scholarly journals The relationship between stress of plate-fin structures and emergency stop operation process in LNG heat exchanger

2021 ◽  
Vol 76 ◽  
pp. 77
Author(s):  
Hongqiang Ma ◽  
Shengxun Wang ◽  
Yue Xie ◽  
Xinmei Luo ◽  
Jianping Han
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Equivalent Stress ◽  
Equilibrium Temperature ◽  
Equilibrium Pressure ◽  
Operation Process ◽  
Maximum Equivalent Stress ◽  
Emergency Stop ◽  
Last Stage ◽  
The Relationship

For insuring the safe operation of LNG heat exchanger in the Emergency Stop Operation Process (ESOP), a numerical method is proposed to investigate the stress of Plate-Fin Structures (PFS) in that. The relationship between stress of PFS and ESOP is analyzed in LNG heat exchanger. The results will be obtained that the maximum equivalent stress of PFS is greater at the initial stage of ESOP than that at the last stage when the HMR pressure is more than 5 MPa. The maximum equivalent stress increases with the equilibrium temperature when is greater than 180 K and reaches peak value at the last stage of ESOP. The maximum equivalent stress is larger at the last stage of ESOP than the other stage and increases with the equilibrium pressure. When the temperature difference is more than 5 K in the ESOP, the influence of that is obvious for the stress of PFS. In the ESOP, the equilibrium temperature and temperature difference should be controlled within 240 K and 5 K, respectively.

Influence of Emergency Stop Operation for Strength of Brazed Structure With Rectangular Fins and Plates in Liquefied Natural Gas Heat Exchanger

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Hongqiang Ma ◽  
Xingpeng Song ◽  
Yemin Liu ◽  
Nuo Liang ◽  
Jianping Han ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Equivalent Stress ◽  
Liquefied Natural Gas ◽  
Structural Safety ◽  
Operation Process ◽  
Brazed Joints ◽  
Emergency Stop ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Peak Value

Abstract In order to ensure the structural safety of a liquefied natural gas (LNG) heat exchanger in emergency stop operation process, the strength of a brazed structure with rectangular fins and plates is investigated by means of the finite element method. The microstructure of brazed joints and brazing filler is tested by metallographic examination with a scanning electron microscope (SEM). The results show that the maximum shear stress is the main reason for the structural failure at the brazing seam while the brazed joint is mainly subjected to the maximum normal stress. The peak value of the Von Mises equivalent stress in brazed structure with rectangular fins and plates linearly increases with the HMR pressure when the temperature difference is less than 10 K between HMR and LMR. At the same time, the peak value of Von Mises equivalent stress also increases with the equilibrium temperature and temperature difference between LMR and HMR. The aggregation of the elemental Si in the brazed joints and brazing seam will exacerbate the structural safety of the brazed structure in the emergency stop operation process. The above results provide some constructive guidance for the emergency stop operational process for an LNG heat exchanger.

Mould Structure Optimization of the Biomass Molding Machine

2013 ◽  
Vol 330 ◽  
pp. 826-829
Author(s):  
Jian Feng Meng ◽  
Bai Tao Feng ◽  
Yu Ping Dong
Keyword(s):  
Renewable Energy ◽  
Curve Fitting ◽  
Optimization Model ◽  
Equivalent Stress ◽  
Structure Optimization ◽  
Molding Machine ◽  
Key Technologies ◽  
Maximum Equivalent Stress ◽  
The Relationship

Biomass is a renewable energy. Its curing and molding technology is one of the key technologies and mould structure is a important factor. A model is set based on ANSYS to simulate the molding, and using curve fitting, the relationship between maximum equivalent stress and mould parameter is founded. Then the optimization model is set and mould parameter is optimized.

Stress Analysis of the Biomass Molding Mould Based on ANSYS

2013 ◽  
Vol 716 ◽  
pp. 713-716
Author(s):  
Jian Feng Meng ◽  
Bai Tao Feng ◽  
Yu Ping Dong
Keyword(s):  
Renewable Energy ◽  
Stress Field ◽  
Stress Analysis ◽  
Frictional Force ◽  
Equivalent Stress ◽  
Force Distribution ◽  
Structure Parameter ◽  
Key Technologies ◽  
Maximum Equivalent Stress ◽  
The Relationship

Biomass is a renewable energy. Its curing and molding technology is one of the key technologies and mould structure parameter is a important factor. A model is set based on ANSYS to simulate the molding, then the equivalent stress field and frictional force distribution of mould are founded. Finally, the relationship between maximum equivalent stress and mould parameter is studied.

