Search

Objectives: Currently available hysteroscopic tubal patency testing relies only on anatomical passage of air bubbles or flow of irrigating fluid and debris via tubal ostia. The aim of this study wa...

Under the high-pressure and low-temperature environment of the deep sea, wax deposition will occur in the wellbore. This study discusses the effect of gas–liquid two-phase bubbly flow on wax deposition. In this study, wax deposition experiments of a gas–liquid two-phase flow in vertical pipelines were carried out using waxy white oil and air as the experimental medium. The results show that under the bubble flow pattern, within a short period of time from the start of wax deposition, it rapidly accumulates to the peak, then rapidly cuts off part of it, and then presents a simple harmonic dynamic trend until the final stability. The average wax-deposit thickness decreases first and then increases with the increase of superficial gas velocity, and it increases first and then decreases with the increase of superficial liquid velocity. The average wax-deposit thickness decreases with the increase of oil temperature. The average wax-deposit thickness was substantially constant and then decreases with the increase of ambient temperature. The wax-deposit thickness increases with the increase of wax content in oil flow. This research is useful for people to further understand the changes in the wax deposition process.

The oscillatory coalescence phenomenon of the Taylor bubble flow subjected to the action of a fluctuating pressure gradient in a pulsating heat pipe was investigated using the front tracking method (FTM). The effects of amplitude and frequency of fluctuating pressure, bubble size, Reynolds number (Re), and Weber number (We) on the bubble coalescence process were studied. The results demonstrated that the lower the pulsation frequency, the longer the period of bubble oscillation, which could provide enough time for bubbles to drain and promoted the coalescence of the bubbles. The larger Euler number (Eu) was, the more easily bubbles coalesced. On the contrary, when Eu was small, the bubbles were slow to coalesce. The size of the top bubble and the bottom bubble had different effects on coalescence. An increase of the length of the top bubble (Lt) was beneficial to bubble coalescence while increasing the length of the bottom bubble (Lb) restrained bubble coalescence. Time required for bubble coalescence increased with the increase of Re and decreased with increasing We.

In the present study, a test chamber filled with perfluorohexane (FC-72) is set up to investigate partial discharge (PD) in phase-cooling bubbles. Under the non-uniform electric field with needle point-to-hemisphere electrodes, thermal bubbles are generated from the needle point. The difference between PD with and without the bubbles is analyzed to identify features of the discharge in the bubbles. It is observed that the bubbles reduce the PD inception and intensify the discharge. A model of bubble motion is established to investigate bubble behavior in an electric field. Based on the observation of the flow and streamer patterns, a mechanism of PD in bubble flow is established and confirmed by phase-distribution of PDs with bubble transit time.

By combining near infrared spectroscopy and differential pressure meter to measure flow rate and phase volume fraction, a new structure of the near infrared system located in the position of the Venturi tube of long throat was proposed. The flow rate and volume fraction of the bubble flow were measured in a vertical experimental line. In terms of volumetric content measurement, based on typical flow characteristics, a void age model was established and experimentally verified. In terms of flow measurement, the classical measurement model is compared, and the uniform flow model is selected as the flow measurement model and corrected. The results show that the measurement error under the bubbly flow condition of the liquid volume fraction and the gas volume fraction was within ±0.52% and ±10%, respectively. The relative error of total flow measurement was within ±1.01%.

The paper presents a study of the slip velocity for almost spherical bubbles in a downward laminar tube flow. The local slip velocity is defined as a difference between the mean liquid velocity (measured with electrodiffusional method) and the mean bubble velocity (measured with a modified LDA tool with a small size of measurement volume). The law for slip velocity for downward flow is significantly different from a similar law for upward flow. This reveals that the bubble flow motion is rather random than structured in the upward flow.

A room temperature liquid metal-based microvalve has been proposed in this work. The microvalve has the advantages of easy fabrication, high flexibility, and a low leak rate. By designing a posts array in the channel, the liquid metal can be controlled to form a deformable valve boss and block the flow path. Besides, through adjustment of the pressure applied to the liquid metal, the microvalve can perform reliable switching commands. To eliminate the problem that liquid metal is easily oxidized, which causes the microvalve to have poor repeatability, a method of electrochemical cathodic protection has been proposed, which significantly increases the number of open/close switch cycles up to 145. In addition, this microvalve overcomes the shortcomings of the traditional microvalve that requires an alignment process to assemble all the parts. When the valve is closed, no leak rate is detected at ≤320 mbar, and the leak rate is ≤0.043 μL/min at 330 mbar, which indicates it has good tightness. As an application, we also fabricate a chip that can control bubble flow based on this microvalve. Therefore, this microvalve has great prospects in the field of microfluidics.

