Investigation On Frictional Pressure Drop Of Water Flowing In Sub-channel With Triangle Distribution In SCWR

The Supercritical Water-cooled Reactor(SCWR)is the only one cooled with water reactor of six Generation IV nuclear reactor systems.A SCWR power plant has advantages of high thermal efficiency,simplified system structure and high security.SCWR is very promising in the future,which has been listed as the key developmental rector in China.The fuel rods sustain high heat flux and strong neutronic-thermo coupling in the narrow and complicated flow sub-channel of SCWR.The research on the thermal-hydraulic characteristics of SCWR exists technological difficulties.The present paper experimentally investigates the frictional pressure drop of water in sub-channel of SCWR.The research results provide experimental basis for thermal-hydraulic design and safe operation of SCWR.In this paper,the frictional resistance characteristics were investigated in the sub-channel with triangle distribution,which was formed that the flue rod diameter D was 8mm and the pitch-to-diameter ratio P/D was 1.4.Within the range of pressure from 11 to 28 MPa across the critical pressure,the heat flux range from 200 to 800 k W/m2,the mass flux range from 700 to 1300 kg/(m2?s).The experimental data was compared with the classical relational,and the forecasting ability and calculation accuracy of the classical relational was evaluated.Then the correlations which were suitable for the calculation of frictional resistance in sub-channel with triangle distribution of SCWR was put forward,the calculation accuracy was also checked.The frictional resistance characteristics of sub-channel with triangle distribution of SCWR were researched in this paper,and the results show that: the friction pressure drop of single-phase water in the sub-channel increases with the rising of bulk enthalpy,but frictional resistance coefficient remains stable;the influence of pressure on friction resistance characteristics is little.The bigger the mass flux,the bigger the frictional pressure drop of single-phase water.Steam quality has a great effect on two-phase friction characteristics in the sub-channel.With the increase of the steam quality,the frictional pressure drop increases,and when the steam quality reaches a high value,the increase trend begins to weaken.Pressure has a great effect on two-phase friction multiplier.With the increase of pressure,frictional pressure drop and two-phase friction multiplier decreased.Mass flux and heat flux have a little effect on two-phase friction multiplier.Supercritical water is liquid at low enthalpy region and the pressure drop is low,but frictional resistance increases obviously when water is at high enthalpy region.The influence of mass flux on the frictional pressure drop is greater than the pressure and heat flux.The existing classical correlations were summarized in this paper,and the experimental data was compared with the calculated results,to evaluate predicted performance of correlations.The results show that: most of the existing correlations in view of the circular tube,so the prediction abilities of frictional resistance characteristics in sub-channel with triangle distribution are not good.The error is big by comparing with the experimental data of the calculated results.Prediction abilities of supercritical water friction correlations are good,and prediction abilities of single-phase and two phase friction correlations are poor.According to experimental data of frictional resistance characteristics in sub-channel with triangle distrbution,the calculation correlations were fitted for single-phase water,rgas-liquid two-phase and supercritical water.The prediction abilities of new correlations to single frictional resistance get obviously promoted,and average calculated error is less than 10%,most of the data into the error of plus or minus 30%.The several correlations of two-phase friction ratio which predict ability is relative good were amen put forward four sets of new correlations.The Calculation error of then is less than 4%,more than 80% experimental data points is in the error of plus or minus 30%.The predict ability of new correlations for supercritical water friction in triangle sub-channel is good,and more than 95% of the data error within ±30%.