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Iraqi journal of mechanical and material engineering

المجلة العراقية للهندسة الميكانيكية وهندسة المواد

ISSN: 20761819
Publisher: Babylon University
Faculty: Engineering
Language: Arabic and English

This journal is Open Access

About

Iraqi journal for mechanical and material engineering is a refereed scientific journal published quarterly by the engineering college/ university of Babylon. It deals with high quality researches in fields of mechanical and material engineering.

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Contact info

Journal E-mail:
j.mec_mat_eng@yahoo.com
Babylon university/Babylon/Iraq P.O.Box(4)
Tel:++96430245387.(1155)

Table of content: 2008 volume:8 issue:3

Article
A NUMERICAL ANALYSIS OF ADIABATIC CAPILLARY TUBE PERFORMANCE IN VAPOR COMPRESSION REFRIGERATION SYSTEMS
تحليل عددي لأداء الأنابيب الشعرية الأديباتيه في منظومات التبريد الأنضغاطيه

Authors: Dr. Ali Hussain Tarrad
Pages: 201-218
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Abstract

This paper represents a numerical analysis intended for the selection and geometry design of the capillary tubes used in the vapor compression refrigeration units. This expansion component is usually selected for small home air conditioning units and domestic refrigerators and freezers for their ease integration with the cooling units and cheap prices. The numerical step by step model suggested in this work depends mainly on the idea of the control volume theory for the conservation of mass, energy and linear momentum of fluid refrigerants flowing inside the capillary tube. The flow regime is divided into a number of increments for which the conservation expressions were solved simultaneously for the physical characteristics parameters. These are temperature, pressure, and vapor quality and mixture velocity along the capillary tube from the entrance at the high pressure side to the exit at the low pressure side of the refrigeration unit. The theoretical prediction for the profile of the characteristics parameters showed a good agreement with available experimental data in the literature and the ASHRAE published rating charts of the capillary tubes.


Article
HEAT TRANSFER BY FREE CONVECTION BETWEEN HORIZONTAL CONCENTRIC PIPES

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Abstract

This research deals with the theoretical and experimental study of free convection heat transfer between horizontal concentric pipes of constant inner and outer cylinders temperature, respectively and (Ti>To). The finite elements method was used to solve the numerical relations of momentum and energy equations. The numerical solution has been included the calculation of the temperature and velocity values between the cylinders by using ANSYS program (finite element analysis structural system). Different models of concentric double pipes were created and tested with different diametral ratios. Nusselt number was obtained for a range of temperature difference (ΔT=Ti-To) of (6.01-120.42C0). The results also showed that the average heat transfer coefficient values at the inner and outer radii respectively increased with the increasing of Rayleigh number and the ratio of outer to inner radius. The theoretical and experimental results were compared with some of researches that presented in the literature to achieve the verification of the results obtained from the numerical analysis and experimental modeling for the heat transfer between concentric double pipes. The results are in good agreement.

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Article
ONE DIMENSIONAL MODEL FOR WATER MANAGEMENT THROUGH THE MEMBRANE OF A HYDROGEN PEM FUEL CELL

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Abstract

This work presents a one dimensional modeling study for water movement through the membrane of a hydrogen fuel cell. The model studies the effect of electro-osmotic drag, pressure gradient and back diffusion on local water concentration through the membrane. It is found that the current density increases the water movement due to electro-osmotic drag while the pressure gradient increases the hydraulic permeation and back diffusion. It is also found that after about 30 seconds both effects are equalized and the water concentration throughout the membrane reaches equilibrium state.


Article
NUMERICAL ANALYSIS OF THE THERMAL –STRESSES OF A PETROL ENGINE PISTON WITH DIFFERENT MATERIALS

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Abstract

In this paper a numerical analysis is used to analyze the stresses due to thermal cycle with different aluminum alloy of piston .Finite element method was used to evaluate the coupling field (thermal –stress) on the piston .ANSYS5.4 Finite element code is used to carry out the modeling process to determine the coupling stress .Two models with three dimensions are created .The first is used to evaluate the temperature distribution through the piston volume, and the second is used to evaluate the thermal stress distribution due to heat gradient and the material different. The result show the maximum range of temperatures is 4.3 °C and increases with decreasing of material thermal conductivity .Thermal stress is concentrated on the piston edges and depends on the material types.

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Article
STRUCTURAL AND THERMAL ANALYSIS OF HEAT EXCHANGER WITH TUBES OF ELLIPTICAL SHAPE
التحليل التركيبي و الحراري لمبادل حراري ذو أنابيب بيضوية الشكل

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Abstract

An approach to select the tube wall thickness distribution of streamlined tubes intended for use in heat exchangers is developed in this study. The main goal is to retain a streamlined outer profile (resist deformation) and to prevent strain failure due to the applied internal pressure. The effect of the tube wall thickness distribution on shaped tube efficiency is also considered. The strain is calculated as a function of several dimensionless geometric ratios and the ratio of the internal pressure to elastic material modulus. Using the finite element method, a set of dimensionless design curves is created for elliptical tube geometries. From these curves, a range of possible materials and tube geometries can be selected that meet a specific strain limit. To illustrate the approach, structure-satisfied elliptical designs are selected and their thermal performance is evaluated for an automotive charge air cooler made of polymeric material.


Article
ANALYSIS OF CRACKING OF CELLULAR CONCRETE BLOCK (THERMOSTONE)

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Abstract

This research deals with a problem that exists during manufacturing of thermostone blocks which are produced in a company for insulation building material. Micro and macro cracks are some of those problems which reduce the resistance to fracture under loads, or causing damage to the product during manufacturing processes. The research applies practical -theoretical method to determine the mechanism of fracture, depending on taking two images, one is a stereo microscope with suitable magnification, so that all different phases can be seen as possible, the second one is a video image to show pores and cracks. A numerical solution (finite element method) was applied on the images. Chemical composition and percentage of elements and their effect on fracture behavior have been studied also.


Article
BEHAVIOR OF END-RESTRAINED SHRINKAGE CRACKS OF CEMENT MORTAR WITH DIFFERENT TYPES OF CEMENT
سلوك تشققات الانكماش المقيدة من النهايات لمونة أنواع مختلفة من السمنت

Authors: Abbass Salim Abbass
Pages: 282-291
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Abstract

The aim of study is to understand the behavior of shrinkage cracks of cement mortar, using different types of cement (O.P.C), (S.R.P.C) & (W.P.C) with mix proportion (1:2.5) cement: sand by weight, and water /cement ratio (0.5) for all series. The samples were cast in (I) shape steel moulds and had lateral restraint to resist volume changes (shrinkage & creep) in cement mortar under wetting and drying cycles (moisture content changes), the study consisted also determining compressive strength and modulus of rapture for the cement mortar. Experimental results showed that compressive strength of mortar of ( O.P.C) was greater than of mortar with (S.R.P.C)&( W.P.C)by (23%,17%,16%) ,(35%,29%,28%) at age (3,7,28) days respectively. The modulus of rapture of mortar with (O.P.C)was greater than of mortar with (S.R.P.C)&( W.P.C) at age (28)days by (23%,25%) respectively. The results showed that shrinkage cracks in samples occurred in mortar with (O.P.C), (S.R.P.C) & (W.P.C) at age (21,24,28)days after casting respectively. The crack width development of the sample with (O.P.C) was higher than the crack width development of the sample with (S.R.P.C) until age of (66) days , and after that decreased , but the crack width development of the sample with (W.P.C)stayed lower than the crack width development of the sample with (O.P.C)& (S.R.P.C) at all ages .

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