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Rectangular Channel (rectangular + channel)
Selected AbstractsEOF using the Ritz method: Application to superelliptic microchannelsELECTROPHORESIS, Issue 18 2007Chang Yi Wang Abstract An efficient Ritz method is developed from the variational principle to solve the Poisson,Boltzmann equation under the Debye,Hückel approximation for studying the EOF in microchannels. The method is applied to the family of superelliptic cross sections which includes the elliptic channel and the rectangular channel as limiting cases. Several accurate tables presented are useful for design of electroosmotic channels, especially rectangular channels with rounded corners. It is shown how the flow rate Q is a sophisticated consequence of the nondimensional electrokinetic width K, the aspect ratio b as well as the superelliptic exponent n. [source] Study on heat transfer characteristics of porous metallic heat sink with conductive pipe under bypass effectHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2009Sheng-Chung Tzeng Abstract The work investigated the forced convection heat transfer of the heat sink situated in a rectangular channel by considering the bypass effect. The fluid medium was air. The relevant parameters were the Reynolds number (Re), the relative top by-pass gap (C/H), and the relative side by-pass gap (S/L). The size of the heat sink was 60 mm (L)×60 mm(W)×24 mm(H). Two heat sinks were employed as test specimens: (A) the 0.9-porosity aluminum foam heat sink and (B) the 0.9-porosity aluminum foam heat sink with a 20 mm diameter copper cylinder. The copper cylinder was used as a conductive pipe of heat sink. The average Nusselt number was examined under various forced convection conditions. Experimental results demonstrate that increasing by-pass space decreased the Nusselt number. Besides, the average Nusselt number of mode B heat sink was higher than that of mode A heat sink by 30% for the case without by-pass flow. The heat transfer enhancement by the copper cylinder would decline as the by-pass space grew. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20247 [source] Hydromagnetic flow and heat transfer of a conducting Casson fluid in a rectangular channelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2006Hazem Ali Attia Abstract The transient hydromagnetic flow of an electrically conducting viscous incompressible non-Newtonian Casson fluid bounded by two parallel non-conducting plates is studied with heat transfer considering the Hall effect. An external uniform magnetic field is applied perpendicular to the plates and the fluid motion is subjected to a pressure gradient in the axial direction. The lower plate is stationary and the upper plate is suddenly set into motion and simultaneously suddenly isothermally heated to a temperature other than the lower plate temperature. Numerical solutions are obtained for the governing momentum and energy equations taking the Joule and viscous dissipations into consideration. The effect of the Hall term and the parameter describing the non-Newtonian behaviour on both the velocity and temperature distributions are studied. Copyright © 2005 John Wiley & Sons, Ltd. [source] The effect of condenser heat transfer on the energy performance of a plate heat pipe solar collectorINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2005Jorge Facão Abstract For a novel prototype solar collector, using a plate heat pipe, condenser heat transfer was analysed in detail. The condenser has the shape of a rectangular channel. Flow and heat transfer of water in the rectangular channel was modelled and the heat transfer coefficient assessed, using the Fluent code. Under typical operating conditions a mixed convection situation occurs. The channel is inclined and heating is through one wall only (upper channel surface). The range of temperature differences considered was similar to the one verified under real operating conditions, covering a wide range of Grashof numbers. Results showed that the Nusselt number is significantly higher than the one for forced convection in a rectangular channel with fully developed boundary layers. In order to enhance heat transfer, a modification to the rectangular channel was analysed, using baffles to improve flow distribution and increase velocity. The effect of this modification on collector energy performance (efficiency) was assessed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Thermal performance analysis of a tube finned surfaceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2002Kadir Bilen Abstract The present work submits an experimental work on the heat transfer and friction loss characteristic, employing a tube finned heating surface kept at a constant temperature in a rectangular channel. The tube fins attached on the surface (o.d.