bluuebunny/crossref_metadata_2025 huggingface dataset:
COLONY: a program for parentage and sibship inference from multilocus genotype data
Authors: JONES OWEN R. , WANG JINLIANG
Published: October 2009

Pedigrees, depicting genealogical relationships between individuals, are important in several research areas. Molecular markers allow inference of pedigrees in wild species where relationship information is impossible to collect by observation. Marker data are analysed statistically using methods based on Mendelian inheritance rules. There are numerous computer programs available to conduct pedigree analysis, but most software is inflexible, both in terms of assumptions and data requirements. Most methods only accommodate monogamous diploid species using codominant markers without genotyping error. In addition, most commonly used methods use pairwise comparisons rather than a full‐pedigree likelihood approach, which considers the likelihood of the entire pedigree structure and allows the simultaneous inference of parentage and sibship. Here, we describe colony, a computer program implementing full‐pedigree likelihood methods to simultaneously infer sibship and parentage among individuals using multilocus genotype data. colony can be used for both diploid and haplodiploid species; it can use dominant and codominant markers, and can accommodate, and estimate, genotyping error at each locus. In addition, colony can carry out these inferences for both monoecious and dioecious species. The program is available as a Microsoft Windows version, which includes a graphical user interface, and a Macintosh version, which uses an R‐based interface.
Anisotropic Two-Dimensional Scattering: Comparison of Experiment with Theory
Authors: Look D. C. , Nelson H. F. , Crosbie A. L.
Published: October 2009

Anisotropic scattering from a semi-infinite medium exposed to a laser beam is studied. The situation is two-dimensional and cylindrical because the laser beam is incident normal to the purely scattering media. The back scattered radiation in the normal direction is predicted and measured as a function of the distance from the beam. The latex particles of uniform size with diameters ranging from 0.03 up to 1.011 μ are used as scattering centers in a water solution. The influence of anisotropic scattering shifts the maximum of the radial distribution of the scattered intensity to larger optical radii as the particle size increases. For large optical thicknesses, the asymmetry factor is used as a correlation coefficient to reduce the anisotropic results to those of isotropic scattering.
Dense, Vertical Jets with Two Opposing Buoyancy Components
Authors: Takao S. , Narusawa U.
Published: October 2009

The height to which dense, vertical jets with two opposing buoyancy components rise was investigated experimentally. In the experiment, the dense, vertical jets were produced by using the temperature difference between the jet at the nozzle and the surroundings as the positive buoyancy component, and by using common salt and CuSO4 alternatingly for the negative buoyancy component. Based on a dimensional argument, it was found that the three nondimensional parameters of (1) the ratio of the jet height to the nozzle diameter, H/rj, (2) the internal Froude number, Fr, and (3) the density ratio, R, all govern the behavior of the jet. The data were well correlated when H/rjFr was plotted against against 1/R in the range of 0 ≤ 1/R ≤ 0.9, showing that H/rjFr tends to fall with an increase of 1/R. A least square fitting of the data yielded the explicit form of the jet height to be H2.67rjFr=1for0≤1/R≤0.27.−0.84R+1.23for0.27≤1/R≤0.9.
Energy Separation in Vortex Tubes with a Divergent Chamber
Authors: Takahama Heishichiro , Yokosawa Hajime
Published: October 2009

The vortex tube is a simple device for separating a compressed gaseous fluid stream into two flows of high and low temperature. In order to produce a high temperature separation effect, the use of a sufficiently long tube with a smooth inner surface has been standard procedure up until now. However, since such a device requires a large installation space, an attempt was made to shorten the length of the vortex chamber without any fall in the temperature separation effect by using some divergent tubes as the vortex chamber. Experimental data obtained in these vortex chambers were compared with those in the commonly used straight vortex chambers. Observation indicates that a divergent tube with a small angle of divergence is effective in obtaining a higher temperature separation and makes possible a shortening of the chamber length.
Thermal Convection at Low Rayleigh Number from Concentrated Sources in Porous Media
Authors: Hickox C. E.
Published: October 2009

A simple mathematical theory is proposed for the analysis of natural convective motion, at low Rayleigh number, from a concentrated source of heat in a fluid-saturated porous medium. The theory consists of retaining only the leading terms of series expansions of the dependent variables in terms of the Rayleigh number, is thus linear, and is valid only in the limit of small Rayleigh number. Based on fundamental results for a variety of isolated sources, superposition is used to provide solutions for situations of practical interest. Special emphasis is given to the analysis of sub-seabed disposal of nuclear waste.
Refilling and Rewetting of a Hot Horizontal Tube: Part I—Experiments
Authors: Chan A. M. C. , Banerjee S.
Published: October 2009

