Thermomechanical Flow Rates of Liquid Helium II Through Channels of Large Hydraulic Diameter

Abstract

Thermomechanical forces (known since the early discovery of superfluidity in the forties [1–4] have recently been utilized in flow control equipment [5,6]. In these applications two classes of thermomechanical flow devices may be distinguished: First, near-ideal superleaks with small hydraulic diameters D h , and second, nonideal devices (superfilters) with large D h . The first class of device permits large static thermomechanical pressure differences ΔP close to the ideal London value ΔP ideal = ρSΔT. In contrast, the absolute mass flow rate is small. Further, viscous forces of normal fluid prevent its backflow as desired for vortex refrigeration [7]. The second class of device no longer permits negligible heat rejection rates and the static pressure differences become quite small. Considerable mass flow rate, however, appears to be possible along with a rapid transfer of liquid [8]. This property may not only be of interest in mass control devices, but also for emergency cooling of cryoelectro-equipment.