Murat TOĞULGA. A Dissertation Submitted to the Graduate School in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE - PDF

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Processing and Characterization of High Performance Piping Materials For Geothermal Applications By Murat TOĞULGA A Dissertation Submitted to the Graduate School in Partial Fulfillment of the Requirements

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Processing and Characterization of High Performance Piping Materials For Geothermal Applications By Murat TOĞULGA A Dissertation Submitted to the Graduate School in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department: Energy Engineering Major: Energy Engineering (Energy and Power Systems) Izmir Institute of Technology Izmir, Turkey July, 2003 We approve the thesis of Murat Toğulga Signature Date of Signature / 07 /2003 Asst. Prof. Dr. Metin Tanoğlu Asst. Professor of Mechanical Engineering Thesis Advisor Signature / 07 /2003 Asst. Prof. Dr. Gülden G. Günerhan Asst. Professor of Mechanical Engineering Thesis Co-Advisor Signature / 07 /2003 Prof. Dr. Zafer İlken Professor of Mechanical Engineering Signature / 07 /2003 Asst. Prof. Dr. Hacer Aygün Asst. Professor of Mechanical Engineering Signature / 07 /2003 Asst. Prof. Dr. Funda Tıhmınlıoğlu Asst. Professor of Chemical Engineering II ACKNOWLEDGEMENTS I wish to express my sincere gratitude to my advisors Asst. Prof. Metin Tanoğlu and Asst. Prof. Gülden Günerhan for their süpervisions, guidance, encouragement and supports during the courses of this thesis and in the experimental study. I acknowledge the supports from IYTE Ar-Fon Project, MÜH 05,2002 and DPT project. I would like to thank to Prof. Dr. Macit Toksoy and Prof. Dr. Zafer İlken for their comments and suggestions during my thesis. Besides, I would like to add my special gratitude to my friends. I am also greatful to Balçova Geothermal A.Ş. for help on accessing to Balçova geothermal facilities. Finally, I would like to thank my family for their understanding, encouragement and supports. i ABSTRACT Polymer composite based pipes are being recently utilized in transportation of geothermal fluids. The utilization of composites is due to their resistance to aggressive chemicals and hot-wet environment with relatively high specific strength and design flexibility. Exposure of materials to wide range of temperatures and humidity level, while under the action of load, may degrade them and cause to severe reduction in their properties and service life. Understanding the complex degradation mechanism of the composites exposed to a variety of temperature and fluid chemistry (including geothermal fluid) is essential to improve their durability. This research focuses on the investigation of interactions between geothermal fluid and composite piping materials made of various matrices and the mechanism of degradation in these composites. The matrix materials include polyester, epoxy and graphite particle added epoxy materials. In this study, E-glass fiber reinforced polymer composites were fabricated by employing filament winding and tube rolling techniques. Fabricated composites and neat polymers were exposed to dry environment, distilled water and geothermal fluid of Balçova geothermal field until the saturation of weight gains due to water uptakes. In addition, the specimens with neat polymers were prepared to simulate and follow the degradation of matrix materials under hot-wet environments. Once the saturation occurred, the specimens were subjected compressive mechanical testing. For both dry and wet specimens, the mechanical testing was performed to obtain stress-strain behavior, modulus of elasticity, strain at failure values and energy absorption during the loading. The results were compared to evaluate the degradation of the properties due to various exposures. Moreover, the thermal conductivity of the various composites fabricated in this research was measured to determine the heat losses and temperature