Study of Dynamic Stresses in Pipe Networks and Pressure Vessels Using Fluid-Solid-Interaction Models

2007 ◽  
Author(s):  
Philip Diwakar ◽  
Lorraine Lin
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Traditional Approach ◽  
Fluid Model ◽  
Pressure Vessels ◽  
Piping System ◽  
Atmospheric Conditions ◽  
Flow Induced Vibration ◽  
Element Analysis ◽  
Fluid Solid Interaction

A lack of understanding of the fluid-structure interactions has resulted in a number of infamous structural failures in the past. For example, the collapses of the Tay Bridge in Scotland in 1879, the Tacoma Bridge in 1948 and three tall cooling towers in Ferrybridge/England in 1965 have been intrinsically related to fluid forces acting on the structure. Flutter, flow-induced vibration, divergence and related phenomena may be studied using the Fluid-Solid-Interaction (FSI) approach. This paper gives three examples of the FSI approach and shows the innovative application of state-of-the-art computational methods to improve realism and accuracy in engineering analyses. Case 1: Study of Hydrodynamic Sloshing Loads: The sloshing of liquid in large vessels under seismic loads is a timely topic. The movement of the free surface of the liquid is simulated using a two-phase volume of fluid model at various liquid heights. The transient forces generated by the fluid on the vessel wall and internals are superimposed as loads on a dynamic non-linear calculation and the fatigue and stresses are computed in an explicit finite element analysis. This approach calculates the local sloshing effects on internals as opposed to the traditional approach of using spring-mass elements. Case 2: Bending of Large Pipes due to Temperature Differentials: Pipe temperature differentials can be caused by either extremely cold liquids or hot liquids flowing at the bottom of a piping system while the top is exposed to atmospheric conditions. Differential expansion can cause pipe deformation resulting in pipe lift-off at its supports and failure at the weld locations and T-joints. Heat transfer from complex multi-phase flows was simulated using CFD. The predicted pipe wall temperatures were then input to an FEA grid and analyzed for heat transfer and thermal stresses. These stresses were compared to ASME standard allowable limits. Based on this analytical approach, a design guide for various diameters of flare header pipes, supports and tees has been established. Details of this paper were previously published in [Ref 1] and are not described in this paper. Case 3: Establishing velocity limits and line sizing criteria in pipes: The original guidelines in Fluid Flow Manuals were developed over the last fifty years based on project experience and economic and best practices technology of the time. The criteria have proven out as good, but overly conservative with regards to line size. Compressor discharge guidelines are based on the erosion velocity limits. Based on a dynamic analysis approach — using unsteady flow rates from compressors — stresses due to flow-induced vibration, noise and fatigue, hydraulic transients such as waterhammer effects for long lines (greater than 1000 feet), flashing and control valve cavitations may be studied. FSI was used to determine if the velocity limit guidelines hold in the current designs and use a parametric approach to mitigate the bottlenecking by supplying a simple fix to the problem. Furthermore the approach was used to define the correct velocity limit and establish optimal layout for the piping network.

Mitigation of Bending Stress and Failure Due to Temperature Differentials in Piping Systems Carrying Multiphase Fluids: Using CFD and FEA

2005 ◽  
Author(s):  
Philip Diwakar ◽  
Vibhor Mehrotra ◽  
Franklin Richardson
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Initial Stresses ◽  
Piping System ◽  
Atmospheric Conditions ◽  
Element Analysis ◽  
Pipe System ◽  
Piping Systems ◽  
The Dead ◽  
Piping Networks

