The Prediction of Pressure Drop and CCFL Breakdown in Countercurrent Two-Phase Flow

1983 ◽  
Vol 105 (4) ◽  
pp. 700-705 ◽  
Author(s):  
A. G. Ostrogorsky ◽  
R. R. Gay ◽  
R. T. Lahey
Keyword(s):  
Pressure Drop ◽  
Analytical Model ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Constitutive Relations ◽  
Computer Code ◽  
Liquid Films ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase

A steady-state analytical model has been developed to predict channel pressure drop as a function of inlet vapor flow rate and applied heat flux during conditions of countercurrent two-phase flow. The interfacial constitutive relations utilized are flow structure dependent and allow for the existence of either smooth or wavy liquid films. A computer code was developed to solve the analytical model. Predictions of Δp versus vapor flow rate were found to agree favorably with experimental data from adiabatic, air/water systems. In addition, the model was used to predict countercurrent flow conditions in heated channels characteristic of a BWR/4 nuclear reactor fuel assembly.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

Experimental Research on Pulsating Two-Phase Flow Pressure Drop Characteristics in Horizontal Rectangular Channel

2014 ◽  
Author(s):  
Siqi Zhang ◽  
Puzhen Gao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Phase Flow ◽  
Two Phase ◽  
Mean Values ◽  
Water Mass Flow Rate

In spite of most previous studies since 1970, the theory of pulsating pipe flows supported by experimental investigations has not yet completed in comparison with the well-defined theory of steady pipe flows. Therefore, it seems that there is much to be done about experimental research in this field. In order to determine the resistance characteristics of two-phase flow under pulsatile conditions, an experimental investigation on two-phase flow with periodically fluctuating flow rates in a narrow rectangular channel is carried out. A frequency inverter is used to obtain experimental conditions with different fluctuating frequencies, amplitudes and mean values of water mass flow rate. After obtaining experimental results, comparisons between experimental frictional pressure drop values and theoretical calculations have been done. Two-phase flow on pulsating conditions is far more complicated than that on steady conditions because pulsating flow is composed of two parts: a steady component and a superimposed periodical time varying component called oscillation. In this paper, the influence of different fluctuating frequencies, amplitudes and mean values of liquid and gas mass flow rate on two-phase flow pressure drop characteristics is also discussed. The results show that the total pressure drop and water mass flow rate change with the same fluctuating period except for a phase difference. The phase lag also changes with the fluctuating frequencies and amplitude. The accelerating pressure drop changes dramatically in a fluctuating period, especially at the end of acceleration. Also, the time when the acceleration pressure drop has its maximum value lags the time when the acceleration reaches its peak, mainly because of the inertial of the fluid.

Machine Learning Approach to Predict the Flow Rate for an Immiscible Two-Phase Flow at Pore Scale for Enhanced Oil Recovery Application

2018 ◽  
Author(s):  
Arturo Rodriguez ◽  
V. M. Krushnarao Kotteda ◽  
Luis F. Rodriguez ◽  
Vinod Kumar ◽  
Arturo Schiaffino ◽  
...  
Keyword(s):  
Machine Learning ◽  
Surface Tension ◽  
Pressure Drop ◽  
Flow Rate ◽  
Oil Recovery ◽  
Two Phase Flow ◽  
Machine Learning Algorithms ◽  
Phase Flow ◽  
Pore Scale ◽  
Two Phase

Due to global demand for energy, there is a need to maximize oil extraction from wet reservoir sedimentary formations, which implies the efficient extraction of oil at the pore scale. The approach involves pressurizing water into the wetting oil pore of the rock for displacing and extracting the oil. The two-phase flow is complicated because of the behavior of the fluid flow at the pore scale, and capillary quantities such as surface tension, viscosities, pressure drop, radius of the medium, and contact angle become important. In the present work, we use machine learning algorithms in TensorFlow to predict the volumetric flow rate for a given pressure drop, surface tension, viscosity and geometry of the pores. The TensorFlow software library was developed by the Google Brain team and is one of the most powerful tools for developing machine learning workflows. Machine learning models can be trained on data and then these models are used to make predictions. In this paper, the predicted values for a two-phase flow of various pore sizes and liquids are validated against the numerical and experimental results in the literature.

