The research was devoted to the problem of measuring geometric parameters of ice by the method of phase triangulation in a limited volume with refraction of optical signals. This method served to develop an algorithm of measurement and calibration. It was also expedient to take into account the reflective properties of ice and the conditions of external lighting, as well as to ensure a minimum error in measuring the geometric parameters of ice. For this purpose, software complexes to control the quality of the measuring system with current parameters and to calculate the geometric parameters of ice, as well as a software and hardware complex for measuring the geometric parameters of ice by the phase triangulation method in a limited volume with refraction of optical signals have been developed. The measuring system was configured for a measuring volume with characteristic dimensions (100×100×60) mm. A measurement error of 12 microns has been achieved. Experiments were carried out to measure the geometric parameters of ice formed on a cylindrical surface. The values of the local thickness of the ice and the statistical value of the thickness of 1.6 mm have been restored. The developed technologies may be used in experiments on an aerodynamic stand for the study of icing processes aimed at creating anti-icing methods in various fields of industry.
A.B. Kruglov, I.I. Konovalov, B.A. Tarasov, V.S. Kharitonov, L.P. Paredes
National Research Nuclear University (MEPhI), Moscow, Russia
Keywords: heat-conducting liquid metal sublayer, pulse heating method, thermal conductivity of lead-sodium and bismuth alloys
The article presents the results of measurements of thermal conductivity coefficients of Pb-Na with the content of the latter of 20 at. % and eutectic (Pb-Bi)-Na 20 at % alloys at temperatures of 350 - 800 °С. The experimental methodology is described and the temperature differences in the heat-conducting sublayer of fuel cells of the studied alloys are estimated.
The density of liquid lithium fluoride and an eutectic mixture of lithium fluoride and sodium fluoride (with a content of 39 mol. % NaF) was measured by the gamma ray method in the temperature range from liquidus to ~1280 K. The obtained results were compared with the available literature data. The study of liquid eutectic LiF - NaF was carried out in a significantly wider temperature range compared to other authors, and the obtained values of the volumetric coefficient of thermal expansion turned out to be the most reliable.
P.P. Bezverkhii1, O.S. Dutova2 1Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk, Russia 2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: methane, combined equation of state, critical point, heat capacities, speed of sound
A new thermal equation of state for methane is proposed in explicit form, including a crossover function. This function comprises new regular and scaling parts with 22 adjustable coefficients written in real temperature-density variables. The coefficients are determined from the ρ, ρ, T-data for CH4. Data on the heat capacities Cv, Cp and the speed of sound W were not involved in calculations, except for the data on the isochoric heat capacity Cv in the ideal gas state and the Cv value at 100 K on the liquid branch of the liquid-gas equilibrium curve. In the regular region, the calculated values of Cv, Cp, and W are close to the experimental and tabulated values. In the critical region, the discrepancies with the tabulated values are no more than 5%, which is associated with the use of the scaling equation of state. The average absolute deviation is 0.3% in the pressure description, the r.m.s. error σp = 0,5 %, and the error in Cv is less than 5%. The calculation results are compared with the known crossover equations of state for CH4. It is concluded that the proposed model of the equation of state is preferable for calculating the thermophysical properties of methane.
a:2:{s:4:"TEXT";s:82:"A.A. Chernov1,2, M.N. Davydov1,3, A.A. Pil’nik1,2";s:4:"TYPE";s:4:"html";} 1Novosibirsk State University, Novosibirsk, Russia 2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia 3Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
Keywords: gas-saturated liquid, gas bubble, decompression, degassing, boundary value problem with a moving boundary, numerical simulation, magmatic melt
Dynamics of gas bubble growth in a highly viscous gas-saturated liquid (magmatic melt) subjected to decompression is investigated. A mathematical model of the process, which is a joint dynamic and diffusion problem, is proposed. An approximate semi-analytical solution is found based on the existence of a quasi-stationary state for the bubble growth process. The influence of certain factors on the process under consideration at all its stages is shown. In particular, a significant dependence of the bubble growth rate on the decompression rate is illustrated. It is shown that, at long times, bubble growth has a self-similar character and occurs only as a result of gas desorption from the surrounding liquid.
The paper considers a model of nucleation of crystal phase during cooling of a modified melt below the liquidus point. We demonstrated a connection between the overcooling factor, nucleus size forming at the particle surface, and the amount of consumed energy. Numerical simulation was performed for solidification of a modified bicomponent aluminum melt in a cylindrical crucible with account for thermodynamics, heterogeneous nucleation and crystallization. We found the conditions of crystal nuclei formations: both for the cases with the size higher or smaller that the size of seeds. It was shown that efficient modification of the metal needs the use of powders with maximally homogeneous size. The reliability of this model is confirmed by reasonable compliance between the simulation and physical experimental data.
The paper presents the results of the main physical processes that ensure the operation of hollow cathodes of vacuum plasma torches with the formation of high-enthalpy plasma inside the cavity. The interaction of the plasma with the inner surface of the cathode determines the temperature field of the hollow cathode and the distribution of heat fluxes in the vacuum discharge. The formation of the temperature field in the cathode body, in addition to temperature processes, is significantly influenced by the conditions of heat exchange between the cathode and the environment, the characteristics of the cathode material and its geometric dimensions. Studies of plasma emission spectra in the cathode cavity have shown that the appearance of spectrum lines depends on the excitation conditions and determines the energy limits of electrons accelerated in the cathode layer.
The paper presents the results of thermodynamic calculations and experimental studies of plasma processing of biomedical waste and fuel biomass, including waste from the woodworking industry and agriculture, which have shown the promise of using plasma-chemical technology for processing various wastes with production of combustible gas and inert mineral material. Comparison of the experimental results and calculations showed their satisfactory agreement. Both in calculations and in experiments, no harmful impurities were found in the products of plasma processing of the investigated wastes.
On November 30, 2022, an outstanding scientist in the field of thermal physics and thermal power engineering, Doctor of Technical Sciences, Professor, Academician of the Russian Academy of Sciences Alexander I. Leontiev passed away.
The paper describes the results of studying the influence of a free-stream disturbance localized in time and space on the structure of the wake behind a symmetric droplet-shaped airfoil in the range of angles of attack from -20° to +20°. It is demonstrated that the existence of such a disturbance leads to suppression of vortex formation at certain angles of attack. Ranges of angles of attack in which the wake structure remains unchanged are found.
