Proposer A.L. Gusev
Russian Federal Nuclear Center -All-Russian Research Institute of Experimental Physics
PROJECT SUMMARY:
Writing of the monograph Electrosorption phenomena in screen-vacuum heat insulation layers"
An unavoidable exhaustion of the world oil resources as well as an aggravating ecological situation cause new energy sources to be looked for [1]. Even at the Soviet Union time A.N. Tupolev Aviation Science and Technology Complex (ASTC) was charged with creating a flying laboratory (based on TU-154 V airplane) using liquid hydrogen as a fuel. This program made it also possible to lay the basis for hypersonic and air-space aviation and improve basically ecological characteristics of engines. During these project activities it was necessary to expand the scope of scientific and research efforts because of a great deficiency of oil fuel and the necessity of its replacement by natural gas. As a result TU-155 airplane using cryogenic fuels such as liquid hydrogen and condensed natural gas was developed that was the first in the world [2].
Application of accumulation of the technically required substances in a cryogenic state is explained by a few factors specifying advantages of liquid substance states over gaseous ones. First, a liquid is 800 times as dense as a gas under normal conditions, which allows the volume and the weight of the container used to store and transport substances to be reduced greatly. Besides, it makes it technically possible to accumulate, store and deliver large amounts of working products to consumers. Storage, transportation, creation of reserves, large volume delivery of liquid-state hydrogen, oxygen, argon and methane at the required time and their gasification during delivery are more advantageous and sometimes are the only way of using the above substances in a particular field of engineering. Thus, only methane transformation into a liquid state allowed the problem of its delivery from extraction areas to consumers by sea transport to be solved; supply of machine-building plants with liquid-state argon and oxygen and their gasification at the consumption site are economically more advantageous. Those countries, whose pipeline supply with natural gas is made difficult because of extended water barriers, have recently developed the technology of gas liquefaction and its transportation in a liquid form using special tankers. For this purpose the appropriate production equipment has been designed: powerful liquefying facilities, tankers with heat-insulated tanks, large storage facilities, pipelines, pumps, gasifiers. Methane-carrying tankers have cargo tanks whose capacity is 50-100 thousand m3 and over. The capacity of surface tanks for liquid natural gas storage is as high as 130,000 m3. Storage of condensed natural gas makes it possible to solve the problem of creating its reserves for supplying regions during its maximum consumption periods. Currently even those countries and regions where natural gas is delivered by pipelines in gaseous state liquefy it to create reserves [3].
However, these energy systems are far from being safe. Safety of the most dangerous and critical elements of large energy systems, of tanks and pipelines in particular, depends on the processes proceeding in the protection cavity of these objects. Cryogenic liquids are mainly explosive. Even cryogenic liquids of inert gases may create prerequisites for a fire or explosion under specific conditions (for example, when pumping liquid nitrogen through a pipeline with a destroyed heat insulation, liquid oxygen is condensed from air onto
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external pipeline walls). Consequences of accidents in pipelines (both manifolds and main pipelines) and in large tanks are unpredictable. The area of continuous destructions at large cryogenic hydrogen facilities ranges from a few hundreds of meters to several kilometers [4, 5, 6 ]. The power of explosion at large cryogenic systems is comparable with the atomic bomb explosion. The power of a hypothetical explosion of "SpaceShuttle" energy hydrogen refueling system may make up 30% of the yield of the atomic bomb dropped over Hiroshima.
After immediate spillage of liquid hydrogen over the area of 1 m2 the energy equivalent to 40 kg of trinitrotoluene is released!
Moreover, the processes proceeding in the protection heat insulation cavity are responsible for the economic efficiency of such systems.