Analysis of Orifice Plate Differential Pressure Noise in Horizontal and Vertical Rising Gas-Water Two-Phase Flow

2010 ◽  
Author(s):  
Xianfa Li ◽  
Shuoping Zhong ◽  
Yanfei Sun
Keyword(s):  
Flow Rate ◽  
Two Phase Flow ◽  
Water Flow Rate ◽  
Differential Pressure ◽  
Orifice Plate ◽  
Vapor Flow ◽  
Phase Flow ◽  
Square Root ◽  
Two Phase ◽  
The Difference

It is an important achievement of modern techniques to determine the mass flow rate and the phase fraction of wet steam by measuring the orifice plate differential pressure noise. The orifice plate differential pressure noise of air-water two-phase flow in horizontal and vertical rising pipelines were analyzed. Kinds of calculation methods were tried to get the differential pressure noise. From the difference waveform of the differential pressure square root that the acquisition card got and the mean square root of the sample that got before, the first in first out (FIFO) principle was used to get the differential pressure noise. Result shows that the differential pressure noise has different level at different vapor flow rate with the same water flow rate, conclusions show that the two-parameter measurement by using orifice plate differential pressure noise may be possibly used in vertical rising gas-water two phase flow.

scholarly journals Role of Pore-Size Distribution on Effective Rheology of Two-Phase Flow in Porous Media

2021 ◽  
Vol 3 ◽  
Author(s):  
Subhadeep Roy ◽  
Santanu Sinha ◽  
Alex Hansen
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Pore Size ◽  
Power Law ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Viscous Forces ◽  
Capillary Bundle

Immiscible two-phase flow of Newtonian fluids in porous media exhibits a power law relationship between flow rate and pressure drop when the pressure drop is such that the viscous forces compete with the capillary forces. When the pressure drop is large enough for the viscous forces to dominate, there is a crossover to a linear relation between flow rate and pressure drop. Different values for the exponent relating the flow rate and pressure drop in the regime where the two forces compete have been reported in different experimental and numerical studies. We investigate the power law and its exponent in immiscible steady-state two-phase flow for different pore size distributions. We measure the values of the exponent and the crossover pressure drop for different fluid saturations while changing the shape and the span of the distribution. We consider two approaches, analytical calculations using a capillary bundle model and numerical simulations using dynamic pore-network modeling. In case of the capillary bundle when the pores do not interact to each other, we find that the exponent is always equal to 3/2 irrespective of the distribution type. For the dynamical pore network model on the other hand, the exponent varies continuously within a range when changing the shape of the distribution whereas the width of the distribution controls the crossover point.

scholarly journals Numerical Simulation of Flow Behavior within a Venturi Scrubber

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
M. M. Toledo-Melchor ◽  
C. del C. Gutiérrez-Torres ◽  
J. A. Jiménez-Bernal ◽  
J. G. Barbosa-Saldaña ◽  
S. A. Martínez-Delgadillo ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Venturi Scrubber

The present work details the three-dimensional numerical simulation of single-phase and two-phase flow (air-water) in a venturi scrubber with an inlet and throat diameters of 250 and 122.5 mm, respectively. The dimensions and operating parameters correspond to industrial applications. The mass flow rate conditions were 0.483 kg/s, 0.736 kg/s, 0.861 kg/s, and 0.987 kg/s for the gas only simulation; the mass flow rate for the liquid was 0.013 kg/s and 0.038 kg/s. The gas flow was simulated in five geometries with different converging and diverging angles while the two-phase flow was only simulated for one geometry. The results obtained were validated with experimental data obtained by other researchers. The results show that the pressure drop depends significantly on the gas flow rate and that water flow rate does not have significant effects neither on the pressure drop nor on the fluid maximum velocity within the scrubber.

Pressure Drop Oscillations with Symmetry Breakdown in Two-Phase Flow Parallel Channels

2020 ◽  
Author(s):  
Md Emadur Rahman ◽  
Suneet Singh
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Symmetry Breakdown ◽  
Flow Maldistribution ◽  
Parameter Values

Abstract Two-phase flow in parallel heated channels is prone to symmetry breakdown resulting in mass flow maldistribution. Moreover, in the presence of compressible volume, such systems also undergo pressure drop oscillations (PDO). The performances of such systems depend on the effect of these flow instabilities. However, the simultaneous occurrence of these two- phenomena has been rarely reported in the literature. In the present work, an approach is applied in a two channels system to demarcate the parameter space of mass flow rate and inlet temperature into several areas, where these two phenomena take place. The loss in the symmetry in the flow rate is observed as the mass flow rate is varied, which leads to flow maldistribution. The PDO are also observed for specific values of mass flow rate in the system. One unique feature of the parallel channel system is the existence of the oscillatory and stable (albeit asymmetric) states at the same parameter values. For these parameter values, the final state of the system is dependent on the type of initial disturbance. The flow maldistribution due to symmetry breakdown is identified by the pitchfork bifurcation, and oscillations of mass flow rate are identified by the presence of Hopf bifurcation. Moreover, the physical interpretation of the different phenomena in the system is carried out using internal and external pressure drop characteristics curves.

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