Resistance Characteristic of Rod Bundle Channel under Pulsating Flow#br#

Under the ocean conditions, the coolant in the loop of floating nuclear reactor (FNR) would fluctuate periodically, which would affect the thermal and hydraulic characteristics of the system. In order to study this phenomenon, the resistance characteristics of 5×5 fuel rods under pulsating flow conditions were experimentally studied. The ranges of the cycle-averaged Reynolds number Reta＝0.8×10³ to 9×10³, pulsating amplitude Au＝0.2 to 0.8 and dimensionless frequency ω′^1/2＝1.26 to 2.81 were covered in this experimental study. The results show that under the pulsating flow, the instantaneous flow resistance will be greater than the steady-state value due to the acceleration, and the flow resistance will be less than the steady-state value due to the deceleration, and the deviation value will increase with the decrease of the velocity. In addition, during the pulsating flow, the cycle-average friction factor and local resistance coefficient in the whole cycle are larger than the steady-state value under the corresponding Reynolds number. The normalization parameters of C_f＝λ_ta/λ_st and C_sg＝k_ta/k_st are proposed to evaluate the effect of pulsating flow on the cycle-averaged flow resistance. C_f and C_sg increase with the increase of Au and ω′^1/2, and decrease with the increase of Reta. Finally, by dimensional analysis, the prediction relation of λ_ta and k_ta is established, and a better prediction result is obtained.