distribution within the materials. The temperature distribution within the cross-section of the pipes for various materials was analyzed using a finite element-modeling tool, LUSAS for uninsulated pipes. The heat loss occurring during the transportation of hot geothermal fluid was calculated as a case study to compare composites and traditional metal piping. It was found that polyester composite pipes have higher mechanical performance under axial and radial compression as compared to the composite with epoxy matrices. For all the composite types, some considerable degradations were ii measured due to exposure to hot-wet environments. The extend of degradation was less for graphite particles added epoxy composite pipes that exhibited the lowest water uptake values. The graphite particles incorporated into the matrix affected the water uptake and thermal conductivity of the epoxy. The water uptake of polyester matrix composite pipes was the highest that might be related to the most extensive degradation of polyester based composite. Moreover, it was found that the thermal conductivity of the composites is much lower than traditional materials. The graphite particles cause reduction in thermal conductivity, simultaneously in heat loss for uninsulated pipes. However, if the isolation is used, heat loss is not sensitive to pipe material. iii ÖZ Polimer kompozit esaslı borular, günümüzde jeotermal sıvıların taşınmasında kullanılmaktadır. Kompozitlerin kullanılması, kuvvetli ve dizayn esnekliğine sahip olmasıyla birlikte onların agresif kimyasallara ve sıcak-nemli ortama direnç gösterebilmesinden kaynaklanmaktadır. Malzemelerin yük altında yüksek sıcaklık ve nemli ortamlara maruz bırakılması onların bozulması ve özelliklerinde ve servis ömürlerinde bir düşüşe neden olabilmektedir. Farklı sıcaklık ve sıvı kimyasına (jeotermal sıvılarda dahil) maruz bırakılmış kompozitlerdeki kompleks bozunum mekanizmaların anlaşılması dayanıklılıklarının geliştirilmesi için gerekmektedir. Bu araştırma, jeotermal sıvıyla değişik matriks malzemelerden oluşan kompozit borular arasındaki etkileşiminin ve bu kompozitlerdeki bozunum mekanizmaları üzerinde odaklanmıştır. Matriks malzemeleri polyester, epoksi ve karbon parçacıkları eklenmiş epoksileri ihtiva eder. Bu çalışmada E tipi cam fiberle güçlendirilmiş polimer kompozitler, filament sarma ve tüp sarma teknikleriyle üretilmişlerdir. Üretilen kompozit boru ve katkısız matriks polimerleri kuru ortam ile saf su ve Balçova jeotermal alanındaki jeotermal sıvıya su emmeleri için doygunluğa ulaşıncaya kadar maruz bırakılmıştır. Ayrıca, sıcak-nemli ortamlar altında matriks polimerlerindeki bozunumun simulasyonun ve izlenmesi için katkısız polimer numuneler hazırlanmıştır. Numuneler su doygunluğuna ulaştığı vakit mekanik basma testine tabi tutulmuştur. Kuru ve nemli numuneler için, stress-uzama davranışları, elastik modülleri, kırılma noktasındaki uzama değerleri ve enerji emme miktarlarının bulunması için mekanik testler gerçekleştirilmiştir. Sonuçlar, farklı ortamlara maruz bırakılmış numunelerin özelliklerindeki düşüşün değerlendirilmesi için karşılaştırılmıştır. Bununla birlikte, üretilen farklı tipteki kompozitlerin ısı kayıpları ve sıcaklık dağılımlarının analizi için ısıl iletkenlik katsayıları bu çalışmada ölçülmüştür. İzolasyonsuz farklı malzemelerden oluşan boruların kesitlerindeki sıcaklık dağılımları LUSAS bilgisayar programı kullanılarak analiz edilmiştir. Sıcak jeotermal sıvıların taşınmasında oluşan ısı kayıpları da hesaplanarak, kompozit borularla geleneksel olarak kullanılan boru malzemeleri karşılaştırılmıştır. Bu çalışmanın sonucunda, polyester kompozit boruların diğer epoksi kompozit borulara göre eksenel ve radyal baskı altında daha yüksek mekanik performansa sahip olduğu bulunmuştur. Ayrıca, her tipteki kompozit boruların sıcak-nemli ortama maruz iv bırakıldıktan sonra mekanik ve termal özelliklerinde önemli derecede bir düşüş olduğu gözlenmiştir. Bu düşüşün en az su çekme değerine sahip olan karbon parçacıkları