Evaluation of Creep Properties in Soldering Ball by Nanoindentation Creep

2005 ◽  
Author(s):  
Tadahiro Shibutani ◽  
Qiang Yu ◽  
Masaki Shiratori
Keyword(s):  
Chemical Potential ◽  
Early Stage ◽  
Hydrostatic Stress ◽  
Equivalent Stress ◽  
Nanoindentation Test ◽  
Diffusion Creep ◽  
Creep Properties ◽  
Last Stage ◽  
Power Law Creep ◽  
The Relationship

In this paper, the behavior the behavior of creep deformation in low melting point alloy during a nanoindentation test was examined. Nanoindentation creep test was performed for eutectic tin-lead solder ball. Estimated creep exponent from the relationship between hardness and indenter dwell-time decreases as a function of time. The morphology of indented area shows that the transition from the deformation due to the tip in the early stage to another one in the last stage. Each grain near the indenter tip was transformed in the last stage. Stress analysis using a finite element method reveals that relaxation of equivalent stress progresses rapidly and the residual hydrostatic stress is dominant. Then, the gradient of the residual hydrostatic stress affects the chemical potential on grain boundaries and diffusion creep is activated. Therefore, the transition from the power-law creep to diffusion creep takes place during the nanoindentaion creep.

Structure Optimization on Sensitivity Analysis for Ultra-Supercritical Bypass Valve

2012 ◽  
Vol 619 ◽  
pp. 282-285
Author(s):  
Long Yu ◽  
Shu Rong Yu
Keyword(s):  
Sensitivity Analysis ◽  
Equivalent Stress ◽  
Target Function ◽  
Structure Optimization ◽  
Mathematics Model ◽  
Sampling Point ◽  
Design Variables ◽  
Bypass Valve ◽  
Maximum Equivalent Stress ◽  
The Relationship

Given mathematics model and boundary conditions of the structure optimization for ultra-supercritical bypass valve (UBV) in operation. FEM results showed that 10 design variables and 178 sampling points are chosen for iteration, and the relationship between maximum equivalent stress and structure parameters are obtained by sensitivity analysis. By using Monte-Carlo method, the quantity of optimized sampling point can be reduced by 17% and calculation time is reduced clearly. The higher sensitivity parameters affecting target function are found by contrasting response degree, and improving the parameters directly is the way that enhances intensity of the UBV. Base on the sensitivity analysis, the linearized equivalent stress of weak place in the UBV can be reduced by 44% with the safety performance enhanced.

scholarly journals Modeling the Temperature Field in the Ground with an Installed Slinky-Coil Heat Exchanger

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4010
Author(s):  
Monika Gwadera ◽  
Krzysztof Kupiec
Keyword(s):  
Temperature Field ◽  
Heat Exchanger ◽  
Surface Temperature ◽  
Ground Surface ◽  
Heat Sources ◽  
Ground Surface Temperature ◽  
Coil Heat Exchanger ◽  
The Relationship ◽  
Temperature Responses ◽  
Coil Heat

In order to find the temperature field in the ground with a heat exchanger, it is necessary to determine temperature responses of the ground caused by heat sources and the influence of the environment. To determine the latter, a new model of heat transfer in the ground under natural conditions was developed. The heat flux of the evaporation of moisture from the ground was described by the relationship taking into account the annual amount of rainfall. The analytical solution for the equations of this model is presented. Under the conditions for which the calculations were performed, the following data were obtained: the average ground surface temperature Tsm = 10.67 °C, the ground surface temperature amplitude As = 13.88 K, and the phase angle Ps = 0.202 rad. This method makes it possible to easily determine the undisturbed ground temperature at any depth and at any time. This solution was used to find the temperature field in the ground with an installed slinky-coil heat exchanger that consisted of 63 coils. The results of calculations according to the presented model were compared with the results of measurements from the literature. The 3D model for the ground with an installed heat exchanger enables the analysis of the influence of miscellaneous parameters of the process of extracting or supplying heat from/to the ground on its temperature field.

scholarly journals Finite Element Modeling of Residual Stress at Joint Interface of Titanium Alloy and 17-4PH Stainless Steel

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 629
Author(s):  
Nana Kwabena Adomako ◽  
Sung Hoon Kim ◽  
Ji Hong Yoon ◽  
Se-Hwan Lee ◽  
Jeoung Han Kim
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Finite Element Modeling ◽  
Equivalent Stress ◽  
Stress Gradient ◽  
Joint Interface ◽  
Element Modeling ◽  
Actual Experiment ◽  
Maximum Equivalent Stress

Residual stress is a crucial element in determining the integrity of parts and lifetime of additively manufactured structures. In stainless steel and Ti-6Al-4V fabricated joints, residual stress causes cracking and delamination of the brittle intermetallic joint interface. Knowledge of the degree of residual stress at the joint interface is, therefore, important; however, the available information is limited owing to the joint’s brittle nature and its high failure susceptibility. In this study, the residual stress distribution during the deposition of 17-4PH stainless steel on Ti-6Al-4V alloy was predicted using Simufact additive software based on the finite element modeling technique. A sharp stress gradient was revealed at the joint interface, with compressive stress on the Ti-6Al-4V side and tensile stress on the 17-4PH side. This distribution is attributed to the large difference in the coefficients of thermal expansion of the two metals. The 17-4PH side exhibited maximum equivalent stress of 500 MPa, which was twice that of the Ti-6Al-4V side (240 MPa). This showed good correlation with the thermal residual stress calculations of the alloys. The thermal history predicted via simulation at the joint interface was within the temperature range of 368–477 °C and was highly congruent with that obtained in the actual experiment, approximately 300–450 °C. In the actual experiment, joint delamination occurred, ascribable to the residual stress accumulation and multiple additive manufacturing (AM) thermal cycles on the brittle FeTi and Fe2Ti intermetallic joint interface. The build deflected to the side at an angle of 0.708° after the simulation. This study could serve as a valid reference for engineers to understand the residual stress development in 17-4PH and Ti-6Al-4V joints fabricated with AM.

