bluuebunny/crossref_metadata_2025 huggingface dataset:
Subcutaneous Fat Necrosis of the Newborn: A 20‐Year Retrospective Study
Authors: Del Pozzo‐Magaña Blanca R. , Ho Nhung
Published: August 2016

Subcutaneous fat necrosis of the newborn (SFN) is a rare form of panniculitis that can be complicated by hypercalcemia and nephrocalcinosis. We conducted a 20‐year retrospective cohort study of 30 patients to describe the clinical characteristics of SFN and the prevalence of hypercalcemia and other complications. Hypoxia and therapeutic hypothermia (TH) seem to play an important role in the development of SFN. Hypercalcemia developed in 63% of patients, three of whom developed nephrocalcinosis. There is a need for well‐controlled prospective studies to determine the natural history, prevalence, and incidence of complications of SFN.
Commentary: The “Club” That Uses Nonprofit Accountability Clubs
Authors: Berger Ken
Published: August 2016

Related Content: Tremblay‐Boire, Prakash, and Gugerty (PAR September/October 2016)
Is Open‐mindedness a Moral Virtue?
Authors: Cremaldi Anna , Kwong Jack M. C.
Published: August 2016

Is open‐mindedness a moral virtue? Surprisingly, this question has not received much attention from philosophers. In this paper, we fill this lacuna by arguing that there are good grounds for thinking that it is. In particular, we show that the extant account of open‐mindedness as a moral virtue faces an objection that appears to show that exercising the character trait may not be virtuous. To offset this objection, we argue that a much stronger argument can be made for the case that open‐mindedness is a moral virtue by appealing to the notion of moral understanding. Specifically, we provide a new rationale as to why we should exercise open‐mindedness and offer several arguments to allay the concern that doing so can at times cause us to be in an epistemically and morally weaker position.
Christ's Passion, Christian tragedy and Ioannes Franciscus Quintianus Stoa's untimely Theoandrothanatos
Authors: Leo Russ
Published: August 2016

Ioannes Franciscus Quintianus Stoa's Theoandrothanatos (1508) is perhaps the first work in early modernity to depict Christ's Passion as a tragedy. Despite its claims to originality, however, Theoandrothanatos rarely appears as more than a curio in critical studies of Renaissance drama or theology. When it is considered at more length, both the tragedy and poet himself are generally derided as effete and uninspired, an enduring critical inclination that obscures Quintianus Stoa's importance in the early sixteenth century as well as the scope of his tragic experiment. Placing Quintianus Stoa's Latin tragedy in conversation with theological interlocutors and classical influences, this essay examines the affective vision of tragedy at work in Theoandrothanatos, a version of tragedy which stands at odds with the humanist textual tradition emerging at the outset of the sixteenth century. Although he shares an interest in antique tragedy with those humanists, Quintianus Stoa endorses an approach to tragedy that quickly falls out of fashion, particularly once sophisticated editions, translations, and textual studies of antique tragedies became widely available. Moreover, an emergent tradition of Christian tragedy defined itself in opposition to Theoandrothanatos — particularly Nicolas Barthélemy de Loches's Christus Xilonicus (1529), which was more representative of the aims of tragedy as well as its Christian appropriations. This essay thus examines Quintianus Stoa's determination of tragedy before demonstrating both how and why this vision, initially celebrated, fell into disgrace and abeyance.
Performing Exile: John Foxe's Christus Triumphans at Magdalen College, Oxford
Authors: Blank Daniel
Published: August 2016

When Laurence Humphrey became President of Magdalen College, Oxford in 1561, one of his earliest endeavours was to commission a production of John Foxe's Christus Triumphans. Although it remains uncertain whether the play was actually performed, this article explores the implications of Humphrey's request, taking his interest in staging the play as a starting point for understanding the value Christus Triumphans held for a generation of returned Protestant exiles. I begin by placing Foxe's apocalyptic comedy alongside the writings of Marian Protestants, situating the play within the concerns of exile and demonstrating the particular importance of conversion to the Protestant cause. I then consider the circumstances of Humphrey's production at Magdalen, using key archival documents to illuminate what that performance might have looked like. Humphrey's proposed staging of Christus Triumphans not only elucidates the salient concerns of the play itself, but also reveals how drama became a potent religious tool at this crucial post‐Marian moment. By realigning the play's engagement with the conditions of religious persecution, Humphrey sought to imbue the play with a retrospective significance, carefully shifting its message for an audience of collegiate spectators. At the same time, his staging of the play reflected – and perhaps heralded – a new interest in the visual capacities of university performance, ultimately demonstrating the vitality and influence of neo‐Latin religious drama in the academic setting.
Measuring domestic water use: a systematic review of methodologies that measure unmetered water use in low‐income settings
Authors: Tamason Charlotte C. , Bessias Sophia , Villada Adriana , Tulsiani Suhella M. , Ensink Jeroen H. J. , Gurley Emily S. , Mackie Jensen Peter Kjær
Published: August 2016

Objective

To present a systematic review of methods for measuring domestic water use in settings where water meters cannot be used.

