Papers by Mohammad Mohammadiun
In this paper a complete three-dimensional and two phase CFD model for flow distribution in an op... more In this paper a complete three-dimensional and two phase CFD model for flow distribution in an open channel investigated. The finite volume method (FVM) with a dynamic Sub grid-scale was carried out for seven cases of different aspect ratios, different inclination angles or slopes and convergencedivergence condition. The volume of fluid (VOF) method was used to allow the free-surface to deform freely with the underlying turbulence. The discharge through open channel flow is often evaluated by velocity-area integration method from the measurement of velocity at discrete locations in the measuring section. The variation of velocity along horizontal and vertical directions is thus very important to decide the location of the sensors. The aspect ratio of the channel, slope of the channel and divergenceconvergence of the channel have investigated and the results show that the depth of water at the end of the channel is higher at AR=0.8 against the AR=0.4 and AR=1.2. Also it is clear that...
Journal of Thermal Analysis and Calorimetry
For the first time, a numerical solution code, based on Levenberg–Marquardt method is presented f... more For the first time, a numerical solution code, based on Levenberg–Marquardt method is presented for solving non-linear problem of inverse heat transfer in axisymmetric stagnation flow impinging on a cylinder rod to determine time-dependent wall temperature by temperature distribution at a specific point in the fluid region. Also, the effect of noisy data on the final result has been studied. For this purpose, the numerical solution of the dimensionless temperature and the convective heat transfer in a radial incompressible flow on a cylinder axis is carried out as a direct problem. In the direct problem, the free stream is steady with an initial flow strain rate of k¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{k}$$\end{document}. Using similarity variable and appropriate transformations, momentum and energy equations are converted into semi-similar equations. The new equation systems are then discretized using an implicit finite difference method and solved by applying the tridiagonal matrix algorithm (TDMA). The wall temperature is then estimated by applying the Levenberg–Marquardt parameter estimation approach. This technique is an iterative approach based on minimizing the least-square summation of the error values, the error being the difference between the estimated and measured temperatures. Results of the inverse analysis indicate that the Levenberg–Marquardt algorithm is an efficient and acceptably stable technique for estimating wall temperature in axisymmetric stagnation flow. The maximum value of the sensitivity coefficient is related to the estimation of polynomial wall temperature and its value is 0.1952 also the minimum value of the sensitivity coefficient is 8.62 × 10–6 which is related to the triangular wall temperature. The results show that the parameter estimation error in calculating the triangular and trapezoidal wall temperature is greater than the others because the maximum value of RMS error is obtained for these two cases, which are 0.451 and 0.479, respectively, the reason for the increase in error in estimating these functions is the existence of points where the first derivative of the function does not exist. This method also exhibits considerable stability for noisy input data.
Inverse Problems in Science and Engineering
ABSTRACT In this paper for the first time, a numerical code based on Levenberg–Marquardt method i... more ABSTRACT In this paper for the first time, a numerical code based on Levenberg–Marquardt method is presented for solving inverse heat transfer problem of axisymmetric stagnation flow impinging on a cylinder with uniform transpiration and to estimate the time-dependent heat flux using temperature distribution at a point. The effect of noisy data on the final result is studied. The maximum value of the sensitivity coefficient is related to estimation of exponential heat flux and its value is 0.1718 also the minimum value of the sensitivity coefficient is 7.50 × 10−6 which is related to the triangular heat flux. The results show that the parameter estimation error in calculating the triangular and trapezoidal heat flux is greater than the exponential and sinus–cosines heat flux because the maximum value of RMS error is obtained for these two cases, which are 0.458 and 0.492, respectively the reason for the increase in error in estimating these functions is the existence of points where the first derivative of the function does not exist. This method also exhibits considerable stability for noisy input data. In most cases, surface blowing decreases the prediction accuracy by removing the boundary layers from the surface whereas suction acts vice versa.
Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering
Micro channels are widely used in different industries. The investgations on heat transfer improv... more Micro channels are widely used in different industries. The investgations on heat transfer improvments of these instruments are of significant inportance. At hte present study, the influence of different nano-fluids and geometrical charectrestics on the thermal performance of a heat sink which is especially for for micro-channels are investigated. In the present study, the authors investigated the Nusselt number and pressure drop in differential geometries and Reynolds numbers (Re). Then the micro-channel was investigated with different heat flux (q).In the first step, the micro-channel was examined and the final numerical results showed that the hexagonal cross-section can improve heat transfer about 9%. At the second step and after selecting appropriate parameters, the effect of three nano-particles (Al2O3 - CuO- TiO2) were studied. The results presented that aluminum oxide (Al2O3) has the best heat transfer rate among the mentioned nano-fluids. With the presence of nano-particles...
Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering
Few papers investigated the effect of different nano-fluids and geometrical parameters of the mic... more Few papers investigated the effect of different nano-fluids and geometrical parameters of the micro channels on the performance of heat sinks. In this study, Nusselt number and pressure drop are investigated in differential geometry and Reynolds numbers. Then the effect of the micro-channel is studied for different heat flux. The results show that hexagonal micro-channels represents a better performance than the rectangular and the heat transfer of without using nano-particles in the hexagonal cross-section is about 9% higher than the rectangular cross-section and with the presence of nanoparticles (Al2O3 - CUO- TiO2, φ = 4%), heat transfer is about 30 to 40% higher than the base liquid.
Alexandria Engineering Journal
Dimensionless temperature, Nusselt number and entropy generation in stagnation flow of incompress... more Dimensionless temperature, Nusselt number and entropy generation in stagnation flow of incompressible nanofluid over an infinite cylinder accompanying uniform suction and blow in steady state have been investigated in this study. Free stream has been steady as well with the initial stream rate of k. Dimensional analysis and similarity solution of Navier-stokes and energy equations have been presented. These equations are simplified implementing appropriate transformations introduced in this research. The similarity equations are solved where the cylinder's wall is under constant Temperature. All these solutions are acceptable for Reynolds numbers Re ¼ ka 2 =2t f of 0.1-1000, various dimensionless surface diffusion S ¼ U o = k a and specific volume fractions of nano particles where a is the cylinder radius and t f is the kinematic viscosity of the basefluid. The results show that for all Reynolds numbers, diffusion depth of radial and axial components of velocity field and wall shear stress increases as a result of decline in nano particles volume fraction and growth in surface diffusion. Moreover, increase in nano particles volume fraction and surface suction raises heat transfer coefficient and Nusselt number. Also the largest amount of entropy generated is calculated.
Case Studies in Thermal Engineering
Journal of Thermophysics and Heat Transfer, 2016
In this paper, the conjugate gradient method, coupled with the adjoint problem, is used to solve ... more In this paper, the conjugate gradient method, coupled with the adjoint problem, is used to solve the inverse heat conduction problem and to estimate the time-dependent heat flux, using temperature distribution at a point in a three-layer system. Also, the effect of noisy data on the final solution is studied. The numerical solution of the governing equations is obtained by employing a finite difference technique. For solving this problem, the general coordinate method and body-fitted coordinate method are used. The irregular region in the physical domain (r, z) is transformed into a rectangle in the computational domain (ξ, η). The present formulation is general and can be applied to the solution of boundary inverse heat conduction problems over any region that can be mapped into a rectangle. The obtained results show the good accuracy of the presented method. Also, the solutions have good stability even if the input data includes noise. The problem is solved in an axisymmetric case. Applications of this ...
5th ANKARA INTERNATIONAL …, 2009
In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we fi... more In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we first calculate the thermodynamic properties behind of the normal shock, for the supersonic flow of the hot gas. After finding these properties, we are able to calculate the boundary layer ...
In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we fi... more In this paper, the aero heating of spherical stagnation point is studied. For this purpose, we first calculate the thermodynamic properties behind of the normal shock, for the supersonic flow of the hot gas. After finding these properties, we can calculate the boundary layer properties and then we will be able to determine the heat flux of the spherical stagnation point. This heat flux can be used as a boundary condition in heat transfer code for axial asymmetric case. After computing transient multilayer heat transfer toward the inner side of the shell (which material varies in each layer), we can determine stagnation point temperature and temperature distribution in various layers. To verify the validity of the used numerical procedure in this work, comparisons with the theoretical and experimental results for the X-33 space vehicle have been conducted.
In this paper, the conjugate gradient method coupled with adjoint problem is used in order to sol... more In this paper, the conjugate gradient method coupled with adjoint problem is used in order to solve the inverse heat conduction problem and estimation of the strength of the time- dependent heat source using the temperature distribution at a point in a three layer system. Also, the effect of noisy data on final solution is studied. The numerical solution of the governing equations is obtained by employing a finite-difference technique. For solving this problem, the general coordinate method is used. We solve the inverse heat conduction problem of estimating the strength of the transient heat source, inside an irregular region. The irregular region in the physical domain (r, z) is transformed into a rectangle in the computational domain (x ,h ). The present formulation is general and can be applied to the solution of inverse heat conduction problems inside any region that can be mapped into a rectangle. The obtained results for few selected examples show the good accuracy of the pres...
