Reduced dimension model for heat transfer of ground heat exchanger in permafrost
Vasilyeva, M.; Stepanov, S.; Sirditov, I.
2017-12-01
In this work, we present reduced dimensional model for heat transfer processes of ground heat exchanger in permafrost. A mathematical model is described by a coupled system of equations for heat transfer in the ground subdomain and in heat exchanger (pipes). Because radius of the pipes is very small compared to the size of surrounding ground, we write heat transfer problem in pipes as reduced dimensional equation, where we consider pipes as one-dimensional lines. We present a computational algorithm and numerical results for model problem.
Shi, Haifeng; Wang, Yi; Fang, Bo; Talmon, Yeshayahu; Ge, Wu; Raghavan, Srinivasa R; Zakin, Jacques L
2011-05-17
Drag-reducing (DR) surfactant fluids based on threadlike micelles are known to suffer from poor heat-transfer capabilities. Accordingly, the use of these fluids is limited to recirculating systems in which heat exchange is not important. Here, we show for the first time that light-responsive threadlike micelles can offer a potential solution to the above problem. The fluids studied here are composed of the cationic surfactant Ethoquad O/12 PG (EO12) and the sodium salt of trans-ortho-methoxycinnamic acid (OMCA). Initially, these fluids contain numerous threadlike micelles and, in turn, are strongly viscoelastic and effective at reducing drag (up to 75% DR). Upon exposure to UV light, OMCA is photoisomerized from trans to cis. This causes the micelles to shorten considerably, as confirmed by cryo-transmission electron microscopy (cryo-TEM). Because of the absence of long micelles, the UV-irradiated fluid shows lower viscoelasticity and much lower DR properties; however, its heat-transfer properties are considerably superior to the initial fluid. Thus, our study highlights the potential of switching off the DR (and in turn enhancing heat-transfer) at the inlet of a heat exchanger in a recirculating system. While the fluids studied here are not photoreversible, an extension of the above concept would be to subsequently switch on the DR again at the exit of the heat exchanger, thus ensuring an ideal combination of DR and heat-transfer properties.
The Impact of Reduced Gravity on Free Convective Heat Transfer from a Finite, Flat, Vertical Plate
Lotto, Michael A.; Johnson, Kirstyn M.; Nie, Christopher W.; Klaus, David M.
2017-09-01
Convective heat transfer is governed by a number of factors including various fluid properties, the presence of a thermal gradient, geometric configuration, flow condition, and gravity. Empirically-derived analytical relationships can be used to estimate convection as a function of these governing parameters. Although it is relatively straightforward to experimentally quantify the contributions of the majority of these variables, it is logistically difficult to assess the influence of reduced-gravity due to practical limitations of establishing this environment. Therefore, in order to explore this regime, a series of tests was conducted to evaluate convection under reduced-gravity conditions averaging 0.45 m/sec2 (0.05 g) achieved aboard a parabolic aircraft. The results showed a reduction in net heat transfer of approximately 61% in flight relative to a 1g terrestrial baseline using the same setup. The average experimental Nusselt Number of 19.05 ± 1.41 statistically correlated with the predicted value of 18.90 ± 0.63 (N = 13), estimated using the Churchill-Chu correlation for free convective heat transfer from a finite, flat, vertical plate. Extrapolating this to similar performance in true microgravity (10-6 g) indicates that these conditions should yield a Nusselt Number of 1.27, which is 2.6% the magnitude of free convection at 1g, or a reduction of 97.4%. With advection essentially eliminated, heat transfer becomes limited to diffusion and radiation, which are gravity-independent and nearly equivalent in magnitude in this case. These results offer a general guideline for integrating components that utilize natural (free) convective gas cooling in a spacecraft habitat and properly sizing the thermal control system.
The Impact of Reduced Gravity on Free Convective Heat Transfer from a Finite, Flat, Vertical Plate
Lotto, Michael A.; Johnson, Kirstyn M.; Nie, Christopher W.; Klaus, David M.
2017-10-01
Convective heat transfer is governed by a number of factors including various fluid properties, the presence of a thermal gradient, geometric configuration, flow condition, and gravity. Empirically-derived analytical relationships can be used to estimate convection as a function of these governing parameters. Although it is relatively straightforward to experimentally quantify the contributions of the majority of these variables, it is logistically difficult to assess the influence of reduced-gravity due to practical limitations of establishing this environment. Therefore, in order to explore this regime, a series of tests was conducted to evaluate convection under reduced-gravity conditions averaging 0.45 m/sec2 (0.05 g) achieved aboard a parabolic aircraft. The results showed a reduction in net heat transfer of approximately 61% in flight relative to a 1 g terrestrial baseline using the same setup. The average experimental Nusselt Number of 19.05 ± 1.41 statistically correlated with the predicted value of 18.90 ± 0.63 (N = 13), estimated using the Churchill-Chu correlation for free convective heat transfer from a finite, flat, vertical plate. Extrapolating this to similar performance in true microgravity (10-6 g) indicates that these conditions should yield a Nusselt Number of 1.27, which is 2.6% the magnitude of free convection at 1 g, or a reduction of 97.4%. With advection essentially eliminated, heat transfer becomes limited to diffusion and radiation, which are gravity-independent and nearly equivalent in magnitude in this case. These results offer a general guideline for integrating components that utilize natural (free) convective gas cooling in a spacecraft habitat and properly sizing the thermal control system.
Barron, Randall F
2016-01-01
Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.
Kamatchi, R.
2018-02-01
In this work, reduced graphene oxide (rGO) is synthesized from graphite powder and various characterization techniques have been used to study the in-plane crystallite size, number of layers, presence of functional groups and surface morphology. The rGO flakes are dispersed in Millipore water to obtain 0.0005, 0.001, and 0.002 wt.% of rGO-water nanofluids. It is then used in the experimental facility to study the nucleate boiling heat transfer with different heating surfaces viz. smooth and sandblasted surface (SBS). Results of this study indicate (i) an enhancement in heat transfer coefficient (HTC) for concentration upto 0.001 wt.% and deterioration beyond this in the case of smooth surface, and (ii) an increase in HTC with concentrations is observed for SBS and shows a maximum enhancement of about 60% in comparison with smooth surface at 0.002 wt.%. It is found that the presence of secondary cavities (acts as nucleation sites) formed by the rGO flakes during boiling is responsible for the observed phenomena in addition to the possible effect of rGO in the fluid flow.
Kamatchi, R.
2017-09-01
In this work, reduced graphene oxide (rGO) is synthesized from graphite powder and various characterization techniques have been used to study the in-plane crystallite size, number of layers, presence of functional groups and surface morphology. The rGO flakes are dispersed in Millipore water to obtain 0.0005, 0.001, and 0.002 wt.% of rGO-water nanofluids. It is then used in the experimental facility to study the nucleate boiling heat transfer with different heating surfaces viz. smooth and sandblasted surface (SBS). Results of this study indicate (i) an enhancement in heat transfer coefficient (HTC) for concentration upto 0.001 wt.% and deterioration beyond this in the case of smooth surface, and (ii) an increase in HTC with concentrations is observed for SBS and shows a maximum enhancement of about 60% in comparison with smooth surface at 0.002 wt.%. It is found that the presence of secondary cavities (acts as nucleation sites) formed by the rGO flakes during boiling is responsible for the observed phenomena in addition to the possible effect of rGO in the fluid flow.
Directory of Open Access Journals (Sweden)
Haifeng Shi
2011-01-01
Full Text Available A novel high-efficiency vortex (HEV static mixer was used to locally enhance the heat transfer coefficient of a drag-reducing fluid, Ethoquad O/12 (EO12 (3 mM with sodium salicylate (NaSal (5 mM. Significant enhancement of heat transfer coefficients was observed. The Nusselt numbers were three to five times those of normal drag-reducing flow without mixer and were close to those of water at high Reynolds number with only modest energy penalty. In contrast, a Helix static mixer increased Nusselt number slightly with very high pressure loss. A performance number was used for comparisons among the HEV static mixer, the Helix static mixer, and water without mixer. The HEV static mixer had a performance number comparable to that of water. The enhanced heat transfer by the HEV static mixer resulted from streamwise vortices generated by the inclined tabs, which increased the convective heat transfer in the radial direction.
SUNDÉN, B
2012-01-01
Presenting the basic mechanisms for transfer of heat, Introduction to Heat Transfer gives a deeper and more comprehensive view than existing titles on the subject. Derivation and presentation of analytical and empirical methods are provided for calculation of heat transfer rates and temperature fields as well as pressure drop. The book covers thermal conduction, forced and natural laminar and turbulent convective heat transfer, thermal radiation including participating media, condensation, evaporation and heat exchangers.
Kakac, Sadik; Pramuanjaroenkij, Anchasa
2014-01-01
Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....
Bacon, D H
2013-01-01
Basic Heat Transfer aims to help readers use a computer to solve heat transfer problems and to promote greater understanding by changing data values and observing the effects, which are necessary in design and optimization calculations.The book is concerned with applications including insulation and heating in buildings and pipes, temperature distributions in solids for steady state and transient conditions, the determination of surface heat transfer coefficients for convection in various situations, radiation heat transfer in grey body problems, the use of finned surfaces, and simple heat exc
Thermal radiation heat transfer
Howell, John R; Siegel, Robert
2016-01-01
Further expanding on the changes made to the fifth edition, Thermal Radiation Heat Transfer, 6th Edition continues to highlight the relevance of thermal radiative transfer and focus on concepts that develop the radiative transfer equation (RTE). The book explains the fundamentals of radiative transfer, introduces the energy and radiative transfer equations, covers a variety of approaches used to gauge radiative heat exchange between different surfaces and structures, and provides solution techniques for solving the RTE.
Aeroplastic, New Composite Materials with Reduced Heat Transfer and Increased Flame Retardancy
Williams, Martha K.; Smith, Trent M.; Nichols, James D.; Roberson, Luke B.; Tate, Lanetra C.
2015-01-01
A new composite system formulated using commodity grade and engineered grade polymers. The composites can be fabricated into fibers, molded, or otherwise processed into useable articles. Use of this technology reduces the thermal conductivity and peak heat releases rates of the base polymer between 20%-50% while maintaining or enhancing the mechanical properties..
REA, The Editors of
1988-01-01
REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Heat Transfer II reviews correlations for forced convection, free convection, heat exchangers, radiation heat transfer, and boiling and condensation.
Hartnett, James P; Cho, Young I; Greene, George A
2001-01-01
Heat transfer is the exchange of heat energy between a system and its surrounding environment, which results from a temperature difference and takes place by means of a process of thermal conduction, mechanical convection, or electromagnetic radiation. Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university-level textbooks by providing in-depth review articles over a broader scope than is allowable in either journals or texts.
Bejan, Adrian
2013-01-01
Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.
Modest, Michael F
2013-01-01
The third edition of Radiative Heat Transfer describes the basic physics of radiation heat transfer. The book provides models, methodologies, and calculations essential in solving research problems in a variety of industries, including solar and nuclear energy, nanotechnology, biomedical, and environmental. Every chapter of Radiative Heat Transfer offers uncluttered nomenclature, numerous worked examples, and a large number of problems-many based on real world situations-making it ideal for classroom use as well as for self-study. The book's 24 chapters cover the four major areas in the field: surface properties; surface transport; properties of participating media; and transfer through participating media. Within each chapter, all analytical methods are developed in substantial detail, and a number of examples show how the developed relations may be applied to practical problems. It is an extensive solution manual for adopting instructors. Features: most complete text in the field of radiative heat transfer;...
Han, Je-Chin
2012-01-01
… it will complete my library … [and] complement the existing literature on heat transfer. It will be of value for both graduate students and faculty members.-Bengt Sunden, Lund University, Sweden
Elementary heat transfer analysis
Whitaker, Stephen; Hartnett, James P
1976-01-01
Elementary Heat Transfer Analysis provides information pertinent to the fundamental aspects of the nature of transient heat conduction. This book presents a thorough understanding of the thermal energy equation and its application to boundary layer flows and confined and unconfined turbulent flows. Organized into nine chapters, this book begins with an overview of the use of heat transfer coefficients in formulating the flux condition at phase interface. This text then explains the specification as well as application of flux boundary conditions. Other chapters consider a derivation of the tra
Lienhard, John H
2011-01-01
This introduction to heat transfer offers advanced undergraduate and graduate engineering students a solid foundation in the subjects of conduction, convection, radiation, and phase-change, in addition to the related topic of mass transfer. A staple of engineering courses around the world for more than three decades, it has been revised and updated regularly by the authors, a pair of recognized experts in the field. The text addresses the implications, limitations, and meanings of many aspects of heat transfer, connecting the subject to its real-world applications and developing students' ins
Karwa, Rajendra
2017-01-01
This textbook presents the classical treatment of the problems of heat transfer in an exhaustive manner with due emphasis on understanding of the physics of the problems. This emphasis is especially visible in the chapters on convective heat transfer. Emphasis is laid on the solution of steady and unsteady two-dimensional heat conduction problems. Another special feature of the book is a chapter on introduction to design of heat exchangers and their illustrative design problems. A simple and understandable treatment of gaseous radiation has been presented. A special chapter on flat plate solar air heater has been incorporated that covers thermo-hydraulic modeling and simulation. The chapter on mass transfer has been written looking specifically at the needs of the students of mechanical engineering. The book includes a large number and variety of solved problems with supporting line diagrams. The author has avoided duplicating similar problems, while incorporating more application-based examples. All the end-...
Yamashiro, Hikaru; Nakashima, Ryou
The effects of ultrasonic vibration on heat transfer characteristics of lithium bromide aqueous solution under the reduced pressures are studied experimentally. Pool boiling curves on horizontal smooth tube are obtained using distilled water and 50 % LiBr aqueous solution as test liquids. The system pressure p is varied from 12 to 101 kPa and the liquid subcooling ΔTsub ranges from 0 to 70 K. The frequency of ultrasonic vibration vi s set at 24 and 44 kHz, and the power input to the vibrator P is varied from 0 to 35 W. The wall superheat at the boiling incipience is found to decrease with increasing P, and the nucleate boiling curve shifts toward the lower wall temperature region. However, the effect of P is not found to be very significant in the high heat flux region, especially in the case of small liquid subcooling. Ultrasonic vibration is also found to improve the nucleate boiling heat transfer coefficient by up to a maximum of 3.5 times and to prevent crystallization of the solution and precipitation of additives.
Thermal radiation heat transfer
Howell, John R; Mengüç, M Pinar
2011-01-01
Providing a comprehensive overview of the radiative behavior and properties of materials, the fifth edition of this classic textbook describes the physics of radiative heat transfer, development of relevant analysis methods, and associated mathematical and numerical techniques. Retaining the salient features and fundamental coverage that have made it popular, Thermal Radiation Heat Transfer, Fifth Edition has been carefully streamlined to omit superfluous material, yet enhanced to update information with extensive references. Includes four new chapters on Inverse Methods, Electromagnetic Theory, Scattering and Absorption by Particles, and Near-Field Radiative Transfer Keeping pace with significant developments, this book begins by addressing the radiative properties of blackbody and opaque materials, and how they are predicted using electromagnetic theory and obtained through measurements. It discusses radiative exchange in enclosures without any radiating medium between the surfaces-and where heat conduction...
Baehr, Hans Dieter
2011-01-01
This comprehensive textbook provides a solid foundation of knowledge on the principles of heat and mass transfer and shows how to solve problems by applying modern methods. The basic theory is developed systematically, exploring in detail the solution methods to all important problems. The thoroughly revised 3rd edition includes an introduction to the numerical solution of Finite Elements. A new section on heat and mass transfer in porous media has also been added. The book will be useful not only to upper-level and graduate students, but also to practicing scientists and engineers, offering a firm understanding of the principles of heat and mass transfer, and showing how to solve problems by applying modern methods. Many completed examples and numerous exercises with solutions facilitate learning and understanding, and an appendix includes data on key properties of important substances.
Thermal radiation heat transfer.
Siegel, R.; Howell, J. R.
1972-01-01
A comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation. Among the topics considered are property prediction by electromagnetic theory, the observed properties of solid materials, radiation in the presence of other modes of energy transfer, the equations of transfer for an absorbing-emitting gas, and radiative transfer in scattering and absorbing media. Also considered are radiation exchange between black isothermal surfaces, radiation exchange in enclosures composed of diffuse gray surfaces and in enclosures having some specularly reflecting surfaces, and radiation exchange between nondiffuse nongray surfaces. The use of the Monte Carlo technique in solving radiant-exchange problems and problems of radiative transfer through absorbing-emitting media is explained.
Energy Technology Data Exchange (ETDEWEB)
Bhattacharyya, A.
1965-11-15
This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table.
Nucleate boiling heat transfer
Energy Technology Data Exchange (ETDEWEB)
Saiz Jabardo, J.M. [Universidade da Coruna (Spain). Escola Politecnica Superior], e-mail: mjabardo@cdf.udc.es
2009-07-01
Nucleate boiling heat transfer has been intensely studied during the last 70 years. However boiling remains a science to be understood and equated. In other words, using the definition given by Boulding, it is an 'insecure science'. It would be pretentious of the part of the author to explore all the nuances that the title of the paper suggests in a single conference paper. Instead the paper will focus on one interesting aspect such as the effect of the surface microstructure on nucleate boiling heat transfer. A summary of a chronological literature survey is done followed by an analysis of the results of an experimental investigation of boiling on tubes of different materials and surface roughness. The effect of the surface roughness is performed through data from the boiling of refrigerants R-134a and R-123, medium and low pressure refrigerants, respectively. In order to investigate the extent to which the surface roughness affects boiling heat transfer, very rough surfaces (4.6 {mu}m and 10.5 {mu}m ) have been tested. Though most of the data confirm previous literature trends, the very rough surfaces present a peculiar behaviour with respect to that of the smoother surfaces (Ra<3.0 {mu}m). (author)
Rathakrishnan, Ethirajan
2012-01-01
1 Basic Concepts and Definitions1.1 Introduction1.1.1 Driving Potential1.2 Dimensions and Units1.2.1 Dimensional Homogeneity1.3 Closed and Open Systems1.3.1 Closed System (ControlMass)1.3.2 Isolated System1.3.3 Open System (ControlVolume)1.4 Forms of Energy1.4.1 Internal Energy1.5 Properties of a System1.5.1 Intensive and Extensive Properties1.6 State and Equilibrium1.7 Thermal and Calorical Properties1.7.1 Specific Heat of an Incompressible Substance1.7.2 Thermally Perfect Gas 1.8 The Perfect Gas1.9 Summary1.10 Exercise ProblemsConduction Heat Transfer2.1 Introduction2.2 Conduction Heat Trans
Directory of Open Access Journals (Sweden)
John White
2016-02-01
Full Text Available The chief objective of this study is the proposal design and CFD simulation of a new compacted copper wire woven fin heat exchanger and silica gel adsorbent bed used as part of an adsorption refrigeration system. This type of heat exchanger design has a large surface area because of the wire woven fin design. It is estimated that this will help improve the coefficient of performance (COP of the adsorption phase and increase the heat transfer in this system arrangement. To study the heat transfer between the fins and porous adsorbent reactor bed, two experiments were carried out and matched to computational fluid dynamics (CFD results.
Measuring of heat transfer coefficient
DEFF Research Database (Denmark)
Henningsen, Poul; Lindegren, Maria
Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...
Kaviany, Massoud
2014-01-01
This graduate textbook describes atomic-level kinetics (mechanisms and rates) of thermal energy storage, transport (conduction, convection, and radiation), and transformation (various energy conversions) by principal energy carriers. The approach combines the fundamentals of molecular orbitals-potentials, statistical thermodynamics, computational molecular dynamics, quantum energy states, transport theories, solid-state and fluid-state physics, and quantum optics. The textbook presents a unified theory, over fine-structure/molecular-dynamics/Boltzmann/macroscopic length and time scales, of heat transfer kinetics in terms of transition rates and relaxation times, and its modern applications, including nano- and microscale size effects. Numerous examples, illustrations, and homework problems with answers that enhance learning are included. This new edition includes applications in energy conversion (including chemical bond, nuclear, and solar), expanded examples of size effects, inclusion of junction quantum tr...
Gas turbine heat transfer and cooling technology
Han, Je-Chin; Ekkad, Srinath
2012-01-01
FundamentalsNeed for Turbine Blade CoolingTurbine-Cooling TechnologyTurbine Heat Transfer and Cooling IssuesStructure of the BookReview Articles and Book Chapters on Turbine Cooling and Heat TransferNew Information from 2000 to 2010ReferencesTurbine Heat TransferIntroductionTurbine-Stage Heat TransferCascade Vane Heat-Transfer ExperimentsCascade Blade Heat TransferAirfoil Endwall Heat TransferTurbine Rotor Blade Tip Heat TransferLeading-Edge Region Heat TransferFlat-Surface Heat TransferNew Information from 2000 to 20102.10 ClosureReferencesTurbine Film CoolingIntroductionFilm Cooling on Rotat
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Energy Technology Data Exchange (ETDEWEB)
Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann
2008-06-12
ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers
Heat Transfer Basics and Practice
Böckh, Peter
2012-01-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author’s experience indicates that students, after 40 lectures and exercises ...
Heat transfer direction dependence of heat transfer coefficients in annuli
Prinsloo, Francois P. A.; Dirker, Jaco; Meyer, Josua P.
2017-11-01
In this experimental study the heat transfer phenomena in concentric annuli in tube-in-tube heat exchangers at different annular Reynolds numbers, annular diameter ratios, and inlet fluid temperatures using water were considered. Turbulent flow with Reynolds numbers ranging from 15,000 to 45,000, based on the average bulk fluid temperature was tested at annular diameter ratios of 0.327, 0.386, 0.409 and 0.483 with hydraulic diameters of 17.00, 22.98, 20.20 and 26.18 mm respectively. Both heated and cooled annuli were investigated by conducting tests at a range of inlet temperatures between 10 °C to 30 °C for heating cases, and 30 °C to 50 °C for cooling cases. Of special interest was the direct measurement of local wall temperatures on the heat transfer surface, which is often difficult to obtain and evasive in data-sets. Continuous verification and re-evaluation of temperatures measurements were performed via in-situ calibration. It is shown that inlet fluid temperature and the heat transfer direction play significant roles on the magnitude of the heat transfer coefficient. A new adjusted Colburn j-factor definition is presented to describe the heating and cooling cases and is used to correlate the 894 test cases considered in this study.
Heat transfer, diffusion, and evaporation
Nusselt, Wilhelm
1954-01-01
Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.
Heat transfer, insulation calculations simplified
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V.
1985-08-19
Determination of heat transfer coefficients for air, water, and steam flowing in tubes and calculation of heat loss through multilayered insulated surfaces have been simplified by two computer programs. The programs, written in BASIC, have been developed for the IBM and equivalent personal computers.
Advances in heat transfer enhancement
Saha, Sujoy Kumar; Sundén, Bengt; Wu, Zan
2016-01-01
This Brief addresses the phenomena of heat transfer enhancement. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to three other monographs including “Critical Heat Flux in Flow Boiling in Microchannels,” this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.
Heat transfer enhancement with nanofluids
Bianco, Vincenzo; Nardini, Sergio; Vafai, Kambiz
2015-01-01
Properties of NanofluidSamuel Paolucci and Gianluca PolitiExact Solutions and Their Implications in Anomalous Heat TransferWenhao Li, Chen Yang and Akira NakayamaMechanisms and Models of Thermal Conductivity in NanofluidsSeung-Hyun Lee and Seok Pil JangExperimental Methods for the Characterization of Thermophysical Properties of NanofluidsSergio Bobbo and Laura FedeleNanofluid Forced ConvectionGilles RoyExperimental Study of Convective Heat Transfer in NanofluidsEhsan B. Haghighi, Adi T. Utomo, Andrzej W. Pacek and Björn E. PalmPerformance of Heat Exchangers Using NanofluidsBengt Sundén and Za
Fundamental principles of heat transfer
Whitaker, Stephen
1977-01-01
Fundamental Principles of Heat Transfer introduces the fundamental concepts of heat transfer: conduction, convection, and radiation. It presents theoretical developments and example and design problems and illustrates the practical applications of fundamental principles. The chapters in this book cover various topics such as one-dimensional and transient heat conduction, energy and turbulent transport, forced convection, thermal radiation, and radiant energy exchange. There are example problems and solutions at the end of every chapter dealing with design problems. This book is a valuable int
Heat transfer. Basics and practice
Energy Technology Data Exchange (ETDEWEB)
Wetzel, Thomas [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany); Boeckh, Peter von
2012-07-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author's experience indicates that students, after 40 lectures and exercises of 45 minutes based on this textbook, have proved capable of designing independently complex heat exchangers such as for cooling of rocket propulsion chambers, condensers and evaporators for heat pumps. (orig.)
Perrocheau, Ludivine; Bakan, Benedicte; Boivin, Patrick; Marion, Didier
2006-04-19
Barley lipid transfer protein (LTP1) is a heat-stable and protease-resistant albumin that concentrates in beer, where it participates in the formation and stability of beer foam. Whereas the barley LTP1 does not display any foaming properties, the corresponding beer protein is surface-active. Such an improvement is related to glycation by Maillard reactions on malting, acylation on mashing, and structural unfolding on brewing. The structural stability of purified barley and glycated malt LTP1 toward heating has been analyzed. Whatever the modification, lipid adduction or glycation, barley LTP1s are highly stable proteins that resisted temperatures up to 100 degrees C. Unfolding of LTP1 occurred only when heating was conducted in the presence of a reducing agent. In the presence of sodium sulfite, the lipid-adducted barley and malt LTP1 displayed higher heat stability than the nonadducted protein. Glycation had no or weak effect on heat-induced unfolding. Finally, it was shown that unfolding occurred on wort boiling before fermentation and that the reducing conditions are provided by malt extract.
Directory of Open Access Journals (Sweden)
WANG Fang
2017-04-01
Full Text Available Aimed to insufficient heat transfer of heat exchanger, research the influence on the heat transfer coefficient impacted by velocity and heat transfer temperature difference of tube heat exchanger. According to the different heat transfer temperature difference and gas velocity，the experimental data were divided into group. Using the control variable method，the above two factors were analyzed separately. K一△T and k一:fitting curve were clone to obtain empirical function. The entire heat exchanger is as the study object，using numerical simulation methods，porous media，k一￡model，second order upwind mode，and pressure一velocity coupling with SIMPLE algorithm，the entire heat exchanger temperature field and the heat transfer coefficient distribution were given. Finally the trend of the heat transfer coefficient effected by the above two factors was gotten.
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the
Annaratone, Donatello
2010-01-01
This book is a generalist textbook; it is designed for anybody interested in heat transmission, including scholars, designers and students. Two criteria constitute the foundation of Annaratone's books, including the present one. The first one consists of indispensable scientific rigor without theoretical exasperation. The inclusion in the book of some theoretical studies, even if admirable for their scientific rigor, would have strengthened the scientific foundation of this publication, yet without providing the reader with further applicable know-how. The second criterion is to deliver practi
Essentials of radiation heat transfer
Balaji
2014-01-01
Essentials of Radiation Heat Transfer is a textbook presenting the essential, fundamental information required to gain an understanding of radiation heat transfer and equips the reader with enough knowledge to be able to tackle more challenging problems. All concepts are reinforced by carefully chosen and fully worked examples, and exercise problems are provided at the end of every chapter. In a significant departure from other books on this subject, this book completely dispenses with the network method to solve problems of radiation heat transfer in surfaces. It instead presents the powerful radiosity-irradiation method and shows how this technique can be used to solve problems of radiation in enclosures made of one to any number of surfaces. The network method is not easily scalable. Secondly, the book introduces atmospheric radiation, which is now being considered as a potentially important area, in which engineers can contribute to the technology of remote sensing and atmospheric sciences in general, b...
Mills, A F
1999-01-01
The Second Edition offers complete coverage of heat transfer with broad up-to-date coverage that includes an emphasis on engineering relevance and on problem solving. Integrates software to assist the reader in efficiently calculations. Carefully orders material to make book more reader-friendly and accessible. Offers an extensive introduction to heat exchange design to enhance the engineering and design content of course to satisfy ABET requirements. For professionals in engineering fields.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, Michael J.; Rubenstein, Francis M.; Whitman, Richard E.
1992-01-01
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.
1992-12-29
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.
Heat transfer in aerospace propulsion
Simoneau, Robert J.; Hendricks, Robert C.; Gladden, Herbert J.
1988-01-01
Presented is an overview of heat transfer related research in support of aerospace propulsion, particularly as seen from the perspective of the NASA Lewis Research Center. Aerospace propulsion is defined to cover the full spectrum from conventional aircraft power plants through the Aerospace Plane to space propulsion. The conventional subsonic/supersonic aircraft arena, whether commercial or military, relies on the turbine engine. A key characteristic of turbine engines is that they involve fundamentally unsteady flows which must be properly treated. Space propulsion is characterized by very demanding performance requirements which frequently push systems to their limits and demand tailored designs. The hypersonic flight propulsion systems are subject to severe heat loads and the engine and airframe are truly one entity. The impact of the special demands of each of these aerospace propulsion systems on heat transfer is explored.
Convective heat transfer in non-uniformly heated corrugated slots
Abtahi, Arman; Floryan, J. M.
2017-10-01
An analysis of heat transfer in non-uniformly heated corrugated slots has been carried out. A sinusoidal corrugation is placed at the lower plate that is exposed to heating consisting of uniform and sinusoidal components, while the upper smooth plate is kept isothermal. The phase difference ΩTL describes the shift between the heating and geometric non-uniformities. The analysis is limited to heating conditions that do not give rise to secondary motions. Depending on ΩTL, the conductive heat flow is directed either upwards, or downwards, or is eliminated. Its magnitude is smallest for the long-wavelength systems and largest for the short-wavelength systems, and it increases proportionally to the corrugation amplitude and heating intensity. The same heating creates horizontal temperature gradients that give rise to convection whose form depends on ΩTL. Convection consists of counter-rotating rolls with the size dictated by the system wavelength when the hot spots (points of maximum temperature) overlap either with the corrugation tips or with the corrugation bottoms. Thermal drift forms for all other values of ΩTL. The convective heat flow is always directed upwards, and it is the largest in systems with wavelengths comparable to the slot height. The magnitude of the overall heat flow increases proportionally to the heating intensity when conductive effects dominate and proportionally to the second power of the heating intensity when convection dominates. It also increases proportionally to the corrugation amplitude. The system characteristics are dictated by convection when the relative position of the heating and corrugation patterns eliminates conduction. Addition of the uniform heating component amplifies the above processes, while uniform cooling reduces them. The processes described above are qualitatively similar for all Prandtl numbers of practical interest with the magnitude of the convective heat flow increasing with Pr.
Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants
Yoshida, Suguru; Fujita, Yasunobu
The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.
A REVIEW ON HEAT TRANSFER THROUGH HELICAL COIL HEAT EXCHANGERS
Surendra Vishvakarma*, Sanjay Kumbhare, K. K. Thakur
2016-01-01
This study presents a brief review of heat transfer through helical coil heat exchangers. Helical coils of circular cross section have been used in wide variety of applications due to simplicity in manufacturing. Enhancement in heat transfer due to helical coils has been reported by many researchers. While the heat transfer characteristics of double pipe helical heat exchangers are available in the literature, there exists no published experimental or theoretical analysis of a helically coile...
Heat transfer coefficient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1998-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio...
Thermodynamics and heat transfer in fire fighting
Romanenko, P. N.; Koshmarov, Y. A.; Bashkirtsev, M. P.
1985-05-01
The book presents the fundamental principles of thermodynamics and heat transfer with particular reference to their application in problems related to fire prevention. Special attention is given to the study of unsteady heat transfer, radiant heat transfer (including radiation from flames to the surrounding), thermodynamic analysis of the growth of fires and theoretical modeling of fires in building.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat Transfer in a Thermoacoustic Process
Beke, Tamas
2012-01-01
Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…
Convective heat transfer enhancement with nanofluids
Rahman, Md. Habibur; Abedin, Z.
2017-12-01
Nanofluids are considered to offer important advantages over conventional heat transfer fluids. Over a decade ago, researchers focused on measuring and modeling the effective thermal conductivity and viscosity of nanofluids. Recently important theoretical and experimental research works on convective heat transfer appeared in the open literatures on the enhancement of heat transfer using suspensions of nanometer-sized solid particle materials, metallic or nonmetallic in base heat transfer fluids. The purpose of this article is to summarize recent research on fluid flow and heat transfer enhancement characteristics of nanofluids and thereby identify opportunities for future research.
Heat transfer coeffcient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1997-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater wich evaporates the R22. With the heat flux assumed constant over...... the whole surface and with measured temperature difference between the inner surface and the evaporation temperature a mean heat transfer coefficient is calculated. The calculated heat transfer coefficient has been compared with the Chart Correlation of Shah. The Chart Correlation predicts too low heat...
HEAT-MASS TRANSFER IN MOVING MELT
Directory of Open Access Journals (Sweden)
R. I. Yesman
2005-01-01
Full Text Available The paper gives mathematical formation and solution of the heat-mass transfer problem when liquid metals are flowing in the channels of complicated geometry. The problem is solved with the help of numerical methods. A method of control volume is used for finite-difference approximation of transfer equations. The research results can be applied for execution of a numerical experiment while investigating heat-mass transfer in liquid-metal heat-transfer and reological media.
A REDUCED ORDER MODEL OF TWO-PHASE FLOW, HEAT TRANSFER AND COMBUSTION IN CIRCULATING FLUIDIZED-BEDS
Energy Technology Data Exchange (ETDEWEB)
Paul Cizmas
2003-12-01
The report summarizes the objectives, tasks and accomplishments of this research project. The report presents the following program deliverables: (1) database generation using MFIX code, (2) development and implementation of an algorithm to calculate the proper orthogonal decomposition (POD) basis functions, (3) visualization tools for reconstructing simulated data, (4) algorithms for reducing the partial differential equations to ordinary differential equations, (5) visualization tools for Galerkin ordinary differential equations, (6) verification and validation of the code by comparing POD and conventional solution results, and (7) development of POD strategy for best energy cut-off values.
Heat transfer and thermal stress analysis in grooved tubes
Indian Academy of Sciences (India)
The maximum thermal stress ratio positions inside the tube have been indicated as MX for all investigated cases. In the light of the thermal stress values, various designs can be applied to reduce thermal stress in grooved tubes. Keywords. Heat transfer; thermal stress; grooved tubes. 1. Introduction. Heat transfer in pipe flow ...
Heat Transfer and Cooling in Gas Turbines
1985-09-01
the detailed component internal heat transfer for a variety of families of cooling schemes, and (c) to choose from among and withir those families to...1965. 32. Metzger, D.E., and Grochowsky, 1.D., "Heat Transfer Between an Impinging Jet and a Rotating Dink ," J. Heat Tranafer, Trans. ASME, 99, pp. 663
REVIEW OF PCMs AND HEAT TRANSFER ENHANCEMENT ...
African Journals Online (AJOL)
HOD
for power applications. The various methods of heat transfer enhancement in latent heat storage systems were also reviewed systematically. The review showed that three commercially-available PCMs are suitable in the operating temperature range of parabolic trough plants. Many heat transfer enhancement methods ...
Engineering calculations in radiative heat transfer
Gray, W A; Hopkins, D W
1974-01-01
Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.
Influence of radiation heat transfer during a severe accident
Energy Technology Data Exchange (ETDEWEB)
Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Ciudad de Mexico (Mexico); Polo L, M. A., E-mail: ricardo-cazares@hotmail.com [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan No. 779, Col. Narvarte, 03020 Ciudad de Mexico (Mexico)
2016-09-15
The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)
Heat transfer analysis of liquid piston compressor for hydrogen applications
DEFF Research Database (Denmark)
Kermani, Nasrin Arjomand; Rokni, Masoud
2015-01-01
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...... 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...
Heat and mass transfer in particulate suspensions
Michaelides, Efstathios E (Stathis)
2013-01-01
Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...
Finite element simulation of heat transfer
Bergheau, Jean-Michel
2010-01-01
This book introduces the finite element method applied to the resolution of industrial heat transfer problems. Starting from steady conduction, the method is gradually extended to transient regimes, to traditional non-linearities, and to convective phenomena. Coupled problems involving heat transfer are then presented. Three types of couplings are discussed: coupling through boundary conditions (such as radiative heat transfer in cavities), addition of state variables (such as metallurgical phase change), and coupling through partial differential equations (such as electrical phenomena).? A re
A literature survey on numerical heat transfer
Shih, T. M.
1982-12-01
Technical papers in the area of numerical heat transfer published from 1977 through 1981 are reviewed. The journals surveyed include: (1) ASME Journal of Heat Transfer, (2) International Journal of Heat and Mass Transfer, (3) AIAA Journal, (4) Numerical Heat Transfer, (5) Computers and Fluids, (6) International Journal for Numerical Methods in Engineering, (7) SIAM Journal of Numerical Analysis, and (8) Journal of Computational Physics. This survey excludes experimental work in heat transfer and numerical schemes that are not applied to equations governing heat transfer phenomena. The research work is categorized into the following areas: (A) conduction, (B) boundary-layer flows, (C) momentum and heat transfer in cavities, (D) turbulent flows, (E) convection around cylinders and spheres or within annuli, (F) numerical convective instability, (G) radiation, (H) combustion, (I) plumes, jets, and wakes, (J) heat transfer in porous media, (K) boiling, condensation, and two-phase flows, (L) developing and fully developed channel flows, (M) combined heat and mass transfer, (N) applications, (O) comparison and properties of numerical schemes, and (P) body-fitted coordinates and nonuniform grids.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Modelling Heat Transfer of Carbon Nanotubes
Yang, Xin-She
2010-01-01
Modelling heat transfer of carbon nanotubes is important for the thermal management of nanotube-based composites and nanoelectronic device. By using a finite element method for three-dimensional anisotropic heat transfer, we have simulated the heat conduction and temperature variations of a single nanotube, a nanotube array and a part of nanotube-based composite surface with heat generation. The thermal conductivity used is obtained from the upscaled value from the molecular simulations or ex...
Convective Heat Transfer in Acoustic Streaming Flows
Gopinath, Ashok
1992-01-01
Convective heat transfer due to acoustic streaming has been studied in the absence of an imposed mean flow. The work is motivated by the need to design and control the thermal features of a suitable experimental rig for the containerless processing of materials by heat treatment of acoustically levitated alloy samples at near zero-gravity. First the problem of heat transfer from an isolated sphere (in a standing sound field) is explored in detail. The streaming Reynolds number, Rs, which characterizes the resulting steady flows, is determined from the acoustic signal. A scale analysis is used to ascertain the importance of buoyancy and viscous dissipation. The steady velocity and temperature fields are determined using asymptotic techniques and numerical methods for the limiting cases of RsKundt tube (supporting a plane axial standing sound wave) with insulated side-wall and isothermal end-walls. Analytical solution techniques are used to determine the steady fields close to the tube walls. For the steady recirculatory transport in the core, the numerical solver PHOENICS is adopted for the solution of the complete elliptic form of the governing equations. A study of the effects of a range of acoustic and geometric parameters on the flow and heat transfer is performed and Nusselt number correlations are obtained for air. PHOENICS is also used to study the effects of variable fluid properties and axial side-wall conduction (coupled with radiation). The role of normal/reduced gravity is assessed and suggestions made for terrestrial testing of the levitation apparatus. Finally, with the sample located at a node in the levitation chamber, the effect of the interaction of the streaming flows (on the sphere and the tube walls) is estimated. Representative calculations for the sample heating/cooling rates are presented and compared with existing data in the literature.
Conjugate heat and mass transfer in heat mass exchanger ducts
Zhang, Li-Zhi
2013-01-01
Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi
Flow and heat transfer enhancement in tube heat exchangers
Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.
2015-11-01
The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.
Heat transfer from humans wearing clothing
Lotens, W.A.
1993-01-01
In this monograph the effects of clothing on human heat transfer are described. The description is based on the physics of heat and mass transfer, depending on the design of the clothing, the climate, and the activity of the wearer. The resulting model has been stepwise implemented in computer
Dynamic Heat Transfer Model of Refrigerated Foodstuff
DEFF Research Database (Denmark)
Cai, Junping; Risum, Jørgen; Thybo, Claus
2006-01-01
their temperature relation. This paper discusses the dynamic heat transfer model of foodstuff inside the display cabinet, one-dimensional dynamic model is developed, and the Explicit Finite Difference Method is applied, to handle the unsteady heat transfer problem with phase change, as well as time varying boundary...
Boiling heat transfer modern developments and advances
Lahey, Jr, RT
2013-01-01
This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the
Heat transfer coefficient of cryotop during freezing.
Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J
2013-01-01
Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).
Heat transfer correlations in mantle tanks
DEFF Research Database (Denmark)
Furbo, Simon; Knudsen, Søren
2005-01-01
Small solar domestic hot water systems are best designed as low flow systems based on vertical mantle tanks. Theoretical investigations of the heat transfer in differently designed vertical mantle tanks during different operation conditions have been carried out. The investigations are based...... on calculations with a CFD-model, which has earlier been validated by means of experiments. The CFD-model is used to determine the heat transfer between the solar collector fluid in the mantle and the walls surrounding the mantle in all levels of the mantle as well as the heat transfer between the wall...... of the inner hot water tank and the domestic water in all levels of the tank. The heat transfer analysis showed that the heat transfer near the mantle inlet port between the solar collector fluid in the mantle and the walls surrounding the mantle is in the mixed convection regime, and as the distance from...
