bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets
Authors: El-Gabry Lamyaa A. , Kaminski Deborah A. 
Published: November 2021

Abstract
Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters.
Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.
Analysis of Heat Exchanger Concepts for Use As Gas Turbine Intercoolers
Authors: Saidi Arash , Eriksson Daniel , Sundén Bengt 
Published: November 2021

Abstract
This paper presents a discussion and comparison of some heat exchanger types readily applicable to use as intercoolers in gas turbine systems. The present study concerns a heat duty of the intercooler for a gas turbine of around 17 MW power output. Four different types of air-water heat exchangers are considered. This selection is motivated because of the practical aspects of the problem. Each configuration is discussed and explained, regarding advantages and disadvantages. The available literature on the pressure drop and heat transfer correlations is used to determine the thermal-hydraulic performance of the various heat exchangers. Then a comparison of the intercooler core volume, weight, pressure drop is presented.
Dimple Enhanced Heat Transfer in High Aspect Ratio Channels
Authors: Ekkad Srinath V. , Nasir Hasan 
Published: November 2021

Abstract
Detailed heat transfer measurements are presented for a rectangular channel with dimples on one wall. Dimpled surfaces provide high heat transfer enhancement comparable to ribbed surfaces with reduced overall pressure drop. The heat transfer coefficients were measured using a transient liquid crystal technique. The effect of channel flow Reynolds number was investigated for a wide range from 10000 to 65000. The channel is a 25.4 mm × 101.6 mm (1” × 4”) rectangular cross-section with the dimples on one of the 101.6 mm wall. Heat transfer enhancement around three times that of a smooth channel were achieved for all flow conditions. The overall pressure drop through the dimpled section of the passage was also measured. The resulting thermal performance of the dimples surfaces is significantly higher compared to channels with protruding ribs.
Investigation of Polymer Based Micro Heat Pipes for a Flexible Spacecraft Radiator
Authors: McDaniels D. , Peterson G. P. “Bud” 
Published: November 2021

Abstract
In response to the space industry’s pursuit of interplanetary travel and a continuous human presence in space, there is increasing focus on spacecraft that change configuration while in space. Flexible thermal radiators are being developed to accommodate various collapse and deployment mechanisms. An analytical model suggests that a lightweight polymeric material with imbedded micro heat pipe arrays can meet heat dissipation requirements while contributing less mass than competing flexible materials. The capillary pumping limit is evaluated as a function of operating temperature using two candidate working fluids. Using water, the maximum heat transport is 18 mW per channel at 140/160 °C. The maximum heat transport using methanol is 2.2 mW at 120 °C, an order-of magnitude difference. A thermal circuit model translates heat transport per channel into total radiator capacity as a function of source temperature and environmental sink temperature. Using water as the working fluid, the radiator capacity was shown to vary from 6.0 kW to 12.2 kW for source temperatures of 20 °C to 50 °C. For source temperatures of 40 °C and higher, the capacity meets or exceeds the dissipation requirements of a reference spacecraft design.
While evaluated, methanol is not recommended as a working fluid because its radiator capacity is two to three times lower than water. Although thermal system constraints place limits on the micro heat pipe operating range, design changes directed at alleviating capillary limitations should increase radiator capacity. Technical issues for further study include effects of film billowing, performance limitations related to vapor viscosity, working fluid diffusion, and chemical reactivity between case and working fluid. Compared to a competing graphite fiber weave, the polymeric material has an effective conductivity over ten times higher. Its area power density (in kW/m2) is 18% to 60% lower than the graphite weave, but its mass power density (in kW/kg) is several times higher. Greater flexibility and lower weight also make it more amenable to structural integration. Recently developed space-stable polymers offer resistance to harsh temperature and radiation environments, helping to clear the path toward a more extensive use of polymers within the space industry.
Inverse Design of a Three Dimensional Furnace With Moving Design Environment
Authors: Ertürk Hakan , Ezekoye Ofodike A. , Howell John R. 
Published: November 2021

Abstract
The inverse design of a three-dimensional furnace that is built to heat an object moving along a conveyor belt of an assembly line is considered. A furnace of this type can be used by the manufacturing industry for applications such as curing of paint, annealing or manufacturing through chemical deposition. The object that is to be heated moves along the furnace as it is heated following a specified temperature history while the spatial temperature distribution is kept isothermal through the whole process. The temperature distribution of the heaters of the furnace should be changed as the object moves so that the specified temperature history can be satisfied. The design problem is a transient design problem where a series of inverse solutions is utilized. The process furnace considered is in the shape of a rectangular tunnel where the heaters are located at top and the design object moves at the bottom.
The inverse formulation of such a system is advantageous over a traditional trial-and-error solution where an iterative solution is required for every position as the object moves. The inverse formulation of the design problem involves ill-posed Fredholm equation of the first kind and the use of a regularized solver rather than an ordinary one such as Gauss-Seidel or Gauss elimination is essential. The radiative transfer is formulated utilizing the Monte Carlo method that enables including further realistic characteristics like specularly reflecting walls.
Sphere-to-Sphere Radiative Transfer Coefficient for Packed Sphere System
Authors: Lee S. H.-K. , Ip S. C.-H. , Wu A. K. C. 
Published: November 2021

