bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamics Analysis on the Interaction Among Water, Cations, Anions and Antifreeze Protein
Authors: Hayakari Kohei , Kanamori Yuki , Hagiwara Yoshimichi
Published: March 2011

We have carried out molecular dynamics simulation on aqueous solution of winter flounder antifreeze protein with ions or a thin ice layer. It is found that the models of the antifreeze protein and the ions do not affect the motion of water molecules in the case without the ice layer. In the case with the ice layer, the water molecules become less mobile due to the cooling caused by the ice, while the protein becomes more mobile. The protein mobility is consistent with the antifreeze activity of the protein. On the other hand, in the case with the ice layer and the ions, the water molecules become more mobile, and the protein gradually becomes so. This fact is consistent with the cooperative effect of the antifreeze protein and the ions on the lowering of the freezing point.
On Thermal Performance of Seawater Cooling Towers
Authors: Sharqawy Mostafa H. , Lienhard John H. , Zubair Syed M.
Published: March 2011

Seawater cooling towers have been used since the 1970’s in power generation and other industries, so as to reduce the consumption of freshwater. The salts in seawater are known to create a number of operational problems including salt deposition, packing blockage, corrosion, and certain environmental impacts from salt drift and blowdown return. In addition, the salinity of seawater affects the thermophysical properties which govern the thermal performance of cooling towers, including vapor pressure, density, specific heat, viscosity, thermal conductivity and surface tension. In this paper, the thermal performance of seawater cooling towers is investigated using a detailed model of a counterflow wet cooling tower. The model takes into consideration the coupled heat and mass transfer processes and does not make any of the conventional Merkel approximations. In addition, the model incorporates the most up-to-date seawater properties in the literature. The model governing equations are solved numerically and its validity is checked by data in the literature. Based on the results of the model, a correction factor is obtained which characterizes the degradation of the cooling tower effectiveness when seawater is used.
Computer Simulation of Drying of Food Products With Superheated Steam in a Rotary Kiln
Authors: Sinhal Koustubh , Ghoshdastidar P. S. , Dasgupta Bhaskar
Published: March 2011

The present work reports a computer simulation study of heat transfer in a rotary kiln used for drying and preheating food products such as fruits and vegetables with superheated steam at 1 bar. The heat transfer model includes radiation exchange among the superheated steam, refractory wall and the solid surface, conduction in the refractory wall, and the mass and energy balances of the steam and solids. Finite-difference techniques are used, and the steady state thermal conditions are assumed. The false transient approach is used to solve the wall conduction equation. The solution is initiated at the inlet of the kiln, and proceeds to the exit. The output data consist of distributions of the refractory wall temperature, solid temperature, steam temperature, and the total kiln length. The inlet of the kiln is the outlet of the gas (superheated steam), since the gas flow is countercurrent to the solid. Thus, for a fixed solid and gas temperature at the kiln inlet, the program predicts the inlet temperature of the gas (i.e. at the kiln exit) in order to achieve the specified exit temperature. In the absence of experimental results for food drying in a rotary kiln, the present model has been satisfactorily validated against numerical results of Sass [1] for drying of wet iron ore in a rotary kiln. The results are presented for drying of apple and carrot pieces. A detailed parametric study indicates that the influence of controlling parameters such as percent water content (with respect to dry solids), solids flow rate, gas flow rate, kiln inclination angle and the rotational speed of the kiln on the axial solids and gas temperature profiles and the total predicted kiln length is appreciable. The study reveals that a good design of a rotary kiln requires medium gas flow rate, small angle of inclination and low rotational speed of the kiln.
A CMOS Compatible Metal-Polymer Microchannel Heat Sink for Monolithic Chip Cooling Applications
Authors: Koyuncuog˘lu Aziz , Okutucu Tuba , Ku¨lah Haluk
Published: March 2011

A novel complementary metal oxide semiconductor (CMOS) compatible microchannel heat sink is designed and fabricated for monolithic liquid cooling of electronic circuits. The microchannels are fabricated with full metal walls between adjacent channels with a polymer top layer for easy sealing and optical visibility of the channels. The use of polymer also provides flexibility in adjusting the width of the channels allowing better management of the pressure drop. The proposed microchannel heat sink requires no design change of the electronic circuitry underneath, hence, can be produced by adding a few more steps to the standard CMOS fabrication flow. The microchannel heat sinks were tested successfully under various heat flux and coolant flow rate conditions. The preliminary cooling tests indicate that the proposed design is promising as a monolithic liquid cooling solution for CMOS circuits.
Air-Heating Solar Collectors for Humidification-Dehumidification Desalination Systems
Authors: Summers Edward K. , Lienhard John H. , Zubair Syed M.
Published: March 2011

