The Experts below are selected from a list of 26802 Experts worldwide ranked by ideXlab platform
Predrag Stojan Hrnjak - One of the best experts on this subject based on the ideXlab platform.
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thermo hydraulic model for steam condensation in a large inclined flattened tube air cooled condenser
Applied Thermal Engineering, 2019Co-Authors: William A Davies, Predrag Stojan HrnjakAbstract:Abstract A thermo-hydraulic model for calculating capacity, heat transfer coefficient and void fraction of an inclined air-cooled steam condenser is presented. The condenser tube has an elongated-slot cross-section, with inner dimensions of 214 × 16 mm. The model was developed for a 10.7 m-long tube, and validated by comparison with experiments in a 5.7 m-long tube. The model is for downward inclination angles from 0 to 90°, with co-current vapor and condensate Flow. The cooling air is in cross Flow. This model is developed based on existing models for inclined, Stratified-Flow condensation. These have been adapted to the flattened-tube air-cooled condenser geometry and conditions. The model couples both air- and steam-side behavior in order to accurately resolve the variations in heat transfer coefficients, temperatures, and heat flux. On the steam side, the model is for Stratified Flow, and separates the Flow into two sections: a falling film along the wall, and an axially-Flowing condensate river along the tube bottom. The axially-Flowing condensate river is modeled using open-channel-Flow theory. On the air side, heat transfer coefficient is determined from a combination of empirical correlation and CFD. The model and experimental results show agreement within 5% for capacity and 20% for void fraction for all tube inclinations.
Tasawar Hayat - One of the best experts on this subject based on the ideXlab platform.
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simulation of magnetohydrodynamics and radiative heat transport in convectively heated Stratified Flow of jeffrey nanofluid
Journal of Physics and Chemistry of Solids, 2019Co-Authors: Muhammad Waqas, Tasawar Hayat, S A Shehzad, Ijaz M Khan, A AlsaediAbstract:Abstract The rising requirement regarding energy worldwide necessitates that consideration be devoted to formulating and functioning thermal mechanisms and heat exchangers to utilize and resuscitate thermal energy. Hence new heat transportation liquids subjected to improved heat transport characteristics are required to rise convection heat transportation, and nanoliquids have been proved effective substitutes to standard heat transportation liquids. With such intention, here we formulated mixed convective Jeffrey nanoliquid Stratified Flow considering magnetohydrodynamics. Heat absorption and heat generation aspects in addition to convective conditions and thermal radiation are considered for formulation. Mathematical modeling is based on theory of boundary-layer. Ordinary systems are acquired from partial ones via implementation of apposite variables. Effectiveness of significant variables is reported through graphical outcomes. It is visualized that thermal radiation consideration corresponds to higher temperature in comparison to stratification phenomenon.
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significance of activation energy in Stratified Flow of tangent hyperbolic fluid
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Sumaira Jabeen, Tasawar Hayat, Sumaira Qayyum, Ahmed AlsaediAbstract:Purpose The purpose of this paper is to address double stratification and activation energy in Flow of tangent hyperbolic fluid. Flow is induced by non-linear stretching sheet of variable thickness. Heat flux by Cattaneo–Christov theory is implemented. Design/methodology/approach Non-linear system is computed for the convergent solutions. Attention is particularly focused to the velocity, temperature and concentration. Findings It is found that temperature and thermal layer thickness are decreased for larger stratification. Originality/value In view of aforementioned communication, the aim of the present study is fourfold: First, to inspect stagnation point Flow of tangent hyperbolic liquid by a stretched sheet; second, to discuss effect of non-Fourier heat flux and double stratification; third, to investigate activation energy; and fourth, to examine variable thickness effect.
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Stratified Flow of sutterby fluid with homogeneous heterogeneous reactions and cattaneo christov heat flux
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Muhammad Ijaz Khan, Sumaira Qayyum, Tasawar Hayat, Ahmed AlsaediAbstract:The purpose of this paper is to analyze the Sutterby fluid Flow by a rotating disk with homogeneous-heterogeneous reactions. Inspection of heat transfer is through Cattaneo–Christov model. Stratification effect is also considered.,Nonlinear equations are solved by the homotopy technique.,Sutterby fluid Flow by rotating disk is not considered yet. Here the authors intend to analyze it with Cattaneo–Christov heat flux and homogeneous-heterogeneous reactions. Thermal stratification is also taken into consideration.,No such work is yet done in the literature.
