Numerical simulation of the effect of different gas injection rates on the natural circulation performance of a liquid lead bismuth eutectic

Injecting gas into the natural circulation loop of a liquid lead bismuth eutectic (LBE) can effectively improve its natural circulation ability. In order to investigate the effect of varying gas injection volumes on the heat transfer characteristics of liquid LBE flowing in the circuit and the efficiency of gas lift, numerical simulations were carried out to investigate the effect of seven different gas injection rate conditions ranging from 0 to 750 NL/h on the velocity field, gas-phase volume fraction, friction pressure drop, heat transfer characteristics, and lifting efficiency of the circuit. The calculation results show that the liquid LBE mass flow rate increases from fast to slow and then decreases slightly with the increasing gas injection rate; the gas phase volume fraction in the rising pipe and the falling pipe increases with increasing gas injection rate; the total pressure drop decreases with increasing gas injection rate, and the rate of decrease slows down, and the pressure drop in the rising pipe decreases rapidly and then rises slightly; the change of the Nu number is affected by the mass flow rate of liquid LBE and the volume fraction of the gas phase; the Nu number increases with increasing Re number in the case of low gas injection rates, and decreases with increasing volume fraction of the gas phase in the case of high gas injection rates; the efficiency of the air-lift shows decreases with increasing injection rate, and the rate of decrease slows down gradually.