Preliminary Study On Thermal-hydraulic Characteristics Of Secondary Side In Steam Generator Based On A Scaled Experimental Facility

Thermal hydraulic characteristics of two-phase flow in secondary side of steam generator (SG) with non-uniform heating bundles using test facility (scaled structure of M310 PWR’s SG) is studied in this thesis. The steam generator of AP1000 has uniform supply of feed water and the actual internal flow characteristics due to variation in flow rate of water at secondary side is not affirmed yet. In this premise, with different ratios of feed water at hot and cold sides with predefined preheating temperature,20 temperature sensors are juxtaposed in five rows to record the data. In addition, to understand the bubble generation and propagation phenomenon, six different points are marked and high speed camera is used to get the visualization of the flow. The simplified model of test facility is computationally analyzed in ANSYS-CFX 16.2 to get the variation of fluid properties along the tubes for both steam and water. Lateral drift movement of bubbles along with upward motion due to density difference explains the phenomenon of natural circulation throughout the heat exchanger. Higher flow rate at cold leg leads to more uniform temperature distribution.The visuals confirm the results of CFD analysis where higher heat transfer rates are observed in the upper region due to vehement vibration and cutting effect of the U-tubes. The experimental vortex shedding phenomenon coupled with eddy currents due to strong turbulent effects in the upper U-bend region underpins the results of numerical simulation. Very little change in temperature of water but significant variation in void fraction in CFD analysis are in conformity with the experimental findings.