Tee Branch Research Articles

Experimental research on liquid entrainment in the inclined up tee branch

The tee branch structure is broadly used in the nuclear power systems, and liquid entrainment in the tee branch has been studied in depth. However, most of the existing research focuses on the vertical tee branch, while the study about the entrainment phenomenon in the inclined tee branch hasn’t formed mature contents. This research aims to analyze the liquid entrainment in the inclined up tee branch. The liquid level measurement method of the Automatic Depressurization and Entrainment TEst Loop (ADETEL) was improved and supplementary experiments were conducted with single-end gas inlet of vertical tee branch. In addition, the test loop was modified to conduct visualization experiments on liquid entrainment experiments of the tee branch with a 45 degree angle. The experimental result reveals that the liquid entrainment phenomenon in the inclined tee branch is significantly different from that in the vertical tee branch. Based on the experimental phenomena and data, a new OLE (Onset of Liquid Entrainment) model is proposed which is well fitted with the existing data. Then, an entrainment rate model is proposed by nondimensionalizing the key parameters affecting the steady-state entrainment, with the error within ± 15% of the experimental data.

Stone Occlusion Device with Drainage Function Is Effective in Ureteral Calculi Treatment: A Preliminary Report

Introduction: The aim of the study was to assess the efficacy and safety of ureterolithotripsy (URS) in treating ureteral calculi with holmium-YAG laser through adding retropulsion prevention and drainage function to ureteral catheter. Methods: An inner wire was fixed at the top of an Fr5 ureteral catheter and run through a tee joint. The proximal catheter was split into 4 strips. When the wire was pulled, the strips become arcuate, thus trapping the stone. The end of the tee branch was connected to the suction evacuation. Continuous irrigation and negative pressure suction were delivered after the strips passed the stones. Eighty-two consecutive patients with solitary ureteral stones underwent URS with the new device. Results: Seventy-eight patients had no observed stone retropulsion with successful insertion of the device. Four patients failed URS owing to the stone retropulsion and excessive kink of the ureter, which was followed by flexible ureteroscopy. Patient with successful insertion of the device had an immediate stone-free rate of 88.5% and 100% in a 1-month follow-up. Complications included one fever and one minor ureteral perforation. Conclusion: This new device has a low stone migration and minor complications and improves visual field with a negative pressure suction. Future studies are needed to evaluate it in randomized trials.

Анализ причин разрушения деталей трассового изготовления

About 4 % of the connecting pieces used in the construction of oil pipelines in the 1950s–1970s were manufactured in the field. Despite the fact that in recent years the number of such parts has significantly reduced, failures associated with their lack of reliability occupy a noticeable share in the total number of failures in the system of oil trunk pipelines. The purpose of this work is to analyze the typical causes of failure of connecting parts using the example of a tee bend with a reinforcing plate. The authors carried out structural and fractographic studies of the defective structure. On the basis of information about the operating conditions and the actual characteristics of the bend metal, as well as data on the centers of destruction and the nature of crack propagation, computer modeling of the stress-strain state of the part was carried out. Based on the results of metallurgical studies and computer modeling, it was established that the cause of the formation of a through crack in the weld at the junction of the main oil pipeline and the reserve branch was excess stresses in the area of welding of the reinforcing plate to the branch, exceeding the tensile strength of the material of the tee branch pipe.

Venturi flowmeter performance installed downstream of the branch of a tee junction

AbstractVenturi flowmeters are robust and can function in many different and difficult installations. One such installation is downstream on the branch of a tee junction. For the most accurate flow measurement, a Venturi in this installation needs a laboratory calibration. Laboratory calibration adds cost to a project, may not be feasible, and in some circumstances, the Venturi has already been installed and cannot be taken out for calibration. For these reasons, this research used computational fluid dynamics (CFD) to determine the percent difference from the manufacturer's straight‐line calibrated or expected discharge coefficient, C, and adjust for it in tee installations. Laboratory data were collected to validate CFD models. The Cs from tee installations, of different distances downstream of the tee branch, were divided by a corresponding straight‐line C at the same Reynolds number to create a ratio to adjust the straight‐line C for a more accurate determination of the flow rate.

Models development of liquid drops entrainment at a T-junction with a large vertical up branch

The liquid entrainment process at the vertical up tee branch is widespread in mass and heat transfer applications. Existing liquid entrainment models mainly apply to T-junctions with small diameter ratios of branch to main line (d/D), which are unable to predict the liquid entrainment under large d/D conditions. The models of liquid entrainment onset and entrainment rate are developed under reasonable assumptions. The entrainment onset model was developed based on the wave theory, force analysis and potential flow theory. The Bond number is innovatively introduced into the model to represent the effect of surface tension acting on the entrainment onset. The model is compared against the relevant experimental data which shows good agreement. In the modeling of the entrainment rate, the key parameters are obtained by nondimensionalizing the conservation equations governing the liquid entrainment process, and the constants in the model are determined by genetic algorithm. The model agrees well with existing experimental data.

