159 research outputs found
Comparison of the thermal performances of two nanofluids at low temperature in a plate heat exchanger
International audienceThe objective of this study is to compare experimentally the thermal performances of two types of commercial nanofluids. The first is composed of oxides of alumina (Al2O3) dispersed in water and the second one is aqueous suspensions of nanotubes of carbons (CNTs). The viscosity of the nanofluids is measured as a function of the temperature between 2 and 10°C. An experimental device, containing three thermal buckles controlled in temperature and greatly instrumented permits to study the thermal convective transfers. The evolution of the convective coefficient permits to study the convective thermal transfers. The evolution of the convective coefficient is presented according to the Reynolds number, at low temperature from 0 to 10°C and for the two aforementioned nanofluids. An assessment of the pressure drops in the circuit as well as of the powers of the circulator and outputs is dealt with
ETUDE EXPERIMENTALE ET SIMULEE D'UN PILOTE DE DISTILLATION MEMBRANAIRE
National audienceUne Ă©tude de caractĂ©risation expĂ©rimentale de l'air gap membrane distillation (AGMD) est effectuĂ©e sur une installation pilote. Lors des essais, nous avons utilisĂ© de l'eau de mer synthĂ©tique (35 g/l de sels). Les rĂ©sultats montrent que le flux de permĂ©at augmente lorsque la tempĂ©rature et le dĂ©bit d'alimentation augmentent et lorsque l'Ă©paisseur de l'air gap diminue (de 3,12 Ă 1,04 mm). En parallĂšle, le phĂ©nomĂšne a Ă©tĂ© modĂ©lisĂ© Ă l'aide du logiciel EES sur les aspects des transferts thermique et de masse. Le modĂšle 1D, construit Ă partir d'Ă©quations de transfert et de corrĂ©lations de la littĂ©rature, rend bien compte des phĂ©nomĂšnes prĂ©sents dans le pilote de distillation membranaire. Le flux de permĂ©at maximal obtenu est de 7,4 kg/mÂČ h avec une tempĂ©rature du fluide chaud de 65°C, un air gap de 1,04 mm et des dĂ©bits chaud et froid Ă©gaux Ă 5 l/min. Sur l'ensemble des mesures, l'Ă©cart relatif maximal entre les rĂ©sultats expĂ©rimentaux et simulĂ©s est de 10 % observĂ© pour la tempĂ©rature de 65 °C. Les rĂ©sultats par faible tempĂ©rature de fluide chaud pourront ĂȘtre intĂ©ressants dans le projet d'un couplage avec une machine frigorifique
CaractĂ©risation expĂ©rimentale dâune unitĂ© de distillation membranaire AGMD pour un couplage avec une thermofrigopompe
National audienceLa croissance dĂ©mographique mondiale entraine une augmentation des besoins en froid commercial et domestique, en rafraĂźchissement ou climatisation ainsi quâen eau potable. Dans l'objectif dâun dĂ©veloppement social et industriel durable, il apparaĂźt indispensable pour certaines populations, en particulier dans les sites isolĂ©s, que de nouveaux systĂšmes Ă©conomes en Ă©nergie pour la production d'eau potable soient dĂ©veloppĂ©s. Lâobjectif gĂ©nĂ©ral est de coupler une thermofrigopompe (TFP) Ă une unitĂ© de distillation membranaire pour la production de froid et le dessalement de lâeau de mer (figure 1). La technique utilisĂ©e pour le dessalement est lâAGMD, air gap membrane distillation. Câest un procĂ©dĂ© thermique et membranaire (figure 2) basĂ© sur la crĂ©ation dâun gradient de pression de vapeur gĂ©nĂ©rĂ© par un gradient de tempĂ©rature de part et dâautre dâune membrane microporeuse hydrophobe. Une Ă©tude de caractĂ©risation expĂ©rimentale de lâAGMD est effectuĂ©e sur une installation pilote. Plusieurs paramĂštres influents tels que les tempĂ©ratures, les dĂ©bits, lâĂ©paisseur de lâair gap et le type dâĂ©coulement