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首页> 外文期刊>Physica, B. Condensed Matter >Generation of first sound by a heater in super fluid and normal He-4
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Generation of first sound by a heater in super fluid and normal He-4

机译：超级流体和普通He-4中的加热器产生的第一声音

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The shape of first-sound waves was studied in both super fluid and normal He-4 at pressures below and above a critical pressure P-cr. The waves were generated by a film heater. The heat flux density Q and the pulse duration tau were varied in the ranges from 1 to 250 W/cm(2) and from 0.3 to 10 mu s. In the superfluid phase (He-II), the bolometer detected first-sound shock waves of compression at small pressures (P < P-cr). These waves were created at high Q due to film boiling. At high pressures (P > P-cr) the boiling is suppressed. At small Q we then observed waves of rarefaction. At higher Q the waves of rarefaction were replaced by waves of compression. These are due to overheating of the helium near the heater into the normal state. In the normal phase (He-I) the bolometer detected waves of compression at all pressures. Thus, in addition to the commonly accepted model of generation of first-sound shock waves in superfluid helium due to film boiling, one should take into account another mechanism - the thermal expansion of the fluid near the heater. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 6]
机译：在超流体和正常He-4中，在低于和高于临界压力P-cr的压力下，都研究了第一声波的形状。这些波是由胶片加热器产生的。热通量密度Q和脉冲持续时间tau在1至250 W / cm（2）和0.3至10μs的范围内变化。在超流体阶段（He-II），辐射热计检测到在较小压力下（P P-cr）下，沸腾得到抑制。然后在小Q处观察到稀疏波。在较高的Q下，稀疏波被压缩波代替。这是由于加热器附近的氦气过热到正常状态所致。在正常阶段（He-I），测辐射热计检测到所有压力下的压缩波。因此，除了由于薄膜沸腾而在超流体氦气中产生第一声音冲击波的公认模型外，还应考虑另一种机制-加热器附近流体的热膨胀。 （C）2000 Elsevier Science B.V.保留所有权利。 [参考：6]

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