bluuebunny/crossref_metadata_2025 huggingface dataset:
Critical Heat Flux for Nearly Saturated Water Flowing Normal to a Cylinder
Authors: Vliet G. C. , Leppert G.
Published: February 2012

Visual and photographic observations are used to construct a physical model of the mechanism of transition from nucleate to film boiling on a cylindrical heater. In this paper, interest is focused on forced-convection boiling of a liquid which is near its saturation temperature, while a companion paper deals with the effects of various degrees of liquid subcooling on the peak flux. An approximate analysis is presented of the saturated nucleate-boiling model which predicts the critical flux, and comparisons are made with experimental observations. Measurements of the peak nucleate-boiling heat flux are reported for water at atmospheric pressure over a velocity range of 1.2 to 9.5 feet per second. Resistively heated, stainless-steel wires and tubes of 0.010 to 0.189-inch diameter, the latter with wall thicknesses of 0.006 to 0.028 in., were used. Within these ranges of variables, the critical flux is found to increase with the square root of the velocity and to be independent of heater wall thickness. Only a weak dependence on the heater diameter is observable, but the tendency is for the peak flux to diminish for larger tubes.
Viscous Fluid Flow Under the Influence of a Resonant Acoustic Field
Authors: Purdy K. R. , Jackson T. W. , Gorton C. W.
Published: February 2012

This paper presents an analytical solution for laminar channel flow under the influence of a resonant acoustic field. The solution predicts that standing vortices exist in the flow and that the size of these vortices, the ratio of the width of the vortex to the half channel width, is dependent upon the parameter M¯/M02 where M is the average Mach number of the through flow and M0 is the acoustic Mach number which is based upon the maximum amplitude of the time dependent velocity. The existence of the standing vortices was confirmed experimentally by a visualization study of tube flow. Typical flow fields are shown photographically. Finally the threshold data of Eastwood for convection heat transfer under the influence of a resonant acoustic field are correlated. It was shown that sound affects the local heat-transfer rate if M¯/M02 is less than 63.
Effects of Oscillation on Free Convection From a Vertical Finite Plate
Authors: Blankenship V. D. , Clark J. A.
Published: February 2012

The effect of transverse oscillation on free convection from a vertical, finite plate is studied analytically. A second paper will consider the experimental results. Consideration is given to perturbations up to second order for potential flows with small vibrational amplitude and high frequency. Theoretical results are given for velocity, temperature, heat-transfer rate, and shear stress. It is shown that oscillations slightly decrease the steady heat-transfer rate for laminar flow. This reduction is thought to be a result of an interaction between the viscous and inertia forces in the laminar boundary layer which causes a net decrease in the connective flow near the plate.
The Thermoelectric-Hydromagnetic Pump
Authors: Osterle J. F. , Angrist S. W.
Published: February 2012

A thermally powered pump for fluids which are electrically conducting, which utilizes the Lorentz force between an electric current induced by the Seebeck effect, and an external magnetic field is examined. The pressure rise in the pump is found to be proportional to the magnetic flux density while the flow rate is found to be inversely proportional to the magnetic flux density. Thus the pumping power and efficiency (both being proportional to the product of pressure rise and flow) are independent of the applied magnetic field. Calculations for a pump with constantan walls handling sodium and utilizing a temperature difference of 300 deg C show that a maximum efficiency of close to seven-tenths of a percent is possible. If the same pump is constructed with optimum thickness walls made of the semiconductor AgSbTe2, it would have an efficiency of nearly six percent.
Heat Transfer by Natural Convection of Mercury in Enclosed Spaces When Heated From Below and Rotated
Authors: Dropkin David , Gelb George
Published: February 2012

This paper presents results of an experimental investigation of convective heat transfer in mercury confined by two horizontal plates, heated from below, and spun about its vertical axis. The experiments covered a range of Rayleigh numbers between 1.1(10)6 and 5.17(10)7, and Taylor numbers from 0 to 7.75(10)10. The Prandtl number was practically constant. The results indicate that for low spin rates, up to a certain critical value of Taylor number, the change in the heat-transfer coefficient is insignificant and the equation derived for the stationary case can be used. The critical Taylor number is given by Ta(critical)=0.68(Ra)1.28 Above the critical Taylor number, the heat-transfer coefficient may be computed from the relationship Nu=0.095(Ra)0.852(Ta)−0.463 In this equation the characteristic dimension of length, for Nu, Ra, and Taylor numbers, is the distance between plates.
Two-Phase Pressure Drop Across Vertically Mounted Thick Plate Restrictions
Authors: Cermak J. O. , Jicha J. J. , Lightner R. G.
Published: February 2012

