Grid Of Tube Research Articles

Study of the intensification of the heat exchange process in the MO-2 turbine oil cooler during the modification of tubes in tube grids.

Study of the intensification of the heat exchange process in the MO-2 turbine oil cooler during the modification of tubes in tube grids.

Fe2O3 nanoparticles encapsulated in the inner walls of integrated 3D carbon tube grid as high-performance anode for lithium-ion batteries

Ferric oxide (Fe2O3) holds huge potential as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity and low cost, however, its battery performance is still limited by the intrinsic poor conductivity and huge volume variation during lithiation and de-lithiation processes. Herein, we developed a self-standing 3D interconnected vertical and lateral carbon tube (3D-CT) grid with Fe2O3 nanoparticles (NPs) encapsulated in the wall of CT (denoted as 3D-CT@Fe2O3-NPs@C), as structurally-integrated anode without any inactive components. The 3D-interconnected vertical and lateral CTs with open channels not only provide plenty of attachment sites for the Fe2O3 NPs and accommodate the strain generated by the volume variation of Fe2O3, but also facilitate the fast ions and electrons transfer. Therefore, the self-supported 3D-CT@Fe2O3-NPs@C electrode delivers superior cycling and high-rate performance with a high stable specific capacity of 896.2 mAh g−1 at the current density of 1.0 A g−1 after 700 cycles. Even at the high current density of 4.0 A g−1, a reversible capacity of 488.1 mAh g−1 can be reached based on the mass of the electrode. This study provides a facile and efficient strategy to improve the electrochemical performance of LIBs through the design of structurally-integrated grid electrode.

Issues of laser welding technology of the ends of heat exchange pipes in pipe gratings.

The paper shows that the reliability and service life of shipboard heat exchangers largely depends on the quality of fixing heat exchange pipes in pipe grids. The methods of fixing pipes in a pipe grid depends on many factors: the type of heat exchanger, the material from which the pipes and pipe grids are made, the thickness of pipes and pipe grids, technological capabilities taking into account the chosen design, etc. One of the most effective ways of fixing pipes in the tube grids of heat exchangers is welding. Welds are characterized by strength, manufacturability, and provide a high service life of the joint.
 In the article, it is proposed to use laser welding to perform welded joints. Laser welding provides a high focused energy density concentrated on a very small area with relatively low energy input and heating of adjacent metal layers. In laser welding, there is no strong ionizing radiation, the magnetization of the workpieces does not affect the laser beam, which is relevant when welding magnetic materials. The effect of laser radiation is highly local, carried out in the air, including in the environment of protective gases. Thanks to this, laser welding can be used without problems to connect large-sized metal structures.
 The laser beam is easily transported with the help of mirror optical systems or through a light guide and is directed to hard-to-reach places. At the same time, reliable and operational control of the laser welding process with adjustable energy characteristics is provided. The article describes the technological equipment that can be used for welding heat exchange pipes and pipe gratings.

ДОСЛІДЖЕННЯ ЕФЕКТИВНОСТІ ТЕПЛООБМІННОГО ПРОЦЕСУ В ОХОЛОДЖУВАЧІ ТУРБІННОГО МАСТИЛА МО-2 В ЗАЛЕЖНОСТІ ВІД СХЕМИ РОЗТАШУВАННЯ ТРУБОК У ТРУБНИХ ҐРАТАХ

Effective cooling of the turbine oil is important for the reliability and optimal operation of the turbogenerator. The oil is used for lubrication and cooling of the support and radial bearings of the turbine, bearings of the generator and reducer, gears and splined rollers. It is also used as a hydraulic fluid in the hydraulic turbine start-up system. For reliable and safe operation of the system, it is necessary to maintain the correct temperature of the lubricant. Research is aimed at studying the influence of the layout of the heat exchange tubes in the tube grids on the cooling efficiency of the TP-22 turbine oil. With the help of the SolidWorks software complex, a geometric model of the MO-2 turbine oil cooler was created with three schemes for the placement of heat exchange tubes in tube grids: corridor, radial and checkerboard. Adhering to the parameters of the technical characteristics of this cooler, the nominal parameters of temperatures and consumption of coolants (cooling water and turbine lubricant TP-22) were chosen. The result of the calculations were the temperature fields of the coolants and the trajectories of the movement of lubricant particles in the intertube space of the cooler. When creating a geometric model and further research, the main technical characteristics of the shell-and-tube horizontal cooler MO2 were adopted, namely: the temperature of the turbine oil at the inlet is 45°С, the nominal flow rate of the oil is 3.1 m3/h, the temperature of the water at the inlet is 20°С, the nominal flow rate water - 15 m3/h. The conducted computer modeling made it possible to investigate the influence of the layout of the heat exchange tubes in the tube grids on the cooling efficiency of the turbine lubricant in the MO-2 shell-and-tube cooler. It was shown that the most effective, among the studied schemes, is the checkerboard arrangement of heat exchange tubes in tube grids. This scheme makes it possible to reduce the consumption of cooling water, relative to the nominal one, which will allow the use of water pumps of lower power.

