Browsing by Author "Stevens, JR"

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    Boiling crisis data for vertical upflow of freon-12 in round tubes and annular channels
    (Australian Atomic Energy Commission, 1980-12) Stevens, JR; Miles, DN
    Results from boiling crisis (burnout) tests including associated pressure drop data are reported for vertical upflow of Freon-12 at a nominal inlet pressure of 1.0 MPa in three round tube test sections (15 to 21 mm internal diameter heated lengths 2.85 to 3.94 m) and four annular test sections of identical cross section dimensions (16 mm diameter inner tube and 21 mm diameter shroud) with different heated lengths. The tests covered a range of values for coolant flowrate and inlet subcooling.
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    Investigation of critical heat fluxes in vertical tubes internally cooled by Freon-12, Part I - critical heat flux experiments with axially uniform and non-uniform heating and comparisons of data with selected correlations.
    (Australian Atomic Energy Commission, 1981-08) Green, WJ; Stevens, JR
    Experiments have been performed using vertical heated tubes cooled internally by Freon-12 to determine critical heat fluxes (CHFs) for both a uniformly heated section and an exit region with a separately controlled power supply. Heated lengths of the main separately were 2870 mm (8.48 and 16.76 mm tube bores) and 3700 mm (for 21.34 mm tube bore); heated length of the exit section was 230 mm. Coolant pressures exit qualities and mass fluxes were in the range 0.9 to 1.3 MPa 0.19 to 0.86 and 380 to 2800 kg m -2 -1 respectively. The data have been compared with published empirical correlations specifically formulated to predict CHFs in Freon-cooled vertical tubes; relevant published CHF data have also been compared with these correlations. These comparisons show that even over the ranges of conditions for which the correlations were developed predicted values are only accurate to within +-20 per cent. Moreover as mass fluxes increase above 3500 kg m - 2 -1 the modified Groeneveld correlation becomes increasingly inadequate and the Bertoletti and modified Bertoletti correlations under-predict CHF values by increasing amounts. At mass fluxes below 750 kg m - 2 -1 the Bertoletti correlations exhibit increasing inaccuracy with a decrease in mass flux. For non-uniform heating the correlations are at variance with the experimental data.
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    A method for measuring the fluid flow distribution at exit from a right cylindrical, randomly packed bed
    (Australian Atomic Energy Commission, 1966-10) Price, J; Stevens, JR
    A method for measuring the fluid flow distribution at exit from a right cylindrical, randomly packed bed of spheres has been investigated using a flow separator to prevent redistribution of the flow between the exit face of the bed and the plane of measurement. Three designs of separator were tested, for each of which steady fluid velocities were measured with a pitot static tube in the exit plane of the separator, and unsteady velocities with a hot wire anemometer. A separator with contracting flow passages was developed which facilitated measurement and reduced turbulence intensities without causing any significant flow redistribution within the bed. Measurements are presented for a loosely packed bed of glass spheres which show that the velocity profile is reasonably uniform over the bed except for a region within a half sphere diameter of the vessel wall. This differs substantially from the profiles measured by most previous investigators.