scholarly journals Prediction of the entropy production and pressure losses in two-phase flow from the mixing length theory

1980 ◽  
Author(s):  
P.F. Maeder ◽  
E.E. Michaelides
Keyword(s):  
Entropy Production ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Mixing Length ◽  
Two Phase ◽  
Pressure Losses ◽  
Mixing Length Theory

Pressure losses of two-phase flow in a variable-diameter tube

2012 ◽  
Vol 47 (11-12) ◽  
pp. 717-724
Author(s):  
V. N. Novozhilov ◽  
D. A. Baranov
Keyword(s):  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Losses ◽  
Variable Diameter

Effects of Quenching Heat Preserving Time on Structure and Properties of Boron-Containing High-Cr White Cast Iron

2012 ◽  
Vol 508 ◽  
pp. 267-270
Author(s):  
Cun Lai Zhang ◽  
Qi Bin Xin
Keyword(s):  
Two Phase Flow ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Pneumatic Conveying ◽  
Backward Facing Step ◽  
Two Phase ◽  
Pressure Losses ◽  
Gas Drilling ◽  
Air Drilling ◽  
Annular Pipe

Air drilling technology has been widely used in the oil and gas exploration, coal, geothermal, geological exploration, nuclear industry and other fields due to its high drilling rate and low cost. However, the design of the pneumatic conveying system for the mineral detritus is still largely based on empiricism. The paper was set in the background of gas drilling, mainly studied the gas-solids two-phase flow characteristics in 90 degree bent annular pipe and backward-facing step of an annular pipe, which are very important parts of air drilling. They refer to the bent part and backward-facing step of an annular channel formed by the drill pipe and the borehole wall. A detailed numerical simulation and experimental studies were carried out for the flow structure and pressure losses of gas-solid two-phase in the annular pipe of gas drilling. Since a unified theory has not been developed for the two-phase flow in annular pipe, a lot of experimental work should be conducted. In the experimental research, the paper independently designed and built an annular pipe pneumatic conveying system with 90 degree bend and backward-facing step, including designing material screw feeder, material receiving hopper, pipeline, control system, data acquisition system, and etc. As known, many parameters, such as gas velocity, diameter and density of the particle, and solids loading ratio, can influence the conveying process. How these primordial influence factors act on the pressure losses of two-phase flow in annular pipe was analyzed in this paper. In the numerical simulation research, turbulent two-phase flow calculations were performed with a commercial CFD computer code referred to as FLUENT to study the gas-solid two phase flow in the sections of backward-facing step and 90 degree bent pipe respectively by using Euler-Lagrange method. The RNG κ-ε model and stochastic tracking were involved in the calculation of turbulence dispersion of two phases. The discrete phase model was performed for the solid phase. In the end, the numerical study 3-D results were translated to 1-D results using the standard averaging transformation to compare with experimental results. Predicted results obtained for pressure drop and velocity variations in full developed flows in the cases examined are in good qualitative agreement and are not in quantitative agreement with experimental data. The deviations between the simulations and experimental data lie in the range of 20%-30%. These results suggest commercial CFD codes such as FLUENT can be used productively for investigations into gas-solid two-phase flow phenomena and as an aid in pneumatic conveying design. The studies of the two-phase flow characteristics in the paper will contribute to reliable determination of the optimal condition of pneumatic conveying in gas drilling.

Two-Phase Flow in Liquid Filled Vessels During the Depressurization by Periodic Venting

2003 ◽  
Author(s):  
Dieter Mewes ◽  
Dirk Schmitz
Keyword(s):  
Single Phase ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Exothermic Reaction ◽  
Liquid Mixtures ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Losses ◽  
Short Period ◽  
Liquid Flows

Pressurized chemical reactors or storage vessels are often partly filled with liquid mixtures of reacting components. In case of an unexpected and uncontrolled exothermic reaction the temperature might increase. By this the pressure follows and would exceed a critical maximum value if there would be no mechanism to decrease the pressure and the temperature in a very short period of time. A sudden venting by the opening of a safety valve or a rupture disc causes a rapid vaporization of the reacting liquid mixture. A two-phase flow will pass the ventline. Since two-phase gas-liquid flows cause high pressure losses and give rise to limited mass flows leaving the reactor, single-phase gas flows are preferred. This is emphasized by a periodic venting mechanism of the pressurized vessel. Each time the two-phase flow from the bubbling-up liquid inside the vessel reaches a certain cross-section close the entrance of the ventline. The outlet-valve is closed. Inside the vessel the increasing pressure stops the two-phase flow and only single phase flow is leaving the vessel. The two-phase bubbly flow inside the vessel is detected by a tomographic measurement device during the venting process. Experimental results for local and time dependant phase void fractions as well as pressures are compared with those obtained by numerical calculations of the instationary bubble swarm behavior inside the vessel.