The objective of this experimental study was to obtain two-phase (water-steam) flow pressure drop for thick-plate flow restrictions. Two-phase pressure drop data for uniformly heated tubular test sections were also obtained. A statistically designed program encompassing 536 runs was conducted employing 30-in. long test sections of six geometries. Two nozzle type, three thick-plate orifice type, and one straight expansion type flow restrictions were investigated. The ranges of parameters investigated were: Quality: 0–23 percent; Flow Rate: 500–1500 lb/hr; Pressure: 800–1600 psia; Tube Diameters: 0.416, 0.500 in. A complete factorial experimental design was employed which enabled an analysis of variance to be conducted to determine the significance of the flow rate, quality, and pressure on the response of the static pressure drop. Each of these factors was found to be highly significant. Inherent in the statistical methods employed was the establishment of the 95 percent confidence limits on the data for each test section studied. These limits ranged from 0.009 psi to 0.306 psi for the largest and smallest restriction diameters, respectively. The precision of the data was well within the limits for experimental two-phase flow technology. The results of an error analysis indicate that the accuracy with which flow rate, pressure, and geometry were determined gave rise to insignificant errors and the resulting maximum possible error in quality was less than the lower limit of the correlation equation confidence limits. The results of this study were compared with only moderate success to the theoretical models presented in the literature by Tippetts, Hoopes, and Mendler, et al. Several attempts at correlating the data resulted in a design equation to calculate the static pressure drop for the flow restrictions investigated. The form of the equation developed was: ΔPs=Zα′νG+1−α′νFgg0+K′νF2g0GR1−x1−α′2
Estimation of Steady-State Steam Void-Fraction by Means of the Principle of Minimum Entropy Production
Authors: Zivi S. M.
Published: February 2012

An analysis of steam-void fraction in two-phase flow is carried out, utilizing the principle that in a steady-state thermodynamic process the rate of entropy production is minimum. The two-phase flow is idealized in the analysis to be a truly steady-state process. The effects of liquid entrainment and wall friction on the void fraction and slip ratio are evaluated. It is found that the slip-ratio in an idealized two-phase flow with zero wall friction and zero entrainment equals (ρf/ρg)1/3. Data from a number of experiments are found to be bracketed between this result and the result obtained by assuming complete entrainment (slip ratio = 1).
Transient Forced Convection From a Flat Plate Subjected to a Step Energy Input
Authors: Adams D. E. , Gebhart B.
Published: February 2012

Transient forced convection from a flat plate subjected to a step energy input to the plate is considered for established laminar boundary-layer flow. Cases considered are a plate of zero heat capacity and a plate of relatively high heat capacity. The zero heat capacity case is solved by an integral method with different velocity profile approximations. A quasistatic solution, based on the plate energy balance, is given for the high heat capacity case. Experimental measurements verify the high heat capacity analysis.
Heat Transfer to the Turbulent Separated Flow of Air Downstream of a Step in the Surface of a Plate
Authors: Seban R. A.
Published: February 2012

Experiments on a system in which separation of a turbulent boundary layer occurred at a downward step in the surface of a plate and reattached on the plate downstream of the step have produced additional results for the local heat-transfer coefficient and for the velocity and temperature distribution in the separated and reattached regions of the flow. In neither region was there found the kind of similarity near the wall that characterizes flows that are dominated by the friction at the wall, so that even this first element of the usual rationalization of the heat transfer is unavailable for the interpretation of the results. The effect of suction or injection through a slot at the base of the step is also indicated and this demonstrates relatively small effects on both the pressure distribution and the local heat-transfer coefficient.
Temperature Distribution in a Cylindrical Rod Moving From a Chamber at One Temperature to a Chamber at Another Temperature
Authors: Horvay G. , Dacosta M.
Published: February 2012

When an infinitely long cylindrical rod travels from a chamber at one temperature ϑa to a chamber (insulated from the first) at a higher temperature ϑf, then heat will leak out along the rod from the second chamber to the first, whose amount decreases as the speed of the rod increases. Using the Wiener-Hopf method of solution, we determine the temperature distribution in the rod for the case where in the second chamber the heat-transfer coefficient h+ is infinite, while in the first chamber it has an arbitrary constant value h. Families of curves illustrate the temperature distribution in the two special cases where h = ∞ (isothermal boundary conditions in lower chamber) and where h = 0 (rod is insulated in lower chamber).
Effects of Selected Gas Stream Parameters and Coolant Properties on Liquid Film Cooling
Authors: Warner C. F. , Emmons D. L.
Published: February 2012

Experimental determinations were made of the effects of changes in the temperature, pressure, and Reynolds number of a hot gas stream upon the required flow rate of a single liquid (water) used for film cooling different lengths (4, 5, 6, 7, and 8 in.) of a cylindrical rocket motor combustion chamber. Experiments were also conducted with other coolants, such as anhydrous ammonia, ethyl alcohol, and Freon-113 for determining the effects of the physical properties of those liquids on the required film-coolant flow rates for a single condition of gas stream temperature, pressure, and Reynolds number. Determinations were also made of the heat flux and wall temperature distributions downstream from the terminus of the liquid film; that is, in the region where there is considerable vaporized film coolant in the vicinity of the chamber wall. The experimental results are correlated by means of a simple analysis based on turbulent boundary-layer theory applicable in pipe flows.
A Rational Equation of State for Water and Water Vapor in the Critical Region
Authors: Nowak E. S.
Published: February 2012

