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Актуальність. Остеохондроз поперекового відділу хребта та його неврологічні прояви є одним із найпоширеніших захворювань, що призводить до порушення працездатності та інвалідності людей переважно в молодому віці. Мета дослідження: вивчення величини густини теплового потоку (ГТП) та температури поверхні тіла людини у пацієнтів з неврологічними проявами остеохондрозу в попереково-крижовому відділі хребта. Матеріали та методи. Обстежений 71 пацієнт (20 — з ознаками люмбоішіалгії на фоні гриж міжхребцевих дисків, 20 — з люмбоішіалгією на фоні гриж міжхребцевих дисків в поєднанні з нестабільністю хребців у цій ділянці,11 пацієнтів — зі стенозом хребетного каналу та 20 осіб контрольної групи). Результати. У осіб контрольної групи фіксувались помірні показники температури та ГТП в паравертебральній зоні. У пацієнтів з люмбоішіалгією без ознак нестабільності відбувалося паралельне коливання температури і ГТП на стороні болю і низькі показники на інтактній стороні. При люмбоішіалгії на фоні нестабільності хребців позитивним був симптом «ножиць» на боці болю та зростання обох теплових показників на інтактній стороні. При стенозі хребетного каналу зменшувалися показники температури і ГТП з обох сторін, але більш інтенсивно на стороні болю. Висновки. Одночасне вимірювання показників температури та ГТП при неврологічних проявах остеохондрозу хребта за допомогою приладу, сконструйованого в Інституті термоелектрики НАН та МОН України, є високоінформативним методом діагностики.

This paper presents the results of computer simulation of optimal dynamic modes of thermoelectric device for cryodestruction. The optimal time function for controlling the supply current to thermoelectric micromodule in a device for cryodestruction is determined, which ensures given cyclic temperature effect on the local area of human body.Keywords: computer simulation, optimal dynamic mode, cryodestruction, thermoelectric cooling.

The paper presents the results of computer simulation of thermophysical processes in human head under given heat fluxes on its surface. The disadvantages of the existing physical models of human head are revealed and the ways for their improvement are proposed. With regard to computer simulation results, an experimental sample of thermoelectric device for human head cooling «ALTEC-7012» which is promising for human brain hypothermia has been designed and manufactured.

The physical model of the thermoelement in the unsteady cooling mode is considered. The heat capacity of the cooling object and the connecting and insulating plates, the heat load, the heat exchange with the ambient, the release of the Joule heat due to the presence of contact resistance between the thermoelectric material and the metallic connecting plate, as well as the Thomson effect impact in the bulk of thermoelement legs are taken into account. A method is described for calculating the optimal dependence of the thermoelement supply current on time, which provides the preset time dependence of the cooling temperature. Examples of computer simulation of current control functions for implementation of the specified time functions of operating temperature in medical devices are given.

The problem of heat recovery from cogeneration installations using thermoelectric generators is of great interest due to steady-state operation of the installations. A theoretical basis for the design of thermoelectric generators used for cogeneration installations has been formed. Fundamental relations used for estimation of the electrical power and efficiency of such generators in different model approximations are given. The main regularities of the generator operation, such as optimal thermal modes, the correlation between heat flows at the inlet and outlet of the generator, as well as thermoelectric materials requirements are established.

The theoretical aspects of evaluating the electrical resistance of a thermoelectric leg–metal contact are considered. A physical model of such a contact and methods for calculating the main components of the contact resistivity, namely, the resistivity of the interfacial layer and the resistivity related to the transfer of charge carriers through a potential barrier at the boundary between a material of the thermoelectric leg and a metal, are proposed. The contact resistivity for thermoelectric legs made of Bi2Te3 based materials with deposited antidiffusion nickel layers is calculated. It was established that the contact resistivity in such thermoelements reaches a value from 0.25 × 10−6 to 2.5 × 10−6 Ω cm2 and depends on the temperature and interfacial layer thickness. It is demonstrated that the findings are in good agreement with the known experimental values of contact resistivity.

