bluuebunny/crossref_metadata_2025 huggingface dataset:
Influences of Subcooling on Burnout of Horizontal Cylindrical Heaters
Authors: Elkassabgi Y. , Lienhard J. H.
Published: October 2009

The peak pool boiling heat flux is observed on horizontal cylindrical heaters in acetone, Freon-113, methanol, and isopropanol over ranges of subcooling from zero to 130° C. Photographs, and the data themselves, revealed that there are three distinct burnout mechanisms at different levels of subcooling. Three interpretive models provide the basis for accurate correlations of the present data, and data from the literature, in each of the three regimes. Burnout is dictated by condensation on the walls of the vapor jets and columns at low subcooling. In the intermediate regime, burnout is limited by natural convection, which becomes very effective as vapor near the heater reduces boundary layer resistance. Burnout in the highsubcooling regime is independent of the layer of subcooling, and is limited by the process of molecular effusion.
Heat Transfer Behavior of a Rectangular Thermosyphon Loop
Authors: Huang B. J. , Zelaya R.
Published: October 2009

The thermal performance of a rectangular thermosyphon loop was studied. The analysis, using a one-dimensional approximation, the conventional friction factor, and an empirical correlation for the overall heat transfer in the cooler, was shown to be able to predict accurately the loop performance at steady state or approaching steady state, if the effective length was used to replace the geometric length in the calculation of loop friction. The steady-state natural circulation flow solution obtained was shown to be a function of a dimensionless group PY or (NuGr/Pr) Y and agrees very well with the experimental results.
Shape Optimization and Identification of Solid Geometries Considering Discontinuities
Authors: Meric¸ R. A.
Published: October 2009

Shape sensitivity analysis of heat-conducting bodies is performed in general terms incorporating interface conditions and boundary singularities. Adjoint variables and the material derivative concept are utilized to obtain the material derivatives of volume and surface integrals of temperature and heat flux. Two illustrative examples are then analyzed by iterative numerical techniques incorporating the boundary element method of discretization. In the first problem, the interface position in a nonhomogeneous material is optimized for a minimum of total surface heat flow. The second problem involves the determination of the solidification interface shape in the so-called steady-state one-phase Stefan problem. Numerical results, checked by exact solutions, where available, indicate that the proposed solution procedure is suitable for free boundary problems in heat transfer.
Conduction Heating of Objects of Simple Shape in a Fluid With Finite Heat Capacity
Authors: Pham Q. T.
Published: October 2009

A unified analytical solution and an approximate method are presented for calculating the time to cool or heat an object of simple shape to a given mean temperature, using a fluid with finite heat capacity in batch, parallel-flow, or counterflow modes. In the approximate method, an equivalent constant fluid temperature is calculated, which would give the same log-mean temperature difference. The cooling time at this equivalent temperature is found by conventional methods, then multiplied by a correction factor calculated from a simple regression equation.
Forced Convection Heat Transfer in a Finitely Conducting Externally Finned Pipe
Authors: Moukalled F. , Acharya S.
Published: October 2009

A numerical study to determine the influence of axial wall conduction on forced convection heat transfer in an externally finned pipe has been made. The effects of wall conductivity, interfin spacing, and external heat transfer coefficient are examined by comparing the results with the corresponding solutions obtained assuming negligible wall conduction. Results indicate that the axial conduction in the pipe walls has a significant influence on the heat transfer behavior. The bulk temperature or the heat transferred to the fluid is underestimated when wall conduction is ignored. At high wall conductivity values, the wall temperatures and Nusselt numbers exhibit a monotonic variation in the axial direction, with the behavior becoming increasingly nonmonotonic as the wall conductivity value is decreased.
Thermal Convection Around a Heat Source Embedded in a Box Containing a Saturated Porous Medium
Authors: Himasekhar K. , Bau H. H.
Published: October 2009

A study of the thermal convection around a uniform flux cylinder embedded in a box containing a saturated porous medium is carried out experimentally and theoretically. The experimental work includes heat transfer and temperature field measurements. It is observed that for low Rayleigh numbers, the flow is two dimensional and time independent. Once a critical Rayleigh number is exceeded, the flow undergoes a Hopf bifurcation and becomes three dimensional and time dependent. The theoretical study involves the numerical solution of the two-dimensional Darcy–Oberbeck–Boussinesq equations. The complicated geometry is conveniently handled by mapping the physical domain onto a rectangle via the use of boundary-fitted coordinates. The numerical code can easily be extended to handle diverse geometric configurations. For low Rayleigh numbers, the theoretical results agree favorably with the experimental observations. However, the appearance of three-dimensional flow phenomena limits the range of utility of the numerical code.
Modeling of Hot Fragment Conductive Ignition of Solid Propellants With Applications to Melting and Evaporation of Solids
Authors: Kuo K. K. , Hsieh W. H. , Hsieh K. C. , Miller M. S.
Published: October 2009

