Experimental And Numerical Study On Heat Transfer Of Supercritical Water Flowing In Typical Channels

Since Supercritical Water-cooled Reactor(SCWR)has such advantages as system simplification and higher efficiency,research activities on it are ongoing worldwide.In the frame of SCWR Fuel Assembly(FA)design,one of the most challenging tasks is to keep the cladding temperature below the design limit,to prevent any destruction due to the temperature and to guarantee the integrity of the fuel rods.Thus,an accurate prediction of heat transfer between the cladding and fluid plays a very important role.However,due to the large variation of thermal-physics properties in the vicinity of pseudo-critical point,heat transfer of supercritical water shows an abnormal behavior compared with that of conventional fluids,especially when the bulk fluid temperature is closed to pseudo-critical point.In order to design the SCWR FA,it is quite necessary to investigate the heat transfer phenomenon and characteristics of supercritical water flowing in typical channels.After reviewing a great number of literatures on heat transfer of supercritical fluid,and based on the core design of SCWR-M proposed by SJTU,the dissertation conducts the following researches using the facility of SWAMUP built by SJTU:(1)The experiments on circle tubes of 7.6mm and 10mm hydraulics diameter were conducted and database for tubes were established.For heat transfer in downward flow,a new correlation based on dimensionless number was proposed.(2)The experiment on annuli of 7.3mm hydraulics diameter was conducted and database for annuli with spacer grids were established.Based on the correlation developed on pressure drop of subcritical conditions,a new correlation was developed to predict the local heat transfer enhancement at supercritical pressure condition.(3)The experiments on 2×2 rod bundles of 4.7mm and 7.6mm hydraulic diameter were conducted and database for 2×2 rod bundles with spacer grids were established.For the sake of getting HTC in rod bundles,3 methods for obtaining fluid temperature including cross section average,CFD sub-channel average and MATRA sub-channel average were proposed.By analyzing the characteristics of heat transfer on circle tube,annuli and 2×2rod bundles,it concludes that parameter effects are similar in 3 types of channels and heat flux,mass flux and flow direction are of great effect on heat transfer.Heat Transfer Deterioration(HTD)occurs on high q/G conditions of circle tube.Spacer grids enhance the heat transfer of downstream and no HTD occurs on annuli and rod bundles.The results of three methods for obtaining HTC including fluid cross section average,CFD sub-channel average and MATRA sub-channel average are numerical similar.New correlations of heat transfer in downward flow based on dimensionless number?_B shows an accuracy prediction on HTC.