Experimental analysis of flow boiling pressure drop through copper metallic foam

This work concerns the flow boiling pressure drop inside a channel filled with metallic foam soldered to its lateral walls. Notice that Open cell metallic foams are increasingly used in the heat and mass exchangers. This is due to the considerable opportunity that this material could offer in terms of hydrodynamic characteristics namely porosity and permeability which are larger than 0.88 and 10-7 m2, respectively. The state of the art shows that the works in this field are still in their early stages. In this study the tested metallic foam is from copper with 97% porosity and 36 PPI (Pore per Inch Linear). The working fluid is n-pentane. The independent variables are: the mass flux in the range from 10 to 100 kg/m2s and heating power which varies between 0 and 25 W/cm2. The dependent variables are: the static pressure and exit quality. The hydrodynamics results represented in terms of pressure drop are qualitatively similar to those found for plain tube. The two-phase friction multiplier is used to compare results of the present work with those in the literature. Hence results are compared to correlations in the literature for metal porous media. As metallic foam occupies only 5% of the channel entire volume, the obtained results are also compared to those given by the homogeneous and separated models for two-phase flow in plain tube. The results concerning pressure drop through metallic foam found in this work are in good agreement with the homogeneous model with a discrepancy of about 25%, for the other models this discrepancy is upper to 50%

Endovascular treatment of acute aortic isthmian ruptures: case study

Traumatic rupture of the aortic isthmus is a rare lesion occurring in patients subjected to violent deceleration. Because of the forces involved, it is frequently associated with concomitant life-threatening injuries. The endovascular intervention has been described to be a feasible and efficient technique which may be proposed as a therapeutic option for patients with multiple traumas instead of delayed classical surgical repair after stabilization. We report the case of an adult who has had an accident with a traumatic rupture of the aortic isthmus associated with other lesions, our patient received endovascular treatment. The aortic prosthesis was imported from France and the surgery was done 3 days after the patient's admission. This procedure was performed for the first time in Morocco in our hospital with a multidisciplinary team. The prosthesis was implemented successfully and the result was very satisfactory on the heart level.Keywords: Endovascular treatment, aortic isthmian ruptures, endovascular prosthesi

Experimental analysis of upward flow boiling heat transfer in a channel provided with copper metallic foam

International audienceThis work deals with the flow boiling heat transfer inside a channel filled with metallic foam soldered to its lateral walls. The survey on this topic shows that the work in this field is at its beginning. The tested metallic foam samples are made from copper with 36 PPI (Pore per Inch Linear) and 97% porosity and the working fluid being used is n-pentane. In the present work the independent variables are the mass flux in the range from 10 to 100 kg/m(2)s and the heating power with values between 0 and 25 W/cm(2). There are two dependent variables which are the temperature (for the heated wall and inside the channel) and the exit quality. The thermal results are compared to those given by Gungor-Winterton and Shah. The comparison with the Gungor-Winterton correlation shows that the metallic foam insert enhances the heat transfer coefficient by a factor in the range of 2-4 for low quality. Furthermore an inversion point is identified where the effectiveness of the channel filled with metallic foam is reversed compared to a plain channel. This point is given for a constant wall temperature superheat. (C) 2012 Elsevier Ltd. All rights reserved

Pressure drop in metallic foam : emphasis on flow laws experimental determination

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Adaptive Observer Based on MLPNN and Sliding Mode for Wearable Robots: Application to an Active Joint Orthosis

International audienceThis paper deals with the design of an adaptive observer based both on a Multi-Layer Perceptron Neural Network (MLPNN) and a sliding mode technique. Its main objective is to construct the complete state of a given exoskeleton worn by a human subject. The observer we propose in this paper can be used for any application: rehabilitation, assistance, etc. The dynamic model of the global system composed of the exoskeleton and the human is complex and supposed completely unknown. The MLPNN chosen for its characteristic of universal approximation has been used here to identify the unknown dynamic. Its parameters have been adjusted by taking into account the structure of the dynamic model of the considered system and the closed-loop stability based on Lyapunov׳s approach. A Taylor series expansion allows resolving the non-linearity problem present in the MLPNN. Besides the fact that the proposed adaptive observer can be integrated in a control scheme, it also allows us to study the behavior of the exoskeleton before any application on the human subject. The proposed study has been validated both in simulation and in experimentation. The obtained results show the effectiveness of the proposed adaptive approach

Experimental analysis of multiphase flow in metallic foam: flow laws, heat transfer and convective boiling

International audienceThe first part of this work deals with flow laws of gas, liquid and mixtures in metallic foam. This experimental work is based on the stationary pressure profile measurement in a channel filled with metallic foam of several grades or materials for several controlled flow rates. Several foam samples with different characteristics (10, 40, 60, 100 ppi) of copper and of nickel are studied. In single‐phase conditions, we evaluate the permeability and inertial the coefficient according to the Forchheimer model. In the gas flow case, compressibility effects are taken into account. Emphasis is given on the relative contributions of inertial and viscous effects. The specific behavior linked to compressibility effect is thoroughly studied. The adiabatic (air‐water) conditions are analyzed; the results are reported in term of biphasic multipliers according to a simple homogeneous model, to study the impact of foam texture and gas quality on flow laws. Several aspects of the two‐phase flow case (i.e. liquid‐vapor) are discussed: phase repartition, pressure drops, characteristic boiling curve …. In single phase conditions, the heat transfer coefficient was improved by two orders of magnitude with the presence of metallic foam with only a limited increase in pressure drop. In biphasic conditions, the study of convective boiling regime also showed significant heat transfer enhancement with very low‐pressure drops. A simple one dimensional homogeneous model was used and allows a good description of global flow behavior across the test section

Hemi-Synthesis of Chiral Imine, Benzimidazole and Benzodiazepines from Essential Oil of Ammodaucus leucotrichus subsp. leucotrichus

The hemi-synthesis of chiral imine, benzimidazole and benzodiazepine structures is reported by the condensation of (S)-(−)-perillaldehyde, the major phytochemical of Ammodaucus leucotrichus subsp. leucotrichus essential oil, with different amine derivatives of 2,3-diaminomaleonitrile, o-phenylenediamine and 3-[(2-aminoaryl)amino]dimedone. The reaction proceeds in situ at ambient temperature without prior isolation of the natural (S)-(−)-perillaldehyde. Final products precipitate in the ethanolic reaction medium. 2D NMR and single-crystal X-ray diffraction studies were used to unequivocally characterize the structures in solution and in the solid state, respectively. Chiral HPLC analysis confirms the formation of unique enantiomers and diastereomeric mixtures