Experimental studies of a typical sprinkler piping system in hospitals

Based on the issue of life safety and immediate needs of emergency medical services provided by hospitals after strong earthquakes, this paper aims to introduce a research programme on assessment and improvement strategies for a typical configuration of sprinkler piping systems in hospitals. The study involved component tests and subsystem tests. Cyclic loading tests were conducted to investigate the inelastic behaviour of components including concrete anchorages, screwed fittings of small-bore pipes and couplings. Parts of a horizontal piping system of a seismic damaged sprinkler piping system were tested using shaking table tests. Furthermore, horizontal piping subsystems with seismic resistant devices such as braces, flexible pipes and couplings were also tested.
 The test results showed that the main cause of damage was the poor capacity of a screwed fitting of the small-bore tee branch. The optimum improvement strategy to achieve a higher nonstructural performance level for the horizontal piping subsystem is to strengthen the main pipe with braces and decrease moment demands on the tee branch by the use of flexible pipes. The hysteresis loops and failure modes of components were further discussed and will be used to conduct numerical analysis of sprinkler piping systems in future studies.

Experimental investigation of liquid entrainment in vertical up tee branch with double-end gas inlets

Tee branches are widely used in nuclear power plants for varying purposes. The tee branch is adopted by the fourth stage Automatic Depressurization System (ADS-4) in Westinghouse AP600/AP1000 to depressurize the primary loop during the small break loss of coolant accident (SBLOCA). However, large amount of coolant will be entrained simultaneously through the ADS-4 branch which poses the threat of core uncovering and melting. Visualization experiments with double-end gas inlets were conducted to investigate the ADS-4 tee branch entrainment phenomena in AP1000. Entrainment process were recorded by high speed camera and analyzed in detail. The onset of liquid entrainment and entrainment rate data were obtained and compared with existing data and correlations, and discrepancies were found in the comparison due to the difference of test section geometric configuration. The gas flow rate has little effect on the branch quality at the same dimensionless gas chamber height in entrainment rate tests. The entrainment frequency was also studied. The test data reveal that the entrainment period decreases rapidly with the increase of entrainment rate in low range of the entrainment rate, and gradually stabilizes in high range of the entrainment rate.

Experimental investigation of liquid entrainment in AP1000 ADS-4 branch line with air–water

ADS-4 branch line provides a controlled depressurization of the Westinghouse AP600/AP1000 primary loop during a small break LOCA. However, the coolant will be entrained to the containment simultaneously which leads to the loss of liquid inventory. ADS-4 Depressurization and Entrainment TEst Loop (ADETEL) scaled after AP1000 was constructed and visualization experiments were conducted to investigate the entrainment phenomenon at the ADS-4 tee branch line. Entrainment phenomena were recorded by high speed camera and analyzed in detail. The entrainment onset and stabilized entrainment rate data were collected and compared with available data. Discrepancies were found between ADETEL experimental data and available data due to the difference of experimental conditions and test section geometric configuration. The test data reveals that the tee branch liquid entrainment model used in RELAP5 cannot estimate the ADS-4 entrainment for AP1000 accurately and therefore more practicable model should be developed. The ADETEL data also manifest that AP1000 has a higher degree of safety performance during ADS-4 branch depressurization process than AP600 design.

Pressure Change in Tee Branch Pipe in Oscillatory Flow

The purpose of this paper is to contribute to the understanding of unsteady flow of branch pipes in pneumatic systems. Branch pipes are used in pneumatic pipe systems in various industrial fields. To predict the unsteady pressure changes in the pneumatic piping systems, it is necessary that the dynamic characteristics of branch pipes are at hand, in addition to the dynamic characteristic of single pipe. However, while so many studies are accumulated for a single pipe dynamics, few studies have reported the pressure changes in branch pipes due to oscillatory flow. This paper reports an experimental study on the dynamic characteristics of the pressure change in a pneumatic branch pipe under given oscillatory flow. The paper also proposes a simulation method to predict the pressure changes in a pneumatic branch pipe under oscillatory flow. The validity of simulation is verified for oscillatory flows up to 5 Hz, comparing with the experimental results.

