• Transactions of Materials Processing
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• v.11 no.6
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• pp.495-502
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• 2002

The welding pressure in extru bending process is affected by the shape of welding chamber of porthole die. It is very important to increase the welding pressure when the tube should be extruded particulary from four billets of the materials. The high circumferential stress of the tube can make the welding pressure increase during the extru-bending. In order to increase the circumferential stress, it is necessary to make the billets pass through the narrow gap between the conical die and the conical plug. This paper describes the welding pressure by the experiments and the analysis with the two types of the chamber. One of them is the chamber between the flat die and straight mandrel, and the other one is the chamber between the conical die and conical plug. The results of the experiments and the analysis shows that the conical chamber makes the welding pressure increase by the effect of the reducing diameter of tube and the welding pressure by the conical dic and plug is stronger than the welding pressure by the flat die and straight mandrel.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.110-114
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• 2001

The welding pressure in porthole die extrusion is affected by the shape of welding chamber. It is very important to increase the welding pressure when the tube is used particulary as the materials of hydroforming processing. The high circumferential stress of the tube would make the welding pressure increase during the porthole die extrusion. In order to increase the circumferential stress, it is necessary to make the billets pass through the narrow gap between the conical die and the conical mandrel. This paper describes the welding pressure by the experiments with the two types of the chamber. One of them is the chamber between the flat die and straight mandrel, and the other one is the chamber between the conical die and conical mandrel. The result of the experiments show that the conical chamber makes the welding pressure increase by the effect of the reducing the diameteres of tube.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.637-644
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• 2022

In this study, the flow characteristics according to the shape of the vortex nozzle was studied by numerical analysis and the amount of microbubble generation was measured experimentally. The shape of the vortex nozzle is cylindrical, diffuser, and conical type. The axial fluid velocity in the induced tube gradually increased from the inlet to the outlet. In particular, the fluid velocity in the nozzle part increased rapidly. The velocity distribution of the fluid at the inlet of the induced tube showed that the flow rotates counterclockwise in the outer region and the inner center of the induced tube. At the outlet of the induced tube, the cylindrical and conical type showed rotational flow, and the diffuser type showed irregular turbulent flow. The dimensionless pressure ratio 𝜂 of the inner region of the induced tube was lower than that of the outer region. Also, 𝜂 near the outlet of the induced tube in cylindrical and conical type showed a similar tendency to the inlet area. At the outer region of inlet of induced tube, intense vorticity was observed on the wall and in lower region. At the inner region of inlet of induced tube, intense vorticity was observed on the inner wall of the induced tube and in the central region of the inlet of the induced tube. At the outlet of induced tube, in the case of the cylindrical and conical type, intense vorticity was observed near the inner wall, the diffuser type showed irregular strong vorticity inside the tube. The total number of bubbles measured was the most in the cylindrical type, and the microbubbles less than 50mm occurred the most in the conical type.

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.7-13
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• 2015

Vortex tube is a thermal static device that separates compressed air into hot and cold streams. In general, the cooling efficiency of vortex tubes is lower than that of traditional air conditioning equipment and vortex tubes are mainly used for industrial spot cooling applications because of their quick responses. In this study, conical frustums are employed in the nozzle chamber to improve the cooling performance. Conical frustums can be used to decrease the ineffective mass fraction that directly passes through the cold exit without energy separation. The shape optimization of conical frustums has been performed using full factorial design. It is found that the height of frustums has the largest main effects on the cooling performance. Computational results show that the cooling performance can be increased by about 10% within the considered range of the design parameters. This is because the ineffective mass fraction toward the cold exit is decreased by about 20%.