Relative to solar water heaters, solar air heaters have received relatively little investigation and have resulted in few commercial products. However, in the context of a Humidification-Dehumidification (HDH) Desalination cycle, air heating accounts for advantages in cycle performance. Solar collectors can be over 40% of an air-heated HDH system’s cost, thus design optimization is crucial. Best design practices and sensitivity to material properties for solar air heaters are investigated, and absorber solar absorptivity and glazing transmissivity are found to have the strongest effect on performance. Wind speed is also found to have an impact on performance. Additionally a well designed, and likely low cost, collector includes a double glazing and roughened absorber plates for superior heat transfer to the airstream. A collector in this configuration performs better than current collectors with an efficiency of 58% at a normalized gain of 0.06 K m2/W.
Flow Fields Investigation and Temperature Distribution on a Rotating Disk Imposed by a Turbulent Impinging Jet
Authors: Karrabi H. , Rasoulipour S.
Published: March 2011

Numerical investigation of fluid flow structure and convective heat transfer due to a circular jet impinging on a rotating disk is performed. Temperature and convection heat transfer coefficient are calculated. Flow is considered to be steady, incompressible and turbulent. k-ε RNG model is used to model the turbulent flow. Results are compared with experimental data showing good agreement. Two new criteria are introduced and used to evaluate the performance of cooling process, the first is maximum temperature difference on the disk, and the second is the average temperature of the disk. The first parameter shows the uniformity of temperature distribution in the disk and the second shows the effect of both thermo physical properties of the disk material and cooling process.
Sensitivity Analysis of Domain Considerations for Numerical Simulations of Film Cooling
Authors: Johnson Perry L. , Nguyen Cuong Q. , Ho Son H. , Kapat Jayanta S.
Published: March 2011

The majority of computational fluid dynamics studies for turbine film cooling have employed the Reynolds-Averaged Navier-Stokes equations with various turbulence modeling techniques to achieve closure, most notably the various two equation (k-ε or k-ω) models. For computational simulation of film cooling, modeling the entire testing domain with a row of multiple holes while sustaining a sufficiently fine mesh would demand a large number of grid cells and a hefty computational expense. A significant reduction in the computational domain can be and has been achieved without much harm to the overall accuracy of the film cooling prediction. The current study aimed to investigate the necessary domain parameters for reducing the grid cell count without significantly affecting the accuracy of the solution. The Box-Behnken design for response surface methodology was employed to determine the relative influence of each parameter on the cooling effectiveness prediction. The experimental design matrix was executed for multiple blowing ratios (0.5, 1.0, 2.0) to include the effects of the blowing ratio on the computational domain. The work was carried out using a three-dimensional computational fluid dynamics finite volume method with the RANS equations and k-ε turbulence model. A cylindrical film cooling hole with a pitch-to-diameter ratio of 3.0, a length-to-diameter ratio of 7.5, and an inclination angle of 35° was studied. The results are compared against existing data in the literature as well as in-house experimental data. The data from each case is compared in terms of spatially-averaged effectiveness. The modeled entrance length was found to be the most important parameter, with the mainflow height a distant second. The size of the modeled plenum was not found to exert any significant influence on the effectiveness results. Explanations are offered for notable trends in the data and conclusions are drawn concerning the grid optimization process.
Simultaneous Identification of Thermophysical Properties and Surface Heat Flux on Plasma Facing Components Inside the Jet Fusion Reactor
Authors: Rigollet Fabrice , Gardarein Jean-Laurent , Corre Yann , Le Niliot Christophe
Published: March 2011

We present here two thermal diagnostics (IR surface and embedded thermocouple temperature measurements) that outfit the same carbon tile inside the JET Fusion reactor and whose combination enables to identify, on one hand, a surface heat flux history and, on the other hand, one thermophysical parameter of an unknown deposited surface carbon layer (SCL). A sensitivity study of the thermal model of the SCL enables to show that only one parameter can be identified here : the thermal contact resistance between the SCL and the bulk substrate.
An Experimental Study of Heat Pipe Performance Using Binary Mixture Fluids That Exhibit Strong Concentration Marangoni Effects
Authors: Armijo Kenneth M. , Carey Van P.
Published: March 2011

This paper summarizes the results of an experimental investigation of the performance characteristics of a gravity/capillary driven heat pipe using water/alcohol mixtures as a working fluid. This investigation specifically explored the use of water/alcohol mixtures that exhibit strong concentration-based Marangoni effects. Experiments to determine heat pipe performance were conducted for pure water and water/alcohol solutions with increasing concentrations of alcohol. Initial tests with pure water determined the optimal working fluid charge for the heat pipe; subsequent performance tests over a wide range of heat input rates were then conducted for each working fluid at this optimum value. The results indicate that some mixtures can significantly enhance the heat transfer coefficient and heat flux capability of the heat pipe evaporator. For the best mixture tested, the maximum evaporator heat flux carried by the coolant without dryout was found to be 52% higher than the value for the same heat pipe using pure water as a coolant under comparable conditions. Peak evaporator heat fluxes above 100 W/cm2 were achieved with some mixtures. Evaporator and condenser heat transfer coefficient data are presented and the trends are examined in the context of the expected effect of the Marangoni mechanisms on heat transfer. Heat pipe design features that take maximum advantage of Marangoni effects are described and the application of these types of heat pipes to electronics cooling and heat removal from concentrating photovoltaic systems is discussed.
An Experimental Investigation of Film Cooling Performance of Louver Scheme
Authors: Ghorab M. , Hassan I. , Lucas T.
Published: March 2011

