bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual Satisfaction in Men with Erectile Dysfunction: Correlates and Potential Predictors
Authors: Althof Stanley E. , Buvat Jacques , Gutkin Stephen W. , Belger Mark , Stothard Diane R. , Fugl-Meyer Axel R.
Published: October 2009

Introduction

Sexual satisfaction is an important treatment objective for men with erectile dysfunction (ED).

Aims

To evaluate potential associations between International Index of Erectile Function (IIEF) satisfaction at study endpoint and a range of baseline, on-treatment, and endpoint variables.

Methods

An exploratory analysis was conducted involving 3,935 subjects with ED randomized to on-demand tadalafil (N=2,824) or placebo (N=1,111) in randomized, controlled trials across 28 countries. Patients achieving scores ≥16 on IIEF questions 7, 8, 13, and 14 at study endpoint were operationally defined as satisfied (vs. <16, not satisfied). Multivariate logistic regression and other analyses were conducted to ascertain correlates and potential predictors of improvements in the IIEF-erectile function domain (IIEF-EF).

Main Outcome Measures

Satisfaction on the IIEF at study endpoint, on-treatment improvements in IIEF-EF, and endpoint sexual frequency.

Results

Patients who were satisfied with sexual function were on average younger and had less severe ED, a shorter history of the condition, and no history of vascular disorders, hypertension, or diabetes mellitus/insulin use at baseline (P <0.01 vs. not satisfied for each). Satisfied patients were also more likely to experience a ≥4-point increase on the IIEF-EF domain on treatment (adjusted odds ratio [OR]=22.4; 95% CI=17.6–28.5; P <0.0001) or IIEF-EF ≥26 at endpoint (adjusted OR=41.0; 95% CI=33.6–50.2; P <0.0001). Satisfaction emerged as a strong correlate of a ≥4-point increase in the IIEF-EF on treatment; however, as a correlate of endpoint sexual frequency, baseline sexual frequency was stronger than endpoint satisfaction.

Conclusions

Satisfaction is associated with certain baseline, on-treatment, and endpoint variables in ED patients. Further studies are needed to confirm these preliminary findings and explore their meaning for female partners.
Impact of Vacuum Cooking Process on the Texture Degradation of Selected Apple Cultivars
Authors: Bourles E. , Mehinagic E. , Courthaudon J.L. , Jourjon F.
Published: October 2009

ABSTRACT:  Thermal treatments are known to affect the textural properties of fruits and vegetables. This study was conducted to evaluate the influence of vacuum cooking process on the mechanical properties of various apple cultivars. A total of 10 apple cultivars were industrially processed by vacuum pasteurization at 95 °C for 25 min. The raw material was characterized by penetrometry, uniaxial double compression, soluble solid content, and titrable acidity. Textural properties of processed apples were analyzed by uniaxial double compression. As expected, for all cultivars, fruit resistance was lower after processing than before. Results showed that texture degradation due to vacuum pasteurization was different from one cultivar to another. Indeed, some cultivars, initially considered as the most resistant ones, such as Braeburn, were less suitable for processing, and became softer than others after thermal treatment. Consequently, it is worth noting that the texture classification of the investigated apple cultivars was changed by the vacuum‐cooking process.
Synchronous Front‐Face Fluorescence Spectroscopy Coupled with Parallel Factors (PARAFAC) Analysis to Study the Effects of Cooking Time on Meat
Authors: Sahar Amna , Boubellouta Tahar , Portanguen Stéphane , Kondjoyan Alain , Dufour Éric
Published: October 2009

ABSTRACT:  In this study, the potential of synchronous front‐face fluorescence coupled with chemometrics has been investigated for the analysis of cooked meat. Bovine meat samples (thin slices of 5 cm diameter) taken from Longissimus dorsi muscle were cooked at 237 °C for 0, 1, 2, 5, 7, and 10 min under control conditions. Synchronous front‐face fluorescence spectra were collected on meat samples in the excitation wavelength range of 250 to 550 nm using offsets (Δλ) of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, and 160 nm between excitation and emission wavelengths. The synchronous fluorescence landscape containing 360 spectra was analyzed using PARAFAC. The best PARAFAC model presented 2 components since core consistency values for the first 2 components were 100% and the explained variance was 67.98%. The loading profiles of 1st and 2nd components had an optimal Δλ of 70 and 40 nm, respectively, allowing to determine the excitation (exc.) and emission (em.) maxima wavelengths of 1st (fluorescence band at about exc.: 340 to 400/em.: 410 to 470 nm, and peak at exc.: 468/em.: 538 nm) and 2nd (exc.: 294 nm/em.: 334 nm) components. As the loading profile of the 1st component of PARAFAC was assigned to Maillard‐reaction products formed during cooking, the profile of the 2nd component corresponded with the fluorescence characteristics of tryptophan residues in proteins. Loadings and scores of the PARAFAC model developed from the synchronous fluorescence spectra enabled to get information regarding the changes occurring in meat fluorophores during cooking of meat at 237 °C from 0 to 10 min.
Effect of Organic Acids and Plant Extracts on Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium in Broth Culture Model and Chicken Meat Systems
Authors: Over K.F. , Hettiarachchy N. , Johnson M.G. , Davis B.
Published: October 2009