Results of development of a thermoelectric device that enables controlled cyclic temperature impact on the damaged area of human organism are presented. Unlike the existing medical devices employing direct supply current for thermoelectric module, the present device controls supply current according to time dependence of temperature change assigned by doctor. It is established that such a device is an efficient means of therapy at herniation of intervertebral disks with marked radiculitis and tunicary syndromes, at meningitis, other spinal diseases and back traumas.

Thermoelectric Thomson relations interrelating the Seebeck, Peltier and Thomson coefficients were generalized for anisotropic thermoelectric media in magnetic field with regard for possible Umkehr effect. From the restrictions imposed by space and time symmetry on the properties of anisotropic media in magnetic field it was shown that the first Thomson relation relating the generalized Peltier coefficient /spl Pi/* to the generalized Seebeck coefficient /spl alpha/* is of the form differing from the Thomson formula for isotropic media. The second Thomson relation was also generalized for anisotropic thermoelectric materials in magnetic field. It was shown that odd with respect to magnetic field Thomson effect can originate in thermoelement material even if thermoelectric coefficient of the material is temperature independent.

The results of computer investigation into mechanical stresses arising in thermoelectric cooling modules under cyclic conditions are given. A method of ultrasonic investigation was used to determine the tensor of elastic constants of Bi/sub 2/Te/sub 3/ based material. The limits of elastic and plastic deformation in these materials were found. Computer design programs were created aimed at improving cyclic stability. The methods for cyclic tests of modules were developed. Experimental investigations into optimized in cyclic stability modules were performed. The test results have confirmed the manufacture of modules of particularly high cyclic stability.

Based on the methods of generalized theory of thermoelectric energy conversion a new thermoelement type was designed that employs eddy thermoelectric currents passing in zone-inhomogeneous media. The distribution of eddy currents in zone-inhomogeneous medium, conditions of their removal to external electric circuit, as well as construction on their basis of spiral structure were studied. The values of eddy current removed to external circuit, electric voltages, as well as thermoelement efficiency were given. The advantages of zone-inhomogeneous spiral thermoelements over conventional thermopiles were demonstrated.

Modern fuel thermoelectric generators (TEG) are widely used in the range of 10-500 W. Chemical sources of current (CSC) that do not always satisfy consumers are used at lower powers. Negative factors are large weight, cost, self-discharge amount, problems in storage and maintenance at low temperatures. CSC manufacture is power-intensive, expensive and ecologically dangerous. That is why fuel TEGs capable of competing with CSCs are of interest. The paper is devoted to fuel TEGs on liquefied gas development for 10-100 mW power ranges. Small power heat sources have been developed on the catalytic counter-flow burner base which stably operates on gas and is suitable for continuous operation on a self-sufficiency basis. The catalytic burner feature at separated fuel and air supply is spontaneous burning resumption after short breaks in fuel supply, changes in air supply and combustion products discharge. The burner's temperature can be maintained within 250-400/spl deg/C. A high efficiency promoted catalyst with service life up to 10000 hours is used in heat sources. The use of results of a series research works in this direction ensured the development of such catalytic heat sources (CHS). TEGs design was made by the computer modelling. TEGs maximum is defined by the following optimizing parameters: a collector aerodynamic drag, burner-collector distance, fuel consumption, load impedance and thermoelectric battery properties.

Factors, which promote microminiaturization of cooling modules have been considered. Results of thermoelectric cooler investigations are presented taking into account all classical factors: electrical and heat resistance of a commutation, contact resistance, heat resistance of heat transfers, all kinds of thermoelectric effects, temperature dependencies of material properties, etc. The influence of all factors on cooling efficiency is analyzed. New factors, which can have influence on a module work, namely strong electric field, large temperature gradient, size effects, and diffusion processes are considered. The influence on microminiaturization and conditions for these factors actions are analyzed. A common analysis for microminiaturization limits and a prognosis of thermoelectric modules development is presented.

Analysis of reliability determination methods used in thermoelectricity is carried out. These methods are based on the classical probability theory and have restricted possibilities for a description of reliability of complicated system and dynamic processes. In the present work, more effective means of the random processes theory are used for creation of reliability determination methods. From the random processes theory point of view, reliability parameters of thermoelectric elements and multi-element systems are considered. Possibilities of the random processes theory for determination and prognosis of thermoelectric module reliability have been considered.