The experimental investigation of the film cooling performance of louver schemes using Thermochromic Liquid Crystal technique is presented in this paper. The louver scheme allows the cooling flow to pass through a bend and impinges with the blade material, which then exits to the outer surface of the aerofoil through the film cooling hole. The cooling performance for the louver scheme was analyzed across blowing ratios of 0.5 to 1.5 at a density ratio of 0.94. The results showed that the louver scheme enhances the local and the average film cooling performances in terms of film cooling effectiveness, and net heat flux reduction better than other published film hole configurations. As well, it provides a widely spread of the secondary flow extensively over the downstream surface, thus, it enhances the lateral film cooling performance. Moreover, the louver scheme produces a lower heat transfer coefficient ratio than other film hole geometries at low and high blowing ratios. As a result, the louver scheme is expected to reduce the gas turbine airfoil’s outer surface temperature and provides superior cooling performance which increases airfoil life time.
Mixed Convection in Vertical Tubes: High Reynolds Number
Authors: Huang LiDong , Farrell Kevin J.
Published: March 2011

The complex interaction of forced and natural convection depends on flow regime and flow direction. Aiding flow occurs when both driving forces act in the same direction (heating upflow fluid and cooling downflow fluid); opposing flow occurs when they act in different directions (cooling upflow fluid and heating downflow fluid). This paper discusses the buoyancy effect on forced convection for single-phase flows in vertical tubes. To evaluate mixed convection methods, Heat Transfer Research, Inc. (HTRI) recently collected water and propylene glycol data in two vertical tubes of different tube diameters. The data cover wide ranges of Reynolds, Grashof, and Prandtl numbers and differing ratios of heated tube length to diameter in laminar, transition, and turbulent forced flow regimes. In this paper, we focus on mixed convection with Reynolds numbers higher than 2000. Using HTRI data and experimental data in literature, we demonstrate that natural convection can greatly increase or decrease the convective heat transfer coefficient. In addition, we establish that natural convection should not be neglected if the Richardson number is higher than 0.01 or the mixed turbulent parameter Ra1/3/(Re0.8 Pr0.4) is higher than 0.05 even in forced turbulent flow with Reynolds numbers greater than 10000. High resolution Reynolds-Averaged Navier-Stokes (RANS) simulations of several experimental conditions confirm the importance of the buoyancy effect on the production of turbulence kinetic energy. We also determine that flow regime maps are required to predict the mixed convection heat transfer coefficient accurately.
Turbulent Flow in a Differentially Heated Cavity: Direct Numerical Simulation and Regularization Modeling
Authors: Trias F. Xavier , Gorobets Andrey , Oliva Assensi , Verstappen Roel
Published: March 2011

We consider regularizations of the convective term that preserve symmetry and conservation properties exactly. This yields a novel class of regularizations that restrain the convective production of small scales in an unconditionally stable manner Numerically, one of the most critical issues is the discrete filtering; properties required are, in general, not preserved by classical LES filters. Alternatively, here we propose to construct filters with the general form F = I + Σm = 1M dmD˜m where D˜ is the discrete diffusive operator. Then, the coefficients, dm, follow from the requirement that, at the smallest grid scale kc, the damping effect to the wavevector-triple (kc, p, kc − p) interactions must be virtually independent of the p-th Fourier-mode. This allows an optimal control of the subtle balance between convection and diffusion to stop the vortex-stretching. Finally, the proposed method is tested for an air-filled differentially heated cavity of aspect ratio 4 by direct comparison with DNS reference results.
Evaporation Induced Cavitation in Nanochannels
Authors: Duan Chuanhua , Karnik Rohit , Lu Ming-Chang , Majumdar Arun
Published: March 2011

Cavitation refers to a nucleation phenomenon that occurs at room temperature when the liquid pressure is below the corresponding saturation vapor pressure. Although water confined by a nanochannel and a liquid-air meniscus is under negative pressure, i.e. much smaller than the corresponding satraton vapor pressure, cavitation has not been observed in any nanochannels. In this work, we report our observation and studies of cavitations in nanochannels for the first time. 1-D confined nanochannels for this work were fabricated based on a sacrificial-layer-etching scheme. The unique cavitation phenomenon occurred when water started evaporation at the nanochannel entrances. Instead of meniscus recession, a bubble was present inside the nanochannel and two meniscii were pinned at the entrances. This bubble started growing along both directions until it totally occupied the whole channel. We found that the bubble grows linearly with time and the bubble growth rate decreases with the increasing channel height. A theoretical model was developed to study this dynamic process. It is found that the bubble growth rate is determined by the evaporation rate at the entrance. Since the total evaporation flux is a constant, the predicted bubble growth rate is reversely proportional to the channel height, quantitatively consistent with the experimental results. Since most current studies for caviation are theoretical studies, our studies provide a new experimental approach to study these phenomena in artificial transparent nanochannel devices.
Critical Heat Flux in Cooling Channels for Flow-Field Probes
Authors: Sykes David M. , Cole Gregory S. , Staples Daniel A. , Kosar Ali , Bergles Arthur E.
Published: March 2011

