University of Technology-IraqEngineering and Technology Journal1681-690025420070425Experimental and Numerical Studies on Water Cooling Tower Performance51253318133510.30684/etj.25.4.1ENWaheed Sh.MohammadJalal M.JalilJournal Article20050405Theoretical and experimental studies were conducted on forced draft<br />water cooling tower. In such towers, the heat and mass transfer take place<br />from the hot water to the bulk air, which passes through the tower. The<br />theoretical study includes two parts, the first part describes the numerical<br />solution for the water cooling tower governing equations, a two dimension air<br />momentum equation (Navier-Stocks equations) and air enthalpy equation<br />(energy equation), moisture content and water enthalpy equation. The effect<br />of turbulence was simulated using the k-ε model. The packing-air resistance is<br />described and added to the air momentum equation in y-direction only. The<br />second part highlights the use of three different packing types. This includes<br />the use of a ceramic packing in two different heights (0.66, 0.48m) in addition<br />to an aluminum packing. A simple comparison between all the above types of<br />packing behavior is conducted. The experimental study was conducted using<br />Hilton water cooling tower, which is a counter flow type. The variation in<br />many variables, which affect the tower efficiency, are described in this part of<br />the research including variation heating loads, entering water mass flow rates<br />and incoming air volume flow rates. The flow field velocity vector for air<br />through the tower is plotted, and an accurate behavior of both air and water<br />properties was found.https://etj.uotechnology.edu.iq/article_181335_a30c3995dafa2e6a5ab22613bf18d95b.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425Numerical Study of Flow InMechanically Ventilated Rooms Under Non- Isothermal Conditions53454218133610.30684/etj.25.4.2ENJalal M.JalilTalib K.MurtadhaHanaa M. MohammedAliJournal Article20050405A computational procedure was conducted in (3x3x3 m) rooms and in a full–<br />scale model building to study the effect of supply temperature on the room<br />flow patterns in mechanically ventilated spaces. The procedure is based on the<br />solution in finite-volume form of 3D equation for the conservation of mass,<br />momentum, energy, kinetic energy and dissipation rate. Effect of buoyancy on<br />the turbulence model has been included. The results are shown to be in<br />reasonable agreement with experimental datahttps://etj.uotechnology.edu.iq/article_181336_5367a938fe1064a223f311dbc23f263d.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425The Effect of Size and Location of a Heating Source on the Buoyant Flow in a Heated Space54355718133710.30684/etj.25.4.3ENWaheed S.MohammedGazy F.SaloomyAbdul-Jabar MuttairAhmedJournal Article20050510A numerical study of two-dimensional turbulent buoyant recirculating flows<br />within a heated space is presented. The study involves the solution of elliptic partial<br />differential equations for the conservation of mass, momentum, energy, turbulence<br />energy and its dissipation rate. These equations were solved together with algebraic<br />expressions for the turbulent viscosity and heat diffusivity in a finite difference form.<br />The simulations of the turbulent buoyant flow within the space were undertaken<br />using two principle geometrical arrangements (A & B) of the room with different<br />locations and sizes of a heating source (b/h=0.08, 0.28, and 0.5 for geometry A and<br />b/h=0.75, 1.45, and 6.0 for geometry B). The study demonstrates that for a thermal<br />comfort conditions in the space the location and size of the heating source are of great<br />importance. When the heating source is located in the middle of the floor it is found to<br />generate a high velocity air stream resulted from vortices produce a local thermal<br />discomfort in the occupation zone. On the other hand its location under a cold<br />window offsets the losses in heat and avoiding the form of the high velocity air<br />streams in the occupation zone. The size of the heating source is also found to<br />influence the occupation zone condition through the effect on the heat transfer rate<br />inside the conditioned space.https://etj.uotechnology.edu.iq/article_181337_2660714d49eb9547ecdfce043d74b987.