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.

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 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.

Rancang Bangun Alat Olahan Minyak Kelapa

2016 ◽  
Vol 10 (1) ◽  
pp. 70-77
Author(s):  
Jantri Sirait ◽  
Sulharman Sulharman
Keyword(s):  
Electric Motor ◽  
Performance Test ◽  
Production Capacity ◽  
Coconut Oil ◽  
Heating Time ◽  
Design Tool ◽  
Coconut Milk ◽  
Heating Process ◽  
And Performance ◽  
Time Required

Has done design tool is a tool of refined coconut oil coconut grater, squeezer coconut milk and coconut oil heating, with the aim to streamline the time of making coconut oil and coconut oil increase production capacity. The research method consists of several stages, among others; image creation tool, procurement of materials research, cutting the material - the material framework of tools and performance test tools. The parameters observed during the performance test tools is time grated coconut, coconut milk bleeder capacity, the capacity of the boiler and the heating time of coconut oil. The design tool consists of three parts, namely a tool shaved coconut, coconut milk wringer and coconut milk heating devices. Materials used for the framework of such tools include iron UNP 6 meters long, 7.5 cm wide, 4 mm thick, while the motor uses an electric motor 0.25 HP 1430 rpm and to dampen the rotation electric motor rotation used gearbox with a ratio of round 1 : 60. the results of the design ie the time required for coconut menyerut average of 297 seconds, coconut milk wringer capacity of 5 kg of processes and using gauze pads to filter coconut pulp, as well as the heating process takes ± 2 hours with a capacity of 80 kg , The benefits of coconut oil refined tools are stripping time or split brief coconut average - average 7 seconds and coconut shell can be used as craft materials, processes extortion coconut milk quickly so the production capacity increased and the stirring process coconut oil mechanically.ABSTRAKTelah dilakukan rancang bangun alat olahan minyak kelapa yaitu alat pemarut kelapa, pemeras santan kelapa dan pemanas minyak kelapa, dengan tujuan untuk mengefisiensikan waktu pembuatan minyak kelapa serta meningkatkan kapasitas produksi minyak kelapa. Metode penelitian terdiri dari beberapa tahapan antara lain; pembuatan gambar alat, pengadaan bahan-bahan penelitian, pemotongan bahan - bahan rangka alat dan uji unjuk kerja alat. Parameter yang diamati pada saat uji unjuk kerja alat adalah waktu parut kelapa, kapasitas pemeras santan kelapa, kapasitas tungku pemanas serta waktu pemanasan minyak kelapa. Rancangan alat terdiri dari tiga bagian yaitu alat penyerut kelapa, alat pemeras santan kelapa dan alat pemanas santan kelapa. Bahan yang dipergunakan untuk rangka alat tersebut  yaitu besi UNP panjang 6 meter, lebar 7,5 cm, tebal 4 mm, sedangkan untuk motor penggerak menggunakan motor listrik 0,25 HP 1430 rpm dan untuk meredam putaran putaran motor listrik dipergunakan gearbox  dengan perbandingan putaran 1 : 60. Hasil dari rancangan tersebut yaitu waktu yang dibutuhkan untuk menyerut kelapa rata-rata 297 detik, kapasitas alat pemeras santan kelapa 5 kg sekali proses dan menggunakan kain kassa untuk menyaring ampas kelapa, serta Proses pemanasan membutuhkan waktu ± 2 jam dengan kapasitas 80 kg. Adapun keunggulan alat olahan minyak kelapa ini adalah waktu pengupasan atau belah kelapa singkat rata – rata 7 detik dan tempurung kelapa dapat digunakan sebagai bahan kerajinan, proses pemerasan santan kelapa cepat sehingga kapasitas produksi meningkat dan proses pengadukan minyak kelapa secara mekanis. Kata kunci : penyerut, pemeras, pemanas,minyak kelapa,olahan minyak kelapa.

scholarly journals Numerical analysis of heat exchange process in the biomass carbonisation reactor

2019 ◽  
Vol 252 ◽  
pp. 05019 ◽  
Author(s):  
Robert Zarzycki ◽  
Justyna Jędras
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Numerical Analysis ◽  
Exchange Process ◽  
Geometrical Model ◽  
Heating Time ◽  
Heating Process ◽  
Hot Air ◽  
Cyclic Operation ◽  
Heat Exchange Process

The study presents the problem of heat exchange in the biomass carbonisation reactor with cyclic operation. Based on the actual parameter of the biomass carbonisation reactor, a geometrical model was developed, and the computation of the heating process was conducted for two cases: an empty reactor and a filled reactor. Its result demonstrated that for the analysed configuration of the reactor, the process of heating biomass in the containers is limited by the capability of heat transfer to the biomass in the container. The results suggest opportunities for the improved heat exchange in the reactor and, accordingly, shortening heating time through installation of the system that forces circulation of hot air inside the reactor.