Methods

We systematically searched EMBASE, PubMed, Water Intelligence Online, Water Engineering and Development Center, IEEExplore, Scielo, and Science Direct databases for articles that reported methodologies for measuring water use at the household level where water metering infrastructure was absent or incomplete. A narrative review explored similarities and differences between the included studies and provide recommendations for future research in water use.

Results

A total of 21 studies were included in the review. Methods ranged from single‐day to 14‐consecutive‐day visits, and water use recall ranged from 12 h to 7 days. Data were collected using questionnaires, observations or both. Many studies only collected information on water that was carried into the household, and some failed to mention whether water was used outside the home. Water use in the selected studies was found to range from two to 113 l per capita per day.

Conclusion

No standardised methods for measuring unmetered water use were found, which brings into question the validity and comparability of studies that have measured unmetered water use. In future studies, it will be essential to define all components that make up water use and determine how they will be measured. A pre‐study that involves observations and direct measurements during water collection periods (these will have to be determined through questioning) should be used to determine optimal methods for obtaining water use information in a survey. Day‐to‐day and seasonal variation should be included. A study that investigates water use recall is warranted to further develop standardised methods to measure water use; in the meantime, water use recall should be limited to 24 h or fewer.
The effect of massive transfusion protocol implementation on pediatric trauma care
Authors: Hwu Ruth S. , Spinella Philip C. , Keller Martin S. , Baker David , Wallendorf Michael , Leonard Julie C.
Published: August 2016

BACKGROUND

Massive transfusion protocols (MTPs) to address hemorrhage are understudied in children. The objective was to determine the effect of MTP implementation on outcomes of injured children.

STUDY DESIGN AND METHODS

This was a retrospective comparison of injured children before and after MTP implementation for children less than 18 years old who presented in 2005 to 2014 and received red blood cells (RBCs) within 24 hours of arrival. Children were divided into groups based on pre‐/post‐MTP implementation and subgrouped based on receipt of massive transfusion (≥40 mL/kg RBCs or ≥80 mL/kg total blood products at 24 hr from arrival). The primary outcome was in‐hospital mortality and secondary outcomes were total blood product use, intensive care unit/ventilator/pressor‐free days, composite morbidity, and Glasgow Outcome Score.

RESULTS

A total of 11,995 children presented for trauma care over 9 years; 235 received RBCs. A total of 120 were in the pre‐MTP group and 115 in the post‐MTP, of whom 26 and 17 received massive transfusion in the pre‐ and post‐MTP groups, respectively; 11 had MTP activations. Children massively transfused after MTP received mean plasma:RBC and platelet (PLT):RBC ratios greater than 1:1 at both 6 and 24 hours with no significant difference in total admission blood product use. There was no difference in in‐hospital mortality between pre‐ and post‐MTP groups (24% vs. 19%) or massive transfusion subgroups (54% vs. 47%). There were no differences in secondary outcomes.

CONCLUSIONS

While we were not able to show improvements in outcome, MTP implementation led to higher plasma and PLT:RBC ratios without an associated change in blood product use or composite morbidity.
Platelet corrected count increments by apheresis platform
Authors: Tobian Aaron A.R. , King Karen E. , Borge Prabhakar D. , Fuller Alice K. , Uglik Kristin , Ness Paul M.
Published: August 2016

BACKGROUND

Automated blood collection platforms use different technological systems to isolate and collect individual blood components. These unique systems could potentially result in differences in platelet in vivo viability, as measured by the corrected count increment (CCI).

STUDY DESIGN AND METHODS

This retrospective study evaluated CCI data of platelet transfusions among oncology patients who received multiple unmanipulated apheresis platelets between January 1, 2006 and December 31, 2009. Apheresis platelets were collected from our community blood center by standard procedures using two different collection systems and were transfused to patients in a blinded manner.

RESULTS

The CCI of the platelet recipient was significantly higher at 0‐2 hours post‐transfusion among the individuals who received platelets collected on Trima Accel (Terumo BCT) (mean = 6281, standard deviation = 3650) compared to the platelets collected by the Amicus system (Fresenius Kabi) (mean = 5251, standard deviation = 3311, p = 0.004).

CONCLUSIONS

These hypothesis‐generating data suggesting improved recovery and survival of Trima Accel platelets demonstrate the need for the investigation and implementation of the best collection methods to provide better platelet transfusion support.
3-D Numerical Heat Transfer for Confined Turbulent Twin Circular Jets Impinging on an Inclined Moving Plate
Authors: Jang Jiin-Yuh , Huang Jyun-Cin
Published: August 2016