Transition from bubbly to slug flow is a well-known phenomenon. In the channel with a swirler, a transition to slug flow at a lower gas superficial velocity than in the same channel without the swirler was observed in this work. The transition phenomenon from bubble flow to slug flow under the effect of swirl in a circular pipe was observed and investigated. Compared to the flow pattern (maintaining the bubble flow along a streamwise direction) in a non-swirling flow, we observe that bubble flow is transformed to a gas column downstream of the swirler, then broken up, and finally separated into gas slugs in the streamwise direction. The dynamic condition for the occurrence of a liquid bridge is proposed, then combined with a swirl decay model of a gas–liquid two-phase swirling flow; thus, the axial position for the transition from a gas column to a slug flow along the streamwise direction can be predicted. Whether slug flow always remains along the streamwise direction is closely related to its size. Under the effect of swirl, the void fraction is decreased and the pressure drop is increased compared with that in a non-swirling flow, and gradually approximates the values of a non-swirling flow along the streamwise direction.

The slip velocity between phases is an important parameter for evaluating the volumetric flow rate of each phase in vertical pipes. This paper presents an improved empirical correction for calculating the slip velocity of two-phase, oil-water bubble flows in large-diameter vertical pipes, based on a series of experimental tests. Water holdup data were obtained through experiments on an oil-water mixture flowing through a transparent test section in a 16-m-long vertical pipe with an inner diameter of 124 mm. The water holdup ranged from 0.58 to 1, and the observed flow pattern was bubble flow. Based on these experimental data, a modified correction was developed to improve the accuracy of the prediction of slip velocity for oil-water bubble flow systems. In addition, the proposed correction was validated against published experimental data for pipes with diameters of 2–6 in. The performance of the proposed correction against an experimental dataset (from our tests and published data) was also compared with that of six other, widely accepted corrections. The proposed correction predicted the slip velocity of two-phase, oil-water bubble flow in large-diameter vertical pipes more accurately than previous corrections did.

We demonstrate a new image processing methodology for resolving gas bubbles travelling through liquid metal from dynamic neutron radiography images with an intrinsically low signal-to-noise ratio. Image pre-processing, denoising and bubble segmentation are described in detail, with practical recommendations. Experimental validation is presented—stationary and moving reference bodies with neutron-transparent cavities are radiographed with imaging conditions representative of the cases with bubbles in liquid metal. The new methods are applied to our experimental data from previous and recent imaging campaigns, and the performance of the methods proposed in this paper is compared against our previously achieved results. Significant improvements are observed as well as the capacity to reliably extract physically meaningful information from measurements performed under highly adverse imaging conditions. The showcased image processing solution and separate elements thereof are readily extendable beyond the present application, and have been made open-source.

Dynamic neutron radiography is used to observe the effect of a transverse magnetic field on argon bubbles rising through a thick layer of liquid gallium without interactions with the container walls.

In this paper, a research of PMMA optical fiber reflectivity changing along with the angle of tips has been studied. A type of integrated conical fiber probe is designed. Nine angles of cone fiber tips were fabricated and tested in 0.4 L /min continuous uniform bubble flow (air) in this study to validate the performance of each cone angle. A simulation model of PMMA optical fiber tip was established based on physical properties of fiber to simulate the reflectivity of different angle tips set into gas/liquid environment. The first and second high peaks of experimental data agree well with the positions of those calculated using the simulation.

The erosion of particles is one of the main reasons of damage to the multiphase flow pipelines in black water treatment systems. In this study, the particle erosion of liquid–solid–gas multiphase bubble flow in a horizontal-vertical-upward elbow was analysed. The optical microscope, scanning electron microscope (SEM) and white light interference microscope were used for detection of failed pipe samples. An erosion simulation method based on the volume of fluid (VOF) model and discrete phase model (DPM) was adopted to study the influencing factors on the erosion. The results showed that the particles and bubbles lead to lots of pits and furrows on the pipe surfaces, and the erosion at the outer elbow is relatively severe due to the effect of multiphase bubble flow. The most severe damage occurred at θ = 25° of the elbow, and erosion rate is positively correlated with the particle diameter, volume fraction and inlet velocity.