Forced convective heat transfer in curved diffusers
Rojas, J.; Whitelaw, J. H.; Yianneskis, M.
1987-01-01
Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heat transfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heat transfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.
Heat transfer research on enhanced heating surfaces in pool boiling
Kalawa, Wojciech; Wójcik, Tadeusz M.; Piasecka, Magdalena
The paper focuses on the analysis of the enhanced surfaces in such applications as boiling heat transfer. The testing measurement module with enhanced heating surfaces was used for pool boiling research. Pool boiling experiments were conducted with distilled water at atmospheric pressure in the vessel using an enhanced sample as the bottom heating surface. The samples are soldered to a copper heating block of the round cross-section .They were placed: in the fluid (saturation temperature measurement), under the sample for temperature determination. A vessel made of four flat glass panes was used for visualization. The heated surfaces in contact with the fluid differed in roughness were smooth or enhanced. This paper analyzes the effects of the microstructured heated surface on the heat transfer coefficient. The results are presented as relationships between the heat transfer coefficient and the heat flux and as boiling curves. The experimental data obtained for the two types of enhanced heated surfaces was compared with the results recorded for the smooth heated surface. The highest local values of the heat transfer coefficient were reported for the enhanced surfaces.
Heat transfer characteristics of rotating triangular thermosyphon
Ibrahim, E.; Moawed, M.; Berbish, N. S.
2012-09-01
An experimental investigation is carried out to study heat transfer characteristics of a rotating triangular thermosyphon, using R-134a refrigerant as the working fluid. The tested thermosyphon is an equilateral triangular tube made from copper material of 11 mm triangular length, 2 mm thickness, and a total length of 1,500 mm. The length of the evaporator section is 600 mm, adiabatic section is 300 mm, and condenser section is 600 mm. The effects of the rotational speed, filling ratio, and the evaporator heat flux on each of the evaporator heat transfer coefficient, he, condenser heat transfer coefficient, hc, and the overall effective thermal conductance, Ct are studied. Experiments are performed with a vertical position of thermosyphon within heat flux ranges from 11 to 23 W/m2 for the three selected filling ratios of 10, 30 and 50 % of the evaporator section volume. The results indicated that the maximum values of the tested heat transfer parameters of the rotational equilateral triangular thermosyphon are obtained at the filling ratio of 30 %. Also, it is found that the heat transfer coefficient of the condensation is increased with increasing the rotational speed. The tested heat transfer parameters of the thermosyphon are correlated as a function of the evaporator heat flux and angular velocity.
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For large thickness dimensions the resulting heat transfer through the
Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.
Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari
2014-01-01
This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.
Conjugate heat transfer characterization in cooling channels
Cukurel, Beni; Arts, Tony; Selcan, Claudio
2012-06-01
Cooling technology of gas turbine blades, primarily ensured via internal forced convection, is aimed towards withdrawing thermal energy from the airfoil. To promote heat exchange, the walls of internal cooling passages are lined with repeated geometrical flow disturbance elements and surface non-uniformities. Raising the heat transfer at the expense of increased pressure loss; the goal is to obtain the highest possible cooling effectiveness at the lowest possible pressure drop penalty. The cooling channel heat transfer problem involves convection in the fluid domain and conduction in the solid. This coupled behavior is known as conjugate heat transfer. This experimental study models the effects of conduction coupling on convective heat transfer by applying iso-heat-flux boundary condition at the external side of a scaled serpentine passage. Investigations involve local temperature measurements performed by Infrared Thermography over flat and ribbed slab configurations. Nusselt number distributions along the wetted surface are obtained by means of heat flux distributions, computed from an energy balance within the metal domain. For the flat plate experiments, the effect of conjugate boundary condition on heat transfer is estimated to be in the order of 3%. In the ribbed channel case, the normalized Nusselt number distributions are compared with the basic flow features. Contrasting the findings with other conjugate and convective iso-heat-flux literature, a high degree of overall correlation is evident.
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
Active chimney effect using heated porous layers: optimum heat transfer
Mehiris, Abdelhak; Ameziani, Djamel-Edine; Rahli, Omar; Bouhadef, Khadija; Bennacer, Rachid
2017-05-01
The purpose of the present work is to treat numerically the problem of the steady mixed convection that occurs in a vertical cylinder, opened at both ends and filled with a succession of three fluid saturated porous elements, namely a partially porous duct. The flow conditions fit with the classical Darcy-Brinkman model allowing analysing the flow structure on the overall domain. The induced heat transfer, in terms of local and average Nusselt numbers, is discussed for various controlling parameters as the porous medium permeability, Rayleigh and Reynolds numbers. The efficiency of the considered system is improved by the injection/suction on the porous matrices frontier. The undertaken numerical exploration particularly highlighted two possible types of flows, with and without fluid recirculation, which principally depend on the mixed convection regime. Thus, it is especially shown that recirculation zones appear in some domain areas under specific conditions, obvious by a negative central velocity and a prevalence of the natural convection effects, i.e., turnoff flow swirls. These latter are more accentuated in the areas close to the porous obstacles and for weak permeability. Furthermore, when fluid injection or suction is considered, the heat transfer increases under suction and reduces under injection. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui
An analytical dynamic model of heat transfer from the heating body to the heated room
Directory of Open Access Journals (Sweden)
Mižáková Jana
2017-01-01
Full Text Available On the base of mathematical description of thermal balance the dynamic model of the hot-water heating body (radiator was designed. The radiator is mathematically described as a heat transfer system between heating water and warmed-up air layer. Similarly, the dynamic model of heat transfer through the wall from the heated space to the outdoor environment was design. Both models were interconnected into dynamic model of heat transfer from the heating body to the heated room and they will be implemented into simulation model of the heating system in Matlab/Simulink environment.
Heat transfer enhancement using 2MHz ultrasound.
Bulliard-Sauret, Odin; Ferrouillat, Sebastien; Vignal, Laure; Memponteil, Alain; Gondrexon, Nicolas
2017-11-01
The present work focuses on possible heat transfer enhancement from a heating plate towards tap water in forced convection by means of 2MHz ultrasound. The thermal approach allows to observe the increase of local convective heat transfer coefficients in the presence of ultrasound and to deduce a correlation between ultrasound power and Nusselt number. Heat transfer coefficient under ultrasound remains constant while heat transfer coefficient under silent conditions increases with Reynolds number from 900 up to 5000. Therefore, heat transfer enhancement factor ranges from 25% up to 90% for the same energy conditions (supplied ultrasonic power=110W and supplied thermal power=450W). In the same time cavitational activity due to 2MHz ultrasound emission was characterized from mechanical and chemical viewpoints without significant results. At least, Particle Image Velocimetry (PIV) measurements have been performed in order to investigate hydrodynamic modifications due to the presence of 2MHz ultrasound. It was therefore possible to propose a better understanding of heat transfer enhancement mechanism with high frequency ultrasound. Copyright © 2017 Elsevier B.V. All rights reserved.
Heat transfer characteristics of building walls using phase change material
Irsyad, M.; Pasek, A. D.; Indartono, Y. S.; Pratomo, A. W.
2017-03-01
Minimizing energy consumption in air conditioning system can be done with reducing the cooling load in a room. Heat from solar radiation which passes through the wall increases the cooling load. Utilization of phase change material on walls is expected to decrease the heat rate by storing energy when the phase change process takes place. The stored energy is released when the ambient temperature is low. Temperature differences at noon and evening can be utilized as discharging and charging cycles. This study examines the characteristics of heat transfer in walls using phase change material (PCM) in the form of encapsulation and using the sleeve as well. Heat transfer of bricks containing encapsulated PCM, tested the storage and released the heat on the walls of the building models were evaluated in this study. Experiments of heat transfer on brick consist of time that is needed for heat transfer and thermal conductivity test as well. Experiments were conducted on a wall coated by PCM which was exposed on a day and night cycle to analyze the heat storage and heat release. PCM used in these experiments was coconut oil. The measured parameter is the temperature at some points in the brick, walls and ambient temperature as well. The results showed that the use of encapsulation on an empty brick can increase the time for thermal heat transfer. Thermal conductivity values of a brick containing encapsulated PCM was lower than hollow bricks, where each value was 1.3 W/m.K and 1.6 W/m.K. While the process of heat absorption takes place from 7:00 am to 06:00 pm, and the release of heat runs from 10:00 pm to 7:00 am. The use of this PCM layer can reduce the surface temperature of the walls of an average of 2°C and slows the heat into the room.
Heat Transfer Phenomena of Supercritical Fluids
Energy Technology Data Exchange (ETDEWEB)
Krau, Carmen Isabella; Kuhn, Dietmar; Schulenberg, Thomas [Forschungszentrum Karlsruhe, Institute for Nuclear and Energy Technologies, 76021 Karlsruhe (Germany)
2008-07-01
In concepts for supercritical water cooled reactors, the reactor core is cooled and moderated by water at supercritical pressures. The significant temperature dependence of the fluid properties of water requires an exact knowledge of the heat transfer mechanism to avoid fuel pin damages. Near the pseudo-critical point a deterioration of heat transfer might happen. Processes, that take place in this case, are not fully understood and are due to be examined systematically. In this paper a general overview on the properties of supercritical water is given, experimental observations of different authors will be reviewed in order to identify heat transfer phenomena and onset of occurrence. The conceptional design of a test rig to investigate heat transfer in the boundary layer will be discussed. Both, water and carbon dioxide, may serve as operating fluids. The loop, including instrumentation and safety devices, is shown and suitable measuring methods are described. (authors)
Heat Transfer Characteristics of Tubular Thermal Reactor
Energy Technology Data Exchange (ETDEWEB)
Yang, Hei Cheon; Park, Sang Kyoo [Chonnam National Univ., Yeosu (Korea, Republic of); Ra, Beong Yeol [Sinsung Plant company, Ansan (Korea, Republic of)
2007-07-01
Heat transfer augmentation based on the process intensification concept in heat exchangers and thermal reactors has received much attention in recent years, mainly due to energy efficiency and environmental considerations. The concept consists of the development of novel apparatuses and techniques that, compared to those commonly used today, are expected to bring dramatic improvements in manufacturing and processing, substantially decreasing equipment size, energy consumption, and ultimately resulting in cheaper, sustainable technologies. The objective of this paper was to investigate the heat transfer characteristics of tubular thermal reactor using static mixing technology. Glycerin and water were used as the test fluids and water was used as the heating source. The results for heat transfer rate were strongly influenced by tube geometry and flow conditions.
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
Radiative Heat Transfer in Fractal Structures
Nikbakht, Moladad
2017-01-01
The radiative properties of most structures are intimately connected to the way in which their constituents are ordered on the nano-scale. We have proposed a new representation for radiative heat transfer formalism in many-body systems. In this representation, we explain why collective effects depend on the morphology of structures, and how the arrangement of nanoparticles and their material affects the thermal properties in many-body systems. We investigated the radiative heat transfer probl...
Heat transfer in an airfoil shaped strut
Crawford, James Douglas
The heat transfer from a hot primary flow stream passing over the outside of an airfoil shaped strut to a cool secondary flow stream passing through the inside of that strut was studied experimentally and numerically. The results showed that the heat transfer on the inside of the strut could be reliably modeled as a developing flow and described using a power law model. The heat transfer on the outside of the strut was complicated by flow separation and stall on the suction side of the strut at high angles of attack. This separation was quite sensitive to the condition of the turbulence in the flow passing over the strut, with the size of the separated wake changing significantly as the mean magnitude and levels of anisotropy were varied. The point of first stall moved by as much as 15% of the chord, while average heat transfer levels changed by 2-5% as the inlet condition was varied. This dependence on inlet conditions meant that comparisons between experiment and steady RANS based CFD were quite poor. Differences between the CFD and experiment were attributed to anisotropic and unsteady effects. The coupling between the two flows was shown to be quite low - that is to say, heat transfer coefficients on both the inner and outer surfaces of the strut were relatively unaffected by the temperature of the strut, and it was possible to predict the temperature on the strut surface quite reliably using heat transfer data from decoupled tests, especially for CFD simulations.
Heat and mass transfer in materials processing
Tanasawa, Ichiro; Lior, Noam
Various papers on heat and mass transfer in materials processing are presented. The topics addressed include: heat transfer in plasma spraying, structure of ultrashort pulse plasma for CVD processing, heat flow and thermal contraction during plasma spray deposition, metal melting process by laser heating, improved electron beam weld design and control with beam current profile measurements, transport phenomena in laser materials processing, perspectives on integrated modeling of transport processes in semiconductor crystal growth, numerical simulation of natural convection in crystal growth in space and on the earth, conjugate heat transfer in crystal growth, effects of convection on the solidification of binary mixtures. Also discussed are: heat transfer in in-rotating-liquid-spinning process, thermal oscillations in materials processing, modeling and simulation of manufacturing processes of advanced composite materials, reaction engineering principles of combustion synthesis of advanced materials, numerical evaluation of the physical properties of magnetic fluids suitable for heat transfer control, and measurement techniques of thermophysical properties of high temperature melts. (For individual items see A93-10827 to A93-10843)
Theory of Periodic Conjugate Heat Transfer
Zudin, Yuri B
2012-01-01
This book presents the theory of periodic conjugate heat transfer in a detailed way. The effects of thermophysical properties and geometry of a solid body on the commonly used and experimentally determined heat transfer coefficient are analytically presented from a general point of view. The main objective of the book is a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body. At the body surface, the true heat transfer coefficient is composed of two parts: the true mean value resulting from the solution of the steady state heat transfer problem and a periodically variable part, the periodic time and length to describe the oscillatory hydrodynamic effects. The second edition is extended by (i) the analysis of stability boundaries in helium flow at supercritical conditions in a heated channel with respect to the interaction between a solid body and a fluid; (ii) a periodic model and a method of heat transfer sim...
Electronic Equipment Cooling by Simultaneous Heat and Mass Transfer,
ELECTRONIC EQUIPMENT, COOLING, HEAT TRANSFER, SUPERSONIC AIRCRAFT, HIGH ALTITUDE, DENSITY, THERMAL STRESSES, AIR, COOLING AND VENTILATING EQUIPMENT, FLUIDS, COOLANTS, HEAT EXCHANGERS, WATER, MASS TRANSFER .
Enhanced heat transfer in confined pool boiling
Rops, C.M.; Lindken, R.; Velthuis, J.F.M.; Westerweel, J.
2009-01-01
We report the results of an experimental investigation of the heat transfer during nucleate boiling on a spatially confined boiling surface. The heat flux as a function of the boiling surface temperature was measured in pool boiling pots with diameters ranging from 15 mm down to 4.5 mm. It was found
Interactive Heat Transfer Simulations for Everyone
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Theory of periodic conjugate heat transfer
Zudin, Yuri B
2016-01-01
This book presents the theory of periodic conjugate heat transfer in detail. It offers a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body.
Osman, Arafa Mohamed
1987-05-01
The inverse heat transfer problem is one of considerable practical interest in the analysis and design of experimental heat transfer investigations. The analytical and experimental investigation of the inverse heat transfer coefficients in multi-dimensional convective heat transfer applications is examined. An application considered is the sudden quenching of a hot solid in a cold liquid. Other applications include thermal analysis of forced convection over impulsively started solid bodies and investigation of short duration wind tunnel experiments. The primary aim is to describe methods and algorithms for the solution of the ill-posed inverse heat transfer coefficient problem. The solution method used is an extension of the sequential future-information method of Beck. Numerical experiments are conducted for a systematic investigation of the developed algorithms on selected heat transfer coefficient test cases. The overall objective of the experimental work is to investigate the early transients in the heat transfer coefficients from spheres in one- and two-dimensional quenching experiments. Several experiments were performed by plunging hollow spheres in either ethylene glycol or water. The developed methods are used for the analysis of the quenching experiments for the estimation of the transient heat transfer coefficients. Analysis of the results indicate that the transient inverse technique has the capability of estimating early transients and subsequent quasi-steady state values of the heat transfer coefficients in a single transient experiment.
Heat transfer with freezing and thawing
Lunardini, VJ
1991-01-01
This volume provides a comprehensive overview on the vast amount of literature on solidification heat transfer. Chapter one develops important basic equations and discusses the validity of considering only conductive heat transfer, while ignoring convection, in the large class of materials which make up the porous media. Chapters 2 to 4 deal with problems that can be expressed in plane (Cartesian) coordinates. These problems are further divided into boundary conditions of temperature, prescribed heat flux, and surface convection. Chapter 5 examines some plane geometries involving three-dime
Heat transfer across the interface between nanoscale solids and gas.
Cheng, Chun; Fan, Wen; Cao, Jinbo; Ryu, Sang-Gil; Ji, Jie; Grigoropoulos, Costas P; Wu, Junqiao
2011-12-27
When solid materials and devices scale down in size, heat transfer from the active region to the gas environment becomes increasingly significant. We show that the heat transfer coefficient across the solid-gas interface behaves very differently when the size of the solid is reduced to the nanoscale, such as that of a single nanowire. Unlike for macroscopic solids, the coefficient is strongly pressure dependent above ∼10 Torr, and at lower pressures it is much higher than predictions of the kinetic gas theory. The heat transfer coefficient was measured between a single, free-standing VO(2) nanowire and surrounding air using laser thermography, where the temperature distribution along the VO(2) nanowire was determined by imaging its domain structure of metal-insulator phase transition. The one-dimensional domain structure along the nanowire results from the balance between heat generation by the focused laser and heat dissipation to the substrate as well as to the surrounding gas, and thus serves as a nanoscale power-meter and thermometer. We quantified the heat loss rate across the nanowire-air interface, and found that it dominates over all other heat dissipation channels for small-diameter nanowires near ambient pressure. As the heat transfer across the solid-gas interface is nearly independent of the chemical identity of the solid, the results reveal a general scaling relationship for gaseous heat dissipation from nanostructures of all solid materials, which is applicable to nanoscale electronic and thermal devices exposed to gaseous environments.
Modeling microscale heat transfer using Calore.
Energy Technology Data Exchange (ETDEWEB)
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Microscale and nanoscale heat transfer fundamentals and engineering applications
Sobhan, CB
2008-01-01
Preface Introduction to Microscale Heat Transfer Microscale Heat Transfer: A Recent Avenue in Energy Transport State of the Art: Some Introductory Remarks Overview of Microscale Transport Phenomena Discussions on Size-Effect Behavior Fundamental Approach for Microscale Heat Transfer Introduction to Engineering Applications of Microscale Heat Transfer Microscale Heat Conduction Review of Conduction Heat Transfer Conduction at the Microscale Space and Timescales Fundamental Approach Thermal Conductivity Boltzmann Equation and Phonon Transport Conduction in Thin Films
Heat transfer enhancement of a single row of tube
Directory of Open Access Journals (Sweden)
Tsutsui Takayuki
2017-01-01
Full Text Available A rod was positioned upstream of a circular cylinder to enhance its heat transfer and reduce its drag in air stream. The results are increasing the overall heat transfer by 40% over and reducing the drag by 30% the value for a single circular cylinder. In the present, this technique applied to a single row of tubes. Heat transfer enhancement and drag reduction are important factor for multi-tube heat exchanger. The present study investigated the heat transfer and surface pressure characteristics of each tube for single row of tubes under various numbers of tubes, pitch and Reynolds number. The tube diameter, D, was 20 mm, and the rod diameter was 5 mm. The distance between the center axes of the rod and the tube was 30mm. The Reynolds number based on D ranged from 5.3×103 to 2.1×104. The result is that this technique is effective for heat transfer enhancement and drag reduction of row of tube.
Evaluation of heat transfer enhancement in air-heating collectors
Energy Technology Data Exchange (ETDEWEB)
Mattox, D. L.
1979-06-01
The present research effort was initiated for the purpose of increasing the thermal efficiency of air heating solar collectors through identification and development of optimum design and operation criteria for solar absorber-to-air heat exchangers. Initially this effort took the form of a solar collector systems analysis to evaluate the impact of various techniques for enhancing the heat transfer between the absorber and air stream on overall thermal performance of the entire solar collector. This systems analysis resulted in the selection of solar collector designs providing ducted cooling air on the absorber shaded side as a base line. A transient heat transfer analysis of a complete solar air heating collector was used to demonstrate that an optimum absorber-to-air heat exchanger design could be provided with several interrupted fin configurations. Additional analyses were performed to establish that the maximum solar collector thermal performance to required pumping power was realized for a Reynolds number range of 1000 to 2000. This Reynolds number range was used to establish a theoretical design limit curve for maximum thermal performance versus required pumping power for all interrupted fin designs as published in the open literature. Heat and momentum transfer empirical relationships were defined for scaling the state-of-the-art high conductance fin designs identified from a compact configuration to the less compact designs needed for solar collectors.
Advanced Computational Methods for Thermal Radiative Heat Transfer
Energy Technology Data Exchange (ETDEWEB)
Tencer, John; Carlberg, Kevin Thomas; Larsen, Marvin E.; Hogan, Roy E.,
2016-10-01
Participating media radiation (PMR) in weapon safety calculations for abnormal thermal environments are too costly to do routinely. This cost may be s ubstantially reduced by applying reduced order modeling (ROM) techniques. The application of ROM to PMR is a new and unique approach for this class of problems. This approach was investigated by the authors and shown to provide significant reductions in the computational expense associated with typical PMR simulations. Once this technology is migrated into production heat transfer analysis codes this capability will enable the routine use of PMR heat transfer in higher - fidelity simulations of weapon resp onse in fire environments.
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
A numerical study of momentum and forced convection heat transfer ...
African Journals Online (AJOL)
ASME J. Heat Transfer, Vol. 99, 180-186. [2] Webb B.W., Ramadhyani S., 1985. Conjugate heat transfer in a channel with staggered ribs, Int. J. Heat Mass. Transfer, Vol. 28, 1679-1687. [3] Kelkar K.M.&Patankar S.V., 1987. Numerical prediction of flow and heat transfer in a parallel plate channel with staggered fins, ASME J.
Heat and Mass Transfer Model in Freeze-Dried Medium
Alfat, Sayahdin; Purqon, Acep
2017-07-01
There are big problems in agriculture sector every year. One of the major problems is abundance of agricultural product during the peak of harvest season that is not matched by an increase in demand of agricultural product by consumers, this causes a wasted agricultural products. Alternative way was food preservation by freeze dried method. This method was already using heat transfer through conduction and convection to reduce water quality in the food. The main objective of this research was to design a model heat and mass transfer in freeze-dried medium. We had two steps in this research, the first step was design of medium as the heat injection site and the second was simulate heat and mass transfer of the product. During simulation process, we use physical property of some agriculture product. The result will show how temperature and moisture distribution every second. The method of research use finite element method (FEM) and will be illustrated in three dimensional.
Bizzy, Irwin; Setiadi, Rachmat
2013-01-01
To reduce production costs, the design of heat exchanger is very effective in advance of buying a ready-made exchanger. The design of a calculation of the dimensions of heat exchanger shell and tube type using computerized analysis method Heat Transfer Research Inc.. (HTRI) and manual calculation methods of analysis. Dimensional calculation of heat exchanger is intended to determine the quality of a heat exchanger based on the overall heat transfer coefficient, fouling factors, and pressure d...
Avoid heat transfer equipment vibration
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V.
1987-06-01
Tube bundles in heat exchangers, boilers, superheaters and heaters are often subject to vibration and noise problems. Vibration can lead to tube thinning and wear, resulting in tube failures. Excessive noise can be a problem to plant operating personnel. Large gas pressure drop across the equipment is also a side effect, which results in large operating costs. With the design checks presented in this paper, one can predict during design if problems associated with noise and vibration are likely to occur in petroleum refineries.
Introduction to heat transfer test setup for the SCRAP receiver
Lubkoll, Matti; Harms, Thomas M.; von Backström, Theodor W.
2017-06-01
The Spiky Central Receiver Air Pre-heater (SCRAP) receiver is a novel external tubular metallic central receiver concept. The SCRAP receiver is designed to increase an air-receivers solar-thermal performance. This is aimed to be achieved by enhancing heat transfer to the pressurized air-stream within the absorber assemblies (spikes) by utilizing an internally finned tube geometry. The fin shape is defined to create rectangular ducts as passages for the air flow, therewith a high heat transfer coefficient. The spikes are arranged in such a way that they trap incoming concentrated radiation (reduce reflection losses) and minimize thermal radiation losses from the receiver to ambient. In previous work, the modeling of a SCRAP receiver was discussed on. This included the modeling of the internal air flow and heat transfer within a spike, analysis of the optical characteristics of a SCRAP receiver and the impingement heat transfer capabilities in the spike tip (exposed to the highest flux). Further, analysis of the thermal interaction of spikes with one another and with ambient (convective and radiative heat loss) permitted drawing of first conclusions of the receiver performance potential. To validate the models predicting the pressurized air flow and heat transfer within a spike, an experimental test setup was designed, constructed and built at the heat transfer laboratories at Stellenbosch University. This work introduces the design of the test setup and will discuss preliminary results obtained during its commissioning. From first analysis the predictions made for the pressure drop within the internally finned section appear adequate. The heat transfer behavior will require further detailed analysis to develop sufficient confidence to allow for conclusions. Initial results, however, show good general agreement between measured and simulated data.
Metallized Gelled Propellant Heat Transfer Tests Analyzed
Palaszewski, Bryan A.
1997-01-01
A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted at the NASA Lewis Research Center. These experiments used a small 20- to 40-lbf thrust engine composed of a modular injector, an igniter, a chamber, and a nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt % loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each channel used water flow to carry heat away from the chamber and the attached thermocouples; flow meters allowed heat flux estimates at each of the 31 stations.
Base fluid in improving heat transfer for EV car battery
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
Heat transfer applications for the practicing engineer
Theodore, Louis
2011-01-01
This book serves as a training tool for individuals in industry and academia involved with heat transfer applications. Although the literature is inundated with texts emphasizing theory and theoretical derivations, the goal of this book is to present the subject of heat transfer from a strictly pragmatic point of view. The book is divided into four Parts: Introduction, Principles, Equipment Design Procedures and Applications, and ABET-related Topics. The first Part provides a series of chapters concerned with introductory topics that are required when solving most engineering problems, inclu
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-09
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Heat flux sensors for infrared thermography in convective heat transfer.
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-11-07
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described.
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Directory of Open Access Journals (Sweden)
Giovanni Maria Carlomagno
2014-11-01
Full Text Available This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors’ research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described.
Heat Transfer in Directional Water Transport Fabrics
Directory of Open Access Journals (Sweden)
Chao Zeng
2016-10-01
Full Text Available Directional water transport fabrics can proactively transfer moisture from the body. They show great potential in making sportswear and summer clothing. While moisture transfer has been previously reported, heat transfer in directional water transport fabrics has been little reported in research literature. In this study, a directional water transport fabric was prepared using an electrospraying technique and its heat transfer properties under dry and wet states were evaluated, and compared with untreated control fabric and the one pre-treated with NaOH. All the fabric samples showed similar heat transfer features in the dry state, and the equilibrium temperature in the dry state was higher than for the wet state. Wetting considerably enhanced the thermal conductivity of the fabrics. Our studies indicate that directional water transport treatment assists in moving water toward one side of the fabric, but has little effect on thermal transfer performance. This study may be useful for development of “smart” textiles for various applications.
Topology optimization for transient heat transfer problems
DEFF Research Database (Denmark)
Zeidan, Said; Sigmund, Ole; Lazarov, Boyan Stefanov
, TopOpt has later been extended to transient problems in mechanics and photonics (e.g. [5], [6] and [7]). In the presented approach, the optimization is gradient-based, where in each iteration the non-steady heat conduction equation is solved,using the finite element method and an appropriate time......The focus of this work is on passive control of transient heat transfer problems using the topology optimization (TopOpt) method [1]. The goal is to find distributions of a limited amount of phase change material (PCM), within a given design domain, which optimizes the heat energy storage [2]. Our...
Cooperative heat transfer and ground coupled storage system
Metz, P.D.
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
The Heat Transfer Coefficient of Recycled Concrete Bricks Combination with EPS Insulation Board Wall
Directory of Open Access Journals (Sweden)
Jianhua Li
2015-01-01
Full Text Available Four tectonic forms samples were conducted to test their heat transfer coefficients. By analyzing and comparing the test values and theoretical values of the heat transfer coefficient, a corrected-value calculation method for determining the heat transfer coefficient was proposed; the proposed method was proved to be reasonably correct. The results indicated that the recycled concrete brick wall heat transfer coefficient is higher than that of the clay brick wall, the heat transfer coefficient of recycled concrete brick wall could be effectively reduced when combined with the EPS insulation board, and the sandwich insulation type was better than that of external thermal insulation type.
Heat Transfer Coefficient Measurement for Downward Facing Flow Boiling Heat Transfer
Energy Technology Data Exchange (ETDEWEB)
Jung, Jun Yeong; Jeong, Yong Hoon [KAIST, Daejeon (Korea, Republic of)
2016-05-15
To evaluate heat transfer capability of the ERVC, estimating heat transfer coefficient (HTC) is important. In this study, the HTCs were experimentally measured, and large break loss of coolant accident (LLOCA) was used as basic accident. At the lower head outer wall, heat transfer phenomenon was downward facing flow boiling heat transfer. Because, natural circulation occurred. Hence, to simulate the flow boiling, water loop was designed. The reactor vessel lower head was simulated as 2-D slice main heater. To simulate the heat transfer characteristics of material and geometry, the main heater was made of SA508 consisting the reactor vessel, and its radius curvature was 2.5 m. The main heater outer surface (facing to air) temperature was measured by infrared (IR) camera, and the inner surface (facing to working fluid) temperature was calculated by solving conduction equation of main heater. The main heater heat flux was under CHF value of previous research. The results of 60 .deg. and 90 .deg. were used as representative angular location data. LLOCA was used as basic accident. Through this experiment, the HTC data was produced for SA508 heat transfer surface material and 2.5 m of radius curvature. The HTCs result shown different trend at each angular location. The HTCs commonly increased with heat flux increment, but the trends were different for angular location.
Supercritical heat transfer in an annular channel with bilateral heating
Energy Technology Data Exchange (ETDEWEB)
Sergeev, V.V.; Gal' chenko, E.F.; Remizov, O.V.
1986-09-01
This paper presents the experimental investigation of the degradation of heat transfer accompanying an ascending flow of a steam-water mixture and the development of an engineering method for calculating supercritical heat transfer in a vertical annular channel with bilateral heating. The experimental setup is described. The temperature of the exothermic surfaces from the indications of the thermocouples are determined taking into account their individual calibration, the temperature drops in the wall, and thermal losses. The temperature distribution along the length and periphery of the exothermic surfaces of the annular channel is shown and the dependence of the critical steam content on the power fed to the outer wall of the channel with different mass velocities is presented.
Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor
Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.
2013-01-01
This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.
Ribeiro, Carla
2017-01-01
The double-wall paper cup is an everyday object that can be used in the laboratory to study heat transfer. The experiment described here has been done by physics students aged 12-13 years; it can also be used in a different context to prompt debate about environmental issues.
Free convection film flows and heat transfer
Shang, Deyi
2010-01-01
Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.
A Paradox in Radiation Heat Transfer
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 4. A Paradox in Radiation Heat Transfer. J Srinivasan. Classroom Volume 12 Issue 4 April 2007 pp 85-91. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/012/04/0085-0091. Keywords. Radiation ...
Endwall convective heat transfer for bluff bodies
DEFF Research Database (Denmark)
Wang, Lei; Salewski, Mirko; Sundén, Bengt
2012-01-01
The endwall heat transfer characteristics of forced flow past bluff bodies have been investigated using liquid crystal thermography (LCT). The bluff body is placed in a rectangular channel with both its ends attached to the endwalls. The Reynolds number varies from 50,000 to 100,000. In this stud...
Conjugate problems in convective heat transfer
Dorfman, Abram S
2009-01-01
The conjugate heat transfer (CHT) problem takes into account the thermal interaction between a body and fluid flowing over or through it, a key consideration in both mechanical and aerospace engineering. Presenting more than 100 solutions of non-isothermal and CHT problems, this title considers the approximate solutions of CHT problems.
Determination of the convective heat transfer coefficient
Spierings, D.; Bosman, F.; Peters, T.; Plasschaert, F.
The value of the convective heat transfer coefficient (htc) is determined under different loading conditions by using a computer aided method. The thermal load has been applied mathematically as well as experimentally to the coronal surface of an axisymmetric tooth model. To verify the assumptions
Forced Convection Heat Transfer in Circular Pipes
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
Heat Transfer Analysis of Fin Tube
Energy Technology Data Exchange (ETDEWEB)
Jeon, Woo-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Choi, Cheng-Ryul [ELSOLTEC Co., Yongin (Korea, Republic of)
2015-10-15
This paper describes a preliminary numerical analysis of fin tube used for a heat exchanger of the air-water cooling system. The internal flow in a fin tube is steam and the external of the fin is cooled by air. Cooling system in a nuclear power plant can be divided into two categories; 1) active pump driven system powered by alternating current and 2) passive cooling system drived by natural circulation phenomena. After the accident in Hukushima Nuclear Power Plants, the importance of the passive cooling system that can provide a long-term cooling of reactor decay heat during station blackout condition is emphasized. However, the effectiveness of passive cooling system based on cooling water is limited by the capacity of water storage tank. To overcome the limit due to the exhaustion of the cooling water, an natural convection air cooling system is proposed. As the air operated cooling system utilizes natural circulation phenomena of air, it does not require cooling water. However, the heat transfer area of the air operated cooling system should be increased much as the heat removal capacity per unit area is much lower than that of water cooling system. The air-water combined cooling system can resolve this excess increase of the heat transfer area in the air operated cooling system. This air-water cooling system can be also used in the passive containment cooling system. The effect of design parameters such as fin tube arrangement, the fin height, and pitch has been analyzed and the chimney effect on the simulation of heat transfer in a heat exchanger is evaluated. The internal flows in a fin tube heat exchanger for natural circulation flow condition and forced convection (suction) condition were investigated.
Miyara, A.; Kariya, K.; Ali, Md. H.; Selamat, S. B.; Jalaluddin
2017-01-01
Three kinds of vertical-type ground heat exchangers, U-tube; double-tube; multi-tube, and two kinds of horizontal-type ground heat exchangers, standing Slinky; reclined Slinky, were experimentally and numerically investigated in order to clarify their heat transfer characteristics. Experiments and simulations were carried out under two operation conditions which are continuous operation mode and discontinuous operation mode and effects of temperature recovery and thermal storage on the heat transfer rate were shown. Differences of the heat transfer rate between standing Slinky and reclined Slinky were also indicated.
Numerical Modeling of Ablation Heat Transfer
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Heat transfer degradation during condensation of non-azeotropic mixtures
Azzolin, M.; Berto, A.; Bortolin, S.; Del, D., Col
2017-11-01
International organizations call for a reduction of the HFCs production and utilizations in the next years. Binary or ternary blends of hydroflourocarbons (HFCs) and hydrofluoroolefins (HFOs) are emerging as possible substitutes for high Global Warming Potential (GWP) fluids currently employed in some refrigeration and air-conditioning applications. In some cases, these mixtures are non-azeotropic and thus, during phase-change at constant pressure, they present a temperature glide that, for some blends, can be higher than 10 K. Such temperature variation during phase change could lead to a better matching between the refrigerant and the water temperature profiles in a condenser, thus reducing the exergy losses associated with the heat transfer process. Nevertheless, the additional mass transfer resistance which occurs during the phase change of zeotropic mixtures leads to a heat transfer degradation. Therefore, the design of a condenser working with a zeotropic mixture poses the problem of how to extend the correlations developed for pure fluids to the case of condensation of mixtures. Experimental data taken are very helpful in the assessment of design procedures. In the present paper, heat transfer coefficients have been measured during condensation of zeotropic mixtures of HFC and HFO fluids. Tests have been carried out in the test rig available at the Two Phase Heat Transfer Lab of University of Padova. During the condensation tests, the heat is subtracted from the mixture by using cold water and the heat transfer coefficient is obtained from the measurement of the heat flux on the water side, the direct measurements of the wall temperature and saturation temperature. Tests have been performed at 40°C mean saturation temperature. The present experimental database is used to assess predictive correlations for condensation of mixtures, providing valuable information on the applicability of available models.
Directory of Open Access Journals (Sweden)
N. A. Nesenchuk
2013-01-01
Full Text Available Directions pertaining to intensification of convective heat transfer in a soft heating device have been experimentally investigated in the paper and the most efficient one has been selected that is creation of artificial roughness on the device surface. The considered heating device for a heat supply system of a mobile object has been made of soft polymer material (polyvinyl chloride. Following evaluation results of heat exchange intensification a criteria equation has been obtained for calculation of external heat transfer with due account of heat transfer intensification.
Stagnation Region Heat Transfer Augmentation at Very High Turbulence Levels
Energy Technology Data Exchange (ETDEWEB)
Ames, Forrest [University of North Dakota; Kingery, Joseph E. [University of North Dakota
2015-06-17
A database for stagnation region heat transfer has been extended to include heat transfer measurements acquired downstream from a new high intensity turbulence generator. This work was motivated by gas turbine industry heat transfer designers who deal with heat transfer environments with increasing Reynolds numbers and very high turbulence levels. The new mock aero-combustor turbulence generator produces turbulence levels which average 17.4%, which is 37% higher than the older turbulence generator. The increased level of turbulence is caused by the reduced contraction ratio from the liner to the exit. Heat transfer measurements were acquired on two large cylindrical leading edge test surfaces having a four to one range in leading edge diameter (40.64 cm and 10.16 cm). Gandvarapu and Ames [1] previously acquired heat transfer measurements for six turbulence conditions including three grid conditions, two lower turbulence aero-combustor conditions, and a low turbulence condition. The data are documented and tabulated for an eight to one range in Reynolds numbers for each test surface with Reynolds numbers ranging from 62,500 to 500,000 for the large leading edge and 15,625 to 125,000 for the smaller leading edge. The data show augmentation levels of up to 136% in the stagnation region for the large leading edge. This heat transfer rate is an increase over the previous aero-combustor turbulence generator which had augmentation levels up to 110%. Note, the rate of increase in heat transfer augmentation decreases for the large cylindrical leading edge inferring only a limited level of turbulence intensification in the stagnation region. The smaller cylindrical leading edge shows more consistency with earlier stagnation region heat transfer results correlated on the TRL (Turbulence, Reynolds number, Length scale) parameter. The downstream regions of both test surfaces continue to accelerate the flow but at a much lower rate than the leading edge. Bypass transition occurs
Heat Transfer in Health and Healing.
Diller, Kenneth R
2015-10-01
Our bodies depend on an exquisitely sensitive and refined temperature control system to maintain a state of health and homeostasis. The exceptionally broad range of physical activities that humans engage in and the diverse array of environmental conditions we face require remarkable strategies and mechanisms for regulating internal and external heat transfer processes. On the occasions for which the body suffers trauma, therapeutic temperature modulation is often the approach of choice for reversing injury and inflammation and launching a cascade of healing. The focus of human thermoregulation is maintenance of the body core temperature within a tight range of values, even as internal rates of energy generation may vary over an order of magnitude, environmental convection, and radiation heat loads may undergo large changes in the absence of any significant personal control, surface insulation may be added or removed, all occurring while the body's internal thermostat follows a diurnal circadian cycle that may be altered by illness and anesthetic agents. An advanced level of understanding of the complex physiological function and control of the human body may be combined with skill in heat transfer analysis and design to develop life-saving and injury-healing medical devices. This paper will describe some of the challenges and conquests the author has experienced related to the practice of heat transfer for maintenance of health and enhancement of healing processes.
Radiative heat transfer in fractal structures
Nikbakht, M.
2017-09-01
The radiative properties of most structures are intimately connected to the way in which their constituents are ordered on the nanoscale. We have proposed a new representation for radiative heat transfer formalism in many-body systems. In this representation, we explain why collective effects depend on the morphology of structures, and how the arrangement of nanoparticles and their material affects the thermal properties in many-body systems. We investigated the radiative heat transfer problem in fractal (i.e., scale invariant) structures. In order to show the effect of the structure morphology on the collective properties, the radiative heat transfer and radiative cooling are studied and the results are compared for fractal and nonfractal structures. It is shown that fractal arranged nanoparticles display complex radiative behavior related to their scaling properties. We showed that, in contrast to nonfractal structures, heat flux in fractals is not of large-range character. By using the fractal dimension as a means to describe the structure morphology, we present a universal scaling behavior that quantitatively links the structure radiative cooling to the structure gyration radius.
Directory of Open Access Journals (Sweden)
Waqar Azeem Khan
Full Text Available The present paper deals with the analysis of melting heat and mass transfer characteristics in the stagnation point flow of an incompressible generalized Burgers fluid over a stretching sheet in the presence of non-linear radiative heat flux. A uniform magnetic field is applied normal to the flow direction. The governing equations in dimensional form are reduced to a system of dimensionless expressions by implementation of suitable similarity transformations. The resulting dimensionless problem governing the generalized Burgers is solved analytically by using the homotopy analysis method (HAM. The effects of different flow parameters like the ratio parameter, magnetic parameter, Prandtl number, melting parameter, radiation parameter, temperature ratio parameter and Schmidt number on the velocity, heat and mass transfer characteristics are computed and presented graphically. Moreover, useful discussions in detail are carried out with the help of plotted graphs and tables. Keywords: Generalized Burgers fluid, Non-linear radiative flow, Magnetic field, Melting heat transfer
Optimizing Reduced-Order Transfer Functions
Spanos, John T.; Milman, Mark H.; Mingori, D. Lewis
1992-01-01
Transfer-function approximations made optimal in special least-squares sense. Algorithm computes reduced-order rational-fraction approximates to single-input/single-output transfer functions. Reduces amount of computation needed for such purposes as numerical simulation of dynamics and design of control subsystems.