The objective of this study is to numerically investigate the 3-D confined turbulent twin circular jets impinging to an inclined moving plate submerged in quiescent water. The effects of different dimensionless plate velocities (Up = −0.2, −0.1, 0, 0.1, 0.2), and the oblique angles (θ = 0°, 10°, 20°, 30°), with Up = 0 and θ= 0° being the conventional vertical jet impingement to a stationary plate, on the velocity field and heat transfer phenomenon were investigated in detail. It is shown that the plate moving direction has tremendous effect on the local and average Nusselt number distributions. In the case of stationary plate (Up = 0), the average Nusselt number is decreased as the plate oblique angle θ is increased. For a positive normalized plate velocity (Up>0), the average Nusselt number is decreased with increasing oblique angle θ, while for a negative normalized plate velocity (Up<0), the opposite trend is true.
An Investigation of Solar Trees for Effective Sunlight Capture Using Monte Carlo Simulations of Solar Radiation Transport
Authors: Verma Navni N. , Mazumder Sandip
Published: August 2016

Solar photovoltaic cells arranged in complex three-dimensional leaf-like configurations — referred to as a solar tree — can potentially collect more sunlight than traditionally used flat configurations. It is hypothesized that this could be because of two reasons. First, the three-dimensional space can be utilized to increase the overall surface area over which the sunlight may be captured. Second, as opposed to traditional flat panel configurations where the capture efficiency decreases dramatically for shallow angles of incidence, the capture efficiency of a solar tree is hampered little by shallow angles of incidence due to the three-dimensional orientation of the solar leaves. In this paper, high fidelity Monte Carlo simulation of radiation transport is conducted to gain insight into whether the above hypotheses are true. The Monte Carlo simulations provide local radiation flux distributions in addition to global radiation flux summaries. The studies show that except for near-normal solar incidence angles, solar trees capture sunlight more effectively than flat panels — often by more than a factor of 5. The Monte Carlo results were also interpolated to construct a daily sunlight capture profile both for mid-winter and mid-summer for a typical North American city. During winter, the solar tree improved sunlight capture by 227%, while in summer the improvement manifested was 54%.
Waste Heat Recovery From Porous LPG Gas Burner Used for Cooking
Authors: Ravindran Narayana Vijesh , Seetharaman ArulmozhiVarman
Published: August 2016

Generally in cooking devices three modes of heat transfer takes place (conduction, convection and radiation). Heat is transferred to the utensils mainly due to conduction and convection. A considerable amount of heat in the form of radiation is dissipated to the surroundings.

The purpose of this project is to recover this waste heat. Surface radiation without participating media is considered in this study. Hence, copper coil is used to absorb the radiant heat and transfer it to water which run through the coil. This low temperature recovery water can be used for cooking or to keep the food hot packed or other similar low grade heat applications.
Numerical Analysis of Convection Heat Transfer on High-Temperature Rotating Disk at Bottom Surface of Air Flow Duct
Authors: Hirasawa Shigeki , Kawanami Tsuyoshi , Shirai Katsuaki
Published: August 2016

Convection heat transfer distribution on a high-temperature rotating disk in a horizontal air flow duct was analyzed by three-dimensional computational fluid dynamics (CFD) code. The temperature of the disk was 1000°C, and the rotation speed was 60–480 rpm. The temperature of the inlet air was 25°C, and the velocity was 0–1 m/s. The air flow pattern was affected by natural convection caused by temperature difference, forced convection flow along the disk surface, rotation flow induced by the disk, and volume expansion of gas. The calculated results show that the ratio of the maximum and minimum values of the average heat flux along the circumstance direction on the disk was large when the rotation speed and air velocity were small.
Liquid Metal Alloy Based Vascular-Like Microchannel Networks for the Thermal Management of Electronics
Authors: He Zhi-Zhu , Xue Xu , Liu Jing
Published: August 2016

In this paper, the heat transfer and hydrodynamics of the liquid metal alloy in the vascular-like microchannel networks based cooling system are numerically investigated and compared with the corresponding coolant by water. The whole microchannel networks are composed of two vascular-like networks which are vertically connected with each other. Each vascular-like network has a single inlet or outlet channel, and uniformly bifurcates over many distributed levels’ microchannels. The vascular-like networks combined with liquid metal alloy are used to design the high efficiency thermal management system for Electronics.
Experimental Study of Phase-Changeable Water/Polyalphaolefin Nanoemulsion Fluids
Authors: Xu Jiajun , Hammouda B. , Cao Fangyu , Yang Bao
Published: August 2016

In this work, thermal properties especially phase change heat transfer properties of one new type of nanostructured heat transfer fluid: Water/Polyalphaolefin (PAO) nanoemulsion fluid are investigated. Water is added into PAO fluid to form nanoemulsion fluids in which dispersed water nanodroplets are formed by self-assembly.