Abstract
Rapid sintering is one of the most attractive metalworking technologies due to its ability to fabricate the final product with different microstructure in an economical manner. During this process, the high heating rate would induce a great thermal gradient to the sintering part. Such temperature differences affect the microstructure of the product, which in turn leads to the occurrence of microstructure defects. However, for this non-isothermal sintering, the present Radiative Transfer Equation approach or Units/Cells approach cannot effectively compute the temperature distributions inside the porous media, so as to predict the part defects. Cumbersome computations are needed for the Radiative Transfer Equation approach. For the Units/Cells approach, the use of regular assembly in the model limits the analysis of complex packed sphere systems. This study seeks to simplify the entire computational process for different packed sphere systems. By introducing a Radiative Transfer Coefficient (RTC) approach, the computation of radiative heat transfer within the porous bed can be enhanced. The newly introduced Radiative Transfer Coefficient is defined as the ratio of radiative energy exchange, including direct and indirect exchange, from the emitting sphere to the receiving sphere, which is a function of the system microstructure and radiative properties. A set of energy-balanced algebraic equations can then be established. With an appropriate initial energy guess for each sphere, these equations can be solved by the Gauss-Seidel iteration scheme, thereby computing the radiative heat transfer in packed sphere systems with different microstructures and radiative properties. The temperature for each sphere can therefore be computed right away. This model has been validated in different perspectives. With this RTC approach, the overall computational time required is significantly shorter, providing a set of fine-resolution temperature solution.
Impact of Die Attach Material and Substrate Design on RF GaAs Power Amplifier Devices Thermal Performance
Authors: Chiriac Victor Adrian , Lee Tien -Yu Tom 
Published: November 2021

Abstract
The latest commercial applications for microelectronics use GaAs material for RF Power Amplifier devices. This leads to the necessity of identifying low cost packaging solutions with high standards for reliability, electrical and thermal performance. A detailed thermal analysis for the wirebonded GaAs devices is performed using numerical simulations. The main interest of the study focuses on the impact of die attach thermal conductivity (1.0 to 7.0 W/mK), substrate’s top metal layer thickness (25 to 50 μm), and via wall thickness (25 to 50 μm) on GaAs IC device overall thermal performance.
The study uses a 2-layer organic substrate; the die attach thickness is 15μm. The peak temperatures reached by PA stages range from 102.7°C to 113.5°C, below the prohibitive/critical value of 150°C (based on 85°C ambient temperature). The increase of die attach thermal conductivity (3 times) led to a slight decrease in peak temperatures (up to 5°C) and the decay is much larger between the cases with 1 and 2.4 W/mK. The largest temperature differences were obtained by varying the thermal via thickness, as opposed to only increasing the top metal layer thickness. The peak temperatures and corresponding junction to ambient thermal resistances are documented. It is determined that for the same die attach thickness, for a thermal conductivity larger than 7 W/mK, the impact on the PA’s peak temperature is insignificant.
MEMS Enabled Micro Spray Cooling System for Thermal Control of Electronic Chips
Authors: Yao S. C. , Amon C. H. , Gabriel K. , Kumta P. , Murthy J. Y. , Wu C. F. , Hsieh C. C. , Boyalakuntla D. , Narumanchi S. V. J. , Rebello K. 
Published: November 2021

