bluuebunny/crossref_metadata_2025 huggingface dataset:
The Present and Future of MFT Doctoral Education in Research‐Focused Universities
Authors: Sprenkle Douglas H.
Published: October 2009

Doctoral education is greatly impacted by context, and the large majority of marital and family therapy (MFT) doctoral programs are PhD programs in research‐focused universities. I believe their primary mission is to equip students to become scientist–practitioners and do original research that will advance the science of the discipline, whereas the mission of the typical master’s program is to produce strong practitioners who are research informed. It is the emphasis on the scientific method, not the content specialty area, that should be the hallmark of PhD programs in research‐focused contexts. I describe metrics for success that include not only research productivity but also the development of a supportive, open, flexible, and generous program culture. The research mission of these programs has been only modestly helped by the Commission on Accreditation for Marriage and Family Therapy Education process and the programs are largely not doing the programmatic intervention research that the field needs. As the universities that house these programs are also “raising the bar,” the long‐term viability of the programs themselves will likely hinge on success in this arena.
Effectiveness of canalicular laceration repair using monocanalicular intubation with Monoka tubes
Authors: Lee Hwa , Chi Mijung , Park Minsoo , Baek Sehyun
Published: October 2009

Purpose:  This study aimed to evaluate the clinical efficacy of canalicular laceration repair using monocanalicular intubation with Monoka tubes.

Methods:  A total of 36 single lacerated canaliculi were repaired using monocanalicular intubation with Monoka tubes, without mucosal anastomosis of the canaliculi, and were retrospectively reviewed. Demographic information, injury locations, associated ocular injuries, complications and outcomes were analysed.

Results:  Mean patient age was 34 years (range 1–64 years). Tubes were removed at a mean of 4.2 months (range 3–6 months). There were 26 lower canalicular lacerations (72%) and 10 upper canalicular lacerations (28%). Overall, 34 of 36 cases (92%) showed improvement in symptoms and exhibited positivity on the dye disappearance test at 4–12 months after the procedure (mean 7.8 months). In total, 21 patients (58%) achieved complete success, 13 patients (36%) achieved partial success and two patients (6%) suffered surgical failure. Complications were seen in five cases and included two early tube protrusions, two punctal slits and one punctal granuloma.

Conclusions:  Monocanalicular intubation with Monoka tubes leads to successful outcomes without significant complications and offers an alternative to bicanalicular intubation in the treatment of monocanalicular lacerations.
Intraocular pressure in keratoconus
Authors: Read Scott A. , Collins Michael J.
Published: October 2009

Purpose:  This study aimed to investigate intraocular pressure (IOP) measurements taken using the dynamic contour tonometer (DCT) and the non‐contact tonometer (NCT) in subjects with keratoconus.

Methods:  Intraocular pressure was measured in 20 keratoconus subjects and 20 age‐matched control subjects using the DCT and NCT instruments. Central and off‐centre measures were taken with the DCT in order to highlight any systematic errors associated with corneal biomechanical factors. Measures of anterior and posterior corneal topography and thickness were also taken in each subject.

Results:  No significant difference was found between the central and off‐centre DCT IOP readings for the keratoconus subjects and age‐matched controls (p > 0.05). The average DCT IOP was 14.2 ± 1.4 mmHg in the keratoconus subjects and 14.2 ± 1.6 mmHg in the controls. However, the average NCT readings differed significantly (p < 0.001) between the keratoconus subjects (9.2 ± 1.5 mmHg) and the controls (12.9 ± 2.4 mmHg). Intraocular pressure measurements taken with the DCT showed no significant (p > 0.05) correlation with the severity of keratoconus as determined through measures of corneal topography and thickness. Equivalent IOP measurements taken with the NCT correlated significantly with certain measures of corneal curvature and thickness in the keratoconus population. The difference between DCT and NCT IOP was strongly correlated with measures of corneal topography and thickness, with differences increasing in more advanced keratoconus.

Conclusions:  The measurements obtained with the DCT do not appear to be dependent upon corneal factors, unlike those taken with the NCT. The presence or severity of keratoconus was not correlated with DCT IOP values.
Globalizing Justice: The Contribution of Christian Spirituality
Authors: Groody Daniel G.
Published: October 2009

This article looks at the role of Christian spirituality in fostering right relationships. It looks first at the integral relationship between spirituality and justice, particularly as it takes shape within the terrain of the human heart. Secondly, it examines the role of social context in a transformative spirituality by looking at one faith community of undocumented immigrants in the United States. And thirdly it looks at migration as a metaphor for a spirituality of transformation, one that orients a pilgrim people towards a homeward journey and awakens in us a social conscience. The central argument is that spiritual transformation is about the movement towards authenticity, where the gift of peace grows from the rebuilding of our relationships with God, ourselves and others.
AMP‐activated protein kinase inhibits TREK channels
Authors: Kréneisz Orsolya , Benoit Justin P. , Bayliss Douglas A. , Mulkey Daniel K.
Published: October 2009