A comprehensive theoretical model has been formulated for studying the degree of vulnerability of various solid propellants being heated by hot spall fragments. The model simulates the hot fragment conductive ignition (HFCI) processes caused by direct contact of hot inert particles with solid propellant samples. The model describes the heat transfer and displacement of the hot particle, the generation of the melt (or foam) layer caused by the liquefaction, pyrolysis, and decomposition of the propellant, and the regression of the propellant as well as the time variation of its temperature distributions. To validate partially the theoretical model in the absence of the necessary chemical kinetic data, an ice melting and evaporation experiment was designed and conducted. These experiments provide features of the conductive heating, melting, and evaporating processes. Calculated results compare well with experimental data in temperature–time traces, spall particle sinking velocity, and displacement.
Stability of Single-Phase Natural Circulation With Inverted U-Tube Steam Generators
Authors: Sanders J.
Published: October 2009

For natural circulation it is shown that parallel flow in the tubes of an inverted U-tube steam generator can be, at certain power levels, unstable. A mathematical model, based on one-dimensional Oberbeck-Boussinesq equations, shows that stability can be attained if in some tubes the water flows backward, opposite to the normal flow direction. The results are compared to measurements obtained from the natural circulation test A2-77A in the LOBI-MOD2 integral system test facility.
Transient Response of Rotary Regenerators
Authors: Romie F. E.
Published: October 2009

Exit gas temperature responses of the counterflow rotary regenerator are found for a unit step increase of the inlet temperature of either gas. An analytic solution applicable during the first part of the transient shows that the responses cannot be smooth. The overall response is found by dividing the regenerator disk into pie-shaped segments and approximating the area-mean gas temperature leaving a segment as the temperature of the gas leaving a small regenerator located at the center of the segment. The method is shown to give good accuracy and is in agreement with predictions of the analytic solution.
Silica Fouling of Heat Transfer Equipment—Experiments and Model
Authors: Chan S. H. , Rau H. , DeBellis C. , Neusen K. F.
Published: October 2009

Silica fouling of heat transfer equipment in geothermal energy systems is studied. The effects of temperature, pH, and salinity on silica solubility and silica polymerization are reviewed. Experimental fouling data are presented for geothermal brines with different pH values, chemical compositions, and thermal-hydraulic conditions. The effects of supersaturation, pH, Reynolds number, and the concentration of ions in the brine solution on the formation of silica scale in the heat exchanger tube are discussed. A silica deposition model is proposed that accounts for supersaturation, pH factor, salinity, and thermal-hydraulic effects. Results based on the analytical model are compared with silica fouling data obtained in the laboratory as well as from two geothermal fields.
Turbulent Transport on the Endwall in the Region Between Adjacent Turbine Blades
Authors: Goldstein R. J. , Spores R. A.
Published: October 2009

The complex three-dimensional flow in the endwall region near the base of a turbine blade has an important impact on the local heat transfer. The initial horseshoe vortex, the passage vortex, and resulting corner vortices cause large variations in heat transfer over the entire endwall region. Due to these large surface gradients in heat transfer, conventional measurement techniques generally do not provide an accurate determination of the local heat transfer coefficients. In the present study, the heat/mass transfer analogy is used to examine the local transport coefficients for two different endwall boundary layer thicknesses and two free-stream Reynolds numbers. A linear turbine blade cascade is used in conjunction with a removable endwall plate. Naphthalene (C10H8) is cast into a mold on the plate and the rate of naphthalene sublimation is determined at 6000 + locations on the simulated endwall by employing a computer-aided data acquisition system. This technique allows one to obtain detailed contour plots of the local convection coefficient over the entire endwall. By examining the mass transfer contours, it is possible to infer information on the three-dimensional flow in the passage between the blades. Extremely high transport coefficients on the endwall indicate locations of potential overheating and failure in an actual turbine.
Film Boiling Heat Transfer From a Sphere and a Horizontal Cylinder Embedded in a Liquid-Saturated Porous Medium
Authors: Orozco J. , Stellman R. , Gutjahr M.
Published: October 2009

This paper analyses both theoretically and experimentally the problem of film boiling from a body embedded in a liquid-saturated porous medium. Two body geometries are investigated thoroughly: a horizontal cylinder and a sphere. The theoretical model relies on the Brinkman-extended flow model to describe the flow field inside the thin vapor layer occupying the neighborhood near the heated surface. The theoretical model also includes an improved formulation of the effective conductivity in the vicinity of the heater as a function of the vapor layer thickness and the geometry of the porous medium material. Solutions are obtained for the vapor layer thickness and the local Nusselt number as a function of angular position. Numerical solutions are also obtained for the overall heat transfer rates from the surface to the fluid for a given vapor superheat. Experimental data for a 12.70 mm stainless steel cylindrical heater embedded in a 3-mm glass particle porous medium were obtained under steady—state operation. The experimental data obtained are compared with the theoretical analysis. The comparison shows that there is a good agreement between theory and experiments. The theoretical model is also compared with the experimental data obtained by other investigators for a spherical geometry. Excellent results are obtained in such comparison.
Forced Condensation in a Tube With Suction at the Wall for Microgravitational Applications
Authors: Faghri A. , Chow L. C.
Published: October 2009

