Chalk River Unidentified Deposits(CRUD)is naturally formed on the fuel cladding during the routine operation of pressurized water reactor(PWR),and its influence mechanism on the boiling heat transfer behavior of cladding is still unclear.In order to investigate the influence of CRUD on the bubble departure diameter(BDD)and bubble departure frequency(BDF),based on the flow boiling visualization experimental platform under atmospheric pressure,the cladding material Zr-4 alloy is used as the substrate,and SiO2 deposition layers with different thicknesses are deposited layer by layer to simulate the CRUD.The bubble dynamics analysis of BDD and BDF is carried out through the flow boiling experiment,with their relationship with the wall superheat considered,and compared with the existing prediction model.It is found that compared with the surface without SiO2 deposit,the BDD and BDF on the surface with SiO2 deposit are larger,and the increase of wall superheat will cause the BDD to become larger and accelerate the bubble departure.Under the same conditions,the influence of fluid subcooling and Reynolds number on the BDF is greater than that on the BDD.The improved prediction equations of BDD for all conditions in this experiment are put forward.The error between the predicted value of the improved prediction equations and the experimental value is less than 30％.
Flow boiling experimentChalk river unidentified depositsBubble departure diameterBubble departure frequency
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