132 results on '"Heat analysis"'
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52. Paketlenmiş gözenekli bir yatakta duyulur ısıl enerji depolamanın sayısal olarak incelenmesi
- Author
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Erkinaci, Tayfun, Baytaş, Ayşe Filiz, and Enerji Bilim ve Teknoloji Anabilim Dalı
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Computational fluids dynamic ,ANSYS ,Energy ,Solar energy systems ,Solar energy ,Heat analysis ,Thermodynamic analysis ,Thermal analysis ,Thermal energy ,Heat storage ,Solar energy plant ,Enerji - Abstract
Isıl enerji duyulur ısı, gizli ısı ve kimyasal enerji olarak termal enerji depolama sistemlerinde (TES) depolanabilmektedir. Duyulur ısı formunda enerji depolamada enerji malzemenin fazında değişiklik olmadan katı ve sıvı ısıtılarak ve soğutularak depolanabilir ve sistemden çekilebilir. Paketlenmiş yatakta duyulur ısıl enerji depolama sistemleri, paketlenmiş katı malzeme ve boşluktaki akışkandan oluşmaktadır. Enerji gözenekli ortamda depolanmaktadır. Gözenekli ortamın türü ve gözeneklilik değeri paketlenmiş yatak ısıl enerji depolama sistemleri için çok önemlidir.Bu tez çalışmasında paketlenmiş yatakta duyulur ısıl enerji depolama sistemi sayısal olarak analiz edilmiştir. Paketlenmiş yatak teknolojisinin kullanıldığı gözenekli ortam, ısı transferi akışkanı olarak havadan ve ısıl enerji depolama malzemesi olarak çelik, cordierite ve kaya parçasından oluşan bilyelerden oluşmaktadır. Bu malzemeler yüksek sıcaklıkta ısıl depolama için uygundur. Korunum denklemleri ANSYS Fluent programı kullanılarak çözülmüştür. Gözenekli ortamda ısı transferi için ısıl dengede olmayan sistem kullanılmıştır. Analizler zamana bağlı olarak gerçekleştirilmiştir. Akışkanın ısıl fiziksel özellikleri sıcaklığa bağlı değişirken, katının ısıl fiziksel özellikleri sabit kabul edilmiştir. Sonuçlarda çeşitli malzemelerin, debinin ve gözenekliliğin depolanan enerji miktarı ve depolama süresine üzerindeki etkisi verilmiştir. Thermal energy is stored as sensible heat, latent heat or chemical energy in thermal energy storage systems (TES). Energy is stored or extracted by heating or cooling a liquid or a solid without phase changing in a sensible heat storage system. TES in packed beds is used for efficient implementation of concentrated solar power. A sensible TES sysytem consists of packed solid material and fluid in voids. The type of porous medium and porosity are important for these systems.A sensible TES system is numerically investigated in this study. The system has air as heat transfer fluid and solid spheres as thermal storage material. Steel, cordierite and rock spheres are used as solid part of porous medium. These materials are convenient for thermal energy storage at high temperature. The governing equations are solved by using ANSYS fluent software. The local thermal non-equilibrium model is used in the porous medium. The problem is analyzed in transient time. The fluid thermo-physical properties are temperature dependent, the solid's properties assumed as constant. The results showed that the kind of material, the porosity of the packed bed, and the mass flow rate effect on the thermal energy storage and the storage time. 101
- Published
- 2017
53. Study on Hydration Heat Analysis of Pier Foundation-Column Using Low Heat Concrete
- Author
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Ki-Hyung Kim, Joong-Kyu Jeon, Sungil Kim, and Chan-Ki Jeon
- Subjects
Pier ,Cement ,Slump ,Cracking ,Compressive strength ,Materials science ,Thermal ,Foundation (engineering) ,Geotechnical engineering ,Composite material ,Heat analysis - Abstract
(Received September 12, 2014 / Revised September 22, 2014 / Accepted September 25, 2014)This study carried out to evaluate the hydration heat analysis and fundamental characteristics such as air content, slump and compressive strength for field application of low heat concrete with premixed cement. The results of experiment show that low heatconcrete with premixed cement have sufficient performances on the workability and compressive strength. In addition, hydration heat analysis shows that low heat concrete with premixed cement make sure of target thermal cracking index. Therefore, it is desirable to apply the low heat concrete with premixed cement on pier foundation-column.키워드 : 저발열 콘크리트, 혼합시멘트, 수화열 해석, 온도균열지수Keywords : Low heat concrete, Premixed cement, Hydration heat analysis, Thermal cracking index* Corresponding author E-mail: ksg85@kolon.com
- Published
- 2014
54. Fundamental Evaluation and Hydration Heat Analysis of Low Heat Concrete with Premixed Cement
- Author
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Ji-Hyun Yoon, Joong-Kyu Jeon, Ki-Hyung Kim, and Chan-Ki Jeon
- Subjects
Cement ,Slump ,Compressive strength ,Materials science ,Air content ,Composite material ,Heat analysis ,Durability ,Shrinkage - Abstract
(Received February 11, 2014 / Revised March 19, 2014 / Accepted March 24, 2014)This study carried out to evaluate the hydration heat analysis and fundamental characteristics such as air content, slump, compressive strength and dry shrinkage according to concrete with premixed cement, ternary concrete and OPC concrete for using concrete wit hpremixed cement. The results of experiment are founded that concrete with premixed cement have sufficient performances such as workability, compressive strength and dry shrinkage. Also, the results of hydration heat analysis are founded that concrete with premixed cement have more performance than ternary concrete and OPC concrete at a point of view for the quality control such as thermal crack reducing and economic benefit. Therefore, it is desirable that concrete with premixed cement should be used to rise durability performance and convenience of maintenance.키워드 : 혼합 시멘트, 기초물성, 수화열 해석, 현장적용Keywords : Premixed cement, Fundamental characteristics, Hydration heat analysis, Field application* Corresponding author E-mail: jkjeon31@kolon.com
- Published
- 2014
55. A Global Heat Compliance Measure Based Topology Optimization for the Transient Heat Conduction Problem
- Author
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Chungang Zhuang and Zhenhua Xiong
- Subjects
Numerical Analysis ,Mathematical optimization ,Mechanics of Materials ,Computer science ,Control theory ,Modeling and Simulation ,Topology optimization ,Peak value ,Condensed Matter Physics ,Thermal conduction ,Heat analysis ,Sensitivity analyses ,Computer Science Applications - Abstract
For topology optimization with transient loads, heat compliance varies with transient heat analysis. The peak value of the transient heat compliance should be minimized. Thus, this article proposes a global heat compliance measure to handle this kind of topology optimization for the transient heat conduction problem. The optimization model is then constructed by the global heat compliance measure. The finite-element, equivalent static loads, and continuum shape based sensitivity analyses are derived using the adjoint variable method. Through case studies, the effectiveness of the proposed global heat compliance measure for the transient heat conduction topology optimization is validated.
- Published
- 2014
56. Heat Analysis of Assembled Steel-truss Concrete Hollow Floor
- Author
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Yue Zhang, Hao-Xue Ju, and Xu-Dong Xing
- Subjects
Materials science ,business.industry ,Truss ,Structural engineering ,Heat analysis ,business - Abstract
The numerical analysis software ABAQUS has been used to study the temperature field of an assembled steel-truss concrete hollow floor in this paper to simulate the assembled steel-truss concrete hollow floor under thermal coupling under the ISO-834 standard heating curve. The distribution principle of temperature field for different sections in the floor system has been obtained to provide a reference for the study of the mechanical properties of assembled steel-truss concrete hollow floor.
- Published
- 2019
57. Heat Analysis for Heat Sink Design Using Finite Element Method
- Subjects
Materials science ,Thermodynamics ,Heat sink ,Heat analysis - Abstract
LED는 저탄소 그린에너지 시대의 등기구로서 각광을 받고 있다. 다른 조명용 광원에 비해 친환경적이고 높 은 에너지 효율을 가지고 있고 수명이 길다는 장점을 가지고 있지만, 공급전력 중 80%이상이 열에너지로 전환되며, 이에 따른 온도상승이 불가피 하여 높은 온도가 단점으로 꼽히고 있다. 온도상승은 LED소자의 수명에 영향을 미치기 때문에 방열시스템이 중요하게 자리 잡고 있다. 따라서 본 논문에서는 방열성능 향상을 위하여 LED 전구의 heat sink 의 형상에 대한 열해석을 통하여 방열 시스템의 효용성을 분석하였다.
- Published
- 2013
58. The Hydration Heat Analysis for Sealing Concrete of Swivel Construction Open Thin Wall Arch
- Author
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Zi Qiang Zhu, Zhi Yong Li, Xiong Hui Feng, and Xin Wu
- Subjects
Arch bridge ,Cracking ,Engineering ,Heat effect ,business.industry ,Thin wall ,Base (geometry) ,General Medicine ,Structural engineering ,Arch ,business ,Heat analysis - Abstract
The sealing concrete of arch bridge will be constructed after swivel construction of it finished. The concrete has such characteristics like huge size, smaller heat radiating area and more complex boundary constraint. According to the cracking situation of this type bridges in recent years, the paper established hydration heat simulation model of it using MIDAS2010 program and numerical analyzed for the model. The hydration heat constant coefficients and placing temperature of the concrete hydration heat effect have been analyzed by simulation parameters base on that. And the results showed that it is an important reason causing the cracking of the concrete.
- Published
- 2012
59. The Heat Analysis of Chinese Enterprises in Laos Transportation Infrastructure Investment under the qThe Belt and Road Initiativeq
- Author
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Ke Yan, Ersi Liu, and Xinran Ge
- Subjects
Finance ,Economic growth ,business.industry ,business ,Investment (macroeconomics) ,Heat analysis ,Transportation infrastructure ,Transport infrastructure - Published
- 2016
60. Analysis of Massive Platform Concerte 3-Dimensional Hydration Heat of Corrugated Steel Webs Bridge
- Author
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Xian Wu Hao, Jun Wang, and Zi Qing Li
- Subjects
Engineering ,business.industry ,General Engineering ,Foundation (engineering) ,Finite element method analysis ,Structural engineering ,Deformation (meteorology) ,business ,Heat analysis ,Durability ,Bridge (interpersonal) - Abstract
with the continuous development of bridge engineering,the massive concrete has been widely used in large-scale bridge foundation engineering. But it often has the problems of crack and deformation, which infuenced the entirety and durability of the whole structure seriously. In this paper, a hydration heat analysis of the platform of a corrugated steel webs bridge is carried out by using MIDAS/Civil structure finite element method analysis program, the analysis summarizes the temperature distribution regulation of platform concrete influenced by hydration heat and the temperature changing regulation affected by time. Meanwhile, some countermeasures of preventing the crack of concrete are put forward.
