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A numerical investigation is adopted for a two dimensional thermal energy storage system (TES), employing finite element method to compute the time of charging or discharging energy from a phase change material (PCM) during day or night to utilize it in free cooling of space applying Baghdad Summer climate conditions (ambient temperature). A computer program is developed to analyze the thermal energy unit for different tube diameters, air flow rates and inlet air temperature for both solidification and melting processes. This study shows that utilizing small tube diameter, low flow rates or air inlet temperature near the fusion temperature lead to increase time of phase change process. It was also shown that the time duration of melting is larger than solidification.

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A numerical investigation of steady two dimensional laminar natural convection heat transfer in plain and wavy solar collector is presented in this work. The parameters adopted are Rayleigh number range (103 to106), aspect ratios (2, and 4) for wavy enclosure with number of undulation(1 to 4), and nanofluid volume fraction range (0 to 10%). The continuity, Navier-Stokes and the energy equations are solved by utilizing (FLUENT 6.3) software which is based on the finite volume method. SIMPLE algorithm with upwind scheme is adopted to compute the velocity components, temperature, pressure and Nusselt number (local and average). This study considers the effect of different boundary conditions on the heat transfer within the air space above the absorber and base fluid or nanofluid below the absorber. It is found that, the heat transfer rate increases with increasing Rayleigh number. The Nusselt number increases with increasing volume fraction in plain enclosure. Nu No. increases with increasing volume fraction. It is found that the heat transfer in plain enclosure decreases as aspect ratio increasing, while it increases in wavy enclosure. The maximum heat transfer occurs when the wavy is designed with two undulations for pure fluid and one undulations for nanofluid. The results show that the Nusselt number in wavy collector is higher than that of flat collector.

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A numerical investigation is adopted for two dimensional thermal analysis of rocket thrust chamber wall (RL10), employing finite difference model with iterative scheme (implemented under relaxation factor of 0.9 for convergence) to compute temperature distribution within thrust chamber wall (which is composed of Nickel and Copper layers). The analysis is conducted for different boundary conditions: only convection boundary conditions then combined radiation, convection boundary conditions also for different aspect ratio (AR) of cooling channel. The results show that Utilizing cooling channels of high aspect ratio leads to decrease in temperature variation across thrust chamber wall, while no effects on heat transferred to the coolant is indicated. The radiation has a considerable effect on the computed wall temperature values.

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The present work presents a new experimental study of the enhancement of turbulent convection heat transfer inside tubes for combined thermal and hydrodynamic entry length of one popular “turbulator” (twisted tape with width slightly less than internal tube diameter) inserted for fire tube boilers. Cylindrical combustion chamber was used to burn (1.6 to 7kg/h) fuel oil #2 to deliver hot gases with ranges of Reynolds number (10500 to 21700), and (11400 to 24150) for both empty and inserted tube respectively.A uniform wall temperature technique was used by keeping approximately constant water temperature difference (25ºC) between inlet and exit cooling water in parallel flow shell and tube heat exchanger. The test tube consisted of smooth carbon steel tube of (2400mm) long and (52mm) internal diameter. This test tube instrumented to derive local heat transfer coefficient and local flue gasses static pressure.The experimental results show that for the same fuel consumption, twisted tape insert with (H/D = 11.15) enhanced the mean Nusselt number in (75.2%), (68.8%), (49.8%), (40.3%), and (16.7%) for fuel consumption (7kg/h), (6.16kg/h), (4.5kg/h), (3.24kg/h), and (1.6kg/h) respectively.A set of empirical correlations that permit the evaluation of the mean Nusselt number (for developing and fully developed region), and average Nusselt number (for developed region) for empty and inserted tube are generated for engineering applications.

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This work includes a numerical investigation of steady two dimensional laminar natural convection heat transfer in glazed rectangular enclosure at different tilt angles ranged from (0° to 90°) for Rayleigh number (10^3-10^6), aspect ratios(4,5, and 8),and Prandtl number (0.7). The study considers the effect of different boundary conditions on the heat transfer within the enclosure. The continuity equation, Navier-Stokes equations and the energy equation are solved by developing a numerical model based on finite volume method using SIMPLE algorithm with hybrid scheme to compute the velocity vectors, temperature, pressure, and Nusselt No. (local and average). Results show an increase in heat transfer rate with increasing of Rayleigh number, and for low Rayleigh numbers, the conduction is the dominant heat transfer mode. At Ra= 10^3, the mean Nusselt number remains constant around unity for all cases. The tilt angle has the major effect on the heat transfer for Rayleigh number larger than 10^4. A comparison of the present results with previously published data is conducted, and good agreement is seen to indicate the effectiveness and flexibility of the developed numerical procedure.