Frictional Pressure Losses for Annular Flow of Drilling Mud and Mud-Gas Mixtures

1985 ◽  
Vol 107 (1) ◽  
pp. 142-151 ◽  
Author(s):  
J. P. Langlinais ◽  
A. T. Bourgoyne ◽  
W. R. Holden
Keyword(s):  
Experimental Data ◽  
Single Phase ◽  
Two Phase Flow ◽  
Hydraulic Diameter ◽  
Phase Flow ◽  
Drilling Mud ◽  
Two Phase ◽  
Bingham Plastic ◽  
Pressure Losses ◽  
Annular Geometry

The calculation of single-phase and two-phase flowing pressure gradients in a well annulus is generally based on an extension of empirical correlations developed for Newtonian fluids in circular pipes. Various techniques for extending pipe flow correlations to an annular geometry have been presented in the literature which involve the representation of the annular well geometry with an equivalent circular diameter and the representation of non-Newtonian fluid behavior with an apparent Newtonian viscosity. Unfortunately, little experimental data have been available which would allow a comparison of the relative accuracy of the various proposed techniques. In this study, experimental pressure gradient data have been taken in two 6000-ft wells. Frictional pressure losses for single-phase flow (mud only) in two annuli were compared to values predicted by the Bingham plastic and power law models. These calculations utilized the equivalent diameters defined by the Crittendon criteria, the hydraulic diameter, and the slot approximation. Also, total pressure difference for two-phase flow was measured for one annular geometry. This data was compared to that predicted by the Poettmann and Carpenter, Hagedorn and Brown, Orkiszewski, and Beggs and Brill correlations. Comparison of experimental data with the various prediction techniques was favorable, each having advantage in certain situations. For the data investigated, the Crittendon criteria using a Bingham plastic model gave the best results. The two-phase flow data was best predicted by the Hagedorn and Brown correlation utilizing an equivalent hydraulic diameter.

Design Methodology and Valve Sizing for Heater Drain Systems

2009 ◽  
Author(s):  
Casey Loughrin
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Losses ◽  
Solution Methods ◽  
Flow Phenomena ◽  
Flow Pressure ◽  
And Control

Heater drain systems in fossil and nuclear power plants have proven to be among the most complex systems to design due to the occurrence of two–phase flow phenomena. The overall performance of heater drain systems directly relates to proper sizing and design of the piping and control valves. Proper sizing is highly dependent upon accurate and conservative calculation of two-phase flow pressure losses. This paper outlines the various options of solution methods available to the engineer and details one possible method which is simple, yet adequate, and based on the homogeneous equilibrium model (HEM) for two phase flow for calculation of heater drain system performance. General comparisons are made to the more complex multi-fluid models, flow regime considerations, and non-equilibrium models.

Phase-distribution mechanisms in turbulent low-quality two-phase flow in a circular pipe

1982 ◽  
Vol 117 ◽  
pp. 91-106 ◽  
Author(s):  
D. A. Drew ◽  
R. T. Lahey
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Outer Region ◽  
Continuous Phase ◽  
Circular Pipe ◽  
Phase Flow ◽  
Two Phase ◽  
Centre Line ◽  
Mixing Length Theory

The radial distribution of the volumetric vapour (or void) fraction in steady, fully developed turbulent two-phase flow is described for vertical low-quality bubbly flows in a circular pipe. The analysis is based on the phasic equations of conservation of momentum in the axial and radial directions. Mixing-length theory is used to model the turbulent stresses in the continuous phase. The predicted flow structure shows three distinct regions. The ‘outer’ region, that is, the region away from the wall and the centre-line, has a uniform void distribution. For upflow, a bubble layer is predicted near the wall, while for downflow, vapour coring is predicted, with a peak in void fraction at the centre-line. These predictions are in agreement with observed void profiles.

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