ABSTRACT: Foodborne illness due to consumption of products contaminated with Salmonella Typhimurium (S.T.), Listeria monocytogenes (L.m.), and Escherichia coli O157:H7 (E.c.) results in many deaths and significant economic losses each year. In this study, acetic (AA), citric acid (CA), lactic acid (LA), malic acid (MA), and tartaric acid (TA) and grape seed (GS), green tea (GT), bitter melon seed (BMS), rasum, and fenugreek (FG) extracts were investigated as inhibitors against S.T., L.m., and E.c. in both broth‐culture and meat systems. Brain Heart Infusion solutions containing 18.7, 37.5, and 75.0 mM organic acids and 5, 10, 20, and 40 mg/mL extracts were challenged with approximately log 6 CFU/mL S.T., L.m., and E.c. A pH‐adjusted control was included to determine pH effect on exhibited antibacterial activity. For the meat system, 1 to 2 g chicken breast pieces were vacuum‐infused with CA/MA/TA acid at 75 and 150 mM and GS and GT at 3000, 6000, and 9000 ppm in a partial factorial arrangement. GT and GS showed considerable activity in broth‐culture. All organic acids were effective in broth‐culture at 75 mM after 24 h (P < 0.05). CA and TA were effective at 37.5 mM. CA/MA/TA at 150.0 mM were the most effective in the meat system, reducing E.c., L.m. and S.T. by >5, >2, and 4‐6 log CFU/g, respectively, although all organic acids showed some antibacterial activity at 75.0 and 150.0 mM. These findings demonstrate the effectiveness of organic acids and plant extracts in the control of S.T., L.m., and E.c. O157:H7.
Effect of Salt, Smoke Compound, and Temperature on the Survival of Listeria monocytogenes in Salmon during Simulated Smoking Processes
Authors: Hwang Cheng‐An , Sheen Shiowshuh , Juneja Vijay K.
Published: October 2009

ABSTRACT:  The objectives of this study were to examine and develop a model to describe the survival of Listeria monocytogenes in salmon as affected by salt, smoke compound (phenol), and smoking process temperature. Cooked minced salmon containing selected levels of salt (0%, 2%, 4%, and 6%) and smoke compound (0, 5, 10, and 15 ppm phenol) were inoculated with a 6‐strain mixture of L. monocytogenes to an inoculum level of 6.0 log10 CFU/g. The populations of L. monocytogenes in salmon during processing at 40, 45, 50, and 55 °C that simulated cold‐ and hot‐smoking process temperatures were determined, and the effects of salt, phenol, and temperature on the survival of L. monocytogenes in salmon were analyzed and described with an exponential regression. At 40 °C, the populations of L. monocytogenes in salmon decreased slightly with inactivation rates of <0.01 log10 CFU/h, and at 45, 50, and 55 °C, the inactivation rates were 0.01 to 0.03, 0.15 to 0.30, and 2.8 to 3.5 log10 CFU/h, respectively. An exponential regression model was developed and was shown to closely describe the inactivation rates of L. monocytogenes as affected by the individual and combined effects of salt, phenol, and smoking process temperature. Temperature was the main effector in inactivating L. monocytogenes while salt and phenol contributed additional inactivation effects. This study demonstrated the inactivation effects of salt, smoke compound, and temperature on L. monocytogenes in salmon under a smoking process. The data and model can be used by manufacturers of smoked seafood to select concentrations of salt and smoke compound and alternative smoking process temperatures at 40 to 55 °C to minimize the presence of L. monocytogenes in smoked seafood.
Natural Convection Heat Transfer Between Cylindrical Tube Bundles and a Cubical Enclosure
Authors: Warrington R. O. , Crupper Gordon
Published: October 2009

Natural convection heat transfer from a fixed array of four isothermal, heated cylinders to an isothermal, cooled cubical enclosure was experimentally investigated for both a horizontal and vertical position of the array. Included in this study are heat transfer, flow visualization, and temperature profile results for Prandtl numbers in the range of .7 to 3.1 × 104 and Rayleigh numbers, based on gap width, in the range of 6.3 × 105 to 6.9 × 108. Several geometric effects were observed. The vertical configuration convected less heat than the horizontal while a rotation about the vertical axis for each of these configurations had negligible effect on the overall heat transfer. The heat transfer results were correlated and compared with previous enclosure results. The heat transfer correlations fit the data with an average deviation of less than 10 percent.
A Study of Some Turbulence Models for Flow and Heat Transfer in Ducts of Annular Cross-Section
Authors: Malik Mujeeb R. , Pletcher R. H.
Published: October 2009

A variable property finite-difference calculation procedure is used to predict turbulent flow and heat transfer parameters in annular passages. Predictions from several turbulence models are compared with measurements over a range of flow and thermal conditions. Of the models considered, one utilizing transport equations for turbulence kinetic energy and characteristic mixing length scale gave the best overall performance. The inclusion of turbulence kinetic energy in the turbulence modeling was found not to be crucial for predicting isothermal flows or for predicting all parameters except the temperature distribution for flows with heat transfer at Reynold numbers greater than 110,000.
Perturbation Solutions of Transient Heat Transfer to a Porous Medium from a Fluid Stream
Authors: Lu P.-C.
Published: October 2009

