(An) experimental investigation of the effects of the sudden contraction on single-and tow-phase pressure drop

Abstract

For the adequate prediction of single-and two-phase pressure drops through a sudden contraction of flow channel, which is one of the important parts perfomred in the hydraulic analysis of the primary coolant system in normal and accidental conditions of nuclear power plants, an experimental investigation of the effects of sudden contraction of flow channel on single-and two-phase pressure drop has been carreied out. In the present work, a series of experiments have been performed to investigate the effect of flow orientation, number of phases, entrance genometry and flow rate of each phases on the pressure drop due to sudden contraction. Singleand Two-phase pressure drop measurements measurements were made for four different entrance shapes of sudden contraction and for both horizontal and vertical flow. The two-phase flow pattern investigated in the present work were vertical bubbly flow and horizontal stratified flow. The measured pressure drops were compared with pressure drops predicted by existing models for single-and two-phase flow. For singlephase flow, there were some discrepancies between experimental data and predictions for two entrace shapes, and the results show that singlephase contraction loss coefficient for specific entrance shape have to be determined experimentally. In the case of two-phase flow, Hoopes twophase multiplier model, which gives a better agreement than homogeneous model, predicts the experimental data within $\pm 10\%$ for vetical bubbly flow and within $\pm 60\%$ for horizontal stratified flow. In addition, the effects of void fraction and liquid-phase mass velocity on the two-phase pressure drop through a sudden contraction of flow channel were also investigated.