- Published
- 2012
61. ADVANCED HEAT ANALYSIS OF TURBINE ROTOR BLADES COUPLED WITH COMBUSTION CHAMBER SIMULATION
- Author
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Vyacheslav Georgievich Latyshev, A. M. Sipatov, Leonid Yulyevich Gomzikov, and Sergey A. Karabasov
- Subjects
Materials science ,business.industry ,Mechanical engineering ,Conjugate heat transfer ,Combustion chamber ,Aerospace engineering ,Turbine rotor ,Heat analysis ,business - Published
- 2012
62. Optimized Design of the SGA-WZ Strapdown Airborne Gravimeter Temperature Control System
- Author
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Danni Cong, Kaidong Zhang, Minghao Wang, Shaokun Cai, Meiping Wu, and Juliang Cao
- Subjects
Engineering ,Thermoelectric cooling ,Field (physics) ,optimized design ,airborne gravimetry ,lcsh:Chemical technology ,Accelerometer ,Biochemistry ,Stability (probability) ,Article ,Analytical Chemistry ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Aerospace engineering ,Instrumentation ,temperature control ,heat analysis ,Electronic circuit ,Temperature control ,Gravimeter ,business.industry ,Electrical engineering ,SGA-WZ-02 ,Atomic and Molecular Physics, and Optics ,Magnet ,business - Abstract
The temperature control system is one of the most important subsystems of the strapdown airborne gravimeter. Because the quartz flexible accelerometer based on springy support technology is the core sensor in the strapdown airborne gravimeter and the magnet steel in the electromagnetic force equilibrium circuits of the quartz flexible accelerometer is greatly affected by temperature, in order to guarantee the temperature control precision and minimize the effect of temperature on the gravimeter, the SGA-WZ temperature control system adopts a three-level control method. Based on the design experience of the SGA-WZ-01, the SGA-WZ-02 temperature control system came out with a further optimized design. In 1st level temperature control, thermoelectric cooler is used to conquer temperature change caused by hot weather. The experiments show that the optimized stability of 1st level temperature control is about 0.1 °C and the max cool down capability is about 10 °C. The temperature field is analyzed in the 2nd and 3rd level temperature control using the finite element analysis software ANSYS. The 2nd and 3rd level temperature control optimization scheme is based on the foundation of heat analysis. The experimental results show that static accuracy of SGA-WZ-02 reaches 0.21 mGal/24 h, with internal accuracy being 0.743 mGal/4.8 km and external accuracy being 0.37 mGal/4.8 km compared with the result of the GT-2A, whose internal precision is superior to 1 mGal/4.8 km and all of them are better than those in SGA-WZ-01.
- Published
- 2015
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63. Experimental Study on the Characteristics of Rapid Chilled Converter Slag by Watering
- Author
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Ja-Sul Koo, Keun-Jae Lee, Hoon-Ha Lee, Bong-Suk Cho, and Seung-Yeup Yoo
- Subjects
Materials science ,Recovery rate ,Metallurgy ,Ocean Engineering ,Slag (welding) ,Porosity ,Heat analysis ,Civil and Structural Engineering - Abstract
In this study, a physical and chemical properties analysis was conducted for PCSP to evaluate properties of its materials and, for comparison purpose, was also conducted for CSP. The result of experiment confirmed improvement of iron recovery rate due to introduction of rapid water-cooling equipment and greater density of exterior and interior structure through SEM observation and porosity measurement. Also, SEM, XRD and DSC-TGA analysis showed that content of f-CaO in PCSP was minuscule so it was decided that problems of material stability including f-CaO-caused bulging failure, which has been problematic, can be solved.
- Published
- 2011
64. Optimization of doping concentration in Er:tellurite glass based on heat analysis
- Author
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Chunlei Yu, Shunguang Li, Lili Hu, Li Chen, Suya Feng, and Wei Chen
- Subjects
Range (particle radiation) ,Materials science ,Tellurite glass ,Doping ,Analytical chemistry ,Mineralogy ,Fraction (chemistry) ,Condensed Matter Physics ,Heat analysis ,Photon upconversion ,Electronic, Optical and Magnetic Materials ,Materials Chemistry ,Ceramics and Composites ,Erbium ions - Abstract
The comprehensive analysis about heat-generating processes is presented in Er:tellutire glass. The heat fraction of each process and total heat fraction during pumping are investigated. The results show that upconversion is an important heat-generation process and heat problem is serious especially at high Er3+ doping level. The influence of pump power on heat fraction is also discussed. Based on the heat analysis, the optimized doping concentration range of Erbium ions is about 0.5 mol% to 1.0 mol%.
- Published
- 2011
65. FIRE TEST AND HEAT ANALYSIS FOR STEEL-CONCRETE COMPOSITE MEMBER WITH FIREPROOF BOARD
- Author
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Akihiro Nakai and Osamu Kiyomiya
- Subjects
Fire test ,Materials science ,Air layer ,Composite number ,Composite material ,Heat analysis ,Fire performance - Abstract
鋼・コンクリート合成構造形式のトンネルでは,鋼板がトンネル内に露出しているため,車両火災に対して耐火対策を行うことが必須である.本研究では,まず耐火板を設置していない大型試験体に対してRABT加熱実験を実施し,構造体の損傷性状および内部コンクリートの劣化程度の確認を行った.また,鋼板および耐火板を使用した要素実験を実施し,中空層の熱の伝達性状を明らかにした.続いて,耐火板を設置した大型試験体に対してRABT加熱実験を実施し,内部温度の分布,中空層の状況を確認した.最後に,中空層での輻射・対流・熱伝導およびコンクリートの潜熱のモデルを導入した有限要素法による熱伝達解析手法を提案し,実験結果と比較することにより,この熱伝達解析手法の有効性を確認した.
- Published
- 2011
66. Heat Conduction Analysis of Magnetic Recording Media for Thermally Assisted Magnetic Recording
- Author
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Y. Moriyama, A. Itoh, Katsuji Nakagawa, Arata Tsukamoto, Tokuei Sako, and Yoshito Ashizawa
- Subjects
Materials science ,business.industry ,Resolution (electron density) ,Near and far field ,Condensed Matter Physics ,Thermal conduction ,Heat analysis ,Electronic, Optical and Magnetic Materials ,Optics ,Thermal ,Recording media ,Electrical and Electronic Engineering ,Antenna (radio) ,business ,Instrumentation ,Plasmon - Abstract
This research applied thermally assisted magnetic recording to analyze both temperature distributions and temperature time transitions of isolated columnar structured media. It was clarified how a higher thermal resolution could be achieved using columnar structured media compared with continuous film media. With the application of a plasmon antenna, bit-patterned media achieved a writing temperature of more than 10 times higher than that of conventional media. Temperatures of adjacent columns strongly depend on the arrangement and the shape of a plasmon antenna.
- Published
- 2009
67. Frictional heat analysis of mine hoist and numerical simulation on temperature field of gasket
- Author
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Xue-ping Du, Shirong Ge, and Dong-tai Han
- Subjects
Computer simulation ,business.industry ,Gasket ,Energy Engineering and Power Technology ,Mechanical engineering ,Wire rope ,Mechanics ,Concentric ,engineering.material ,Geotechnical Engineering and Engineering Geology ,Heat analysis ,Heat flux ,Geochemistry and Petrology ,Heat transfer ,engineering ,Hoist (device) ,business - Abstract
The frictional performance of gaskets is greatly affected by frictional heat in operational mine hoists. Based on frictional mechanism and heat transfer theory, the mathematical model of the temperature field of the PVC gasket in an operational mine hoist was investigated, a numerical simulation using ANSYS is presented and the distribution of the temperature and heat flux were studied under basic assumptions. The results show that the temperature gradually decreases as the radius of the model increases and the isotherms are arcs of concentric semi-circle. The heat flux is of bilateral symmetry in the model and decreases radially. The theoretical values correspond with the measured values for a short time (τ ≤ 100 s) when the steel wire rope slides.
- Published
- 2009
68. Applicability of Temperature Distribution for Estimation of Medium Constants Using Temperature Rise due to Absorption of Ultrasound
- Author
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Hiroshi Inoue and Chiaki Yamaya
- Subjects
Physics and Astronomy (miscellaneous) ,Computer simulation ,business.industry ,Chemistry ,Ultrasound ,General Engineering ,General Physics and Astronomy ,Heat analysis ,Computational physics ,Optics ,Distribution (mathematics) ,Thermal ,business ,Constant (mathematics) ,Absorption (electromagnetic radiation) - Abstract
The analysis of temperature rise due to the absorption of ultrasound is important for the clarification of the effect of ultrasound waves and the estimation of medium constants. The thermal behavior of ultrasound is used not only for thermotherapy but also in measurement techniques. The estimation of a medium constant becomes possible by analyzing the temperature rise because the temperature change of the medium is particular to each medium. The purpose of this research is to establish a method of estimating medium constants and to develop a numerical simulation method that can be applied to the estimation of medium constants. We elucidated the requirements under which the simulation result corresponds to the experimental result. Good agreement between the experimental and simulation results is shown in this paper, and the validity of this method is described.
- Published
- 2008
69. Inverse Lagrangian Analysis of Heat, Vapor, and Gas Exchange in Plant Canopies
- Author
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Ray Leuning, F. X. Dunin, O. T. Denmead, J. R. Freney, and Michael R. Raupach
- Subjects
Thermodynamics ,Environmental science ,Inverse ,Mechanics ,Thermal stratification ,Heat analysis ,Lagrangian analysis - Published
- 2015
70. Structural design for power probe of W-band power meter
- Author
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Zi-Cheng Wang, Siyuan Ma, Tong Feng, and Jirun Luo
- Subjects
Absorption rate ,Engineering ,W band ,business.industry ,Electricity meter ,Electrical engineering ,Calibration ,Mechanical engineering ,Temperature difference ,business ,Heat analysis ,Temperature measurement ,Power (physics) - Abstract
A structure for power probe of W-band power meter is designed under the premise of ensuring absorption rate and steady working of materials at high temperature. Basing on heat analysis ANSYS code, the temperature distribution of the probe has been simulated with 0–50mW input power. The designed probe meets the requirements of calibration and measurement according to the simulation results for temperature difference, heat-balance time and heat-withstanding capability of the material.
