A comprehensive overview of advancements, applications, and impact of supercritical fluid natural circulation loops

Nowadays, many researches are persistently exploring to comprehend the various characteristic of the supercritical fluid natural circulation loop (SCFNCL) such as use of SCFNCL at normal operating condition as well as a passive system for heat removal from the core, steady state and transient behavior of the loop, heat transfer rate, heat transfer coefficient and optimizing mass flow rate of the loop. In last two decade, a significant research has been seen in the form of analytical, computational and experimental works which highlight the notable use of SCFNCL as an active and passive system in nuclear power plant (NPPs). However, very limited state of arts have been reported based on the loop geometry and their effects, different types of supercritical fluids (SCFs) and applications of the loops. Therefore, steady and transient behaviours of loop in single and parallel channels, thermal–hydraulic (TH) instability, effects of the geometrical and operating parameters on SCFNCL and deterioration of heat transfer (DHT) in SCFNCL are the main emphasis of this review. Performance criteria such as instability, transient, and steady-state requirements, along with methods for containing instability, have been covered. It even emphasizes how crucial it is to validate the numerical codes. Since nuclear reactors use coupled SCFNCL as passive cooling systems, different topologies and combinations of fluids are shown. Very limited experimental studies have been reported in the coupled loop, an initial analysis was conducted and the results demonstrated the effectiveness of the system. The review also demonstrated the need for numerical analysis with using different supercritical fluids and combine with the NPP systems as well as experimental investigations, which can be connected to applications in renewable and sustainable energy.