Effects of fouling in heat transfer equipment
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V. (ABCO Industries, Abilene, TX (United States))
1993-03-04
Fouling between the hot and cold streams in heat transfer equipment is a major reason boilers, heaters, and heat exchangers do not perform according to original specifications. Commonly used fluids such as water and air have well-established fouling factors. However, the factors for some industrial effluents, particularly for flue gas streams resulting from the combustion or incineration of solid or liquid fuels, can be determined only through operating experience. The paper discusses the signs of fouling, and how expensive fouling can be illustrating the second with three example problems.
Energy Technology Data Exchange (ETDEWEB)
Bednarski, A.; Ligeza, S.; Montewski, W.; Ozga, A.; Steinmec, E.
1979-10-01
An oil heat-transfer agent, suitable for operation in the temperature range of 30-360 degrees, containing hydrocarbon oil with a boiling point of 5% above 360 degrees and 2% alkylphenolate or alkaline or alkaline-earth metal with a reserve alkalinity to 300 mg KOH/g, and to 5% alkenylksuccinic anhydride with a molar weight of 1000-1600 and content of nitrogen to 2.5%, or alkylthiophosphonate with a molecular weight to 1500 and phosphorus content to 2%. The oil used in the heat-transfer agent contains over 25% aromatic hydrocarbons containing 4-40% aromatic C atoms, 3-40% naphthene carbon atoms and 25-75% paraffin carbon atoms, and to 3% tar. Data are given describing the high oxidation stability and low tendency to deposit formation of oil compositions obtained according to the patent.
Heat transfer modeling an inductive approach
Sidebotham, George
2015-01-01
This innovative text emphasizes a "less-is-more" approach to modeling complicated systems such as heat transfer by treating them first as "1-node lumped models" that yield simple closed-form solutions. The author develops numerical techniques for students to obtain more detail, but also trains them to use the techniques only when simpler approaches fail. Covering all essential methods offered in traditional texts, but with a different order, Professor Sidebotham stresses inductive thinking and problem solving as well as a constructive understanding of modern, computer-based practice. Readers learn to develop their own code in the context of the material, rather than just how to use packaged software, offering a deeper, intrinsic grasp behind models of heat transfer. Developed from over twenty-five years of lecture notes to teach students of mechanical and chemical engineering at The Cooper Union for the Advancement of Science and Art, the book is ideal for students and practitioners across engineering discipl...
Principles of heat and mass transfer
Incropera, Frank P; Bergman, Theodore L; Lavine, Adrienne S
2013-01-01
Completely updated, the seventh edition provides engineers with an in-depth look at the key concepts in the field. It incorporates new discussions on emerging areas of heat transfer, discussing technologies that are related to nanotechnology, biomedical engineering and alternative energy. The example problems are also updated to better show how to apply the material. And as engineers follow the rigorous and systematic problem-solving methodology, they'll gain an appreciation for the richness and beauty of the discipline.
Heat transfer in multi-phase materials
Öchsner, Andreas
2011-01-01
This book provides a profound understanding, which physical processes and mechanisms cause the heat transfer in composite and cellular materials. It shows models for all important classes of composite materials and introduces into the latest advances. In three parts, the book covers Composite Materials (Part A), Porous and Cellular Materials (Part B) and the appearance of a conjoint solid phase and fluid aggregate (Part C).
Heat transfer studies on spiral plate heat exchanger
Directory of Open Access Journals (Sweden)
Rajavel Rangasamy
2008-01-01
Full Text Available In this paper, the heat transfer coefficients in a spiral plate heat exchanger are investigated. The test section consists of a plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot water (hot fluid is varying from 0.5 to 0.8 kg/s and the mass flow rate of cold water (cold fluid varies from 0.4 to 0.7 kg/s. Experiments have been conducted by varying the mass flow rate, temperature, and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the Nusselt number which can be used for practical applications is proposed.
Heat transfer with freezing in a scraped surface heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Lakhdar, M.B. [LGL France Refrigerating Division, Genas (France); Cerecero, R.; Alvarez, G.; Guilpart, J. [Cemagref, Antony cedex (France). Food Process Engineering; Flick, D. [Institut National Agronomique, Paris (France); Lallemand, A. [Institut National des Sciences Appliquees de Lyon (France). Centre de Thermique
2005-01-01
An experimental study was carried out on a scraped surface heat exchanger used for freezing of water-ethanol mixture and aqueous sucrose solution. The influence of various parameters on heat transfer intensity was established: product type and composition, flow rate, blade rotation speed, distance between blades and wall. During starting (transient period) the solution is first supercooled, then ice crystals appear on the scraped surface (heterogeneous nucleation) and no more supercooling is observed. It seems that, when blades are 3 mm far from the surface, a constant ice layer is formed having this thickness and acting as a thermal resistance. But when the blades rotate at 1 mm from the surface, periodically all the ice layer is removed despite the surface is not really scraped. This could simplify ice generator technology. An internal heat transfer coefficient was defined; it depends mainly on rotation speed. Correlations were proposed for its prediction, which could be applied, at least as a first approach, for the most common freezing applications of scraped surface heat exchanger i.e. ice creams (which are derived from sucrose solutions) and two-phase secondary refrigerants (which are principally ethanol solutions). (author)
Refrigeration. Heat Transfer. Part I: Evaporators and Condensers
DEFF Research Database (Denmark)
Knudsen, Hans-Jørgen Høgaard
2002-01-01
The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation.......The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation....
Conjugate Problems in Convective Heat Transfer: Review
Directory of Open Access Journals (Sweden)
Abram Dorfman
2009-01-01
Full Text Available A review of conjugate convective heat transfer problems solved during the early and current time of development of this modern approach is presented. The discussion is based on analytical solutions of selected typical relatively simple conjugate problems including steady-state and transient processes, thermal material treatment, and heat and mass transfer in drying. This brief survey is accompanied by the list of almost two hundred publications considering application of different more and less complex analytical and numerical conjugate models for simulating technology processes and industrial devices from aerospace systems to food production. The references are combined in the groups of works studying similar problems so that each of the groups corresponds to one of selected analytical solutions considered in detail. Such structure of review gives the reader the understanding of early and current situation in conjugate convective heat transfer modeling and makes possible to use the information presented as an introduction to this area on the one hand, and to find more complicated publications of interest on the other hand.
Conformal mapping technique for two-dimensional porous media and jet impingement heat transfer
Siegel, R.
1974-01-01
Transpiration cooling and liquid metals both provide highly effective heat transfer. Using Darcy's law in porous media and the inviscid approximation for liquid metals, the local fluid velocity in these flows equals the gradient of a potential. The energy equation and flow region are simplified when transformed into potential plane coordinates. In these coordinates, the present problems are reduced to heat conduction solutions which are mapped into the physical geometry. Results are obtained for a porous region with simultaneously prescribed surface temperature and heat flux, heat transfer in a two-dimensional porous bed, and heat transfer for two liquid metal slot jets impinging on a heated plate.
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Free convection effects and radiative heat transfer in MHD Stokes ...
Indian Academy of Sciences (India)
which controls the gasification rate of the energetic material for estimating heat transfer. Radiation effect on flow and heat transfer is important in the context of space technology and processes involving high temperature. In recent years, the problems of free convective and heat transfer flows through a porous medium under ...
Enhancement of heat transfer using varying width twisted tape inserts
African Journals Online (AJOL)
user
width twisted tape inserts, ASME Transactions, Vol. 122, pp. 143-149. Naphon P., 2006. Heat transfer and pressure drop in the horizontal double pipes with and without twisted tape insert, International communications in Heat and Mass Transfer, Vol. 33, pp. 166-175. Promvonge P. and Eiamsa-ard S., 2007. Heat transfer ...
Low-Flow Film Boiling Heat Transfer on Vertical Surfaces
DEFF Research Database (Denmark)
Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.
1976-01-01
The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer...... length, an average film boiling heat transfer coefficient is obtained....
Low heat transfer oxidizer heat exchanger design and analysis
Kanic, P. G.; Kmiec, T. D.; Peckham, R. J.
1987-01-01
The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487.
An immersed-boundary method for conjugate heat transfer analysis
Energy Technology Data Exchange (ETDEWEB)
Song, Jeong Chul; Lee, Joon Sik [Seoul National University, Seoul (Korea, Republic of); Ahn, Joon [Kookmin University, Seoul (Korea, Republic of)
2017-05-15
An immersed-boundary method is proposed for the analysis of conjugate problems of convective heat transfer in conducting solids. In- side the solid body, momentum forcing is applied to set the velocity to zero. A thermal conductivity ratio and a heat capacity ratio, between the solid body and the fluid, are introduced so that the energy equation is reduced to the heat diffusion equation. At the solid fluid interface, an effective conductivity is introduced to satisfy the heat flux continuity. The effective thermal conductivity is obtained by considering the heat balance at the interface or by using a harmonic mean formulation. The method is first validated against the analytic solution to the heat transfer problem in a fully developed laminar channel flow with conducting solid walls. Then it is applied to a laminar channel flow with a heated, block-shaped obstacle to show its validity for geometry with sharp edges. Finally the validation for a curvilinear solid body is accomplished with a laminar flow through arrayed cylinders.
Infrared thermography for convective heat transfer measurements
Energy Technology Data Exchange (ETDEWEB)
Carlomagno, Giovanni Maria; Cardone, Gennaro [University of Naples Federico II, Department of Aerospace Engineering, Naples (Italy)
2010-12-15
This paper deals with the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior. Measurement of convective heat fluxes must be performed by means of a thermal sensor, where temperatures have to be measured with proper transducers. By correctly choosing the thermal sensor, IR thermography can be successfully exploited to resolve convective heat flux distributions with both steady and transient techniques. When comparing it to standard transducers, the IR camera appears very valuable because it is non-intrusive, it has a high sensitivity (down to 20 mK), it has a low response time (down to 20 {mu}s), it is fully two dimensional (from 80 k up to 1 M pixels, at 50 Hz) and, therefore, it allows for better evaluation of errors due to tangential conduction within the sensor. This paper analyses the capability of IR thermography to perform convective heat transfer measurements and surface visualizations in complex fluid flows. In particular, it includes the following: the necessary radiation theory background, a review of the main IR camera features, a description of the pertinent heat flux sensors, an analysis of the IR image processing methods and a report on some applications to complex fluid flows, ranging from natural convection to hypersonic regime. (orig.)
46 CFR 153.430 - Heat transfer systems; general.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, Jos; van der Geld, C.W.M.
1996-01-01
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall
Heat transfer model for quenching by submerging
Energy Technology Data Exchange (ETDEWEB)
Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)
2011-05-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Heat transfer enhancement by dynamic corrugated heat exchanger wall: Numerical study
Kumar, P.; Schmidmayer, K.; Topin, F.; Miscevic, M.
2016-09-01
A new concept of heat exchanger at sub-millimeter scale is proposed for applications in cooling on-board electronics devices, in which the quality of the exchanges between fluid and wall is very critical. In the proposed system, the upper wall of the channel is deformed dynamically to obtain a sinusoidal wave on this surface. The lower wall is exposed to constant heat flux simulating the imprint of an electronic component. A systematic 3-D numerical study in transient regime on the different deformation parameters allowed obtaining both the pumping characteristics and the heat transfer characteristics of the system. It was observed that the dynamic deformation of the wall induces a significant pumping effect. The intensification of the heat transfer is very important even for highly degraded waveforms, although the pumping efficiency is reduced in this case.
Fouling-the silent heat transfer thief
Energy Technology Data Exchange (ETDEWEB)
Ganapathy, V. (ABCO Industries, Inc., Abilene, TX (United States))
1992-10-01
Boilers or heat recovery steam generators perform efficiently under clean conditions. Their performance is significantly affected by fouling either on the tube or gas side whether it is a fire tube or water tube exchanger. In addition to reduced duty, steam side cleanliness impacts the tube wall temperature leading to its overheating and failure in the long run. This paper reports that good water chemistry is an easy, efficient way to reduce the effects of steam-side fouling on boiler performance and tube wall temperature. Water tube waste heat recovery boilers will be used as examples. The concept applies to fired water tube or fire tube boilers and heat recovery steam generators also.
Heat transfer unit and method for prefabricated vessel
Energy Technology Data Exchange (ETDEWEB)
Tamburello, David A.; Kesterson, Matthew R; Hardy, Bruce J.
2017-11-07
Vessel assemblies, heat transfer units for prefabricated vessels, and methods for heat transfer prefabricated vessel are provided. A heat transfer unit includes a central rod, and a plurality of peripheral rods surrounding the central rod and connected to the central rod. The plurality of peripheral rods are movable between a first collapsed position and a second bowed position, wherein in the second bowed position a midpoint of each of the plurality of peripheral rods is spaced from the central rod relative to in the first position. The heat transfer unit further includes a heat transfer element connected to one of the plurality of peripheral rods.
Various methods to improve heat transfer in exchangers
Pavel, Zitek; Vaclav, Valenta
2015-05-01
The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.
Heat Transfer Model for Hot Air Balloons
Llado-Gambin, Adriana
A heat transfer model and analysis for hot air balloons is presented in this work, backed with a flow simulation using SolidWorks. The objective is to understand the major heat losses in the balloon and to identify the parameters that affect most its flight performance. Results show that more than 70% of the heat losses are due to the emitted radiation from the balloon envelope and that convection losses represent around 20% of the total. A simulated heating source is also included in the modeling based on typical thermal input from a balloon propane burner. The burner duty cycle to keep a constant altitude can vary from 10% to 28% depending on the atmospheric conditions, and the ambient temperature is the parameter that most affects the total thermal input needed. The simulation and analysis also predict that the gas temperature inside the balloon decreases at a rate of -0.25 K/s when there is no burner activity, and it increases at a rate of +1 K/s when the balloon pilot operates the burner. The results were compared to actual flight data and they show very good agreement indicating that the major physical processes responsible for balloon performance aloft are accurately captured in the simulation.
Heat transfer in rotor/stator cavity
Tuliszka-Sznitko, Ewa; Majchrowski, Wojciech; Kiełczewski, Kamil
2011-12-01
In the paper we analyze the results of DNS/LES of the flow with heat transfer in the rotor/stator cavity. The rotor and the outer cylinder are heated. Computations have been performed for wide range of Reynolds numbers and aspect ratios. Computations are based on the efficient pseudo-spectral Chebyshev-Fourier method. In LES we used a Lagrangian dynamic subgrid-scale model of turbulence. Analysis allowed to check the influence of the aspect ratio and Reynolds number on the statistics and the structure of the flow. We analyzed all six Reynolds stress tensor components, turbulent fluctuations, three turbulent heat fluxes and different structural parameters which can be useful for modeling purposes. The distributions of Nusselt numbers obtained for different Re and aspect rations along disks are given. We also investigated influence of thermal Rosssby number as well as distributions of temperature along heated disk on statistics. Computations have shown that turbulence is mostly concentrated in the stator boundary layer with a maximum at the junction between the stator and the outer cylinder. The results are compared to the experimental and numerical data taken from literature.
Porous media heat transfer for injection molding
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Computational fluid mechanics and heat transfer
Pletcher, Richard H; Anderson, Dale
2012-01-01
""I have always considered this book the best gift from one generation to the next in computational fluid dynamics. I earnestly recommend this book to graduate students and practicing engineers for the pleasure of learning and a handy reference. The description of the basic concepts and fundamentals is thorough and is crystal clear for understanding. And since 1984, two newer editions have kept abreast to the new, relevant, and fully verified advancements in CFD.""-Joseph J.S. Shang, Wright State University""Computational Fluid Mechanics and Heat Transfer is very well written to be used as a t
The impact of heat transfer on Murphree tray efficiency
Energy Technology Data Exchange (ETDEWEB)
Kaeser, M.; Pritchard, C.L. [University of Edinburgh (United Kingdom). Institute for Energy Systems
2006-12-15
This work features the experimental determination of heat transfer coefficients and Murphree tray efficiencies on a diabatic (heat-transferring) distillation tray. The present investigation, focussing on the impact of heat transfer on sieve tray performance, is part of a long-term project on heat integrated distillation columns (HIDiC). Heat transfer coefficients and tray efficiencies have been determined experimentally for the methanol/water system in a 150mm diameter distillation column. The heat-transferring tray was operated in both heating and cooling modes, with heat fluxes up to 50 and 100kWm{sup -2}, respectively. The experimental data from these diabatic experiments were compared with data obtained from the same column in adiabatic mode and were correlated with the vapour velocity and the heat flux to/from the tray. (author)
A SINDA '85 nodal heat transfer rate calculation user subroutine
Cheston, Derrick J.
1992-01-01
This paper describes a subroutine, GETQ, which was developed to compute the heat transfer rates through all conductors attached to a node within a SINDA '85 thermal submodel. The subroutine was written for version 2.3 of SINDA '85. Upon calling GETQ, the user supplies the submodel name and node number which the heat transfer rate computation is desired. The returned heat transfer rate values are broken down into linear, nonlinear, source and combined heat loads.
Heat and mass transfer in building services design
Moss, Keith
1998-01-01
Building design is increasingly geared towards low energy consumption. Understanding the fundamentals of heat transfer and the behaviour of air and water movements is more important than ever before. Heat and Mass Transfer in Building Services Design provides an essential underpinning knowledge for the technology subjects of space heating, water services, ventilation and air conditioning. This new text: *provides core understanding of heat transfer and fluid flow from a building services perspective *complements a range of courses in building services engineering *
Method of calculating heat transfer in furnaces of small power
Directory of Open Access Journals (Sweden)
Khavanov Pavel
2016-01-01
Full Text Available This publication presents the experiences and results of generalization criterion equation of importance in the analysis of the processes of heat transfer and thermal calculations of low-power heat generators cooled combustion chambers. With generalizing depending estimated contribution of radiation and convective heat transfer component in the complex for the combustion chambers of small capacity boilers. Determined qualitative and quantitative dependence of the integrated radiative-convective heat transfer from the main factors working combustion chambers of small volume.
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Energy Technology Data Exchange (ETDEWEB)
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-10-03
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.
Heat and mass transfer during baking: product quality aspects
Asselman, A.; Straten, van G.; Hadiyanto, H.; Boom, R.M.; Esveld, D.C.; Boxtel, van A.J.B.
2005-01-01
Abstract Most food product qualities are developed during heating processes. Therefore the internal heating and mass transfer of water are important aspects in food processing. Heating of food products is mostly induced by convection heating. However, the number applications of convective heating in
Heat Transfer Analysis in Wire Bundles for Aerospace Vehicles
Rickman, S. L.; Iamello, C. J.
2016-01-01
Design of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.
Transient critical heat flux and blowdown heat-transfer studies
Energy Technology Data Exchange (ETDEWEB)
Leung, J.C.
1980-05-01
Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.
Boiling local heat transfer enhancement in minichannels using nanofluids
Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony
2013-03-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance.
Boiling local heat transfer enhancement in minichannels using nanofluids
2013-01-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445
Convective heat transfer in porous media
Cheng, P.
Recent emerging technologies on the extraction of geothermal energy, the design of insulation systems for energy conservation, the use of aquifers for hot-water storage, the disposal of nuclear wastes in sub-seabeds, the enhanced recovery of oils by thermal methods, and the design of catalyst-bed reactors have demanded an improved understanding of heat transfer mechanisms in fluid-filled porous media. Experiments have been conducted to investigate the onset of free convection in rectangular and cylindrical enclosures filled with porous media and heated from below. The Nusselt numbers determined from these experiments during steady conditions are correlated in terms of the Rayleigh number. The data for free convection in rectangular geometries show considerable scattering among investigators using different porous media and fluids. Recently, some data has been obtained for free convect on in water-filled glass beads adjacent to a heated vertical flat plate, a horizontal cylinder and between vertical concentric cylinders. The data obtained at low Rayleigh numbers is found to be in good agreement with theoretical predictions based on Darcy's law.
Heat transfer and fluid friction in bundles of twisted tubes
Dzyubenko, B. V.; Dreitser, G. A.
1986-06-01
The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.
Measurement of heat transfer coefficient using termoanemometry methods
Directory of Open Access Journals (Sweden)
Dančová P.
2014-03-01
Full Text Available This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.
Boiling Heat-Transfer Processes and Their Application in the Cooling of High Heat Flux Devices
1993-06-01
presented previously in Eq. (8). Bjorge , et al. (Ref. 170) and Stephan and Auracher (Ref. 171) later presented variations of the superposition approach...ofHeat Transfer, Vol. 90, May 1968, pp. 239-247. 170. Bjorge , R. W., Hall, G. R., and Rohsenow, W. M. "Correlation of Forced Convection Boiling Heat... Communications on Heat Mass Transfer, Vol. 18, No.5, September-October 1991, pp. 659-667. 383. Boyd, R. D., Sr. "Critical Heat Flux and Heat Transfer
Influence of structural design condensing part of NH3 heat pipe to heat transfer
Directory of Open Access Journals (Sweden)
Vantúch Martin
2014-03-01
Full Text Available The article describes influence design heat exchangers to efficiency condensation liquid ammonia in the gravitational heat pipe. Analyse adverse factors in the operation and flow of ammonia in heat pipe. Also describes heat transfer characteristics of heat pipe in low-potential geothermal heat transport simulations.
Loop heat pipes - highly efficient heat-transfer devices for systems of sun heat supply
Energy Technology Data Exchange (ETDEWEB)
Maydanik, Yu. [Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Thermophysics
2004-07-01
Loop heat pipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heat pipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heat pipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)
Directory of Open Access Journals (Sweden)
Kalidas Das
2016-10-01
Full Text Available The present work is concerned with heat and mass transfer of an electrically conducting second grade MHD fluid past a semi-infinite stretching sheet with convective surface heat flux. The analysis accounts for thermophoresis and thermal radiation. A similarity transformations is used to reduce the governing equations into a dimensionless form. The local similarity equations are derived and solved using Nachtsheim-Swigert shooting iteration technique together with Runge–Kutta sixth order integration scheme. Results for various flow characteristics are presented through graphs and tables delineating the effect of various parameters characterizing the flow. Our analysis explores that the rate of heat transfer enhances with increasing the values of the surface convection parameter. Also the fluid velocity and temperature in the boundary layer region rise significantly for increasing the values of thermal radiation parameter.
Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
National Research Council Canada - National Science Library
Tomasz Muszyński; Sławomir Marcin Kozieł
2016-01-01
Two-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evaporator...
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers
de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries
2014-01-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic
Nonequilibrium Fluctuational Quantum Electrodynamics: Heat Radiation, Heat Transfer, and Force
Bimonte, Giuseppe; Emig, Thorsten; Kardar, Mehran; Krüger, Matthias
2017-03-01
Quantum-thermal fluctuations of electromagnetic waves are the cornerstone of quantum statistics and inherent to phenomena such as thermal radiation and van der Waals forces. Although the principles are found in elementary texts, recent experimental and technological advances make it necessary to come to terms with counterintuitive consequences at short scales—the so-called near-field regime. We focus on three manifestations: (a) The Stefan-Boltzmann law describes radiation from macroscopic bodies but fails for small objects. (b) The heat transfer between two bodies at close proximity is dominated by evanescent waves and can be orders of magnitude larger than the classical (propagating) contribution. (c) Casimir forces, dominant at submicron separation, are not sufficiently explored for objects at different temperatures (at least experimentally). We explore these phenomena using fluctuational quantum electrodynamics (QED), introduced by Rytov in the 1950s, combined with scattering formalisms. This enables investigation of different material properties, shapes, separations, and arrangements.
Kissing heat transfer between the wraps of a scroll pump
Energy Technology Data Exchange (ETDEWEB)
Sunder, S.; Smith, J.L. Jr. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Mechanical Engineering
1996-12-31
Conductances associated with the various modes of internal heat transfer in a scroll pump are estimated. Heat transfer through transient contact between scroll wraps (kissing heat transfer) is found to be a dominant mode of heat transfer between discharge and suction sides of the pump. Such heat transfer is characterized by significant steady-state heat fluxes across the wraps of a scroll pump. Experiments on a specially instrumented scroll compressor provide evidence of significant heat fluxes across the wraps of the scroll pump. Estimation of the contact angle between wraps based on Hertzian stresses, as well as an oil film demonstrate that kissing heat transfer is a plausible mechanism of heat transfer in these pumps. Contact angles inferred from experimental data are also shown to be of the same order of magnitude as those predicted by Hertzian stress calculations. It is shown that the heat fluxes observed in the kissing heat transfer experiment are too large to be explained by convection between gas and wall in the scroll pump.
Heat transfer in heated industrial premises with using radiant heating system
Directory of Open Access Journals (Sweden)
Nagornova Tatiana A.
2017-01-01
Full Text Available The results of mathematical modeling of heat transfer processes in a closed air volume surrounded by enclosing constructions, heated by supplying energy to the upper contour of gas infrared radiators are represented. Regimes of turbulent natural conjugate convection in the region bounded by solid walls are investigated. Two-dimensional nonstationary problem is solved in the framework of the Navier -Stokes equations for gas and thermal conductivity for solid walls. Nonstationary processes of heat propagation in course of time and essential heterogeneity of temperature fields and heat fluxes are established.
Heat and mass transfer in flames
Faeth, G. M.
1986-01-01
Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.
HEAT TRANSFER AND TRITIUM PRODUCING SYSTEM
Johnson, E.F.
1962-06-01
This invention related to a circulating lithium-containing blanket system in a neution source hav'ing a magnetic field associated therewith. The blanket serves simultaneously and efficiently as a heat transfer mediunm and as a source of tritium. The blanket is composed of a lithium-6-enriched fused salt selected from the group consisting of lithium nitrite, lithium nitrate, a mixture of said salts, a mixture of each of said salts with lithium oxide, and a mixture of said salts with each other and with lithium oxide. The moderator, which is contained within the blanket in a separate conduit, can be water. A stellarator is one of the neutron sources which can be used in this invention. (AEC)
Submersible pumping system with heat transfer mechanism
Hunt, Daniel Francis Alan; Prenger, F. Coyne; Hill, Dallas D; Jankowski, Todd Andrew
2014-04-15
A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.
Liu, Jiawei; Zhou, Xingqiu; Wu, Jiangdong; Gao, Wen; Qian, Xu
2017-10-01
The temperature is the essential factor that influences the efficiency of anaerobic reactors. During the operation of the anaerobic reactor, the fluctuations of ambient temperature can cause a change in the internal temperature of the reactor. Therefore, insulation and heating measures are often used to maintain anaerobic reactor's internal temperature. In this paper, a simplified heat transfer model was developed to study heat transfer between cylindrical anaerobic reactors and their surroundings. Three cylindrical reactors of different sizes were studied, and the internal relations between ambient temperature, thickness of insulation, and temperature fluctuations of the reactors were obtained at different reactor sizes. The model was calibrated by a sensitivity analysis, and the calibrated model was well able to predict reactor temperature. The Nash-Sutcliffe model efficiency coefficient was used to assess the predictive power of heat transfer models. The Nash coefficients of the three reactors were 0.76, 0.60, and 0.45, respectively. The model can provide reference for the thermal insulation design of cylindrical anaerobic reactors.
Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger
Kuznetsov, V. V.; Shamirzaev, A. S.
2015-11-01
The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.
Heat Transfer Study of Heat-Integrated Distillation Column (HIDiC) Using Simulation Techniques
Pulido, Jeffrey León; Martínez, Edgar Leonardo; Wolf, Maria Regina; Filho, Rubens Maciel
2011-08-01
Separation processes is largely used in petroleum refining and alcohol industries. Distillation columns consume a huge amount of energy in industrial process. Therefore, the concept of Heat-Integrated Distillation Column (HIDiC) was studied using simulation techniques in order to overcome this drawback. In this configuration the column is composed for two concentric sections called rectifying and stripping. The heat transfer is conducted from the rectifying section (which works at higher pressure and temperature) to the stripping section (which works at lower pressure and temperature) using the heat present in the process and decreasing the energy charge required by the reboiler. The HIDiC column offers great potential to reduce energy consumption compared to conventional columns. However, the complexity of the internal configuration requires the development of rigorous works that enable a better understanding of the column operation. For this reason, techniques of simulation were used through of computational software. The current work presents a heat transfer study in a concentric stage of a HIDiC column. The results obtained by Aspen Plus and CFD simulation showed the internal heat transfer in a concentric tray as a promissory configuration in order to decrease energy consumption in distillation processes.
Energy Technology Data Exchange (ETDEWEB)
Ma, Zhiwen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Martinek, Janna G [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-06-03
Concentrating solar power (CSP) technology is moving toward high-temperature and high-performance design. One technology approach is to explore high-temperature heat-transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (s-CO2) Brayton power cycle. The s-CO2 Brayton power system has great potential to enable the future CSP system to achieve high solar-to-electricity conversion efficiency and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat-transfer medium that is inexpensive and stable at high temperatures above 1,000 degrees C. The particle/heat exchanger provides a connection between the particles and s-CO2 fluid in the emerging s-CO2 power cycles in order to meet CSP power-cycle performance targets of 50% thermal-to-electric efficiency, and dry cooling at an ambient temperature of 40 degrees C. The development goals for a particle/s-CO2 heat exchanger are to heat s-CO2 to =720 degrees C and to use direct thermal storage with low-cost, stable solid particles. This paper presents heat-transfer modeling to inform the particle/s-CO2 heat-exchanger design and assess design tradeoffs. The heat-transfer process was modeled based on a particle/s-CO2 counterflow configuration. Empirical heat-transfer correlations for the fluidized bed and s-CO2 were used in calculating the heat-transfer area and optimizing the tube layout. A 2-D computational fluid-dynamics simulation was applied for particle distribution and fluidization characterization. The operating conditions were studied from the heat-transfer analysis, and cost was estimated from the sizing of the heat exchanger. The paper shows the path in achieving the cost and performance objectives for a heat-exchanger design.
Transient Heat Transfer Properties in a Pulse Detonation Combustor
2011-03-01
Applications,” M.S. Thesis, Naval Postgraduate School, Monterey, CA, March 2010. [7] F.P. Incropera , and D.P. Dewitt, Fundamentals of Heat and Mass Transfer ...cooling water mass flow rates through each individual cooling jacket was used to determine the average heat transfer rate in Watts. The maximum...DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Transient Heat Transfer Properties in a Pulse Detonation Combustor 6. AUTHOR(S) Dion Glenn
Fink, Richard
2015-01-01
The increasing use of power electronics, such as high-current semiconductor devices and modules, within space vehicles is driving the need to develop specialty thermal management materials in both the packaging of these discrete devices and the packaging of modules consisting of these device arrays. Developed by Applied Nanotech, Inc. (ANI), CarbAl heat transfer material is uniquely characterized by its low density, high thermal diffusivity, and high thermal conductivity. Its coefficient of thermal expansion (CTE) is similar to most power electronic materials, making it an effective base plate substrate for state-of-the-art silicon carbide (SiC) super junction transistors. The material currently is being used to optimize hybrid vehicle inverter packaging. Adapting CarbAl-based substrates to space applications was a major focus of the SBIR project work. In Phase I, ANI completed modeling and experimentation to validate its deployment in a space environment. Key parameters related to cryogenic temperature scaling of CTE, thermal conductivity, and mechanical strength. In Phase II, the company concentrated on improving heat sinks and thermally conductive circuit boards for power electronic applications.
Heat Transfer of DE-Series MOSFETs
Directory of Open Access Journals (Sweden)
Arthur James Swart
2011-01-01
Full Text Available MOSFET devices have developed significantly over the past few years to become the number one choice for high-power applications in power electronics and electronic communication. Commercially available devices (such as the IXYS RF manufactured now operate into the VHF range with output RF powers of up to 300 W. They are optimized for linear operation and suitable for broadcast and communication applications. This paper presents the heat transfer out of an IXZ210N50L MOSFET which is sandwiched between two identical heatsinks. The results reveal a linear decrease in heat flowing away from the top of the MOSFET when compared to the bottom of the MOSFET for each step increase of drain current. Two graphs (representing the top and bottom heatsinks connected to the MOSFET device contrast the temperature rise for the Bisink technique when the drain current through the IXZ210N50L MOSFET is kept constant at 5 A. The Bisink technique has the advantages of lower on-state resistances and higher output powers when compared to the traditional mounting using only one heatsink, resulting in improved reliability and performance. Results further reveal that the ambient temperature must be measured in the vicinity of the heatsink.
Personalized recommendation based on heat bidirectional transfer
Ma, Wenping; Feng, Xiang; Wang, Shanfeng; Gong, Maoguo
2016-02-01
Personalized recommendation has become an increasing popular research topic, which aims to find future likes and interests based on users' past preferences. Traditional recommendation algorithms pay more attention to forecast accuracy by calculating first-order relevance, while ignore the importance of diversity and novelty that provide comfortable experiences for customers. There are some levels of contradictions between these three metrics, so an algorithm based on bidirectional transfer is proposed in this paper to solve this dilemma. In this paper, we agree that an object that is associated with history records or has been purchased by similar users should be introduced to the specified user and recommendation approach based on heat bidirectional transfer is proposed. Compared with the state-of-the-art approaches based on bipartite network, experiments on two benchmark data sets, Movielens and Netflix, demonstrate that our algorithm has better performance on accuracy, diversity and novelty. Moreover, this method does better in exploiting long-tail commodities and cold-start problem.
Liquid-Infused Smooth Surface for Improved Condensation Heat Transfer.
Tsuchiya, Hirotaka; Tenjimbayashi, Mizuki; Moriya, Takeo; Yoshikawa, Ryohei; Sasaki, Kaichi; Togasawa, Ryo; Yamazaki, Taku; Manabe, Kengo; Shiratori, Seimei
2017-09-12
Control of vapor condensation properties is a promising approach to manage a crucial part of energy infrastructure conditions. Heat transfer by vapor condensation on superhydrophobic coatings has garnered attention, because dropwise condensation on superhydrophobic surfaces with rough structures leads to favorable heat-transfer performance. However, pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation of superhydrophobic surfaces limit their heat-transfer increase. Recently, slippery liquid-infused surfaces (SLIPS) have been investigated, because of their high water sliding ability and surface smoothness originating from the liquid layer. However, even on SLIPS, condensed water droplets are eventually pinned to degrade their heat-transfer properties after extended use, because the rough base layer is exposed as infused liquid is lost. Herein, we report a liquid-infused smooth surface named "SPLASH" (surface with π electron interaction liquid adsorption, smoothness, and hydrophobicity) to overcome the problems derived from the rough structures in previous approaches to obtain stable, high heat-transfer performance. The SPLASH displayed a maximum condensation heat-transfer coefficient that was 175% higher than that of an uncoated substrate. The SPLASH also showed higher heat-transfer performance and more stable dropwise condensation than superhydrophobic surfaces and SLIPS from the viewpoints of condensed water droplet mobility and the thermodynamic energy barrier for nucleation. The effects of liquid-infused surface roughness and liquid viscosity on condensation heat transfer were investigated to compare heat-transfer performance. This research will aid industrial applications using vapor condensation.
An introduction to heat transfer principles and calculations
Ede, A J; Ower, E
1967-01-01
An Introduction to Heat Transfer Principles and Calculations is an introductory text to the principles and calculations of heat transfer. The theory underlying heat transfer is described, and the principal results and formulae are presented. Available techniques for obtaining rapid, approximate solutions to complicated problems are also considered. This book is comprised of 12 chapters and begins with a brief account of some of the concepts, methods, nomenclature, and other relevant information about heat transfer. The reader is then introduced to radiation, conduction, convection, and boiling
Influence of wall properties on peristaltic transport with heat transfer
Radhakrishnamacharya, G.; Srinivasulu, Ch.
2007-07-01
The effect of elasticity of the flexible walls on peristaltic transport of an incompressible viscous fluid, with heat transfer, in a two dimensional uniform channel has been investigated under long wave length approximation. The perturbation solution has been obtained in terms of wall slope parameter and closed form expressions have been derived for velocity, temperature and heat transfer. The effects of elastic tension, damping and mass characterizing parameters on temperature and heat transfer have been studied. It is found that heat transfer increases with elastic tension and mass characterizing parameters. To cite this article: G. Radhakrishnamacharya, Ch. Srinivasulu, C. R. Mecanique 335 (2007).
Control of heat transfer in engine coolers by Lorentz forces
Karcher, C.; Kühndel, J.
2016-09-01
In engine coolers of off-highway vehicles convective heat transfer at the coolant side is a limiting factor of both efficiency and performance density of the cooler. Here, due to design restrictions, backwater areas and stagnation regions appear that are caused by flow deflections and cross-sectional expansions. As appropriate coolants, mixtures of water and glysantine are commonly used. Such coolants are characterized by their electrical conductivity of some S/m. This gives rise to control coolant flow and therefore convective heat transfer by means of Lorentz forces. These body forces are generated within the weakly conducting fluid by the interactions of an electrical current density and a localized magnetic field both of which being externally superimposed. In application this may be achieved by inserting electrodes in the cooler wall and a corresponding arrangement of permanent magnets. In this paper we perform numerical simulations of such magnetohydrodynamic flow in three model geometries that are frequently apparent in engine cooling applications: Carnot-Borda diffusor, 90° bend, and 180° bend. The simulations are carried out using the software package ANSYS Fluent. The present study demonstrates that, depending on the electromagnetic interaction parameter and the specific geometric arrangement of electrodes and magnetic field, Lorentz forces are suitable to break up eddy waters and separation zones and are thus significantly increasing convective heat transfer in these areas. Furthermore, the results show that due to the action of the Lorentz forces the hydraulic pressure losses can be reduced.
Convective heat transfer in engine coolers influenced by electromagnetic fields
Karcher, C.; Kühndel, J.
2017-08-01
In engine coolers of off-highway vehicles, convective heat transfer at the coolant side limits both efficiency and performance density of the apparatus. Here, due to restrictions in construction and design, backwater areas and stagnation regions cannot be avoided. Those unwanted changes in flow characteristics are mainly triggered by flow deflections and sudden cross-sectional expansions. In application, mixtures of water and glysantine are used as appropriate coolants. Such coolants typically show an electrical conductivity of a few S/m. Coolant flow and convective heat transfer can then be controlled using Lorentz forces. These body forces are generated within the conducting fluid by the interactions of an electrical current density and a localized magnetic field, both of which are externally superimposed. In future application, this could be achieved by inserting electrodes in the cooler wall and a corresponding arrangement of permanent magnets. In this paper we perform numerical simulations of such magnetohydrodynamic flow in three model geometries that frequently appear in engine cooling applications: Carnot-Borda diffusor, 90° bend, and 180° bend. The simulations are carried out using the software package ANSYS Fluent. The present study demonstrates that, depending on the electromagnetic interaction parameter and the specific geometric arrangement of electrodes and magnetic field, Lorentz forces are suitable to break up eddy waters and separation zones and thus significantly increase convective heat transfer in these areas. Furthermore, the results show that hydraulic pressure losses can be reduced due to the pumping action of the Lorentz forces.
Heat transfer mechanisms in poplar wood undergoing torrefaction
Sule, Idris O.; Mahmud, Shohel; Dutta, Animesh; Tasnim, Syeda Humaira
2016-03-01
Torrefaction, a thermal treatment process of biomass, has been proved to improve biomass combustible properties. Torrefaction is defined as a thermochemical process in reduced oxygen condition and at temperature range from 200 to 300 °C for shorter residence time whereby energy yield is maximized, can be a bridging technology that can lead the conventional system (e.g. coal-fired plants) towards a sustainable energy system. In efforts to develop a commercial operable torrefaction reactor, the present study examines the minimum input condition at which biomass is torrefied and explores the heat transfer mechanisms during torrefaction in poplar wood samples. The heat transfer through the wood sample is numerically modeled and analyzed. Each poplar wood is torrefied at temperature of 250, 270, and 300 °C. The experimental study shows that the 270 °C-treatment can be deduced as the optimal input condition for torrefaction of poplar wood. A good understanding of heat transfer mechanisms can facilitate the upscaling and downscaling of torrefaction process equipment to fit the feedstock input criteria and can help to develop treatment input specifications that can maximize process efficiency.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Energy Technology Data Exchange (ETDEWEB)
Phillips, Benjamin A. (Benton Harbor, MI); Zawacki, Thomas S. (St. Joseph, MI); Marsala, Joseph (Glen Ellyn, IL)
1994-11-29
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Energy Technology Data Exchange (ETDEWEB)
Phillips, B.A.; Zawacki, T.S.; Marsala, J.
1994-11-29
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. 13 figures.
HEAT AND MASS TRANSFER. VOLUME 2, 1968 (COLLECTION OF ARTICLES),
are quite thoroughly investigated. Also treated are such problems as internal heat and mass transfer during filtration of gases through a porous...boundary layer of a multi-component gas, critical heat fluxes during the boiling of organic heat carriers, the intensification of heat and mass ... transfer , entropy during the melting of polymers, the thermodynamics of plasma flows, process of sublimation by various methods of energy supply, and others
Bubble Impingement and the Mechanisms of Heat Transfer
Robinson, Anthony; ALBADAWI, ABDULALEEM; MURRAY, DARINA
2014-01-01
PUBLISHED Heat transfer augmentation resulting from the effects of two phase flow can play a significant role in convective cooling applications. To date, the interaction between a rising gas bubble impinging on a heated horizontal surface has received limited attention. Available research has focused on bubble dynamics and the associated heat transfer has not been reported. To address this, this study investigates the effect of a single bubble impinging on a heated horizontal surface. Loc...
