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Heat transfer by liquid jets impinging on a hot flat surface
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB, Corporate Research, Västerås, Sweden. (FEC, Track 3, Modeling and Simulation)ORCID iD: 0000-0002-9490-9703
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB, Corporate Research, Västerås, Sweden.ORCID iD: 0000-0001-8849-7661
ABB AB, Corporate Research, Västerås, Sweden.
2016 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 164, no 15, 934-943 p.Article in journal (Refereed) Published
Abstract [en]

Runout Table (ROT) cooling is one of the most important factors for controlling quality of hot rolled steel. ROT cooling uses large quantities of water to cool the steel plate. Optimizing heat transfer in the ROT would reduce the amount of water used, which will lower the amount of energy needed for pumping, filtering, storage and use of water. Optimization will therefore result in a direct energy saving as well as increasing the product quality.

This study investigates heat transfer by turbulent water jets impinging on a hot flat steel plate at temperatures below the boiling point in order to understand convection heat transfer phenomena. This is an important stage that precedes the boiling and addresses the applicability of the heat transfer correlations available in the literature.

A single axisymmetric jet and a pair of interacting jets are simulated using Computational Fluid Dynamics (CFD). The Reynolds Averaged Navier Stokes (RANS) model under steady and transient conditions and the kɛ turbulence model are used in both 2D axisymmetric and 3D simulations. We investigate the influence of the water flow rate on the jet cooling characteristics and develop a correlation for the radial position of the maximum Nusselt number based on numerical results.

Two sets of boundary conditions – constant temperature and constant heat flux – are applied at the surface of the steel plate and evaluated. The single jet numerical results compare favourably with published data based on measurements and analytical models. The thermal performance of a two-jet system was found to be no better than a single jet because the jets were too far from each other to generate any additional thermal interaction.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 164, no 15, 934-943 p.
Keyword [en]
Liquid jets; Impingement; CFD; Heat transfer; Flat surface; Interaction
National Category
Applied Mechanics Fluid Mechanics and Acoustics
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-29812DOI: 10.1016/j.apenergy.2015.08.038ISI: 000372379700082Scopus ID: 2-s2.0-84941008933OAI: oai:DiVA.org:mdh-29812DiVA: diva2:874861
Projects
MR-OMDO ((Model Reduction for Online Multi-Disciplinary Optimization))
Available from: 2015-11-29 Created: 2015-11-29 Last updated: 2017-12-01Bibliographically approved
In thesis
1. TOWARDS ACCELERATED SIMULATIONS FOR FLUID FLOW AND HEAT TRANSFER OF LARGE INDUSTRIAL PROCESSES
Open this publication in new window or tab >>TOWARDS ACCELERATED SIMULATIONS FOR FLUID FLOW AND HEAT TRANSFER OF LARGE INDUSTRIAL PROCESSES
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The manufacturing sector is one of the biggest energy consumers. The iron and steel markets in China are growing very fast. Several studies have been performed to evaluate the Chinese steel sector in terms of energy savings and CO2 emissions. The results of the studies showed that the major energy savings expected within 2020 and 2030 timeframe will be from industrial furnaces in steel mills. For the Swedish steel industry, it is important to be very efficient in order to remain competitive. The hot rolling process in the steel industry is a long process, where big slabs are heated in a furnace above the recrystallization temperature to roll the metal into a thin sheet and then the sheet is cooled at the Runout table using water. The amount of energy used during the process directly influences the price of the products. Moreover, the government policy on energy usage and CO2 emissions, the competitive market and the water scarcity, demand an optimal process operation to reduce energy consumption and greenhouse gas emission. Computer simulation is the best and most convenient way to approximate real-world processes; therefore, there is a need to have a real-time online simulation tool for process optimisation, decision support and diagnostics in different industries.

