The performance of a vapor compression refrigeration system (VCRS)-based residential air conditioner operating in a high-ambient temperature (HAT) country was investigated using six zero-ODP (ozone depletion potential) refrigerants as replacements to R22. The non-flammable alternative refrigerants considered in the present research were R134a, R404A, R407C, R410A, R448A, and R507A. Using the basic conservation laws, the VCRS was modeled during steady-state operation and solved using engineering equation solver (EES) software. Coefficient of performance (COP), pressures and temperatures at compressor suction and discharge, Global Warming Potential (GWP), critical pressure and temperature, compressor pressure ratio, volumetric cooling capacity (VCC) specific cooling capacity (SCC), and refrigeration effect were utilized as assessment criteria for the alternative refrigerants considered. From these refrigerants, the highest values of suction pressure, discharge temperature, and condenser pressure were attained by R410A. In addition, the discharge temperatures for all refrigerants, except R134a, were all higher than their corresponding critical values, causing a quicker drop in the VCRS’s performance. As an alternative refrigerant, R407C showed the highest SCC of 141.0 kJ/kg followed directly by 139.2 and 138.0 kJ/kg for R410A and R448A, respectively. A reverse trend was found for VCC with respective values of 4722 and 3775 kJ/m3 for R410A and R448A. Lower volume flow rates and smaller-sized compressors are expected for higher VCC refrigerants. The same trend was found for the compressor’s specific work input and condenser’s specific heat transfer with values of (51.14, 46.82, and 45.38 kJ/kg) and (190.3, 187.8, and 183.4 kJ/kg) for R410A, R407C, and R448A, respectively. For applications in HAT countries, larger condenser’s specific heat transfer makes the refrigerant more applicable. Conversely, with respect to COP, refrigerant R134a with a value of 3.075 was the superior alternative followed by R448A and R407C with respective COPs of 3.042 and 3.011. Based on the overall assessment in terms of environmental obligation, COP, compressor input power, refrigerant flow rate required, and all the evaluations made in this research, refrigerant R448A was recommended as the most appropriate substitute to R22 which can effectively be used in residential air conditioners in a HAT country.
Variation in the numbers of pectoral fin spines and rays, pelvic fin rays, gill rakers on the first gill arch, anal fin rays, and the number of vertebrae of Silurus triostegus Heckel were examined in specimens from 16 localities that span its entire distribution range in the Tigris, Euphrates, and Shatt al-Arab rivers in Iraq. The mean number of the six meristic traits increases toward high latitudes with maximum and minimum values in the north and south of Iraq. Based on cluster analysis and PCA, the Mesopotamian river samples were clearly separated into three distinct groups. The upper Tigris populations were isolated from those of the middle and southern populations of this river and from those of
The 3-aminoacetophenone and 4-aminoantipyrine were used as precursors to prepare new six ligands. The three new ligands (L1,L2 and L3) were synthesis by reacting one mole of 3-aminoacetophenone with one mole of (Acetyl chloride), (benzoyl chloride), (4-methoxybenzoyl chloride) and ammonium thiocyanat in acetone as a solvent, they are:- L1 (AAA) =[N-(3-acetylphenylcarbamothioyl)acetamide] L2 (BAA) =[N-(3-acetylphenylcarbamothioyl)benzamide] L3 (MAA) =[N-(3-acetylphenylcarbamothioyl)-4-methoxy benzamide] Also three new derivatives of 4-aminoantipyrine were synthesis by reacting one mole of 4-aminoantipyrine with one mole of (Acetyl chloride), (benzoyl chloride), (4-methoxybenzoyl chloride) and ammonium thio
... Show MoreThe activity of Alanine aminopeptidase( AAP ) was measured in the urine of healthy and urinary tract cancer patients , the results showed higher activity of (AAP) in patients compared to healthy . AAP was Purified from the urine of healthy and patients with urinary tract cancer by dialysis and gel filtration (Sephadex G – 50) and two isoenzymes of (AAP) were separated from urine by using ion-exchang resin (DEAE – Sephadex A – 50 ) in previous study. The kinetics studies showed that both isoenzymes I and II obeyed Michaelis – Menton equation . with optimal concentration of alanine-4-nitroanilide as substrate for isoenzymes I and II which was (2 x 10-3 mol/L ). The two isoenzymes obeyed Arrhenius equation up two 37° C and t
... Show MoreTo evaluate the shear bond strength and interfacial morphology of sound and caries-affected dentin (CAD) bonded to two resin-modified glass ionomer cements (RMGICs) after 24 hours and two months of storage in simulated body fluid at 37°C.