Asymptotic behavior of the two-phase, thermal response of a porous medium, with a fluid throughflow, to a sudden change of the oncoming stream temperature is examined via four cases of perturbation solutions: (1) massive blowing, fast interphase (thermal) link, small conductivity, and small (thermal) interaction at the entrance, (2) moderate blowing, and fast interphase link, (3) massive blowing, moderate interphase link, and small interaction at the entrance, and (4) small conductivity, as well as weak interphase link. Schumann’s classical, two-phase, and non-diffusive model is shown to be just the outer limit of Case (1). The “single-phase model” is derived. Associated boundary layers are displayed. Certain numerical trend reported in the literature is also explained.
Correlation of Pressure Undershoot During Hot-Water Depressurization
Authors: Alamgir Md. , Lienhard J. H.
Published: October 2009

A method is devised for correlating the extent that the pressure of a system undershoots the saturation pressure during a rapid depressurization in water. The dependent variables in the correlation are the initial water temperature and the depressurization rate. The correlation is motivated by classical nucleation theory, and based on data from a variety of sources. The probable error of pressure undershoots predicted by the correlation is ±10.4 percent.
Prediction of Transient Inception of Boiling in Terms of a Heterogeneous Nucleation Theory
Authors: Nghiem L. , Merte H. , Winter E. R. F. , Beer H.
Published: October 2009

Transient boiling in water and Freon 113 with various heater surfaces was investigated experimentally with step power inputs. It was observed that the inception or onset of boiling depends not only on the temperature, but is time dependent as well. This dependence can be explained in terms of a heterogeneous nucleation theory based on the homogeneous nucleation theory. The influence of the heater surface was accounted for by a nucleation factor which is liquid-specific. With this factor and one experimental value of inception for a given system, the time dependence of inception temperature can be computed.
The Transition from Natural-Convection-Controlled Freezing to Conduction-Controlled Freezing
Authors: Sparrow E. M. , Ramsey J. W. , Harris J. S.
Published: October 2009

Experiments were performed to study the transition between freezing controlled by natural convection in the liquid adjacent to a freezing interface and freezing controlled by heat conduction in the solidified material. The freezing took place on a cooled vertical tube immersed in an initially superheated liquid contained in an adiabatic-walled vessel. At early and intermediate times, temperature differences throughout the liquid induce a vigorous natural convection motion which retards freezing, but the temperature differences diminish with time and natural convection ebbs. At large times, the freezing rate is fully controlled by heat conduction in the solidified material. The frozen specimens for short and intermediate freezing times are smooth-surfaced and tapered, while those for large times are straight-sided and have surfaces that are overlaid with a thicket of large discrete crystals. These characteristics correspond respectively to those of natural-convection-controlled freezing and conduction-controlled freezing. At early times, the measured mass of the frozen material is identical to that for natural-convection-controlled freezing. At later times, the frozen mass tends to approach that for conduction-controlled freezing, but a residual deficit remains.
Droplet Evaporation in High Temperature Environments
Authors: Harpole G. M.
Published: October 2009

Axisymmetric-stagnation-point convective heat and mass transfer solutions are presented for water evaporating into dry air and into pure steam for free stream temperatures from 373K to 1450K and radiative to convective heat flux ratios from 0 to 2. Effects of (1) blowing (evaporation), (2) variable fluid properties, (3) interdiffusion (binary diffusion with nonequal heat capacities), and (4) radiation are all included. A simple correlation which fits these stagnation point solutions within 3 percent is presented. Whole droplet heat transfer is shown to behave much like stagnation-point heat transfer when the Reynolds number is on the order of 100. Blowing and other high temperature effects on whole droplet heat and mass transfer can be estimated with stagnation point solutions. The ratio of stagnation point solutions with and without high temperature effects should multiply no-blowing constant-fluid-properties whole-droplet heat transfer correlations as a correction factor. Such a corrected whole-droplet correlation compares favorably with experimental data in the literature.
Optimized Performance of Condensers with Outside Condensing Surfaces
Authors: Mori Y. , Hijikata K. , Hirasawa S. , Nakayama W.
Published: October 2009

The purpose of this paper is to find an optimum surface geometry of vertical condenser tubes where condensation takes place on the outer surfaces. The guiding principle on optimum condensation performance is to make the thickness of condensate liquid on the surfaces as thin as possible. A vertical tube with longitudinally parallel tiny fins is preferable because condensate is made thinner over the widest possible region. According to an analysis, there are four controlling factors for the optimum fin; sharp leading edge, gradually changing curvature of fin surface from tip to the root, wide groove between fins to collect condensate and horizontal discs attached to the tube to remove condensate. The analytical result is checked by experiments using R-113. The optimum fin shape, fin pitch and spacing of discs are found by numerical calculations for R-113 and water.
A Natural Convection Fin with a Solution-Determined Nonmonotonically Varying Heat Transfer Coefficient
Authors: Sparrow E. M. , Acharya S.
Published: October 2009