Computational fluid dynamics (CFD) is a robust tool for simulating almost any kind of real-world process related to fluid flow, heat transfer and combustion. However, simulating real-world processes in real-time using CFD is very challenging due to the complexity involved in the physical phenomena studied. In this thesis, CFD simulations have been performed in small scale to understand the physics and perceive the complexity involved in the heating process of steel slabs and the cooling process of the steel sheets at hot rolling steel industries. The results from the simulations are successfully validated using experimental and theoretical results published in open literature. Past experience suggests using mesh-based commercial CFD solvers for simulating industrial processes, only if accurate and detail results are desired. However, the computational performance of these solvers shows limitations from a real-time perspective and indicates the need for alternative CFD methods and solvers. In the literature review performed as part of the first stage of this work, we have identified different alternative methods which can be used to perform CFD simulations in real-time or near real-time for large industrial processes. The thesis discusses the limitations of different types of CFD methods and points out the difficulties and challenges in utilising these methods for simulating large industrial processes. Our preliminary simulation work brings light towards the goal of multi-phase multi-physics real-time simulations.

Abstract [sv]

Tillverkningsindustrin är en av de största energikonsumenterna.  Järn och stålindustrin i Kina växer väldigt fort. Flera studier har genomförts för att utvärdera den kinesiska stålindustrisektorn vad gäller energieffektivisering och utsläpp av CO2. Resultaten av studierna visade att de stora energibesparingarna som kan genomföras mellan 2020 – 2030 kommer från industriella ugnar i stålverken. För den svenska stålindustrin är det viktigt att vara mycket effektiv för att bibehålla konkurrenskraft. Varmvalsningsprocessen i stålindustrin är en lång process, där stora skivor hettas upp i en ugn över den temperatur där materialet rekristalliseras och metallen valsas sedan i tunna skivor. Skivorna kyls sedan på utrullningsbordet med vatten. Energimängden som används under processen påverkar direkt priset på produkterna. Dessutom kräver stränga statliga bestämmelser, en konkurrenskraftig marknad och bristen på vatten optimala processförhållanden för att reducera energikonsumtionen och utsläppen av klimatgaser. Datasimulering är det bästa och mest pålitliga verktyget att approximera en verkliga processer. Det finns därför ett behov att ha ett online simuleringsverktyg för processoptimering, beslutsstöd och diagnostik i olika industrier.

CFD-simulering (Computational fluid dynamics) är ett robust simuleringsverktyg för nästan alla typer av verkliga processer relaterade till vätskeflöde, värmeöverföring och förbränning. Dock är simulering av verkliga processer med CFD mycket utmanande på grund av komplexiteten i de fysikaliska fenomenen som ska studeras.  I den här avhandlingen har CFD-simulering använts i liten skala för att förstå fysikaliska egenskaper och komplexiteten i värmningsprocesser av stålskivor och kylningsprocessen av de tunna stålplåtarna vid varmvalsningsprocessen i stålindustrin. Resultaten från simuleringarna är framgångsrikt validerade från experimentella och teoretiska resultat publicerade i litteraturen. Tidigare erfarenheter föreslår nätverksbaserade kommersiella CFD verktyg för att simulera industriella processer om korrekta och detaljerade resultat ska fås. Dock är prestandan för dessa verktyg begränsade ur ett verklighetsperspektiv och indikerar behovet av alternativa CFD-metoder och verktyg. Det första steget i detta arbete var att genomföra en litteraturgenomgång av tidigare studier. Vi identifierade då alternativa metoder som skulle kunna användas för att genomföra CFD-simulering i realtid och i nära realtid för stora industriella processer. Avhandlingen diskuterar begränsningar av olika CFD-metoder och synliggör svårigheter och utmaning i att utnyttja dessa metoder för att simulera stora industriella processer. Vårt preliminära simuleringsarbete är ett litet steg på vägen i målet att producera flerfasiga och multifysikaliska realtidssimuleringar.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2016
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 235
National Category
Environmental Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-31443 (URN)978-91-7485-264-6 (ISBN)
Presentation
2016-06-09, Kappa, Mälardalens högskola, Västerås, 13:15 (English)
Opponent
Supervisors
Available from: 2016-04-21 Created: 2016-04-20 Last updated: 2016-06-07Bibliographically approved

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Hosain, Md LokmanBel Fdhila, Rebei

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