Multi-criteria decision analysis and experimental study on heat pipe thermoelectric generator for waste heat recovery

In the realm of heat conversion and utilization, gravity heat pipes have garnered significant attention due to their exceptional heat conduction efficiency. As a strategy to effectively enhance the efficiency of thermoelectric generator (TEG) systems through shallow geothermal heat recovery, optimizing the performance of gravity heat pipes holds significant implications for their widespread application in the field of sustainable energy. Experimental evaluations comprehensively assessed the performance of a 6 m gravity heat pipe within a temperature difference power generation system, employing multi-criteria decision-making to test thermal performance, efficiency, reliability, stability, and working fluid studies. The study demonstrates that the heat transfer efficiency of gravity heat pipes is highest under film boiling conditions at 250 °C to 350 °C. By adjusting the inclination angle to 60° to 90° and the filling ratio to 30 %–60 %, the power generation efficiency can be improved to 9.71 %. With an increase in wind speed to 8 m/s, the cold end temperature decreases by 30 %, resulting in a peak power generation efficiency of up to 11.3 %. Additionally, CHIME connection methods reduce energy losses to 8.1 %, providing crucial scientific foundations for the design and optimization of temperature difference power generation systems. These findings not only elucidate the heat transfer mechanisms of gravity heat pipes but also offer technical guidance for efficient energy conversion in thermoelectric generator systems.