Nanomaterials can increase water boiling efficiency

Oh yes, and I have this fantastic perpetual motion machine for sale for just $200…

Not that far fetched. If you get a more efficient conduction and heat transfer the water will boil faster. Nano Technology can change the metal at the molecular level and could lead to a better pot. I'm waiting for the tent poles or bear canisters!

"Rensselaer’s nanotechnology center has a particularly strong reputation in carbon nanotubes — perhaps the most enticing class of nano-materials. These nanoscale cylinders have been hailed as some of the lightest, strongest materials ever made."

Physiological activity of nanoparticles is not well understood, but the cause of much concern and the focus of quite a bit of health research. Using for cooking, I would say, is jumping the gun just a little.

From the article:

"Bringing water to a boil, and the related phase change that transforms the liquid into vapor, requires an interface between the water and air. […] Even though most of the water inside of the pot has reached 100 degrees Celsius and is at boiling temperature, it cannot boil because it is surrounded by other water molecules and there is no interface — i.e., no air — present to facilitate a phase change. […]

Koratkar and his team found that by depositing a layer of copper nanorods on the surface of a copper vessel, the nanoscale pockets of air trapped within the forest of nanorods “feed” nanobubbles into the microscale cavities of the vessel surface and help to prevent them from getting flooded with water. This synergistic coupling effect promotes robust boiling and stable bubble nucleation, with large numbers of tiny, frequently occurring bubbles."

Hmmm.

There are several things going on with the bubbles that form on the bottom of a pan as it heats. One of them is that they insulate the heat from the water, and vibrating a pot to dislodge them does improve boil times. I'm playing with a few ideas around this.

The bottoms of lager glasses are etched to produce a surface with sharp points to facilitate the formation of bubbles in the beverage. In the UK they are called "headkeepers". Maybe these nanotubes are also facilitating the production of lots of very small bubbles, and encouraging them to migrate off the bottom surface, thus improving heat conduction and convection currents in the water.

I find the study of fluid dynamics fascinating and my 2oz kettle is now down to 6mins 45secs for a US pint from 10C to boiling using 10g of ethanol. I just dreampt up a new design last night which I'll be trying out later. It's a sunny day here and I'm off for a walk.

I think a few have missed the entire point here. The primary controlling factor on how fast a pot of water comes to the boil *from cold* is the amount of heat being poured into the pot from the flame outside.

So "an order of magnitude increase in efficiency" is amusing, but probably the result of some utterly uneducated reporter waffling on.

If it sounds too good to be true, it probably isn't true.

Yep – totally right. This doesn't help the water get to 100C any faster. All that this would help with is, once you get it to 100C the conversion from liquid to vapor would be much faster. Great for your high power backcountry steam engine.

So this just prevents water from becoming superheated?

Snuffy

"The primary controlling factor on how fast a pot of water comes to the boil *from cold* is the amount of heat being poured into the pot from the flame outside."

And how much of that heat escapes up the sides without transferring as much of itself to the water as it might have done with a bit more consideration to design.

Possibly a concave pot bottom?

I generally agree with the caution of using unproven materials in cookpots that are in direct contact with hot food.

Further, and this may be an old tale without foundation, but I remember being cautioned that copper pots were not good to cook in because of too much copper leaching into the food. Hence, the propensity of copper "clad" cookware in which a layer of copper is applied to the outside of the pot to enhance conductivity.

OK for many uses. IIRC acidic foods react unsafely with copper.

Now, what would be better would be a boil suppressor, like a pressure cooker. It would delay the energy wasting liquid/gas phase change (boiling), increasing the pressure and forcing more of the energy to actually go into the heating of the liquid. The container would be a bit heavy, and I can't imagine the efficiency gain would be much. Unfortunately, an "order of magnitude" increase in the kind of efficiency we're interested in (energy released from fuel to energy absorbed by water) would be impossible unless your original system was <10% efficient, which is far below even the worst systems.

What we really need is an adiabatic water heater – just compress the surrounding air hard enough and there you go! Talk about carbon neutral.

The boil suppressor you outline would have the added benefit of not removing vitamins and minerals from whatever you are cooking, thus providing nutritional benefits. Pressure cookers work on this principle and that is why they are so attractive. Problem is, they're heavy as all hell.

Does anyone make a titanium pressure cooker? Ti should be more than strong enough to hold the pressure and would be lighter than standard aluminium.

Oh boy, I doubt it. I sure wouldn't want to be the one to see how light I could make one – it sounds like a good recipe for steam grenade! I do love vitamins though…