Results of experimental and numerical investigations of heat transfer and wall shear stress, in upward bubble flow in a flat inclined channel, are presented. The hydrodynamic structure is measured using the electrochemical method with miniature friction sensors. Miniature platinum thermoresistors are employed to measure the wall temperature. The set of RANS equations is used to account for the feedback effect of bubbles on mean and fluctuating flow parameters. It is shown that we can observe a significant dependence of shear stress and heat transfer on angle of channel inclination, in the bubble gas-liquid flow. The largest values of wall shear stress and heat transfer correspond to channel inclination angles of 30–50°. Intensification of wall shear stress in inclined two-phase bubble flow leads to values of 30%, and up to 15% for heat transfer. For inclination angles close to horizontal, suppression of shear stress and heat transfer of 10% and 25% respectively, was registered. Bubble size distributions along the channel length were obtained for different regimes of two-phase flow.

Under pressure-driven conditions of gas, the bubble size was experimentally studied in different types of T-junction microchannels having widths of 300 μm and heights of 100 μm. The bubble length increases with the flow rate, and we observed that it also increased with the driving pressure. This was proved through the published formulas for the bubble flow pressure difference using the experimental results. Three types of downstream channels—normal, movable, and deformed walls (of different lengths)—were used to study emerging bubbles, and a nonlinear relationship was observed between them. The channel type directly influenced the bubble size by affecting the resistance of the channel with bubbles. Furthermore, the difference between the resistances of a normal channel and a deformed channel with the same typical dimension was determined using a comparator structure between two parallel channels to evaluate the effect of flow resistance on bubble generation. The adjustment of the flow rate at downstream will give feedback to the bubble generation in the double T-junction channel.

The hydrodynamic structure of the flow in a flat channel with sudden expansion was studied at constant flow rates of liquid and gas in the vertical flow at Re = 6600 and gas content β = 0.03. The measurements were carried out using the PLIF method; and with this view, fluorescent particles for PIV studies and the dye Rhodamine G were added to distilled water. An optical threshold filter was installed on the lens of the video camera. When processing images to obtain data on the local gas content, only bubbles falling into the plane of the laser beam were considered (the boundary glows, casting a shadow).

Bubble flow is a phenomenon in which gas flows with liquid in the form of bubbles, which widely exists in production and life. As an important part of fluid mechanics, bubble flow also has a certain impact on the actual production process. This work briefly summarizes the development of research on bubble flow in recent years. Firstly, a brief introduction to the development process and current situation of bubble flow in chronological order is presented, and the main difficulties related to the research and development of bubble flow are also pointed out, including the complicated gas-liquid distribution pattern and the exchange of materials and energy between gas and liquid phases, which slow down scholars’ research progress. Then, several theoretical models for bubble flow research are introduced. These models take bubble parameters into account, including the ultimate velocity of bubble rising, the transfer of energy and matter in the coalescence, and rupture of the bubble, the phase distribution of the bubble in the tube, and the interaction between the bubble and the liquid (the shear stress produced by bubbles affecting the turbulence field). This work briefly explains the ideas of each model and the results obtained, compares and analyzes their advantages, disadvantages and limitations, and predicts the theoretical and technical means required for subsequent theoretical model construction. Finally, part of the experimental research is summarized, along with the process and technical means of each experiment as well as the relationship between the experimental results and the theoretical research. It is hoped that this work could help to have a preliminary understanding of the research process and research methods of bubble flow, and provide some perspectives for incorporating bubble flow hydrodynamic theory into industrial applications and real life.

Bioreactors are of interest for value-upgrading of stranded or waste industrial gases. Reactor intensification requires development of low cost bioreactors with fast gas–liquid mass transfer rate. Here we assess published reactor technology in comparison with a novel downward bubble flow created by a micro-jet array. Compared to known technology, the advanced design achieves higher volumetric gas transfer efficiency (kLa per power density) and can operate at higher kLa. We measure the effect of four reactor heights (height-to-diameter ratios of 12, 9, 6, and 3) on the gas transfer coefficient kL, total interfacial area a, liquid residence time distribution, energy consumption, and turbulent hydrodynamics. Leading models for predicting kL and a are appraised with experimental data. The results show kL is governed by “entrance effects” due to Higbie penetration dominate at short distances below the micro-jet array, while turbulence dominates at intermediate distances, and finally terminal rise velocity dominates at large distances. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1399–1411, 2018

