Influence of a Variable in Time Heat Transfer Coefficient on Stresses in Model of Power Plant Components

2013 ◽  
Author(s):  
Jerzy Okrajni ◽  
Mariusz Twardawa
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Mechanical Behaviour ◽  
Power Plants ◽  
Thermal Loading ◽  
Computer Modelling ◽  
Temperature Fields ◽  
Fluid Medium ◽  
Stress Changes ◽  
Plant Components

The paper discusses the issue of modelling of strains and stresses resulting from heating and cooling processes of components in power plants. The main purpose of the work is to determine the mechanical behaviour of power plant components operating under mechanical and thermal loading. Finite element method (FEM) has been used to evaluate the temperature and stresses changes in components as a function of time. Temperature fields in the components of power plants are dependent, among parameters, on variable heat-transfer conditions between components and the fluid medium, which may change its condition, flowing inside them. For this reason, evaluation of the temperature field and the consequent stress fields requires the use of heat-transfer coefficients as time-dependent variables and techniques for determining appropriate values for these coefficients should be used. The methodology of combining computer modelling of the temperature fields with its measurements performed at selected points of the pipelines may be used in this case. The graphs of stress changes as a function of time have been determined for the chosen plant components. The influence of the heat transfer conditions on the temperature fields and mechanical behaviour of components have been discussed.

Influence of a Variable in Time Heat Transfer Coefficient on Stresses in Model of Power Plant Components

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Jerzy Okrajni ◽  
Mariusz Twardawa
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Mechanical Behavior ◽  
Power Plants ◽  
Thermal Loading ◽  
Computer Modelling ◽  
Temperature Fields ◽  
Fluid Medium ◽  
Stress Changes ◽  
Plant Components

The paper discusses the issue of the modelling of strains and stresses resulting from heating and cooling processes of components in power plants. The main purpose of the work is to determine the mechanical behavior of power plant components operating under mechanical and thermal loading. The finite element method (FEM) has been used to evaluate the temperature and stresses changes in components as a function of time. Temperature fields in the components of power plants are dependent, among parameters, on variable heat-transfer conditions between components and the fluid medium, that may change its condition, flowing inside them. For this reason, an evaluation of the temperature field and the consequent stress fields requires the use of heat-transfer coefficients as time-dependent variables and techniques for determining appropriate values for these coefficients should be used. The methodology that combines computer modelling of the temperature fields with its measurements performed at selected points of the pipelines may be used in this case. The graphs of stress changes as a function of time have been determined for the chosen plant components. The influence of the heat transfer conditions on the temperature fields and mechanical behavior of components in question have been discussed.

The Influence of the Grade of Materials and their State on the Thermo-Mechanical Behaviour of the Chosen Power Plant Components

2016 ◽  
Vol 250 ◽  
pp. 238-243 ◽  
Author(s):  
Mariusz Twardawa ◽  
Jerzy Okrajni
Keyword(s):  
Mechanical Properties ◽  
Power Plant ◽  
Mechanical Behaviour ◽  
Power Plants ◽  
Thermal Loading ◽  
Stress Strain ◽  
The Real ◽  
Properties Of Materials ◽  
Operation Parameters ◽  
Plant Components

The paper discusses the issue of the influence of the growth of the operation parameters of power plant components on the fatigue phenomena that take place under mechanical and thermal loading. The loading characteristics have been taken as measurements results in industrial conditions. Stress-strain characteristics of such components, which take into consideration the changeable properties of materials subject to fatigue, have been described. The hardening processes of the materials, which are assumed to be used in designed power plants, have also been discussed. The aim of the paper is the description of the mechanical behaviour of the power plant components taking into consideration the real industrial conditions of their operation and changeable mechanical properties of the components’ materials.

