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Thermodynamic Performance and Flammability studies of Hydrocarbon Based Low Global Warming Potential Refrigerant Mixtures

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Journal of Thermal science 2022年第5期31卷 1487-1502页

作者： Nagarjuna KUMMA s s Harish KRUTHIVENTI Department of Mechanical Engineering Low Temperature LaboratoryNational Institute of TechnologyTiruchirappalliTrichy620015India

This paper presents a theoretical method to calculate the minimum inerting concentration(MIC)of binary and ternary blends(refrigerants)that are used in small refrigeration *** is the concentration of the dilutant which makes the flammable mixture into just non-flammable(at non-zero quenching potential).In this study,the refrigerant safety parameters such as flammability,Global Warming Potential(GWP)and performance(COP)are analyzed for twelve binary and thirteen ternary blends containing one flammable and two nonflammable(dilutant)*** investigation was carried out with the hydrocarbon refrigerants R290,R600,R600a each mixed with dilutants R227ea,R125,R245fa,R13I1 and R134a at different concentrations *** methods,thermal balance method(TBM)and modified thermal balanced method(MTBM),are used to estimate the MIC(which decides the flammable zone).Thirteen ternary blends were identified based on the MIC values estimated using *** the case of ternary blends,it was observed that the non-flammable zone is high for the compositions of the Mixture G,Mixture H and Mixture *** was also estimated that the COPs of the proposed mixtures M22,M24,M25 and M27 are 4%greater than the COP of R134a(for the same operating conditions).Further,it was also understood that the corresponding GWP value is reduced by 90%to 97%for the mixtures(M21,M22,M24,M25 and M27)when compared to R134a(GWP=1300).Therefore,out of the thirteen proposed ternary mixtures(M15 to M27),the mixtures(M21,M22,M24,M25 and M27)are safe in terms of flammability,GWP and possess reasonable COP which can be a potential alternative refrigerant mixture to R134a in small refrigeration systems.

关键词： hydrocarbons minimum inerting concentration ternary Global Warming Potential

Unstable mode of ion-acoustic waves with two temperature q-nonextensive distributed electrons

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Chinese Physics B 2021年第9期30卷 313-319页

作者： s Bukhari Nadeem Hussain s Ali Department of Physics The University of Azad Jammu and KashmirMuzaffarabad 13100Azad KashmirPakistan National Center for Physics at QAU Campus Shahdra Valley RoadIslamabad 44000Pakistan

The linear characteristics of the unstable mode of ion-acoustic waves are examined in an electrostatic electron-ion plasma composed of streaming hot electrons,non-streaming cold electrons and dynamical positive *** plasma under consideration is modeled by using a non-gyrotropic nonextensive q-distribution function in which the free energy source for wave excitation is provided by the relative directed motion of streaming hot electrons with respect to the other plasma *** the frame work of kinetic model,a linearized set of Vlasov-Poisson's equations are solved to obtain the analytical expressions for dispersion relation and Landau damping *** threshold condition for the unstable ion-acoustic wave is derived to assess the stability of the wave in the presence of nonextensive *** in the wave spectrum and nontrivial effects of q-nonextensive parameter on the ion-acoustic waves can be of interest for the readers in the regions of saturns's magnetosphere.

关键词： non-gyrotropic nonextensivity saturns's magnetosphere

structural and magnetic properties of BiFe_(1-x)Cr_xO_3 synthesized samples

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Chinese Physics B 2014年第6期23卷 398-400页

作者： s.s.Arafat Department of Physics College of Science King Faisal University Department of Physics College of Science Fayoum University

Chromium doping effects on the structure and the magnetic properties of bismuth ferrite BiFe1-xCrxO3 （x = 0-0.3）（BFCxO） polycrystalline samples are examined. The Perovskite-type oxide samples are synthesized by the conventional solid state reaction at a high pressure of 7 GPa and a temperature of 1273 K. The X-ray powder diffraction patterns at room temperature show that all the samples with x = 0.0-0.3 are described by the rhombohedral structure. In the meantime, it is revealed that the doping of Cr can induce noticeable lattice distortions in the doping samples, and the largest distortion is observed in the case x = 0.1. The magnetic hysteresis loops measured at room temperature exhibit week ferromagnetic behaviors of the samples and the magnetization is found to increase with the increase in Cr concentration. The temperature- dependent magnetization curves indicate antiferromagnetic features in samples. Moreover, Cr-doping tends to reduce the ordering temperature.

