Mohamed A Teamah - Academia.edu (original) (raw)

Papers by Mohamed A Teamah

Thermal Science, 2017

In this study, a numerical simulation of the thermal performance of two ribs mounted over a horiz... more In this study, a numerical simulation of the thermal performance of two ribs mounted over a horizontal flat plate and cooled by Cu-water nanofluid is performed. The plate is heated and maintained at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The top wall is considered as an adiabatic condition. The effects of related parameters such as Richardson number (0.01 ≤ Ri ≤ 10), the solid volume fraction (0.01 ≤ ϕ ≤ 0.06), the distance ratio between the two ribs (d/W = 5, 10, and 15), and the rib height ratio (b/W = 1, 2, and 3) on the ribs thermal performance are studied. The numerical simulation results indicate that the heat transfer rate is significantly affected by the distance and the rib height. The heat transfer rate is improved by increasing the nanoparticles volume fraction. The influence of the solid volume fraction with the increase of heat transfer is more noticeable for lower values of the Richardson number. The numerical results are summarized in the effect of pertinent parameters on the average Nusselt number with the assistance of both streamlines and isothermal ones. Throughout the study, the Grashof and Prandtl numbers, for pure water are kept constant at 10 3 and 6.2, respectively. The numerical work was displayed out using, an in-house computational fluid dynamic code written in FORTRAN, which discretizes non-dimensional forms of the governing equations using the finite volume method and solves the resulting system of equations using Gauss-Seidal method utilizing a tri diagonal matrix algorithm.

Ocean Engineering, 2018

Slug flow is one of the main flow regimes encountered in multiphase flow systems especially in oi... more Slug flow is one of the main flow regimes encountered in multiphase flow systems especially in oil and gas production systems. In the present study, the rise of single Taylor bubble through vertical stagnant Newtonian liquid is investigated by performing complete dimensionless treatment followed by an order of magnitude analysis of the terms of equations of motion. Based on this analysis, it is concluded that Froude, Eötvös and Reynolds numbers are the sole physical parameters influencing the dimensionless slug flow equations. Using the guidelines of the order of magnitude analysis, computational fluid dynamics simulation is carried out to investigate the dynamics of Taylor bubbles in vertical pipe using the volume-of-fluid (VOF) method. Good agreement with previous experimental data and models available in the literature is established confirming that the density ratio, viscosity ratio and the initial ratio of bubble size to pipe diameter (/) have minimal effect on the main hydrodynamic features of slug flow. Based on the developed results, correlations for the terminal velocity of the Taylor bubble and the dimensionless wall shear stress are proposed showing the significance of these main dimensionless parameters and support other important theoretical and experimental work available in the literature.

Journal of Energy Storage

Archive of Mechanical Engineering, 2012

This numerical research is devoted to introducing the concept of helical cone coils and comparing... more This numerical research is devoted to introducing the concept of helical cone coils and comparing the performance of helical cone coils as heat exchangers to the ordinary helical coils. Helical and spiral coils are known to have better heat and mass transfer than straight tubes, which is attributed to the generation of a vortex at the helical coil. This vortex, known as the Dean Vortex, is a secondary flow superimposed on the primary flow. The Dean number, which is a dimensionless number used in describing the Dean Vortex, is a function of Reynolds Number and the square root of the curvature ratio, so varying the curvature ratio for the same coil would vary the Dean Number. Numerical investigation based on the commercial CFD software fluent is used to study the effect of changing the structural parameters (taper angle of the helical coil, pitch and the base radius of curvature changes while the height is kept constant) on the Nusselt Number, heat transfer coefficient and coil outlet...

Alexandria Engineering Journal, 2018

Abstract A casted leaded-bronze block was impinged by a circular water jet. A 30-fps digital came... more Abstract A casted leaded-bronze block was impinged by a circular water jet. A 30-fps digital camera was used to video record the wet front propagation process on the surface of the block. The video frames were analyzed to illustrate the effect of different key parameters on the wetting front propagation. Regression correlations were developed to describe the effect of the jet Reynolds number (Red), the ratio of the degree of jet subcooling to the initial temperature of the block Δ T sub T i and the nozzle-to-surface spacing (H) on the wetting front propagation. The correlation is applicable for the experimental ranges investigated; 12,155 ≤ Red ≤ 36,460, 0.085 ≤ T sub T i ≤ 0.107 and H ≥ 30 mm. Good agreement was found between the experimental results and the correlation predictions with a maximum deviation of 25%. At high Reynolds number, the wetting front propagation was faster due to the high velocity and flow inertia. As the ratio Δ T sub T i increased, the wetting front propagation was accelerated. The effect of the nozzle-to-surface height on the propagation speed was negligible for H ≥ 30 mm. The effect of the increased liquid head on the terminal velocity was weakened by the drag forces on the jet as well as the jet instabilities associated with the large spacing.

