Who Wrought The Book Of Luke

jumping

is interesting how a simple cooking pan can speak of chaotic systems, surface tension and gravity with the help of a drop of water. The experiment is so simple that most certainly you have done even if inadvertently. Dropping a drop of water on a frying pan hot and, in many cases, the drop will begin to jump and move violently across its surface.




It's called the Leidenfrost effect that in the case of water, takes place on a surface that is 200 - 300 degrees Celsius . A simplified explanation is that some water will evaporate in contact with the surface, forming a vapor layer. The surface tension attracts other molecules forming a drop whose characteristics depend on the liquid and the surface. And the gravity, in addition to affecting the shape of the drop, keeps bonded to the surface preventing exit off like a rocket. So steam can escape only by the edges, resulting in chaotic motion of the drop in the opposite direction.

And why does not evaporate all the water at once? This is because the steam has a heat transfer capacity of relatively low at these temperatures. In the graph we can see how they vary depending on the temperature of the contact surface. Shortly before 100 degrees begins to decrease reaching a minimum between 200 to 300 degrees. Is an effect that can be very dangerous. For example in a heat exchanger could be increasing temperature and decreasing the transmission heat to cause serious damage to the device.


few months ago, the Leidenfrost effect became popular when researchers at the University of Oregon discovered how to use the motion of liquid droplets to cool hot surfaces as computer chips. They used a surface with a profile similar to a saw that what they "ran" out of steam and thus the movement of the drop.




More information on the page research group that discovered it. Below you can see a very cortito video of how it works.





I recommend you see this more detailed picture drawn by the New York Times , explaining the effect and its applications in the other direction you can find a collection of videos to slow motion on the movement of various fluids such as water or liquid nitrogen.


As you can see is a fun, but probably too inefficient to directly convert heat into motion. And as a cooling system has the advantage that it does not need pumps or moving parts. A little ingenuity and the laws of physics do all the work.


Category: Physical