Flow Phase Distribution Research Articles

Enhancing the phase distribution in parallel vertical channels with single and double chamber coaxial headers

In this paper, in order to maximize the degree of flow rate uniformity of the two phase flow distribution into parallel vertical channels, a number of distributor fittings have been tested with respect to a test section characterized by a horizontal header and a series of vertical upward channels. The fluids are air and water and the flow regimes at the header cover the intermittent and annular flow pattern conditions. The ranges of liquid and gas superficial velocities are 0.45–1.2 and 1.5–16.5 m/s, respectively. A header geometry without any inserts, such as the smooth reference header, is taken as a reference case. Data from a number of inserts to enhance the uniformity of distribution are compared to the reference case, such as a series of cylindrical distributors with in-line holes along their length (“flutes”). New data in particular are presented for the “double chamber flute” fitting. As in previous studies by the Authors, extracted mass flow rates of liquid and gas from parallel channels are recast in terms of normalized flow rates and normalized standard deviation of phases. A new overall performance parameter is used for data reduction and for summarizing the comparison between the flute fitting configurations.

A study on steam-water two phase flow distribution in a rectangular channel with different channel orientations

Experimental study on steam-water two phase vertical and inclined upward flow (15–90°) was performed in a rectangular channel with cross section of 17 mm × 10 mm under atmospheric pressure to investigate the phase distribution and the average void fraction in the cross section which were obtained from the local void fraction measurement by a conductivity probe. The inlet superficial velocities of the steam and water varied from 0.72 to 3.85 m/s and from 0.11 to 0.3 m/s respectively. A high speed camera was used to identify the flow patterns. Experimental results show that the phase distribution curves are significantly affected by channel orientation and the average void fraction first decreases and then increases with the increase of orientation. Based on the drift-flux model, two parameters, namely, the distribution parameter (C0) and the drift velocity (Ugm) have been studied in detail. Both the distribution parameter and the drift velocity are found to be functions of orientation. The distribution parameter decreases with the increase of orientation while the drift velocity first increases and then decreases with the increase of orientation., Based on the experimental data, an improved drift-flux model is proposed especially for the slug and churn flow, which predicts the void fraction in an inclined channel with good accuracy.

Water-in-oil emulsification in a bifurcated tree-like network: Flow distribution properties and their impact on the emulsion polydispersity

This paper presents a numerical study on the water-in-oil emulsification process through the parallelization of micro/mini-channels. Firstly, the single-phase fluid flow distribution uniformity in the bifurcated tree-like fluidic network is discussed. Secondly, the separate roles of the oil viscosity and the interfacial tension on the plug details are clarified. Finally, the impact of flow distribution non-uniformity among the parallel mini-channels on polydispersity of the produced emulsion is evaluated by modelling.The obtained results show that for bifurcated tree-like fluidic network, the single phase flow distribution is the flow distribution non-uniformity increases linearly with the increasing mean Rech once a transitional Re is reached. The water plug length and volume increase with the increasing interfacial tension and the decreasing oil viscosity under our tested conditions. Correcting factors relevant to the modified liquid properties have to be added in the predictive correlations for plug length and volume. For water-in-oil emulsification in parallel channels, its polydispersity Pw is affected by the single phase flow distribution uniformity, the total water/oil flow-rate ratio and most importantly by the flow-rate ratio distribution non-uniformity. An empirical correlation has been proposed to predict the emulsion Pw based on these influencing factors.

Application of Optical Tomography for Monitoring Gas Bubbles Flow Based on Independent Component Analysis Algorithm

This paper presents the monitoring process of gas bubbles flow in water using an optical tomography system. The system is aided by an Independent Component Analysis (ICA) algorithm for distinguishing the gas bubbles in pure water. The optical attenuation model is implemented for studying the light transmissions to different media which is water and air. Several quantities of air are inserted using an air pump which is installed at the bottom of a flow pipe in order to produce the gas bubbles flow upwards. The quantity of air is controlled by using a valve and five types of bubble flow are investigated; a single bubble flow, double bubble’s flow, 25% of air opening, 50% of air opening and 100% of air opening. The concentration profiles of the gas bubble flow are constructed. The concentration profile obtained from the experiments shows that the ICA algorithm can be used as a tool for imaging the two-phase flow phase distribution.

Computational Analysis of Two Phase Flow Distribution in a Horizonatal Pipe

In this paper, a two phase flow distribution in a horizontal pipe is numerically analyzed by solving one dimensional steady state momentum equation for predicting the pressure drop (∆P), quality of steam at outlet of the pipe (X), void fraction (α). The heat absorbed by the pipe (Q) and the mass flow rate (W) of water are varied over a wide range to investigate the above parameters. The locations of the two phase mixture are discussed. Pressure drop along the pipe is inconsistent for different flow rate so, the stable and unstable steady state solution is also carried out using Linear Stability analysis. The present numerical results are compared with the reported data from the literature and found that they are in good agreement. This study is used to calculate the pressure, temperature, hold up and quality within the horizontal pipe.