Alexandria Engineering Journal, 2017

Impinging jet is one of various methods of cooling with the ability to achieve high heat transfer... more Impinging jet is one of various methods of cooling with the ability to achieve high heat transfer rates and improve average surface's Nusselt number. This method has vast industrial applications including integrated use in solar collectors, gas turbine cooling, refrigeration, air conditioning and electronics cooling. A numerical study is conducted to study the effects of using nanofluids on impinging slot jet over a flat plate with a ribbed surface. The main objective of the study was to investigate the possibility of improving the overall heat transfer rate by focusing on the improvements in the local and average surface Nusselt number values. Several parameters effects are studied including Solid Volume Fraction, Richardson number and Reynolds number. These results indicated a marked improvement in average Nusselt number with the increase in the solid volume fraction. Also, there is an amended value when the buoyancy effect is dominant over the whole domain. The results are shown in the form of streamlines, isotherms and Nusselt numbers contra other variables. The current work was simulated using a FORTRAN CFD Code, which discretizes the nondimensional forms of the governing equations utilizing the finite volume method and solving the consequent algebraic equations using Gauss-Seidel method Utilizing TDMA.

Alexandria Engineering Journal, 2011

Double-diffusive convective flow in an inclined rectangular enclosure with the shortest sides bei... more Double-diffusive convective flow in an inclined rectangular enclosure with the shortest sides being insulated and impermeable is investigated numerically. Constant temperatures and concentration are imposed along the longest sides of the enclosure. In addition, a uniform magnetic field is applied in a horizontal direction. Laminar regime is considered under steady state condition. The transport equations for continuity, momentum, energy and species transfer are solved using the finite volume technique. The validity of the numerical code used is ascertained and good agreement was found with published results. The numerical results are reported for the effect of thermal Rayleigh number on the contours of streamline, temperature, and concentration. In addition, results for the average Nusselt and Sherwood numbers are presented and discussed for various parametric conditions.

The gas path over the turbine blades is a very complex flow field due to the variation of flow re... more The gas path over the turbine blades is a very complex flow field due to the variation of flow regime and the corresponding heat transfer, This investigation is devoted to study the two and three-dimensional predictive modeling capability for airfoil external heat transfer by using pressure based solver PBS and density based solver DBS. The results show the effects of strong secondary vortexes, laminar-to-turbulent transition, and also show stagnation region characteristics. Simulations were performed on an irregular quadratic two and three-dimensional grids with the Fluent 6.3 software package employing several turbulence models (Spalart-Allmaras, RNG k-Є and SST k-ω model). Detailed heat transfer predictions are given for a power generation turbine rotor with 127° of nominal turning, axial chord of 130 mm and blade aspect ratio of 1.17. The comparison was made with the experimental and the numerical results of Giel et al. and a good agreement was found with the DBS and Spalart-All...

Egyptian electricity demands have increased in recent years and are projected to grow further wit... more Egyptian electricity demands have increased in recent years and are projected to grow further with significant economic and social impacts. Recently, mandatory and voluntary building codes based on international standards have been increasingly adopted. The performance of existing Egyptian buildings is not well understood making the impact of these new codes uncertain. This paper aims to provide insights into existing Egyptian building performance, and elaborate a process for developing a representative model to assist in future policy. The work presented is for office buildings but intended to be widely replicable. An energy survey was carried out for 59 Egyptian offices, categorised by building service type, it was observed that energy use increases as building services increase, and existing Egyptian offices use less energy than benchmarks. A more detailed investigation for a case study office was carried out, to inform detailed model calibration. This provided insight into energ...