Probes (sampling, temperature, pressure) for high-temperature environments, such as gas turbine combustors, can survive only if they are cooled. To keep probe size small, the cooling passages must be microchannels, [O] 100 micrometer internal diameter. For logistical reasons, the length-to-diameter ratio is considerable. Heat fluxes are high, so that boiling occurs even with high velocities. The limiting factor for probe survivability, then, is the critical heat flux (CHF). This paper summarizes an experimental study of CHF in cooling channels that might be used for probes. A CHF correlation for water coolant is developed for design. An orifice at the channel inlet, originally conceived for enhancement, was found to dramatically improve the flow stability and increase the CHF. Pumping power requirements for plain tubes and orificed tubes are also documented.
Design of a Climate Chamber to Study Transient Performance of a Proton Exchange Membrane Fuel Cell at Near Freezing Temperatures
Authors: Cassar Daniel , Wang Xia
Published: March 2011

Freezing temperature startup of fuel cells is a serious issue for smaller applications such as auxiliary or backup power units. To accurately test and examine this problem, a laboratory climate chamber is required which can accurately represent possible environments. This research designed a climate chamber using thermoelectric (peltier) heat pumps to provide temperatures down up to −10 degrees Celsius. The internal heat absorption from air utilized forced convection while heat emitted by the thermoelectric device was removed by flowing water channels. A copper plate was used to provide separation between the heat absorbing plate and the thermoelectric heat pump. The unit showed accurate temperature control and successful operation at sub-zero temperatures. Two proton exchange membrane fuel cells with 117 Nafion membrane and 212 Nafion membrane were tested in the climate chamber under various operating conditions. The startup performance was examined under both freezing and non-freezing temperatures. Heated and humidified feed gasses were shown to greatly improve the steady state time of the 117 setup by over 30%.
Parametric Dependence of Annular Flow Heat Transfer in Microgaps
Authors: Rahim Emil , Bar-Cohen Avram
Published: March 2011

Forced flow of refrigerants and dielectric liquids, undergoing phase change in a heated microgap channel between chips or in parallel microchannels in a compact cooler, is a promising candidate for the thermal management of advanced semiconductor devices. It has been found that Annular flow is the dominant flow regime in such miniature channels and that relatively high heat transfer coefficients are encountered in the moderate-to-high quality sections of such channels. Following a discussion of flow regimes and thermal characteristics of miniature channels, attention turns to exploring the parametric dependence of annular flow thermal transport in microgaps including the effects of channel diameter, mass flux, and working fluid on the two-phase heat transfer coefficients.
Tuning Thermal Conductivity With Mechanical Strain
Authors: Li Xiaobo , Liu Jun , Yang Ronggui
Published: March 2011

Mechanical strain provides an efficient way for tuning thermal conductivity of materials. In this study, molecular dynamics (MD) simulation is performed to systematically study the strain effects on the lattice thermal conductivity of silicon and carbon based materials (mainly nanostructures: Si nanowire and thin film, single-walled carbon naotube (SWCNT) and single layer graphene) and bulk polymer materials. Results show that thermal conductivity of the strained silicon nanowires and thin films decreases continuously when the strain changes from compressive to tensile. However, the thermal conductivity has a peak value under compressive strain for SWCNT and at zero strain for single layer graphene. In contrast, thermal conductivity of polymer materials increases with increasing tensile strain. The underlying mechanisms are analyzed in this paper for both types of materials. We found that the thermal conductivity of silicon and carbon based materials can be related to the phonon dispersion curve shift and structural buckling under strain and for polymer chains thermal conductivity directly connects to the orientations of the chains. This thermal conductivity dependence with strain can guide us to tune the thermal conductivity for materials in applications.
Turbulence Radiation Interaction: From Theory to Application in Numerical Simulations
Authors: Coelho Pedro J.
Published: March 2011

Theoretical analysis and experimental investigations have shown that the mean heat fluxes in turbulent gaseous flows are influenced not only by the mean scalar fields (temperature and molar fraction of the species), but also by the scalar fluctuations. It is widely recognized that the increase of radiative fluxes in comparison with laminar flows may exceed 100%. This interaction between turbulence and radiation is mainly due to the non-linearity between radiative emission and temperature. It is particularly important in reactive flows, since temperature fluctuations are typically higher in these flows than in non-reactive ones. In this article, a survey of the theory concerning turbulence-radiation interaction (TRI) is presented, along with applications in numerical simulations. We firstly present experimental and theoretical fundamentals on TRI. Then, direct numerical simulation and stochastic methods are addressed. Although they provide reliable information on TRI, they are too computationally demanding for practical applications. We will then focus on methods based on the solution of the time-averaged form of the conservation equations. Although many different approaches are available, we will concentrate on two methods. One is based on the solution of the time-averaged form of the radiative transfer equation using the optically thin fluctuation approximation, and a combustion model based on a prescribed probability density function (pdf) approach. The second one is based on the photon Monte Carlo method for radiative transfer calculations in media represented by discrete particle fields, and a combustion model based on the Monte Carlo solution of the transport equation for the joint pdf of scalars. Finally, the role of TRI in large eddy simulation is discussed, and the main consequences of TRI in combustion systems are summarized.
Whole-Body Human Thermal Modeling, an Alternative to Immersion in Cold Water and Other Unpleasant Endeavors
Authors: Wissler Eugene H.
Published: March 2011

