Numerical Study On The Flow Behavior And Heat Transfer Of Water Film In The Passive Cooling Containment System

In advanced passive pressurized water reactor,the Passive Containment Cooling System(PCCS)plays an important role in protecting the containment integrity,furthermore,studying the film flow and heat transfer behavior is the key to study PCCS,so the study of water film flow and heat transfer has the extremely important significance.In the first part of this paper,the existing test facility with large scale and wide range of test parameters for the study of water film flow and heat transfer on large flat plates is introduced.The characteristics of film flow and distribution,heat transfer by film evaporation and behavior of film splashing under different inlet conditions on the large plate are studied by relevant water film tests,and abundant experimental data are accumulated.Based on the Water Film Test(WAFT)facility,the Eulerian Wall Film(EWF)model in the FLUENT,which is a kind of commercial computational fluid dynamics software,is used to establish corresponding numerical simulation schemes in this paper,and film flow and distribution,film evaporation and film splashing on the inner and outer walls of the passive containment are analyzed respectively.In the numerical calculation of the film flow and distribution,by comparing with the relevant test results,the comparison error is within 20%,which indicates that the rationality and applicability of the relevant numerical simulation schemes are verified.It provides a certain reference for the study of the film flow and distribution on the upper part of the containment.In the numerical calculation of film evaporation,through comparison with related experimental results,the comparison errors are in 20%,which indicates that the rationality and applicability of the relevant numerical simulation scheme are verified;furthermore,a 20 m long plate water film evaporation model is established based on this calculation scheme.By comparing the numerical results,smaller water film temperature gradient and more stable evaporation process are found during the film evaporation on the longer plate,which provides a certain reference for the study of film evaporation on the vertical outer wall of the containment.In the calculation of the film splashing behavior,by comparing with the relevant test results,the comparison error is controlled in 10%,which verifies the rationality and applicability of the relevant numerical simulation schemes;four specific stages are divided during the process of film splashing after impinging on the attached plate by analyzing the numerical simulation results.The relationship between the film loss ratio,the Weber number,and the number of liquid film space is established.The EWF model is found that it cannot simulate the process of film impinging on the attached plate with low welding foot height.Based on the above results,a film splashing model with 20m-long plate is established by extending the plate surface,it is found that the extension of the plate surface has less influence on the film loss during the splashing process.