| The global energy crisis is becoming more and more serious.Nuclear energy is one of the main ways to solve the global energy crisis.However,the treatment of a large number of nuclear waste generated in the process of nuclear power generation restricts the rapid development of nuclear energy.ADS can solve the problem of nuclear material shortage,but ADS subcritical reactor core will generate a lot of heat in operation.In order to ensure the safe operation of the whole reactor,it is necessary to have an efficient and stable secondary cooling system.Compared with other coolants,such as water and alkali metal,liquid Lead-Bismuth Eutectic alloy(LBE)has many outstanding advantages,such as low melting point,high boiling point,good neutron performance and good natural circulation ability.It is the first choice material for the hash target and loop coolant in ADS system design.Under the above background,this paper mainly studies the convective heat transfer characteristics of liquid LBE.Due to the difference between LBE and conventional liquid water,the Prandtl number of LBE is far lower than that of water,even in the full turbulent flow field,molecular diffusion still plays an important role.Therefore,in the process of numerical simulation,it is necessary to choose the appropriate turbulent Prandtl number model to modify the numerical simulation method based on Reynolds average.In this paper,firstly,different turbulence models and turbulent Prandtl number models are used to simulate the convective heat transfer of liquid LBE in the annular channel.The numerical results are compared with the experimental measurements.It is found that the accuracy of the numerical results is higher when the realizable k-? turbulence model and SST k-? turbulence model combined with Cheng turbulence Prandtl number model are used.Then the main heat exchanger principle prototype is simulated.The numerical simulation of the principle prototype of the primary heat exchanger mainly includes three aspects.(1)The k-? turbulence model and Cheng turbulence Prandtl number model are used to calculate the flow field,pressure field and temperature field of the heat exchanger.The effectiveness of the numerical simulation results is verified by the heat transfer performance experiment of the heat exchanger on the LETEA test bench.(2)Based on the verification of the mathematical model and numerical results,the influence of the flow rate and inlet temperature at the shell side and tube side of the heat exchanger on the heat exchange performance is analyzed by using numerical simulation method.It is found that the decrease of the inlet temperature of high pressure water can enhance the heat exchange.Besides,the increase of the inlet temperature of liquid LBE and the increase of the mass flow rate of the two working fluids have the same effect.However,compared with the change of temperature,the enhancement of mass flow rate of working fluid makes the enhancement of heat transfer capacity more obvious.This enhancement will gradually decrease with the increase of mass flow rate.Based on the results of numerical simulation,the accuracy of four empirical equations of LBE is compared under different Pe numbers(235-798).The Subbotin empirical equation is recommended to calculate the convective heat transfer coefficient of LBE side.(3)On the basis of the above work,the influence of the number of support plates on the heat exchanger performance is studied,the structure of the heat exchanger is optimized,taking JF factor as the evaluation standard.It is found that 5 supporting plates of heat exchanger is the best.In this paper,the turbulent model and the turbulent Prandtl number model suitable for the flow and heat transfer of liquid LBE outside the tube have been studied.The factors affecting the heat transfer performance of the liquid LBE-water with high pressure heat exchanger are analyzed,which provides a reference for the design optimization of the heat exchanger with the liquid LBE as the flowing working fluid. |
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