AMP‐activated protein kinase (AMPK) is a serine/threonine kinase activated by conditions that increase the AMP : ATP ratio. In carotid body glomus cells, AMPK is thought to link changes in arterial O2 with activation of glomus cells by inhibition of unidentified background K+ channels. Modulation by AMPK of individual background K+ channels has not been described. Here, we characterize effects of activated AMPK on recombinant TASK‐1, TASK‐3, TREK‐1 and TREK‐2 background K+ channels expressed in HEK293 cells. We found that TREK‐1 and TREK‐2 channels but not TASK‐1 or TASK‐3 channels are inhibited by AMPK. AMPK‐mediated inhibition of TREK involves key serine residues in the C‐terminus that are also known to be important for PKA and PKC channel modulation; inhibition of TREK‐1 requires Ser‐300 and Ser‐333 and inhibition of TREK‐2 requires Ser‐326 and Ser‐359. Metabolic inhibition by sodium azide can also inhibit both TREK and TASK channels. The effects of azide on TREK occlude subsequent channel inhibition by AMPK and are attenuated by expression of a dominant negative catalytic subunit of AMPK (dnAMPK), suggesting that metabolic stress modulates TREK channels by an AMPK mechanism. By contrast, inhibition of TASK channels by azide was unaffected by expression of dnAMPK, suggesting an AMPK‐independent mechanism. In addition, prolonged exposure (6–7 min) to hypoxia (= 11 ± 1 mmHg) inhibits TREK channels and this response was blocked by expression of dnAMPK. Our results identify a novel modulation of TREK channels by AMPK and indicate that select residues in the C‐terminus of TREK are points of convergence for multiple signalling cascades including AMPK, PKA and PKC. To the extent that carotid body O2 sensitivity is dependent on AMPK, our finding that TREK‐1 and TREK‐2 channels are inhibited by AMPK suggests that TREK channels may represent the AMPK‐inhibited background K+ channels that mediate activation of glomus cells by hypoxia.
Laminar Wake Flame Heights
Authors: Kinoshita C. M. , Pagni P. J.
Published: October 2009

One important measure of material fire hazard is the flame height a given polymer produces upon burning in a specified ambience. Six systems are considered here—two fuel geometries: wall-mounted and free standing; and three flow fields: forced, free and mixed-mode. In each case, the extent of the combusting gas downstream of a pyrolyzing slab is obtained as a function of the fuel’s thermochemical properties. The flow is modeled as a steady, laminar, two-dimensional, nonradiative boundary layer. The combustion is described by a single Shvab-Zeldovich energy-species equation assuming unit Lewis number and a fast one-step overall gas phase reaction. Numerical methods are employed due to the abrupt change in boundary conditions at the end of the pyrolyzing slab. However, an approximate similarity solution is found for forced flow which yields explicit flame heights. Based on these results, explicit functional fits to numerical flame heights are obtained for free and mixed-mode flows. Comparisons between theory and experiment indicate quantitative agreement.
The Prediction of Surface Discharge Jets by a Three-Dimensional Finite-Difference Model
Authors: Raithby G. D. , Schneider G. E.
Published: October 2009

A three-dimensional model is presented which describes the thermal and hydrodynamic behavior of a turbulent heated jet entering at the surface of a receiving body of water. A two-equation turbulence model, together with a semi-empirical description of the preferential attenuation of vertical turbulent exchange due to buoyancy, is used to predict non-isotropic turbulent diffusivities. A finite-difference solution method, involving several novel features, has been used. Predictions are compared with both field and laboratory measurements, for both deep and shallow receiving basins, for the special case of a quiescent ambient fluid. Good agreement is found, indicating that the model can be reliably used as a design tool, or to evaluate the environmental impact of surface discharges.
Correlations for the Determination of the Inception Conditions of Density-Wave Oscillations for Forced and Natural Circulation Steam Generator Tubes
Authors: U¨nal H. C.
Published: October 2009

Accurate and simple correlations are presented to determine the inception conditions of density-wave oscillations in steam generator tubes. The correlations predict the power at the start of the density-wave oscillations within about 6.5 percent accuracy for long (i.e., L ≥ 10 m) forced circulation steam generator tubes and within about 20 percent accuracy for natural circulation and short forced circulation steam generator tubes. The ranges of the operating conditions and geometries for the data used to establish the correlations are as follows: Forced circulation tubes: Geometry: circular-straight tubes and serpentines, a circular coil and a rectangular straight tube; type of heating: electrical or sodium heating; the ratio of the heated length to diameter: 153–9502; pressure: 4.1–17.3 MN/m2; outlet steam quality: 0.27–1.85; inlet subcooling: 2.8–245.9 K; mass velocity: 118–2088 kg/m2s. Natural circulation tubes: Geometry and heating conditions: electrically heated circular tubes and annuli; ratio of the heated length to diameter: 34–489; pressure: 0.2–7.1 MN/m2; outlet steam quality: 0.04–0.62; inlet subcooling: 0–244 K; mass velocity: 529–1230 kg/m2s. The number of data considered is 106 for forced circulation tubes and 110 for natural circulation tubes.
Effect of Velocity on Heat Transfer to Boiling Freon-113
Authors: Yilmaz Salim , Westwater J. W.
Published: October 2009