3D Grid of Carbon Tubes with Mn3O4‐NPs/CNTs Filled in their Inner Cavity as Ultrahigh‐Rate and Stable Lithium Anode

Transition metal oxides are regarded as promising candidates of anode for next‐generation lithium‐ion batteries (LIBs) due to their ultrahigh theoretical capacity and low cost, but are restricted by their low conductivity and large volume expansion during Li+ intercalation. Herein, we designed and constructed a structurally integrated 3D carbon tube (3D‐CT) grid film with Mn3O4 nanoparticles (Mn3O4‐NPs) and carbon nanotubes (CNTs) filled in the inner cavity of CTs (denoted as Mn3O4‐NPs/CNTs@3D‐CT) as high‐performance free‐standing anode for LIBs. The Mn3O4‐NPs/CNTs@3D‐CT grid with Mn3O4‐NPs filled in the inner cavity of 3D‐CT not only afford sufficient space to overcome the damage caused by the volume expansion of Mn3O4‐NPs during charge and discharge processes, but also achieves highly efficient channels for the fast transport of both electrons and Li+ during cycling, thus offering outstanding electrochemical performance (865 mAh g−1 at 1 A g−1 after 300 cycles) and excellent rate capability (418 mAh g−1 at 4 A g−1) based on the total mass of electrode. The unique 3D‐CT framework structure would open up a new route to the highly stable, high‐capacity, and excellent cycle and high‐rate performance free‐standing electrodes for high‐performance Li‐ion storage.

Structurally integrated 3D carbon tube grid-based high-performance filter capacitor.

Filter capacitors play a critical role in ensuring the quality and reliability of electrical and electronic equipment. Aluminum electrolytic capacitors are the most commonly used but are the largest filtering components, limiting device miniaturization. The high areal and volumetric capacitance of electric double-layer capacitors should make them ideal miniaturized filter capacitors, but they are hindered by their slow frequency responses. We report the development of interconnected and structurally integrated carbon tube grid-based electric double-layer capacitors with high areal capacitance and rapid frequency response. These capacitors exhibit excellent line filtering of 120-hertz voltage signal and volumetric advantages under low-voltage operations for digital circuits, portable electronics, and electrical appliances. These findings provide a sound technological basis for developing electric double-layer capacitors for miniaturizing filter and power devices.

The assessment of stressed-deformed state of tube bundle of the heat-exchange apparatus with the fixed pipe grids

Ensuring reliable operation of heat exchange equipment is the key to continuous and efficient operation of the entire technological unit or assembly as a whole. During installation, repair or operation, various deviations of the construction elements of the heat exchangers from the values specified by the project are possible. One of the possible scenarios of such deviations is the deviation of the transverse baffles of the tube bundle from the vertical design position during installation. Since the transverse baffles in the tube bundle play the role of supporting constructions, when they deviate from the vertical design position and at the same time are exposed to operational loads, it is possible to form zones of concentration of increased stresses in the heat transfer pipes, and then the occurrence of defects in these zones. Currently, the work on modeling heat-exchange equipment using specialized software systems for assessing the stress-deformed state taking into account the influencing factors and identifying the most unfavorable zones with maximum effective stresses is relevant. This paper investigates the interconnection between the magnitude and direction of deviation of the transverse baffles from the vertical design position on the stress-deformed state of the tube bundle of the heat exchanger with fixed tube grids along the rows of heat transfer tubes.

