Optimization of heat extraction performance of gravity heat pipe under multiple working conditions

The orthogonal experiment method was used to investigate the heat transfer performance of the gravity heat pipe under the influence of multiple factors such as types of working fluid, filling rate, and the aspect ratio. The Multi-index weighting method and rescaled range analysis were introduced to analyze the experimental results to propose an appropriate combination scheme of factors for the best heat transfer performance of the gravity heat pipe. The results show that gravity heat pipe can effectively reduce the internal temperature of the coal pile, thereby inhibiting the increase of the temperature of the coal pile. Moreover, the cooling capacity and effective pore radius of gravity heat pipe are positively correlated with the temperature of the coal pile. Specifically, when the coal pile temperature is about 70 ℃, the most appropriate combination of various factors is as follows, the working fluid is Al₂O₃-water nanofluid, the liquid filling rate is 15%, and the aspect ratio is 25.0. When the temperature of the coal pile rose to 210 ℃, the most appropriate combination of each factor is as follows, the working fluid is Al₂O₃-water nanofluid, the liquid filling rate is 25%, and the aspect ratio is 25.0.