Defeating the Leidenfrost EffectCategory: Science & Technology
Posted: November 19, 2013 07:49AM
One classic physics experiment I have seen multiple times is to quickly submerge one's hand in molten lead. Normally molten lead would immediately burn your flesh, but thanks some water and the Leidenfrost effect, a barrier protects your hand from the heat. Sometimes you actually do not want such a barrier, such as when trying to cool a reactor, and researchers at MIT have found a way to potentially dial back the effect.
In the molten-lead example, the person first dips their hand in water and then quickly dips it in the molten lead. When the lead touches the water, it causes the water film to evaporate, creating a vapor barrier to block the heat from reaching your skin (if done correctly), giving you a brief window to withdraw your undamaged digits. In a reactor the same thing happens when water is sprayed onto it, causing some of the water to bounce off of the vapor barrier, and not carry away any heat. What the researchers have found is that if you put a pattern of microscale posts with nanoparticles attached to them that vapor barrier will not form until a much higher temperature.
While reactors and steam generators are two obvious applications for this research, it could also find use in fuel-inject engines and potentially electronics. It depends on if a spray cooling system could be made to fit inside an electronic device.