The human thermal regulatory system is remarkable. It allows humans to live under environmental temperatures that range from −45 °C in Arctic regions to + 50 °C in the Saharan desert, while maintaining the temperature of critical organs within ± 1 °C of 37 °C, without employing heating and cooling systems that we now take for granted. Of course, that requires building suitable shelters and wearing appropriate clothing, but it is still quite remarkable.
Design and Batch-Fabrication of Diamond Thermocouple Probes for the Quantitative Thermopower Profiling of Silicon IC Devices
Authors: Lee Byeonghee , Kim Kyeongtae , Lee Seungkoo , Kwon Ohmyoung , Kim Jong Hoon , Lim Dae Soon , Lee Woo Il , Lee Joon Sik
Published: March 2011

We developed a measurement technique that can quantitatively map out the dopant density profile of a silicon integrated-circuit device. This method obtains the quantitative doping density profile by simultaneously carrying out local heating, temperature sensing, and thermoelectric voltage measurement at the tip of a diamond thermocouple probe. This probe, which is the key component of the proposed scheme, is fabricated through a nano-fabrication technique that makes use of boron-doped diamond film that can resist stress up to 10 Gpa, which is necessary for stable electric contact with silicon samples. The tip and cantilever of the probe are made of B-doped diamond by means of the silicon lost-mold technique that guarantees a sharper tip apex than that of a diamond-coated probe. A gold-chromium thermocouple junction is integrated at the tip apex for simultaneous heating and sensing. The size of the thermocouple is about 500 nm and the radius of the tip apex is less than 50 nm. The measurement technique is demonstrated by measuring the thermopower distribution across a silicon p-n junction and the result is compared with the theoretical values.
Inverse Problems in Heat Transfer: New Trends on Solution Methodologies and Applications
Authors: Orlande Helcio R. B.
Published: March 2011

Systematic methods for the solution of inverse problems have developed significantly during the last twenty years and have become a powerful tool for analysis and design in engineering. Inverse analysis is nowadays a common practice in which the groups involved with experiments and numerical simulation synergistically collaborate throughout the research work, in order to obtain the maximum of information regarding the physical problem under study. Inverse problems are mathematically classified as ill-posed, that is, their solutions do not satisfy either one of the requirements of existence, uniqueness or stability. The solution approaches generally consist of the reformulation of the inverse problem in terms of an approximate well-posed problem. In this paper we briefly review various approaches for the solution of inverse problems, including those based on classical regularization techniques and those based on the Bayesian statistics. Applications of inverse problems are then presented for cases of practical interest, such as the characterization of non-homogeneous materials and the prediction of the temperature field in oil pipelines.
CVD Growth and Heat Transfer of Carbon Nanotubes
Authors: Maruyama Shigeo
Published: March 2011

Carbon nanotubes and graphene are extra-ordinal material with remarkable electrical, optical, mechanical and thermal properties. Films of vertically aligned (VA-) SWNTs and horizontally aligned (HA-) SWNTs are synthesized on quartz and crystal quartz substrates, respectively. These aligned film should inherit the remarkable properties of SWNTs. The recent progress in growth control and characterization techniques will be discussed. The CVD growth mechanism of VA-SWNTs is discussed based on the in-situ growth monitoring by laser absorption during CVD. For the precisely patterned growth of SWNTs, we recently propose a surface-energy-difference driven selective deposition of catalyst for localized growth of SWNTs. For a self assembled monolayer (SAM) patterned Si surface, catalyst particles deposit and SWNTs grow only on the hydrophilic regions. The proposed all-liquid-based approach possesses significant advantages in scalability and resolution over state-to-the-art techniques, which we believe can greatly advance the fabrication of nano-devices using high-quality as-grown SWNTs. The optical characterization of the VA-SWNT film using polarized absorption, polarized Raman, and photoluminescence spectroscopy will be discussed. The extremely high and peculiar thermal conductivity of single-walled carbon nanotubes has been explored by non-equilibrium molecular dynamics simulation approaches. The thermal properties of the vertically aligned film and composite materials are studied by several experimental techniques and Monte Carlo simulations based on molecular dynamics inputs of thermal conductivity and thermal boundary resistance. Current understanding of thermal properties of the film is discussed.
Use of CFD in the Analysis of Heat Transfer Related Problems That Arise in Building Energy Studies
Authors: Oosthuizen Patrick H. , Lightstone Marilyn
Published: March 2011