The optimal control methods are used in the present work for a search of the best function of thermoelectric material inhomogeneity. The possibility of an increase in low-temperature cooler coefficient of performance due to the use of thermoelectric material inhomogeneity, has been demonstrated.

The study and design results of multi-element thermoelectric batteries with small section of legs for low-powered thermoelectric generators, weak current cooling modules and high-sensitivity sensors have been presented. The production technology of thermoelectric modules with leg cross-section more than 0.5 x 0.5 mm and length of 1-5 mm and more has been well developed. With such modules the problems of thermoelectric generators of more than 1-10 W and thermoelectric coolers with supply current of more than 1 A production have been solved. The analysis shows that possibilities for thermoelectricity practical application is substantially extended if development engineers of thermoelectric equipment have the possibility to use thermoelectric converters with small leg cross-section. In this case low-powered thermoelectric generators competitive in a number of cases to chemical electrical sources can be developed, the need in such sources is rather great.

The results of 200 kW thermoelectric generator developments of liquid-liquid type have been given. Operating temperatures are the following: hot side temperature is 250/spl deg/C, cold side temperature is 50/spl deg/C. Heat transfer from a source is effected by high temperature liquid circulation. Heat removal from the generator is effected by water circulation. The generator is arranged from 400 blocks of 500 W each. A block volume is about 15 liters, its weight is about 15 kg. Specially designed highly effective heat exchangers together with Altek 1018 thermoelectric modules specially designed for that purpose have been used in the blocks. The generator's efficiency is about 6%. The generator's reliability is about 600 times greater than the reliability of known analogues. Depending on heat source, power generators of required power can be developed on the basis of such blocks. The generators are designed for utilization of waste heat from internal combustion engines, gas turbines, garbage combustion and from other industrial heat waste.

The effort of various technological and structural factors on the efficiency and reliability of thermoelectric cooling modules has been analyzed. The specific ways of increasing the efficiency and reliability of modules have been determined. The methods of modules testing have been described, the validity and correctness of their use have been verified. The necessary requirements to testing equipment have been considered, the basic technical parameters of nonstandard equipment used to determine the efficiency and reliability of thermoelectric cooling modules have been given. The results of Altek cooling modules testing for prolonged action of various factors confirming their higher performance have been given. "Altec" company together with Institute of Thermoelectricity regularly conducts a work focused on improvement of thermoelectric cooling modules quality. The works are conducted in several directions.

The methods for precise and fast determination of thermoelectric cooling and generation module parameters, as well as software and hardware used in the realization of these measurements are described. Absolute measurements of thermal flows by standard heat sources and special-purpose heat flow meters have served the basis of these methods. Gradient screens used for automatic upkeep of desired temperature distribution guarantee the adiabaticity of measurement conditions. The problems of metrological support of measurement process, the accuracy and validity of measurement results have been considered. The variant of concrete software and hardware realization of the above method has been considered. Typical results of cooling and generation module measurements have been given. Comparative analysis has been made with respect to the existing measuring means and the advantages of the above methods have been shown. A set of measuring equipment for precise metrological (1-1.5%) measurement of module parameters and measuring devices for module testing in the process of their production under industrial conditions is described.

Results of works on the phenomenological and microscopic theory of thermoelectricity together with the theory of thermoelectric energy conversion have been presented. New thermoelectric effects, generalizations of the basic Thomson relations, generalizations of the electric current induction phenomena for the case of a thermoelectric medium, generalizations in thermoelements description as well as methods for new types of thermoelements discovery have been examined.

The results of investigations and development of catalytic heat sources with thermoelectric energy converters have been given. The efficiency of the catalytic oxidizers are about 5+6%. Heat passed through thermobatteries is used for heating, electric energy is used where necessary. Structures and characteristics of such devices with heat power of 1,2,3 kW have been given. Fields of practical applications have been analyzed.

It has been shown that eddy thermoelectric currents could be used for conducting inhomogeneous and anisotropic media parameters determination. Eddy currents flowing in a media bulk lead to surface electric potential distributions which are used for nondestructive test methods. Methods and devices for eddy currents excitation and measurement have been described.