Experiments on refilling and rewetting of hot horizontal tubes indicate that gravitational effects are important and lead to flow stratification. The tube is quenched at a given location upwards from the bottom and there is a significant time lag before the top is quenched. The rewetting front is preceded by a liquid layer that is supported by film boiling and forms a “liquid tongue”. Significant pre-cooling is observed at the bottom due to the presence of this tongue. No well defined rewetting temperature exists. The channel quenches at temperatures which can vary considerably between the top and bottom of the tube, and along the tube. The results cannot be explained by a conduction controlled rewetting model. Average rewetting velocities decrease with increases in initial wall temperature, and increase with increases in inlet flow rates and subcooling. These trends are consistent with other investigations in vertical reflood. For low inlet flows and low initial wall temperatures rewetting velocities can be higher than the constant inlet liquid flow velocity. This is due to the flow stratification effect that allows the front of the liquid tongue to move with a higher initial velocity than the inlet velocity.
Prediction of Horizontal and Vertical Turbulent Buoyant Wall Jets
Authors: Ljuboja M. , Rodi W.
Published: October 2009

A buoyancy-extended version of the k – ε turbulence model is described which predicts well the main features of turbulent buoyant wall jets. The model relates the turbulent shear stress and heat flux to the mean velocity and temperature gradients respectively and to the turbulent kinetic energy k and the dissipation rate ε by way of the Kolmogorov-Prandtl eddy viscosity/diffusivity relation and determines k and ε from semi-empirical transport equations. The empirical constant cμ in the Komogorov-Prandtl expression and the usually constant turbulent Prandtl number σt are replaced by functions which are derived by reducing model forms of the Reynolds-stress and heat-flux transport equations to algebraic expressions, retaining the buoyancy terms and the wall-damping correction to the pressure-strain/scrambling model in these equations. The extended k – ε model is applied to buoyant wall jets along a horizontal wall and to α plume developing along a vertical wall. The predictions are compared with experimental data whenever possible and are found to be in good agreement with the data.
Evaluation of the Radiative Heat Flux in Absorbing, Emitting and Linear-Anisotropically Scattering Cylindrical Media
Authors: Azad F. H. , Modest M. F.
Published: October 2009

The contribution of thermal radiation to heat transfer in an emitting, absorbing and linear-anisotropically scattering medium of one-dimensional cylindrical geometry is investigated. It is assumed that the radial temperature distribution in the medium is known or is found in conjunction with overall conservation of energy. The exact solution results in a first-order integral equation in the radial coordinate which is a substantial improvement over previous formulations developed for nonscattering media. Also, two approximate methods are established and tested for their accuracy. The first method is the differential approximation modified to accommodate linear-anisotropic scattering. The second method consists of an exponential kernel approximation in which the geometric integrand functions are replaced by simple exponential functions. The results presented indicate that in engineering applications either approximate method may be used to accurately model the radiative contribution to overall heat transfer rates, reducing the nonlinear integrodifferential energy conservation equation to a nonlinear differential equation.
Carbon Particulate in Small Pool Fire Flames
Authors: Bard S. , Pagni P. J.
Published: October 2009

Flame radiation, the dominant heat transfer mechanism in many combustion and fire safety related problems, is primarily controlled by the fraction of flame volume occupied by solid carbon particulate. A multi-wavelength laser transmission technique is used here to measure carbon particulate volume fractions and approximate particle size distributions in ten common solid, cellular and liquid fueled small scale, 0 (10 cm dia), pool fire diffusion flames. The most probable particle radius, rmax, and concentration, N0, are two parameters in the assumed gamma function size distribution form which are determined for each fuel by simultaneously measuring light transmission of two superimposed laser wavelengths. The resulting soot volume fractions range from fv ∼ 4 × 10−6 for cellular polystyrene to fv ∼ 7 × 10−8 for alcohol. Cellular polystyrene has the largest particles, rmax ∼ 60 nm while wood has the smallest, rmax ∼ 20 nm. The carbon particulate optical properties used in the analysis are shown to be representative of actual flame soot and are more accurate than the soot refractive index usually assumed in the literature. Finally, mean particle sizes obtained for all fuels indicate that the small particle absorption limit assumption is a reasonable approximation for infrared flame radiation calculations.
Ice Formation in a Pipe Containing Flows in the Transition and Turbulent Regimes
Authors: Gilpin R. R.
Published: October 2009

The form of the ice growth that occurs in a pipe containing flows which are initially in the transition and turbulent regimes was investigated. The ice-band structure reported previously [1] for Reynolds numbers near transition was observed to be of steady state ice structure formed in a pipe for flows with Reynolds numbers over the entire range of the present investigation (up to ReD = 1.4 × 104). Difference were, however, observed in the nature of the transient approach to this steady state ice structure. The influence of the ice-band structure on pressure drop and on pipe freeze-off were also investigated.
Water Vapor Contribution to the Erosion of Steel by High Temperature Flows
Authors: Gany Alon , Caveny L. H. , Johnson J. W.
Published: October 2009