The liquid-to-vapor phase change results, expressed in terms of surface heat flux and heater temperature, have shown that the presence of water nanodroplets has a drastic impact on the liquid-to-vapor phase change behavior of the nanoemulsion fluid studied: the water nanodroplet formed inside can enhance its heat transfer coefficient by over 300% after the incipience of its phase change. In addition to that, the vaporization of the water nanodroplet inside is found to be different depending on the concentration of water inside, which happens to coincide with the structure change with different water concentrations as observed in SANS measurement. On the other hand, the effective specific heat is also found to increase with higher water concentration until reaching a maximum value which also happens to coincide with the structure transition from spherical to cylinder shape with the increasing of water concentrations as observed from SANS measurement. More study is still needed to understand the mechanism behind these phenomena.
High Weissenberg Number Stress Boundary Layer for the Upper Convected Maxwell Fluid
Authors: Ashrafi N. , Mohamadali M. , Najafi M.
Published: August 2016

The classic Blassius problem of steady boundary-layer flow of the upper convected Maxwell over a flat plate in a moving fluid is studied. According to scaling parameters the equations represent the viscoelastic stress boundary layer. By means of an exact similarity transformation, the non-linear viscoelastic momentum and constitutive equations transform into a system of highly nonlinear coupled ordinary differential equations. Numerical solution may be achieved by a variable stepping method for the initial-value problem. The stepping numerical method chosen fifth order Runge-Kutta for solving the resulting nonlinear algebraic equations at each step. It is seen that there is a stress boundary layer and there is no velocity boundary layer.
Experimental Investigation of Jet Impingement Heat Transfer in Cross-Flow Modified by a V-Shaped Rib
Authors: Wang Chenglong , Wang Lei , Sundén Bengt
Published: August 2016

Experimental studies are carried out to investigate the jet impingement heat transfer characteristics in cross-flow with and without the presence of a 45 deg V-shaped rib. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. The ratio of nozzle-to-surface spacing to jet diameter is 3.56, the jet Reynolds number is kept at 17,000, the cross-flow Reynolds number spans from 32,700 to 65,000, the velocity ratio of jet to cross-flow ranges from 1.5 to 3.0. The impingement heat transfer characteristics in cross-flow are changed from the results without the cross-flow, and they are strongly affected by the velocity ratio. The presence of a V-shaped rib significantly modifies the heat transfer patterns of the impinging jet in cross-flow. Compared to the results without ribs, the heat transfer over the ribbed surface is enhanced for a low velocity ratio but retarded for a high velocity ratio, depending on the interaction between the rib induced flow and the impinging jet.
Electrical Resistance and Natural Convection Heat Transfer Modeling of Shape Memory Alloy Wires
Authors: Eisakhani Anita , Gao Xiujie , Gorbet Rob , Culham J. Richard
Published: August 2016

Shape memory alloy (SMA) actuators are becoming increasingly popular in recent years due to their properties such as large recovery strain, silent actuation and low weight. Actuation in SMA wires depends strongly on temperature which is difficult to measure directly. Therefore, a reliable model is required to predict wire temperature, in order to control the transformation, and hence the actuation, and to avoid potential degradation due to overheating. The purpose of this investigation is to develop resistance and natural convection heat transfer models to predict temperature of current-carrying SMA wires using indirect temperature measurement methods.

Experiments are performed on electrically heated 0.5 mm diameter NiTi SMA wire during phase transformation. Convection heat transfer experiments are performed in an environment of air that allows for control of the ambient pressure and in turn the thermofluid properties, such as density and viscosity. By measuring convective heat loss at a range of pressures, an empirical natural convection heat transfer correlation is determined for inclination angles from horizontal to vertical, in the Rayleigh number range of 2.6 × 10−8 ≤ RaD ≤ 6.0 × 10−1. Later, effect of temperature changes on electrical resistance and other control parameters such as applied external stress, wire inclination angle, wire length and ambient pressure is investigated. Based on experimental results a resistance model is developed for SMA wires that combined with the heat transfer correlation previously derived can be used to predict temperature and natural convection heat transfer coefficient of NiTi SMA wires during phase transformation for different wire lengths and inclination angles under various applied external stresses.
Heat Modeling of the Catenary’s Contact Wire During the Electrical Power Supply of Trains in Station
Authors: Bausseron Thomas , Baucour Philippe , Glises Raynal , Verschelde Sylvain , Chamagne Didier
Published: August 2016

The overheating problem of the railroad catenary at the contact with the pantograph when the train is stopped and electrically fed is responsible of many incidents. This paper describes an experimental study and a numerical model of a catenary/pantograph system used during the preconditioning of the train. Several incidents of wire breakage have highlighted the importance of the catenary/pantograph heating problem, in those incidents the contact wire had melted and broke itself. The experimental setups consists of estimating the contact’s thermal resistance and area in order to calculate which part of the interface heat flux go throught the catenary’s contact wire and which part go throught the pantograph’s collector strip. The numerical model is based on several phenomena as heat conduction into the wires, heat exchange with ambiance through convection, Joule effects and heat flux from the interface.
Natural Convective Heat Transfer From a Horizontal Rectangular Isothermal Element Imbedded in a Plane Adiabatic Surface With a Parallel Adiabatic Covering Surface
Authors: Oosthuizen Patrick H.
Published: August 2016

