L. I. Anatychuk, Î. J. Luste, Î. V. Nitsovich. TEMPERATURE DEPENDENCES OF PARAMETERS OF A DOUBLE-LAYER THERMOELEMENT WITH PERIODICALLY PROFILED SURFACE.
Thermoelectric and mechanical properties of bismuth-doped lead telluride. Institute of Thermoelectricity, Chernivtsi, Ukraine. 2008, No.2. - p.7-14.
Computer model of a double-layer thermoelement with periodically profiled surface taking into account temperature dependence of kinetic coefficients of thermoelectric materials has been developed. The temperature, current density and electric potential distribution in thermoelement working medium has been found. Optimization of thermoelement geometry, transverse thermoEMF and efficiency has been made.
À. L. Vainer, V. I. Perepeka. UNSTEADY OPERATING MODE OF THERMOPILES. State Enterprise Research Institute "Shtorm",
Odessa, Ukraine. 2008, No.2. - p.15-21.
Methods of mathematical simulation for unsteady operating modes of stage thermopiles are proposed. Thermopile model is presented as a system of solids with lumped parameters (solids having heat capacity, wherein thermoelectric processes of thermal absorption or heat release take place), communicating with each other and the environment through thermal conductivities. Such model of stage thermopile is described by the system of ordinary inhomogeneous nonlinear differential equations, which allowed using for its analysis an effective method of finite elements, well elaborated in computational physics and adapted by the authors for mathematical simulation of unsteady modes of thermopiles. Owing to the fact that calculation of thermal conductivities is performed with regard to real geometry and thermophysical properties of thermopile parts (sides) and nonlinear dependences of these conductivities on temperature, the accuracy of calculation is achieved that enables to apply proposed methods in all stages of thermoelectric device development. In the initial stages the methods are used for design statement formatting, in the subsequent stages - for confirmatory calculation.
A. A. Nikolaeva1,2, L. À. Konopko1,2, D. V. Gitsu1, T. E. Huber3, G. I. Para1, A. Tsurkan1. EFFECT OF MAGNETIC FIELD, ELASTIC STRETCH AND DIMENSIONS ON THERMOELECTRIC PROPERTIES OF BISMUTH NANOWIRES.
1Institute of Electronic Engineering and Industrial Technologies, Republic of Moldova,
2International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw, Poland,
3Department of Chemistry, Howard University, Washington, USA. 2008, No.2. - p.21-36.
Single-crystal glass-encapsulated Bi wires with diameters 50 nm-2 µm obtained by casting from liquid phase have been investigated. Integrated research on thermoelectric properties of thin single-crystal Bi wires depending on diameter d, temperature Ò, magnetic field Í and elastic stretch e has been made; power factor has been estimated and its optimal values under different external effects have been found. It has been established that a weak magnetic field (µ Í < 1) increases positive contribution to thermopower, and elastic stretch - negative. For the first time, the wires with d < 200 nm were investigated. Sign reversal and formation of positive maximum in the region of 25-50 K on temperature dependence of thermopower a(Ò) depending on the wire diameter d has been discovered. It has been shown that "semiconductor" run of temperature dependence R(Ò), the presence of two slopes on the dependence R(1/d) and thermopower sign reversal on a(Ò) are related to the manifestation of quantum size effect.
I. À. Popov, P.P. Bodiul, Å. F. Moloshnik, Î. Botnar. ENHANCEMENT OF THERMOELECTRIC FIGURE OF MERIT OF Bi1-õSbõ THIN WIRES UNDER ELASTIC STRETCH IN A MAGNETIC FIELD.
Institute for Electronic Engineering and Industrial Technologies, Academy of Sciences of Moldova. 2008, No.2. - p.37-46.
This paper studied a combined effect of a longitudinal magnetic field and elastic stretch on thermoelectric properties of Bi0.88Sb0.12, thin wires obtained by the Ulitovski method and doped with donor and acceptor impurities. Measurements were performed in the temperature range of 4.2 - 300 K, in magnetic fields up to 14 Ò. Maximum value of relative elongation under elastic stretch made up 1.3% at Ò = 4.2 - 200 K. Diameter of samples varied from 200 nm to 5 µm and was controlled on a SEM. It was established that at temperature 120 K in a magnetic field up to 0.4 Ò a growth in thermopower by 14-20% is observed. By means of elastic stretch, drastic resistance growth in the region of magnetic fields 0.4 Ò typical of the bulk bismuth samples and non-deformed wires could be suppressed. This brought about considerable power factor increase in the region of temperatures beyond 120 K.
