The enhancement of heat exchanger performance was investigated using dimpled tubes tested at different Reynolds numbers, in the present work four types of dimpled tubes with a specified configuration manufactured, tested and then compared performance with the smooth tube and other passive techniques performance. Two dimpled arrangements along the tube were investigated, these are inline and staggered at constant pitch ratio X/d=4, the test results showed that Nusselts number (heat transfer) of the staggered array is higher than the inline array by 13%. The effect of different depths of the dimple (14.5 mm and 18.5 mm) has been also investigated; a tube with large dimple diameter enhanced the Nusselts number by about 25% for the range of Reynolds number between 4000- 20000. The overall enhancement ratio was used to differentiate the passive technique and comparison of different configurations for the technique itself, the result depicted that the 10 mm dimple diameter with a pitch ratio of X/d= 4 gives better performance than the static mixer and twisted tape techniques. The overall enhancement ratio of the 10 mm dimple diameter is varied from (1.21 to 1.65) that means good performance for a range of Reynolds numbers (4000-20000). This indicates that 21- 65 % of heat transfer area can be saved at the same pumping power compared with the smooth tube heat exchanger.
Issam al-Din al-Asfrani's footnote
On the interpretation of the oval
Imam
Issam al-Din Ibrahim Arbashah al-Asfrani
(Th 159 e)
Surah Al-Baqarah (verse 55-911)
Pregnancy pose an additional burden on the body of the mother so as to meet their needs and the needs of the fetus and the body's need to iron increases excessively during pregnancy and iron is an essential element for the formation of hemoglobin blood Either hemoglobin is the key ingredient for red blood cells which carries oxygen to parts of the body, alas, most of the pregnant women begin their pregnancy inadequate stocks of iron in their bodies, which does not cover their need and requirement of the fetus, especially in the second and third trimesters of pregnancy When you reach the mother to the period in which they did not have the adequate amount of iron to produce hemoglobin become the mother was anemic So emerged the problem of
... Show MoreThe spherical double pole-piece electron lens i§ depend on some
fact0rs : the- minimum va}ue-of projector fo·cal length (Fp)i:J,Iill • the
maximum value of magnetic flux density (Bm) , the total hal[ width
,(W) o'f asyriunetrical clln'e of magnetic field distribution [because there are differe_nt values of bore diameter (D1) • i. &
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The research aims to diagnose the reality of applying the eighth requirement (operation) of the business continuity management system according to the international standard (ISO 22301: 2019), in the General Tax Authority, which is related to planning, implementing and controlling specific processes and procedures to address risks and opportunities, and the research adopted the checklist of the standard ( ISO 22301: 2019), in obtaining information, to measure the extent of application and documentation, the percentages and the weighted arithmetic mean were relied upon, and the research reached a set of result
... Show MoreNovel bidentate Schiff bases having nitrogen-sulphur donor sequence was synthesized from condensation of racemate camphor, (R)-camphor and (S)-camphor with Methyl hydrazinecarbodithioate (SMDTC). Its metal complexes were also prepared through the reaction of these ligands with silver and bismuth salts. All complexes were characterized by elemental analyses and various physico-chemical techniques. These Schiff bases behaved as uninegatively charged bidentate ligands and coordinated to the metal ions via ?-nitrogen and thiolate sulphur atoms. The NS Schiff bases formed complexes of general formula, [M(NS)2] or [M(NS)2.H2O] where M is BiIII or AgI, the expected geometry is octahedral for Bi(III) complexes while Ag(I) is expected to oxidized t
... Show Morenew six mixed ligand complexes of some transition metal ions Manganese (II), Cobalt(II), Iron (II), Nickel (II) , and non transition metal ion zinc (II) And Cadmium(II) with L-valine (Val H ) as a primary ligand and Saccharin (HSac) as a secondary ligands have been prepared. All the prepared complexes have been characterized by molar conductance, magnetic susceptibility infrared, electronic spectral, Elemental microanalysis (C.H.N) and AA . The complexes with the formulas [M(Val)2(HSac)2] M= Mn (II) , Fe (II) , Co(II) ,Ni(II), Cu (II),Zn(II) and Cd(II) L- Val H= (C5H11NO2) , C7H5NO3S The study shows that these complexes have octahedral geometry; The metal complexes have been screened for their in microbiological activities against bacteria.
... Show MoreThis study deals with examining UCAS students’ attitudes in Gaza towards learning Arabic grammar online during the Corona pandemic. The researcher has adopted a descriptive approach and used a questionnaire as a tool for data collection. The results of the study have statistically shown significant differences at the level of "0.01" between the average scores of students in favor of the students of the humanities specializations. It has also been found that the students’ attitudes at the Department of Humanities and Media towards learning Arabic grammar online are positive. Additionally, the results revealed no statistical significant differences due to the variable of UCAS students’ scientific qualifications. The results stressed
... Show MoreIn this work , the ligand [N-(4-Methoxybenzoyl amino)-thioxomethyl] Methionine acid has been synthesized by the reaction of 4- Methoxybenzoyl isothiocyanate with methionine acid . The metal complexes were prepared through the reaction of metals chlorides of Co(II) , Ni(II), Cu(II), Zn(II) and Cd(II) in ethanol as solvent . The ligand (MbM) and its metal complexes have been characterized by elemental analysis (CHNS), IR, 1H-13CNMR and UV- Vis spectra, magnetic susceptibility measurements, molar conductivity, melting points and atomic absorption. The metal-ligand ratio was determined by mole ratio method. The suggested structures for the Co(II), Ni(II), Cd(II) and Zn(II) complexes are tetrahedral geometry and the Cu(II) complex
... Show MoreDiabetic kidney disease is an illness of the glomerulus that interferes with the glomerular filtration barrier (GFB), which is worked to enable kidney to selective purification of water and solutes in addition to limiting the movement of large macromolecules such as albumin. In the glomerular endothelium, mesangial cells, foot cells, and the brush border of the proximal tubules, ACE-2 is expressed and that the kidneys represent the highest-expressing region of this enzyme. Thus, the current study aimed to evaluate ACE-2 level in this case compared to healthy condition. The study Conducted with 120 male and female ranging in age (30-65) years old. Ninety patients with type 2 diabetes subdivided into three groups on the basis of A
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