The condensation of vapor within a tube is examined for a tube wall that has a constant temperature and uniform suction in a microgravitational environment. The motion of the condensate is due to the interfacial shear between the vapor and the liquid as well as the suction at the wall. The decrease in the vapor flow rate due to condensation has been taken into account. The governing boundary layer momentum and energy equations have been solved by approximating the convective and inertial terms. It is concluded that simultaneous suction and vapor shear can effectively drain the condensate to ensure the continuous operation of space condensers.
Convection Heat Transfer in Electronic Equipment Cooling
Authors: Incropera F. P.
Published: October 2009

To maintain the best possible thermal environment in electronic packages, the engineer must establish the most efficient path for heat transfer from the electronic devices to an external cooling agent. The path is typically subdivided into internal and external components, representing, respectively, heat transfer by conduction through different materials and interfaces separating the devices from the package surface and heat transfer by convection from the surface to the coolant. Depending on the scale and speed of the electronic circuits, as well as on constraints imposed by nonthermal considerations, the coolant may be a gas or a liquid and heat transfer may be by natural, forced, or mixed convection or, in the case of a liquid, by pool or forced convection boiling. In this paper a comprehensive review of convection cooling options is provided.
Transitions and Bifurcations in Laminar Buoyant Flows in Confined Enclosures
Authors: Yang K. T.
Published: October 2009

Recent advances in experimental and numerical studies of flow instability, bifurcation, and transition to turbulence for buoyant flow in three-dimensional rectangular enclosures heated from below and from the sides are reviewed, with emphasis on the physical causes of various instabilities and bifurcations as well as the observed and calculated routes to chaotic motions. Also discussed are the current successes and shortcomings of numerical simulations of experimental data and observations. Finally, unresolved critical issues and needs for future research are also addressed.
Thermal Radiation in Participating Media: The Past, the Present, and Some Possible Futures
Authors: Howell J. R.
Published: October 2009

A review of major events in the development of the engineering treatment of radiative transfer in participating media is presented. This review is followed by a discussion of the major analytical methods presently used for this class of problems, along with their strengths and limitations. Some comments are added concerning important areas of research that remain to be completely treated, and some areas of potential future application.
Direct-Contact Heat Transfer for Process Technologies
Authors: Jacobs H. R.
Published: October 2009

Direct-contact heat transfer processes between fluid streams are reviewed for situations that may be found in process technologies. While not all of the past work could be referenced in the space available, many current and review articles are cited that provide sources of detailed information. Included in this review are topics that relate to direct contact evaporation, condensation, and boiling as well as simple sensible heat transfer between the fluid streams.
Comparative Performance of Rippled Fin Plate Fin and Tube Heat Exchangers
Authors: Maltson J. D. , Wilcock D. , Davenport C. J.
Published: October 2009

Continuous rippled fins are preferred to interrupted fins in applications where fouling by fibrous matter or insects is a problem. The performance characteristics of three rippled fin heat exchangers have been measured in a thermal wind tunnel. The results of these measurements are reported and comparisons are made with published data on similar surfaces. The performance evaluation criteria used as the basis for the comparisons were those recommended by Shah (1978). The tested rippled fin surfaces were found to have a higher performance than a similar surface reported in Kays and London (1984). The heat transfer enhancement was found to be dependent upon the profile of the fin.
Turbulent Heat Transfer and Friction in Pin Fin Channels With Lateral Flow Ejection
Authors: Lau S. C. , Han J. C. , Kim Y. S.
Published: October 2009

Experiments were conducted to study the effects of lateral flow ejection on the overall heat transfer and pressure drops for turbulent flow through pin fin channels. The two test sections of the investigation were rectangular channels with staggered arrays of six and eight streamwise rows of pins, respectively. The pin length-to-diameter ratio was one and both the streamwise and spanwise pin spacings were 2.5 times the pin diameter. Heat transfer and friction data were obtained for various ejection exit geometries, for ejection ratios between 0 and 1, and for Reynolds numbers between 6000 and 60,000. The results of the study show that, for any given ejection ratio, the overall Nusselt number increases with increasing Reynolds number. However, the overall Nusselt number is reduced by as much as 25 percent as the ejection ratio is increased from 0 to 1 over the range of Reynolds number studied. The Nu–Re–ε relationship, which is insensitive to varying the ejection exit geometry, can be correlated by the equation (Nu/Nu0) = (Nu1/Nu0)ε, where Nu0 = c0Rem and Nu1 = c1Ren are the overall Nusselt numbers in the 0 and 100 percent lateral flow ejection cases, respectively. The results also show that the overall friction factor is independent of the flow Reynolds number over the range of Reynolds number studied. However, the friction factor is strongly dependent on the ejection ratio as well as the geometries of the straight flow exit and lateral ejection flow exit.
Transient Destratification in a Rectangular Enclosure
Authors: Gnafakis C. , Manno V. P.
Published: October 2009

