Simulation Experiments on Two-phase Natural Circulation in a Freon-113 Flow Visualization Loop
Author | : Sang-Yong Lee |
Publisher | : |
Total Pages | : 66 |
Release | : 1988 |
Genre | : Nuclear reactors |
ISBN | : |
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Author | : Sang-Yong Lee |
Publisher | : |
Total Pages | : 66 |
Release | : 1988 |
Genre | : Nuclear reactors |
ISBN | : |
Author | : |
Publisher | : |
Total Pages | : |
Release | : 1987 |
Genre | : |
ISBN | : |
In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed using two different thermal-hydraulic loops. The main focus of the experiment was the two-phase flow behavior in the hot-leg U-bend typical of BandW LWR systems. The first group of experiments was carried out in the nitrogen gas-water adiabatic simulation loop and the second in the Freon 113 boiling and condensation loop. Both of the loops have been designed as a flow visualization facility and built according to the two-phase flow scaling criteria developed under this program. The nitrogen gas-water system has been used to isolate key hydrodynamic phenomena such as the phase distribution, relative velocity between phases, two-phase flow regimes and flow termination mechanisms, whereas the Freon loop has been used to study the effect of fluid properties, phase changes and coupling between hydrodynamic and heat transfer phenomena. Significantly different behaviors have been observed due to the non-equilibrium phase change phenomena such as the flashing and condensation in the Freon loop. The phenomena created much more unstable hydrodynamic conditions which lead to cyclic or oscillatory flow behaviors.
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Total Pages | : |
Release | : 1988 |
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In order to study the two-phase natural circulation during a small break loss of coolant accident in LWR, simulation experiments have been performed using Freon-113 boiling and condensation loop. In quasi-steady state, the flow became relatively stabilized and certain regular patterns of flow oscillations were detected with ranges of periods in 8-(approximately)35 seconds and 2.5-(approximately)4 minutes. In order to find out the nature of these oscillations, one-dimensional field equations for the single-phase (liquid) and two-phase region were set up, and these field equations were integrated along the loop. The homogeneous flow model was used for the two-phase region. Then the characteristic equation was derived using perturbation method. Thermal non-equilibrium and compressibility of each phase were not considered in the present analysis. The characteristic equation derived can be used to obtain the stability criteria. A simplified approach showed that the short-period oscillation were the manometer oscillation. The longer period oscillations were the density wave oscillation which had the period of oscillations close to the residence time of a fluid around the loop.
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Total Pages | : |
Release | : 1986 |
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In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed. Based on the two-phase flow scaling criteria developed under this program, an adiabatic hot leg U-bend simulation loop using nitrogen gas and water and a Freon 113 boiling and condensation loop were built. The nitrogen-water system has been used to isolate key hydrodynamic phenomena from heat transfer problems, whereas the Freon loop has been used to study the effect of phase changes and fluid properties. Various tests were carried out to establish the basic mechanism of the flow termination and reestablishment as well as to obtain essential information on scale effects of parameters such as the loop frictional resistance, thermal center, U-bend curvature and inlet geometry. In addition to the above experimental study, a preliminary modeling study has been carried out for two-phase flow in a large vertical pipe at relatively low gas fluxes typical of natural circulation conditions.
Author | : American Nuclear Society. Thermal Hydraulics Division. Meeting |
Publisher | : |
Total Pages | : 828 |
Release | : 1990 |
Genre | : Nuclear reactors |
ISBN | : |
Author | : |
Publisher | : |
Total Pages | : 1600 |
Release | : 1988 |
Genre | : Government reports announcements & index |
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