Experimental results on the role of water vapor in the mass loss mechanism of steel by hot, high pressure flows are described and interpreted in terms of a surface reaction model. Situations in which highly transient heat transfer and chemical interactions at the gas-metal interface produce erosion of the surface occur in a variety of systems, e.g., gun barrels, gas turbines, vents, nozzles, and furnaces. This research is directed at conditions in which the metal surface temperature remains below the melting point and mass loss is the result of chemical attack. The rate of reaction depends on the unsteady pressure and surface temperature. The study reveals that in high shearing flows, when the build-up of oxide protective layer is limited, surface chemical attack of the steel by water vapor can be the main erosion source in combustion gas atmospheres, and the process is controlled mainly by turbulent transport phenomena.
Effect of Plenum Length and Diameter on Turbulent Heat Transfer in a Downstream Tube and on Plenum-Related Pressure Losses
Authors: Lau S. C. , Sparrow E. M. , Ramsey J. W.
Published: October 2009

A systematic experimental study was carried out to determine how the heat transfer characteristics of a turbulent tube flow are affected by the length and diameter of a cylindrical plenum chamber which delivers fluid to the tube. The net pressure loss due to the presence of the plenum was also measured. The experimental arrangement was such that the fluid experiences a consecutive expansion and contraction in the plenum before entering the electrically heated test section. Air was the working fluid, and the Reynolds number was varied over the range from 5,000 to 60,000. It was found that at axial stations in the upstream portion of the tube, there are substantially higher heat transfer coefficients in the presence of longer plenums. Thus, a longer plenum functions as an enhancement device. On the other hand, the plenum diameter appears to have only a minor influence in the range investigated (i.e., plenum diameters equal to three and six times the tube diameter). The fully developed Nusselt numbers are independent of the plenum length and diameter. With longer plenums in place, the thermal entrance length showed increased sensitivity to Reynolds number in the fully turbulent regime. The pressure loss coefficient, which compares the plenum-related pressure loss with the velocity head in the tube, increases more or less linearly with the plenum length. With regard to experimental technique, it was demonstrated that guard heating/cooling of the electrical bus adjacent to the tube inlet is necessary for accurate heat transfer results at low Reynolds numbers but, although desirable, is less necessary at higher Reynolds numbers.
Heat Transfer in a Capillary Flow Emerging from a Reservoir
Authors: Papoutsakis Eleftherios , Ramkrishna Doraiswami
Published: October 2009

An extended Graetz problem is analyzed, with a semi-infinite axial domain and the Robin boundary condition on the heat-transfer wall. The heat-transfer problem examines a viscous fluid entering a cylindrical capillary from a reservoir. The capillary fluid is exchanging heat with the surrounding environment of prescribed temperature and thus the Robin boundary condition is employed on the wall. Since axial heat conduction is included in the analysis, a generalized Danckwerts boundary condition is shown to be most appropriate for the tube entrance. The energy equation is decomposed into a system of first-order partial differential equations, as in [4, 8, 9], to obtain a selfadjoint formalism. The Gram-Schmidt orthonormalization process is finally used to obtain what is technically an analytical solution, which is computationally simple and efficient. Other entrance boundary conditions are also discussed and analyzed.
Surface Contamination, Rejuvenation, and the Reproducibility of Results in Nucleate Pool Boiling
Authors: Joudi K. A. , James D. D.
Published: October 2009

Contamination of stainless steel boiling surfaces at nucleation sites by corrosion products in water, and by oxide deposits in methanol are investigated experimentally. Reproducibility of boiling data is achieved by nitrogen sparging of test liquids and employing inert components in the apparatus. Heating surface rejuvenation is effected by boiling in refrigerant R-113. The order of testing a surface with various liquids is investigated.
An Experimental Investigation of Boiling Heat Transfer of Fluorocarbon R-11 Refrigerant for Concentric-Tube Thermosyphon
Authors: Seki N. , Fukusako S. , Koguchi K.
Published: October 2009

The characteristics of the boiling heat transfer for a concentric-tube open thermosyphon are examined in detail. Fluorocarbon R-11 refrigerant as a testing fluid is utilized. Out of a number of possible controlling variables, the effects of the heat flux, the void ratio, and the diametric ratio of the concentric-tube on the heat-transfer performance are determined. From the present experimental results it is demonstrated that total heat flux can be appropriately predicted by a superposition of the heat flux due to the available correlations for free convection and due to the correlations experimentally determined for boiling heat flux.
Natural Convection from a Horizontal Cylinder—Laminar Regime
Authors: Farouk B. , Gu¨c¸eri S. I˙.
Published: October 2009

A finite-difference numerical method has been adopted to generate flow patterns and heat transfer characteristics for laminar, steady-state, two-dimensional natural convection around a circular cylinder submerged in an unbounded Boussinesq fluid. The approach allows the use of nonuniform as well as uniform specified temperature and heat flux distributions over the cylindrical surface. Part of the results are generated for reverse convective flows with recirculation zones which occur when part of the cylinder is below the ambient temperature while the remaining part is above. The results for uniform temperature boundary condition are in good agreement with the experimental data and other solutions available in literature.
Transient Natural Convection Heat Transfer of Water with Maximum Density Effect and Supercooling
Authors: Robillard L. , Vasseur P.
Published: October 2009

