Effect Of Void Fraction Research Articles

Analysis of reactivity coefficients of Chernobyl reactor by cell calculation.

A series of cell calculations for the Chernobyl reactor was performed using the SRAC code system to provide its fundamental neutronic characteristics for the accident analysis at JAERI. The calculations are based on a two-step cell modelling. The primary cell is supposed on a unit square graphite block of 25cm × 25cm which contains a fuel assembly or a control channel. The secondary cell IS supposed on a unit of 16 channels where 14 fuel and 2 control channels are located so as to simulate the whole core. Detailed Investigation on fractional change of reaction rates for each nuclide along with increase of void fraction was carried out. The analysis clarified the mechanism to induce the positive void coefficient, together with its burn-up dependence and the increase due to withdrawal of control rod. A comparison of the effect of void fraction on the reaction rates in the primary cell between a Monte Carlo code VIM and SRAC shows consistent results within the statistical error. The calculated results for th...

EXPERIMENTAL MEASUREMENTS OF RADIANT TRANSMISSION THROUGH PACKED AND FLUIDIZED MEDIA

Abstract Using a modulated flux technique, radiant transmission through packed and fluidized beds of 820- and 440-u.m glass beads was measured. An increase in transmission was observed in going from a packed bed to a minimally fluidized bed for the smaller particles. At velocities greater than minimum fluidization, increases were found to vary directly with void fraction. The two-flux model for radiative transfer, with absorption and scattering coefficients determined from large-particle independent scattering theory, underpredicted transmission and the effects of void fraction

Mechanical disturbances for a cable-in-substructure superconductor

Abstract Frictional cable movement, due to the electromagnetic force, was studied for a cable-in-substructure conductor. Both axial extent and dissipation energy density for the movement were determined experimentally. The void fraction effect was also studied.

ChemInform Abstract: BIPOLAR ELECTROLYSIS WITH INTRA PHASE CONDUCTION IN TWO PHASE MEDIA

AbstractDie zum Stromtransport unter Gleich‐ oder Wechselspannung beitragenden Mechanismen werden für starre Anordnungen dispergierter Teilchen in einem kontinuierlichen Elektrolytmedium theoretisch analysiert.

Bipolar electrolysis with intra phase conduction in two phase media

The mechanisms contributing to current transfer under alternating and steady voltage conditions through fixed arrays of particles dispersed in a continuous electrolyte medium are discussed. Lumped parameter expressions for the effective conductivity of the dispersed phase incorporating the intraparticle and double layer resistances are proposed which can be substituted in equations of the Maxwell type to predict the conductivity of dispersed media. Experimental measurements of the conductivity of arrays of copper cylinders in acid copper sulphate electrolyte over a range of void fractions and potential gradients under both dc and ac conditions are compared with the conductivities predicted by the model equations. Satisfactory agreement is taken to confirm the broad theoretical approach in predicting the effects of void fraction, phase geometry, interfacial resistance, and intra phase resistance on static two phase media conductivity.

Transfert de matière par diffusion en fluidisation liquide

The individual effects of void fraction and Reynolds number are determined using data on fluidized beds only. A semi-empirical correlation is proposed ▪ and the mean deviation is 4·5 per cent. It is also established that mass transfer is modified by a dilution of active particles by inert particles, even when both solids have similar geometrical and physical properties.

Void Fraction and Current Density Distributions in a Water Electrolysis Cell

An analytical basis defining the steady‐state conditions occurring in an electrolysis cell is stated. Several assumptions are made which permit a theoretical determination of the void fraction and current density distributions. The effect of void fraction and inlet velocity on cell performance is shown. Experimental data for the void fraction and slip ratio occurring in an electrolysis cell are presented. It is found that the slip ratio is near unity. This result is of importance in defining the cell void fraction distributions and is prerequisite to an analysis of pressure drop in electrolysis cells.

Heat transfer characteristics of porous rocks

AbstractEquations are derived for predicting the effective thermal conductivity of beds of unconsolidated particles containing stagnant fluid. The effective thermal conductivity at these conditions, called the stagnant conductivity, is a function of the thermal conductivities of the solid and fluid phases, the void fraction, and, if radiation is important, the emissivity, mean temperature, and diameter of the solid particles. Comparison with the available experimental data indicates that the equations are satisfactory for fluids and solid particles of both high and low thermal conductivities.To extend the theory to beds of consolidated particles, it is supposed that consolidated beds are formed by partial clogging and cementing of beds of unconsolidated particles. With this assumption the theoretical equations for packed beds are extended to include such materials as sandstone and porous metals. The resulting expressions for the stagnant conductivity involve a consolidation parameter characteristic of the solid material. This quantity accounts for the heat transfer across the contact surfaces between cemented or clogged particles. The equations correctly predict the effect of void fraction and solid and fluid thermal conductivities on the heat transfer properties of sandstones and sintered metal systems.