sont Ă©tĂ© Ă©tudiĂ©s. Lors des essais nous avons utilisĂ© de lâeau de mer synthĂ©tique (35g/l). Les rĂ©sultats montrent que le flux de permĂ©at augmente lorsque la tempĂ©rature et le dĂ©bit dâalimentation augmentent et lorsque lâĂ©paisseur de lâair gap diminue. Le taux de rejet de sel est de 99,9%. Le type dâĂ©coulement (co-courant ou contre-courant) Ă une faible influence sur le flux de permĂ©at. Cette Ă©tude expĂ©rimentale confirme que le couplage dâune thermofrigopompe avec une unitĂ© de distillation membranaire est rĂ©alisable grĂące aux faibles tempĂ©ratures de fonctionnement (25 Ă 65°C) qui correspondent Ă la gamme de tempĂ©rature en production de chaleur de la TFP. Une modĂ©lisation du comportement du pilote a Ă©tĂ© effectuĂ©e et validĂ©e. Ce modĂšle permet de caractĂ©riser les phĂ©nomĂšnes mĂ©caniques et thermiques dans lâinstallation. Il sera utilisĂ© pour dimensionner un prototype de TFP couplĂ© Ă lâAGMD puis pour simuler une installation de climatisation et de production dâeau douce pour des bĂątiments Ă taille rĂ©elle
Experimental study of heat transfer in a double pipe exchanger using nanofluids: solar application
Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.Recently, a new class of fluid made up of metal nano-particles in suspension in a liquid, called nanofluid, appeared. Some numerical studies have shown that these new fluids have a higher heat transfer performance, compared with the conventional liquids. In the present study, we have attempted to study, by experimentation, the thermal performances of a particular nanofluid composed of aluminum oxide (ÎłAl2O3) particles dispersed in ethylene glycol 30% for various concentrations ranging from 0 to 2 %. The experimental set up is a coaxial exchanger, which is destined to solar application, in which the heating liquid used is the nanofluid studied.vk201
COMPARAISON ENERGETIQUE ET EXERGETIQUE DE SYSTEMES DE DESSALEMENT
National audienceDans certaines zones du monde, l'eau potable n'est pas une ressource abondante et est produite par des systĂšmes de dessalement. Par ailleurs, les ressources en Ă©nergie doivent ĂȘtre rationalisĂ©es. Les performances des systĂšmes de dessalement sont difficiles Ă comparer car les technologies peuvent ĂȘtre trĂšs diffĂ©rentes et faire appel Ă des procĂ©dĂ©s thermiques, Ă©lectriques ou mĂ©caniques, membranaires ou non. L'exergie correspond Ă l'Ă©nergie mĂ©canique potentiellement produite par une quantitĂ© de chaleur, une quantitĂ© d'Ă©nergie chimique ou Ă©lectrique. L'Ă©nergie mĂ©canique est considĂ©rĂ©e comme une forme pure d'exergie. Cette Ă©tude Ă©mane d'une Ă©tude bibliographique menĂ©e dans le cadre d'un projet de couplage d'une machine frigorifique avec un systĂšme de dessalement. Cet article prĂ©sente les quantitĂ©s d'exergie consommĂ©e et les indices de comparaison usuels (GOR, Gained Output Ratio et PR, Performance Ratio) pour diffĂ©rents systĂšmes de dessalement testĂ©s dans notre laboratoire ou dont les donnĂ©es ont Ă©tĂ© rĂ©coltĂ©es dans la littĂ©rature. Les systĂšmes Ă©tudiĂ©s dans cet article sont des installations d'osmose inverse, de distillation membranaire, de distillation multiple-effet et un distillateur solaire. Les rĂ©sultats montrent que la distillation membranaire prĂ©sente des caractĂ©ristiques intĂ©ressantes, notamment dans le cadre d'un couplage avec une source de chaleur Ă basse tempĂ©rature
Implementation of active management of the third period of childbirth for the prevention of immediate post-partum bleeding in four regional maternity hospitals of Conakry, Guinea