Measurements were made of the heat transfer to Freon-113 at near atmospheric pressure, boiling outside a 6.5 mm dia horizontal steam-heated copper tube. Tests included pool boiling and also forced flow vertically upward at uelocities of 2.4, 4.0 and 6.8 m/s. The metal-to-liquid ΔT ranged from 13 to 125° C, resulting in nucleate, transition, and film boiling. The boiling curves for different velocities did not intersect or overlap, contrary to some prior investigators. The peak heat flux was proportional to the square root of velocity, agreeing with the Vliet-Leppert correlation, but disagreeing with the Lienhard-Eichhorn prediction of an exponent of 0.33. The forced-flow nucleate boiling data were well correlated by Rohsenow’s equation, except at high heat fluxes. Heat fluxes in film boiling were proportional to velocity to the exponent 0.56, close to the 0.50 value given by Bromley, LeRoy, and Robbers. Transition boiling was very sensitive to velocity; at a ΔT of 55° C the heat flux was 900 percent higher for a velocity of 2.4 m/s than for zero velocity.
Augmentation of Direct-Contact Heat Transfer to Drops with an Intermittent Electric Field
Authors: Kaji N. , Mori Y. H. , Tochitani Y. , Komotori K.
Published: October 2009

The characteristics of the augmentation technique previously proposed by the authors has been studied experimentally with water drops 3.9 to 5.9 mm in diameter rising in methylphenyl silicone oil. Each drop is subjected to an intermittent electric field applied periodically perpendicular to its trajectory, and the drop responds by periodic elongation in the direction of the field. The dependence of heat transfer coefficient on the strength, frequency and duty ratio of the field is presented and discussed.
Experiments on In-line Pin Fin Arrays and Performance Comparisons with Staggered Arrays
Authors: Sparrow E. M. , Ramsey J. W. , Altemani C. A. C.
Published: October 2009

Heat transfer and pressure drop experiments were performed for in-line pin fin arrays to obtain basic data to complement available information for staggered arrays. The experimental data were utilized as input to analyses aimed at establishing performance relationships between in-line and staggered arrays. In the experiments, mass transfer measurements via the naphthalene sublimation technique were employed to determine the row-by-row distribution of the heat (mass) transfer coefficient. Fully developed conditions prevailed for the fourth row and beyond. In general, the fully developed heat transfer coefficients for the in-line array are lower than those for the staggered array, but the pressure drop is also lower. The deviations between the two arrays increase with increasing fin height. With regard to performance, the in-line array transfers more heat than the staggered array under conditions of equal pumping power and equal heat transfer area. On the other hand, at a fixed heat load and fixed mass flow rate, the staggered array requires less heat transfer surface than the in-line array.
Simultaneous Wall and Fluid Axial Conduction in Laminar Pipe-Flow Heat Transfer
Authors: Faghri M. , Sparrow E. M.
Published: October 2009

Consideration is given to a laminar pipe flow in which the upstream portion of the wall is externally insulated while the downstream portion of the wall is uniformly heated. An analysis of the problem is performed whose special feature is the accounting of axial conduction in both the tube wall and in the fluid. This conjugate heat transfer problem is governed by two dimensionless groups—a wall conductance parameter and the Peclet number, the latter being assigned values from 5 to 50. From numerical solutions, it was found that axial conduction in the wall can carry substantial amounts of heat upstream into the non directly heated portion of the tube. This results in a preheating of both the wall and the fluid in the upstream region, with the zone of preheating extending back as far as twenty radii. The preheating effect is carried downstream with the fluid, raising temperatures all along the tube. The local Nusselt number exhibits fully developed values in the upstream (non directly heated) region as well as in the downstream (directly heated) region. Of the two effects, wall axial conduction can readily overwhelm fluid axial conduction.
Axial Development of Unusual Velocity Profiles due to Heat Transfer in Variable Density Fluids
Authors: Hauptmann E. G. , Malhotra A.
Published: October 2009

Velocity profiles exhibiting maxima away from the axis of symmetry have been calculated for supercritical carbon dioxide flowing vertically in a heated circular duct. The analysis was carried out at the two-dimensional level and the turbulent fluxes are represented by a two equation model of turbulence. The existence of such velocity profiles has been accepted previously but the nature of their growth along a pipe was not known previous to this work.
Free Convection Heat Transfer across Rectangular-Celled Diathermanous Honeycombs
Authors: Smart D. R. , Hollands K. G. T. , Raithby G. D.
Published: October 2009

Experimentally obtained Nusselt number-Rayleigh number plots are presented for free convective heat transfer across inclined honeycomb panels filled with air. The honeycomb cells were rectangular in shape with very long cell dimensions across the slope and comparatively short dimensions up the slope. Elevation aspect ratios, AE, investigated were 3, 5 and 10; angles of inclination, θ, measured from the horizontal, were 0, 30, 60, 75 and 90 deg. The effect on the Nusselt number, of the emissivities of the plates bounding the honeycomb, and of the emissivity of honeycomb material, was also investigated. The measurements confirmed that the critical Rayleigh number and the post-critical heat transfer depend on the radiant properties of the honeycomb cells. The critical Rayleigh numbers at θ = 0 were well predicted by the methods of Sun and Edwards. For 0 < θ ≤ 75 deg, the critical Rayleigh numbers and the Nusselt-Rayleigh relations were both found to be essentially the same as their horizontal counterparts provided the Rayleigh number was first scaled by cos θ. For θ = 90 deg, the form of the Nusselt-Rayleigh relation was found to be very different from that for θ ≤ 75 deg and similar to that observed for square-celled honeycombs for θ ≥ 30 deg. The θ = 90 deg data were found to be closely correlated by an equation of the form recently proposed by Bejan and Tien.
Combined Natural Convection and Radiation in a Volumetrically Heated Fluid Layer
Authors: Chawla T. C. , Chan S. H. , Cheung F. B. , Cho D. H.
Published: October 2009

