Analysis of co-generation combustion chamber inlet line

Purpose The catastrophic failures of these thick-wall cylinders are mainly due to the presence of inherent cracks in the material. The present study aims to deal with the analysis of stress for a given range of inside pressure. The paper deals with the calculation of radial and tangential stresses for various external pressure-to-internal pressure ratios and external radius to internal radius of the thick-walled cylinder. Design/methodology/approach The inlet line to the combustion chamber normally has an internal diameter of 150 mm and has a thickness of 25 mm. Normal temperature of the working fluid is about 80°C and the outside temperature is kept as room temperature. The present work deals with the stress analysis of the inlet line with and without internal crack. Also the stress intensity factors are calculated to check with the fracture toughness. Analysis is done both theoretically and by FEM by using the well-known software ANSYS. Findings Results show that the radial stress is independent of the external radius-to-internal radius ratio, while the tangential stress increases. Practical implications In process industries like nuclear or chemical, etc., structures in the form of thick-walled cylinders play a vital role, as its failure can affect humans and the environment. Because of this, the design and analysis of the above cylinders are of much significance. Originality/value Due to constant or cyclic operating pressure of pressure vessels and its corresponding pipelines usually in the form of thick-walled cylinders, reliability of the materials and structures used is of critical importance, as its failure can be deadly and possess lethal dangers when the cylinder contains flammable, toxic or reactive working fluid. The major ruling factors for the failure are none other than stress-related defects and presence of cracks.

Analysis of Radiofrequency Lesions in Egg Whites in Vitro Produced by Application of the Tew Electrode for Different Temperatures and Times

BACKGROUND: Understanding the size and shape of radiofrequency lesions is important to reduce side effects when applied to patients.OBJECTIVES: To investigate the radiofrequency lesions produced by the application of the Tew electrode for different temperatures and times.METHODS: The white from a fresh hen’s egg was placed in a rectangular glass container and warmed to 37°C. After immersion of the Tew electrode in the egg white, radiofrequency lesions were produced at 65°C, 70°C, 75°C, 80°C, 85°C and 90°C. For each temperature, photographs were taken at 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s and 120 s. The size of the lesion was measured at each temperature and time. A mixed model was used to analyze the data.RESULTS: The size of the lesion increased with increasing temperature and time. There were statistically significant differences in the size of the internal radius between the 65°C and 70°C groups and the 70°C and 75°C groups, as well as in the 70°C and 75°C groups in the size of the external radius and the 60°C to 80°C groups in the size of the distal radius. The maximum lesion size was produced at 90°C and 120 s, and was 1.06±0.16 mm in internal radius, 0.37±0.15 mm in external radius, 0.39±0.04 mm in distal radius.CONCLUSION: The Tew electrode produces lesions following the contour of the tip, and the internal radius is larger than the external and distal radius. The best combination of temperature and time for lesioning using the Tew electrode is 80°C, for 60 s to 90 s.

Remarks on Residual Stress Measurement by Hole-Drilling and Electronic Speckle Pattern Interferometry

Hole drilling is the most widespread method for measuring residual stress. It is based on the principle that drilling a hole in the material causes a local stress relaxation; the initial residual stress can be calculated by measuring strain in correspondence with each drill depth. Recently optical techniques were introduced to measure strain; in this case, the accuracy of the final results depends, among other factors, on the proper choice of the area of analysis. Deformations are in fact analyzed within an annulus determined by two parameters: the internal and the external radius. In this paper, the influence of the choice of the area of analysis was analysed. A known stress field was introduced on a Ti grade 5 sample and then the stress was measured in correspondence with different values of the internal and the external radius of analysis; results were finally compared with the expected theoretical value.

Axial Stiffness of Multiwalled Carbon Nanotubes as a Function of the Number of Walls

The axial stiffness of multiwalled carbon nanotubes (MWCNTs) is studied as a function of the number of walls and their parameters. It is demonstrated that the axial stiffness is determined only by several external shells (usually 3–5 and up to 15 for the extremely large nanotubes and high elongations) which is in good agreement with the experimentally observed inverse relation between the radius and the Young modulus (i.e., stiffness) of MWCNTs. Such behavior isa consequence of the van der Waals intershell interaction. An interpolating formula for the MWCNT's actual axial stiffness as a function of the external radius and the elongation of a tube is obtained.

Application of Thomas-Fermi model to fullerene molecule and nanotube

Semiclassical description, based on electrostatics and Thomas-Fermi model is applied here to calculate dimensions of the electronic shell of a fullerene molecule and a nanotube. The internal radius of the electronic shell of a fullerene molecule, calculated within the framework of the model is 0.2808 nm. The external radius is 0.4182 nm. The experimental values are 0.279 nm and 0.429 nm correspondingly. This shows that semiclassical approach provides rather good description of the dimensions of the electronic shell in a fullerene molecule. Two types of dipole oscillations in a fullerene molecule are considered and their frequencies are calculated. Similar calculations are performed for a nanotube also. For a nanotube with a radius of the cylinder of the ions, Rn = 0.7 nm, the internal radius of the electronic shell, calculated within the framework of the model is 0.577 nm. The external radius is 0.816 nm. Three types of dipole oscillations in nanotube are considered and their frequencies are calculated.

A Proposed Method for Anticipated-Allowable Piping, Mechanical and Seismic Nozzle Load Design

Nozzle loads impose an important constraint in the design of pressure containing equipment. Pressure vessels are connected to external piping by a nozzle welded to the vessel wall and a flange connection. The nozzle loads are due to the piping expansion or contraction caused by the difference between the installation and operating temperatures. Pressure vessel designers need to know, early in the design process, the piping loads that a nozzle may be subjected to. It is important that such loads do not overstress the vessel-nozzle intersection. However the actual piping loads many times are only determined long after the pressure vessel materials are ordered and even procured. The intention of this paper is to provide an empirical but also realistic load set as a function of nozzle external radius, r, vessel external radius, R, vessel thickness, t, and allowable stress, S. The basis of this work is practical experience and also existing theoretical work. This will be a valuable tool in the hands of the pressure vessel mechanical designer. It will allow him to prescribe an early-heuristic estimate of the allowable nozzle loads that will cover external piping loads. These “anticipated” or design loads will allow a pressure vessel mechanical designer to reinforce his design early into the manufacturing of a pressure vessel. Finally, piping engineers will know the terminal allowable loads and thus determine the best piping routing and support arrangements if space constraints allow it.