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Energy Technology Data Exchange (ETDEWEB)
Phillips, B.A.; Zawacki, T.S.
1996-12-03
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium. 7 figs.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Energy Technology Data Exchange (ETDEWEB)
Phillips, Benjamin A. (Benton Harbor, MI); Zawacki, Thomas S. (St. Joseph, MI)
1996-12-03
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium.
Thermal performance analysis for heat exchangers having a variable overall heat transfer coefficient
Conklin, J. C.; Granryd, E.
The classic, conventional analysis for the thermal performance of heat exchangers is based on three assumptions: constant fluid flow rate, constant specific heat fluids, and constant overall heat transfer coefficient. Our analysis describes a general approach for analyzing the thermal performance of heat exchangers in which the overall heat transfer coefficient varies as a function of enthalpy, with the other two basic assumptions of constant mass flow rates and constant specific heats unchanged. Many heat exchangers have an overall heat transfer coefficient that is not constant. The conventional heat exchanger thermal performance analysis is correct as long as a true, area-weighted mean value is used. In many applications, however, fluids undergo a change in phase, and the heat transfer coefficient is a function of the local quality or enthalpy; hence, the true, area-weighted, mean heat transfer coefficient will be a function of the heat flux distribution. Examples are presented that illustrate the variation in overall heat transfer coefficient for an evaporation process. We present a general method for computing a true, area-weighted mean overall heat transfer coefficient that permits use of a local overall heat transfer coefficient that is an arbitrary function of enthalpy. This method allows a simple yet accurate analysis of the effects of a variable overall heat transfer coefficient to be made without the use of a large mainframe computer. We then investigate: (1) linear variation of local overall heat transfer coefficient with respect to enthalpy; and (2) two heat transfer correlations applicable to flow-boiling inside a tube.
Optimization of heat saving in buildings using unsteady heat transfer model
Directory of Open Access Journals (Sweden)
Dedinec Aleksandra
2015-01-01
Full Text Available Reducing the energy consumption growth rate is increasingly becoming one of the main challenges for ensuring sustainable development, particularly in the buildings as the largest end-use sector in many countries. Along this line, the aim of this paper is to analyse the possibilities for energy savings in the construction of new buildings and reconstruction of the existing ones developing a tool that, in terms of the available heating technologies and insulation, provides answer to the problem of optimal cost effective energy consumption. The tool is composed of an unsteady heat transfer model which is incorporated into a cost-effective energy saving optimization. The unsteady heat transfer model uses annual hourly meteorological data, chosen as typical for the last ten-year period, as well as thermo physical features of the layers of the building walls. The model is tested for the typical conditions in the city of Skopje, Macedonia. The results show that the most cost effective heating technology for the given conditions is the wood fired stove, followed by the inverter air-conditioner. The centralized district heating and the pellet fired stoves are the next options. The least cost effective option is the panel that uses electricity. In this paper, the optimal insulation thickness is presented for each type of heating technology.
Heat transfer enhancement using tip and junction vortices
Gentry, Mark Cecil
1998-10-01
Single-phase convective heat transfer can be enhanced by modifying the heat transfer surface to passively generate streamwise vortices. The swirling flow of the vortices modifies the temperature field, thinning the thermal boundary layer and increasing surface convection. Tip vortices generated by delta wings and junction vortices generated by hemispherical protuberances were studied in laminar flat-plate and developing channel flows. Local and average convective measurements were obtained, and the structure of the vortices was studied using quantitative flow visualization and vortex strength measurements. The pressure drop penalty associated with the heat transfer enhancement was also investigated. Tip vortices generated by delta wings enhanced local convection by as much as 300% over a flat-plate boundary layer flow. Vortex strength increased with Reynolds number based on chord length, wing aspect ratio, and wing angle of attack. As the vortices were advected downstream, they decayed because of viscous interactions. In the developing channel flow, tip vortices produced a significant local heat transfer enhancement on both sides of the channel. The largest spatially averaged heat transfer enhancement was 55%; it was accompanied by a 100% increase in the pressure drop relative to the same channel flow with no delta-wing vortex generator. Junction vortices created by hemispherical surface protuberances provided local heat transfer enhancements as large as 250%. Vortex strength increased with an increasing ratio of hemisphere radius to local boundary layer thickness on a flat plate. In the developing channel flows, heat transfer enhancements were observed on both sides of the channel. The largest spatially averaged heat transfer enhancement was 50%; it was accompanied by a 90% pressure drop penalty relative to the same channel flow with no hemispherical vortex generator. This research is important in compact heat exchanger design. Enhancing heat transfer can lead to
Double tube heat exchanger with novel enhancement: part II—single phase convective heat transfer
Tiruselvam, R.; Chin, W. M.; Raghavan, Vijay R.
2012-08-01
The study is conducted to evaluate the heat transfer characteristics of two new and versatile enhancement configurations in a double tube heat exchanger annulus. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Heat transfer coefficients are determined by the Wilson Plot technique in laminar and turbulent flow and correlations are proposed for Nusselt numbers. Comparisons are then made between heat transfer and flow friction.
Turbulent Heat Transfer Behavior of Nanofluid in a Circular Tube Heated under Constant Heat Flux
Directory of Open Access Journals (Sweden)
Shuichi Torii
2010-01-01
Full Text Available The aim of the present study is to disclose the forced convective heat transport phenomenon of nanofluids inside a horizontal circular tube subject to a constant and uniform heat flux at the wall. Consideration is given to the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity, viscosity, and pressure loss in the turbulent flow region. It is found that (i heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with the increase of the particle volume fraction, (ii its augmentation is affected by three different nanofluids employed here, and (iii the presence of particles produces adverse effects on viscosity and pressure loss that also increases with the particle volume fraction.
Directory of Open Access Journals (Sweden)
Qiming Men
2014-01-01
Full Text Available Aiming at the heat transfer calculation of the Passive Residual Heat Removal Heat Exchanger (PRHR HX, experiments on the heat transfer of C-shaped tube immerged in a water tank were performed. Comparisons of different correlation in literatures with the experimental data were carried out. It can be concluded that the Dittus-Boelter correlation provides a best-estimate fit with the experimental results. The average error is about 0.35%. For the tube outside, the McAdams correlations for both horizontal and vertical regions are best-estimated. The average errors are about 0.55% for horizontal region and about 3.28% for vertical region. The tank mixing characteristics were also investigated in present work. It can be concluded that the tank fluid rose gradually which leads to a thermal stratification phenomenon.
Non intrusive measurement of the convective heat transfer coefficient
Energy Technology Data Exchange (ETDEWEB)
Rebay, M.; Mebarki, G.; Padet, J. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Arfaoui, A. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM; Maad, B.R. [Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM
2010-07-01
The efficiency of cooling methods in thermal systems such as radiators and heat exchangers must be improved in order to enhance performance. The evaluation of the heat transfer coefficients between a solid and a fluid is necessary for the control and the dimensioning of thermal systems. In this study, the pulsed photothermal method was used to measure the convective heat transfer coefficient on a solid-fluid interface, notably between an air flow and a heated slab mounted on a PVC flat plate. This configuration simulated the electronic air-cooling inside enclosures and racks. The influence of the deflector's inclination angle on the enhancement of heat transfer was investigated using 2 newly developed identification models. The first model was based on a constant heat transfer coefficient during the pulsed experiment, while the second, improved model was based on a variable heat transfer coefficient. The heat transfer coefficient was deduced from the evolution of the transient temperature induced by a sudden deposit of a luminous energy on the front face of the slab. Temperature evolutions were derived by infrared thermography, a camera for cartography and a detector for precise measurement in specific locations. The results show the improvement of measurement accuracies when using a model that considers the temporal evolution of the convective heat transfer coefficient. The deflection of air flow on the upper surface of the heated slab demonstrated better cooling of the slab by the deflection of air flow. 11 refs., 1 tab., 8 figs.
Viscous flow and heat transfer over an unsteady stretching surface
Directory of Open Access Journals (Sweden)
Ene Remus-Daniel
2016-01-01
Full Text Available In this paper we have studied the flow and heat transfer of a horizontal sheet in a viscous fluid. The stretching rate and temperature of the sheet vary with time. The governing equations for momentum and thermal energy are reduced to ordinary differential equations by means of similarity transformation. These equations are solved approximately by means of the Optimal Homotopy Asymptotic Method (OHAM which provides us with a convenient way to control the convergence of approximation solutions and adjust convergence rigorously when necessary. Some examples are given and the results obtained reveal that the proposed method is effective and easy to use.
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1996-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
THE ELECTRONIC COURSE OF HEAT AND MASS TRANSFER
Directory of Open Access Journals (Sweden)
Alexander P. Solodov
2013-01-01
Full Text Available The Electronic course of heat and mass transfer in power engineering is presented containing the full Electronic book as the structured hypertext document, the full set of Mathcad-documents with the whole set of educative computer models of heat and mass transfer, the computer labs, and selected educational presentations.
Computational heat transfer analysis and combined ANN–GA ...
Indian Academy of Sciences (India)
In the present work, the heat transfer characteristics of hollow cylindrical pin fin array on a vertical rectangular base plate is studied using commercial CFD code ... The analysis using the numerical simulation and neural network shows that the hollow fins provide an increased heat transfer and a weight reduction of about ...
Heat transfer and thermal stress analysis in grooved tubes
Indian Academy of Sciences (India)
Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...
On local fractional Volterra integral equations in fractal heat transfer
Directory of Open Access Journals (Sweden)
Wu Zhong-Hua
2016-01-01
Full Text Available In the article, the fractal heat-transfer models are described by the local fractional integral equations. The local fractional linear and nonlinear Volterra integral equations are employed to present the heat transfer problems in fractal media. The local fractional integral equations are derived from the Fourier law in fractal media.
Improving Heat Transfer Performance of Printed Circuit Boards
Schatzel, Donald V.
2009-01-01
This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.
The porosity in a fluidized bed heat transfer model
Visser, G; Visser, G.; Valk, M.
1993-01-01
A mathematical model of heat transfer between a fluidized bed and an immersed surface and a model of gas flow and porosity, both recently published, were combined and further modified in the area of low velocities where the particle convective component of heat transfer is low or neglectable.
Analytical Evalution of Heat Transfer Conductivity with Variable Properties
DEFF Research Database (Denmark)
Rahimi, Masoume; Hosseini, Mohammad Javad; Barari, Amin
2011-01-01
The homotopy analysis method (HAM) as a new technique which is powerful and easy-to-use, is applied to solve heat transfer problems. In this paper, we use HAM for heat transfer conductivity equation with variable properties which may contain highly nonlinear terms. The obtained results are also...
Experimental Investigation of Heat Transfer during Night-Time Ventilation
DEFF Research Database (Denmark)
Artmann, Nikolai; Jensen, Rasmus Lund; Manz, H.
2010-01-01
is the heat transfer at the internal room surfaces. Increased convection is expected due to high air flow rates and the possibility of a cold air jet flowing along the ceiling, but the magnitude of these effects is hard to predict. In order to improve the predictability, heat transfer during night...
Numerical simulation of heat transfer in a micro channel heat sinks using nanofluids
Farsad, E.; Abbasi, S. P.; Zabihi, M. S.; Sabbaghzadeh, J.
2011-04-01
In this study, a numerical simulation of copper microchannel heatsink (MCHS) using nanofluids as coolants is presented. The nanofluid is a mixture of pure water and nanoscale metallic or nonmetallic particles with various volume fractions. Also, the effects of various volume fractions, volumetric flow rate and various materials of nanoparticles on the performance of MCHS have been developed. A three-dimensional computational fluid dynamics model was developed using the commercial software package FLUENT, to investigate the conjugate fluid flow and heat transfer phenomena in micro channel heatsinks. The results show that the cooling performance of a microchannel heat sink with water based nanofluid containing Al2O3 (vol 8%) is enhanced by about 4.5% compared with micro channel heatsink with pure water. Nanofluids reduce both the thermal resistance and the temperature difference between the top (heated) surface of the MCHS and inlet nanofluid compared with that pure water. The cooling performance of a micro channel heat sink with metal nanofluids improves compared with that of a micro channel heat sink with oxide metal nanofluids because the thermal conductivity of metal nanofluid is higher than oxide metal nanofluids. Micro channel heat sinks with nanofluids are expected to be good candidates as the next generation cooling devices for removing ultra high heat flux.
Heat transfer in open-cell metal foams
Energy Technology Data Exchange (ETDEWEB)
Lu, T.J.; Ashby, M.F. [Univ. of Cambridge (United Kingdom). Dept. of Engineering; Stone, H.A. [Harvard Univ., Cambridge, MA (United States). Div. of Engineering and Applied Sciences
1998-06-12
The paper explores the use of open-celled metal foams as compact heat exchangers, exploiting convective cooling. An analytical model is developed for model foams with simple cubic unit cells consisting of heated slender cylinders, based on existing heat transfer data on convective crossflow through cylinder banks. A foam-filled channel having constant wall temperatures is analyzed to obtain the temperature distribution inside the channel as a function of foam density, cell size and other pertinent heat transfer parameters. Two characteristic length scales of importance to the problem are discussed: the minimum channel length required for heating the fluid to its goal temperature and the thermal entry length beyond which the transfer of heat between fluid and channel wall assumes a constant coefficient. The overall heat transfer coefficient of the heat exchanging system is calculated, and the pressure drop experienced by the fluid flow obtained. The present model perhaps oversimplifies the calculation of transport in a metal foam consisting of non-circular, possibly sharp-edged ligaments, and so likely leads to overestimates. Nevertheless the trends of heat transfer predicted by the model (for dependence on foam relative density, duct geometries, fluid velocity, etc.) are expected to be valid for a wide range of open-cell foams and are in reasonable agreement with available experimental data on aluminum foams (Bastawros and Evans, Proceedings Symposium Application of Heat Transfer in Microelectronics Packaging, IMECE, Dallas, TX, 1997).
Heat transfer through metal-graphene interfaces
Directory of Open Access Journals (Sweden)
Tomasz Wejrzanowski
2015-07-01
Full Text Available The paper presents the results of Molecular Dynamics (MD studies of the thermal properties of Cu and Ag composites with single- (SLG and multi-layered (MLG graphene. We show that the thermal boundary conductance (TBC of the metal-graphene interface drops significantly for the systems containing more than one layer of graphene. It is also concluded that the TBC for a single graphene layer is significantly higher for silver than for copper. For both systems, however, we found that the interface is a barrier for heat transfer with the thermal conductance being at least two orders of magnitude lower than for metal. Moreover, we found that the TBC decreases with an increase in the number of graphene layers. The interfacial effect becomes negligible for a thickness bigger than two graphene layers. Above this thickness the thermal conductivity of the region of multilayered graphene is not influenced by the interface and becomes similar to that of graphite. The results are compared with available experimental data and discussed in terms of the rules for designing composites of a high thermal conductivity.
Fem Formulation of Coupled Partial Differential Equations for Heat Transfer
Ameer Ahamad, N.; Soudagar, Manzoor Elahi M.; Kamangar, Sarfaraz; Anjum Badruddin, Irfan
2017-08-01
Heat Transfer in any field plays an important role for transfer of energy from one region to another region. The heat transfer in porous medium can be simulated with the help of two partial differential equations. These equations need an alternate and relatively easy method due to complexity of the phenomenon involved. This article is dedicated to discuss the finite element formulation of heat transfer in porous medium in Cartesian coordinates. A triangular element is considered to discretize the governing partial differential equations and matrix equations are developed for 3 nodes of element. Iterative approach is used for the two sets of matrix equations involved representing two partial differential equations.
Second Law Analysis in Convective Heat and Mass Transfer
Directory of Open Access Journals (Sweden)
A. Ben Brahim
2006-02-01
Full Text Available This paper reports the numerical determination of the entropy generation due to heat transfer, mass transfer and fluid friction in steady state for laminar double diffusive convection, in an inclined enclosure with heat and mass diffusive walls, by solving numerically the mass, momentum, species conservation and energy balance equations, using a Control Volume Finite-Element Method. The influences of the inclination angle, the thermal Grashof number and the buoyancy ratio on total entropy generation were investigated. The irreversibilities localization due to heat transfer, mass transfer and fluid friction is discussed for three inclination angles at a fixed thermal Grashof number.
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo;
2012-01-01
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
Experimental study of heat transfer to falling liquid films
Fagerholm, N. E.; Kivioja, K.; Ghazanfari, A. R.; Jaervinen, E.
1985-12-01
This project was initiated in order to obtain more knowledge about thermal design of falling film heat exchangers and to find methods to improve heat transfer in film flow. A short literature survey of film flow characteristics and heat transfer is presented. An experimental apparatus designed and built for studying falling film evaporation is described. The first experiments were made with smooth Cu tube 25/22 mm and refrigerant R114 as evaporating liquid. A significant amount of droplet entrainment was observed during the tests. The measured average heat transfer coefficient varied from 1000 to 1800 W/m K when Re=1300 to 11000 respectively and when the transfer mode is surface evaporation. This could be predicted accurately with the experimental correlation of Chun and Seban. When nucleate boiling is dominant the heat transfer could be predicted well with pool boiling correlation of VDI-84.
Non-Uniform Heat Transfer in Thermal Regenerators
DEFF Research Database (Denmark)
Jensen, Jesper Buch
This thesis presents investigations on the heat transfer in complex heat ex- changers in general and in regenerative heat exchangers (regenerators) in par- ticular. The motivation for this work is a result of inconsistencies obeserved in the results from a series of experiments on active magnetic...... regenerators (AMRs) with parallel plates. The results suggest that random variations in the regenerator geometries causes maldistributed fluid flow inside the regener- ators, which affects the regenerator performance. In order to study the heat transfer processes in regenerators with non-uniform geometries......, a numerical model, which simulates a single-blow operation in a parallel-plate regenerator, was developed and used to model the heat transfer under various conditions. In addition to the modeling of the heat transfer, a series of experiments on passive regenerators with non-uniform, but precisely controlled...
Mathematical Model of Moving Heat-Transfer Agents
Directory of Open Access Journals (Sweden)
R. I. Yesman
2010-01-01
Full Text Available A mathematical model of moving heat-transfer agents which is applied in power systems and plants has been developed in the paper. A paper presents the mathematical model as a closed system of differential convective heat-transfer equations that includes a continuity equation, a motion equation, an energy equation.Various variants of boundary conditions on the surfaces of calculation flow and heat exchange zone are considered in the paper.
Dynamic measurement of near-field radiative heat transfer
Lang, S.; G. Sharma; Molesky, S.; Kränzien, P. U.; Jalas, T.; Z. Jacob; Petrov, A. Yu.; Eich, M.
2017-01-01
Super-Planckian near-field radiative heat transfer allows effective heat transfer between a hot and a cold body to increase beyond the limits long known for black bodies. Until present, experimental techniques to measure the radiative heat flow relied on steady-state systems. Here, we present a dynamic measurement approach based on the transient plane source technique, which extracts thermal properties from a temperature transient caused by a step input power function. Using this versatile me...
Heat transfer to the adsorbent in solar adsorption cooling device
Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin
2014-08-01
The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.
Droplet Evaporator For High-Capacity Heat Transfer
Valenzuela, Javier A.
1993-01-01
Proposed heat-exchange scheme boosts heat transfer per unit area. Key component is generator that fires uniform size droplets of subcooled liquid at hot plate. On impact, droplets spread out and evaporate almost instantly, removing heat from plate. In practice, many generator nozzles arrayed over evaporator plate.
The heat transfer mechanisms in fluidized beds; Laemmoensiirtomekanismit leijukerroksessa
Energy Technology Data Exchange (ETDEWEB)
Fogelholm, C.J.; Blomster, A.M.; Kojola, H. [Helsinki Univ. of Technology, Espoo (Finland)
1996-12-01
The goal of the research project is to improve the accuracy of the heat transfer correlation in circulating fluidized beds and to define how the heat transfer is distributed in radiation and convection in the different parts of the fluidized bed. This will be carried out by studying the behaviour and heat transfer of the fluidized bed in the boundary layer near the wall. The total and radiative heat transfer as well as the particle concentration will be measured. Based on the data a correlation will be created. Two different measurement systems are used. The particle concentration is measured by a image-analysis system. A video camera and a Super VHS recorder are used to capture live images from the bed. The images are digitized and stored on a PC. The system has been used in previous research projects at our laboratory. In earlier projects all measurements have been carried out in cold environments. In this project the system will be modified for hot environments. The radiative heat transfer is measured by a radiative heat transfer probe connected to a PC via an A/D converter. The probe consists of a heat flow detector which is isolated from the bed by a sapphire window so that only the radiative part of the heat transfer is detected. The probe will be calibrated in a black body oven so that the effect of the conduction and the sapphire window can be separated. (author)
Energy Technology Data Exchange (ETDEWEB)
Park, Chun Dong; Lee, Dong Hyun; Park, Byung-Sik; Choi, Jaejoon [Korea Institute of Energy Research (KIER), Daejeon (Korea, Republic of)
2017-02-15
In this study, the flow and heat transfer characteristics of the finned annular passage were investigated numerically. The annular passage simulates co-axial geothermal heat exchanger, and fins are installed on its inner wall to reduce heat loss from the production passage (annulus) to injection passage (inner pipe). A commercial CFD program, Ansys Fluent, was used with SST k-ω turbulence model. The effects of the geometric parameters of the fin on the inner tube were analyzed under the periodic boundary condition. The result indicated that most parameters had a tendency to increase with an increase in the height and angle of the fin. However, it was confirmed that the Nusselt number of the inner tube on the coaxial 15, 5, 0.3 was lower than that of the smooth tube. Additionally, the Nusselt number of the inner tube exhibited a tendency of decreasing with a decrease in the spacing in Coaxial 15, S{sub f}, 0.3.
Directory of Open Access Journals (Sweden)
Kumar Hitesh
2009-01-01
Full Text Available The boundary layer steady flow and heat transfer of a viscous incompressible fluid due to a stretching plate with viscous dissipation effect in the presence of a transverse magnetic field is studied. The equations of motion and heat transfer are reduced to non-linear ordinary differential equations and the exact solutions are obtained using properties of confluent hypergeometric function. It is assumed that the prescribed heat flux at the stretching porous wall varies as the square of the distance from origin. The effects of the various parameters entering into the problem on the velocity field and temperature distribution are discussed.
Energy Technology Data Exchange (ETDEWEB)
Tafreshi, H. Vahedi; Ercan, E.; Pourdeyhimi, B. [North Carolina State University, Nonwovens Cooperative Research Center, Raleigh, NC (United States)
2006-07-15
In this note, the evaporation rate from a vertical wet fabric sheet is calculated using a free convection heat transfer correlation. Chilton-Colburn analogy is used to derive a mass transfer correlation from a heat transfer correlation proposed by Churchill and Chu for free convection from a vertical isothermal plate. The mass transfer rate obtained from this expression has shown excellent agreement with experimental data. (orig.)
Modeling the film condensate fluid dynamics and heat transfer within the bubble membrane radiator
Energy Technology Data Exchange (ETDEWEB)
Pauley, K.A. [Pacific Northwest Lab., Richland, WA (United States); Thornborrow, J.O. [National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center
1992-01-01
An analytical model of the fluid dynamics and heat transfer characteristics of the condensate within the rotating Bubble Membrane Radiator is developed. The steady-state, three-dimensional heat transfer and flow equations were reduced to a set of third-order ordinary differential equations by employing similarity transformation techniques. These equations are then solved for the radial, axial, and angular flow distributions in the film condensate. Pressure, temperature, heat transfer, film thickness and mass flow rate distributions are also calculated. The analytical model is the basis of the SCRABBLE code which is used both as a zero-g design tool and a ground-test bed analyzer.
Heat transfer in flow past a continuously moving porous flat plate with heat flux
Digital Repository Service at National Institute of Oceanography (India)
Murty, T.V.R.; Sarma, Y.V.B.
The analysis of the heat transfer in flow past a continuously moving semi-infinite plate in the presence of suction/ injection with heat flux has been presented. Similarity solutions have been derived and the resulting equations are integrated...
Heat and mass transfer analysis in unsaturated ground soils around the buried heating pipe
National Research Council Canada - National Science Library
JAHANGIR, Mohammad Hossein
2015-01-01
.... the pipe-soil interface. Thus, the model takes into account coupled heat and moisture transfer in the unsaturated soil, allowing for more accurate predictions of the soil thermal response to the heat fluxes induced...
Heat transfer burnout of Mark VIII fuel
Energy Technology Data Exchange (ETDEWEB)
Bernath, L.
1956-08-01
The operating conditions to which the special Mark VIII quatrefoils will be exposed during the proposed piloting program have been compared with the conditions required to cause burnout, using an established method of calculating these conditions. The results of this comparison permit the following conclusions to be drawn: (1) With normal flow of coolant through the special elements the heat flux to be encountered in the R-8 cycle (1400 MW) will be 70% or that required to cause burnout (30% margin from burnout). (2) With a reduction of coolant flow to 82% of normal through one tube of a special element, burnout of that fuel column is possible in the R-8 cycle. (3) In the R-6 cycle (1280 MW), the margin from burnout in the special Mark VIII quatrefoils is 42% with full flow and 20% with the above reduced coolant flow. A similar comparison of operating conditions predicted for the L-3 cycle (full Mark VIII charge) shows that, even at the highest power level (1250 MW), the margin from burnout is greater than 55% with normal flow and 40% with reduced flow.
Nucleate pool boiling heat transfer in aqueous surfactant solutions
Wasekar, Vivek Mahadeorao
Saturated, nucleate pool boiling in aqueous surfactant solutions is investigated experimentally. Also, the role of Marangoni convection, driven both by temperature and surfactant concentration gradients at the vapor-liquid interface of a nucleating bubble is computationally explored. Experimental measurements of dynamic and equilibrium sigma using the maximum bubble pressure method indicate dynamic sigma to be higher than the corresponding equilibrium value, both at room and elevated temperatures. Also, nonionic surfactants (Triton X-100, Triton X-305) show larger sigma depression than anionic surfactants (SDS, SLES), and a normalized representation of their dynamic adsorption isotherms is shown to be helpful in generalizing the surfactant effectiveness to reduce surface tension. The dynamic sigma has a primary role in the modification of bubble dynamics and associated heat transfer, and is dictated by the adsorption kinetics of the surfactant molecules at boiling temperatures. In general, an enhancement in heat transfer is observed, which is characterized by an early incipience and an optimum boiling performance at or around the critical micelle concentration of the surfactant. The optimum performances, typically in the fully developed boiling regime ( q''w > 100 kW/m2), show a reverse trend with respect to surfactant molecular weights M, i.e., higher molecular weight additives promote lower enhancement. Normalized boiling performance using the respective solution's dynamic sigma correlates heat transfer coefficient by M-0.5 for anionics and M 0 for nonionics. This has been shown to be brought about by the surfactant concentration and its interfacial activity in a concentration sublayer around the growing vapor bubble, which governs the bubble growth behavior through the mechanism of dynamic sigma. The ionic nature of the surfactant influences the thickness and molecular makeup of the enveloping sublayer, thereby affecting the bubble dynamics and boiling heat
The influence of longitudinal vibrations on the heat transfer performance of inclined heat pipes
National Research Council Canada - National Science Library
Chen, Rong-Horng; Kuo, LW; Lai, Chi-Ming
2015-01-01
This study focused on investigating the influence of longitudinal vibrations, the condensation section temperature, and the inclination angles on the heat transfer performance of grooved cylindrical...
Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity
Tassone, A.; Nobili, M.; Caruso, G.
2017-11-01
The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.
A study of heat-transfer processes in a countercurrent cyclone heat exchanger
Energy Technology Data Exchange (ETDEWEB)
M.G. Abuov; P.A. Kovgan [TOO Gornoe Byuro (Mining Bureau), Alma Aty (Kazakhstan)
2009-07-01
Heat-transfer processes in a countercurrent cyclone heat exchanger are investigated on a pilot installation. Volumetric coefficients of heat transfer from gases to a flow of solid particles are determined during operation with tangentially swirled flow of gas suspension, separation of solid particles on the heat-exchanger walls, and deceleration of flue gas flows as they collide with the charge mixture fed to the apparatus.
Radiative heat transfer in low-dimensional systems -- microscopic mode
Woods, Lilia; Phan, Anh; Drosdoff, David
2013-03-01
Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.
Estimating local heat transfer coefficients from thin wall temperature measurements
Gazizov, I. M.; Davletshin, I. A.; Paereliy, A. A.
2017-09-01
An approach to experimental estimation of local heat transfer coefficient on a plane wall has been described. The approach is based on measurements of heat-transfer fluid and wall temperatures during some certain time of wall cooling. The wall was a thin plate, a printed circuit board, made of composite epoxy material covered with a copper layer. The temperature field can be considered uniform across the plate thickness when heat transfer is moderate and thermal resistance of the plate in transversal direction is low. This significantly simplifies the heat balance written for the wall sections that is used to estimate the heat transfer coefficient. The copper layer on the plate etched to form a single strip acted as resistance thermometers that measured the local temperature of the wall.
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.
de Jong, J A; Wijnant, Y H; de Boer, A
2014-03-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.
Radiation Heat Transfer Procedures for Space-Related Applications
Chai, John C.
2000-01-01
Over the last contract year, a numerical procedure for combined conduction-radiation heat transfer using unstructured grids has been developed. As a result of this research, one paper has been published in the Numerical Heat Transfer Journal. One paper has been accepted for presentation at the International Center for Heat and Mass Transfer's International Symposium on Computational Heat Transfer to be held in Australia next year. A journal paper is under review by my NASA's contact. A conference paper for the ASME National Heat Transfer conference is under preparation. In summary, a total of four (4) papers (two journal and two conference) have been published, accepted or are under preparation. There are two (2) to three (3) more papers to be written for the project. In addition to the above publications, one book chapter, one journal paper and six conference papers have been published as a result of this project. Over the last contract year, the research project resulted in one Ph.D. thesis and partially supported another Ph.D. student. My NASA contact and myself have formulated radiation heat transfer procedures for materials with different indices of refraction and for combined conduction-radiation heat transfer. We are trying to find other applications for the procedures developed under this grant.
Cryogenic apparatus for study of near-field heat transfer.
Kralik, T; Hanzelka, P; Musilova, V; Srnka, A; Zobac, M
2011-05-01
For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10(0) to 10(3) μm. The heat transferred from the hot (10 - 100 K) to the cold sample (∼5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within ∼2 nW∕cm(2) and ∼30 μW∕cm(2) is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer.
Enhancing Convective Heat Transfer over a Surrogate Photovoltaic Panel
Fouladi, Fama
This research is particularly focused on studying heat transfer enhancement of a photovoltaic (PV) panel by putting an obstacle at the panel's windward edge. The heat transfer enhancement is performed by disturbing the airflow over the surface and increasing the heat and momentum transfer. Different objects such as triangular, square, rectangular, and discrete rectangular ribs and partial grids were applied at the leading edge of a surrogate PV panel and flow and the heat transfer of the panel are investigated experimentally. This approach was selected to expand understanding of effect of these different objects on the flow and turbulence structures over a flat surface by analyzing the flow comprehensively. It is observed that, a transverse object at the plate's leading edge would cause some flow blockage in the streamwise direction, but at the same time creates some velocity in the normal and cross stream directions. In addition to that, the obstacle generates some turbulence over the surface which persists for a long downstream distance. Also, among all studied objects, discrete rectangular ribs demonstrate the highest heat transfer rate enhancement (maximum Nu/Nu0 of 1.5). However, ribs with larger gap ratios are observed to be more effective at enhancing the heat transfer augmentation at closer distances to the rib, while at larger downstream distances from the rib, discrete ribs with smaller gap ratios are more effective. Furthermore, this work attempted to recognize the most influential flow parameters on the heat transfer enhancement of the surface. It is seen that the flow structure over a surface downstream of an object (flow separation-reattachment behaviour) has a significant effect on the heat transfer enhancement trend. Also, turbulence intensities are the most dominant parameters in enhancing the heat transfer rate from the surface; however, flow velocity (mostly normal velocity) is also an important factor.
A Compact Remote Heat Transfer Device for Space Cryocoolers
Yan, T.; Zhao, Y.; Liang, T.
In this paper a compact remote heat transfer device (CRHD) for cryocoolers is proposed. This device is especially attractive in cases where cryocoolers are not easy to set near the heat source, generally the infrared sensor. The CRHD is designed on basis of the concept of loop heat pipes, while the primary evaporator is located near the cryocooler cold head and a simple tube-in-tube secondary evaporator is remotely located and thermally connected with the heat source for cooling. With such a device a cooling power of 1 W is achieved across a heat transfer distance of about 2 m. The major problem of this device is the low heat transfer efficiency (1 W of net cooling power at the cost of about 7 W of cooling power from the cryocooler), and in the future a secondary wicked evaporator will be used instead of the tube-in-tube evaporator in order to improve the efficiency.
NANOFLUID PROPERTIES FOR FORCED CONVECTION HEAT TRANSFER: AN OVERVIEW
Directory of Open Access Journals (Sweden)
W.H.Azmi
2013-06-01
Full Text Available Nanoﬂuids offer a significant advantage over conventional heat transfer ﬂuids and consequently, they have attracted much attention in recent years. The engineered suspension of nano-sized particles in a base liquid alters the properties of these nanofluids. Many researchers have measured and modeled the thermal conductivity and viscosity of nanofluids. The estimation of forced convective heat transfer coefficients is done through experiments with either metal or nonmetal solid particles dispersed in water. Regression equations are developed for the determination of the thermal conductivity and viscosity of nanofluids. The parameters influencing the decrease in convection heat transfer, observed by certain investigators, is explained.
Process heat transfer principles, applications and rules of thumb
Serth, Robert W
2014-01-01
Process Heat Transfer is a reference on the design and implementation of industrial heat exchangers. It provides the background needed to understand and master the commercial software packages used by professional engineers in the design and analysis of heat exchangers. This book focuses on types of heat exchangers most widely used by industry: shell-and-tube exchangers (including condensers, reboilers and vaporizers), air-cooled heat exchangers and double-pipe (hairpin) exchangers. It provides a substantial introduction to the design of heat exchanger networks using pinch technology, the mos
Heat transfer and thermoregulation in the largemouth blackbass, Micropterus salmoides
Energy Technology Data Exchange (ETDEWEB)
Erskine, D. J.
1976-01-01
An energy budget equation, based on energy budget theory for terrestrial organisms, was developed to describe the heat energy exchange between a largemouth bass (Micropterus salmoides) and its aquatic environment. The energy budget equation indicated that convection and a combined conduction-convection process were major avenues of heat exchange for a fish. Solid aluminum castings were used to experimentally determine heat transfer coefficients for the largemouth bass at water velocities covering the free and forced convection ranges. Heat energy budget theory was applied to the casting data and the derived coefficients were used to characterize heat exchange between the bass and its aquatic habitat. The results indicate that direct transfer of heat from the body surface is the major mechanism of heat exchange for a fish.
Energy Technology Data Exchange (ETDEWEB)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.
1995-09-01
RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {+-}5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.
Scalable graphene coatings for enhanced condensation heat transfer.
Preston, Daniel J; Mafra, Daniela L; Miljkovic, Nenad; Kong, Jing; Wang, Evelyn N
2015-05-13
Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating to promote dropwise condensation of water in industrial conditions with the potential for scalable application via CVD.
Heat and mass transfer in frozen porous media
Loon, van W.
1991-01-01
In this thesis processes and parameters associated with heat and mass transfer in frozen porous media both on a theoretical and empirical basis are studied. To obtain the required measurements some existing measuring methods needed to be
Natural convective heat transfer from short inclined cylinders
Oosthuizen, Patrick H
2014-01-01
Natural Convective Heat Transfer from Short Inclined Cylinders examines a heat transfer situation of significant, practical importance not adequately dealt with in existing textbooks or in any widely available review papers. Specifically, the book introduces the reader to recent studies of natural convection from short cylinders mounted on a flat insulated base where there is an “exposed” upper surface. The authors considers the effects of the cylinder cross-sectional shape, the cylinder inclination angle, and the length-to-cross sectional size of the cylinder. Both numerical and experimental studies are discussed and correlation equations based on the results of these studies are reviewed. This book is ideal for professionals involved with thermal management and related systems, researchers, and graduate students in the field of natural convective heat transfer, instructors in graduate level courses in convective heat transfer.
Heat and Mass Transfer in an L Shaped Porous Medium
Salman Ahmed, N. J.; Azeem; Yunus Khan, T. M.
2017-08-01
This article is an extension to the heat transfer in L-shaped porous medium by including the mass diffusion. The heat and mass transfer in the porous domain is represented by three coupled partial differential equations representing the fluid movement, energy transport and mass transport. The equations are converted into algebraic form of equations by the application of finite element method that can be conveniently solved by matrix method. An iterative approach is adopted to solve the coupled equations by setting suitable convergence criterion. The results are discussed in terms of heat transfer characteristics influenced by physical parameters such as buoyancy ratio, Lewis number, Rayleigh number etc. It is found that these physical parameters have significant effect on heat and mass transfer behavior of L-shaped porous medium.
Convective heat and mass transfer in rotating disk systems
Shevchuk, Igor V
2009-01-01
The book describes results of investigations of a series of convective heat and mass transfer problems in rotating-disk systems. Methodology used included integral methods, self-similar and approximate analytical solutions, as well as CFD.
Exact solutions for the differential equations in fractal heat transfer
Directory of Open Access Journals (Sweden)
Yang Chun-Yu
2016-01-01
Full Text Available In this article we consider the boundary value problems for differential equations in fractal heat transfer. The exact solutions of non-differentiable type are obtained by using the local fractional differential transform method.
Heat radiation and transfer for point particles in arbitrary geometries
Asheichyk, Kiryl; Müller, Boris; Krüger, Matthias
2017-10-01
We study heat radiation and heat transfer for pointlike particles in a system of other objects. Starting from exact many-body expressions found from scattering theory and fluctuational electrodynamics, we find that transfer and radiation for point particles are given in terms of the Green's function of the system in the absence of the point particles. These general expressions contain no approximation for the surrounding objects. As an application, we compute the heat transfer between two point particles in the presence of a sphere of arbitrary size and show that the transfer is enhanced by several orders of magnitude through the presence of the sphere, depending on the materials. Furthermore, we compute the heat emission of a point particle in front of a planar mirror. Finally, we show that a particle placed inside a spherical mirror cavity does not radiate energy.
Near-field radiative heat transfer between metasurfaces
DEFF Research Database (Denmark)
Dai, Jin; Dyakov, Sergey A.; Bozhevolnyi, Sergey I.
2016-01-01
Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve a controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two...
Heat Transfer Performance for Evaporator of Absorption Refrigerating Machine
Kunugi, Yoshifumi; Usui, Sanpei; Ouchi, Tomihisa; Fukuda, Tamio
An experiment was conducted to check the heat transfer performance of evaporators with grooved tubes for absorption refrigerating machines. Heat transfer rate of evaporators were 35kW and 70kW. The range of the flow rate of the sprayed refrigerant per unit length Γ was 1 to 50kg/hm, and the outside diameters of the tubes, D0 were 16 and 19.6 mm. About 80 to 100 % increase of heat transfer rate over a plane surfaced tube is obtained by using grooved tube. The heat transfer coefficients for evaporation are correlated by the equation αE0=(Γ/D0)1/2. The substantial surface area, which is about three times larger than that of plane surfaced tube, is used in the above correlation.
Study of heat and mass transfer in evaporative coolers
Perez-Blanco, H.; Bird, W. A.
1982-06-01
Evaporative coolers are generally considered efficient and economical devices for rejecting waste heat. In these coolers, a hot fluid circulates inside tubes, rejecting heat to a mixture of air and water. Water is sprayed on the tubes and flows downward while air circulates upward; thus, latent and sensible heat is transferred from the water to the air. Commercially available coolers are of the horizonal tube type; a vertical tube evaporative cooler is studied because it is possible to enhance condensing heat transfer coefficients by using vertical fluted tubes. A mathematical model describing the performance of a single tube is formulated which can predict performance for varied inlet conditions, thereby eliminating the need for extensive testing. The validity of the model rests on the accuracy of the controlling heat and mass transfer coefficients used, so these coefficients are measured experimentally in a single tube cooler and found to agree with existing empirical correlations.
COSTEA M.; Petrescu, S; K. Le Saos; Michel Feidt
2010-01-01
The purpose of this study is to determine the optimal distribution of the heat transfer surface area or conductance among the Stirling engine heat exchangers when the minimum of the total heat transfer surface area of the heat exchangers is sought. The optimization procedure must fulfill one of the following constraints: (1) fixed power output of the engine, (2) fixed heat transfer rate available at the source, or (3) fixed power output and heat transfer rate at the source. Internal and exter...
Heat Transfer and Flow Structure Evaluation of a Synthetic Jet Emanating from a Planar Heat Sink
Manning, Paul; Persoons, Tim; Murray, Darina
2014-07-01
Direct impinging synthetic jets are a proven method for heat transfer enhancement, and have been subject to extensive research. However, despite the vast amount of research into direct synthetic jet impingement, there has been little research investigating the effects of a synthetic jet emanating from a heated surface, this forms the basis of the current research investigation. Both single and multiple orifices are integrated into a planar heat sink forming a synthetic jet, thus allowing the heat transfer enhancement and flow structures to be assessed. The heat transfer analysis highlighted that the multiple orifice synthetic jet resulted in the greatest heat transfer enhancements. The flow structures responsible for these enhancements were identified using a combination of flow visualisation, thermal imaging and thermal boundary layer analysis. The flow structure analysis identified that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process. Flow visualisation revealed entrainment of local air adjacent to the heated surface; this occurred from vortex roll-up at the surface of the heat sink and from the highly sheared jet flow. Furthermore, a secondary entrainment was identified which created a surface impingement effect. It is proposed that all three flow features enhance the heat transfer characteristics of the system.