P. M. Gorley1, Î. Î. Galochkina1, Yu. V.Vorobiev2, J. Gonzalez-Hernandez3. TEMPERATURE DEPENDENCES OF KINETIC COEFFICIENTS AND THERMOPOWER OF p-CuInSe2 CRYSTALS.
1Yu.Fedkovych Chernivtsi National University, Chernivtsi, Ukraine,2CINVESTAV-IPN Unidad Querétaro, Querétaro, México,3CIMAV, Chihuahua, México). 2008, No.2. - p.47-56.
The results of theoretical research on the influence of a term linear in wave vector k in the dispersion relationship E(k) on the temperature dependences of the Hall factor, carrier mobility and thermopower of crystals with chalcopyrite structure are represented in this paper by the example of p-CuInSe2 compound. Calculations were made for the case of nondegenerate statistics of carriers gas with regard to their simultaneous scattering in the relaxation time approximation on impurity ions and acoustic fluctuations of crystal lattice. For the top à -7 and à -6 valence bands the values of factors were estimated that characterize the degree of E(k) deviation from the parabolic dispersion law and yield satisfactory agreement between calculated and experimental temperature dependences of the Hall factor and the total Hall mobility of carriers in p-CuInSe2. It is shown that taking into account in theoretical calculations of a term linear in k in E(k) brings about sign reversal of the anisotropy factor of thermopower tensor components in crystals with chalcopyrite structure
G. Kavei, Y. Zare and A. Seyyedi.TENTATIVE DESIGN FOR MEASUREMENTS OF ABSOLUTE VALUE OF THERMAL CONDUCTIVITY OF SEMI-CONDUCTING THERMOELECTRIC ELEMENTS.
Material and Energy Research Centre, P.O. Box 14155-4777, Tehran, Iran. 2008, No.2. - p.57-63.
Thermal conductivity is an important characteristic of materials in particular semi-conductors and ceramics. Since it varies within a wide range and is measured in a variety of methods, no commercial device has, so far, been established to measure thermal conductivity. Hence, it sounds necessary to develop a device to meet all needs of scholars in laboratory with a general application. Development of such a device, beside relevant calculations, is evaluated in this paper where thermal conductivity of a thermoelectric semi-conductor ingot (approximately 8 mm in diameter and 24 mm in length) at the range of room temperature is considered. At lower temperatures, thermal conductivity is almost invariant and measured in both comparative and absolute methods. Absolute value method is still widely used at temperatures below room temperature. A great deal of practical error is due to heat leakage via radiation, convection and heat transfer. Within the range of room temperature, heat leakage shares a smaller contribution in error, but not an ignorable one. At higher temperatures heat leakage plays more important role and increasing temperature makes it more and more difficult parameter to define.
R. Ahiska1, I. Güler1, A. H. Yavuz2, A. Toprak1. NEURO-FUZZY INFERENCE SYSTEM FOR CONTROL OF A THERMOELECTRIC BRAIN COOLER.
1Gazi University, Department of Electronics and Computer Education, Besevler, Ankara, Turkiye,
2Gaziosmanpasa University, Niksar MYO, Department of Electronics and Computer, Niksar, Tokat, Turkiye. 2008, No.2. - p.64-70.
The object of the present study is to determine the most suitable method for control design for thermoelectric cooler headgear developed for brain hypothermia applications. Hypothermia refers to a medical treatment method protecting the brain in which the temperature of the brain drops below the level required for reducing oxygen consumption of tissues. The temperature of the headgear is controlled by current. We were examined by using Fuzzy Logic Control, one of the artificial intelligence techniques. Initial membership functions were determined and used for obtaining the data by an expert. ANFIS model were constructed on MATLAB medium and new membership functions were determined. The optimal results will be obtained by re-programming the system with these new membership functions.
S. O. Filin, B. Zakrzewski. CURRENT STATUS AND PROSPECTS FOR THE DEVELOPMENT AND PRODUCTION OF STATIONARY THERMOELECTRIC COOLERS.
Sczecin University of Technology, Poland. 2008, No.2. - p.71-84.
Comparison and analysis of designs and technical characteristics of various-purpose stationary thermoelectric coolers elaborated and produced worldwide: for beverages, wine, transport facilities. Revealing major tendencies in the development of this type of refrigerating engineering related to cabinet and unit design, chamber temperature control, expansion of application fields