The effect of radiation in combination with turbulent natural convection on the rates of heat transfer in volumetrically heated fluid layers characterized by high temperatures has been considered in this study. It is demonstrated that even at high Rayleigh numbers the radiation mode is as effective as the turbulent natural convection mode in removing the heat from the upper surface of the molten pools with adiabatic lower boundary. As a result of this improved heat transfer, it is shown that considerably thicker molten pools with internal heat generation can be supported without boiling inception. The total Nusselt number at a moderate but fixed value of conduction-radiation parameter, can be represented as a function of Rayleigh number in a simple power-law form. As a consequence of this relationship it is shown that maximum nonboiling pool thicknesses vary approximately inversely as the 0.9 power of internal heat generation rate. A comparison between exact analysis using the integral formulation of radiation flux and Rosseland approximation shows that the latter approximation bears out very adequately for optically thick pools with conduction-radiation parameter ≳ 0.4 inspite of the fact that individual components of Nusselt number due to radiation and convection, respectively, are grossly in error. These errors in component heat fluxes are compensating due to the total heat balance constraint. However, the comparison between Rosseland approximation and exact formulation gets poorer as the value of conduction-radiation parameter decreases. This increase in error is principally incurred due to the error in estimating wall temperature differences.
The Influence and Treatment of Mie-Anisotropic Scattering in Radiative Heat Transfer
Authors: Modest M. F. , Azad F. H.
Published: October 2009

The influence of highly anisotropic Mie scattering on radiative heat transfer is investigated. Exact solutions for temperature distributions and radiative flux are found for scattering functions with up to 35 terms in their Legendre polynomial series expansion. Approximation by linear anisotropic scattering is found to describe radiative transfer excellently as long as the phase function is relatively smooth and as long as there is only insignificant backscattering. The linear-anisotropic differential approximation also yields very accurate results (within its limitations) and can account for backscattering as well.
Enhancement of Natural Convection Heat Transfer by a Staggered Array of Discrete Vertical Plates
Authors: Sparrow E. M. , Prakash C.
Published: October 2009

An analysis has been performed to determine whether, in natural convection, a staggered array of discrete vertical plates yields enhanced heat transfer compared with an array of continuous parallel vertical plates having the same surface area. The heat transfer results were obtained by numerically solving the equations of mass, momentum, and energy for the two types of configurations. It was found that the use of discrete plates gives rise to heat transfer enhancement when the parameter (Dh/H)Ra > ∼2 × 103 (Dh = hydraulic diameter of flow passage, H = overall system height). The extent of the enhancement is increased by use of numerous shorter plates, by larger transverse interplate spacing, and by relatively short system heights. For the parameter ranges investigated, the maximum heat transfer enhancement, relative to the parallel plate case, was a factor of two. The general degree of enhancement compares favorably with that which has been obtained in forced convection systems.
Experiments on Natural Convection from Vertical Parallel Plates with Either Open or Closed Edges
Authors: Sparrow E. M. , Bahrami P. A.
Published: October 2009

Natural convection heat transfer from the face-to-face surfaces of parallel, square vertical plates was investigated experimentally. The experiments encompassed three types of hydrodynamic conditions along the lateral edges: (1) fully open to ambient, (2) blockage of one of the edge gaps, (3) blockage along both of the edge gaps. Measurements were made for ten interplate spacings. Use of a mass transfer measurement technique (the naphthalene sublimation technique) instead of direct heat transfer enabled elimination of radiation effects, extraneous connective/conductive heat losses, and variable property effects. The results for the fully open-edged case cast substantive doubt on the oft-quoted data of Elenbaas in the low range of the parameter (b/H)Ra, where b is the interplate spacing and H is the plate height. Uncertainties in Elenbaas’ results owing to large fluid property variations are also demonstrated (the present results correspond to constant properties). Suppression of fluid flow along one lateral edge gap generally has only a modest effect on the transfer coefficients and no effect for (b/H)Ra > 4. When both edges are blocked, 30 percent (or more) reductions in the coefficients occur at lower (b/H)Ra. When (b/H)Ra > 10, the lateral edge conditions do not affect the results.
Boundary Layer Regime for Laminar Free Convection between Horizontal Circular Cylinders
Authors: Jischke M. C. , Farshchi M.
Published: October 2009