High-Power Liquid-Metal Heat-Transfer Loop
Bhandari, Pradeep; Fujita, Toshio
1991-01-01
Proposed closed-loop system for transfer of thermal power operates at relatively high differential pressure between vapor and liquid phases of liquid-metal working fluid. Resembles "capillary-pumped" liquid-metal heat-transfer loop except electric field across permselective barrier of beta alumina keeps liquid and vapor separate at heat-input end. Increases output thermal power, contains no moving parts, highly reliable and well suited to long-term unattended operation.
Imaging Heat and Mass Transfer Processes Visualization and Analysis
Panigrahi, Pradipta Kumar
2013-01-01
Imaging Heat and Mass Transfer Processes: Visualization and Analysis applies Schlieren and shadowgraph techniques to complex heat and mass transfer processes. Several applications are considered where thermal and concentration fields play a central role. These include vortex shedding and suppression from stationary and oscillating bluff bodies such as cylinders, convection around crystals growing from solution, and buoyant jets. Many of these processes are unsteady and three dimensional. The interpretation and analysis of images recorded are discussed in the text.
Advanced turbine cooling, heat transfer, and aerodynamic studies
Energy Technology Data Exchange (ETDEWEB)
Je-Chin Han; Schobeiri, M.T. [Texas A& M Univ., College Station, TX (United States)
1995-10-01
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect on Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Investigation of radiative heat transfer in fixed bed biomass furnaces
Energy Technology Data Exchange (ETDEWEB)
T. Klason; X.S. Bai; M. Bahador; T.K. Nilsson; B. Sunden [Lund Institute of Technology, Lund (Sweden). Division of Fluid Mechanics
2008-08-15
This paper presents an investigation of the radiative heat transfer process in two fixed bed furnaces firing biomass fuels and the performance of several widely used models for calculation of radiative heat transfer in the free-room of fixed bed furnaces. The effective mean grey gas absorption coefficients are calculated using an optimised version of the exponential wide band model (EWBM) based on an optical mean beam length. Fly-ash and char particles are taken into account using Mie scattering. In the investigated updraft small-scale fixed bed furnace radiative transfer carries heat from the bed to the free-room, whereas in the cross-current bed large-scale industry furnace, radiative transfer brings heat from the hot zones in the free-room to the drying zone of the bed. Not all the investigated models can predict these heat transfer trends, and the sensitivity of results to model parameters is fairly different in the two furnaces. In the small-scale furnace, the gas absorption coefficient predicted by using different optical lengths has great impact on the predicted temperature field. In the large-scale furnaces, the predicted temperature field is less sensitive to the optical length. In both furnaces, with the same radiative properties, the low-computational-cost P1 model predicts a temperature field in the free-room similar to that by the more time consuming SLW model. In general, the radiative heat transfer rates to the fuel bed are not very sensitive to the radiative properties, but they are sensitive to the different radiative heat transfer models. For a realistic prediction of the radiative heat transfer rate to the fuel bed or to the walls, more computationally demanding models such as the FGG or SLW models should be used. 37 refs., 7 figs., 2 tabs.
Viscoelastic fluids: A new challenge in heat transfer
Energy Technology Data Exchange (ETDEWEB)
Hartnett, J.P. (Univ. of Illinois, Chicago (United States))
1992-05-01
A review of the current knowledge on the fluid mechanics and heat transfer behavior of viscoelastic aqueous polymer solutions in channel flow is presented. Both turbulent and laminar flow conditions are considered. For fully established turbulent channel flow, it was found that the friction factor, f, and the dimensionless heat transfer factor, j{sub H}, were functions of the Reynolds number and a dimensionless elasticity value, the Weissenberg number. For Weissenberg values greater than approximately 10 (the critical value) the friction factor was found to be a function only of the Reynolds number; for values less than 10 the friction factor was a function of both Re and Ws. For the dimensionless heat transfer coefficient j{sub H} the corresponding critical Weissenberg value was found to be about 100. The heat transfer reduction is always greater than the friction factor reduction; consequently, the heat transfer per unit pumping power decreases with increasing elasticity. For fully established laminar pipe flow of aqueous polymer solutions, the measured values of the friction factor and dimensionless heat transfer coefficient were in excellent agreement with the values predicted for a power law fluid. For laminar flow in a 2:1 rectangular channel the fully developed friction factor measurements were in agreement with the power law prediction. In contrast, the measured local heat transfer coefficients for aqueous polymer solutions in laminar flow through the 2:1 rectangular duct were two or three times the values predicted for a purely viscous power law fluid. It is hypothesized that these high heat transfer coefficients are due to secondary motions, which come about as a results of the unequal normal stresses occurring in viscoelastic fluids. The anomalous behavior of one particular aqueous polymer solution-namely, polyacrylic acid (Carbopol)-is described in some detail, raising some interesting questions as to how viscoelastic fluids should be classified.
Advanced turbine cooling, heat transfer, and aerodynamic studies
Energy Technology Data Exchange (ETDEWEB)
Han, Je-Chin; Schobeiri, M.T. [Texas A & M Univ., College Station, TX (United States). Dept. of Mechanical Engineering
1995-12-31
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect of Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi
2016-03-01
For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.
Influence of gas emission on heat transfer in porous ceramics
Energy Technology Data Exchange (ETDEWEB)
Gambaryan-Roisman, T.; Shapiro, M.; Litovsky, E.; Shavit, A. [Laboratory of Transport Processes in Porous Materials, Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel)
2003-01-01
It is known that thermal diffusivity, a, of several types of porous ceramic and refractory materials decreases with decreasing gas pressure. However, a of several ceramics (e.g., magnesite refractories with porosity about 25%) measured in vacuum by the monotonous heating exceeds the comparable data registered at atmospheric pressure. A similar effect was found for thermal diffusivity of several insulating materials. However, for some porous ceramics this phenomenon is absent or less prominent. It had been known that several heterogeneous physico-chemical processes take place on pore surfaces of ceramic materials. These processes include heterogeneous chemical reactions accompanied by emission of gaseous products. It had been conjectured that these processes affect thermophysical properties of ceramic materials, especially during fast heating or cooling. In this paper we substantiate this conjecture. Namely, we develop a quantitative model for the apparent thermal diffusivity, as measured by the nonstationary monotonous heating method. It takes into account the emission and adsorption of the gas on the opposite pore sides along the temperature gradient, the diffusive gas motion inside the pores and its removal from the pores due to the material gas permeability. The effect of these processes is shown to produce an additional heat flux inside the pore or crack and, hence, to increase the measured thermal diffusivity. In the presence of the passive gas, the rates of gas emission and its transport within the pore are significantly reduced, which leads to diminution of the effect of gas emission-adsorption on the heat transfer across the pore. Consequently, we show that this leads to a situation (observed in experiment) where thermal diffusivity of a material measured at high temperature in vacuum may exceed the comparable property at atmospheric pressure. When the reaction terminates due to the full conversion of the available solid reactant, the additional heat flow
Investigation of heat transfer inside a PCM-air heat exchanger: a numerical parametric study
Herbinger, Florent; Bhouri, Maha; Groulx, Dominic
2017-07-01
In this paper, the use of PCMs for thermal storage of energy in HVAC applications was investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study was dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.
Two phase flow and heat transfer characteristics of a separate-type heat pipe
Tang, Zhiwei; Liu, Aijie; Jiang, Zhangyan
2011-07-01
Two phase flow and heat transfer characteristics of a separate-type heat pipe have been studied experimentally and theoretically. The experimental apparatus have the same geometry for the evaporator and the condenser which consist of 5-tube-banks, with working temperature ranges of 80-125°C. The experimental working fluid is dual-distilled water with corrosion-resistant agents. Heat transfer coefficients for boiling and condensation along with heat flux and working temperature are measured at different filling ratio. According to the results of the experiments, the optimized filling ratio ranges from 16 to 36%. Fitted correlations of average heat transfer coefficients of the evaporator and Nusselt numbers of the condenser at the proposed filling ratio are obtained. Two phase flow characteristics of the evaporator and the condenser as well as their influence on heat transfer are described on the basis of simplified analysis. Reasons for the pulse-boiling process remain to be studied.
Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation
Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.
2012-01-01
Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.
Literature survey of heat transfer enhancement techniques in refrigeration applications
Energy Technology Data Exchange (ETDEWEB)
Jensen, M.K.; Shome, B. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical Engineering, Aeronautical Engineering and Mechanics
1994-05-01
A survey has been performed of the technical and patent literature on enhanced heat transfer of refrigerants in pool boiling, forced convection evaporation, and condensation. Extensive bibliographies of the technical literature and patents are given. Many passive and active techniques were examined for pure refrigerants, refrigerant-oil mixtures, and refrigerant mixtures. The citations were categorized according to enhancement technique, heat transfer mode, and tube or shell side focus. The effects of the enhancement techniques relative to smooth and/or pure refrigerants were illustrated through the discussion of selected papers. Patented enhancement techniques also are discussed. Enhanced heat transfer has demonstrated significant improvements in performance in many refrigerant applications. However, refrigerant mixtures and refrigerant-oil mixtures have not been studied extensively; no research has been performed with enhanced refrigerant mixtures with oil. Most studies have been of the parametric type; there has been inadequate examination of the fundamental processes governing enhanced refrigerant heat transfer, but some modeling is being done and correlations developed. It is clear that an enhancement technique must be optimized for the refrigerant and operating condition. Fundamental processes governing the heat transfer must be examined if models for enhancement techniques are to be developed; these models could provide the method to optimize a surface. Refrigerant mixtures, with and without oil present, must be studied with enhancement devices; there is too little known to be able to estimate the effects of mixtures (particularly NARMs) with enhanced heat transfer. Other conclusions and recommendations are offered.
Immersion Condensation on Oil-Infused Heterogeneous Surfaces for Enhanced Heat Transfer
Xiao, Rong; Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N.
2013-01-01
Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil. The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles. Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases. This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer. PMID:23759735
Nonlinear behavior of micro bubbles under ultrasound due to heat transfer
Energy Technology Data Exchange (ETDEWEB)
Lim, Chan Soo; Kwak, Ho Young [Chung-Ang University, Seoul (Korea, Republic of); Kim, Jeong Eun; Lee, Jae Young [Han Dong University, Pohang (Korea, Republic of)
2009-09-15
We investigated the nonlinear behavior of a microbubble under ultrasound, taking into account the heat transfer inside the bubble and through the bubble wall. The polytropic relation, which has been used for the process of pressure change depending on the volume variation of ideal gases, cannot properly treat heat transfer involving the oscillating bubble under ultrasound. In this study, a set of solutions of the Navier-Stokes equations for the gas inside the bubble along with an analytical treatment of the Navier-Stokes equations for the liquid adjacent to the bubble wall was used to treat properly the heat transfer process for the oscillating bubble under ultrasound. Entropy generation due to finite heat transfer, which induces the lost work during bubble evolution, reduces the collapsing process and considerably affects the nonlinear behavior of the bubble
Heat Transfer Characteristics of Calcined Petroleum Coke in Waste Heat Recovery Process
Directory of Open Access Journals (Sweden)
Bin Zheng
2016-01-01
Full Text Available This paper reports the results of heat transfer characteristics of calcined petroleum coke in waste heat recovery process. The model of heat exchanger was set up. The model has been used to investigate the effects of porosity (0.58 to 0.79, equivalent heat conductivity coefficient (0.9 to 1.1, and equivalent specific heat (0.9 to 1.1. The calculated values of calcined petroleum coke temperature showed good agreement with the corresponding available experimental data. The temperature distribution of calcined petroleum coke, the calcined petroleum coke temperature at heat exchanger outlet, the average heat transfer coefficient, and the heat recovery efficiency were studied. It can also be used in deriving much needed data for heat exchanger designs when employed in industry.
Analytical prediction of forced convective heat transfer of fluids ...
Indian Academy of Sciences (India)
Several phenomenological models have been proposed to explain the anomalous heat transfer enhancement in nanoﬂuids. This paper presents a systematic literature survey to exploit the characteristics of nanoﬂuids, viz., thermal conductivity, speciﬁc heat and other thermal properties. An empirical correlation for the ...
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...
Free convection effects and radiative heat transfer in MHD Stokes ...
Indian Academy of Sciences (India)
The present note deals with the effects of radiative heat transfer and free convection in MHD for a ﬂow of an electrically conducting, incompressible, dusty viscous ﬂuid past an impulsively started vertical non-conducting plate, under the inﬂuence of transversely applied magnetic ﬁeld. The heat due to viscous dissipation and ...
Students' Misconceptions about Heat Transfer Mechanisms and Elementary Kinetic Theory
Pathare, S. R.; Pradhan, H. C.
2010-01-01
Heat and thermodynamics is a conceptually rich area of undergraduate physics. In the Indian context in particular there has been little work done in this area from the point of view of misconceptions. This prompted us to undertake a study in this area. We present a study of students' misconceptions about heat transfer mechanisms, i.e. conduction,…
An experimental investigation of turbulent flow heat transfer through ...
African Journals Online (AJOL)
An experimental investigation has been carried out to study the turbulent flow heat transfer and to determine the pressure drop characteristics of air, flowing through a tube with insert. An insert of special geometry is used inside the tube. The test section is electrically heated, and air is allowed to flow as the working fluid ...
Analysis of slip flow heat transfer between two unsymmetrically ...
Indian Academy of Sciences (India)
This paper presents an analytical investigation to study the heat transfer and fluid flow characteristics in the slip flow region for hydrodynamically and thermally fully developed flow between parallel plates.Both upper and lower plates are subjected to asymmetric heat flux boundary conditions. The effect of first ordervelocity ...
Radius ratio effects on natural heat transfer in concentric annulus
DEFF Research Database (Denmark)
Alipour, M.; Hosseini, R.; Kolaei, Alireza Rezania
2013-01-01
This paper studies natural convection heat transfer in vertical and electrically heated annulus. The metallic cylinders mounted concentrically in a parallel tube. Measurements are carried out for four input electric powers and three radius ratios with an apparatus immersed in stagnant air...
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic solutions for the steady velocity, temperature and concentration. The parameters ...
Verification of Conjugate Heat Transfer Models in a Closed Volume with Radiative Heat Source
Directory of Open Access Journals (Sweden)
Maksimov Vyacheslav I.
2016-01-01
Full Text Available The results of verification of mathematical model of convective-conductive heat transfer in a closed volume with a thermally conductive enclosing structures are presented. Experiments were carried out to determine the temperature of floor premises in the working conditions of radiant heating systems. Comparison of mathematical modelling of temperature fields and experiments showed their good agreement. It is concluded that the mathematical model of conjugate heat transfers in the air cavity with a heat-conducting and heat-retaining walls correspond to the real process of formation of temperature fields in premises with gas infrared heaters system.
Heat transfer and heating rate of food stuffs in commercial shop ovens
Indian Academy of Sciences (India)
The CFD analysis of ﬂow and temperature distribution in heating ovens used in bakery shop, to keep the foodstuffs warm, is attempted using ﬁnite element technique. The oven is modelled as a two-dimensional steady state natural convection heat transfer problem. Effects of heater location and total heat input on ...
A Conceptual Change Model for Teaching Heat Energy, Heat Transfer and Insulation
Lee, C. K.
2014-01-01
This study examines the existing knowledge that pre-service elementary teachers (PSETs) have regarding heat energy, heat transfer and insulation. The PSETs' knowledge of heat energy was initially assessed by using an activity: determining which container would be best to keep hot water warm for the longest period of time. Results showed that PSETs…
Campbell, A N
2015-07-14
When any exothermic reaction proceeds in an unstirred vessel, natural convection may develop. This flow can significantly alter the heat transfer from the reacting fluid to the environment and hence alter the balance between heat generation and heat loss, which determines whether or not the system will explode. Previous studies of the effects of natural convection on thermal explosion have considered reactors where the temperature of the wall of the reactor is held constant. This implies that there is infinitely fast heat transfer between the wall of the vessel and the surrounding environment. In reality, there will be heat transfer resistances associated with conduction through the wall of the reactor and from the wall to the environment. The existence of these additional heat transfer resistances may alter the rate of heat transfer from the hot region of the reactor to the environment and hence the stability of the reaction. This work presents an initial numerical study of thermal explosion in a spherical reactor under the influence of natural convection and external heat transfer, which neglects the effects of consumption of reactant. Simulations were performed to examine the changing behaviour of the system as the intensity of convection and the importance of external heat transfer were varied. It was shown that the temporal development of the maximum temperature in the reactor was qualitatively similar as the Rayleigh and Biot numbers were varied. Importantly, the maximum temperature in a stable system was shown to vary with Biot number. This has important consequences for the definitions used for thermal explosion in systems with significant reactant consumption. Additionally, regions of parameter space where explosions occurred were identified. It was shown that reducing the Biot number increases the likelihood of explosion and reduces the stabilising effect of natural convection. Finally, the results of the simulations were shown to compare favourably with
Determining convective heat transfer coefficient using phoenics software package
Energy Technology Data Exchange (ETDEWEB)
Kostikov, A.; Matsevity, Y. [Institute of Mechanical Engineering Problems of National Academy of Sciences of Ukraine, Kharkov (Ukraine)
1997-12-31
The two methods of determination of such important quantity of heat exchange on a body surface using PHOENICS are suggested in the presentation. The first method consists in a post-processing of results of conjugate heat transfer problem solved by PHOENICS. The second one is solving an inverse heat conduction problem for solid body using PHOENICS. Comparative characteristic of these two methods is represented. (author) 4 refs.
Spray mist cooling heat transfer in glass tempering process
Sozbir, Nedim; Yao, S. C.
2017-05-01
Energy saving is a very important issue in glass plants, especially in a glass tempering process, where very high velocity air jet impingement is applied during the cooling process of glass tempering. In fact, air compressor energy may be reduced by a spray cooling due to its high heat transfer capabilities. Presently, in this paper, both pure air and water mist spray cooling are investigated in the glass tempering process. The test results indicate that thin and low-cost tempered glass can be made by mist cooling without fracture. It is possible to find the optimal water flux and duration of mist application to achieve a desirable temperature distribution in the glass for deep penetration of the cooling front but without inducing cracking during the tempering. The use of mist cooling could give about 29 % air pressure reduction for 2-mm glass plate and 50 % reduction for both 3- and 4-mm glass plates.
Supercritical water gasification with decoupled pressure and heat transfer modules
Dibble, Robert
2017-09-14
The present invention discloses a system and method for supercritical water gasification (SCWG) of biomass materials wherein the system includes a SCWG reactor and a plurality of heat exchangers located within a shared pressurized vessel, which decouples the function of containing high pressure from the high temperature function. The present invention allows the heat transfer function to be conducted independently from the pressure transfer function such that the system equipment can be designed and fabricated in manner that would support commercial scaled-up SCWG operations. By using heat exchangers coupled to the reactor in a series configuration, significant efficiencies are achieved by the present invention SCWG system over prior known SCWG systems.
Dynamic measurement of near-field radiative heat transfer.
Lang, S; Sharma, G; Molesky, S; Kränzien, P U; Jalas, T; Jacob, Z; Petrov, A Yu; Eich, M
2017-10-24
Super-Planckian near-field radiative heat transfer allows effective heat transfer between a hot and a cold body to increase beyond the limits long known for black bodies. Until present, experimental techniques to measure the radiative heat flow relied on steady-state systems. Here, we present a dynamic measurement approach based on the transient plane source technique, which extracts thermal properties from a temperature transient caused by a step input power function. Using this versatile method, that requires only single sided contact, we measure enhanced radiative conduction up to 16 times higher than the blackbody limit on centimeter sized glass samples without any specialized sample preparation or nanofabrication.
Triple vacuum glazing: Heat transfer and basic mechanical design constraints
Energy Technology Data Exchange (ETDEWEB)
Manz, H.; Brunner, S.; Wullschleger, L. [Swiss Federal Laboratories for Materials Testing and Research (EMPA), Laboratory for Applied Physics in Building, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)
2006-12-15
Given the major role played by windows with regard to energy losses from buildings in cold climates, low thermal transmittance is an indispensable property of glazing in low-energy buildings. Evacuation offers the only means of achieving negligible gaseous conduction in glazing cavities. Application of low-emittance coatings to glass sheet surfaces inside the cavity reduces the radiative heat transfer. The feasibility of double vacuum glazing using arrays of support pillars between the glass sheets has been shown by other authors. This type of glazing is commercially manufactured today. Based on these achievements, our study set out to investigate heat transfer in triple vacuum glazing by means of (i) an analytical thermal network model and (ii) a numerical finite difference model. The study focused on the impact of the following parameters on thermal transmittance: emittances of glass sheet surfaces inside the cavity, support pillar radius, support pillar separation and thermal conductivity of support pillar material. The design procedure for triple vacuum glazing taking into account not only thermal but also mechanical stresses due to atmospheric pressure, i.e., to enable identification of favourable parameter sets, is presented. Our findings suggest that use of the triple vacuum glazing concept can significantly reduce the thermal transmittances achieved by the best insulation glazing units currently on the market. E.g., a centre-of-glazing thermal transmittance of less than 0.2Wm{sup -2}K{sup -1} is achievable using stainless steel support pillars, 6mm/4mm/6mm sheets of untempered soda-lime glass and four low-emittance coatings ({epsilon}=0.03). (author)
Heat transfer enhancement in two-start spirally corrugated tube
Directory of Open Access Journals (Sweden)
Zaid S. Kareem
2015-09-01
Full Text Available Various techniques have been tested on heat transfer enhancement to upgrade the involving equipment, mainly in thermal transport devices. These techniques unveiled significant effects when utilized in heat exchangers. One of the most essential techniques used is the passive heat transfer technique. Corrugations represent a passive technique. In addition, it provides effective heat transfer enhancement because it combined the features of extended surfaces, turbulators and artificial roughness. Therefore, A Computational Fluid Dynamics was employed for water flowing at low Reynolds number in spiral corrugated tubes. This article aimed for the determination of the thermal performance of unique smooth corrugation profile. The Performance Evaluation Criteria were calculated for corrugated tubes, and the simulation results of both Nusselt number and friction factor were compared with those of standard plain and corrugated tubes for validation purposes. Results showed the best thermal performance range of 1.8–2.3 for the tube which has the severity of 45.455 × 10−3 for Reynolds number range of 100–700. The heat transfer enhancement range was 21.684%–60.5402% with friction factor increase of 19.2–36.4%. This indicated that this creative corrugation can improve the heat transfer significantly with appreciably increasing friction factor.
Intensification of heat transfer across falling liquid films
Ruyer-Quil, Christian; Cellier, Nicolas; Stutz, Benoit; Caney, Nadia; Bandelier, Philippe; Locie Team; Legi Team
2017-11-01
The wavy motion of a liquid film is well known to intensify heat or mass transfers. Yet, if film thinning and wave merging are generally invoked, the physical mechanisms which enable this intensification are still unclear. We propose a systematic investigation of the impact of wavy motions on the heat transfer across 2D falling films on hot plates as a function of the inlet frequency and flow parameters. Computations over extended domains and for sufficient durations to achieve statistically established flows have been made possible by low-dimensional modeling and the development of a fast temporal solver based on graph optimizations. Heat transfer has been modeled using the weighted residual technique as a set of two evolution equations for the free-surface temperature and the wall heat flux. This new model solves the shortcomings of previous attempts, namely their inability to capture the onset of thermal boundary layers in large-amplitude waves and their limitation to low Prandtl numbers. Our study reveals that heat transfer is enhanced at the crests of the waves and that heat transfer intensification is maximum at the maximum of density of wave crests, which does not correspond to the natural wavy regime (no inlet forcing). Supports from Institut Universitaire de France and Région Auvergne-Rhones-Alpes are warmly acknowledged.
Resolving the Mantle Plume Heat Transfer Discrepancy
Hoggard, M.; Parnell-Turner, R. E.; White, N.
2016-12-01
Estimates of the buoyancy and heat flux of upwelling mantle plumes are important for understanding many aspects of convection within the Earth. These fluxes influence melt productivity and geochemistry at mid-oceanic spreading centres and hotspots, dynamic topography, mantle mixing timescales and Earth's bulk heat budget. The majority of existing plume flux estimates are calculated from the cross-sectional area of swells multiplied by either plate velocities or spreading rates. Hawaii and the other Pacific hotspots dominate these estimates, which indicate a total heat flux carried by plumes to the base of plates at ˜ 2 TW. Here, we use an alternative approach that calculates buoyancy flux using the swell volume constrained from a new map of dynamic topography, scaled by a characteristic swell decay time. This method avoids the assumption that plume material moves at or below the velocity of the overriding plate. Our results indicate that the Icelandic plume has a buoyancy flux of ˜ 27 ± 4 Mg/s , which is significantly larger than the Hawaiian plume and an order of magnitude greater than some previous estimates. These new values match independent geophysical constraints from Hawaii and the North Atlantic Ocean. All magmatic and amagmatic swells have been included in our global analysis, which reveals a total heat flux carried to the base of the plates of ˜ 10 ± 2 TW. This increased global heat flux is consistent with recent global seismic tomographic images of large upwelling plumes in the mid-mantle and predictions of heat flux through the core-mantle boundary.
Modeling of Radiative Heat Transfer in an Electric Arc Furnace
Opitz, Florian; Treffinger, Peter; Wöllenstein, Jürgen
2017-12-01
Radiation is an important means of heat transfer inside an electric arc furnace (EAF). To gain insight into the complex processes of heat transfer inside the EAF vessel, not only radiation from the surfaces but also emission and absorption of the gas phase and the dust cloud need to be considered. Furthermore, the radiative heat exchange depends on the geometrical configuration which is continuously changing throughout the process. The present paper introduces a system model of the EAF which takes into account the radiative heat transfer between the surfaces and the participating medium. This is attained by the development of a simplified geometrical model, the use of a weighted-sum-of-gray-gases model, and a simplified consideration of dust radiation. The simulation results were compared with the data of real EAF plants available in literature.
Heat Transfer in Large Two-Stroke Marine Diesel Engines
DEFF Research Database (Denmark)
Jensen, Michael Vincent
Heat transfer between the cylinder gas and the piston surface during combustion in large two-stroke uniflow scavenged marine diesel engines has been investigated in the present work. The piston surface experiences a severe thermal load during combustion due to the close proximity of the combustion...... is thus important for the engine manufactures. The piston surface heat transfer was studied in the event of impingement of hot combustion products on the piston during combustion, and an estimate was obtained of the peak heat flux level experienced on the piston surface. The investigation was carried out...... numerically by performing simulations with a CFD code of the heat transfer between gas and wall in a jet impingement configuration where a hot round turbulent gas jet impinged normally onto a wall under conditions approximating the in-cylinder conditions in the engine during combustion. A jet impingement...
Modelling of heat and mass transfer processes in neonatology
Energy Technology Data Exchange (ETDEWEB)
Ginalski, Maciej K [FLUENT Europe, Sheffield Business Park, Europa Link, Sheffield S9 1XU (United Kingdom); Nowak, Andrzej J [Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, 44-100 Gliwice (Poland); Wrobel, Luiz C [School of Engineering and Design, Brunel University, Uxbridge UB8 3PH (United Kingdom)], E-mail: maciej.ginalski@ansys.com, E-mail: Andrzej.J.Nowak@polsl.pl, E-mail: luiz.wrobel@brunel.ac.uk
2008-09-01
This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices.
Heat Transfer Simulation for Reciprocating Compressor with Experimental Validation
Zhou, Ruixin; Guo, Bei; Chen, Xiaole; Tuo, Jinliang; Wu, Rui; Fagotti, Fabian; Zhao, Yali; Yang, Song; Xu, Bo
2017-08-01
The efficiency of reciprocating compressor can be influenced by heat transfer and the reliability can be also affected by the temperature distribution in compressor. In consideration of the complex relationship of heat transfer, the compressor is divided into six control volumes including the suction muffler, the cylinder, the discharge chamber, the discharge muffler, the discharge line and the compressor shell. The steady state energy balance equations of the open system for each control volume are built up after the crankshaft rotates one cycle. The heat flux of the cylinder is calculated by the existing correlation. The heat transfer coefficient correlations in energy equations are chosen in references and revised by experimental results. Three same type reciprocating compressors used in R290 system installed with themocouples are tested under some planed conditions in order to ensure accuracy. The simulation results are compared with the experimental results. It shows that the simplified method presented in this paper is effective.
BROWNIAN HEAT TRANSFER ENHANCEMENT IN THE TURBULENT REGIME
Directory of Open Access Journals (Sweden)
Suresh Chandrasekhar
2016-08-01
Full Text Available The paper presents convection heat transfer of a turbulent flow Al2O3/water nanofluid in a circular duct. The duct is a under constant and uniform heat flux. The paper computationally investigates the system’s thermal behavior in a wide range of Reynolds number and also volume concentration up to 6%. To obtain the nanofluid thermophysical properties, the Hamilton-Crosser model along with the Brownian motion effect are utilized. Then the thermal performance of the system with the nanofluid is compared to the conventional systems which use water as the working fluid. The results indicate that the use of nanofluid of 6% improves the heat transfer rate up to 36.8% with respect to pure water. Therefore, using the Al2O3/water nanofluid instead of water can be a great choice when better heat transfer is needed.
Free shear layer and swirl flow heat transfer enhancement
Wirtz, R. A.; Greiner, M.; Snyder, B.
1990-05-01
Two wall shape induced convective heat transfer enhancement mechanisms for channel flows are investigated. The first uses transverse grooves in a channel wall to produce unstable free shear layers which cause traveling waves to be superimposed on the mean flow, thus augmenting heat transfer. The second uses streamline curvature to produce a swirling secondary flow. In this case, a serpentine channel is investigated. Flow visualization and heat transfer/pressure drop measurements with both air and water show that the expected augmentation mechanisms are operable in both the grooved and serpentine channel configurations at flow rates normally encountered in compact heat exchanger applications. When compared to other enhanced surfaces (such as offset strip fins or corrugated plate fins) on an equal pumping power basis, both the grooved and serpentine configurations of the present study produce performance curves which are comparable to, and in some cases superior to other conventional techniques.
Comparative study of convective heat transfer characteristics of nanofluids
Muryam, Hina; Ramzan, Naveed; Umer, Asim; Awan, Gul Hameed; Hassan, Ali
2017-07-01
The present research is about to draw a comparison between heat transfer characteristics of gold/deionized water (DIW) and silver/DIW based nanofluid under same heat flux for laminar flow. Experiments are performed on both nanofluid by using different concentrations (0.015, 0.045, 0.0667%) of nano-particles (NPs) in DIW as a base fluid. The experimental study concludes that an appreciable intensification in heat transfer coefficient (HTC) of both nanofluid has been attained as compare to base fluid. However, gold/DIW based nanofluid exhibit better convective heat transfer intensification compared with silver/DIW based nanofluid but Shah correlation cannot predict as much augmentation as in experimental work for both nanofluid. It is also noticed that the anomalous enhancement in Nusselt number and HTC is not only due to the accession in thermal properties but also by the formation of thinner thermal boundary layer at the entrance of the tube due to NPs.
A note on convective heat transfer of an MHD Jeffrey fluid over a stretching sheet
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Jawad; Shahzad, Azeem [Department of Basic Sciences, University of Engineering and Technology, Taxila 47050 (Pakistan); Khan, Masood [Department of Mathematics, Quaid-i-Azam University, Islamabad 44000 (Pakistan); Ali, Ramzan, E-mail: alian.qau@gmail.com [Department of Applied Mathematics, TU-Dortmund (Germany); University of Central Asia, 720001 Bishkek (Kyrgyzstan)
2015-11-15
This article focuses on the exact solution regarding convective heat transfer of a magnetohydrodynamic (MHD) Jeffrey fluid over a stretching sheet. The effects of joule and viscous dissipation, internal heat source/sink and thermal radiation on the heat transfer characteristics are taken in account in the presence of a transverse magnetic field for two types of boundary heating process namely prescribed power law surface temperature (PST) and prescribed heat flux (PHF). Similarity transformations are used to reduce the governing non-linear momentum and thermal boundary layer equations into a set of ordinary differential equations. The exact solutions of the reduced ordinary differential equations are developed in the form of confluent hypergeometric function. The influence of the pertinent parameters on the temperature profile is examined. In addition the results for the wall temperature gradient are also discussed in detail.
A note on convective heat transfer of an MHD Jeffrey fluid over a stretching sheet
Directory of Open Access Journals (Sweden)
Jawad Ahmed
2015-11-01
Full Text Available This article focuses on the exact solution regarding convective heat transfer of a magnetohydrodynamic (MHD Jeffrey fluid over a stretching sheet. The effects of joule and viscous dissipation, internal heat source/sink and thermal radiation on the heat transfer characteristics are taken in account in the presence of a transverse magnetic field for two types of boundary heating process namely prescribed power law surface temperature (PST and prescribed heat flux (PHF. Similarity transformations are used to reduce the governing non-linear momentum and thermal boundary layer equations into a set of ordinary differential equations. The exact solutions of the reduced ordinary differential equations are developed in the form of confluent hypergeometric function. The influence of the pertinent parameters on the temperature profile is examined. In addition the results for the wall temperature gradient are also discussed in detail.
Koca, Aliihsan; Acikgoz, Ozgen; Çebi, Alican; Çetin, Gürsel; Dalkilic, Ahmet Selim; Wongwises, Somchai
2017-08-01
Investigations on heated ceiling method can be considered as a new research area in comparison to the common wall heating-cooling and cooled ceiling methods. In this work, heat transfer characteristics of a heated radiant ceiling system was investigated experimentally. There were different configurations for a single room design in order to determine the convective and radiative heat transfer rates. Almost all details on the arrangement of the test chamber, hydraulic circuit and radiant panels, the measurement equipment and experimental method including uncertainty analysis were revealed in detail indicating specific international standards. Total heat transfer amount from the panels were calculated as the sum of radiation to the unheated surfaces, convection to the air, and conduction heat loss from the backside of the panels. Integral expression of the view factors was calculated by means of the numerical evaluations using Matlab code. By means of this experimental chamber, the radiative, convective and total heat-transfer coefficient values along with the heat flux values provided from the ceiling to the unheated surrounding surfaces have been calculated. Moreover, the details of 28 different experimental case study measurements from the experimental chamber including the convective, radiative and total heat flux, and heat output results are given in a Table for other researchers to validate their theoretical models and empirical correlations.
Koca, Aliihsan; Acikgoz, Ozgen; Çebi, Alican; Çetin, Gürsel; Dalkilic, Ahmet Selim; Wongwises, Somchai
2018-02-01
Investigations on heated ceiling method can be considered as a new research area in comparison to the common wall heating-cooling and cooled ceiling methods. In this work, heat transfer characteristics of a heated radiant ceiling system was investigated experimentally. There were different configurations for a single room design in order to determine the convective and radiative heat transfer rates. Almost all details on the arrangement of the test chamber, hydraulic circuit and radiant panels, the measurement equipment and experimental method including uncertainty analysis were revealed in detail indicating specific international standards. Total heat transfer amount from the panels were calculated as the sum of radiation to the unheated surfaces, convection to the air, and conduction heat loss from the backside of the panels. Integral expression of the view factors was calculated by means of the numerical evaluations using Matlab code. By means of this experimental chamber, the radiative, convective and total heat-transfer coefficient values along with the heat flux values provided from the ceiling to the unheated surrounding surfaces have been calculated. Moreover, the details of 28 different experimental case study measurements from the experimental chamber including the convective, radiative and total heat flux, and heat output results are given in a Table for other researchers to validate their theoretical models and empirical correlations.
Bibliography on augmentation of convective heat and mass transfer
Energy Technology Data Exchange (ETDEWEB)
Bergles, A.E.; Webb, R.L.; Junkhan, G.H.; Jensen, M.K.
1979-05-01
Heat transfer augmentation has developed into a major specialty area in heat transfer research and development. A bibliography of world literature on augmentation is presented. The literature is classified into passive augmentation techniques, which require no external power, and active techniques, which do require external power. The fourteen techniques are grouped in terms of their application to the various modes of heat transfer. Mass transfer is included for completeness. Key words are included with each citation for technique/mode identification. The total number of publications cited is 1,967, including 75 surveys of various techniques and 42 papers on performance evaluation of passive techniques. Patents are not included as they will be the subject of a future topical report.
Energy Technology Data Exchange (ETDEWEB)
Rao, Bala Bhaskara [Dept. of Mechanical Engineering, SISTAM College, JNTU, Kakinada (India); Raju, V. Ramachandra [Dept. of Mechanical Engineering, JNTU, Kakinada (India); Deepak, B. B V. L. [Dept. of Industrial Design, National Institute of Technology, Rourkela (India)
2017-01-15
Most thermal/chemical industries are equipped with heat exchangers to enhance thermal efficiency. The performance of heat exchangers highly depends on design modifications in the tube side, such as the cross-sectional area, orientation, and baffle cut of the tube. However, these parameters do not exhibit a specific relation to determining the optimum design condition for shell and tube heat exchangers with a maximum heat transfer rate and reduced pressure drops. Accordingly, experimental and numerical simulations are performed for a heat exchanger with varying tube geometries. The heat exchanger considered in this investigation is a single-shell, multiple-pass device. A Generalized regression neural network (GRNN) is applied to generate a relation among the input and output process parameters for the experimental data sets. Then, an Artificial immune system (AIS) is used with GRNN to obtain optimized input parameters. Lastly, results are presented for the developed hybrid GRNN-AIS approach.
Directory of Open Access Journals (Sweden)
Lin Wei
2015-01-01
Full Text Available Heat recovery unit (HRU is a heat exchange device in drying process. In HRU, room air is preheated by waste hot air and then transported to drying oven to remove moisture, which helps to save both energy and time. The main purpose of this paper is to build a heat transfer model of HRU and study its characteristics. A numerical method based on fluid-solid coupling was used to calculate the heat transfer between tube and fluids, and the actual structure was simplified to improve computation efficiency. The results were validated by theoretical calculation and experiments. Effects of Reynolds number (Re on outlet temperature, Nusselt number, and pressure drop were investigated. It was found that the thermal resistance of shell side is large, by reducing which the total heat transfer coefficient can be improved. The difference between finned tube and smooth tube is in the shell side. Larger Re of shell side leads to good heat transfer performance but also larger pressure drop which increases the flow resistance.
Directory of Open Access Journals (Sweden)
Nee Alexander
2015-01-01
Full Text Available Mathematical modeling of radiant heating of a closed rectangular area under conditions of convective heat transfer at the external boundaries is passed. The fields of temperature and stream function, illustrating the unsteady nature of the heat transfer were obtained. The extent influence of convective heat transfer at the external boundaries on the circulating flows formation in the gas cavity are shown.
Directory of Open Access Journals (Sweden)
Cieśliński Janusz T.
2016-09-01
Full Text Available This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx. The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side.
Particle shape effect on heat transfer performance in an oscillating heat pipe
Directory of Open Access Journals (Sweden)
Chen Hsiu-hung
2011-01-01
Full Text Available Abstract The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP was investigated experimentally. A binary mixture of ethylene glycol (EG and deionized water (50/50 by volume was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Energy Technology Data Exchange (ETDEWEB)
Phillips, Benjamin A. (Benton Harbor, MI); Zawacki, Thomas S. (St. Joseph, MI)
1998-07-21
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Energy Technology Data Exchange (ETDEWEB)
Phillips, B.A.; Zawacki, T.S.
1998-07-21
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration. 5 figs.
REVIEW OF PCMs AND HEAT TRANSFER ENHANCEMENT ...
African Journals Online (AJOL)
HOD
compatibility with other materials of the system. In general, candidate ... Cesium Hydroxide (CsOH) and Lead Bromide (PbBr2) have low latent heat of fusion ..... Steam from test facility. DISTOR. II. 100. 55. KNO3/NaNO3. 2000. 225. Steam from parabolic trough. During discharging an average specific power of 42.5. kWth/m3.
Electromagnetic enhancement of turbulent heat transfer
Kenjeres, S.
2008-01-01
We performed large eddy simulations (LES) of the turbulent natural convection of an electrically conductive fluid (water with 7% Na2SO4 electrolyte solution) in a moderate (4:4:1) aspect ratio enclosure heated from below and cooled from above and subjected to external nonuniformly distributed
Aspects of forced convective heat transfer in geothermal systems
Energy Technology Data Exchange (ETDEWEB)
Kilty, K.; Chapman, D.S.; Mase, C.
1978-07-01
A knowledge of convective heat transfer is essential to understanding geothermal systems and other systems of moving groundwater. A simple, kinematic approach toward convective heat transfer is taken here. Concern is not with the cause of the groundwater motion but only with the fact that the water is moving and transferring heat. The mathematical basis of convective heat transfer is the energy equation which is a statement of the first law of thermodynamics. The general solution of this equation for a specific model of groundwater flow has to be done numerically. The numerical algorithm used here employs a finite difference approximation to the energy equation that uses central differences for the heat conduction terms and one-sided differences for the heat convection terms. Gauss--Seidel iteration is then used to solve the finite difference equation at each node of a non-uniform mesh. The Monroe and Red Hill hot springs, a small hydrothermal system in central Utah, provide an example to illustrate the application of convective heat transfer theory to a geophysical problem. Two important conclusions regarding small geothermal systems follow immediately from the results of this application. First, the most rapid temperature rise in the convecting part of a geothermal system is near the surface. Below this initially rapid temperature increase the temperature increases very slowly, and thus temperatures extrapolated from shallow boreholes can be seriously in error. Second, the temperatures and heat flows observed at Monroe and Red Hill, and probably at many other small geothermal areas, can easily result from moderate vertical groundwater velocities in faults and fracture zones in an area of normal heat flow.
