• Journal of the Korean Solar Energy Society
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• 제30권6호
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• pp.137-143
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• 2010

In this study, the ejector design was modeled using Fluent 6.3 of FVM(Finite Volume Method) CFD(Computational Fluid Dynamics) techniques to resolve the flow dynamics in the ejector. A vacuum system with the ejector has been widely used because of its simple construction and easy maintenance. Ejector is the main part of the desalination system, of which designs determine the efficiency of system. The effects of the ejector was investigated geometry and the operating conditions in the hydraulic characteristics. The ejector consists mainly of a nozzle, suction chamber, mixing tube(throat), diffuser and draft tube. Liquid is supplied to the ejector nozzle, the fast liquid jet produced by the nozzle entrains and the non condensable gas was sucked into the mixing tube. In the present study, the multiphase CFD modeling was carried out to determine the hydrodynamic characteristics of seawater-air ejector. Two-dimensional geometry was considered with the quadrilateral-mashing scheme. The gas suction rate increases with increasing Motive flow circulating rate.

• Journal of the Korean Society for Nondestructive Testing
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• 제32권5호
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• pp.545-550
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• 2012

Steam generator is one of the major components of nuclear power plant and steam generator tubes are the pressure boundary between primary and secondary side, which makes them critical for nuclear safety. As the operating time of nuclear power plant increases, not only damage mechanisms but also scaled deposits on steam generator tubes are known to be problematic causing tube support flow hole blockage and heat fouling. The ability to assess the extent and location of scaled deposits on tubes became essential for management and maintenance of steam generator and eddy current bobbin data can be utilized to measure thickness of scale on tubes. In this paper, tube reference standards with various thickness of scaled deposit has been set up to provide information about the overall deposit condition of steam generator tubes, providing essential tool for steam generator management and maintenance to predict and prevent future damages. Also, methodology to automatically measure scale thickness on tubes has been developed and applied to field data to estimate overall scale amount.

• Journal of the Korean earth science society
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• 제22권6호
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• pp.512-527
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• 2001

Separated flows passed complex geometries are modeled by discrete vortex techniques. The flows are assumed to be rotational and inviscid, and a new techlnique is described to determine the stream functions for linear shear profiles. The geometries considered are the snow cornice and the backward-facing step, whose edges allow for the separation of the flow and reattachment downstream of the recirculation regions. A point vortex has been added to the flows in order to constrain the separation points to be located at the edges, while the conformal mappings have been modified in order to smooth the sharp edges and to let the separation points free to oscillate around the points of maximum curvature. Unsteadiness is imposed to the flow by perturbing the vortex location, either by displacing the vortex from the equilibrium, or by imposing a random perturbation with zero mean to the vortex in equilibrium. The trajectories of passive scalars continuously released upwind of the separation point and trapped by the recirculating bubble are numerically integrated, and concentration time series are calculated at fixed locations downwind of the reattachment points. This model proves to be capable of reproducing the trapping and intermittent release of scalars, in agreement with the simulation of the flow passed a snow cornice performed by a discrete multi-vortex model, as well as with direct numerical simulations of the flow passed a backward-facing step. The results of simulation indicate that for flows undergoing separation and reattachment the unsteadiness of the recirculating bubble is the main mechanism responsible for the intense large-scale concentration fluctuations downstream.