Human reliability in non-destructive inspections of nuclear power plant components: modeling and analysis

2019 ◽  
Vol 7 (2B) ◽  
Author(s):  
Vanderley Vasconcelos ◽  
Wellington Antonio Soares ◽  
Raissa Oliveira Marques ◽  
Silvério Ferreira Silva Jr ◽  
Amanda Laureano Raso
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Human Factors ◽  
Nuclear Power ◽  
Power Plants ◽  
Failure Modes ◽  
Cooling System ◽  
Human Reliability ◽  
Non Destructive ◽  
Plant Components

Non-destructive inspection (NDI) is one of the key elements in ensuring quality of engineering systems and their safe use. This inspection is a very complex task, during which the inspectors have to rely on their sensory, perceptual, cognitive, and motor skills. It requires high vigilance once it is often carried out on large components, over a long period of time, and in hostile environments and restriction of workplace. A successful NDI requires careful planning, choice of appropriate NDI methods and inspection procedures, as well as qualified and trained inspection personnel. A failure of NDI to detect critical defects in safety-related components of nuclear power plants, for instance, may lead to catastrophic consequences for workers, public and environment. Therefore, ensuring that NDI is reliable and capable of detecting all critical defects is of utmost importance. Despite increased use of automation in NDI, human inspectors, and thus human factors, still play an important role in NDI reliability. Human reliability is the probability of humans conducting specific tasks with satisfactory performance. Many techniques are suitable for modeling and analyzing human reliability in NDI of nuclear power plant components, such as FMEA (Failure Modes and Effects Analysis) and THERP (Technique for Human Error Rate Prediction). An example by using qualitative and quantitative assessesments with these two techniques to improve typical NDI of pipe segments of a core cooling system of a nuclear power plant, through acting on human factors issues, is presented.

scholarly journals The use of a solution of the inverse heat conduction problem to monitor thermal stresses

2019 ◽  
Vol 108 ◽  
pp. 01003
Author(s):  
Jan Taler ◽  
Piotr Dzierwa ◽  
Magdalena Jaremkiewicz ◽  
Dawid Taler ◽  
Karol Kaczmarski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Power Plants ◽  
Thermal Stresses ◽  
Thermal Power ◽  
Temperature Fields ◽  
Thick Wall ◽  
Fluid Temperature ◽  
Unsteady Temperature

Thick-wall components of the thermal power unit limit maximum heating and cooling rates during start-up or shut-down of the unit. A method of monitoring the thermal stresses in thick-walled components of thermal power plants is presented. The time variations of the local heat transfer coefficient on the inner surface of the pressure component are determined based on the measurement of the wall temperature at one or six points respectively for one- and three-dimensional unsteady temperature fields in the component. The temperature sensors are located close to the internal surface of the component. A technique for measuring the fastchanging fluid temperature was developed. Thermal stresses in pressure components with complicated shapes can be computed using FEM (Finite Element Method) based on experimentally estimated fluid temperature and heat transfer coefficient

scholarly journals Comparative Modeling of a Parabolic Trough Collectors Solar Power Plant with MARS Models

Energies ◽  
2017 ◽  
Vol 11 (1) ◽  
pp. 37 ◽  
Author(s):  
Jose Rogada ◽  
Lourdes Barcia ◽  
Juan Martinez ◽  
Mario Menendez ◽  
Francisco de Cos Juez
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Power Plant ◽  
Solar Radiation ◽  
Thermal Energy ◽  
Power Plants ◽  
Solar Power ◽  
Rankine Cycle ◽  
Heat Transfer Fluid ◽  
Solar Field

Power plants producing energy through solar fields use a heat transfer fluid that lends itself to be influenced and changed by different variables. In solar power plants, a heat transfer fluid (HTF) is used to transfer the thermal energy of solar radiation through parabolic collectors to a water vapor Rankine cycle. In this way, a turbine is driven that produces electricity when coupled to an electric generator. These plants have a heat transfer system that converts the solar radiation into heat through a HTF, and transfers that thermal energy to the water vapor heat exchangers. The best possible performance in the Rankine cycle, and therefore in the thermal plant, is obtained when the HTF reaches its maximum temperature when leaving the solar field (SF). In addition, it is necessary that the HTF does not exceed its own maximum operating temperature, above which it degrades. The optimum temperature of the HTF is difficult to obtain, since the working conditions of the plant can change abruptly from moment to moment. Guaranteeing that this HTF operates at its optimal temperature to produce electricity through a Rankine cycle is a priority. The oil flowing through the solar field has the disadvantage of having a thermal limit. Therefore, this research focuses on trying to make sure that this fluid comes out of the solar field with the highest possible temperature. Modeling using data mining is revealed as an important tool for forecasting the performance of this kind of power plant. The purpose of this document is to provide a model that can be used to optimize the temperature control of the fluid without interfering with the normal operation of the plant. The results obtained with this model should be necessarily contrasted with those obtained in a real plant. Initially, we compare the PID (proportional–integral–derivative) models used in previous studies for the optimization of this type of plant with modeling using the multivariate adaptive regression splines (MARS) model.