Heat transfer performance of Al2O3/water nanofluids in a mini channel heat sink.
Dominic, A; Sarangan, J; Suresh, S; Sai, Monica
2014-03-01
The high density heat removal in electronic packaging is a challenging task of modern days. Finding compact, energy efficient and cost effective methods of heat removal is being the interest of researchers. In the present work, mini channel with forced convective heat transfer in simultaneously developing regime is investigated as the heat transfer coefficient is inversely proportional to hydraulic diameter. Mini channel heat sink is made from the aluminium plate of 30 mm square with 8 mm thickness. It has 15 mini channel of 0.9 mm width, 1.3 mm height and 0.9 mm of pitch. DI water and water based 0.1% and 0.2% volume fractions of Al2O3/water nanofluids are used as coolant. The flow rates of the coolants are maintained in such a way that it is simultaneously developing. Reynolds number is varied from 400 to 1600 and heat input is varied from 40 W to 70 W. The results showed that heat transfer coefficient is more than the heat transfer coefficient of fully developed flow. Also the heat transfer is more for nanofluids compared to DI water.
Kuznetsov, V. V.; Kozulin, I. A.; Shamirzaev, A. S.
2012-11-01
Flow boiling in microchannel heat sinks is significantly influenced by capillary forces and by boundary constrains affecting the flow pattern and the heat transfer. In the present work, some characteristics of flow boiling heat transfer are explained using measurements of statistical parameters of gas-liquid two-phase flow in a rectangular microchannel. Such statistical characteristics of the flow as length distributions of elongated bubbles and liquid plugs, and also velocity distribution of the elongated bubbles are determined by dual laser scanning of the horizontal adiabatic nitrogen-water flow in a microchannel with the cross-section of 370×217 μm. Pressure gradients in gas-liquid flow are measured, and the results found well matching the predictions that account for capillary pressure on the gas-liquid interface. Heat transfer coefficients are measured for a horizontal copper microchannel heat sink with refrigerant R-21 as the working fluid. The heat sink contains 21 channels with cross section dimensions 930×335-μm. Distribution of local heat transfer coefficients along the length and the width of the microchannel plate is measured in the range of heat fluxes from 14 to 63 kW/m2; vapour quality was varied within 0.05-0.8, and pressure was about 1.6 bar. For flow boiling of R-21 refrigerant, contributions of nucleate boiling and forced convection are comparable. This allows us to examine the heat transfer mechanism for these complex conditions.
Heat Transfer Analysis of Thermal Protection Structures for Hypersonic Vehicles
Zhou, Chen; Wang, Zhijin; Hou, Tianjiao
2017-11-01
This research aims to develop an analytical approach to study the heat transfer problem of thermal protection systems (TPS) for hypersonic vehicles. Laplace transform and integral method are used to describe the temperature distribution through the TPS subject to aerodynamic heating during flight. Time-dependent incident heat flux is also taken into account. Two different cases with heat flux and radiation boundary conditions are studied and discussed. The results are compared with those obtained by finite element analyses and show a good agreement. Although temperature profiles of such problems can be readily accessed via numerical simulations, analytical solutions give a greater insight into the physical essence of the heat transfer problem. Furthermore, with the analytical approach, rapid thermal analyses and even thermal optimization can be achieved during the preliminary TPS design.
An investigation of heat pipe meniscus heat transfer
Saaski, E. W.; Franklin, J. L.; Mccreight, C. R.
1978-01-01
The use of grooved evaporator surfaces in heat pipes has increased in popularity in the past few years primarily due to the reproducibility achievable with grooved walls and the relatively low costs of the threading or extrusion processes involved in their production. The present study combines both analyses and experiments on square groove geometries, with special emphasis on overcoming the limitations of earlier analyses with finite-difference methods and groove-fillet hydrodynamic simplifications. The groove fillet, which has in previous analyses been assumed constant in radius of curvature, is permitted to change in thickness and curvature consistent with hydrodynamics and heat loss from the groove. A model is developed for accurate determination of the effect of constriction resistance on groove performance. The grooved-surface tests to be conducted are briefly described which will provide data under closely controlled operation to allow comparison and verification of the analyses.
Effects of ridged walls on the heat transfer in a heated square duct
Energy Technology Data Exchange (ETDEWEB)
Vazquez, M.S.; Rodriguez, W.V. [Ciudad Universitaria, Mexico DF (Mexico). Instituto de Ingenieria, UNAM, Coordinacion de Ingenieria de Procesos Industrails y Ambientales, Circuito Interior; Issa, R. [LEGI-MOST, INPG, Grenoble (France)
2005-05-01
Turbulent flows in rectangular cooling ducts of rocket engine thrust chambers are characterized by secondary motions of Prandtl's first and second kinds. These secondary currents play a prominent part in heat transfer between the thrust chamber and the cooling gas conveyed in the duct. Previous numerical and experimental works reveal that attaching ridges on the walls of the duct causes the formation of new secondary flows of Prandtl's second kind. These new structures are likely to increase the heat transfer. The present study has investigated numerically, through large eddy simulations, the effects of different forms of ridges on heat transfer in straight square duct flows. (author)
Heat transfer in cooled porous region with curved boundary
Siegel, R.; Snyder, A.
1981-01-01
Heat transfer characteristics are analyzed for a cooled two-dimensional porous medium having a curved boundary. A general analytical procedure is given in combination with a numerical conformal mapping method used to transform the porous region into an upper half plane. To illustrate the method, results are evaluated for a cosine shaped boundary subjected to uniform external heating. The results show the effects of coolant starvation in the thick regions of the medium, and the extent that internal heat conduction causes the heated surface to have a more uniform temperature.
Heat transfer and fluid flow in minichannels and microchannels
Kandlikar, Satish; Li, Dongqing; Colin, Stephane; King, Michael R
2014-01-01
Heat exchangers with minichannel and microchannel flow passages are becoming increasingly popular due to their ability to remove large heat fluxes under single-phase and two-phase applications. Heat Transfer and Fluid Flow in Minichannels and Microchannels methodically covers gas, liquid, and electrokinetic flows, as well as flow boiling and condensation, in minichannel and microchannel applications. Examining biomedical applications as well, the book is an ideal reference for anyone involved in the design processes of microchannel flow passages in a heat exchanger. Each chapter is accompan
HEAT TRANSFER ENHANCEMENT WITH NANOFLUIDS – A REVIEW
Directory of Open Access Journals (Sweden)
A.M. Hussein
2013-06-01
Full Text Available This paper presents a review of the studies undertaken on convection heat transfer with nanofluids. Initial studies were directed towards the determination of the properties of nanofluids, especially their thermal conductivity and viscosity. The studies indicate that thermal conductivity and viscosity increase with an increase in the concentration of the nanofluid. Experiments were conducted with different nanofluids, at various concentrations and temperature ranges, for the estimation of the heat transfer coefficient and friction factor for water-based nanofluids. All the studies confirmed enhancement of the heat transfer coefficient with an increase in concentration. The experimental ranges of temperature undertaken by the authors were different for different nanofluids. Certain studies with smaller particle sizes indicated an increase in heat transfer enhancements when compared with values obtained when using larger particle sizes. It is observed that the concentration of the nanofluid, the operating temperature, the particle size and shape, together with the material of the nanoparticle dispersed in the base liquid, have significant influence on the heat transfer coefficient. All the studies indicate a nominal increase in pressure drop.
Gravity and Heater Size Effects on Pool Boiling Heat Transfer
Kim, Jungho; Raj, Rishi
2014-01-01
The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.
Super-Planckian far-field radiative heat transfer
Fernández-Hurtado, V.; Fernández-Domínguez, A. I.; Feist, J.; García-Vidal, F. J.; Cuevas, J. C.
2018-01-01
We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2. These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevices.
Radiative heat transfer estimation in pipes with various wall emissivities
Robin, Langebach; Christoph, Haberstroh
2017-02-01
Radiative heat transfer is usually of substantial importance in cryogenics when systems are designed and thermal budgeting is carried out. However, the contribution of pipes is commonly assumed to be comparably low since the warm and cold ends as well as their cross section are fairly small. Nevertheless, for a first assessment of each pipe rough estimates are always appreciated. In order to estimate the radiative heat transfer with traditional “paper and pencil“ methods there is only one analytical case available in literature - the case of plane-parallel plates. This case can only be used to calculate the theoretical lower and the upper asymptotic values of the radiative heat transfer, since pipe wall radiation properties are not taken into account. For this paper we investigated the radiative heat transfer estimation in pipes with various wall emissivities with the help of numerical simulations. Out of a number of calculation series we could gain an empirical extension for the used approach of plane-parallel plates. The model equation can be used to carry out enhanced paper and pencil estimations for the radiative heat transfer through pipes without demanding numerical simulations.
Energy Technology Data Exchange (ETDEWEB)
Horel, J. D.; de Winter, F.
1978-04-20
A study was made of the methods available to transfer heat from the collector to the water storage tank in water heating systems. In counterflow heat exchangers used in double loop water heating systems, it was found to be more important to use a high water flowrate than a high heat transfer fluid flowrate. It was earlier thought to be best to have matched WC/sub p/ (mass flowrate-specific heat) products in the loops. It was shown in this study that the water WC/sub p/ product should be about twice as large as that of the heat transfer fluid. It was found that neither the heat exchanger type nor the size was very critical, so that very simple criteria were adequate in determining optimum heat exchanger size. It was found that there is a definite system size below which one should use a traced tank or a coil in a tank. Equations and optimization criteria were developed for traced tanks or tanks with coils. At present, there is no quantitative understanding of liquid to liquid (direct contact) heat exchangers, though they are clearly quite effective. Draindown systems are discussed, and several appendices are included on heat transfer and other characteristics of fluid and of equipment.
Directory of Open Access Journals (Sweden)
HAROON IMTIAZ
2017-04-01
Full Text Available In this paper, we investigate numerically the effect of thermal boundary conditions on conjugated conduction-free convection heat transfer in an annulus between two concentric cylinders using Fourier Spectral method. The inner wall of the annulus is heated and maintained at either CWT (Constant Wall Temperature or CHF (Constant Heat Flux, while the outer wall is maintained at constant temperature. CHF case is relatively more significant for high pressure industrial applications, but it has not received much attention. This study particularly focuses the latter case (CHF. The main influencing parameters on flow and thermal fields within the annulus are: Rayleigh number Ra; thickness of inner wall Rs; radius ratio Rr and inner wall-fluid thermal conductivity ratio Kr. The study has shown that the increase in Kr increases the heat transfer rate through the annulus for heating at CWT and decreases the inner wall dimensionless temperature for heating at CHF and vice versa. It has also been proved that as the Rs increases at fixed Ra and Rr, the heat transfer rate decreases for heating at CWT and the inner wall dimensionless temperature increases for heating at CHF at Kr 1 depends on Rr. It has been shown that for certain combinations of controlling parameters there will be a value of Rr at which heat transfer rate will be minimum in the annulus in case of heating at CWT, while
Heat transfer performance of an oscillating heat pipe under ultrasonic field with dual frequency
Fu, B. W.; Zhao, N. N.; Ma, H. B.; Su, F. M.
2015-01-01
The oscillating motion and heat transfer capacity in an oscillating heat pipe (OHP) under the effect of ultrasound was investigated experimentally. Using the electrically- controlled piezoelectric ceramics, the ultrasonic sound was applied to the evaporating section of the OHP. The heat pipe was tested with or without the ultrasonic sound. The effect of ultrasound on the heat transfer performance was conducted with ultrasound of single frequency or dual frequency. The experimental results demonstrate that the OHP under the effect of the ultrasonic sound with dual frequency performs better than that one with single frequency.
The thermodynamics of enhanced heat transfer: a model study
Hovhannisyan, Karen; Allahverdyan, Armen E.
2010-06-01
Situations where a spontaneous process of energy or matter transfer is enhanced by an external device are widespread in nature (the human sweating system, enzyme catalysis, facilitated diffusion across biomembranes, industrial heat-exchangers and so on). The thermodynamics of such processes remains, however, open. Here we study enhanced heat transfer by using a model junction immersed between two thermal baths at different temperatures Th and Tc (Th > Tc). The transferred heat power is enhanced via controlling the junction by means of external time-dependent fields. Provided that the spontaneous heat flow process is optimized over the junction Hamiltonian, any enhancement of this spontaneous process demands consumption and subsequent dissipation of work. The efficiency of the enhancement is defined via the increment in the heat power divided by the amount of work done. We show that this efficiency is bounded from above by Tc/(Th - Tc). Formally this is identical to the Carnot bound for the efficiency of ordinary refrigerators which transfer heat from cold to hot bodies. It also shares some (but not all) physical features of the Carnot bound.
LOCAL HEAT TRANSFER AT THE END FACES CHANNEL PROFILES OF TURBINE NOZZLES FOR INTENSE SECONDARY FLOWS
Directory of Open Access Journals (Sweden)
A. Kashchenko
2015-07-01
Full Text Available Results of experimental study of local heat transfer at the end surfaces of channel profiles of turbine nozzles in secondary currents, the intensity of which was varied by reducing the height of the profiles are presented. The thickness of the boundary layer on the inlet in the channel profiles was reduced to the minimum possible in the experiment. The data characterizing the distribution of local heat transfer coefficients on the end surface in a wide range of characteristic parameters change is obtained.
Effect of Channel Configurations for Tritium Transfer in Printed Circuit Heat Exchangers
Energy Technology Data Exchange (ETDEWEB)
Chang Oh; Eung Kim; Robert Shrake; Mike Patterson
2009-05-01
total heat transfer area divided by the volume of the heat exchanger. In the case of PCHE units, the heat transfer surface area density may be as high as 2,500 m2/m3. This high compactness implies an appreciable reduction in material reducing cost. In this study, heat transfer and tritium penetration analyses have been performed for two different channel configurations of the PCHE; (1) standard and (2) off-set. One of the goals of this study was to determine whether offsetting the hot and cold streams would significantly reduce the tritium flux, and whether or not it would affect the heat transfer significantly.
Directory of Open Access Journals (Sweden)
Jang-Won Seo
2015-05-01
Full Text Available Performance tests were carried out for a microchannel printed circuit heat exchanger (PCHE, which was fabricated with micro photo-etching and diffusion bonding technologies. The microchannel PCHE was tested for Reynolds numbers in the range of 100‒850 varying the hot-side inlet temperature between 40 °C–50 °C while keeping the cold-side temperature fixed at 20 °C. It was found that the average heat transfer rate and heat transfer performance of the countercurrrent configuration were 6.8% and 10%‒15% higher, respectively, than those of the parallel flow. The average heat transfer rate, heat transfer performance and pressure drop increased with increasing Reynolds number in all experiments. Increasing inlet temperature did not affect the heat transfer performance while it slightly decreased the pressure drop in the experimental range considered. Empirical correlations have been developed for the heat transfer coefficient and pressure drop factor as functions of the Reynolds number.
Directory of Open Access Journals (Sweden)
Aboaltabooq Mahdi Hatf Kadhum
2016-01-01
Full Text Available This paper analyzes the heat transfer characteristics of an ORC evaporator applied on a diesel engine using measured data from experimental work such as flue gas mass flow rate and flue gas temperature. A mathematical model was developed with regard to the preheater, boiler and the superheater zones of a counter flow evaporator. Each of these zones has been subdivided into a number of cells. The hot source of the ORC cycle was modeled. The study involves the variable heat input's dependence on the ORC system's heat transfer characteristics, with especial emphasis on the evaporator. The results show that the refrigerant's heat transfer coefficient has a higher value for a 100% load from the diesel engine, and decreases with the load decrease. Also, on the exhaust gas side, the heat transfer coefficient decreases with the decrease of the load. The refrigerant's heat transfer coefficient increased normally with the evaporator's tube length in the preheater zone, and then increases rapidly in the boiler zone, followed by a decrease in the superheater zone. The exhaust gases’ heat transfer coefficient increased with the evaporator’ tube length in all zones. The results were compared with result by other authors and were found to be in agreement.
Forced convection heat transfer in integrated microchannel heat sinks
Lee, Man
A microchannel heat sink, integrated with pressure and temperature microsensors, was fabricated to study convective boiling under uniform heat flux boundary condition. Utilizing a wafer bond and etch back technology, the heat source, temperature and pressure sensors were separated from the fluid flow by a membrane only 1.5mum in thickness; thus allowing good control of the thermal boundary conditions. Temperature and pressure distributions for various power levels and flow rates were measured. Single-phase liquid flow results, compared with numerical simulations, confirm that the heat flux boundary condition is indeed nearly uniform. The sensor arrays, particularly for two-phase flow, provide the spatial and temporal dependence of both the temperature and pressures fields. During two-phase flow, a pressure peak appears at the location of the liquid-vapor interface region. Simultaneously, qualitative visualizations of the evolving flow patterns have been correlated with quantitative temperature and pressure measurements. Based on the temperature and pressure measurements inside the microchannels, the empirical correlations of local pressure fluctuation frequency and pressure fluctuation amplitude are found to increase with increasing input power and Suratman number, but with decreasing Reynolds number. A flow regime map is plotted to distinguish the different kinds of flow pattern in microchannels. Moreover, the activity of nucleation sites as well as the ensuing bubble dynamics, from incipience to departure, was found to depend on the channel height. The critical size for active nucleation site increases with increasing microchannel height. Furthermore, size and shape effects on two-phase flow patterns in forced convection boiling were investigated in near rectangular microchannels with silicon substrate. Although detected, in contrast with triangular microchannels, annular flow was observed to be unstable. Instead, the dominant flow pattern was an unsteady
Heat Transfer in Porous Crystals Containing Adsorbed Gases
Babaei, Hasan; Wilmer, Christopher
Using molecular modeling, we investigated heat transfer phenomena in a porous crystal containing gases. This study was motivated by the challenge of quickly dissipating heat generated in metal-organic frameworks (MOFs) during gas adsorption. Our study reveals that thermal conductance is dominated by lattice thermal conductivity in the crystal, and that conductance decreases as the density of gas in the pores increases. We show that the observed decreased conductivity is due to phonon scattering in the crystal due to interactions with gas molecules. We have also investigated the effect of pore size and shape on thermal transport in these structures. We show that thermal conductivity of pure nanoporous crystals decreases with pore size. For nanoporous crystals with small pores, gas adsorption reduces thermal conductivity due to more phonon scatterings, whereas for larger pores, the increase in gas loading does not affect lattice thermal conductivity. We show that the probability of gas-crystal collisions is smaller for larger pores, which explains why loaded gases do not significantly affect thermal conductivity of large pore structures.
Heat Transfer Enhancement for Finned-tube Heat Exchangers with Winglets
Energy Technology Data Exchange (ETDEWEB)
O' Brien, James Edward; Sohal, Manohar Singh
2000-11-01
This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51 x 10-3 to 14.0 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 670 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean finsurface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal air-cooled condensers), the enhancement level is nearly a factor of two. At higher Reynolds numbers, the enhancement level is close to 50%.
Reducing Income Transfers to Refugee Immigrants
DEFF Research Database (Denmark)
Rosholm, Michael; Vejlin, Rune Majlund
2010-01-01
We estimate the effect of lowering income transfers to refugee immigrants in Denmark - labeled start-help - using a competing risk framework. Refugee immigrants obtaining residence permit before July 2002 received larger income transfers than those who obtained their residence permit later...
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...
Taha, T.J.; Thakur, D.B.; van der Meer, Theodorus H.
2012-01-01
In this work, heat transfer surface modification and heat transfer measurement technique is developed. Heat transfer investigation was aimed to study the effect of carbon nano fibers (extremely high thermal conductive material) on the enhancement level in heat transfer. Synthesis of these carbon
Optimal Prandtl number for heat transfer in rotating Rayleigh-Benard convection
Stevens, Richard J A M; Lohse, Detlef
2009-01-01
Numerical data for the heat transfer as a function of the Prandtl (Pr) and Rossby (Ro) numbers in turbulent rotating Rayleigh-Benard convection are presented for Rayleigh number Ra = 10^8. When Ro is fixed the heat transfer enhancement with respect to the non-rotating value shows a maximum as function of Pr. This maximum is due to the reduced efficiency of Ekman pumping when Pr becomes too small or too large. When Pr becomes small, i.e. for large thermal diffusivity, the heat that is carried by the vertical vortices spreads out in the middle of the cell, and Ekman pumping thus becomes less efficient. For higher Pr the thermal boundary layers (BLs) are thinner than the kinetic BLs and therefore the Ekman vortices do not reach the thermal BL. This means that the fluid that is sucked into the vertical vortices is colder than for lower Pr which limits the efficiency of the upwards heat transfer.
Directory of Open Access Journals (Sweden)
Guo Zerong
2016-01-01
Full Text Available To study the effect of variable heat transfer coefficient of fireworks and crackers on thermal explosion critical ambient temperature and time to ignition, considering the heat transfer coefficient as the power function of temperature, mathematical thermal explosion steady state and unsteady-state model of finite cylindrical fireworks and crackers with complex shell structures are established based on two-dimensional steady state thermal explosion theory. The influence of variable heat transfer coefficient on thermal explosion critical ambient temperature and time to ignition are analyzed. When heat transfer coefficient is changing with temperature and in the condition of natural convection heat transfer, critical ambient temperature lessen, thermal explosion time to ignition shorten. If ambient temperature is close to critical ambient temperature, the influence of variable heat transfer coefficient on time to ignition become large. For firework with inner barrel in example analysis, the critical ambient temperature of propellant is 463.88 K and the time to ignition is 4054.9s at 466 K, 0.26 K and 450.8s less than without considering the change of heat transfer coefficient respectively. The calculation results show that the influence of variable heat transfer coefficient on thermal explosion time to ignition is greater in this example. Therefore, the effect of variable heat transfer coefficient should be considered into thermal safety evaluation of fireworks to reduce potential safety hazard.
Natural convection heat transfer along vertical rectangular ducts
Energy Technology Data Exchange (ETDEWEB)
Ali, M. [King Saud University, Mechanical Engineering Department, Riyadh (Saudi Arabia)
2009-12-15
Experimental investigations have been reported on steady state natural convection from the outer surface of vertical rectangular and square ducts in air. Seven ducts have been used; three of them have a rectangular cross section and the rest have square cross section. The ducts are heated using internal constant heat flux heating elements. The temperatures along the vertical surface and the peripheral directions of the duct wall are measured. Axial (perimeter averaged) heat transfer coefficients along the side of each duct are obtained for laminar and transition to turbulent regimes of natural convection heat transfer. Axial (perimeter averaged) Nusselt numbers are evaluated and correlated using the modified Rayleigh numbers for laminar and transition regime using the vertical axial distance as a characteristic length. Critical values of the modified Rayleigh numbers are obtained for transition to turbulent. Furthermore, total overall averaged Nusselt numbers are correlated with the modified Rayleigh numbers and the area ratio for the laminar regimes. The local axial (perimeter averaged) heat transfer coefficients are observed to decrease in the laminar region and increase in the transition region. Laminar regimes are obtained at the lower half of the ducts and its chance to appear decreases as the heat flux increases. (orig.)
Exergy in near-field electromagnetic heat transfer
Iizuka, Hideo; Fan, Shanhui
2017-09-01
The maximum amount of usable work extractable from a given radiative heat flow defines the exergy. It was recently noted that the exergy in near-field radiative heat transfer can exceed that in the far-field. Here, we derive a closed form formula of exergy in the near-field heat transfer between two parallel surfaces. This formula reveals that, for a given resonant frequency, the maximum exergy depends critically on the resonant linewidth, and there exists an optimal choice of the linewidth that maximizes the exergy. Guided by the analytical result, we show numerically that with a proper choice of doping concentration, the heat flow between two properly designed SiC-coated heavily doped silicon regions can possess exergy that is significantly higher compared to the heat flow between two SiC regions where the heat flow is carried out by phonon-polaritons. Our work indicates significant opportunities for either controlling material properties or enhancing the fundamental potential for near-field heat transfer in thermal energy conversion through the approach of meta-material engineering.
Zipf, Verena; Willert, Daniel; Neuhäuser, Anton
2016-05-01
An innovative active latent heat storage concept was invented and developed at Fraunhofer ISE. It uses a screw heat exchanger (SHE) for the phase change during the transport of a phase change material (PCM) from a cold to a hot tank or vice versa. This separates heat transfer and storage tank in comparison to existing concepts. A test rig has been built in order to investigate the heat transfer coefficients of the SHE during melting and crystallization of the PCM. The knowledge of these characteristics is crucial in order to assess the performance of the latent heat storage in a thermal system. The test rig contains a double shafted SHE, which is heated or cooled with thermal oil. The overall heat transfer coefficient U and the convective heat transfer coefficient on the PCM side hPCM both for charging and discharging have been calculated based on the measured data. For charging, the overall heat transfer coefficient in the tested SHE was Uch = 308 W/m2K and for discharging Udis = 210 W/m2K. Based on the values for hPCM the overall heat transfer coefficients for a larger SHE with steam as heat transfer fluid and an optimized geometry were calculated with Uch = 320 W/m2K for charging and Udis = 243 W/m2K for discharging. For pressures as high as p = 100 bar, an SHE concept has been developed, which uses an organic fluid inside the flight of the SHE as working media. With this concept, the SHE can also be deployed for very high pressure, e.g. as storage in solar thermal power plants.
Thermal Regulation of Heat Transfer Processes
2014-10-02
Wang, R. T. Zheng, J. W. Gao, and G. Chen, Heat Conduction Mechanisms in Nanofluids and Suspensions, Nano Today , 7, 124-136 (2012). 3. P. C...the catalysis properties of hollow Cr2O3 structure, Journal of Materials Chemistry A, 2, 12270-12775 (2014). 12770-12775 8. Y. Yang, S. W. Lee, H...W.; Chen, G. Nano Today 2012, 7, (2), 124-‐136. 9. Albanis, V. Light-‐Induced Structural Transition
Transient Heat Transfer in Coated Superconductors.
1982-10-29
account for tran- sient effects as pointed out by Iwasa. 23 To model these transient conditions the following form was used qFB = (200(TL - Tbath)’ Ŗ...QNB*FRACTNB+ QFB *FRACTFB FJ=QTB*AREA GOTO 900 C C C TRANSITION BOILING - OUT OF THE BOUNDARY LAYER C C OTHSS (THE STEADY STATE HEAT FLUX IN C...THE FLUID C PROPERTIES WILL DROP OUT IN THE RATIO. C QFB =QFBSS*(EFBSS/EBLPUA) IF(PATHTB.GT.1.)GOTO 420 FJ= QFB *AREA GOTO 900 C C C FILM BOILING - OUT OF
Energy Technology Data Exchange (ETDEWEB)
Orloff, D.; Hojjatie, B.; Bloom, F.
1995-07-01
Results of this study indicate that under the conditions where the two boundaries are maintained at the same temperature, the viscous heat dissipation within the lubricant, due to viscous drag and inertial effects, plays a major role in the net heat transfer. However, when the inner surface temperature is much greater than that of the shoe, the effect of viscous heat dissipation is reduced significantly. For the conditions analyzed in this study, the regions under the solid part of the shoe, which are associated with a greater lubricant velocity, had a significant influence on the magnitude of the heat transfer from the oil to the roll; because of a greater lubricant thickness for the left-hand sub-channel, the dissipated heat, and net heat transfer under the solid part in the left-hand sub-channel was greater than that for the corresponding region in the right-hand sub-channel. Numerical techniques such as finite difference or finite element analysis should be utilized to determine the thermal performance of the press roll subjected to a temperature dependent viscosity. and other types of boundary conditions. The temperature distributions predicted from such a model should be incorporated in a finite element model to determine the stress distribution within the roll coating for various design and operating conditions.
Characterizations of Nanofluid Heat Transfer Enhancements
2013-09-06
and ZnO) on waste activated sludge anaerobic digestion . Bioresource Technology, 2011. 102(22): p. 10305-10311. 62. Jiang, W., H. Mashayekhi, and B...manufacturer reported porosity of 18.8%. Based on the modified form of Renkin’s equation [1], the membrane pore size is large enough that the...can be determined experimentally. The overall NaCl mass transfer resistance (RT) can be calculated using equation 1. t vR A C C T pt 2 ln 0
Fem Formulation of Heat Transfer in Cylindrical Porous Medium
Azeem; Khaleed, H. M. T.; Soudagar, Manzoor Elahi M.
2017-08-01
Heat transfer in porous medium can be derived from the fundamental laws of flow in porous region ass given by Henry Darcy. The fluid flow and energy transport inside the porous medium can be described with the help of momentum and energy equations. The heat transfer in cylindrical porous medium differs from its counterpart in radial and axial coordinates. The present work is focused to discuss the finite element formulation of heat transfer in cylindrical porous medium. The basic partial differential equations are derived using Darcy law which is the converted into a set of algebraic equations with the help of finite element method. The resulting equations are solved by matrix method for two solution variables involved in the coupled equations.
Nuclear reactor fuel element having improved heat transfer
Garnier, J.E.; Begej, S.; Williford, R.E.; Christensen, J.A.
1982-03-03
A nuclear reactor fuel element having improved heat transfer between fuel material and cladding is described. The element consists of an outer cladding tube divided into an upper fuel section containing a central core of fissionable or mixed fissionable and fertile fuel material, slightly smaller in diameter than the inner surface of the cladding tube and a small lower accumulator section, the cladding tube being which is filled with a low molecular weight gas to transfer heat from fuel material to cladding during irradiation. A plurality of essentially vertical grooves in the fuel section extend downward and communicate with the accumulator section. The radial depth of the grooves is sufficient to provide a thermal gradient between the hot fuel surface and the relatively cooler cladding surface to allow thermal segregation to take place between the low molecular weight heat transfer gas and high molecular weight fission product gases produced by the fuel material during irradiation.
Magnetic nanofluid properties as the heat transfer enhancement agent
Directory of Open Access Journals (Sweden)
Roszko Aleksandra
2016-01-01
Full Text Available The main purpose of this paper was to investigate an influence of various parameters on the heat transfer processes with strong magnetic field utilization. Two positions of experimental enclosure in magnetic environment, two methods of preparation and three different concentrations of nanoparticles (0.0112, 0.056 and 0.112 vol.% were taken into account together with the magnetic field strength. Analysed nanofluids consisted of distilled water (diamagnetic and Cu/CuO particles (paramagnetic of 40–60 nm size. The nanofluids components had different magnetic properties what caused complex interaction of forces’ system. The heat transfer data and fluid flow structure demonstrated the influence of magnetic field on the convective phenomena. The most visible consequence of magnetic field application was the heat transfer enhancement and flow reorganization under applied conditions.
Radiative heat transfer by the Monte Carlo method
Hartnett †, James P; Cho, Young I; Greene, George A; Taniguchi, Hiroshi; Yang, Wen-Jei; Kudo, Kazuhiko
1995-01-01
This book presents the basic principles and applications of radiative heat transfer used in energy, space, and geo-environmental engineering, and can serve as a reference book for engineers and scientists in researchand development. A PC disk containing software for numerical analyses by the Monte Carlo method is included to provide hands-on practice in analyzing actual radiative heat transfer problems.Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university level textbooks by providing in-depth review articles over a broader scope than journals or texts usually allow.Key Features* Offers solution methods for integro-differential formulation to help avoid difficulties* Includes a computer disk for numerical analyses by PC* Discusses energy absorption by gas and scattering effects by particles* Treats non-gray radiative gases* Provides example problems for direct applications in energy, space, and geo-environmental engineering
Stagnation Point Heat Transfer with Gas Injection Cooling
Vancrayenest, B.; Tran, M. D.; Fletcher, D. G.
2005-01-01
The present paper deals with an experimental study of the stagnation-point heat transfer to a cooled copper surface with gas injection under subsonic conditions. Test were made with a probe that combined a steady-state water-cooled calorimeter that allows the capability to study convective blockage and to perform heat transfer measurements in presence of gas injection in the stagnation region. The copper probe was pierced by 52 holes, representing 2.4% of the total probe surface. The 1.2 MW high enthalpy plasma wind tunnel was operated at anode powers between 130 and 230 kW and a static pressures from 35 hPa up to 200 hPa. Air, carbon dioxide and argon were injected in the mass flow range 0-0.4 g/s in the boundary layer developed around the 50 mm diameter probe. The measured stagnation-point heat transfer rates are reported and discussed.
Representation of Elementary School Teachers on Concept of Heat Transfer
Anam, R. S.; Widodo, A.; Sopandi, W.
2017-09-01
The purpose of this study is to get a decription of how elementary teachers represent the understanding on the concept of heat transfer both conduction and convection to their students. This is a descriptive research, data collect by asking teacher to give their picture and explanation about the heat transfer concept. Subjects in this study there are six teachers who already have experience teaching over five years. Based on the analysis results obtained that the representation of teachers in the concept of heat transfer there are many alternative conceptions and in the description of the given phenomenon is less able to provide optimal explanation for students. The impact of teacher representation that is not in accordance with scientific rules will cause the learners not optimal for students to understand the concepts. Therefore to produce a better and tangible learning for students the teacher needs to improve his understanding that will support his representation in explaining the concept to the students more better.
Energy Technology Data Exchange (ETDEWEB)
Gotovsky, M.A. [Polzunov Institute, Saint Petersburg (Russian Federation)
2001-07-01
Forced convection boiling is the process used widely in a lot of industry branches including NPP. Heat transfer intensity under forced convection boiling is considered in different way in dependence on conditions. One of main problems for the process considered is an influence of interaction between forced flow and boiling on heat transfer character. For saturated water case a transition from ''pure'' forced convection to nucleate boiling can be realized in smooth form. (author)
Heat and mass transfer and hydrodynamics in swirling flows (review)
Leont'ev, A. I.; Kuzma-Kichta, Yu. A.; Popov, I. A.
2017-02-01
Research results of Russian and foreign scientists of heat and mass transfer in whirling flows, swirling effect, superficial vortex generators, thermodynamics and hydrodynamics at micro- and nanoscales, burning at swirl of the flow, and technologies and apparatuses with the use of whirling currents for industry and power generation were presented and discussed at the "Heat and Mass Transfer in Whirling Currents" 5th International Conference. The choice of rational forms of the equipment flow parts when using whirling and swirling flows to increase efficiency of the heat-power equipment and of flow regimes and burning on the basis of deep study of the flow and heat transfer local parameters was set as the main research prospect. In this regard, there is noticeable progress in research methods of whirling and swirling flows. The number of computational treatments of swirling flows' local parameters has been increased. Development and advancement of the up to date computing models and national productivity software are very important for this process. All experimental works are carried out with up to date research methods of the local thermoshydraulic parameters, which enable one to reveal physical mechanisms of processes: PIV and LIV visualization techniques, high-speed and infrared photography, high speed registration of parameters of high-speed processes, etc. There is a problem of improvement of researchers' professional skills in the field of fluid mechanics to set adequately mathematics and physics problems of aerohydrodynamics for whirling and swirling flows and numerical and pilot investigations. It has been pointed out that issues of improvement of the cooling system and thermal protection effectiveness of heat-power and heat-transfer equipment units are still actual. It can be solved successfully using whirling and swirling flows as simple low power consumption exposing on the flow method and heat transfer augmentation.
Heat Transfer in High-Temperature Fibrous Insulation
Daryabeigi, Kamran
2002-01-01
The combined radiation/conduction heat transfer in high-porosity, high-temperature fibrous insulations was investigated experimentally and numerically. The effective thermal conductivity of fibrous insulation samples was measured over the temperature range of 300-1300 K and environmental pressure range of 1.33 x 10(exp -5)-101.32 kPa. The fibrous insulation samples tested had nominal densities of 24, 48, and 72 kilograms per cubic meter and thicknesses of 13.3, 26.6 and 39.9 millimeters. Seven samples were tested such that the applied heat flux vector was aligned with local gravity vector to eliminate natural convection as a mode of heat transfer. Two samples were tested with reverse orientation to investigate natural convection effects. It was determined that for the fibrous insulation densities and thicknesses investigated no heat transfer takes place through natural convection. A finite volume numerical model was developed to solve the governing combined radiation and conduction heat transfer equations. Various methods of modeling the gas/solid conduction interaction in fibrous insulations were investigated. The radiation heat transfer was modeled using the modified two-flux approximation assuming anisotropic scattering and gray medium. A genetic-algorithm based parameter estimation technique was utilized with this model to determine the relevant radiative properties of the fibrous insulation over the temperature range of 300-1300 K. The parameter estimation was performed by least square minimization of the difference between measured and predicted values of effective thermal conductivity at a density of 24 kilograms per cubic meters and at nominal pressures of 1.33 x 10(exp -4) and 99.98 kPa. The numerical model was validated by comparison with steady-state effective thermal conductivity measurements at other densities and pressures. The numerical model was also validated by comparison with a transient thermal test simulating reentry aerodynamic heating
A numerical study of vorticity-enhanced heat transfer
Wang, Xiaolin; Alben, Silas
2012-11-01
The Glezer lab at Georgia Tech has found that vorticity produced by vibrated reeds can improve heat transfer in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we simulate the heat transfer process in a 3-dimensional plate-fin heat sink. We propose a simplified model by considering flow and temperature in a 2-D channel, and extend the model to the third dimension using a 1-D heat fin model. We simulate periodically steady-state solutions. We determine how the global Nusselt number is increased, depending on the vortices' strengths and spacings, in the parameter space of Reynolds and Peclet numbers. We find a surprising spatial oscillation of the local Nusselt number due to the vortices. Support from NSF-DMS grant 1022619 is acknowledged.
A Mathematical Model of Heat Transfer in Spheroplastic
Directory of Open Access Journals (Sweden)
V. S. Zarubin
2016-01-01
Full Text Available Spheroplastics are composite materials composed of a polymer or organosilicate binder and hollow spherical inclusions (mostly, of glass, but there are also of carbon, phenol, and epoxy, which are called microspheres and have a diameter within a millimeter with the wall thickness of several micrometers. To reduce the material density in watercraft constructions sometimes are used so called macrospheres of up to 40 mm in diameter and shell thickness of 0,5--1,5 mm from spheroplastic with microspheres.Microspheres may contain inert gases such as nitrogen. Many countries have commercialised quartz microspheres. The USA, in particular, produces Q-Gel microspheres with density of 300 kg / m3, the bulk density - 100 kg / m3 and the average diameter of 75 microns,characterized by a high mechanical strength and low cost. Carbon microspheres having low mechanical properties can absorb radio waves in certain frequency ranges. Spheroplastic with silicone microspheres combine relatively high mechanical and dielectric properties.In virtue of low thermal conductivity spheroplastics are used in various heat-insulating structures. As the thermal insulation coatings, the spheroplastic covers the outer surface of the pipes, in particular oil and gas pipelines in the permafrost zones, regions of swampy ground, and underwater. The effective heat conductivity factor, primarily, determines the specific application of spheroplastic as a thermal insulation material. To quantify the value of this factor is necessary to have a mathematical model describing heat ransfer in spheroplastic.The paper presents a four-phase mathematical model of the heat transfer in a representative element of a spheroplastic structure placed in an unlimited array of homogeneous material, the thermal conductivity of which is to be determined as desired characteristics of spheroplastic. This model in combination with a dual variational formulation of stationary heat conduction problem in the
Heat and mass transfer in porous cavity: Assisting flow
Energy Technology Data Exchange (ETDEWEB)
Badruddin, Irfan Anjum [Dept. of Mechanical Engineering, University of Malaya, Kuala Lumpur, 50603 (Malaysia); Quadir, G. A. [School of Mechatronic Engineering, University Malaysia Perlis, Pauh Putra, 02600 Arau, Perlis (Malaysia)
2016-06-08
In this paper, investigation of heat and mass transfer in a porous cavity is carried out. The governing partial differential equations are non-dimensionalised and solved using finite element method. The left vertical surface of the cavity is maintained at constant temperature and concentration which are higher than the ambient temperature and concentration applied at right vertical surface. The top and bottom walls of the cavity are adiabatic. Heat transfer is assumed to take place by natural convection and radiation. The investigation is carried out for assisting flow when buoyancy and gravity force act in same direction.
Numerical prediction of flow, heat transfer, turbulence and combustion
Spalding, D Brian; Pollard, Andrew; Singhal, Ashok K
1983-01-01
Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion: Selected Works of Professor D. Brian Spalding focuses on the many contributions of Professor Spalding on thermodynamics. This compilation of his works is done to honor the professor on the occasion of his 60th birthday. Relatively, the works contained in this book are selected to highlight the genius of Professor Spalding in this field of interest. The book presents various research on combustion, heat transfer, turbulence, and flows. His thinking on separated flows paved the way for the multi-dimensional modeling of turbu
Simple heat transfer correlations for turbulent tube flow
Directory of Open Access Journals (Sweden)
Taler Dawid
2017-01-01
Full Text Available The paper presents three power-type correlations of a simple form, which are valid for Reynolds numbers range from 3·103 ≤ Re ≤ 106, and for three different ranges of Prandtl number: 0.1 ≤ Pr ≤ 1.0, 1.0 < Pr ≤ 3.0, and 3.0 < Pr ≤ 103. Heat transfer correlations developed in the paper were compared with experimental results available in the literature. The comparisons performed in the paper confirm the good accuracy of the proposed correlations. They are also much simpler compared with the relationship of Gnielinski, which is also widely used in the heat transfer calculations.