Laminar single phase flow distribution in a multi-tube mini-channel heat exchanger using fractal distribution

Mini-channel technology is a promising solution in a world where there is a growing demand for product miniaturization. In this paper a new geometry for a distributor of a multi-tube mini-channel shell and tube exchanger is proposed which should distribute the flow equally over the tubes. The tubes have an internal diameter of 0.5mm while the shell has a hydraulic diameter of 1.8mm. The flow in the heat exchanger is pure counter current flow; no baffles have been used in the shell. Experimental data for laminar single phase water in both the tube and shell side are reported. A mathematical model is developed which can predict the performance of the multi-tube mini-channel that uses the newly proposed distributor. This model considers both heat transfer and pressure drop and makes use of prediction methods proposed in the literature for similar geometries. It has been experimentally validated that the newly proposed distributor gives a good distribution for laminar single phase flows. The mathematical model can predict the experimental performance of the multi-tube mini-channel exchanger within 10% accuracy.

H225 分岐合流を伴う並列管系における二相流の動的挙動(OS-11:沸騰・二相流(6))

Two phase flow distribution and the flow stability are substantial problems in designing heat exchangers with parallel-channel system. Fundamental experiment was conducted with air-water mixture in parallel-channels jointed sinuously in series. The observed flow-mal-distribution was serious at low volumetric fluxes of air and water. An installation of compressible volume upstream the mixing section brought about significant oscillation in the flow and pressure drop, mainly in the upper flow section. This oscillation was well-known pressure drop oscillation induced by dynamic interaction between negative resistance and the compressible capacity.

Adiabatic two phase flow distribution and visualization in scaled microchannel heat sinks

The present work investigates the characteristics of adiabatic two-phase flow, and compares the flow distribution in two different multi-channel configurations. One is a standard straight channel design, and the second is similar, except that it has two cross-linked paths located at one-third and two-thirds of the channel length. Each test section consists of 45 rectangular channels with a hydraulic diameter of 1.59 mm and is fabricated out of acrylic to enable flow visualization. The test facility operates with water and air as the working fluids. Gas and water superficial velocities range from 0.03 to 9.93 and 0.04 to 0.83 m/s, respectively, corresponding to a flow quality between 0 and 0.25, whereby the mass flux range is from 41 to 834 kg/m2s. Four channels were selected for flow distribution tracking, and the results showed that the straight and cross-linked designs both have unequal flow distributions. Flow patterns are presented in terms of a fractional time function to gain insight into the flow characteristics. Compared to a single channel flow regime map, the intermittent flow regime was observed 65 to 85% of the times expected, whereas the dispersed flow regime only occurred ∼40% of the times expected for both designs. Further discussion on flow distribution and flow patterns are also documented.

Two-phase flow distribution in 2D trickle-bed reactors

An extended discrete cell model (DCM), based on minimization of energy dissipation rate, is applied to predict two-phase flow distribution in the two-dimensional trickle-bed reactors. The main advantages of DCM are that it can qualitatively capture the experimental observations, and readily distinguish between flow distribution in prewetted and non-prewetted beds, as well as reflect the effects of bed structure and inlet liquid distributor on two phase flow distribution. For comparison purpose, the results of liquid distribution obtained by DCM are compared with both computational fluid dynamics (CFD) simulations and experimental observations in a 2D bed. The achieved qualitative and quantitative agreement justifies the use of DCM in predicting two phase flow distribution in packed beds. A particle wetting factor ( f) has been introduced into DCM to account for the influence of particle surface wetting on liquid flow distribution. Analysis of DCM simulations presented based on maldistribution factor (mf ) provides a convenient way of quantifying the effects of particle surface wetting, distributor design and bed depth on the two-phase flow field.

Effect of interfacial drag terms on simulation of two phase flow distribution through narrow channels

The two-dimensional formulation of the separated model conservation equations has been modified, and the advection and diffusion effects on the hydrodynamic behavior of two-component (air/water) two-phase flows have been investigated theoretically. The interfacial transport terms are modeled and imported to the governing equations, solved by numerical computation. They give a good fit with experimental data obtained previously. Basically, three flow regimes, bubble, complex and annular flows in a narrow channel have been modeled, and the general characteristics of the prediction have been discussed. Because of the considerable difficulties in modeling, the flow is assumed as steady state, and transient terms are canceled. However, comparison of the measured pressure-drop values and the calculated ones, by using the interfacial transport terms, the interfacial area and the driving force, is quite satisfactory. Thus, it is concluded that the discrepancies between the measured and the calculated pressure-drop values reported in the literature are due to the lack of advection and diffusion terms derived from both shear stresses and interfacial drag forces.

5625112 Method of indirect heat exchange for two phase flow distribution

5625112 Method of indirect heat exchange for two phase flow distribution

Expert System for Traffic Signal Setting Assistance

An experimental knowledge-based expert system to assist in traffic signal setting for isolated intersections is presented. In contrast to existing computer aids, the system can be applied to intersections of highly irregular geometries. Algorithmic processes to evaluate signal settings and decision tables to identify traffic flow conflicts are invoked by the expert system; phase distribution of flows is performed by applying heuristic rules. The system was written in the OPS5 expert system environment. Advantages and disadvantages of the expert system programming approach relative to conventional algorithmic processes in the traffic engineering domain are described.

A calculation procedure for two phase flow distribution in manifolds with and without heat transfer

A finite-difference procedure has been developed for calculating two phase flows with heat transfer in parallel, reverse and mixed flow manifolds. The flows are assumed to be homogeneous and one dimensional. An iterative numerical scheme is used to solve the differential equations for longitudinal momentum and continuity, while in the lateral direction an integral equation for momentum is solved. Numerical predictions compare well with the available experimental results for a combining flow manifold. The effect of total flow rate, heat input on the lateral flow distribution and pressure drop characteristics have been demonstrated.