Optimum Heating of Pressure Vessels With Holes

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Piotr Dzierwa ◽  
Jan Taler
Keyword(s):  
Stress Concentration ◽  
Circumferential Stress ◽  
Pressure Vessels ◽  
Heating Process ◽  
Fluid Temperature ◽  
Medium Temperature ◽  
Temperature Variations ◽  
Temperature Changes ◽  
Constant Rate ◽  
Optimum Heating

A method for determining time-optimum medium temperature changes is presented. The heating of the pressure elements will be conducted so that the circumferential stress caused by pressure and fluid temperature variations at the edge of the opening at the point of stress concentration does not exceed the allowable value. In contrast to present standards, two points at the edge of the opening are taken into consideration. Optimum fluid temperature changes are assumed in the form of simple time functions. It is possible to increase the fluid temperature stepwise at the beginning of the heating process and then the fluid temperature can be increased with a constant rate.

scholarly journals Optimum heating of cylindrical pressure components weakened by holes

2012 ◽  
Vol 33 (3) ◽  
pp. 106-116
Author(s):  
Piotr Dzierwa ◽  
Jan Taler
Keyword(s):  
Circumferential Stress ◽  
Longitudinal Section ◽  
Heating Time ◽  
Heating Process ◽  
Practical Reasons ◽  
Fluid Temperature ◽  
Optimum Temperature ◽  
Medium Temperature ◽  
Temperature Changes ◽  
Constant Rate

Abstract A method for determining time-optimum medium temperature changes is presented. The heating of the pressure elements will be conducted so that the circumferential stress caused by pressure and fluid temperature variations at the edge of the opening at the point of stress concentration, do not exceed the allowable value. In contrast to present standards, two points at the edge of the opening are taken into consideration. The first point, P1, is located at the cross section and the second, P2, at the longitudinal section of the vessel. It will be shown that the optimum temperature courses should be determined with respect to the total circumferential stress at the point P2, and not, as in the existing standards due to the stress at the point P1. Optimum fluid temperature changes are assumed in the form of simple time functions. For practical reasons the optimum temperature in the ramp form is preferred. It is possible to increase the fluid temperature stepwise at the beginning of the heating process and then increase the fluid temperature with the constant rate. Allowing stepwise fluid temperature increase at the beginning of heating ensures that the heating time of a thick-walled component is shorter than heating time resulting from the calculations according to EN 12952-3 European Standard.

Determining Optimum Temperature Changes During Heating of Pressure Vessels With Holes

2013 ◽  
Author(s):  
Jan Taler ◽  
Piotr Dzierwa ◽  
Dawid Taler
Keyword(s):  
Circumferential Stress ◽  
Longitudinal Section ◽  
Heating Time ◽  
Pressure Vessels ◽  
Heating Process ◽  
Practical Reasons ◽  
Fluid Temperature ◽  
Optimum Temperature ◽  
Medium Temperature ◽  
Temperature Changes

A method for determining time-optimum medium temperature changes is presented. The heating of the pressure elements will be conducted so that the circumferential stress caused by pressure and fluid temperature variations at the edge of the opening at the point of stress concentration, does not exceed the allowable value. In contrast to present standards, two points at the edge of the opening are taken into consideration. The first point P1 is located at the cross section and the second P2 at the longitudinal section of the vessel. It will be shown that the optimum temperature courses should be determined with respect to the total circumferential stress at the point P2, and not, as in the existing standards due to the stress at the point P1. Optimum fluid temperature changes are assumed in the form of simple time functions. For practical reasons the optimum temperature in the ramp form is preferred. It is possible to increase the fluid temperature stepwise at the beginning of the heating process and then the fluid temperature can be increased with a constant rate. By the stepwise increase in fluid temperature heating time of a thick-walled component is shorter than heating time resulting from the calculations according to EN 12952-3 European Standard.

scholarly journals New method for determining the optimum fluid temperature when heating pressure thick-walled components with openings