The steady, buoyancy-driven, laminar motion induced in the annulus of two horizontal, concentric, circular cylinders by a difference in the boundary temperatures is studied analytically in the large Rayleigh number limit. The flowfield is divided into five physically distinct regions: (1) an inner free convection boundary layer near the inner cylinder, (2) an outer free convection boundary layer near the outer cylinder, (3) a vertical plume above the inner cylinder, (4) a stagnant region below the inner cylinder, and (5) a core region surrounded by the other four regions. Zeroth-order solutions which account for the coupling of those five regions are obtained in the high Prandtl number limit using a boundary-layer approximation and integral methods. Comparisons of the calculated heat transfer and temperature fields with experiment and numerical finite-difference results are favorable.
The Experimental Measurement of Natural Convective Heat Transfer in Rectangular Enclosures with Concentrated Energy Sources
Authors: Turner B. L. , Flack R. D.
Published: October 2009

Heat transfer rates were experimentally measured for laminar convection air flows in rectangular enclosures with one isothermal heated vertical wall, a concentrated cooling strip on the opposing wall, and adiabatic top and bottom plates. Both local and overall heat transfer data were obtained by the use of a Wollaston prism schlieren interferometer. The aspect ratio of the enclosure and size and location of the cooling strip were parametrically varied for Grashof numbers of 5 × 106 to 9 × 106. Results are compared to previously available theoretical predictions for low Grashof numbers (105). Correlations are presented such that the theoretical predictions can be extended to Grashof numbers up to 107. The present data also indicate the dependence of heat transfer rates on the geometric parameters.
Natural Convection of a Heat Generating Fluid in a Closed Cavity
Authors: Bergholz R. F.
Published: October 2009

Thermal convection of a heat generating fluid in a rectangular enclosure, cooled at the side walls, is investigated in the boundary-layer regime at large internal Rayleigh numbers. A boundary-layer analysis is employed to derive a system of equations valid near the vertical walls and a corresponding system valid in the core of the enclosure. The boundary-layer equations were solved using a modified Oseen linearization method. It was found that the primary convective flow consists of a bicellular circulation in which the cold, descending boundary layers at the lateral walls generate a nearly uniform, upward flow in the core. In addition, a strong, stable, vertical temperature gradient is established in the core by the process of upward transport of heat. The side-wall heat flux distribution shows that most of the heat generated within the cavity is removed along the upper one-half of each vertical wall. It is expected that the results of this work can be applied in studies of the containment of heat generating radioactive materials and in analyses of convection driven by electrical currents or exothermic chemical reactions.
Steady Thermal Convection from a Concentrated Source in a Porous Medium
Authors: Hickox C. E. , Watts H. A.
Published: October 2009

Solutions for the steady, axisymmetric velocity and temperature fields associated with a point source of thermal energy in a fluid-saturated porous medium are obtained numerically through use of similarity transformations. The two cases considered are those of a point source located on the lower, insulated boundary of a semi-infinite region and a point source embedded in an infinite region. Numerical results are presented from which complete descriptions of the velocity and temperature fields can be constructed for Rayleigh numbers of 0.1, 1.0, 10.0, and 100.0.
Effects of Nonuniform Thermal Gradient and Adiabatic Boundaries on Convection in Porous Media
Authors: Rudraiah N. , Veerappa B. , Balachandra Rao S.
Published: October 2009

The effects of different combinations of thermally insulated boundaries and nonuniform thermal gradient caused by either sudden heating or cooling at the boundaries or by distributed heat sources on convective stability in a fluid saturated porous medium are investigated using linear theory by considering the Brinkman model. In the case of sudden heating or cooling, solutions are obtained using single-term Galerkin expansion and attention is focused on the situation where the critical Rayleigh number is less than that for uniform temperature gradient and the convection is not maintained. Numerical values are obtained for various basic temperature profiles and some general conclusions about their destabilizing effects are presented. In particular, it is shown that the results of viscous fluid (σ = 0) and the usual Darcy porous medium (σ → ∞) emerge from our analysis as special cases. In the case of convection caused by heat source, since the effect of heat source is not brought out by the single-term Galerkin expansion, the critical internal Rayleigh number is determined using higher order expansion by specifying the external Rayleigh number. It is shown that, for values of σ2 ≥ 2.45 × 105, the different combinations of bounding surfaces give almost the same Rayleigh number and an explanation, following Lapwood, for this surprising behavior is given. It is found that the heat source’s effect on convection decreases for wave numbers up to the value 2.2 and drops suddenly around the critical value of 2.4 and then increases up to 2.5.
Effect of Combined Free and Forced Convection on the Stability of Flow in a Horizontal Tube
Authors: El-Hawary Magdy A.
Published: October 2009

The effect of wall heating on the stability of low Reynolds number flows in a horizontal tube is investigated in the present study. Experiments were conducted for the flow of water in a tube with length to diameter ratio of 300. Wide ranges of mass flow rate and heating power were examined under constant wall heat flux. Stability was detected by examining signals of a thermocouple probe and a hot-film annemometer probe placed in the flow at the test section outlet. The onset of a turbulent flow was also marked by significant increases in the value of pressure drop measured across the test section. Results revealed regions of laminar flows, turbulent flows, and flows intermediate in behavior between laminar and fully turbulent. A stability map is presented showing regions of different flows on nondimensional co-ordinates representing forced and natural convection effects.
Developing Flow and Heat Transfer in Strongly Curved Ducts of Rectangular Cross Section
Authors: Yee G. , Chilukuri R. , Humphrey J. A. C.
Published: October 2009