Penstock failure detection system at the "Valsan" hydro power plant

"Valsan" is a small Hydro Power Plant, 5 MW, situated at about 160 km north of Bucharest, Romania, on the small "Valsan" river in a remote mountainous area. It is equipped with a single Francis turbine. The penstock is located in the access shaft of the HPP. "Hidroelectrica", the Romanian company that operates the HPP, was trying to implement a remote penstock failure detection system. Starting from a classic hydraulic problem, the authors of the paper derived a method for failure detection and localization on the pipe. The method assumes the existence of 2 flow meters and 2 pressure transducers at the inlet and outlet of the pressurized pipe. Calculations have to be based on experimental values measured in a permanent regime for different values of the flow rate. The method was at first tested on a pipe, in the Hydraulic Laboratory of the Technical University of Civil Engineering Bucharest. Pipe failure was modelled by opening of a valve on a tee branch of the analyzed pipe. Experimental results were found to be in good agreement with theoretical ones. The penstock of the "Valsan" HPP, was modelled in EPANET, in order to: i) test the method at a larger scale; ii) get the right flow and pressure transducers that are needed to implement it. At the request of "Hidroelectrica" a routine that computes the efficiency of the turbine was added to the monitoring software. After the system was implemented, another series of measurements were performed at the site in order to validate it. Failure was modelled by opening an existing valve on a branch of the penstock. Detection of the failure was correct and almost instantaneous, while failure location was accurate within 5% of the total penstock length.

Manifold Flow in Pressure-Distribution Systems

Manifolds are used extensively in pipeline engineering applications. They may be classified as combining-flow in which the flow rate increases along the length of the manifold, and dividing-flow in which the flow rate decreases along the manifold length. The present paper addresses dividing-flow manifolds with the emphasis on pressure-distribution systems. The seminal theoretical and experimental work of McNown on discrete tee takeoffs, applicable to pressure-distribution-system manifolds, is discussed and elaborated upon for flow across the run of the tee and into the tee branch. Pertinent theoretical and experimental work for discrete orifice takeoffs is summarized. The information thus presented facilitates discussion of certain concepts presently incorporated in pressure-distribution-system design. Certain erroneous concepts are identified. A perspective is provided and improvements in related aspects of manifold design are suggested. A separate paper, presented at the ASCE/EWRI World Environmental an...

Finite Element Prediction of Residual Stress Distributions in a Multipass Welded Piping Branch Junction

Piping branch junctions and nozzle attachments to main pressure vessels are common engineering components used in the power, oil and gas, and shipbuilding industries amongst others. These components are usually fabricated by multipass welding. The latter process is known to induce residual stresses at the fabrication stage, which can have severe adverse effects on the in-service behavior of such critical components. It is thus desirable if the distributions of residual stresses can be predicted well in advance of welding execution. This paper presents a comprehensive study of three dimensional residual stress distributions in a stainless steel tee branch junction during a multipass welding process. A full three dimensional thermomechanical finite element model has been developed for this purpose. A newly developed meshing technique has been used to model the complex intersection areas of the welded junction with all hexahedral elements. Element removal/reactivate technique has been employed to simulate the deposition of filler material. Material, geometry, and boundary nonlinearities associated with welding were all taken into account. The analysis results are presented in the form of stress distributions circumferentially along the weld line on both run and branch pipes as well as at the run and branch cross sections. In general, this computational model is capable of predicting three dimensional through-thickness welding residual stress, which can be valuable for structural integrity assessments of complex welded geometries.

RESEARCH ON RESISTANCE PROPERTIES FOR BRANCH PIPE IN PNEUMATIC CONVEYING

Pneumatic conveying experiment of average particle diameter 0.25 mm sand is carried out using compress air at horizontal tee branch pipe. The result shows the change of conveying velocity and the flow valve opening of branch pipe has some noticeable effect on the respective and mutual resistance properties of branch pipe when the operation pressure keep to a constant value. When the conveying velocity is less and less, the pressure drop between the branch pipes decreases, at the same time, the respective unit length pressure drop declines at first, but when the conveying velocity reduces to some extent, the respective pressure drop begin to rise. With the difference value rising of the flow valve opening, it is found that the pressure drop curve of the respective branch pipe is away from each other and the pressure drop between the branch pipes increase.

Finite Element Predictions of Temperature Distributions in a Multipass Welded Piping Branch Junction

This contribution deals with the complex temperature profiles that are generated by the welding process in the intersection region of thick walled, cylinder-cylinder junctions. These affect material microstructure, mechanical properties and residual stresses. Knowledge of the thermal history and temperature distributions are thus critical in developing control schemes for acceptable residual stress distributions to improve in-service component behavior. A comprehensive study of three-dimensional temperature distributions in a stainless steel tee branch junction during a multipass welding process is presented. A newly developed partitioning technique has been used to mesh the complex intersection areas of the welded junction. Various phenomena associated with welding, such as temperature dependent material properties, heat loss by convection and latent heat have been taken into consideration. The temperature distribution at various times after deposition of certain passes and the thermal cycles at various locations are reported. The results obtained in this study will be used for on-going and future analysis of residual stress distributions. The meshing technique and modeling method can also be applied to other curved, multipass welds in complex structures.

