منصة إيفاد العلمية

د. لمى فاضل علي

إرسال رسالة

التخصص: هندسة ميكانيكية

الجامعة: جامعة بغداد

النقاط:

29.5

معامل الإنتاج البحثي

الخبرات العلمية

thermo-fluid

الأبحاث المنشورة

Numerical investigation of natural convection in a square enclosure partially filled with horizontal layers of a porous medium

المجلة: Heat transfer wiley

سنة النشر: 2022

تاريخ النشر: 2022-09-07

Two‐dimensional buoyancy‐induced flow and heat trans- fer inside a square enclosure partially occupied by copper metallic foam subjected to a symmetric side cooling and constant heat flux bottom heating was tested numerically. Finite Element Method was employed to solve the governing partial differential equations of the flow field and the Local Thermal Equilibrium model was used for the energy equation. The system boundaries were defined as lower heated wall by constant heat flux, cooled lateral walls, and insulated top wall. The three parameters elected to conduct the study are heater length (7≤ζ≤20cm), constant heat flux (150≤q′′≤600Wm−2), and porous material thickness (5≤H≤20cm). The porous material used was the copper metal foam of porosity = 0.9 and pore density PPI=10, and saturated with a fluid of Prandtl number = 0.7. On the basis of the results obtained, it was concluded that at the porous layer thickness=5cm, the rate of heat transferred was (74.6%) higher than when the layer height was 20 cm (the cavity is fully filled) and at the same thickness it was found that the heat rate is (51.4%) higher than when using the half filling (H=10cm). Further, the local and mean Nusselt number is maximum when using the largest heater size and smallest porous layer thickness. Finally, better circulation and convective modes were observed at high values of heat flux.

Numerical Investigation of Natural Convection Heat Transfer in Partially Filled Porous Enclosure Subjected to Constant Heat Flux

المجلة: Journal of Mechanical Engineering Research and Developments

سنة النشر: 2021

تاريخ النشر: 2021-07-21

Steady natural convection in a square enclosure with wall length (L= 20 cm) partially filled by saturated porous medium with same fluid (lower layer) and air (upper layer) is investigated. The conceptual study of the achievements of the heat transfer is performed under effects of bottom heating by constant heat flux (q= 150,300,450,600 W/m2) for three heaters size (0.2, 0.14, 0.07) m with symmetrically cooling with constant temperature on two vertical walls and adiabatic top wall. The relevant filled studied parameters are four different porous medium heights (Hp= 0.25 L, 0.5 L, 0.75 L, L), Darcey number (Da1) 3.025× 10-8 and (Da2) 8.852× 10-4) and Rayleigh number range (60.354-241.41),(1.304× 106–5.2166× 106) for Da1 and Da2 cases respectively. Numerically, COMSOL Multiphysics 5.5 a® based on the Galerkin finite element method is used for solving the governing equations with depending Brinkman-Darcy …

Mixed Convection in a Square Cavity Filled with Porous Medium with Bottom Wall Periodic Boundary Condition

المجلة: Journal of Engineering

سنة النشر: 2014

تاريخ النشر: 2014-04-21

Transient mixed convection heat transfer in a confined porous medium heated at periodic sinusoidal heat flux is investigated numerically in the present paper. The Poisson-type pressure equation, resulted from the substituting of the momentum Darcy equation in the continuity equation, was discretized by using finite volume technique. The energy equation was solved by a fully implicit control volume-based finite difference formulation for the diffusion terms with the use of the quadratic upstream interpolation for convective kinetics scheme to discretize the convective terms and the temperature values at the control volume faces. The numerical study covers a range of the hydrostatic pressure head,,,, and ), sinusoidal amplitude range of⁄ and time period values of (). Numerical results show that the pressure contours lines are influenced by hydrostatic head variation and not affected with the sinusoidal amplitude and time period variation. It is found that the average Nusselt number decreases with time and pressure head increasing and decreases periodically with time and amplitude increasing. The time averaged Nusselt number decreases with imposed sinusoidal amplitude and cycle time period increasing.