A numerical study of heat transfer in 90 deg, constant cross section curved duct, steady, laminar, flow is presented. The work is aimed primarily at characterizing the effects on heat transfer of duct geometry and entrance conditions of velocity and temperature by considering, especially, the role of secondary motions during the developing period of the flow. Calculations are based on fully elliptic forms of the transport equations governing the flow. They are of engineering value and are limited in accuracy only by the degree of computational mesh refinement. A comparison with calculations based on parabolic equations shows how the latter can lead to erroneous results for strongly curved flows. Buoyant effects are excluded from the present study so that, strictly, the results apply to heat transfer flows in the absence of gravitational forces such as arise in spacecraft.
Combined Radiation Convection in Thermally Developing Poiseuille Flow with Scattering
Authors: Chawla T. C. , Chan S. H.
Published: October 2009

The solution for thermally developing Poiseuille flow with scattering is obtained by using the method of collocation. The results show that scattering tends to decrease radiation component without affecting the convective component at low optical thicknesses. For moderate to high values of optical thicknesses, both the convective and radiation components are reduced. The relative effect of scattering both on convective and radiation Nusselt numbers appears to be unaffected by a change in the surface emissivity. A significant feature of combined radiation-convection in thermally developing flows appears to be that the total Nusselt number increases downstream of position of minimum rather than approaching an asymptotic value as is the case with corresponding pure convection. Another departure in the behavior appears to be the lack of existence of similarity in the temperature profiles, particularly at low values of conduction-radiation parameter.
Continuum Modeling of Low Frequency Heat Conduction in Laminated Composites with Bonds
Authors: Nayfeh Adnan H.
Published: October 2009

Two model analyses are constructed in order to determine the influence of bonding materials on the heat diffusion in otherwise bilaminated composites. The geometric arrangement of the composite with the bond is treated as a special type of trilaminated composite in which each of its major constituents is sandwiched between two bonding layers. In the first model, the recently developed continuum mixture theories of heat conduction in bilaminated composites [1] are extended to treat the trilaminated composite. Here details of the diffusion process in the major components and also in the bonding layers are derived. In the second model, the entire effect of the bonds is treated as a modifier to interfacial continuity conditions. In this model the details of the diffusion process in the bonding material are ignored. It is found that the results of both models correlate well with each others and also with some exact solutions especially for low frequency ranges.
On Lack of Uniqueness in Heat Conduction through a Solid to Solid Contact
Authors: Comninou Maria , Dundurs J.
Published: October 2009

If two solids are pressed together and made to exchange heat by conduction, one possible steady state corresponds to the solids remaining in contact along the entire interface. It is shown that this state is not unique, and that it is possible to construct solutions involving localized separation if heat flows in one of the two possible directions.
An Experimental Study of Falling Liquid Film Breakdown on a Horizontal Cylinder During Heat Transfer
Authors: Ganic E. N. , Roppo M. N.
Published: October 2009

In this study, an experimental investigation was conducted with subcooled water film flowing over an electrically heated horizontal cylinder. The combinations of film flow rate and heat flux at which film breakdown occurs (i.e., dry patches appear on the surface) were determined. At the conditions prior to dry patch formation, the heat transfer coefficient was determined as well. The results showed that the heat flux needed to cause a dry patch increases with film flow rate. Also, prior to dry patch formation, the heat transfer coefficient increases with film flow rate. The effects of the tube spacing and the liquid film inlet temperature on the breakdown heat flux and heat transfer coefficient were also studied.
The Optimum Dimensions of Circular Fins with Variable Thermal Parameters
Authors: Razelos P. , Imre K.
Published: October 2009

Optimum dimensions of circular fins of trapezoidal profile with variable thermal conductivity and heat transfer coefficients are obtained. Linear variation of the thermal conductivity is considered of the form k = k0(1 + εT/T0), and the heat transfer coefficient is assumed to vary according to a power law with distance from the bore, expressed as h = K[(r − r0)/(r0 − re)]m. The results for m = 0, 0.8, 2.0, and −0.4 ≤ ε ≤ 0.4, have been expressed by suitable nondimensional parameters which are presented graphically. It is shown that considering the thermal conductivity as constant, the optimum base thickness and volume of the fin are inversely proportional to the thermal conductivity of the material of the fin, while the optimum length and effectiveness are independent of the properties of the material used.
Measurements of Heat Transfer and Pressure Drop for an Array of Staggered Plates Aligned Parallel to an Air Flow
Authors: Sparrow E. M. , Hajiloo A.
Published: October 2009

The heat transfer and pressure drop characteristics of an array of staggered plates, aligned parallel to the direction of a forced convection air flow, have been studied experimentally. During the course of the experiments, the plate thickness and Reynolds number were varied parametrically. Mass transfer measurements employing the naphthalene sublimation technique were made to obtain the heat transfer results via the heat-mass transfer analogy. For a given operating condition, the per-plate heat transfer coefficients were found to be the same for the second and all subsequent rows. The fully developed heat transfer coefficients increase with Reynolds number for all the plate thicknesses investigated, but in a different manner for the different thicknesses. In general, thicker plates give rise to higher heat transfer coefficients, especially at the larger Reynolds numbers. The measured friction factors also increase with plate thickness. For the thickest plates, the friction factor was found to be independent of the Reynolds number, signalling the dominance of inertial losses.
The Nature of Nucleation Site Interaction
Authors: Judd R. L. , Lavdas C. H.
Published: October 2009