Thermal Runaway of the BaCO3 + Fe2O3 Homogenous Mixture and Mechanical Alloys at the Microwave Heating

2013 ◽  
Vol 837 ◽  
pp. 185-189 ◽  
Author(s):  
I. Danut Savu ◽  
Sorin Vasile Savu ◽  
Gabriel Constantin Benga
Keyword(s):  
Electrical Properties ◽  
Heat Source ◽  
Microwave Heating ◽  
Structural Changes ◽  
Critical Phenomenon ◽  
Ceramic Materials ◽  
Heating Time ◽  
Thermal Runaway ◽  
Heating Process ◽  
Active System

Microwave heating represents a modern technique to sintering the composites materials. The microwaves absorbance property of the materials is depending by the electrical permittivity of the materials. Researchers showed that the ceramic materials are suitable for sintering using microwave heating. The most important advantage of that sintering procedure is the reduced sintering time and temperatures. However, during the heating process these properties are changing and a pattern of the heating process cannot be established. The penetration depth of microwaves into materials depends on the electrical properties of them, and gives rise to a heat source. The electromagnetic wave absorption is responsible for the macro and micro structural changes in the materials morphology, and consequently for their electrical properties. Thermal runaway is one phenomenon which should be avoided during the microwave processing of the materials. The microwave heating consists in direct introduction of the energy in the volume of the material. If the absorbance properties of the material are increasing with temperature, than a critical phenomenon, called thermal runaway, appears during the heating process. This paper aims to study the thermal runaway of the BaCO3 + Fe2O3 homogenous mixture and mechanical alloy in a mono-mode applicator, when the heat source is a microwave generator at 2,45 Ghz. A special mono-mode chamber has been designed with dimensions 140 x 140 x 70 mm and an active system for rotating the samples, in order to record the values of the temperature and to assure a uniform exposure of the samples to the high frequency electromagnetic field. The materials used in experiments were homogenous mixture of BaCO3 + Fe2O3 which have been milled in a planetary ball mill for 5 and 20 hours. The experimental procedure consists in establishing the levels of the temperatures during the microwave heating process when the thermal runaway appears. These experiments have been done for fixed levels of microwave injected power from 0 1250 W. Numerical simulation for different heating conditions (microwave power, heating time, position of the samples inside the chamber) has been performed in order to elaborate a predictable mathematical model for continuous microwave heating and avoiding the thermal runaway of the homogenous mixture.

Effects of Activated Carbon in Microwave Induction of Lateritic Ore

2013 ◽  
Vol 372 ◽  
pp. 433-436 ◽  
Author(s):  
He Chen ◽  
Rui Guo ◽  
Na Su ◽  
Yue Hong Zhang ◽  
Xuan Wen Liu
Keyword(s):  
Activated Carbon ◽  
Microwave Irradiation ◽  
Stable Process ◽  
Heating Time ◽  
Heating Process ◽  
Roasting Process ◽  
Reductive Roasting ◽  
Lateritic Ore ◽  
Composition Of Products

Lateritic ore can be heated and deoxidized rapidly via microwave irradiation with activated carbon as deoxidizer. In this paper, we studied the reductive roasting behavior of carbon-containing lateritic ore in microwave field and the composition of products through different heating process with varying carbon content. The results show that the heating process of the lateritic ore is a thermally stable process. The reductive level of lateritic ore can be adjusted by changing the proportion of carbon powders and the heating time of microwave irradiation. During this reductive roasting process, the quality of the added carbon powders will make a great impact on the phase composition of the product and then affect the heating rate. The reductive calcite product mainly consists of magnetite and wastage. With the rising of the content of reducing agent, the reductive level of lateritic ore will increase, which cause Ni and a small quantity of Fe to be deoxidized and forms Ni-Fe alloy.

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 Numerical Study of Natural Convection Heat Loss from Cylindrical Solar Cavity Receivers

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
M. Prakash
Keyword(s):  
Natural Convection ◽  
Cylindrical Cavity ◽  
Numerical Study ◽  
Three Dimensional ◽  
Working Fluid ◽  
Helical Coil ◽  
Fluid Temperature ◽  
Medium Temperature ◽  
Inclination Angles ◽  
Temperature Levels

The numerical study of the natural convection loss occurring from cylindrical solar cavity receivers is reported in this communication. These cavity receivers can be used with solar dish concentrators for process heat applications at medium temperature levels. Three cylindrical cavity receivers of diameter 0.2, 0.3, and 0.4 m with aspect ratio equal to one and opening ratios of 1 and 0.5 are used for the analysis. Fluent CFD software is used for the analysis of the three-dimensional (3D) receiver models. In this study the receiver tubes within the cylindrical cavity are modeled as a helical coil similar to those existing in actual systems. The flow of the working fluid within the helical coil is also modeled. The simulations are performed for fluid inlet temperatures of 150°C and 250°C and for receiver inclination angles of 0 (sideways-facing cavity), 30, 45, 60, and 90 degree (vertically downward-facing receiver). It is found that the convective loss increases with increasing mean fluid temperature and decreases with, increase in receiver inclination. The convective loss is found to increase with, opening ratio. These observations are true for all cavity receivers analysed here. A Nusselt number correlation involving Rayleigh numbers, receiver inclinations, and opening ratios is proposed for the convective loss.

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