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  • Open Access

    ARTICLE

    Taguching the Atmospheric Plasma Spraying Process: Influence of Processing Factors on Droplet Impact Properties Obtained on Dense ZrO2 and H2Ar75% Plasma Gas

    Ridha Djebali1, Mohsen Toujani2, Bernard Pateyron3

    CMC-Computers, Materials & Continua, Vol.37, No.3, pp. 147-160, 2013, DOI:10.3970/cmc.2013.037.147

    Abstract In this paper a study of the atmospheric plasma spraying process was conducted. The Jets&Poudres code was used to solve the partial differential equations for the conservation of mass, momentum and energy involved in the problem together with the K-e turbulent model. The Taguchi technique was used to study the influence of processing factors on droplet impact properties obtained on dense zirconia (ZrO2) under H2Ar75% plasma gas that allow optimal functioning condition. The test of the operating parameters for the studied ranges showed that the "thermal power" factor plays a key role on the state of sprayed More >

  • Open Access

    ARTICLE

    A CRITICAL REVIEW OF RECENT INVESTIGATIONS ON TWO-PHASE PRESSURE DROP IN FLOW BOILING MICRO-CHANNELS

    Sira Saisorna,b, Somchai Wongwisesb,c,∗

    Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3007

    Abstract Two-phase pressure drop during flow boiling has been studied for several decades. Obviously, the publications available on micro-channels are relatively small compared with those for ordinarily sized channels. Although the use of micro-channels yields several advantages, the pressure drop taking p lace in these extremely small channels is higher than that in the ordinarily sized channels because of the increased wall friction. The knowledge of the two-phase pressure drop characteristics in addition to heat transfer phenomena is essential to the design and evaluation of the micro-systems. In this paper, recent research on the flow boiling More >

  • Open Access

    ARTICLE

    PRESSURE DROP MEASUREMENTS WITH BOILING IN DIVERGING MICROCHANNEL

    Amit Agrawala,*, V.S. Duryodhana, S. G. Singhb

    Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3005

    Abstract An experimental study of flow boiling through diverging microchannels has been carried out in this work, with the aim of exploring reduction in flow instabilities during boiling in diverging microchannels. Effect of mass flux, heat flux and divergence angle on two phase pressure drop has been studied using deionized water as the working fluid. The experiments are carried out on three test sections with divergence angle of 4, 8 and 12 deg with nearly constant hydraulic diameter (146, 154 and 157 µm respectively), for inlet mass flux and heat flux range of 117 - 1197 kg/m2 More >

  • Open Access

    ARTICLE

    MODELLING OF COMBINED HEAT AND MASS TRANSFER OF WATER DROPLETS IN THERMAL TECHNOLOGY EQUIPMENT

    Gintautas Miliauskas*, Stasys Sinkunas, Kristina Norvaisiene, Kestutis Sinkunas

    Frontiers in Heat and Mass Transfer, Vol.3, No.2, pp. 1-6, 2012, DOI:10.5098/hmt.v3.2.3006

    Abstract Water droplet evaporation process is numerically modelled under various heat and mass transfer conditions. Regularities of heat transfer process interaction are examined. Modelling in this work was performed using the combined analytical – numerical method to investigate heat and mass transfer in the two-phase droplets-gas flow system. The influence of forced liquid circulation on the thermal state of droplets is taken into account by the effective coefficient of thermal conductivity. Calculating the rate of droplet evaporation and the intensity of convective heating, the influence of the Stefan’s hydrodynamic flow is taken into account. Balancing energy More >

  • Open Access

    ARTICLE

    Seasonal testicular changes in Dendropsophus minutus Peters, 1872 (Anura, Hylidae)

    ADELINA FERREIRA1,* AND MAHMOUD MEHANNA2

    BIOCELL, Vol.36, No.2, pp. 57-62, 2012, DOI:10.32604/biocell.2012.36.057

    Abstract The reproductive cycle in anurans may be either continuous or discontinuous. These differences may be connected to seasonal climate changes and/or to anthropic activity. Forty adult male individuals of the Dendropsophus minutus species were collected during one year, in the municipality of Chapada dos Guimarães (Mato Grosso, Brazil). The testicles were studied under light and transmission electron microscopy. No variations were observed when the diameter of the seminiferous tubules and the thickness of the interstitial tissue were studied. However, changes in spermatogenesis were conspicuous and indicated that the reproductive cycle of D. minutus in Chapada dos Guimarães More >