Energy simulation (ES) computer programs have been and still are widely used in the design and analysis of building energy systems. However, most ES programs assume that the air in the indoor building space is well mixed. As a result such programs cannot accurately predict building energy consumption for buildings with non-uniform air temperature distributions in the indoor space. They also cannot predict variations in thermal comfort levels in different parts of the building. Computational Fluid Dynamics (CFD), as a result, has become quite widely used in the design and evaluation of buildings energy systems in recent years. CFD can be used, for example, to predict the thermal comfort, natural lighting, natural ventilation, spread of smoke and contaminants in the building, and indoor air quality in a building. As a result it is proving to be an extremely valuable tool in the design of buildings and building systems. This, together with the fact that today’s commercial CFD software packages are relatively easy to use, has led to this quite widespread adoption of CFD methods in building energy analysis. Energy usage in buildings can be decreased by, for example, the use of daylighting (use of solar illumination in place of artificial lighting), by the use of natural ventilation, and by solar heating. CFD analysis provides a means of relatively accurately studying the effect of building design on the effectiveness of daylighting, natural ventilation, and solar heating. Another example of the use of CFD is in the study of the effect of various window blind arrangements on the building performance. In order for a CFD package to be used effectively in building energy analysis it should allow the use of a wide range of turbulence models, it should allow the incident solar radiation on the building to be found and used in the calculation of the indoor flow and temperature fields, it should allow the radiant heat exchange in the building to be incorporated into the calculation, and it should allow the effects of the thermal masses of the walls, floors, etc. to be easily incorporated into the calculation when they are deemed to be important. In this paper, the use of CFD methods in building energy analysis will be discussed as will some applications of CFD in building design. The use of CFD methods in developing design guidelines for particular types of buildings will also be briefly discussed.
Macroscale and Microscale Phenomena Encountered in Multiphase Energy Storage and Transport System
Authors: Kawaji Masahiro
Published: March 2011

Complex macroscale and microscale heat and mass transfer phenomena encountered in several thermal energy storage and transport systems are discussed. Thermal storage and transport systems involving ice slurries and nanoemulsions of phase change materials can be used for either cooling or heating applications or both, which can contribute to the reduced usage of electricity during peak hours. But heat and mass transfer and stability issues are encountered in the production, transport and storage of the heat storage media. Both the heat transfer enhancement effect and detrimental effects such as Ostwald ripening and supercooling will be discussed. Another interesting microscale phenomenon recently encountered in energy transport devices such as heat pipes is the enhancement of heat transport with the use of self-rewetting fluids. Critical heat fluxes in boiling can be enhanced by up to 300% and this helps prevent liquid dryout at high heat fluxes in different types of heat pipes. Both the nature of the enhancement effect and possible mechanisms will be discussed.
The Characteristics of CO2 Flow and Thermal Field in a Porous Media
Authors: Choi Hang Seok , Choi Yeon Seok , Park Hoon Chae , Huh Cheol , Kang Seong-Gil , Cho Meang-Ik , Kim Yong-Hwan
Published: March 2011

International attention has been considerably paid for the technology of CO2 capture and storage (CCS) these days because of global warming. Among the technologies of CCS, the prediction of CO2 behavior in underground is very crucial for CO2 storage design. In the present study, a pore-scale level model is developed to mimic real porous structure and by using CFD (computational fluid dynamics) the characteristics of the CO2 flow and thermal fields are investigated in the pore-level micro porous structure. Varying the CO2 injection conditions such as flow rate, pressure and temperature, the behavior of CO2 is calculated. Especially, the physical conditions such as temperature and pressure are set up equivalent to the underground condition at which CO2 is injected. From the results, the injection condition of CO2 is very critical to the characteristics of the flow and thermal fields in the micro-scale porous structure.
Effect of Non-Isothermal Conditions on Liquid Breakup Mechanisms
Authors: Sher Ilai
Published: March 2011

Liquid breakup mechanism utilization is prevalent in numerous applications. One of the most common uses of this phenomenon is in fuel injection systems. Liquid fuel is injected into an ambient air, to prepare a combustible mixture. Generally, evenly spread tiny fuel droplets are desirable. This is usually achieved through multiple liquid breaking mechanisms: Primary breakup of liquid jet, Secondary breakup of travelling liquid droplets, and Secondary breakup of wall-impinging liquid droplets. Indeed, many studies are devoted to the modelling of those phenomena. However, the absolute majority of those studies are limitedly focused on the isothermal case, where liquid is assumed to be of ambient gas’ temperature. Conversely, practical conditions, under which rather cold fuel is normally injected into hot ambient air, suggest the real case to be non-isothermal. Moreover, the non-isothermal nature of that process seems to have its effect at the most relevant to breakup regions, i.e. the breaking interfacial surfaces. It is shown that as these surfaces can be in instant contact with a hot ambient, breakup can be greatly altered by the extent of this sudden thermal exposure, through its mostly transient and even spatial effect on physical properties of breaking interfaces. This is shown to be of significant effect on all breakup mechanisms: primary and secondary. New models are suggested for these non-isothermal phenomena, which combine transient heat-transfer with inter-phase hydrodynamic breakup, through physical properties’ dependency on temperature. Results are discussed in terms of effect on spray breakup products, and a careful comparison with the trend of a limited number of so-far available experimental results is presented.
Manipulation of a Thermal Emission by Use of Micro- and Nanoscale Structures
Authors: Hasman Erez , Kleiner Vladimir , Dahan Nir , Balin Igal
Published: March 2011