Numerical Investigation for Natural Convection in a Square Enclosure with Partially Active Thermal Sides’ Wall

المجلة: Journal of Mechanical Engineering Research and Developments

سنة النشر: 2021

تاريخ النشر: 2021-05-21

Three-dimensional cavity was investigated numerical in the current study filled with porous medium from a saturated fluid. The problem configuration consists of two insulated bottom and right wall and left vertical wall maintained at constant temperatures at variable locations, using two discretized heaters. The porous cavity fluid motion was represented by the momentum equation generalized model. The present investigation thermophysical parameters included the local thermal equilibrium condition. The isotherms and streamlines was used to examine energy transport and momentum. The meaning of changing parameters on the established average Nusselt number, temperature and velocity distribution are highlighted and discussed.

Numerical study of natural convection in an annulus between two concentric cylinders provided with metal foam fins

المجلة: Journal of Engineering

سنة النشر: 2022

تاريخ النشر: 2022-04-21

Natural convection in an annular space provided with metal foam fins attached to the inner cylinder is studied numerically. The metal foam fins made of copper were inserted in different axial sections with three fins in each section. The temperature of the inner cylinder is kept constant while the annular outer surface is adiabatic. The thickness effect of the inner pipe wall was considered. Naiver Stokes equation with Boussinesq approximation is used for the fluid regime while Brinkman-Forchheimer Darcy model is used for metal foam. In addition, the local thermal non-equilibrium condition in the energy equation of the porous media is presumed. The effect of Rayleigh number and number of foam fins in the axial direction, on fluid flow and heat transfer characteristics, were examined. The current model was valid with the available published results and good agreement is noticed. Results showed that as the Rayleigh number increases the dominated of convection mode increases and average Nusselt increases. It was found that at Rayleigh of 10 6 Nusselt reached its higher value which is 4.6 for the case of adding seven axial metal foams. A comparison between adding foam fins and copper fins was established for a range of Rayleigh numbers between 10 4 and 10 6. It showed a good enhancement in Nusselt number and the greatest enhancement percentage was 45.9% at Rayleigh equal 10 6 for the case of using seven sections of foam fins.

CONJUGATE NATURAL CONVECTION IN A POROUS ENCLOSURE SANDWICHED BY FINITE WALLS AND SUBJECTED TO CONVECTION COOLING CONDITION

المجلة: Journal of Engineering and Sustainable Development

سنة النشر: 2021

تاريخ النشر: 2021-05-21

Steady conjugate natural convection heat transfer in a two-dimensional enclosure filled with fluid saturated porous medium is studied numerically. The two vertical boundaries of the enclosure are kept isothermally at same temperature, the horizontal upper wall is adiabatic, and the horizontal lower wall is partially heated. The Darcy extended Brinkman Forcheimer model is used as the momentum equation and Ansys Fluent software is utilized to solve the governing equations. Rayleigh number (1.38≤ Ra≤ 2.32), Darcy number (3.9* 10-8), the ratio of conjugate wall thickness to its height (0.025≤ W≤ 0.1), heater length to the bottom wall ratio (1/4≤≤ 3/4) and inclination angle (0, 30 and 60) are the main considered parameters. The presented results show the effect of these parameters on the heat transfer and fluid flow characteristics. These results include streamlines, isotherm patterns, and local and average Nusselt number for different values of the governing parameters. It is found that either increasing the Rayleigh number and the ratio of conjugate wall thickness to its height (d/H) or decreasing the ratio of heat source width to bottom wall (l/L), the average Nusselt number is increased. Also, it was observed that the average Nusselt number does not change substantially with inclination angle.

Natural and Mixed Convection in Square Vented Enclosure Filled with Metal Foam

المجلة: Journal of Engineering

سنة النشر: 2015

تاريخ النشر: 2015-11-21

Steady natural and mixed convection flow in a square vented enclosure filled with water-saturated aluminum metal foam is numerically investigated. The left vertical wall is kept at constant temperature and the remaining walls are thermally insulated. Forced convection is imposed by providing an inlet at cavity bottom surface, and a vent at the top surface. Natural convection takes place due to the temperature difference inside the enclosure. Darcy-Brinkman-Forchheimer model for fluid flow and the two-equation of the local thermal non-equilibrium model for heat flow was adopted to describe the flow characteristics within the porous cavity. Numerical results are obtained for a wide range of width of the inlet as a fraction of the height of the enclosure (⁄), the porosity of aluminum foams (,), Grashof numbers (), and Reynolds number (). Effects of pertinent physical parameters are performed in terms of the flow and temperature fields, as well as the average Nusselt number variations. The results show that the average Nusselt number increases with⁄ and and decreases with the porosity increasing. The fluid temperature distribution has a little difference from the solid matrix temperature