Natural convective heat transfer from a horizontal flat rectangular isothermal heated element imbedded in a flat rectangular adiabatic surface has been numerically studied. The surface of the heated rectangular element is in the same plane as the surface of the surrounding adiabatic material. A rectangular flat horizontal adiabatic surface is mounted parallel to and at a relatively short distance from the heated element. The heated element is facing upwards with the covering surface above the element. For the conditions considered laminar, transitional, and turbulent flows can occur. The flow has been assumed to be steady. Constant fluid properties have been assumed except for the density change with temperature which gives rise to the buoyancy forces. This was dealt with using the Boussinesq approach. To obtain the solution, the commercial CFD solver ANSYS FLUENT© was used to numerically solve the governing equations. The k-epsilon turbulence model was employed with account being taken of buoyancy force effects. The effects of the dimensionless distance of the rectangular covering surface from the heated rectangular element and of the ratio of the side lengths of the rectangular element on the variation of the Nusselt number with Rayleigh number have been examined.
A Numerical Study of the Effect of Inlet Vent Position and Size on the Velocity and Temperature Distributions in a Smaller Naturally Ventilated Theater in Canada
Authors: Oosthuizen Patrick H.
Published: August 2016

Many smaller churches and similar buildings in Canada have been converted into small theaters. Such theatres are often not fitted with an air-conditioning system. For performances in the fall these theaters sometimes rely on buoyancy driven natural ventilation to moderate the indoor air temperature. Such ventilation systems usually involve near floor inlet vents and a roof level air discharge system. A preliminary numerical study of the effect of inlet vent position and size on the performance of such a system has been undertaken. A simple model of a typical theater building of the type considered has been used. The heat generated by the audience has been represented by a uniform heat flux distributed over the audience area. Inlet vents have been assumed to be located low on the side walls of the theater and the air-flow leaving the theatre has been assumed to be through vents at the top of a chimney system. The flow has been assumed to be steady and symmetrical about the vertical center-line through the building. The Boussinesq approach has been adopted. The standard k-epsilon turbulence model has been used. The solution has been obtained using the commercial CFD solver ANSYS FLUENT©.
Non-Surface Polaritonic Peaks in Near-Field Radiative Transfer
Authors: Czapla Braden , Zheng Yi , Sasihithlu Karthik , Narayanaswamy Arvind
Published: August 2016

Near-field effects in radiative transfer refer to the collective influence of interference, diffraction, and tunneling of electro-magnetic waves on energy transfer between two or more objects. Most studies of near-field radiative transfer have so far focused on the enhancement due to tunneling of surface polaritons. In this work, we show the existence of sharp peaks in the radiative transfer spectrum between two spheres of polar materials that are not due to surface polaritons. The peaks, which are present on either side of the restrahlen band, are because of Mie resonances.
Predicting Phonon Transport in Two-Dimensional Boron Nitride-Graphene Superlattices
Authors: da Silva Carlos , Sborz Julia , Romero David A. , Amon Cristina H.
Published: August 2016

The synthesis of boron nitride (BN) - graphene hybrid materials is now a reality that has opened opportunities for creation of new nanostructures with enhanced mechanical, electronic and thermal properties, of particular interest for nanoelectronics applications. Properties of these materials are still not well understood, and modelling approaches are needed to support engineering design of these novel nanostructures. In this work, we study thermal transport in BN-graphene superlattices from a phonon transport perspective. We predict phonon properties (phonon group velocities and phonon lifetimes) using normal mode analysis based on phonon spectral energy density (SED) in these superlattices, with especial emphasis on the role of the orientation of the atoms at the BN - graphene interfaces. We consider various superlattices compositions with two highly symmetric orientation, i.e., zig-zag and armchair. Our results show that phonon group velocities are higher for the zig-zag interface orientation. We also found that phonon modes at small frequencies are more sensitive to the superlattice configurations.
Diesel Engine Simulations and Experiments: Fuel Variability Effects on Ignition
Authors: Huang Mingdi , Gowdagiri Sandeep , Cesari Xander M. , Oehlschlaeger Matthew A.
Published: August 2016

The chemical composition and properties of fuels used in compression-ignition engines can influence engine performance significantly. Consequently, the modeling of fuel chemistry within computational fluid dynamics (CFD) simulations of diesel and other compression ignition engines is important. Modern detailed chemical mechanisms may provide predictive modeling of fuel chemistry; however, they are generally far too computationally expensive for use in CFD. We present simulations of diesel engine combustion, focusing on the prediction of ignition, using the CONVERGE CFD software package. A CFD simulation framework with models for turbulence and spray breakup and atomization is presented with a reduced global reaction model to describe fuel oxidation and ignition. The global reaction model incorporates a single parameter, the derived cetane number (DCN), to describe fuel reactivity variability. CFD simulations are compared to experiments carried out in a single-cylinder diesel engine for compositionally diverse conventional and alternative diesel and jet fuels. Model-experiment comparisons show general agreement for ignition timing and the influence of fuel variability on ignition timing. In addition, the sensitivity of CFD predictions on the chemistry, turbulence, and spray models is illustrated.
Study on Flow Field Characteristics of Low Swirl Injector
Authors: Deng Yangbo , Dong Jingming , Zhen Xu
Published: August 2016

