Kapitza temperature jump, a phenomenon in superfluid liquid helium discovered by P. L. Kapitza (1941), in which a temperature difference ΔT arises at the interface when heat passes from a solid body to liquid helium. It was later established that the Kapitza temperature jump is a general physical phenomenon at low temperatures: it arises at the interface between any dissimilar media (at least one of which is a dielectric) when there is a heat flow across the boundary, from one medium into the other. The temperature jump ΔT is directly proportional to the heat flux density Q and inversely proportional to T3:
ΔT=RQ=(A/T3)Q,
where the coefficient A depends on the elasticity of the substances in contact and also on the thermal and mechanical treatment of the surface. At the annealed copper — liquid 4He boundary, at a temperature of 0.1 K and Q=10-4 W/m2, ΔT=2.4*10-3 K. Thus R=2.4*10-2/T3(m2*K/W). For other metals (under the same conditions) R has similar values. The quantity R is called the Kapitza resistance, or the boundary thermal resistance. It has been shown theoretically (I. M. Khalatnikov, 1952) that at low temperatures heat is exchanged between a liquid and a solid body by means of thermal phonons, while the Kapitza temperature jump at the boundary arises from the difference between the acoustic impedances of the two media. The Kapitza temperature jump hinders the cooling of bodies to ultralow temperatures.
ΔT=RQ=(A/T3)Q,
where the coefficient A depends on the elasticity of the substances in contact and also on the thermal and mechanical treatment of the surface. At the annealed copper — liquid 4He boundary, at a temperature of 0.1 K and Q=10-4 W/m2, ΔT=2.4*10-3 K. Thus R=2.4*10-2/T3(m2*K/W). For other metals (under the same conditions) R has similar values. The quantity R is called the Kapitza resistance, or the boundary thermal resistance. It has been shown theoretically (I. M. Khalatnikov, 1952) that at low temperatures heat is exchanged between a liquid and a solid body by means of thermal phonons, while the Kapitza temperature jump at the boundary arises from the difference between the acoustic impedances of the two media. The Kapitza temperature jump hinders the cooling of bodies to ultralow temperatures.