Natural convection in annulus between two concentric cylinders partially filled with metal foam distributed with new suggested design

المجلة: IOP Conference Series: Earth and Environmental Science

سنة النشر: 2022

تاريخ النشر: 2022-01-21

The investigation of natural convection in an annular space between two concentric cylinders partially filled with metal foam is introduced numerically. The metal foam is inserted with a new suggested design that includes the distribution of metal foam in the annular space, not only in the redial direction, but also with the angular direction. Temperatures of inner and outer cylinders are maintained at constant value in which inner cylinder temperature is higher than the outer one. Naiver Stokes equation with Boussinesq approximation is used for fluid regime while Brinkman-Forchheimer Darcy model used for metal foam. In addition, the local thermal equilibrium condition in the energy equation of the porous media is presumed to be applicable for the present investigation. CFD ANSYS FLUENT software package (version 18.2) is used as a solver to this problem. Various parameters are examined; Rayleigh number …

Output Feedback Adaptive Sliding Mode Control Design for a Plate Heat Exchanger

المجلة: Al-Nahrain Journal for Engineering Sciences

سنة النشر: 2018

تاريخ النشر: 2018-12-21

The heat exchanger is a device used to transfer heat energy between two fluids, hot and cold. In this work, an output feedback adaptive sliding mode controller is designed to control the temperature of the outlet cold water for plate heat exchanger. The measurement of the outlet cold temperature is the only information required. Hence, a sliding mode differentiator was designed to estimate the time derivative of outlet hot water temperature, which it is needed for constructing a sliding variable. The discontinuous gain value of the sliding mode controller is adapted according to a certain adaptation law. Two constraints which imposed on the volumetric flow rate of outlet cold (control input) were considered within the rules of the proposed adaptation law in this work. These are the control input is a positive quantity, and it limited by a maximum value. The maximum allowable desired outlet cold water has been estimated as function of heat exchanger parameters and maximum control input. The simulation results demonstrate the performance of the proposed adaptive sliding mode control where the outlet cold water was forced to follow desired temperature equal to 45𝑜. Additionally, the robustness of the proposed controller was tested for the case where the cold water inlet temperature is not constant, and also for the case of heat exchanger parameters uncertainty. The results were revealed the robustness of the proposed controller.

Natural convective heat transfer in an inclined open porous cavity with non-uniformly heated wall

المجلة: Association of Arab Universities Journal of Engineering Sciences

سنة النشر: 2018

تاريخ النشر: 2018-10-21

Theoretical and experimental investigations of free convection through a cubic cavity with sinusoidal heat flux at bottom wall, the top wall is exposed to an outside ambient while the other walls are adiabatic saturated in porous medium had been approved in the present work. The range of Rayleigh number was and Darcy number values were.

Mixed Convection in a Square Cavity Filled with Porous Medium with Heated Bottom Wall

المجلة: International Journal of Computer Applications

سنة النشر: 2013

تاريخ النشر: 2013-01-21

Two-dimensional unsteady mixed convection in a porous cavity with heated bottom wall is numerically studied in the present paper. The forced flow conditions are imposed by providing a hydrostatic pressure head at the inlet port that is located at the bottom of one of the vertical side walls and an open vent at the top of the other vertical side wall. The Darcy model is adopted to model the fluid flow in the porous medium and the combination effects of hydrostatic pressure head and the heat flux quantity parameters are carefully investigated. These governing parameters are varied over wide ranges and their effect on the heat transfer characteristics is studied in detail. It is found that the time required to reach a desired temperature at the bottom wall decreases with heat flux and pressure head increase. The higher heat flux quantities leaves wider regions near the top wall at lower temperatures which is important in most engineering applications like drying.