A conjugate conduction-convection analysis has been made for a vertical plate fin which exchanges heat with its fluid environment by natural convection. The analysis is based on a first-principles approach whereby the heat conduction equation for the fin is solved simultaneously with the conservation equations for mass, momentum, and energy in the fluid boundary layer adjacent to the fin. The natural convection heat transfer coefficient is not specified in advance but is one of the results of the numerical solutions. For a wide range of operating conditions, the local heat transfer coefficients were found not to decrease monotonically in the flow direction, as is usual. Rather, the coefficient decreased at first, attained a minimum, and then increased with increasing downstream distance. This behavior was attributed to an enhanced buoyancy resulting from an increase in the wall-to-fluid temperature difference along the streamwise direction. To supplement the first-principles analysis, results were also obtained from a simple adaptation of the conventional fin model.
A Numerical Study of Laminar Natural Convection in Shallow Cavities
Authors: Shiralkar G. S. , Tien C. L.
Published: October 2009

Heat transfer by natural convection in a horizontal cavity with adiabatic horizontal walls and isothermal side walls is investigated numerically for high aspect ratios (width/height). Comparison is made with existing analytical and experimental results. Agreement is generally good at moderate and high Prandtl numbers to which most previous works have been restricted. Improvements of the existing correlation have been proposed in regions of discrepancy. Extension to the low Prandtl number case, including the range of liquid metals, has been made on the basis of an analytical model for high Rayleigh numbers as well as by numerical solution of the full equations. The agreement between the two is found to be very good. A correlation for the heat transfer is proposed for each of the two different cases of high and low Prandtl number.
Analysis of Transient Three-Dimensional Natural Convection in Porous Media
Authors: Chan Y. T. , Banerjee S.
Published: October 2009

Transient multidimensional natural convection in porous media has been studied using a numerical method based on the simplified marker and cell technique with local cancellation of low order, diffusional truncation errors. The conservation equations and boundary conditions were phrased in terms of the primitive variables, velocity and temperature. Differences in temperature between the fluid and the solid matrix are considered. Heat transfer between the solid and liquid phases was modelled by representing the porous medium as an assemblage of spherical particles, and solving the conduction problem within the spheres at every time step. Nusselt numbers at walls were calculated from the temperature and velocity profiles. Numerical results for heat transfer through fluid saturated porous media heated from below are in good agreement with published experiments. Consideration of heat transfer between the solid and fluid phase leads to Nusselt numbers that vary with the thermophysical properties of the solid material, even when the Rayleigh number and fluid thermophysical properties are kept constant. This is also observed in experiments. The calculations also show convective instabilities of the right period at high Rayleigh numbers.
An Interferometric Study of Combined Free and Forced Convection in a Horizontal Isothermal Tube
Authors: Yousef W. W. , Tarasuk J. D.
Published: October 2009

A Mach-Zehnder interferometer was employed to determine the three-dimensional temperature field, and the circumferential and average Nusselt numbers for laminar flow of air in the entrance region of an isothermal horizontal tube where the velocity and the temperature profiles were developing simultaneously. The influence of free convection due to buoyancy on forced convection heat transfer was investigated. The Reynolds numbers ranged from 120 to 1200, the Grashof numbers ranged from 0.8 × 104 to 8.7 × 104, and the ratio L/D was varied from 6 to 46. The free convection increases, substantially, the average Nusselt number, by up to a factor of 2.0 from the analytical predictions, which account for forced convection only, near the tube inlet. Far from the tube inlet the free convection tends to decrease the average Nusselt number below the analytical predictions.
Experimental Study of Countercurrent Steam Condensation
Authors: Segev A. , Flanigan L. J. , Kurth R. E. , Collier R. P.
Published: October 2009

An experimental study of steam condensation on subcooled liquid films in countercurrent flow has been conducted in a small inclined test apparatus having a rectangular cross-section. Condensation heat transfer coefficients were determined and the dependence on steam and water flow rates, the degree of subcooling, and test section inclination were all studied. The results were correlated in terms of local parameters for the complete penetration and bypass regions. It was found that the local Nusselt number increases with steam and liquid Reynolds numbers and liquid Prandtl number when no bypass occurs. In the bypass region the Nusselt number drops sharply due to the strong effects of the reduced liquid film flow rate. It is shown that the local heat transfer coefficient may be related to the turbulence intensity in the liquid film which suggests that a general turbulence-centered model can be constructed.
A Radioisotope Method for Interfacial Area Measurements in Two-Component Systems
Authors: Banerjee S. , Khachadour A.
Published: October 2009