Background: The objective of this study was to determine the frequency, skills level of health care service providers; to identify complications and difficulties related to the implementation of AMTPC/GATPA.Methods: It was about prospective study, descriptive of 6 months (1st March to 31st August 2014) carried out in the maternity hospitals of Faranah, Kindia, Mamou and Nzérékoré. It concerned the parturient women who had recently given birth and the personnel that carried out AMTPC/GATPA in these hospitals.Results: During the study period of 1,254 out of 1,305 births had benefited of AMTPC/GATPA, a frequency of 96.1%. The midwives were the most represented personnel in the implementation of GATPA (44.1%). In 46.4% of the cases, the health care service providers acquired this competence from the initial training. The release was obtained in the first trial in 64.9% cases. The duration of implementation of GATPA was less than 5 minutes in 72.6% cases. The different stages were respected in 91.5% cases. Complications were dominated by retention of placental fragments (10.2%). Lack of oxytocin was the main difficulty (36.6%).Conclusions: The sustainability of this achievement would depend on the systematic and correct implementation of AMTPC/GATPA at all childbirth attendants and the effective management of oxytocin
Parasitoses Intestinales Et Statut Nutritionnel Chez Lâenfant Ă GuĂ©diawaye Au SĂ©nĂ©gal
Introduction : Les parasitoses intestinales constituent un problĂšme majeur de santĂ© dans le monde particuliĂšrement dans les pays en voie de dĂ©veloppement. Afin de rĂ©duire lâampleur de ces affections, le MinistĂšre de la SantĂ© du SĂ©nĂ©gal a introduit en 2005 le dĂ©parasitage de masse systĂ©matique des enfants conformĂ©ment aux recommandations de lâOrganisation Mondiale pour la SantĂ© (OMS). Lâobjectif de ce travail Ă©tait de dĂ©terminer la prĂ©valence des parasitoses intestinales et leur impact sur lâanĂ©mie et la nutrition quelques annĂ©es aprĂšs lâinstauration de la chimiothĂ©rapie prĂ©ventive. MatĂ©riels et mĂ©thodes : Etude transversale du 1er septembre 2017 au 28 fĂ©vrier 2018 au niveau du service de pĂ©diatrie du Centre Hospitalier Roi Baudouin de GuĂ©diawaye. Un effectif de 375 enfants avait participĂ© Ă lâĂ©tude, avec un Ăąge moyen 44 mois et une prĂ©dominance masculine (54,1%). Pour chaque enfant reçu, un examen direct de selles et aprĂšs une concentration par technique de Ritchie Ă©taient effectuĂ©s. LâĂ©tat nutritionnel a Ă©tĂ© apprĂ©ciĂ©s et les paramĂštres hĂ©matologiques Ă©valuĂ©s. RĂ©sultats : Au total, 103 enfants Ă©taient porteurs de parasites soit une prĂ©valence globale de 27,5%. Les helminthes Ă©taient beaucoup plus reprĂ©sentatifs que les protozoaires et les espĂšces parasitaires les plus frĂ©quentes Ă©taient Ascaris lumbricoides (18,14%), TrichocĂ©phales (3,74%), et Entamoeba coli (2,67%). LâĂ©tat nutritionnel Ă©tait normal chez 265 enfants tandis que 18,9% et 10,5% avaient respectivement une malnutrition aigĂŒe modĂ©rĂ©e (MAM) et une malnutrition aigĂŒe sĂ©vĂšre (MAS). Nous avons notĂ© une association significative entre la parasitose intestinale et la malnutrition (p=0,035 et OR=1,66). LâanĂ©mie Ă©tait sĂ©vĂšre chez 4,8% des enfants et modĂ©rĂ©e chez 68,6%. Une corrĂ©lation entre les parasitoses intestinales et la survenue dâune anĂ©mie a Ă©tĂ© dĂ©montrĂ©e (p=0,001 et OR=2,6). Conclusion : La prĂ©valence des parasitoses intestinales reste Ă©levĂ©e en banlieue dakaroise malgrĂ© le dĂ©parasitage de masse. LâamĂ©lioration des conditions de vie et lâĂ©largissement du dĂ©parasitage aux enfants de plus de 5 ans pourraient rendre plus efficiente cette stratĂ©gie.