Evaluation of the Properties of Alternative Construction Combined Tube Joints from Heat Exchanger Tube Grids Made of Steel 2Cr18Ni10Ti

One of the most effective ways of excluding heat treatment during the manufacture if tube bundles is replacement of arc welding by rotary friction welding. The corrosion resistance of welded joints of 12Cr18Ni10Ti steel, prepared by friction welding and not subjected to heat treatment is evaluated. The corrosion properties of such welded joints, including those not subjected to heat treatment, are evaluated. Measurements of the electrode potential of welded samples are performed to determine zones prone to brittle fracture. It is established that the spread of electrode potential values is small that makes it possible to propose that there is uniform corrosion in a welded joint. Tests for welded joint specimen resistance to intergranular corrosion show that there is no grain boundary breakdown to a depth of more than 30 μm in 12Cr18Ni10Ti steel specimens, which indicates joint intergranular corrosion resistance.

Quality and reliability improvement of “tube-tube plate” welded joints during welding by pulse pressure

The possibility of controlling the impact parameters for improving the quality and reliability of the welded joint of the tube-grid of the heat-exchange apparatus by adjusting the parameters of the discharge circuit of the electrotechnical-logical unit and the angle of cutting the opening of the tube grid is considered. A mathematical model is proposed and simulation is performed to estimate the impact parameters. The results of the simulation showed good agreement with the experimental ones, and the model can be used to calculate the optimum welding regime and improve the quality of the welded joint.

The algorithm of constructor and technological

On the basis of the pulse-pressure model of the velocity-induced de-formation of metal pipes proposed by the authors [1] the expanding plas-ma channel of an electric spark, the influence of the collision angle and the contact point speed on the quality of welding of pipes with a tube grid of a heat exchanger were investigated. An algorithm for estimating welding zones is proposed. The applicability of the algorithm is tested on pairs of pipe made of alloy AD1 + tube made of alloy AMg6.

Purification of water from dissolved gases in a film unit with discrete-rough walls

This paper analyzes the use of a highly effective film unit for water purification from dissolved corrosive gases, in order to increase the resource efficiency and reliability of various equipment using water circulation systems at industrial plants and thermal power plants. The unit consists of a vertical bundle of tubes contained in tube grids and operates in the upward co-current gas and liquid in a pipe. The gas moves at a speed of 10 – 30 m/s (strong interaction of phases) and carries a liquid film from the bottom up. In this mode, there is a significant intensification of heat and mass transfer (5 – 15 times) in comparison with counter current. In addition, the inner surface of the tubes may have artificial discrete roughness (rectangular projections), which further increases the effectiveness of the processes. The paper presents the mathematical model and the efficiency calculation results for a film contact device with rough walls at strong phase interaction. The mathematical description is based on the models of the flow structure and the diffusion boundary layer. Expressions are given for calculating the mass transfer coefficient in a turbulent film with co-current gas, as well as parameters of the flow structure model in a contact tube. The main parameters of the equation for calculation of the mass transfer coefficient are the dynamic friction velocity on the interfacial film surface and the dimensionless thickness of the viscous sublayer. The dynamic speed is calculated using the equation of balance of forces in the contact tube, and the dimensionless thickness of the viscous sublayer-based on the known values on the plate adjusted for the phase interaction conditions. The cell model of the flow structure is used, and an expression is obtained for calculating the concentration profile of gas dissolved in water at the height of the pipes. The paper also presents an expression to calculate the number of cells in a complete mixing. The paper presents the calculated and experimental dependences of decarbonization efficiency for tubes with smooth and rough walls. The influence of spacing between roughness elements (projections) on water purification efficiency is shown. Conclusions are made about the design of a unit with a rising film at higher concentrations of dissolved gases in the water.

MANAGEMENT OF PATIENT DOSES FROM DIGITAL X-RAY CHEST SCREENING EXAMINATIONS.

An anthropomorphic phantom study was carried out in 2013-14 in two hospitals, one located in Russia (Mariinsky Hospital, Saint Petersburg) and the other in Sweden (Skåne University Hospital, Malmö). The aim of the study was to investigate the possibilities to reduce the patient dose from digital X-ray chest screening examinations. The existing chest imaging protocols were adjusted by changing the tube voltage, total filtration and grid in order to determine the most dose-effective combination of the examination parameters. It was possible to achieve up to 50 % dose-area product (DAP) and 30 % effective dose reduction by raising the tube voltage from 100 to 125 or 150 kV, and simultaneously decrease the total filtration to the minimum allowed by the X-ray unit (3 mm Al). The absence of a grid allowed to further reduce the DAP and effective dose by up to 80 %. Comparison between Russian and Swedish X-ray units showed the same trend in DAP and effective dose reduction, but the absolute dose values were lower by almost a factor of 10 for the Swedish units due to different image receptors and automatic exposure control settings.

