Irregular pentagon loop for nuclear reactor natural circulation system test apparatus

The natural circulation loop has become a crucial topic for investigating a heat transfer system without a recirculation pump. This study aimed to analyze the steady-state condition of an irregular pentagon natural circulation loop design. The loop was constructed using stainless pipes and equipped with a real-time data acquisition and control system capable of handling high-temperature fluids without human contact. The data acquisition and control system was based on Python programming and operated on a Raspberry Pi mini computer. The heater in the loop was designed from a pipe wrapped around a nichrome wire, and the voltage source could be adjusted using Variac. The cooling system utilized the wind from the blower flowing in the annulus between the pipe inside the larger diameter pipe. The experimental results were used as parameters and boundary conditions in modeling using ANSYS Fluent software. The results showed that the deviation of the modeled temperature from the experimental results was below 1.5%. In addition, the results provided that the higher the power applied to the heater, the greater the Reynolds number value at steady-state, with the difference in value between the highest and lowest power reaching 38.7%. This research contributes to the understanding of the natural circulation system as an efficient heat transfer method and can potentially be used in the design of passive safety systems for generation IV nuclear reactors.