once the heat is picked up by the coolant and carried from the source, it has to be cooled or exchanged at the other end—the radiator or heat exchanger. That’s prompted additional investigations into newer and more efficient units capable of releasing the extra heat brought in by the new fluids.
These products show a lot of promise, and there is a lot of development going on to bring them to market. You probably won’t see these new coolants and lubricants soon, but you will see them.
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