scholarly journals The Performance of Drag Reducing Agent in Three Phase Slug Flow and Annular Flow

2000 ◽  
Author(s):  
C. Kang ◽  
D. Vedapuri ◽  
W. P. Jepson
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Annular Flow ◽  
Maximum Pressure ◽  
Average Pressure ◽  
Effective Height ◽  
Pressure Drops ◽  
Three Phase ◽  
Water Cut ◽  
Maximum Pressure Drop

Experiments have been carried out in a 36-m long, 10-cm diameter multiphase horizontal flow system to examine the effect of drag reducing agents (DRA) on average pressure drop, maximum pressure drop and slug characteristics with the presence of water. Superficial liquid velocities between 0.5 and 1.5 m/s and superficial gas velocities between 2 and 14 m/s were investigated. Oil with a viscosity of 2.5 cP at 25 °C was used for the study. ASTM salt was used as a substitute for seawater and carbon dioxide was used as the gas. Water cut was 50%. Temperature and pressure were maintained at 25 °C and 0.13 MPa. The DRA concentrations of 0, 20 and 50 ppm were used in this study. The results show that the average pressure drop in both slug flow and annular flow decreased significantly with addition of DRA. Under special conditions, it was found that DRA changed the flow pattern from pseudo-slug to annular resulting in a 74% reduction in pressure drop. For annular flow, the average pressure drop reduction of up to 53% was achieved. The maximum pressure drop across the slug also decreased with the presence of DRA. The average and maximum pressure drops at a DRA concentration of 50 ppm were more effective than 20 ppm for all cases. The slug frequency and effective height of the liquid film decreased significantly when DRA concentrations were added. This led to a decrease in the average pressure drop. However, the slug translational velocity did not change significantly with addition of DRA.

Mountain-Top Vortices as Causes of Large Errors in Altimeter Heights

1949 ◽  
Vol 30 (2) ◽  
pp. 39-44 ◽  
Author(s):  
F. A. Brooks
Keyword(s):  
Pressure Drop ◽  
Ground Surface ◽  
Maximum Error ◽  
Maximum Pressure ◽  
Strong Wind ◽  
High Mountains ◽  
Pressure Drops ◽  
Pressure Distributions ◽  
Maximum Pressure Drop ◽  
Vortex Axis

There have been uncontradicted reports of large altimeter errors in the vicinity of high mountains. A brief survey of pressure distributions over an airfoil with flaps shows a maximum pressure drop below static pressure of twice the velocity head. Applying this ratio to a 14,000-foot mountain in a 100-mph wind a maximum error of 700 feet is indicated. This is important, but not enough to explain the occasional reports of 2 to 3,000-foot errors. Pressure drops of this magnitude exist in tropical cyclones, and even greater depression is known in tornadoes. The pressure drop at the ground surface is seen to have an axial connection with the natural low pressure aloft. The strength of the vortex is shown to depend on the outside tangential input by the wind where the whirl velocity can be very moderate, and the superspeed spin inside a vortex is shown to be dependent on radial inflow of air which is discharged along the vortex axis. Procedures are suggested for locating mountain tornadoes and thorough investigation urged so that the great hazards of mountain vortices in a strong wind will become generally known.

Swirling Annular Flow in a Steam Separator

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Hironobu Kataoka ◽  
Yusuke Shinkai ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Pressure Drop ◽  
Annular Flow ◽  
Nuclear Reactor ◽  
Water Pressure ◽  
Interfacial Friction ◽  
Pressure Drops ◽  
Pressure Transducers ◽  
Ring Configuration ◽  
Film Flows ◽  
Steam Separator

Effects of pick-off ring configuration on the separator performance of a downscaled model of a steam separator for a boiling water nuclear reactor are examined using various types of pick-off rings. The experiments are conducted using air and water. Pressure drops in a barrel and a diffuser and diameters and velocities of droplets at the exit of the barrel are measured using differential pressure transducers and particle Doppler anemometry, respectively. The separator performance does not depend on the shape of the pick-off ring but strongly depends on the width of the gap between the pick-off ring and the barrel wall. The pressure drop in the barrel is well evaluated using the interfacial friction factor for unstable film flows. Carry-under can be estimated using a droplet velocity distribution at the exit of the separator.