Purpose The purpose of this paper is to the study the multiphase bubbles flow motion in a vertical channel with an electroconducting liquid without and under the influence of a magnetic field. Design/methodology/approach For numerical calculations, the lattice Boltzmann method (LBM) is used, which is based on the kinetic theory for solving fluid mechanics and other physical problems. The phase-field lattice Boltzmann model is developed to simulate the behaviour of multiphase bubble–bubble interaction while rising in the fluid with high density ratios. Findings The behaviour of the rising bubble flow in a rectangular column of two phases is investigated with the two-dimensional LBM. Originality/value The multiphase flow in electroconducting liquids with high ratio of density is studied using the LBM.

In this paper we describe the extended routing rules in the low-latency high-bandwidth Angara interconnect with torus topology. The Angara interconnect supports 4D torus topology with routing based on the direction order routing (DOR) implemented using direction bits and additional first and last steps. To avoid deadlocks in a ring bubble flow control is used. Implementation of the First and Last Steps method allows to violate the DOR rule. We propose an algorithm for generation and analysis of routing tables that guarantees no deadlocks in the Angara interconnect. The proposed algorithm increases the number of different routable systems and improves fault tolerance.

The paper presents an idea of a new measuring method based on image tomography. This method focuses on registration of images of bubbles moving in two perpendicular directions. Two images are used for determination of the center of mass, movement trajectory and local velocities. Volume and area of bubbles are defined by using approximation of the bubble shape with the known geometric figures. The paper also presents the algorithm of reconstruction of the bubble shapes and movement trajectories, as well as exemplary test results. The obtained results were compared with empirical correlations in the published literature.

A CFD-ABND coupling model was used to study the flow characteristic of gas-liquid two-phase flow in the process of gas passing through the liquid bath of a water-coal-slurry entrained-flow gasifier. In this model, an average bubble number density (ABND) approach was employed and merged with the two-fluid model. A two-phase version of the RNG k-ε turbulence model was used for the liquid and gas, respectively. Comparisons of computational results with experimental data are done. The results show that the gas gathers along the outer wall of the cooling pipe and rises. The higher turbulent kinetic energy of gas and liquid, the larger bubble and the higher interfacial area concentration exist mainly near the exit and outer wall of the cooling pipe. The existence of a separator inserter is very helpful to strengthen the turbulence between gas and liquid; this can reduce the bubble diameter and increase the interfacial area effectively.

The experimental study of the process of bubble detachment from a single capillary in downward liquid flow was performed. The glycerin was used as a working liquid. In order to study the effect of physical properties of liquid on the formation of bubbles experiment was conducted at different temperatures. Presented average bubble size is depended on parameters such as gas flow rate, temperature and volume velocity of liquid, as well as the capillary diameter. The data about the most characteristic mode of formation of the gas-liquid mixture was obtained. It is shown that coalescence of bubbles near the capillary is the process that determines the type of bubbles size distribution in the fluid flow. The regimes of bubble formation most suitable for the generation of a monodisperse, and bidisperse gas-liquid mixture are presented in the study.

The work is devoted to the experimental study of the wall shear stress in the vertical assembly of rods in a square arrangement for a bubble flow. The measurements were carried out using the electrodiffusion technique. The data obtained during the experiment show that the void fraction has a significant effect on the flow structure near the walls of the rods. The change in wall shear stress with distance from the spacer grid does not occur monotonously, in contrast to the single-phase case.

The experiments on the air-water two-phase flow patterns in a 24 mm diameter vertical circular pipe under both static and rolling conditions were conducted. The superficial velocities were in the range of 0.05–4.07 m/s and 0.02–20.55 m/s for water and air, respectively. Five typical flow pattern morphologies resulting from a rolling motion were observed: dispersed bubbles; bubbles; slug; churn; and annular flow. Flow pattern transitions were identified by analysis of visual images and a bubble chord-length probability distribution function (PDF). The static experimental data was used to validate existing flow pattern transition models that were then modified to fit rolling conditions by considering the additional forces caused by rolling motion. These models also agreed well with the experimental data. Investigation of the influence of the rolling motion on flow pattern transition showed that, as the rolling amplitude increases, the formation of dispersed bubble flow requires a higher superficial liquid velocity. It was also found that, the greater the rolling amplitude, the larger region of churn. The rolling period, however, has little impact on flow pattern transitions.

