Mechanical Aspects of Structural Optimization in a Bi-Te Thermoelectric Module for Power Generation
- PDF / 927,320 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 150 Views
S4.7.1
Mechanical Aspects of Structural Optimization in a Bi-Te Thermoelectric Module for Power Generation Yujiro Nakatani1, Reki Takaku1, Takehisa Hino1, Takahiko Shindo1 and Yoshiyasu Itoh1 1 Power & Industrial System R&D Center, Toshiba Corporation, 1-9, Suehiro-cho, Turumi-ku, Yokohama 230-0045, Japan. ABSTRACT The thermal stress and strain occurring on a Bi-Te thermoelectric module subjected to variable thermal conditions were estimated based on three-dimensional elastic-plastic finite element method (FEM) analysis. The analysis showed that mechanical integrity of the interface between a Bi-Te thermoelement and electrodes of Al and Mo coatings formed by atmospheric plasma spraying was significantly reduced and that shear strain rose to 0.6~1.1% in the vicinity of the interface. Furthermore, to estimate the sensitivity of configurational parameters of the module to the thermal strain, statistical sensitivity analysis based on the design of experiment (DoE) and response surface method (RSM) was conducted. The statistical analysis revealed that the thickness of electrode coatings of Al and Mo affected the thermal strain and that the thinner Al coating and the thicker Mo coating reduced the thermal strain. In this study, a thermal fatigue test machine was newly developed with a view to verifying these analytical studies. INTRODUCTION We are currently developing a high-performance bismuth-tellurium (Bi-Te) thermoelectric module for power generation. This module aims at heat recovery at temperatures of 150°C or less. Although the total amount of waste heat energy below 150°C is considerable, it has not been utilized for heat recovery because the density of energy is low [1]. In addition, the utilization of such low-density energy is not considered economically competitive. Therefore, our objective is to enhance the thermoelectric efficiency and to improve the cost performance of the module. One method of improving the cost performance of the module is to achieve a long-range run without maintenance, based on the enhanced reliability of the module. Our module consists of the Bi-Te thermoelements and electrodes of Al and Mo formed by atmospheric plasma spraying (APS). In such multilayer coating structures, thermal stress and/or strain is induced owing to the difference in the thermal expansion coefficients of the individual materials, and this can reduce long-period reliability. Although the behavior of the thermal stress and/or strain is significant for designing the module, the influence of configurations and the material characteristics of the thermoelements and the thermally sprayed electrodes on thermal stress or strain have not been ascertained [2,3]. In this study, the effect of the configurational parameters of the thermoelectric module upon the thermal strain is evaluated from numerical analysis, and the optimum coating thickness to improve the integrity of the interface of the thermoelements and electrodes is discussed. EXPERIMENTAL DETAILS Finite element method analysis To evaluate the strain state on a Bi-
Data Loading...
