Esmail Lakzian

Andong National University · Department of Mechanical Engineering

Coughing and sneezing are the main ways of spreading coronavirus-2019 (SARS-CoV-2). People sometimes need to work together at close distances. This study presents the results of the computational fluid dynamics (CFD) simulation of the dispersion and transport of respiratory drop-lets emitted by an infected person who coughs in an indoor space with...

In some copper, iron, and other mineral product mines, pipes are used to transfer solid–liquid slurry by gravity. In these sloping pipes in the slack state (half-filled), fluid flow is simulated in an open channel, and a hydraulic jump occurs in the pipe with sudden changes in the slope downstream; also, the type of jump is determined based on the...

The rapid expansion of steam leads to non-equilibrium condensation of steam in the supersonic region which the performance of the turbines is reduced. The achievement of an accurate numerical method in a wide range of regimes to capture the aerodynamic and condensation shocks with minimum computation and numerical errors has always been of interest...

The outbreak of the COVID-19 has affected all aspects of people's lives around the world. As air transmits the viruses, air-conditioning systems in buildings, surrounded environments, and public transport have a significant role in restricting the transmission of airborne pathogens. In this paper, a computational fluid dynamic (CFD) model is deploy...

The leakage, caused by design problems, pipe breakage, and fittings' failure, is a critical challenge that the beneficiaries face in the water distribution networks (WDNs). Control and management of the network pressure have always been considered helpful solutions to reduce the leakage in these systems. In the present study, locating and setting o...

Due to the decrease in steam temperature in the low-pressure steam turbine, nucleation occurs, and liquid droplets form, reducing thermodynamic efficiency and damaging the blades. A new flow control method and optimization of two-phase flow among stator blades are discussed in this paper. During this flow control, steam is taken from upstream flow...

Machining operation and presence of water droplets cause increase the surface roughness of wet steam ejector walls and change its performance in the refrigeration cycle. The purpose of this work is to investigate the influences of the primary nozzle surface roughness on wet steam ejectors in the refrigeration cycle with steam water as a working flo...

This research develops the non-equilibrium condensation model with sliding mesh technology to solve the unsteady condensing flow inside a 3D wet steam stage of steam turbine with transient rotor-stator interaction. The maximum fluctuation of time-dependent condensation parameters is predicted. The condensation loss and entropy generation considerin...

This paper investigates the performance of the earth-to-air heat exchanger (EAHE) system in the winter for Mashhad. A three-dimensional model of novel serpentine geometry for use in the passive building heating system is proposed. A new and visual method of recovery analysis is performed for regaining the soil energy by considering a period of time...

Due to the high height of the refinery flares, the wind velocity plays an important role in flame shape and the resulting temperature distribution in flare body. The investigation of wind velocity effect on flame pulldown (downwash) can provide effective solution to avoid the flame pulldown problem and burning the flare tip. In this study, using th...

Investigation of the spread of pollutants and especially pathogenic particles in the interior of today's buildings has become an integral part of the design of such buildings. At a time when the coronavirus is prevalent in the world, it is necessary to pay attention to the spread of the virus in the interior of residential apartments. In the presen...

In the present study, the effect of droplet injection of Moore A (MA), and De Laval nozzles (De) on the condensation shock, has been modeled and compared. The Eulerian-Eulerian method has been used in two-dimensional, compressible, viscous, and turbulent using the k-ω SST turbulence model to simulate the condensation flow field numerically. Four di...

Nowadays, an enormous amount of electricity is gained from steam turbines, and solid salt injection into the steam turbines is used to control pH. Therefore, the heterogeneous nucleation will occur because of the presence of impurity (solid salt) in the steam turbine's low-pressure stage; and some changes take place in the operation of the turbine...

Stilling basins are one of the most important parts of hydraulic structures to dissipate the kinetic energy of the flow. The dissipation of the energy is an essential problem in the design of any stilling basin. USBR VI stilling basin is one of the oldest basins designed for dissipating the pipe outlet flow. This basin looks like a box with the int...

Steam turbines play an undeniable role in the power generation cycle. In this paper, in order to increase the efficiency of steam turbines, hot steam is injected between the steam turbine blades in 3D mode. Therefore, by defining five comparative criteria (liquid mass fraction, condensation loss, kinetic energy, hot steam injection ratio, and econo...

