Dynamic measurements of thermal transport coefficients and boundary resistance I. Normal {sup 4}He

Journal Article · Sat Mar 01 04:00:00 EST 1997 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF02395931· OSTI ID:530549

Olafsen, J S; Behringer, R P ^[1]

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1. Duke Univ., Durham, NC (United States)

The thermal conductivity, {kappa}, and the thermal diffusivity, D{sub T}, of normal liquid {sup 4}He have been obtained from the temperature response, {Delta}T ({omega}), across a fluid layer of thickness, d, to an ac heat flux, Q(t) = Q{sub o}exp(i{omega}t). Previous transient heat flux experiments measured the thermal relaxation of the fluid towards equilibrium and assumed the dominance of a single slowest mode. The present ac technique allows measurements under steady-state conditions while driving the system at a single frequency, {omega}. The response curve for {Delta}T({omega})/Q{sub o} yields data for {kappa}, D{sub T} and the boundary resistance, R{sub b}. Boundary effects appear at frequencies higher than {tau}{sup {minus}1}{triple_bond} D{sub T}/d{sup 2} where the fluid is unresponsive to bulk heat transport. The authors use this fact to obtain R{sub b} with high accuracy in the normal phase from the high frequency response. In addition, the apparatus permits the fluid thickness, d, to be varied continuously and in situ from zero to 3 mm, allowing for further consistency in the fluid measurements. This work also includes data for the onset of convection where Q{sub o}>Q{sub c}, and Q{sub c} corresponds to the heat amplitude at convective onset.

• Sponsoring Organization: USDOE
• OSTI ID: 530549
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 5-6 Vol. 106; ISSN 0022-2291; ISSN JLTPAC
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
HELIUM 4
THERMAL BOUNDARY RESISTANCE
THERMAL CONDUCTIVITY
THERMAL DIFFUSIVITY