- Published
- 2015
71. Physical factors affecting chloroquine binding to melanin
- Author
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J.P. Gerber, Phillip Pendleton, R.L. Schroeder, Schroeder, RL, Pendleton, P, and Gerber, JP
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isosteric heat ,Melanin ,chloroquine ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Adsorption ,Chloroquine ,medicine ,Competitive interaction ,Physical and Theoretical Chemistry ,Sepia ,Melanins ,integumentary system ,Chemistry ,pH ,Temperature ,Binding potential ,Surfaces and Interfaces ,General Medicine ,Buffer solution ,Heat analysis ,melanin ,Biochemistry ,adsorption ,sense organs ,Biotechnology ,medicine.drug ,sepia - Abstract
Chloroquine is an antimalarial drug but is also prescribed for conditions such as rheumatoid arthri-tis. Long-term users risk toxic side effects, including retinopathy, thought to be caused by chloroquine accumulation on ocular melanin. Although the binding potential of chloroquine to melanin has been investigated previously, our study is the first to demonstrate clear links between chloroquine adsorption by melanin and system factors including temperature, pH, melanin type, and particle size. In the cur-rent work, two Sepia melanins were compared with bovine eye as a representative mammalian melanin.Increasing the surface anionic character due to a pH change from 4.7 to 7.4 increased each melanin’s affin-ity for chloroquine. Although the chloroquine isotherms exhibited an apparently strong interaction with each melanin, isosteric heat analysis indicated a competitive interaction. Buffer solution cations com-peted effectively at low surface coverage; chloroquine adsorption occurs via buffer cation displacement and is promoted by temperature-influenced secondary structure swelling. Refereed/Peer-reviewed
- Published
- 2015
72. Lineer ısı akış metoduyla In-Bi intermetalik alaşımlarının ısıl iletkenlik katsayısının ölçümü
- Author
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Ata, Pinar, Aksöz, Sezen, and Fizik Anabilim Dalı
- Subjects
Metalurji Mühendisliği ,Fizik ve Fizik Mühendisliği ,Metals ,Thermoelectric ,Alloys ,Metallurgical Engineering ,Phonons ,Heat analysis ,Physics and Physics Engineering - Abstract
Bi-12 ağ.% In (Bi4In), Bi-15 ağ.% In (Bi3In), Bi-35.4 ağ.% In (BiIn), Bi-45 ağ.% In (Bi2In3), Bi-47.6 ağ.% In (Bi3In5), Bi-53 ağ.% In (BiIn2), Bi-62 ağ.% In (BiIn3) In-Bi intermetalik alaşımlar için ısı iletkenliğin sıcaklıkla değişimi lineer ısı akış metodu, elektriksel iletkenliğin sıcaklıkla değişimi d.c. dört nokta prob metoduyla ölçüldü. Isıl iletkenliğe elektron ve fonon katkıları, In-Bi intermetalik alaşımlarında Wiedemann-Franz kanunuyla hesaplanan ısıl ve elektriksel iletkenlik değerleri kullanılarak belirlendi. Isıl iletkenliğin fonon bileşeninin yüzdesi, 313-373 K sıcaklık aralığında Bi-12 ağ.% In, Bi-15 ağ.% In, Bi-35.4 ağ.% In, Bi-45 ağ.% In, Bi-47.6 ağ.% In, Bi-53 ağ.% In, Bi-62 ağ.% In intermetalik alaşımları için sırasıyla 49-54 %, 49-57 %, 37-52 %, 23-39 %, 30-40 % , 49-52 % , 35-46 % olarak bulundu. In-Bi intermetalik alaşımları için elektriksel iletkenliğin sıcaklık katsayısı sırasıyla 2.41x10-3, 1.61x10-3, 1.95x10-3, 2.28x10-3, 2.54x10-3, 0.46x10-3, 1.65x10-3 K-1 bulundu. İntermetalik alaşımlar için erime sıcaklığındaki katı fazın ısıl iletkenlikleri ve ısıl sıcaklık katsayıları sırasıyla 14.50, 16.23, 19.42, 25.63, 25.63, 31.83, 35.93 W/Km ve 1.36x10-3, 1.29x10-3, 3.27x10-3, 2.86x10-3, 2.47x10-3, 1.79x10-3 ve 4.34x10-3 K-1'dir. Aynı zamanda In-Bi intermetalik alaşımlarının mikroyapı ve yapısal karakteristikleri X-ışını kırınımı (XRD) ve Taramalı Elektron Mikroskobu (SEM) ile araştırıldı. The electrical and thermal conductivity variations with temperature for In-Bi intermetallic alloys, namely Bi-12 wt.% In (Bi4In), Bi-15 wt.% In (Bi3In), Bi-35.4 wt.% In (BiIn), Bi-45 wt.% In (Bi2In3), Bi-47.6 wt.% In (Bi3In5), Bi-53 wt.% In (BiIn2), Bi-62 wt.% In (BiIn3) alloys were measured by d.c. four-point probe method and linear heat flow apparatus, respectively. The contributions of electron and phonon to the thermal conductivity have been separately determined by using the measured values of thermal and electrical conductivities from Wiedemann-Franz law in the In-Bi intermetallic alloys. The percentages of phonon component of thermal conductivity were found to be in the range of 49-54 %, 49-57 %, 37-52 %, 23-39 %, , 30-40 % , 49-52 % , 35-46 % for Bi-12 wt.% In , Bi-15 wt.% In, Bi-35.4 wt.% In, Bi-45 wt.% In, Bi-47.6 wt.% In, Bi-53 wt.% In, Bi-62 wt.% In alloys at the ranges of 313-373 K temperature, respectively. The temperature coefficients () of electrical conductivity for the In-Bi intermetallic alloys were found to be 2.41x10-3, 1.61x10-3, 1.95x10-3, 2.28x10-3, 2.54x10-3, 0.46x10-3, 1.65x10-3 K-1, respectively. The thermal conductivities of the solid phases at their melting temperature and the thermal temperature coefficients for In-Bi intermetallic were also found to be 14.50, 16.23, 19.42, 25.63, 25.63, 31.83, 35.93 W/Km and 1.36x10-3, 1.29x10-3, 3.27x10-3, 2.86x10-3 , 2.47x10-3 , 1.79x10-3 and 4.34x10-3 K-1, respectively. Also, the microstructure and structural characteristics of In-Bi intermetallic alloys were investigated by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM). 117
- Published
- 2015
73. Toplinska analiza procesa - I. Sinteza mreže izmjenjivača topline pinch-postupkom
- Author
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Lj. Matijašević
- Subjects
heat exchanger network ,lcsh:Chemistry ,lcsh:QD1-999 ,pinch method ,Pinch method ,heat exchanger networks: thermal analysis ,mreža izmjenjivača topline ,pinch-postupak ,toplinska analiza ,heat analysis - Abstract
In the last twenty-five years in the chemical process industry an important point of interest has been, how to minimize total costs, i.e. capital and operating costs expressed as annual charges. Pinch method is thermodynamically oriented method for the synthesis of heat exchanger networks with extended to combined heat and power system, separation schemes, integrated distillation columns and general process design. There have been two schools of the heat exchanger network synthesis. One relies on thermodynamic principles where the designer manually or interactively if software is available, synthesizes the network. The heat exchanger network of a nitric acid plant has been studied and it was found that it is possible to reduce requirements for cooling water and medium pressure steam. In order to enable these savings, three heat exchangers should be replaced with new ones. Energy consumption in steam power system increases slightly. However, the final result is a reduction of energy costs and a payback time of 14.5 months. The other approach relies on mathematical methods like linear and nonlinear programming. In this work thermodynamically oriented method is presented for the synthesis of heat exchanger network., Jedan od najvažnijih interesa posljednjih dvadesetak i više godina je minimaliziranje ukupnih godišnjih investicijskih i pogonskih troškova u kemijskoj procesnoj industriji. U radu je prikazana metodologija pinch-postupka na primjeru sinteze mreže izmjenjivača topline kojim se mogu postići znatne uštede energije. Pinch-postupak je termodinamički orijentirana metoda za sintezu mreže izmjenjivača topline i mreže ostalih energetski aktivnih jedinica unutar procesa. Postoje dva pristupa sinteze mreže izmjenjivača topline; jedan se temelji na termodinamičkim principima gdje korisnik pješice ili pomoću programskih sustava sintetizira mrežu i drugi koji primjenjuju matematičke metode linearnog i nelinearnog programiranja. U radu je prikazana termodinamički orijentirana metoda za sintezu mreže izmjenjivača topline.
- Published
- 2006
74. Heat transfer analysis of liquid piston compressor for hydrogen applications
- Author
-
Kermani, Nasrin Arjomand, Rokni, Masoud, Kermani, Nasrin Arjomand, and Rokni, Masoud
- Abstract
A hydrogen compression technology using liquid as the compression piston is investigated from heat transfer point of view. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber. The model is developed based on the mass and energy balance of the hydrogen, liquid, and the wall of the compression chamber at each time step and positional node with various compression ratios, to calculate the temperature distribution of the system. The amount of heat extracted from hydrogen, directly at the interface and through the walls, is investigated and compared with the adiabatic case. The results show that depending on heat transfer correlation, the hydrogen temperature reduces slightly between 0.2% and 0.4% compared to the adiabatic case, at 500bar, due to the large wall resistance and small contact area at the interface. Moreover, the results of the sensitivity analysis illustrates that increasing the total heat transfer coefficients at the interface and the wall, together with compression time, play key roles in reducing the hydrogen temperature. Increasing the total heat transfer coefficient at the interface (10,000 times) or at the wall (200 times), leads to 22% or 33% reduction of hydrogen, compared to the adiabatic case, at 500bar, during 3.5s compression, respectively.
- Published
- 2015
75. A Study on the Mix Design of the Self-Compaction Concrete for the LNG Tank
- Author
-
Cheol Won, Sang Joon Park, Sang Soo Lee, and Dong-Seok Kim
- Subjects
Cement ,Materials science ,visual_art ,visual_art.visual_art_medium ,Compaction ,Slag ,Composite material ,Heat analysis ,Mix design ,Expansive ,Shrinkage - Abstract
The purpose of this study was to design the self-compaction concrete mixture, having not only high strength but also compensation of shrinkage without thermal crack under 4 sides outer restraint of the member. In the experimental mix, replacement ratio of limestone Powder, CSA expansive additives, and unit water were selected as parameters, using portland blast-furnace slag cement. And, bleeding test, expansibility test, hydration heat analysis were performed. As a results, when 35% of limestone Powder, 6% CSA expansive additives are replaced at unit water 175kg/, demanded performances of fresh and hardened self-compaction concrete are accomplished.
- Published
- 2004
76. Using PSPICE for electrical heat analysis
- Author
-
T.G. Burke and D.R. Schiller
- Subjects
Engineering ,business.industry ,Strategy and Management ,Thermal resistance ,Spice ,Heat analysis ,Education ,law.invention ,law ,Control system ,Heat transfer ,Electronic engineering ,Electrical analysis ,Electrical and Electronic Engineering ,Resistor ,business ,Electronic circuit - Abstract
There are many tools available for thermal analysis and many available for electrical analysis. However, for those that require both (e.g. heater control systems, device temperature models, TEC modeling), the authors find that Orcad PSPICE, a registered trademark of ORCAD Corporation, is among the best. In fact, PSPICE is a fast and accurate tool for the thermal modeling of systems with a relatively small number of nodes. The authors aim to explain to the reader through step-by-step examples how to use PSPICE to perform this thermal modeling.