关键词： X-ray diffraction magnetic properties

Hot Forging of Nitrogen Alloyed Duplex stainless steels

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Journal of Materials science & Technology 2007年第1期23卷 111-117页

作者： P. Chandramohan s.s.Mohamed Nazirudeen s. s.Ramakrishnan Department of Mechatronics Eng Sri Krishna College of Eng and TechCoimbatore 641008India Dept. of Metallurgy PSG College of TechnologyCoimbatore 641004India Mechanical Eng VLB Janakiammal college of Eng and TechCoimbatore 641004India

Duplex stainless steels are gaining global importance because of the need for a high strength corrosion resistant material. Three compositions of this group were selected with three different nitrogen contents ciz, 0.15 wt pct （alloy 1）, 0.23 wt pct （alloy 2） and 0.32 wt pct （alloy 3）. The steels were melted in a high frequency induction furnace and hot forged to various reductions from 16% to 62%. In this work, the effect of hot forging on the ferrite ***, hardness, yield strength, impact strength and grain orientation （texture） were studied. Fracture analysis on all the forged specimens using sEM reveals that a size reduction of 48% results in maximum ductility and impact strength as well as minimal ferrite content and grain size. Thus the mechanical properties are found to have a direct correlation to ferrite content and grain size. The highest impact strength was observed in specimens with the smallest grain size, which was observed in specimens forged to 48% reduction in size.

关键词： Duplex Austenite Ferrite Forging solutionizing

Temperature Effects on the Microstructures of Mg-Gd-Y Alloy Processed by Multi-direction Impact Forging

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Acta Metallurgica sinica(English Letters) 2020年第2期33卷 243-251页

作者： s.s.A.shah D.Wu R.s.Chen G.s.song school of Material science and Engineering Anhui University of Technology The Group of Magnesium Alloys and Their Applications Institute of Metal ResearchChinese Academy of Sciences

A high strain rate multi-directional impact forging(MDIF) was applied to a solutionized Mg-Gd-Y-Zr alloy in the temperature range of 350-500℃.Results demonstrate that the dominant deformation mode is twinning at a temperature below 400℃,whereas at a medium temperature of 450℃ considerable continuous dynamic recrystallization was promoted by{10-12} extension *** a higher temperature of 500℃,twinning activation was *** DRX grains were observed but their sizes were much bigger than those resulting from the MDIFed 50 passes at 450℃,which are ascribed to the larger grain boundary mobility and atomic diffusion at 500℃.Moreover,a non-basal weak texture was gained afterward MDIF at each temperature,which is credited to the MDIF process and the minor strain applied in each pass.

关键词： Magnesium alloys Twinning Dynamic recrystallization Forging Texture

Adsorptive removal of heavy metal ions from industrial effluents using activated carbon derived from waste coconut buttons

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Journal of Environmental sciences 2011年第12期23卷 1989-1998页

作者： T. s. Anirudhan s. s. sreekumari Department of Chemistry University of Kerala Kariavattom Trivandrum-695 581 India

Activated carbon （AC） derived from waste coconut buttons （CB） was investigated as a suitable adsorbent for the removal of heavy metal ions such as Pb（II）, Hg（II） and Cu（II） from industrial effluents through batch adsorption process. The AC was characterized by elemental analysis, fourier transform infrared spectroscopy, X-ray diflraction, scanning electron microscopy, thermal gravimetric and diflerential thermal analysis, surface area analyzer and potentiometric titrations. The eflects of initial metal concentration, contact time, pH and adsorbent dose on the adsorption of metal ions were studied. The adsorbent revealed a good adsorption potential for Pb（II） and Cu（II） at pH 6.0 and for Hg（II） at pH 7.0. The experimental kinetic data were a better fit with pseudo second-order equation rather than pseudo first-order equation. The Freundlich isotherm model was found to be more suitable to represent the experimental equilibrium isotherm results for the three metals than the Langmuir model. The adsorption capacities of the AC decreased in the order： Pb（II） Hg（II） Cu（II）.