Seven Years of Putnam Plant Operation: Part 1–2

1984 ◽  
Author(s):  
V. C. Tandon ◽  
D. A. Moss
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Heat Rate ◽  
Combined Cycle ◽  
High Availability ◽  
Fuel Utilization ◽  
Residual Oil ◽  
L System ◽  
Efficient Power ◽  
Plant Components

Florida Power and Light Company’s Putnam Station, one of the most efficient power plants in the FP&L system, is in a unique and enviable position from an operational viewpoint. Its operation, in the last seven years, has evolved through a triple phase fuel utilization from distillate to residual oil and finally to natural gas. This paper compares the availability/reliability of the Putnam combined cycle station and the starting reliability of the combustion turbines in each of the operating periods. A review of the data shows that high availability/reliability is not fuel selective when appropriate actions are developed and implemented to counteract the detractors. This paper also includes experience with heat rate and power degradation of various power plant components and programs implemented to restore performance.

scholarly journals Study of the soil temperature effect on the operation of a low-capacity power plant’s condenser

2020 ◽  
Vol 6 (1) ◽  
pp. 118-134
Author(s):  
Aleksandr E. Kishalov ◽  
Almir A. Zinnatullin
Keyword(s):  
Power Plant ◽  
Soil Temperature ◽  
Power Plants ◽  
Heat Removal ◽  
Energy Generation ◽  
Temperature Fields ◽  
Working Fluid ◽  
Stable Operation ◽  
Temperature State ◽  
Decentralized Energy

Every year, the share of decentralized energy generation in Russia is increasing. The following factors contribute to the development of this scenario: increased wear of the country’s energy system equipment, energy shortages, and lack of centralized energy supply in a number of regions and constantly rising tariffs. One of the methods of decentralized energy generation is the use of low-capacity power plants based on the Rankine cycle with an organic working fluid. The operation of such plants requires cooling and condensation of the working fluid by transferring its heat to the environment. This study discusses the design of such a power plant and the heat removal system to a cold source. is the authors consider the design of a condenser which is a horizontal pipeline placed in the ground. Seasonal fluctuations of the soil temperatures affect the operation of the condenser. Thereby, to ensure the stable operation of the power plant, it is necessary to quantitatively assess the effect of the annual dynamics of the soil temperature state on cooling and condensation of the coolant. The study of the temperature fields of the soil, pipeline and working fluid, as well as the lengths required for cooling and condensation of the working fluid, was carried out in the ANSYS CFX software package for numerical hydrodynamic modeling. A homogeneous flow model was chosen to simulate the momentum and condensation of a vapor-liquid medium. Also, the calculations were conducted in a one-dimensional formulation using an engineering method. A methodology for modeling complex processes of heat transfer to the soil using numerical modeling has been developed and verified. 12 calculations were made; the distributions of the steam dryness and temperature in the simulated region depending on the time of the year were obtained. The functions of the total length of the pipeline, cooling and condensation lengths on the soil temperature are analyzed. It has been established that the harmonic change in the temperature of the soil set as the initial condition determines a similar change in the lengths required for cooling and condensation of the working fluid. Using this technique, it is possible to calculate pipelines of more complex shapes. The obtained temperature distributions in cross sections allow to establish the optimal distance between the axes of the pipes when designing a condenser in the form of a bundle of horizontal pipes or a bent pipeline.

Steam Turbine Hot Standby: Electrical Pre-Heating Solution

2019 ◽  
Author(s):  
Y. Kostenko ◽  
D. Veltmann ◽  
S. Hecker
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Steam Turbine ◽  
Power Plants ◽  
Heating System ◽  
Heating Process ◽  
Steam Turbines ◽  
Start Up ◽  
New Apparatus ◽  
General Aspects