Laminar mixed convection heat transfer from an isothermal horizontal triangular cylinder was expe... more Laminar mixed convection heat transfer from an isothermal horizontal triangular cylinder was experimentally investigated. The experimental study includes designing and constructing the test rig to fulfill the research requirements. Three equilateral triangular cylinders have been investigated in the present study with side length of 37, 50 and 70 mm respectively. The mixed convection experiments were established for Grashof numbers ranging from 26.32×104 to 213.46×104, Reynolds number ranging from 75.3 to 1251.6, and the attack angles from 0o to 180o. The experimental results gave the average Nusselt number for air with Prandtl number of 0.7 as a working fluid. The results are presented as Nusselt numbers for different values of triangular cylinders side length and attack angle at different Reynolds number for mixed convection heat transfer.

Experimental Thermal and Fluid Science, 2018

Turbulent natural convection between two horizontal concentric cylinders with different orientati... more Turbulent natural convection between two horizontal concentric cylinders with different orientation and axis ratios for the outer cylinder with both open-ended has been investigated experimentally and numerically. A Constant heat flux was imposed at the outer cylinder at five different heat fluxes 503, 751, 1002, 1251 and 1508 W/m 2, while the inner cylinder was insulated. The hydraulic diameter was kept constant at 60 mm. The Rayleigh number Ra was varied from 1.017 × 10 7 to 3.25 × 10 7. The outer cylinder orientation angle, ϕ was varied from 0° to 90° with 15° increment. The influence of the axis ratio (major to minor axis) for the outer cylinder was studied at range from 1.0 to 2.0. A finite difference method for the governing equations related with the standard k-e model has been utilized. The surface temperature distribution at outer cylinder, the axial velocity and average Nusselt number were estimated at different orientation angles and axis ratios of the outer cylinder. Tur...

Most of the desalination technologies consume a huge quantity of energy resulting from petroleum ... more Most of the desalination technologies consume a huge quantity of energy resulting from petroleum products in the form of heat or electrical energy. Solar desalination is a promisingly sustainable freshwater production technology. Solar desalination humidification dehumidification process showed the best approach as it is of the highest overall energy efficiency. In this review paper, a detailed study of the previous work is performed on solar humidification dehumidification desalination techniques experimentally and theoretically. Also in this review, different types of HDH systems were mentioned. The review showed that the humidification dehumidification desalination systems are suitable for decentralized demand. On the other hand, capacity of HDH units is not as large as conventional methods or small as solar stills. Finally, this study threw light on the scope of the parameters which have a considerable influence on increasing the freshwater output of the HDH systems as feed wate...

In this paper, simulation of NGL train consisting of four distillation columns has been performed... more In this paper, simulation of NGL train consisting of four distillation columns has been performed by using Aspen-Hysys. The main objective of this research is studying the different factors that enhance the separation process efficiency such as changing the number of trays, reflux ratio and the feed tray location. Simulation results showed that the design of distillation column with 40 trays is the proper design for this study giving the optimum results and reduces the capital cost. The results also showed that number of trays has an important role in the separation process efficiency where the lowest heat duties and the highest composition for top products were obtained at the highest number of trays.

Laminar mixed convection in a three-dimensional lid driven cavity is numerically investigated. Th... more Laminar mixed convection in a three-dimensional lid driven cavity is numerically investigated. The top lid of the cavity is moving rightwards with a constant speed at a cold temperature. The bottom wall is maintained at an isothermal hot temperature, while the other vertical walls of the cavity are assumed to be insulated. In this study the mass diffusion was not taken into account and the fluid used was air. The flow and heat transfer behavior is studied for various Richardson number ranging from 5 × 10−5 to 3 × 10−4 at a fixed Prandtl number of 0.71 through analyzing the local Nusselt number distribution at different sections inside the cavity. Lewis number Le is assumed to be unity and the buoyancy ratio parameter N is equal to zero. Computations were done using an in-house code based on a finite volume method. The results showed a good agreement with previous two dimensional studies, while the three dimensional study gives different results at different sections inside the cavit...

