Specifics of nucleation in superheated water and supersaturated vapor

This work is dedicated to the experimental studying of the nucleation kinetics in superheated water and supersaturated water vapor. A percolation model for the liquid water structure that explains a number of anomalous thermophysical properties of water and water vapor in the metastable region is proposed.     

On the formation of ball lightning

Summary A plasma continuum model for the formation of ball lightning is developed based on a substantial number of reports that the ball is often in the discharge column of a previous lightning stroke. The usual method of setting up the plasma equation for a one-component electron plasma is used. An approximate equation for the plasma is derived from the describing equation which is then solved exactly in terms of the Jacobi elliptic functions. The formation of the ball is based on a nonlinearity of the plasma equation which under certain circumstances permits the field to collapse into a small region. Thiscollapse is interpreted to be ball lightning. The approximate equation derived for the plasma has the same form as a previous equation used to describe the formation of the fireball plasma.

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Riassunto Si sviluppa un modello continuo del plasma per la formazione del fulmine globulare basandosi su un consistente numero di lavori in cui risulta che il globulo si forma spesso nella colonna di scarica di un precedente colpo di fulmine. Si usa il metodo consueto di formulare l'equazione del plasma per il plasma di elettroni ad una componente. Si deriva un'equazione approssimata per il plasma dall'equazione descrittiva che è in seguito risolta esattamente mediante le funzioni ellittiche di Jacobi. La formazione del globulo si basa su una non linearità nell'equazione del plasma che in alcune circostanze permette che il campo collassi in una piccola regione. Questocollasso si interpreta come un fulmine globulare. L'equazione approssimata derivata per il plasma ha la stessa forma di un'equazione precedente, usata per descrivere la formazione del plasma della sfera di fuoco.

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Резюме Развивается плазменная непрерывная модель для образования щаровой молнии, основанная на больщом количестве сообшений, что щаровая молния часто образуется в столбе разряда предыдушей молнии. Используется обычный метод вывода плазменного уравнения для однокопонентной электронной плазмы, Выводутся приближенное уравнение для плазмы, которое затем точно рещается в терминах эллиптических функций Якоби. Образование щара основано на нелинейности в плазменном уравнении, которое при определенных условиях допускает возможность полю коллансировать в небольщую область. Этотколланс интерпретируется как щаровая молния. Приближенное уравнение, выведенное для плазмы, имеет ту же форму, что и предыдушее уравнение, использованное для описания образования файрболов в плазме.

     

The properties and the nature of ball lightning

The observed properties of ball lightning are given. A model of mean ball lightning taking average iarameters is based on observed data. By comparing the observed data with contemporary information on the processes occuring in activated air, different aspects of the ball lightning phenomenon are analysed. Among these are the ways of energy storage in ball lightning, the mechanisms of thermal processes, the form and structure of ball lightning, and the electrical phenomena and luminous processes in ball lightning. The separate problems are investigated on the basis of model experiments. Numerical analysis of various aspects of the phenomenon allows us to construct a phenomenological model of ball lightning. This model conforms well with the observed data and up-to-date information on the different physical processes. The experimental modelling of ball lightning is analysed. Analogues of ball lightning are considered. A general phenomenological scheme of ball lightning is given.     

Long-lived plasmoids produced in humid air as analogues of ball lightning

The results of an experimental study of long-lived plasmoids, analogues of ball lightning, are presented. The study focuses mainly on the establishment of the conditions for the prolonged existence of plasmoids in the atmosphere. Experimental setup is described and the observation data displayed in the form of photographic pictures.     

Modelling of condensation at spherical expansion of water vapor into vacuum

The mathematical model of water vapor condensation was developed for the direct simulation Monte Carlo method. This model describes a chain of reactions providing formation and decay of water clusters with consideration of accompanying energy transfer processes. One-dimensional expansion of water vapor into vacuum from an evaporating spherical surface was studied numerically within the range of parameters, corresponding to the flows transitional by the Knudsen number. The influence of condensation on the gas-dynamic pattern of the flow, including the parameters of the Knudsen layer, is discussed. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-01-00354-a).     