A parametric equation of state was derived for water and water vapor in the critical region from experimental P-V-T data. It is valid in that part of the critical region encompassed by pressures from 3000 to 4000 psia, specific volumes from 0.0400 to 0.1100 ft3/lb, and temperatures from 698 to 752 deg F. The equation of state satisfies all of the known conditions at the critical point. It also satisfies the conditions along certain of the boundaries which probably separate “supercritical liquid” from “supercritical vapor.” The equation of state, though quite simple in form, is probably superior to any equation heretofore derived for water and water vapor in the critical region. Specifically, the deviations between the measured and computed values of pressure in the large majority of the cases were within three parts in one thousand. This coincides approximately with the overall uncertainty in P-V-T measurements. In view of these factors, the author recommends that the equation be used to derive values for such thermodynamic properties as specific heat at constant pressure, enthalpy, and entropy in the critical region.
Combined Radiation and Convection in an Asymmetrically Heated Parallel Plate Flow Channel
Authors: Keshock E. G. , Siegel R.
Published: February 2012

An analysis is made of the effects of radiation exchanges upon the wall-temperature distributions in a parallel plate channel through which a gas transparent to thermal radiation is flowing. A uniform heat flux is applied at one wall, while the other wall has no imposed heat flux and only receives energy by radiation or convection from the heated wall. This situation approximates that found in the outer passage of a nuclear reactor fuel element where one channel wall is a fuel plate while the other is the support structure. Axial heat conduction is neglected in the channel walls and the gas, and constant fluid properties are assumed. The effects of a number of independent parameters, such as Stanton number, inlet gas temperature, and length-spacing ratio, are illustrated.
An Improved Pohlhausen-Type Method of Calculating the Two-Dimensional Laminar Boundary Layer in a Pressure Gradient
Authors: Launder B. E.
Published: February 2012

A method of calculating the two-dimensional laminar boundary layer is presented following closely the approximate solution of Pohlhausen. The boundary layer is divided into two regions, each described by third-order polynomials. By assuming that the point of intersection of the two curves is linearly related to the displacement thickness, the boundary layers are reduced to a one-parameter family. The method of solution thus becomes identical with the Pohlhausen method using the reevaluated auxiliary functions presented here. Comparison with some exact solutions clearly shows the improvement effected by the present technique.
The Determination of Forced-Convection Surface-Boiling Heat Transfer
Authors: Bergles A. E. , Rohsenow W. M.
Published: February 2012

The characteristics of the boiling curve for forced-convection surface boiling are examined in detail. In the region of low wall superheat, the heat transfer can be predicted by available correlations for forced convection. An analysis is presented for the inception of first significant boiling. Experimental results are in good agreement with analytical predictions. Pool-boiling data were taken under saturated and subcooled conditions for surfaces similar to those used in forced-convection surface boiling. These data indicate that the curves for forced-convection surface boiling cannot be based on data for saturated pool boiling but must rather be based on actual forced-convection data.
An Exact Solution of the Inverse Problem in Heat Conduction Theory and Applications
Authors: Burggraf O. R.
Published: February 2012

An inverse problem in unsteady heat conduction is one for which boundary conditions are prescribed internally, the surface conditions being unknown. By specifying the boundary conditions at a single location, an exact solution is obtained as a rapidly convergent series with the well-known, lumped capacitance approximation as the leading term. Specific forms of the series are determined for sample inverse problems: solid slab, cylinder, sphere, and transpiration-cooled slab. The solution also is applied to direct problems, involving two-point boundary conditions. By truncating the series, approximate solutions of simple form result. The one-term and two-term approximations compare well with exact solutions.
Laminar Free Convection From a Sphere
Authors: Chiang T. , Ossin A. , Tien C. L.
Published: February 2012

The present paper is concerned with the solution to the problem of external free-convective flow from a sphere with various prescribed thermal conditions on the surface. Exact numerical solutions and heat-transfer results of the boundary-layer equations were obtained for the case of uniform surface temperature and the case of uniform surface heat flux, both at a Prandtl number of 0.70. Temperature and velocity profiles at various angular positions along the sphere surface and local heat-transfer results are presented. A comparison between the exact solution and the approximate solution from the integral method is also presented.
The Use of Analog Computers for Determining Surface Parameters Required for Prediction of Thermal Contact Conductance
Authors: Henry J. J. , Fenech H.
Published: February 2012

The mathematical analysis of a thermal contact by Fenech and Rohsenow requires knowledge of certain parameters describing the geometry of the contact interface. These parameters are volume average thickness of the void above and below the plane of the contact, the number of contacts per unit area, and the ratio of the actual contact area to the total area. The authors outline a method for determining these parameters graphically. This paper describes a method for obtaining analog voltages of surface profiles of contacting surfaces and the application of a general purpose analog computer to determine the geometric parameters of contact as a function of contact pressure. The results of applying this method are combined with the analysis of Fenech and Rohsenow. The predicted contact conductance is found to agree well with experimental data at mean contact temperatures of 100, 200, and 300 F for load pressures of 100 to 20,000 psi.
The Transient Temperature Distribution in a Slab Subject to Thermal Radiation
Authors: Zerkle R. D. , Sunderland J. Edward
Published: February 2012