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425Dopping Effect On Optical Constants of Polymethylmethacrylate (PMMA)55856818133810.30684/etj.25.4.4ENAhmad A.HAwatif A.MZeid Abdul-MajiedNJournal Article20050512The optical constants (refractive index (n) , extinction coefficient (k) , real<br />and imaginary parts of dielectric constant(ε1&ε2)) of polymethyl methacrylate<br />(PMMA) doped with methylene blue (mb) and methyl red (mr) with<br />thickness in the range (0.1-0.2) mm were measured in the wavelength range<br />(200-900) nm. Refractive index (n) and extinction coefficient (k) showed<br />irregular changes with increasing (mb) dopant concentrations, while (n) and<br />(k) of PMMA doped with (mr) declared a systematic increase with increasing<br />dopant concentrations. The data showed that (n) values of PMMA doped with<br />(mr) are lower than the values of samples doped with (mb) which is<br />atteributed to the progressive increase of absorbance in the wavelength range<br />(400-550) nm with increasing (mr) concentration .https://etj.uotechnology.edu.iq/article_181338_8d782f6229e3bf81f5bb4d22a04e42f0.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425A Finite Element Analysis of Orthogonal Machining Using Different Tool Edge Geometries56958318133910.30684/etj.25.4.5ENMaan AabidTawfiqSuha KareemShahabJournal Article20050905This paper summarizes the effects of edge preparation of the cutting tool in<br />orthogonal cutting on the following variables: stress distributions at the tool<br />rake face, cutting forces and tool-chip contact length. The Finite Element<br />Method (FEM) is selected using the ANSYS /V4.5 code. Six models of cutting<br />tools have been suggested having edge radii of (0.01, 0.05, 0.1, 0.15, 0.2, and<br />0.25) mm. The results obtained provide a fundamental understanding of the<br />process mechanics for cutting with realistic cutting tool edge radius in order to<br />assist in the optimization of tool edge design. The results show that the<br />optimum edge radius from the six simulated models is (0.05) mm; this edge<br />radius gives minimum value of effective stress. The results show also that the<br />optimum edge radius that shows minimum tangential cutting and feed forces<br />is (0.01) mm. The results investigated that the tool-chip contact length is<br />increased, until reaching maximum value of (2.4) mm at (r=0.15mm), and<br />minimum value of (0.75) mm at (r=0.01mm). The maximum relative<br />difference between simulated results of this work and other previous paper<br />results is (2% - 17%) for the tool effective stresses, (5%) for the tangential<br />force, and (11%) for the feed force.https://etj.uotechnology.edu.iq/article_181339_453bf8064bb2df16ad01223c7252b3d0.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425Normalized Characteristics of Laser-Induced Diffusion of Arsenic Dopants in Silicon58459018134010.30684/etj.25.4.6ENOday A.HamadiSalma M.HussainJournal Article20051228In this work, normalized characteristics of laser-induced diffusion of<br />arsenic in silicon are presented. These characteristics are considered as are<br />enhancing the As-doped silicon-based devices. This enhancement is attributed<br />to the increasing in the diffusion length within a certain layer of the active<br />region in the device. Laser-induced diffusion is a perfect technique for<br />improving the characteristics of electronic devices because it is flexible,<br />contactless, clean and well controlled.https://etj.uotechnology.edu.iq/article_181340_8ee05de2f8dd5fd277770343f2eb21e0.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425The Effect of Surfactants on Characteristics of Hydrodynamic and Mass Transfer Coefficient in Gas-Liquid Dispersion Column59160718134110.30684/etj.25.4.7ENThamer J.MohammedFadi Z.HannaJournal Article20060222This work studis the effect of liquid properties (water, solution 0.2-1.5 wt<br />% for each of i-propanol, and n-butanol), temperature (26-55 oC) and<br />superficial air velocity (1-15cm/s) on the gas holdup and mass transfer<br />coefficient in air-liquid dispersion column. The experimental procedure was<br />carried out by QVF column (10 cm i.d, 1.5 m height) and air bubbling by<br />multi-orifice distributor (2 mm, 49 holes in square pitch). The experimental<br />results are presented in two and three dimension graphs, these graphs<br />indicate, increases in holdup and mass transfer coefficient with increasing<br />weight percent of alcohols, temperature, and superficial velocity of air. The<br />gas holdup and mass transfer coefficient are in the following order<br />n-butanol > i-propanol > water. Also the experimental results were correlated<br />by fitting empirical correlations.<br />Some of the results have been correlated on the basis of drift flux model<br />in order to express the effect of surface active agent on radial uniformity flow<br />and gas holdup profileshttps://etj.uotechnology.edu.iq/article_181341_c68ee8e24fb9c674c26f455274b02cc4.