scholarly journals Computational and Experimental Study on Pressure Drop in a Fluidised Bed with Different Air Distributor Designs

2020 ◽  
Vol 17 (2) ◽  
pp. 8043-8051
Author(s):  
A. S. M. Yudin ◽  
A. N. Oumer ◽  
N. F. M. Roslan ◽  
M. A. Zulkarnain
Keyword(s):  
Pressure Drop ◽  
Perforated Plate ◽  
Area Ratio ◽  
Maximum Pressure ◽  
Fluidised Bed ◽  
Key Factor ◽  
Minimum Number ◽  
Maximum Pressure Drop ◽  
Free Area ◽  
Distributor Plate

Fluidised bed combustion (FBC) has been recognised as a suitable technology for converting a wide variety of fuels into energy. In a fluidised bed, the air is passed through a bed of granular solids resting on a distributor plate. Distributor plate plays an essential role as it determines the gas-solid movement and mixing pattern in a fluidised bed. It is believed that the effect of distributor configurations such as variation of free area ratio and air inclination angle through the distributor will affect the operational pressure drop of the fluidised bed. This paper presents an investigation on pressure drop in fluidised bed without the presence of inert materials using different air distributor designs; conventional perforated plate, multi-nozzles, and two newly proposed slotted distributors (45° and 90° inclined slotted distributors). A 3-dimensional Computational Fluid Dynamics (CFD) model is developed and compared with the experimental results. The flow model is based on the incompressible isothermal RNG k-epsilon turbulent model. In the present study, systematic grid-refinement is conducted to make sure that the simulation results are independent of the computational grid size. The non-dimensional wall distance,  is examined as a key factor to verify the grid independence by comparing results obtained at different grid resolutions. The multi-nozzles distributor yields higher distributor pressure drop with the averaged maximum value of 749 Pa followed by perforated, 45° and 90° inclined distributors where the maximum pressure drop recorded to be about one-fourth of the value of the multi-nozzles pressure drop. The maximum pressure drop was associated with the higher kinetic head of the inlet air due to the restricted and minimum number of distributor openings and low free area ratio. The results suggested that low-pressure drop operation in a fluidised bed can be achieved with the increase of open area ratio of the distributor.

scholarly journals Analytical and numerical study of entropy generation in small scale heat exchangers

2019 ◽  
Author(s):  
Mahyar Pourghasemi
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Energy Harvesting ◽  
Aspect Ratio ◽  
Entropy Generation ◽  
Heat Sink ◽  
Optimum Operating ◽  
Maximum Pressure ◽  
Channel Height ◽  
Maximum Pressure Drop

In present work, the entropy generation minimization technique (EGM) is applied to study the performance of a microchannel heat sink combined with a new proposed parameter called irreversibility index and energy harvesting concept. Three different cases have been investigated using geometry of a microchanel heat sink selected from experimental work in the literature. The constraints considered in this study, are fixed channel height and maximum pressure drop. It has been observed that with fixed channel height constraint, while the aspect ratio changes from 1 to 10, the optimum operating condition fall in the range of Reynolds number equal to 2000 and aspect ratio of 2.25. Moreover, the extra constrain on maximum pressure drop imposes a limitation on applicable aspect ratio range. The maximum aspect ratio of the channel for stable flow field in this case cannot be higher than 5 imposed by criteria of laminar flow regime. The obtained optimum values are Reynolds number of 1850 and aspect ratio of 2. Using a combined new defined irreversibility index and Energy Harvesting Concept (EHC), it has been shown that the optimum design values for industrial applications are not necessary ones obtained from EGM method and may shift to a new operating point based on the method considered for energy harvesting.