This study has used shape optimization by the genetic algorithm to gain the suitable pitch to axial chord ratio for a cascade turbine blade. The innovation of the present paper is the modification of the Zweifel coefficient for the wet steam flow passing through the steam turbine cascade. Wetness fraction (WF), average droplet radius (ADR), momentu...

Coughing and sneezing are the main ways of spreading coronavirus-2019 (SARS-CoV-2). Strategically critical facilities such as power plants cannot be shut down even in challenging situations like the COVID-19 outbreak. The personnel of the power plants' control room need to work together at close distances. This study presents the computational flui...

Steam turbines play a critical role in power generation systems. Therefore, increasing the efficiency of steam turbines is highly desirable, especially in LP stages. One of the suggested techniques to reduce wetness losses in LP stages is the hot steam injection. In the first section of the present study, the effect of 3D turbine blade span length...

Ejectors have been utilized in many industries such as steam power plants, nuclear reactors, desalination system, refrigeration, etc. However, due to the low coefficient of ejector performance, the ejector refrigeration systems are less used than the other methods (compression or absorption refrigeration systems). On the other hand, nucleated dropl...

Thermodynamic losses and blade erosion occur due to formation of wetness in the low-pressure steam turbine. By changing the trailing edge angle of turbine blade can reduce blade erosion and condensation losses. This research optimized the best of the trailing edge rotation to improve the turbine's operation at the low-pressure part of the steam tur...

Steam ejector plays a key role in the refrigeration system. The water has been used as a working fluid because water is more economical and non-toxic. The operating fluid often enters the evaporator as a water liquid and droplets evaporate by absorbing heat. Cooling load changing causes the vapor in the outlet of the evaporator to be accompanied by...

Nowadays, one of the concerns of the searchers is the increasing performance of industrial equipment. The phenomenon of spontaneous non-equilibrium condensation and the presence of droplets have caused efficiency and economic losses for industrialists. The hot steam injection causes reduction of the averaged radius droplets, liquid mass fraction, a...

Nowadays, the presence of droplets in industrial devices such as ejectors, turbine blades, and nozzles causes the reduction of efficiency and reduces the life-cycle of the device by the erosion of walls. The wet steam model is validated by the experimental data. The purpose of this study is to dehumidify and increase the power-saving via the suctio...

Convection heat transfer in an annulus with pair sources and the inner rotating circular cylinder is studied numerically. Cu-water nanofluid is used to fill between the cylinders. Two pair sources (Tc and Th) were placed around outer and inner cylinders, and others were considered adiabatic. The governing equations were solved on a non-uniform comp...

In this study, the motion and distribution of droplets containing coronaviruses emitted by coughing of an infected person in front of a classroom (e.g., a teacher) were investigated using CFD. A 3D turbulence model was used to simulate the airflow in the classroom, and a Lagrangian particle trajectory analysis method was used to track the droplets....

Renewable energy resources are considered as alternative sources of energy for future generations. Wells turbines can be used to convert the reciprocating energy of waves in oceans and seas into rotational energy. Low aerodynamic efficiency is the main drawback of Wells turbines. The present study showed that the addition of the guide vanes, endpla...

This paper proposes to use a blackbox optimization to obtain the optimal volumetric heating required to reduce the wetness at the last stages of steam turbines. For this purpose, a global multiobjective optimization is utilized through the automatic linking of genetic algorithm and CFD code, where the blackbox function evaluations are performed by...

The present paper focuses on exergoeconomic optimization of a proposed system with the goal of cogenerating freshwater and power, simultaneously. The cogeneration system includes Internal Combustion Engine, Organic Rankine Cycle, and Reverse Osmosis desalination unit. The thermodynamic model of the cogeneration system is investigated from energy, e...

In this paper, the impact of existence of wetness in the inflow of stationary cascades of steam turbine blades has been numerically investigated. A new mesh generation method based on non-uniform rational B-splines (NURBS) has been adopted to reduce the numerical error of the wet inflow simulation. Moreover, two common meshing scenarios namely blad...

Today, the use of heat exchangers for heat transfer is very popular. A type of heat exchanger that is used extensively is a shell-tube type heat exchanger. In this report, first introduce the pipe shell transformer and in the next step, it introduces the components and then the factors affecting its efficiency. At the end, the effective factors for...

In the present study, entropy generation analysis of turbulent boundary layer was carried out to examine the effects of the wall curvature and adverse pressure gradient (APG) on air distribution ducts in HVAC systems considering both individual and simultaneous effects of these parameters and using the empirical data. Six walls, including straight...