=29 mm) were arranged as either in-line or staggered. The parameters for the study were Reynolds number (3700,30 000), depending on hydraulic diameter, the distance between the tube fins in the flow direction (Sy/D=1.72,3.45) and the fin arrangement. The change in the Nusselt number with these parameters was determined. For both tube fin arrangements, it was observed that increasing Reynolds number increased Nusselt number, and maximum heat transfer occurred at Sy/D=2.59. Thermal performances for both arrangements were also determined and compared with respect to heat transfer from the same surface without fins. With staggered array, a heat transfer enhancement up to 25 per cent for Sy/D=3.45 in staggered array was achieved in constant pumping power. Copyright © 2002 John Wiley & Sons, Ltd. [source] A three-dimensional pyrazine-2,5-dicarboxylate CdII coordination framework with new (4,4,4)-connected three-nodal topologyACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Ping Yang Poly[(,4 -pyrazine-2,5-dicarboxylato)cadmium(II)], [Cd(C6H2N2O4)]n or [Cd(pzdc)]n (pzdc is the pyrazine-2,5-dicarboxylate dianion), has been synthesized hydrothermally. The asymmetric unit consists of a CdII atom and two independent halves of pzdc ligands that can be expanded via inversion through the centres of the ligands so that each ligand binds to four CdII atoms with the same binding mode using six donor atoms. The CdII centre is in a distorted octahedral coordination geometry with four O- and two N-atom donors from four pzdc ligands. The infinite linkage of the metal atoms and ligands forms a three-dimensional framework with a rectangular channel which is so narrow that there is no measurable void space in the overall structure. This coordination polymer represents the first example of (4,4,4)-connected three-nodal framework. [source] Cover Picture: Electrophoresis 14/2008ELECTROPHORESIS, Issue 14 2008Article first published online: 23 JUL 200 Issue 14 is a regular issue including an Emphasis Section offering a series of 9 papers on ,Microfluidics and Miniaturization". These 9 research papers report on various topics including studying single DNA molecules, selective release of intracellular molecules on the single cell level, isoelectric focusing of proteins in an ordered micropillar array, sample stream focusing in a microchip, integrated microfluidic system for sensing infectious viral disease, EOF in annulus and rectangular channels, confinement effects on monolith morphology, accumulation and filtering of nanoparticles in microchannels, and carbon nanotubes disposable detectors. [source] EOF using the Ritz method: Application to superelliptic microchannelsELECTROPHORESIS, Issue 18 2007Chang Yi Wang Abstract An efficient Ritz method is developed from the variational principle to solve the Poisson,Boltzmann equation under the Debye,Hückel approximation for studying the EOF in microchannels. The method is applied to the family of superelliptic cross sections which includes the elliptic channel and the rectangular channel as limiting cases. Several accurate tables presented are useful for design of electroosmotic channels, especially rectangular channels with rounded corners. It is shown how the flow rate Q is a sophisticated consequence of the nondimensional electrokinetic width K, the aspect ratio b as well as the superelliptic exponent n. [source] Nickel-Organic Coordination Layers with Different Directional CavitiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006Youfu Zhou Abstract The two new metal-organic coordination frameworks [Ni2(pydc)2(4,4,-bpy)(H2O)4]n·0.5n(4,4,-bpy)2H2O (1) and [Ni2(pydc)2(2,2,-bpy)2(H2O)2]n·2nH2O (2) (H2pydc = pyridine-3,4-dicarboxylic acid; bpy = bipyridine) have been synthesised under hydrothermal conditions and characterised by single-crystal X-ray diffraction analysis. The structure of 1 contains parallel rectangular channels that accommodate large 4,4,-bpy guests while that of 2 contains vertical channels coordinated to 2,2,-bpy ligands. Their magnetic analyses show that they exhibit different magnetic interactions. The red shifts of the peak in their emission spectra relative to those of the the free ligands could be attributable to the metal,ligand coordination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Modeling of velocity distribution among microchannels with triangle manifoldsAICHE JOURNAL, Issue 8 2009Minqiang Pan Abstract A model of velocity distribution among microchannels with triangle manifolds is proposed. According to the flow behaviors analyzed by Fluent, the manifolds are divided into several approximate rectangular channels, and then an equivalent simplified resistance network model is developed to establish the relationships between the velocities and pressure drops in microchannels and approximate rectangular channels. The velocity distributions are calculated under two situations, respectively, considering and ignoring singular losses. The outcomes of the present study are compared with Fluent's simulated results to analyze the effects of singular losses on the velocity distributions. It indicates that the proposed model is suitable for the calculation of velocity distribution among microchannels with obtuse angled or right triangle manifolds under low Reynolds numbers. The premise of ignoring singular losses is that the frictional pressure drops are three times larger than the singular pressure drops in each flow loop. The manifold optimization results indicate that the velocity distribution among microchannels with right triangle manifolds is much more uniform than that of the corresponding one with obtuse angled manifolds. © 2009 American Institute of Chemical Engineers AIChE J, 55: 1969,1982, 2009 [source] | |||||||||||||