eklenmiş epoksi kompozitlerde daha az olduğu görülmüştür. Bu karbon parçaçıkları matriksin su emmesini ve epoksinin ısıl iletkenlik katsayısını etkilediği görülmüştür. Polyester kompozit boruların performansındaki düşüşün en yüksek mertebede olması diğer tip borulara oranla daha fazla su emme özelliği ile bağlantılandırabilinir. Bununla beraber karbon parçacıklarının ısıl iletkenlik katsayısında düşüşe neden olduğu ve aynı zamanda izolasyonsuz borularda oluşan ısı kayıplarını azalttığı gözlenmiştir. Ancak izolasyon kullanıldığı zaman malzemenin cinsinin ısı kayıplarında fazla bir etkisi olmadığı görülmüştür. v TABLE OF CONTENTS NOMENCLATURE ix LIST OF FIGURES xi LIST OF TABLES xix Chapter 1 INTRODUCTION 1 Chapter 2 GEOTHERMAL ENERGY What is Geothermal Energy? Geothermal Fluid Geothermal Fluid Chemistry Material Problems Associated with Geothermal Fluid Chemistry Corrosion Scaling 11 Chapter 3 PIPING MATERIALS IN GEOTHERMAL APPLICATIONS Types of Piping Materials Performances of Piping Materials Subject To Geothermal Fluid Carbon and Galvanized Steel Ductile Iron Copper Cross-Linked Polyethylene (PEX) Polyvinyl Chloride (PVC) and Chlorinated Polyvinyl Chloride Polyethylene (PE) Fiberglass (RTRP) 18 Chapter 4 PROCESSING AND PERFORMANCE OF COMPOSITE MATERIALS Composites Fundamentals of Composites Polymers Classes of Polymers and Properties Effect of Temperature on Polymer Properties Fibers Composite Fabrication Techniques Pultrusion Centrifugal Casting 30 vi 4.2.3 Filament Winding Tube Rolling Durability of Composites Factors That Control the Durability of Composites Degradation Mechanism Under Hot-Wet Environment Testing Methods For Composite Tubing (Pipe) Materials Introduction Compressive Mechanical Testing on Composite Pipes 38 Chapter 5 EXPERIMENTAL Materials Processing of Composite Pipes Processing by Filament Winding Technique Processing by Tube Rolling Technique Measurement of Fiber Volume Fraction Water Uptake Measurements of The Composite Pipes and Neat Polymers Determination of Diffusion Coefficient Mechanical Testing Analysis of the Residues on the Surfaces Exposed to Geothermal Fluid Measurement of Thermal Conductivity Analysis of the Temperature Distribution Within the Pipes and Calculation of Heat Losses 52 Chapter 6 RESULTS AND DISCUSSIONS Composite Processing Fiber Volume Fraction Water Absorption and Diffusion Coefficients of the Composites and Neat Polymers Water Absorption of the Composites and Neat Polymers Diffusion Coefficients of the Composites and Neat Polymers Compressive Mechanical Properties of Composite Tubes and Neat Polymers Filament Wound Composite Tubes Mechanical Behavior Under Dry Environment Mechanical Behavior Under Wet Environments 64 vii Energy Absorption Tube Rolled Composite Tubes Mechanical Behavior Under Dry Environment Mechanical Behavior Under Wet Environments Energy Absorption Neat Polymers Mechanical Behavior Under Dry Environment Mechanical Behavior Under Wet Environments Residues on Surfaces Exposed To Geothermal Fluid and Distilled Water Thermal Conductivity of the Composite Pipes Temperature Distribution and Heat Losses Within the Composite Pipes 101 Chapter 7 CONCLUSIONS AND RECOMMENDATIONS 108 Refferences 111 Appendix 117 viii NOMENCLATURE ε Stress (MPa) σ Strain M t m o m Water content percentage Weight of dry specimen (gr) Weight of wet specimen (gr) D Diffusivity (m 2.s -1 ) M m h v f Maximum water content Thickness of the composite specimen (m) Volume fraction V f Volume of fiber (cm 3 ) V m Volume of matrix (cm 3 ) m f m m Mass of fiber (gr) Mass of matrix (gr) ρ f Density of fiber (gr/cm 3 ) ρ m Density of matrix (gr/cm 3 ) E s Specific energy (J/kg) A The cross-sectional area of pipe (mm 2 ) P(δ) Applied load (N) ρ The material density (gr/cm 3 ) δ f Q r 1 r 2 r 3 r 4 v f The final crush displacement (m) Heat Transfer Rate (W/m) Inner radius of Geothermal Pipe (m) Outer radius of Geothermal Pipe (m) Radius of Insulating Foam (m) Radius of Coat with Insulation Foam (m) Velocity of The