Mechanocaloric Effect

mechanocaloric effect [¦mek·ə·nō·kə′lȯr·ik i‚fekt]

(cryogenics)

An effect resulting from the fact that a temperature gradient in helium II is invariably accompanied by a pressure gradient, and conversely; examples are the fountain effect, and the heating of liquid helium left behind in a container when part of it leaks out through a small orifice.

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Mechanocaloric Effect 

an effect observed in liquid helium below the temperature of the transition into the super-fluid state (below 2.19°K): when helium flows out of a vessel through a narrow (approximately 1 μ) capillary or orifice, the helium remaining in the vessel is heated. This effect was discovered in 1939 by the British physicists J. G. Daunt and K. Mendelssohn; the effect was explained by the quantum theory of superfluidity. The inverse effect—the flow of helium induced by the introduction of heat—is called the thermomechanical effect.