Papers by Keyword: Tube

Abstract: In a nuclear power plant, the tubes array component that constitutes a cooling water heat exchanger is often subjected to cold and hot fluid flow impact, which are affected by axial stress due to thermal strain cause by these cold and hot flow impact. So, the dynamic characteristics of this tube would be changed significantly by this flow impact and even lead to failure. The axial load caused by thermal strain, the cold and hot flow impact, also markedly changes the dynamic characteristics of the tube.

Abstract: A technique for studying contact stresses in the connection of heat-exchange tubes with tube sheets using roller rolling is described. Formulas for the determination of contact stresses, taking into account the formation of local deformation of the tube due to force action of each roller and features of axial movement of the tool spindle are given. Calculation was based on the assumption of medium continuity, known relations between normal stresses and deformations, as well as experimental oscillograms of the process.

Abstract: Nanofluid is an efficient fluid when used in heat exchanger system because of its larger thermal conductivity compared to conventional fluids such as water, oil, and ethylene glycol (EG). This research used MnFe₂O₄ nanoparticle due to its higher magnetic sensitivity compared to other ferrite nanoparticles and larger thermal conductivity than TiO₂. This research used the MnFe₂O₄ nanoparticle with a combination of EG-Water base fluids in ratios of 40:60, 60:40, and 80:20. MnFe₂O₄ nanofluid mixed with EG-Water base fluids was made using the two-step method with 0.05% MnFe₂O₄ volume fraction in each base fluid ratio. This research used shell and tube type heat exchanger with heat temperature of 60°C and cold temperature of 26°C that were carried out at volumetric flowrate in each base fluid ratio for 0.22 l/m, 0.44 l/m, and 0.66 l/m. This research aimed to find the best combination ratio of EG-Water in thermophysical (thermal conductivity, specific heat, density, and viscosity) and to find the effect of volumetric flowrate variations on the heat exchange characteristics (the Reynold number, the Nusselt number, ∆T LMTD, convection coefficient, heat transfer, and overall heat transfer coefficient). The results of this research were that the sample of EG-Water with 40:60 ratio had the best heat transfer characteristics compared to samples with 60:40 and 80:20 ratios. Meanwhile, for the volumetric flow rate, a higher volumetric flow rate resulted in a larger result.

Abstract: The manufacture of tubes by a fixed mandrel drawing is one of the technologies in the manufacture of seamless tubes. This is the oldest tube drawing method. It uses a mandrel at the end of the die to shape the internal diameter of the tube. This process is slow and the area reductions are limited (lengths of tubes are limited), but it gives the best inner surface finish of any of the processes. The use of a fixed mandrel by the drawing of small-diameter tubes makes it possible to increase the accuracy of the inner surface and improve the quality. The paper presents the results of solving a partial task in this area. It deals with the reconstruction of the microgeometry of the inner surface of a tube drawn by a fixed mandrel. Tubes (STN 41 1353) were drawn through dies with different reduction angles. There were grounds the straight and spiral grooves on used fixed mandrels. On the inner surface of the tube were formed grooves after drawn that had a different surface roughness compared to the mandrel surface. The paper graphically presents the morphology of obtained surfaces under various conditions (reduction angles, straight/spiral grooves on the fixed mandrel) as well as measured surface roughness values. At the end of the paper, the knowledge gained through experimental research are summarized.

Abstract: A large number of blockage appeared in gas wells and pipeline appeared, which causedplugging, corrosion and the increasing of wellbore pressure difference, and seriously affect thenormal production of gas well of problems. In this paper, the water quality of produced water fromthe severe cases of single wells or pipeline water were analyzed, also include the composition ofblockage and core with the chemical volumetric method (CVM) , X-Ray Diffraction (XRD) and x-rayfluorescence (XFS) method. Meanwhile, the core powder was leached in simulated acid worksolution, and then the leaching solution was analyzed with CVM. The experimental results show thatThe produced water has high salinity, high contents of Ca2+, Ba2+ and Sr2+, low pH value, which leadto corrosion and scaling. The main components of the blockage are acid insoluble strontium sulfate(barium) scale or corrosion product or mixture of corrosion and CaCO3 scaling product. Ca2+, Ba2+and Sr2+ were easy to scale in wellbore or pipeline when they encountered other produced water fromdifferent formation. The Ca2+, Mg2+, Ba2+, Sr2+ and Fe 2+/3+ mainly derived from the dissolution offormation debris in formation water and working fluid (especially acidic working fluid) to reservoirrock, so the salinity of the produced water increased, and the trend of scaling and corrosion alsoincreased with the gas field development.

