Proposing linear structure for annular thermoelectric generators; thermal, exergetic, mechanical, and economic analysis

Annular thermoelectric generators have been the subject of many studies in recent years due to their structure which improves the efficiency when recovering heat from round surfaces. A novel linear arrangement of legs is proposed in this paper which greatly increases the flexibility of design compared to the conventional π structure of annular thermoelectric generators. Every geometric feature of the legs in the linear annular thermoelectric generator can be changed and optimized independently. Numerical simulations are carried out to study the effect of various parameters such as height ratio (θ_h), total height (h), angle ratio (θ_φ), total angle (φ), thickness ratio (θ_t), total thickness (t), hot and cold side temperature on the output power, efficiency, mechanical and economic performance of the linear shape annular thermoelectric generator. Results indicated that the height ratio, angle ratio, and thickness ratio of 0.5 lead to the highest conversion and exergy efficiencies while producing the lowest thermal stress on the legs and having the least cost per watt of output power. Additionally, it is found that the increment of the total combined height, total angle, or total thickness of the thermoelectric legs increases the costs per watt of output power. For example, the dollar/watt value is grown by 7% when the total thickness is increased from 8 mm to 16 mm for an angle ratio of 0.5. The increase of the heat source temperature can boost the output power, and conversion efficiency, and lower the cost but also impose larger stress as well.