A fully coupled thermal-fluid-electric-mechanics multiphysics numerical model for comprehensive performance evaluation of annular thermoelectric generators

The maximum thermal stress is an important indicator for evaluating the thermal reliability of thermoelectric generators (TEGs), but theoretical models to simultaneously predict the thermoelectric and thermomechanical performance of TEGs are lacking. Therefore, a fully coupled thermal-fluid-electric-mechanics multiphysics numerical model is established, and it is adopted to conduct a comprehensive numerical analysis of an annular TEG. Additionally, the influences of geometric parameters (height h and angle $\theta$) of thermoelectric elements and exhaust conditions on the performance of the annular TEG are studied. Numerical results reveal that reducing the thermoelectric element height (h) from 5 mm to 2 mm under T_in = 550 K and ṁ_ex = 30 g/s enhances output power by 27.6 % (10.97 W–14.02 W) but lowers conversion efficiency from 3.41 % to 2.99 %, while maximum thermal stress decreases by 11.6 % (289.72 MPa–256.07 MPa). Increasing the angle (θ) from 4° to 7° elevates output power by 11.6 % (12.94 W–14.44 W) yet reduces efficiency by 14.4 % (3.34 %–2.86 %), with thermal stress amplified for larger θ–θ_s mismatches. Both the thermoelectric and thermomechanical performance of the annular TEG are more significantly affected by exhaust temperature compared to mass flow rate. This model integrates fluid dynamics and thermal-electric-mechanics coupling, overcoming limitations of prior studies that simplified boundary conditions. It provides actionable insights for optimizing annular TEGs in automotive waste heat recovery, balancing thermoelectric performance and thermomechanical performance.