- Published
- 2003
77. Thermal Analysis of High Brightness LED Headlight Heat Sink for Railway Vehicle
- Author
-
Seong-Hyeon Jeong, Seung-Il Lee, and Moon-Shuk Song
- Subjects
Brightness ,Mechanical engineering ,Environmental science ,Heat sink ,Heat analysis ,Thermal analysis ,Automotive engineering - Published
- 2017
78. Gearbox design for lifting on a bridge crane
- Author
-
Tumpej, Gregor and Belšak, Aleš
- Subjects
tiho obratovanje ,žerjavni reduktor ,design ,SolidWorks ,KISSsoft ,gearbox ,dvižni reduktor ,reduktor ,crane gearbox ,toplotna analiza ,zasnova ,udc:621.874.061-11(043.2) ,low noise operation ,gearbox for lifting ,heat analysis - Abstract
Diplomsko delo obsega zasnovo štiristopenjskega dvižnega reduktorja na mostnem žerjavu. Na primeru iz prakse je prikazana uporaba sodobne inženirske programske opreme za reduktorje. Zajeti so optimizacija za tišje obratovanje gonila, toplotna analiza, preračun togosti ohišja reduktorja in preprečevanje vibracij. The thesis is about the design of a four-stage gearbox for lifting on a bridge crane. In the case study it is shown, how to use modern engineering software for gearboxes. It also includes optimisation for low noise operation, heat analysis, calculation of gearbox housing stiffness and prevention of vibration.
- Published
- 2014
79. Heat Analysis of Liquid piston Compressor for Hydrogen Applications
- Author
-
Kermani, Nasrin Arjomand and Rokni, Masoud
- Subjects
Hydrogen compression ,Heat analysis ,Energy balance ,Liquid piston ,Thermodynamic model - Abstract
A new hydrogen compression technology using liquid as the compression piston is investigated from heat transfer point of view. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber. The model is developed based on the mass and energy balance of the hydrogen, liquid and the wall of the compression chamber at each time step and positional node with various compression ratios to calculate the temperature distribution of the system. The amount of heat extracted from hydrogen, directly at the interface and through the walls, is investigated and compared with the adiabatic case. The amount of heat transfer towards the wall is assessed according to widely used heat transfer models available in the literature.The results show very low sensitivity of the model to different heat transfer correlations. Deviation of hydrogen temperature from adiabatic case is very small, due to large wall resistance and small contact area at the interface. Moreover, the results illustrates that the increasing of the total heat transfer coefficient at the interface and the wall will play a key role in reducing the hydrogen temperature
- Published
- 2014
80. Heat Analysis of Air Cooling of Strawberry. Determination of Effective Heat Transfer Coefficient
- Author
-
Shun-ichiro Tanaka, Shi-Qing Wang, Fumihiko Tanaka, and Kazuo Morita
- Subjects
Air cooling ,Materials science ,Thermodynamics ,Heat transfer coefficient ,Heat analysis ,Food Science - Abstract
イチゴ果実の通風冷却試験を行い,果実内部の経時的・空間的温度変化を有限要素法により解析するとともに,冷風の速度(空塔速度)と有効熱伝達係数との関係について調べ,次の知見を得た.(1) 有限要素法により解析した,冷却時の果実内部の経時的・空間的温度変化は果実の中心および果実表皮部の温度変化の実測値とよく一致し,同解析方法が妥当であることが明らかになった.(2) 有限要素法により決定した有効熱伝達係数は,空塔速度の関数となり,その関係は次式で示される.h=-3.97v2+55.3v+50.0ここで,hは有効熱伝達係数(kJ/m2・h・K)およびvは空塔速度(m/s)である.
- Published
- 1998
81. Rapid partial charging of lead/acid batteries
- Author
-
T.G. Chang and D.M. Jochim
- Subjects
Stationary conditions ,Waste management ,Renewable Energy, Sustainability and the Environment ,Chemistry ,business.industry ,Electrical engineering ,Energy Engineering and Power Technology ,Electrolyte ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Heat analysis ,Lead–acid battery ,business - Abstract
Rapid partial-charge cycling tests, in which the battery received only 5 or 15 min of high-current charge in each cycle, were carried out for a number of commercial lead/acid batteries. It was found that valve-regulated batteries retained their capacity well, and their full discharge capacity was usually recovered in an extended recharge following five to ten rapid partial-charge cycles. Flooded batteries, tested under stationary conditions, did not perform as well as the valve-regulated batteries, which may have been caused by electrolyte stratification. The experimental data indicated that rapid charging was beneficial to the cycle life of a battery. Heat analysis indicated that the ohmic heat was the major contributor to the total heat generated in the rapid partial-charging process.
- Published
- 1997
82. Sequential simulation of thermal stresses in disc brakes for repeated braking
- Author
-
Niclas Strömberg and Asim Rashid
- Subjects
Materials science ,Applied Mechanics ,Teknisk mekanik ,business.industry ,Mechanical Engineering ,Sequential simulation ,Eulerian path ,Surfaces and Interfaces ,Structural engineering ,disc brake ,Heat analysis ,Maskinteknik ,Surfaces, Coatings and Films ,law.invention ,Eulerian framework ,symbols.namesake ,thermal stresses ,law ,Thermal ,Brake ,symbols ,frictional heat ,Disc brake ,business ,repeated braking - Abstract
In this paper, an efficient sequential approach for simulating thermal stresses in brake discs for repeated braking is presented. First, a frictional heat analysis is performed by using an Eulerian formulation of the disc. Then, by using the temperature history from the first step of the sequence, a plasticity analysis with temperature dependent material data is performed in order to determine the corresponding thermal stresses. Three-dimensional geometries of a disc and a pad to a heavy truck are considered in the numerical simulations. The contact forces are computed at each time step taking the thermal deformations of the disc and pad into account. In such manner, the frictional heat power distribution will also be updated in each time step, which in turn will influence the development of heat bands. The plasticity model is taken to be the von Mises yield criterion with linear kinematic hardening, where both the hardening and the yield limit are temperature dependent. The results show that during hard braking, high compressive stresses are generated on the disc surface in the circumferential direction which cause yielding. But when the disc cools down, these compressive stresses transform to tensile residual stresses. For repeated hard braking when this kind of stress history is repeated, we also show that stress cycles with high amplitudes are developed which might generate low cycle fatigue cracks after a few braking cycles.
- Published
- 2013
83. Gemi ıslak alanının ısı değiştirici olarak kullanılmasına yönelik sayısal ve analitik inceleme
- Author
-
Yurtseven, Ahmet, Üst, Yasin, and Gemi İnşaatı ve Gemi Makineleri Mühendisliği Anabilim Dalı
- Subjects
Heat exchangers ,Shipbuilding ,Mechanical Engineering ,Gemi Mühendisliği ,Heat transfer ,Heat analysis ,Engineering Sciences ,Makine Mühendisliği ,Mühendislik Bilimleri ,Marine Engineering - Abstract
Son zamanlarda enerji verimliliğine verilen önem gemi inşaat sektöründe de derinden görülmektedir. Gemi ana makinelerinde enerji ve maliyet düşürücü birçok önlem uygulanmaktadır. Bu uygulamaların en temel olanları emisyon düşürücü ve ısıl önlemlerdir. Bilindiği gibi enerjinin en kalitesiz formu ısı enerjisidir. Mekanik veya kimyasal enerjinin ısı enerjisine dönüşmesi tüm proseslerde kaçınılmazdır. Bu nedenle enerji verimliliğinin artırılması için etkin ısıl yönetime ihtiyaç duyulmaktadır.Bu çalışmada gemi ana makine ceket suyu soğutması için mevcut deniz suyu soğutma devresi haricinde bir konsept tasarlanmakta ve böylelikle bu ısıl yönetim daha etkin bir şekilde sağlanmaktadır. Deniz suyu devresinin bertaraf edilmesi hem kurulum ve bakım-tutum maliyeti hem de devrenin canlı kalması için harcanacak enerjiden tasarruf edilmesini sağlamaktadır. Çalışmada modelin CFD ve analitik yönlemlerle simulasyonu yapılmakta, 5.14 m/s, 2.57 m/s , 0.1028 m/s gemi hızlarında ve deniz suyu 0 ile 40 C arasında 9 sıcaklık değerinde değiştirilerek sonuçlar elde edilmiş bu sonuçlar analitik sonuçlarla kıyaslanmıştır. Sonuç olarak bu konseptin istenilen soğutma yükünü karşılayabildiği görülmüştür. Recently, Importance of energy efficiency has been realized obviously in naval architecture. Many precautions have been practiced for reduction of energy and expenditure in ship main engines. The best known examples of these applications are thermic and emission reducer precautions. Everybody knows that heat energy is the worst form of energy. Mechanical or chemical energy transform heat energy in all processes. Because of this reason to increse of energy efficiency must be used an effective thermic control.With this study, except of current sea water cooling system for jacket water cooling system of ship main engines, a new concept is designed and with this way, thermic control is done more efficiently. Disposal of sea water circuit is enable energy conservation for system configuration and maintenance. Model is examined with CFD and analytic methods, simulation of model is done appropriately, in addition, the results are obtained for three different ship speed (5,14m/s- 2,57 m/s-0,1028m/s) and nine different potential temperature ( between 0 and 40 C ) are found, these results are compared with analytic results. In conclusion, this concept is enough for required cooling load. 94
- Published
- 2012
84. Duman borulu kazanlarda duman borularında ısı transferini iyileştirme yöntemlerinin deneysel olarak incelenmesi
- Author
-
Özhan, Ayhan, Boran, Kurtuluş, and Makine Eğitimi Anabilim Dalı
- Subjects
Energy ,Heat exchangers ,Mechanical Engineering ,Heat transfer ,Heat analysis ,Engineering Sciences ,Makine Mühendisliği ,Enerji ,Mühendislik Bilimleri - Abstract
Endüstriyel tip kazanlarda ve kalorifer kazanlarında ısı transferinin, dolayısıyla kazan veriminin arttırılması için akış saptırıcı kullanımı oldukça yaygınlaşmıştır. Bu araştırmada içi içe borulu tip bir ısı değiştirici tasarlanarak deneysel bir sistem kurulmuştur. Eşmerkezli iç içe borulu ısı değiştiricisinin iç borusunda sıcak hava akışı, dış taraftaki boruda ise zıt akışlı su akışı olmaktadır. Burada kullanılan akış saptırıcılarla akıştaki tübülans arttırılarak ısı transferinde bir iyileşme gerçekleştirileceği araştırılmıştır.Anahtar Kelimeler : Kazanlar duman borulu, ısı transferi, akı? saptırıcı The increasing of heat transfer in the heat exchanger means that energy saving, efficient and effective use of energy. In this study, concentric tube heat exchanger has been designed and an experimental system has been set up. Hot air flows in the internal pipe of the concentric tube heat exchanger and water flows in the external pipe of the concentric tube heat exchanger in the opposing direction. It has been that there is agreement between the results obtained by experiments and the results reported in the literature.Key Words : Smoke-tube boilers, heat transfer, heat deflector 85
- Published
- 2012
85. Numerical simulation of turbine internal cooling and conjugate heat transfer problems with rans based turbulence models
- Author
-
Görgülü, İlhan, Akmandor, İ. Sinan, and Havacılık ve Uzay Mühendisliği Anabilim Dalı
- Subjects
Havacılık Mühendisliği ,Heat transfer ,Cooling channels ,Heat analysis ,Heat transfer coefficient ,Aeronautical Engineering ,Uçak Mühendisliği ,Aircraft Engineering ,Jet engines ,Aviation ,Aviation industry ,Gas turbine engines ,Turbine - Abstract
Mevcut çalışma, iç soğutmalı bir gaz türbin palesinin konjuge ısı transferi analizinin içerdiği farklı akış tiplerinin sayısal benzeşimini kapsamaktadır. Konjuge benzeşmeler, akışkan alanlarlardaki konvektif ısı transferi ile katı alanlara nüfus eden ısının tam eşleşmesini gerektirmektedir. Bu nedenle, hem dış hem de iç yüzeylerdeki ısı transferi değerlerinin doğru tahmin edilmesi öncelikli öneme sahiptir ve büyük ölçüde kullanılan türbülans modelinin performansına bağlıdır. İç soğutmalı türbin palelerinin her iki yüzeyindeki karmaşık akışa, sınır tabakanın laminerden türbülanslı akışa geçişi, sınır tabaka ile şok dalgasının etkileşimi, yüksek akış çizgisi eğilimi ve birbirini izleyen akış ayrılması sebep olmaktadır. Farklı türbülans modellerinin bu akış tiplerindeki performansını bulmak amacıyla, her biri farklı akış ve ısı transferi özellikleriyle ilgili beş farklı deneysel çalışma üzerinde analizler yapılmıştır. En uygun RANS temelli türbülans modeline karar vermek için her deneysel çalışma ticari kodda (ANSYS FLUENT13.0) mevcut olan dört farklı türbülans modeli ile incelenmiştir. Sayısal benzeşimlerde Realizable k-? modeli, Shear Stress Transport k-? modeli, Reynolds Stress Model ve son bir kaç yılda giderek popüler olan V2-f modeli kullanılmıştır. Yürütülen analizlere göre, bir kaç makul olmayan tahmine rağmen, sayısal benzeşimlerin genelinde V2-f modeli diğer birinci derece türbülans modellerine (Realizable k-? ve Shear Stress Transport k-?) doğrulukta ve Reynolds Stress Modeli'ne yakınsamada üstün gelmiştir. The present study considers the numerical simulation of the different flow characteristics involved in the conjugate heat transfer analysis of an internally cooled gas turbine blade. Conjugate simulations require full coupling of convective heat transfer in fluid regions to the heat diffusion in solid regions. Therefore, accurate prediction of heat transfer quantities on both external and internal surfaces has the uppermost importance and highly connected with the performance of the employed turbulence models. The complex flow on both surfaces of the internally cooled turbine blades is caused from the boundary layer laminar-to-turbulence transition, shock wave interaction with boundary layer, high streamline curvature and sequential flow separation. In order to discover the performances of different turbulence models on these flow types, analyses have been conducted on five different experimental studies each concerned with different flow and heat transfer characteristics. Each experimental study has been examined with four different turbulence models available in the commercial software (ANSYS FLUENT13.0) to decide most suitable RANS-based turbulence model. The Realizable k-? model, Shear Stress Transport k-? model, Reynolds Stress Model and V2-f model, which became increasingly popular during the last few years, have been used at the numerical simulations. According to conducted analyses, despite a few unreasonable predictions, in the majority of the numerical simulations, V2-f model outperforms other first-order turbulence models (Realizable k-? and Shear Stress Transport k-?) in terms of accuracy and Reynolds Stress Model in terms of convergence. 134
- Published
- 2012
86. Heat Analysis of an Optical Disc Drive with Natural Cooling
- Author
-
Manabu Ochi, Kohei Takita, Masato Nakanishi, and Shigeo Ohashi
- Subjects
Materials science ,business.product_category ,Optical disc drive ,Mechanics ,Heat analysis ,business ,Natural (archaeology) - Published
- 2002
87. Heat Analysis and Thermodynamic Effects
- Author
-
Amimul Ahsan
- Subjects
Materials science ,Thermodynamics ,Sensible heat ,Material properties ,Heat analysis ,Thermodynamic system ,Thermodynamic process - Published
- 2011
88. Prediction of the Thermal Injury Around Exhaust System of Passenger Car by Practical Procedure: 1st Report—Development of 1D Model for Heat Analysis
- Author
-
Shuji Miyamoto, Tohru Komoriya, Eriko Hara, and Ituhei Kohri
- Subjects
Engineering ,Thermal injury ,business.industry ,Computational fluid dynamics ,business ,Heat analysis ,Automotive engineering - Abstract
In case that heat injury performance is analyzed with CFD, large calculations are required to solve heat and mass flow field inside the exhaust pipes, in the engine compartment and around vehicle body simultaneously. Since it spends much time for the generation of the analytic models and their solution by full CFD, such calculations are not practical to the industrial development of the vehicle in which many parameter studies on various conditions are required. Wherein, we suggest new method for prediction of the heat injury on exhaust systems, which is simplified with 1 dimensional models though the engine compartment flow is calculated with 3 dimensional calculations, i.e. CFD. Basic idea of this method is to divide exhaust systems into several elemental modules where heat transfer characteristics are given individually and to imitate actual systems by connecting them. Then 3D calculation is processed coupling heat and flow field with radiant filed outside exhaust systems. Above all, chemical reaction occurs in the catalytic converter is solved carefully to estimate heat production. This report introduces an overview of their 1-dimensional model and the calculation results.
- Published
- 2011
89. Thermodynamic and economic analysis of geothermal energy use in hydrogen production and liquefaction
- Author
-
Yilmaz, Ceyhun, Söylemez, M. Sait, Kanoğlu, Mehmet, and Makine Mühendisliği Anabilim Dalı
- Subjects
Thermal oxidation ,Energy ,Thermodynamic design ,Thermoeconomic analysis ,Heat exchangers ,Mechanical Engineering ,Science ,Heat equation ,Thermoelectric ,Makine Mühendisliği ,Electrical energy systems ,Econometric models ,Heat systems ,Enerji ,Thermodynamic parameters ,Electrolysis ,Electrochemical cells ,Thermodynamical model ,Thermodynamic cycle ,Electrochemical oxidation ,Thermal systems ,Thermophysical properties ,Heat analysis ,Thermodynamics - Abstract
Hidrojen, bazılarınca geleceğin enerji kaynağı olarak görülen ve üzerinde çok sayıda araştırmanın yapıldığı alternatif bir enerji kaynağıdır. Hidrojenin geleceğin enerjisi olabilmesi için yenilenebilir enerji kaynakları kullanılarak üretilmesi, üretim, depolama, taşıma ve kullanımı gibi konulardaki teknik ve ekonomik problemlerin aşılması gerekmektedir. Hidrojen üretiminde kullanılan birçok yöntem vardır. Hem elektrik hem de ısı girdisi gerektirebilen bu metotlarda güneş, rüzgâr ve hidroelektrik gibi yenilenebilir enerji kaynaklarının yanı sıra nükleer enerjinin kullanımı da üzerinde çokça çalışılan konular arasındadır. Hidrojen sıkıştırılmış gaz olarak depolanabileceği ve taşınabileceği gibi sıvılaştırılarak sıvı fazında çok daha küçük bir hacimde muhafaza edilebilir. Hidrojen sıvılaştırması yüksek miktarda enerji tüketimi gerektiren ve ileri soğutma tekniklerinin kullanıldığı bir işlemdir.Bu tezde, jeotermal enerjinin hidrojen üretimi ve sıvılaştırmasında kullanımının termodinamik ve ekonomik olarak araştırılması yapılmıştır. Bu amaçla hidrojenin farklı üretim ve sıvılaştırma teknikleri incelenerek jeotermal enerjinin kullanımına uygun metotlar tespit edilmiş ve jeotermal enerjinin kullanılabileceği uygun modeller oluşturulmuştur. Bu modeller, bilgisayar ortamında simüle edilerek modellerin termodinamik ve ekonomik analizleri gerçekleştirilmiş ve farklı modeller, termodinamik ve ekonomik performans kriterleri yardımıyla karşılaştırılmıştır. Modellerde hem jeotermal ısı hem de jeotermalden üretilen elektrik girdi olarak kullanılmıştır. Güç üretimi için çift akışkanlı jeotermal çevrim seçilmiştir. Hidrojen üretimi için elektroliz ve yüksek sıcaklıkta elektroliz metotları kullanılmıştır. Hidrojen sıvılaştırmasında ön soğutmalı Linde-Hampson çevrimi kullanılmış ve sıvılaştırma öncesi ön soğutma için absorpsiyonlu soğutma sistemi uygun modellere entegre edilmiştir.Bu sistemlerle geliştirilen 7 modelin termodinamik ve ekonomik analizleri gerçekleştirilerek birim kg ile üretilebilecek ve sıvılaştırılabilecek hidrojen miktarları her bir model için hesaplanmış ve birim kg hidrojenin üretim ve sıvılaştırma maliyeti araştırılmıştır. Bu performans parametrelerinin jeotermal kaynak sıcaklığı ile değişimi incelenmiş ve birim kg başına üretilebilecek hidrojen miktarının jeotermal sıcaklıkla arttığı ve birim hidrojen maliyetinin azaldığı tespit edilmiştir. Toplam maliyet incelemesi sonucunda sıvılaştırma ünitesi olan modellerin toplam yatırım maliyetinin daha fazla olduğu ortaya çıkmıştır. Elde edilen sonuçların güneş, rüzgâr ve nükleer gibi diğer enerji kaynaklarının kullanımı ile ilgili literatürden elde edilen sonuçlarla karşılaştırması yapılmıştır. Jeotermal destekli hidrojen üretimi, diğer yenilenebilir kaynaklarla hidrojen üretimine benzer bir performans göstermektedir. Geliştirilen 7 modelin Türkiye'deki jeotermal kaynaklara uygulaması yapılarak, bu modeller yardımıyla Türkiye'deki jeotermal kaynaklardan elde edilebilecek hidrojen miktarları tahmini yapılmıştır. Bu çalışmada yapılan analizler ve elde edilen sonuçlar, jeotermal enerjiden hidrojen üretimi ve sıvılaştırmasının mevcut teknolojilerle gerçekleştirilebilecek uygun bir alternatif olduğunu ve muhtemel bir hidrojen ekonomisinde önemli bir yer tutabileceğini göstermektedir.Anahtar Kelimeler: Hidrojen, jeotermal enerji, hidrojen üretimi, hidrojen sıvılaştırılması, hidrojen ekonomisi, hidrojen maliyeti. Hydrogen, an alternative energy source, is subject of a lot of research work and some consider it as the energy of the future. If hydrogen is to become the energy of the future, it must be produced using renewable energy sources and the technical and economic problems on its production, storage, transportation, and use should be solved. There are various methods used in hydrogen production. These methods may require both electricity and heat inputs and renewable energies such as solar, wind, hydro and nuclear energy use are being investigated. Hydrogen can be stored and transported either as compressed gas or as a liquid occupying a small volume after being liquefied. Hydrogen liquefaction requires considerable energy consumption and involves advanced refrigeration techniques.The subject of this thesis is the thermodynamic and economic investigation of geothermal energy use in hydrogen production and liquefaction. For this aim, various methods used in hydrogen production and liquefaction are examined, the methods most suitable for geothermal energy use are identified, and appropriate models for using geothermal energy are structured. These models are simulated in computer environment, thermodynamic and economic analyses are done, and these models are compared using thermodynamic and economic performance criteria. When structuring the models, alternatives such as direct use of geothermal heat and/or the use of produced electricity are considered. A binary geothermal cycle is selected for power production. Electrolysis and high-temperature electrolysis are used for hydrogen production and a precooled Linde-Hampson cycle is used for hydrogen liquefaction. Also, an absorption refrigeration system is incorporated into the models for precooling of hydrogen before liquefaction.Seven models are developed and their thermodynamic and economic analyses are performed. The amount of hydrogen production and liquefaction per unit mass of geothermal water and the cost of producing and liquefying a unit mass of hydrogen are calculated for each model. The effects of geothermal water temperature on these performance parameters are studied. It appears that the amount of hydrogen production per unit mass of geothermal water increases and the cost of hydrogen production decreases as the geothermal temperature increases. An economic analysis indicates that the initial costs of the models involving hydrogen liquefaction are higher compared to the models not including liquefaction. The results of this thesis are compared to those involving wind, solar, and nuclear-based hydrogen production. The models developed in this study are applied to the geothermal resources in Turkey, and the potential amounts of hydrogen production are estimated.The results of this thesis indicate that geothermal-based hydrogen production and liquefaction may take an important place in a future renewable-based hydrogen economy as it can be accomplished with the current systems and technology.Keywords: Hydrogen, geothermal energy, hydrogen production, hydrogen liquefaction, hydrogen economy, hydrogen cost. 171
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- 2011
90. Heat Analysis of the Eye Using Finite Element Method
- Author
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R. Heydari Forushani and Kamran Hassani
- Subjects
Maximum temperature ,Computational model ,medicine.anatomical_structure ,Steady state (electronics) ,Distribution (mathematics) ,Heat transfer ,medicine ,Human eye ,Mechanics ,Heat analysis ,Finite element method ,Mathematics - Abstract
Invasive methods in measuring eye temperature are normally dangerous. Therefore, computational models can be used as a useful tool to study the heat transfer in human eye. The previous two-dimensions (2D) models were not able to describe the heat analysis of the eye precisely. This study presents a 3D finite element eye model which simulates the eye temperature distribution in steady state condition. Our results show a discrepancy of 3.61%, maximum, when compared to the experimental ones. We calculated a maximum temperature of 36.966 C and minimum of 34.606 C which are in reasonable agreement with literatures.
- Published
- 2011
91. Joining of AISI 316 and Ck 45 steels with friction welding, the simulation of the welding process and heat analysis
- Author
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Ersözlü, İsmail, Çelik, Sare, and Fen Bilimleri Enstitüsü
- Subjects
Sürtünme Kaynağı Simülasyonu ,Sürtünme Kaynağı ,Isı Analizi ,Friction Welding ,AISI 316 and Ck 45 Steels ,Simulation of Friction Welding ,Heat Analysis ,AISI 316 ve Ck 45 Çeliği - Abstract
Balıkesir Üniversitesi, Fen Bilimleri Enstitüsü, Makina Mühendisliği Ana Bilim Dalı, İmalat sektörü, daha az maliyetli, daha uzun ömürlü seri üretim yapmak için ham madde fiyatı ve işçilik giderlerini minimuma indirmenin yollarını araştırmıştır. Ekonomik ve rekabetçi üretim düzeni, aynı parçanın üretiminin değişik aşamalarında farklı malzemelerin birleştirilerek birlikte kullanımını ortaya koymuştur. Bu nedenle, su pompalarının imalatında kullanılması avantaj sağlayacak olan, AISI 316 ostenitik paslanmaz çelik ile Ck 45 alaşımsız asal çelik çiftinin sürtünme kaynağı ile birleştirilebilirliğinin ve birleştirme parametrelerinin belirlenmesi için bu çalışma yapılmıştır. Ayrıca çalıştığımız malzeme çifti ve sürtünme kaynağı birleştirme işlemlerinde kullanılacak olan simülasyon "Visual Studio 2008 Express Edition" programı ile gerçekleştirilmiştir. Bu program, deneme yanılma sürecini en aza indirecek, atık malzeme miktarını azaltacak, en kısa sürede en az maliyet ile kaynak işlemine geçilmesine olanak sağlayacaktır. Üç boyutlu sıcaklık dağılımı ısı analizi "cfdesign" programı ile gerçekleştirilmiştir. Deney sonuçlarından elde edilen değerler ile simülasyon programından elde edilen sonuçlar kıyaslandığında uyumluluk gösterdiği görülmüştür. Isı analizi sonucunda, Ck 45 malzemesi üzerinde ısının, AISI 316 malzemesinden daha çabuk yayıldığı görülmüştür. Numunelerin birleştirilmesinde bilgisayar kontrollü sürekli tahrikli sürtünme kaynak makinesi kullanılmıştır. Sürtünme kaynağı işlemi 19 farklı kaynak parametresi ile gerçekleştirilmiştir. Kaynak sırasında, kızıl ötesi sıcaklık ölçme cihazı ile kaynak ara yüzeyinin zamana bağlı sıcaklık değişimleri ölçülmüştür. Kaynak sonrası numunelere çekme ve mikrosertlik testleri uygulanmış, mikroyapıları optik mikroskop ve taramalı elektron mikroskobu (SEM) ile incelenmiş ve enerji dağılım spektroskopisi (EDS) analizi ile element dağılımı belirlenerek optimum kaynak parametreleri saptanmıştır. 3000 dev/dk dönme hızında, sürtünme basıncı 100 MPa, sürtünme süresi 10 s, yığma basıncı 200 MPa ve yığma süresi 20 s optimum kaynak parametreleri olarak belirlenmiştir. En yüksek çekme dayanımı 702.15 MPa ile ana malzemeden (AISI 316: 663.53 MPa) % 5.8 daha fazla çıkmıştır. Yapılan mikroyapı incelemesi sonucunda AISI 316 çeliğinde kaynak sonrası dinamik yeniden kristalleşmiş yapının gerçekleştiği, Ck 45 çeliğinde ise kaynak ara yüzeyine yakın bölgelerde martenzit yapının oluştuğu tespit edilmiştir., The production sector has searched for ways of reducing the costs of raw materials and labor for less costly and longer lasting mass production. Economic and competitive production system has introduced the use of different materials welded together in different phases of the production of the same part. Therefore, this study is conducted to find the possibility of jointing the pair of AISI 316 austenitic stainless steel and Ck 45 unalloyed basic steel, the materials which will provide advantage in the production of water pumps, with friction welding and the parameters for joint. Also, the simulation for friction welding procedures and the material pair we had worked on was realized by "Visual Studio 2008 Express Edition" program. This program would reduce trial and error process time to the minimum and it would decrease the quantity of waste material and would make it possible to start welding process with the least finance in the shortest time. Three dimensional heat analysis was realized by "cfdesign" program. It has been observed that values between the experiment results and the ones from the simulation program are determined by experiment results are consistent. As a result of heat analysis, it has been observed that the heat on Ck 45 material spreads faster than AISI 316 material. In joining the specimens, computer controlled continuous drive friction welding machine was used. Friction welding process was performed with 19 different parameters. During the welding process, the heat changes of welding interface in relation to the time was measured by an infrared temperature measurement device during welding. In obtaining optimum welding parameters, after welding process, the tests of tensile and micro hardness were applied, the microstructures were observed by scanning electron microscope (SEM), and ratios of elements were found by energy dispersive spectroscopy (SEM) analysis. The optimum welding parameters of 100 MPa of friction pressure, 10 sec of friction time, 200 MPa of upset pressure and 20 sec of upset time were determined with 3000 rpm rotation speed. The highest tensile strength, which is 702.15 MPa, has resulted 5.8 % more than that of the parent material (AISI 316: 663.53 MPa). As a result of microstructure analysis, it is found that after the welding, dynamic recrystallization structure was formed up on AISI 316 steel while martenzitic structure was formed up on Ck 45 steel on areas close to the welding interface.
- Published
- 2011
92. Atık baca gazlarından ısı geri kazanımının deneysel olarak incelenmesi
- Author
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Ürün, Emre, Kurt, Hüseyin, and Makine Eğitimi Anabilim Dalı
- Subjects
Heat pipes ,Mechanical Engineering ,Heat recovery ,Heat analysis ,Waste heat ,Makine Mühendisliği ,Waste gases - Abstract
Bu çalışmada, yerçekimi destekli ısı borulu atık baca gazlarından ısı geri kazanım sisteminin ısıl performansı deneysel olarak incelenmiştir. Isı geri kazanım sistemi, bakır borudan yapılmış 16 adet ısı borusundan oluşmaktadır. Çalışma akışkanı olarak, R-134a ve R-410a soğutucu akışkanları kullanılmıştır. Sistem, baca içerisine yerleştirilen evaporatör bölgesinin atık baca gazlarında almış olduğu ısı enerjisinin soğutma suyunun dolaştığı bir depo içerisine yerleştirilen kondenser bölgesine taşınması şeklinde çalışmaktadır. Deneyler, beş farklı baca gazı sıcaklığında (75, 100, 125, 150, 175 ºC), dört farklı baca gazı hızında (1, 1.5, 2, 2.5 m/s) ve soğutma suyu debisinde (1, 2, 3, 4 lt/dk) yapılmıştır. Deneylerden elde edilen sonuçlara göre, R-134a için ısı borusu etkenliği %57.7 olurken, aynı şartlar altında R-410a için %44.1 olmuştur. Isı borulu ısı geri kazanımında, R-134a, R-410a soğutucu akışkanına göre daha etkili olmaktadır.Anahtar Kelimeler: Yerçekimi destekli ısı borusu, ısı geri kazanımı, atık baca gazı. In this study, thermal performance of heat recovery system gravity assisted heat pipe has been investigated experimentally. The heat recovery system consists of 16 pieces heat pipe made copper pipe. R-134a and R-410a refrigerants were used as working fluids. System works transporting to heat energy obtained from waste flue gases in the evaporator region to the condenser region that placed inside a store which is circulated cooling water. Experiments are carried out five different flue gases temperature (75, 100, 125, 150, 175 ºC), different flue gases velocity (1, 1.5, 2, 2.5 m/s) and different cooling water flow rates (1, 2, 3, 4 lt/dk). According to the results obtained from experiments, while the heat pipe efficiency was 57.7% for R-134a, under the same conditions was 44.1% for R-410. At the end of the study, it showed that R-134a working fluids more efficiency than R-410 in the heat pipe heat recovery system.Key Words: Gravity assisted heat pipe, heat recovery, waste flue gas. 71
- Published
- 2010
93. The Mass Concrete Temperature Simulation Analysis with Fuzzy Factors
- Author
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Liu Haiqing, Wang Guijun, and Wang Jinli
- Subjects
Mass concrete ,business.industry ,Slab ,Structural engineering ,Transmission coefficient ,business ,Heat analysis ,Fuzzy logic ,Membership function ,Large size ,Mathematics ,Fuzzy membership function - Abstract
In mass concrete casting process of concrete curing because the thickness, strength and anti-permeability level etc a series of uncertain factors exist, and degree of the foundation slab due to a relatively large size and thickness of planar thicker, concrete slabs and the control of temperature cannot effectively, it is difficult to make analysis with classical mathematical model, can not truly reflect the massive concrete hydration heat of the actual effect. Based on the basic concept of fuzzy membership function, establishing the transmission coefficient of membership functions, and carrying on the comprehensive analysis and judgment. So example analysis results indicate that the established membership function can be used for mass concrete hydration heat analysis.
- Published
- 2010
94. Gömülü tip konvektörlerin ısıl analizi
- Author
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Okay, Serkan, Çakır, Kemal, and Makine Mühendisliği Anabilim Dalı
- Subjects
Energy ,Heat exchangers ,Mechanical Engineering ,Embedded systems ,Heat analysis ,Makine Mühendisliği ,Convector ,Heating systems ,Enerji - Abstract
Gömülü tip konvektörlerin ısıtıcı elemanlar içerisindeki yeri bu tip ısıtıcıların ortaya çıkmasına neden olan etkenlerden bahsedildi. Gömülü tip konvektörlerin bileşenleri üzerinde duruldu. Bu bileşenlerin ısı geçişi etkisi değerlendirildi. Isı geçişi ve ısı geçiş mekanizmalarının doğru geometriye ulaşmak için etkin parametrelerin ne olduğu nasıl olması gerektiğine ait literatür çalışmalarından bahsedildi. Gömülü tip konvektörlerin ısı kapasitesini hesaplamak için bir model öne sürülüp çözüme gidildi.Çözüm sonuçları üretici firma sonuçları ile karşılaştırıldı. Modelin doğruluk derecesi değerlendirildi. Modelin yakınsamasını arttırmak için nasıl bir geliştirmeye gidilir fikir yürütmelerinde bulunuldu. Gömülü tip konvektörler için dilimize ait uygulamaya yönelik bir çalışma gerçekleştirildi.Anahtar kelimeler: Konvektör, gömülü, gömme, ısı değiştirici, ısıtıcı eleman, radyatör, gömülü tip konvektör, Its was mentioned about the effects, which caused to come out these types of heaters and tje role of underfloor convectors on the heater elements. It was dwelled on the components of the underfloor convectors. Heat transmission effect of these components was evaluated. It was mentioned abouth the literature studies abouth that what are the effectice parameters of the transmission mechanism to reach to the correct geometry and how must be they. A model was brought forward to estimate the heat capacity of the underfloor convectors and it was looked for a solution.Solution results were compared with the company results. Degree of accuracy of the model was considered. It was given opinions abouth that what can be done to raise the convergence of the model. An application-oriented study was done for being estimated the heat transmission at the underfloor convectors.Key Words: Convector, underfloor, heat exchanger, heater element, radiator, under floor convector 67
- Published
- 2010
95. Gözenekli ortam ve komşu akışkan tabakadan oluşan bileşik sistemde akışın analitik olarak incelenmesi
- Author
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Kulga, İhsan Burak, Baytaş, Ayşe Filiz, Enerji Bilim ve Teknoloji Anabilim Dalı, Baytaş, Filiz, Enerji Bilim ve Teknoloji, and Energy Sciences and Technologies
- Subjects
Flow ,Heat distribution ,Porous medium ,Isı analizi ,Gözenekli ortam ,Isı dağılımı ,Mühendislik Bilimleri ,Akış ,Isı akısı ,Flow velocity ,Fluid dynamics ,Akış hızı ,Heat analysis ,Engineering Sciences ,Heat flux ,Akışkanlar dinamiği - Abstract
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Enerji Enstitüsü, 2010, Thesis (M.Sc.) -- İstanbul Technical University, Energy Institute, 2010, Bu tez çalışmasında, birbirini periyodik bir yapıda takip eden kanallardan oluşan gözenekli ortam ve bu ortama komşu akışkan tabakadan oluşan bileşik sistemdeki hız ve sıcaklık dağılımlarının analitik çözümleri elde edilmiştir. Bu çalışmada elde edilen arayüz koşulları ve daha önceki çalışmalarda elde edilen gerilim ve akı sıçrama koşullarının karşılaştırılması sonucunda gerilim ve akı sıçrama koşullarında bulunan bilinmeyen gerilim sıçrama katsayısı, analitik olarak elde edilmiş ve gözeneklilik, Darcy sayısı ve boşluk çapına bağlı olduğu bulunmuştur. Gerilim sıçrama katsayısının çözümüne benzer olarak Nusselt sayısı için de bir analitik çözüm elde edilmiştir ve Nusselt sayısının gözenekliliğe, boşluk çapına ve akışkan tabakanın kalınlığına bağlı ifadesi elde edilmiştir. Çalışmada yapılan analitik çözümlerin sonuçları, farklı gözeneklilik, akışkan tabakası kalınlığı ve Darcy sayısına bağlı olarak hız ve sıcaklık dağılımları, gerilim sıçrama katsayısının değişimi ve Nusselt sayısı değişimi için çizilen eğrilerle sunulmuştur., In this study, analytical solutions of velocity and temperature distributions were obtained in a composite system which consists of a porous medium and an adjacent fluid layer, where solid and fluid phases repeat themselves in a regular pattern. By comparing interfacial conditions derived from this study and the stress and flux jump conditions developed by previous studies, the unknown stress jump coefficient, was analytically determined and is shown to depend on porosity, Darcy number and pore diameter. Similar to determination of stress jump coefficient, a solution for the Nusselt number was provided and found out that it is depended on porosity, pore diameter and the thickness of adjacent fluid layer. Results of the analytical solutions were represented by different porosity and thickness of adjacent fluid layer, and velocity and temperature distributions dependent on Darcy number, and different stress jump coefficient, and Nusselt number., Yüksek Lisans, M.Sc.
- Published
- 2010
96. Çelik boru imalatında kullanılan ısıl işlem fırını modellenmesi ve tasarımı
- Author
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Genç, Sertan, Uysal, Ünal, and Makine Mühendisliği Anabilim Dalı
- Subjects
Pipe industry ,Metal drawing ,Normalization ,Stress removal method ,Furnaces ,Mechanical Engineering ,Heat transfer ,Steel pipes ,Heat analysis ,Metal alloys ,Makine Mühendisliği ,Heat treatment - Abstract
Fırınlar;demir ve diğer metal ve alaşımlarının ergitme ve rafinasyonunda;metallerin sıcak şekillendirilmesinde;ısıl işlemlerinde;cevher hazırlamada zenginleştirme, topaklamada;seramik, çimento, tuğla vb. üretiminde;emaye vb. diğer kaplama yöntemlerinde;cam endüstrisinde;kimyasal tesislerde ve plastik üretiminde;laboratuar fırınları;kağıt, tekstil ve diğer endüstri dallarında;kok, havagazı gibi yakıt üretiminde kullanılır.Fırınlar ısıl işlem için çok önemlidir.Isıl işlem;METAL ve alaşımlarının özelliklerini değiştirmek için katı halde iken uygulanan ısıtma ve soğutma işlemleridir. Gereken ısıtma ve soğutma işlemleri belirli bir kontrol altında olmalıdır.ISIL İŞLEMLER aşağıdaki amaçları gerçekleştirmek için uygulanır.Sıcak ve soğuk biçimlendirme gerginliklerini gidermek;talaş çıkaran işçilikleri kolaylaştırmak;sertlik ve dayanım kazandırmak;darbelere direnç'i yükseltmek;elektirik ve magnetit özellikleri yükseltmek;kristal yapıyı ayarlamak;ısı ve korozyon direncini yükseltmek;kimyasal bileşimi değiştirerek özellik kazandırmak;zamanla sertleşmeyi sağlamak;metal ve alaşımların gazlarını uzaklaştırmak için uygulanır. Industrial Ovens are commonly used in smelting and refining of iron, various types of metal and their alloys; thermal processing in metals; enrichment or preparation of metal ores; manufacturing of ceramics, bricks, cement etc. ; glazing, chemical and plastic industry and some overcasting methods. Laboratory ovens are commonly used in packaging and fabric industry and also used to product fuel like coke and coal gas.Industrial ovens are so important for thermal processing. Thermal processing is a heating and cooling process to transform metals and other alloys physical properties in their solid phase. Required heating and cooling process must due to a specific control.Thermal Processing is used to achieve that given below.To overcome defects of hot and cool moulding, to simplify non-trimming operations, to gain strength and stiffness for metals, to upgrade impact resistance, to increase electrical and magnetic properties, to adjust crystal structure, to raise thermal and corrosion resistance, to gain intended properties by changing the chemical composition and to suspend the gases that metals and other alloys have. 156
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- 2010
97. PEM tipi yakıt hücresinin ısıl, mekanik, elektro-kimyasal ve akış davranışlarının modellenmesi
- Author
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Esmer, Mustafa, Ata, Ali, and Makine Mühendisliği Ana Bilim Dalı
- Subjects
Energy ,Fluid dynamics ,Mechanical Engineering ,Stress analysis ,Heat analysis ,Makine Mühendisliği ,Fuel cells ,Enerji - Abstract
Yakıt hücresi reaktantların sahip olduğu kimyasal enerjiyi yanma olmadan doğrudan elektrik enerjisine dönüştüren elektro-kimyasal bir cihazdır. Kabaca yakıt hücresi anot ve katotu oluşturan elektrotlar ile seçici geçirgen elektrolitten (membran) oluşur. Anotta hidrojen elektron ve protonlarına ayrılır. Protonlar membrandan geçerken, elektronlar membranın elektriksel olarak yalıtkan olması nedeniyle harici bir devre üzerinden akarak katota ulaşır. Burada oksijen, proton ve elektronlar ile birleşerek elektrik, su ve ısıyı oluşturur. Teorik olarak reaktantlar dışarıdan beslendiği sürece elektrik üretimi sonsuza kadar devam eder. Yakıt pilleri, yanma gerçekleşmediğinden dolayı yüksek verime, yüksek akım yoğunluğuna, düşük emisyon değerlerine sahip olmaları ve hareketli parçaları barındırmamaları nedeniyle mobil uygulamalarda, içten yanmalı motorlar ile pillerin yerini almaya adaydırlar.Bu çalışmada yakıt hücrelerinin çalışma parametrelerinden basınç, sıcaklık ve havanın stokiyometrik oranının hücre performansına etkisi Hesaplamalı Akışkanlar Dinamiği (CFD) programı kullanılarak incelenmiştir. Deneysel ve teorik I-V eğri sonuçları matematiksel modelin doğruluğu açısından karşılaştırılmıştır. Proses sırasında oluşan sıcaklık farkları ile yakıt hücresine uygulanan sıkma kuvveti etkisi, Sonlu Elemanlar Analizi (FEM) programında incelenerek hücre içerisindeki gerilme dağılımı bulunmuştur. Fuel cell is an electro-chemical equipment that converts the chemical energy directly to the electrical energy without combustion. Basically, fuel cell is composed of electrodes which are anode, cathode and a selective electrolyte (membrane). At anode side hydrogen gas is broken into electrons and protons. Protons pass through the membrane, whereas electrons reach the cathode over an external circuit. At the cathode side, oxygen gas reacts with the hydrogen ion and the electrons which generate electricity and heat as outputs and water as a product. Theoretically, electricity generation can continue forever if the reactants are supplied. Fuel cell technology is a candidate for being used at mobile applications instead of internal combustion engines, since they have higher efficiency and zero or lower emissions. The process doesn?t involve burning or moving parts.In this study, the effect of fuel cell working parameters, such as pressure, heat and reactant stoichiometric ratios, on fuel cell performance is analyzed by using Computational Fluid Dynamics (CFD) prgramming. Theoretical I-V curve results obtained from the mathematical model are verified with the real time performance measurements. Stress distribution in the fuel cell cross section is analyzed with Finite Elements Analysis (FEM) programs. 59
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- 2010
98. MATHEMATICAL MODEL FOR UNSTEADY STATE HEAT ANALYSIS OF A LARGE SPACE, INCLUDING THE PREDICTION OF VERTICAL AIR TEMPERATURE DISTRIBUTION : Study on a thermal environment design system for large spaces Part 2
- Author
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Yoshinobu Arai, Katsuhiro Miura, and Satoshi Togari
- Subjects
Distribution (mathematics) ,Air temperature ,Thermal ,Environmental science ,State (functional analysis) ,Mechanics ,Space (mathematics) ,Heat analysis - Published
- 1992
99. Optimum design of parallel, horizontal and laminar forced convection air-cooled rectangular channels with insulated lateral surfaces
- Author
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Özdemir, Mehmet Ozan, Yüncü, Hafit, and Makine Mühendisliği Anabilim Dalı
- Subjects
Heat control ,Optimization ,Energy ,Mechanical Engineering ,Makine Mühendisliği ,Air flow ,Enerji ,Electronic packaging ,Mechanical engineering ,Laminar flow ,Mühendislik Bilimleri ,Heat transfer ,Heat analysis ,Engineering Sciences ,Forced convection ,Heat flow - Abstract
Bu tezin amacı, paralel ısı yayan plakaların optimum dizilişinin nümerik olarak incelenmesidir. İzotermal plakalar, yalıtılmış yan yüzeylerle çevrili olan sabit hacimli bir elektronik sistem paketinde bulunmakta ve öngörülmüş basınç farkı kullanılarak havanın laminer zorlanmış taşınımı ile soğutulmaktadır. Sabit veya öngörülmüş basınç varsayımı, elektronik malzemelerdeki birkaç paralel plakanın fan gibi ortak bir kaynak tarafından soğutulduğu donanımlar için kabul edilebilir bir modeldir.Hazırlanan nümerik algoritmada, dikdörtgen kesitli bir kanaldaki sabit özellikli sıkıştırılamaz akış için zorlanmış taşınımı temsil eden denklemler çözülmüştür. Her bir dikdörtgen kesitli kanaldaki akış ve sıcaklık dağılımının nümerik sonuçları, plakalardan havaya olan ısı transferinin en yüksek seviyede elde edilmesi amacıyla plakaların optimum uzaklığının belirlenmesini sağlamıştır. Optimizasyon işleminin sonuçları verildikten sonra, en yüksek ısı transferi değerini ve paralel plakaların optimum uzaklığını veren bağıntılar, öngörülmüş basınç farkı, plaka uzunluğu, havanın yoğunluğu ve havanın kinematik viskozitesi cinsinden ayrı ayrı türetilmiştir.Sonuç olarak; bu tezde elde edilen bilgiler, literatürde bulunan sonsuz genişliğe sahip izotermal paralel plakalar hakkındaki iki boyutlu çalışmalar ile karşılaştırılmış ve değerlendirilmiştir. Buna ilaveten, sabit hacimde bulunan paralel plakaların optimizasyonuna ilişkin iki boyutlu sonuçlar, ilgili tezin sonunda daha genellenmiş bir üç boyutlu modele genişletilmiştir.Anahtar Kelimeler: Optimizasyon, Dikdörtgen Kanallar, Laminer Hava Akışı, Zorlanmış Taşınım, Elektronik Termal Paketleme The objective of this thesis is to predict numerically the optimal spacing between parallel heat generating boards. The isothermal boards are stacked in a fixed volume of electronic package enclosed by insulated lateral walls, and they are cooled by laminar forced convection of air with prescribed pressure drop. Fixed pressure drop assumption is an acceptable model for installations in which several parallel boards in electronic equipment receive the coolant from the same source such as a fan.In the numerical algorithm, the equations that govern the process of forced convection for constant property incompressible flow through one rectangular channel are solved. Numerical results of the flow and temperature field in each rectangular channel yield the optimal board-to-board spacing by which maximum heat dissipation rate from the package to the air is achieved. After the results of the optimization procedure are given, the correlations for the determination of the maximum heat transfer rate from the package and optimal spacing between boards are, respectively, derived in terms of prescribed pressure difference, board length, and density and kinematic viscosity of air.In conclusion, the obtained correlations are compared and assessed with the available two-dimensional studies in literature for infinite parallel plates. Furthermore, existing two-dimensional results are extended to a more generalized three-dimensional case at the end of the thesis.Keywords: Optimization, Rectangular Channels, Laminar Air Flow, Forced Convection, Electronic Thermal Packaging 114
- Published
- 2009
100. Design of an air condenser for tumble dryers
- Author
-
Hartoka, Onur, An, Erdem, and Makine Mühendisliği Anabilim Dalı
- Subjects
Heat change ,Heating ,Heat exchangers ,Mechanical Engineering ,Drying theory ,Heat transfer ,Heat loss ,Heat analysis ,Makine Mühendisliği ,Heat transfer model - Abstract
Doğal enerji kaynaklarının giderek azaldığı günümüz dünyasında en fazla enerji tüketen beyaz eşyalardan biri olması nedeni ile yoğuşturuculu çamaşır kurutma makinalarının performanslarını iyileştirmek için yapılan çalışmalar büyük önem taşımaktadır. Bu çalışmanın ilk amacını çamaşır kurutma makinalarının en önemli komponenti olan yoğuşturucucun (kondenserin) performansını etkileyen faktörlerin belirlenmesi oluşturmuştur. Bu amaçla ilk olarak basit bir sayısal kurutucu modeli oluşturularak kondenserin kurutucu enerji tüketimi üzerine olan etkisi incelenmiştir. Mevcut ve geliştirilecek olan kondenserlerin test edilebilmesi amacıyla bir kondenser test düzeneği tasarlanıp kurulmuştur. Bir deney tasarımı oluşturularak mevcut kondenserin performansını etkileyen faktörler belirlenmiştir. Çalışmanın ikinci adımında iki farklı kondenser tasarlanıp prototipleri ürettirilmiştir. Prototip kondenserlerden biri kondenser test ünitesine bağlanarak performans sonuçları mevcut kondenser ile karşılaştırılmıştır. Çalışmanın son adımında ise biri mevcut, diğerleri tasarlananlar olmak üzere üç kondenser de çamaşır kurutma makinasına takılarak test edilmiştir. Sonuçta tasarlanan kondenserlerden ilkinin kondenser verimi, yoğuşma hızı, su toplama verimi ve enerji tüketimi değerleri bakımından mevcut kondenserden çok daha iyi sonuçlar verdiği tespit edilmiştir. Tasarlanan ikinci kondenserin performansının ise ilk kondenser kadar olmasada mevcut kondenserden daha iyi olduğu görülmüştür. Air condenser tumble dryers are those of the most energy consuming home appliances. Therefore, improving the performance of the condenser tumble dryers has recently drawn much attention in today?s world where the energy reserves continuously reduce. Among the various components of the tumble dryers, the condenser is the most important one. The first object of this study was to determine the factors that affect the performance of the condenser which is of the air-to-air heat exchangers. For this purpose a simple air condenser dryer energy model was developed and the effect of the condenser on energy consumption was investigated. A condenser testing unit was designed and constructed to measure the performance of the condensers. The test matrix was formed according to a ?Design of Experiment (DOE).? The tests of the existing benchmark condenser were conducted to determine the factors that affect the condenser performance. In the second part of the study two new condensers were designed and prototyped. One of two new condensers was tested in the condenser testing unit and the results were compared with the existing benchmark condenser. Finally, three condensers, that is, the existing benchmark condenser and two newly designed condensers, were tested in a benchmark air condenser tumble dryer. The test results showed that one of the newly designed condensers had much better performance than the benchmark condenser in terms of the condenser efficiency, the condensation rate, the water collecting efficiency and the energy consumption values, while the other newly designed condenser was slightly better than the benchmark one. 94
- Published
- 2009
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