Experimental study on nitrate natural circulation loop

[Background] Nitrate natural circulation loop (NNCL) system is an important platform for studying molten salt natural circulation characteristics. The experimental data can be used to develop or validate thermalhydraulic analysis codes. [Purpose] This study aims to explore natural circulation characteristics of nitrate and verify the functional relationship of related parameters. [Methods] Different experimental conditions were obtained by controlling the temperature of molten salt pool at 310, 340, 370 centigrade and the opening of air cooling tower throttle at 0%, 25%, 50%, 75%, 100%. Both the transient and steady state characteristics were observed. Combining theoretical analysis and experimental data, the analytical solution was obtained by the method of fitting approximation. [Results] The response time of the temperature difference of the DRACS heat exchanger (DHX) to the temperature change of molten salt pool is more than 20 h, and the response time to the wind speed change is several minutes. The natural circulation flow rate of nitrate in the NNCL system is proportional to the m-th power of DHX heat exchange power, and the resistance of the NNCL system is proportional to the (1-m)/m-th power of the flow;the m value of the NNCL system is between 0.47 ∼ 0.49. [Conclusions] The relationship between the natural circulation flow-power of the DHX and the natural circulation pressure drop-flow is well verified by the experimental results. (authors)