Abstract: Technological processes have a significant influence on the properties of the metallic formed pieces during production. Due to the plastic deformation, the shape of the component is changed and the degree of the structural anisotropy is increased - the orientation of the grain boundaries in the different parts of the component. It is important to identify these changes, to analyse them and optimize the technological processes. We get an important knowledge of relationship “technological parameters – microstructure – properties”. The article presents the results of the solution of a partial task from this area. It deals with changing of the geometric shape of the component when it is deformed. Specifically, the tubes (material EN SPT 360, STN 411 353) were drawn through the dies with different reduction angles. The dimensions (length and angle), roundness, cylindricity, coaxiality and surface roughness were evaluated.

Abstract: The purpose of this research is to determine the state inside the material using finite-element analysis and to improve the performance of a rotary-draw bending forming by clarifying the mechanism of wrinkle generation. An analytical model of rotational drawing was made by using the general-purpose nonlinear finite-element analysis software MSC Marc, and the analytical results were compared with experimental results to verify the validity of the model. Furthermore, the mechanism of wrinkle generation was investigated. With the progress of processing, wrinkles occur not in the R part but in the original tube-side straight-tube part. The coefficient of friction between the tube material and the R portion of the bending mold promotes the occurrence of wrinkles and the growth of the generated wrinkles. Because wrinkles occur even if the friction coefficient between the tube material and bending mold R part is ignored, the generation condition of wrinkles also depends on parameters other than the friction coefficient.

Abstract: Flexible-bending is an advanced bending method, especially suitable for small batch production of tubes. The shape of forming parts is mainly related to the offset of the bend die instead of the geometry of it. Based on flexible-bending technology, 3D bending of tubes was carried out by finite element method and the effects of primary parameters on the bending results were studied. The analysis results showed that3D continuous bending of tubes can be obtained by flexible-bending process; die offset, offset speed and feeding speed of tube have a great influence on the bending effect. Bending experiments of 3D tube were carried out by flexible-bending equipment and bending radii of the forming part were measured, the results were very close to that of simulations which proved the effectiveness of simulation.

Abstract: This paper presents the determination of Remote Field Testing (RFT) frequencies to accomplish the inspection of duplex stainless steel tubes grade ASME/ASTM SA 789. The tube specimen was 25.4 mm of outside diameter, and thickness of 1.65 mm with the different artificial flaws. A dual-pickup coils type of RFT probe was employed to inspect the specimen by inserting a probe within the tube. Optimum of testing frequency Range was determined based on an eddy current through transmission generation to produce different magnetic field density. RFT inspection frequency range for duplex stainless steel was consequently determined from 5 to 25 kHz which was different than those inspection frequencies of general ferromagnetic steel tube. In the experiment, calculated frequencies were then generated to the Eddy current (ET) and RFT probes for detecting the flaws of the tube specimen. The inspection signals were specifically shown in function of impedance plane to identify the flaw characters. The results showed that the RFT can be utilized to quantify the wall loss levels of duplex stainless-steel tube better than the ET. Especially, phase angle of inspection signals can be used to evaluate the different depths of the wall losses. Sensitivity of RFT showed the detection performance at minimum 20% of tube wall loss.

Abstract: Chassis or cabin designs in the transportation sector are currently manufactured out of several single structural elements. To save handling steps and energy intensive joining processes and furthermore support lightweight design, bending processes can be used that offer the direct production of structural parts that incorporate the functionality of several single elements. In recent years, several processes for the kinematic bending of three-dimensional tubes and profiles have been developed. Additionally, three-roll push bending has gained in importance in manufacturing three-dimensional tubes. In this kinematic process, three-dimensional bending is achieved by continuously changing the bending plane relative to the workpiece during the forming process. Several studies exist that investigate the mechanisms that lead to three-dimensional bending contours. These were, however, based on the generation of empirical models, e.g. characteristic maps. Up until now, no analytical model exists, which describes the process of bending three-dimensional tubes in a comprehensive manner, especially taking into account tube torsion. In the following case study, the tube rotation needed to produce helices is measured and compared to helix radii and helix height. The results were subsequently used to set up an analytical model, which, first of all, describes the tube rotation needed to produce the torsion of the investigated helices and, more importantly, can be generalized to describe the tube rotation needed for the torsion of arbitrary bending curves.