Convective heat transfer on an inlet guide vane.
Holmer, M L; Eriksson, L E; Sunden, B
2001-05-01
The flow and temperature fields around an inlet guide vane are determined numerically by a CFD method. Outer surface temperatures, heat transfer coefficient distributions, and static pressure distributions are presented. Three different thermal boundary conditions on the vane are analysed. The computed results are compared with experimental data. The governing equations are solved by a finite-volume method with the low Reynolds number version of the k-omega turbulence model by Wilcox implemented. It is found that the calculated results agree best with measurements if a conjugate heat transfer approach is applied and thus this wall condition is recommended for future investigations of film cooling of guide vanes and turbine blades.
Theory of heat transfer with forced convection film flows
Shang, Deyi
2010-01-01
Developing a new treatment of ""Free Convection Film Flows and Heat Transfer"" began in Shang's first monograph and is continued in this monograph. The current book displays the recent developments of laminar forced convection and forced film condensation. It is aimed at revealing the true features of heat and mass transfer with forced convection film flows to model the deposition of thin layers. The novel mathematical similarity theory model is developed to simulate temperature - and concentration - dependent physical processes. The following topics are covered in this book: Mathematical meth
Heat Transfer in a Fixed Bed of Straw Char
DEFF Research Database (Denmark)
Fjellerup, Jan Søren; Henriksen, Ulrik Birk; Jensen, Anker
2003-01-01
A model for the thermal conductivity of a straw char bed has been developed. The model extends the work of Yagi and Kunii to describe heat transfer in a bed of cylinders, using a relationship between the interparticle distance and the external porosity. To verify the model, thermal conductivity...... the experimental uncertainty over the range of conditions investigated. The heat transfer model was used in a parametric study to evaluate the effect of gas flow rate, particle diameter, porosity, and temperature on the thermal conductivity in a straw char bed....
Heat Transfer Enhancement in Turbulent Flows by Blocked Surfaces
Directory of Open Access Journals (Sweden)
Onur YEMENİCİ
2013-04-01
Full Text Available In this study, the heat transfer analyses over flat and blocked surfaces were carried out in turbulent flow under the influence of the block height. A constant-temperature hot wire anemometer was used to the velocity and turbulent intensity measurements, while temperature values were measured by copper-constantan thermocouples. The average Stanton numbers for block heights of 15 and 25 mm were higher than those of flat surface by %38 and %84, respectively. The results showed that the presence of the blocks increased the heat transfer and the enhancement rose with block heights
Radiative Heat Transfer Between Core-Shell Nanoparticles
Nikbakht, Moladad
2017-01-01
Radiative heat transfer in systems with core-shell nanoparticles may exhibit not only a combination of disparate physical properties of its components but also further enhanced properties that arise from the synergistic properties of the core and shell components. We study the thermal conductance between two core-shell nanoparticles (CSNPs). We predict that the radiative heat transfer in a dimer of Au@SiO$_2$ CSNPs (i.e., silica-coated gold nanoparticles) could be enhanced several order of ma...
Numerical Analysis of Heat Transfer in Fire-Protective Coatings Deformable upon Heating
Rudzinsky, V. P.; Garashchenko, A. N.
2016-02-01
Numerical studies of heat transfer in fire-protective coatings deformable (intumescent) upon heating have been conducted. The optimum combination of the computation-scheme parameters providing stability, convergence and satisfactory accuracy of solutions has been determined. An effect of basic characteristics of materials in real range of their change that made it possible to estimate the degree of influence of properties on the fire-protective efficiency of coatings and the level of warm-up (flame resistance) of structures to be protected with them has been studied. The possibility of using developed models and techniques to estimate and provide the required level of fire safety of polymer-based materials (in particular, elastomers and structures and products on their basis) is considered. The results of estimating the mass rate of evolving gaseous thermal-decomposition products that determine, in a considerable extent, the material combustibility have been presented. The numerical analysis results have demonstrated the potentiality of reducing the combustibility of such materials and increasing limits of their fire resistance at the expense of organizing the intumescence of a material upon heating by means of modification of their initial formulations as well as with the aid of an additional layer made of the intumescent coating compatible with an elastomer.
Combined heat and mass transfer device for improving separation process
Tran, Thanh Nhon
1999-01-01
A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area.
Heat Transfer Principles in Thermal Calculation of Structures in Fire.
Zhang, Chao; Usmani, Asif
2015-11-01
Structural fire engineering (SFE) is a relatively new interdisciplinary subject, which requires a comprehensive knowledge of heat transfer, fire dynamics and structural analysis. It is predominantly the community of structural engineers who currently carry out most of the structural fire engineering research and design work. The structural engineering curriculum in universities and colleges do not usually include courses in heat transfer and fire dynamics. In some institutions of higher education, there are graduate courses for fire resistant design which focus on the design approaches in codes. As a result, structural engineers who are responsible for structural fire safety and are competent to do their jobs by following the rules specified in prescriptive codes may find it difficult to move toward performance-based fire safety design which requires a deep understanding of both fire and heat. Fire safety engineers, on the other hand, are usually focused on fire development and smoke control, and may not be familiar with the heat transfer principles used in structural fire analysis, or structural failure analysis. This paper discusses the fundamental heat transfer principles in thermal calculation of structures in fire, which might serve as an educational guide for students, engineers and researchers. Insights on problems which are commonly ignored in performance based fire safety design are also presented.
Direct numerical simulation of heat transfer over riblets
Energy Technology Data Exchange (ETDEWEB)
Stalio, E.; Nobile, E
2003-06-01
Riblets are well-known as a passive mean for drag reduction in turbulent flow conditions, but their effectiveness for heat transfer is quite controversial. In this paper we present the numerical results for fully developed laminar and turbulent flow and heat transfer in a channel with triangular riblets. The turbulent study is performed by means of direct numerical simulation at a Reynolds number Re{sub {tau}}=180 based on the wall-shear velocity, for a fluid with a Prandtl number Pr=0.71. Four different ribbed channels are considered, under a constant heat flux boundary condition, and correspond to ridge angle {alpha}=45 deg. and 60 deg., and riblet spacing s{sup +}=20 and s{sup +}=40. The results obtained, for the flow and turbulent quantities, are in good agreement with past experimental and numerical studies, and correctly reproduce drag reduction over the smaller s{sup +}=20 riblets and drag increase over the larger s{sup +}=40 riblets. The predicted heat transfer efficiency of riblets do not agree with some experimental results, and is below that of a flat plate for all the configurations. The conditions for heat transfer enhancement are discussed.
Enhanced boiling heat transfer in horizontal test bundles
Energy Technology Data Exchange (ETDEWEB)
Trewin, R.R.; Jensen, M.K.; Bergles, A.E.
1994-08-01
Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.
Transient Heat Transfer Model for Car Body Primer Curing
D. Zabala; N. Sánchez; J. Pinto
2010-01-01
A transient heat transfer mathematical model for the prediction of temperature distribution in the car body during primer baking has been developed by considering the thermal radiation and convection in the furnace chamber and transient heat conduction governing equations in the car framework. The car cockpit is considered like a structure with six flat plates, four vertical plates representing the car doors and the rear and front panels. The other two flat plates are the...
Linearization properties, first integrals, nonlocal transformation for heat transfer equation
Orhan, Özlem; Özer, Teoman
2016-08-01
We examine first integrals and linearization methods of the second-order ordinary differential equation which is called fin equation in this study. Fin is heat exchange surfaces which are used widely in industry. We analyze symmetry classification with respect to different choices of thermal conductivity and heat transfer coefficient functions of fin equation. Finally, we apply nonlocal transformation to fin equation and examine the results for different functions.
Near-field heat transfer between multilayer hyperbolic metamaterials
Energy Technology Data Exchange (ETDEWEB)
Biehs, Svend-Age [Oldenburg Univ. (Germany). Inst. fuer Physik; Ben-Abdallah, Philippe [Univ. Paris-Sud 11, Palaiseau (France). Lab. Charles Fabry; Univ. Sherbrooke, PQ (Canada). Dept. of Mechanical Engineering
2017-05-01
We review the near-field radiative heat flux between hyperbolic materials focusing on multilayer hyperbolic meta-materials. We discuss the formation of the hyperbolic bands, the impact of ordering of the multilayer slabs, as well as the impact of the first single layer on the heat transfer. Furthermore, we compare the contribution of surface modes to that of hyperbolic modes. Finally, we also compare the exact results with predictions from effective medium theory.
Numerical Modeling of Transient Heat Transfer in Longitudinal Fin
Farshad Panahizadeh; Mohammed Hasnat; Ashkan Ghafour
2017-01-01
The main objective of the present numerical study is to investigate the transient heat transfer in one kind of all-purpose longitudinal fin with the triangular profile. The lateral surface of the concerned fin and the tip of it are subjected to general situations included heat flux at the base and insulation on the tip. For this study developed a one dimensional in house code written by Fortran 90 programming language by using finite difference method with an implicit scheme...
Heat Transfer Analysis of a Diesel Engine Head
M. Diviš; R. Tichánek; M. Španiel
2003-01-01
This paper documents the research carried out at the Josef Božek Research Center of Engine and Automotive Engineering dealing with extended numerical stress/deformation analyses of engines parts loaded by heat and mechanical forces. It contains a detailed description of a C/28 series diesel engine head FE model and a discussion of heat transfer analysis tunning and results. The head model consisting of several parts allows a description of contact interaction in both thermal and mechanical an...
Heat transfer phenomena during thermal processing of liquid particulate mixtures-A review.
Singh, Anubhav Pratap; Singh, Anika; Ramaswamy, Hosahalli S
2017-05-03
During the past few decades, food industry has explored various novel thermal and non-thermal processing technologies to minimize the associated high-quality loss involved in conventional thermal processing. Among these are the novel agitation systems that permit forced convention in canned particulate fluids to improve heat transfer, reduce process time, and minimize heat damage to processed products. These include traditional rotary agitation systems involving end-over-end, axial, or biaxial rotation of cans and the more recent reciprocating (lateral) agitation. The invention of thermal processing systems with induced container agitation has made heat transfer studies more difficult due to problems in tracking the particle temperatures due to their dynamic motion during processing and complexities resulting from the effects of forced convection currents within the container. This has prompted active research on modeling and characterization of heat transfer phenomena in such systems. This review brings to perspective, the current status on thermal processing of particulate foods, within the constraints of lethality requirements from safety view point, and discusses available techniques of data collection, heat transfer coefficient evaluation, and the critical processing parameters that affect these heat transfer coefficients, especially under agitation processing conditions.
Enhanced heat transfer characteristics of conjugated air jet impingement on a finned heat sink
Directory of Open Access Journals (Sweden)
Qiu Shuxia
2017-01-01
Full Text Available Air jet impingement is one of the effective cooling techniques employed in micro-electronic industry. To enhance the heat transfer performance, a cooling system with air jet impingement on a finned heat sink is evaluated via the computational fluid dynamics method. A two-dimensional confined slot air impinging on a finned flat plate is modeled. The numerical model is validated by comparison of the computed Nusselt number distribution on the impingement target with published experimental results. The flow characteristics and heat transfer performance of jet impingement on both of smooth and finned heat sinks are compared. It is observed that jet impingement over finned target plate improves the cooling performance significantly. A dimensionless heat transfer enhancement factor is introduced to quantify the effect of jet flow Reynolds number on the finned surface. The effect of rectangular fin dimensions on impingement heat transfer rate is discussed in order to optimize the cooling system. Also, the computed flow and thermal fields of the air impingement system are examined to explore the physical mechanisms for heat transfer enhancement.
Numerical study on condensation heat transfer of trapezoid grooved surfaces
Directory of Open Access Journals (Sweden)
Baojin Qi
2016-05-01
Full Text Available This article presents a numerical analysis and experimental study on condensation heat transfer and fluid flow for filmwise condensation on trapezoid grooved surfaces. First, a physical model was properly simplified based on some reasonable assumptions. Then, the coupled non-linear governing equations for the mass transfer, fluid flow, and two-dimensional thermal conduction were developed. The relationship between z-coordinate and heat transfer was obtained by solving the equations numerically. The influences of groove length and basic angle were discussed. The calculation results showed that the heat flux decreased with increase in groove length, and the decline range also decreased gradually. The calculation results also suggested that the heat flux through groove with α = 60° was lower than the groove with α = 75° at the top of the groove, while the opposite conclusion was obtained at the low parts. The distributions of wall temperature and heat flux on trapezoid groove were also studied systematically. The distribution of surface temperature and heat flux presents obvious lateral inhomogeneity, and the maximum wall temperature and heat flux were both obtained in region II. The thermal resistance of groove with α = 60° was lower but the liquid-discharged ability was better than that of groove with α = 75°. In order to validate the feasibility and reliability of the present analyses and to further investigate the heat transfer performance of trapezoid grooved surfaces, experiments were carried out with three condensing plates including two trapezoid grooved surfaces in different physical dimensions and one smooth surface. The experimental data obtained under various schooling were compared with the calculations, and the experimental results for different condensing plates are all in good agreement with the numerical model, with a maximum deviation less than 15%. Moreover, the trapezoid grooves can enhance the
Improvement of heat transfer by means of ultrasound: Application to a double-tube heat exchanger.
Legay, M; Simony, B; Boldo, P; Gondrexon, N; Le Person, S; Bontemps, A
2012-11-01
A new kind of ultrasonically-assisted heat exchanger has been designed, built and studied. It can be seen as a vibrating heat exchanger. A comprehensive description of the overall experimental set-up is provided, i.e. of the test rig and the acquisition system. Data acquisition and processing are explained step-by-step with a detailed example of graph obtained and how, from these experimental data, energy balance is calculated on the heat exchanger. It is demonstrated that ultrasound can be used efficiently as a heat transfer enhancement technique, even in such complex systems as heat exchangers. Copyright © 2012 Elsevier B.V. All rights reserved.
Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A
2014-11-15
Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for
Khaled, A.-R. A.
2014-01-01
Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost. PMID:24719572
Influence of Local Zones of Intensive Heat Transfer on Thermal Regime of Heat Supply Objects
Directory of Open Access Journals (Sweden)
Maksimov Vyacheslav I.
2015-01-01
Full Text Available The results of mathematical simulation of conjugate heat transfer for heat supply object are represented. The turbulent regime of air motion in a closed cavity with the enclosing walls from reinforced concrete and glass is examined. On the outer boundary, which includes window aperture, the conditions of convective-radiation heat exchange with environment are realized. Is solved the system of the dimensionless equations within the framework of thermal conductivity model for the solid walls and Navier-Stokes for the gas. The influence of the local zones of intensive heat transfer on the thermal regime of the heat supply objects is established. Are determined the values of the dimensionless heat exchange coefficient on division border “air - wall”. The analysis of the values of mean temperatures of the solution region is carried out.
Khaled, A-R A
2014-01-01
Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost.
Heat transfer at the sintered layer-polysynthetic material interface inside heat micro pipes
Sprinceana, Siviu; Mihai, Ioan
2016-12-01
If micro heat pipe heat transfers, the inside working fluid goes through a biphasic state. The flow of the liquid and the vapor thereof by the capillary beds of frittered copper and the layer of capillary polysynthetic material and migration of vapors liquid from the end, takes the heat flow towards the end where a transfer of heat may occur only if there is a difference in temperature between the end of a flat micro heat pipe that gives the acquirer heat and heat flux. The porosity of the material is total pore of the total material volume. In the analysis of heat and mass transfer through porous media, both convective and conductive transfer forms can not be separated, because of the surfaces in contact between the two capillar layers. It had been studied the dependence of the rate of flow of liquid through the frittered porous media, and Reynolds polysynthetic. It tracks changes in the Reynolds number based on the interior capillary porosity. They traced in Mathcad [1] the graphs for changing the Reynolds number of capillary pressure by capillary porosity.
A Review of Boiling Heat Transfer Processes at High Heat Flux
1991-04-01
Bjorge , et al. (Ref. 168) and Stephan and Auracher (Ref. 169) later presented variations of the superposition approach. For additional approaches... Bjorge , R. W., Hall, G. R., and Rohsenow, W. M., "Correlation of Forced Convection Boiling Heat Transfer Data," Int. J. Heat Mass Trans., Vol. 25, No
Convective Heat Transfer Analysis in Fluid Flow with Turbulence Promoters with Heat Pipes
Directory of Open Access Journals (Sweden)
Theodor Mateescu
2007-01-01
Full Text Available The present paper proposes the analysis and the simulation of the convection heat transfer into the fluid flow with turbulence promoters utilizing heat pipes. The study is based on the necesity of the unconventional energy forms capitalization, increasing of the energy efficiency and leads to the energy consumtion decrease in concordance with the sustainable development concept.
Rojas-Trigos, J. B.; Bermejo-Arenas, J. A.; Marin, E.
2012-01-01
In this paper, some heat transfer characteristics through a sample that is uniformly heated on one of its surfaces by a power density modulated by a periodical square wave are discussed. The solution of this problem has two contributions, comprising a transient term and an oscillatory term, superposed to it. The analytical solution is compared to…
Heat transfer and heating rate of food stuffs in commercial shop ovens
Indian Academy of Sciences (India)
Heat transfer and heating rate of food stuffs in commercial shop ovens. P NAVANEETHAKRISHNAN. ∗. , P S S SRINIVASAN and. S DHANDAPANI. Department of Mechanical Engineering, Kongu Engineering College,. Perundurai 638 052 e-mail: pnkmech@gmail.com, pnkmech@yahoo.co.in. MS received 24 May 2006; ...
Jiao, Anjun; Zhang, Yuwen; Ma, Hongbin; Critser, John
2010-01-01
Heat and mass transfer in a circular tube subject to the boundary condition of the third kind is investigated. The closed form of temperature and concentration distributions, the local Nusselt number based on the total external heat transfer and convective heat transfer inside the tube, as well as the Sherwood number were obtained. The effects of Lewis number and Biot number on heat and mass transfer were investigated. PMID:20862211
Claudia Toro; Rocco, Matteo V; Emanuela Colombo
2016-01-01
The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP) plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the heat transfer fluid for a Rankine thermal cycle as an alternative to more traditional working fluids thereby reducing maintenance operations and providing the power section with a higher degree of flexibility To suppl...
Similarity Solutions for Flow and Heat Transfer of Non-Newtonian Fluid over a Stretching Surface
Atta Sojoudi; Ali Mazloomi; Saha, Suvash C.; Gu, Y. T.
2014-01-01
Similarity solutions are carried out for flow of power law non-Newtonian fluid film on unsteady stretching surface subjected to constant heat flux. Free convection heat transfer induces thermal boundary layer within a semi-infinite layer of Boussinesq fluid. The nonlinear coupled partial differential equations (PDE) governing the flow and the boundary conditions are converted to a system of ordinary differential equations (ODE) using two-parameter groups. This technique reduces the number of ...
Study of heat production and transfer in shredded tires
Sellassie, Kassahun G.
The purpose of this study is to determine the cause(s) of initial exothermic reactions in shredded tire. The primary hypothesis was that the oxidation of exposed steel wires, the oxidation of rubber, or sulfur causes the exothermic reactions in shredded tire. Laboratory tests were conducted to determine the heat transfer properties of the shredded tires by using a hot-plate apparatus. The experiments were conducted by varying the physical and environmental conditions as follows: (1) Tire size, (2) Wire content, (3) Water content, (4) Effective stress, (5) Air supply, (6) pH, (7) Humic Acid. First, laboratory testing was conducted to determine the effects of tire size on the heat transfer properties of shredded tires. The heat coefficient and diffusivity ranged from 3.0 to 3.5 W/m-K and 0.0002 to 0.00084 m 2/hour, respectively. Next, experiments were conducted to determine the effects of wire content on the exothermic reaction rate of tire shreds. When various amounts of wire (i.e., 5% to 15%) were exposed, the reaction rate increased, 2800 Btu for every lb of iron that is oxidized. In comparison, tire shreds with no wire were also tested under the same experimental conditions as above, however, no exothermic reaction occurred. These tests (i.e., with no wire) illustrate that carbon black in rubber molecule considers not oxidize. It was postulated that the reaction between iron in the wire and sulfur in the tire may be a potential cause of the exothermic reaction under low oxygen conditions. Experiments without air supply yielded no exothermic reaction. Thus, sulfur did not cause exotherm, because it is at low energy level and immobilized in the vulcanization process. In addition, experiments were conducted as the air supply was varied from 0 to 4 psi. With air pressure of less than 4-psi, no reaction occurred until 4-psi air was provided for the experiment. In conclusion, the design of an embankment with tire shreds should include shredded tires of bigger size
Activated-Carbon Sorbent With Integral Heat-Transfer Device
Jones, Jack A.; Yavrouian, Andre
1996-01-01
Prototype adsorption device used, for example, in adsorption heat pump, to store natural gas to power automobile, or to separate components of fluid mixtures. Device includes activated carbon held together by binder and molded into finned heat-transfer device providing rapid heating or cooling to enable rapid adsorption or desorption of fluids. Concepts of design and fabrication of device equally valid for such other highly thermally conductive devices as copper-finned tubes, and for such other high-surface-area sorbents as zeolites or silicates.
Convective heat transfer in ribbed channels with a 180 turn
Energy Technology Data Exchange (ETDEWEB)
Astarita, T.; Cardone, G.; Carlomagno, G.M. [University of Naples Federico II, DETEC, P. le Tecchio, 80-80125 Naples (Italy)
2002-07-01
Detailed quantitative maps of the heat transfer distribution near a 180 sharp turn of a square channel with rib turbulators are measured by means of infrared thermography associated with the heated-thin-foil technique. Air flows into the channel where ribs are mounted on two opposite walls and placed at 60 with respect to its axis. Two rib pitches, two different rib arrangements and two heating conditions are investigated. Results are presented in terms of local and averaged Nusselt numbers which are normalized with the classical Dittus and Boelter correlation for three different Reynolds numbers. (orig.)
Heat Transfer in a Concrete Composite Cross-Section
Directory of Open Access Journals (Sweden)
Klabník Maroš
2016-12-01
Full Text Available The work is concerned with the spread of heat in 2D coupled cross section with respect to the material characteristics and boundary conditions of calculation. Heat transfer was simulated in the program ANSYS in time interval up to 180 minutes. Nine various models were created to investigate the rate of influence of the changes in thermal material characteristics such as the specific heat capacity coefficient and thermal conductivity, upon the course and difference of temperature in the concrete cross-section. The comparison of results obtained using non-linear and constant values of the variables in simulation was made, too.
Heat transfer function of the VENUS vertex chamber
Energy Technology Data Exchange (ETDEWEB)
Ohama, T.; Ishihara, N.; Yamada, Y.
1996-05-01
In order to estimate the temperature distribution in the VENUS vertex chamber at TRISTAN, a heat transfer function has been derived from the temperature information of a beam pipe flange. The function obtained suggests that the temperature of the flange and that in the chamber gas are simply in proportional relation to the equivalent heat input. Consequently, it is possible to easily correct the velocity of drift electrons in the chamber gas on the basis of the temperature distribution patterns, which are calculated from the typical heat input. (author)
Directory of Open Access Journals (Sweden)
Finnikov K.A.
2010-11-01
Full Text Available The power of the internal heat source sufficient to maintain a positive temperature of plants during one of the possible form of cold stress - radiation frost was determined with the help of numerical simulation.The simulation of unsteady heat transfer in the soil-plant-air system in the conditions of radiation frost showed that the the ground part of plants is cooling most rapidly, and this process is partially slowed down by the natural-convection heat transfer with warmer air. If the frost is not continuous, the radiative cooling is the main danger for plant. The necessary power of heat-production inside plant that allows it to avoid hypothermia depends both on natural conditions and the size of the plant. For plants with a typical diameter of the stem about 2 mm this heat-production should be from 50 to 100 W / kg. Within 2 hours a total amount of heat about 0.5 MJ / kg in the plant should be allocated. Larger plants will have a smaller surface to mass ratio, and the maintaining of it's temperature will require a lower cost of nutrients per unit, accordingly. Modeling of the influence of plant surface trichomes presence on the process of its cooling showed that the role of trichomes in the protection of plants from hypothermia during radiation frost usually is negative due to the fact that the presence of trichomes increases the radiative heat transfer from the plant and the impediment in air movement near the plant reduces heat flux entering the plant from a warmer air. But in cases where the intensity of heat generation within the plant is sufficient for the maintenance of the plant temperature higher than the air temperature, the presence of trichomes impairs heat transfer from plant to air, and therefore contributes to a better heating of plants.
Computational Model of Heat Transfer on the ISS
Torian, John G.; Rischar, Michael L.
2008-01-01
SCRAM Lite (SCRAM signifies Station Compact Radiator Analysis Model) is a computer program for analyzing convective and radiative heat-transfer and heat-rejection performance of coolant loops and radiators, respectively, in the active thermal-control systems of the International Space Station (ISS). SCRAM Lite is a derivative of prior versions of SCRAM but is more robust. SCRAM Lite computes thermal operating characteristics of active heat-transport and heat-rejection subsystems for the major ISS configurations from Flight 5A through completion of assembly. The program performs integrated analysis of both internal and external coolant loops of the various ISS modules and of an external active thermal control system, which includes radiators and the coolant loops that transfer heat to the radiators. The SCRAM Lite run time is of the order of one minute per day of mission time. The overall objective of the SCRAM Lite simulation is to process input profiles of equipment-rack, crew-metabolic, and other heat loads to determine flow rates, coolant supply temperatures, and available radiator heat-rejection capabilities. Analyses are performed for timelines of activities, orbital parameters, and attitudes for mission times ranging from a few hours to several months.
Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E
2015-07-01
This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions. Copyright © 2014 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
P. Raveendiran
2015-06-01
Full Text Available The heat transfer coefficients and friction factors of a baffled shell and heat pipe heat exchanger with various inclination angles were determined experimentally; using methanol as working fluid and water as heat transport fluid were reported. Heat pipe heat exchanger reported in this investigation have inclination angles varied between 15o and 60o for different mass flow rates and temperature at the shell side of the heat exchanger. All the required parameters like outlet temperature of both hot and cold side of heat exchanger and mass flow rate of fluids were measured using an appropriate instrument. Different tests were performed from which condenser side heat transfer coefficient and friction factor were calculated. In all operating conditions it has been found that the heat transfer coefficient increases by increasing the mass flow rate and angle of inclination. The reduction in friction factor occurs when the Reynolds number is increased. The overall optimum experimental effectiveness of GABSHPHE has found to be 42% in all operating conditioning at ψ = 45o.
COOLING, *POROUS MATERIALS), (*HEAT TRANSFER, *COMBUSTION), (* MASS TRANSFER , COMBUSTION), CONVECTION(HEAT TRANSFER), GAS FLOW, INJECTION, CHEMICAL REACTIONS, LAMINAR BOUNDARY LAYER, TURBULENT BOUNDARY LAYER, THERMAL INSULATION, USSR
Heat Transfer and Latent Heat Storage in Inorganic Molten Salts for Concentrating Solar Power Plants
Energy Technology Data Exchange (ETDEWEB)
Mathur, Anoop [Terrafore Inc.
2013-08-14
A key technological issue facing the success of future Concentrating Solar Thermal Power (CSP) plants is creating an economical Thermal Energy Storage (TES) system. Current TES systems use either sensible heat in fluids such as oil, or molten salts, or use thermal stratification in a dual-media consisting of a solid and a heat-transfer fluid. However, utilizing the heat of fusion in inorganic molten salt mixtures in addition to sensible heat , as in a Phase change material (PCM)-based TES, can significantly increase the energy density of storage requiring less salt and smaller containers. A major issue that is preventing the commercial use of PCM-based TES is that it is difficult to discharge the latent heat stored in the PCM melt. This is because when heat is extracted, the melt solidifies onto the heat exchanger surface decreasing the heat transfer. Even a few millimeters of thickness of solid material on heat transfer surface results in a large drop in heat transfer due to the low thermal conductivity of solid PCM. Thus, to maintain the desired heat rate, the heat exchange area must be large which increases cost. This project demonstrated that the heat transfer coefficient can be increase ten-fold by using forced convection by pumping a hyper-eutectic salt mixture over specially coated heat exchanger tubes. However,only 15% of the latent heat is used against a goal of 40% resulting in a projected cost savings of only 17% against a goal of 30%. Based on the failure mode effect analysis and experience with pumping salt at near freezing point significant care must be used during operation which can increase the operating costs. Therefore, we conclude the savings are marginal to justify using this concept for PCM-TES over a two-tank TES. The report documents the specialty coatings, the composition and morphology of hypereutectic salt mixtures and the results from the experiment conducted with the active heat exchanger along with the lessons learnt during
Heat transfer performance test of PDHRS heat exchangers of PGSFR using STELLA-1 facility
Energy Technology Data Exchange (ETDEWEB)
Hong, Jonggan, E-mail: hong@kaeri.re.kr; Yeom, Sujin; Eoh, Jae-Hyuk; Lee, Tae-Ho; Jeong, Ji-Young
2017-03-15
Highlights: • Heat transfer performance test of heat exchangers of PGSFR PDHRS is conducted using STELLA-1 facility. • Steady-state test results of DHX and AHX show good agreement with theoretical results of design codes. • Design codes for DHX and AHX are validated by STELLA-1 experimental results. • Heat transport capability of DHX and AHX is turned out to be satisfactory for reliable plant operation. - Abstract: The STELLA-1 facility was designed and constructed to carry out separate effect tests of the decay heat exchanger (DHX) and natural draft sodium-to-air heat exchanger (AHX), which are key components of the safety-grade decay heat removal system in PGSFR. The DHX is a sodium-to-sodium heat exchanger with a straight tube arrangement, and the AHX is a sodium-to-air heat exchanger with a helically coiled tube arrangement. The model heat exchangers in STELLA-1 have been designed to meet their own similitude conditions from the prototype ones, of which scale ratios were set to be unity in height (or length) and 1/2.5 in heat transfer rate. Consequently, the overall heat transfer coefficients and log-mean temperature differences of the prototypes have been preserved as well. The steady-state test results for each model heat exchanger obtained from STELLA-1 showed good agreement with the theoretical results of the computer design codes for thermal-sizing and a performance analysis of the DHX and AHX. In the DHX result comparison, the discrepancies in the heat transfer rate ranged from −4.4% to 2.0%, and in the AHX result comparison, they ranged from −11.1% to 12.6%. Therefore, the first step in thermal design codes validation for sodium heat exchangers, e.g., DHX and AHX, has been successfully completed with the experimental database obtained from STELLA-1. In addition, the heat transfer performance of the DHX and AHX was found to be satisfactory enough to secure a reliable decay heat removal performance.
Ultrasonic Heat Transfer Enhancement with Obstacle in Front of Heating Surface
Nomura, Shinfuku; Nakagawa, Masafumi; Mukasa, Shinobu; Toyota, Hiromichi; Murakami, Koichi; Kobayashi, Ryousuke
2005-06-01
Heat transfer enhancement using a horn-type transducer was carried out in the natural convection region while a flat plate was used as a wall-like obstacle in front of the heating surface. Three types of plate were used as obstacles: acrylic, aluminum, and Styrofoam. A horn tip of 6 mm diameter and 60.7 kHz was used as the ultrasonic transducer. The acoustic cavitation jet induced by the ultrasonic vibration exhibited the same tendency as the axisymmetric free jet. The acoustic jet from the horn tip was shut out by the flat plate; however, the ultrasound passed through the flat plate and transferred the flow effect and agitation effect to the area behind the plate. By applying ultrasonic vibration, the heat transfer coefficient of the heating surface behind the flat plate was increased by up to threefold. The heat transfer coefficient decreased as the thickness of the flat plate increased. The heat transfer coefficient was the highest for the acrylic plate, then the aluminum plate, and lowest for the Styrofoam plate.
Transient natural convection heat and mass transfer in crystal growth
Han, Samuel S.
1990-01-01
A numerical analysis of transient combined heat and mass transfer across a rectangular cavity is performed. The physical parameters are selected to represent a range of possible crystal growth in solutions. Good agreements with measurement data are observed. It is found that the thermal and solute fields become highly oscillatory when the thermal and solute Grashof numbers are large.
A Course in Advanced Topics in Heat and Mass Transfer.
Shaeiwitz, Joseph A.
1983-01-01
A three or four semester-hour graduate course was designed to provide basic instruction in heat/mass transfer topics relevant to chemical engineering problems and to train students to develop mathematical descriptions for new situations encountered in problem-solving. Course outline and list of references used in the course are provided. (JM)
Computational heat transfer analysis and combined ANN–GA ...
Indian Academy of Sciences (India)
transfer from the base plate is carried out using Genetic Algorithm (GA) applied on the trained neural .... parameters. Genetic Algorithm is applied on the trained neural network to find the optimal fin geometry for ..... Sparrow E M and Lee L 1975 Effects of fin base-temperature depression in a multifin array. J. Heat Transf.
Heat transfer and pressure drop in microchannels with random roughness
Pelevic, N.; van der Meer, Theodorus H.
2016-01-01
The effect of surface roughness on heat transfer and fluid flow phenomena within a microchannel has been investigated by using the lattice Boltzmann method. The surface roughness has been generated by using Gaussian function. Gaussian function is an efficient and convenient method to create surface
On some group properties of heat and mass transfer equations
Stepanova, I. V.
2017-10-01
Heat and mass transfer equations with variable transport coefficients are under study. The forms of unknown thermal conductivity, diffusion and Dufour coefficients are found by means of Lie group theory. It is shown that arbitrary elements have the power-law, logarithmic and exponential dependencies on temperature and concentration.
A Rotating Plug Model of Friction Stir Welding Heat Transfer
Raghulapadu J. K.; Peddieson, J.; Buchanan, G. R.; Nunes, A. C.
2006-01-01
A simplified rotating plug model is employed to study the heat transfer phenomena associated with the fiction stir welding process. An approximate analytical solution is obtained based on this idealized model and used both to demonstrate the qualitative influence of process parameters on predictions and to estimate temperatures produced in typical fiction stir welding situations.
Study of coupled heat and mass transfer during absorption of ...
Indian Academy of Sciences (India)
Performance studies on MmNi4·6Al0·4 based hydrogen storage device are carried out by varying the hydrogen supply pressure, absorption (cooling ﬂuid) temperature, overall heat transfer coefﬁcient and hydride bed thickness. Effect of convection terms in the energy equation on hydrogen storage performance is found to ...
Simultaneous measurement of aerodynamic and heat transfer data ...
Indian Academy of Sciences (India)
namic and the heat transfer data presented here are very valuable for the validation of CFD codes used ... Hypersonic research activities around the globe has been in major focus in recent times because of the ... dynamics (CFD) tools are increasingly being used in most aerodynamic designs even in the hypersonic flight ...
Heat transfer with thermal radiation on MHD particle–fluid ...
Indian Academy of Sciences (India)
2017-09-12
Sep 12, 2017 ... In this article, effects of heat transfer on particle–fluid suspension induced by metachronal wave have been examined. The influence of magnetohydrodynamics (MHD) and thermal radiation are also taken into account with the help of Ohm's law and Roseland's approximation. The governing flow problem for ...
Stagnation point flow and heat transfer for a viscoelastic fluid ...
Indian Academy of Sciences (India)
M REZA
2017-11-09
Nov 9, 2017 ... increasing lateral interface velocity. It is observed that lateral interface velocity increases with increasing viscoelastic parameter for fixed values of density and viscosity ratio of the two fluids. The convective heat transfer is investigated base on the similarity solutions for the temperature distribution of the two ...
Atomic recombination rate determination through heat-transfer measurement.
Park, C.; Anderson, L. A.; Sheldahl, R. E.
1973-01-01
A theoretical and experimental demonstration is presented which shows that under suitable conditions the volume recombination coefficient can be determined by measuring the heat transfer rate into the wall of a cylinder through which a dissociated stream is passing. The experimental results obtained are in agreement with those of other investigators.
Heat Transfer Performance of Functionalized Graphene Nanoplatelet Aqueous Nanofluids
Directory of Open Access Journals (Sweden)
Roberto Agromayor
2016-06-01
Full Text Available The low thermal conductivity of fluids used in many industrial applications is one of the primary limitations in the development of more efficient heat transfer systems. A promising solution to this problem is the suspension of nanoparticles with high thermal conductivities in a base fluid. These suspensions, known as nanofluids, have great potential for enhancing heat transfer. The heat transfer enhancement of sulfonic acid-functionalized graphene nanoplatelet water-based nanofluids is addressed in this work. A new experimental setup was designed for this purpose. Convection coefficients, pressure drops, and thermophysical properties of various nanofluids at different concentrations were measured for several operational conditions and the results are compared with those of pure water. Enhancements in thermal conductivity and in convection heat transfer coefficient reach 12% (1 wt % and 32% (0.5 wt %, respectively. New correlations capable of predicting the Nusselt number and the friction factor of this kind of nanofluid as a function of other dimensionless quantities are developed. In addition, thermal performance factors are obtained from the experimental convection coefficient and pressure drop data in order to assess the convenience of replacing the base fluid with designed nanofluids.
Simultaneous measurement of aerodynamic and heat transfer data ...
Indian Academy of Sciences (India)
An aluminum model incorporating a three-component accelerometer-based balance system for measuring the aerodynamic forces and an array of platinum thin-ﬁlm gauges deposited on thermally insulating backing material ﬂush mounted on the model surface is used for convective surface heat transfer measurement in the ...
Simulation Tests in Whole Building Heat and Moisture Transfer
DEFF Research Database (Denmark)
Rode, Carsten; Peuhkuri, Ruut Hannele; Woloszyn, Monika
2006-01-01
An important part of the International Energy Agency project, ECBCS, Annex 41 is about modelling the integral heat, air and moisture transfer processes that take place in “whole buildings”. Such modelling deals with all most relevant elements of buildings: The indoor air, the building envelope...
Estimation of convection heat and mass transfer coefficients for ...
African Journals Online (AJOL)
Estimation of convection heat and mass transfer coefficients for constant-rate drying period during tape casting. Y T Puyate. Abstract. No Abstract. Global Journal of Engineering Research Vol. 6 (1) 2007: pp. 75-77. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.
Heat Transfer Measurements for a Film Cooled Turbine Vane Cascade
Poinsatte, Philip E.; Heidmann, James D.; Thurman, Douglas R.
2008-01-01
Experimental heat transfer and pressure measurements were obtained on a large scale film cooled turbine vane cascade. The objective was to investigate heat transfer on a commercial high pressure first stage turbine vane at near engine Mach and Reynolds number conditions. Additionally blowing ratios and coolant density were also matched. Numerical computations were made with the Glenn-HT code of the same geometry and compared with the experimental results. A transient thermochromic liquid crystal technique was used to obtain steady state heat transfer data on the mid-span geometry of an instrumented vane with 12 rows of circular and shaped film cooling holes. A mixture of SF6 and Argon gases was used for film coolant to match the coolant-to-gas density ratio of a real engine. The exit Mach number and Reynolds number were 0.725 and 2.7 million respectively. Trends from the experimental heat transfer data matched well with the computational prediction, particularly for the film cooled case.
Versatile Desktop Experiment Module (DEMo) on Heat Transfer
Minerick, Adrienne R.
2010-01-01
This paper outlines a new Desktop Experiment Module (DEMo) engineered for a chemical engineering junior-level Heat Transfer course. This new DEMo learning tool is versatile, fairly inexpensive, and portable such that it can be positioned on student desks throughout a classroom. The DEMo system can illustrate conduction of various materials,…
Heat transfer between two parallel porous plates for Couette flow ...
Indian Academy of Sciences (India)
The aim of the present paper is to study the unsteady magneto-hydrodynamic viscous Couette flow with heat transfer in a Darcy porous medium between two ... Basic and Applied Science Department, College of Engineering and Technology, Arab Academy for Science, Technology, and Maritime Transport, Cairo 2033, ...
Atmospheric composition affects heat- and mass-transfer processes
Blakely, R. L.; Nelson, W. G.
1970-01-01
For environmental control system functions sensitive to atmospheric composition, components are test-operated in helium-oxygen and nitrogen-oxygen mixtures, pure oxygen, and air. Transient heat- and mass-transfer tests are conducted for carbon dioxide adsorption on molecular sieve and for water vapor adsorption on silica gel.
Advective heat transfer and fabric development in a shallow crustal ...
Indian Academy of Sciences (India)
dependent among other things, on the ratio of mineral crystals to melt, spatial distribution of the phases and strain rate (Vigneresse et al 1996;. Keywords. Advective heat transfer; granite pluton; deformation microstructures; rate of cooling; quartz c-axis fabric;. Nallamalai fold belt. J. Earth Syst. Sci. 116, No. 5, October 2007 ...
Heat and mass transfer over slippery, superhydrophobic surfaces
Haase, A. Sander; Lammertink, Rob G.H.
2016-01-01
The classical Graetz-Nusselt problem is extended to describe heat and mass transfer over heterogeneously slippery, superhydrophobic surfaces. The cylindrical wall consists of segments with a constant temperature/concentration and areas that are insulating/impermeable. Only in the case of mass
The effect of heating direction on flow boiling heat transfer of R134a in micro-channels
Xu, Mingchen; Jia, Li; Dang, Chao; Peng, Qi
2017-04-01
This paper presents effects of heating directions on heat transfer performance of R134a flow boiling in micro- channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500μm width 500μm depth and 30mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm2 and 373.3 to 1244.4 kg/m2s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 kW/m2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.