Labware, Lab Supplies, and Microplates

Labware, Lab Supplies, and Microplates

Research of X-ray pulsar navigation simulation source

As an autonomous navigation method, X-ray pulsar navigation can provide position, timing and attitude information for various spacecrafts. Since the X-rays (1-20 keV) from the pulsar can not penetrate the earth atmosphere, an X-ray source in laboratory needs to be set up to test and calibrate the detector. In this paper an arbitrary X-ray pulse source to simulate the neutron pulsar signal is proposed. The main components of the simulation source are a grid controlled X-ray tube and arbitrary pulse generation electronics. With the arbitrary pulse voltage applied to the tube grid, the X-ray intensity is controlled. Through electron optics design, the tube electrode parameters are optimized. A grid controlled X-ray tube is fabricated and tested. Using a micro-channel plate detector to detect and reconstruct the generated X-ray pulses, the similarity between the accumulated profile and the original pulsar profile is better than 95%. The frequency stability of the pulsar source emulator is about 2×10-11.

An analog modulated simulation source for X-ray pulsar-based navigation

In this paper a high resolution X-ray simulation source is proposed and designed to verify the navigation based on X-ray pulsar in the simulation experience system. The simulation source consists of an arbitrary signal generator and a grid controlled X-ray tube. According to the grid tube's characteristic curve, the data of the pulsar standard pulse template are converted. Then using the method of direct digital frequency synthesis, the converted data are synthesized to waveforms, called the analog modulated grid voltage. In the grid controlled X-ray tube, the grid voltage changes the number of electrons hitting on the target and controls the X-ray intensity. With an analog modulated pulse profile applied on the tube grid electrode, the tube will emit X-rays which will match photons' statistical distribution and simulate the X-ray pulsar profile extremely well. The properties of Crab pulsar simulation source are tested in X-ray pulsar navigation simulation experience system. The results of the test are as follows: Comparing the tested pulse profile with the standard pulsar profile, we have time correlation coefficient is 0.9774, and frequency correlation coefficient is 0.9853. The X-ray photon flux is 1.90 ph·cm-2·s-1, the pulsed fraction is 76.15%, and the half-width half maximum is 1.879 ms. These results show that the X-ray simulation source has several merits, such as: strong ability to simulate the X-ray, low cost and simple operation. So it is an important means for the improvement of X-ray pulsar navigation.

Super High-Rise Building (H =266m) of New Concrete Core Tube and Assembly Integral Spatial Steel Grid Cassette Tube in Tube Hybrid Structure Research and Design

With the development of economy and society, urban construction rose to a new level in China. High-rise and super high-rise building increase rapidly. In the high-rise and super high-rise buildings (H≥150 m), the structural system usually adopts the conventional reinforced concrete, including frame tube structure, tube in tube structure, steel frame with reinforced concrete core tube hybrid structure and tube in tube steel - concrete mixed structure. These traditional structural systems often lead to the problems of fat beam fat column and high expenditure, which is not economic and unfriendly to the environment. This paper not only presents a new type of concrete core wall and prefabricated space steel grid cassette tube in tube structure system, but also discusses the superiority of the new type structure through the innovation and practice of a super high (266 m) five-star hotel and office building integrated engineering construction.

Development of material and manufacturing technology for tubes with a collar in order to protect the metal tube grid of a Klaus boiler from the action of high temperature