An experimental study of transient destratification in a rectangular air-filled enclosure is described. The test cell, which is 1 m high, 0.5 m wide, and 0.25 m deep, is made of plexiglass with a variety of side and bottom thermal boundary conditions. The initial vertical stratification is 30°C. A number of transient tests are reported in which a destabilizing heat source is introduced after the initial stratification. Temperature maps of the middepth plane are recorded and analyzed. Basic enclosure destratification dynamics are described in terms of developing thermal and flow fields. Separate effects of horizontal partitioning, stabilizing side heating, and asymmetric heating are studied. Certain large fractional horizontal blockages are shown to enhance destratification, while side heating is demonstrated to be a stablizing effect that produces a steady-state inversion.
On the Thermal Shock Wave Induced by a Moving Heat Source
Authors: Tzou D. Y.
Published: October 2009

Analytical solutions for the temperature field around a moving heat source in a solid with finite speed of heat propagation are obtained via the method of Green’s functions. When the speed of the moving heat source is equal to or faster than that of the thermal wave propagated in the solid, the thermal shock wave is shown to exist in the thermal field. The shock wave angle is obtained as sin−1 (1/M) for M ≥1. Orientation of crack initiation in the vicinity of the heat source is also estimated by considering the temperature gradient T,θ along the circumference of a continuum circle centered at the heat source. Such an orientation is established as a function of the thermal Mach number in the subsonic, transonic, and supersonic regimes, respectively.
Techniques for in Situ Determination of Thermal Resistance of Lightweight Board Insulations
Authors: Courville G. E. , Beck J. V.
Published: October 2009

Four techniques for determining the in situ thermal resistance of rigid board insulation installed in conventional low-sloped roofs are described and compared. All techniques use measured temperature distributions and heat fluxes in the roof systems. The limitations of the techniques are discussed. Test results are presented to allow a comparison of the methods.
Two-Dimensional Effects on the Response of Packed Bed Regenerators
Authors: Khan J. A. , Beasley D. E.
Published: October 2009

Packed beds have a wide range of applications as heat transfer and energy storage devices. Employed as a regenerator, a packed bed is subject to the flow of a heat transfer fluid, which alternately stores and recovers energy from a packing of discrete particles. The flow direction reverses during the addition and removal of energy. The nature of a packing of discrete particles in a container is such that variations in the resistance to flow and in the void fraction occur across the cross section of the packing. Particularly, the region of the bed near the boundary of the container has a markedly reduced resistance to flow. In addition, the wall effect on the packing geometry changes the void fraction in the near-wall region. The purpose of the present study is to quantify the two-dimensional effects of nonuniform void fraction, velocity, and temperature distributions in a packed bed regenerator on the dynamic and steady periodic behavior. A two-dimensional numerical model of the transient response of a packed bed subject to the flow of a heat transfer fluid has been developed and verified through comparison with measured responses. The model includes the effects of nonuniform velocity and porosity in the bed, and the effects of axial and radial thermal dispersion. The results of the present computations are compared with one-dimensional transient periodic results to demonstrate the two-dimensional effects on the transient response of a packed bed regenerator to a step change in fluid temperature. The classical dimensionless parameters, such as reduced length and reduced time, are not sufficient to characterize the two-dimensional transient nature of a packed bed regenerator. This study identifies the range of bed-to-particle-diameter ratios over which the transient response is significantly influenced by the wall effect on void fraction and flow.
Friction and Heat Transfer Characteristics of Helical Turbulent Air Flow in Annuli
Authors: Gupte N. S. , Date A. W.
Published: October 2009

Friction and Nusselt number data have been measured and semi-empirically evaluated for twisted tape generated helical flow in annuli. Results have been obtained for radius ratios of 0.41 and 0.61 and twist ratios of ∞, 5.302, 5.038, and 2.659. The increase in pressure drop and heat transfer rates obtained are comparable to those reported for twisted tape generated swirl flow in tubes. Also, for the same heat transfer rates the pumping power requirements compare favorably with those for empty annuli. The analytical predictions based on the principle of superposition of pressure drops and analogy between heat and momentum transfer have yielded excellent predictions for y = ∞ and 5.302 but somewhat poor agreement at y = 2.659.
Turbulent Natural Convection Flow on a Heated Vertical Wall Immersed in a Stratified Atmosphere
Authors: Kulkarni A. K. , Chou S. L.
Published: October 2009