The present study is concerned numerically with the mixed convection in a square lid-driven cavit... more The present study is concerned numerically with the mixed convection in a square lid-driven cavity with moving upper surface filled with saturated porous material. Both upper and lower surfaces are being insulated while the vertical walls of the enclosure subjected to sinusoidal temperatures variation with different amplitude and phase angle in order to enhance the heat transfer. Steady state laminar regime is considered. The transport equations for continuity, momentum, energy are solved. The numerical results are reported for the effect of Richardson number (Ri), Darcy number (Da), Prandtl number (Pr), amplitude ratio (ε) and phase deviation angle (φ) on the iso-contours of streamline, and temperature. In addition, the predicted results for both local and average Nusselt numbers are presented and discussed for various parametric conditions. This study was done for 10 ≤ Da ≤ 10, 0 ≤ ε ≤ 1, 0 ≤ φ ≤ π and 0.01 ≤ Pr ≤ 10. Through the study the Grashof number is kept constant at 10, wh...

The aim of this work is to study the effect of injecting certain amount of cold water through the... more The aim of this work is to study the effect of injecting certain amount of cold water through the hot air stream flowing over the outer surfaces of plain tubes, of water-cooled heat exchanger on the air temperature distributions in a narrow region around the point jet position. The traces of water are injected from a single jet placed at the center of the inlet section of heat exchanger. Injecting water over the heat exchanger tubes is a simulation to the case of water leakage from a heat exchanger tube due to crake or hole in the heat exchanger tube. A three dimensional turbulent flow model including the equations of continuity, momentum and energy together with the particle model are solved numerically using the ANSYS-CFX 12.1 software for the simulation of flow and heat transfer of air inside the heat exchanger. The software has also been used to construct the contours of the air/water mixture temperature, coefficient of heat transfer, heat flux and mass fraction.

The inclination circular liquid jet impingement on a horizontal target smooth plate has been inve... more The inclination circular liquid jet impingement on a horizontal target smooth plate has been investigated experimentally. The hydrodynamic flow structure of unique nocircular profile due to oblique jet is studied in the present work. The nozzle inclination angle is varied from [30 to 90 from horizontal], while the water flow rate is varied from 2 to 5lpm at constant nozzle-to-target separation distance of 30 mm. The nozzle used during the experiments is of circular shape of 5.5 mm diameter. A circular hydraulic jump symmetrical profile was observed due to normal impinging of free water surface jet, but the radial spreading flow structure due to oblique circular jet was different and the hydrodynamic profile of the jump location having elliptical shape structure. The effect of jet inclination angle and the water flow rate on the dimensionless film thickness and the dimensionless hydraulic jump profile in azimuthal direction. The experimental investigation shows that the thin layer fi...

The economic and environmental impacts of gas turbine inlet air cooling were investigated for Nub... more The economic and environmental impacts of gas turbine inlet air cooling were investigated for Nubaria (around 130 km south East of Alexandria, Egypt) combined cycle power plant as a case study. Thermodynamic model was developed to simulate the combined cycle before and after the integration to the proposed single stage Li Br and H2O absorption cooling system. Inlet air-cooling by 10 oC can increase the annual power generation by 6.4 %. The 20-year Life Cycle Cost Analysis of the proposed integration indicates a net present value of MM$ 20 for each generation module with payback period of 3.5 years. Sensitivity analysis was conducted for potential changes in both fuel and electricity prices. Despite of the overall increase of the plant fuel demand by 6.5%, the specific fuel consumption has been decreased by 0.5 g / kWh from 164 g /kWh to 163.5 g/kWh. This decrease means an improvement of the combined cycle heat rate by 0.3%. This decrease in heat rate means a considerable reduction i...

INTERNATIONAL JOURNAL OF ADVANCED SCIENTIFIC AND TECHNICAL RESEARCH, 2018

INTRODUCTION Natural gas (NG) supplies share about 23% of the total word energy. It is considered... more INTRODUCTION Natural gas (NG) supplies share about 23% of the total word energy. It is considered as one of the safest, cleanest and more efficient energy of all energy sources. It can replace coal and oil because natural gas gives less harmful emissions when burn. The processing of natural gas is easier and less complicated than the processing of crude oil, with equally important before it is used by the end users. [1] Natural gas liquids (NGLs) is a term applied to those hydrocarbons, ethane (C 2), propane (C 3), butane (C 4), pentane (C 5), and heavier (C 5+) which must be illuminated from natural gas streams to consider