Variable transfer rates in superfluid helium films

1966 ◽  
Vol 290 (1420) ◽  
pp. 1-13 ◽  
Keyword(s):  
Thick Film ◽  
Superfluid Helium ◽  
Transfer Rate ◽  
Bath Surface ◽  
Helium Films ◽  
Third Sound ◽  
Transfer Rates ◽  
Superfluid Flow ◽  
Helium Bath ◽  
The Difference

From an experimental investigation of superfluid film transfer in narrow beakers in helium II it emerges that there are probably two kinds of film. A ‘normal’ film is formed by superfluid creep over a dry substrate. A ‘thick’ film remains when liquid has drained from a substrate that has previously been immersed in the liquid helium bath. A comparison has been made of the superfluid flow between the two types of film. Scatter of values of transfer rate associated with a normal film is attributed to third sound generated by bath waves impinging on the meniscus at the base of the film. The thick film shows an enhanced rate of transfer which can persist for long periods of time in quiet conditions, but which can be abruptly diminished by disturbances such as bath surface agitation. There is a maximum stable length for a thick film exhibiting the full enhanced rate. The enhanced rate can be as much as 60% greater than the normal rate at 1° K, but the difference between the two rates of transfer disappears above 1.8 °K. No enhanced rate of transfer at any temperature is observed in beakers as large as 8 mm diameter.

Comments on the article: ‘The two-fluid model of the helium film’

1973 ◽  
Vol 333 (1593) ◽  
pp. 261-263 ◽  
Keyword(s):  
Superfluid Helium ◽  
Fluid Model ◽  
Convection Velocity ◽  
Thermodynamic Approach ◽  
Helium Film ◽  
Helium Films ◽  
Third Sound ◽  
Superfluid Flow ◽  
Two Fluid Model ◽  
Two Fluid

It is argued that the thermodynamic approach used by Goodstein and Saffman in their theory of thin superfluid helium films is incorrect. Their theory does not explain Keller’s experiment. The value they obtained for the convection velocity of third sound in a film with superfluid flow is consequently unfounded theoretically. Their calculation of third sound attenuation is shown to be incomplete.

scholarly journals Experiments on the attenuation of third sound in saturated superfluid helium films

1976 ◽  
Vol 14 (11) ◽  
pp. 4883-4888 ◽  
Author(s):  
Kenneth L. Telschow ◽  
Robert K. Galkiewicz ◽  
Robert B. Hallock
Keyword(s):  
Superfluid Helium ◽  
Helium Films ◽  
Third Sound

Nonlinear third sound in thin superfluid helium films

1983 ◽  
Vol 2 (5) ◽  
pp. 1311-1318
Author(s):  
P. Du ◽  
T. van der Merwe
Keyword(s):  
Superfluid Helium ◽  
Helium Films ◽  
Third Sound

Effect of Film Thickness on Fatigue Strength of TiAl Alloy Coated with TiAlN Film at Elevated Temperature

2005 ◽  
Vol 297-300 ◽  
pp. 1446-1451 ◽  
Author(s):  
Takeshi Kasuya ◽  
Hideto Suzuki
Keyword(s):  
Thin Film ◽  
Fatigue Strength ◽  
Film Thickness ◽  
Thick Film ◽  
Physical Vapor Deposition ◽  
Tial Alloy ◽  
Testing Machine ◽  
Intermetallic Alloy ◽  
Fracture Control ◽  
The Difference

The fatigue strength of TiAl intermetallic alloy coated with TiAlN film was studied in vacuum at 1073K using a SEM-servo testing machine. In addition, three kinds of TiAlN films were given by physical vapor deposition (1, 3, and 10μ m). The fatigue strength of 3μ m was highest. Also, the fatigue strength of 1μ m was lowest. From this result, existence of optimum film thickness was suggested because the difference of fatigue strength arose in each film thickness. The justification for existence of optimum film thickness is competition of 45-degree crack and 90-degree crack. The 45-degree crack is phenomenon seen in the thin film (1μ m), and is caused by plastic deformation of TiAl substrate. The 45-degree crack is the factor of the fatigue strength fall by the side of thin film. In contrast, the 90-degree crack is phenomenon in the thick film (10μ m), and is caused as result of reaction against load to film. The 90-degree crack is the factor of the fatigue strength fall by the side of thick film. In conclusion, the optimum film thickness can perform meso fracture control, and improves fatigue strength.

scholarly journals Critical Velocity of Superfluid Helium Films

1976 ◽  
Vol 56 (3) ◽  
pp. 996-997
Author(s):  
Y. Ichikawa ◽  
T. Usui
Keyword(s):  
Critical Velocity ◽  
Superfluid Helium ◽  
Helium Films

Design of a Plane-Type Bidirectional Thermal Diode

1988 ◽  
Vol 110 (4) ◽  
pp. 299-305 ◽  
Author(s):  
K. Chen
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Transfer Rate ◽  
Reverse Bias ◽  
Energy Utilization ◽  
Heat Transfer Analysis ◽  
Transfer Rates ◽  
One Dimensional ◽  
Plane Type ◽  
Solar Energy Utilization

The design of a plane-type, bidirectional thermal diode is presented. This diode is composed of two vertical plates and several fluid-filled loops with their horizontal segments soldered to the vertical plates. This invention is simple in construction and low in cost. The direction of heat transfer in the invented thermal diode can be easily reversed. These features of the present invention make it very attractive to solar energy utilization. Natural convection analysis for thermosyphon operations was adopted for heat transfer calculations of the fluid-filled loops. A one-dimensional heat transfer analysis was employed to estimate the heat transfer rate and ratio of heat transfer rates of the diode under forward and reverse bias.

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