The Effect of Liquid Solidification on Turbulent Flow Heat Transfer of a Heat Generating Fluid in a Cold Tube

A theoretical study has been conducted to investigate the effect of liquid solidification (freezing) on the heat transfer characteristics for the turbulent flow of a heat generating fluid in a cooled circular tube. Steady-state conditions and a uniform wall temperature, which is lower than the liquid freezing temperature, are assumed. The radius of the liquid-solid interface and the local Nusselt number are determined as a function of position along the tube for several different values of the Reynolds number and the Prandtl number. The thickness of the frozen shell increases with distance down the tube. It approaches its fully developed value, depending upon a single dimensionless freezing parameter which measures the relative rate of wall cooling and internal heating. The local Nusselt number, however, first decreases rapidly and then approaches its fully developed value, which depends on the Reynolds number and the Prandtl number

Buoyancy Effects on Forced Convection Flow and Heat Transfer

Buoyancy effects on a forced convection laminar flow with uniform internal heat generation along a vertical flat plate are theoretically studied. Solutions are obtained by means of the integral equation method (the approximate Kármán-Pohlhausen method) and are compared with the solutions obtained by the series expansion method in which the stream function and the temperature function are expanded into power series in terms of the parameter Gr/Re for Pr≧l, whereas in terms of the parameter Gr/(RePr) for Pr<1. Velocity and temperature distributions of fluid are presented for various values of the governing parameters

Statistical Analysis of Pressure Fluctuations in Vertical Two-Phase Flow

An experimental study was conducted on pressure fluctuations in vertical two-phase air-water flow. Statistical analysis of measured fluctuations was used to identify flow regimes in two-phase flow. Random ripple fluctuations were observed in bubbly flow. In slug and churn flows, however, violent oscillations were caused by the periodic passage of liquid and gas slugs. These oscillations-were weakened with a further in-crease of gas flowrate, and small ripple fluctuations again appeared in annular flow

Particle Size Measurement of Reaction Product Aerosol of Sodium-Oxygen

A multi-level scenario simulation system as a safety infrastructure technology is required for design optimization, safety margin adjustment, and innovative technology developments of sodium-cooled fast reactor (SFR). In order to properly implement the Verification and Validation (V & V) of the simulation system, it is indispensable to ensure experimental database of sodium chemistry as specific SFR safety issue. In this study, measurement results of aerosols generated by sodium-oxygen reaction for sodium fire event were reported with the aim of clarifying the radiation heat transport phenomena in the reaction field. The sodium-oxygen counter-flow diffusion flame was formed one-dimensionally above the sodium pool by the reaction between sodium vapour and oxygen. Argon (Ar) including 2% oxygen were introduced to a liquid sodium pool (temperature: 820K) under the reduced pressure condition (0.05MPa). Ar guard flows were employed to stabilize the reaction. The reaction continued more than 600 seconds without any changes in terms of flame shape and position. Aerosol size was measured as a function of Z (the distance from the sodium pool surface) and r (the distance from the center of the sodium pool). Laser Induced Incandescence (LII) and the Mie scattering method using the different wavelength laser beams (405nm, 450nm, 520nm, 532nm, 638nm and 650nm) were employed to ensure the measurement accuracy. Aerosol sizes from several hundred nm to 1 μm were measured in this reaction field and the aerosol size increased toward the sodium pool. This stemmed largely from aerosol growth and polymerization because the flow rate decreased near the sodium pool. It was also confirmed that the size of aerosol measured by LII was in good agreement with the measurement using the Mie scattering method under the same conditions. The refractive index of the aerosol was also evaluated to be 1.42-0.5i