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.

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.

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.

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.

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.

Optimum Heating Control Method to Keep a Given Temperature Rising Speed of a Plate During Rapid Thermal Processing

2008 ◽  
Author(s):  
Shigeki Hirasawa ◽  
Sadanori Toda
Keyword(s):  
Thermal Processing ◽  
Thermal Model ◽  
Control Method ◽  
Rapid Thermal Processing ◽  
Good Method ◽  
Correlation Equation ◽  
Measuring Error ◽  
Heating Process ◽  
Time Step ◽  
Optimum Heating

In rapid thermal processing of semiconductor wafers, it is very important to keep a given temperature rising speed of the wafer during the heating process. We calculated the effect of various heating control methods on the error of the temperature rising speed of the wafer. We calculated the PID control, the control method by correcting with temperature rising speed, the control using a thermal model, the control using a prepared correlation equation, and the combined methods. We found that the combined method with a thermal model and rising speed is a good method to decrease the error of the temperature rising speed. The minimum error of the temperature rising speed at 700°C is less than 0.1°C/s during the temperature rising process of 100°C/s and the monitoring time step of 0.05 s. We calculated the effects of control-delay-time and measuring error of the monitoring temperature on the error of the temperature rising speed.

scholarly journals Evaporator Heating with Optimum Fluid Temperature Changes

2016 ◽  
Vol 157 ◽  
pp. 29-37 ◽  
Author(s):  
Piotr Dzierwa ◽  
Dawid Taler ◽  
Marcin Trojan ◽  
Jan Taler
Keyword(s):  
Fluid Temperature ◽  
Temperature Changes

scholarly journals A CFD ANALYSIS IN SOLIDWORKS FLOW SIMULATION FOR TWO MIXING FLUIDS WITH DIFFERENT TEMPERATURES IN NOZZLES

2020 ◽  
Vol 26 (1) ◽  
Author(s):  
IONEL OLARU
Keyword(s):  
Complex Analysis ◽  
Flow Simulation ◽  
Additional Stress ◽  
Fluid Temperature ◽  
Electronic Components ◽  
Temperature Changes ◽  
Different Temperatures ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Mechanical Elements

<p>The heat can have a direct impact on the mechanical elements by creating deformations and by causing the induction of additional stress in them. In designing of the heat exchangers or for the electronic components, the temperature changes for structural analysis as well as structural performance of thermal impact for the entire element must be analyzed. The study from this paper proposes an analysis and a simulation of flow through the convergent-divergent nozzle type to optimize the inlet of warm fluid to have minimum impact on the nozzle walls This analysis will be performed with a computer program specialized in complex analysis of Computational Fluid Dynamics (CFD), which will also take into account the fluid temperature and its influence throughout the system.</p>

scholarly journals Effect of temperature changes on the cercarial-shedding rate of two trematodes

2016 ◽  
Vol 106 (0) ◽  
Author(s):  
Cecilia L. Achiorno ◽  
Sergio R. Martorelli
Keyword(s):  
Effect Of Temperature ◽  
Optimum Temperature ◽  
Significance Level ◽  
Temperature Changes ◽  
Significant Difference ◽  
Light:Dark Cycle ◽  
Cercarial Emergence

ABSTRACT Since temperature is a key condition in the initiation of cercarial emergence, the objective of the work reported here was to evaluate the effect of that variable on the shedding of two morphologic and taxonomic types of cercariae. Bioassays were accordingly performed with snails naturally infected with either monostome or pleurolophocercous cercariae because those two cercarial types were found to be the most prevalent in the environment under study. The snails were placed in 6-ml circular plastic dishes with soft plastic stoppers containing 3 ml of reconstituted water and then sequentially exposed for 24 h to a 14:10-h light:dark cycle at 20, 25, or 30 °C. The data were analyzed at a significance level of p <0.05 by means of the InfoStat program. The optimum temperature for cercarial emergence was typically in the range of 25 °C and decreased significantly at 30 °C. We observed no significant difference in the number of cercariae emerging between the two morphologic types.

The rennet hysteresis of heated milk

1969 ◽  
Vol 36 (3) ◽  
pp. 333-341 ◽  
Author(s):  
P. A. Morrissey
Keyword(s):  
Calcium Phosphate ◽  
Calcium Ions ◽  
Calcium Ion ◽  
Heating Process ◽  
Second Stage ◽  
Heated Milk ◽  
Rennet Coagulation ◽  
Micellar Casein ◽  
Induced Changes ◽  
Β Lactoglobulin

SummaryThe phenomenon of rennet hysteresis in heated milk is essentially due to reversible heat-induced changes of calcium phosphate equilibrium which affect the second or calcium ion stage of the rennet coagulation. The phenomenon is shown not only by heated milk but also by all heated caseinate systems provided they contain sufficient calcium to permit of coagulation with rennet and enough phosphate to ensure some degree of colloidal phosphate precipitation during the heating process; its occurrence does not require the presence of micellar casein or of β-lactoglobulin, or the initial presence of colloidal phosphate. Nevertheless, rennet hysteresis is greatly increased in these heated systems if β-lactoglobulin is present owing to the formation of a calcium caseinate/β-lactoglobulin complex which in its renneted condition is much less sensitive to calcium ions than is calcium para-caseinate. The resulting relative prolongation of the second stage of the rennet coagulation renders this phenomenon more apparent by increasing the proportion of the total time occupied by the hysteresis effect.

Micro-Fibrillated Cellulose Fabrication from Empty Fruit Bunches of Oil Palm

2020 ◽  
Vol 1000 ◽  
pp. 272-277
Author(s):  
Marcelinus Christwardana ◽  
Aniek Sri Handayani ◽  
Shirley Savetlana ◽  
Riana Herlina Lumingkewas ◽  
Muchamad Chalid
Keyword(s):  
Oil Palm ◽  
Morphological Analysis ◽  
Average Length ◽  
Heating Process ◽  
Empty Fruit Bunches ◽  
Second Stage ◽  
Treatment Stage ◽  
Coarse Fibers ◽  
Cellulose Crystals ◽  
Thermal Stability Of

Micro-fibrillated celluloses (MFCs) are made from oil palm empty fruit bunches (EFB). EFB is processed through several stages of the process, including washing, alkalization, and bleaching to remove impurities, lignin, and hemicellulose. Each treatment stage was characterized by differential scanning calorimeter (DSC) and thermogravimetric (TGA) analysis. Morphological analysis was characterized using Scanning Electron Microscope (SEM). The process results show that MFC has an average length and thickness of 450 and 80 microns for coarse fibers respectively, averaging 50 and 5 microns for fine fibers, respectively. Fibrillation fibers appear on the surface of fibers which are treated using alkalization and bleaching processes. The TGA results showed a decrease in weight occurred at a temperature of 40 to 109 °C for the first stage of the heating process and at a temperature of 247 to 382 °C for the second stage. The decrease in fiber weight is caused by evaporation of water content and degradation of cellulose compounds at each stage. The glass transition temperature of MFC was obtained at 236 °C. The thermal stability of cellulose from fibers treated using alkalization and bleaching processes proved the formation of cellulose crystals. Removal of lignin and hemicellulose is shown by the absorption of O-H and C-C bonds in FTIR spectroscopy. From these results, it is stated that micro-fibrillation cellulose is formed well through a series of processes given.

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