Investigation of Binary Liquids in Unstable States—An Experimental Approach

In this article, we present a methodology for conducting measurements based on pulse heating of a wire probe in partially soluble binary liquids. These liquids, which can be rapidly transferred to the region of unstable states above the diffusional spinodal, are novel research objects for the thermophysics of extreme states. Using the example of aqueous solutions of polypropylene glycol and glycol monobutyl ether having a lower critical solution temperature, the key hypothesis of the study on the general measurability of the properties of unstable solutions has been confirmed. The characteristic heating times from 1 to 15 milliseconds corresponded to the thickness of the heated layer comprising a few micrometers. The pressure was varied from units of MPa to 100 MPa. The conditions for the transition from measurements on pure components to those on solutions are formulated. The characteristic thermal patterns of the decay of unstable states depending on pressure and heating rate are revealed. The general possibility of using partially soluble binary liquids as a promising coolant in processes involving powerful local heat release is demonstrated.

Mathematical modelling of thermal stresses within the borehole walls in terms of plasma action

Purpose is the development of a mathematical model to study and describe thermal processes within the borehole wall in terms of plasma-based rock breaking. Methods. The following has been applied: theoretical analysis in the framework of a theory of brittle thermoelasticity breaking, methods of mathematical modeling, and computational experiment. Findings. Brief information on the results of the development of advanced plasma-based technology for borehole reaming for hard mineral mining has been represented. The results of industrial tests of plasma plant of 150-200 kW·s power with plasma-generating gas in the air for hard rock breaking have been represented. The plant and plasma-based technology of borehole reaming were tested in underground conditions of Kryvbas mines while reaming a perimeter hole to drive a ventilation rise in silicate-magnetite quartzites. A mathematical model has been proposed to analyze heat and mechanical fields in the rock during the plasma-based action on the borehole walls. Numerical studies of the temperature dynamics and thermal stresses within the borehole-surrounding rock layer have been carried out. It has been demonstrated that if low-temperature plasma is used (Т = 3500-4000°С), thermal compressing stresses are induced within the thin rock layer; the stresses may exceed the boundary admissible ones. It has been identified that plasma-based effect on the borehole wall makes it possible to create the conditions for intense rock fracturing and breaking. Originality. Solution of a new problem of thermoelastic state of a borehole wall in terms of plasma action has been obtained. The proposed mathematical model has been formulated in a cylindrical coordinate system and considers convective and radiation heat exchange between a plasma jet and a borehole wall. Practical implications. The obtained results make it possible to assess the rock state depending on the plasma jet parameters. The proposed methods of calculations will help carry out research to evaluate breaking parameters (the required heating time, thickness of the heated layer, and approximate spall dimensions) and develop different methods for the breaking process control.

Summer phytoplankton 24-hours dynamics in the lake Svetloyar (Nizhny Novgorod region)

In this research the information of structural parameters of algocenoses (species richness, proportions of leading groups, abundance, biomass) in the photosynthetic zone of a unique karst lake Svetloyar (Nizhny Novgorod region) is provided according to the data for the summer of 2012. During the studied 24-hours period the main components of plankton were coccoid green and diatom algae, colonial and filamentous cyanobacteria, whose daily vertical migration was poorly expressed. The maximum of abundance and biomass of these species were noted at the afternoon (the period from 13:30 to 16:30) and in the most heated layer (0–4 m). Motile algae (mainly from phylum Dinophyta) were characterized with more noticeable daily activity. They were present in the algocenoses only in the daytime and evening hours and moved at night and in the morning below the photosynthetic zone. The daily dynamics of the species richness of algae demonstrated was similar with the indicators of quantitative development, while the number of dominant species remained stable during the day (amounting to 1–4 taxa in the sample).

Analisys of thermal processes during induction surfacing

Aspects of thermal phenomena associated with the production process of bimetallic billets in conditions of small penetration depths of eddy currents compared to the size of the heated body are considered. Various conditions of heat distribution in the heated layer and its removal are modeled using differentiated thermal resistance. Based on the analysis of the temperature distribution in various situational variants, promising ways to improve this technology are identified.

Constraints on Io’s interior by combining small- and large-scale characteristics of the volcanic pattern