Bubble flow is present in many processes that are the subject of chemical engineering research. Many correlations for determination of the equivalent bubble diameter can be found in the scientific literature. However, there are only few describing the formation of gas bubbles in flowing liquid. Such a phenomenon occurs for instance in airlift apparatuses. Liquid flowing around the gas bubble creates a hydraulic drag force that leads to reduction of the formed bubble diameter. Usually the value of the hydraulic drag coefficient, cD, for bubble formation in the flowing liquid is assumed to be equal to the drag coefficient for bubbles rising in the stagnant liquid, which is far from the reality. Therefore, in this study, to determine the value of the drag coefficient of bubbles forming in flowing liquid, the diameter of the bubbles formed at different liquid velocity was measured using the shadowgraphy method. Using the balance of forces affecting the bubble formed in the coflowing liquid, the hydraulic drag coefficient was determined. The obtained values of the drag coefficient differed significantly from those calculated using the correlation for gas bubble rising in stagnant liquid. The proposed correlation allowed the determination of the diameter of the gas bubble with satisfactory accuracy.

To study the flow pattern mechanism of cavitation and erosion in water hydraulic valves, a visualized water hydraulics experiment for testing the bubble flow was designed and conducted in this paper. An ergonomic design method was adopted to ensure with the characteristics of the visualized experiment platform of being modular, movable, networked, adopting a virtual three-dimensional vision and safety, respectively, were adhered. An experimental video acquisition subsystem with an optimized arrangement of 5 plane mirrors was presented to observe and analyze the bubble flow pattern in a transparent hydraulic valve. An algorithm was developed to extract the 2-D bubble features and reconstruct the 3-D bubble flow pattern. The 2-D and 3-D calculated results were analyzed, which effectively reconstructed the bubble flow. During the 2-D and 3-D results analysis for a selected period of time, the visualized water hydraulics experiment system in this paper met the expected performance requirements.

Water or air-water bubble flow passing through tube bundle can be seen in many industrial equipments such as heat exchanger and chemical equipment. In addition, tube bundle can be used as a flow-straightener, -mixer, -resistor, and -damping device. In this study, the effects of tube arrangement of equally or unequally spaced in-line and staggered tube bundle and of void fraction on the flow characteristics such as flow pattern and flow resistance of a tube or tube bundle are examined experimentally.

The goal of this study was to determine feasible numbering-up laws to model the gas–liquid distribution in multiple microchannels. Comb-like microchannels were constructed by closely arranging eight capillaries of 0.5-mm inner diameter. The air–water flow in the parallel microchannels was recorded by a high speed CCD camera. After collecting and analyzing a very large number of images, the flow patterns were classified into two zones, zone I and zone II, which were the bubble flow and phase splitting zones, respectively. A model was established to describe the mean sizes and velocities of bubbles and liquid slugs in the two zones at different inlet flow rates of air and water, as well as to distinguish the two-zone operating limits by determining inlet flow rate intervals of the fluids. The calculated results agreed well with the experimental data. Therefore, the model showed a potential application to numbering up comb-like microchannels.

Aqueous foam is regarded as a versatile medium in numerous scientific and engineering applications due to its high viscosity and low density. The objective of this study is to investigate the flow characteristics of aqueous foams through the jet device and horizontal pipe. The pressure distribution and foam production capacity are measured at different operating conditions. Experimental results show that the pressure fluctuations reduce significantly by increasing the foam liquid concentration, especially in the downstream of jet device. The bubble flow turns into homogeneous foams gradually when the concentration increases from 0.025% to 0.35%, while the foam behaviors take little change at a higher concentration, and the foamability reaches a limit. Subjected to the large pressure difference produced between the top and bottom of horizontal pipe, aqueous foams undergo a gas–liquid separation at a high terminal pressure, resulting in bubbles at the top and liquid at the bottom. Therefore, the terminal pr...

Based on the vacuum electron beam welding with deep-penetration process, the convection phenomenon of the bubble flow in partially penetrated and fully penetrated molten pool of AZ91D magnesium alloy was simulated under the unsteady-state conditions. At the same time, the distributions of the cavity-type defects in deep-penetration weld were studied. The results showed that the cavity-type defects are more prone to distribute at the bottom of the weld and accumulate along the axis of the weld for the partially penetrated weld seam; there is a high incidence of cavity-type defects in the middle of the weld for the fully penetrated weld seam. As a smooth escape channel for the gas phase is formed in the fully penetrated molten pool, the possibility of gas escaping is much higher than that in the partially penetrated molten pool. A high liquid convection velocity is more conducive to the escape of the gas in molten pool. The liquid convection velocity in the fully penetrated molten pool is higher than that in the partially penetrated molten pool. So, the final gas fraction in the fully penetrated molten pool is low. Therefore, the appearance of cavity-type defects in the fully penetrated weld seam is less than that in the partially penetrated weld seam.