The nucleation phenomenon and its consequence formation of droplets are destructive effects that occur as a result of the sudden expansion of the flow through the steam turbine blades. The formation of these droplets causes blade corrosion and severe thermodynamic losses, thereby reducing the turbine efficiencyg.In this paper, two holes on the pres...

This reply is based on the discussion by Ghisu and Cambuli. With great interest, the authors have read the comments made by Ghisu and Cambuli. The comments severely criticizes our methodology and results, which actually provide us with fortunate opportunity to discuss our work in more details to complement our work, thankfully to this available spa...

In many industrial pieces of equipment, such as ejectors, thermo-compressors, supersonic separators, etc., in which the condensation phenomenon occurs spontaneously, steam enters the nozzle in a saturated condition. Liquid droplets are likely to be present in the saturated vapor. In the present paper, the effect of the existence of a number (9 case...

The isogeometric finite volume analysis is utilized in this research to numerically simulate the two-dimensional viscous wet-steam flow between stationary cascades of a steam turbine for the first time. In this approach, the analysis-suitable computational mesh with “curved” boundaries is generated for the fluid flow by employing a non-uniform rati...

Nowadays, wind energy plays a great role in the world's energy production. Detection and experimental measurement of the effective parameters on the transient lift and drag coefficients in the blades are very important in the wind turbine design. In this study, the aerodynamic coefficients of an oscillating wind turbine airfoil are evaluated. Due t...

In this paper, sediment deposition and trapping efficiency in shallow rectangular reservoirs were numerically estimated considering secondary flows. In order to do this, three dimensional (3D) steady, incompressible, Reynolds-averaged Navier-Stokes (RANS) equations with the standard k−ε turbulence model were used as the governing equations. The dri...

Steam ejector, as a heat pump, plays a key role in ejector refrigeration system which operates with water vapor as an available, economic and environmentally friendly refrigerant. In this research, supersonic steam flow through the ejector is simulated by CFD methods to investigate effects of ejector geometry on its performance. Basic design criter...

In the last stages of steam turbines, the formation of liquid droplets causes losses and reduces turbine efficiency. One of the major problems of wet steam flow is the presence of the liquid phase, which volumetric heating reduces the wetness. One of the disadvantages of adding volumetric heating is increasing entropy generation and cost. Consideri...

In this research, the improvement of an ejector performance has been studied as crucial part of an ejector refrigeration system by means of applying changes in its geometry. Water steam is taken as a non-expensive, non-toxic, and available refrigerant and wet steam model has been employed to more accurate numerical simulation and analysis. It is in...

The condensation phenomenon in the steam turbines creates a complex spectrum of droplet size. As known, the droplet size distribution can provide important information for steam turbine designers. In simulations, droplets radius are often modeled in the monodispersed model. One size of droplet radius is reported at each location in this model. In t...

In the power plant industry, a major part of energy losses in the thermodynamic cycle is related to the steam turbines, which are not made to work with wet steam flow, and the presence of the liquid phase causes efficiency reduction and mechanical damages such as erosion, which leads to high expenses due to the high cost of steam turbines. The pres...

In the steam turbine, the wetness loss due to vapor condensation is one of the most crucial losses at low-pressure stage. This study focused on entropy generation and exergy destruction of condensing steam flow in turbine blade with the roughness. The governing equations including entropy transport equation combined with condensation model, transit...

In this paper, the entropy generation is introduced as a criterion to analyze the impact of variation of expansion rate in a two-dimensional viscous wet-steam flow through stationary cascades of a steam turbine. In addition, for the first time the NURBS-based mesh generation method is introduced and assessed in the field of wet-steam flow. In the m...

In the present research, the entropy generation analysis has been done in the dam-break flow with obstacles in different shapes. The damage to the downstream of dams is done by fluid energy. So, entropy generation was introduced as a measurement criterion of destruction. In this way, a numerical model has been developed to evaluate the dam-break ph...

Offshore wind turbines are of special interest due to their growing importance, and hence comprehensively discussed in this research. Three popular offshore wind turbine airfoil geometries (S822, S825, and SD7062) are studied in this research considering entropy generation. There is no similar work in literature considering entropy generation aroun...

In the present study, a novel equation is presented for entropy generation (EG) in dam-break flows of Herschel-Bulkley fluids. The Herschel-Bulkley model is an idealized model of viscoplastic behavior. The dam-break phenomena can cause floods and widespread destruction in the path of the flow. Therefore, finding a measure for destruction analysis i...

