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Tube Diameter (tube + diameter)
Selected AbstractsAnode-Supported Tubular Micro-Solid Oxide Fuel CellINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2007Partho Sarkar A tubular anode-supported "micro-solid oxide fuel cell" (,SOFC) has been developed for producing high volumetric power density (VPD) SOFC systems featuring rapid turn on/off capability. An electrophoretic deposition (EPD)-based, facile manufacturing process is being refined to produce the anode support, anode functional and electrolyte layers of a single cell. ,SOFCs (diameter <5 mm) have two main potential advantages, a substantial increase in the electrolyte surface area per unit volume of a stack and also rapid start-up. As fuel cell power is directly proportional to the active electrolyte surface area, a ,SOFC stack can substantially increase the VPD of an SOFC device. A decrease in tube diameter allows for a reduction in wall thickness without any degradation of a cell's mechanical properties. Owing to its thin wall, a ,SOFC has an extremely high thermal shock resistance and low thermal mass. These two characteristics are fundamental in reducing start-up and turn-off time for the SOFC stack. Traditionally, SOFC has not been considered for portable applications due to its high thermal mass and low thermal shock resistance (start-up time in hours), but with ,SOFCs' potential for rapid start-up, new possibilities for portable and transportable applications open up. [source] Adiabatic capillary tube flow of carbon dioxide in a transcritical heat pump cycleINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2007Neeraj Agrawal Abstract Flow characteristics of an adiabatic capillary tube in a transcritical CO2 heat pump system have been investigated employing the homogeneous model. The model is based on fundamental equations of mass, energy and momentum which are solved simultaneously. Two friction factor empirical correlations (Churchill, Lin et al., Int. J. Multiphase Flow 1991; 17(1):95,102) and four viscosity models (Mcadams, Cicchitti, Dukler and Lin) are comparatively used to investigate the flow characteristics. Choked condition at the outlet is also investigated for maximum mass flow rate. Subcritical and supercritical thermodynamic and transport properties of CO2 are calculated employing a precision property code. Choice of viscosity model causes minor variation in results unlike in chlorofluorocarbons (CFCs) refrigerants. Relationships between cooling capacity with capillary tube diameter, length and maximum mass flow rate are presented. A lower evaporating temperature yields a larger cooling capacity due to the unique thermodynamic properties of CO2. It is also observed that an optimum cooling capacity exists for a specified capillary tube. Copyright © 2006 John Wiley & Sons, Ltd. [source] COMPUTATIONAL FLUID DYNAMICS MODELING OF FLUID FLOW IN HELICAL TUBESJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2002T. KORAY PALAZOGLU ABSTRACT The effect of different processing parameters on the degree of mixing and axial and radial pressure drops, during single-phase flow in helical tubes was investigated by using CFD software. Correlations were developed to calculate axial and radial pressure drops, and also the ratio of maximum to average fluid velocities. All of these quantities were found to be dependent on curvature ratio (ratio of tube diameter to coil diameter). Flow visualization experiments were performed to assess the degree of mixing in different configurations. At identical conditions, the degree of mixing was higher in the system with the large curvature ratio, which is in agreement with the simulation results. A minimum ratio of maximum to average fluid velocities of 1.61 was achieved, representing a 20% reduction in hold tube length for Newtonian fluid in laminar flow. [source] Transcervical hysteroscopic sterilization using cyanoacrylate: A long-term experimental study on sheepJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 6 2009Sergio Bigolin Abstract Aim:, We investigated the transcervical hysteroscopy application of n-butyl-2-cyanoacrylate in the uterine tube lumen of a non-rodent animals (sheep) with fallopian tube dimensions similar those in humans. Methods:, Standard hysteroscopic procedures were performed on female Texel sheep (n = 26). The right and left ostia were identified. For each ewe, a urethral catheter (5Fr) was used for the delivery of 0.5 mL of saline or an equal volume of n-butyl-2-cyanoacrylate into the uterine tube. Following the procedure, ewes were housed with males of proven fertility for 90 days (equivalent to 5.5 estrous cycles). Postmortem (dye and burst pressure) and in vivo (hysterosalpingogram) testing for tube patency were both performed 90 days and 180 days following the procedure. Results:, All animals receiving the saline treatment became pregnant. Gross inspection of uterine tubes following n-butyl-2-cyanoacrylate treatment revealed no visceral adhesions or fibrosis. However, postmortem testing revealed total obstruction within the fallopian