Analysis of the Thermal Stress at the Tubesheet in Floating-Head or U-Tube Heat Exchangers

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Jiuyi Liu ◽  
Caifu Qian ◽  
Huifang Li
Keyword(s):  
Thermal Stress ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Influence Factors ◽  
Area Ratio ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Numerical Tests ◽  
Hole Area

Thermal stress is an important factor influencing the strength of a heat exchanger tubesheet. Some studies have indicated that, even in floating-head or U-tube heat exchangers, the thermal stress at the tubesheet is significant in magnitude. For exploring the value, distribution, and the influence factors of the thermal stress at the tubesheet of these kind heat exchangers, a tubesheet and triangle arranged tubes with the tube diameter of 25 mm were numerically analyzed. Specifically, the thermal stress at the tubesheet center is concentrated and analyzed with changing different parameters of the tubesheet, such as the temperature difference between tube-side and shell-side fluids, tubesheet diameter, thickness, and the tube-hole area ratio. It is found that the thermal stress of the tubesheet of floating-head or U-tube heat exchanger was comparable in magnitude with that produced by pressures, and the distribution of the thermal stress depends on the tube-hole area and the temperature inside the tubes. The thermal stress at the center of the tubesheet surface is high when tube-hole area ratio is very low. And with increasing the tube-hole area ratio, the stress first decreases rapidly and then increases linearly. A formula was numerically fitted for calculating the thermal stress at the tubesheet surface center which may be useful for the strength design of the tubesheet of floating-head or U-tube heat exchangers when considering the thermal stress. Numerical tests show that the fitted formula can meet the accuracy requirements for engineering applications.

scholarly journals Numerical Simulation and Experimental Study on Axial Stiffness and Stress Deformation of the Braided Corrugated Hose

2021 ◽  
Vol 11 (10) ◽  
pp. 4709
Author(s):  
Dacheng Huang ◽  
Jianrun Zhang
Keyword(s):  
Numerical Simulation ◽  
Geometric Model ◽  
Equivalent Stress ◽  
Element Model ◽  
Maximum Error ◽  
Structural Features ◽  
Axial Stiffness ◽  
Frictional Stress ◽  
Maximum Equivalent Stress ◽  
Simulation Results

To explore the mechanical properties of the braided corrugated hose, the space curve parametric equation of the braided tube is deduced, specific to the structural features of the braided tube. On this basis, the equivalent braided tube model is proposed based on the same axial stiffness in order to improve the calculational efficiency. The geometric model and the Finite Element Model of the DN25 braided corrugated hose is established. The numerical simulation results are analyzed, and the distribution of the equivalent stress and frictional stress is discussed. The maximum equivalent stress of the braided corrugated hose occurs at the braided tube, with the value of 903MPa. The maximum equivalent stress of the bellows occurs at the area in contact with the braided tube, with the value of 314MPa. The maximum frictional stress between the bellows and the braided tube is 88.46MPa. The tensile experiment of the DN25 braided corrugated hose is performed. The simulation results are in good agreement with test data, with a maximum error of 9.4%, verifying the rationality of the model. The study is helpful to the research of the axial stiffness of the braided corrugated hose and provides the base for wear and life studies on the braided corrugated hose.

Research in Destruction of Concrete Bridge Expanded Joint Influenced by Temperature Difference

2015 ◽  
Vol 744-746 ◽  
pp. 803-806 ◽  
Author(s):  
Xiao Lei ◽  
Yue Yao ◽  
Shi Cao ◽  
Zhi Gang Guo
Keyword(s):  
Temperature Difference ◽  
Curve Fitting ◽  
Effective Temperature ◽  
Joint Damage ◽  
Measured Data ◽  
Concrete Bridge ◽  
Box Girder ◽  
Concrete Box Girder ◽  
Extremum Value ◽  
The Relationship

Destruction of bridge expanded joint is a serious problem for concrete bridge. Based on 5 years measured data, the temperature in the different positions of the concrete box girder was systemically analyzed to illuminate the cause of the bridge expanded joint damage. A method for predicting the extremum value of the temperature difference of concrete girder was proposed by use of the extrema analysis and curve fitting based on the temperature in the different positions of the concrete box girder. The relationship is quite useful in estimating the destruction of bridge expanded joint by effective temperature difference in concrete box-girder.

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