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In this work, the turbulent buoyancy driven fluid flow and heat transfer in a differentially heated tall rectangular enclosure filled with nanofluid is quantified numerically. The two dimensional governing differential equations (continuity, momentum, energy and low Reynolds number LRN k-ω turbulence equations) are discretized using the finite volume method. SIMPLE algorithm is employed to obtain stabilized solution for high Rayleigh numbers. Two types of nanofluids namely, Al2O3-water and Cu-water, were considered. The effect of Rayleigh number (1010 to 1012), diameter of nanoparticles in the range 25-100 nm, nanoparticle volume fraction in range 0-0.08 and the aspect ratio (30, 40 and 50) on fluid flow and heat transfer are investigated. The present results are compared with previously published work and a qualitative agreement with good validation is obtained. Results show that addition of nanoparticles makes the liquid be more viscous which decreases the vertical velocity component and also decreases the temperature gradient near the walls. Also an announced heat transfer enhancement is obtained with nanoparticle volume fraction reaching a maximum point called optimal volume loading, at which the maximum convective heat transfer is obtained, and then it decreased with further increase of volume fraction.Keywords: Natural convection; turbulent; tall enclosure; finite volume method; nanofluid.

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In this work an experimental study is performed to evaluate the thermal performance of locally made closed loop solar hot water system using a shell and helical coiled tube heat exchanger as a storage tank. Several measurements are taken include inlet and outlet temperatures of both collectors and supply water and temperature distribution within the storage tank. This is beside the water flow rate in both collectors and load cycle. The main parameters of the system are obtained

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Simulation of welding process (TIG or GTAW) of butt joint using finiteelement analysis is presented. The base metal is ST(304). The numerical modeldeveloped by include moving heat source, temperature dependent materialproperties, phase change and transformation, and mechanical analysis. Theparameters studied numerically were welding current ranging between (80-150A)depending on, welding velocity, plate thickness (2.5mm -5mm), and material of theheat sink (carbon steel and copper). The numerical results show that increasing thewelding current with increasing of welding speed decreases the fusion zone area.Using copper plate underneath the welded plates acts as a dissipation heat sinkwhich generates stronger heat gradient compared with carbon steel plate. Theexperimental results show that increasing welding current leads to increasing themicro hardness, and the microstructure becomes smaller. Due to increasing coolingrate the microhardness have maximum value at the boundary between the Fusionzone and heat affected zone.

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Determining the aerodynamic characteristics of iced airfoil is an important step in aircraft design. The goal of this work is to study experimentally and numerically an iced airfoil to assess the aerodynamic penalties associated with presence of ice on the airfoil surface. Three iced shapes were tested on NACA 0012 straight wing at zero and non-zero angles of attack, at Reynolds No. equal to (3.36*105). The 2-D steady state continuity and momentum equations have been solved utilizing finite volume method to analyze the turbulent flow over a clean and iced airfoil. The results show that the ice shapes affected the aerodynamic characteristics due to the change in airfoil shape. The experimental results show that the horn iced airfoil consumes more power than the other shapes of ice, its value was (44.4W). The horn iced shape has the worst effect on the airfoil than the other shapes. The present results are compared with previously reported results; it is found there is a very good agreement between them. A comparison between the experimental and computational results of the presented work were pursing the same behavior.

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Heat transfer process and fluid flow in a solar chimney used for natural ventilation are investigated numerically in the present work. Solar chimney was tested by selecting different positions of absorber namely: at the back side, front side, and at the middle of the air gap. CFD analysis based on finite volume method is used to predict the thermal performance, and air flow in two dimensional solar chimney under unsteady state condition, to identify the effect of different parameters such as solar radiation. Results show that a solar chimney with absorber at the middle of the air gap gives better ventilation performance. A comparison between the numerical and previous experimental results shows fair agreement.

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