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Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J1: Heat and Mass Transfer".

Deadline for manuscript submissions: closed (20 November 2022) | Viewed by 6681

Special Issue Editors

Prof. Dr. Jerzy Okrajni

E-Mail Website
Guest Editor
Faculty of Materials Engineering, Silesian University of Technology, 44-200 Gliwice, Poland
Interests: mechanics of materials; fatigue; durability of power plant components
Special Issues, Collections and Topics in MDPI journals
Dr. Krzysztof Wacławiak

E-Mail Website
Guest Editor
Faculty of Materials Engineering, Silesian University of Technology, 44-200 Gliwice, Poland
Interests: mechanics; heat transfer; computer modelling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We invite you to submit your original research or overview papers to this Special Issue on the “Heat transfer in the components of power boilers and related technological and endurance problems" in Energies.

Renewable energy becomes a decisive factor in power energy, as their activity alters the stable operation of conventional power units to unsteady, with fast start-ups and shout-downs.

Newly built power units (coal- or gas-fired, nuclear) have higher efficiency, that results from raised parameters of steam.

As a result, new materials with appropriate mechanical and physical properties are employed in order to withstand the challenging parameters of operation. In nuclear energy, additional ionizing radiation makes the operation of parameters more demanding.

The material evolution requires new technology of manufacturing, ensuring appropriate heat transfer and the enhancement of materials durability. The presentation of research results and studies focusing on this problem will be the subject of this Special Issue of Energies.

Topics include, but are not limited to:

  • experimental and modeling study of heat transfer on surface and inside thick-walled elements,
  • stress-strain behavior resulting from heat transfer and mechanical loading,
  • methods of enhancement of heat transfer,
  • manufacturing of heat exchangers and other components under mechanical and thermal loading.

Prof. Dr. Jerzy Okrajni
Dr. Krzysztof Wacławiak
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Heat transfer
  • Boiler efficiency
  • Thermal stress
  • Durability of components
  • Mechanical and thermal loading

Published Papers (5 papers)

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Editorial

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4 pages, 166 KiB  
Editorial
Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems
by Jerzy Okrajni and Krzysztof Wacławiak
Energies 2023, 16(12), 4799; https://0-doi-org.brum.beds.ac.uk/10.3390/en16124799 - 19 Jun 2023
Viewed by 599
Abstract
Issues related to the generation of electricity are currently particularly important in Europe due to the need to ensure basic conditions for the function and development of the economy during crises caused by political conflicts with a global impact [...] Full article
(This article belongs to the Special Issue Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems)