A technique for measuring interfacial area in two-component two-phase flows, based on the transmission of short-range beta or alpha particles across interfaces is proposed. One of the phases contains the radioisotope source, whereas the other contains scintillating material. For short-range particles, it was hypothesized that the number crossing interfaces would originate from very thin layers that are immediately adjacent, and therefore, would lead to a scintillation rate directly proportional to the interfacial area and radioisotope concentration. A series of experiments to check this hypothesis was done with solid-liquid and liquid-liquid systems of known interfacial area. It was found that the scintillation count rate was independent of the orientation of the interfaces and directly proportional to their area. The count rate was also essentially independent of thicknesses of the radioisotope-bearing fluid and the solid scintillating material. However, when a liquid scintillator was used the count rate was found to increase slowly with the scintillator thickness. If this problem can be resolved, it should be possible to measure interfacial area in two-phase systems by this method.
Streamwise Flow and Heat Transfer Distributions for Jet Array Impingement with Crossflow
Authors: Florschuetz L. W. , Truman C. R. , Metzger D. E.
Published: October 2009

Two-dimensional arrays of circular jets of air impinging on a heat transfer surface parallel to the jet orifice plate are considered. The air, after impingement, is constrained to exit in a single direction along the channel formed by the surface and the jet plate. The downstream jets are subjected to a crossflow originating from the upstream jets. Experimental and theoretical results obtained for streamwise distributions of jet and crossflow velocities are presented and compared. Measured Nusselt numbers resolved to one streamwise hole spacing are correlated with individual spanwise row jet Reynolds numbers and crossflow-to-jet velocity ratios. Correlations are presented for both inline and staggered hole patterns including effects of geometric parameters: streamwise hole spacing, spanwise hole spacing, and channel height, normalized by hole diameter. The physical mechanisms influencing heat transfer coefficients as a function of flow distribution and geometric parameters are also discussed.
Pioneering Contributions to Our Knowledge of Convective Heat Transfer: One Hundred Years of Heat Transfer Research
Authors: Eckert E. R. G.
Published: October 2009

This paper describes the development of our knowledge of heat transfer during the past 100 years. The foundations to a systematic and coherent body of knowledge were laid in 1880–1930. The contributions were applied to a variety of situations as they were encountered in new technical developments in 1930–1980.
Effects of Axial Conduction and Convective Boundary Conditions in Slug Flow inside a Circular Tube
Authors: Vick B. , O¨zis¸ik M. N.
Published: October 2009

An exact solution is presented for the temperature distribution and the local Nusselt number in slug flow of a low Pe´cle´t number fluid inside an infinitely long tube by including in the analysis the axial conduction in the fluid and convection from the walls for both the upstream and downstream regions. It is shown that the Pe´cle´t number and the relative magnitudes of the upstream and downstream Biot numbers significantly effect the local Nusselt number and the wall and mean fluid temperatures in the thermal entrance region. A particularly interesting result of the present investigation is the crossover of the wall and the mean fluid temperatures in such a manner as to give rise to a negative Nusselt number in the thermal entry region. Depending on the Pe´cle´t number and the relative magnitudes of the upstream and downstream Biot numbers, the negative Nusselt number can occur in the upstream or downstream region.
Boiling Burnout During Crossflow over Cylinders, beyond the Influence of Gravity
Authors: Hasan M. Z. , Hasan M. M. , Eichhorn R. , Lienhard J. H.
Published: October 2009

New observations of burnout during the upflow and downflow of isopropanol and methanol over horizontal cylinders are added to previous observations. A criterion is developed to determine whether or not gravity influences burnout in any such flow. A prediction that depends on one empirical constant is then developed to predict burnout when gravity is not influential. Those of the existing data that are uninfluenced by gravity are represented within ± 20 percent by the prediction. It is also shown that a low-speed downflow can cause the hydrodynamic burnout to be replaced with a very inefficient buoyancy burnout mechanism.
Mixed Convection Heat Transfer from Horizontal Cylinders in the Crossflow of a Finite Water Layer
Authors: Bennon W. D. , Incropera F. P.
Published: October 2009

Heat transfer measurements and flow visualization studies have been performed for a single horizontal cylinder, a single row of six horizontal cylinders, and two rows of 13 horizontal cylinders submerged in an open channel flow. Regimes associated with free convection, combined convection, and forced convection have been delineated, and the effects of finite boundaries have been resolved. For a restricted set of space ratios, correlations of heat transfer data have been developed for the combined convection regime.
Developing Laminar Free Convection in an Open Ended Vertical Annulus with a Rotating Inner Cylinder
Authors: El-Shaarawi M. A. I. , Sarhan A.
Published: October 2009

A finite-difference scheme is developed for solving the boundary layer equations governing the laminar free convection flow in open ended vertical concentric annuli with rotating inner walls. Numerical results are presented for a fluid of Pr = 0.7 in an annulus of radius ratio 0.5 under the thermal boundary conditions of one wall being isothermal and the opposite wall adiabatic. Comparing the present results for the development of δθ (tangential boundary layer displacement thickness) with those corresponding results of forced flows shows that heating the inner cylinder has always stabilizing effects while heating the outer cylinder has either destabilizing or stabilizing effects.
Reference Temperatures for Supercritical Laminar Free Convection on a Vertical Flat Plate
Authors: Ghajar A. J. , Parker J. D.
Published: October 2009