Introduction: Intestinal parasitosis is a major health problem in the world, particularly in developing countries. In order to reduce the scale of these diseases, the Ministry of Health of Senegal introduced, in 2005, the systematic mass deworming of children in accordance with the recommendations of the World Health Organisation (WHO). This paper focuses on determining the prevalence of intestinal parasites and their impact on anemia and nutrition a few years after the initiation of preventive chemotherapy. Materials and methods: A cross-sectional study was conducted from 1st September 2017 to 28th February 2018 at the pediatric ward of the hospital center Roi Baudouin in Guédiawaye, Senegal. A total of 375 children participated in the study, with a mean age of 44 months and a male predominance (54.1%). Each child received a direct stool examination after a concentration using Ritchie techniques was obtained. The nutritional status was assessed and the hematological parameters evaluated. Results: A total of 103 children had parasites, with an overall prevalence of 27.5%. Helminths were much more representative than the protozoa, and the most common parasitic species were Ascaris lumbricoides (18.14%), whipworms (3.74%), and Entamoeba coli (2.67%). Nutritional status was normal in 265 children, while 18.9% and 10.5% respectively had moderate acute malnutrition (MAM) and severe acute malnutrition (SAM). A significant association between intestinal parasitosis and malnutrition was found (p = 0.035 and OR = 1.66). Anemia was severe in 4.8% of children and moderate in 68.6%. There was a link between intestinal parasitosis and the occurrence of anemia (p = 0.001 and OR = 2.6). Conclusion: The prevalence of intestinal parasitosis remains high in the suburbs of Dakar despite mass deworming. Improving living conditions and expanding deworming to children over 5 years of age could make this strategy more efficient
Bis(2-{[2-(2-hyÂdroxyÂbenzylÂamino)ÂethÂyl]aminoÂmethÂyl}phenolato-Îș3 N,NâČ,O 1)cobalt(III) nitrate monohydrate
In the title compound, [Co(C16H19N2O2)2]NO3·H2O, the CoIII ion is located on an inversion center and is six-coordinated by two phenolate O atoms and four amino N atoms from two diamine ligands, forming an octaÂhedral geometry. The water molÂecule and the nitrate anion are located close to an inversion center, and are thus equally disordered by symmetry. The crystal packing is stabilized by interÂmolecular OâHâŻO hydrogen bonds involving the uncoordinated water molÂecule and the free phenol hydroxyl group with the nitrate anion. NâHâŻO hydrogen bonds involving the amino groups and the nitrate anions connect the complex molÂecules along the c axis
Obstetric emergencies in the maternity ward of the Ignace Deen national hospital CHU of Conakry: sociodemographic, therapeutic and maternal fetal prognosis aspects
Background: Despite government efforts to reduce maternal mortality, the risk of a woman dying from obstetric complications is about one in six in the poorest regions of the world compared to one in thirty thousand in North Europe. The objective was therefore to describe the clinical socio-demographic aspects and to establish the maternal and fetal prognosis of obstetric emergencies.Methods: This was a descriptive cross-sectional prospective study over a 6-month period from January 1 to June 30, 2020 carried out at the maternity ward of the Ignace Deen national hospital (Conakry university hospital) in Guinea. The study looked at a continuous series of 662 obstetric emergency cases.Results: The frequency of admission of obstetric emergencies was 22.62%. They concerned young women (29.5 years old) on average, first-time mothers (53.32%), with low income professional activities, evacuated from a peripheral maternity unit (63.14%), no schooling (44.9%), married (92.3%), using the more often a means of public transport (66.5%) and whose pregnancies were poorly monitored (63.9%). Fetal emergencies were dominated by acute fetal distress (91.3%) and maternal emergencies were dominated by hypertensive emergencies (pre-eclampsia and eclampsia 37.44%) followed by hemorrhagic emergencies (last trimester hemorrhage and postpartum hemorrhage 34.34%). Pregnant and parturient women were more frequently admitted to labor (62.7%) and gave birth more frequently by caesarean section (86.70%). the staff reacted promptly to make a treatment decision in 75.5% of cases within fifteen minutes. emergency procedures were performed in less than fifteen minutes in almost all cases (97.4%), specific treatment was carried out in less than an hour in the majority of cases (68.3%). The maternal case fatality rate was 4.1% with the main cause of death being hemorrhagic shock of 51.8%. The stillbirth rate was 17.4%.Conclusions: The anticipation of emergency obstetric care (SOU) and close collaboration between the obstetrician, the anesthesiologist-resuscitator are essential in the management of obstetric emergencies
3,3âČ-Dibenzoyl-1,1âČ-(3,6-dioxaoctane-1,8-diÂyl)dithioÂurea
In the molÂecule of the title compound, C22H26N4O4S2, the central OâCH2âCH2âO chain adopts a synclinal conformation [torsion angle = 65.0â
(2)°]. The crystal structure is stabilized by intraÂmolecular NâHâŻO=C and interÂmolecular NâHâŻOâC hydrogen bonds
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