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Fluid Flow and Heat Transfer Simulations for Complex Industrial Applications: From Reynolds Averaged Navier-Stokes towards Smoothed Particle Hydrodynamics
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (SOFIA)ORCID iD: 0000-0002-9490-9703
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optimal process control can significantly enhance energy efficiency of heating and cooling processes in many industries. Process control systems typically rely on measurements and so called grey or black box models that are based mainly on empirical correlations, in which the transient characteristics and their influence on the control parameters are often ignored. A robust and reliable numerical technique, to solve fluid flow and heat transfer problems, such as computational fluid dynamics (CFD), which is capable of providing a detailed understanding of the multiple underlying physical phenomena, is a necessity for optimization, decision support and diagnostics of complex industrial systems. The thesis focuses on performing high-fidelity CFD simulations of a wide range of industrial applications to highlight and understand the complex nonlinear coupling between the fluid flow and heat transfer. The industrial applications studied in this thesis include cooling and heating processes in a hot rolling steel plant, electric motors, heat exchangers and sloshing inside a ship carrying liquefied natural gas. The goal is to identify the difficulties and challenges to be met when simulating these applications using different CFD tools and methods and to discuss the strengths and limitations of the different tools.

The mesh-based finite volume CFD solver ANSYS Fluent is employed to acquire detailed and accurate solutions of each application and to highlight challenges and limitations. The limitations of conventional mesh-based CFD tools are exposed when attempting to resolve the multiple space and time scales involved in large industrial processes. Therefore, a mesh-free particle method, smoothed particle hydrodynamics (SPH) is identified in this thesis as an alternative to overcome some of the observed limitations of the mesh-based solvers. SPH is introduced to simulate some of the selected cases to understand the challenges and highlight the limitations. The thesis also contributes to the development of SPH by implementing the energy equation into an open-source SPH flow solver to solve thermal problems. The thesis highlights the current state of different CFD approaches towards complex industrial applications and discusses the future development possibilities.

The overall observations, based on the industrial problems addressed in this thesis, can serve as decision tool for industries to select an appropriate numerical method or tool for solving problems within the presented context. The analysis and discussions also serve as a basis for further development and research to shed light on the use of CFD simulations for improved process control, optimization and diagnostics.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2018.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 282
Keywords [en]
Computational Fluid Dynamics, Heat transfer, Industrial applications, Reynolds Averaged Navier-Stokes, Smoothed Particle Hydrodynamics, Energy enginnering, Thermal Management, Process control
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-41277ISBN: 978-91-7485-415-2 (print)OAI: oai:DiVA.org:mdh-41277DiVA, id: diva2:1260308
Public defence
2018-12-14, Delta, Mälardalens högskola, Västerås, 13:00 (English)
Opponent
Supervisors
Available from: 2018-11-02 Created: 2018-11-01 Last updated: 2018-11-12Bibliographically approved
List of papers
1. CFD Modeling of Real Scale Slab Reheating Furnace
Open this publication in new window or tab >>CFD Modeling of Real Scale Slab Reheating Furnace
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(English)Conference paper, Published paper (Refereed)
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-31446 (URN)
Conference
12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa del Sol, Spain,11-13 July, 2016
Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2018-11-01Bibliographically approved
2. Numerical Investigation of Liquid Sloshing in Carrier Ship Fuel Tanks
Open this publication in new window or tab >>Numerical Investigation of Liquid Sloshing in Carrier Ship Fuel Tanks
2018 (English)In: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 51, no 2, p. 583-588Article in journal (Refereed) Published
Abstract [en]

