Thermal Conductivity of FluidHe3andHe4at Temperatures between 1.5 and 4.0° K and for Pressures up to 34 atm

Measurements of the thermal-conductivity coefficient $\kappa$ are reported for liquid ${\mathrm{He}}^4$ I between 1.77 and 3.95°K, for fluid ${\mathrm{He}}^3$ between 1.5 and 3.95°K, both at pressures up to 34 atm, and for gaseous ${\mathrm{He}}^3$ and ${\mathrm{He}}^4$ between 1.5 and 3.95°K at ∼10 Torr. Special attention is given the liquid-vapor critical region of ${\mathrm{He}}^3$ and the $\lambda$-transition line of ${\mathrm{He}}^4$. Corrections for effects of thermal boundary resistance and convection are discussed for the fixed-separation parallel-plate apparatus used for these experiments. Taking into account these corrections, the over-all accuracy of the data is considered to be better than ±3%, though the precision is better than ±1%. Away from the singular regions ${\left(\frac{\partial \kappa }{\partial T}\right)}_P$ is anomalously positive and increases with pressure for both ${\mathrm{He}}^3$ and ${\mathrm{He}}^4$. Isobars of $\kappa$ for ${\mathrm{He}}^4$ I pass through shallow minima and then rise sharply as the $\lambda$ line is approached from higher temperature. Isotherms of $\kappa$ for ${\mathrm{He}}^3$ in the neighborhood of the critical point display distinct cusps. Scaling laws predict that near the $\lambda$ temperature $T_{\lambda }$ the coefficient $\kappa$ should be proportional to ${(T-T_{\lambda })}^{-\frac{1}{3}}$, and near the critical temperature $T_c$ it should be proportional to ${|T-T_c|}^{-\frac{2}{3}}$; other theories predict $\kappa$ to be proportional to ${|T-T_c|}^{-\frac{1}{2}}$ near $T_c$. The experimental data are found to agree qualitatively, but not quantitatively, with these predictions.