Bubble emission at a nucleation site is capable of either initiating or terminating bubble emission at an adjacent nucleation site. The former ensues from the creation of a nucleus by a bubble which covers a potentially active nucleation site with its dry spot whereas the latter ensues from interference between a bubble and the nucleus standing at an active nucleation site. Photographic evidence of both these occurrences is presented. Site interaction is at least partly responsible for overlapping of areas of influence surrounding the nucleation sites; the extent of the influence exerted by the emission of bubbles at an active nucleation site is presented herein.
Measurement of Vapor Superheat in Post-Critical-Heat-Flux Boiling
Authors: Nijhawan S. , Chen J. C. , Sundaram R. K. , London E. J.
Published: October 2009

A differentially-aspirated superheat probe was developed to measure vapor temperatures in post-critical-heat-flux, dispersed-flow boiling. Measurements obtained for water, at low-to-moderate pressures and mass flow rates in a tube, indicated very significant non-equilibrium, with vapor superheats of several hundred degrees (°C). Predictions of published correlations showed unsatisfactory agreement with the experimental results.
Experiments on Transient Condensing Flow through a Porous Medium
Authors: Nilson R. H. , Montoya P. C.
Published: October 2009

A cold, initially-dry column of sand receives a sudden inflow of dry saturated Freon vapor (CCl3F) from a high-pressure high-temperature reservoir. Condensation occurs as the hot vapor penetrates into the cold sand, resulting in a co-current liquid/vapor flow. The axial distribution of condensate is wave-like with a (Buckley/Leverett-type) saturation-jump on the leading edge. Temperature and pressure profiles are in good agreement with a simple integral analysis which includes the essential features of the process: vapor-phase mass transfer, fluid/solid energy transfer by condensation, and liquid-phase flooding of the pore volume. The reported ensemble of experiments confirms the theoretical model over a broad range of saturation (from nearly dry to liquid-full) and over a broad range of Reynolds number (from Darcy flow to inertia-dominated flow). The considered problem is exemplary of the phase-change flows which occur in a number of geologic applications: containment of underground nuclear tests, steam stimulation of oil fields, geothermal energy, and in situ combustion processes.
Transient and Frequency Response Characteristics of Two-Phase Condensing Flows: With and without Compressibility
Authors: Bhatt B. L. , Wedekind G. L.
Published: October 2009

In a tube-type condenser, involving complete condensation, small changes in the inlet vapor flowrate momentarily cause very large transient surges in the outlet liquid flowrate. Experimental data are presented which indicate that compressibility effects tend to attenuate the amplitude of these flow surges. The system mean void fraction model was extended to include compressibility effects and its predictions are shown to agree well with experimental data. The model is further extended to predict the response characteristics to an oscillatory inlet flowrate and compared with predictions based upon the drift-flux model.
An Analysis of Heat Transfer to Axial Dispersed Flow between Rod Bundles under Reactor Emergency Cooling Conditions
Authors: Wong S. , Hochreiter L. E.
Published: October 2009

Analysis is carried out for dispersed flow heat transfer under reactor emergency cooling conditions. The present formulation explicitly reveals an extra dependence of the heat transfer coefficient and Nusselt number on the mean vapor temperature for droplet dispersed flow which is not found in single phase flow heat transfer. The heat transfer results obtained from three different geometries—an infinite square array of cylindrical rods, an annulus and a circular pipe—are compared; all have the same hydraulic diameter. It is found that, within the framework of the present analysis, results for the annulus and the rod bundles agree well when the pitch-to-diameter ratio is 1.5 or greater. The circular pipe is in general a poor approximation for rod bundle geometries except at a pitch-to-diameter ratio of about 1.3 which is typical of present day light water reactor fuel assemblies.
Heat Transfer from a Flat Plate in Two-Component Mist Flow
Authors: Hishida K. , Maeda M. , Ikai S.
Published: October 2009

An experimental study concerning the characteristics of heat transfer from a dry isothermal flat plate in two-component (water-air) mist flow has been performed for lower water-air mass flow ratios up to 2.3 percent. Heat transfer coefficients in mist flow increase several times corresponding to single phase coefficients with increasing mass flow ratio and free stream velocity, and with decreasing wall temperature. The measurements of droplet velocity employing laser Doppler anemometry indicate the similarity of velocity distributions in boundary layer of mist flow, which approximately fit the laminar single phase one. It is confirmed that an augmentation of heat transfer is attributable to a latent heat due to evaporation of water droplets within the boundary layer, and that, at a constant Reynolds number and wall temperature, the enhanced rates of heat transfer coefficients are linearly correlated to water mass flow rates for unit cross-sectional area.
Heat Transfer to Curved Surfaces from Heat Generating Pools
Authors: Gabor J. D. , Baker L. , Cassulo J. C. , Erskine D. J. , Warner J. G.
Published: October 2009

