An experimental investigation of natural convection heat transfer from an isothermal horizontal,vertical and inclined heated square flat plates with and without circular hole, were carried out in two cases, perforated plates without an impermeable adiabatic hole "open core" and perforated plates with an impermeable adiabatic hole "closed core" by adiabatic plug. The experiments covered the laminar region with a range of Rayleih number of (1.11x106 ≤RaLo≤4.39x106 ), at Prandtle number (Pr=0.7). Practical experiments have been done with variable inclination angles from horizon (Ф=0o ,45o,90o,135oand 180o),facing upward (0o≤Ф<90o), and downward (90o
≤Ф<180o). The results showed that the temperature gradient increases while the thermal boundary layer thickness decreases when Grashof number and perforation ratio (m) increase . The temperature gradient for inclined position facing upward is less than facing downward,while the thermal boundary layer thickness is greater. The temperature gradient decreases while the thermal boundary layer thickness increases for perforated plates with an adiabatic core as compared with perforated plates without an adiabatic core. The value of average Nusselt number increases with increasing perforation ratio, and Grashof number for all specimens with and without an adiabatic core, also increases by increase in inclination of plates approaching the higher value at vertical position (Ф=90o
), then decreases with increasing inclination of plates till horizontal position (Ф=180o). The average Nusselt number values for perforated plates with an adiabatic core are lower than for perforated plates without an adiabatic core for all perforation ratios. Maximum heat transfer rate occurs at perforated plate with perforation ratio of (m=0.1) without adiabatic core for vertical position (Ф=90o), at a range of Grashof number (1.576x106≤GrLo≤6.292x106 ), while the rate of heat transfer decreases with increasing perforation ratio for plates with and without adiabatic core for decrease in heat transfer rate area. The rate of heat transfer for
perforated plates with circular hole is more than for perforated plates with square hole at the same perforation ratios (m=0.1,0.16,0.24 and 0.36). It found that the lack of core flow decreases the overall heat transfer rate by (6.477%) . There was a good agreement for the experimental present work results compared with other pervious results .
Interested current Research measuring damage currency Swap by converting The ministry of higher Education and scientific Research money The Iraqi dinar To U.S dollar by Trade Bank Of Iraq , And that The damage Generated resulting from Deferent Between the Exchange Rate adopted From Central Bank of Iraq and Market Exchange Rate adopted by The Trade Bank Of Iraq , and Which led to the greet damage ( losses ) in Bearing by the ministry, which led to the reduction of the financial allocations for licensed curriculum outside of Iraq , and this in turn leads to reduction in the number of students Sender ( scholarships ) outside Iraq.
Where the estimated loss (damage) that suffer by the Ministry of H
... Show MoreThe problem of the research is focused on importance limited of Iraq industrial companies in application of scientific measurements of supply chains performance, The research sought to achieve a group of goals, the most important are , identifying the strengths and weaknesses in the reality of supply chain in General Company for Cotton Industries, The data and information required are gathered from the dependence company, records through the field observations and personal interviews, the research used some quantitative indicators to measure of supply chain performance, The research reached to many conclusions , the most outstanding among them is the existence of a strong inverse correlatio
... Show MoreObjective: To study the effect of epidural spinal injection over one year in case of spinal stenosis. Methodology: This prospective study included 566 patients with spinal stenosis seen at Al-Kindy Teaching and Al-Sader, Hospitals who were treated by local epidural steroid injection. They were followed up for at least five subsequent visits after seven days, one month, three months, six months, and one year to assess efficacy. Result: Mean age of patients was 49.5 years, with a predominance of females (65%). L4/L5 was the most involved level in the spinal stenosis (70%). Grade II stenosis accounted for (45.4%) of cases. The pairwise comparison revealed that there was significant decrease in proportions of patients with pain in day
... Show MoreBackground :Evening preparation for colonoscopy is often unsatisfactory and inconvenient. This study was performed to compare the efficacy of bowel preparation at two different timings: night before and morning of endoscopy and to compare the cecal intubation rate and disturbance of sleep hours between these two groups.
Methods: In this prospective randomized endoscopist- blinded trial, 150 patients were enrolled between March 2010 and August 2011. Patients aged between 18 to 80 years needing colonoscopy were included. Patients with prior bowel surgery, suspected bowel obstruction or those who didn't completely fulfill the preparation instructions were excluded. Patients received polyethyelen glycol electrolyte preparation in a mornin
In the present study, the effect of new cross-section fin geometries on overall thermal/fluid performance had been investigated. The cross-section included the base original geometry of (triangular, square, circular, and elliptical pin fins) by adding exterior extra fins along the sides of the origin fins. The present extra fins include rectangular extra fin of 2 mm (height) and 4 mm (width) and triangular extra fin of 2 mm (base) 4 mm (height). The use of entropy generation minimization method (EGM) allows the combined effect of thermal resistance and pressure drop to be assessed through the simultaneous interaction with the heat sink. A general dimensionless expression for the entropy generation rate is obtained by con
... Show MoreA paraffin wax and copper foam matrix were used as a thermal energy storage material in the double passes air solar chimney (SC) collector to get ventilation effect through daytime and after sunset. Air SC collector was installed in the south wall of an insulated test room and tested with different working angles (30o, 45o and 60o). Different SC types were used; single pass, double passes flat plate collector and double pass thermal energy storage box collector (TESB). A computational model based on the finite volume method for transient tw dimensional domains was carried out to describe the heat transfer and storage in the thermal energy storage material of collector. Also, equivalent specific heat metho
... Show MoreComplexes of Cr+3, Ni+2 and Cu+2 with the ligand 2-(p- nitrobenzoyl) thiobenzimidazol) (L) were prepared and characterized by FT-IR ,UV-Visible, TG analysis ,Atomic absorption spectroscopy , Molar conductivity and magnetic moments measurements .The general formula has been suggested for all the prepared complexes [Cr(L)2Cl2]Cl.4H2O, [Ni(L)2(H2O)2]Cl2.2H2O and [Cu(L)2(H2O)2]Cl2.2C2H5OH to be an octahedral geometry. A theoretical treatment of these compounds in gas phase was done using HyperChem.8.7 program. Semi –empirical PM3 method was performed to evaluate the ∆H° ƒ, ∆ Eb and ∆ET for all compounds, also vibration frequencies, electronic spectra and electrostatic potential HOMO and LUMO energies for the ligand was estimated to de
... Show MoreThe analytical results of the failure types of six limestone islands in the Ha Long bay of Vietnam have been identified. The calculated results of safety factor for 03 plane failure blocks lie within 0.9 and 2, have high potential failure. The analytical results have been also simulated these islands in three-dimensional space and have been also analyzed their potential failure on the fracture surfaces. The results obtained in this paper have important significance for planning and development of the Ha Long bay area, as World Natural Heritage, Quang Ninh province of Vietnam.