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Stratified Flow of an oldroyd b nanoliquid with heat generation
Results in physics, 2017Co-Authors: M Waqas, Tasawar Hayat, Ijaz M Khan, A AlsaediAbstract:Abstract Here modeling and computations are made to explore the characteristics of mixed convection Flow of Oldroyd-B nanoliquid. Linear stretchable surface creates the Flow. Brownian motion and thermophoretic aspects in nanoliquid modeling are retained. Thermal and solutal stratifications along with heat generation/absorption are considered for heat and mass transfer processes. Boundary layer approach is implemented in the mathematical formulation. The resulting problems are computed by homotopic algorithm. Salient features of Deborah numbers, mixed convection parameter, ratio of thermal to concentration buoyancy forces, Brownian motion parameter, Prandtl number, thermophoretic parameter, thermal/concentration stratification parameter, heat generation/absorption parameter and Schmidt number on the velocity, temperature, nanoparticles concentration and Nusselt and Sherwood numbers are reported through graphs and tables. Besides this the results of presented analysis have been compared with the available works in limiting situations and good agreement is noted.
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on 2d Stratified Flow of an oldroyd b fluid with chemical reaction an application of non fourier heat flux theory
Journal of Molecular Liquids, 2016Co-Authors: M Waqas, Tasawar Hayat, S A Shehzad, Ahmed AlsaediAbstract:Abstract This research work explores the double Stratified Flow of an Oldroyd-B liquid induced by linear stretching surface with first order chemical reaction. Characteristics of heat transfer are investigated by considering non-Fourier heat flux model. Formulation is arranged for variable thermal conductivity. Flux model under consideration is the modified form of Fourier's classical expression which studies the fascinating characteristic of thermal relaxation time. Implementation of appropriate transformations yields ordinary differential systems which are then computed through homotopic procedure. Impacts of various sundry parameters on the non-dimensional velocity, temperature, concentration and Sherwood number are scrutinized. Moreover it is seen that temperature distribution has opposite behavior for thermal relaxation time and variable thermal conductivity parameter.
Gene Kouba - One of the best experts on this subject based on the ideXlab platform.
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critical sand deposition velocity for gas liquid Stratified Flow in horizontal pipes
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Ramin Dabirian, Ram S Mohan, Ovadia Shoham, Gene KoubaAbstract:Abstract Sand is frequently produced along with production fluids from a reservoir with low formation strength. Sand deposition in pipeline causes problems such as equipment failure, pipeline erosion, excessive pressure drop, and production decline. Operating above critical sand deposition velocity, which is the velocity that keeps particles moving all the time at the pipe bottom, is the best strategy to manage sand deposition and simultaneously optimizing production Flow rates. In this paper, a comprehensive study of sand Flow regimes in air – PAC (Polyanionic Cellulose) water Stratified Flow in horizontal pipelines for various sand concentrations upto 10,000 ppm is presented. Six sand Flow regimes are observed, namely, fully dispersed solid Flow, dilute solids at wall, concentrated solids at wall, moving dunes, stationary dunes and stationary bed. Critical sand deposition velocities are determined based on the transition between moving (concentrated solids at wall/moving dunes, as appropriate) and stationary (stationary dunes/bed, as appropriate) sand particles. The viscosity of water is increased to 5 cp by using PAC to investigate the effect of viscous sublayer. The experimental data for tested conditions show that for concentrations above 4000 ppm, stationary beds are observed at the pipe bottom, and bigger particle size has higher critical sand deposition velocities, while for concentrations less than 4000 ppm, stationary dune and stationary bed are observed, and the critical sand deposition velocity depends on which sand Flow regime occurs at the pipe bottom.
Ahmed Alsaedi - One of the best experts on this subject based on the ideXlab platform.
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Stratified Flow of sutterby fluid with homogeneous heterogeneous reactions and cattaneo christov heat flux
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Muhammad Ijaz Khan, Sumaira Qayyum, Tasawar Hayat, Ahmed AlsaediAbstract:The purpose of this paper is to analyze the Sutterby fluid Flow by a rotating disk with homogeneous-heterogeneous reactions. Inspection of heat transfer is through Cattaneo–Christov model. Stratification effect is also considered.,Nonlinear equations are solved by the homotopy technique.,Sutterby fluid Flow by rotating disk is not considered yet. Here the authors intend to analyze it with Cattaneo–Christov heat flux and homogeneous-heterogeneous reactions. Thermal stratification is also taken into consideration.,No such work is yet done in the literature.
