| Nuclear energy is an important energy source in the process of human development,and its safety research is of paramount importance.Natural circulation relies on the density difference between the hot and cold sections to drive the fluid,which can greatly simplify the system and improve the inherent safety of the reactor.It is also a main cooling method for passive natural circulation reactors.Using CFX to numerically simulate the natural circulation flow heat transfer of liquid metal,the heat transfer coefficient,flow rate,outlet temperature,and thermal stratification were studied.Factors affecting the heat transfer coefficient and flow were studied using factor analysis,and the influence of the interaction between the factors and the contribution rate of each factor were analyzed.The commonalities and differences of natural circulation flow heat transfer of different liquid metals were found.The common characteristics of liquid sodium,sodium-potassium alloy,lead,and lead-bismuth alloy heat transfer are that their heat transfer coefficient is mainly affected by power,but pressure and inlet temperature have less effect on it.Especially for pressure,it has almost no effect on the flow rate,flow velocity and outlet temperature of different liquid metals.The flow of liquid metal is not affected by the interaction of factors.In addition,due to the large viscosity of liquid metals,almost all of them have thermal stratification.There are also many differences in the natural circulation heat transfer of different liquid metals.Under the same power condition,the heat transfer coefficient of liquid sodium is much larger than that of sodium-potassium alloy,lead,lead-bismuth,and its heat transfer effect is better.Among the four liquid metals,the outlet velocity of the sodium-potassium alloy is the largest,and its natural circulation ability is the strongest.For the outlet temperature,the sodium-potassium alloy is also much larger than the other three liquid metals.Compared with liquid sodium and sodium-potassium alloy,the thermal stratification of lead and lead-bismuth alloy is more serious.The flow rate of liquid metal is mainly affected by power and temperature.The flow rate of sodium is most affected by the inlet temperature,with a contribution rate of 62.34%;and the flow rate of sodium-potassium alloy,lead,and lead-bismuth alloy is most affected by power,with contribution rates of 54.25%,79.09%,and 66.60%.The interaction between factors also has an important effect on the heat transfer coefficient.The factors affecting the heat transfer coefficient of liquid sodium,sodium-potassium alloy,and lead-bismuth are affected by power-pressure,pressure-inlet temperature,and power-inlet temperature interactions,respectively.There is no interaction between the factors influencing the heat transfer coefficient of liquid lead. |
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