This paper presents a mathematical model for bubble flow in a vertical borehole under non-isothermal conditions and the results of calculations of the volume fraction and temperature of the phases. The influence of the bubble size on the formation phase of the temperature fields of the phases.

Short and long packets co-exist in cache-coherent NoCs. Existing designs for torus networks do not efficiently handle variable-size packets. For deadlock free operations, a design uses two VCs, which negatively affects the router frequency. Some optimizations use one VC. Yet, they regard all packets as maximum-length packets, inefficiently utilizing the precious buffers. We propose flit bubble flow control (FBFC), which maintains one free flit-size buffer slot to avoid deadlock. FBFC uses one VC, and does not treat short packets as long ones. It achieves both high frequency and efficient buffer utilization. FBFC performs 92.8 and 34.2 percent better than LBS and CBS for synthetic traffic in a $4 \times 4$ torus. The gains increase in larger networks; they are 107.2 and 40.1 percent in an $8 \times 8$ torus. FBFC achieves an average 13.0 percent speedup over LBS for PARSEC workloads. Our results also show that FBFC is more power efficient than LBS and CBS, and a torus with FBFC is more power efficient than a mesh.

Piles of perfectly smooth spherical particles are able to sustain a non-zero angle of repose as a result of geometrical constraints. Here we report on a study of piles made of soft frictionless grains and their angle of repose. The piles are formed by a continuous bubbling of air into a soapy solution in a narrow container of rectangular cross section. For wide containers, the angle of repose of the pile is $$3.75\pm 0.11$$ degrees, independent of bubble flow rate. However, we find that the angle of repose is sensitive to confinement effects. In contrast with sand piles, surface avalanches are nearly absent and the fluidized region along the interface is several layers deep. In addition, the bubble pile is metastable, i.e. upon interruption of the gas flux the slope relaxes back to zero as a result of liquid drainage.

This paper follows the reports [4] and gives instructions on how to theoretically determine the bubble size and its distribution using the distribution function of Nukiyama-Tanasawa with friction factors.

The early characteristic of the pressure buildup test is usually dominated by wellbore storage effect. These wellbore phase redistribution effects, which are transient in nature, including phase re-injection, bubble flow and hammering effect, sometimes lead to the pressure oscillation in early pressure buildup. And, these phenomena are characterized with the changing wellbore storage effect. But the present changing wellbore storage models vary with time monotonically, which could not describe these periodic processes. This paper presents a new changing wellbore storage model for analysis of the pressure oscillation process at wellbore or near wellbore region during the pressure buildup test. First, the physical processes of the phase re-injection, bubble flow and hammering effect are analyzed for reasons of the pressure oscillation. Then, a periodic correlation is introduced to describe these processes based on experiments. Finally, a new model is proposed by taking account of the combination of the Fair model and a cosine function. Then, the Stehfest algorithm and Crump algorithm are used to simulate the process of pressure oscillation. The results show that Stehfest algorithm has a significant error on high frequency pressure oscillation, but Crump algorithm could simulate the whole process of pressure oscillation more accurately than that of Stehfest algorithm. When the pressure oscillation occurs in the well test, the pressure and pressure derivative of the proposed model could match the experimental data and oil field data very well. With this model, the pressure oscillation in the pressure buildup test can be understood and predicted better. And the proposed model is a supplement to the phase redistribution model and yields an insight into the corresponding impact on well test transient pressure behavior.

In this work an experimental study of local void fraction distribution in square arrangement rod bundle channel 3 * 3 under bubble flow regime was carried out. Measurements were performed with conductivity probe help, which was introduced into the flow through an angular or side rod at an angle of 15° to the flow. This method made it possible to determine the local void fraction close to the walls of the rods and in the narrow gap between them. Measurements have shown that a dome-shaped profile of local void fraction is realized in the gap between the side rode and the central one, while a saddle-shaped distribution of the void fraction is observed on the line connecting the central and angular rods. Also the effect of the spacer grid on the distribution of the gas phase in the channel was shown.