Abstract Growing renewable energy generation share causes more irregular and more flexible operational regimes of conventional power plants than in the past. It leads to long periods without dispatch for several days or even weeks. As a consequence, the required pre-heating of the steam turbine leads to an extended power plant start-up time [1]. The current steam turbine Hot Standby Mode (HSM) contributes to a more flexible steam turbine operation and is a part of the Flex-Power Services™ portfolio [2]. HSM prevents the turbine components from cooling via heat supply using an electrical Trace Heating System (THS) after shutdowns [3]. The aim of the HSM is to enable faster start-up time after moderate standstills. HSM functionality can be extended to include the pre-heating option after longer standstills. This paper investigates pre-heating of the steam turbine with an electrical THS. At the beginning, it covers general aspects of flexible fossil power plant operation and point out the advantages of HSM. Afterwards the technology of the trace heating system and its application on steam turbines will be explained. In the next step the transient pre-heating process is analyzed and optimized using FEA, CFD and analytic calculations including validation considerations. Therefor a heat transfer correlation for flexible transient operation of the HSM was developed. A typical large steam turbine with an output of up to 300MW was investigated. Finally the results are summarized and an outlook is given. The results of heat transfer and conduction between and within turbine components are used to enable fast start-ups after long standstills or even outages with the benefit of minimal energy consumption. The solution is available for new apparatus as well as for the modernization of existing installations.

Assessment of Remaining Life for Class 1 Piping Components Experiencing Wall Thinning

2004 ◽  
Author(s):  
Rajnish Kumar
Keyword(s):  
Power Plant ◽  
Nuclear Power ◽  
Power Plants ◽  
Life Extension ◽  
Remaining Life ◽  
Original Design ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
Class 1 ◽  
Plant Components

Assessment of remaining life of power plant components is important in light of plant life management and life extension studies. This information helps in planning and minimizing plant outages for repairs and refurbishments. Such studies are specifically important for nuclear power plants. Nuclear Safety Solutions Limited (NSS) is involved in conducting such studies for plant operators and utilities. Thickness measurements of certain piping components carrying fluids at high temperature and high pressure have indicated higher than anticipated wall thinning rates. Flow accelerated corrosion (FAC) has been identified as the primary mechanism for this degradation. The effect of FAC was generally not accounted for in the original design of the plants. Carbon steel piping components such as elbows, tees and reducers are prone to FAC. In such cases, it is important to establish the remaining life of the components and assess their adequacy for continued service. Section XI of the ASME Boiler and Pressure Vessel Code is applicable for evaluation of nuclear power plant components in service. This Section of the Code does not specifically deal with wall thinning of the piping components. Code Case N-597 provides guidelines for evaluation for continued service for Class 2 and Class 3 piping components. For Class 1 piping components, this Code Case suggests that the plant owner should develop the methodology and criteria for evaluation. This paper presents methodology and procedure for establishing the remaining life and assessment of Class 1 piping components experiencing wall thinning effects. In this paper, the rules of NB-3600 and NB-3220 and Code Case N-597 have been utilized for assessment of the components for continued service. Details of various considerations, criteria and methodology for assessment of the remaining life and adequacy for continued service are provided.

Effects of Variation of the Overall Heat Transfer Coefficient in the Feedwater Heaters on the Thermodynamic and Economic Performance of Power Stations

2000 ◽  
Author(s):  
Józef Portacha ◽  
Idris A. Elfeituri ◽  
Adam Smyk ◽  
Jerzy K. Fiszdon
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Power Plant ◽  
Transfer Coefficient ◽  
Economic Performance ◽  
Power Plants ◽  
Economic Effects ◽  
Operating Conditions ◽  
Plant Design ◽  
Overall Heat Transfer Coefficient

Abstract This paper examines the effect of the variation of the overall heat transfer coefficient (U) in feedwater heaters on the thermodynamic and economic performance of a coal-fired steam power plant. The changes in the values of U are caused by the heat transfer surface fouling or by errors in the power plant design. These errors often result from the use of approximate heat transfer equations when selecting power plants elements. Low and high pressure feedwater heaters of a power plant equipped with a condensing turbine and a natural circulation steam generator with one reheat stage are considered in this work. The research was conducted using the overall heat transfer coefficients from 50% to 150% of the nominal value. The thermodynamic and economic effects on the power plant were calculated using the mathematical model of the power plant. The power plant components’ mathematical models evaluate the influence of the changes in the heaters’ overall heat transfer coefficient on the thermodynamic (especially exergetic) losses and economic effects. They take into account off-design operating conditions. The decomposition method and multi-level iterative process was used to solve the problem. The research proved that, during operation, the capacity of the power plant might change by up to 2% due to above-mentioned variations. For a 600 MW power plant that means variation of the electric power delivery of approximately 12 MW and increase of the operating costs of up to 4 million dollars per year. The obtained results are particularly useful in the decision-making process in planning renovation and feedwater heaters’ replacement periods.

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