<p>Intensive tidal heating makes the Galilean satellite Io to an outstanding example of a volcanically active world. Most of the heat generated in the interior is lost through a large number of active volcanoes. The distribution of Io's volcanoes on the surface could help us to constrain properties below Io’s crust, regulating the heat transport mechanism. For this study, we assume that (1) the presence of global volcanism is linked to the presence of melt in the upper mantle; that (2) the large-scale variation in volcanic density is inherited from non-uniform tidal heating and smoothed by vigorous convection; and that (3) the total number of hot-spots is controlled by the spatial frequency of thermal instabilities in the convecting layer. Three unknown parameters are explored: the fraction of convective heat transport compared to magmatic heat transport, the mantle viscosity, and the thickness of the heated layer. In order to evaluate which combinations of interior properties can explain Io's present volcanic distribution, we develop a model based on parameterised heat flow scalings to approximate different spatial characteristics of Io's interior convection pattern. Our model combines internal heating, and convective and magmatic heat flow. Parts of the parameter space that are not in agreement with the observation-derived conditions are ruled out.</p> <p>Our results show that the observed small- and large-scale characteristics of Io's volcanic pattern can be explained by sub-lithospheric anomalies caused by convection. Solutions that allow for active volcanism and Io's specific large-scale variations in volcanic activity range from a thick mantle of high viscosity (10<sup>17</sup> Pa s) to a thin asthenosphere of low viscosity (10<sup>12</sup> Pa s). If Io's volcanos are correlated to the spatial frequency of thermal instabilities, the range of Io's total volcanic features between 250 and 3030 can further constrain the parameter space. This favours a mantle with a low melt fraction, a low mantle viscosity, and a magmatic heat transport of >80%.</p>

Determination of thermal diffusivity of the material by numerical-analytical model of a semi-bounded body

A mathematical description of the material thermal diffusivity aт in a semi-bounded body is proposed with a relatively simple algorithm for its numerical and analytical by solving the inverse problem of thermal conductivity. To solve the problem, it is necessary to obtain the temperature values of the unbounded plate as a result of a thermophysical experiment. A plate can be conditionally considered as a semi-bounded body as long as the Fourier number Fo ≤ Foк (Foк ≈ 0.04–0.06). It is assumed that the temperature distribution over cross-section of the heated layer of the plate R is sufficiently described by a power function whose exponent depends linearly on the Fourier number. A simple algebraic expression is obtained for calculating aт in the time interval ∆τ from the dynamics of temperature change T(Rп , τ) of a plate surface with thickness Rп heated under boundary conditions of the second kind. Temperature of the second surface of the plate T(0, τ) is used only to determine the time of the end of experiment τк. The moment of time τк, in which the temperature perturbation reaches the adiabatic surface x = 0, can be set by the condition T(Rп , τк) – T(0, τ = 0) = 0,1 K. The method of approximate calculation of dynamics of changes in depth of the heated layer R by the values of Rп , τк , and τ is proposed. Calculation of a т for the time interval ∆τ is reduced to an iterative solution of a system of three algebraic equations by matching the Fourier number, for example, using a standard Microsoft Excel procedure. Estimation of the accuracy of a т calculation was made by the test (initial) temperature field of the refractory plate with the thickness Rп = 0.05 m, calculated by the finite difference method under the initial condition T(x, τ = 0) = 300 (0 ≤ x ≤ Rп) at radiation-convective heating. The heating time was 260 s. Calculation of aт, i was performed for 10 time moments τi + 1 = τi + Δτ, τ = 26 s. Average mass temperature of the heated layer for the whole time was T = 302 K. The arithmetic-mean absolute deviation of aт(T = 302 K) from the initial value at the same temperature was 2.8 %. Application of the method will simplify the conduct and processing of experiments to determine the thermal diffusivity of materials.

An Analysis of Heat Exchange Crisis in the Capillary Porous System for Cooling Parts of Heat and Power Units

A model of dynamics of the vapor bubbles that emerge on solid surfaces of porous structures and the steam generating wall (bottom layer) is presented in this work. The model was filmed and photographed by a high-speed camera SKS-1М. The discharge of high heat flows (up to 2·106 W/m2) was maintained by the joint action of capillary and mass forces with the help of intensifiers. An analytical model was developed based on the theory of thermoelasticity. The limit state of the porous coating with poor thermal conductivity and the metal bottom layer was determined. Heat flows were calculated from the spontaneous birth of the vapour nucleus (10–8) to the material destruction (102–103 s), thus the interval from the process of relaxation to the maximum process (destruction) was described. The size of the pullout particles determined in the model at the moment of porous coating destruction showed good congruence with the experimental data obtained at the optic stand. The destruction of coating under the compression forces occurs much earlier than the tension forces. It is probable that the destruction will happen under the impact of the compression and shear forces. The intervals of the heat flow when such destruction takes place are different for quartz and granite coating. Each thickness of the pullout particles under the impact of compression forces has its limit values of the heat flows, which are located within the mentioned intervals. As the specific heat flow in the heated layer increases and, therefore, the heating time decreases, the impact of the compression stresses increases as well. Despite the high resistance to compression, destruction from the compressive heat tension occurs in more favorable conditions immediately, and in diminutive volumes. Experimental testing units, test conditions, the outcome of the heat exchange crisis, the limit state of the surface and the calculation of critical heat flows are presented. The capillary porous system that works under the joint action of capillary and mass forces is studied. The system has advantages compared to pool boiling, thin-film evaporators and heat pipes.