Heat pipe heat exchangers are characterized by high heat transfer coefficient, compact size, and environmental adaptability, etc. The use of heat pipe heat exchangers in mobile heat pipe reactors provides high safety and flexibility, and is suitable for applications in fields such as deep-sea exploration, aerospace power systems, and integrated energy systems. By studying the heat transfer characteristics of the fluid outside the condensing section of the heat exchanger in a mobile heat pipe reactor, the effects of the changes in the mass inlet flow rate, heat pipe wall temperature and heat exchanger tilt angle on the mass outlet temperature and convective heat transfer coefficient were obtained. The results show that: with the increase of heat pipe wall temperature, the exit temperature of the fluid in the channel shows a gradual increase trend, while the convective heat transfer coefficient shows a gradual decrease trend; with the increase of the fluid inlet flow rate, the exit temperature of the fluid in the channel shows a gradual decrease trend, while the convective heat transfer coefficient shows a gradual increase trend; with the increase of the fluid inlet flow rate, the exit temperatures of the heat exchanger under the four conditions of heat exchanger tilting angle all show a gradual decrease trend. With the increase of workpiece inlet flow rate, the exit temperature of the four heat exchanger tilt angle conditions show a gradual decrease in the trend, and the trend is basically the same; and the convective heat transfer coefficient show a gradual increase in the trend, and the trend is basically the same.