Experimental study of natural convection heat transfer on an enclosure partially filled porous medium heated from below by constant heat flux

المجلة: AIP Conference Proceedings

سنة النشر: 2023

تاريخ النشر: 2023-03-21

This study reports on natural convection heat transfer in a square enclosure of length (L= 20 cm) with a saturated porous medium (solid glass beads) having same fluid (air) at lower horizontal layer and free air fill in the rest of the cavity’s space. The experimental work has been performed under the effects of heating from bottom by constant heat flux q= 150,300,450,600 W/m2 for four porous layers thickness Hp (2.5, 5, 7.5, 1) cm and three heaters length δ (20, 14, 7) cm. The top enclosure wall was good insulated and the two side walls were symmetrically cooled at constant temperature. Four layers of porous media with small porosity, Rayleigh number range (60.354-241.41) and (Da) 3.025× 10-8 has been investigated. The obtained data of temperature from testing rig are used to extract the temperature distribution, local Nusselt number and average Nusselt number. Moreover, a comparison between the numerical …

FORCED CONVECTION THERMAL BOUNDARY LAYER DEVELOPMENT IN A POROUS MEDIA NEAR A WALL WITH VARIABLE TEMPERATURE BOUNDARY CONDITION

المجلة: Journal of Engineering

سنة النشر: 2011

تاريخ النشر: 2011-04-21

The behavior of forced convection heat transfer characteristics through and over porous layer near a heated flat plate at variable temperature has been investigated numerically. Two cases of variable wall temperature boundary condition are studied. The first case is of linear temperature variation with position along the flat plate and the second case is of sinusoidal temperature variation with time of heating. The flow field in the porous region is governed by the Darcy-Brinkman-Forchheimer equation, the thermal field in the porous region by the energy equation and the part over the porous matrix includes flow and heat transfer equations. Solutions of the problem have been carried out using a finite difference method through the use of a stream function-vorticity transformation. The effects of various governing dimensionless parameters, Darcy number, Reynolds number, Prandtle number as well as the inertia parameter are thoroughly explored. The variation of the non-dimensional period and amplitude values of the sinusoidal temperature distinction with time was also studied. Good results were obtained and reported graphically. It was found that the local Nusselt number on the flat plate increases with the increasing of the increasing non-dimensional values of period and amplitude individually.

NUMERICAL AND EXPERIMENTAL INVESTIGATION OF STEAM FILM CONDENSATION ON A VERTICAL TUBE

المجلة: Journal of Engineering

سنة النشر: 2010

تاريخ النشر: 2010-12-21

Film condensation of steam on a vertical tube is investigated numerically and experimentally, in the present work. A mathematical model was set based on the basic conservation laws of mass and energy, Nusselt′ s analysis of film condensation, and empirical equations available in the literature. Then, a simulation program in FORTRAN language was developed which simulates the film condensation of steam on a vertical tube. A complete steam tables subprogram was also developed and incorporated with the main program. The experimental work was carried out using a steam condensation test bench. The inlet and outlet cooling water temperatures, steam temperature and pressure, tube surface temperature at center, and cooling water flow rate are recorded during each experimental test run. The inlet cooling water temperature, steam temperature, and cooling water flow rate are used as an input for the numerical program, then the program calculates tube surface temperature distribution, cooling water temperature distribution, local heat transfer rate, local condensation heat transfer coefficient, condensate boundary layer thickness distribution, total heat transfer rate, and average condensation heat transfer coefficient. The effect of various parameters on the condensation heat transfer coefficient, such as steam temperature, steam-surface temperature difference, and the presence of non-condensable gas were investigated and reported graphically. It was found that increasing (steam-surface) temperature difference while keeping the steam temperature constant results in an increase in condensate boundary layer thickness, which in turn …

An Investigation into Thermal Performance of a Tapered Glass Window

المجلة: Journal of Engineering

سنة النشر: 2006

تاريخ النشر: 2006-04-21

The conjugate heat transfer problem through a glass window with non-uniform thickness is presented. The problem was studied using the fully implicit finite difference numerical technique. The tapered glass window is subjected to a convective boundary condition on the outer uniform side of the window and the heat transfer coefficient depends on the direction of the flow. While the inside boundary condition is at constant comfortable temperature. The upper and lower edge of the tapered section is also at constant temperature but equal to the mean temperature between the indoor and the outdoor temperature. In the first part a rectangular cross section an area of 4mm width and I'm height was taken under study. While, in the second part of the study, a tapered cross section with different tapered angles of 0.05, 0.1, 0.15, and 0.2 degree was held. Another case of the equal cross section area of the tapered and the rectangular cross section was also studied. Good results were obtained and reported graphically. It was found that the ratio of the heat loss by convection from the linear tapered to the rectangular section increases with the increasing of time and the tapered angle