This paper presents a comprehensive mathematical model and numerical solutions for a natural convection flow over an isothermal, heated, vertical wall immersed in an ambient atmosphere that is thermally stratified. The model assumes a laminar flow near the leading edge, which then becomes a transitional flow, and finally becomes fully turbulent away from the leading edge. Effects of several typical cases of ambient stratification on heat transfer to the wall, peak velocity, and temperature are examined. It is found that the velocity field is affected more significantly by the “memory” of upstream ambient conditions than the temperature field.
Numerical Calculation of Bubble Growth in Nucleate Boiling From Inception Through Departure
Authors: Lee R. C. , Nydahl J. E.
Published: October 2009

The relative contributions of the fundamental mechanisms accounting for the enhanced heat transfer in nucleate boiling are difficult to quantify analytically or experimentally. A comprehensive model was developed that permits some accurate insights into this problem. An essential feature involved the numerical mapping of the complicated geometry to a plane where the bubble and wall boundaries lie along constant coordinate lines. The results show that microlayer evaporation accounts for 87 percent of the enhanced wall heat transfer during saturated boiling of water at 1 atm and 8.5 K wall superheat. In contrast, enhanced convective effects were essentially nonexistent during growth and minimal following departure. The analysis predicts an extremely nonuniform thermal boundary layer around the bubble, and shows that the wall thermal boundary layer regenerates almost immediately following departure.
Effects of Two-Phase Pressure Drop on the Self-Sustained Oscillatory Instability in Condensing Flows
Authors: Bhatt B. L. , Wedekind G. L. , Jung K.
Published: October 2009

This paper presents the results of an extension of an experimental and theoretical investigation of an unstable flow phenomenon that leads to self-sustained limit-cycle-type oscillations of large amplitude, and which, under certain conditions, can involve flow reversals. The influence of two-phase pressure drop is examined and shown to have a stabilizing effect on the instability. Inclusion of the two-phase pressure drop as part of the downstream throttling allows the utilization of a previously developed linearized analysis, based on the system mean void fraction model, to predict successfully the experimentally observed stability boundary.
Temperature Response of a Heated Cylinder Subject to Side Cooling: Asymptotic and Numerical Solutions
Authors: Ramakrishna K. , Cohen I. M. , Ayyaswamy P. S.
Published: October 2009

The temperature response of a cylinder, subject to heat input at one end and heat loss from its side by radiation and natural convection, is studied analytically and numerically. A singular perturbation expansion gives the limiting case of large heat flux. The governing equations for arbitrary heat flux are solved numerically. The results of this investigation are useful for application to the microelectronic interconnection process using the ball bonding technique.
Induction Electrohydrodynamic Pump in a Vertical Configuration: Part 1—Theory
Authors: Seyed-Yagoobi J. , Chato J. C. , Crowley J. M. , Krein P. T.
Published: October 2009

An induction electrohydrodynamic (EHD) pump in an axisymmetric, vertical configuration is studied theoretically. The model includes the effect of entrance conditions, buoyancy effects, secondary flow, and Joule heating. Primarily the forward (cooled wall) and to a lesser extent the backward (heated wall) modes are investigated. A finite difference technique is used to obtain the numerical solutions. A set of these solutions is presented to show the influence of the controlling factors of operating an induction EHD pump. The results indicate that the entrance temperature profile plays an important role in the operation of the pump because steeper profiles produce higher velocities. The pump must be operated at an optimum frequency, wavelength, and electric conductivity level.
Mixed Convection in an Annulus of Large Aspect Ratio
Authors: Yao L. S. , Rogers B. B.
Published: October 2009

Mixed convection in an annulus of large aspect ratio is studied. At an aspect ratio of 100, the effect of wall curvature is minimal, and both the base flow and the stability characteristics approach those of a two-dimensional channel flow. The linear-stability results demonstrate that the fully developed flow is unstable in regions of practical interest in an appropriate parameter space. Consequently, commonly assumed steady parallel countercurrent flows in many idealized numerical and analytical studies are unlikely to be observed experimentally.
Transient Radiative Heat Transfer From a Sphere Surrounded by a Participating Medium
Authors: Bayazitoglu Y. , Suryanarayana P. V. R.
Published: October 2009

Transient radiative cooling of a solid or liquid sphere in space, surrounded by a radiatively participating vapor cloud, is considered. A quasi-steady assumption is applied to the radiation transfer in the medium, with the unsteadiness being retained at the inner spherical boundary. The problem is solved by applying the third-order (P3) spherical harmonics approximation to the radiative transfer equation for the participating cloud, and a finite difference scheme for transient conduction in the sphere. In general, the presence of a participating medium decreases the cooling rate of the sphere, and cooling curves are presented to show this effect. Effective emissivity of the surface in the presence of a surrounding medium is evaluated, and an approximate explicit equation is given.
Energy Storage in a Fluidized Bed
Authors: Merry N. , Rubinsky B.
Published: October 2009

