CFD analysis Of printed circuit heat exchanger

Printed Circuit compact heat exchangers that are increasingly being used for viscous media thermal processing applications have semicircular flow channels. But due to some manufacturing constraints, these become semi elliptical in nature. In practice, these channels have very small hydraulic diameters and relatively large (L/dh). Because of length scales and the viscous nature of the fluids being handled, the flows are generally laminar and both hydro dynamically and thermally fully developed. At first, fully developed laminar flow and heat transfer in straight circular smooth duct under constant heat flux has been studied using FLUENT and fanning friction factor, Nusselt no. and Colburn factor have been calculated to check the accuracy of the solution using this package. Then following the same procedure, fully developed laminar flow and heat transfer in three-dimensional, periodic straight duct as well as sinusoidal duct with semiellptic cross section with different aspect ratios are considered. Computational Fluid Dynamics (CFD) using FLUENT is used to investigate the effect of Reynolds number (50 ≤ Re ≤ 500), aspect ratio of semi elliptical cross-sections for straight duct and amplitude to wavelength ratio(A/L=0.3 & 0.5) for sinusoidal channel(with L/D=4.5) on heat transfer enhancement and pressure drop for steady, incompressible, constant property, air (Pr=0.7044) flows under the constant wall heat flux boundary conditions. Velocity, temperature fields, Fanning friction factor, Colburn factor, good ness factor are being studied. Due to the interruption of the boundary layers formed near the solid surface and replacement of the boundary layer with the fluid from the core, thus creating a new boundary layer with an increased temperature gradient, the overall heat transfer coefficient as well as the pressure drop penalty in case of sinusoidal ducts increase as compared to straight ducts. Finally correlations between the Fanning friction factor and Colburn factor with Reynolds number and geometrical parameters have been found out for the above geometries

Towards Learning and Explaining Indirect Causal Effects in Neural Networks

Recently, there has been a growing interest in learning and explaining causal effects within Neural Network (NN) models. By virtue of NN architectures, previous approaches consider only direct and total causal effects assuming independence among input variables. We view an NN as a structural causal model (SCM) and extend our focus to include indirect causal effects by introducing feedforward connections among input neurons. We propose an ante-hoc method that captures and maintains direct, indirect, and total causal effects during NN model training. We also propose an algorithm for quantifying learned causal effects in an NN model and efficient approximation strategies for quantifying causal effects in high-dimensional data. Extensive experiments conducted on synthetic and real-world datasets demonstrate that the causal effects learned by our ante-hoc method better approximate the ground truth effects compared to existing methods

Experimental Observation of the Thin-Shell Instability in a Collision-less Plasma

We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.Funding agencies: EPSRC [EP/I031766/1, EP/K022415/1, EP/I029206/1, SFB-TR18, GRK1203, ENE2013-45661-C2-1-P, PEII-2014-008-P]; Vetenskapsradet [Dnr 2010-4063]; Triangle de la Physique RTRA network (ULIMAC)</p

Scaling of X-ray flux from high-intensity laser-solid interactions as a function of energy

The bremsstrahlung x-rays from a laser-solid interaction have been investigated for the use of radiography. The scaling of the x-rays as a function of energy has been characterized and modelled and agrees with previous measurements

Evaluating laser-driven Bremsstrahlung radiation sources for imaging and analysis of nuclear waste packages

A small scale sample nuclear waste package, consisting of a 28 mm diameter uranium penny encased in grout, was imaged by absorption contrast radiography using a single pulse exposure from an X-ray source driven by a high-power laser. The Vulcan laser was used to deliver a focused pulse of photons to a tantalum foil, in order to generate a bright burst of highly penetrating X-rays (with energy >500 keV), with a source size of <0.5 mm. BAS-TR and BAS-SR image plates were used for image capture, alongside a newly developed Thalium doped Caesium Iodide scintillator-based detector coupled to CCD chips. The uranium penny was clearly resolved to sub-mm accuracy over a 30 cm2 scan area from a single shot acquisition. In addition, neutron generation was demonstrated in situ with the X-ray beam, with a single shot, thus demonstrating the potential for multi-modal criticality testing of waste materials. This feasibility study successfully demonstrated non-destructive radiography of encapsulated, high density, nuclear material. With recent developments of high-power laser systems, to 10 Hz operation, a laser-driven multi-modal beamline for waste monitoring applications is envisioned

Innovative Education and Training in high power laser plasmas (PowerLaPs) for plasma physics, high power laser-matter interactions and high energy density physics - Theory and experiments

The Erasmus Plus programme 'Innovative Education and Training in high power laser plasmas', otherwise known as PowerLaPs, is described. The PowerLaPs programme employs an innovative paradigm in that it is a multi-centre programme where teaching takes place in five separate institutes with a range of different aims and styles of delivery. The 'in class' time is limited to four weeks a year, and the programme spans two years. PowerLaPs aims to train students from across Europe in theoretical, applied and laboratory skills relevant to the pursuit of research in laser-plasma interaction physics and inertial confinement fusion (ICF). Lectures are intermingled with laboratory sessions and continuous assessment activities. The programme, which is led by workers from the Technological Educational Institute (TEI) of Crete, and supported by co-workers from the Queen's University Belfast, the University of Bordeaux, the Czech Technical University in Prague, Ecole Polytechnique, the University of Ioannina, the University of Salamanca and the University of York, has just completed its first year. Thus far three Learning Teaching Training (LTT) activities have been held, at the Queen's University Belfast, the University of Bordeaux and the Centre for Plasma Physics and Lasers (CPPL) of TEI Crete. The last of these was a two-week long Intensive Programme (IP), while the activities at the other two universities were each five days in length. Thus far work has concentrated upon training in both theoretical and experimental work in plasma physics, high power laser-matter interactions and high energy density physics. The nature of the programme will be described in detail and some metrics relating to the activities carried out to date will be presented

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Promjene sadržaja aminokiselina u testisu štakora trovanih manganom

Rats were given manganese chloride (8 mg/kg) intraperitoneally daily. Manganese content and various amino acids were estimated in the testis at 30 and 60 days. In this period manganese content of the testis showed a 4- and 9-fold increase respectively. Amino acids remained unaltered al 30 days while at 60 days, the amounts of alanine, cysteine, leucine, proline, phenylalanine and glutamine were significantly greater than the levels in the control animals. The present experiments show a great affinity of testicular tissue for manganese resulting in biochemical alterations.Nakon intraperitonealnih aplikacija manganova klorida štakorima u dnevnim dozama od 8 mg/kg, određivan je sadržaj mangana i različitih aminokiselina u testisu. Nakon 30-dnevne aplikacije sadržaj mangana bio je 4 puta veći, a nakon 60-dnevne 9 puta veći nego u kontrolnih životinja. Sadržaj aminokiselina pak nije se bitno promijenio 30 dana nakon tretiranja, ali nakon 60 dana količina alanina, cisteina, leucina, prolina, fenilalanina i glutamina bila je statistički značajno veća nego u kontrolnih životinja. Ovi pokusi upozoravaju na veliki afinitet tkiva testisa prema manganu, što dovodi do biokemijskih promjena

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