Transient two-dimensional laminar convective cooling of water in an enclosed rectangular cavity with a convective boundary condition is approached by a numerical method. The maximum density effect and supercooling are considered in order to understand the flow and temperature fields in a mass of water cooled to a temperature near its freezing point. The time dependent flow and temperature fields, mixed mean, center point, maximum wall temperature and the heat transfer rate on each wall are presented. The computations are performed mainly for the case of a square cavity but the influence of the aspect ratio of the cavity is also discussed.
A General Theory of Wet Surface Heat Exchangers and its Application to Regenerative Evaporative Cooling
Authors: Maclaine-cross I. L. , Banks P. J.
Published: October 2009

Wet surface heat exchangers such as cooling towers and wet plate heat exchangers are important in air conditioning. A linear approximate model of wet surface heat exchangers is proposed. The equations of the model are rearranged, enabling solutions for wet bulb depression and wet bulb temperature to be obtained independently, by analogy from published solutions for dry bulb temperature in dry surface heat exchangers. Performance predictions by this method for a crossflow cooling tower are found to agree with those from a prevous finite difference solution. Published performance measurements for a crossflow wet plate heat exchanger are lower than predicted by the method possibly due to poor wetting or excessive water flow. Excellent performance is predicted for a proposed regenerative evaporative cooler using such an exchanger.
Conduction of Heat across Rectangular Cellular Enclosures
Authors: Eftekhar J. , Darkazalli G. , Haji-Sheikh A.
Published: October 2009

A simplified analytical model for the computation of thermal conduction across rectangular-celled enclosures based on the assumption of quasi-one-dimensional conduction in the cell partitions is presented. The rectangular enclosures may contain solid or liquid for which the conduction is two or three-dimensional depending on the geometrical configuration. Additional assumptions concerning radiation interchange between participating surfaces are necessary when the enclosure contains a stagnant gas. This analytical model leads to a closed form solution for temperature distribution in the partitions and the multidimensional conductive region. A parametric study of heat flux is presented. The numerical data define a range of parameters for which a one-dimensional conduction model is satisfactory.
Effect of Vertical Separation Distance and Cylinder-to-Cylinder Temperature Imbalance on Natural Convection for a Pair of Horizontal Cylinders
Authors: Sparrow E. M. , Niethammer J. E.
Published: October 2009

Experiments were performed to study the interactive natural convection from a pair of heated horizontal cylinders situated one above the other in a vertical plane. Prime attention was focused on how the heat transfer characteristics of the upper cylinder are affected by the presence of the lower cylinder. The vertical center-to-center separation distance between the cylinders was varied from two to nine cylinder diameters. The cylinder-to-cylinder temperature imbalance was also varied independently and systematically, with the wall-to-ambient temperature difference for the lower cylinder ranging from zero to three times that for the upper cylinder. Experiments were carried out for upper-cylinder Rayleigh numbers from 20,000 to 200,000. It was found that for a given temperature imbalance and upper-cylinder Rayleigh number, the upper-cylinder Nusselt number takes on a maximum value as a function of separation distance. The separation distance for which the maximum occurs is in the range of seven to nine cylinder diameters. The enhancement or degradation of the upper-cylinder Nusselt number relative to that for a single cylinder is strongly dependent on the separation distance, with degradation of the Nusselt number being more common at small separations and enhancement prevailing at larger separations. With regard to the temperature imbalance, its effect on the Nusselt number is of major importance at small separations but not at large separations.
Steam Condensation on Various Gold Surfaces
Authors: Woodruff D. W. , Westwater J. W.
Published: October 2009

Gold surfaces were investigated as promoters of dropwise condensation (DWC) of steam at atmospheric pressure. Very high heat fluxes at low ΔT’s may be achieved in this manner. Seven gold electroplating baths, one electroless immersion gold bath, and vacuum vapor deposition of gold were used. Five surface preparations for pure gold were tested. Gold deposits ranged in thickness up to 20,000 A.U. Auger electron spectroscopy and scanning electron microscopy were used to describe the surfaces chemically and physically. Deposits from the bright pure gold plating baths and the “acid, hard” baths promoted DWC. Deposits from alloyed baths, the ultrapure bath, and vapor deposition gave mixed or filmwise condensation. Two surface preparations on solid gold gave DWC, one gave mixed, and two gave filmwise condensation. The results indicate that gold provides an oxide-free surface which adsorbs trace organics from the surroundings. These promote DWC.
Heat-Exchanger Effectiveness in Thermoelectric Power Generation
Authors: Bohn M. S.
Published: October 2009

This paper presents a method for calculating the electrical power generated by a thermoelectric heat exchanger. The thermoelectric heat exchanger transfers heat from a hot fluid to a cold fluid through a thermoelectric generator located in the heat-exchanger wall separating the two fluid streams. The method presented here is an extension of the NTU method used to calculate heat-exchanger heat-transfer effectiveness. The effectiveness of thermoelectric power generation is expressed as the ratio of the actual power generated to the power that would be generated if the entire heat-exchanger area were operating at the inlet fluid temperatures. This method collapses results for several heat-exchanger configurations and allows a concise presentation of the results. It is shown that the NTU method of calculating heat-exchanger heat-transfer effectiveness can be modified in a similar way.
Modeling of a Rotary Dry Cooling Tower
Authors: Valenzuela J. A. , Glicksman L. R.
Published: October 2009