A reference temperature method was developed by which heat transfer to fluids in the supercritical region under variable property conditions in laminar free convection on a vertical flat plate can be readily evaluated. Based on this method three generalized plots for Refrigerant-114, water, and carbon dioxide were developed. The results obtained with the reference temperature scheme showed good agreement with the existing experimental data and theoretical results for these three variable property fluids.
Experimental and Analytical Investigation of a Natural Circulation System with Parallel Loops
Authors: Zvirin Y. , Jeuck P. R. , Sullivan C. W. , Duffey R. B.
Published: October 2009

A theoretical and experimental study of a natural circulation loop is presented. The analysis is based on a one-dimensional model in which the continuity, momentum, and energy equations are given and solved. Expressions for the steady-state and transient flow rates and temperature distributions are derived. The apparatus consisted of an electrically-heated section and two parallel loops with heat exchangers. Steady-state and transient experiments were conducted to study the effects of core flow resistance, power distribution and upper plenum design. Flow oscillations were observed under certain conditions, which were accompanied by instabilities and flow reversals. Reasonable agreement (±30 percent) is obtained between the analytical and experimental results.
Critical Heat Flux in Helically Coiled Tubes
Authors: Jensen M. K. , Bergles A. E.
Published: October 2009

A study of boiling R-113 in electrically heated coils of various diameters is reported. Subcooled critical heat flux (CHF) is lower with coils than with straight tubes. The difference increases as mass velocity and ratio of tube diameter to coil diameter (d/D) increases. On the contrary, quality CHF is enhanced and increases with d/D; CHF initially increases with increasing mass velocity, but decreases after a maximum is reached. Operational problems, in particular upstream dryouts, can occur if a coiled tube is operated with low to moderate subcooling near the inlet and with moderately high heat fluxes.
Prediction of Heat Transfer Coefficients in Gas Flow Normal to Finned and Smooth Tube Banks
Authors: Biery J. C.
Published: October 2009

A new method is presented to predict heat transfer coefficients for gas flow normal to smooth and finned tube tanks with triangular pitch. A transformation from the actual tube bank to an equivalent equilateral triangular pitch infinite smooth tube bank (ETP-I-STB) is made. A function of Ch(Ch = NSTNPR2/3NRe0.4) versus (Xt D0)Δ, ratio of transverse pitch to tube diameter for the ETP-I-STB, was developed. The Ch for the equivalent ETP-I-STP then applies to the actual tube bank. The method works with circular finned tubes, smooth tubes, continuous finned tubes, and segmented finned tubes with any triangular pitch. Also, fair predictions were made for in-line tubes with high Reynolds numbers.
Heat Transfer in Cooled Porous Region with Curved Boundary
Authors: Siegel R. , Snyder A.
Published: October 2009

Heat transfer characteristics are analyzed for a cooled two-dimensional porous medium having a curved boundary. A general analytical procedure is given in combination with a numerical conformal mapping method used to transform the porous region into an upper half plane. To illustrate the method, results are evaluated for a cosine shaped boundary subjected to uniform external heating. The results show the effects of coolant starvation in the thick regions of the medium, and the extent that internal heat conduction causes the heated surface to have a more uniform temperature.
An Integral Analysis for Heat Transfer in Turbulent Incompressible Boundary Layer Flow
Authors: Thomas L. C. , Al-Sharif M. M.
Published: October 2009

The integral approach is utilized in this paper to analyze incompressible turbulent thermal boundary layer flow over a flat plate for nonuniform wall heating. This approach involves the use of inner variables and laws for u+ and T+ that apply to the important wall region as well as to the remainder of the flow field. Predictions developed for Stanton number are found to be in excellent agreement with published experimental data for uniform, step, double-step, and linear wall temperature heating of air. The results of this integral analysis compare favorably with those of the traditional numerical approach. Because of its computational efficiency, this integral approach provides a useful supplementary tool for analyzing turbulent thermal boundary layers.
Steady Laminar Flow through Twisted Pipes: Heat Transfer in Square Tubes
Authors: Masliyah J. H. , Nandakumar K.
Published: October 2009

The potential of a twisted square pipe for heat transfer applications is examined. A numerical solution of the energy equation in a rotating frame of reference is used for the analysis. The case of axially uniform wall temperature is considered. The rectilinear nature of the axial velocity profile makes the overall Nusselt number insensitive to changes in Reynolds and Prandtl numbers. However, the swirling motion provides significant enhancement in heat transfer across individual walls. Hence the use of twisted square pipes in a multichannel configuration is proposed.
A Numerical Study of Natural Convection in a Horizontal Porous Layer Subjected to an End-to-End Temperature Difference
Authors: Hickox C. E. , Gartling D. K.
Published: October 2009

A numerical study of steady, natural convection in a fluid-saturated, horizontal, porous layer subjected to an end-to-end temperature difference is reported. The analysis is performed using a finite element computer program based on the Galerkin form of the finite element method. Heat transfer rates are predicted for aspect ratios ranging from 0.1 to 0.5 and Rayleigh numbers in the range 25 to 200. Representative plots of temperature and velocity fields are presented. Comparisons are made with an approximate analytical solution and regions of validity are identified for the analytical solution.
A Simplified Approach to the Evaluation of the Geometric-Mean Transmittance and Absorptance for Gas Enclosures
Authors: Yuen W. W.
Published: October 2009