FSCT水蒸气冷凝回收装置设计软件研究

为实现对新建机械通风冷却塔水蒸气深度回收,提出了自由空间型冷却塔(FSCT,Free Space Cooling Tower)概念,基于新建机械通风冷却塔的空间结构设计了FSCT水蒸气冷凝回收装置结构模型,并建立装置设计数学模型。构建水蒸气冷凝回收装置设计软件流程,基于C++Builder 6.0耦合水物性数据库开发了FSCT水蒸气冷凝回收装置设计软件。在不影响机械通风冷却塔正常运行的情况下,实现水蒸气深度回收。研究结果为新建机械通风冷却塔减少蒸发损失、水蒸气冷凝回收装置设计和计算软件开发提供理论基础和工具性软件支持。     

Properties of short-living ball lightning produced in the laboratory

An experimental setup for highly reproducible generation of artificial ball lightnings is implemented. Thousands of floating glowing plasmoids 12–20 cm in diameter are produced. Research facilities for studying the plasmoids are developed. It is found that short-lived ball lightnings live for about 1 s and carry an electric charge. The lightnings are shown to have a complex structure: a central kernel containing a rich variety of hydrated ions and aerosol of decay products is surrounded by a thin negatively charged shell.     

Catalytic action of the products of photodissociation of some atmospheric impurities on water vapor condensation

A significant effect of the photodissociation products of atmospheric impurities, such CF₂Cl₂, CCl₄,H₂S, and NH₃, on the condensation of supersaturated water vapor is demonstrated. The experiments are performed in a cloud chamber, with irradiation being carried out by an ArF excimer laser (λ = 193 nm). The results obtained in the absence and presence of photodissociation are interpreted. The impact of the initial water vapor pressure in the chamber on the process of condensation is observed and explained.     

Influence of thunderstorm atmospheric conditions on the properties of ball lightning

Rank-correlation methods are used to investigate the influence of thunderstorm atmospheric conditions on the lifetime (observation time) and diameter of ball lightning on the basis of an analysis of observations from the Stakhanov-Cole-Bychkov ball lightning PC database. For the analysis ball lightning events are ranked by diameter, the weather conditions are ranked in relation to humidity, which correlates with the charge state of the atmosphere, and thunderstorm conditions are ranked in relation to the electric field of the atmospheric ground layer. A statistical analysis shows that the lifetime and diameter of ball lightning decrease under conditions of increasing humidity and increasing electric field. The plausibility of this result from the standpoint of various existing ball lightning models is discussed. Zh. Tekh. Fiz. 67, 117–122 (April 1997)     

Boiling-up of superheated water and water solutions under ultrasound influence

Boiling-up kinetics of superheated distilled water and sodium chloride solution in a glass cell at atmospheric pressure and low superheating of 15–35 °C has been studied far from the boundary of attainable superheating in the area of heterogeneous nucleation. Temperature dependences of average waiting time of superheated liquids boiling-up have been studied experimentally under natural conditions and in the ultrasonic field Waiting time of boiling-up at these temperatures reaches 1000 s, and average time is 600 s. Empirical distribution functions have been found with the use of the waiting time samples obtained by the method of order statistics. Omega-square goodness-of-fit test has shown that they disagree with exponential distribution describing stationary random process of supercritical embryo generation separating the system to macroscopic phases. Thus, it is shown that this random process is not stationary, consequently, nucleation rate to be depending on time.     

Gravitational collapse of a charged and radiating fluid ball in the diffusion limit

The collapse of a charged and radiating ball in the diffusion limit is studied using a method reported by Herrera and collaborators. The interior solution is matched with the exterior Reissner-Nordström-Vaidya metric to obtain a system of differential equations at the surface of the distribution, which can be integrated numerically for some set of initial data. For one model, the profiles of the physical variables are obtained at any piece of the material in terms of Schwarzschild-like coordinates.     

螺旋扁管管外蒸汽冷凝双侧强化传热试验研究

为促进螺旋扁管在冷凝换热装置上的应用,对螺旋椭圆管管外蒸汽冷凝工况下的传热特性进行了试验研究。研究结果表明,螺旋椭圆管在强化管内无相变对流传热的同时也可以强化管外冷凝传热。相同工况下,同圆管相比,所用螺旋椭圆扁管的总传热系数高11%-16%,管内传热系数高约18%,管外冷凝传热系数高约9%。并从二次流减薄传热边界层及冷凝表面利于排除冷凝液的角度,分析了螺旋椭圆扁管的双侧强化传热机理。     

Acoustical method of studying the growth and collapse of a vapor bubble in boiling

A new method is proposed for determining the characteristics of the dynamics of the vapor bubble volume variation from the parameters of the sound pulse generated by this bubble. The accuracy of the method is estimated, and its application is illustrated by a specific example.     

On the theory of laser heating of water drops

It is shown that pressure caused by the law of momentum conservation and a nonuniform distribution of energy sources over a drop volume should be taken into account when describing the evaporation of large water drops subjected to high-intensity optical radiation.