The bending of large pipes due to temperature differentials between the bottom and top of the pipe is a very serious problem. The temperature differentials can either be caused by extremely cold liquids (such as methane or ethylene flowing from a lateral into a flare header) or hot liquids flowing at the bottom of a piping system (such as in a Vacuum transfer line) while the top is exposed to atmospheric conditions. In some cases liquids may be produced by Joule-Thompson cooling of high pressure cold gas as it expands through a safety-relief or emergency depressurization valve. The liquid so formed can accumulate, for example, on the dead leg side of a flare header. The differential expansion can deform the pipe so that it lifts off its supports. It takes a finite amount of time for the heat transfer by conduction to equilibrate the temperature to a more benign level. The initial stresses induced due to large thermal differential may even cause the pipe to crack in the region of the supports and T-joints to the laterals. This phenomenon has been observed in several industries, most predominantly in the petrochemical industry. This paper recounts the use of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) to study this important phenomenon. The liquid flowing from the lateral into the main header pipe is multiphase in the dispersed, stratified, slug or annular flow re´gime. Multiphase flows with heat transfer are analyzed using CFD. The temperatures on the walls of the pipe system are then transferred to the FEA and analyzed for heat transfer and thermal stresses. These stresses are compared to ASME standards to see if they are within allowable limits. This paper also recounts efforts to reduce the bending effect by preventing liquid accumulation on the dead leg side. Other methods that provide better supports for bent piping are studied. Further, methods of equilibrating the temperature faster to prevent the bowing of the pipe are also studied. It is hoped that this presentation will benefit people designing piping networks with varying liquid and vapor traffic by providing a safe environment free of cracks and spills.

Mitigation of Bending Stress and Failure Due to Temperature Differentials in Piping Systems Carrying Multiphase Fluids: Using CFD and FEA

2005 ◽  
Author(s):  
Philip Diwakar ◽  
Vibhor Mehrotra ◽  
Frank Richardson
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Initial Stresses ◽  
Piping System ◽  
Atmospheric Conditions ◽  
Element Analysis ◽  
Pipe System ◽  
Piping Systems ◽  
The Dead ◽  
Piping Networks

The bending of large pipes due to temperature differentials between the bottom and top of the pipe is a very serious problem. The temperature differentials can either be caused by extremely cold liquids (such as methane or ethylene flowing from a lateral into a flare header) or hot liquids flowing at the bottom of a piping system (such as in a Vacuum transfer line) while the top is exposed to atmospheric conditions. In some cases liquids may be produced by Joule-Thompson cooling of high pressure cold gas as it expands through a safety-relief or emergency depressurization valve. The liquid so formed can accumulate, for example, on the dead leg side of a flare header. The differential expansion can deform the pipe so that it lifts off its supports. It takes a finite amount of time for the heat transfer by conduction to equilibrate the temperature to a more benign level. The initial stresses induced due to large thermal differential may even cause the pipe to crack in the region of the supports and T-joints to the laterals. This phenomenon has been observed in several industries, most predominantly in the petrochemical industry. This paper recounts the use of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) to study this important phenomenon. The liquid flowing from the lateral into the main header pipe is multiphase in the dispersed, stratified, slug or annular flow re´gime. Multiphase flows with heat transfer are analyzed using CFD. The temperatures on the walls of the pipe system are then transferred to the FEA and analyzed for heat transfer and thermal stresses. These stresses are compared to ASME standards to see if they are within allowable limits. This paper also recounts efforts to reduce the bending effect by preventing liquid accumulation on the dead leg side. Other methods that provide better supports for bent piping are studied. Further, methods of equilibrating the temperature faster to prevent the bowing of the pipe are also studied. It is hoped that this presentation will benefit people designing piping networks with varying liquid and vapor traffic.

Conjugated Heat Transfer in Skirt Hot Box in Pressure Vessels

2006 ◽  
Author(s):  
Hossein Shokouhmand ◽  
Manoochehr Bozorgmehrian
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Temperature Gradient ◽  
Thermal Stresses ◽  
Weld Line ◽  
Pressure Vessels ◽  
Conductive Heat ◽  
Air Pocket ◽  
Cyclic Operation ◽  
Conjugated Heat Transfer

Pressure vessels are common equipment in oil, gas and petrochemical industries. In a hot containing fluid vessel, excessive temperature gradient at junction of skirt to head (weld line), can cause unpredicted high thermal stresses; Thereby fracture of the vessel may occur as a result of cyclic operation. Providing a hot box (air pocket) in crotch space is a economical, applicable and easy mounted method in order to reduce the intensity of thermal stresses. Natural convection due to temperature difference between the wall of pocket, will absorb heat near the hot wall (head of the vessel) and release that near the cold wall (skirt of the vessel), then the skirt wall conducts heat to the earth as a fin. This conjugated heat transfer removes the temperature gradient boundary at welded junction. This phenomena will lead the temperature gradient on the weld line from a sudden to smooth behavior, thereby the skirt-head junction, that is a critical region, could be protected from excessive thermal stresses. In this paper the profit of hot box and conjugated heat transfer in cavity has been demonstrated experimentally. As a result it is shown that the conductive heat transfer through the skirt (which acts as a fin) ensures the continuation of natural convection in the box. Also the governing equations has been solved numerically and compared with experimental results.