Experiments were conducted on heat transfer from internally heated ZnSO4-H2O pools to curved surfaces. These experiments extended existing data for nonboiling pools to higher Rayleigh numbers. The data for convective downward heat transfer from nonboiling pools to a curved surface were reasonably close to the Mayinger correlation extrapolated to higher Rayleigh numbers and lower ratios of pool depth to radius of curvature. Sideward heat transfer to a surface could be described by Nu = 0.7 Ra0.2. Insulating the upper pool surface from the atmosphere had no effect on either sideward or downward heat transfer. An investigation was also made on effects of curvature on heat transfer from boiling pools. Nusselt numbers for sideward heat transfer were proportional to a boiling Reynolds number based on superficial vapor velocity to the 0.275 power and quite close to the correlation for a pool with flat vertical walls. Downward boiling heat transfer to a curved surface was proportional to the Reynolds number to the 0.1 power.
A Numerical Investigation of Thermal Convection in a Heat-Generating Fluid Layer
Authors: Emara A. A. , Kulacki F. A.
Published: October 2009

Finite difference solutions of the equations governing thermal convection driven by uniform volumetric energy sources are presented for two-dimensional flows in a rectangular domain. The boundary conditions are a rigid, (i.e., zero slip), zero heat-flux lower surface, rigid adiabatic sides, and either a rigid or free (i.e., zero shear) isothermal upper surface. Computations are carried out for Prandtl numbers from 0.05 to 20 and Rayleigh numbers from 5 × 104 to 5 × 108. Nusselt numbers and average temperature profiles within the layer are in good agreement with experimental data for rigid-rigid boundaries. For rigid-free boundaries, Nusselt numbers are larger than in the former case. The structure of the flow and temperature fields in both cases is dominated by rolls, except at larger Rayleigh numbers where large-scale eddy transport occurs. Generally, low velocity upflows over broad regions of the layer are balanced by higher velocity downflows when the flow exhibits a cellular structure. The hydrodynamic constraint at the upper surface and the Prandtl number are found to influence only the detailed nature of flow and temperature fields. No truly steady velocity and temperature fields are found despite the fact that average Nusselt numbers reach steady values.
Effects of Water Temperature and Salt Concentration on the Characteristics of Horizontal Buoyant Submerged Jets
Authors: Riester J. B. , Bajura R. A. , Schwartz S. H.
Published: October 2009

This paper summarizes the results of an analytical/experimental study of submerged buoyant fresh water and salt water jets injected horizontally into a quiescent, unstratified reservoir. Fresh water jets of a fixed exit Froude number penetrated to a greater horizontal distance before surfacing as the temperature of the reservoir was lowered. The overall flow characteristics were markedly affected by changes in the reservoir temperature, but were only slightly dependent upon the jet exit temperature for a given reservoir. Salt water jets of a fixed exit Froude number penetrated shorter horizontal distances into the reservoir as the salt concentration was increased. An analytical model was developed for fresh water jets which includes the effect of temperature on the thermal expansion coefficient and the effective buoyancy of the jet. The model successfully predicts the observed temperature dependence in the experiments and is applicable to salt water jets at low concentration levels. A correlation is proposed to minimize the effect of the reservoir temperature on the jet trajectory. The dependence of the flow characteristics on temperature and salt concentration is shown to be a significant factor contributing to the wide discrepancy in the data reported by previous investigators.
Laminar Heat Transfer in an Externally Finned Circular Tube
Authors: Sparrow E. M. , Charmchi M.
Published: October 2009

An analysis has been carried out for laminar heat transfer in a circular tube subjected to an axially periodic variation of the external heat transfer coefficient (or of its dimensionless counterpart, the Biot number). This thermal boundary condition serves to model flow in a tube fitted with a regularly spaced array of annular fins. It was found from numerical solutions that external finning yields substantial heat transfer enhancement compared with an unfinned tube, especially when the Biot number of the unfinned tube is low. The degree of enhancement is quite insensitive to the period of the Biot number variation provided that the overall proportions of the unfinned and finned surface are maintained and the Biot number level is also maintained. An increase in the interfin spacing tends to diminish the enhancement. A constant-Biot-number model intended to approximate the heat transfer results for the periodic-Biot-number case was devised and tested. The predictions of this simplified model are especially accurate at low Biot numbers. The results of the laminar flow analysis have suggested ways of modeling turbulent heat transfer in externally finned tubes.
A Study of Heat Transfer in a Rotating Cylindrical Tube
Authors: Woods J. L. , Morris W. D.
Published: October 2009

The paper reports the results of a numerical solution for laminar fluid flow and heat transfer in the developed region of a tube rotating about a parallel axis. The results cover a wide range of Prandtl number and the eccentricity and Coriolis effects are included in the solution. By transforming the variables in the governing equations, it is shown that the Rayleigh and Reynolds numbers only occur as the product Ra Re, and at large Prandtl number an asymptotic solution is defined by the product Ra Re Pr and the eccentricity alone. The numerical solution of the full governing equations confirms this and indicates that for sufficiently large radius of rotation Nu = f(Ra Re Pr) is a good approximation over a wide range of Prandtl number. The Fanning friction factor is better described by Gr Re. The solution is compared with other analyses and experimental data for air, water, and glycerol.