关键词： coconut buttons heavy metal ions adsorption isotherm wastewater desorption

CaMoO_4:Dy^(3+),K^+ near White Light Emitting Phosphor:structural,Optical and Dielectric Properties

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Journal of Materials science & Technology 2013年第7期29卷 633-638页

作者： s.K.sharma s.Dutta s.som P.s.Mandal Department of Applied Physics Indian School of MinesDhanbad 826004India

Undoped, Dy^3＋ doped and Dy^3＋, K^＋ codoped calcium molybdate phosphors have been synthesized by solid-state reaction method. X-ray diffraction studies reveal the tetragonal structure of the prepared phosphors having crystallite size 15-50 nm. scanning electron microscopy （sEM） studies reveal the morphology and crystallite size of the prepared phosphors. Photoluminescence studies indicate that there are blue and yellow emissions at 489 and 576 nm, respectively corresponding to Dy^3＋ ion. The introduction of K＋ ion significantly influences the blue and yellow emissions which causes the near white light emission from this codoped phosphor. The intense absorption peak of the codoped phosphor at 210 nm is attributed to the band gap and a shoulder at 240 nm appears due to charge transfer from oxygen ions to neighbouring molybdenum ions. The band gap of the codoped phosphor is calculated as 5.5 eV from the absorption studies. The dielectric properties such as permittivity and dielectric loss are studied as a function of *** The authors are thankful to the Department of science and Technology, New Delhi （Government of India） for funding this work under the Project sR/FTP/Ps-087/2010.

关键词： X-ray diffraction Photoluminescence Absorption Dielectric

Theoretical analysis of slip flow on a rotating cone with viscous dissipation effects

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Journal of Hydrodynamics 2015年第4期27卷 616-623页

作者： sALEEM s. NADEEM s. Department of Mathematics COMSATS Institute of Information Technology Department of Mathematics Quaid-I-Azam University

This paper is concerned with the mutual effects of viscous dissipation and slip effects on a rotating vertical cone in a viscous fluid. similarity solutions for rotating cone with wall temperature boundary conditions provides a system of nonlinear ordinary differential equations which have been treated by optimal homotopy analysis method（OHAM）. The obtained analytical results in comparison with the numerical ones show a noteworthy accuracy for a special case. Effects for the velocities and temperature are revealed graphically and the tabulated values of the surface shear stresses and the heat transfer rate are entered in tables. From the study it is seen that the slip parameter γ enhances the primary velocity while the secondary velocity reduces. Further it is observed that the heat transfer rate Nu Re-1/2x increases with Eckert number Ec and Prandtl number Pr.

关键词： mixed convection incompressible flow differential equations slip effects viscous dissipation

Multiwavelets domain singular value features for image texture classification

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Journal of Zhejiang University-science A(Applied Physics & Engineering) 2007年第4期8卷 538-549页

作者： RAMAKRIsHNAN s. sELVAN s. Department of Information Technology PsG College of Technology Coimbatore 641 004India

A new approach based on multiwavelets transformation and singular value decomposition (sVD) is proposed for the classification of image textures. Lower singular values are truncated based on its energy distribution to classify the textures in the presence of additive white Gaussian noise (AWGN). The proposed approach extracts features such as energy, entropy, local homogeneity and max-min ratio from the selected singular values of multiwavelets transformation coefficients of image textures. The classification was carried out using probabilistic neural network (PNN). Performance of the proposed approach was compared with conventional wavelet domain gray level co-occurrence matrix (GLCM) based features, discrete multiwavelets transformation energy based approach, and HMM based approach. Experimental results showed the superiority of the proposed algorithms when compared with existing algorithms.

关键词： Image texture classification Multiwavelets transformation Probabilistic neural network (PNN)