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Title:Experimental study of rapid pressure transients in a two-fluid, two-phase system and comparison to RELAP5
Author(s):Heald, Alex
Advisor(s):Brooks, Caleb S
Contributor(s):Kozlowski, Tomasz
Department / Program:Nuclear, Plasma, & Rad Engr
Discipline:Nuclear, Plasma, Radiolgc Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Particle Image Velocimetry
Pressure Transient
Abstract:The six-equation two-fluid two-phase model is a prevalent tool used to estimate the behavior of nuclear thermal hydraulic systems. This model requires use of closure relations, which have been developed over decades to provide greater accuracy and reliability to the simulations that utilize this model. Experimental work has been vital to the development of accurate closure relations. Fast transients can be particularly difficult to model, so experimental datasets are important for developing closure relations that apply to these scenarios. Previously, experiments like the Edwards pipe experiment (ISL, 2010) and the pipe experiment by Takeda and Toda (Takeda and Toda, 1971) have been instrumental to improving the modelling of transients. In this work, state-of-the-art measurement techniques and particle image velocimetry (PIV) are utilized to demonstrate the ability to record high fidelity measurements around an air-water interface during a fast pressure transient. Previously, it has not been possible to take high fidelity measurements for such an experiment due to the rapid measurement rate and accuracy required as well as the inability to take measurements directly on either side of a phase interface. By setting the phase interface in a glass viewport with piezoresistive pressure transducers on either side, pressure can be measured accurately at the rapid rate required, the water level can be tracked, and phase velocities on either side of the interface can be measured. The two experiments described in this thesis, a blowdown and a pressure surge, are designed to create a fast pressure transient wherein the interfacial behavior between the two fluids can be measured reliably. These measurements are compared against a RELAP5 simulation to support the validity of the methods described in this work. Both experiments produce high fidelity measurements that match the expected behavior. The pressure measurements from either side of the interface change concurrently with the movement of the phase interface and accurately capture dynamic pressure behavior during flow reversals. The PIV measurements show the phase velocities on either side of the interface match closely, as expected, and demonstrates the ability to perform PIV measurements on two distinct fluids from a single high-speed video. The blowdown experiment shows that pressure data align well with expected behavior predicted via RELAP5 simulation. With the pressure surge experiment, a slower variation showed good agreement with the simulation while faster cases resulted in significant instabilities in the simulation, showing that this fast pressure transient behavior can be difficult to simulate.
Issue Date:2019-12-13
Rights Information:Copyright 2019 Alex Heald
Date Available in IDEALS:2020-03-02
Date Deposited:2019-12

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