Thermal transport in very dilute /sup 3/He-/sup 4/He mixtures near the superfluid transition

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6638698

Dingus, M L

Measurements of the average thermal conductivity K/sub exp/ = hQ/..delta..T were made in the superfluid phase for dilute mixtures of /sup 3/He in /sup 4/He. Here h is the cell height, Q is the heat flux, and ..delta..T is the temperature difference across the fluid layer. The measurements were made over the impurity range 2 x 10/sup -9/ < X < 3 x 10/sup -2/, where X is the /sup 3/He molar concentration, and with heat fluxes 0.3 < Q < 160 ..mu..W/cm/sup 2/. K/sub exp/ was calculated assuming that the boundary resistance R/sub b/, measured for X < 10/sup -5/, to be independent of X for all X values investigated. For Q smaller than a well defined critical heat flux Q/sub c/(X), K/sub exp/ was found to be independent of Q and could be independent of the reduced temperature epsilon = (T - T/sub lambda/)T/sub lambda/ for absolute value of epsilon < T/sub lambda/. The value of K/sub eff/ extrapolated to T/sub lambda/ was found to depart from the prediction K/sub lambda/ varies as X/sup -1/ for X < 10/sup -3/, tending instead to a weaker divergence K/sub lambda/ approx.X/sup -a/ with a approx. =0.08. For Q > Q/sub c/, a nonlinear regime is entered. For X approximately less than or equal to 10/sup -6/, the measurements with the available temperature resolution are limited to the nonlinear regime, but can be extrapolated is not the linear regime for X > 2 x 10/sup -7/. A finite conductivity as X ..-->.. 0 is not excluded by the data. The results fr K/sub exp/(Q), Q/sub c/(X), and K/sub eff/(X) are found to be internally consistent. The data obtained in the nonlinear regime are presented, and unexplained phenomena observed in this regime are discussed.

• Research Organization: Duke Univ., Durham, NC (USA)
• OSTI ID: 6638698
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRITICAL HEAT FLUX
DISPERSIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HEAT FLUX
HELIUM 3
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MIXTURES
NONLINEAR PROBLEMS
NUCLEI
PHYSICAL PROPERTIES
STABLE ISOTOPES
SUPERFLUIDITY
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES