Search results for: transfer
2512 Partial Knowledge Transfer Between the Source Problem and the Target Problem in Genetic Algorithms
Authors: Terence Soule, Tami Al Ghamdi
Abstract:To study how the partial knowledge transfer may affect the Genetic Algorithm (GA) performance, we model the Transfer Learning (TL) process using GA as the model solver. The objective of the TL is to transfer the knowledge from one problem to another related problem. This process imitates how humans think in their daily life. In this paper, we proposed to study a case where the knowledge transferred from the S problem has less information than what the T problem needs. We sampled the transferred population using different strategies of TL. The results showed transfer part of the knowledge is helpful and speeds the GA process of finding a solution to the problem.
Keywords: transfer learning, partial transfer, evolutionary computation, genetic algorithmProcedia PDF Downloads 51
2511 University-Industry Technology Transfer and Technology Transfer Offices in Emerging Economies
Authors: José Carlos Rodríguez, Mario Gómez
Abstract:The aim of this paper is to get insight on the nature of university-industry technology transfer (UITT) and technology transfer offices (TTOs) activity at universities in the case of emerging economies. In relation to the process of transferring knowledge/technology in the case of emerging economies, knowledge/technology transfer in these economies are more reactive than in developed economies due to differences in maturity of technologies. It is assumed in this paper that knowledge/technology transfer is a complex phenomenon, and thus the paper contributes to get insight on the nature of UITT and TTOs creation in the case of emerging economies by using a system dynamics model of knowledge/technology transfer in these countries. The paper recognizes the differences between industrialized countries and emerging economies on these phenomena.
Keywords: university-industry technology transfer, technology transfer offices, technology transfer models, emerging economiesProcedia PDF Downloads 160
2510 Jet Impingement Heat Transfer on a Rib-Roughened Flat Plate
Authors: A. H. Alenezi
Abstract:Cooling by impingement jet is known to have a significant high local and average heat transfer coefficient which make it widely used in industrial cooling systems. The heat transfer characteristics of an impinging jet on rib-roughened flat plate has been investigated numerically. This paper was set out to investigate the effect of rib height on the heat transfer rate. Since the flow needs to have enough spacing after passing the rib to allow reattachment especially for high Reynolds numbers, this study focuses on finding the optimum rib height which would be the best to maximize the heat transfer rate downstream the plate. This investigation employs a round nozzle with hydraulic diameter (Dh) of 13.5 mm, Jet-to-target distance of (H/D) of 4, rib location=1.5D and and finally jet angels of 45˚ and 90˚ under the influence of Re =10,000.
Keywords: jet impingement, CFD, turbulence model, heat transferProcedia PDF Downloads 280
2509 Experimental Study of Heat Transfer Enhancement Using Protruded Rectangular Fin
Authors: Tarique Jamil Khan, Swapnil Pande
Abstract:The investigation deals with the study of heat transfer enhancement using protruded square fin. This study is enough to determine whether protrusion in forced convection is enough to enhance the rate of heat transfer. It includes the results after performing experiments by using a plane rectangular fin of aluminum material and the same dimension rectangular fin of the same material but having protruded circular shape extended normally. The fins made by a sand casting method. The results clearly mentioned that the protruded surface is effective enough to enhance the rate of heat transfer. This research investigates a modern fin topologies heat transfer characteristics that will clearly outdated the conventional fin to increase the rate of heat transfer. Protruded fins improve the rate of heat transfer compared to solid fin by varying shape of the protrusion in diameter and height.
Keywords: heat transfer enhancement, forced convection, protruted fin, rectangular finProcedia PDF Downloads 252
2508 Exergy Losses Relation with Driving Forces in Heat Transfer Process
Authors: S. Ali Ashrafizadeh, M. Amidpour, N. Hedayat
Abstract:Driving forces along with transfer coefficient affect on heat transfer rate, on the other hand, with regard to the relation of these forces with irriversibilities they are effective on exergy losses. Therefore, the driving forces can be used as a relation between heat transfer rate, transfer coefficients and exergy losses. In this paper, first, the relation of the exergetic efficiency and resistant forces is obtained, next the relation between exergy efficiency, relative driving force, heat transfer rate and heat resistances is considered. In all cases, results are argued graphically. Finally, a case study inspected by obtained results.
Keywords: heat transfer, exergy losses, exergetic efficiency, driving forcesProcedia PDF Downloads 527
2507 Forster Energy Transfer and Optoelectronic Properties of (PFO/TiO2)/Fluorol 7GA Hybrid Thin Films
Authors: Bandar Ali Al-Asbahi, Mohammad Hafizuddin Haji Jumali
Abstract:Forster energy transfer between poly (9,9'-di-n-octylfluorenyl-2,7-diyl) (PFO)/TiO2 nanoparticles (NPs) as a donor and Fluorol 7GA as an acceptor has been studied. The energy transfer parameters were calculated by using mathematical models. The dominant mechanism responsible for the energy transfer between the donor and acceptor molecules was Forster-type, as evidenced by large values of quenching rate constant, energy transfer rate constant and critical distance of energy transfer. Moreover, these composites which were used as an emissive layer in organic light emitting diodes, were investigated in terms of current density–voltage and electroluminescence spectra.
Keywords: energy transfer parameters, forster-type, electroluminescence, organic light emitting diodesProcedia PDF Downloads 320
2506 Capacitive Coupling Wireless Power Transfer System with 6.78 MHz Class D Inverter
Authors: Kang Hyun Yi
Abstract:Wireless power transfer technologies are inductive coupling, magnetic resonance, and capacitive coupling methods, typically. Among them, the capacitive coupling wireless power transfer, also named Capacitive Coupling Wireless Power Transfer (CCWPT), has been researched to overcome the drawbacks of other approaches. The CCWPT has many advantages such as a simple structure, low standing power loss, reduced Electromagnetic Interference (EMI) and the ability to transfer power through metal barriers. In this paper, the CCWPT system with 6.78MHz class D inverter is proposed and analyzed. The proposed system is consisted of the 6.78MHz class D inverter with the LC low pass filter, the capacitor between a transmitter and a receiver and impedance transformers. The system is verified with a prototype for charging mobile devices.
Keywords: wireless power transfer, capacitive coupling power transfer, class D inverter, 6.78MHzProcedia PDF Downloads 563
2505 Key Issues in Transfer Stage of BOT Project: Experience from China
Authors: Wang Liguang, Zhang Xueqing
Abstract:The build-operate-transfer (BOT) project delivery system has provided effective routes to mobilize private sector funds, innovative technologies, management skills and operational efficiencies for public infrastructure development and have been widely used in China during the last 20 years. Many BOT projects in China will be smoothly transferred to the government soon and the transfer stage, which is considered as the last stage, must be studied carefully and handled well to achieve the overall success of BOT projects. There will be many issues faced by both the public sector and private sector in the transfer stage of BOT projects, including project post-assessment, technology and documents transfer, personal training and staff transition, etc. and sometimes additional legislation is needed for future operation and management of facilities. However, most previous studies focused on the bidding, financing, and building and operation stages instead of transfer stage. This research identifies nine key issues in the transfer stage of BOT projects through a comprehensive study on three cases in China, and the expert interview and expert discussion meetings are held to validate the key issues and give detail analysis. A proposed framework of transfer management is prepared based on the experiences derived and lessons drawn from the case studies and expert interview and discussions, which is expected to improve the transfer management of BOT projects in practice.
Keywords: BOT project, key issues, transfer management, transfer stageProcedia PDF Downloads 177
2504 Heat Transfer Studies on CNT Nanofluids in a Turbulent Flow Heat Exchanger
Authors: W. Rashmi, M. Khalid, O. Seiksan, R. Saidur, A. F. Ismail
Abstract:Nanofluids have received much more attention since its discovery. They are believed to be promising coolants in heat transfer applications due to their enhanced thermal conductivity and heat transfer characteristics. In this study, the enhancement in heat transfer of CNT-nanofluids under turbulent flow conditions is investigated experimentally. Carbon nanotube (CNTs) concentration was varied between 0.051-0.085 wt%. The nanofluid suspension was stabilized by gum arabic (GA) through a process of homogenisation and sonication. The flow rates of cold fluid (water) is varied from 1.7-3 L/min and flow rates of the hot fluid is varied between 2-3.5 L/min. Thermal conductivity, density and viscosity of the nanofluids were also measured as a function of temperature and CNT concentration. The experimental results are validated with theoretical correlations for turbulent flow available in the literature. Results showed an enhancement in heat transfer range between 9-67% as a function of temperature and CNT concentration.
Keywords: nanofluids, carbon nanotubes (CNT), heat transfer enhancement, heat transferProcedia PDF Downloads 432
2503 CFD Simulation of Forced Convection Nanofluid Heat Transfer in the Automotive Radiator
Authors: Sina Movafagh, Younes Bakhshan
Abstract:Heat transfer of coolant flow through the automobile radiators is of great importance for the optimization of fuel consumption. In this study, the heat transfer performance of the automobile radiator is evaluated numerically. Different concentrations of nanofluids have been investigated by the addition of Al2O3 nano-particles into the water. Also, the effect of the inlet temperature of nanofluid on the performance of radiator is studied. Results show that with an increase of inlet temperature the outlet temperature and pressure drop along the radiator increase. Also, it has been observed that increase of nono-particle concentration will result in an increase in heat transfer rate within the radiator.
Keywords: heat transfer, nanofluid, car radiator, CFD simulationProcedia PDF Downloads 235
2502 A Transfer Function Representation of Thermo-Acoustic Dynamics for Combustors
Authors: Myunggon Yoon, Jung-Ho Moon
Abstract:In this paper, we present a transfer function representation of a general one-dimensional combustor. The input of the transfer function is a heat rate perturbation of a burner and the output is a flow velocity perturbation at the burner. This paper considers a general combustor model composed of multiple cans with different cross sectional areas, along with a non-zero flow rate.
Keywords: combustor, dynamics, thermoacoustics, transfer functionProcedia PDF Downloads 290
2501 A Novel Comparison Scheme for Thermal Conductivity Enhancement of Heat Transfer
Authors: Islam Tarek, Moataz Soliman
Abstract:With the amazing development of nanoscience’s and the discovery of the unique properties of nanometric materials, the ideas of scientists and researchers headed to take advantage of this progress in various fields, and one of the most important of these areas is the field of heat transfer and benefit from it in saving energy used for heat transfer, so nanometric materials were used to improve the properties of heat transfer fluids and increase the efficiency of the liquid. In this paper, we will compare two types of heat transfer fluid, one industrial type (the base fluid is a mix of ethylene glycol and deionized water ) and another natural oils(the base fluid is a mix of jatropha oil and expired olive oil), explaining the method of preparing each of them, starting from the method of preparing CNT, collecting and sorting jatropha seeds, and the most appropriate method for extracting oil from them, and characterization the both of two fluids and when to use both.
Keywords: nanoscience, heat transfer, thermal conductivity, jatropha oilProcedia PDF Downloads 112
2500 Investigation of Heat Transfer of Nanofluids in Circular Microchannels
Authors: Bayram Sahin, Hourieh Bayramian, Emre Mandev, Murat Ceylan
Abstract:In industrial applications, the demand for the enhancement of heat transfer is a common engineering problem. The use of additives to heat transfer fluid is a technique applied to enhance the heat transfer performance of base fluids. In this study, the thermal performance of nanofluids consisting of SiO2 particles and deionized water in circular microchannels was investigated experimentally. SiO2 nanoparticles with diameter of 15 nm were added to water to prepare nanofluids with 0.2% and 0.4% volume fractions. Heat transfer characteristics were calculated by using temperature, flow and pressure measurements. The thermal conductivity and viscosity values required for the calculations are measured separately. It is observed that the Nusselt number increases at the all volume fraction of particles, by increasing the Reynolds number and the volumetric ratios of the particles. The highest heat transfer enhancement is obtained at Re = 2160 and 0.4 % vol. by 14% under the condition of a constant pumping power.
Keywords: nanofluid, microchannel, heat transfer, SiO2-water nanofluidProcedia PDF Downloads 312
2499 Mixed Convection Heat Transfer of Copper Oxide-Heat Transfer Oil Nanofluid in Vertical Tube
Authors: Farhad Hekmatipour, M. A. Akhavan-Behabadi, Farzad Hekmatipour
Abstract:In this paper, experiments were conducted to investigate the heat transfer of Copper Oxide-Heat Transfer Oil (CuO-HTO) nanofluid laminar flow in vertical smooth and microfin tubes as the surface temperature is constant. The effect of adding the nanoparticle to base fluid and Richardson number on the heat transfer enhancement is investigated as Richardson number increases from 0.1 to 0.7. The experimental results demonstrate that the combined forced-natural convection heat transfer rate may be improved significantly with an increment of mass nanoparticle concentration from 0% to 1.5%. In this experiment, a correlation is also proposed to predict the mixed convection heat transfer rate of CuO-HTO nanofluid flow. The maximum deviation of both correlations is less than 14%. Moreover, a correlation is presented to estimate the Nusselt number inside vertical smooth and microfin tubes as Rayleigh number is between 2´105 and 6.8´106 with the maximum deviation of 12%.
Keywords: mixed convection, heat transfer, nanofluid, vertical tube, microfin tubeProcedia PDF Downloads 266
2498 Heat Transfer from a Cylinder in Cross-Flow of Single and Multiphase Flows
Authors: F. A. Hamad, S. He
Abstract:In this paper, the average heat transfer characteristics for a cross flow cylinder of 16 mm diameter in a vertical pipe has been studied for single-phase flow (water/oil) and multicomponent (non-boiling) flow (water-air, water-oil, oil-air and water-oil-air). The cylinder is uniformly heated by electrical heater placed at the centre of the element. The results show that the values of average heat transfer coefficients for water are around four times the values for oil flow. Introducing air as a second phase with water has very little effect on heat transfer rate, while the heat transfer increased by 70% in case of oil. For water–oil flow, the heat transfer coefficient values are reflecting the percentage of water up to 50%, but increasing the water more than 50% leads to a sharp increase in the heat transfer coefficients to become close to the values of pure water. The enhancement of heat transfer by mixing two phases may be attributed to the changes in flow structure near to cylinder surface which lead to thinner boundary layer and higher turbulence. For three-phase flow, the heat transfer coefficients for all cases fall within the limit of single-phase flow of water and oil and are very close to pure water values. The net effect of the turbulence augmentation due to the introduction of air and the attenuation due to the introduction of oil leads to a thinner boundary layer of oil over the cylinder surface covered by a mixture of water and air bubbles.
Keywords: circular cylinder, cross flow, hear transfer, multicomponent multiphase flowProcedia PDF Downloads 309
2497 An Improved Heat Transfer Prediction Model for Film Condensation inside a Tube with Interphacial Shear Effect
Authors: V. G. Rifert, V. V. Gorin, V. V. Sereda, V. V. Treputnev
Abstract:The analysis of heat transfer design methods in condensing inside plain tubes under existing influence of shear stress is presented in this paper. The existing discrepancy in more than 30-50% between rating heat transfer coefficients and experimental data has been noted. The analysis of existing theoretical and semi-empirical methods of heat transfer prediction is given. The influence of a precise definition concerning boundaries of phase flow (it is especially important in condensing inside horizontal tubes), shear stress (friction coefficient) and heat flux on design of heat transfer is shown. The substantiation of boundary conditions of the values of parameters, influencing accuracy of rated relationships, is given. More correct relationships for heat transfer prediction, which showed good convergence with experiments made by different authors, are substantiated in this work.
Keywords: film condensation, heat transfer, plain tube, shear stressProcedia PDF Downloads 181
2496 Diversity and Intensity of International Technology Transfer and their Impacts on Organizational Performance
Authors: Seongryong Kang, Woonjin Kim, Sungjoo Lee
Abstract:Under the environment of fierce competition and globalized economy, international technology collaboration has gained increasing attention as a way to improve innovation efficiency. While international technology transfer helps a firm to acquire necessary technology in a short period of time, it also has a risk; embedding external technology from overseas partners may cause a transaction cost due to the regional, cultural and language barriers, which tend to offset the benefits of such transfer. Though a number of previous studies have focused on the effects of technology in-transfer on firm performance, few have conducted in the context of international technology transfer. To fill this gap, this study aims to investigate the impact of international technology in-transfer on firm performance – both innovation and financial performance, with a particular emphasis on the diversity and intensity of such transfer. To do this, we adopted technology balance payment (TBP) data of Korean firms from 2010 to 2011, where an intermediate regression analysis was used to identify the intermediate effects of absorptive capacity. The analysis results indicate that i) the diversity and intensity of international technology transfer influence innovation performance by improving R&D capability positively; and ii) the diversity has a positive impact but the intensity has a negative impact on financial performance through the intermediation of R&D intensity. The research findings are expected to provide meaningful implications for establishing global technology strategy and developing policy programs to facilitate technology transfer.
Keywords: diversity, intensity, international technology acquisition, performance, technology transferProcedia PDF Downloads 287
2495 Comparison of Particle Size for ɑ(Alpha) Fe2O3 and ɤ(Gamma)Fe2O3 on Heat Transfer Performance in an Copper Oscillating Heat Pipe
Authors: Hamid Reza Goshayeshi
Abstract:The effect of ɑ(alpha) Fe2O3 and ɤ(gamma)Fe2O3 particles on the heat transfer performance of an oscillating heat pipe was investigated experimentally. Kerosene was used as the base ﬂuid for the OHP. Six size particles with average diameters of 10 nm, 20 nm, and 30 nm ɑFe2O3 and ɤFe2O3 were investigated, respectively. Experimental results show that the ɤFe2O3 particles added in the OHP signiﬁcantly affect the heat transfer performance. When the OHP was charged with kerosene and 20 nm ɤ Fe2O3 particles, the OHP can achieve the best heat transfer performance among six particles investigated in this research.
Keywords: copper oscillating heat pipe, heat transfer, flow, comparison of ɑ(alpha)Fe2O3 and ɤ(gamma)Fe2O3, increase heat transferProcedia PDF Downloads 209
2494 Heat Transfer Characteristics on Blade Tip with Unsteady Wake
Authors: Minho Bang, Seok Min Choi, Jun Su Park, Hokyu Moon, Hyung Hee Cho
Abstract:Present study investigates the effect of unsteady wakes on heat transfer in blade tip. Heat/mass transfer was measured in blade tip region depending on a variety of strouhal number by naphthalene sublimation technique. Naphthalene sublimation technique measures heat transfer using a heat/mass transfer analogy. Experiments are performed in linear cascade which is composed of five turbine blades and rotating rods. Strouhal number of inlet flow are changed ranging from 0 to 0.22. Reynolds number is 100,000 based on 11.4 m/s of outlet flow and axial chord length. Three different squealer tip geometries such as base squealer tip, vertical rib squealer tip, and camber line squealer tip are used to study how unsteady wakes affect heat transfer on a blade tip. Depending on squealer tip geometry, different flow patterns occur on a blade tip. Also, unsteady wakes cause reduced tip leakage flow and turbulent flow. As a result, as strouhal number increases, heat/mass transfer coefficients decrease due to the reduced leakage flow. As strouhal number increases, heat/ mass transfer coefficients on a blade tip increase in vertical rib squealer tip.
Keywords: gas turbine, blade tip, heat transfer, unsteady wakesProcedia PDF Downloads 285
2493 Fluid Flow and Heat Transfer Characteristics Investigation in Spray Cooling Systems Using Nanofluids
Authors: Lee Derk Huan, Nur Irmawati
Abstract:This paper aims to investigate the heat transfer and fluid flow characteristics of nanofluids used in spray cooling systems. The effect of spray height, type of nanofluids and concentration of nanofluids are numerically investigated. Five different nanofluids such as AgH2O, Al2O3, CuO, SiO2 and TiO2 with volume fraction range of 0.5% to 2.5% are used. The results revealed that the heat transfer performance decreases as spray height increases. It is found that TiO2 has the highest transfer coefficient among other nanofluids. In dilute spray conditions, low concentration of nanofluids is observed to be more effective in heat removal in a spray cooling system.
Keywords: numerical investigation, spray cooling, heat transfer, nanofluidsProcedia PDF Downloads 390
2492 Estimation of Natural Convection Heat Transfer from Plate-Fin Heat Sinks in a Closed Enclosure
Authors: Han-Taw Chen, Chung-Hou Lai, Tzu-Hsiang Lin, Ge-Jang He
Abstract:This study applies the inverse method and three-dimensional CFD commercial software in conjunction with the experimental temperature data to investigate the heat transfer and fluid flow characteristics of the plate-fin heat sink in a closed rectangular enclosure for various values of fin height. The inverse method with the finite difference method and the experimental temperature data is applied to determine the heat transfer coefficient. The k-ε turbulence model is used to obtain the heat transfer and fluid flow characteristics within the fins. To validate the accuracy of the results obtained, the comparison of the average heat transfer coefficient is made. The calculated temperature at selected measurement locations on the plate-fin is also compared with experimental data.
Keywords: inverse method, FLUENT, k-ε model, heat transfer characteristics, plate-fin heat sinkProcedia PDF Downloads 360
2491 Transfer Knowledge From Multiple Source Problems to a Target Problem in Genetic Algorithm
Authors: Terence Soule, Tami Al Ghamdi
Abstract:To study how to transfer knowledge from multiple source problems to the target problem, we modeled the Transfer Learning (TL) process using Genetic Algorithms as the model solver. TL is the process that aims to transfer learned data from one problem to another problem. The TL process aims to help Machine Learning (ML) algorithms find a solution to the problems. The Genetic Algorithms (GA) give researchers access to information that we have about how the old problem is solved. In this paper, we have five different source problems, and we transfer the knowledge to the target problem. We studied different scenarios of the target problem. The results showed combined knowledge from multiple source problems improves the GA performance. Also, the process of combining knowledge from several problems results in promoting diversity of the transferred population.
Keywords: transfer learning, genetic algorithm, evolutionary computation, source and targetProcedia PDF Downloads 60
2490 Steady Conjugate Heat Transfer of Two Connected Thermal Systems
Authors: Mohamed El-Sayed Mosaad
Abstract:An analytic approach is obtained for the steady heat transfer problem of two fluid systems, in thermal communication via heat conduction across a solid wall separating them. The two free convection layers created on wall sides are assumed to be in parallel flow. Fluid-solid interface temperature on wall sides is not prescribed in analysis in advance; rather, determined from conjugate solution among other unknown parameters. The analysis highlights the main conjugation parameters controlling thermal interaction process of involved heat transfer modes. Heat transfer results of engineering importance are obtained.