In high temperature and vacuum applications, when heat transfer is predominantly by radiation, the material’s surface texture is of substantial importance. Several micro and nanostructures designs have been proposed to enhance a material’s emissivity and its radiative coherence, as control of thermal emission is of crucial concern in the design of infrared sources, in electronic chip coolants, in high-efficiency photovoltaic cells, and in solar energy conversion.
Geometrical Optimization of Solar Concentrating Collectors Through Quasi-Monte Carlo Simulation
Authors: Marston A. J. , Daun K. J. , Collins M. R.
Published: March 2011

Monte Carlo (MC) ray-tracing simulation coupled with stochastic programming has recently been shown to be a powerful technique for optimizing the design of solar concentrating collectors, but this procedure is complicated by the statistical uncertainty that MC introduces into the objective function. This paper shows how using quasi-Monte Carlo (QMC) methods instead of MC to simulate radiation heat transfer reduces these uncertainties, allowing the Kiefer-Wolfowitz technique to perform required gradient estimations using much smaller sample sizes. Consequently, QMC greatly increases the computational speed of the overall concentrating collector design optimization algorithm. In an attempt to ensure that the minimum required sample size is used at each design iteration, a novel condition-based iterative approach is introduced which starts at a low sample size and increases in a logarithmic manner until the estimate reaches the required degree of accuracy.
Phononics: A New Science and Technology of Controlling Heat Flow and Processing Information by Phonons
Authors: Wang Lei , Zhang Gang , Wu Gang , Yang Nuo , Li Baowen
Published: March 2011

Heat due to lattice vibration (phonons) is traditionally regarded as harmful for information processing. In this paper, we will demonstrate via numerical simulation, theoretical analysis and experiments that, phonons, can be manipulated like electrons. They can be used to carry and process information. Basic phononic devices such as thermal diode, thermal transistor, thermal logic gate and thermal memory will be discussed via nonlinear lattice model. Moreover, we will also discuss how to manipulate and tune thermal conductivity of nanostructure so that to control heat flow. Both theoretical and experimental works will be shown.
Use of Analytical Expressions of Convection in Conjugated Heat Transfer Problems
Authors: Karvinen R.
Published: March 2011

The heat transfer coefficient of convection from the wall to the flow depends on flow type, on surface temperature distribution in a stream-wise direction, and in transient cases also on time. In so-called conjugated problems, the surface temperature distribution of the wall and flow are coupled together. Thus, the simultaneous solution of convection between the flow and wall, and conduction in the wall is required because heat transfer coefficients are not known. For external and internal flows very accurate approximate analytical expressions have been derived for heat transfer in different kinds of boundary conditions which change in flow direction. Due to the linearity of the energy equation the superposition principle can be adopted to couple with these expressions the surface temperature and heat flux distributions in conjugated problems. In the paper this type of approach is adopted and applied to a number of industrial applications ranging from flat plates of electroluminecence displays to the optimization of heat transfer in fins, fin arrays and mobile phones.
Recent Advances in Turbine Heat Transfer: With a View of Transition to Coal Gas Based Systems
Authors: Chyu Minking K.
Published: March 2011

The performance goal of modern gas turbine engines, both land-base and air-breathing engines, can be achieved by increasing the turbine inlet temperature (TIT). The level of TIT in the near future can reach as high as 1700°C for utility turbines and over 1900°C for advanced military engines. To ensure the turbine airfoil component integrity operated under such a condition, advanced cooling capacity by both external and internal means is necessary to remove the excessive heat load from the turbine airfoil. This paper discusses state-of-the-art airfoil cooling technologies along with the associated thermal transport issues. Discussion is given based on five key regions on and around an airfoil: leading edge, main body, trailing edge, endwall and near tip. Potential implications and challenges of near-term developments in coal-gas based turbines on the cooling technologies are identified. A literature survey focusing primarily on the past four to five years since the last International Heat Transfer Conference has also been performed.
Fluid to Fluid Modeling Scaling Factors of R134a-Water for Critical Heat Flux
Authors: Chen Chang-Nian , Han Ji-Tian , Shao Li , Jen Tien-Chien
Published: March 2011

A series of calculations of the critical heat flux (CHF) fluid to fluid modeling scaling factors were performed to obtain relative data between R134a and water for CHF modeling method. The pressure range of R134a used in calculation was 0.15–3.59Mpa (liquid-gas density ratio 172.45–2.88), water-equivalent pressure range 1–20Mpa. Based on Ahmad model and Y. Katto model, four modeling scaling factors FL, FP, FH and FG were determined. According to the thermophysical properties of saturated R134a and saturated water, data near triple point and critical point temperature were discarded. The middle values were obtained by using a data interpolation or data fitting method, and 23 pairs of data in total were used in the whole calculation process. From the analysis of the calculation results, it was determined that the difficulty in performing CHF experiments would be drastically reduced by 70%–80% and costs reduction by about 80%, using R134a as modeling fluid. Considering the difference between the two kinds of FG derived by Ahmad model and Y. Katto model, an average method was developed to apply for modeling technique, which works well for CHF prediction at higher mass flux conditions in helically-coiled tubes.
The Role of Liquid Layering on the Enhancement of Thermal Conductivity in Nanofluids
Authors: Azizian M. Reza , Doroodchi Elham , Moghtaderi Behdad
Published: March 2011