A novel design of a rotary heat exchanger to be used as a dry cooling tower is described. The heat exchanger consists of a matrix of thin steel disks which rotate between a hot water bath and a forced draft air stream. On top of the water floats a 2 cm thick layer of oil which coats the rotating disks and thus eliminates evaporation. An analytical model of the heat exchanger was developed and validated with experimental measurements taken on a 1.5 m dia test section. The model was then used to determine the net effect of the oil on the heat transfer performance. Although the oil film that coats the disks presents an additional resistance to the transfer of heat, it also contributes to the heat capacity of the disks. It was found that the reduction in the overall heat transfer rate due to the presence of the oil is small, of the order of 5 to 10 percent.
Heat Transfer and Interface Motion During Melting and Solidification around a Finned Heat Source/Sink
Authors: Bathelt A. G. , Viskanta R.
Published: October 2009

The effectiveness of extended surfaces on a horizontal, cylindrical heat source/sink was studied experimentally during solid-liquid phase change heat transfer. Melting and freezing experiments were performed in a test cell suitable for photographic and shadowgraphic observations using a circular cylinder with three rectangular fins parallel to the axis and evenly distributed around the circumference of the heat exchanger. Results are reported for n-heptadecane as the phase change material. Orientation of fins on the heat exchanger with respect to the gravitational field are found to have more influence on the melting than on the freezing processes. The use of fins was found to be more effective for melting than for freezing. The instantaneous local and circumferentially averaged heat transfer coefficients at the heat source surface for melting from a cylinder with fins were usually within ±20 percent of those for melting from a bare cylinder. During solidification the degree of heat transfer enhancement due to finning is greatest when the frozen layer is thin and decreases as the layer grows thicker.
On the Prediction of Fusion Rate of Ice by Finite Element Analysis
Authors: Hsu T. R. , Pizey G.
Published: October 2009

A finite element algorithm including phase change is presented for the prediction of the rate of freezing of fresh water under general ambient conditions. This method has shown to be highly versatile in dealing with multi-phase materials of complicated geometries. Experiments were performed to verify the code prediction on the fusion of fresh water and a case with oil inclusion. Close agreement was observed between the predicted and measured values.
Comparison of Profiles and Fluxes of Heat and Momentum Above and Below an Air-Water Interface
Authors: Howe B. M. , Chambers A. J. , Klotz S. P. , Cheung T. K. , Street R. L.
Published: October 2009

The velocity and temperature fields on both sides of an air-water interface were examined experimentally in order to understand better the physical processes of momentum and heat transfer through the surface layers about the interface. An examination of temperature and velocity profiles plotted in “law-of-the-wall” coordinates leads to the conclusion that, both in the air and in the water, the mechanism of momentum transfer is affected by surface roughness changes, but the mechanism of heat transfer is not. In the water surface layer the velocity fluctuations due to the wave-related motions are of the same order as the purely turbulent motions. The turbulent components closely resemble those found in boundary layers over solid walls. The measured total energy flux from the interface agrees well with the measured single-phase, vertical heat transport through the water surface layer.
Evaluation of Coefficients for the Weighted Sum of Gray Gases Model
Authors: Smith T. F. , Shen Z. F. , Friedman J. N.
Published: October 2009

The weighted sum of gray gases model postulates that total emissivity and absorptivity may be represented by the sum of a gray gas emissivity weighted with a temperature dependent factor. The gray gas emissivity is expressed in terms of a temperature-independent absorption coefficient, absorbing gas partial pressure, and path length. The weighting factors are given by polynomials in gas temperature with associated polynomial coefficients. For absorptivity, a second polynomial for the irradiation temperature is introduced. A regression scheme is employed to fit the model to total emissivity and absorptivity values obtained from the exponential wide-band model. Absorption and polynomial coefficients are reported for carbon dioxide, water vapor, and mixtures of these gases. The model with these coefficients more accurately represents the total properties over a wider range of temperatures and partial pressure-path length products than previously available coefficients.
Fin Geometry for Minimum Entropy Generation in Forced Convection
Authors: Poulikakos D. , Bejan A.
Published: October 2009

This paper establishes a theoretical framework for the minimization of entropy generation (the waste of exergy, or useful energy) in extended surfaces (fins). The entropy generation rate formula for a general fin is derived first. Based on this general result, analytical methods and graphic results are developed for selecting the optimum dimensions of pin fins, rectangular plate fins, plate fins with trapezoidal cross section, and triangular plate fins with rectangular cross section.
Measurements and Calculations of Transient Natural Convection in Water
Authors: Sammakia B. , Gebhart B. , Qureshi Z. H.
Published: October 2009

