Details

Autor(en) / Beteiligte

• Olafsen, J S
• Behringer, R P

Titel

Dynamic measurements of thermal transport coefficients and boundary resistance I. Normal super(4)He

Ist Teil von

• Journal of low temperature physics, 1997-01, Vol.106 (5-6), p.673-704

Erscheinungsjahr

1997

Quelle

SpringerLINK Contemporary (Konsortium Baden-Württemberg)

Beschreibungen/Notizen

• The thermal conductivity, Kappa , and the thermal diffusivity, D sub(T), of normal liquid super(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) identical with Q sub(0)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(0) yields data for Kappa , D sub(T) and the boundary resistance, R sub(b). Boundary effects appear at frequencies higher than tau super(-1) = D sub(T)/d super(2) where the fluid is unresponsive to bulk heat transport. We 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(0) > Q sub(c), and Q sub(c) corresponds to the heat amplitude at convective onset.