Liquid sloshing inside a partially filled tank has a great impact on the fragile internal tank coating and also on the stability of carrier ships. Several studies highlighted the challenges encountered due to the sloshing and proposed anti-sloshing tank structures. However, sloshing of liquefied natural gas fuel in high pressure vessels during transportation still remain a challenge. In the present numerical study we consider a downscaled 2D geometry to investigate the sloshing. Non-dimensional numbers are used to downscale the geometry. The purpose is to understand the flow structures and validate the downscaling approach based on the similarity scale laws. In the present work, Computational Fluid Dynamics (CFD) based on the Reynolds Averaged Navier-Stokes equations (RANS) with the Volume of Fluid (VOF) method in one hand and the Smooth Particle Hydrodynamics (SPH) method in the other hand, are used to simulate the downscaled model. The results from both methods are compared and validated using experimental data. A full scale model have also been simulated using SPH to verify the applicability of the scaling laws. The SPH model shows the capability to efficiently capture the sloshing phenomena. The VOF and SPH provide similar results in terms of flow dynamics, pressure and forces. The overall numerical results agree with the measurements and show that SPH can be an efficient tool to be used in modelling sloshing phenomena, compared to the RANS-VOF approach which is expensive in terms of CPU time. However, features like turbulence need to be further investigated. 

Place, publisher, year, edition, pages
Elsevier B.V., 2018
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-39302 (URN)10.1016/j.ifacol.2018.03.098 (DOI)000435693000100 ()2-s2.0-85046702547 (Scopus ID)
Available from: 2018-05-24 Created: 2018-05-24 Last updated: 2018-11-01Bibliographically approved
3. Air Flow inside Rotating Electrical Machines: A Comparison between Finite Volume and SPH Method
Open this publication in new window or tab >>Air Flow inside Rotating Electrical Machines: A Comparison between Finite Volume and SPH Method
2017 (English)In: Conference Proceedings of NAFEMS World Congress 2017 (NWC17), 2017Conference paper, Published paper (Refereed)
Abstract [en]

A general, sufficiently accurate, applicable and reasonably fast approach to thermal analysis of rotating electrical machines is of high interest for motor and generator developers and manufacturers. The thermal performance and the lifetime of a machine is limited by the temperature distribution and the hot spot temperature. The most commonly encountered cooling medium is air and the temperature distribution is driven by the air flow pattern inside the machine. Two different Computational Fluid Dynamics methods, the mesh based Finite Volume Method (FVM) and the mesh free particle based Smoothed Particle Hydrodynamics (SPH) method are employed in this paper to model the airflow inside a rotating machine. Mesh based methods are quite robust, however, they are very expensive in terms of meshing effort and CPU time to be used extensively in R&D. Analysing and optimizing products with complex geometrical shapes need mesh generation for every specific design change and this may be the major part of the modelling process. This challenging task is not necessary for the SPH method. SPH method can also provide high quality 3D visualization that can improve the design process.

This work investigates the usability of the SPH method when applied to rotating machinery for rotor speeds normally encountered in motors and generators. A comparison with an FVM based approach is also performed. Both the FVM and the SPH solvers show good agreement for the overall flow pattern inside the machine with some disagreement for the airflow inside the air-gap between the rotor and the stator. The FVM solver successfully captures the Taylor vortex flow inside the annulus air-gap which is in general a great modelling challenge. The SPH solver on the other hand shows great capability to couple rotation of the rotor and well represent the overall flow pattern inside the machine. However, the 3D SPH solver could not capture the complex Taylor vortices inside the air-gap which may be due to the limited number of particles used for the simulation. An increase in the number of particles would certainly improve the accuracy of the results as confirmed by the 2D SPH simulation. The present study shows that the SPH solver can be used to predict the air flow pattern inside rotating machines within an acceptable accuracy.

Keywords
Air-gap flow; Rotating machines; CFD simulation; SPH method; Taylor vortices
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-36522 (URN)
Conference
NAFEMS World Congress 2017 (NWC17)
Projects
MR-OMDO
Available from: 2017-09-27 Created: 2017-09-27 Last updated: 2018-11-01Bibliographically approved
4. Literature Review of accelerated CFD Simulation Methods towards Online Application
Open this publication in new window or tab >>Literature Review of accelerated CFD Simulation Methods towards Online Application
2015 (English)In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 75, p. 3307-3314Article, review/survey (Refereed) Published
Abstract [en]