The flow characteristics of six kinds of LSIs, which are designed by different pore sizes in the center channel screen, are analyzed. The velocity vectors on the spanwise sections and the vertical sections in a channel at atmospheric condition are captured using a Particle Image Velocimetry (PIV) system. The swirl number of the airflow through the LSIs ranges from 0.5 to 0.58, and the inlet velocity is kept at 14m/s. The results show that the swirl number under a threshold can form low swirl flow. The velocity vector distribution of the low swirl flow is a diffuse shape without recirculation, and has the self-similar characteristic. The separation of low speed flow in the center zone and the high speed in the annulus zone generates the unique “W” shape distribution of the through the LSI. With the swirl number increasing, the area of the low vorticity zone decreases, and the vorticity value of the flow in the outer annular zone increases.
Fully Coupled Elliptic Numerical Model for Film Condensation From Vapour-Gas Mixtures in Vertical Parallel Plate Channels
Authors: Hassaninejadfarahani Foad , Ormiston Scott
Published: August 2016

Laminar film condensation is an important phenomenon which occurs in numerous industrial applications such as refrigeration, chemical processing, and thermal power generation industries. It is well known that film condensation heat transfer is greatly reduced in the presence of a non-condensing gas. The present work performs a numerical analysis of the steady-state, laminar film condensation from a vapour-gas mixture in vertical parallel plate channels to demonstrate a computer model that could assist engineering analysts designing systems involving these phenomena. The present model has three new aspects relative to other current work. First, the complete elliptic two-dimensional governing equations are solved in both phases. Thus, the entire channel domain is solved rather than using an approach that marches along the channel from inlet to a prescribed length. Second, a dynamically determined sharp interface is used between the phases. This sharp interface is determined during the solution on a non-orthogonal structured mesh. Third, the governing equations are solved in a fully-coupled approach. The equations for two velocities, pressure, temperature, and gas mass fraction are solved in a coupled method simultaneously for both phases. Discretisation has been done based on a finite volume method and a co-located variable storage scheme. An in-house computer code was developed to implement the numerical solution scheme. Detailed results are presented for laminar film condensation from steam-air mixtures flowing in vertical parallel-plate channels. The results include velocity and pressure profiles, as well as axial variations of film thickness, Nusselt number and interface gas mass fraction. Detailed comparisons are made with results from a parabolic solution approach.
A Simplified ‘Effective Circuit’ Fluid Flow Model for Forced Convection in Oblique Fin Configuration
Authors: Mou Nasi , Lee Poh Seng , Khan Saif A.
Published: August 2016

In this paper, a simplified ‘effective circuit’ fluid flow model is proposed to complement full-domain (geometry based) simulations of fluid flow in novel discrete oblique fin heat sinks. In the proposed model, the discrete flow paths are modeled as effective resistances, and the intersections between discrete flow paths are modeled as ‘nodes’. In an electrical circuit, the current of each branch can be derived from the current division rule, and hence the actual flow rates in the effective circuit are determined by the effective resistances. Simulink R2011b, a graphical extension to MATLAB for modeling and simulation of systems, is chosen to construct the equivalent circuit. The effective resistances are calculated using the well-known friction factor expressions for laminar flow in micro-channels. A full-domain geometry-based simulation is performed on CFX 14.0 serving as a benchmark for the developed ‘effective circuit’ fluid flow model. The results show that for a given total current value and mass flow rate, the difference of pressure drop over the whole heat sink between the simplified flow model and CFX simulation is within 13%. The mass flow distributions obtained from the simplified flow model and the CFX simulation exhibit a common distribution pattern. Interestingly, the simplified flow model is even able to capture flow migration — a distinctive phenomenon of flow in oblique fin geometries. We thus confirm the feasibility of the method of construction of our simplified ‘effective circuit’ fluid flow model.
Heat Transfer Analysis of a Buoyancy-Induced Flow of Nanofluids Along a Vertical Hot Plate: Effect of Nanoparticle Type and Diameter
Authors: Koronaki I. P. , Nitsas M. T.
Published: August 2016

Nanofluids is a term to describe fluids engineered by dispersing nanometer-scale structures such as particles, tubes and fibers in base fluids. Nanofluids are viewed as effective means of enhancing heat and mass transfer and thus they can be implemented in many engineering applications. The present paper examines the two dimensional-steady state-natural convection during the buoyancy-induced flow of the incompressible Al2O3-water nanofluid along a vertical plate under two different scenarios: the uniform and non-uniform heated plate. Both dynamic and static models are proposed in the literature for the conductivity and viscosity of the nanofluids. Nevertheless, in this work, dynamic models for the nanofluids thermal conductivity and viscosity have been assumed so as the Brownian motion of the nanoparticles to be considered. The governing equations of continuity, momentum and energy are reduced to a system of two non-linear differential equations by means of introducing the Pohlhausen stream function, and are solved numerically with the Runge-Kutta method with the Prandtl number being the only parameter of the dimensionless differential equations. The results show that the convection heat transfer coefficient is enhanced due to the nanofluids and it increases further by augmenting the volume concentration of the nanoparticles. The results of the aforementioned analysis are validated with the Finite Difference Method (FDM) selecting the proper grid density for the field. In addition, the impact of the nanoparticle diameter and the type of the base fluid on maximizing heat transfer through free convection for the isothermal plate is investigated. Finally, the two ways of expressing the temperature of the plate are compared in terms of influencing the convection coefficient.
A Review on the Thermal Conductivity and Viscosity Models of Nanofluids: Impact on Convection Coefficient Calculations
Authors: Koronaki I. P. , Nitsas M. T. , Papaefthimiou V.
Published: August 2016

