MHD Effect And Heat Transfer Characteristic And Corrosion Behavior Of DCLL Blanket With Nano-Coating Walls

Magnetohydrodynamic(MHD)effect,heat transfer characteristic and channel corrosion behavior are the key issues for design of Dual Coolant Lead Lithium(DCLL)blanket.The high MHD pressure drops caused by Lorentz forces which are induced in the fluid under strong magnetic fields.Although Flow Channel Insert(FCI)is applied to decrease MHD pressure drop by decouple the liquid metal from the steel walls and decrease heat losses from the breeder and increase bulk exit temperatures of the blanket then decrease the temperature of First Wall(FW).However,there are still big pressure drops and a higher velocity jet located at the gap flow.Moreover,the FCI made from silicon carbide(SiC)constitutes a complex blanket structures and may cause special flow problems.Besides,it can not be ignored the influence of the channel wall corrosion on the channel structure safety.Therefore,it is necessary and feasible to study the MHD effects,heat transfer characteristic and corrosion behavior of DCLL channel by numerical simulation.In this paper,numerical simulations are performed to investigate the liquid metal flow and heat transfer characteristics in the DCLL channel,and the Discrete Phase Model(DPM)is used to simulate the channel wall corrosion behaviors.The research contents and related numerical results are as follows:First of all,a kind of no-wetting nano material is sprayed on the FW inner surface of the DCLL channel to replace the FCI.The pressure drop and heat transfer characteristic of different parameters(including different magnetic field intensity,entrance velocity,wall condition and FCI pressure)are investigated in present work.The results show that the MHD pressure drop is obviously decreased when DCLL channel sprayed nano-structured Coating,and no matter the channel applied the coating or not,the MHD pressure drop will increase with the increase of magnetic field intensity and entrance velocity.The maximum MHD pressure drop under the coating condition is decreased by 11.7 times,30 times and 44.1 times comparing with no coating condition when the magnetic field strength is 0.5T,1T and 1.5T.At the same time,the heat transfer loss of nano coating DCLL channel has declined 1time.The flow and heat transfer performance of four typical channel structures are analyzed and compared,and concluded that the optimal performance of the four channels is no FCI and coating channel.On the basis of numerical simulation results,the heat transfer criterion equation of the no FCI,coating DCLL channel was derived,which provides a theoretical basis for the optimization of the channel structure and the practical application of the no-wetting material.Secondly,the numerical simulation of DCLL channel wall corrosion is carried out by appling DPM method when liquid metal flow through the DCLL channel,and The channel corrosion characteristic differences with or without coating condition were found for different conditions(including different velocity of entrance channel,magnetic field strength,temperature field and FCI).The results show that no matter how the channel external environment(except without magnetic field environment)change,the corrosion of channel inner wall is significantly reduced after the nano coating is sprayed,and a sharp deterioration in the corrosion of channel wall can caused by the use of channel FCI.The various of channel corrosion with time is the“parabolic”form then the“linear”form at without coating condition,and it has a very huge influence of the various parameters(including velocity of entrance channel,magnetic field strength and temperature field)on the channel corrosion.The channel entrance speed increased from 0.6m/s to 1m/s would makes the channel wall corrosion increase 2 times,the channel field strength increased from 0.5T to 0.8T would makes the channel wall corrosion increase 3.5 times,the channel neutron source increased from 3×10~8J to 8×10~8J makes the channel wall corrosion increase 1.7 times.While the channel corrosion various with time is the"linear"form at coating condition,and the influence of different parameters(including velocity of entrance channel,magnetic field strength and temperature field)on channel corrosion has little effect.The entrance speed of channel increased from 0.6m/s to 1m/s just makes the channel wall corrosion increase by 5%,the channel field strength increased from 0.5T to 0.8T only makes the channel wall corrosion increase by 28%,the channel neutron source increased from 3×10~8J to 8×10~8J makes the channel wall corrosion increase only 1%,which indicates that the coating has a good protective effect on the channel wall structure.