The transient, one-dimensional temperature distribution is determined for a slab, insulated on one face, and subjected to thermal radiation at the other face. The slab is initially at a uniform temperature and is assumed to be homogeneous, isotropic, and opaque; the physical properties are assumed to be independent of temperature. Transient temperature distributions for both heating and cooling situations are obtained by means of a thermal-electrical analog computer. A diode limiter circuit is used to simulate the nonlinear radiant heat flux. The transient temperature distributions are presented in a dimensionless, graphical form for a wide range of variables. Approximate analytical solutions are also given which complement and extend the solution charts over ranges of parameters not covered in the charts.
Heat Transfer by Natural Convection in Liquids Confined by Two Parallel Plates Which Are Inclined at Various Angles With Respect to the Horizontal
Authors: Dropkin D. , Somerscales E.
Published: February 2012

This paper presents results of an experimental investigation of convective heat transfer in liquids confined by two parallel plates and inclined at various angles with respect to the horizontal. The experiments covered a range of Rayleigh numbers between 5(10)4 and 7.17(10)8, and Prandtl numbers between 0.02 and 11,560. Tests were made in rectangular and circular containers having copper plates and insulating walls. The liquids used were water, silicone oils, and mercury. The test results indicate that the heat transfer coefficients for all liquids investigated at the various angles, from horizontal to vertical, may be determined from the relationship Nu=C(Ra)1/3(Pr)0.074 The constant, C, is a function of the angle of inclination. It varies from C = 0.069 for the horizontal case when heated from below to C = 0.049 for the vertical case. For the test cells used, no effect on the Nusselt number had been detected for the vertical case by the change of the ratio of height of cell to distance between plates. The ratio for these tests was varied from 4.41 to 16.56.
Design Analysis of Multistream Hampson Exchanger With Paired Tubes
Authors: Kao S.
Published: February 2012

The heat exchange relationship for a multistream heat exchanger of Giaque-Hampson type is analyzed and a design method using matrix approach established. Typical performance of this type of exchanger is illustrated with and without paired tubes and is compared with that of multistream plate-fin type exchanger.
Heat Transfer in Magnetohydrodynamic Flow in an Entrance Section
Authors: Dhanak A. M.
Published: February 2012

Based on the Ka´rma´n-Pohlhausen method and the associated iterative procedures developed herein the analysis shows that the presence of a transverse magnetic field in the entrance section of a channel has significant effects on the velocity and pressure distributions, and on the displacement and momentum thicknesses. The calculations further reveal that the heat transfer from the channel, in contrast with the flat plate case, increases with the Hartmann number. This increase is, however, significant only at high Prandtl numbers. The influence of Joulean dissipation appears to be negligible for a Joulean parameter up to 1.0 and at a Prandtl number of unity.
A Reappraisal of the Critical Constants for Water
Authors: Bridgeman O. C. , Aldrich E. W.
Published: February 2012

A reappraisal of the critical constants for water has been made, based on the calorimetric data of the National Bureau of Standards for saturated liquid and vapor. The temperature tc at which the enthalpy of vaporization becomes zero was found to be 374.02 C on the International Practical Temperature Scale or 374.136 C on the thermodynamic scale, within a few thousandths of a deg C. From the experimental data for γ = VV·TdP/dT and β = VL·TdP/dT, the value of γc = βc at the critical point where γ − β = L = 0 was found to be 541.382 ± 0.065 int.J/g. Using the present authors’ vapor-pressure equation for water, the critical volume Vc becomes 3.1547 cm3/g and the critical pressure Pc equals 225.268 kg/cm2, at a temperature of 374.02 C (IPTS). A comparison is made with the values reported by previous investigators.
Mechanism of Dropwise Condensation
Authors: Umur A. , Griffith P.
Published: February 2012

From a study of surface phenomena, information is obtained about conditions under which net condensation can occur. An experimental examination of the surface, using an optical method capable of detecting thin films of molecular dimensions, shows that no film greater than a monolayer in thickness exists on the area between the drops. Wetted pits and grooves in the surface are considered to be the most probable drop nucleation sites. A model for drop growth gives results which are compatible with experimentally observed values, and which show the growth rate to be a function of the vapor pressure.
Biangular Reflectance of an Electric Nonconductor as a Function of Wavelength and Surface Roughness
Authors: Torrance K. E. , Sparrow E. M.
Published: February 2012

An experiment has been performed to determine the directional reflection characteristics of electric nonconductors. The test material was fused polycrystalline magnesium-oxide ceramic. Measurements were made for surface roughnesses ranging from 0.16 to 5.8 microns over a wavelength range extending from 0.5 to 12 microns. The test specimens were illuminated by a narrow pencil of rays inclined at either 10 or 45 deg to the surface normal. The reflected radiation was collected at various directions in the hemispherical space over the surface. The experimental results indicate that the reflection characteristics of a given surface approach a diffuse distribution at short wavelengths and a specular distribution at long wavelengths. Increased surface roughness accelerates the former and retards the latter. Moreover, a given surface becomes effectively smoother when illuminated at larger angles of incidence. For the case of incidence at 45 deg, it was found that maxima in the biangular reflectance distribution occurred in angular directions other than the specular; within the knowledge of the authors, such off-specular peaks have not been discussed previously. The measured specular reflectance could be correlated in a restricted parameter range using a theory originally derived for electric conductors.
End-Wall Heat Transfer in a Rarefraction Wave Tube
Authors: Chao B. T.
Published: February 2012