Recent advances in technology have given the opportunity of developing structures of nanometer scale suitably dispersed in base fluids. The term nanofluids, introduced by Stephen U.S Choi, describes the liquid suspensions which contain these structures (nanoparticles, nanotubes, nanodroplets etc). Even though the branch of nanotechnology, where nanofluids can be categorized, is in its infancy the growth of research work in terms of engineering applications that has been done already indicates the interest of researchers in nanofluids. As mentioned above a lot of research work, both experimental and computational, has been done in the field of nanofluids. As far as heat transfer is concerned, all researchers reach the same conclusion: heat transfer is enhanced while using nanofluids as means of cooling or heating due to the improved, among others, thermal conductivity of nanofluids compared to the conductivity of the base fluid which in most cases is water. The purpose of this review is to present the research that has been done on heat transfer calculations as well as the basic properties of the nanofluids. For this reason the structure of the review is divided into two topics. In the first topic models of calculating the effective thermal conductivity and the effective dynamic viscosity of nanofluids are presented. The aforementioned models have derived from both theoretical and experimental analysis. The second section concentrates on summarizing the correlations which calculate the Nusselt number and thus the convection coefficient.
Computational Modeling of a Solar Thermoelectric Generator
Authors: Ofoegbu Chukwunyere , Mazumder Sandip
Published: August 2016

Solar Thermoelectric Generators (STEGs) convert solar energy to electricity. The solar energy is first used to heat an absorber plate that serves as the high temperature reservoir. Power is generated by connecting the hot reservoir and cold (ambient) reservoirs with a pair of p- and n-doped thermoelectric legs. Experimental studies have shown that the efficiency of a STEG can reach values of about 5% if the entire setup is placed in near-vacuum conditions. However, under atmospheric conditions, the efficiency decreases by more than an order of magnitude, presumably due to heat loss from the absorber plate by natural convection. A coupled fluid-thermal-electric three-dimensional computational model of a STEG is developed with the objective of understanding the various loss mechanisms that contribute to its poor efficiency. The governing equations of mass, momentum, energy and electric current, with the inclusion of thermoelectric effects, are solved on a mesh with 60,900 cells, and the power generated by the device is predicted. The computational model predicts a temperature difference (ΔT) of 16.5K, as opposed to the experimentally measured value of 15K. This corresponds to a peak power of 0.031W as opposed to the experimentally measured peak power of 0.021W. When only radiative losses are considered (i.e., perfect vacuum), the ΔT increases drastically to 131.1K, resulting in peak power of 1.43W. The predicted peak efficiency of the device was found to be 0.088% as opposed to the measured value of 0.058%.
Application of Artificial Neural Network as Digital Filter for Online Heat Flux Estimation
Authors: Najafi Hamidreza , Woodbury Keith A.
Published: August 2016

Online heat flux measurement can greatly enhance the controllability in several industrial processes. Using heat flux estimation techniques based on temperature measurements is the best approach in many cases. Estimating the unknown heat flux (boundary condition) at the surface when temperature measurements are available in the interior points of the medium is an inverse heat conduction problem (IHCP). Several IHCP solution methods need the whole time domain data for the analysis and cannot be applied for real-time applications. Digital filter representation is one of the methods which can be used for near real-time heat flux estimation by using available temperature measurements. The idea of the filter algorithm is that the solution for the heat flux at any time is only affected by the recent temperature history and a few future time steps. Artificial Neural Network (ANN) is utilized in this study as a digital filter, for near real-time heat flux estimation by using temperature measurements. The performance of the ANN is compared with the digital filter coefficient method. ANN consists of a set of interconnected neurons that can evaluate outputs from inputs by feeding information through the network and adjusting the weights. Considering temperatures as the inputs and heat flux as the output, the weights can be interpreted as the filter coefficients. In using ANN, calculation of sensitivity coefficients is not needed which can lead to less computational cost. It is showed that the ANN method can estimate the heat flux closer to real-time comparing with digital filter approach. The developed method is tested through several numerical test cases using exact solutions.
Transient Thermal Analysis of Gas Turbine Shut Down Physics: Normal and Forced Cooling
Authors: Selvam Kathiravan , De Prosperis Roberto , Vanga Nageswara Rao
Published: August 2016

For industrial gas turbine plant, Reliability, Availability & Maintainability (RAM) are the critical parameters that yield maximum production. As gas turbines work in high temperature environment, periodic maintenance of the machine is important for life evaluation & to detect any early failures. During major inspection, all critical components need to be disassembled, which reduces the availability of gas turbine & impacts the plant production. Minimizing the duration of the scheduled outage helps to increase the availability of a gas turbine unit. During every major inspection, it’s necessary to ensure that the turbine is cooled below the allowable temperature. Gas turbine maintenance phases are often delayed because of slow natural convection cooling during normal shutdown. To reduce the cool-down time, it’s necessary to accelerate the cooling & one of industry practices is to spin the unit at a certain speed for an extended period of time which enables low temperature ambient air circulation. However, this forced cooling of the machine imposes additional thermal stresses on the components that may result in overall life reduction.