Keywords: conjugate heat transfer, boundary layer, convection, thermal systemsProcedia PDF Downloads 295
2489 Assessment of Academic Knowledge Transfer Channels in Field of Environment
Authors: Jagul Huma Lashari, Arabella Bhutto
Abstract:Last few years have shown increased an interest of researchers in knowledge and technology transfer. However, facts show fewer types of knowledge transfer practices in the developing countries. This article focuses on assessment transfer channels of academic research produced by highly qualified academicians working in universities in Sindh offering degrees in field of an Environment in Sindh Pakistan. The academic field has been chosen because in field of the environment there is alarming need of research into practice for sustainable development. Using case study approach; in this research qualitative interviews have been conducted from PhD faculty members working in the universities offering degrees in field of environment. Obtained data is analyzed using descriptive statistics and chi-square test with the help of statistical packages for social sciences (SPSS). Research explored 31 channels of academic knowledge transfer from detailed review of literature and exploratory interviews with participants. Identified knowledge transfer channels have been grouped together in 6 groups of knowledge transfer channels; As knowledge transfer through publications, networking, mobility of researchers, joint research, intellectual property and co-operations. Results revealed that academic knowledge have been transferred through publications, networking, and co-operation. However, less number of academic knowledge has been transferred through groups of knowledge transfer channels such as Intellectual Property and joint research.
Keywords: environment, research knowledge, transfer channels, universitiesProcedia PDF Downloads 221
2488 Numerical Analysis of Heat Transfer Enhancement in Heat Exchangers by using Dimpled Tube
Authors: Bader Alhumaidi Alsubaei, Zahid H. Akash, Ali Imam Sunny
Abstract:The heat transfer coefficient can be improved passively by using a dimpled surface on the tube. The contact area where heat transfer takes place can be enlarged and turbulence will be purposefully produced inside the duct; as a consequence, higher heat transfer quality will be achieved by employing an extended inner or outer surface (dimpled surface). In order to compare the rate and quality of heat transfer between a regular-shaped pipe and a dimpled pipe, a dimpled tube with a fixed dimple radius was created. Numerical analysis of the plain and dimpled pipes was performed using ANSYS. A 23% increase in Nusselt number was seen for dimpled tubes compared to plain tubes. In comparison to plain tubes, dimpled tubes' increase in thermal performance index was found to be between 8% and 10%. An increase in pressure drop of 18% was noted.
Keywords: heat transfer, dimpled tube, CFD, ANSYSProcedia PDF Downloads 36
2487 Hohmann Transfer and Bi-Elliptic Hohmann Transfer in TRAPPIST-1 System
Authors: Jorge L. Nisperuza, Wilson Sandoval, Edward. A. Gil, Johan A. Jimenez
Abstract:In orbital mechanics, an active research topic is the calculation of interplanetary trajectories efficient in terms of energy and time. In this sense, this work concerns the calculation of the orbital elements for sending interplanetary probes in the extrasolar system TRAPPIST-1. Specifically, using the mathematical expressions of the circular and elliptical trajectory parameters, expressions for the flight time and the orbital transfer rate increase between orbits, the orbital parameters and the graphs of the trajectories of Hohmann and Hohmann bi-elliptic for sending a probe from the innermost planet to all the other planets of the studied system, are obtained. The relationship between the orbital transfer rate increments and the relationship between the flight times for the two transfer types is found. The results show that, for all cases under consideration, the Hohmann transfer results to be the least energy and temporary cost, a result according to the theory associated with Hohmann and Hohmann bi-elliptic transfers. Saving in the increase of the speed reaches up to 87% was found, and it happens for the transference between the two innermost planets, whereas the time of flight increases by a factor of up to 6.6 if one makes use of the bi-elliptic transfer, this for the case of sending a probe from the innermost planet to the outermost.
Keywords: bi-elliptic Hohmann transfer, exoplanet, extrasolar system, Hohmann transfer, TRAPPIST-1Procedia PDF Downloads 118
2486 Exciting Voltage Control for Efficiency Maximization for 2-D Omni-Directional Wireless Power Transfer Systems
Authors: Masato Sasaki, Masayoshi Yamamoto
Abstract:The majority of wireless power transfer (WPT) systems transfer power in a directional manner. This paper describes a discrete exciting voltage control technique for WPT via magnetic resonant coupling with two orthogonal transmitter coils (2D omni-directional WPT system) which can maximize the power transfer efficiency in response to the change of coupling status. The theory allows the equations of the efficiency of the system to be determined at all the rate of the mutual inductance. The calculated results are included to confirm the advantage to one directional WPT system and the validity of the theory and the equations.