An analysis is presented for the title problem based on the governing conservation equations and the measured free-stream temperature variation with time as reported by Levy and Potter. The results compare very favorably with the published data. Several temperature profiles are illustrated which confirm a posteriori the validity of the thin thermal boundary-layer assumption used.
Momentum Transfer in Thermally Asymmetric Turbulent Jets
Authors: Hetsroni G. , Hall C. W. , Dhanak A. M.
Published: February 2012

A study is presented of a two-dimensional turbulent air jet. The jet was subjected to either symmetrical or asymmetrical ambient temperatures. Theoretical analysis of a symmetrical turbulent jet, based on Reichardt’s theory, led to solutions for the stream function, shear distribution, and apparent eddy viscosity. A thermally asymmetric jet was studied at relatively low air velocities and small temperature differences. An equation was proposed for the temperature profile. Coefficients in the momentum transfer and energy transfer equations were determined experimentally and found to agree with predictions based on the symmetric jet distribution.
Average Volumetric Concentration in Two-Phase Flow Systems
Authors: Zuber N. , Findlay J. A.
Published: February 2012

A general expression which can be used either for predicting the average volumetric concentration or for analyzing and interpreting experimental data is derived. The analysis takes into account both the effect of nonuniform flow and concentration profiles as well as the effect of the local relative velocity between the phases. The first effect is taken into account by a distribution parameter, whereas the latter is accounted for by the weighted average drift velocity. Both effects are analyzed and evaluated. The results predicted by the analysis are compared with experimental data obtained for various two-phase flow regimes, with various liquid-gas mixtures in adiabatic, vertical flow over a wide pressure range. Good agreement with experimental data is shown.
Heat Transfer in Parallel Rod Arrays
Authors: Sutherland W. A. , Kays W. M.
Published: February 2012

The general problem of turbulent flow heat transfer in parallel rod arrays is considered. To accommodate the complexity introduced by this configuration, a method of analysis is developed using the technique of superposition of fundamental solutions. Fundamental solutions are determined experimentally which may be used to predict heat transfer in parallel rod arrays of various spacings and with arbitrary power distribution from rod to rod and around the periphery of the rods. The experimental investigation was conducted with airflow (Pr = 0.70) past electrically heated rods. Rod center-to-center spacing to rod diameter ratios of 1.15 and 1.25 were investigated for fully developed turbulent flow. Experimentally determined fundamental solutions are presented for Reynolds numbers from 7000 to 200,000.
Heat Transfer From a Shrouded Rotating Disk With Film Cooling
Authors: Metzger D. E. , Mitchell J. W.
Published: February 2012

A study of the cooling effect of secondary fluid injection on the heat transfer between a shrouded rotating disk and a radially inward main flow stream is presented. The investigation is intended as a model study of film-cooled, radial-flow gas turbines. The film-cooling method is reviewed, and the nondimensional parameters governing the heat transfer are obtained. Experimental results, covering the range of radial-flow, gas-turbine operating conditions, were obtained from a film-heated, rotating-disk facility. The heat-transfer behavior of the main stream only was determined separately, and the film-cooling results are presented as ratios of the heat transfer obtained with film cooling to the heat transfer obtained with only the single radial inflow.
Thermal Flowmeters: The Effect of Axial Conduction
Authors: Zinsmeister G. E. , Dixon J. R.
Published: February 2012

An analysis of a thermal flowmeter is presented incorporating the normally neglected effect of axial conduction along the tube. It is assumed that heat flow from the tube to the fluid is proportional to the temperature difference between the tube wall and the bulk temperature of the fluid. The solution is given in analytical form, and a numerical example is included.
Condensation On and Evaporation From Radially Grooved Rotating Disks
Authors: Bromley L. A. , Humphreys R. F. , Murray W.
Published: February 2012

Heat transfer coefficients on smooth plate rotating evaporator-condensers are reliably predicted by equation (2). Radial machine grooving of the condensing surface improves the heat transfer coefficient in filmwise condensation on this surface by reducing the resistance up to 65 percent. The overall coefficient was improved some 13 percent. Surfaces radially scratched by coarse sandpaper exhibited higher coefficients than smooth surfaces. Sanding the condensation side improved the overall coefficient about 8 percent, and sanding the evaporation side improved it about 10 percent. Care should be used in applying grooves to the evaporation side, however, as they increase the tendency toward local overevaporation and, hence, scale formation. Machined grooves on the evaporation side reduced overall coefficients.
The Effect of Suction and Injection on the Heat Transfer and Flow in a Turbulent Separated Airflow
Authors: Seban R. A.
Published: February 2012

The heat transfer and flow in a separated region downstream of a backward facing step have been investigated for fixed rates of suction and injection through a slot at the base of the step, with air velocities in the free stream in the range from 50 to 150 fps to demonstrate the relative effects of the suction and injection. In this way the length of the separated region was altered substantially, with consequent changes in the magnitude and distribution of the local heat-transfer coefficient.
Heat Transfer in Cylindrical Pipes With Fully Established Turbulent Flow and Exposed to a Uniform Temperature Environment
Authors: Goresh J. W.
Published: February 2012