An experimental study was performed to investigate the possible use of a compound that undergoes solid-to-solid phase transformation for energy storage in a fluidized bed configuration, and to determine the heat transfer characteristics of this system. It was shown that the heat transfer coefficients from a surface immersed in the fluidized bed are a function of the bed temperature and of the temperature of the immersed surface. The heat transfer process is enhanced by the phase transformation by as much as a factor of four relative to the heat transfer in the same material without phase transformation. The experimental results suggest the possible existence of a thermal resistance between the surface immersed in the fluidized bed and the particles, which is responsible for the particular experimentally observed thermal behavior.
Framework for a Unified Model for Nucleate and Transition Pool Boiling
Authors: Dhir V. K. , Liaw S. P.
Published: October 2009

An area and time-averaged model for saturated pool boiling heat fluxes has been developed. In the model, which is valid in the upper end of nucleate boiling and in transition boiling, the existence of stationary vapor stems at the wall is assumed. The energy from the wall is conducted into the liquid macro/micro thermal layer surrounding the stems and is utilized in evaporation at the stationary liquid–vapor interface. The heat transfer rate into the thermal layer and the temperature distribution in it are determined by solving a two-dimensional steady-state conduction equation. The evaporation rate is given by the kinetic theory. The heater surface area over which the vapor stems exist is taken to be dry. Employing experimentally observed void fractions, not only the nucleate and transition boiling heat fluxes but also the maximum and minimum heat fluxes are predicted from the model. The maximum heat fluxes obtained from the model are valid only for surfaces that are not well wetted and includes the contact angle as one of the parameters.
The Effect of Surface Motion on Forced Convection Film Boiling Heat Transfer
Authors: Zumbrunnen D. A. , Viskanta R. , Incropera F. P.
Published: October 2009

The growth in demand for high-quality metallic alloys has placed greater emphasis on the predictability of cooling methods used in manufacturing processes. Several methods involve forced convection film boiling, which can occur on metallic strips or plates cooled by water jet impingement or on strips inside cooling jackets of continuous annealing processes. Since surface temperatures are typically well above the boiling point of water, a substantial portion of the surface area can involve film boiling. The strip or plate speed often exceeds the water velocities and strongly influences boundary layer development in the vapor and liquid. The purpose of this paper is to estimate the effect of plate motion on heat transfer in the film boiling regime. Conservation equations for mass, momentum, and energy have been solved by the integral method for film boiling in forced convection boundary layer flow on a flat isothermal plate in motion parallel to the flow direction. Unlike previous studies, which have shown that heat transfer is chiefly governed by the plate and subcooled liquid temperatures, heat transfer is shown to also depend on the plate velocity. For large velocities, the importance of radiation heat transfer across the vapor layer is reduced. However, when the velocities of the plate and liquid are oppositely directed and of nearly equal magnitude, radiation across the vapor layer can become significant, even at low plate temperatures.
Stability of a Direct-Contact Spray Column Heat Exchanger
Authors: Golafshani M. , Jacobs H. R.
Published: October 2009

The governing equations for the transient multiphase flow in a liquid–liquid spray column are developed. Using the model, numerical calculations are presented that represent typical fluctuations observed in the operation of the direct contact tower of the U.S. Department of Energy’s 500-kWe geothermal power plant at East Mesa, CA. The response time is determined for the column and conditions leading to local flooding are determined.
A Heuristic Evaluation of the Governing Mode of Heat Transfer in a Liquid–Liquid Spray Column
Authors: Jacobs H. R. , Golafshani M.
Published: October 2009

A steady-state one-dimensional multiphase flow model is developed to describe the characteristics of a spray column type direct-contact liquid–liquid heat exchanger. Several models are assumed to describe the interphase heat exchange between water as the continuous phase and organic liquids as the dispersed phase. For small-diameter droplets, it is shown that existing experimental data are best described by a model that assumes the heat transfer is controlled by conduction within the drops.
The Measurement of Surface Heat Flux Using the Peltier Effect
Authors: Shewen E. C. , Hollands K. G. T. , Raithby G. D.
Published: October 2009

Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5–50°C) and heat flux (15–500 W/m2), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.
Mean and Fluctuating Radiation Properties of Nonpremixed Turbulent Carbon Monoxide/Air Flames
Authors: Kounalakis M. E. , Gore J. P. , Faeth G. M.
Published: October 2009

Mean and fluctuating spectral radiation intensities were measured for horizontal chordlike paths through turbulent nonpremixed carbon monoxide/air flames. Measurements in the 2700 nm radiation band of carbon dioxide revealed radiation fluctuations exceeding 50 percent in some locations even though mean radiation levels were not strongly influenced by turbulence/radiation interactions. Both time-independent and time-dependent stochastic simulations were developed to treat turbulence/radiation interactions as well as the temporal properties of flame radiation. The stochastic simulations were based on the laminar flamelet concept to relate scalar properties to mixture fracture, methods analogous to statistical time-series techniques to treat the probability density functions and spatial and temporal correlations of mixture fraction along the radiation path, and a narrow-band radiation model. The simulations yielded encouraging predictions of mean and fluctuating values, probability density functions, and temporal power spectra of spectral radiation intensities.
On the Thermal Conductivity of Dispersed Ceramics
Authors: Peterson G. P. , Fletcher L. S.
Published: October 2009