2019 ◽  
Vol 128 ◽  
pp. 01025
Author(s):  
Dawid Taler ◽  
Piotr Dzierwa ◽  
Jan Taler
Keyword(s):  
Circumferential Stress ◽  
Heating Process ◽  
Fluid Temperature ◽  
Allowable Stress ◽  
Optimum Temperature ◽  
Temperature Changes ◽  
Second Stage ◽  
Optimum Heating ◽  
Steady Temperature Field ◽  
Start Ups

A new approximate method of optimum heating cylindrical pressure elements weakened by openings was proposed. Optimum variations in fluid temperature when heating the pressure component were determined from the condition that the total circumferential stress at the edge of the opening, resulting from the thermal load and pressure is equal to the allowable stress. The allowable stress is determined from the Wöhler fatigue diagram for a given number of start-ups and shutdowns of a power unit from the cold state. Optimum temperature changes are difficult to estimate at the beginning of the heating, usingboth exact analytical and numerical methods. In case of analytical methods, this is due to the very slow convergence of a series for near-zero time in the exact solution. In this paper, the optimum temperature changes of the fluid at the beginning of heating were determined using the heat balance integralmethod (HBIM). This method makes it possible to determine with high accuracy the temperature of the fluid for times close to zero, i.e., at the beginning of the heating process. In the second stage of heating, the optimum fluid temperature was determined on the assumption of a quasi-steady temperature field in the pressure element.

Optimum Heating of Thick Wall Pressure Components of Steam Boilers

2014 ◽  
Author(s):  
Piotr Dzierwa ◽  
Dawid Taler ◽  
Jan Taler ◽  
Marcin Trojan
Keyword(s):  
Heating Time ◽  
Thick Wall ◽  
Heating Process ◽  
Fluid Temperature ◽  
European Standard ◽  
Temperature Changes ◽  
Constant Rate ◽  
Steam Boilers ◽  
Optimum Heating ◽  
Temperature Heating

A method for determining time-optimum fluid temperature changes is presented. In contrast to present standards, two points at the edge of the opening are taken into consideration. The optimum fluid temperature changes are assumed in the form of a simple time function. It is possible to increase the fluid temperature stepwise and then the fluid temperature can be increased with a constant rate at the beginning of the heating process. Due to the stepwise increase in fluid temperature, heating time of a thick-walled component is of the same order as in the case of calculations according to EN 12952-3 European Standard, but the total circumferential stresses on the edge of the hole do not exceed the allowable value.

Design of Flat Ends in Pressure Boilers with Circular and Elliptical Stress Relieve Grooves

2013 ◽  
Vol 477-478 ◽  
pp. 49-53 ◽  
Author(s):  
Bogdan Szybiński
Keyword(s):  
Numerical Analysis ◽  
Stress Concentration ◽  
Circumferential Stress ◽  
Stress Relief ◽  
Pressure Vessels ◽  
Optimal Choice ◽  
Circular Shape ◽  
Relief Groove ◽  
Two Parameters

Flat ends in cylindrical pressure vessels are a certain alternative for commonly used in boilers dished ends. These ends can have different form and one of the admitted proposals is the plate with the internally introduced circumferential stress relief groove. In codes [1, the grooves of circular shape are recommended. Three parameters describe the groove configuration, namely the groove radius, the minimum endplate thickness under the relief groove and the chamfer angle. The respective formulas for calculations of the first two parameters are expressed in the form of inequalities. This means that a certain range of their variation is possible. The existing codes do not give the clear suggestion about the optimal choice of values of the groove parameters, leading to the minimal value of the stress concentration in the groove area. This is usually done by numerical analysis. The significant reduction of stress concentration is observed when changing the shape of the groove from the circular to the elliptical one, which is also shown in the paper.

Temperature-Dependent Photoluminescence Spectra of PbSe Quantum Dots for Temperature Markers

2012 ◽  
Vol 482-484 ◽  
pp. 2547-2550
Author(s):  
Peng Fei Gu ◽  
Ya Nan Wang ◽  
Jia Jia Cao ◽  
Yu Yan ◽  
Tie Qiang Zhang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Temperature Sensitivity ◽  
Peak Position ◽  
Strong Temperature Dependence ◽  
Photoluminescence Spectra ◽  
Temperature Dependent ◽  
Temperature Variations ◽  
Temperature Changes ◽  
Optical Readout ◽  
Temperature Dependent Photoluminescence

We here report the temperature effect on photoluminescence(PL) spectra of PbSe quantum dots (QDs), which exhibit a strong temperature dependence on their spectra position and intensity. They potentially act as the temperature marker, sensing temperature variations and reporting temperature changes remotely through optical readout. In addition, the temperature sensitivity characterized by peak position of PbSe QDs was found to be 0.39nm/°C in a range of 10-100 °C.

