Papers by Mohamed A Teamah
CFD simulations of hydrodynamic characteristics of gas-liquid slug flow in vertical pipes
Journal of Applied Mechanical Engineering, Sep 7, 2016
Potential energy saving opportunities in big box retail stores in Northern climates––Case study towards sustainable buildings
e-Prime, Mar 1, 2023
Potential retrofits in office buildings located in harsh Northern climate for better energy efficiency, cost effectiveness, and environmental impact
Chemical Engineering Research & Design, Jun 1, 2022
Numerical study of laminar natural convection inside square enclosure with single horizontal fin
International Journal of Thermal Sciences, 2016
Abstract A numerical study for laminar natural convection inside a square enclosure with a single... more Abstract A numerical study for laminar natural convection inside a square enclosure with a single horizontal fin attached to its hot wall has been carried out. The enclosure horizontal surfaces are adiabatic, the left wall is hot while the right one is cold. The Prandtl number for the flow inside the enclosure is 0.71. A parametric study has been carried out to investigate the effect of Rayleigh number, fin length, conductivity ratio, thickness and position on heat transfer. The fin thickness showed negligible effect on the average Nusselt number for all values of fin conductivity ratios. The fin efficiency and temperature distribution were examined. The fin effectiveness was also studied and it was found that the fin effectiveness enhanced in general with the increase of fin length. Also, the maximum fin effectiveness was found at the lowest Rayleigh number for a given fin conductivity ratio. A correlation has been proposed for the relation between Nusselt number and the parameters of study.
CFD Letters, Sep 27, 2014
A numerical study of double-diffusive mixed convection within a horizontal rotating annulus has b... more A numerical study of double-diffusive mixed convection within a horizontal rotating annulus has been investigated. The outer cylinder is fixed but the inner cylinder is considered to rotate in clockwise and anti-clockwise directions to introduce the forced convection effect. In addition, the solutal and thermal buoyancy forces are sustained by maintaining the inner and outer cylinder at uniform temperatures and concentrations but their values for the inner are higher than the outer. The flow is considered laminar regime under steady state conditions. The transport equations for the continuity, momentum, energy and mass transfer are solved using the finite volume technique. The considered domains in this investigation are: -15 ≤ N ≤ 15, 0.01 ≤ Ri ≤ 100 and 0.01 ≤ Pr ≤ 100. While the thermal Grashof number, Lewis number and the radius ratio are kept constant at values equal to10 4 , 1 and 2 respectively. The effect of the selected parameters on the local and average Nusselt and Sherwood numbers are presented and studied. Finally, this investigation concerned with selection the best direction of the inner cylinder rotation to enhance both heat and mass transfer. A comparison was made with the published results and a good agreement was found.
International journal of research in engineering, 2019
Thermo physical properties such as specific heat, thermal conductivity and density are unique for... more Thermo physical properties such as specific heat, thermal conductivity and density are unique for any material. Within a conductive material, thermal conductivity is the main property in the thermal energy transfer. Specific heat and density are the important components involved in the analysis of energy and mass balances. When combining these three properties, we get the thermal diffusivity, which is used in the analysis of unsteady-state heat transfer. Two major methods are used to measure the thermal conductivity of any material. The steady state method named guarded plate method which depends on a constant temperature difference achieved in the specimen of the material. This method needs complicated measurement system, it is unsuitable for the field application . The transient (unsteady-state) techniques generally use a heater of a particular geometry inserted in the sample, and heated within a period of time. These measurement systems are less complex with respect to steady state methods and are better suited for field measurements. The experimental studies for determination of the thermal properties in a transient state has been conducted with numerous methods and techniques. The linear heat source method relies on a steady heat source ,for example, a hot wire, that generate s a temperature field inside an infinite volume of a material. Based on the thermal conductivity of the desired material, the temperature rise in its sample will vary from one material to other. The thermal conductivity, then, can be calculated from the temperature rise at two unique times and the power of the heater. This method was used to measure the thermal conductivity of many solids , fluids and soil .
Numerical Study of Mixed Convective Cooling in a Ventilated Cavity Utilizing a Guide Baffle
ABSTRACT Laminar mixed convective flow in ventilated square cavity with inlet and outlet ports ha... more ABSTRACT Laminar mixed convective flow in ventilated square cavity with inlet and outlet ports has been executed. The natural convection effect is attained by heating from the constant flux heat source which is symmetrical located at the bottom wall and cooling from the injected flow. An external Newtonian fluid flow (Air, Pr =0.71) enters the cavity through an opening at the bottom of the left vertical wall and exits from another opening at the top of the right vertical wall, which is creating the forced convection flow conditions. Laminar regime is considered under steady state condition. The governing equations including continuity, momentum, and energy are transformed into non-dimensional form and the resulting partial differential equations are solved by the finite volume technique. In addition, horizontal guide baffle with different locations was attached from the left vertical wall to enhance the cooling effect of the source part. A parametric study was performed presenting the influence of Reynolds' number (50≤Re≤500), Richardson number (0.01≤Ri≤10), and hence the effect of heat flux represented in the Grashof number automatically generated from both values of Reynolds and Richardson numbers.