MIXED CONVECTION HEAT TRANSFER IN A TEE BRANCH

The heat transfer characteristics of a Newtonian fluid in a two-dimensional, planar, right-angled tee branch are studied over a range of inlet Reynolds numbers and Grashof numbers. The flow and heat transfer equations, subject to the Boussinesq approximation, are solved using a finite-element discretization. The effects of the branch length and the grid size on the interior flow field are examined to assess the accuracy of the solutions. Results are presented for two types of experimentally realizable boundary conditions—equal exit pressure at the outlet of each branch and specified flow split between the branches. The thermal boundary condition of uniform wall temperature is examined. The effect of increasing Reynolds number is to increase the size and strength of the recirculation zones in both the main and side branches, while that of increasing Grashof number is to decrease such an effect. For the case of equal exit pressures there is a significant flow reversal in the side branch and the exit flow ra...

Steady laminar flow in a 90 degree planar branch

The flow characteristics of a Newtonian fluid in a two-dimensional, planar, right angled Tee branch are studied over a range of inlet Reynolds number of 10–800 by solving the Navier-Stokes equations using a finite element discretization. The effects of the branch length and the grid size on the interior flow field are examined to assess the accuracy of the solutions. In one case the computed velocity field is compared with the Laser Doppler anemometry measurements available in the literature and excellent agreement has been obtained. The computed velocity field is believed to be accurate within about 5%. Results are presented for two types of experimentally realizable boundary conditions—viz. equal exit pressure at the outlet of each branch and specified flow split between the branches. For the case of equal exit pressures the fractional flow in the main duct increases with increasing Reynolds number and the flow characteristics in the side branch become akin to that in a cavity. For the case of specified flow split, the number, size and strength of the recirculation zones increase as more fluid is forced to go into the side branch. The length of the side branch appears to have very little influence on the interior flow field, particularly at higher Reynolds number. This observation is rationalized as being due to the parabolized approximation becoming more valid at higher Reynolds numbers. The critical Reynolds number at which the first recirculation zone appears in the side branch increases with increasing fractional flow in the side branch and with decreasing side branch width.

Approximate Elastic-Plastic Analysis of Intersecting Equal Diameter Cylindrical Shells

Design of connections of pipes and pressure vessels on the basis of a calculated maximum elastic stress often proves to be too conservative in the case of ductile materials. Elastic-plastic analysis by the finite element method proves to be too costly. This paper presents an alternative method which reduces the calculations to those of a rotationally symmetric shell subjected to axisymmetric loading. Using this approach approximate elastic-plastic deformations on the meridian passing through the crotch of a tee branch connection of cylindrical shells of equal diameter and thickness are determined. The method is limited to cases of the normal intersection of very thin shells of identical diameter, thickness, and material and to internal pressure loading. Numerical results for the intersection of two shells of R/t equal to 100 are given for an elastic-perfectly plastic material satisfying the von Mises yield condition.

Approximate Elastic Stresses in a Tee Branch Pipe Connection Under Internal Pressure

An approximate method for calculating the elastic stresses at the crotch of a tee branch pipe connection under internal pressure is presented. The analaysis is based on shell theory together with stress multipliers for the peak bending stress in the fillet. A table of factors for rapid calculation is given.

Approximate Elastic Stresses in Pipe Junctions with Chamfer Corners

Elastic stress analysis of a right angle tee branch pipe connection of two pipes of identical diameter and thickness connected through 45-deg chamfer corner sections is developed for internal pressure loading. Stresses in the crotch portion of the vessel are determined. These results are presented in the form of a table of factors useful for rapid calculation of approximate values of the peak stresses. The existence of a structurally optimum size of chamfer is demonstrated.

Precision Microwave Admittance Measurements of Active Elements

A new instrument is discussed for measuring negative conductance of an active element at the microwave region with enough stability and with high precision. The fundamental principle of the instrument is that of the impedance comparator. This instrument has a small rotating shielded loop located just above the center of the Tee branch, the three terminals of which are connected to the active element, to the standard susceptance, and to the signal generator, respectively. The instrument has the following special features: 1) the use of a shielded loop, 2) the use of negative standard susceptance for allowing the normalized conductance of the sample to be positive, 3) no restriction for the value of the negative conductance, and 4) the use of a short-circuit line as the susceptance standard for the dc return circuit of the active element. Analytical considerations are given for errors concerned with the loss in the short circuit, with the position and the shape of the small shielded loop, and with the phase difference between the current on the Tee branch and the magnetic field at the center of the loop. This instrument has proved to have high precision in measuring the admittance of an Esaki diode at 1 GHz. (The residual VSWR is less than 1.03). Therefore, it can be said that this instrument is an excellent aid for measuring negative conductance up to several GHz.