Engineering advanced methods for example Computational Fluid Dynamics (CFD) are heavily used to solve, design and model complex industrial applications. They provide high accuracy however, the simulation time is too long and this limit its generalized use dramatically as for control purposes. CFD tools and methods are often used to analyze the energy distribution and management in different industrial processes like hot rolling industries, furnaces and boilers as well as a number of areas where mixing and thermal management are of importance. Huge amounts of energy are often fed into such processes. A small amount of optimization can provide a very large energy saving. It is now an urgent need to have a tool like real-time CFD to analyze, control and optimize on-line various industrial processes. This tool or method can contribute to build efficient and sustainable energy systems. The scope of this work is to find alternative simulation techniques that can also address industrial applications and provide solutions within a decent accuracy and resolution. In this paper we provide a literature review of those methods that can be categorized as mesh based, mesh free and hybrid that are capable of providing appropriate results in some key areas of interest. As a next step one of these methods will be implemented and coupled to CFD simulation of cooling impinging jets used to control the heat transfer and temperature behavior of a hot flat surface in a hot rolling process where thermal energy and cooling water are used with excess. (C) 2015 The Authors. Published by Elsevier Ltd.

National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-29341 (URN)10.1016/j.egypro.2015.07.714 (DOI)000361030005054 ()2-s2.0-84947093405 (Scopus ID)
Conference
7th International Conference on Applied Energy (ICAE), MAR 28-31, 2015, Abu Dhabi, U ARAB EMIRATES
Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2018-11-01Bibliographically approved
5. Smoothed Particle Hydrodynamics modeling of transient conduction and convection heat transfer
Open this publication in new window or tab >>Smoothed Particle Hydrodynamics modeling of transient conduction and convection heat transfer
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Smoothed Particle Hydrodynamics (SPH) is a mesh-free particle method that has been widely used in the last years to model some complex flows. SPH was mainly used to investigate problems related to hydrodynamics and maritime engineering where heat transfer is of no importance. Thermal problems have seldom been addressed due to the limitation of the main commercial and open-source SPH codes.

In this article, the energy equation is implemented in the SPH based open-source code DualSPHysics to solve conduction and forced convection heat transfer problems. Laminar flow cases are simulated as the first validation cases of the implemented model. The studied cases include conduction in an aluminum block, conduction in still water in a cavity, laminar water flow between two infinite parallel plates and tube bank heat exchanger. The thermal solutions obtained from SPH are benchmarked with the solutions from Finite Volume Method (FVM) and also validated using available analytical solutions. The obtained results are in good agreement with FVM and available analytical models, which combined with the advantages of the meshless approach, show the high potential for industrial heat transfer applications.

This development is an important step towards thermal optimization of several industrial applications that can’t benefit from the conventional FVM approach due to geometry or process complexities. The demonstrated SPH simulation and visualization capabilities contribute to build the future reliable energy-saving solutions.

Keywords
Smoothed Particle Hydrodynamics, Finite Volume Method, transient heat transfer, CFD analysis
National Category
Energy Engineering Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-41276 (URN)
Projects
MR-OMDO
Available from: 2018-11-01 Created: 2018-11-01 Last updated: 2018-12-11Bibliographically approved
6. Simulation and validation of flow and heat transfer in an infinite mini-channel using Smoothed Particle Hydrodynamics
Open this publication in new window or tab >>Simulation and validation of flow and heat transfer in an infinite mini-channel using Smoothed Particle Hydrodynamics
2018 (English)In: Energy Procedia, Elsevier, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Fluid flow and heat transfer in small channels have a wide range of engineering and medical applications. It has always been a topic of numerous theoretical, numerical and experimental studies. Several numerical methods have been used to simulate such flows. The most common approaches are the finite volume method (FVM) and the direct numerical simulation (DNS), which are numerically expensive to solve cases involving complex engineering problems. The main purpose of this work is to investigate the usability of the mesh-free particle based Smoothed Particle Hydrodynamics (SPH) method to simulate convective heat transfer. To validate our approach, as a starting point, we choose to solve a simple well-established problem which is the laminar flow and heat transfer through an infinitely long mini-channel. The solution obtained from SPH method has been compared to the solution from FVM method and analytical solution with good accuracy. The results presented in this paper show that SPH is capable to solve laminar forced convection heat transfer, however, turbulent flow cases need to be considered to be able to utilize the SPH method for engineering thermal applications.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Poiseuille flow, mini-channel, CFD analysis, Heat transfer, SPH, FVM
National Category
Energy Engineering Fluid Mechanics and Acoustics
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-41275 (URN)
Conference
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, China
Projects
MR-OMDO
Available from: 2018-11-01 Created: 2018-11-01 Last updated: 2018-12-11Bibliographically approved
7. Taylor-Couette flow and transient heat transfer inside the annulus air-gap of rotating electrical machines
Open this publication in new window or tab >>Taylor-Couette flow and transient heat transfer inside the annulus air-gap of rotating electrical machines
2017 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 207, p. 624-633Article in journal (Refereed) Published
Abstract [en]

