Evaluation of the technical condition of medium-sized boilers

The recent trend in the steam and electricity production has been both to increase the efficiency of the facility and to keep tightening legislation concerning emission limits. The lifetime of energy equipment is greatly influenced by the operating temperature, pressure and operating characteristics. The new conditions lead the operator to more often changes of these parameters, which has negative influence to the facility in terms of service life. Precise knowledge of the facility being operated and the ability to predict the residual life of its key parts in time is therefore necessary. A new methodology for determining the residual life and evaluating problematic situations of medium size boilers was developed at Brno University of Technology. Its approaches and advantages will be presented in this paper. The methodology provides the user with approaches for the lifetime evaluation of an equipment as a whole, based on detailed knowledge of the equipment being investigated and the ongoing damage. Additionally, if the equipment is continuously evaluated, it is possible to extend the inspection interval or to achieve a significantly higher lifetime of the entire equipment, thereby reducing the economic cost. If defined criteria are met, the methodology also allows inclusion of FEM and CFD simulations for achieving higher relevance of the results

Thermal load non-uniformity estimation for superheater tube bundle damage evaluation

Industrial boiler damage is a common phenomenon encountered in boiler operation normally which usually lasts several decades. Since boiler shutdown may be required because of localized failures, it is crucial to predict the most vulnerable parts. If damage occurs, it is necessary to perform root cause analysis and devise corrective measures (repairs, design modification, etc.). Boiler tube bundles, such as those in superheaters, preheaters and reheaters, are the most exposed and often the most damaged boiler parts. Both short-term and long-term overheating are common causes of tube failures. In these cases, the design temperatures are exceeded, which often results in decrease in remaining creep life. Advanced models for damage evaluation require temperature history, which is available only in rare cases when it has been measured for the whole service life. However, in most cases it is necessary to estimate the temperature history from available operation history data (inlet and outlet pressures and temperatures etc.). The task may be very challenging because of the combination of complex flow behavior in the flue gas domain and heat transfer phenomena. This paper focuses on estimating thermal load on superheater tubes via Computational Fluid Dynamics (CFD) simulation of flue gas flow including heat transfer within the domain consisting of a furnace and a part of the first stage of the boiler

Transient Thermal Stress Calculation of a Shell and Tube Condenser with Fixed Tubesheet

The present article deals with transient thermal stress calculation on a safety horizontal shell and tube condenser. This condenser is used in a power plant for cooling of hot steam diverted from the turbine in the case of its emergency shutdown. The standard stress calculation was provided according to the EN 13445 standard in steady regime. As consistent with this calculation, an expansion joint must be used on the shell. The main aim of this article is to describe a detailed calculation of the transient temperature field on the shell and tubes, using finite element method analysis, and longitudinal thermal stresses on the shell and tubes during the start-up process. Transient analyses are useable for more accurate EN 13445 calculation and, furthermore, for fatigue calculation

Nonlinear Finite Element Analysis-Based Flow Distribution and Heat Transfer Model

A new strategy for fast, approximate analyses of fluid flow and heat transfer is presented. It is based on Finite Element Analysis (FEA) and is intended for large yet structurally fairly simple heat transfer equipment commonly used in process and power industries (e.g., cross-flow tube bundle heat exchangers), which can be described using sets of interconnected 1-D meshes. The underlying steady-state model couples an FEA-based (linear) predictor step with a nonlinear corrector step, which results in the ability to handle both laminar and turbulent flows. There are no limitations in terms of the allowed temperature range other than those potentially stemming from the usage of fluid physical property computer libraries. Since the fluid flow submodel has already been discussed in the referenced conference paper, the present article focuses on the prediction of the tube side and the shell side temperature fields. A simple cross-flow tube bundle heat exchanger from the literature and a heat recovery hot water boiler in an existing combined heat and power plant, for which stream data are available from its operator, are evaluated to assess the performance of the model. To gain further insight, the results obtained using the model for the heat recovery hot water boiler are also compared to the values yielded by an industry-standard heat transfer equipment design software package. Although the presented strategy is still a “work in progress” and requires thorough validation, the results obtained thus far suggest it may be a promising research direction