Utilizing a simple mathematical relation and Stoke’s theorem, the geometric-mean transmittance and total absorptance between an infinitesimal area and a finite planar element is reduced to a line integral around the planar element and an area integral. A concept of fundamental solutions is introduced. These are solutions in which the finite areas are horizontal right triangle with three specific orientations. Based on superposition, solutions for arbitrary finite areas are shown to be readily generated algebraically from these fundamental solutions. The geometric-mean transmittance and total absorptance between two finite areas are reduced to single numerical integrations, thus reducing much of the mathematical complexity. Fundamental solutions for mean beam lengths of the geometric-mean total absorptance in the weak-band, strong-band and very-strong-band limits are generated analytically in closed form. Based on the existing one-dimensional wide band correlation, these limiting expressions are shown to be sufficient for the calculation of the geometric-mean total absorptance at all optical thicknesses. A sample calculation is presented.
High Rayleigh Number Laminar Convection in Low Aspect Ratio Enclosures With Adiabatic Horizontal Walls and Differentially Heated Vertical Walls
Authors: Tichy J. , Gadgil A.
Published: October 2009

Laminar flow in shallow horizontal cavities (aspect ratio a < < 1) at high Rayleigh numbers (> 106) is investigated using an approximate analysis based on first principles, and also with numerical solutions to the full equations. A Prandtl number of approximately one is assumed. It is found that the flow regime at such high values of Ra is characterized by boundary layers lining both vertical as well as horizontal walls of the enclosure, and is qualitatively different from the flow regimes at lower Rayleigh numbers. The internal region of the core (near to the horizontal centerline) exhibits linear velocity and temperature profiles. Typical isotherms and streamlines characteristic of this flow regime are presented, based on the numerical solutions. The velocity and temperature profiles predicted from the approximate analysis are found to compare well with those obtained from the numerically obtained solutions. The Nusselt numbers predicted from the analysis are also in good agreement with the numerical solutions, and with the limited experimental data in the literature. The various physical processes in this type of flow are discussed based on the findings of the analytical and numerical studies.
Temperature Profiles and Aquifer Mass Transfer in a Circulating Well
Authors: Oster C. A. , Scheffler W. A.
Published: October 2009

A method is described for determining the temperature distribution in a circulating drilling fluid when aquifers are present in the formation. The depth of an aquifer relative to the well depth is shown to be an important parameter. An aquifer near the surface has much less influence on the temperature distributions than one located near the bottom of the well. If the drilling fluid has much greater density than the entering formation water, then the temperature distributions are altered significantly.
The Possibility of Multiple Temperature Maxima in Geologic Repositories for Spent Fuel From Nuclear Reactors
Authors: Beyerlein S. W. , Claiborne H. C.
Published: October 2009

Heat transfer studies for CANDU spent fuel repositories showed that two temperature maxima at the source could occur: one at ∼60 and another one at ∼13,000 yrs. Spent fuel from pressurized water reactors (PWRs) did not exhibit this phenomenon. Because CANDU spent fuels display a monotonically decreasing heat generation rate, it is not immediately obvious why such behavior occurs. This paper demonstrates that the “double-peak” phenomenon is due to the presence of the right mixture of short and long-lived nuclides in the fuel and that the second peak does not occur for repository sizes less than ∼1 km2. For larger repositories, radial and surface heat transfer reduces the magnitude of the second peak.
Melting Within a Spherical Enclosure
Authors: Moore F. E. , Bayazitoglu Y.
Published: October 2009

Melting of a phase change material within a spherical enclosure is considered. The phase change material is initially at its saturation temperature. Suddenly the enclosure temperature is increased to a fixed value. The density of the solid is assumed to exceed the density of the liquid, the implication being that the solid continually drops toward the bottom of the shell as melting progresses. This motion of the solid generates a flow field within the liquid. A mathematical model is developed and confirmed by experimental evidence. The interface positions and the temperature profiles for various Stefan and Fourier numbers are determined, and the energy storage characteristics are studied. It is found that the convective effects can be neglected only at small Stefan numbers.
A Simpler Formulation for Radiative View Factors From Spheres to a Class of Axisymmetric Bodies
Authors: Chung B. T. F. , Naraghi M. H. N.
Published: October 2009

A simpler formulation is developed for radiative view factor from a sphere to a class of axisymmetric bodies. The new formulation is semianalytical in nature and only requires a single numerical integration at most.
Scaling Anisotropic Scattering in Radiation Heat Transfer for a Planar Medium
Authors: Lee H. , Buckius R. O.
Published: October 2009

Radiation heat transfer in a planar participating medium which scatters anisotropically is scaled to an isotropically scattering medium. Only isotropic scattering problems need to be solved with a scaled optical depth and albedo. The scaling is derived from approximate solution methods to the equation of transfer. From the P-1 approximation, the two-flux method, and the modified linear anisotropic scattering model, three scalings are derived. The scaling that gives the best results when comparing the scaled solutions to exact solutions is the one derived from the P-1 approximation.
Turbulent Heat Transfer in a Symmetrically or Asymmetrically Heated Flat Rectangular Duct With Flow Separation at Inlet
Authors: Sparrow E. M. , Cur N.
Published: October 2009