  • Open Access

    ARTICLE

    Optimization and comparison of two different 3D culture methods to prepare cell aggregates as a bioink for organ printing

    RANA IMANI1, SHAHRIAR HOJJATI EMAMI1, HOSSEIN FAKHRZADEH2, NAFISEH BAHEIRAEI1, ALI M SHARIFI* 2,3,4

    BIOCELL, Vol.36, No.1, pp. 37-45, 2012, DOI:10.32604/biocell.2012.36.037

    Abstract The ultimate goal of tissue engineering is to design and fabricate functional human tissues that are similar to natural cells and are capable of regeneration. Preparation of cell aggregates is one of the important steps in 3D tissue engineering technology, particularly in organ printing. Two simple methods, hanging drop (HD) and conical tube (CT) were utilized to prepare cell aggregates. The size and viability of the aggregates obtained at different initial cell densities and pre-culture duration were compared. The proliferative ability of the cell aggregates and their ability to spread in culture plates were also… More >

  • Open Access

    ARTICLE

    Numerical Modelling of Turbulence Effects on Droplet Collision Dynamics using the Level Set Method

    Ashraf Balabel1,

    CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.4, pp. 283-301, 2012, DOI:10.3970/cmes.2012.089.283

    Abstract This paper presents a novel numerical method for solving the twophase flow problems with moving interfaces in either laminar or turbulent flow regimes. The developed numerical method is based on the solution of the Reynolds- Averaged Navier Stokes equations in both phases separately with appropriate boundary conditions located at the interface separating the two fluids. The solution algorithm is performed on a regular and structured two-dimensional computational grid using the control volume approach. The complex shapes as well as the geometrical quantities of the interface are determined via the level set method. The numerical method More >

  • Open Access

    ARTICLE

    Thermal Effects on the Spreading and Solidification of a Micrometric Molten Particle Impacting onto a Rigid Substrate

    S. Oukach1,2,3, H. Hamdi2, M. El Ganaoui4, B. Pateyron1

    FDMP-Fluid Dynamics & Materials Processing, Vol.8, No.2, pp. 173-196, 2012, DOI:10.3970/fdmp.2012.008.173

    Abstract The splat formation is one of the basic processes in thermal spray coatings. The performance of these coatings is strongly related to the process of spreading and solidification of molten droplets. The aim of the present paper is to simulate the fluid flow, heat transfer and phase-change that occur when a micrometric molten droplet impacts onto a rigid substrate and to examine the effect of the substrate conditions, such as initial temperature and material on the solidification time and spreading process. The effect of thermal contact resistance is also investigated. The simulation model used is More >

  • Open Access

    ARTICLE

    NUMERICAL SIMULATION OF DROPLET IMPACT AND SOLIDIFICATION INCLUDING THERMAL SHRINKAGE IN A THERMAL SPRAY PROCESS

    Sina Alavi, Mohammad Passandideh-Fard*

    Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-9, 2011, DOI:10.5098/hmt.v2.2.3007

    Abstract In this paper, a numerical study is performed to investigate the effects of thermal shrinkage on the deposition of molten particles on a substrate in a thermal spray process using the Volume-of-Fluid (VOF) method. Thermal shrinkage is a phenomenon caused by the variation of density during cooling and solidification of a molten metal. The Navier-Stokes equations along with the energy equation including phase change are solved using a 2D/axisymmetric mesh. The VOF method is used to track the free surface of molten particles, and an enthalpy-porosity formulation is used to model solidification. For the normal More >

  • Open Access

    ABSTRACT

    Lattice Boltzmann Simulation of Dynamic Behavior of Liquid Droplets on Solid Surfaces

    Masato Yoshino, Yoshito Tanaka, Keisuke Yano

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.18, No.4, pp. 131-132, 2011, DOI:10.3970/icces.2011.018.131

    Abstract Dynamics of droplet impact on solid surfaces is of great importance in many engineering applications such as ink-jet printing and rapid spray cooling of hot surfaces. In this study, the lattice kinetic scheme based on the lattice Boltzmann method for immiscible two-phase fluids [Inamuro (2006)] is applied to such micro-fluid problems. The present method enables us to perform stable calculations of two-phase flows with large density ratios of up to 1000. The boundary condition based on the wetting potential that is calculated according to a prescribed static contact angle is used on solid surfaces [Briant,… More >

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