Thermostat on levitating drops

The Leidenfrost effect is a rather strange phenomenon, due to which droplets of liquid can levitate, float in the air or even move upwards along an inclined surface. Now physicists from Bath University (UK) have managed to use this effect to construct a thermostat without moving parts . Unlike existing thermostats, it also does not use electrical circuits.



When the temperature of the water droplets passes the Leidenfrost point, they gather into small balls and move over the hot surface, keeping themselves on an evaporating layer of vapor. The effect can be observed if you drop water in a hot frying pan (200 ° C or more).



Physicists from Bath University have previously found a way to make the drops move in a given direction, changing the surface temperature below them. They also noticed that in this way you can make drops climb up over the surface, overcoming the force of gravity.



The created thermostat is able to automatically maintain a constant temperature using the Leidenfrost effect. If the temperature rises, the droplets are sent to the side (dropped on a metal fence) with a cooling effect. If the temperature drops, the droplets are dropped in the other direction, allowing the system to warm to the desired level. When the desired temperature is reached, the droplets are guided along a standard route.

')





The operation of the device is shown in a small video shot by students.







The conceptual device demonstrates that the Leidenfrost effect can be used to control temperature. Since this thermostat does not use electronics and there are no moving mechanical parts (except for water droplets), it should, theoretically, be more reliable than existing thermostats.



Now scientists are trying to make a thermostat model useful in practice and are studying in what temperature range it can work. Indeed, in reality it rarely happens when it is necessary to maintain the ambient temperature at the level of 200-250 ° C.



The scientific work "Thermostat Leidenfrost" published in the journal Journal of Heat Transfer.