Abstract
The calculation of the recovery heat flux density is considered for superfluid helium boiling on the cylindrical heater inside porous structure. System of equations is based on the methods ...of continuum mechanics and molecular kinetic theory. The new type of boundary condition on the vapor-liquid interface based on the two-fluid model is formulated. Heat transfer in a free liquid is described by the Gorter-Mellink semi-empirical theory. Inside the porous structure the processes is discussed by the two-fluid model and filtration equation. Experimental data on the boiling of superfluid helium inside the porous structure are interpreted based on the formulated mathematical model. The qualitative and in some cases quantitative agreement between the calculated and experimental values of the recovery heat flux were obtained in the considered range of parameters
•The Boltzmann kinetic equation by the moment method is solved for the problem of the film boiling on a spherical heating surface.•The analytical expressions for the heat flux is obtained.•The ...obtained nonlinear relation is transformed into the corresponding flat heating surface formula.•The measured and calculated data on the thin films thickness are in good agreement.
Special nonlinear relations can determine the heat flux in a film boiling on a spherical heating surface. They are obtained by transforming the system of moment conservation equations derived from the Boltzmann kinetic equation based on a two-sided Maxwellian distribution approximation. We solve the Boltzmann kinetic equation by the moment method elaborating on the approach of L. Lees for describing thermal conductivity through a gas-filled spherical gap between two impermeable interfaces. The obtained analytical expressions for the heat flux can be used for any value of the Knudsen number.
This study presents an experimental and numerical investigation on a surface sliding discharge in a supersonic airflow in the presence of an oblique shock wave. In experiments, flow Mach numbers were ...1.20–1.68 in the shock tube combined with the discharge chamber. A single high-voltage 25 kV pulse sustains the plasma; the discharge current has a duration of ~500 ns. A surface sliding discharge is developed as a localized channel in a zone of interaction of an oblique shock wave with a boundary layer on the upper wall of the discharge chamber. The discharge channel acts as a linear source of heat and is at the origin of the induced shock wave. The flow field in the discharge chamber is spatio-temporally surveyed using high-speed shadowgraphy imaging with a frequency of up to 525,000 frames per second. The experiments show that the perturbed flow restored the initial structure after more than 100 μs. Numerical simulation with local energy input into the supersonic flow in a flat channel is carried out on the base of unsteady two-dimensional Navier–Stokes equations. It is determined that the dynamics of an induced shock wave are dependent on the energy input regime and on the flow parameters. The thermal energy release in the discharge channel of 0.22–0.29 J was estimated from a comparison of experimental data and numerical simulations.
The paper is devoted to study of interface matter transfer during evaporation and condensation. At the beginning different definitions of evaporation and condensation coefficients are analyzed. Then ...brief history of study development about mass flux density determination at evaporation and condensation is presented. The possibilities of molecular dynamics simulation concerning these processes are discussed. Then interpretation of Furukawa and Murakami (1999)
16 experimental data about determination of evaporation and condensation coefficients on helium vapor and its condensed superfluid phase (HeII) interface has been done. As a resume conclusion is made that at weak evaporation of high thermal conductivity matters as evaporation and as condensation coefficients are close to unit approximately.
The modern evolution of the dynamics of the structure of the hydrocarbon resource base in various regions is characterized, as a rule, by the gradual replacement of traditional sources with more ...complex ones. The latter are currently classified as hard-to-recover reserves (HTRR). The process of mastering and involvement in the development of HTRR is closely related to the transition to an innovative path of development, the creation of new technologies, the strengthening of the role of local knowledge, the accumulation of experience working with non-trivial sources of raw materials, and most importantly, with the efforts cooperation of various participants involved both in scientific and technological processes and in the development of subsurface areas. All of the above is impossible without the formation of an appropriate institutional framework with regional specifics. One example of an approach implemented in this area is the Canadian province - Alberta. There is also some experience in this field in Russia – in the Republic of Tatarstan. In a comparison with the initial conditions and approaches to the development of hard-to-recover hydrocarbon resources in these territories shows that there are both common and distinct features within the framework of the implemented approaches. Consideration of the latter is important from the point of view of choosing the directions for the formation a domestic working model in this area.
Experimental data on the study of boiling of superfluid helium (helium II) on a cylindrical heater inside a porous structure are considered. Based on an analysis of video recordings, the heat and ...mass transfer modes characterized by significant modification of the shape of the phase interface are classified. The values of heat fluxes and heater temperatures are presented, and the degree of nonequilibrium of the corresponding transfer processes is assessed.
Abstract
The presented work is devoted to the study of heat-mass transfer in vapor and liquid, taking into account multi-particle interactions in the condensed phase. An appropriate numerical ...procedure is proposed to solve the kinetic equation, both in the vapor and in the liquid. Using this approach, the problems of thermal conductivity in liquid argon, as well as the problem of evaporation-condensation, are solved.
Abstract
The research presents a method to synthesize lens data of an air meniscus built into the optical layout and acting as a correction element that fixes the field curvature of the entire ...optical system. The practical application of the proposed method is relevant when creating miniature lenses for medical video endoscopes when a small number of lenses and a flat image field for a CCD/CMOS sensor are important. Analytical dependencies for the lens data of the air meniscus are obtained and significant conditions for the field curvature correction are formed. A numerical example of a front stop lens design is demonstrated and confirms the correctness of the formulated conditions. A comparison of the aberration values of the original lens and an upgraded system is carried out. It is shown that, the values of the field curvature and astigmatism have been compensated as a result of introducing the synthesized parameters of the air meniscus into the optical layout. The correction is achieved while keeping the values of coma, distortion, focal length, and optical system total length at the level of the initial values.
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