A Review of Temperature Reduction Methods in Codes and Standards for Pipe Supports

2020 ◽  
Author(s):  
Alex Mayes ◽  
Phillip Wiseman ◽  
Kshitij P. Gawande
Keyword(s):  
Heat Transfer ◽  
Computational Models ◽  
Thermal Stresses ◽  
Geometrical Parameters ◽  
Atmospheric Conditions ◽  
Closed Form Solutions ◽  
Temperature Reduction ◽  
Reduction Methods ◽  
American Society ◽  
Transient Thermal

Abstract American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF, Subparagraph NF-3121.11 does not require that thermal stresses in supports be evaluated. Historically, pipe support engineers have not been concerned with thermal stresses of pipe and component supports, but determining material temperature limits and allowable stresses have been a major role in designing and analyzing supports. Thus, heat transfer is often investigated in finding the temperature of pipe supports and parts of pipe supports that are not in direct contact with pipe or pipe components. There are also other Codes and standards that permit a reduction of temperature away from the outer surface of pipe or pipe components. In some but not all cases, Codes and standards explicitly address reduction of temperature for applications of utilizing thermal insulation. Additionally, the temperature distribution is established by specific geometrical parameters and their respective equations for employment by the pipe support engineer. These reductions are explored by utilizing fundamentals of heat transfer. Additionally, steady-state and transient thermal Finite Element Analyses (FEA) are used to establish computational models of simple geometric bodies in a range of atmospheric conditions. The effects of insulation on the thermal distribution are also represented through closed form solutions and FEA. The results of these analyses allow for assessment of, and recommendations for, the treatment of temperature reduction in Codes and standards.

Thermal Barrier Coating on IC Engine Piston to Improve Engine Efficiency

2017 ◽  
Vol 9 (1) ◽  
pp. 47 ◽  
Author(s):  
Balbheem Kamanna ◽  
Bibin Jose ◽  
Ajay Shamrao Shedage ◽  
Sagar Ganpat Ambekar ◽  
Rajesh Somnath Shinde ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Thermal Stresses ◽  
Mechanical Efficiency ◽  
Project Work ◽  
Element Analysis ◽  
Ic Engine ◽  
Engine Efficiency ◽  
Piston Crown ◽  
Barrier Coating

The piston is considered as most important part of I.C engine. High temperature produced in an I.C engine may contribute to high thermal stresses. Without appropriate heat transfer mechanism, the piston crown would operate ineffectively which reduce life cycle of piston and hence mechanical efficiency of engine. The literature survey shows that ideal piston consumes heat produced by burnt gases resulting in decrease of Engine overall Efficiency. In this project work an attempt is made to redesign piston crown using TBC on piston surface and to study its Performance. A 150 cc engine is considered and TBC material with different thickness is coated on the piston. 3D modeling of the piston geometry is done 3D designing software Solidworks2015. Finite Element analysis is used to calculate temperature and heat flux distribution on piston crown. The result shows TBC as a coating on piston crown surface reduces the heat transfer rate within the piston and that will results in increase of engine efficiency. Results also show that temperature and heat flux decreases with increase in coating thickness of YSZ.

Elastic-Plastic Analysis of Thick-Walled Toroidal Pressure Vessels

2008 ◽  
Author(s):  
R. Adibi-Asl
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Toroidal Shell ◽  
Piping System ◽  
Straight Pipe ◽  
Element Analysis ◽  
Process Industries ◽  
Piping Systems

Piping systems in process industries and nuclear power plants include straight pipe runs and various fittings such as elbows, miter bends etc. Elbows and bends in piping systems provide additional flexibility to the piping system along with performing the primary function of changing the direction of fluid flow. Distinctive geometry of these toroidal shell components result in a structural behavior different from straight pipe. Hence, it would be useful to predict the behavior of these components with acceptable accuracy for design purposes. Analytical expressions are derived for stresses set up during loading and unloading in a toroidal shell subjected to internal pressure. Residual stresses in the component are also evaluated. The proposed solutions are then compared with three-dimensional finite element analysis at different locations including intrados, extrados and flanks.