Abstract
Liquid cooling of electronic devices becomes necessary when the chip-level heat fluxes increase and traditional air cooling encounters ever-increasing difficulties. From all the liquid cooling processes, spray cooling appears more successful due to its high critical heat flux, relatively low liquid flow rates, highly controllable, and the non-existence of boiling incipient hysterisis. This paper describes the development of the EDIFICE project (Embedded Droplet Impingement For Integrated Cooling of Electronics), which seeks to develop an integrated droplet impingement cooling device for removing chip heat fluxes in the range 50–100 W/cm2, employing latent heat of vaporization of dielectric fluids. Micro-spray nozzles are fabricated on silicon using MEMS technology to produce 100 micron droplets with odd shaped nozzles and swirling nozzles. The effects of shape, size, type of fluid, and swirling are tested and discussed. Spray heat transfer on silicon surfaces is studied with various surface texturing on the backside of the chip to promote spreading and evaporation of cold fluids as well as at heated conditions. The effects of configuration and fluids are revealed. Numerical modeling is used to study preliminary designs at both the device and system level. The paper describes progress made in the development of the EDIFICE device.
A Case Study of Hyperthermia Induced Temperature Computations in Human Sarcomas Using Discrete Vasculature and Relative Perfusion Maps
Authors: Craciunescu Oana I. , Raaymakers Bas W. , Kotte Alexis N. T. J. , Das Shiva K. , Samulski Thaddeus V. , Lagendijk Jan J. W. 
Published: November 2021

Abstract
One of the most important technical aspects in clinical hyperthermia is the ability to measure and/or simulate the 3D temperature fields. Related to that, an essential part is the way in which the complex heat transfer related to vasculature is described. We report here the results of a collaboration between the hyperthermia modeling groups from the UMC Utrecht, The Netherlands, and Duke UMC, USA. Utrecht’s hyperthermia group has developed a flexible, discrete vasculature thermal model (DIVA) (Kotte et al. 1996) that describes the heat transfer related to discrete vasculature. The vasculature was imaged using MR angiography. To account for the smaller vessels that are responsible for the significant bioheat transport, relative perfusion maps measured at Duke using dynamic enhanced-magnetic resonance imaging were used. Alternatively, the VAMP program (Van Leeuwen et al. 1998) was used to artificially generate smaller vasculature. The cases with discretized vasculature were compared to continuum models where either heterogeneous isotropic perfusion, or relative perfusion maps were used. All simulations were compared to MR thermometry data. The conclusion is that for tumors crossed by or near large vessels, a combination of large vessels discretization and perfusion maps yields temperatures that match very well the MR thermometry data.
Elastic Wave Propagation in Circumferential Direction in Anisotropic Pipes
Authors: Towfighi S. , Kundu T. , Ehsani M. 
Published: November 2021

Abstract
Ultrasonic nondestructive inspection of large diameter pipes is important for health monitoring of ailing infrastructure. Longitudinal stress-corrosion cracks are detected more efficiently by inducing circumferential waves; hence, the study of elastic wave propagation in the circumferential direction of a pipe is essential. The current state of knowledge lacks a complete solution of this problem. Only when the pipe material is isotropic a solution of the wave propagation problem in the circumferential direction exists. Ultrasonic inspections of reinforced concrete pipes and pipes retrofitted by fiber composites necessitate the development of a new theoretical solution for elastic wave propagation in anisotropic pipes in the circumferential direction. Mathematical modeling of the problem to obtain dispersion curves for anisotropic materials leads to coupled differential equations. Unlike isotropic materials for which the Stokes-Helmholtz decomposition technique simplifies the problem, in anisotropic case no such general decomposition technique works. These coupled differential equations are solved in this paper. Dispersion curves for anisotropic pipes of different curvatures have been computed and presented. Some numerical results computed by the new technique have been compared with those available in the literature.
Strength and Stiffness of Aluminum/PTFE Reactive Composites
Authors: Saigal A. , Joshi V. S. 
Published: November 2021

Abstract
Aluminum/Polytetrafluoroethylene mixtures are currently being studied as reactive material compositions, with focus on shock or impact ignition. In addition, there is an emphasis on increasing the strength of these composites to survive high strain-rate deformation. In this research, an analytical model, based on Eshelby’s approach, and a three-dimensional elastoplastic finite element model were developed along with experimental measurements to investigate the effect of the shape and size of aluminum: spherical particles, whiskers, and fibers, on the strength and stiffness of Aluminum/Polytetrafluoroethylene composites. It was found that the existing surface and size characteristics of aluminum particles (e.g. texturing) play an important role on the mechanical behavior of these composites.
Draft System for Enhanced Impact Protection and Train Action Control: Validation by Testing and Computer Modeling
Authors: Clark Marlin E. 
Published: November 2021