The problem considered is that of determining the heat losses from a gas flowing turbulently in a poorly insulated pipe where the heat lost from the outer surface is by free convection and radiation. The approach employed in solving the heat equation is analogous to that first introduced by Latzko for the solution of the uniform wall temperature problem. Later, in 1957, Fettis obtained a solution to the same problem in terms of Jacobi polynomials. A method for coupling the inner convection with the environment is given in the later portion of the paper. The results obtained for a numerical case are also presented.
Film Free Convection in Helium II
Authors: Rivers W. J. , McFadden P. W.
Published: February 2012

Free-convection heat transfer from a solid surface to liquid Helium II in the presence of a film of either liquid Helium I or helium gas is analyzed mathematically. The analysis includes two heater shapes, a vertical flat plate and a horizontal circular cylinder, each with an isothermal surface. The integral forms of the boundary-layer equations are used to describe the heat transfer and fluid flow processes that occur within the film. The velocity and temperature profiles within the film are approximated by fourth degree polynomials whose coefficients were evaluated by applying a system of boundary conditions which were derived in the usual fashion but are based on assumed discontinuities in both the velocity and temperature profiles at the film-Helium II interface. Calculated results, which include the film thickness, the heat transfer coefficient, and the mass flow in the film, are presented and discussed.
Flow and Heat Transfer in Ducts of Arbitrary Shape With Arbitrary Thermal Boundary Conditions
Authors: Sparrow E. M. , Haji-Sheikh A.
Published: February 2012

A computation-oriented method of analysis is presented for determining closed-form solutions for fully developed laminar flow and heat transfer in ducts of arbitrary cross section. The analytical method can accommodate both uniform and circumferentially varying thermal boundary conditions. The solutions provide information for local quantities such as the velocity and the temperature distributions as well as for overall quantities such as the friction factor and the Nusselt number. As an application of the method, solutions are presented for flow and for heat transfer in ducts of circular-segment cross section, a configuration that is of current interest in space technology.
Heat Transfer From an Oscillating Horizontal Wire to Water and Ethylene Glycol
Authors: Penney W. R. , Jefferson T. B.
Published: February 2012

An experimental investigation has been conducted to investigate the effect of low-frequency, large-amplitude, horizontal oscillations on convection from a heated horizontal wire (0.008 in. dia) to water and ethylene glycol. Frequencies to 4.5 cps and amplitudes to 2.5 in. were employed. Comparison with a previous investigation has shown that, in the range of this investigation, heat transfer for vertical oscillations is greater than for horizontal oscillations. Comparison of data for water and ethylene glycol showed that previous methods of presenting mixed convection (free plus forced convection) data would not suffice for widely varying fluid properties. A correlating method was developed which successfully correlated the data of this investigation but failed to correlate data of previous investigations. Deficiencies of this method are discussed, and recommendations are given for future correlating methods.
Empirical Correlation of Factors Influencing Departure From Nucleate Boiling in Steam-Water Mixtures Flowing in Vertical Round Tubes
Authors: Pasint D. , Pai R. H.
Published: February 2012

An empirical correlation of forced convection DNB for steam-water mixtures between 500 and 3000 psia in uniformly heated vertical tubes is proposed. DNB quality is expressed in terms of pressure, mass flow, inlet enthalpy, heated length from inlet to DNB point, and tube dia. The experimental data of the authors at 2000–3000 psia, 250,000–1,000,000 lb/hr sq ft2 mass flow, and 40,000–180,000 Btu/hr sq ft heat flux, obtained from a 6 ft long, 3/4-in-ID electrically heated vertical tube, are correlated with other published results ranging from 500 to 2000 psia.
Heat-Transfer and Flow-Friction Characteristics of Nine Pin-Fin Surfaces
Authors: Theoclitus G.
Published: February 2012

Experimental results for convective heat-transfer and flow-friction characteristics are presented for pin-fin surfaces with in-line square pin spacing of 2D0, 3D0 and 4D0 and with plate spacings of 4D0, 8D0, 12D0.
Convection Heat Transfer for Turbulent Flow in Subsonic Diffusers
Authors: VanSant J. H. , Larson M. B.
Published: February 2012

Heat-transfer rates from a heated, plane-wall, symmetrical, two-dimensional, subsonic diffuser to air were measured at total divergence angles ranging from 0 to 45 deg, at diffuser-wall, length-to-throat width ratios ranging from 6 to 18 and at Reynolds numbers based on throat velocity and throat width ranging from approximately 40,000 to 300,000. Diffuser flow conditions developed were: No “appreciable” separation, large transitory stall (separation) and fully developed, two-dimensional stall. Fluid boundary layers on the diffuser walls were always turbulent and were assumed to be incompressible. Flow studies were made in conjunction with the heat-transfer measurements by observing flow patterns with tufts and smoke. Velocity measurements were made in fully developed, two-dimensional stall. Predictions of heat transfer were made for the conditions of no “appreciable” separation and fully developed two-dimensional stall.
Heat Transfer Measurements From a Partially Dissociated Gas With High Lewis Number
Authors: Woodruff L. W. , Giedt W. H.
Published: February 2012