Geothermal Fluid (m/s) T s Geothermal Fluid Temperature ( 0 C) T 1 Outer Surface Temperature of Pipe ( 0 C) h f k p k f Heat Transfer Coefficient of Geothermal Fluid (W/m 2.K) Thermal Conductivity of Pipe (W/m.K) Thermal Conductivity of Insulating Material (W/m.K) ix k c S z L k s Thermal Conductivity of Glass Fiber Coat (Insulating Material) (W/m.K) Conduction Shape Factor Distance From The Ground Surface (m) Length of The Pipe (m) Thermal Conductivity of Soil (W/m.K) T 2 Ground Temperature ( 0 C) D Diameter of The Buried Pipe (m) m Mass Flow Rate (kg/s) c p Specific Heat (J/kg. 0 C) T o Outer Fluid Temperature ( 0 C) M t a Water Uptake Percentages at Time, t Radius of Specimen (m) x LIST OF FIGURES Figure 2.1 Temperatures in earth and layer of the earth 4 Figure 2.2 Geothermal reservoir 5 Figure 2.3 Geothermal power plant and turbine generator 5 Figure 2.4 A sample of district heating system 6 Figure 2.5 Installation of heat pump and the circulation of water in summer and winter 7 Figure 3.1 Maximum service temperatures for typical piping materials used in geothermal applications 12 Figure 3.2 (a) Dry steel pipe and (b) corrosion on steel pipe under geothermal fluid for 45 days 14 Figure 3.3 Carbon steel pipe that is used in Balçova Geothermal District Heating System in İzmir 15 Figure 3.4 Fiberglass pipe (composite) that is used in Çeşme Geothermal District Heating System 18 Figure 4.1 Differences between (a) thermoplastics and (b) thermosets 23 Figure 4.2 Crosslinking of unsaturated polyester 25 Figure 4.3 Crosslinking of epoxy groups 26 Figure 4.4 Variation of Young s modulus with temperature for thermoplastics and thermosets 27 Figure 4.5 Pultrusion process 30 Figure 4.6 Centrifugal casting process 31 Figure 4.7 Schematic of filament winding process 32 Figure 4.8 Tube rolling process 34 Figure 4.9 Microcracks (a) in the matrix and (b) within the intrabundle of fiber 37 Figure 4.10 Delamination 37 Figure 4.11 The four possible modes of buckling for braided circular tubes in axial compression a. Fiber microbuckling b. diamond shaped buckling c. Concertina buckling d. Euler macrobuckling 40 Figure 4.12 The three failure modes for filament wound composite pipes in axial compression a. Collapse in transverse shearing xi b. Collapse in local buckling c. Collapse in lamina bending 40 Figure 4.13 (a) Nominal stress±nominal strain behavior for braids of initial helix angle θ=23 and 30 failing by microbuckling in compression. (b) The sawtooth fracture path of a compressive specimen which has failed by microbuckling 41 Figure 4.14 (a) Compressive nominal stress vs nominal strain curves for braided tubes with braid angles θ = 40 and 55 that have failed by diamond shaped buckling (b) Photograph of a θ = 40 braid which has failed by diamond shaped buckling 41 Figure 5.1 (a) The micrograph of graphite short fibers and (b) weight percentages of the elements in graphite fiber 43 Figure 5.2 The experimental setup (filament winding machine) 44 Figure 5.3 The experimental setup (resin bath) 45 Figure 5.4 Pre-impregnation of the fiber 46 Figure 5.5 Rolling of pre-impregnated fiber on the mandrel 46 Figure 5.6 (a) Distilled water tank and (b) geothermal fluid bath 48 Figure 5.7 Example of the graph of water uptake percentage vs square root of time 48 Figure 5.8 Dry E-Glass/Epoxy composite pipe specimens under compressive loading in axial loading 49 Figure 5.9 Dry E-Glass/Epoxy composite pipe specimens under compressive loading in radial loading 49 Figure 5.10 Typical load-stroke and stress-strain graphs for composite tubes compressed under axial loading 50 Figure 5.11 The range of thermal conductivity of various materials at room temperature 52 Figure 5.12 Cross-section of pipe with insulation. 