Optimum design selection of a cryogenic tank

Předkládaná práce je zaměřena na nalezení optimální konstrukce pro uchycení kryogenní nádoby v rámu ISO kontejneru. Řešení vychází z pevnostních analýz několika navržených variant a jejich následného posouzení. Na základě příslušných norem je vytvořen soubor testů, při kterých musí každý kryogenní kontejner obstát před uvedením do provozu. Testy se provádí pevnostními analýzami metodou konečných prvků (MKP) pomocí softwaru ANSYS. V počáteční fázi jsou výsledky analýz použity jako podklady pro případné úpravy cílené na splnění požadavků normy, v konečné fázi pak umožní volbu optimálního řešení.The purpose of this work is to find optimal design for mounting cryogenic tank into ISO container frame. Solution is based on stress analyses of several designs and theirs interpretation. According to standards, set of tests, which all cryogenic containers have to pass before being put into operation, is created. Designs are tested by final element method using software ANSYS. At first, results of the stress analyses provide base for improvements targeted to better meeting with needs of the standards. In final stage, the results participate in optimum design selection.

Software Aided Design and Assessment of Shell and Tube Heat Exchangers

Subject of this work is a development of an integrated software environment for mechanical design and check of shell and tube heat exchangers. Processes of mechanical design and checks well as software which perform these processes are broken down to basic methods and parts. Mechanical design is usually performed according to some standards. In this work, ČSN EN 13445 is used. This standard describes mostly design check calculations which can be easily algorithmized. On the contrary, design calculations are described to some extent in few simple cases and mechanical design of shell and tube heat exchanger has not been fully algorithmized yet. Subject of this work is design of software, which will be capable of automatically performing mechanical design from datasheet as an input. Based on breakdown of design and check processes, requirements for key software features are derived. Important part of presented work is design and implementation of key modules – data model of shell and tube heat exchanger, module for mechanical design check according to ČSN EN 13445. These modules form basis of the software which will be developed further in future work

Software Aided Design and Assessment of Shell and Tube Heat Exchangers

Tato práce se zabývá vývojem integrovaného softwarového prostředí a postupů pro usnadnění konstrukčního návrhu a kontroly tepelných výměníků se svazkem trubek v plášti. V práci jsou rozebrány procesy konstrukčního návrhu a kontroly tepelných výměníků se svazkem trubek v plášti a možnosti komerčních softwarů, které v praxi tyto procesy usnadňují. Konstrukční návrh se většinou provádí v souladu s normami, v této práci je použita ČSN EN 13445. Kontrolní výpočty podle této normy lze plně automatizovat, avšak návrhový proces je automatizován pouze částečně nebo vůbec. Předmětem práce je vývoj a realizace integrované softwarové podpory, jejíž hlavní motivací je právě automatizace návrhového procesu tepelných výměníků se svazkem trubek v plášti s využitím nové výpočtové filozofie zahrnující také některé nové dílčí postupy řešení. Na základě rozboru procesů návrhu a kontroly jsou nejprve formulovány realistické požadavky na takový software, který by tyto procesy usnadnil. Stěžejní části práce se pak věnují zpracování klíčových modulů vyvíjeného integrovaného softwaru – datového modelu výměníku a jeho okolí a modulu pro pevnostní kontrolu podle ČSN EN 13445. Tyto moduly tvoří nosný základ vyvíjeného softwaru, který lze dále rozšiřovat, což bude předmětem navazující práce.Subject of this work is a development of an integrated software environment for mechanical design and check of shell and tube heat exchangers. Processes of mechanical design and checks well as software which perform these processes are broken down to basic methods and parts. Mechanical design is usually performed according to some standards. In this work, ČSN EN 13445 is used. This standard describes mostly design check calculations which can be easily algorithmized. On the contrary, design calculations are described to some extent in few simple cases and mechanical design of shell and tube heat exchanger has not been fully algorithmized yet. Subject of this work is design of software, which will be capable of automatically performing mechanical design from datasheet as an input. Based on breakdown of design and check processes, requirements for key software features are derived. Important part of presented work is design and implementation of key modules – data model of shell and tube heat exchanger, module for mechanical design check according to ČSN EN 13445. These modules form basis of the software which will be developed further in future work.