Convective heat transfer from a partially dissociated hot gas stream with a Lewis number of 3 was investigated. The hot gas was composed of carbon monoxide and hydrogen resulting from the combustion of oxygen and acetylene. The percentage of atomic and molecular hydrogen by weight was 3.5 percent. A thin molybdenum test plate was mounted in the stream to obtain local heat transfer measurements for parallel flow up to surface temperatures of 3500 deg R. The recombination of atomic hydrogen was found to account for as much as 35 percent of the heat transfer. Results were correlated by theory based on a chemically reacting binary mixture in thermodynamic equilibrium.
Chemoattractant Signaling in
Dictyostelium
: Adaptation and Amplification
Authors: Iglesias Pablo A.
Published: February 2012

Dictyostelium
cells sense and interpret gradients by combining an incoherent feedforward loop and an amplification step.
How Sweet It Is
Authors: Wong Wei
Published: February 2012

Fructose activates sweet taste receptors in β cells to promote glucose-stimulated insulin secretion.
Coupling Lipid and Amino Acid Metabolism
Authors: Gough Nancy R.
Published: February 2012

A lipid-binding protein in yeast integrates lipid and amino acid metabolism to establish growth or quiescence as appropriate.
Dosing Regimen Matters: the Importance of Early Intervention and Rapid Attainment of the Pharmacokinetic/Pharmacodynamic Target
Authors: Martinez Marilyn N. , Papich Mark G. , Drusano George L.
Published: February 2012

To date, the majority of pharmacokinetic/pharmacodynamic (PK/PD) discussions have focused on PK/PD relationships evaluated at steady-state drug concentrations. However, a concern with reliance upon steady-state drug concentrations is that it ignores events occurring while the pathogen is exposed to intermittent suboptimal systemic drug concentrations prior to the attainment of a steady state. Suboptimal (inadequate) exposure can produce amplification of resistant bacteria. This minireview provides an overview of published evidence supporting the positions that, in most situations, it is the exposure achieved during the first dose that is relevant for determining the therapeutic outcome of an infection, therapeutic intervention should be initiated as soon as possible to minimize the size of the bacterial burden at the infection site, and the duration of drug administration should be kept as brief as clinically appropriate to reduce the risk of selecting for resistant (or phenotypically nonresponsive) microbial strains. To support these recommendations, we briefly discuss data on inoculum effects, persister cells, and the concept of time within some defined mutation selection window.
Population Pharmacokinetic Analysis and Pharmacogenetics of Raltegravir in HIV-Positive and Healthy Individuals
Authors: Arab-Alameddine Mona , Fayet-Mello Aurélie , Lubomirov Rubin , Neely Michael , di Iulio Julia , Owen Andrew , Boffito Marta , Cavassini Matthias , Günthard Huldrych F. , Rentsch Katharina , Buclin Thierry , Aouri Manel , Telenti Amalio , Decosterd Laurent Arthur , Rotger Margalida , Csajka Chantal ,   the Swiss HIV Cohort Study Group
Published: February 2012

The objectives of this study were to characterize raltegravir (RAL) population pharmacokinetics in HIV-positive (HIV
+
) and healthy individuals, identify influential factors, and search for new candidate genes involved in UDP glucuronosyltransferase (UGT)-mediated glucuronidation. The pharmacokinetic analysis was performed with NONMEM. Genetic association analysis was performed with PLINK using the relative bioavailability as the phenotype. Simulations were performed to compare once- and twice-daily regimens. A 2-compartment model with first-order absorption adequately described the data. Atazanavir, gender, and bilirubin levels influenced RAL relative bioavailability, which was 30% lower in HIV
+
than in healthy individuals.
UGT1A9
*
3
was the only genetic variant possibly influencing RAL pharmacokinetics. The majority of RAL pharmacokinetic variability remains unexplained by genetic and nongenetic factors. Owing to the very large variability, trough drug levels might be very low under the standard dosing regimen, raising the question of a potential relevance of therapeutic drug monitoring of RAL in some situations.
Daptomycin and Tigecycline Have Broader Effective Dose Ranges than Vancomycin as Prophylaxis against a Staphylococcus aureus Surgical Implant Infection in Mice
Authors: Niska Jared A. , Shahbazian Jonathan H. , Ramos Romela Irene , Pribaz Jonathan R. , Billi Fabrizio , Francis Kevin P. , Miller Lloyd S.
Published: February 2012

