Stability of the interphase surface in the freezing of moist ground

1980 ◽  
Vol 39 (1) ◽  
pp. 781-785 ◽  
Author(s):  
Yu. S. Dani�lyan ◽  
P. A. Yanitskii
Keyword(s):  
Interphase Surface ◽  
Moist Ground

Self-preservation Effect of Gas Hydrates

2021 ◽  
Vol 23 ◽  
pp. 346-355
Author(s):  
Anatoliy Pavlenko
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Experimental Studies ◽  
Interphase Surface ◽  
Quantitative Characteristics ◽  
Nonequilibrium Conditions ◽  
Water Simulation ◽  
Gas Loss ◽  
Physical And Mathematical Models ◽  
And Storage

This work was performed to improve the storage and transportation technology of gas hydrates in nonequilibrium conditions. At atmospheric pressure and positive ambient temperature, they gradually dissociate into gas and water. Simulation of the gas hydrate dissociation will determine optimal conditions for their transportation and storage, as well as minimize gas loss. Thermodynamic parameters of adiabatic processes of forced preservation of pre-cooled gas hydrate blocks with ice layer were determined theoretically and experimentally. Physical and mathematical models of these processes were proposed. The scientific novelty is in establishing quantitative characteristics that describe the gas hydrates thermophysical parameters thermophysical characteristics influence on the heat transfer processes intensity on the interphase surface under conditions of gas hydrates dissociation. Based on the results of experimental studies, approximation dependences for determining the temperature in the depths of a dissociating gas hydrate array have been obtained. Gas hydrates dissociation mathematical model is presented.

The phase transition in superconductors - I. Nucleation

1952 ◽  
Vol 214 (1118) ◽  
pp. 392-412 ◽  
Keyword(s):  
Surface Tension ◽  
Room Temperature ◽  
Lattice Distortion ◽  
Impurity Content ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Local Lattice Distortion ◽  
Surface Conditions ◽  
Local Lattice ◽  
Crystal Boundaries

A detailed study of ‘supercooling' in tin rods has confirmed the hypothesis that this is caused by the difficulty of forming a nucleus of the superconducting phase. The experiments show that when nucleation does occur it only happens at certain flaws in the metal, which have been proved to lie at the surface and to be between 10 -4 and 10 -3 cm in size. These flaws do not appear to be necessarily associated with surface conditions, impurity content, or crystal boundaries. Any handling of the specimen affects them, but simply warming it to room temperature often does not, in which case the supercooling observed in separate experiments is reproducible. The degree of supercooling ϕ l defined as ( H 2 c - H 2 l )/ H 2 c , where H l is the field at which nucleation is first possible, varies in magnitude from flaw to flaw (0⋅8 is the largest value found), but it always depends on temperature in the same way, rising as T → T c , The supercooling can sometimes be increased by applying a high field to the specimen beforehand, indicating that some of the flaws can be temporarily destroyed by such treatment. The behaviour of the flaws can be accounted for if they are assumed to be domains where the interphase surface tension has become negative, perhaps as the result of local lattice distortion produced by dislocations. Using a simple model based on this picture the magnitude and temperature dependence of ϕ l have been explained quantitatively in terms of the characteristic flaw size and the positive surface tension in the undistorted metal (as estimated from work on the intermediate state). Slight superheating (up to 1⋅5% of H c ) has also been observed.

scholarly journals Interphase Surface Stability in Liquid-Liquid Membrane Contactors Based on Track-Etched Membranes

Membranes ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 949
Author(s):  
Stepan Bazhenov ◽  
Olga Kristavchuk ◽  
Margarita Kostyanaya ◽  
Anton Belogorlov ◽  
Ruslan Ashimov ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Porous Structure ◽  
Pore Size ◽  
Aqueous Phase ◽  
Liquid Membrane ◽  
Target Component ◽  
Interphase Surface ◽  
Asymmetric Membrane ◽  
Interface Stability ◽  
Membrane Contactors

A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, it is preferable to supply the aqueous phase from the side of the asymmetric membrane with the larger pore size. The asymmetry of the porous structure of the membrane makes it possible to increase the range of pressure drop values between the phases by at least two times (from 5 to 10 kPa), which does not lead to mutual dispersion of the liquids. The liquid–liquid contactor based on the asymmetric track-etched membranes allows for the extraction of impurities from the organic phase into the aqueous phase by using a 1% solution of acetone in hexadecane as an example.

The interphase surface energy in some pure and impure superconductors

1960 ◽  
Vol 255 (1282) ◽  
pp. 407-426 ◽  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Surface Energy ◽  
Detailed Analysis ◽  
Energy Parameter ◽  
Transverse Magnetic ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Dilute Alloys ◽  
The Magnetic Field

A new method has been developed for obtaining relative values of the surface energy parameter, Δ, in superconductors. It involves the measurement of the resistance of thin films subjected to a transverse magnetic field. The method has been applied to tin, indium and aluminium and to dilute alloys of the first two. The principal new results are that Δ is 1⋅48 times larger in indium than in tin and that the addition of impurity to either metal lowers Δ without changing the nature of its temperature dependence. These conclusions are compared with current theories of the interphase surface energy. An attempt has been made to deduce the absolute magnitude of Δ, which requires a detailed analysis of the way in which the last traces of the superconducting phase are eliminated from the film by the action of the magnetic field. The analysis is necessarily over-simplified but it does give a figure for Δ in pure tin which is reasonably consistent with the previous estimates of Faber and Sharvin.

The phase transition in superconductors II. Phase propagation above the critical field

1953 ◽  
Vol 219 (1136) ◽  
pp. 75-88 ◽  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Relaxation Time ◽  
Surface Energy ◽  
Field Strength ◽  
Eddy Currents ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Electromagnetic Damping ◽  
Phase Propagation

Detailed measurements have been made of the rate at which the superconducting phase collapses radially in cylindrical rods of tin, when they are suddenly subjected to a magnetic field greater than the critical. This is probably the simplest example of phase propagation in superconductors. The results in most respects confirm the theory of Pippard (1950 a ) and Lifshitz (1950), according to which the propagation is controlled by an electromagnetic damping associated with the setting up of eddy currents. This theory explains in detail the way in which the rate of propagation depends on specimen radius and conductivity, and on field strength; its only failure is at the higher temperatures, where the magnitude of the rate of propagation tends to be slightly less than the theory predicts. Other factors besides eddy currents which might be retarding the transition are latent heat, the interphase surface energy, and a finite relaxation time governing the destruction of superconductivity by a magnetic field; but none of these proves altogether adequate to account for the discrepancy mentioned. The experiments provide evidence that the relaxation time is less than 2 x 10 -7 s in tin.

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