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significance of activation energy in Stratified Flow of tangent hyperbolic fluid
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Sumaira Jabeen, Tasawar Hayat, Sumaira Qayyum, Ahmed AlsaediAbstract:Purpose The purpose of this paper is to address double stratification and activation energy in Flow of tangent hyperbolic fluid. Flow is induced by non-linear stretching sheet of variable thickness. Heat flux by Cattaneo–Christov theory is implemented. Design/methodology/approach Non-linear system is computed for the convergent solutions. Attention is particularly focused to the velocity, temperature and concentration. Findings It is found that temperature and thermal layer thickness are decreased for larger stratification. Originality/value In view of aforementioned communication, the aim of the present study is fourfold: First, to inspect stagnation point Flow of tangent hyperbolic liquid by a stretched sheet; second, to discuss effect of non-Fourier heat flux and double stratification; third, to investigate activation energy; and fourth, to examine variable thickness effect.
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on 2d Stratified Flow of an oldroyd b fluid with chemical reaction an application of non fourier heat flux theory
Journal of Molecular Liquids, 2016Co-Authors: M Waqas, Tasawar Hayat, S A Shehzad, Ahmed AlsaediAbstract:Abstract This research work explores the double Stratified Flow of an Oldroyd-B liquid induced by linear stretching surface with first order chemical reaction. Characteristics of heat transfer are investigated by considering non-Fourier heat flux model. Formulation is arranged for variable thermal conductivity. Flux model under consideration is the modified form of Fourier's classical expression which studies the fascinating characteristic of thermal relaxation time. Implementation of appropriate transformations yields ordinary differential systems which are then computed through homotopic procedure. Impacts of various sundry parameters on the non-dimensional velocity, temperature, concentration and Sherwood number are scrutinized. Moreover it is seen that temperature distribution has opposite behavior for thermal relaxation time and variable thermal conductivity parameter.
Hiroshi Honda - One of the best experts on this subject based on the ideXlab platform.
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prediction of evaporation heat transfer coefficient based on gas liquid two phase annular Flow regime in horizontal microfin tubes
Applied Thermal Engineering, 2009Co-Authors: Yueshe Wang, Yanling Wang, Guoxiang Wang, Hiroshi HondaAbstract:Abstract A physical model of gas–liquid two-phase annular Flow regime is presented for predicting the enhanced evaporation heat transfer characteristics in horizontal microfin tubes. The model is based on the equivalence of a periodical distortion of the disturbance wave in the substrate layer. Corresponding to the Stratified Flow model proposed previously by authors, the dimensionless quantity Fr0 = G/[gdeρv(ρl − ρv)]0.5 may be used as a measure for determining the applicability of the present theoretical model, which was used to restrict the transition boundary between the Stratified-wavy Flow and the annular/intermittent Flows. Comparison of the prediction of the circumferential average heat transfer coefficient with available experimental data for four tubes and three refrigerants reveals that a good agreement is obtained or the trend is better than that of the previously developed Stratified Flow model for Fr0 > 4.0 as long as the partial dry out of tube does not occur. Obviously, the developed annular model is applicable and reliable for evaporation in horizontal microfin tubes under the case of high heat flux and high mass flux.
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modified theoretical models of film condensation in horizontal microfin tubes
International Journal of Heat and Mass Transfer, 2002Co-Authors: Hua Sheng Wang, Hiroshi Honda, Shigeru NozuAbstract:The previously proposed theoretical models of film condensation in horizontal microfin tubes have been modified to describe the characteristics of condensing two-phase Flow more accurately. The Stratified Flow regime and the annular Flow regime were considered. For the Stratified Flow regime, the previously proposed theoretical model was modified to take account of the curvature of Stratified condensate due to the surface tension force. For the annular Flow regime, a more accurate expression for the interfacial shear stress was incorporated. Generally, the modified theoretical models predicted a lower circumferential average heat transfer coefficient than the previously proposed ones. Comparison of the theoretical predictions with available experimental data for six tubes and five refrigerants revealed that a good agreement (r.m.s error of less than 21.1%) was obtained for all cases when the higher of the two theoretical predictions were adopted as the calculated value.