Comparison of the Performance of Drag Reducing Agent Between 2.5 cP Oil and 6.0 cP Oil in Multiphase Flow in Horizontal Pipes

2001 ◽  
Author(s):  
C. Kang ◽  
W. P. Jepson
Keyword(s):  
Pressure Drop ◽  
Multiphase Flow ◽  
Gas Phase ◽  
Annular Flow ◽  
Experimental Studies ◽  
Reducing Agent ◽  
Average Pressure ◽  
Flow Loop ◽  
Oil Viscosity ◽  
Horizontal Pipes

Abstract Experimental studies have been performed in a 10 cm diameter, 36 m long, multiphase flow loop to examine the effect of drag reducing agents using 6 cP oil. Studies were performed for superficial liquid velocities of 0.5, 1.0 and 1.5 m/s and superficial gas velocities between 2 and 12 m/s. Carbon dioxide was used as the gas phase. The drag reducing agent (DRA) concentrations were 20 and 50 ppm. The system was maintained at a pressure of 0.13 MPa and a temperature of 25 °C. The comparison of the conditioning of flow with DRA between 2.5 cP oil and 6 cP oil is presented. The results show that pressure drop in both 2.5 cP oil and 6 cP oil was reduced significantly in multiphase flow with addition of DRA. A DRA concentration of 50 ppm was more effective than 20 ppm DRA for all cases. As the oil viscosity was increased from 2.5 cP to 6 cP oil, the transition to annular flow was observed to occur at lower superficial gas velocities. For slug flow and lower superficial gas velocities, the effectiveness in 2.5 cP oil was much higher than that in 6 cP oil with addition of DRA. However, for higher superficial gas velocities, the effectiveness in both oils was similar. For annular flow, the effectiveness in 2.5 cP oil was higher than in 6 cP oil with 50 ppm DRA. At low superficial gas velocities, DRA in 2.5 cP oil was more effective in reducing the slug frequency. This led to a higher average pressure drop reduction in 2.5 cP oil. However, at higher superficial gas velocities, the slug frequency decreased in both oils almost the same magnitude.

The Visualization of Flow Boiling in a Uniformly Heated Micro Capillary Tube

2006 ◽  
Author(s):  
X. H. Yan ◽  
J. Z. Xu ◽  
D. W. Tang
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Annular Flow ◽  
Capillary Tube ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Inner Diameter

This work presents experiments on the visualization of flow boiling of water in a horizontally placed and uniformly heated micro capillary tube. Three micro capillary tubes of quartz glass with inner diameters of 520, 315 and 242 μm are prepared. Experiments are performed with deionized water over a mass flux range from 39.3 to 362.5kg/m2s, and the inlet temperatures of 30, 45, and 60 °C respectively. By a video system with microscope and high-speed camera, the vapor-water two-phase flow’s patterns are recorded and analyzed. It has been found that periodic change of two-phase flow patterns and dramatic fluctuations of pressure drop occur in the micro capillary tubes. A new arch flow pattern, liquid film evaporating, and liquid droplet have been observed firstly. Bubbly flow has not been observed during our visual experiments for the inner diameter of 242 μm, the flow patterns are only made up of single liquid phase flow and two-phase elongate slug flow. The main flow regimes in these micro-tubes are single-liquid flow, slug flow, and annular flow with liquid film surrounded in the micro-tube with inner diameter of 520 and 315μm. Trends of pressure drop and flow patterns’ transition are compared and the results show that the increasing process of pressure drop is approximately in the single-liquid flow and bubbly flow, while the decreasing process of pressure drop is in the state of annular flow.

scholarly journals Effects of Pressure Drops on the Performance Characteristics of Air Standard Otto Cycle

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Mahmoud Huleihil
Keyword(s):  
Pressure Drop ◽  
Constant Pressure ◽  
Performance Characteristics ◽  
Maximum Efficiency ◽  
Maximum Pressure ◽  
Otto Cycle ◽  
Pressure Drops ◽  
Internal Irreversibility ◽  
Expansion Model ◽  
Engine Size

The effects of pressure drops on the performance characteristics of the air standard Otto cycle are reported. The pressure drops are assumed as constant values independent of the engine size. It has been shown that the pressure drops to about 60% of the maximum pressure in the ideal cycle (Curto-Risso et al., 2008). Three different models are studied: constant pressure model, reversible adiabatic expansion model and polytropic expansion model. The findings of this study show that, at this level of pressure drop, the maximum efficiency of the Otto cycle is reduced by 15% approximately based on the constant pressure model. The combined effect of pressure drop with other modes of irreversibility, for example, internal irreversibility and heat leaks, could reduce the maximum efficiency into very low values (approximately 30%). The reversible adiabatic model predicts reduction of 13% in efficiency at 40% pressure drop levels but at the price of zero power production. On the other hand, the polytropic expansion model predicts 40% reduction in efficiency for the same level of pressure drop (40%). All three models show that the power output is very sensitive to pressure drop.

