Elasto-thermoelectric non-linear, fully coupled, and dynamic finite element analysis of pulsed thermoelectrics

Abstract

This paper presents a numerical study on the influence of pulsed electric signals applied to the overcooling of thermoelectric devices. To this end, an experimental setup taken from the literature and a commercial cell are simulated using a complete, specially developed research finite element code. The electro-thermal coupling is extended to include the elastic field, demonstrating that the increment of cooling can produce mechanical failure. Numerical results are developed and the variation of overcooling versus pulse gain and versus duration is validated towards a new analytical expression and the experimental data. The issue of optimal intensity at steady-state is also newly developed. Thermal and mechanical trends are presented using constant and variable (with temperature) material properties for a single thermoelement. While some of the first trends are similar to those of published works, others are different or directly new, all closer to those of the experiments. The mechanical results have not been thoroughly studied until recently. The three-dimensional finite element mesh includes non-thermoelectric materials that are fundamental for the current study. Distribution of stresses during steady and transient states are shown inside the thermoelement, for five components and for the combined Tresca stress. Concentrations at corners of the lower side appear close to the cold face. Due to these concentrations, 27-node isoparametric, quadratic brick elements are used. It is shown that the mechanical field is an important factor in the design of pulsed thermoelectrics, since for practical applications the stress levels are close or slightly above the admissible limits.

Plasticity coupled with thermo-electric fields: Thermodynamics framework and finite element method computations

“…In the steady-state, the maximum stresses are similar since the yield stress has not been reached yet. However, with the increase of electric flux, the stress increments seen in [18] due to accumulation of Joule heating, are no longer the same. When the pulse is introduced reaching the yield stress σ y , the subsequent stress-rate increase is reduced, due to the corresponding increase in plastic strains.…”

“…A complete simulation for elastic regime can be found in [18]. The material properties for this problem are presented in Table 3.…”

“…4 top. First, an electric flux j ss = I op /A is introduced, where I op is an optimal electric current that maximizes the temperature differenceT t − T b in steady-state (more details in [18]) with A as the transversal area of the copper. This electric flux value is kept fixed until evolution for all the degrees of freedom has been stabilized, and a steady-state has been reached.…”

“…[11][12][13][14]), but without considering the numerical implementation, nor general multi-field coupling. In terms of completeness of presented developments for thermomechanics and electromagnetic coupling, the recent ones that come closest to this work are homogenization scheme in [15] and hypo-elastic approach in [16][17][18], but they remain limited to elastic behavior.…”

Computational Thermoelectricity Applied to Cooling Devices

“…Furthermore, this method is optimal for applying to nonlinear coupled problems as thermoelectricity. In this connection, the authors of the present chapter have extensive experience in developing thermodynamic consistent FE formulations, which are implemented in the research code FEAP [20], see [21][22][23][24][25] and [26]. Regarding commercial FE codes, the authors in [27,28] use ANSYS to perform a comprehensive numerical analysis focusing on the cooling performance of miniaturized thermoelectric coolers for microelectronics applications.…”