Том 61, № 4 (2023)

n analytical expression is found for the transverse dielectric permittivity of a nondegenerate electron plasma in the approximation of the effective collision frequency for a weakly nonideal gas, taking into account electron spin. The resulting expression takes into account both Landau diamagnetism and Pauli paramagnetism in an electron plasma.

A system of mutually consistent equations describing the pressure 
, vapor density 
, and liquid density 
 on the phase equilibrium line of technically important substances in the range from the triple to critical points has been proposed. At the stage of development of this system, the following have been considered: (a) the features of the behavior of a number of properties ( is the average diameter of the saturation line, and 
 is the order parameter) in the critical region; (b) some concepts of the scale theory of critical phenomena and renormalization group theory, which was adapted by Wang L. et al. (2013) for substances with a given molecular structure, including SF6; (c) the Clausius–Clapeyron equation, in which the “apparent” vaporization heat 
 is used instead of the vaporization heat 
. At the stage of approbation of this system of equations, a method for calculating the adjustable coefficients included in this system using the example of SF6, for which precision data on the thermal properties including the experimental () data are available, has been proposed. Using the proposed technique, the coefficients of the system of equations have been determined using the precision data for SF6 and the calculated values of the SF6 properties in a given temperature range have been obtained. The uncertainty of the calculated data has been statistically analyzed; in particular, the average squared deviations of the experimental () data from the corresponding equations have been found. It has been shown that the proposed system describes the listed properties with less uncertainty than that of the properties corresponding to the original equations of Funke et al. (2001). The temperature dependence 
 of the proposed model satisfactorily agrees with the model 
 developed by Wang et al. (2013) for the SF6 critical region

In this study, the stability of graphene oxide based aqueous nanofluids are tested under boiling–condensation conditions. The graphene oxide nanofluids remain very stable, and their transmittance in solar spectral region varies less than 6% after 630g centrifugation for 3 h at 90°C without boiling. However, when undergoing boiling and condensation processes, the solar transmittance of the graphene oxide nanofluids declines quickly, from 38 to 4%, during the first 24 h of testing, before leveling out in the final 120 h of testing. A decrease in the fluid transmittance is due to the partial reduction of graphene oxide nanosheets, as evidenced by X-ray photoelectron spectrometer and Fourier transform infrared spectroscopy technique measurements. It is surprising that thermal reduction of graphene oxide in aqueous fluids occurs at such a low temperature (~100°C), when undergoing boiling and condensation. This temperature is much lower than the previously reported thermal reduction temperature (180°C and above) without boiling. The low-temperature thermal reduction of graphene oxide may be attributed to the bubble cavitation associated with boiling in aqueous fluids.

The processes in a flat palladium target irradiated with an intense picosecond laser pulse are studied. In the experiment, the parameters of the irradiating pulse, as well as the depth of the spall cavity formed as a result of the complex flow of compression and expansion waves through the substance are determined. The interaction dynamics of these waves are modeled using a new equation of state for palladium over a wide range of densities and pressures. Based on the results of the experiment and numerical simulation, the maximum tensile stress in the spall plane at a high tensile rate is estimated.

Inverse heat transfer problems are used to study the thermophysical properties of promising highly porous cellular materials. The article presents the results of thermal tests on samples of these materials with different structures determined by the diameter of the cells. The thermophysical characteristics of the samples were obtained, which can be used to construct and verify mathematical models of heat transfer in highly porous cellular materials.

The parameters of heat transfer at compressible gas flow with a favorable pressure gradient have been experimentally studied. The heat transfer coefficients and the temperature of thermally insulated (adiabatic) wall are determined using the transient heat transfer method. To estimate the degree of flow laminarization, the results obtained are compared with the known dependences for the turbulent boundary layer developing on a plate in a zero-pressure gradient flow. Some regularities of the effect of flow acceleration on the heat transfer law are revealed for the studied configurations of supersonic nozzles.

We present the results of a three-dimensional numerical simulation of the dynamics of a falling film of a mixture of refrigerants, 0.9 mol fraction R21 + R114, considering the liquid flow along the outer lateral surface of a round vertical cylinder for a Reynolds number of 104 and contact angles of 10°, 30°, 50°, 70°, and 90°. The simulation was carried out using the volume of fluid (VOF) method in the OpenFOAM software. The contact angle has a significant effect on the area of the wetted surface due to a change in the modes of liquid falling down the cylinder. The following flow modes are identified: continuous film, stable jet mode, cascade jet mode, and massive jet mode. These modes are similar to the modes of fluid flow on horizontal tubes.

The spontaneous boiling-up kinetics of liquid alkanes (methane, ethane, and propane) saturated with one of the following gases: helium, hydrogen, nitrogen, or methane is studied. The solution nucleation rate temperature, baric, and concentration dependences in the interval (104–108) m–3 s–1 are determined using the mean lifetime method. The measurements were carried out at pressures of 1–2 MPa and volatile component concentrations up to 6 mol %. The experimental results are compared with the classical nucleation theory in a macroscopic approximation. In contrast to pure liquid and liquid saturated with helium or hydrogen, the attainable superheating temperatures of solutions containing nitrogen or methane as a dissolved substance exceed their theoretically predicted values. The factors causing this mismatch are discussed.

The work demonstrates the possibility of theoretical modeling of hydrodynamics and heat transfer processes in complex channels of steam generators of integral-type shipboard nuclear power plants. A diagram is given and the operating principle of a nuclear reactor and steam generator cassette is briefly outlined. A grid model of a prototype heat exchange channel with double-sided heating was built to perform thermal-hydraulic calculations in the ANSYS CFX software package, and the calculation scheme was verified by comparing the results obtained with experimental data.

The authors studied the dynamics of thinning of the zona pellucida (ZP) in mouse embryo as a result of laser-assisted hatching performed at the blastocyst stage. Mouse embryos previously subjected to a freeze–thaw cycle (cryo-embryos) were selected as model embryos. For ZP microsurgery, femtosecond laser pulses were used (radiation wavelength 512 nm, pulse duration 100 fs, intensity 2.5 TW/cm2). The thickness of the ZP was measured before microsurgery at the blastocyst stage (~E3.5, i.e., 3.5 days of embryonic development) and at the hatching stage (~E5). It was found that the ZP of control group embryos (cryo-embryos not subjected to laser exposure) thinned more strongly (from 6.6 (E3.5) to 4.9 µm (E5)) compared to experimental embryos after the laser-assisted hatching procedure (from 7.1 ( E3.5) to 6.4 µm (E5)). In both the first and second cases, changes in ZP thickness were statistically significant. The results were compared with data for “fresh” embryos not subjected to cryopreservation. There was no pronounced effect of ZP hardening in cryo-embryos compared to fresh embryos. The use of the laser-assisted hatching procedure for cryo-embryos made it possible to increase the probability of successful hatching compared to embryos in the control group from 38.5 to 52.5%.