Oil-Gas-Water Three-Phase Slug Flow Liquid Holdup Model in Horizontal Pipeline

2006 ◽  
Author(s):  
Jing Mei Zhao ◽  
Jing Gong ◽  
Da Yu
Keyword(s):  
Slug Flow ◽  
Water Film ◽  
Mineral Oil ◽  
Superficial Velocity ◽  
Oil Viscosity ◽  
Liquid Holdup ◽  
Three Phase ◽  
Water Based ◽  
Water Cut ◽  
Oil Gas

According to experiments and relational documents, slug regime, appeared in this experiment, can be divided into the following flow regimes: oil-based separated slug, oil-based dispersed slug, water-based separated and water-based dispersed slug. Experiments for oil-gas-water three-phase flow in a stainless steel pipe loop (25.7mm inner diameter, 52m long) are conducted. Compressed air, mineral oil and water are used as experiment medium. Mineral oil Viscosity is 64.5mPa.s at 20°C. Gas superficial velocity, liquid superficial velocity and water cut ranges are 0.5∼15 m/s, 0.05∼0.5 m/s and 0∼100% respectively. There are some strange observed in this experiment. At the very low gas superficial velocity less than 1m/s, the average liquid holdup of low liquid superficial velocity was larger than that of higher liquid superficial velocity especially in higher inlet water cut experiments. This is because at very low gas superficial velocity, the regime is separated slug flow which has water film below their liquid film zone, velocity difference between oil film and water film will affect the average liquid holdup greatly. With the increase of gas and liquid superficial velocity, the regime becomes dispersed slug flow which oil and water are homogeneous. It will be more obvious with the increasing of water cut for the thicker water film. A new liquid holdup model of oil-based and water-based separated slug has been developed. Based on statistical analysis, it is observed that the new model gives excellent results against the experimental data.

In Vitro Pressure Flow Relationship in Model of Significant Coronary Artery Stenosis

2004 ◽  
Author(s):  
Abhijit Sinha Roy ◽  
Lloyd H. Back ◽  
Ronald W. Millard ◽  
Saeb Khoury ◽  
Rupak K. Banerjee
Keyword(s):  
Coronary Artery ◽  
Pressure Drop ◽  
Power Law ◽  
Flow Rate ◽  
In Vitro Model ◽  
Maximum Pressure ◽  
Vitro Model ◽  
Maximum Pressure Drop

Simultaneous measurement of pressure and flow rate has been found to be helpful in evaluating the physiologic significance of obstructive coronary artery disease and in the diagnosis of microvascular disease. This experimental study seeks to find important pressure-flow relationship in an in-vitro model of significant coronary artery stenoses using a non-Newtonian liquid, similar to blood showing a shear thinning behavior, using significant stenotic in-vitro model (minimal area stenosis = 90%). The geometry for the stenotic model is based on data provided in an in vivo study by Wilson et al., (1988). For 90% area stenosis, the maximum recorded pressure drop for steady flow rate of 55, 79 and 89 are 14, ~24 and ~32 mmHg respectively. The maximum pressure drop at flow rate of 115 ml/min (the physiological limit) is 50.3 mmHg respectively. Using a power law curve fit, the maximum pressure drop (in mmHg) related with flow rate (in ml/min) provided a power law index of 1.72. Shorter distal length than required in the in-vitro model did not allow the recording of complete pressure recovery. This preliminary data provides reference values for further experimentation both in vitro with pulsatile flow as in physiological conditions, and in vivo.

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