Sixty-four permanent human mandibular first molars (32 sound and 32 with occlusal caries, following the International Caries Detection and Assessment System) were selected. Each prepared substrate (sound and CAD) was co
Green synthesis is depending on preparation of nano composited SiO2/V2O5 by using the modified sol-gel method depending on rice husk ash as a source for the extraction of silica gel and the product powder of nano composited SiO2/V2O5 characterization by many techniques such as X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and N2 adsorptions/desorption isotherms (BET). This study also includs the biological effectiveness of SiO2/V2O5 and its effect on inhibiting bacterial growth after the prepared nanomaterial was applied to wound dressings, which gave a promising result for its use as
... Show MoreHumanity is confronted with a growing array of environmental challenges that demand immediate attention and cannot be disregarded. One of the issues the world faces is air pollution, which presents a significant risk to both the environment and human well-being. The capitalist system has a great impact on the exacerbation of air pollution and environmental deterioration. This impact is reflected in Caryl Churchill’s post-apocalyptic play Not Not Not Not Not Enough Oxygen (1971). The play presents a futuristic scenario in which humanity faces grave consequences due to the polluting practices of capitalism and the unsustainable exploitation of natural resources. It depicts a future in which environmental degradation drives people
... Show MoreABSTRACT. A new three metal complexes of La(III), Ce(IV) and UO2(II) ions have been synthesized based on a Schiff base derived from the condensation of L-histidine and anisaldehyde. All prepared compounds were characterized by different spectroscopic techniques and Density-functional theory (DFT) calculations. The complexes were proposed to have an octahedral structure based on the investigated results. The optimized shape, numbering system, and dipole moment vector of Ligand and La, Ce, and UO2 (1:1) chelates were investigated. The Schiff base ligand and complexes exhibit moderate action against all of the bacteria tested, with P. aeruginosa, Klebsiella sp., and E. faecalis respectively being the order of inhibition.
... Show MoreAl2O3 and Al2O3–Al composite coatings were deposited on steel specimens using Oxy-acetylene gas thermal spray gun. Alumina was mixed with Aluminum in six groups of concentrations (0, 5, 10,12,15 and 20% ) Al2O3, Specimens were tested for corrosion using Potentiodynamic polarization technique. Further tests were conducted for the effect of temperature on polarization curve and the hardness tests for the coated specimens. At first, Modelling was carried out using MINITAB-19, least square method, as a 2nd degree nonlinear model, bad results were achieved because of the high nonlinearity. Better result w
New complexes of the type [ML2(H2O)2] ,[FeL2(H2O)Cl] and [VOL2] were M=Co(II),Ni(II) and Cu(II) ,L=4-(2-methyl-4-oxoquinazoline-3(4H)-yl) benzoic acid were synthesized and characterized by element analysis, magnetic susceptibility ,molar conductance ,FT-IR and UV-visible. The studies indicate that the L acts as doubly monodentate bridge for metal ions and form mononuclear complexes. The complexes are found to be octahedral except V(IV) complex is square pyrimde shape . The structural geometries of compounds were also suggested in gas phase by theoretical treatments, using Hyper chem-6 program for the molecular mechanics and semi-empirical calculations, addition heat of formation(?Hf ?) and binding energy (?Eb)for the free ligan
... Show MoreThe imposition of (state) policy on the South Kuril Islands.In the Pacific was a subject
of borders dispute between Japan and Soviet Union which appeared clearly afterthe second
Great War and during the cold war. Despite the end of the Cold War and the collapse of the
Soviet Union in 1991, this conflict has continued, thus both countries had to made a historic
and legitimate claims to demand the rights of sovereignty and ownership of four islands
occupied by the Soviet Union after World War II under the international conventions and
treaties, but these claims are proven failures through the continuation of the regional conflict.