Research

Jump to: Editorial

16 pages, 6232 KiB  
Article
The Effect of the Welding Technology on the Thermal Performance of Welded Finned Tubes Used in Heat Exchangers
by Janusz Adamiec and Michał Urbańczyk
Energies 2023, 16(3), 1320; https://0-doi-org.brum.beds.ac.uk/10.3390/en16031320 - 26 Jan 2023
Cited by 2 | Viewed by 1428
Abstract
Due to the use of welded finned tubes in heat exchangers, gas blocks are characterized by very good electric energy production performance, and their reliability can reach 98%. Finned tubes used in heat exchangers are usually welded. Such tubes should be characterised by [...] Read more.
Due to the use of welded finned tubes in heat exchangers, gas blocks are characterized by very good electric energy production performance, and their reliability can reach 98%. Finned tubes used in heat exchangers are usually welded. Such tubes should be characterised by the following properties: high thermal performance, good resistance to high-temperature corrosion in a flue gas atmosphere, and appropriate joint strength and hardness. The most popular technology for welding finned tubes is MAG. MAG-welded joints are characterised by considerable spattering, weld discontinuities (up to 60%), and non-axial fin alignment. Such irregularities result in a considerably reduced heat flux due to the heat transfer resistance occurring in the welded joint. It has been shown that with weld discontinuities of 20%, the thermal performance of welded finned tubes reduces considerably. This paper proposes the possibility of welding finned tubes with a laser. The thermal properties of laser-welded finned tubes were compared with those of MAG-welded tubes. It was found that the thermal performance of welded finned tubes was three times higher than that of plain tubes. However, the thermal performance was not found to be affected by the welding technology. The correct heat flow at the level of 95% occurs in the tube/fin joint even with joint penetration of 0.01 mm, however, the absence of metallic continuity in a joint results in a drastically reduced thermal performance (by 50%) and the overheating of fins, which affects their durability. Full article
(This article belongs to the Special Issue Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems)
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21 pages, 13911 KiB  
Article
Assessment of the Hot-Cracking Susceptibility of Welded Joints of the 7CrMoVTiB10-10 Bainitic Steel Used in Heat Exchangers
by Janusz Adamiec
Energies 2023, 16(1), 162; https://0-doi-org.brum.beds.ac.uk/10.3390/en16010162 - 23 Dec 2022
Cited by 1 | Viewed by 982
Abstract
Bainitic steel containing approx. 2.25% Cr and 0.6 Mo with micro-additions of V, Ti, and B, designated as 7CrMoVTiB10-10 (T/P24), is one of the new construction materials used in new supercritical power units. The weldability of 7CrMoVTiB10-10 is defined as the hot-cracking susceptibility, [...] Read more.
Bainitic steel containing approx. 2.25% Cr and 0.6 Mo with micro-additions of V, Ti, and B, designated as 7CrMoVTiB10-10 (T/P24), is one of the new construction materials used in new supercritical power units. The weldability of 7CrMoVTiB10-10 is defined as the hot-cracking susceptibility, it should be stated that the hot cracking in the welded joints of 7CrMoVTi10-10 is determined by phenomena occurring in the high-temperature brittleness range (HTBR). In this work, the HTBR is established for both the base material and welding conditions, taking into account the critical temperature-strain intensity (CST) and the critical strain speed (CSS). The HTBR for 7CrMoVTi10-10 is 122 °C wide and covers temperatures from 1394 °C to 1516 °C. Under imposed deformation conditions (typical during welding), the HTBR extends to a width of 293 °C towards lower temperatures, i.e., from 1516 °C to 1223 °C. The CSS = 0.83 1/s, the CST = 0.003 1/°C, and the Rf index = 0.12, which can be adopted as the criteria for the susceptibility of 7CrMoVTiB 10-10 to hot cracking under imposed deformation conditions. The hot cracking in 7CrMoVTiB10-10 occurs as a result of the loss of cohesion by the thin liquid layer crystallising between the growing weld crystals. Such cracks appear when the CSS or the CST is exceeded within the HTBR. Full article
(This article belongs to the Special Issue Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems)
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19 pages, 5560 KiB  
Article
The Impact of Conventional Power Block Startup Procedures on the Fatigue Behavior of Drum Materials
by Jerzy Okrajni, Krzysztof Wacławiak, Mariusz Twardawa and Grzegorz Junak
Energies 2022, 15(10), 3528; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103528 - 11 May 2022
Viewed by 1414
Abstract
Varying demands for electricity within the energy sector require the modification of operating modes to ensure both an uninterrupted electricity supply and the upholding of safety standards. This paper presents a method for the prediction of drum fatigue life, via the local analysis [...] Read more.
Varying demands for electricity within the energy sector require the modification of operating modes to ensure both an uninterrupted electricity supply and the upholding of safety standards. This paper presents a method for the prediction of drum fatigue life, via the local analysis of stress–strain fields and low-cycle fatigue tests of the drum material. The analysis compares the fatigue properties of an unused material and a material that has undergone many years of operation. In addition, this paper suggests drum operating conditions based on the results of load testing under industrial conditions. The drum model was developed on the basis of technical documentation. The analysis includes the calculations of time-dependent temperature distributions, stresses, and strains for various drum startup modes. The drum material fatigue properties are determined under low-cycle conditions. Using the modeling results and fatigue properties, predictions of drum life for different startup modes are presented. The paper summarizes the impact of a range of startup procedures and the drum material fatigue properties on the fatigue life of a working drum, under various mechanical and thermal loads. In addition, this paper proposes a methodological approach to fatigue life assessment, as a combination of multiple research methods. Full article
(This article belongs to the Special Issue Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems)
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21 pages, 6457 KiB  
Article
On-Line Control of Stresses in the Power Unit Pressure Elements Taking Account of Variable Heat Transfer Conditions
by Andrzej Rusin, Martyna Tomala, Henryk Łukowicz, Grzegorz Nowak and Wojciech Kosman
Energies 2021, 14(15), 4708; https://0-doi-org.brum.beds.ac.uk/10.3390/en14154708 - 03 Aug 2021
Cited by 7 | Viewed by 1407
Abstract
Coal-fired power units, now balancing power shortages in the power system, must be characterised by increasingly higher flexibility of operation. This means faster start-ups and the capacity for frequent decreases and increases in the power output. These processes cause large temperature gradients in [...] Read more.
Coal-fired power units, now balancing power shortages in the power system, must be characterised by increasingly higher flexibility of operation. This means faster start-ups and the capacity for frequent decreases and increases in the power output. These processes cause large temperature gradients in elements of the power unit and the turbine and lead to an increase in the stress level. At such an operating regime it is impossible to ensure safety based on start-up characteristics only—it becomes necessary to constantly monitor stress levels in critical areas of machinery and equipment elements. The stress level in turbine elements can be monitored on-line using algorithms based on Green’s functions and Duhamel’s integral. This paper presents examples of modifications of stress calculations in turbine valves and casings during start-ups. By modifying basic algorithms, it is possible to take into account the impact of the variability of heat transfer coefficients on the thermal stress level. Additionally, individual Green’s functions and correction factors were determined for specific stages of start-ups. Due to modifications, it is possible to obtain satisfactory agreement with the results obtained from FEM-based calculations for the entire heating process. Equations are also given that enable estimation of values of the heat transfer coefficient in turbine valves. The proposed modification of the algorithm will substantially improve the accuracy of stress modelling in transient states of the turbine operation. On-line stress monitoring will enable an increase in the flexibility of the power unit operation and facilitate operational control, ensuring safety of individual elements at the same time. The stress values calculated in the on-line mode can also be used to estimate fatigue life consumption and forecast the residual lifetime of individual components. Full article
(This article belongs to the Special Issue Heat Transfer in the Components of Power Boilers and Related Technological and Endurance Problems)
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