Marine

Hot hulls might mean slipperier ships

Hot hulls might mean slipperie...
A scientist has proposed that ships could move through the ocean with less friction, if their hulls were heated to above the boiling point of water
A scientist has proposed that ships could move through the ocean with less friction, if their hulls were heated to above the boiling point of water
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A scientist has proposed that ships could move through the ocean with less friction, if their hulls were heated to above the boiling point of water
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A scientist has proposed that ships could move through the ocean with less friction, if their hulls were heated to above the boiling point of water

Want to make a ship move faster through the water? Well, one thing that you can do is paint its hull with low-friction or anti-biofouling paint, to keep barnacles and other marine organisms from growing on it. According to Prof. Derek Chan, from the University of Melbourne's Department of Mathematics and Statistics, another approach that should work is to heat that hull up to a temperature of over 100C (212F). His proposed method is based on a 255 year-old principle known as the Leidenfrost effect.

Named for its discoverer, German doctor Johann Gottlob Leidenfrost, the Leidenfrost effect is the phenomenon wherein a liquid, when exposed to a solid that is significantly above that liquid's boiling point, forms an insulating vapor layer between itself and that solid. This is the reason that water droplets dance across a sufficiently-hot skillet, instead of just evaporating on the spot.

Applying that principle to a ship, Chan believes that a hull kept at an outer temperature significantly above the boiling point of water, should cause a low-friction vapor layer to form between that hull and the water. He tested the theory by analyzing high-speed footage of polished balls being dropped through liquid - their drag was reportedly greatly reduced when they were heated to the point at which the Leidenfrost effect occurred.

Not only could this be used to reduce transportation costs and greenhouse emissions from shipping, he suggests, but it could also be used to speed the flow rate of liquid through pipes.

Chan does, however, admit that keeping the hull so hot could increase the rate of corrosion, and is further researching that possibility. There is also the question of whether the energy required to heat the hull (and keep it hot, as it's exposed to cold ocean water) would be significantly less than the amount of energy that would be saved through the reduction of friction.

The University of Melbourne worked with Saudi Arabia's King Abdulla University on the research, which was recently published in the journal Physical Review Letters.

44 comments
Mohamed Zeid
ok thats good but do not forget that you need more fuel and more just to heat the hull
Todd Dunning
Great idea, fascinating forward-looking technology. And thankfully without a word of eco-Kool-Aid or C02.
Nodeity
What about the incredible amount of steam that would presumably envelop the ship when it is at stand still!!
Gadgeteer
Any hull much bigger than a personal watercraft will need a huge amount of fuel to create that much heat. It\'s not only exposed to cold water, it has to boil that water instantly, and the heat of vaporization of water is enormous. Schemes already being researched using air bubble lubrication would be far less energy intensive.
Adrien
I\'m struggling to recall a more stupid idea. Maybe the one idea that was more stupid was to dump particles into the atmosphere to reflect heat and combat global warming - by flying hundreds of planes 24/7 (I heard a professor at Stanford describe it). Vast amount of energy required to keep a hull above 100deg, especially when it\'s constantly being quenched by the ocean. Much easier to do something like a hydrofoil.
quax
There is also the question of whether the energy required to heat the hull (and keep it hot, as it\'s exposed to cold ocean water) would be significantly less than the amount of energy that would be saved through the reduction of friction. This must be the understatement of the year. While academically interesting you really don\'t need to have a clear understanding of the huge thermal capacity of water as well as very high heat conductivity of metal nor and advanced physics degree to quickly conclude that the idea that you could save energy this way is ludicrous.
Mark Temple
and 6 months after navies adopt this technology, the first heat seeking torpedoes will be deployed...
Adrien
I also think (apart from cooking the sailors) the other major problem would be bouyancy. Metal doesn\'t float as well in steam as it does in water. If the hull were able to be kept hot enough to continue vapourising the water around it, I think it would sink straight to the bottom of the ocean. Kinda like trying to swim in the aerated water at the bottom of a waterfall.
Robert Burke
They may be able to pipe the excess heat from the engines up to the bow and heat it that way. Maybe it doesn\'t have to boil to be effective? Say 50% or less is better than nothing. Maybe heated air bubbles would be better than heating the water?
joeblake
@Robert Burke They may be able to pipe the excess heat from the engines up to the bow and heat it that way. Good idea to harness \"waste\" heat. This wouldn\'t increase the overall energy consumption since it would be utilising heat from fuel which has already been consumed. (Same as using heat from an internal combustion exhaust to run a stirling engine or a thermocouple (eg Peltier device) to generate electricity.) This could possibly be useful in making a combat craft more stealthy by reducing its atmospheric heat signature. I think the rise in water temperature would be far less than venting to atmosphere, because of water\'s greater latent heat capacity. But a simpler thought, why not have a couple of Venturi tubes which would take in cold water, use the waste heat to warm it and increase its velocity as it is expelled, thus giving a minute propulsion power boost? Simpler still, heat up the hull and thus \"cook\" any barnacles to death, and thus you\'ve got a \"self anti-fouling hull\" which doesn\'t rely on chemicals, thereby reducing drag. (And Barnacle Chowder? ;-) )