International Journal of Energy, Environment and Economics
Abstract In this paper a complete three-dimensional and two phase CFD model for flow distribution... more Abstract In this paper a complete three-dimensional and two phase CFD model for flow distribution in an open channel investigated. The finite volume method (FVM) with a dynamic Sub grid-scale was carried out for seven cases of different aspect ratios, different inclination angles or slopes and convergencedivergence condition. The volume of fluid (VOF) method was used to allow the free-surface to deform freely with the underlying turbulence. The discharge through open channel flow is often evaluated by velocity-area integration method from the measurement of velocity at discrete locations in the measuring section. The variation of velocity along horizontal and vertical directions is thus very important to decide the location of the sensors. The aspect ratio of the channel, slope of the channel and divergenceconvergence of the channel have investigated and the results show that the depth of water at the end of the channel is higher at AR=0.8 against the AR=0.4 and AR=1.2. Also it is c...
International Journal of Scientific World, Mar 30, 2015
The steady-state, viscous flow of Nanofluid in the vicinity of an axisymmetric stagnation point o... more The steady-state, viscous flow of Nanofluid in the vicinity of an axisymmetric stagnation point of a stationary cylinder is investigated. The impinging free-stream is steady and with a constant strain rate. Exact solution of the Navier-Stokes equations is derived in this problem. A reduction of these equations is obtained by use of appropriate transformations introduced in this research. The general self-similar solution is obtained when the wall temperature of the cylinder is constant. All the solutions above are presented for Reynolds numbers ranging from 0.1 to 1000 and selected values of particle. For all Reynolds numbers, as the particle fraction increases, the depth of diffusion of the fluid velocity field in radial direction, the depth of the diffusion of the fluid velocity field in-direction, shear-stresses and pressure function decreases. Nomenclature Density of the nanofluid Particle fraction Density of the base fluid Density of the particles Equivalent diameter of a base fluid molecule Equivalent diameter of a particle molecule Dynamic viscosity of the nanofluid Dynamic viscosity of the base fluid Similarity variable Reynolds number for nanofluid Reynolds number for base fluid free stream strain rate Cylinder radius Cylindrical coordinates
International Journal of Scientific World, Feb 6, 2015
In order to separating benzene and toluene (BT), in the aromatic distillation unit of BuAli petro... more In order to separating benzene and toluene (BT), in the aromatic distillation unit of BuAli petrochemical are used of a distillation column containing 55 trays. For condensing steam in the upper part of air cooler and down, a natural gas furnace,which the fuel is sharply 1 million cubic foot (MMscfd) is applied.It was equipped with two ultra-high energy consumption so that energy costs has been estimated 93384 $in the year. in this study,According to the need of reduce energy consumption in consumer industries,especially oil, gas and petrochemical,we decided to investigate the energy recovery for aromatic distillation unit of BuAli petrochemical and with using of specialized software AspenPlus we provided a method for this purpose.In this regard,According to information taken from BuAli complex,several simulations were performed, and finally,the least investments expensive model with reducing energy consumption has been selected.The results of the selected model can be cited to remove completely power consumption of the air conditioner,45% reduction in fuel consumption in furnaces and heat exchangers,and ultimately58% reduction in the production of pollutant emissions that play important role in damaging the environment.
International Journal of Scientific World, 2014
ABSTRACT Exergy rate profiles, exergetic efficiency and irreversibility were used to examine the ... more ABSTRACT Exergy rate profiles, exergetic efficiency and irreversibility were used to examine the driving forces in multicomponent distillation system with the view to identifying feasible and efficient operating parameters. The mixture comprised of 5% propane, 15% iso butane, 25% n-butane, 20% iso pentane and 35% n-pentane. Operating variables were feed temperature (-30oC and -80oC), pressure (800KPa and 1200KPa), and reflux-ratio (2 and 6). Sensitivity analysis was carried out to examine the effect of varying operating parameters on the systems. Stage-by-stage system exergy analysis was estimated. Column profiles of a base case -30oC, -80oC, -30oC-reflus ratio 6,80oC -80oC reflux ratio 6 and base case reflux ratio 6 did not cross thus are thermodynamically feasible. Base case -30oC-reflux ratio 2, -80oC-reflux ratio 2, and base case-reflux ratio 2 were crossed and constricted and are infeasible. Base case results gave efficiency of 81.7% at depropanizer and 65.2% at debutanizer. Base cases sensitivity results with -30oC, -80oC and reflux ratio 6, efficiency range 57.40 – 70% and 65.20% - 54.90% for depropanizer and debutanizer respectively. Spitted cases gave 81.7% and 62.20% with more scatter profiles. Splitted feed base case -30oC design gave the lowest overall system exergy loss rate of 1.12E+6 and efficiency of 95.70%.
