G.E. Sims

Onsets of entrainment during dual discharge from a stratified two-phase region through horizontal branches with centrelines falling in an inclined plane: Part 1 – Analysis of liquid entrainment

Abstract A theoretical investigation has been conducted for predicting the critical liquid height and the location of liquid entrainment during dual discharge from a stratified two-phase region through branches mounted on a vertical wall. The two branches are horizontal and their centrelines fall in a common inclined plane. Two models have been developed; a simplified point-sink model and a more-accurate finite-branch model. Predictions from the two models are shown to be in good agreement for the condition of high flow rates from the branches, while the finite-branch model is necessary for good predictions at low branch flow rates. Influences of the various independent parameters on the predicted onset are presented and discussed. Comparisons with experimental results are shown in Part 2 of this paper.

Discharge from a smooth stratified two-phase region through two horizontal side branches located in the same vertical plane

Abstract Experimental data are presented for the mass flow rate and quality of two-phase (air-water) discharge from a stratified region through two side branches (6.35 mm W.) with their parallel centrelines located in a vertical plane. These data correspond to different values of the interface level between the onset of gas entrainment at the upper branch to the onset of liquid entrainment at the lower branch for test-section pressures of 316 and 517 kPa, test-section-to-separators pressure difference ranging from 40 to 235 kPa, branch separating distance to diameter ratio ranging from 1.5 to 8 and different hydraulic resistances of the lines connecting the test section to the separators. Normalized plots are shown to be capable of absorbing the effects of some independent variables within the tested range of operating conditions. Empirical relations were developed for the prediction of the two-phase mass flow rate and quality in terms of normalized parameters. These relations represent the data with a high degree of correlation.

Single and multiple discharge from a stratified two-phase region through small branches

Abstract Experimental data are presented for the mass flow rate and quality during single, dual and triple discharge from a stratified air–water region through small side branches ( d =6.35 mm) installed on a semicircular wall. Dimensions of the semicircular wall and branches were chosen such that interaction among the branches is possible under certain flow conditions. All the branches were adjusted to have the same hydraulic resistance ( R =1000 (kg m) −1/2 ) and for the cases of dual and triple discharge, the same pressure drop Δ P was imposed across all active branches. Tests were conducted at two system pressures P 0 =316 and 517 kPa and the pressure drop was varied within the range 40≤Δ P ≤235 kPa. Data analysis is presented with emphasis on the effect of wall curvature and also the effect of additional discharges on the flow from a certain branch. The present data can serve as benchmark data for testing numerical safety codes and they should guide future research on the flow from two-phase headers.

Experimental investigation of the two-phase discharge from a stratified region through two side branches oriented horizontally

Abstract Experimental data are presented for the mass flow rate and quality of two-phase (air-water) discharge from a stratified region through two side branches (6.35 mm I.D.) with their parallel centerlines located in a horizontal plane. These data correspond to different values of the interface level between the onset of gas entrainment and that of liquid entrainment for test section pressures of 316 and 517 kPa, test section-separator pressure difference 40–235 kPa, branch separating-distance-to-diameter ratio 1.5–8, and different hydraulic resistances of the lines connecting the test section to the separators. The influences of these independent variables on the deviation between the present results (of mass flow rate and quality) and those corresponding to a single discharge are presented and discussed. Normalized plots are presented showing that the present data of dual discharge and those of a single discharge can be collapsed for the whole test range when specific definitions are used for the dimensionless height of the interface and mass flow rate. Excellent agreement is demonstrated between single-discharge correlations and the present data using these dimensionless quantities.

Turbulent fluid flow, heat transfer and onset of nucleate boiling in annular finned passages

Abstract An analytical model has been formulated for fully-developed turbulent flow and heat transfer in finned annuli using a modified mixing-length turbulence model. The model accounts for the conjugate heat transfer in the fluid and the solid, and the finite thickness of the fins. Solutions were obtained using the finite element method adopting a mesh that exactly fits the solution domain with fine elements near the solid boundaries. Predictions of the model have been compared with experimental results for smooth and finned annuli with generally good agreement between data and predictions. The model has been extended to predict the conditions at the onset of nucleate boiling using the criterion of Davis and Anderson. Again, these predictions agreed well in magnitude and trend with experimental data of finned annuli.

The Effect of Outlet Inclination on Two-Phase Flow Splitting in an Equal-Sided Impacting Tee Junction

Phase-distribution data have been generated for two-phase (air-water) flow splitting at an impacting tee junction with a horizontal inlet and inclined outlets. This investigation also considers the full-separation capabilities of the junction and the effect of the outlet angle of inclination on partial separation at various inlet conditions. A flow loop with the ability to incline the outlets from −90° downward to +90° upward was constructed. The operating conditions were as follows: test-section inside diameter of 13.5 mm, nominal junction pressure (Ps ) of 200 kPa (abs), near ambient temperature (Ts ), inlet superficial gas velocities (JG1 ) ranging from 2.0 to 40 m/s, inlet superficial liquid velocities (JL1 ) ranging from 0.01 to 0.18 m/s, mass split ratios (W3 /W1 ) from 0 to1.0 and inlet flow regimes of stratified, wavy, and annular. The data reveal that the degree of maldistribution of the phases depended on the inlet conditions, the mass split ratio at the junction, and the inclination angle of the outlets.Copyright