Analysis of multiple factors influencing the efficiency of gravity thermal pipe waste heat recovery: A case study of heat accumulation management in spoil tips

The escalating accumulation of coal gangue has led to a significant rise in waste pile temperatures, resulting in the production of harmful gases due to spontaneous combustion, thereby posing a threat to the surrounding ecological environment. Traditional remediation methods for gangue hills, which involve significant engineering efforts and frequent combustion incidents, highlight the need for innovative and environmentally friendly thermal management strategies. This study presents a novel approach using heat pipes to regulate temperatures in gangue hills, while also addressing the critical need to improve waste heat recovery efficiency. However, traditional heat pipes require additional energy for low-grade heat dissipation, underscoring the necessity for advanced cooling and heat recovery technologies. We propose a Thermoelectric Power Generation system that combines efficient thermal conduction with cyclic heat recovery. Through theoretical analysis, we investigated key factors affecting heat pipe thermal performance and thermoelectric generation, supported by extensive CFD simulations. Our study included five heat pipe configurations, six working fluids, and three filling ratios, focusing on aspect ratio, thermophysical properties, and filling volume. The optimal parameters were found at an aspect ratio of 80, using a 3:2 water-ethylene glycol mixture at a 60 % filling ratio, achieving a peak power generation efficiency of 7.64 %. The application of the Chiem connection increased power output by 18.9 %, with a 12.53 % deviation between experimental and simulated results, confirming the model's reliability. Numerical simulations effectively reduced the number of experimental iterations, optimized design parameters, and lowered research costs, demonstrating that optimizing heat pipe structural parameters, working fluids, and thermoelectric module configurations significantly improves waste heat utilization efficiency in coal gangue remediation.