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Product Name: Computational Fluid Dynamics
Product Description
 Computational Two-Phase Flow Dynamics and Heat Transfer for Analysis of
LWR Transients
The principle objective of this project is to develop a computational fluid
dynamic (CFD) model to simulate the two-phase flow and heat transfer in a
water-steam system. The CFD model is based on the Navier-Stokes formulation in
conjunction with a k-turbulence model and a set of constitutive equations. The
Boussinesq approximation is used to generate conventional buoyancy force and
body force for bulk fluid. The Clausius-Clapeyron equation is utilized to
describe the relation between saturation pressure and temperature A novel
energy-based algorithm is employed to track and delineate the dynamic
liquid-vapor interfacial boundary. The need for temporal and spatial averaging
is completely eliminated. The geometrical void fraction in this formulation is
replaced by a dynamic vapor-phase fraction, which identifies the heat transfer
regimes in the two-phase flow system. Preliminary results have demonstrated the
computational efficiency and the applicability of the CFD model to a variety of
two-phase flow and heat transfer problems of interest to light water reactor (LWR)
safety, such as Loss-of-Coolant Accident (LOCA), Critical Heat Flux (CHF),
Departure-from-Nucleate Boiling (DNB) and DRYOUT.
As a part of validation studies, the two-phase flow model is used to simulate a
thermionic fuel element (TFE) involving bulk evaporation and condensation
associated with internal heat generation and natural convection. It is assumed
that both top and bottom walls are insulated, the side wall is cooled externally
by a constant outward heat flux which removes heat from the system, and the
internal heat generation provides heat to evaporate the liquid phase. Those
conditions are imposed to activate the pure bulk evaporation and condensation
and to avoid the bubble generation. Figure 1 shows the evolution of water-steam
interface, which indicates the formation and development of the liquid film
covering the side wall surface. Figure 2 shows the evolutions of temperature
distribution.
The significant advance made in the developing model is the simulation of a
full sequence of single bubble formation and growth in a nuclear reactor core.
Due to the order of magnitude type change in flow properties between bubble and
its surrounding water, simulation of flow boiling is a challenging problem. In
particular, buoyancy force and surface tension which plays a pivotal role in the
boiling nucleation and bubble dynamics make the governing equations rather
complicated. The two-phase flow and heat transfer model incorporates interfacial
models of momentum transfer to account for effects of buoyancy force, surface
tension and shear stress discontinuities at water-steam interface. The energy
equation is modified to incorporate the latent heat of phase change. The single
bubble generation without departure was simulated with the CFD model. Figures 3
and 4 show the single bubble generation and corresponding temperature
distributions, respectively.
Company Details
Founded in 1985, INSPI research covers a broad range of activities including feasibility analysis for ultracompact nuclear power reactor concepts as well as experimental and theoretical research to establish the fundamental properties of high... more
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