Transient natural convection adjacent to a flat vertical surface with appreciable thermal capacity is investigated both experimentally and numerically. The surface is immersed in initially quiescent water, and has the same uniform temperature distribution. It is then suddenly loaded with a uniform and constant heat flux thereby generating a buoyancy induced flow adjacent to the surface. Surface temperature response was recorded by means of thermocouples embedded inside the surface, and boundary layer temperature measurements were also taken. An explicit finite difference numerical scheme is used to obtain solutions to the partial differential equations describing the conservation of mass, momentum, and energy in their time dependent form. Good agreement between the calculated and measured results is observed for both the heating and cooling transient processes.
Developing Heat Transfer in Rectangular Ducts With Staggered Arrays of Short Pin Fins
Authors: Metzger D. E. , Berry R. A. , Bronson J. P.
Published: October 2009

Streamwise heat transfer variation, overall array heat transfer, and overall flow friction behavior are presented for large aspect ratio ducts containing uniformly spaced staggered arrays of circular pin fins which span the entire duct height. The array geometries investigated have short pin heights (length-to-diameter ratio of 1) and moderate spanwise (transverse) and streamwise (longitudinal) pin spacings (pitch-to-diameter ratios of 1.5 and 2.5). Such staggered array geometries are typical of applications found in internally cooled gas turbine engine airfoils. The uncovered duct walls comprise a substantial fraction of the total heat transfer area. Ten pin rows in the streamwise direction are utilized in all the experiments, with a segmented construction allowing determination of spanwise-averaged heat transfer coefficients resolved to a single row spacing in the streamwise direction. Comparisons are made with results of prior studies which are mainly restricted to flow normal to banks of circular cylinders with long length-to-diameter ratios.
An Experimental Study of Upper Hot Layer Stratification in Full-Scale Multiroom Fire Scenarios
Authors: Cooper L. Y. , Harkleroad M. , Quintiere J. , Rinkinen W.
Published: October 2009

This paper describes an experimental study of the dynamics of smoke filling in realistic, full-scale, multiroom fire scenarios. A major objective of the study was to generate an experimental data base for use in the verification of mathematical fire simulation models. The test space involved 2 or 3 rooms, connected by open doorways. During the course of the study the areas were partitioned to yield four different configurations. One of the rooms was a burn room containing a methane burner which produced either a constant energy release rate of 25, 100, or 225 kW or a time-varying energy release rate which increased linearly with time from zero at ignition to 300 kW in 10 min. An artificial smoke source near the ceiling of the burn room provided a means for visualizing the descent of the hot layer and the dynamics of the smoke filling process in the various spaces. The development of the hot stratified layers in the various spaces was monitored by vertical arrays of thermocouples and photometers. A layer interface was identified and its position as a function of time was determined. An analysis and discussion of these results are presented.
A New Flow Regimes Map for Condensation Inside Horizontal Tubes
Authors: Tandon T. N. , Varma H. K. , Gupta C. P.
Published: October 2009

The problem of predicting flow patterns during condensation inside horizontal tubes is discussed. Using the condensation flow pattern data of several investigators, a new flow regimes map with dimensionless gas velocity jg* as ordinate and (1-α)/α as abscissa, where α is the void fraction, is generated. Based on these data, a set of new criteria for the transition between different flow regimes is suggested. The proposed flow regimes map gives excellent agreement for annular, semiannular, and wavy flows which exist over a major part of the condensing length during condensation inside horizontal tubes.
Modes of Circulation in an Inverted U-Tube Array With Condensation
Authors: Calia C. , Griffith P.
Published: October 2009

An experiment and analysis was performed on an inverted U-tube steam condenser (similar to a steam generator) to determine the modes of flow that can exist as the rate of steam flow into the condenser is reduced. The condenser consisted of four glass tubes connected to a common inlet plenum and a common exit plenum. Heat-transfer and flow-rate measurements, as well as visual observations were made. Four different modes of operation were identified. Noncondensables were found to substantially alter the plenum to plenum pressure difference and aid flow stability. Satisfactory analytical descriptions of the observations have been developed as well as application of the results to the condensing behavior of nuclear steam generators under abnormal operating conditions.
An Experimental Study of Free Convection Heat Transfer From a Horizontal Cylinder in a Vertical Array Set in Free Space Between Parallel Walls
Authors: Tokura Ikuo , Saito Hakaru , Kishinami Koki , Muramoto Kazuo
Published: October 2009

Empirical formulas are proposed from experiments on free convective heat transfer from a cylinder array arranged in a vertical line. Subsequently, experiments were carried out to examine the effect of two parallel plates enclosing the array as a heat transfer promoter. Finally, through a discussion of the heat transfer from the entire cylinder systems, both in open and in restricted spaces, a recommendation is made for designing a heat exchanger of a single-line type of cylinder bank.
Natural Convection Heat Transfer Between Eccentric Horizontal Cylinders
Authors: Prusa J. , Yao L. S.
Published: October 2009