Keywords: wireless power transfer, omni-directional, orthogonal, efficiencyProcedia PDF Downloads 252
2485 Numerical and Experimental Study on Bed-Wall Heat Transfer in Conical Fluidized Bed Combustor
Authors: Ik–Tae Im, H. M. Abdelmotalib, M. A. Youssef, S. B. Young
Abstract:In this study the flow characteristics and bed-to-wall heat transfer in a gas-solid conical fluidized bed combustor were investigated using both experimental and numerical methods. The computational fluid dynamic (CFD) simulations were carried out using a commercial software, Fluent V6.3. A two-fluid Eulerian-Eulerian model was applied in order to simulate the gas–solid flow and heat transfer in a conical sand-air bed with 30o con angle and 22 cm static bed height. Effect of different fluidizing number varying in the range of 1.5 - 2.3, drag models namely (Syamlal-O’Brien and Gidaspow), and friction viscosity on flow and bed-to-wall heat transfer were analyzed. Both bed pressure drop and heat transfer coefficient increased with increasing inlet gas velocity. The Gidaspow drag model showed a better agreement with experimental results than other drag model. The friction viscosity had no clear effect on both hydrodynamics and heat transfer.
Keywords: computational fluid dynamics, heat transfer coefficient, hydrodynamics, renewable energyProcedia PDF Downloads 335
2484 Mathematical Modeling of Skin Condensers for Domestic Refrigerator
Authors: Nitin Ghule, S. G. Taji
Abstract:A mathematical model of hot-wall condensers used in refrigerators is presented. The model predicts the heat transfer characteristics of condenser and the effects of various design and operating parameters on condenser tube length and capacity. A finite element approach was used to model the condenser. The condenser tube is divided into elemental units, with each element consisting of adhesive tape, refrigerant tube and outer metal sheet. The heat transfer characteristics of each section are then analyzed by considering the heat transfer through the tube wall, tape and the outer sheet. Variations in inner heat transfer coefficient and pressure drop are considered depending on temperature, fluid phase, type of flow and orientation of tube. Variation in outer heat transfer coefficient is also taken into account. Various materials were analysed for the tube, tape and outer sheet.
Keywords: condenser, domestic refrigerator, heat transfer, mathematical modelProcedia PDF Downloads 401
2483 The Effect of Adding CuO Nanoparticles on Boiling Heat Transfer Enhancement in Horizontal Flattened Tubes
Authors: M. A. Akhavan-Behabadi, M. Najafi, A. Abbasi
Abstract:An empirical investigation was performed in order to study the heat transfer characteristics of R600a flow boiling inside horizontal flattened tubes and the simultaneous effect of nanoparticles on boiling heat transfer in flattened channel. Round copper tubes of 8.7 mm I.D. were deformed into flattened shapes with different inside heights of 6.9, 5.5, and 3.4 mm as test areas. The effect of different parameters such as mass flux, vapor quality and inside height on heat transfer coefficient was studied. Flattening the tube caused a significant enhancement in heat transfer performance, so that the maximum augmentation ratio of 163% was obtained in flattened channel with lowest internal height. A new correlation was developed based on the present experimental data to predict the heat transfer coefficient in flattened tubes. This correlation estimated 90% of the entire database within ±20%. The best flat channel with the point of view of heat transfer performance was selected to study the effect of nanoparticle on heat transfer enhancement. Four homogenized mixtures containing 1% weight fraction of R600a/oil with different CuO nanoparticles concentration including 0.5%, 1% and 1.5% mass fraction of R600a/oil/CuO were studied. Observations show that heat transfer was improved by adding nanoparticles, which lead to maximum enhancement of 79% compare to the pure refrigerant at the same test condition.
Keywords: nano fluids, heat transfer, flattend tube, transport phenomenaProcedia PDF Downloads 275