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Numerics Applied Nanofluid Analysis in a Square Array Subchannel
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | Kune Y. Suh | - |
dc.contributor.author | 주바이르 | - |
dc.date.accessioned | 2017-07-14T03:19:45Z | - |
dc.date.available | 2017-07-14T03:19:45Z | - |
dc.date.issued | 2015-08 | - |
dc.identifier.other | 000000067004 | - |
dc.identifier.uri | https://hdl.handle.net/10371/123496 | - |
dc.description | 학위논문 (석사)-- 서울대학교 대학원 : 에너지시스템공학부(원자핵공학과), 2015. 8. 서균렬. | - |
dc.description.abstract | This dissertation treats the thermohydrodynamic performance of
alumina (Al2O3) nanofluid in a square array subchannel featuring pitch-to diameter (P/D) ratio of 1.25 and 1.35 to check its applicability in a typical Pressurized Water Reactor (PWR) rod bundle under single phase turbulent flow condition. Two fundamental aspects of thermal hydraulics viz. augmentation of convective heat transfer coefficient and accompanied pressure drop have been discussed using pure water and different volume concentrations (0.5%, 1.5% and 3.0%) of water/alumina (Al2O3) nanofluids as coolant. A widely used and commercially available CFD package STARCCM+ (ver. 9.06.011) has been utilized to carry out numerical simulation by setting up flow as single phase, incompressible and turbulent for different inlet Reynolds number, Re spanning from 3×105 to 6×105. The realizable k-ε model is implemented to simulate turbulence inside subchannel. Despite the results of a simulation performed in a single subchannel may not be reliable for analyzing the entire rod bundle, however, their quantitative and qualitative similarity can readily be utilized as a preliminary step in fixing thermohydrodynamic parameters of a rod bundle. The numerical results revealed that convective heat transfer coefficient, h (W/m2.K) is augmented with increasing nanoparticle volume concentration in the subchannel geometry. While for the same inlet Re, maximum heat transfer increment of about 22% is achieved for 3.0% particle volume concentration of alumina nanofluid, using same mass flow rate at inlet boundary and for same vol.% it is observed that convective heat transfer coefficient of nanofluid is slightly lower compared to pure water. The pressure drop is found to be increased significantly with the augmentation of particle volume concentration of alumina nanofluid due to increased viscosity and density and in case of 3.0% volume concentration pressure drop increment is about 56% compared to that of pure water. Finally, a multiple regression analysis has been performed to propose a new correction factor for an existing correlation of square array subchannel to obtain Nusselt number, Nu more accurately for nanofluids in such geometry. | - |
dc.description.tableofcontents | Contents
Abstract……………………………………………….... i Acknowledgement……………………………………... iii Contents………………………………………………... iv List of Tables…………………………………………... vii List of Figures………………………………………….. viii Acronyms………………………………………………. x Chapter 1 Introduction…………………………………. 1 1.1 Background and Motivation………………………... 5 1.2 Nuclear Applications of Nanofluid…………………. 7 1.2.1 PWR Main Coolant Application………………… 8 1.2.2 ECCS Application………………………………. 9 1.2.3 Severe-Accident Application……………………. 9 1.3 State of the Art on Convective Heat Transfer Enhancement by Nanofluid………………………… 10 1.3.1 Experimental Studies…………………………… 11 1.3.2 Numerical Studies………………………………. 14 1.4 State of the Art on Simulation of Rod Bundles…….. 16 Chapter 2 Overview of Nanofluid Heat Transfer……… 19 2.1 Parameters Affecting Thermal Conductivity of Nanofluids…………………………………………... 19 2.1.1 Effect of Particle Volume Fraction (?)………….. 20 2.1.2 Effect of Base Fluid……………………………... 20 2.1.3 Effect of Particle Size…………………………… 21 2.1.4 Effect of Temperature…………………………… 22 2.2 Thermal Conductivity Enhancement Mechanisms of Nanofluid…………………………………………… 23 2.2.1 Brownian Motion……………………………….. 23 2.2.2 Clustering of Nanoparticles……………………... 25 2.2.3 Liquid Layering around Nanoparticles………….. 27 2.2.4 Ballistic Phonon Transport in Nanoparticles……. 27 2.2.5 Near Field Radiation…………………………….. 28 2.3 Effect of Particle Deposition of Heater Surface……. 28 v 2.4 Chemical and Physical Stability of Nanofluid……… 29 Chapter 3 Overview of CFD and Star-CCM+…………. 31 3.1 Definition of CFD…………………………………... 31 3.2 Governing Equations of CFD………………………. 31 3.3 Elements of a CFD Code…………………………… 32 3.3.1 Pre-processor……………………………………. 33 3.3.2 Solver……………………………………………. 33 3.3.3 Post-processor…………………………………… 34 3.4 Properties of Numerical Solutions………………….. 35 3.4.1 Consistency……………………………………… 35 3.4.2 Stability………………………………………….. 35 3.4.3 Convergence…………………………………….. 36 3.4.4 Conservation…………………………………….. 36 3.4.5 Boundedness…………………………………….. 36 3.4.6 Realizability……………………………………... 37 3.5 Introduction to Star-CCM+…………………………. 37 Chapter 4 Methodology of Numerical Modeling……… 39 4.1 Determination of Physical Properties of Nanofluid… 39 4.2 Methodology of Numerical Modeling……………… 41 4.2.1 Computational Domain…………………………. 41 4.2.2 Boundary Conditions……………………………. 42 4.2.3 Physics Set-up…………………………………... 43 4.2.4 Selection of Turbulence Model…………………. 44 4.2.5 Convergence of Numerical Solution……………. 46 4.2.6 Wall y+ Values…………………………………… 48 Chapter 5 Numerical Results and Discussion………….. 50 5.1 Mesh Convergence Test ……………………………. 50 5.2 Validation of Numerical Model…………………….. 52 5.3 Validation of Turbulence Model for Nanofluid…….. 54 vi 5.4 Results and Discussion……………………………... 55 5.4.1 Temperature……………………………………... 55 5.4.2 Velocity………………………………………….. 56 5.4.3 Pressure………………………………………….. 56 5.4.4 Turbulent Kinetic Energy……………………….. 57 5.4.5 Nu and h for Constant Inlet Re………………….. 58 5.4.6 Comparison of Numerical Results against Correlations……………………………………... 61 5.4.7 Heat Transfer Coefficient for Constant Mass Flow Rate………………………………………... 63 5.4.8 Pressure Drop…………………………………… 64 5.5 Proposed New Correction Factor…………………… 66 Conclusion……………………………………………… 67 Nomenclature…………………………………………... 69 References……………………………………………… 71 | - |
dc.format | application/pdf | - |
dc.format.extent | 13019164 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | Subchannel Analysis | - |
dc.subject | Numerical Simulation | - |
dc.subject | PWR Type Reactor | - |
dc.subject.ddc | 622 | - |
dc.title | Numerics Applied Nanofluid Analysis in a Square Array Subchannel | - |
dc.type | Thesis | - |
dc.description.degree | Master | - |
dc.citation.pages | 90 | - |
dc.contributor.affiliation | 공과대학 에너지시스템공학부 | - |
dc.date.awarded | 2015-08 | - |
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