• Journal of Korean Vacuum Science & Technology
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• v.2 no.1
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• pp.1-8
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• 1998

The uniform distributed pumping model is used to derive analytic expressions of the pressure profile for the molecular flow regime in linearly tapered or flared(conical or pyramidal) tubes with wall sorption. The concept of transmission conductance for sticky tubes of arbitrary shape is newly introduced to calculate the transmission probability using the pressure profile. The transmission probability obtained analytically for a conical sticky tube is compared with that from the Monte Carlo simulation.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.274-281
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• 2018

Experimental studies of the hydrodynamic performance of the draft tube conical spout-fluid bed (DCSF) were conducted using pharmaceutical pellets. The experiments were carried out in a DCSF consisted of two sections: (a) a conical section with the cross section of $120mm{\times}250mm$ and the height of 270 mm, (b) a cylindrical section with the diameter of 250 mm and the height of 600 mm. The flow characteristics of solids were investigated with a high speed camera and a pezoresistive absolute pressure transducer simultaneously. These characteristics revealed different flow regimes in the DCSF: packed bed at low gas velocities, fluidized bed in draft tube at higher gas velocities until minimum spouting, and spouted bed. The stable spouting was identified by the presence of two dominant frequencies of the power spectrum density of pressure fluctuation signature: (i) the frequency band 6-9 Hz and (ii) the frequency band 12-15 Hz. The pressure drops across the draft tube as well as the annulus measured in order to better recognize the flow structure in the DCSF. It was observed that the pressure drop across the draft tube, the pressure drop across the annulus, and the minimum spouting velocity increase with the increase in the height of draft tube and distance of the entrainment zone, but with the decrease in the distributor hole pitch. Finally, this study provided novel insight into the hydrodynamic of DCSF, particularly minimum spouting and stable spouting in the DCSF which contains valuable information for process design and scale-up of spouted bed equipment.

• Advances in nano research
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• v.13 no.6
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• pp.545-559
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• 2022

This paper studies the buckling response of nonuniform functionally graded micro-sized tubes according to the high-order tube theory (HOTT) and classical beam theory (CBT) in addition to nonlocal strain gradient theory. The microtube is made of axially functionally graded material (AFGM). Both inner and outer tube radiuses are changed along the tube length; the microtube is the truncated conical type of tube. The nonlinear partial differential (PD) the formulations are obtained on the basis of the energy conservation method. Then, the linear and nonlinear results are computed via a powerful numerical approach. Finally, the impact of various parameters on the stability of axially functionally graded (AFG) microtube regarding the buckling analysis is discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.42-51
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• 2000

The performances of the simple expansion, perforated tube, and conical-connector type as an exhaust muffler are shown in this study. Applying a model in which the method of four-pole parameter is used makes theoretical estimation of the insertion loss. Experiment is performed for the measurement of the insertion loss under four cases according to the variation of the tail pipe length. By comparing the theoretical prediction with the experimental results, the validity of the modeling using the method of four-pole parameter is verified. The personal computer simulation programs for the above mentioned theory on the muffler design have been developed and exhaust sound level measurements have been carried out for simple expansion muffler, conical-connector muffler, perforated tube mufflers and the combined type of conical-connector and simple expansion muffler. The measured results for attenuation characteristics of noise for each muffler are compared with the computed theoretical results to verity the confidence and applicable limits of the theoretical equation derived.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1009-1014
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• 2001

A numerical investigation on nonlinear oscillations of gas in an axisymmetric resonant tube is presented. When a tube is oscillated at a resonant frequency, acoustic variables such as density, velocity, and pressure undergo very large perturbation, often described as nonlinear oscillation. In order to analyze these phenomena, axisymmetric 2-D nonlinear governing equations have been derived and solved numerically. Numerical simulations were accomplished for cylindrical, conical, and 1/2 cosine-shape tubes, which have same volume and length. For conical and 1/2 cosine-shape tubes, very large variation of pressures can be induced without shock formation except the cylindrical tube. In addition, the results well agree to those of 1-D simple model analysis.

• International Journal of Fluid Machinery and Systems
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• v.3 no.1
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• pp.91-101
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• 2010

Based on the one-dimensional stability analysis, the self-excited oscillation in hydraulic power generating systems was studied by a simple experiment and numerical simulation. It was shown that a cavity in a conical diffuser can cause surge. With the diffuser, a high amplitude and low frequency oscillation occurs at low cavitation number. This oscillation was not observed with the straight pipe. It was confirmed that the diffuser effect of the draft tube can be the cause of the full load surge in hydraulic power system. Numerical results were also analyzed to check the validity of the one-dimensional stability analysis.