The proposed monograph will for the first time consider and analyze the data on electroadsorption processes in screen-vacuum heat-insulation layers of large cryogenic tanks, pipelines and other thermostatted facilities that have been collected up to now. Their effects produced on vaporability of cryogenic products [7] as well as on decrease of the safety level of thermostatted facilities will be also demonstrated. Particular emphasis will be placed to review of the activities related to the field effect [8], electroadsorption effect [9-13], kinetics and dynamics of residual atmosphere of cryogenic tanks [7], vaporability of the cryogenic liquid, determination of values of the cryogenic liquid heat inflows under the environment parameter change conditions.
The work will analyze the interrelation between adsorption and reflection properties of screen films. In work [14] a newly-deposited aluminum film showed an abrupt reflectivity decrease after a short contact with air oxygen caused by the fact that crystallite boundaries in a skin layer were subjected to oxidation due to oxygen diffusion.
Based on studies of screen heat insulation systems, the algorithm for economically substantiated selection of screen materials will be given. To increase the exergetic efficiency of superinsulation using the trade-off between reflection and sorption screen properties as the basis, special exergizers will be proposed [15] that change selectivity, anisotropy, polarization of reflection screens while providing the given adsorptivity of coatings. In terms of control over variation of excitation levels of surface plasmons the existing technological cycles for making a metallized superinsulation screen coating will be analyzed and new methods for making metal coatings will be proposed.
In general, from the known Drude formula it follows that the surface reflectivity in infrared radiation region will be increased, if the surface is made of metals having the highest electric conductivity. However, it is known that the theoretical formula of Drude that has been experimentally verified by Hagen and Rubens for infrared spectrum region with ^>10 ^ is no more true for the range of low temperatures [16]. This fact is explained by the so-called abnormal skin effect. Skin effect is concentration of high-frequency electrical current on the conductor surface. The normal skin effect phenomenon is well explained based on Maxwell's equations and Ohm's law. At low temperatures the depth of high-frequency field penetration in a metal decreases due to conductivity increase, while the mean free path of electrons increases and it may become several times as large
International Scientific Journal for Alternative Energy and Ecology Copyright©2000 by STC "TATA" July 2000, Vol. 1 235
as the skin layer depth. Therefore an electron will travel through the areas with different field strengths during its mean free time. An additional velocity that it will gain will depend on the field strength along the entire movement path. The results of a strict mathematical solution [17] show that the electrical field strength is determined by a complicated expression, but it has no exponential form that is predicted by the classical theory. Since the wave propagation is no more exponential, the classical notion of a complex refractive index in the general theory loses its physical meaning. However, all the measured values may be expressed as a function of a "surface impedance" that is equal to the ratio between the strengths of electrical and magnetic fields on the metal surface multiplied by 4n/c. The abnormal skin effect phenomenon results in a great increase of the absorptivity as compared with that calculated from Drude equation. As a result, the absorptivity of pure metals reduces as the temperature decreases and this reduction is much less than can be expected according to the classical theory. Based on the classical theory, the absorptivity of pure metals at 70 K must be about 4 times less than at the room temperature. Actually the ratio is no more than 2. The reason for this discrepancy is abnormal skin effect. The discrepancy is still more pronounced at the liquid helium temperature [17].
The monograph will propose new approaches to engineering processes of storing and loading cryogenic substances. The author will describe the unique technique for conducting full-scale experiments aimed at determining the kinetics and dynamics of the residual environment in heat-insulation cavities of large cryogenic tanks. A review of low-temperature absorbers that should be used as a selective means of pumping out during experiments of this kind will be made. A large body of bibliographic materials on these and related problems is supposed to be given. There is also a lot of reference information.
Within the next five-ten years specialists in thermonuclear physics will give a final answer to the question about the possibility of applying thermonuclear reaction energy for everyday domestic purposes. Accumulation and storage of the energy of gas and liquid cryogenic environments will remain topical unless this problem is solved.
A vacuum- powder heat insulation most often used in large cryogenic systems of the USA is easy in operation, but has a thermal conductivity that is several tens of times higher than that of a screen- vacuum heat insulation (SVHI) rather widely used in large cryogenic systems of R
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