Laminar natural convection flow between vertically eccentric horizontal cylinders is studied numerically. The inner and outer cylinders are heated and cooled, respectively, to maintain constant surface temperatures. A physical model is introduced which accounts for the effects of fluid buoyancy as well as the eccentricity of the outer cylinder. A radial transformation is used to map the eccentric outer boundary into a concentric circle. Both eccentricity and buoyancy have a significant influence on the heat transfer and flow field of a fluid between horizontal cylinders. The effect of buoyancy, which enhances average heat transfer, increases with the Grashof number. Eccentricity influences the flow in two ways. First, by decreasing the distance between the two cylinders over part of their surfaces, it increases the local heat transfer due to conduction. Second, the eccentricity influences the connective mode of heat transfer. Results show that moderate positive values of eccentricity, enhance convective heat transfer. Results for a range of Grashof number are given, for varying eccentricity, for a radius ratio of 2.6 and a Prandtl number of 0. 706. Detailed predictions of the temperature and flow fields, and local heat transfer rates are given for representative cases. Also presented is the variation of average heat transfer rate and average shear stress with Grashof number and eccentricity. Comparisons with earlier numerical, experimental and analytic results are made.
Natural Convection Correlations for Vertical Surfaces Including Influences of Variable Properties
Authors: Clausing A. M.
Published: October 2009

New correlations are presented for natural convective heat transfer from vertical isothermal surfaces in gases. The influences of variable properties are accounted for by using empirical equations which are of the general form Nu = g(Ra) • f(Ra, Tw/T∞). The influence of the reference temperature at which the thermal properties are evaluated is also established. Comparisons with available data are made over a Rayleigh number range 104 < Ra < 1012 and a range in the surface-to-ambient temperature ratio of 1 < Tw/T∞ < 2.6. Five data sets, which represent over 200 test points, are examined.
The Calculation of a Fire in a Large Building
Authors: Emmons H. W.
Published: October 2009

The complex picture presented by a fire growing in a large building can be understood by considering the process as made up of a large number of space, time, and phenomena zones each one of which is to some degree independent of all others. This approach is explained in detail, the appropriate equations now in use in the Computer Fire Code V are listed and some results compared with full-scale experimental results.
Heat Transfer During Melting Inside a Horizontal Tube
Authors: Rieger H. , Projahn U. , Bareiss M. , Beer H.
Published: October 2009

The melting process of a phase change material (PCM) enclosed in a horizontal, isothermal circular tube has been investigated analytically and by experiment for an interesting range of parameters. The physical process was analyzed by numerical methods, whereby the underlying mathematical model involves heat conduction as well as natural convection as the basic heat transport mechanisms. Difficulties associated with the complex and timewise changing melt region whose shape is also part of the solution, have been overcome by applying a numerical mapping technique. Computations and experiments were performed for Rayleigh numbers in the range 105 ≤ Ra ≤ 106. For lower Rayleigh numbers the numerical calculations predict a streamlined design of the PCM at later times, similar to the experiment. At higher Rayleigh numbers, three-dimensional Bernard convection was observed in the bottom region of the melt layer, which was unsteady in their timewise behaviour. The appearance of several roll-cells have also been predicted by the calculations, although the mathematical model was restricted to two-dimensional flow. The experiments were performed with n-octadecane (Pr ≃ 50) as PCM. The test cell basically consists of a short tube filled with the PCM. The tube is closed with plexiglass disks on both ends, thus allowing the melting front to be recorded photographically with time. As a result, the interface positions as well as the overall and local heat transfer coefficients are presented as function of time. The agreement between experimental and numerical data is reasonably good.
The Effect of Wall Conduction on the Stability of a Fluid in a Right Circular Cylinder Heated From Below
Authors: Buell J. C. , Catton I.
Published: October 2009

The onset of natural convection in a cylindrical volume of fluid bounded above and below by rigid, perfectly conducting surfaces and laterally by a wall of arbitrary thermal conductivity is examined. The critical Rayleigh number (dimensionless temperature difference) is determined as a function of aspect (radius to height) ratio and wall conductivity. The first three asymmetric modes as well as the axisymmetric mode are considered. Two sets of stream functions are employed to represent a velocity field that satisfies the no-slip boundary condition on all surfaces and conservation of mass everywhere. The Galerkin method is then used to reduce the linearized perturbation equations to an eigenvalue problem. The results for perfectly insulating and conducting walls are compared with the work of Charlson and Sani[9].
Release Rate Model for Developing Fires
Authors: Smith E. E. , Satija S.
Published: October 2009

A mathematical model for predicting the course of a developing fire in a compartment is described. The model uses release rate data obtained from laboratory-scale tests to calculate the rate of heat and smoke generation within the compartment. From these data, the model predicts rate of involvement of combustible surfaces, upper layer temperatures, and smoke concentration as a function of time. The model is described by relationships used to determine: (i) ignition and rate of vertical fire propagation, (ii) release rates based on total heat released and incident flux, and (ii) heat losses by venting and accumulation within the boundaries of the compartment. Results of predicted by the model and observed in full-scale tests of furnished compartments are compared.
Recent Developments in the Analysis and Design of Extended Surface
Authors: Snider A. D. , Kraus A. D.
Published: October 2009

Earlier papers by the authors developed a new set of parameters for characterizing heat transfer properties of single fins and fins in arrays of extended surface. The use of these parameters has facilitated the solutions to several interesting fin problems, namely: a more careful characterization of one-dimensional flow configurations, a method for accommodating continuously distributed heat sources along the fin, a perturbation approach for the approximate computation of the parameters, and new insights into the precepts of the optimal fin shape. These developments are reported in this paper.
Heat Transfer From Horizontal Serrated Finned Tubes in an Air-Fluidized Bed of Uniformly Sized Particles
Authors: Krause W. B. , Peters A. R.
Published: October 2009