In order to clean hydrocarbon gases, enterprises of the oil, oil processing and gas industries use various absorption methods with application of ethanol amine solutions and other alkaline adsorbants. During this cleaning of hydrocarbon gases from sulphur compounds there is formation of highly toxic hydrogen sulphide. The most widespread method of utilizing hydrogen sulphide gases is processing them into elementary sulphur by the Klaus method [1]. In a recovery boiler with combustion of hydrogen sulphide the temperature in its upper part is held steadily at the level of 1350°C. Here it should be noted that various nonstandard situations are possible, particularly with start-up for the boiler after maintenance when the temperature reaches 1550°C. The gas mixture contains 47% (wt.) H 2 S, 23% (wt.) SO 2 , and 30% (wt.) N 2 . Metals normally used in chemical engineering are not suitable for operation at these high temperatures, since there is chemical corrosion of them, loss of strength, and as a result structural failure. Protection of the tube grid of a recovery boiler from the action of high temperature is obtained by two methods. The first method is the application of high-temperature coatings and it is the simplest, although due to strongly differing linear thermal expansion coefficients of the coating material and metal the service life of this protection is short. The second method is the use of tubes with a collar made of refractory material that is much more effective although it requires considerable time for their installation. In addition, with periodic maintenance for the recovery boiler replacement of individual (damaged) elements is possible. We consider a method for protecting a metal tube grid by means of tubes with a collar made of refractory material (Fig. 1). The geometric shape of a tube with a collar in the form of a six-sided prism provides protection from the action of high temperature for the tube grid itself and part of the metal tube. These tubes are made both in our country and abroad (Table 1). Within the composition of the metal of Lafarge tubes there is a greater amount of aluminum oxide, and as a consequence they have higher heat resistance properties than the tubes of domestic firms. The manufacturing technology for these tubes consists of several stages. In the first stage, they are formed by slip casting or extrusion, then dried and calcined. In the second stage, semi-dry compaction is used to form a six-sided prism with a hole that is also dried and calcined. Then these two parts are glued with a high alumina cement or high-temperature glue based on orthophosphoric acid in a special attachment providing coaxiality for joining two tubes. From the results of marketing studies, the requirement for these tubes by Russian enterprises is estimated at 20‐25 thousand per year. The main disadvantages of these tubes (in the opinion of the main customer enterprises) are: • breaking in the area of the glued joint during transport; • deviation from the prescribed geometric shape, particularly with respect to coaxiality;

Phase formation and corrosion behavior of nitrogen implanted Zr–Sn–Nb alloy in alkaline environment

Fretting induced corrosion occurring at the tube–grid contact is a very important problem for cladding materials and ion implantation has been considered an effective technology capable of improving the corrosion resistance of fuel cladding material without noticeably changing in dimensional integrity. In this paper, Zr–Sn–Nb specimens were implanted by nitrogen with fluence range from 5 × 10 16 to 4 × 10 17 ions/cm 2, and then subjected to electrochemical study in a solution with pH = 10 in order to determine the optimum fluence that can give good corrosion resistance in a simulated nuclear reactor condition. Glancing angle X-ray diffraction (GAXRD) was employed on the implanted to understand phase formation with increasing fluences. The depth profile of the oxides in the scale was analyzed by Auger electron spectroscopy (AES). The results showed the corrosion resistance of Zr–Sn–Nb was sensitive to the ion fluence and the substrate temperature during the implantation. The alloy implanted at below 473 K exhibited an inferior corrosion resistance to the unimplanted sample irrespective of the ion fluence. A drastic increase in the resistance to pitting corrosion in alkaline solution of the implanted alloy, were found to be associated with the formation of ZrN layer with a stoichiometric ratio of N to Zr. The worse corrosion resistance of the alloy implanted at below 473 K may be attributed to the increase in structural defects produced by ion bombardment.

Small-size pulsed X-ray source for measurements of scintillator decay time constants

A small-size short-pulsed X-ray source is described whose main components are a three-electrode X-ray tube operating at 30 kV and 0.5 A and a fast GaAs modulator connected coaxially to the tube grid. The ultimate parameters of the source are subnanosecond pulse duration and 100-kHz repetition pulse rate. The detection system allows the measurements to be carried out in the 200-800 nm spectral range over the time intervals from 0.5 ns to 50 /spl mu/s with resolution not worse than 0.1 ns. The decay time curves of an organic scintillator and CdI/sub 2/, Gd/sub 2/O/sub 2/S:Pr, and Cs/sub 2/NaCeCl/sub 6/ crystals are presented.

A source of short X-ray pulses

A small-sized source of short X-ray pulses is described, whose basic components are a three-electrode X-ray tube operating at 30 kV and 0.5 A and a fast GaAs modulator connected coaxially to the tube grid. The limiting operating parameters of the source are a subnanosecond pulse duration and a pulse repetition rate as high as 100 kHz.