Hot hulls might mean slipperier ships
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.
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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.