A primary objective of this work was to gather experimental convective heat transfer coefficient data for extended surfaces. The results were then compared with bare horizontal tubes in a similar flow environment. The finned tube configurations were considered an extension of the bare tube arrangements to enhance heat transfer. Heat transfer coefficients were computed from the heated tube surface temperature, the fluidized bed temperature, and the power input to the tube. Selected serrated finned tubes were used. The experimental heat transfer data were measured as a function of fluidized bed flow parameters and finned tube geometry. Several tests were performed using two different uniformly sized glass particles (.21 mm and .43 mm). Fin efficiency factors were determined and presented as a function of mass velocity and as a function of a fin length parameter. The finned tube demonstrated a better heat transfer capacity over bare tubes for similar fluidization conditions.
Two-Dimensional Radiation in Absorbing-Emitting Media Using the P-N Approximation
Authors: Ratzel A. C. , Howell J. R.
Published: October 2009

Radiative energy transfer in a gray absorbing and emitting medium is considered in a two-dimensional rectangular enclosure using the P-N differential approximation. The two-dimensional moment of intensity partial differential equations (PDE’s) are combined to yield a single second-order PDE for the P-1 approximation and four coupled second-order PDE’s for the P-3 approximation. P-1 approximation results are obtained from separation of variables solutions, and P-3 results are obtained numerically using successive-over-relaxation methods. The P-N approximation results are compared with numerical Hottel zone results and with results from an approximation method developed by Modest. The studies show that the P-3 approximation can be used to predict emissive power distributions and heat transfer rates in two-dimensional media with opacities of unity or greater. The P-1 approximation is identical to the diffusion solution and is thus applicable only if the medium is optically dense.
Transient Forced Convection Heat Transfer to Helium During a Step in Heat Flux
Authors: Giarratano P. J. , Steward W. G.
Published: October 2009

Transient forced convection heat transfer coefficients for both subcritical and supercritical helium in a rectangular flow channel heated on one side were measured during the application of a step in heat flux. Zero flow data were also obtained. The heater surface which served simultaneously as a thermometer was a fast response carbon film. Operating conditions covered the following range: Pressure, 1.0 × 105 Pa (1 bar) to 1.0 × 106 Pa (10 bar); Temperature, 4 K–10 K; Heat Flux, 0.1 W/cm2−10 W/cm2; Reynolds number, 0–8 × 105. The experimental data and a predictive correlation are presented.
The Thermal Performance of the Wet Surface Plastic Plate Heat Exchanger Used as an Indirect Evaporative Cooler
Authors: Kettleborough C. F. , Hsieh C. S.
Published: October 2009

A mathematical model of the plate heat exchanger (PHE) cooling unit has been developed and solved using a digital computer. The equations of temperature distribution on each plate in a counterflow PHE cooling unit are derived using an energy balance analysis. The results are presented in the form of numerical values of the “overall effectiveness” of the heat exchanger. Factors affecting the effectiveness of the PHE cooling units have been investigated. The change of temperatures and humidity ratios of the air flows in the heat exchanger are also analyzed. Finally, the high performance of the PHE cooling unit is explained by introducing the concept of “enthalpy potential.” This unit is of particular interest as a component in solar-assisted cooling systems.
Experimental Study of Droplet Evaporation in a High-Temperature Air Stream
Authors: Renksizbulut M. , Yuen M. C.
Published: October 2009

Heat transfer rates to simulated and freely suspended liquid droplets were measured in an atmospheric hot air tunnel. The experiments were limited to water, methanol, and heptane droplets in a Reynolds number range of 25 to 2000, and a mass transfer number range of 0.07 to 2.79. The present experimental data together with data by others can best be correlated by Nuf(1+Bf).7 = 2 + 0.57 ReM1/2 Prf1/3, where properties are evaluated at film conditions except for the density in the Reynolds number which is the free-stream density. Thus the data shows that at higher temperatures, evaporation reduces heat transfer rates directly by a factor of (1 + Bf).7. Indirectly, evaporation affects heat transfer rates through the changes in both the composition and temperature of the surrounding gaseous medium.
Single-Blow Transients in Packed-Bed Storage Units With Solid-Phase Conduction by Crump’s Numerical Inversion of Laplace Transforms
Authors: Lu P. -C.
Published: October 2009

A robust and fast scheme for the numerical inversion of Laplace transforms, recently established by Crump, is applied to the linear problem of two-phase (solid-and-fluid) response of a packed-bed thermal storage unit during a single-blow operation, with solid conduction in the flow direction properly considered (while neglecting the conduction and energy storage in the fluid). The scheme is shown to be capable of handling implicit solutions in the transformed domain, which are themselves to be calculated numerically on a computer. The numerical results compare very well with those obtained by other methods of attack. The comparison also discloses some rather large errors in a set of data generated by a finite difference scheme as reported in the literature.