Numerical simulation of double-diffusive mixed convective flow in rectangular enclosure with insulated moving lid
International Journal of Thermal Sciences, Sep 1, 2010
ABSTRACT The present study is concerned with the mixed convection in a rectangular lid-driven cav... more ABSTRACT The present study is concerned with the mixed convection in a rectangular lid-driven cavity under the combined buoyancy effects of thermal and mass diffusion. Double-diffusive convective flow in a rectangular enclosure with moving upper surface is studied numerically. Both upper and lower surfaces are being insulated and impermeable. Constant different temperatures and concentration are imposed along the vertical walls of the enclosure, steady state laminar regime is considered. The transport equations for continuity, momentum, energy and spices transfer are solved. The numerical results are reported for the effect of Richardson number, Lewis number, and buoyancy ratio on the iso-contours of stream line, temperature, and concentration. In addition, the predicted results for both local and average Nusselt and Sherwood numbers are presented and discussed for various parametric conditions. This study was done for 0.1 ≤ Le ≤ 50 and Prandtl number Pr = 0.7. Through out the study the Grashof number and aspect ratio are kept constant at 104 and 2 respectively and −10 ≤ N ≤ 10, while Richardson number has been varied from 0.01 to 10 to simulate forced convection dominated flow, mixed convection and natural convection dominated flow.
International Journal of Thermal Sciences, Aug 1, 2012
Experimental and numerical investigation of turbulent natural convection between two horizontal concentric cylinders at different axis ratios and orientation angles
Experimental Thermal and Fluid Science, Feb 1, 2018
Abstract Turbulent natural convection between two horizontal concentric cylinders with different ... more Abstract 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. Turbulent intensity and axial velocity distribution were estimated numerically. Both experimental and numerical results for the average Nusselt number show good agreement. The results show that the heat transfer enhancement starts as the outer cylinder orientation angle increase more than the critical angle. The maximum increase in the average Nusselt number reaches 25% at vertical position and axis ratio at 2 for the outer cylinder.
International Journal of Thermal Sciences, Aug 1, 2011
This work used a porous approach model to numerically investigate the fluid flow and heat transfe... more This work used a porous approach model to numerically investigate the fluid flow and heat transfer characteristics of the pin-fin heat-sink array in a rectangular channel with in-line arrangement. The air flow through the channel was laminar. The pin-fin heat sinks with various porosities and pin-fin numbers were employed. The relative center-to-center longitudinal and transverse distances between adjacent heat sinks were changed. The results indicate that the Nusselt number of various heat-sink arrays increased with decreasing the relative center-to-center transverse distance, but not varied with the relative center-to-center longitudinal distance. For the typical pin-fin heat-sink arrays, the Nusselt number changed slightly for the heat sinks with 0.358-0.556 porosity, but increased by 11.7%-24.8% when the porosity increased from 0.556 to 0.750, and then dropped obviously when the porosity exceeded 0.750. Increasing the number of pin fins continuously could increase Nusselt number. However, when the number of pin fins was large, the Nusselt number increased with the number of pin fins slowly. The present numerical simulation has been validated by the typical experiment. Finally, a semi-empirical correlation of Nusselt number for each heat sink in the heat-sink array was proposed.
Building Simulation Conference Proceedings
In Egypt, energy use in buildings has grown in the last 20 years mainly due to the increases in p... more In Egypt, energy use in buildings has grown in the last 20 years mainly due to the increases in population, number of households, number of offices, as well as increase in service demand, such as more air conditioners and computers. The aim of this study is to create a thermal model for Egyptian office building to represent actual building energy consumption trying the best fit for user behaviors and actual weather data. The simulation model was created using IES VE 2014 and calibrated against measured data for an Egyptian office. The calibration process, intermediate and final results are presented and illustrated for a range of output parameters including internal temperatures, CO 2 , lighting, equipment, and cooling energy use for different weather periods. This calibrated model can then be used together with uncertainty analysis to evaluate future building upgrade scenarios in order to help improve the energy performance for Egyptian office buildings.
In Egypt, energy use in buildings has grown in the last 20 years mainly due to the increases in p... more In Egypt, energy use in buildings has grown in the last 20 years mainly due to the increases in population, number of households, number of offices, as well as increase in service demand, such as more air conditioners and computers. The aim of this study is to create a thermal model for Egyptian office building to represent actual building energy consumption trying the best fit for user behaviors and actual weather data. The simulation model was created using IES VE 2014 and calibrated against measured data for an Egyptian office. The calibration process, intermediate and final results are presented and illustrated for a range of output parameters including internal temperatures, CO2, lighting, equipment, and cooling energy use for different weather periods. This calibrated model can then be used together with uncertainty analysis to evaluate future building upgrade scenarios in order to help improve the energy performance for Egyptian office buildings.
Egypt has been experiencing recurrent power cuts especially at the summer, with the problem being... more Egypt has been experiencing recurrent power cuts especially at the summer, with the problem being made worse by the extra demands placed on the electrical grid by the advent of the holy month of Ramadan. Electricity shortages are now a problem in Cairo, Alexandria, Sohag, Qena, Luxor, Aswan, and Nubia, as well as in the Nile Delta governorates of Beheira and Qalioubiya. The aim of this study is to develop a model for the Egyptian residential building using Building Performance Simulation Program and make sensitivity analysis on some variables effecting the electric power consumption in order to help faceting the growing problem in Egypt. The model was created using the IES-VE 2012 (Integrated Environmental Solution ). The simulation model was verified against the survey data for the Egyptian apartment and same model simulated using energy Plus simulation tool. The results of the program describing different situations for energy using profile for the air conditions, lighting and equ...
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.
Integration of phase change material in flat plate solar water collector: A state of the art, opportunities, and challenges
Journal of Energy Storage
Thermal Performance Analysis of Corrugated Plate Solar Air Heater Integrated with Vortex Generator
SSRN Electronic Journal
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...
Wet front propagation for water jet impingement on flat surface
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.
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Papers by Mohamed A Teamah