tubes. This was confirmed by hysterosalpingogram, in that iodine contrast did not escape into the abdominal cavity. Conclusion:, The cyanoacrylate promoted a reliable fallopian tube obstruction without fibrosis in an animal model exhibiting a similar tube diameter to that found in women. The technique can be evaluated for efficacy in vivo using hysterosalpingography. [source] Pressure-induced structural transitions in multi-walled carbon nanotubesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2009Hiroyuki Shima Abstract We demonstrate a novel cross-sectional deformation, called the radial corrugation, of multi-walled carbon nanotubes (MWNTs) under hydrostatic pressure. Theoretical analyses based on the continuum elastic approximation have revealed that MWNTs consisting of more than ten concentric walls undergo elastic deformations at critical pressure , above which the circular shape of the cross-section becomes radially corrugated. Various corrugation modes have been observed by tuning the innermost tube diameter and the number of constituent walls, which is a direct consequence of the core,shell structure of MWNTs. Cross-sectional views of MWNT under high hydrostatic pressure: elliptic deformation with the mode index n,=,2 (left), and radial corrugations with n,=,5 (center), and n,=,6 (right). The index n indicates the circumferential wave number of the deformed cross-section. [source] Operation of an industrial steam reformer under severe condition: A simulation studyTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008J. Shayegan Abstract A rigorous two-dimensional model is developed for simulating the operation of a less-investigated type steam reformer having a considerably lower operating Reynolds number, higher tube diameter, and non-availability of extra steam in the feed compared with conventional steam reformers. Simulation results show that reasonable predictions can only be achieved when certain correlations for wall to fluid heat transfer equations are applied. In all cases, strong radial temperature gradients inside the reformer tubes have been found. Furthermore, the results show how a certain catalyst loading profile will affect the operation of the reformer. Un modèle bidimensionnel rigoureux est mis au point pour simuler le fonctionnement d'un reformeur à vapeur d'un type qui a été moins étudié, ayant un nombre de Reynolds de fonctionnement bas, un diamètre de tube élevé et une non disponibilité de vapeur excédentaire dans l'alimentation comparativement aux reformeurs de vapeur classiques. Les résultats de simulation montrent que des prédictions raisonnables peuvent être obtenues seulement lorsque certaines corrélations pour les équations de transfert de chaleur de la paroi vers le fluide sont appliquées. Dans tous les cas, de forts gradients de température radiaux dans les tubes de reformeur ont été trouvés. En outre, les résultats montrent comment un certain profil de chargement de catalyseur influe le fonctionnement du reformeur. [source] Effect of the Equipment Configuration and Operating Conditions on Process Performance and on Physical Characteristics of the Product During Coating in Spouted BedTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2004M. C. P. Publio Abstract The effects of the configuration and operating conditions on the performance of the spouted bed tablet coating process have been studied. The configuration parameters analyzed were the ratio between the draft tube diameter and the inlet orifice diameter, dT/di, and the conical base angle, ,. To analyze the equipment performance the adhesion coefficient, ,, and the increase rate of the tablet mass, K1, were measured as a function of the mass flow rate of the coating material, Ws, of the ratio between the mass feed flow rate of coating suspension relative to mass feed flow rate of the spouting gas, W*s/W*g, of the air flow rate relative to minimum spouting, Q/Qms, and of the feed flow rate of atomising air, Wat. Procedures for the evaluation of the growth kinetics and for measuring the product uniformity are presented. On a étudié les effets de la configuration et des conditions opératoires sur la performance du procédé d'enrobage de tablettes en lit jaillissant. Les paramètres de configuration étudiés sont le rapport entre le diamètre du tube d'aspiration et le diamètre de l'orifice d'entrée, dT/di, et l'angle de base conique, ,. Pour analyser la performance de l'équipement, le coefficient d'adhésion, ,, et la vitesse d'augmentation du poids de la tablette, K1, ont été mesurés en fonction du débit massique du matériau d'enrobage, Ws, du rapport entre le débit d'alimentation massique de la suspension d'enrobage et le débit d'alimentation massique du gaz jaillissant, W*s/W*g, du débit d'air et du jaillissement minimal, Q/Qms, et du débit d'alimentation de l'air d'atomisation, Wat. On présente des méthodes pour évaluer les cinétiques de croissance et mesurer l'uniformité de produit. [source] Catalytic Effects on Thermal Oxidation of Single-Walled Carbon Nanotubes by Alkali Metal ChloridesCHEMCATCHEM, Issue 4 2010Yuki Kobayashi The