Losses in an electric motor amount to between 4–24% of the total electrical power, and are converted to heat. The maximum hot spot temperature is one of the design constraints of thermal and electrical performance. Several studies have explored flow and thermal characteristics inside the air-gap between two concentric rotating cylinders such as those found in electric motors, however the transient flow and thermal effects still remain a challenge. This study uses Computational Fluid Dynamics to predict the thermal behaviour of a machine rotating at the kind of speed usually encountered in motors. The Reynolds Averaged Navier-Stokes model together with the realizable k-ε turbulence model are used to perform transient simulations. Velocity profiles and temperature distribution inside the air-gap are obtained and validated. The transient flow features and their impact on thermal performance are discussed. The numerical results show turbulent Taylor vortices inside the air-gap that lead to a periodic temperature distribution. When compared to correlations from published literature, the simulated average heat transfer coefficient at the rotor surface shows overall good agreement. The transient effects introduce local impacts like oscillations to the Taylor-Couette vortices. These flow oscillations result in oscillations of the hotspots. However, this transient oscillatory behaviour does not show any additional impact on the global thermal performance.

Keywords
Air-gap, Rotating electrical machines, CFD simulation, Thermal analysis, Motor simulation, Taylor vortices
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-37476 (URN)10.1016/j.apenergy.2017.07.011 (DOI)000417229300055 ()2-s2.0-85024104684 (Scopus ID)
Available from: 2017-12-18 Created: 2017-12-18 Last updated: 2018-11-01Bibliographically approved
8. Heat transfer by liquid jets impinging on a hot flat surface
Open this publication in new window or tab >>Heat transfer by liquid jets impinging on a hot flat surface
2016 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 164, no 15, p. 934-943Article 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
Keywords
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:nbn:se:mdh:diva-29812 (URN)10.1016/j.apenergy.2015.08.038 (DOI)000372379700082 ()2-s2.0-84941008933 (Scopus ID)
Projects
MR-OMDO ((Model Reduction for Online Multi-Disciplinary Optimization))
Available from: 2015-11-29 Created: 2015-11-29 Last updated: 2018-11-01Bibliographically approved
9. Air-Gap Heat Transfer in Rotating Electrical Machines: A Parametric Study
Open this publication in new window or tab >>Air-Gap Heat Transfer in Rotating Electrical Machines: A Parametric Study
2017 (English)In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 4176-4181Article in journal (Refereed) Published
Abstract [en]

More than half of all electrical energy is consumed by motors and generators in an industrialized country. About 5-25% of this energy is lost and converted to heat. This heat produced by the losses has adverse effect on the lifetime and performance of a machine. A machine has to be operated at a given temperature to achieve maximum efficiency, therefore heat transfer study of machines is of special interest to rotating machines manufacturers. In this paper we investigate the heat transfer in the air-gap between the rotor and the stator of a simplified induction motor using Computational Fluid Dynamics. We consider three different air-gap widths and rotation speeds to explore the change in air-gap heat transfer when changing the air-gap width and the rotation speed. The simulated average heat transfer coefficients for all the models are in good agreement with the correlations from published literature. The Taylor-Couette vortical flow pattern is observed in the air-gap in our simulation results for the models with large air-gaps. The numerical results show that the presence of Taylor-Couette vortices in the air-gap enhance the heat transfer. The heat transfer coefficient increases with the increase in the rotation speed and decreases with the decrease in the air-gap width. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2017
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-38716 (URN)10.1016/j.egypro.2017.12.343 (DOI)2-s2.0-85041542591 (Scopus ID)
Available from: 2018-03-01 Created: 2018-03-01 Last updated: 2018-11-01Bibliographically approved

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