Because of high operating temperatures, advanced high-performance gas turbines will require the use of new types of material. Included among these materials will be dispersed ceramic composites capable of withstanding high temperatures and providing the required strength and wear characteristics. Presented here is a review of several analytical methods by which the effective thermal conductivity of these materials can be determined. In addition, the description and results of an experimental investigation designed to measure the effective thermal conductivity of four of these materials, tungsten carbide–cobalt, tungsten–copper, silicon nitride, and titanium diboride, are presented. Measurements were made over a temperature range of 300 K to 900 K in order to determine the mean effective thermal conductivity and the temperature dependence of this conductivity. The results of the experimental investigation are compared to the values obtained from several of the analytical methods presented and also with other data available in the literature.
Design of Cooling Towers by the Effectiveness-NTU Method
Authors: Jaber H. , Webb R. L.
Published: October 2009

This paper develops the effectiveness-NTU design method for cooling towers. The definitions for effectiveness and NTU are totally consistent with the fundamental definitions used in heat exchanger design. Sample calculations are presented for counter and crossflow cooling towers. Using the proper definitions, a person competent in heat exchanger design can easily use the same basic method to design a cooling tower of counter, cross, or parallel flow configuration. The problems associated with the curvature of the saturated air enthalpy line are also treated. A “one-increment” design ignores the effect of this curvature. Increased precision can be obtained by dividing the cooling range into two or more increments. The standard effectiveness-NTU method is then used for each of the increments. Calculations are presented to define the error associated with different numbers of increments. This defines the number of increments required to attain a desired degree of precision. The authors also summarize the LMED method introduced by Berman, and show that this is totally consistent with the effectiveness-NTU method. Hence, using proper and consistent terms, heat exchanger designers are shown how to use either the standard LMED or effectiveness-NTU design methods to design cooling towers.
Measurements of the Thermal Characteristics of Heated Turbulent Jets in Crossflow
Authors: Sherif S. A. , Pletcher R. H.
Published: October 2009

An experimental investigation of the thermal characteristics of heated turbulent jets discharging into a cross-flowing stream in a water channel is reported. Hot water was injected vertically upward from a circular pipe located near the channel bottom to simulate the heated jet. Fiber-film probes along with appropriate anemometers and bridges were operated in the constant-current mode as cold films to measure both mean and fluctuating temperatures. Profiles of mean and rms temperatures are presented for heated turbulent jets at velocity ratios of 1, 4, and 7 and for jet discharge temperatures approximately 28 to 42° C higher than the free-stream temperature. Measurements were carried out in the jet and its wake both in and outside the jet plane of symmetry.
Natural Convection in a Cylindrical Porous Enclosure With Internal Heat Generation
Authors: Prasad V. , Chui A.
Published: October 2009

A numerical study is performed on natural convection inside a cylindrical enclosure filled with a volumetrically heated, saturated porous medium for the case when the vertical wall is isothermal and the horizontal walls are either adiabatic or isothermally cooled. When the horizontal walls are insulated, the flow in the cavity is unicellular and the temperature field in upper layers is highly stratified. However, if the top wall is cooled, there may exist a multicellular flow and an unstable thermal stratification in the upper region of the cylinder. Under the influence of weak convection, the maximum temperature in the cavity can be considerably higher than that predicted for pure conduction. The local heat flux on the bounding walls is generally a strong function of the Rayleigh number, the aspect ratio, and the wall boundary conditions. The heat removal on the cold upper surface decreases with the aspect ratio, thereby increasing the Nusselt number on the vertical wall. The effect of Rayleigh number is, however, not straightforward. Several correlations are presented for the maximum cavity temperature and the overall Nusselt number.
Mixed Convection Along a Wavy Surface
Authors: Ghosh Moulic S. , Yao L. S.
Published: October 2009

The results of a study of mixed-convection flow along a wavy surface are presented. The forced-convection component of the heat transfer contains two harmonics. The amplitude of the first harmonic is proportional to the amplitude of the wavy surface; the second harmonic is proportional to the square of this amplitude. Thus, for a slightly wavy surface, only the influence of the first harmonic can be detected. The natural-convection component is a second harmonic, with a frequency twice that of the wavy surface. Since natural convection has a cumulative effect, the second harmonic eventually becomes the dominant component far downstream from the leading edge where forced convection is the dominant heat transfer mode. The results also demonstrate that the total mixed-convection heat flux along a wavy surface is smaller than that of a flat surface.
Experiments on Solidification of an Aqueous Sodium Carbonate Solution in a Horizontal Cylindrical Annulus
Authors: Christenson M. S. , Incropera F. P.
Published: October 2009