Air ejectors are, practically, applicable devices used to remove air following a membrane integrity test (MIT). In the present work, investigations of the influence of geometrical parameters on the air ejector performance are performed numerically. Simulations have been performed by solving the steady compressible two-dimensional Reynolds-averaged...

The inherent disadvantages, due to the narrow operational range and low efficiency of Wells turbine, are investigated based on aerodynamic and entropy generation analysis. To overcome these issues, the effects of blade thickness on the performance of a Wells turbine are discussed. In this study, two kinds of blade profiles are being investigated: t...

In this study, the natural convection heat transfer and entropy generation in horizontal eccentric cylinders with different arrangements of two constant temperature sources are investigated numerically. The distance between eccentric cylinders was filled with pure fluid and Cu_ water nanofluid. The sources with constant temperature Th and Tc were l...

In this study, a numerical model is developed to simulate an air ejector pump that is proposed for the carpet industry. Simulations have been performed by solving the compressible, steady-state, two-dimensional Reynolds-averaged Navier–Stokes equations, and k–ε Realizable model is used to simulate a turbulent flow. A comparison of the computed resu...

The maneuver-induced liquid cargo motion in the partly-filled tanks called, sloshing poses a serious threat to the stability and controllability of this phenomenon. The entropy generation in the sloshing phenomenon is obtained for the first time in the rectangular storage tank. In this paper, a numerical model is developed to simulate the sloshing...

In this paper, a novel explicit equation is presented for the friction factor prediction in the annular flow with drag reducing polymer (DRP). By using dimensional analyses and curve fitting on the published experimental data, the suggested equation is derived based on the logarithmic velocity profiles and power law in boundary layers. In the next...

Purpose The purpose of this paper is to report the result of a numerical investigation of film cooling performance on a flat plate for finding optimum blowing ratios. Design/methodology/approach Steady-state simulations have been performed, and the flow has been considered incompressible. Calculations have been performed with 3D finite-volume meth...

In this paper, natural convection heat transfer is studied in two-dimensional horizontal concentric cylindrical annulus with discrete source-sink pairs. The effects of Cu nanoparticles on natural convection of water near its density maximum were considered in numerical simulations. Geometry consisting of two hot and cold sources (constant temperatu...

In this paper, quenching in high-temperature materials processing is modeled as a superheated isothermal flat plate. In these phenomena, a liquid flows over the highly superheated surfaces for cooling. So the surface and the liquid are separated by the vapor layer that is formed because of the liquid which is in contact with the superheated surface...

Determination of the pipe thickness is a key work in designing of pipelines. In order to have a safe and economic design, an appropriate equation for erosion rate prediction should be selected. Karabelas equation is one of the most important equations in prediction of the erosion wear rate of slurry pipelines. Since the effect of pressure is not co...

Wells turbine is a promising self-rectifying device in the field of ocean wave energy conversion. This study presents an Entropy Generation Analysis (EGA) of isothermal ow through a monoplane Wells turbine. The numerical computation has performed by solving the steady, incompressible, and three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equ...

Wells turbine is a promising self-rectifying device in the field of ocean wave energy conversion. This study presents an entropy generation analysis (EGA) of isothermal flow through a monoplane Wells turbine. The numerical computation have been performed by solving the steady, incompressible, three-dimensional Reynolds-averaged Navier–Stokes (RANS)...

In this paper, a comparison of total entropy generation between a suggested design and a constant chord Wells turbine is presented. A variable chord rotor Wells turbine design is suggested in order to have a more uniform axial velocity distribution at blades leading edge in comparing conventional design to improve turbine efficiency. Each model is...

The effect of coalescence process on entropy generation (exergy loss) in a condensing flow in 1D convergent-divergent nozzle B of Moore is studied. The paper offers governing equations considering coalescence between droplets, and case 1 of Scott is used for solving the coalescence equations. Also a valid model is used to work out the entropy gener...

In this paper a new method in using microwaves is provided for melting the ice around a floating equipment in a freezing condition in cold regions. The numerical simulation’s results for validation are compared with the simple model’s experimental data. Using microwave in melting the ice around a floating equipment is caused by lack of the mechanic...

Condensing flows in nozzles and blades of steam turbines have always been the subject of many studies. Creation of liquid phase in vapor causes significant changes in the flow. Sudden release of latent heat in supersonic steam flow due to nucleation of liquid droplets and phase change causes the important phenomenon of condensation shock. Modeling...