Optimization of Segmented Thermoelectric Generator with Wavy Structure and Nanofluid Cooling: Variable Structure

Thermoelectric generators (TEGs) are highly sensitive to both geometric configuration and thermal boundary conditions, particularly the heat dissipation mechanisms at the cold side. Despite extensive research on thermoelectric materials, cooling strategies, and geometric optimization, the coupled influence of hollow sinusoidal geometries and convective cooling conditions remains insufficiently understood. Therefore, this work presents an integrated electrothermal optimization of a segmented hollow sinusoidal thermoelectric generator using a finite element model developed in ANSYS Workbench 2023 R1. The proposed TEG is composed of hollow thermoelements segmented with Bi₂Te₃ and skutterudite using a fixed segmentation ratio. Attention is given to the effects of the revolution distance (dr) and inter-leg spacing (D), geometric parameters that have received limited attention in previous studies. The performance of the device was evaluated by varying the revolution distance from 0.15 mm to 0.58 mm under applied heat fluxes (q″) ranging from 5000 to 35,000 W/m2. Additionally, the influence of inter-leg spacing on voltage generation was systematically investigated. Cooling conditions included both an idealized constant-temperature boundary condition of 25 °C, employed for model validation, and convective cooling conditions based on TiO2, graphene, distilled water, Fe3O4, and Al2O3 nanofluids. The convective heat transfer coefficients were determined from nanofluid thermoelectric properties and implemented as thermal boundary conditions at the cold side of the thermoelectric generator. Among the cooling media evaluated, TiO2-based cooling exhibited the closest performance to constant-temperature condition. Nevertheless, the assumption of a constant cold-side temperature was found to overestimate the thermoelectric performance compared with convective cooling conditions scenarios. The results revealed that both geometric parameters and cooling conditions significantly affect the electrothermal behavior of the device. The maximum output voltage of approximately 0.39 V was obtained for dr=0.15 mm under TiO2-based cooling and an applied heat flux of 35,000 W/m2. Increasing the revolution distance from 0.15 mm to 0.58 mm reduced voltage generation. Furthermore, the inter-leg spacing exhibited a non-linear influence on voltage generation, highlighting the complex interaction between geometry and thermal transport mechanisms. The findings also demonstrate the importance of simultaneously considering revolution distance, inter-leg spacing, thermal loading, and convective nanofluid-based cooling conditions during thermoelectric generator design and optimization.