Heat transfer experiments were performed for a high-aspect-ratio (∼18) rectangular duct having a sharp-edged inlet, with air being drawn into the inlet from a large upstream space. The experiments encompassed data runs where both of the principal walls of the duct were isothermal (at the same temperature) and other runs where one wall was isothermal while the other was adiabatic. Local heat transfer coefficients were determined for all runs. It was found that flow separation at the duct inlet played a decisive role in shaping the axial distribution of the heat transfer coefficient in the thermal entrance region. Of particular note is a high heat transfer peak at the point of flow reattachment. The peak is situated at an axial station less than one hydraulic diameter from the inlet and moves upstream with increasing Reynolds number. The heat transfer coefficients for symmetric and asymmetric heating are identical in the initial portion of the thermal entrance region. Deviations occur farther downstream but do not exceed more than about 7 percent. The entrance length for asymmetric heating is significantly greater than that for symmetric heating.
The Effect of Molecular Gas Absorption on Radiative Heat Transfer With Scattering
Authors: Buckius R. O.
Published: October 2009

Radiative heat transfer in an isotropically scattering and nongray absorbing planar medium is investigated. General wide-band absorption quantities, including the effects of gray absorption and scattering by the scattering components and nongray absorption by the gaseous components, are considered. Analysis for the reflection, transmission, and emission from isothermal layers is presented. Numerical calculations are presented for the wide-band absorption quantities in the high-pressure limit. The effects of the scattering and absorption properties on the wide band absorption quantities are discussed.
Combined Conductive and Radiative Heat Transfer in an Absorbing, Emitting, and Scattering Cylindrical Medium
Authors: Fernandes R. , Francis J.
Published: October 2009

The purpose of this study was to formulate and solve the problem of transient combined conduction and radiation in a grey absorbing, emitting, and scattering medium of cylindrical geometry. The medium is bounded by grey diffuse surfaces at known temperatures. The problem was solved by the Galerkin finite element method using linear interpolating functions. The transient terms were handled using the Crank-Nicolson scheme with the time steps chosen to avoid temperature fluctuations at early times. The results were compared with exact solutions for the extreme cases, i.e., pure conduction and radiative equilibrium. Results are also compared with an approximate solution for the case of combined conduction and radiation. The effects of various parameters on the solutions are presented in tabular as well as graphical forms. The results obtained compare well with the exact solutions. The Galerkin finite element technique is well suited to this problem because of the ease with which integrals with variable limits can be handled.
Combined Radiation-Convection in Gray Fluids Enclosed in Vertical Cavities
Authors: Lauriat G.
Published: October 2009

The interaction of thermal radiation with natural convection in a gray fluid contained inside a cavity is numerically examined. The radiation part of the problem is treated by using the two-dimensional P-1 approximation. The effect of radiation on the conduction, transition, and boundary layer regimes is investigated. The results show that radiation decreases the intensity of the flow at low Rayleigh numbers and, in contrast, leads to an increased flow in convection regimes. The influence of the radiative parameters on the flow and heat transfer is discussed.
Vortex Instability of Free Convection Flow Over Horizontal and Inclined Surfaces
Authors: Chen T. S. , Tzuoo K. L.
Published: October 2009

The vortex instability characteristics of laminar free convection flow over horizontal and inclined isothermal surfaces are studied analytically by linear theory. As a prelude to the analysis, the effects of the angle of inclination on the main flow and thermal fields are re-examined by a new approach. Numerical results are presented for wall shear stress, surface heat transfer, neutral stability curve, and critical Grashof number for Prandtl numbers of 0.7 and 7 over a wide range of angles of inclination, φ, from the horizontal. It is found that as the angle of inclination increases the rate of surface heat transfer increases, whereas the susceptibility of the flow to the vortex mode of instability decreases. The present study provides new vortex instability results for small angles of inclination (φ≤30 deg) and more accurate results for large angles of inclination (φ ≥ 30 deg) than previous studies. The present results are also compared with available wave instability results.
Numerical Study of the Onset of Double-Diffusive Cellular Convection Due to a Uniform Lateral Heat Flux
Authors: Takao S. , Tsuchiya M. , Narusawa U.
Published: October 2009

When a fluid with a vertical solute gradient of (−dS/dy)0 is heated laterally, roll cells start to form at the boundary, developing into a series of convective layers. Numerical experiments were performed to investigate the onset of the abovementioned double-diffusive convection under the application of a uniform lateral heat flux. The paper reports the results and discussion of the following aspects of the stability of double-diffusive convection; (i) the relationship between the critical value, (Ra/Rs)c, above which convection cells form along the vertical wall and the nondimensional slot width, (d/L), (ii) the effect of the Lewis number on (Ra/Rs)c. It was also confirmed that values of (Ra/Rs)c as well as H/L (the nondimensional vertical size of incipient cells) obtained in this numerical experiment for wide slot widths (d/L>∼30), agreed well with those obtained previously by physical experiments.