Calculation methods of the thermoelectric eddy currents and electric potentials distributions in the nonisotermetral medium under arbitrary boundary conditions have been described. The problem of the thermoelectric eddy currents control have been formulated and solved for description of known energy converters and for finding new ones. The examples of thermoelectric eddy currents control have been given.

Investigation results of state of the art and prospects of the theory, technology and practical use of thermoelectric FGM development have been presented. Computer technologies for the optimal predicted inhomogeneities determination have been considered. Data on the limiting possibilities of thermoelectric conversion efficiency improvement by means of FGM use as well as the data on the FGM technologies have been given. New possibilities of thermoelectric use have been considered.

The possibilities of optimal control theory use for cooler simulation under the conditions of combination optimal leg inhomogeneity with optimal magnetic field nonuniformity are investigated in the present paper. The essential improvement of low-temperature cooling performance is demonstrated in this case.

The results of generalizations of the Maxwell equations and Faraday law of electromagnetic induction for nonisothermal media are given. It is shown that this generalization creates a radically new description of the processes of thermoelectric energy conversion based on the use of of eddy thermoelectric fields and eddy thermoelectric currents. The basic postulates of the generalized theory of thermoelectric energy conversion are given. New thermoelement types discovered by computer solutions of the inverse thermoelectricity problems are given. Classification of thermoelements is given, including new thermoelement types discovered by solving the inverse problems. The properties of such thermoelements and their peculiarities that allow successful use of thermoelements in thermoelectric instruments and devices are considered. Typical examples of such use in measuring techniques, power engineering and thermoelectric cooling are given and the prospects of using such thermoelements are considered. Figures of merit of materials for new thermoelement types are given, as well as physical and technological methods of attaining the maximum figure of merit. Information is given on the progress in creating thermoelectric cooling modules of increased reliability, with increased supply voltages, increased refrigerating capacity and cyclic stability. Information is also given on the new developments of thermoelectric generator modules with improved characteristics of efficiency, reliability and resistance to temperature cyclic effects. Systems based on such modules with liquid heat-exchangers are considered. The structure of such systems makes possible their easy adaptation to customer demands for electric and thermal characteristics, pressures and flow rates in liquid circuits, etc. Examples are given of using such modules and systems in refrigerators, air-conditioners, heat and electricity generators. Information is given on the Ukrainian program of investigations and thermoelectricity applications.

The results of the optimal control theory use have been presented for program creation of functionally graded material computer modeling. Modeling results such as limiting values for FGM generators efficiency, functionally graded material advantages resulting from the computer modeling have been.

The present paper reports the results achieved in the process of the solution of the problem for the magnetic field optimal control in low‐temperature cascade colors.

The present paper reports the results of studies on the optimal control methods used for effective combined thermoelectric cooler design.

The results of investigation of possible figure of merit increase of thermoelectric materials through the use of superlattices are given. It has been established that phonon thermal conductivity has a considerable effect on the figure of merit of such thermoelectric materials. It has been discovered that additional periodicity caused by the superlattice structure results in phonon spectrum transformation which affects /spl kappa//sub ph/. By example of Si/sub n//Ge/sub m/ superlattices the vibration spectrum has been calculated for various number of superlattice layers. It has been also established that thermal conductivity of such systems is decreased as compared to bulk thermal conductivity of Si and Ge. At the same time /spl alpha/ and /spl sigma/ increase with reduction of the number of superlattice layers m which indicates the possibility of considerable thermoelectric figure of merit growth for short-period superlattices.

The investigation results of thermal compensation systems for thermoelectric cooling modules parameters determination have been given. Thermoelectric thermal meters were used at heat balance sensors, stage thermoelectric batteries were used as compensating heat and cold sources. Methods and devices made it possible to determine parameters of thermoelectric cooling modules with increased accuracy.

The dependence of thermoelectric properties on the texture layer thickness was investigated. The electric and thermal conductivities decrease is caused by decrease of texture layer thickness. Seebeck coefficient and figure of merit remain constant.

The investigation results of rational fields of single- and two-stage thermoelectric cooling module use, in the context of their energetic efficiency and economical utility in refrigeration applications, are presented by the authors.