High Temperature最新文献

Abstract

As a soot particle grows, it undergoes a number of significant morphological changes (called aging), which lead to a decrease in reactivity of the particle surface. This work uses reactive molecular dynamics to study the interaction between acetylene molecules in the gas phase and the surface of soot particles of varying degrees of maturity. It is demonstrated that the branched morphology of “young” soot particles and the presence of nanosized voids on their surface can be another effect that has a significant impact on the higher reactivity of soot particles.

Abstract

We report on the thermal diffusivities, specific heats, thermal conductivities, and electrical resistivities of 21 alloys of the nickel–vanadium system. It is found that heat transfer in NiV alloys is mainly executed by electrons. The behavior of temperature dependences of these properties shows that in the temperature range under investigation, the thermophysical characteristics of samples in the state of solid solutions and intermetallic compounds differ significantly because of the dependence of the energy structure of collectivized electrons on the system composition and temperature. It is shown that the concentration range in which the mutual solubility of component is ensured expands upon heating. The Nordheim rule for the alloys under investigation holds at temperatures close to the melting point and indicates the dependence of the density of states of collectivized electrons on the concentration of components.

Abstract

Gas oscillations and aerosol dynamics at a resonance frequency in an open pipe with a changing cross section have been studied. The dependences of the amplitude of gas pressure oscillations and the time of aerosol deposition were obtained for different amplitudes of piston displacement at resonance. The presence of a changing cross section made it possible to obtain more intense oscillations as compared to a homogeneous pipe, while the shape of the pressure wave remained continuous and close to harmonic for all considered excitation amplitudes. A decrease in the concentration of aerosol droplets over time was revealed, accelerating with increasing amplitude of piston displacement.

Abstract

A method for determining the formation energy of vacancies in phlogopite is proposed, based on an analysis of how elementary defects in its crystal lattice, associated into complexes, influence the temperature dependence of its electric conductivity. The existence of a linear relationship between the melting temperature and vacancy formation energy for the studied phlogopite samples with different impurity contents was shown. The author calculated the dependence of the obtained melting temperatures on the content of the Al, Mg, and F components in phlogopite samples, which, when associated into complexes, activate the formation of elementary lattice defects.

A thermodynamic calculation of the electron work function and the composition of the charge component of a saturated vapor has been performed for congruently evaporated alkali metals and Na₃AlF₆. It has been shown that similar calculations are valid for alkaline-earth metal oxides.

Abstract

The article presents the results of physical and mathematical modeling of the temperature distribution in an oil source rock sample under monodirectional microwave irradiation. The studies were performed at a radiation frequency of 2.45 GHz. The mathematical model was validated based on the results of physical modeling of dielectric heating of the source rock to 115°C. Predictive calculations were carried out on the scale of a real object. The results demonstrate the volumetric nature of sample heating under microwave irradiation. The intensities of dielectric heating of the oil source rock at kerogen pyrolysis temperatures were determined, as well as the penetration depth of the electromagnetic field during kerogen pyrolysis.

Abstract

The article presents a refined mathematical model of thermochemical destruction of a multilayer composite material, which was developed on the basis of theoretical and known experimental results. The consideration of heat overflow across a body allows the state of a protected wood structure has under fire conditions to be predicted in a more accurate manner. The numerical computation results are compared with the known data.

An Erratum to this paper has been published: https://doi.org/10.1134/S0018151X23010236

Abstract

A mathematical model is proposed for a metal hydride plant, which can be used to utilize low-grade heat. As an example, the study considers a low-grade heat source, an HT PEMFC fuel cell with a high-temperature proton exchange membrane based on polybenzimidazole doped with phosphoric acid, with an operating temperature range 120–200°C. At temperatures near the lower limit of the operating range, the metal hydride utilization cycle appears preferable to the traditional Rankine cycle.

Abstract

The problem of heat conduction is studied for a point nonstationary heat source located inside or outside a plane-layered medium. A solution is found for a harmonic heat source, followed by a solution for an arbitrary time dependence of point heat release. The harmonic solution to the problem for arbitrary plane-layered media is obtained in the form of a one-dimensional integral.