While flow restriction caused by various obstacles in reactor coolant loop can be treated insignificantly in normal operation condition it may be an important factor which characterize the thermalhydraulic behavior in the reactor when two-phase flow or natural circulation occurs by accidents. Therefore it is necessary that the pressure drop by flow restriction should be predicted as exactly as possible.
For this purpose, a series of experiments have been performed to investigate the effect of entrance geometry of flow channel contraction on pressure drop. This subject is directly applicable to such situations as rod spacing devices, core flow channel entrance and U-tube entrance in steam generators.
Five test sections were made to simulate typical geometrics of entrance. And the pressure drops were measured for single and two-phase flow in each case of five sections to analyze the effects of various parameters such as flow rate, steam quality, etc.
In case of two-phase flow, the experimental results were compared with the predicted value calculated by homogeneous model.