Directory of Open Access Journals (Sweden)
Qixiang Yan
2017-07-01
Full Text Available In cold regions, heat-insulating layers play a crucial role in frost prevention in tunnels. This paper presents a numerical study on the anti-freezing behavior of a cold region tunnel (the Dege tunnel with heat-insulating layers. A numerical model based on the temperature field coupling theory is firstly proposed and validated using field test data of the Dege tunnel. Subsequently, a comprehensive parametric study is carried out to investigate the influences of heat-insulating layers on the temperature characteristics of airflows inside the tunnel, the surrounding rock, and the tunnel lining. Furthermore, a numerical investigation based on the proposed numerical model is carried out to propose reasonable design parameters of heat-insulating layers for different velocities of mechanical ventilation, and different heat-insulating materials for cold region tunnels. The numerical results show that using the heat-insulating layer can effectively reduce the heat transfer between the surrounding rock and the airflow inside the tunnel. It is also found that the design parameters for the heat-insulating layer are greatly affected by the tunnel ventilation conditions and heat-insulating materials.
DEFF Research Database (Denmark)
Sadeghinezhad, Emad; Mehrali, Mohammad; Akhiani, Amir Reza
2017-01-01
The effect of a permanent magnetic field on the heat transfer characteristics of hybrid graphene-magnetite nanofluids (hybrid nanofluid) under forced laminar flow was experimentally investigated. For this purpose, a reduced graphene oxide-Fe3O4 was synthesized by using two-dimensional (2D) graphe...
Numerical investigation on the convective heat transfer in a spiral coil with radiant heating
Directory of Open Access Journals (Sweden)
Đorđević Milan Lj.
2016-01-01
Full Text Available The objective of this study was to numerically investigate the heat transfer in spiral coil tube in the laminar, transitional, and turbulent flow regimes. The Archimedean spiral coil was exposed to radiant heating and should represent heat absorber of parabolic dish solar concentrator. Specific boundary conditions represent the uniqueness of this study, since the heat flux upon the tube external surfaces varies not only in the circumferential direction, but also in the axial direction. The curvature ratio of spiral coil varies from 0.029 at the flow inlet to 0.234 at the flow outlet, while the heat transfer fluid is water. The 3-D steady-state transport equations were solved using the Reynolds stress turbulence model. Results showed that secondary flows strongly affect the flow and that the heat transfer is strongly asymmetric, with higher values near the outer wall of spiral. Although overall turbulence levels were lower than in a straight pipe, heat transfer rates were larger due to the curvature-induced modifications of the mean flow and temperature fields. [Projekat Ministarstva nauke Republike Srbije, br. 42006
Castor-1C spent fuel storage cask decay heat, heat transfer, and shielding analyses
Energy Technology Data Exchange (ETDEWEB)
Rector, D.R.; McCann, R.A.; Jenquin, U.P.; Heeb, C.M.; Creer, J.M.; Wheeler, C.L.
1986-12-01
This report documents the decay heat, heat transfer, and shielding analyses of the Gesellschaft fuer Nuklear Services (GNS) CASTOR-1C cask used in a spent fuel storage demonstration performed at Preussen Elektra's Wurgassen nuclear power plant. The demonstration was performed between March 1982 and January 1984, and resulted in cask and fuel temperature data and cask exterior surface gamma-ray and neutron radiation dose rate measurements. The purpose of the analyses reported here was to evaluate decay heat, heat transfer, and shielding computer codes. The analyses consisted of (1) performing pre-look predictions (predictions performed before the analysts were provided the test data), (2) comparing ORIGEN2 (decay heat), COBRA-SFS and HYDRA (heat transfer), and QAD and DOT (shielding) results to data, and (3) performing post-test analyses if appropriate. Even though two heat transfer codes were used to predict CASTOR-1C cask test data, no attempt was made to compare the two codes. The codes are being evaluated with other test data (single-assembly data and other cask data), and to compare the codes based on one set of data may be premature and lead to erroneous conclusions.
A novel investigation of heat transfer characteristics in rifled tubes
Jegan, C. Dhayananth; Azhagesan, N.
2017-12-01
The experimental investigation of heat transfer of water flowing in a rifled tube was explored at different pressures and at various operating conditions in a rifled tube heat exchanger. The specifications for the inner and outer diameters of the inner tube are 25.8 and 50.6 mm, respectively. The working fluids used in shell side and tube side are cold and hot water. The rifled tube was made of the stainless steel with 4 ribs, 50.6 mm outer diameter, 0.775 mm rib height, 58o helix angle and the length 1500 mm. The effect of pressure, wall heat flux and friction factor were discussed. The results confirm that even at low pressures the rifled tubes has an obvious enhancement in heat transfer compared with smooth tube. Results depicts that the Nusselt number increases with Reynolds number and the friction factor decreases with increase in Reynolds number and the heat transfer rate is higher for the rifled tube when compared to smooth tube, because of strong swirl flow due to centrifugal action. It also confirms that, the friction factor obtained from the rifled tube is significantly higher than that of smooth tube.
Hendricks, R. C.
1979-01-01
Specific examples are cited herein to illustrate the universal needs and demands for thermophysical property data. Applications of the principle of similarity in fluid mechanics and heat transfer and extensions of the principle to fluid mixtures are discussed. It becomes quite clear that no matter how eloquent theories or experiments in fluid mechanics or heat transfer are, the results of their application can be no more accurate than the thermophysical properties required to transform these theories into practice, or in the case of an experiment, to reduce the data. Present-day projects take place on such a scale that the need for international standards and mutual cooperation is evident.
Hydrodynamics and Heat Transfer of Discrete Droplets in Microfluidic Devices
Weber, Robert; Shajiee, Shervin; Mohseni, Kamran
2009-11-01
Electrostatic manipulation of surfaces tension forces is now a standard fluid handling technique in microfluidic devices. In this investigation electrowetting on dielectric (EWOD) is employed in order to use discrete droplets for thermal management of compact micro systems. Both hydro- and thermodynamics of digitized droplets are investigated by experimental, theoretical and computational means. EWOD devices have been built on silicon substrates with highly doped layers replacing metal electrodes, and higher quality thermal oxides replacing the more expensive PECVD oxides. In parallel, an experimental test rig has been built to measure the heat transfer rate of the slug flow at a macro scale. Droplets at several length and speed are created systematically. Average heat transfer rates and Nusselt numbers in constant heat flux in a tube has been experimentally measured for continuous and discrete water flow cases and the results have been compared with numerical results.
Biodegradability and ecotoxicity of commercially available geothermal heat transfer fluids
Schmidt, Kathrin R.; Körner, Birgit; Sacher, Frank; Conrad, Rachel; Hollert, Henner; Tiehm, Andreas
2016-03-01
Commercially available heat transfer fluids used in borehole heat exchangers were investigated for their composition, their biodegradability as well as their ecotoxicity. The main components of the fluids are organic compounds (often glycols) for freezing protection. Biodegradation of the fluids in laboratory studies caused high oxygen depletion as well as nitrate/iron(III) reduction under anaerobic conditions. Additives such as benzotriazoles for corrosion protection were persistent. Ecotoxicity data show that the commercially available fluids caused much higher ecotoxicity than their main organic constituents. Consequently, with regard to groundwater protection pure water as heat transfer medium is recommended. The second best choice is the usage of glycols without any additives. Effects on groundwater quality should be considered during ecological-economical cost-benefit-analyses of further geothermal energy strategies. The protection of groundwater as the most important drinking water resource must take priority over the energy gain from aquifers.
Numerical prediction of nucleate pool boiling heat transfer coefficient under high heat fluxes
Directory of Open Access Journals (Sweden)
Pezo Milada L.
2016-01-01
Full Text Available This paper presents CFD (Computational Fluid Dynamics approach to prediction of the heat transfer coefficient for nucleate pool boiling under high heat fluxes. Three-dimensional numerical simulations of the atmospheric saturated pool boiling are performed. Mathematical modelling of pool boiling requires a treatment of vapor-liquid two-phase mixture on the macro level, as well as on the micro level, such as bubble growth and departure from the heating surface. Two-phase flow is modelled by the two-fluid model, which consists of the mass, momentum and energy conservation equations for each phase. Interface transfer processes are calculated by the closure laws. Micro level phenomena on the heating surface are modelled with the bubble nucleation site density, the bubble resistance time on the heating wall and with the certain level of randomness in the location of bubble nucleation sites. The developed model was used to determine the heat transfer coefficient and results of numerical simulations are compared with available experimental results and several empirical correlations. A considerable scattering of the predictions of the pool boiling heat transfer coefficient by experimental correlations is observed, while the numerically predicted values are within the range of results calculated by well-known Kutateladze, Mostinski, Kruzhilin and Rohsenow correlations. The presented numerical modeling approach is original regarding both the application of the two-fluid two-phase model for the determination of heat transfer coefficient in pool boiling and the defined boundary conditions at the heated wall surface. [Projekat Ministarstva nauke Republike Srbije, br. 174014
Heat transfer performance of a pulsating heat pipe charged with acetone-based mixtures
Wang, Wenqing; Cui, Xiaoyu; Zhu, Yue
2017-06-01
Pulsating heat pipes (PHPs) are used as high efficiency heat exchangers, and the selection of working fluids in PHPs has a great impact on the heat transfer performance. This study investigates the thermal resistance characteristics of the PHP charged with acetone-based binary mixtures, where deionized water, methanol and ethanol were added to and mixed with acetone, respectively. The volume mixing ratios were 2:1, 4:1 and 7:1, and the heating power ranged from 10 to 100 W with filling ratios of 45, 55, 62 and 70%. At a low filling ratio (45%), the zeotropic characteristics of the binary mixtures have an influence on the heat transfer performance of the PHP. Adding water, which has a substantially different boiling point compared with that of acetone, can significantly improve the anti-dry-out ability inside the PHP. At a medium filling ratio (55%), the heat transfer performance of the PHP is affected by both phase transition characteristics and physical properties of working fluids. At high heating power, the thermal resistance of the PHP with acetone-water mixture is between that with pure acetone and pure water, whereas the thermal resistance of the PHP with acetone-methanol and acetone-ethanol mixtures at mixing ratios of 2:1 and 4:1 is less than that with the corresponding pure fluids. At high filling ratios (62 and 70%), the heat transfer performance of the PHP is mainly determined by the properties of working fluids that affects the flow resistance. Thus, the PHP with acetone-methanol and acetone-ethanol mixtures that have a lower flow resistance shows better heat transfer performance than that with acetone-water mixture.
Analysis of the flow structure and heat transfer in a vertical mantle heat exchanger
DEFF Research Database (Denmark)
Knudsen, Søren; Morrison, GL; Behnia, M
2005-01-01
The flow structure inside the inner tank and inside the mantle of a vertical mantle heat exchanger was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the inner tank and in the mantle were measured using a Particle Image...... Velocimetry (PIV) system. A Computational Fluid Dynamics (CFD) model of the vertical mantle heat exchanger was also developed for a detailed evaluation of the heat flux at the mantle wall and at the tank wall. The flow structure was evaluated for both high and low temperature incoming flows and for both...... initially mixed and initially stratified inner tank and mantle. The analysis of the heat transfer showed that the flow in the mantle near the inlet is mixed convection flow and that the heat transfer is dependent on the mantle inlet temperature relative to the core tank temperature at the mantle level. (C...
Heat transfer of Al2O3 nanofluids in microchannel heat sink
Razali, A. A.; Sadikin, A.; Ibrahim, S. A.
2017-04-01
Microchannel heat sink creates an innovative cooling technology to remove large amount of heat from small area. Recently, nanotechnology gain interest to explore the microchannel cooling benefits of nanofluids as working fluid. The objective of this study is to investigate the effect of heat transfer to Al2O3 nanofluids after used as working fluid in the microchannel. In this study, the microchannel was design in square shape with a cross section of 0.5×0.5 mm2 and made by copper. The experiment was conducted in laminar flow with Reynolds number ranging approximately from 633 to 1172. The present study was focused on heat transfer of Al2O3 nanofluids in microchannel heat sink at concentration of 1.0 wt. % and 2.5 wt. % dispersed in water. The heat was produced at bottom of the heat sink is 325 W. The computational simulation method was carried out to validate the experimental results. It was observed that the heat transfer rate is higher when using Al2O3 nanofluids compared to water. However, according to X-ray diffraction method (XRD), it is found that the structure of Al2O3 particles tends to more integrity and the crystallite size grows up after increased the temperature in the microchannel.
Simulation and experimental research of heat leakage of cryogenic transfer lines
Deng, B. C.; Xie, X. J.; Pan, W.; Jiang, R. X.; Li, J.; Yang, S. Q.; Li, Q.
2017-12-01
The heat leakage of cryogenic transfer lines directly influences the performance of large-scale helium refrigerator. In this paper, a thermal model of cryogenic transfer line considering numerical simulation of support coupled with MLI was established. To validate the model, test platform of cryogenic transfer lines with the merits of disassembly outer pipe and changeable easily multi-layer insulation has been built. The experimental results of heat leakage through overall length of cryogenic transfer lines, support and multi-layer insulation were obtained. The heat leakages of multi-layer insulation, a support and the overall leakage are 1.02 W/m, 0.44 W and 1.46 W/m from experimental data, respectively. The difference of heat leakage of MLI between experiment and simulation were less than 5%. The temperature distribution of support and MLI obtained in presented model in good agreement with experimental data. It is expected to reduce the overall heat leakage of cryogenic transfer lines further by optimizing structure of support based on the above thermal model and test platform in this paper.
Experimental studies on radiation heat transfer enhancement on a standard muffle furnace
Directory of Open Access Journals (Sweden)
Minea Alina Adriana
2013-01-01
Full Text Available One of the sources of increased industrial energy consumption is the heating equipment, e.g., furnaces. Their domain of use is very wide and due to its abundance of applications it is key equipment in modern civilization. The present experimental investigations are related to reducing energy consumptions and started from the geometry of a classic manufactured furnace. During this experimental study, different cases have been carefully chosen in order to compare and measure the effects of applying different enhancement methods of the radiation heat transfer processes. The main objective work was to evaluate the behavior of a heated enclosure, when different radiant panels were introduced. The experimental investigation showed that their efficiency was influenced by their position inside the heating area. In conclusion, changing the inner geometry by introducing radiant panels inside the heated chamber leads to important time savings in the heating process.
Heat Transfer in Boiling Dilute Emulsion with Strong Buoyancy
Freeburg, Eric Thomas
Little attention has been given to the boiling of emulsions compared to that of boiling in pure liquids. The advantages of using emulsions as a heat transfer agent were first discovered in the 1970s and several interesting features have since been studied by few researchers. Early research focuses primarily on pool and flow boiling and looks to determine a mechanism by which the boiling process occurs. This thesis looks at the boiling of dilute emulsions in fluids with strong buoyant forces. The boiling of dilute emulsions presents many favorable characteristics that make it an ideal agent for heat transfer. High heat flux electronics, such as those seen in avionics equipment, produce high heat fluxes of 100 W/cm2 or more, but must be maintained at low temperatures. So far, research on single phase convection and flow boiling in small diameter channels have yet to provide an adequate solution. Emulsions allow the engineer to tailor the solution to the specific problem. The fluid can be customized to retain the high thermal conductivity and specific heat capacity of the continuous phase while enhancing the heat transfer coefficient through boiling of the dispersed phase component. Heat transfer experiments were carried out with FC-72 in water emulsions. FC-72 has a saturation temperature of 56 °C, far below that of water. The parameters were varied as follows: 0% ≤ epsilon ≤ 1% and 1.82 x 1012 ≤ RaH ≤ 4.42 x 1012. Surface temperatures along the heated surface reached temperature that were 20 °C in excess of the dispersed phase saturation temperature. An increase of ˜20% was seen in the average Nusselt numbers at the highest Rayleigh numbers. Holography was used to obtain images of individual and multiple FC-72 droplets in the boundary layer next to the heated surface. The droplet diameters ranged from 0.5 mm to 1.3 mm. The Magnus effect was observed when larger individual droplets were injected into the boundary layer, causing the droplets to be pushed
Heat Transfer Characteristics in Crank-Shape Thermosyphons
Imura, Hedeaki; Koito, Yasushi
A two-phase closed thermosyphon is applied to gas-to-gas heat exchangers, the cooling of heat generation devices, the melting of snow, the prevention from icing of water on roads and so on. Generally, straight tubes are used as the thermosyphon. However, because of the limited space for the straight thermosyphon to be installed, it is considered that a bent thermosyphon is enforced to employ. In response to this, fundamental experiments are conducted on the heat transfer characteristics in a two-phase crank shape closed thermosyphon, in which an evaporator and a condenser are vertically positioned, and a connecting adiabatic section is horizontal. Ethylene glycol aqueous solutions which have lower freezing points and hydrofluoroether 7100 and 7200 which do not contain chloride are used as the working fluids Heat transfer coefficients and critical heat fluxes in the thermosyphon are measured by changing the amount of charged working fluid (0.30,0.40,0.50 and 0.60 of the evaporator volume),the temperature of the adiabatic section (40,50,60,70 and 80°C) and heat flux (from 4.0 kW /m2 to critical). The experimental results are shown and compared with those taken using water as the working fluid.
46 CFR 153.434 - Heat transfer coils within a tank.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...
Taha, T.J.; Mojet, Barbara; Lefferts, Leonardus; van der Meer, Theodorus H.
2016-01-01
In this work, heat transfer surface modification is made by layers of carbon nanofiber (CNF) on a 50 μm nickel wire using Thermal chemical vapor deposition process (TCVD). Three different CNF layer morphologies are made, at 500 °C, 600 °C and 700 °C, to investigate the influence of morphology on
Directory of Open Access Journals (Sweden)
Yoshinori Itaya
2017-06-01
Full Text Available Heat and mass transfer of a LiBr/water absorption heat pump system (AHP was experimentally studied during working a heating-up mode. The examination was performed for a single spiral tube, which was simulated for heat transfer tubes in an absorber. The inside and outside of the tube were subjected to a film flow of the absorption liquid and exposed to the atmosphere, respectively. The maximum temperature of the absorption liquid was observed not at the entrance but in the region a little downward from the entrance in the tube. The steam absorption rate and/or heat generation rate in the liquid film are not constant along the tube. Hence the average convective heat transfer coefficient between the liquid film flowing down and the inside wall of the tube was determined based on a logarithmic mean temperature difference between the tube surface temperature and the film temperature at the maximum temperature location and the bottom. The film heat and mass transfer coefficients rose with increasing Reynolds number of the liquid film stream. The coefficients showed opposite trend to the empirical correlation reported for laminar film flow on a straight smooth tube in a refrigeration mode in the past work. The fact can be caused due to a turbulent promotion effect of the liquid in a spiral tube.
Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger
Directory of Open Access Journals (Sweden)
S. Sathiyan
2013-06-01
Full Text Available This work presents new predictive correlations for heat transfer to immiscible liquid-liquid mixtures in a spiral plate heat exchanger. Liquid-liquid heat transfer studies were carried out in spiral plate heat exchangers for the water-octane, water-kerosene, and water-dodecane systems. For each composition of the mixture, the mass flow rate of the cold fluid was varied, keeping that of the hot fluid and the fluid inlet temperatures constant. Two-phase cold flow rates were in the laminar range, while the hot fluid flow was turbulent. Calculations of the LMTD (log mean temperature difference correction factor showed that the flow was countercurrent. Heat transfer coefficients of the two-phase liquids were found to be strongly dependent on the composition of the liquid mixture and exhibited abrupt transitions as a function of the compositions. Given the absence of predictive correlations in the literature that sufficiently capture this compositiondependence, new empirical correlations were developed using part of the experimental data, with the composition of the cold fluid as an explicit variable. Statistical analysis of the regression yielded satisfactory results. The correlations were tested against the rest of the experimental data and were found to predict heat transfer coefficients within ± 15%. These preliminary studies should be useful in designing compact exchangers for handling two-phase water-organics mixtures.
Numerical study of the conjugate heat transfer in a horizontal pipe heated by Joulean effect
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Touahri Sofiane
2012-01-01
Full Text Available The three dimensional mixed convection heat transfer in a electrically heated horizontal pipe conjugated to a thermal conduction through the entire solid thickness is investigated by taking into account the thermal dependence of the physical properties of the fluid and the outer heat losses. The model equations of continuity, momentum and energy are numerically solved by the finite volume method. The pipe thickness, the Prandtl and the Reynolds numbers are fixed while the Grashof number is varied from 104to107. The results obtained show that the dynamic and thermal fields for mixed convection are qualitatively and quantitatively different from those of forced convection, and the local Nusselt number at the interface solid-fluid is not uniform: it has considerable axial and azimuthally variations. The effect of physical variables of the fluid depending on temperature is significant, which justifies its inclusion. The heat transfer is quantified by the local and average Nusselt numbers. We found that the average Nusselt number of solid-fluid interface of the duct increases with the increase of Grashof number. We have equally found out that the heat transfer is improved thanks to the consideration of the thermo dependence of the physical properties. We have tried modelling the average Nusselt number as a function of Richardson number. With the parameters used, the heat transfer is quantified by the correlation: NuA=12.0753 Ri0.156
Local Heat Transfer for Finned-Tube Heat Exchangers using Oval Tubes
Energy Technology Data Exchange (ETDEWEB)
O' Brien, James Edward; Sohal, Manohar Singh
2000-08-01
This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with either a circular tube or an elliptical tube in crossflow. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.56 x 10-3 to 15.6 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 630 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. The elliptical tube had an aspect ratio of 3:1 and a/H equal to 4.33. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of circular and oval tubes and their relationship to the complex horseshoe vortex system that forms in the flow stagnation region. Fin surface stagnation-region Nusselt numbers are shown to be proportional to the square-root of Reynolds number.
Heat transfer measurements with a four-core optical fiber
Güvenç, Sema; Inci, Mehmet Naci
2017-05-01
A four-core optical fiber is used to investigate one-dimensional heat transfer measurements. Heat pulses from a Nd:YAG laser of 600 ms duration with a repetition rate of the order of 10 s are delivered onto one of the fiber cores. This results in an optical path length difference between the guiding cores due to the change in the refractive index and physical length of the targeted fiber core. As a result of this process, a phase shift of 1.30 rad is measured with a digital camera for 140 mW pulses in reflection scheme. The heat diffusion length in the selected fiber core is determined to be 2.8 mm, which contains 33.2 kJ/m2s heat, causing a temperature rise of 4.30 K.
Heat transfer at nanometric scales described by extended irreversible thermodynamics
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Machrafi Hatim
2016-06-01
Full Text Available The purpose of this work is to present a study on heat conduction in systems that are composed out of spherical and cylindrical micro- and nanoparticles dispersed in a bulk matrix. Special emphasis is put on the dependence of the effective heat conductivity on various selected parameters as particle size and also its shape, surface specularity and density, including particle-matrix interaction. The heat transfer at nanometric scales is modelled using extended irreversible thermodynamics, whose main feature is to elevate the heat flux vector to the status of independent variable. The model is illustrated by a Copper-Silicium (Cu-Si system. It is shown that all the investigated parameters have a considerable influence, the particle size being especially useful to either increase or decrease the effective thermal conductivity.
Design of horizontal fin array for radiative heat transfer
Ali, Mutari Hajara; Shuaibu, Bilyaminu
2017-08-01
This paper presents the analytical and simulation results of optimizing the radiative heat transfer performance of horizontal rectangular fin array heat sink. The fin thickness and inter-fin spacing need to be properly designed to eliminate surface area changes accompanying the creation of fin structures. Analytical expression for this change in area is developed in this work and used in identifying the optimum number of fins and their corresponding inter-fin spacing for a given rectangular space of a radiative heat sink. COMSOL Multiphysics software is used to simulate the structures considered in the above analysis. The performances of the simulated structures as radiative heat sinks are compared with the ones suggested by the developed empirical equation. The results from the two methods agreed with each successfully in the sense that the structures with large numerical radiative power from the simulations are found to also be the optimum structures suggested by the analytical formula derived in this work.
Heat Transfer Correlations for Free Convection from Suspended Microheaters
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David GOSSELIN
2016-08-01
Full Text Available Portability and autonomy for biomedical diagnostic devices are two rising requirements. It is recognized that low-energy heating of such portable devices is of utmost importance for molecular recognition. This work focuses on screen-printed microheaters based on on Joule effect, which constitute an interesting solution for low-energy heating. An experimental study of the natural convection phenomena occurring with such microheaters is conducted. When they are suspended in the air, and because of the thinness of the supporting film, it is shown that the contributions of both the upward and downward faces have to be taken into account. A total Nusselt number and a total convective heat transfer coefficient have been used to describe the natural convection around these microheaters. In addition a relation between the Nusselt number and the Rayleigh number is derived, leading to an accurate prediction of the heating temperature (MRE< 2 %.
Kamatchi, R.; Venkatachalapathy, S.; Nithya, C.
2016-11-01
In the present study, reduced graphene oxide (rGO) is synthesized from graphite using modified Hummer and chemical reduction methods. Various characterizations techniques are carried out to study the in-plane crystallite size, number of layers, presence of functional groups and surface morphology. Different concentrations of 0.01, 0.1, and 0.3 g/l of rGO/water nanofluids are prepared by dispersing the flakes in DI water. The colloidal stability of 0.3 g/l concentration is measured after 5 days using Zetasizer and found to be stable. The rGO/water nanofluids are then used to study the effect on the enhancement of critical heat flux (CHF) in pool boiling heat transfer. Results indicate an enhancement in CHF ranging from 145 to 245 % for the tested concentrations. The mechanisms of CHF enhancement are analyzed based on surface wettability, surface roughness, and porous layer thickness. The macrolayer dryout model sufficiently supports the mechanism of CHF enhancement of thin wire with rGO deposits, which is not reported yet.
Evaluation of heat transfer characteristics of a sphere-packed pipe for Flibe blanket
Energy Technology Data Exchange (ETDEWEB)
Watanabe, Atsushi, E-mail: awata@karma.qse.tohoku.ac.jp [Tohoku University, Sendai (Japan); Ebara, Shinji [Tohoku University, Sendai (Japan); Sagara, Akio [National Institute for Fusion Science, Toki (Japan); Hashizume, Hidetoshi [Tohoku University, Sendai (Japan)
2013-10-15
A Flibe blanket has been proposed to be used in FFHR. Since Flibe has poor heat transfer performance, heat transfer promoter is required, and a sphere-packed pipe (SPP) has been proposed to enhance the heat transfer performance in the Flibe blanket. In this paper, the fluid flow and heat transfer characteristics in the SPP is evaluated numerically using a k–ε turbulent model for the flow field and an algebraic model for the thermal field. As a result, it was shown that bypass flows in the SPP play a significant role in heat transfer. Also it is thought that the turbulent energy can strongly affect heat transfer performance.
CONVECTIVE HEAT TRANSFER IN CYCLONE DEVICE WITH EXTERNAL GAS RECIRCULATION
Directory of Open Access Journals (Sweden)
S. V. Karpov
2016-01-01
Full Text Available The article considers the convective heat transfer on the surface of a hollow cylinder or several billets in a cyclone device with the new principle of external gas recirculation. According to this principle, transport of coolant from the lateral surface of the chamber, where the temperature is the highest, in the axial region is being fulfilled due to the pressure drop between the wall and axial areas of cyclonic flow. Dependency analysis of average and local heat transfer coefficients from operational and geometrical parameters has been performed; the generalized similarity equations for the calculation of the latter have been suggested. It is demonstrated that in case of download of a cyclone chamber with several billets, the use of the considered scheme of the external recirculation due to the specific characteristics of aerodynamics practically does not lead to noticeable changes in the intensity of convective heat transfer. Both experimental data and the numerical simulation results obtained with the use of OpenFOAM platform were used in the work. The investigations fulfilled will expand the area of the use of cyclone heating devices.
Heat transfer and pressure drop characteristics of nanofluids in a plate heat exchanger.
Kwon, Y H; Kim, D; Li, C G; Lee, J K; Hong, D S; Lee, J G; Lee, S H; Cho, Y H; Kim, S H
2011-07-01
In this paper, the heat transfer characteristics and pressure drop of the ZnO and Al2O3 nanofluids in a plate heat exchanger were studied. The experimental conditions were 100-500 Reynolds number and the respective volumetric flow rates. The working temperature of the heat exchanger was within 20-40 degrees C. The measured thermophysical properties, such as thermal conductivity and kinematic viscosity, were applied to the calculation of the convective heat transfer coefficient of the plate heat exchanger employing the ZnO and Al2O3 nanofluids made through a two-step method. According to the Reynolds number, the overall heat transfer coefficient for 6 vol% Al2O3 increased to 30% because at the given viscosity and density of the nanofluids, they did not have the same flow rates. At a given volumetric flow rate, however, the performance did not improve. After the nanofluids were placed in the plate heat exchanger, the experimental results pertaining to nanofluid efficiency seemed inauspicious.
Studies on Heat Transfer in Agricultural Products by Far-infrared Ray
劉, 厚清; 毛利, 建太郎; 難波, 和彦
1998-01-01
Heat is transferred when the objected has temperature differences. In this research, the difference of two heating methods (far-infrared ray heating and hot wind heating) was analyzed. To compare their differences, the heat flux was measured by setting a heat flux meter beneath the surface of the object at different depths, then the heat conductivities and heat diffusion rates were analyzed. 1. Compared with hot wind, far-infrared ray heating has more heat flux before reaching a definite dept...
POST CRITICAL HEAT TRANSFER AND FUEL CLADDING OXIDATION
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Vojtěch Caha
2016-12-01
Full Text Available The knowledge of heat transfer coefficient in the post critical heat flux region in nuclear reactor safety is very important. Although the nuclear reactors normally operate at conditions where critical heat flux (CHF is not reached, accidents where dryout occur are possible. Most serious postulated accidents are a loss of coolant accident or reactivity initiated accident which can lead to CHF or post CHF conditions and possible disruption of core integrity. Moreover, this is also influenced by an oxide layer on the cladding surface. The paper deals with the study of mathematical models and correlations used for heat transfer calculation, especially in post dryout region, and fuel cladding oxidation kinetics of currently operated nuclear reactors. The study is focused on increasing of accuracy and reliability of safety limit calculations (e.g. DNBR or fuel cladding temperature. The paper presents coupled code which was developed for the solution of forced convection flow in heated channel and oxidation of fuel cladding. The code is capable of calculating temperature distribution in the coolant, cladding and fuel and also the thickness of an oxide layer.
A multilevel method for conductive-radiative heat transfer
Energy Technology Data Exchange (ETDEWEB)
Banoczi, J.M.; Kelley, C.T. [North Carolina State Univ., Raleigh, NC (United States)
1996-12-31
We present a fast multilevel algorithm for the solution of a system of nonlinear integro-differential equations that model steady-state combined radiative-conductive heat transfer. The equations can be formulated as a compact fixed point problem with a fixed point map that requires both a solution of the linear transport equation and the linear heat equation for its evaluation. We use fast transport solvers developed by the second author, to construct an efficient evaluation of the fixed point map and then apply the Atkinson-Brakhage, method, with Newton-GMRES as the coarse mesh solver, to the full nonlinear system.
Heat transfer and fluid flow in nuclear systems
Fenech, Henri
1982-01-01
Heat Transfer and Fluid in Flow Nuclear Systems discusses topics that bridge the gap between the fundamental principles and the designed practices. The book is comprised of six chapters that cover analysis of the predicting thermal-hydraulics performance of large nuclear reactors and associated heat-exchangers or steam generators of various nuclear systems. Chapter 1 tackles the general considerations on thermal design and performance requirements of nuclear reactor cores. The second chapter deals with pressurized subcooled light water systems, and the third chapter covers boiling water reacto
Macro- to microscale heat transfer the lagging behavior
Tzou, D Y
2014-01-01
Physical processes taking place in micro/nanoscale strongly depend on the material types and can be very complicated. Known approaches include kinetic theory and quantum mechanics, non-equilibrium and irreversible thermodynamics, molecular dynamics, and/or fractal theory and fraction model. Due to innately different physical bases employed, different approaches may involve different physical properties in describing micro/nanoscale heat transport. In addition, the parameters involved in different approaches, may not be mutually inclusive. Macro- to Microscale Heat Transfer: The Lagging Behav
Heat Transfer Analysis of a Diesel Engine Head
Directory of Open Access Journals (Sweden)
M. Diviš
2003-01-01
Full Text Available This paper documents the research carried out at the Josef Božek Research Center of Engine and Automotive Engineering dealing with extended numerical stress/deformation analyses of engines parts loaded by heat and mechanical forces. It contains a detailed description of a C/28 series diesel engine head FE model and a discussion of heat transfer analysis tunning and results. The head model consisting of several parts allows a description of contact interaction in both thermal and mechanical analysis.
Directory of Open Access Journals (Sweden)
Younsi Ramdane
2015-01-01
Full Text Available In the present paper, three-dimensional equations for coupled heat and mass conservation equations for wood are solved to study the transient heat and mass transfer during high thermal treatment of wood. The model is based on Luikov’s approach, including pressure. The model equations are solved numerically by the commercial package FEMLfor the temperature and moisture content histories under different treatment conditions. The simulation of the proposed conjugate problem allows the assessment of the effect of the heat and mass transfer within wood. A parametric study was also carried out to determine the effects of several parameters such as initial moisture content and the sample thickness on the temperature, pressure and moisture content distributions within the samples during heat treatment.
Heat transfer and flow studies of the liquid droplet heat exchanger
Bruckner, A. P.; Shariatmadar, A.
1987-01-01
This paper describes a lightweight, highly effective liquid droplet heat exchanger (LDHX) concept for thermal management in space. Heat is transferred by direct contact between fine droplets (100 to 300 micron diameter) of a low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the microgravity environment is accomplished by configuring the LDHX as a vortex chamber. A quasi-one-dimensional, two-phase heat transfer model of the LDHX is developed and used to investigate the potential use of the LDHX for both heating and cooling the working gas in a 100-k W(e) Braytoan cycle. Experimental studies on a small scale LDHX chamber, using air and water as the two media, show excellent agreement with the theoretical model.
Li, Huiping; He, Lianfang; Zhang, Chunzhi; Cui, Hongzhi
2016-04-01
The thermal physical parameters have significant effects on the calculation accuracy of physical fields, and the boundary heat transfer coefficient between the die and water is one of the most important thermal physical parameters in the hot stamping. In order to attain the boundary heat transfer coefficient, the testing devices and test procedures are designed according to the characteristic of heat transfer in the hot stamping die. A method of estimating the temperature-dependent boundary heat transfer coefficient is presented, and an inverse heat conduction software is developed based on finite element method, advance-retreat method and golden section method. The software is used to calculate the boundary heat transfer coefficient according to the temperatures measured by NiCr-NiSi thermocouples in the experiment. The research results show that, the convergence of the method given in the paper is well, the surface temperature of sample has a significant effect on the boundary heat transfer coefficient between the die and water. The boundary heat transfer coefficient increases as the surface temperature of sample reduces, and the variation is nonlinear.
O-Uchi, Masaki; Hirose, Koichi; Saito, Futami
The inside heat transfer coefficient, overall heat transfer coefficient, and heat flow rate at the heating section of the thermosiphon were determined for each heating method. In order to observe the heat transfer mechanism in the evaporator, a thermosiphon unit made of glass was assembled and conducted separately. The results of these experiments with these two units are summarized as follows. (1) Nucleate boiling due to the internal heat transfer mechanism improves the heat transfer characteristics of the thermosiphon unit. Under the specific heating conditions with dropwise condensation, there are two types of heat transfer mechanism occur in the evaporator accompanying nucleate boiling, i. e. latent heat transfer and sensible heat transfer. (2) In the case of latent heat transfer, the inside heat transfer coefficient has an upper limit which can be used as a criterion to determine the type of internal heat transfer mechanism.
Energy Technology Data Exchange (ETDEWEB)
Longo, Giovanni A. [University of Padova, Department of Management and Engineering, Str.lla S.Nicola 3, I-36100 Vicenza (Italy)
2010-08-15
This paper presents the heat transfer coefficients and pressure drop measured during HC-600a, HC-290 and HC-1270 saturated vapour condensation inside a brazed plate heat exchanger: the effects of refrigerant mass flux, saturation temperature (pressure) and fluid properties are investigated. The heat transfer coefficients show weak sensitivity to saturation temperature (pressure) and great sensitivity to refrigerant mass flux and fluid properties. A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 15-18 kg m{sup -2} s{sup -1}. In the forced convection condensation region the heat transfer coefficients show a 35-40% enhancement for a 60% increase of the refrigerant mass flux. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. HC-1270 shows heat transfer coefficients 5% higher than HC-600a and 10-15% higher than HC-290, together with frictional pressure drop 20-25% lower than HC-290 and 50-66% lower than HC-600a. (author)
Heat Transfer Characterization Using Heat and Solute Tracer Tests in a Shallow Alluvial Aquifer
Dassargues, A.
2013-12-01
Very low enthalpy geothermal systems are increasingly considered for heating or cooling using groundwater energy combined with heat pumps. The design and the impact of shallow geothermal systems are often assessed in a semi-empirical way. It is accepted by most of the private partners but not by environmental authorities deploring a lack of rigorous evaluation of the mid- to long-term impact on groundwater. In view of a more rigorous methodology, heat and dye tracers are used for estimating simultaneously heat transfer and solute transport parameters in an alluvial aquifer. The experimental field site, is equipped with 21 piezometers drilled in alluvial deposits composed of a loam layer overlying a sand and gravel layer constituting the alluvial aquifer. The tracing experiment consisted in injecting simultaneously heated water and a dye tracer in a piezometer and monitoring evolution of groundwater temperature and tracer concentration in 3 control panels set perpendicularly to the main groundwater flow. Results showed drastic differences between heat transfer and solute transport due to the main influence of thermal capacity of the saturated porous medium. The tracing experiment was then simulated using a numerical model and the best estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale. On the field: view from the injection well in direction of the pumping well through the three monitoring panels Temperature monitoring in the pumping well and in the piezometers of the three panels: heat transfer is faster in the lower part of the aquifer (blue curves) than in the upper part (red curves). Breakthrough curves are also more dispersed in the upper part with longer tailings.
Qasim, Muhammad; Khan, Zafar Hayat; Khan, Waqar Ahmad; Ali Shah, Inayat
2014-01-01
This study investigates the magnetohydrodynamic (MHD) flow of ferrofluid along a stretching cylinder. The velocity slip and prescribed surface heat flux boundary conditions are employed on the cylinder surface. Water as conventional base fluid containing nanoparticles of magnetite (Fe3O4) is used. Comparison between magnetic (Fe3O4) and non-magnetic (Al2O3) nanoparticles is also made. The governing non-linear partial differential equations are reduced to non-linear ordinary differential equations and then solved numerically using shooting method. Present results are compared with the available data in the limiting cases. The present results are found to be in an excellent agreement. It is observed that with an increase in the magnetic field strength, the percent difference in the heat transfer rate of magnetic nanoparticles with Al2O3 decreases. Surface shear stress and the heat transfer rate at the surface increase as the curvature parameter increases, i.e curvature helps to enhance the heat transfer.
Improved boundary layer heat transfer calculations near a stagnation point
Ahn, Kyung Hwan
1990-01-01
A thermal design of a solar receiver has been developed for the solutions of problems involving phase-change thermal energy storage and natural convection loss. Two dimensional axisymmetrical solidification and melting of materials contained between two concentric cylinders of finite length has been studied for thermal energy storage analysis. For calculation of free convection loss inside receiver cavity, two dimensional axisymmetrical, laminar, transient free convection including radiation effects has been studied using integral/finite difference method. Finite difference equations are derived for the above analysis subject to constant or variable material properties, initial conditions, and boundary conditions. The validity of the analyses has been substantiated by comparing results of the present general method with available analytic solutions or numerical results reported in the literature. Both explicit and implicit schemes are tested in phase change analysis with different number of nodes ranging from 4 to 18. The above numerical methods have been applied to the existing solar receiver analyzing computer code as additional subroutines. The results were computed for one of the proposed Brayton cycle solar receiver models running under the actual environmental conditions. Effect of thermal energy storage on the thermal behavior of the receiver has been estimated. Due to the thermal energy storage, about 65% reduction on working gas outlet temperature fluctuation has been obtained; however, maximum temperature of thermal energy storage containment has been increased about 18%. Also, effect of natural convection inside a receiver cavity on the receiver heat transfer has been analyzed. The finding indicated that thermal stratification occurs during the sun time resulting in higher receiver temperatures at the outlet section of the gas tube, and lower temperatures at the inlet section of the gas tube when compared with the results with no natural convection. Due
Energy Technology Data Exchange (ETDEWEB)
Chyu, M.K. [Carnegie Mellon Univ., Pittsburgh, PA (United States)
1995-10-01
This paper describes a novel approach based on fluorescence imaging of thermographic phosphor that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The film cooling model demonstrated consists of a single row of three discrete holes on a flat plate. The transient temperature measurement relies on the temperature-sensitive fluorescent properties of europium-doped lanthanum oxysulfide (La{sub 2}O{sub 2}S:EU{sup 3+}) thermographic phosphor. A series of full-field surface temperatures, mainstream temperatures, and coolant film temperatures were acquired during the heating of a test surface. These temperatures are used to calculate the heat transfer coefficients and the film effectiveness simultaneously. Because of the superior spatial resolution capability for the heat transfer data reduced from these temperature frames, the laser-induced fluorescence (LIF) imaging system, the present study observes the detailed heat transfer characteristics over a film-protected surface. The trend of the results agrees with those obtained using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is the capability to record a large number of temperature frames over a given testing period. This offers multiple-sample consistency.