Stress Concentration Factors in Auxetic Rods and Plates

2013 ◽  
Vol 394 ◽  
pp. 134-139 ◽  
Author(s):  
Teik Cheng Lim
Keyword(s):  
Stress Concentration ◽  
Circumferential Stress ◽  
Axial Direction ◽  
Thin Plates ◽  
Auxetic Materials ◽  
Circular Holes ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Future Work ◽  
Poissons Ratio

Auxetic materials are solids that possess negative Poissons ratio. Although rare, such materials do occur naturally and also have been artificially produced. Due to their unique properties, auxetic materials have been extensively investigated for load bearing applications including in biomedical engineering and aircraft structures. This paper considers the effect of Poissons ratio on the stress concentration factors on rods with hyperbolic groove and large thin plates with circular holes and rigid inclusions. Results reveal that the use of auxetic materials is useful for reducing stress concentration in the maximum circumferential stress of the rods with grooves, and in plates with circular holes and rigid inclusions. However, the use of auxetic materials increases the stress concentration in the axial direction of the rod. Therefore a procedure to accurately select and/or design materials with precise negative Poissons ratio for optimal design is suggested for future work.

Stress Analysis and Structure Optimization for the Opening Flat Cover of Pressure Vessels

2012 ◽  
Vol 538-541 ◽  
pp. 3253-3258 ◽  
Author(s):  
Jun Jian Xiao
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Analysis ◽  
Structure Optimization ◽  
Pressure Vessels ◽  
Secondary Stress ◽  
Element Analysis ◽  
Primary Stress ◽  
Flat Cover

According to the results of finite element analysis (FEA), when the diameter of opening of the flat cover is no more than 0.5D (d≤0.5D), there is obvious stress concentration at the edge of opening, but only existed within the region of 2d. Increasing the thickness of flat covers could not relieve the stress concentration at the edge of opening. It is recommended that reinforcing element being installed within the region of 2d should be used. When the diameter of openings is larger than 0.5D (d>0.5D), conical or round angle transitions could be employed at connecting location, with which the edge stress decreased remarkably. However, the primary stress plus the secondary stress would be valued by 3[σ].

scholarly journals The isotopic record at an alpine glacier and its implications for local climatic changes and isotopic homogenization processes

2001 ◽  
Vol 47 (156) ◽  
pp. 147-151 ◽  
Author(s):  
He Yuanqing ◽  
Wilfred H. Theakstone ◽  
Yao Tandong ◽  
Shi Yafeng
Keyword(s):  
Equilibrium Line Altitude ◽  
Temperature Variations ◽  
Alpine Glacier ◽  
Temperature Changes ◽  
Natural Factors ◽  
Air Temperatures ◽  
Regional Temperature ◽  
The Mean ◽  
A Site ◽  
The Relationship

AbstractStratigraphic variations of oxygen isotopes in the snow which accumulates during the winter at the Norwegian glacier Austre Okstindbreen are not entirely eliminated after 1–2 months of ablation in the following summer. The relationship between regional temperature changes and δ18O values in the snowpack is affected by many natural factors, but 1989/90 winter air temperatures were reflected in the snow which remained on Austre Okstindbreen at 1350 m a.s.l. in July 1990. There were many variations of δ18O values in the 4.1m of snow above the 1989 summer surface, but variations in the underlying firn were relatively small. Meltwater percolation modifies the initial variations of δ18O values in the snowpack. At a site below the mean equilibrium-line altitude on Austre Okstindbreen, increased isotopic homogenization within a 10 day period in July accompanied an increase of the mean δ18O value. Although the isotopic record at a temperate glacier is likely to be influenced by more factors than is that at polar glaciers, it can provide an estimate of the approximate trend of local temperature variations.

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