Optimization study of chimney parameters for coal mine gangue hills gravity heat pipe

Coal mine gangue hills have a significant impact on the ecological environment. To address this challenge, gravity heat pipes have been recognized as an effective means of controlling deep-seated temperature in coal mine gangue hills. Among various factors affecting heat transfer efficiency, the magnitude of external airflow velocity in the heat dissipation section of the heat pipe is critical. In this study, we develop a novel chimney effect model for gravity heat pipes in coal mine gangue hills. We employ the non-isothermal flow multi-physics transient solution method to analyze the single-factor effects of entrance radius, height of outlet section, and radius of outlet section on the average velocity at the chimney outlet. Furthermore, we utilize a comprehensive factorial response surface research method to fit the functional relationship between the average velocity at the chimney outlet and various chimney parameters. Notably, our study introduces the height and radius of the outlet section as constraint conditions based on field conditions. As a result, we determine the optimal chimney parameters for achieving the chimney effect in gravity heat pipes within coal gangue hills. Specifically, we set the chimney inlet radius at 1.05 m, the chimney outlet height at 0.03 m, and the chimney outlet radius at 0.145 m. Comparative analysis reveals that introducing the chimney improves the heat dissipation efficiency of the gravity heat pipe by 2.6%. Overall, our study offers innovative approaches to addressing the challenges associated with coal gangue hills and provides valuable insights into the optimization of gravity heat pipes for efficient heat dissipation.