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425Modelling Pressure Drop to Calculate Conversion of Silicon and Methyl Chloride in a Fluidized bed Reactor60861818134210.30684/etj.25.4.8ENIhsan B.HamawandJournal Article20060201Three experiments were curried out at different reaction temperatures [ 250, 300,<br />330 oC ], for the reaction of silicon with methyl chloride in a fluidized bed reactor, in<br />order to evaluate a new predicted model that calculate both conversions of reacted solid<br />(silicon) and reacted gas (methyl chloride) as function of pressure drop along the bed.<br />The reacted gas velocity was selected to be above the minimum fluidization<br />velocity [velocity selected 2.6 cm/s, minimum fluidization velocity 1.8 cm/s] for the solid<br />particles (size used 130 μm). A digital pressure drop measuring device was used at three<br />points of the reactor (before and after the distributor and finally 50 cm above the<br />distributor), to determine the pressure drop along the column, also an online GC was<br />connected to the outlet reacted gas to analyze the product.<br />A comparison between the conversions of methyl chloride and silicon calculated<br />from pressure drop data and that detected by the online GC, show a proper agreement<br />with less than 5 %absolute average error.<br />Two equations [16, 18], derived analytically, were equation [8, 18] used to<br />calculate the conversion of silicon and methyl chloride as function of pressure drop,<br />equation [16] used to calculate the conversion of silicon as function of conversion of<br />methyl chloride.https://etj.uotechnology.edu.iq/article_181342_b032ad64963920f38e417bbaf1f9deec.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425A Numerical Model For Thermal-Hydraulic Design of a Shell And Single Pass Low Finned Tube Bundle Heat Exchanger61964518134310.30684/etj.25.4.9ENAli HussainTarradJournal Article20060322This investigation represents a computerized model for the thermal-hydraulic<br />design of a single shell – single pass of enhance tube bundle heat exchanger using<br />the step by step technique (SST). The design procedure suggested in this study is<br />also suitable for multi-tube passes using the most familiar methods of design of<br />shell and tube heat exchanger such as Kern and Bell-Delaware. The (SST) was<br />considered as a basic in order to incorporate the effect of the physical property<br />change due to temperature variation along the heat exchanger. The model basic<br />design depends on the selection of the low finned tube characteristics. The use of<br />such surface will have the advantage of avoiding the space restrictions of the<br />equipment layout in the industrial applications and reduction in the cost of<br />manufacture machining as well. The model was intended to be a choice for the<br />lubricating oil cooling system of a gas turbine power station in Debis-Kirkuk<br />plant. The verification of the model showed that using such enhanced tubes in the<br />cooling system will improve the operating conditions especially during summer<br />season in Iraq.https://etj.uotechnology.edu.iq/article_181343_6686b3d8695ca27bedfe3bc1c9512fd8.pdfUniversity of Technology-IraqEngineering and Technology Journal1681-690025420070425Secure E-Mail System Using S/Mime and Ib-Pkc64666818134410.30684/etj.25.4.10ENSufyan T.FarajMohammed T.IbrahemJournal Article20060404Although e-mail security solutions have been introduced for<br />more than two decades, most of the e-mail messages are sent nowadays<br />without being secured by any of these techniques. This is due to the<br />complexity of using these secure e-mail systems and protocols. The<br />complexity mainly arises from the difficulty associated with managing<br />certificates and public keys. The main objective of this study was to find<br />a solution that can make secure e-mail systems easier to use while<br />maintaining the same level of security. This paper proposes a secure email<br />system that is based on the S/MIME standard where the public<br />key and signature algorithms have been replaced by their Identity-<br />Based Cryptography analogue algorithms.<br />Using Identity-Based Cryptography has eliminated the need for<br />digital certificates, and provided a solution to the usability problem<br />present in the existing secure e-mail systems. Users can determine the<br />public key of the recipient without having to contact any trusted third<br />party, and can start encrypting or verifying messages as long as they<br />have the public system parameters that can be publicly available. Users<br />need to contact the Private Key Generator (PKG) only once in order to<br />retrieve their private key before being able to decrypt or sign messageshttps://etj.uotechnology.edu.iq/article_181344_6ea9aef8f59e61b1bf184061436acde3.pdf