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International Heat Transfer Conference 13

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

STUDY OF THE THERMAL WAVE BEHAVIOUR IN A HE II-FILLED CUBIC CAVITY

Peng Zhang
Institute of Refrigeration and Cryogenics, MOE Key Laboratory of Power Machinery and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Rd. Minhang District, Shanghai 200240, China

Masahide Murakami
University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan

R Z Wang
Shanghai Jiao Tong University

DOI: 10.1615/IHTC13.p27.10
12 pages

Abstrakt

Thermal wave (Second sound wave) in superfluid helium (He II) is a very interesting thermo-fluidic phenomenon, in which heat is transported in a wave mode and it is different from the diffusion heat transfer mechanism described by Fourier principle. In the present study, the behaviour of the pulsed thermal wave emitted from a planar heater initiated by the pulsed heat input transmitting in a He II-filled cavity is studied. The thermal wave phenomenon is numerically investigated by Landau's two-fluid model with Vinen's vortex equation. From the analytical results, some unique features are characterized in two-dimensional thermal wave. It is found that a rarefaction (temperature decrease) in wave profile follows the positive temperature rise, which is very different from the planar thermal wave in one-dimensional case. The positive amplitude of thermal wave results from the counterflow between the superfluid and normal fluid components of He II, while it is the first time to point out that the counterflow between two components in the rarefaction portion becomes inverse. The thermal wave may develop into thermal shock wave when it is subjected to quantized vortices. When the input heat flux is large, the vortex line density (VLD) of quantized vortices develops very fast from the initial value and reaches a higher equilibrium level, which in turn depresses the amplitudes of both the positive and negative thermal wave (rarefaction) portion. As the thermal wave transmits in He II, the amplitude gradually decreases due to highly non-linear feature of He II and the interaction with quantized vortices. When the thermal wave reaches the boundaries of the cavity, it will be reflected. The thermal wave will keep oscillating and higher temperature zones always exist in He II when it is free from quantized vortices, while the thermal wave attenuates quite quickly when it is subjected to quantized vortices and the temperature of He II in the whole cavity is quickly equilibrated. This fact indicates that quantized vortices play a role in effectively mediating the exchange of the momentum between the superfluid and normal fluid components, which accelerates the heat transfer in He II.

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