In a steel plant, waste heat recovery systems of hot-blast furnace are characterized by high-temperature exhaust gas from a hot stove that flows through heat pipe heat exchangers. By heating gas in a hot stove and combustion air in a blast furnace, stable and balanced heat exchange efficiency is achieved in this system. The thermosyphon, which is also known as a gravitational heat pipe, uses latent heat to transfer the heat. In this article, heat pipe performance limits, including entrainment and boiling limits, are experimentally and theoretically investigated. Heat pipe tube lengths of 130 mm, 200 mm, and 300 mm were used in the experiment, and the operating temperature and heat transfer rates obtained were compared in a MATLAB prediction program to determine when boiling and entrainment limits occur. The precision comparisons of the theoretical and experimental results were 8.7% and 6.7%, respectively. Therefore, a standard test method and prediction program for boiling and entrainment limits are presented in this study, and the heat transfer phenomena in heat pipes of any scale are explained when these limits occur. Additionally, according to data from the China Steel Corporation, the capacity limit of the heat transfer rate for the heat pipe in this study is calculated at 8,370 W.

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