Abstract
Certain types of freight cars that are normally equipped with conventional draft gears to protect car structure from coupling impact forces can benefit from additional buff travel. This reduces the coupler force experienced by the car structure; limiting the potential for structural and fatigue damage and improving wear characteristics. This can be accomplished within the standard draft pocket dimensions, allowing for improvements in both retrofit and new applications. Impact test data will show reductions in coupler force as compared to conventional draft gear systems under identical impact conditions. With additional buff travel available, greater protection is afforded against encounters with higher speed impacts.
Train action control can be enhanced through the application of an elastomeric spring with a stiffer non-linear spring rate. Conventional draft systems use a yoke around the draft gear, permitting the full travel of the device in both the draft and buff modes. The free slack transversed in reversal from buff to draft mode, followed by the relatively soft spring rate of a conventional draft gear, especially at low velocity, can result in over-solid conditions and high force peaks. Car separation and car closure velocities are typically low, such as two miles per hour, so the effect of softer spring rate can be detrimental.
The stiffer non-linear spring rate offers improved force transfer through each car as the force wave propagates through the train; the gradual and simultaneous buildup of force at each end of the car reduces relative car velocities and thus the severity of force transfer through each coupled connection. The elimination of a mechanical oversolid stop, replaced by the elastomeric spring, as it becomes stiffer with travel, also limits the end force experienced by the freight car structure. Computer modeling will show the advantages of this system during severe transient events, such as train startups and dynamic braking.
A large-scale investigation by ultrasound of fetal hepatic venous system variants in China
Authors: Gou Zhongshan , Yan Xinxin , Sun Baojuan , Zhang Jie , Liu Hongmei , Ni Caifang 
Published: November 2021

Aim: To investigate the types, associated anomalies and postnatal outcomes of fetal hepatic venous system (HVS) variants by ultrasound in China.Material and methods: A large-scale and prospective investigation of HVS variants for low-risk singleton pregnant women was performed in three academic tertiary referral care centers in China. Ultrasound imaging wasused for the identification and follow-up of anatomical variants. Follow-up was conducted once every four weeks prenatally and every two months postnatally, mainly concerned on the adverse events that may appear.Results: There were 20848 cases with anatomical variants of fetal HVS identified from 46179 candidates during the study period. Following the anatomical position of variants occurring, four main divisions were present: main portal vein variants (17.9%), intrahepatic portal vein variants (21.30%), intrahepatic persistent right umbilical vein (0.27%) and hepatic vein variants (5.67%). In the fetal period, the pregnancy of all cases was normally continued, except that the pregnancy of two cases, which were associated with multiple anomalies and were terminated by their parents. After birth, approximately 99.47% of the cases with isolated variants orbeing associated no clinic significant anomalies were normally alive. Approximately 0.50% cases were associated with simple ventricular septum defect or tetralogy of Fallot and further treatment was needed.Conclusion: The anatomical variants of fetal HVS may appear as numerical, morphological or positional variants of MPV, intrahepatic PV branches, intrahepatic PRUV and HVs. The majority of cases are isolated or their associated anomalies are not clinically significant and have normal lifeafter birth.
Paediatric pneumonia: deriving a model to identify severe disease
Authors: Haggie Stuart , Barnes Elizabeth H , Selvadurai Hiran , Gunasekera Hasantha , Fitzgerald Dominic A 
Published: November 2021

BackgroundCommunity-acquired pneumonia (CAP) is a leading cause of childhood hospitalisation. Limited data exist on factors predicting severe disease with no paediatric-specific predictive tools.MethodsRetrospective cohort (2011–2016) of hospitalised CAP cases. We analysed clinical variables collected at hospital presentation against outcomes. Stratified outcomes were mild (hospitalised), moderate (invasive drainage procedure, intensive care) or severe (mechanical ventilation, vasopressors, death).ResultsWe report 3330 CAP cases, median age 2.0 years (IQR 1–5 years), with 2950 (88.5%) mild, 305 (9.2%) moderate and 75 (2.3%) severe outcomes. Moderate-severe outcomes were associated with hypoxia (SaO2<90%; OR 6.6, 95% CI 5.1 to 8.5), increased work of breathing (severe vs normal OR 5.8, 95% CI 4.2 to 8.0), comorbidities (4+ comorbidities vs nil; OR 8.8, 95% CI 5.5 to 14) and being indigenous (OR 4.7, 95% CI 2.6 to 8.4). Febrile children were less likely than afebrile children to have moderate-severe outcomes (OR 0.57 95% CI 0.44 to 0.74). The full model receiver operating characteristic (ROC) area under the curve (AUC) was 0.78. Sensitivity analyses showed similar results with clinical or radiological CAP definitions. We derived a clinical tool to stratify low, intermediate or high likelihood of severe disease (AUC 0.72). High scores (≥5) had nearly eight times higher odds of moderate-severe disease than those with a low (≤1) score (OR 7.7 95% CI 5.6 to 10.5).ConclusionsA clinical risk prediction tool is needed for child CAP. We have identified risk factors and derived a simple clinical tool using clinical variables at hospital presentation to determine a child’s risk of invasive or intensive care treatment with an ROC AUC comparable with adult pneumonia tools.