Vancomycin is widely used for intravenous prophylaxis against surgical implant infections. However, it is unclear whether alternative antibiotics used to treat methicillin-resistant
Staphylococcus aureus
(MRSA) infections are effective as prophylactic agents. The aim of this study was to compare the efficacies of vancomycin, daptomycin, and tigecycline as prophylactic therapy against a methicillin-sensitive
S. aureus
(MSSA) or MRSA surgical implant infection in mice. MSSA or MRSA was inoculated into the knee joints of mice in the presence of a surgically placed medical-grade metallic implant. The efficacies of low- versus high-dose vancomycin (10 versus 110 mg/kg), daptomycin (1 versus 10 mg/kg), and tigecycline (1 versus 10 mg/kg) intravenous prophylaxis were compared using
in vivo
bioluminescence imaging,
ex vivo
bacterial counts, and biofilm formation. High-dose vancomycin, daptomycin, and tigecycline resulted in similar reductions in bacterial burden and biofilm formation. In contrast, low-dose daptomycin and tigecycline were more effective than low-dose vancomycin against the implant infection. In this mouse model of surgical implant MSSA or MRSA infection, daptomycin and tigecycline prophylaxis were effective over a broader dosage range than vancomycin. Future studies in humans will be required to determine whether these broader effective dose ranges for daptomycin and tigecycline in mice translate to improved efficacy in preventing surgical implant infections in clinical practice.
Complete Genome Sequence of Rickettsia slovaca, the Agent of Tick-Borne Lymphadenitis
Authors: Fournier Pierre-Edouard , El Karkouri Khalid , Robert Catherine , Médigue Claudine , Raoult Didier
Published: February 2012

The present study reports the complete and annotated genome sequence of the human pathogen
Rickettsia slovaca
strain 13-B, which was isolated from a
Dermacentor
tick in Slovakia in 1968. The 1.27-Mb genome provides further insights into the acquisition of virulence related to genome reduction in
Rickettsia
species.
Genome Sequence of Staphylococcus aureus Strain 11819-97, an ST80-IV European Community-Acquired Methicillin-Resistant Isolate
Authors: Stegger Marc , Price Lance B. , Larsen Anders R. , Gillece John D. , Waters Andrew E. , Skov Robert , Andersen Paal S.
Published: February 2012

The European methicillin-resistant
Staphylococcus aureus
(MRSA) clone ST80-IV has historically dominated community-associated infections in major parts of Europe and is a lineage strongly linked to skin and soft tissue infections. Here, we report the genome sequence of an ST80-IV representative, 11819-97, isolated from a skin infection in Denmark in 1997.
Complete Genome Sequence of Mycoplasma haemocanis Strain Illinois
Authors: do Nascimento Naíla C. , Guimaraes Ana M. S. , Santos Andrea P. , SanMiguel Phillip J. , Messick Joanne B.
Published: February 2012

Mycoplasma haemocanis
is a blood pathogen that may cause acute disease in immunosuppressed or splenectomized dogs. The genome of the strain Illinois is a single circular chromosome with 919,992 bp and a GC content of 35%. Analyses of the
M. haemocanis
genome will provide insights into its biology and
in vitro
cultivation requirements.
Can antiherbivory resistance explain the abundance of woody species in a Neotropical savanna?
Authors: Dantas Vinícius de Lima , Batalha Marco Antônio
Published: February 2012

The disturbance resistance model states that, in nutrient-poor communities, species more resistant to herbivory should dominate over the more palatable ones. Here we postulated that the disturbance resistance model should explain the species abundances in a nutrient-poor Neotropical savanna community. If so, the highly resistant species should be the commonest, whereas the poorly resistant ones should be rare. In an area of 2500 m2of woodland cerrado, a type of savanna, we measured the abundance of all 61 species as the total basal area and 9 antiherbivore defence traits from 10 individuals of each species. We used multiple and simple linear regressions to test the relationships between abundance and each trait or total investment in defence. Abundance was negatively related to specific leaf area (R2 = 0.18, b = –0.87, P < 0.001), but not with the other traits nor with total defence. The relationship between specific leaf area and abundance showed that plant functional traits may influence species abundance and supported the idea that nonrandom and resource-mediated processes should prevail at a fine scale. Nevertheless, we did not find strong evidence that antiherbivory resistance can explain species abundance in resource-poor communities, in contrast to the prediction of the disturbance resistance model.
Significance of leaf structure and emission of volatile organic compounds in ozone tolerance of oat and wheat
Authors: Hartikainen Kaisa , Kivimäenpää Minna , Nerg Anne-Marja , Holopainen Toini
Published: February 2012

To study the possible differences in tropospheric ozone (O3) tolerance of oat (Avena sativa L.) and wheat (Triticum aestivum L.), two oat and two wheat cultivars were exposed to 0, 50, or 100 nL·L–1O3concentrations in growth chambers. Measurements on volatile organic counpound emission and physiological, biochemical, and leaf structural characteristics were conducted with 2- and 4-week-old seedlings. Neither of the studied species was particularly O3sensitive, but O3sensitivity should rather be defined on the basis of the characteristics of the cultivars within species. Visible leaf injuries increased with leaf age and with increasing O3concentration. Net photosynthesis (Pn), stomatal conductance (gs), and chlorophyll fluorescence (Fv/Fm) of 2-week-old seedlings were more detrimentally affected by O3compared with older seedlings. Wheat generally invested more in photosynthesis and related processes, such as gs, Fv/Fm, concentrations of Rubisco, chlorophylls and carotenoids, and synthesis of starch compared with oat. O3increased Rubisco concentration in 2-week-old and carotenoid concentration in 4-week-old seedlings, especially in wheat. Lower extent of O3-caused visible leaf injuries in the other oat cultivar can supposedly be explained by its low stomatal conductance and high monoterpene production.