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=150,300,450,600W/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=0.25L,0.5L, 0.75L, 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 5.5a® based on the Galerkin finite element method is used for solving the governing equations with depending Brinkman- Darcy extended mode for porous media region. The results show that, effects of increasing the Rayleigh number on the temperature profile besides the progressively increasing the average Nusselt number. Moreover, symmetrical distribution of local Nu along the bottom heated wall and it is be minimum at midpoint of bottom. Also, the heat transfer and fluid flow are affected by thickness of porous layer and are maximum at porous layer thickness (0.25L) which clearly observed with large heater size to be approximately (93%) for the average Nu. Generally, the heat transfer is enhanced for large Darcy number (8.852×10-4 ) and influenced by the convection regime improvement while it is mainly conduction mode for (Da1) for all Raleigh number with a little effect of convection when increase (Ra).
Abstract
Natural gas is characterized by features that made from it a fuel and a raw material for many industries. Deepening its position as a favorite fossil supplier between other types of fossil fuel is the efficiency, diversity of its uses, low costs and compatibility with the environment which leads to increasing of its uses then increased global demand. So, the natural gas must take its place as an important resource in Iraq and participate the oil in the economic development process of building and financing of the general budget.
Iraq is planning to continue of increasing the export capacity of raw oil to meet ambitious production targets emanating from the mai
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When an electron moves from one atom or molecule to another, a charge-transfer complex is formed. The other objects must be able to accept these electrons, and one entity must have free electrons or a tendency to donate them. This resembles an internal oxidation-reduction reaction more. This research aims to shed light on charge transfer complexes formed by polyenes and carotenes, which act as electron-donating molecules due to their alternating double and single bonds. This allows them to create such complexes when interacting with organic molecules that lack electrons. These complexes exhibited distinctive optical and physicochemical properties, enabling them to be adapted for a wide range of applications. In addition, th
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Simple, sensitive and economical spectrophotometric methods have been developed for the determination of cefixime in pure form. This method is based on the reaction of cefixime as n-electron donor with chloranil to give highly colored complex in ethanol which is absorb maximally at 550 nm. Beer's law is obeyed in the concentration ranges 5-250 µg ml-1 with high apparent molar absorptivities of 1.52×103 L.mole-1. cm-1.
the physical paraneters of oxadizole derivaties as donor molecules have been measured the charge transfer and methanol as solvent have been estimated from the electonic spectra
Mass transfer was examined at a stationary rectangular copper electrode (cathode) by using the reduction of cupric ions as the electrochemical reaction. The influence of electrolyte temperature (25, 45, and 65 oC), and cupric ions concentration (4, 8, and 12 mM) on mass transfer coefficient were investigated by using limiting current technique. The mass transfer coefficient and hence the Sherwood number was correlated as Sh =
Increasing world demand for renewable energy resources as wind energy was one of the goals behind research optimization of energy production from wind farms. Wake is one of the important phenomena in this field. This paper focuses on understanding the effect of angle of attack (α) on wake characteristics behind single horizontal axis wind turbines (HAWT). This was done by design three rotors different from each other in value of α used in the rotor design process. Values of α were (4.8˚,9.5˚,19˚). The numerical simulations were conducted using Ansys Workbench 19- Fluent code; the used turbulence model was (k-ω SST). The results showed that best value for extracted wind energy was at α=19˚, spread distance of wak
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The objective of this study was to develop neural network algorithm, (Multilayer Perceptron), based correlations for the prediction overall volumetric mass-transfer coefficient (kLa), in slurry bubble column for gas-liquid-solid systems. The Multilayer Perceptron is a novel technique based on the feature generation approach using back propagation neural network. Measurements of overall volumetric mass transfer coefficient were made with the air - Water, air - Glycerin and air - Alcohol systems as the liquid phase in bubble column of 0.15 m diameter. For operation with gas velocity in the range 0-20 cm/sec, the overall volumetric mass transfer coefficient was found to decrease w
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