R. E. Mironov

Thermal expansion of bismuth telluride

The results of X-ray and dilatometric measurements of the thermal expansion of bismuth telluride in the temperature range of 4.2–850 K have been critically analyzed. The joint statistical processing of the experimental data has been performed by the least squares method and the most reliable temperature dependences of the linear thermal expansion coefficients along the principal crystallographic axes αa and αc and the average linear coefficient

Current state of thermoelectric material science and the search for new effective materials

\bar \alpha _L

Mathematical models and hardware & software for highly accurate electronic temperature meters

, as well as the density of Bi2Te3, have been recommended. The results indicate that the linear thermal expansion coefficients along the directions parallel and perpendicular to the cleavage planes decrease with an increase in the temperature in a narrow temperature range. At temperatures below 298 K, the character of the temperature dependences of the linear thermal expansion coefficients of Bi2Te3 has been analyzed in terms of the anharmonicity of the chemical bonding forces in the layer structure and anisotropy of the elastic constants. In terms of the deviations of the composition of the Bi2Te3 compound from the stoichiometric one and the real (defect) structure of the compound, a model has been proposed to explain the minimum in the (αaT) dependence of Bi2Te3 near the melting temperature of bismuth. A method for calculating the temperature dependence of the linear thermal expansion coefficients of the anisotropic layer crystals using the data on the specific heat has been discussed, which provides good agreement of the calculated linear thermal expansion coefficients with the experimental data within the accuracy of the measurements of the linear thermal expansion coefficients.

A heat transfer model of a horizontal ground heat exchanger

The reasons for the recent increased interest in thermoelectricity are considered. Modern thermoelectric materials for practical use are reviewed. Criteria to be met by effective thermoelectric materials are analyzed. It is shown that the solid-solution method has almost completely exhausted itself. Directions in the search for new thermoelectric material classes are analyzed. The development of new bulk thermoelectric materials is connected with the search for and design of materials in which the peculiarities of the structure determine the strong scattering of phonons and decrease in thermal conductivity while maintaining high transport properties of charge carriers. The concept ‘phonon glass–electron crystal’ is of practical interest. Scientific and technological advances over the last decade give hope that more effective thermoelectric materials will be developed in the nearest future. One of the perspective applications of new thermoelectric materials is connected with the development of thermoelectric generators with segmented thermoelectric elements.

Methods of determining individual heat energy consumption using an intelligent system for monitoring power supplies

Optimal mathematical models accurately describing the dependence of thermometric parameters of sensors within the range of operational temperatures were suggested. Circuit and design concepts, and also algorithms and hardware & software implementing the developed mathematical models in electronic temperature-measuring instruments were developed.

A Procedure and a Hardware-Software System for the Automated Calibration of Temperature Measuring Instruments

Ground-source heat pumps are gaining popularity in Eastern Europe, especially those which are using the horizontal ground heat exchanger (GHX). Due to the difficulty of accessing GHX after the installation, materials and the quality of the installation must satisfy the very high requirements. An inaccurate calculation of GHX can be the reason of a scarcity of heat power in a crucial moment. So far, there isn’t any appropriate mathematical description of the horizontal GHX which takes into account the mutual influence of GHX pipes on each other. To solve this problem we used the temperature wave approach. As a result, a mathematical model which describes the dependence of the heat transfer rate per unit length of the horizontal GHX pipe on the thermal properties of soil, operating time of GHX and the distance between pipes was obtained. Using this model, heat transfer rates per unit length of a horizontal GHX were plotted as functions of the distance between pipes and operating time. The modeling shows tha...