Liquid layering is considered to be one of the key mechanisms responsible for the remarkably high thermal conductivities exhibited by nanofluids. A number of models have been presented in recent years to quantify the effect of liquid layering. However, many of these models are either based on unrealistic assumptions or have been incorrectly formulated. In this study we propose a new, yet simple, model that resolves the shortcomings of earlier models. The new model is based on the Maxwell theory and takes into account the effect of nanolayering. The model was compared with several sets of experimental data on Copper Oxide-in-ethylene glycol, Copper Oxide-in-water, Alumina-in-water, and Gold-in-toluene. The results indicate that the contribution of nanolayering to the enhancement of thermal conductivity in nanofluids is relatively modest and as such cannot be solely responsible for the observed enhancements.
Conjugate Heat Transfer Within a Heterogeneous Hierarchical Structure
Authors: Catton Ivan
Published: March 2011

Optimization of heat exchangers (HE), compact heat exchangers (CHE) and micro-heat exchangers by design of their basic structure is the focus of this work. Consistant models are developed to describe transport phenomena in a porous medium that take into account the scales and other characteristics of the medium morphology. Equation sets allowing for turbulence and two-temperature or two-concentration diffusion are obtained for non-isotropic porous media with interface exchange. The equations differ from known equations and were developed using a rigorous averaging technique, hierarchical modeling methodology, and fully turbulent models with Reynolds stresses and fluxes in the space of every pore. The transport equations are shown to have additional integral and differential terms. The description of the structural morphology determines the importance of these terms and the range of application of the closure schemes. A natural way to transfer from transport equations in a porous media with integral terms to differential equations with coefficients that could be experimentally or numerically evaluated and determined is described. The relationship between CFD, experiment and closure needed for the volume averaged equations is discussed. Mathematical models for modeling momentum and heat transport based on well established averaging theorems are developed. Use of a ‘porous media’ length scale is shown to be very beneficial in collapsing complex data onto a single curve yielding simple heat transfer and friction factor correlations. The general transport equations developed for a single phase fluid in a heat exchange medium have many more integral and differential terms than the homogenized or classical continuum mechanics equations. Once these terms are dealt with by closure, the resulting equation set is relatively simple and their solution is obtained using simple numerical methods quickly enough for multiple parameter optimization using Design of Experiment (DOE) or Genetic Algorithms (GA). Current efforts to significantly improve the performance of a HE for electronic cooling, a two temperature problem, and of a finned tube heat exchanger, a three temperature problem, are described.
Recent Advances in Measurement of Turbulent Reacting Flows in Which Heat Transfer is Dominated by Radiation
Authors: Nathan G. J. , Kalt P. A. M. , Alwahabi Z. T. , Dally B. B. , Medwell P. R. , Chan Q. N.
Published: March 2011

Recent advances in diagnostic methods are providing new capacity for detailed measurement of turbulent, reacting flows in which heat transfer is dominant. Radiation typically becomes dominant in flames containing soot and/or with sufficient physical size, so is important in many flames of practical significance. The presence of particles, including soot, increases the coupling between the turbulence, chemistry and radiative heat transfer processes. Particles also increase the difficulties of laser-based measurements by increasing the interferences to the signal and the attenuation of the beam. The paper reviews recent advances in techniques to measure temperature, mixture fraction, soot volume fraction, velocity, particle number density and the scattered, absorbed and transmitted components of radiation propagation through particle laden systems.
Direct comparison of the x-ray emission and absorption of cerium oxide
Authors: Tobin J. G. , Yu S. W. , Chung B. W. , Waddill G. D. , Denlinger J. D.
Published: March 2011

X-ray emission spectroscopy and x-ray absorption spectroscopy have been used to investigate the photon emission and absorption associated with the Ce 3d5/2 and Ce 3d3/2 core levels in Ce oxide. A comparison of the two processes and their spectra will be made.
Formation of single-domain homogeneous Au nanoparticle monolayer at the water/oil interface and its application to surface-enhanced Raman scattering
Authors: Kim Su Il , Pradal Fabien , Song Hyunjoon , Kim Sehun
Published: March 2011

We fabricated a closely packed Au nanoparticle monolayer with millimeter dimensions on a hydrophilic Si substrate using a water/oil interface method. The surface-enhanced Raman scattering of Rhodamine 6G dye molecules adsorbed on these substrates was measured. For this structure, we simulated the electromagnetic-field enhancement when the laser light was focused on the sample, assuming the hexagonal unit cell. We suggest that the strong field enhancement arises from interstitial gaps between nanoparticles.