In the industry, most of the heating equipment of the thermal system could not achieve complete constant heating in theory. It is more complicated in nuclear power system. Even if the effect of burn up life is not considered, the distribution of power still presents a special function distribution. However, in order to simplify the problem, the heat release unit is often replaced by uniform heat flux. In the process of system characteristics research, the effect of local heat transfer usually will not have a great impact on the overall performance of the device. But from the perspective of safety design, once the local heat pipe is burned out, it will directly restrict and determine the design limit of the whole device. Therefore, it is of great engineering significance to study the characteristics of unconventional thermal boundary conditions.

In order to reveal the principle of heat transfer character under specific boundary conditions, a series of investigations are conducted. Based on the conventional test section with uniform heat flux, steady-state and transient conduction differential equations are derived theoretically and extended to the experimental channel with axial cosine heating. The theoretical deduction results indicate that the amplitude and phase difference of wall temperature are influenced by Fourier number when flowrate oscillates. Meanwhile, numerical simulation is conducted on heating tube with different thermal boundary conditions. The wall temperature field of axial nonuniform heating channel is studied under steady and unsteady flow. It includes the position of peak wall temperature, excess temperature, and the non-linear distribution of fluid temperature along the channel. The results indicate that a great difference exist between uniform and non-uniform heating flux. The simulation of heat and flow characteristics in reactor core is not suggested to use conventional test channel with uniform heat flux. The related investigations could lend some experience to nuclear safety design.

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