This paper compares the thermal behaviour of normal cool down and forced cool down phenomena by simulating the critical gas turbine components. A 2D axi-symmetric flange to flange thermal modelling approach is used to predict the temperature distribution of the gas turbine components. Conduction, convection and radiation effects are captured using GE in-house methodology. Compressor and turbine casings as well as rotors are studied in detail to understand the transient thermal gradients. The results show that a high rim to bore gradient exists during forced cool down, which results in high stresses in the compressor and turbine wheel regions.
Experimental Measurements of Spectral Emissivity of Al-Si Coated Steel Blanks Undergoing Rapid Heating
Authors: Chester N. L. , Wells M. A. , Daun K. J.
Published: August 2016

Detailed knowledge of the blank temperature history is essential in hot forming die quenching, in order to ensure adequate austenitization of the steel and transformation of a protective Al-Si later into a permanent Al-Si-Fe coating. This, in turn, requires detailed knowledge of the blank emissivity, which is complicated by the fact that the coating undergoes rapid changes in surface chemistry, and surface roughness as it is heated. This paper spectral emissivity of Usibor® 1500 P as it undergoes heating. Samples were heated in a DSI Gleeble® 3500 under prescribed heating rates. The spectral emissivity was measured ex situ using an FTIR reflectometer, and in situ with a NIR-spectrometer. While the trends agree with manufacturer data in the cases of the as-received and final furnace heating temperature of 900°C, the spectral emissivity changes at a faster rate than previously reported.
Steady and Unsteady Simulations for Annular Internal Condensing Flows in a Channel
Authors: Naik Ranjeeth , Narain Amitabh , Mitra Soumya
Published: August 2016

This paper highlights: (i) numerical methods developed to solve annular/stratified internal condensing flow problems, and (ii) the assessed effects of transverse gravity and surface tension on shear driven (horizontal channels) and gravity driven (inclined channels) internal condensing flows. A comparative study of the flow physics is presented with the help of steady and unsteady computational results obtained from the numerical solutions of the full two-dimensional governing equations for annular internal condensing flows. These simulations directly apply to recently-demonstrated innovative condenser operations which make the flow regime annular over the entire length of the condenser. The simulation algorithm is based on an active integration of our own codes developed on MATLAB with the standard single-phase CFD simulation codes available on COMSOL. The approach allows for an accurate wave simulation technique for the highly sensitive shear driven annular condensing flows.

This simulation approach employs a sharp-interface model and uses a moving grid technique to accurately locate the dynamic interface by the solution of the interface tracking equation (employing the method of characteristics) along with the rest of the governing equations. The 4th order time-step accuracy in the method of characteristics has enabled, for the first time, the ability to track time-varying interface locations associated with wave phenomena and accurate satisfaction of all the interface conditions — including the more difficult to satisfy interfacial mass-flux equalities.

A combination of steady and unsteady simulation results are also used to identify the effects of transverse gravity, axial gravity, and surface tension on the growth of waves. The results presented bring out the differences within different types of shear driven flows and differences between shear driven and gravity driven flows.

The unsteady wave simulation capability has been used here to do the stability analysis for annular shear-driven steady flows. In stability analysis, an assessment of the dynamic response of the steady solutions to arbitrary instantaneous initial disturbance are obtained. The results mark the location beyond which the annular regime transitions to a non-annular regime (experimentally known to be a plug-slug regimes).

The computational prediction of heat-flux values agree with the experimentally measured values (at measurement locations) obtained from relevant runs of our in-house experiments. Also, a comparison between the computationally predicted and experimentally measured values regarding the length of the annular regime is possible, and will be presented elsewhere.
Time Resolved Laser Induced Incandescence for Sizing Aerosolized Iron Nanoparticles
Authors: Sipkens T. A. , Singh N. R. , Daun K. J. , Bizmark N. , Ioannidis M. , Titantah J. T. , Karttunen M.
Published: August 2016

This paper summarizes the results of Time-Resolved Laser-Induced Incandescence (TiRe-LII) measurements of iron nanoparticles in He, Ne, Ar, N2, CO, CO2, and N2O. The iron nanoparticles are formed in solution and then aerosolized with a pneumatic atomizer using various carrier gases, so the nanoparticle size is the same for each aerosol and the TiRe-LII signal only differs due to the different thermal accommodation coefficient (TAC). Thermal accommodation coefficients for the Fe-Ar, and Fe-N2 aerosols, derived from molecular dynamics using ab initio potentials, are compared with values inferred from the TiRe-LII measurements.