International Journal of Scientific World, 2014
Electricity is an indispensable amenity in present society. Among all those energy resources, coa... more Electricity is an indispensable amenity in present society. Among all those energy resources, coal is readily available all over the world and has risen only moderately in price compared with other fuel sources. As a result, coal-fired power plant remains to be a fundamental element of the world's energy supply. IGCC, abbreviation of Integrated Gasification Combined Cycle, is one of the primary designs for the power-generation market from coal-gasification. This work presents a in the proposed process, diluted hydrogen is combusted in a gas turbine. Heat integration is central to the design. Thus far, the SGR process and the HGD unit are not commercially available. To establish a benchmark. Some thermodynamic inefficiencies were found to shift from the gas turbine to the steam cycle and redox system, while the net efficiency remained almost the same. A process simulation was undertaken, using Aspen Plus and the engineering equation solver (EES).The The model has been developed using Aspen Hysys® and Aspen Plus®. Parts of it have been developed in Matlab, which is mainly used for artificial neural network (ANN) training and parameters estimation. Predicted results of clean gas composition and generated power present a good agreement with industrial data. This study is aimed at obtaining a support tool for optimal solutions assessment of different gasification plant configurations, under different input data sets.
Heat and Mass Transfer, 2015
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Ber... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
International Journal of Scientific World, 2014
ABSTRACT In this paper, energy recycling for distillation tower condenser was done by use of heat... more ABSTRACT In this paper, energy recycling for distillation tower condenser was done by use of heat integration method. At first, we calculated the amount of condensation energy (QAir Cooler), in air cooler, and then we calculated energy consumption in this equipment based on annual balance (5460 GJ per year). Then, based on heat integration (energy unification), two conditions were proposed to use the current energies in the process for supplying condensation energy (QAir Cooler): first, its must be lesser than condensing temperature of condenser (55 ° C) (the major condition). Second, it must have much more flow rate than the overhead flow. According to two above conditions, the food flow as chosen as the integration factor and its amount of energy (EStream) is calculated from the Enthalpy equation as 9863964 kj/h. As EFeed >>> QAir Cooler and food flow temperature to condense an overhead vapor is satisfying. The food flow can be used to condense the saturated vapor to 55 ° C. in case of using food energy and using heat exchanger instead of air cooler; 5460 GJ energy will be saved annually. By using heat exchanger and omitting air cooler, the unit103 operating costs will be reduced considerably. Economically, conducting such a project will demand investing costs. However, obtainable incomes from doing this project (electricity consumption recycling and cost's reduction) reveal this fact that capital return rate and the project benefits for unit103 of South Pars phases2&3 are beneficial.
International Journal of Scientific World, 2014
The steady-state, viscous flow of Nanofluid in the vicinity of an axisymmetric stagnation point o... more The steady-state, viscous flow of Nanofluid in the vicinity of an axisymmetric stagnation point of a stationary cylinder is investigated. The impinging free-stream is steady and with a constant strain rate . Exact solution of the Navier-Stokes equations is derived in this problem. A reduction of these equations is obtained by use of appropriate transformations introduced in this research. The general self-similar solution is obtained when the wall temperature of the cylinder is constant. All the solutions above are presented for Reynolds numbers ranging from 0.1 to 1000 and selected values of particle. For all Reynolds numbers, as the particle fraction increases, the depth of diffusion of the fluid velocity field in radial direction, the depth of the diffusion of the fluid velocity field in -direction, shear-stresses and pressure function decreases. Density of the nanofluid Particle fraction Density of the base fluid Density of the particles Equivalent diameter of a base fluid molecule Equivalent diameter of a particle molecule Dynamic viscosity of the nanofluid Dynamic viscosity of the base fluid Similarity variable Reynolds number for nanofluid Reynolds number for base fluid free stream strain rate Cylinder radius Cylindrical coordinates
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Papers by Mohammad Mohammadiun