An investigation of flow problems and solutions, associated with bulk solids discharging from conical-bottom cylindrical storage containers, is presented in this paper. The feasibility and efficiency of bulk solids discharging from these containers are directly associated with the flow pattern of the solids. The influence of a new vessel design on the flow pattern and the discharge rate of solids was examined. Glass beads of fixed particle size distribution and density were used to conduct the study. Retrofitting techniques that are commonly used to improve the flow pattern characteristics in silos were reviewed. Two techniques, utilization of inserts and hopper in hopper were investigated, and the results from the first technique are discussed. This technique is based on the usage of a double pyramid-shaped insert to manipulate the flow pattern of discharging solids. Both dry and wet tests were conducted under a wide range of low to moderate pressures. The results from both dry and wet tests showed that the pyramid insert was able to significantly change the flow pattern from the undesired funnel flow to the most desired mass flow and also increase the rate of discharge.
The purpose of this study is to statistically evaluate the influence of various sampling methodologies and flow conditions on the quality and comparability of total phosphorus concentration data collected over the course of 27 months at the South Florida Water Management District (SFWMD) S-65E structure. The data was obtained from the following sampling methodologies: U.S. Geological Survey (USGS) (Reston, Virginia) equal width increment spatially composite grab samples, USGS replicate samples, SFWMD grab samples, and SFWMD autosampler samples. Both significant and insignificant differences were reported from these comparisons. Parametric and nonparametric standard statistical tests for significance were carried out to evaluate the differences between the data. To avoid invalid conclusions of insignificant differences, we conducted tests for equivalence of the means and variances. The results from the data analysis revealed that both flow conditions and sampling methodology affected the water quality data. Water Environ. Res., 79, 147 (2007).
The Turner model is widely used in industry to estimate critical gas velocity to flow a gas well and unload its liquid content under steady state conditions. The Zhou model introduced improvements to the Turner model by taking into account the influence of total Liquid (condensate and water) to Gas Ratio (LGR) on critical gas velocity. While fairly acceptable at low LGR, current models do not address the impact of liquid holdup on wellhead flowing conditions and subsequent changes in critical gas unloading rates. Multiphase modeling is used in this study to validate the applicability of current models at various wellbore conditions and LGR.
This study finds important applications in offshore and onshore gas field developments because it provides moe reliable assessment especially for gas fields in the depletion phase, or when liquid breakthrough occurs resulting in high LGR.
Dynamic simulations indicate that at low to moderate LGR existing models under predict critical gas flowrate because they under estimate critical velocity, especially at high wellhead pressures, and don't take into account the impact of increasing liquid holdup on gas flowrate. Moreover, an inversion in critical flowrate occurs at very high LGR because the film holdup is sufficient to restrict the flow of gas and offsets any increase in critical velocity at such high LGR. The onset of liquid loading (well choking) is associated with the transition from annular to churn/slug flow. This is well demonstrated from the calculated trends of entrained droplet holdup.
The significance of the current work to our understanding of critical flow in gas wells is illustrated by utilizing a multiphase simulator to better characterize the impact of entrained droplet and film holdup on critical flowrate and by predicting the inversion in critical gas flowrate at high LGR. The results of this study provide an enhanced understanding of well loading during all development phases and various production conditions to evaluate the applicability and accuracy of widely used models in a broad range of well conditions and liquid loads.
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