walled is not enough: Alkali metal chlorides lower the combustion temperature of single-walled carbon nanotubes by more than 100,K. Unlike ordinary reactions of nanotubes, the oxidation reaction in the presence of these salts is independent of the tube diameter, defects, and the degree of bundling. Furthermore, they produce no additional soot upon combustion. [source] Modelling and experimental studies on heat transfer in the convection section of a biomass boilerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2006Jukka Yrjölä Abstract This paper describes a model of heat transfer for the convection section of a biomass boiler. The predictions obtained with the model are compared to the measurement results from two boilers, a 50 kWth pellet boiler and a 4000 kWth wood chips boiler. An adequate accuracy was achieved on the wood chips boiler. As for the pellet boiler, the calculated and measured heat transfer rates differed more than expected on the basis of the inaccuracies in correlation reported in the literature. The most uncertain aspect of the model was assumed to be the correlation equation of the entrance region. Hence, the model was adjusted to improve the correlation. As a result of this, a high degree of accuracy was also obtained with the pellet boiler. The next step was to analyse the effect of design and the operating parameters on the pellet boiler. Firstly, the portion of radiation was established at 3,13 per cent, and the portion of entrance region at 39,52 per cent of the entire heat transfer rate under typical operating conditions. The effect of natural convection was small. Secondly, the heat transfer rate seemed to increase when dividing the convection section into more passes, even when the heat transfer surface area remained constant. This is because the effect of the entrance region is recurrent. Thirdly, when using smaller tube diameters the heat transfer area is more energy-efficient, even when the bulk velocity of the flow remains constant. Copyright © 2006 John Wiley & Sons, Ltd. [source] FLOW PROPERTIES AND TUBE FRICTION FACTOR OF MILK CREAM: INFLUENCE OF TEMPERATURE AND FAT CONTENTJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2010RODRIGO DIAZ FLAUZINO ABSTRACT The rheological behavior of milk cream was studied for different fat contents (0.10 to 0.31) and for a wide temperature range (2 and 87C) using a rotational rheometer. Newtonian behavior was observed, except for fat content between 0.20 and 0.31 and temperature between 2 and 33C, where viscoplastic behavior was remarkable. The rheological parameters (Newtonian viscosity, plastic viscosity and yield stress) and density were well correlated to temperature and fat content. Tube friction factor during flow of cream was experimentally obtained at various flow rates, temperatures and tube diameters (86 , Re , 2.3 × 104, 38 , ReB , 8.8 × 103, 1.1 × 103 , He , 6.7 × 103). The proposed correlations for density and rheological parameters were applied for the prediction of friction factor for laminar and turbulent flow of cream using well-known equations for Newtonian and viscoplastic flow. The good agreement between experimental and predicted values confirms the reliability of the proposed correlations for describing the flow behavior of cream. PRACTICAL APPLICATIONS This paper presents correlations for the calculation of density and rheological parameters (Newtonian viscosity, Bingham plastic viscosity and yield stress) of milk cream as functions of temperature (2,87C) and fat content (0.10,0.31). Because of the large temperature range, the proposed correlations are useful for process design and optimization in dairy processing. An example of practical application is presented in the text, where the correlations were applied for the prediction of friction factor for laminar and turbulent tube flow of cream using well-known equations for Newtonian and viscoplastic flow, which are summarized in the text. The comparison with experimental data obtained at various flow rates, temperatures and tube diameters showed a good agreement, which confirms the reliability of the proposed correlations. [source] Structure, stability and electronic properties of composite Mo1,xNbxS2 nanotubesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2006V. V. Ivanovskaya Abstract The effect of Mo , Nb substitution on the electronic structure of MoS2 nanotubes has been investigated using the density functional tight binding method (DFTB). It has been found that composite Mo1,xNbxS2 nanotubes (with Nb contents of 5, 10 and 25 at%) are more stable than the corresponding pure tubes, especially for larger tube diameters. The defect-formation energy indicates that the most stable dopant arrangement is a NbS2 stripe along the tube direction. However, entropy effects may favor a random arrangement of Nb dopant atoms at high temperatures in the tubes with a larger diameter. All of the studied Mo1,xNbxS2 nanotubes have metallic properties, independent of their chirality, diameters and ordering type of substitutional atoms. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||