53 Figure 5.13 Schematic picture of a two-dimensional pipe buried in semi-infinite medium 54 Figure 5.14 The mesh construction used in LUSAS software program 55 Figure 6.1 The photos of the composite pipes fabricated by (a) filament winding and (b) tube rolling methods 56 Figure 6.2 Water uptake vs time graphs for three types of xii filament wound composite tubes exposed to distilled water 58 Figure 6.3 Water uptake vs time graphs for three types of filament wound composite tubes exposed to geothermal fluid 59 Figure 6.4 Water uptake vs time for three types of tube rolled composite tubes exposed to geothermal fluid 59 Figure 6.5 Water uptake vs time graphs for three types of neat polymers exposed to distilled water 60 Figure 6.6 Water uptake vs time graphs for three types of neat polymers exposed to geothermal fluid 61 Figure 6.7 Load vs stroke graph of filament wound E-glass composite pipes with three different matrix material compressed under axial loading in dry environment 63 Figure 6.8 Stress vs strain graph of filament wound E-glass composite pipes with three different matrix material compressed under axial loading in dry environment 63 Figure 6.9 Load vs stroke graph of filament wound E-glass composite pipes with three different matrix material compressed under radial loading in dry environment 64 Figure 6.10 Load vs stroke graph of E-glass / epoxy filament wound composite tube exposed to various environments and subjected to compressive loading in axial direction 65 Figure 6.11 Stress vs strain graph of E-glass / epoxy filament wound composite tube exposed to various environments and subjected to compressive loading in axial direction 65 Figure 6.12 Load vs stroke graph of E-glass / epoxy filament wound composite tube exposed to various environments and subjected to compressive loading in radial direction 66 Figure 6.13 Load vs stroke graph of E-glass / polyester filament wound composite tube exposed to various environments and subjected to compressive loading in axial direction 66 Figure 6.14 Stress vs strain graph of E-glass / polyester filament wound composite tube exposed to various environments and subjected to compressive loading in axial direction 67 xiii Figure 6.15 Load vs stroke graph of E-glass / polyester filament wound composite tube exposed to various environments and subjected to compressive loading in radial direction 67 Figure 6.16 Load vs stroke graph of E-glass / graphite particle added epoxy filament wound composite tube exposed to various environments and subjected to compressive loading in axial direction 68 Figure 6.17 Stress vs strain graph of E-glass / graphite particle added epoxy filament wound composite tube exposed to various environments and subjected to compressive loading in axial direction 68 Figure 6.18 Load vs stroke graph of E-glass / graphite particle added epoxy filament wound composite tube exposed to various environments and subjected to compressive loading in radial direction 69 Figure 6.19 Stress at max values of three types of filament wound composite tubes exposed to various environments and subjected to compressive loading in axial direction 69 Figure 6.20 Strain at max values of three types of filament wound composite tubes exposed to various environments and subjected to compressive loading in axial direction 70 Figure 6.21 Modulus of elasticity values of three types of filament wound composite tubes exposed to various environments and subjected to compressive loading in axial direction 71 Figure 6.22 Photos of the mechanical testing specimens of filament wound E-glass composite tubes loaded along axial direction and exposed to (a) dry environment (b) distilled water and (c) geothermal fluid 72 Figure 6.23 Photos of the mechanical testing specimens of filament wound E-glass composite tubes loaded along radial direction and exposed to (a) dry environment (b) distilled water and (c) geothermal fluid 73 Figure 6.24 Specific energy absorption graph of filament wound E-glass composite tubes with various matrix polymers and compressed along axial direction 74 Figure 6.25 Energy absorption graph of filament wound E-glass composite tubes with various matrix polymers and compressed along radial direction 74 xiv Fig
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