Experimental Determination of Friction Factors in Two Phase Flow Through a Porous Medium

In a severe accident, the decay heat from the fuel located in the calandria may boil the water circulated through the end shields of a CANDU reactor, causing a two phase flow of water and steam. This two phase mixture may interfere with heat transport if a thin film of steam forms on the inside surface of the end shields. As water and steam run through the end shields, frictional energy loss results in a pressure gradient. The pressure gradient is directly related to the velocity of the fluid, which can be inferred from the permeability of the end shield. Therefore, this project serves to determine the friction factors that cause pressure drop in the end shields of a CANDU Reactor and aims to examine the safety mechanism of the existing end shields. The results of this project corroborated the Gibilaro equation for one phase flow and implied the lack of proper handling of important friction factors in equations for two phase flow. Therefore, further studies on two phase flow through porous medium are needed.

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A Model for the Two-Phase Flow Through a Dual-Scale Porous Medium in Liquid Composite Molding

Volume 13: Processing and Engineering Applications of Novel Materials ◽

10.1115/imece2007-41226 ◽

2007 ◽

Author(s):

N. K. Yamaleev ◽

R. V. Mohan

Keyword(s):

Porous Medium ◽

Two Phase Flow ◽

Fiber Bundles ◽

Phase Flow ◽

Liquid Composite Molding ◽

Two Phase ◽

Individual Fiber ◽

Composite Molding ◽

Flow Through ◽

Dual Scale

The macroscopic flow during processing of composite structures by liquid composite molding is accompanied by the microscopic flow through individual fiber bundles. This concurrent microscopic flow occurs at length and time scales different than those of the macroscopic flow and influences the macroscopic flow behavior, impacting the void formation during composite manufacturing. A reduced-order model developed by the authors of this paper in [Proc. 2005 ASME Conf., IMECE2005-82436] for modeling the microscopic impregnation of individual fiber bundles is currently used to simulate the transient dynamics of the 1-D two-phase flow though a dual-scale porous medium during resin transfer molding (RTM). As has been show in our previous work [Inter. J. of Multiphase Flow, Vol. 32, pp. 1219–1233, 2006] the vapor-liquid phase transition and multidimensional effects of the gas entrapped inside fiber tows can play a significant role in the advancement of the macroscopic resin front and the formation of voids, thus indicating the need to account for these phenomena in the simulation of liquid composite molding processes. These effects are quantified by introducing a nonzero sink term into the right hand side of the mass conservation equation for the dual-scale porous medium, which couples the microscopic two-phase flow inside fiber bundles with the macro-flow through the perform. Two numerical methods, one of which is based on the moving coordinate system associated with the macroscopic resin front and the other one based on the fill factor technique on a fixed Eulerian coordinate system, are used to solve the resin flow through the preform. The comparative analysis of the fill factor and moving front methods as well as the results demonstrating the effect of phase transition and impregnation of individual fiber bundles on macroscopic flow parameters during RTM are presented.

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Measurements of Two-Phase Pressure Drop in a Simulated Debris Bed

Volume 9: Student Paper Competition ◽

10.1115/icone25-67927 ◽

2017 ◽

Author(s):

Milka Hebi Nava Rivera ◽

Daisuke Ito ◽

Yasushi Saito ◽

Mitsuhiro Aoyagi ◽

Kenji Kamiyama ◽

...

Keyword(s):

Porous Media ◽

Pressure Drop ◽

Gas Flow ◽

Two Phase Flow ◽

Severe Accident ◽

Phase Flow ◽

Two Phase ◽

Experimental Database ◽

Flow Through ◽

Measured Pressure

Two-phase flow through porous media should be well understood to develop a severe accident analysis code not only for light water reactor but also sodium cooled fast reactor (SFR). When a core disruptive accident occurs in SFR, the fuel inside the core may become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. Thus, as first step, present work focuses on the characteristics of pressure drop in single- and two-phase flows in different porous media conditions (porous size, liquid and gas flow velocity). In addition, in order to construct an experimental database, the measured pressure drop under different conditions was compared with existing correlations.

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