Fountain Effect
Also known as the thermomechanical effect. When radiation warms a superfluid, the expansion pushes up the free surface of the liquid forming a fountain. This causes liquid helium II to flow up the sides of open containers. Allen and Harry Jones discovered thethermomechanical effect in helium II, popularly known asthe "fountain effect." This was an accidental discoverymade in the process of investigating thermal conduction in fine tubes. Allen found that in the experiments the conductivity of heat appeared to increase as the size of the capillary borecarrying the heat became smaller. For the smallest tubes and lowest temperatures, the rise in liquid level shown in was observed for the first time. In addition, in the same dewar, was a small tubewith an open bulb at the bottom containing emery powder, since Allen thought that he would examine the flow through powder to compare itwith the flow through a smooth tube. To makesure that the right piece of apparatus appeared in the clear strip he had a small pocket torch[flashlight]. As the emery powder tube cameinto view in the light of the torch helium spurtedout of the top of the tube. It continued to spurtas long as the torch light shone on the powderand ceased when a card cut off the light, andtherefore the radiant heat, to the bulb. Thefountain had appeared. Admittedly it was onlyone or two millimeters high, but it was there.
Great excitement, everybody in the lab wasbrought in to see it, and a camera rigged to take
a picture. By the next week he had a properly designedtube to produce a real fountain about 15 cm high when irradiated by a 60 watt desk lamp bulb.
Great excitement, everybody in the lab wasbrought in to see it, and a camera rigged to take
a picture. By the next week he had a properly designedtube to produce a real fountain about 15 cm high when irradiated by a 60 watt desk lamp bulb.
Superleaks
oscillating superleak transducer!
Another interesting property of superfluid is super-leaks .A liquid(which can turn into super fluid when cooled) initially placed in a container when cooled to it’s critical point (the point where it turns into super fluid) will drip through molecule-thin cracks in the container.i.e, they pass through the tiniest cracks.this happens because of their weak intermolecular forces.