An experimental study of solidification has been performed for a binary Na2CO3–H2O solution in a horizontal cylindrical annulus with varying initial concentration. Solutally driven flows and double-diffusive layering were found to influence solidification rates and macroscopic solute redistribution strongly.
Two Mechanistically and Temporally Distinct NF-κB Activation Pathways in IL-1 Signaling
Authors: Yamazaki Kohsuke , Gohda Jin , Kanayama Atsuhiro , Miyamoto Yusei , Sakurai Hiroaki , Yamamoto Masahiro , Akira Shizuo , Hayashi Hidetoshi , Su Bing , Inoue Jun-ichiro
Published: October 2009

The cooperative activation of NF-κB by two distinct pathways that diverge at TRAF6 critically contributes to the IL-1–dependent inflammatory response.
p53 Promotes Polarity
Authors: Wong Wei
Published: October 2009

Loss of p53 in mammary cancer stem cells is associated with increased self-replication.
STAT3 Revs Up the Powerhouse
Authors: Reich Nancy C.
Published: October 2009

The transcription factor STAT3 stimulates mitochondria to augment Ras-dependent oncogenic transformation.
Nicotine Irritation
Authors: Gough Nancy R.
Published: October 2009

Treatments to stop smoking contain nicotine at concentrations sufficient to activate TRPA1 channels, which contribute to irritation.
IL-17 Receptor Signaling: Ubiquitin Gets In On the Act
Authors: Levin Steven D.
Published: October 2009

Ubiquitin ligase can be added to the functions of Act1 as it mediates IL-17 signaling.
Subcortical Network Regulation
Authors: Stern Peter
Published: October 2009

A form of subcortical control of cortical information processing is mediated by a synaptic release of serotonin and glutamate.
Schizophrenia: The “BLOC” May Be in the Endosomes
Authors: Ryder Pearl V. , Faundez Victor
Published: October 2009

Genetic polymorphisms that affect processes regulated by or participating in endosomal trafficking may increase susceptibility to schizophrenia.
G Protein–Coupled Receptors, Cholinergic Dysfunction, and Aβ Toxicity in Alzheimer’s Disease
Authors: Thathiah Amantha , De Strooper Bart
Published: October 2009

β-amyloid may induce neurodegeneration by affecting G protein–coupled receptor signaling.
DESIGN AND INTELLIGENT CONTROL OF A PIANO PLAYING ROBOT
Authors: ZHANG DAN , LI BEIZHI , YANG JIANGUO , LEI JIANHE
Published: October 2009

This paper presents the development of a piano-playing robot in order to provide people a means of entertainment. The design and development of this project includes two parts: the design of a dexterous hand for manipulating a piano and a linear motion control system. The paper first discusses the design of dexterous hand. Then, a motion control solution is determined, a linear railing along with a rack and pinion gear are applied to produce the linear motion. Also, in order to improve the control performance of the linear motion system, the Extended Kalman Filter (EKF) Algorithm is adopted. Finally, a flow chart of the control system is presented. Experimental results show that the piano robot can play designated notes.
Novel canine models of obese prediabetes and mild type 2 diabetes
Authors: Ionut Viorica , Liu Huiwen , Mooradian Vahe , Castro Ana Valeria B. , Kabir Morvarid , Stefanovski Darko , Zheng Dan , Kirkman Erlinda L. , Bergman Richard N.
Published: October 2009

Human type 2 diabetes mellitus (T2DM) is often characterized by obesity-associated insulin resistance (IR) and β-cell function deficiency. Development of relevant large animal models to study T2DM is important and timely, because most existing models have dramatic reductions in pancreatic function and no associated obesity and IR, features that resemble more T1DM than T2DM. Our goal was to create a canine model of T2DM in which obesity-associated IR occurs first, followed by moderate reduction in β-cell function, leading to mild diabetes or impaired glucose tolerance. Lean dogs ( n = 12) received a high-fat diet that increased visceral (52%, P < 0.001) and subcutaneous (130%, P < 0.001) fat and resulted in a 31% reduction in insulin sensitivity (SI) (5.8 ± 0.7 × 10−4to 4.1 ± 0.5 × 10−4μU·ml−1·min−1, P < 0.05). Animals then received a single low dose of streptozotocin (STZ; range 30–15 mg/kg). The decrease in β-cell function was dose dependent and resulted in three diabetes models: 1) frank hyperglycemia (high STZ dose); 2) mild T2DM with normal or impaired fasting glucose (FG), 2-h glucose >200 mg/dl during OGTT and 77–93% AIRgreduction (intermediate dose); and 3) prediabetes with normal FG, normal 2-h glucose during OGTT and 17–74% AIRgreduction (low dose). Twelve weeks after STZ, animals without frank diabetes had 58% more body fat, decreased β-cell function (17–93%), and 40% lower SI. We conclude that high-fat feeding and variable-dose STZ in dog result in stable models of obesity, insulin resistance, and 1) overt diabetes, 2) mild T2DM, or 3) impaired glucose tolerance. These models open new avenues for studying the mechanism of compensatory changes that occur in T2DM and for evaluating new therapeutic strategies to prevent progression or to treat overt diabetes.