Development of Predicted Stress and Strain during Conventional and after Mitigation of Welded Aluminium-Manganese Alloy

2013 ◽  
Vol 762 ◽  
pp. 596-601
Author(s):  
F. Soul ◽  
M. Ateeg
Keyword(s):  
Heat Transfer ◽  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Stress And Strain ◽  
Manganese Alloy ◽  
Element Analysis ◽  
Longitudinal Residual Stress ◽  
Mitigation Technique

The trend in automotive, aircraft, and marine industries is the increasing use of sheet materials to reduce weight in components and optimize materials performance. Welding is the main fabrication and assembly process in many of these industrial applications. However, in using thin-shell structures in such applications, welding may results in significant residual stresses and out-of-plane distortion. Transient thermal stresses, residual stresses, and distortion sometimes cause cracking and mismatching of joints. High tensile residual stresses are undesirable since they can contribute to fatigue failure. The analysis and measurement of temperature and stresses in component are often too complex to conduct in practise, and thus finite element models provide feasible approach to examine these matters. In this paper, finite element analysis has been performed using the ANSYS package to study the behaviour of longitudinal residual stress and strain in a welded thin aluminium-manganese alloy. The model presented simulates conventional welding and welding with the introduction of welding mitigation technique for enhancement of heat transfer, in which a trailing heat sink was applied. The thermal profiles obtained using the mitigation technique is completely different from those obtained in the conventional cooling. The localized transient residual stress and through-thickness strain after applying a cooling sink are discussed. The transient residual stress behaviour was highly affected by the modified temperature distribution and magnitude due to introducing the heat transfer enhancement.

Coupled Thermomechanical Analyses for Thermal Shock of Ceramic/Metal Gradient Thermal Barrier Coatings

2008 ◽  
Vol 368-372 ◽  
pp. 1341-1343
Author(s):  
Jin Sheng Xiao ◽  
Yong Hua Cai ◽  
Zai Li Zhao
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Shock Intensity ◽  
Thermal Stresses ◽  
Thermal Barrier ◽  
Element Analysis ◽  
Barrier Coatings

A coupled and uncoupled non-linear thermomechanical finite element analysis using ANSYS have been carried out to analyze the heat transfer and associated thermal stresses during different simulated thermal shock processes, and the results of two analyses are discussed. It indicates that piezocaloric effect can be neglect when thermal shock intensity is mild and piezocaloric effect should be taken into account when thermal shock intensity is severe.

Investigation on the Failures Experienced in Deaerators and Solution Recommendation

2010 ◽  
Author(s):  
Aun Ming Lim ◽  
Simon Yuen
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Thermal Stresses ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Flow Induced Vibration ◽  
Element Analysis ◽  
Root Cause ◽  
Bottom Side ◽  
Refinery Plant

The internals in the deaerators of a refinery plant were reported to have experienced a series of failures since their installation in 1985. These failures included development of cracks in the floor plates, damage of supports and breakage of fillet welds. Two possible root causes were initially identified; thermal stresses due to transient conditions and flow induced vibration. The former cause was classified as unlikely since the deaerators were always operating on steady-state conditions. No cyclic operating conditions were imposed on these deaerators. Vibrations however posed as the most likely root cause for the series of failures. The refinery plant inspectors reported that vibrations on the deaerators, although have not been measured, could be physically felt. These vibrations appear to be continuous and increase linearly with load. A finite element analysis was performed to determine the natural frequency of the deaerators. Mode shapes predicted from this calculation show that vibrations could have caused the failures of the internals. Furthermore, the lowest natural frequency of the deaerators appeared to fall within the actual vibration frequency on site (∼20 Hz). Although not confirmed, it is highly suspected that the vibration was excited by the flow (low pressure steam). Several repair options were explored to overcome this problem. These options were concentrated in increasing the stiffness of the steam inlet pipe and the deaerator floor. Finite element assessments demonstrated that the current flexible deaerator floor was the reason for the low natural frequency. An option of introducing reinforcement strips to the bottom side of the floor was identified as the best option to increase the natural frequency of the deaerator and this is expected to overcome the vibration problem. Only one vessel was assessed but the results apply to the other vessels since they are similar in design.

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